{"id": "0807.5065", "abstract": "  In the hierarchical search for periodic sources of gravitational waves, the candidate selection, in the incoherent step, can be performed with Hough transform procedures. In this paper we analyze the problem of sensitivity loss due to discretization of the parameters space vs computing cost, comparing the properties of the sky Hough procedure with those of a new frequency Hough, which is based on a transformation from the time - observed frequency plane to the source frequency - spin down plane. Results on simulated peak maps suggest various advantages in favor of the use of the frequency Hough. The ones which show up to really make the difference are 1) the possibility to enhance the frequency resolution without relevantly affecting the computing cost. This reduces the digitization effects; 2) the excess of candidates due to local disturbances in some places of the sky map. They do not affect the new analysis because each map is constructed for only one position in the sky. Pacs. numbers: 04.80Nn,07.05Kf,97.60Jd 1. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.5065v1.pdf"}
{"id": "0908.1812", "abstract": "  I summarize what we have learned about the nature of stars that ultimately explode as core-collapse supernovae from the examination of images taken prior to the explosion. By registering pre-supernova and post-supernova images, usually taken at high resolution using either space-based optical detectors, or ground-based infrared detectors equipped with laser guide star adaptive optics systems, nearly three dozen core-collapse supernovae have now had the properties of their progenitor stars either directly measured or (more commonly) constrained by establishing upper limits on their luminosities. These studies enable direct comparison with stellar evolution models that, in turn, permit estimates of the progenitor stars' physical characteristics to be made. I review progenitor characteristics (or constraints) inferred from this work for each of the major core-collapse supernova types (II-Plateau, II-Linear, IIb, IIn, Ib/c), with a particular focus on the analytical techniques used and the processes through which conclusions have been drawn. Brief discussion of a few individual events is also provided, including SN 2005gl, a type IIn supernova that is shown to have had an extremely luminous – and thus very massive – progenitor that exploded shortly after a violent, luminous blue variable-like eruption phase, contrary to standard theoretical predictions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.1812v1.pdf"}
{"id": "0909.1602", "abstract": "  Starting from the WKB approximation, a new barrier penetration formula is proposed for potential barriers containing a long-range Coulomb interaction. This formula is especially proper for the barrier penetration with penetration energy much lower than the Coulomb barrier. The penetrabilities calculated from the new formula agree well with the results from the WKB method. As a first attempt, this new formula is used to evaluate alpha decay half-lives of atomic nuclei and a good agreement with the experiment is obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.1602v1.pdf"}
{"id": "1001.0199", "abstract": "  SOFIA is a 2.5 meter airborne infrared telescope, mounted in a Boeing 747SP aircraft. Due to the large size of the telescope, only a few degrees of azimuth are available at the telescope bearing. This means the heading of the aircraft is fundamentally associated with the telescope's observation targets, and the ground track necessary to enable a given mission is highly complex and dependent on the coordinates, duration, and order of observations to be performed. We have designed and implemented a Flight Management Infrastructure (FMI) product in order to plan and execute such missions in the presence of a large number of external constraints (e.g. restricted airspace, international boundaries, elevation limits of the telescope, aircraft performance, winds at altitude, and ambient temperatures). We present an overview of the FMI, including the process, constraints and basic algorithms used to plan and execute SOFIA missions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.0199v1.pdf"}
{"id": "1004.5347", "abstract": "  Primordial black hole (PBH) abundance limits constrain the primordial power spectrum, and hence models of inflation, on scales far smaller than those probed by cosmological observations. Single field inflation models which are compatible with all cosmological data can have large enough perturbations on small scales to overproduce PBHs, and hence be excluded. The standard formulae for the amplitude of perturbations do not hold for modes that exit the horizon close to the end of inflation however. We use a modified flow analysis to identify models of inflation where the amplitude of perturbations on small scales is large. For these models we then carry out a numerical evolution of the perturbations and use the PBH constraints on the power spectrum to eliminate models which overproduce PBHs. Significant PBH formation can occur in models in which inflation can continue indefinitely and is ended via a secondary mechanism. We demonstrate that PBHs constrain these types of inflation models and show that a numerical evaluation of the power spectrum decreases the number of otherwise viable models of inflation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.5347v3.pdf"}
{"id": "1307.2735", "abstract": "  Multiplication is one of the most important operation in computer arithmetic. Many integer operations such as squaring, division and computing reciprocal require same order of time as multiplication whereas some other operations such as computing GCD and residue operation require at most a factor of log n time more than multiplication. We propose an integer multiplication algorithm using Nikhilam method of Vedic mathematics which can be used to multiply two binary numbers efficiently. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.2735v1.pdf"}
{"id": "1412.2508", "abstract": "  Evolutionary tracks and pulsational analysis of models with masses of 13-18 M_⊙ are presented. We address two important questions. The first one deals with one of the most unresolved problems in astrophysics, i.e., the existence of a blue loop after core helium ignition; the so called \"to loop or not to loop\" problem. We show that inward overshooting from the outer convective zone in the red giant phase is prerequisite for the development of the blue loop. Our second question concerns pulsational instability of models in the core helium burning phase. We present for the first time that models on the blue loop can have unstable modes driven by the κ mechanism operating in the Z-bump. Contrary to post-main sequence models in the shell hydrogen burning phases, pulsational instability of the blue loop models depends mainly on effective temperature and metallicity is of secondary importance. Finally, we try to interpret the oscillation spectrum of the blue supergiant HD 163899, the only member of the SPBsg class, and to get some clue on the evolutionary status of the star. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.2508v1.pdf"}
{"id": "1512.03812", "abstract": "  We study a novel class of numerical integrators, the adapted nested force-gradient schemes, used within the molecular dynamics step of the Hybrid Monte Carlo (HMC) algorithm. We test these methods in the Schwinger model on the lattice, a well known benchmark problem. We derive the analytical basis of nested force-gradient type methods and demonstrate the advantage of the proposed approach, namely reduced computational costs compared with other numerical integration schemes in HMC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.03812v3.pdf"}
{"id": "1512.07656", "abstract": "  We consider one-dimensional mixtures of an atomic Bose-Einstein condensate (BEC) and Tonks- Giradeau (TG) gas. The mixture is modeled by a coupled system of the Gross-Pitaevskii equation for the BEC and the quintic nonlinear Schroedinger equation for the TG component. An immiscibility condition for the binary system is derived in a general form. Under this condition, three types of BEC-TG interfaces are considered: domain walls (DWs) separating the two components; bubble-drops (BDs), in the form of a drop of one component immersed into the other (BDs may be considered as bound states of two DWs); and bound states of bright and dark solitons (BDSs). The same model applies to the copropagation of two optical waves in a colloidal medium. The results are obtained by means of systematic numerical analysis, in combination with analytical Thomas-Fermi approximations (TFAs). Using both methods, families of DW states are produced in a generic form. BD complexes exist solely in the form of a TG drop embedded into the BEC background. On the contrary, BDSs exist as bound states of TG bright and BEC dark components, and vice versa. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.07656v1.pdf"}
{"id": "1512.09139", "abstract": "  We study the detectability of circular polarization in a stochastic gravitational wave background from various sources such as supermassive black hole binaries, cosmic strings, and inflation in the early universe with pulsar timing arrays. We calculate generalized overlap reduction functions for the circularly polarized stochastic gravitational wave background. We find that the circular polarization can not be detected for an isotropic background. However, there is a chance to observe the circular polarization for an anisotropic gravitational wave background. We also show how to separate polarized gravitational waves from unpolarized gravitational waves. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.09139v1.pdf"}
{"id": "hep-lat0105026", "abstract": "  We have simulated two-colour four-flavour QCD at non-zero chemical potential μ for quark number. Simulations were performed on 8^4 and 12^3 × 24 lattices. Clear evidence was seen for the formation of a colourless diquark condensate which breaks quark number spontaneously, for μ > μ_c ∼ m_π/2. The transition appears to be second order. We have measured the spectrum of scalar and pseudoscalar bosons which shows clear evidence for the expected Goldstone boson. Our results are in qualitative agreement with those from effective Lagrangians for the potential Goldstone excitations of this theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0105/0105026v1.pdf"}
{"id": "hep-ph0701277", "abstract": "  We present a phenomenological study of the single-transverse spin asymmetry in azimuthal correlations of two jets produced nearly \"back-to-back\" in pp collisions at RHIC. We properly take into account the initial- and final-state interactions of partons that can generate this asymmetry in QCD hard-scattering. Using distribution functions fitted to the existing single-spin data, we make predictions for various weighted single-spin asymmetries in dijet correlations that are now readily testable at RHIC. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0701/0701277v1.pdf"}
{"id": "hep-ph9602267", "abstract": "  We compute the one-loop corrections to the Z → bb̅ vertex in the U(1)_R symmetric minimal supersymmetric extension of the standard model. We find that the predicted value of R_b is consistent with experiment if the mass of the lighter top squark is no more than 180 GeV. Furthermore, other data combines to place a lower bound of 88 GeV on the mass of the light top squark. A top squark in this mass range should be accessible to searches by experiments at FNAL and LEP. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9602/9602267v4.pdf"}
{"id": "nlin0001046", "abstract": "  We discuss several novel types of multi-component (temporal and spatial) envelope solitary waves that appear in fiber and waveguide nonlinear optics. In particular, we describe multi-channel solitary waves in bit-parallel-wavelength fiber transmission systems for high performance computer networks, multi-colour parametric spatial solitary waves due to cascaded nonlinearities of quadratic materials, and quasiperiodic envelope solitons due to quasi-phase-matching in Fibonacci optical superlattices. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0001/0001046v2.pdf"}
{"id": "quant-ph0305125", "abstract": "  The mutual dipole-dipole interaction of atoms in a trap can affect their fluorescence. Extremely large effects were reported for double jumps between different intensity periods in experiments with two and three Ba^+ ions for distances in the range of about ten wave lengths of the strong transition while no effects were observed for Hg^+ at 15 wave lengths. In this theoretical paper we study this question for configurations with three and four levels which model those of Hg^+ and Ba^+, respectively. For two systems in the Hg^+ configuration we find cooperative effects of up to 30", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0305/0305125v2.pdf"}
{"id": "quant-ph0307206", "abstract": "  Strong subadditivity inequality for a three-particle composite system is an important inequality in quantum information theory which can be studied via a four-particle entangled state. We use two three-level atoms in Λ configuration interacting with a two-mode cavity and the Raman adiabatic passage technique for the production of the four-particle entangled state. Using this four-particle entanglement, we study for the first time various aspects of the strong subadditivity inequality. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0307/0307206v1.pdf"}
{"id": "1111.4135", "abstract": "  We analyze the dynamics of a single-level quantum dot with Coulomb interaction, weakly tunnel coupled to an electronic reservoir, after it has been brought out of equilibrium, e.g. by a step-pulse potential. We investigate the exponential decay towards the equilibrium state, which is governed by three time scales. In addition to the charge and spin relaxation time there is a third time scale which is independent of the level position and the Coulomb interaction. This time scale emerges in the time evolution of physical quantities sensitive to two-particle processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.4135v2.pdf"}
{"id": "1601.05253", "abstract": "  We report on a high-statistics measurement of the most basic double pionic fusion reaction n⃗p → dπ^0π^0 over the energy region of the d^*(2380) resonance by use of a polarized deuteron beam and observing the double fusion reaction in the quasifree scattering mode. The measurements were performed with the WASA detector setup at COSY. The data reveal substantial analyzing powers and confirm conclusions about the d^* resonance obtained from unpolarized measurements. We also confirm the previous unpolarized data obtained under complementary kinematic conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.05253v1.pdf"}
{"id": "astro-ph0011128", "abstract": "  Specially-designed microlensing searches, some of which have been underway for several years, are sensitive to extrasolar planets orbiting the most common stars in our Galaxy. Microlensing is particularly well-suited to the detection of Jupiter-mass planets orbiting their parent stars at several AU. Since Jovian analogs are thought to influence the subsequent evolution of most planetary systems, they are particularly important to study. The orbital radii and distances to the planetary systems probed by microlensing are larger than those currently studied by radial velocity techniques; the two methods are thus complementary. Recent results from microlensing searches are discussed, including constraints on Jovian analogs orbiting typical Galactic stars. Benefits and drawbacks of the technique for the characterization of planetary systems, and future prospects are briefly reviewed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011128v1.pdf"}
{"id": "astro-ph0205340", "abstract": "  We present new equilibrium component distribution functions that depend on three analytic integrals in a Stackel potential, and that can be used to model stellar discs of galaxies. These components are generalizations of two-integral ones and can thus provide thin discs in the two-integral approximation. Their most important properties are the partly analytical expression for their moments, the disc-like features of their configuration space densities (exponential decline in the galactic plane and finite extent in the vertical direction) and the anisotropy of their velocity dispersions. We further show that a linear combination of such components can fit a van der Kruit disc. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0205/0205340v1.pdf"}
{"id": "astro-ph9605008", "abstract": "  Using HST and the WFPC2 we have acquired very deep V- and I-band photometry of stars in NGC 2420 and NGC 2477 to study cluster luminosity functions at approximately solar metallicity. We have determined these cluster luminosity functions down to M_I = 10.5 (0.2 M_⊙) and find that the luminosity function of NGC 2420 turns over at M_I ≈ 9.0, and possibly stops altogether by M_I ≈ 9.5. The luminosity function of NGC 2477 may flatten at M_I ≥ 9.5. We compare our open cluster luminosity functions to the solar neighborhood field star luminosity function of Kroupa, Tout & Gilmore (1993) and the four published HST globular cluster luminosity functions: ω Cen (Elson et al. 1995), 47 Tuc (De Marchi & Paresce 1995b), M 15 (De Marchi & Paresce 1995a), and NGC 6397 (Paresce, De Marchi & Romaniello 1995). We find a smooth relation between the location of the luminosity function turn-over and the metallicity for all these low mass star samples which matches the expected M_I versus [Fe/H] trend for a model star of ≈ 0.27 M_⊙ (Saumon 1995; Alexander et al. 1996). We interpret this smooth and systematic behavior in the cluster luminosity functions as strong evidence in favor of an invariant initial mass function and a metallicity-dependent mass-luminosity relation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9605/9605008v1.pdf"}
{"id": "hep-ex0307059", "abstract": "  The HiRes Collaboration has recently announced preliminary measurements of the energy spectrum of ultra-high energy cosmic rays (UHECR), as seen in monocular analyses from each of the two HiRes sites. This spectrum is consistent with the existence of the GZK cutoff, as well other aspects of the energy loss processes that cause the GZK cutoff. Based on the analytic energy loss formalism of Berezinsky et al., the HiRes spectra favor a distribution of extragalactic sources that has a similar distribution to that of luminous matter in the universe, both in its local over-density and in its cosmological evolution. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0307/0307059v1.pdf"}
{"id": "0704.0689", "abstract": "  The recently updated data of the twin kilohertz quasi-periodic oscillations (kHz QPOs) in the neutron star low-mass X-ray binaries are analyzed. The power-law fitting ν_1=a(ν_2/1000)^b and linear fitting ν_2=Aν_1+B are applied, individually, to the data points of four Z sources (GX 17+2, GX 340+0, GX 5-1 and Sco X-1) and four Atoll sources (4U 0614+09, 4U 1608-52, 4U 1636-53 and 4U 1728-34). The χ^2-tests show that the power-law correlation and linear correlation both can fit data well. Moreover, the comparisons between the data and the theoretical models for kHz QPOs are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.0689v1.pdf"}
{"id": "0704.0802", "abstract": "  This paper develops a contention-based opportunistic feedback technique towards relay selection in a dense wireless network. This technique enables the forwarding of additional parity information from the selected relay to the destination. For a given network, the effects of varying key parameters such as the feedback probability are presented and discussed. A primary advantage of the proposed technique is that relay selection can be performed in a distributed way. Simulation results find its performance to closely match that of centralized schemes that utilize GPS information, unlike the proposed method. The proposed relay selection method is also found to achieve throughput gains over a point-to-point transmission strategy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.0802v1.pdf"}
{"id": "0704.1346", "abstract": "  In the previous study (Hiremath 2006a), the solar cycle is modeled as a forced and damped harmonic oscillator and from all the 22 cycles (1755-1996), long-term amplitudes, frequencies, phases and decay factor are obtained. Using these physical parameters of the previous 22 solar cycles and by an autoregressive model, we predict the amplitude and period of the future fifteen solar cycles. Predicted amplitude of the present solar cycle (23) matches very well with the observations. The period of the present cycle is found to be 11.73 years. With these encouraging results, we also predict the profiles of future 15 solar cycles. Important predictions are : (i) the period and amplitude of the cycle 24 are 9.34 years and 110 (± 11), (ii) the period and amplitude of the cycle 25 are 12.49 years and 110 (± 11), (iii) during the cycles 26 (2030-2042 AD), 27 (2042-2054 AD), 34 (2118-2127 AD), 37 (2152-2163 AD) and 38 (2163-2176 AD), the sun might experience a very high sunspot activity, (iv) the sun might also experience a very low (around 60) sunspot activity during cycle 31 (2089-2100 AD) and, (v) length of the solar cycles vary from 8.65 yrs for the cycle 33 to maximum of 13.07 yrs for the cycle 35. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1346v1.pdf"}
{"id": "0704.1509", "abstract": "  Spectral diagnostic features formed in the solar chromosphere are few and difficult to interpret – they are neither formed in the optically thin regime nor in local thermodynamic equilibrium (LTE). To probe the state of the chromosphere, both from observations and theory, it is therefore necessary with modeling. I discuss both traditional semi-empirical modeling, numerical experiments illustrating important ingredients necessary for a self-consistent theoretical modeling of the solar chromosphere and the first results of such models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1509v1.pdf"}
{"id": "0704.1550", "abstract": "  Density-functional theory has been applied to investigate systematics of sodium clusters Na_n in the size range of n= 39-55. A clear evolutionary trend in the growth of their ground-state geometries emerges. The clusters at the beginning of the series (n=39-43) are symmetric and have partial icosahedral (two-shell) structure. The growth then goes through a series of disordered clusters (n=44-52) where the icosahedral core is lost. However, for n>52 a three shell icosahedral structure emerges. This change in the nature of the geometry is abrupt. In addition, density-functional molecular dynamics has been used to calculate the specific heat curves for the representative sizes n= 43, 45, 48 and 52. These results along with already available thermodynamic calculations for n= 40, 50, and 55 enable us to carry out a detailed comparison of the heat capacity curves with their respective geometries for the entire series. Our results clearly bring out strong correlation between the evolution of the geometries and the nature of the shape of the heat capacities. The results also firmly establish the size-sensitive nature of the heat capacities in sodium clusters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1550v1.pdf"}
{"id": "0704.1749", "abstract": "  VIMOS is a wide-field imager and spectrograph mounted on UT3 at the   VLT, whose FOV consists of four 7'x8' quadrants. Here we present the measurements of total transmission profiles – i.e. the throughput of telescope + instrument – for the broad band filters U, B, V, R, I, and z for each of its four quadrants. Those measurements can also be downloaded from the public VIMOS web-page. The transmission profiles are compared with previous estimates from the VIMOS consortium. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1749v1.pdf"}
{"id": "0704.1752", "abstract": "  The Lifshitz-type formulas describing the free energy and the force of the van der Waals interaction between an atom (molecule) and a single-wall carbon nanotube are obtained. The single-wall nanotube is considered as a cylindrical sheet carrying a two-dimensional free electron gas with appropriate boundary conditions on the electromagnetic field. The obtained formulas are used to calculate the van der Waals free energy and force between a hydrogen atom (molecule) and single-wall carbon nanotubes of different radia. Comparison studies of the van der Waals interaction of hydrogen atoms with single- and multi-wall carbon nanotubes show that depending on atom-nanotube separation distance the idealization of graphite dielectric permittivity is already applicable to nanotubes with only two or three walls. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1752v1.pdf"}
{"id": "0704.2606", "abstract": "  Recently H(z) data obtained from differential ages of galaxies have been proposed as a new geometrical probe of dark energy. In this paper we use those data, combined with other background tests (CMB shift and SNIa data), to constrain a set of general relativistic dark energy models together with some other models motivated by extra dimensions. Our analysis rests mostly on Bayesian statistics, and we conclude that LCDM is at least substantially favoured, and that braneworld models are less favoured than general relativistic ones. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.2606v2.pdf"}
{"id": "0704.3412", "abstract": "  Based on the results of numerical modeling, it is shown that dipole-dipole interactions among atoms in the active medium influences strongly the character of the associated superradiation. The main effect is to make the nuclear subsystem behave chaotically. Its strength increases with the atom density, and leads to the suppression of distant collective correlations and superradiation. Near correlations between the atoms are established, causing a confinement effect: a shielding of radiation in the active medium. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.3412v1.pdf"}
{"id": "0704.3550", "abstract": "  We update the analytical estimate of the final spin of a coalescing black-hole binary derived within the Effective-One-Body (EOB) approach. We consider unequal-mass non-spinning black-hole binaries. It is found that a more complete account of relevant physical effects (higher post-Newtonian accuracy, ringdown losses) allows the analytical EOB estimate to `converge towards' the recently obtained numerical results within 2", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.3550v2.pdf"}
{"id": "0704.3708", "abstract": "  This paper includes a reflection on the role of networks in the study of English language acquisition, as well as a collection of practical criteria to annotate free-speech corpora from children utterances. At the theoretical level, the main claim of this paper is that syntactic networks should be interpreted as the outcome of the use of the syntactic machinery. Thus, the intrinsic features of such machinery are not accessible directly from (known) network properties. Rather, what one can see are the global patterns of its use and, thus, a global view of the power and organization of the underlying grammar. Taking a look into more practical issues, the paper examines how to build a net from the projection of syntactic relations. Recall that, as opposed to adult grammars, early-child language has not a well-defined concept of structure. To overcome such difficulty, we develop a set of systematic criteria assuming constituency hierarchy and a grammar based on lexico-thematic relations. At the end, what we obtain is a well defined corpora annotation that enables us i) to perform statistics on the size of structures and ii) to build a network from syntactic relations over which we can perform the standard measures of complexity. We also provide a detailed example. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.3708v2.pdf"}
{"id": "0705.0578", "abstract": "  In this paper, we propose a quantum field theoretical renormalization group approach to the vortex dynamics of magnetically coupled layered superconductors, to supplement our earlier investigations on the Josephson-coupled case. We construct a two-dimensional multi-layer sine-Gordon type model which we map onto a gas of topological excitations. With a special choice of the mass matrix for our field theoretical model, vortex dominated properties of magnetically coupled layered superconductors can be described. The well known interaction potentials of fractional flux vortices are consistently obtained from our field-theoretical analysis, and the physical parameters (vortex fugacity and temperature parameter) are also identified. We analyse the phase structure of the multi-layer sine–Gordon model by a differential renormalization group method for the magnetically coupled case from first principles. The dependence of the transition temperature on the number of layers is found to be in agreement with known results based on other methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.0578v3.pdf"}
{"id": "0705.0999", "abstract": "  In this paper the benefits provided by multi-cell processing of signals transmitted by mobile terminals which are received via dedicated relay terminals (RTs) are assessed. Unlike previous works, each RT is assumed here to be capable of full-duplex operation and receives the transmission of adjacent relay terminals. Focusing on intra-cell TDMA and non-fading channels, a simplified uplink cellular model introduced by Wyner is considered. This framework facilitates analytical derivation of the per-cell sum-rate of multi-cell and conventional single-cell receivers. In particular, the analysis is based on the observation that the signal received at the base stations can be interpreted as the outcome of a two-dimensional linear time invariant system. Numerical results are provided as well in order to provide further insight into the performance benefits of multi-cell processing with relaying. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.0999v1.pdf"}
{"id": "0705.1617", "abstract": "  With the great success in simulating many intelligent behaviors using computing devices, there has been an ongoing debate whether all conscious activities are computational processes. In this paper, the answer to this question is shown to be no. A certain phenomenon of consciousness is demonstrated to be fully represented as a computational process using a quantum computer. Based on the computability criterion discussed with Turing machines, the model constructed is shown to necessarily involve a non-computable element. The concept that this is solely a quantum effect and does not work for a classical case is also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.1617v1.pdf"}
{"id": "0705.3195", "abstract": "  The behavior of interacting populations typically displays irregular temporal and spatial patterns that are difficult to reconcile with an underlying deterministic dynamics. A classical example is the heterogeneous distribution of plankton communities, which has been observed to be patchy over a wide range of spatial and temporal scales. Here, we use plankton communities as prototype systems to present theoretical approaches for the analysis of the combined effects of turbulent advection and stochastic growth in the spatiotemporal dynamics of the population. Incorporation of these two factors into mathematical models brings an extra level of realism to the description and leads to better agreement with experimental data than that of previously proposed models based on reaction-diffusion equations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.3195v1.pdf"}
{"id": "0705.3498", "abstract": "  The composite torsional ultrasonic oscillator, a versatile experimental system, can be used to investigate slip of Newtonian fluid at a smooth surface. A rigorous analysis of slip-dependent damping for the oscillator is presented. Initially, the phenomenon of finite surface slip and the slip length are considered for a half-space of Newtonian fluid in contact with a smooth, oscillating solid surface. Definitions are revisited and clarified in light of inconsistencies in the literature. We point out that, in general oscillating flows, Navier's slip length b is a complex number. An intuitive velocity discontinuity parameter of unrestricted phase is used to describe the effect of slip on measurement of viscous shear damping. The analysis is applied to the composite oscillator and preliminary experimental work for a 40 kHz oscillator is presented. The Non-Slip Boundary Condition (NSBC) has been verified for a hydrophobic surface in water to within  60 nm of |b|=0 nm. Experiments were carried out at shear rate amplitudes between 230 and 6800 /s, corresponding to linear displacement amplitudes between 3.2 and 96 nm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.3498v3.pdf"}
{"id": "0706.3122", "abstract": "  Adaptive populations such as those in financial markets and distributed control can be modeled by the Minority Game. We consider how their dynamics depends on the agents' initial preferences of strategies, when the agents use linear or quadratic payoff functions to evaluate their strategies. We find that the fluctuations of the population making certain decisions (the volatility) depends on the diversity of the distribution of the initial preferences of strategies. When the diversity decreases, more agents tend to adapt their strategies together. In systems with linear payoffs, this results in dynamical transitions from vanishing volatility to a non-vanishing one. For low signal dimensions, the dynamical transitions for the different signals do not take place at the same critical diversity. Rather, a cascade of dynamical transitions takes place when the diversity is reduced. In contrast, no phase transitions are found in systems with the quadratic payoffs. Instead, a basin boundary of attraction separates two groups of samples in the space of the agents' decisions. Initial states inside this boundary converge to small volatility, while those outside diverge to a large one. Furthermore, when the preference distribution becomes more polarized, the dynamics becomes more erratic. All the above results are supported by good agreement between simulations and theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.3122v2.pdf"}
{"id": "0706.3376", "abstract": "  We propose a method to perform precision measurements of the interaction parameters in systems of N ultra-cold spin 1/2 atoms. The spectroscopy is realized by first creating a coherent spin superposition of the two relevant internal states of each atom and then letting the atoms evolve under a squeezing Hamiltonian. The non-linear nature of the Hamiltonian decreases the fundamental limit imposed by the Heisenberg uncertainty principle to N^(-2), a factor of N smaller than the fundamental limit achievable with non-interacting atoms. We study the effect of decoherence and show that even with decoherence, entangled states can outperform the signal to noise limit of non-entangled states. We present two possible experimental implementations of the method using Bose-Einstein spinor condensates and fermionic atoms loaded in optical lattices and discuss their advantages and disadvantages. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.3376v2.pdf"}
{"id": "0706.3673", "abstract": "  The ground state carrier dynamics in self-assembled (In,Ga)As/GaAs quantum dots has been studied using time-resolved photoluminescence and transmission. By varying the dot design with respect to confinement and doping, the dynamics is shown to follow in general a non-exponential decay. Only for specific conditions in regard to optical excitation and carrier population, for example, the decay can be well described by a mono-exponential form. For resonant excitation of the ground state transition a strong shortening of the luminescence decay time is observed as compared to the non-resonant case. The results are consistent with a microscopic theory that accounts for deviations from a simple two-level picture. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.3673v1.pdf"}
{"id": "0706.4086", "abstract": "  We propose a scenario in which the dark components of the Universe are manifestations of a single bulk viscous fluid. Using dynamical system methods, a qualitative study of the homogeneous, isotropic background scenario is performed in order to determine the phase space of all possible solutions. The specific model which we investigate shares similarities with a generalized Chaplygin gas in the background but is characterized by non-adiabatic pressure perturbations. This model is tested against supernova type Ia and matter power spectrum data. Different from other unified descriptions of dark matter and dark energy, the matter power spectrum is well behaved, i.e., there are no instabilities or oscillations on small perturbation scales. The model is competitive in comparison with the currently most popular proposals for the description of the cosmological dark sector. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.4086v2.pdf"}
{"id": "0707.0962", "abstract": "  The total entropy production generated by the dynamics of an externally driven systems exchanging energy and matter with multiple reservoirs and described by a master equation is expressed as the sum of three contributions, each corresponding to a distinct mechanism for bringing the system out of equilibrium: nonequilibrium initial conditions, external driving, and breaking of detailed balance. We derive three integral fluctuation theorems (FTs) for these contributions and show that they lead to the following universal inequality: an arbitrary nonequilibrium transformation always produces a change in the total entropy production greater or equal than the one produced if the transformation is done very slowly (adiabatically). Previously derived fluctuation theorems can be recovered as special cases. We show how these FTs can be experimentally tested by performing the counting statistics of the electrons crossing a single level quantum dot coupled to two reservoirs with externally varying chemical potentials. The entropy probability distributions are simulated for driving protocols ranging from the adiabatic to the sudden switching limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.0962v2.pdf"}
{"id": "0707.1250", "abstract": "  I utilize the Petrov-Galerkin formulation and develop a new method for solving the unsteady collisionless Boltzmann equation in both the linear and nonlinear regimes. In the first order approximation, the method reduces to a linear eigenvalue problem which is solved using standard numerical methods. I apply the method to the dynamics of a model stellar disk which is embedded in the field of a soft-centered logarithmic potential. The outcome is the full spectrum of eigenfrequencies and their conjugate normal modes for prescribed azimuthal wavenumbers. The results show that the fundamental bar mode is isolated in the frequency space while spiral modes belong to discrete families that bifurcate from the continuous family of van Kampen modes. The population of spiral modes in the bifurcating family increases by cooling the disk and declines by increasing the fraction of dark to luminous matter. It is shown that the variety of unstable modes is controlled by the shape of the dark matter density profile. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.1250v1.pdf"}
{"id": "0707.1856", "abstract": "  There is a strong connection between the formation of a disk galaxy and the properties of the interstellar medium (ISM). Theoretical work has typically either focused on the cosmological buildup of a galaxy with a relatively crude model for the gas physics, or examined local processes in the ISM and ignored the global evolution of the galaxy itself. Here, I briefly review what has been learned from both of these approaches, and what can be done to bridge the gap between them. I argue that cosmological simulations need to learn from observational and theoretical work on local ISM properties and adopt more sophisticated models for the processes that they cannot resolve. Since the ISM is still incompletely understood, there are a number of reasonable approaches for these \"subgrid\" models, and I will discuss the strengths and limitations of each. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.1856v1.pdf"}
{"id": "0707.2328", "abstract": "  In order to understand the first stages of the nucleation of carbon nanotubes in catalytic processes, we present a tight-binding Monte Carlo study of the stability and cohesive mechanisms of different carbon structures deposited on nickel (100) surfaces. Depending on the geometry, we obtain contrasted results. On the one hand, the analysis of the local energy distributions of flat carbon sheets, demonstrate that dangling bonds remain unsaturated in spite of the presence of the metallic catalyst. Their adhesion results from the energy gain of the surface Ni atoms located below the carbon nanostructure. On the other hand, carbon caps are stabilized by the presence of carbon atoms occupying the hollow sites of the fcc nickel structure suggesting the saturation of the dangling bonds. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.2328v1.pdf"}
{"id": "0707.3057", "abstract": "  The impact of HST photometry and European astronomy in studies concerning the star formation histories of resolved galaxies is described. Our current knowledge of the star formation history of systems within 10-20 Mpc, as derived from the colour-magnitude diagrams of their resolved stellar populations, is reviewed, as well as the impact of these results on our understanding of galaxy evolution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.3057v1.pdf"}
{"id": "0707.3782", "abstract": "  In earlier work, the Abstract State Machine Thesis – that arbitrary algorithms are behaviorally equivalent to abstract state machines – was established for several classes of algorithms, including ordinary, interactive, small-step algorithms. This was accomplished on the basis of axiomatizations of these classes of algorithms. Here we extend the axiomatization and, in a companion paper, the proof, to cover interactive small-step algorithms that are not necessarily ordinary. This means that the algorithms (1) can complete a step without necessarily waiting for replies to all queries from that step and (2) can use not only the environment's replies but also the order in which the replies were received. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.3782v2.pdf"}
{"id": "0708.0432", "abstract": "  An analysis of some modified gravity models, based on the study of pure Schwarzschild and of Schwarzschild-de Sitter black holes, and involving the use of the Noether charge method, is carried out. Corrections to the classical Einsteinian black hole entropy appear. It is shown explicitly how the condition of positive entropy can be used in order to constrain the viability of modified gravity theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.0432v2.pdf"}
{"id": "0708.3012", "abstract": "  We fit the volatility fluctuations of the S   P 500 index well by a Chi distribution, and the distribution of log-returns by a corresponding superposition of Gaussian distributions. The Fourier transform of this is, remarkably, of the Tsallis type. An option pricing formula is derived from the same superposition of Black-Scholes expressions. An explicit analytic formula is deduced from a perturbation expansion around a Black-Scholes formula with the mean volatility. The expansion has two parts. The first takes into account the non-Gaussian character of the stock-fluctuations and is organized by powers of the excess kurtosis, the second is contract based, and is organized by the moments of moneyness of the option. With this expansion we show that for the Dow Jones Euro Stoxx 50 option data, a Delta-hedging strategy is close to being optimal. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.3012v1.pdf"}
{"id": "0708.3176", "abstract": "  We use 1+1 dimensional large N Gross-Neveu models as a laboratory to derive microscopically effective Lagrangians for positive energy fermions only. When applied to baryons, the Euler-Lagrange equation for these effective theories assumes the form of a non-linear Dirac equation. Its solution reproduces the full semi-classical results including the Dirac sea to any desired accuracy. Dynamical effects from the Dirac sea are encoded in higher order derivative terms and multi-fermion interactions with perturbatively calculable, finite coefficients. Characteristic differences between models with discrete and continuous chiral symmetry are observed and clarified. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.3176v2.pdf"}
{"id": "0708.3469", "abstract": "  We investigate the electronic structure of the InAs/InP quantum dots using an atomistic pseudopotential method and compare them to those of the InAs/GaAs QDs. We show that even though the InAs/InP and InAs/GaAs dots have the same dot material, their electronic structure differ significantly in certain aspects, especially for holes: (i) The hole levels have a much larger energy spacing in the InAs/InP dots than in the InAs/GaAs dots of corresponding size. (ii) Furthermore, in contrast with the InAs/GaAs dots, where the sizeable hole p, d intra-shell level splitting smashes the energy level shell structure, the InAs/InP QDs have a well defined energy level shell structure with small p, d level splitting, for holes. (iii) The fundamental exciton energies of the InAs/InP dots are calculated to be around 0.8 eV (∼ 1.55 μm), about 200 meV lower than those of typical InAs/GaAs QDs, mainly due to the smaller lattice mismatch in the InAs/InP dots. (iii) The widths of the exciton P shell and D shell are much narrower in the InAs/InP dots than in the InAs/GaAs dots. (iv) The InAs/GaAs and InAs/InP dots have a reversed light polarization anisotropy along the [100] and [11̅0] directions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.3469v1.pdf"}
{"id": "0709.2015", "abstract": "  We discuss the relevance of studying ecology within the framework of Complexity Science from a statistical mechanics approach. Ecology is concerned with understanding how systems level properties emerge out of the multitude of interactions amongst large numbers of components, leading to ecosystems that possess the prototypical characteristics of complex systems. We argue that statistical mechanics is at present the best methodology available to obtain a quantitative description of complex systems, and that ecology is in urgent need of “integrative” approaches that are quantitative and non-stationary. We describe examples where combining statistical mechanics and ecology has led to improved ecological modelling and, at the same time, broadened the scope of statistical mechanics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.2015v1.pdf"}
{"id": "0709.3093", "abstract": "  We analyze 205 ks of imaging data of the active binary, Capella, obtained with the Chandra High Resolution Camera Imager (HRC-I) to determine whether Capella shows any variability at timescales < 50 ks. We find that a clear signal for variability is present for timescales < 20 ks, and that the light curves show evidence for excess fluctuation over that expected from a purely Poisson process. This overdispersion is consistent with variability at the 2-7", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.3093v1.pdf"}
{"id": "0709.3724", "abstract": "  We analyze the effect of the long-range interaction on the transport properties through ordered and disordered one-dimensional metallic nanoparticle arrays. We discuss how the threshold voltage, the I-V curves and the voltage drop through the array are modified as compared to the case in which interactions are restricted to charges placed on the same island. We show that some of these modifications are due to finite interactions between charges in different nanoparticles while other ones are due to interactions between charges in the islands and those at the electrodes, what produces a polarization potential drop through the array. We study the screening of the disorder potential due to charges impurities trapped in the substrate and find that long-range interactions introduce correlations between the disorder potentials of neighboring islands. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.3724v1.pdf"}
{"id": "0709.3988", "abstract": "  We consider a modified action functional with a non-minimum coupling between the scalar curvature and the matter Lagrangian, and study its consequences on stellar equilibrium. Particular attention is paid to the validity of the Newtonian regime, and on the boundary and exterior matching conditions, as well as on the redefinition of the metric components. Comparison with solar observables is achieved through numerical analysis, and constraints on the non-minimum coupling are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.3988v2.pdf"}
{"id": "0710.0405", "abstract": "  Advances in micro deformable mirror (DM) technologies such as MEMs, have stimulated interest in the characteristics of systems that include a high stroke mirror in series with a high actuator count mirror. This arrangement is referred to as a woofer-tweeter system. In certain situations it may be desirable or necessary to operate the woofer DM in open-loop. We present a simple method for controlling a woofer DM in open loop provided the device behaves in an approximately linear fashion. We have tested a mirror that we believe meets our criterion, the ALPAO DM52 mirror. Using our open-loop method we fit several test Kolmogorov wavefronts with the mirror and have achieved an accuracy of approximately 25 nm rms surface deviation over the whole clear aperture, and 20 nm rms over 90", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.0405v1.pdf"}
{"id": "0710.0658", "abstract": "  Measuring network flow sizes is important for tasks like accounting/billing, network forensics and security. Per-flow accounting is considered hard because it requires that many counters be updated at a very high speed; however, the large fast memories needed for storing the counters are prohibitively expensive. Therefore, current approaches aim to obtain approximate flow counts; that is, to detect large elephant flows and then measure their sizes.   Recently the authors and their collaborators have developed [1] a novel method for per-flow traffic measurement that is fast, highly memory efficient and accurate. At the core of this method is a novel counter architecture called \"counter braids.” In this paper, we analyze the performance of the counter braid architecture under a Maximum Likelihood (ML) flow size estimation algorithm and show that it is optimal; that is, the number of bits needed to store the size of a flow matches the entropy lower bound. While the ML algorithm is optimal, it is too complex to implement. In [1] we have developed an easy-to-implement and efficient message passing algorithm for estimating flow sizes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.0658v2.pdf"}
{"id": "0710.1429", "abstract": "  We describe a new paradox for ideal fluids. It arises in the accretion of an ideal fluid onto a black hole, where, under suitable boundary conditions, the flow can violate the generalized second law of thermodynamics. The paradox indicates that there is in fact a lower bound to the correlation length of any real fluid, the value of which is determined by the thermodynamic properties of that fluid. We observe that the universal bound on entropy, itself suggested by the generalized second law, puts a lower bound on the correlation length of any fluid in terms of its specific entropy. With the help of a new, efficient estimate for the viscosity of liquids, we argue that this also means that viscosity is bounded from below in a way reminiscent of the conjectured Kovtun-Son-Starinets lower bound on the ratio of viscosity to entropy density. We conclude that much light may be shed on the Kovtun-Son-Starinets bound by suitable arguments based on the generalized second law. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.1429v2.pdf"}
{"id": "0710.2790", "abstract": "  We extend the Polyakov-Nambu-Jona-Lasinio (PNJL) model for two degenerate flavours by including the effect of the SU(3) measure with a Van der Monde (VdM) term. This ensures that the Polyakov loop always remains in the domain [0,1]. The pressure, energy density, specific heat, speed of sound and conformal measure show small or negligible effects from this term. However various quark number and isospin susceptibilities are all found to approach their respective ideal gas limits around 2 T_c. We compare our methods with other similar approaches in PNJL model and also present a quantitative comparison with Lattice QCD data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.2790v2.pdf"}
{"id": "0710.3745", "abstract": "  We study the joint spectral properties of photon pairs generated by spontaneous parametric down-conversion in a one-dimensional nonlinear photonic crystal in a collinear, degenerate, type-II geometry. We show that the photonic crystal properties may be exploited to compensate for material dispersion and obtain photon pairs that are nearly factorable, in principle, for arbitrary materials and spectral regions, limited by the ability to fabricate the nonlinear crystal with the required periodic variation in the refractive indices for the ordinary and extraordinary waves. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.3745v1.pdf"}
{"id": "0710.4373", "abstract": "  Strangeness production is calculated in a pQCD-based model (including nuclear effects) in the high transverse momentum sector, where pQCD is expected to work well. We investigate pion, kaon, proton and lambda production in pp and heavy-ion collisions. Parton energy loss in AA collisions is taken into account. We compare strange-to-non-strange meson and baryon ratios to data at RHIC, and make predictions for the LHC. We find that these ratios significantly deviate from unity not only at RHIC but also at the LHC, indicating the special role of strangeness at both energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.4373v1.pdf"}
{"id": "0710.4582", "abstract": "  We compare the stellar structure of the isolated, Local Group dwarf galaxy Pegasus (DDO216) with low resolution HI maps from Young et al. (2003). Our comparison reveals that Pegasus displays the characteristic morphology of ram pressure stripping; in particular, the HI has a “cometary” appearance which is not reflected in the regular, elliptical distribution of the stars. This is the first time this phenomenon has been observed in an isolated Local Group galaxy. The density of the medium required to ram pressure strip Pegasus is at least 10^-5 - 10^-6, cm^-3. We conclude that this is strong evidence for an inter-galactic medium associated with the Local Group. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.4582v1.pdf"}
{"id": "0710.5036", "abstract": "  We study the 37 brightest radio sources in the Subaru/XMM-Newton Deep Field (SXDF). Using mid-IR (Spitzer MIPS 24 micron) data we expect to trace nuclear accretion activity, even if it is obscured at optical wavelengths, unless the obscuring column is extreme. Our results suggest that above the `FRI/FRII' radio luminosity break most of the radio sources are associated with objects that have excess mid-IR emission, only some of which are broad-line objects, although there is one clear low-accretion-rate FRI. The fraction of objects with mid-IR excess drops dramatically below the FRI/FRII break, although there exists at least one high-accretion-rate QSO. Investigation of mid-IR and blue excesses shows that they are correlated as predicted by a model in which a torus of dust absorbs  30", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.5036v1.pdf"}
{"id": "0710.5730", "abstract": "  We review models for neutrino mass, with special emphasis in supersymmetric models where R-parity is broken either explicitly or spontaneously. The simplest unified extension of the MSSM with explicit bilinear R-parity violation provides a predictive scheme for neutrino masses and mixings which can account for the observed atmospheric and solar neutrino anomalies. Despite the smallness of neutrino masses R-parity violation is observable at present and future high-energy colliders, providing an unambiguous cross-check of the model. This model can be shown to be an effective model for the, more theoretically satisfying, spontaneous broken theory. The main difference in this last case is the appearance of a massless particle, the majoron, that can modify the decay modes of the Higgs boson, making it decay invisibly most of the time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.5730v1.pdf"}
{"id": "0711.0551", "abstract": "  In the standard supernova picture, type Ib/c and type II supernovae are powered by the potential energy released in the collapse of the core of a massive star. In studying supernovae, we primarily focus on the ejecta that makes it beyond the potential well of the collapsed core. But, as we shall show in this paper, in most supernova explosions, a tenth of a solar mass or more of the ejecta is decelerated enough that it does not escape the potential well of that compact object. This material falls back onto the proto-neutron star within the first 10-15 seconds after the launch of the explosion, releasing more than 1e52erg of additional potential energy. Most of this energy is emitted in the form of neutrinos and we must understand this fallback neutrino emission if we are to use neutrino observations to study the behavior of matter at high densities. Here we present both a 1-dimensional study of fallback using energy-injected, supernova explosions and a first study of neutrino emission from fallback using a suite of 2-dimensional simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.0551v1.pdf"}
{"id": "0711.0658", "abstract": "  We study the mechanism of particle production in the world-volume of a probe anti D6-brane (or D6 with SUSY breaking) moving in the background created by a fixed stack of D6-branes. We show that this may occur in a regime of parametric resonance when the probe's motion is non-relativistic and it moves at large distances from the source branes in low eccentricity orbits. This leads to an exponential growth of the particle number in the probe's world-volume and constitutes an effective mechanism for producing very massive particles. We also analyze the evolution of this system in an expanding universe and how this affects the development of the parametric resonance. We discuss the effects of transverse space compactification on the probe's motion, showing that it leads to the creation of angular momentum in a similar way to the Affleck-Dine mechanism for baryogenesis. Finally, we describe possible final states of the system and their potential relevance to cosmology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.0658v3.pdf"}
{"id": "0711.0684", "abstract": "  We present 21 cm HI line observations of 5x1 square degrees centered on the local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment Survey. One hundred sources are detected (79 new HI measurements and 50 new redshifts), more than half belonging to the cluster core and its infalling region. Combining the HI data with SDSS optical imaging we show that our HI selected sample follows scaling relations similar to the ones usually observed in optically selected samples. Interestingly all galaxies in our sample appear to have nearly the same baryon fraction independently of their size, surface brightness and luminosity. The most striking difference between HI and optically selected samples resides in their large scale distribution: whereas optical and X-ray observations trace the cluster core very well, in HI there is almost no evidence of the presence of the cluster. Some implications on the determination of the cluster luminosity function and HI distribution for samples selected at different wavelength are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.0684v1.pdf"}
{"id": "0711.0725", "abstract": "  We present Suzaku X-ray observations of the recurrent nova T CrB in quiescence. T CrB is the first recurrent nova to be detected in the hard-X-ray band (E   40.0 keV) during quiescence. The X-ray spectrum is consistent with cooling-flow emission emanating from an optically thin region in the boundary layer of an accretion disk around the white dwarf. The detection of strong stochastic flux variations in the light curve supports the interpretation of the hard X-ray emission as emanating from a boundary layer. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.0725v1.pdf"}
{"id": "0711.1260", "abstract": "  We investigated the influence of efficacy of synaptic interaction on firing synchronization in excitatory neuronal networks. We found spike death phenomena, namely, the state of neurons transits from limit cycle to fixed point or transient state. The phenomena occur under the perturbation of excitatory synaptic interaction that has a high efficacy. We showed that the decrease of synaptic current results in spike death through depressing the feedback of sodium ionic current. In the networks with spike death property the degree of synchronization is lower and unsensitive to the heterogeneity of neurons. The mechanism of the influence is that the transition of neuron state disrupts the adjustment of the rhythm of neuron oscillation and prevents further increase of firing synchronization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.1260v2.pdf"}
{"id": "0711.1699", "abstract": "  Necessary and sufficient conditions for deterministic remote extraction and destruction of qubit information encoded in bipartite states using only local operations and classical communications (LOCC) are presented. The conditions indicate that there is a way to asymmetrically spread qubit information between two parties such that it can be remotely extracted with unit probability at one of the parties but not at the other as long as they are using LOCC. Remote destruction can also be asymmetric between the two parties, but the conditions are incompatible with those for remote extraction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.1699v1.pdf"}
{"id": "0711.2297", "abstract": "  We study spherically symmetric thin-shell wormholes in a string cloud background in (3+1)-dimensional spacetime. The amount of exotic matter required for the construction, the traversability and the stability under radial perturbations, are analyzed as functions of the parameters of the model. Besides, in the Appendices a non perturbative approach to the dynamics and a possible extension of the analysis to a related model are briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.2297v1.pdf"}
{"id": "0711.3481", "abstract": "  We present a geometrodynamical method for determining distances to orbital streams of HI gas in the Galaxy. The method makes use of our offset from the Galactic centre and assumes that the gas comprising the stream nearly follows a planar orbit about the Galactic centre. We apply this technique to the Magellanic Stream and determine the distances to all points along it; a consistency check shows that the angular momentum is approximately constant. Applying this technique to the Large Magellanic Cloud itself gives an independent distance which agrees within its accuracy of around 10", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.3481v2.pdf"}
{"id": "0711.3649", "abstract": "  We study the modification of the far-field cross sections and the near-field enhancement for gold and silver nanospheres illuminated by a tightly focused beam. Using a multipole-expansion approach we obtain an analytical solution to the scattering problem and provide insight on the effects of focusing on the optical response. Large differences with respect to Mie theory are found especially when the nanoparticle supports quadrupole or higher-order resonances. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.3649v1.pdf"}
{"id": "0711.4125", "abstract": "  When a shallow layer of inviscid fluid flows over a substrate, the fluid particle trajectories are, to leading order in the layer thickness, geodesics on the two-dimensional curved space of the substrate. Since the two-dimensional geodesic equation is a two degree-of-freedom autonomous Hamiltonian system, it can exhibit chaos, depending on the shape of the substrate. We find chaotic behaviour for a range of substrates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.4125v2.pdf"}
{"id": "0711.4608", "abstract": "  This tutorial article introduces the physics of spin transfer torques in magnetic devices. We provide an elementary discussion of the mechanism of spin transfer torque, and review the theoretical and experimental progress in this field. Our intention is to be accessible to beginning graduate students. This is the introductory paper for a cluster of \"Current Perspectives\" articles on spin transfer torques published in volume 320 of the Journal of Magnetism and Magnetic Materials. This article is meant to set the stage for the others which follow it in this cluster; they focus in more depth on particularly interesting aspects of spin-torque physics and highlight unanswered questions that might be productive topics for future research. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.4608v3.pdf"}
{"id": "0712.1590", "abstract": "  We present a spectroscopic analysis of over 38,000 low-mass stars from the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Analysis of this unprecedentedly large sample confirms the previously detected decrease in the fraction of magnetically active stars (as traced by H-alpha emission) as a function of vertical distance from the Galactic Plane. The magnitude and slope of this effect varies as a function of spectral type. Using simple 1-D dynamical models, we demonstrate that the drop in activity fraction can be explained by thin disk dynamical heating and a rapid decrease in magnetic activity. The timescale for this rapid activity decrease changes according to the spectral type. By comparing our data to the simulations, we calibrate the age-activity relation at each M dwarf spectral type. We also present evidence for a possible decrease in the metallicity as a function of height above the Galactic Plane. In addition to our activity analysis, we provide line measurements, molecular band indices, colors, radial velocities, 3-D space motions and mean properties as a function of spectral type for the SDSS DR5 low-mass star sample. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.1590v1.pdf"}
{"id": "0712.2054", "abstract": "  The fairness of IEEE 802.11 wireless networks (including Wireless LAN and Ad-hoc networks) is hard to predict and control because of the randomness and complexity of the MAC contentions and dynamics. Moreover, asymmetric channel conditions such as those caused by capture and channel errors often lead to severe unfairness among stations. In this paper we propose a novel distributed scheduling algorithm that we call VLS, for “variable-length scheduling”, that provides weighted fairness to all stations despite the imperfections of the MAC layer and physical channels. Distinct features of VLS include the use of variable transmission lengths based on distributed observations, compatibility with 802.11's contention window algorithm, opportunistic scheduling to achieve high throughput in time-varying wireless environments, and flexibility and ease of implementation. Also, VLS makes the throughput of each station more smooth, which is appealing to real-time applications such as video and voice. Although the paper mostly assumes 802.11 protocol, the idea generally applies to wireless networks based on CSMA (Carrier Sensing Multiple Access). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.2054v1.pdf"}
{"id": "0712.2199", "abstract": "  The interaction of compact objects with an infinitely extended mirror plane due to quantum fluctuations of a scalar or electromagnetic field that scatters off the objects is studied. The mirror plane is assumed to obey either Dirichlet or Neumann boundary conditions or to be perfectly reflecting. Using the method of images, we generalize a recently developed approach for compact objects in unbounded space [1,2] to show that the Casimir interaction between the objects and the mirror plane can be accurately obtained over a wide range of separations in terms of charge and current fluctuations of the objects and their images. Our general result for the interaction depends only on the scattering matrices of the compact objects. It applies to scalar fields with arbitrary boundary conditions and to the electromagnetic field coupled to dielectric objects. For the experimentally important electromagnetic Casimir interaction between a perfectly conducting sphere and a plane mirror we present the first results that apply at all separations. We obtain both an asymptotic large distance expansion and the two lowest order correction terms to the proximity force approximation. The asymptotic Casimir-Polder potential for an atom and a mirror is generalized to describe the interaction between a dielectric sphere and a mirror, involving higher order multipole polarizabilities that are important at sub-asymptotic distances. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.2199v1.pdf"}
{"id": "0712.2203", "abstract": "  Two of the most attractive spectral windows for spectropolarimetric investigations of the physical properties of the plasma structures in the solar chromosphere and corona are the ones provided by the spectral lines of the He I 10830 A and 5876 A (or D3) multiplets, whose polarization signals are sensitive to the Hanle and Zeeman effects. However, in order to be able to carry out reliable diagnostics, it is crucial to have a good physical understanding of the sensitivity of the observed spectral line radiation to the various competing driving mechanisms. Here we report a series of off-the-limb non-LTE calculations of the He I D3 and 10830 A emission profiles, focusing our investigation on their sensitivity to the EUV coronal irradiation and the model atmosphere used in the calculations. We show in particular that the intensity ratio of the blue to the red components in the emission profiles of the He I 10830 A multiplet turns out to be a good candidate as a diagnostic tool for the coronal irradiance. Measurements of this observable as a function of the distance to the limb and its confrontation with radiative transfer modeling might give us valuable information on the physical properties of the solar atmosphere and on the amount of EUV radiation at relevant wavelengths penetrating the chromosphere from above. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.2203v1.pdf"}
{"id": "0712.3394", "abstract": "  Graphene outstanding properties directly come from its pecular electronic structure and thus from the honeycomb lattice symmetry. The way interaction with the substrate impact this lattice is of primary importance. This is peculiarly true for epitaxial graphene because of the SiC substrate. The advantage of this system that produces macroscopic samples in registry with a substrate could turn to a major drawback if the graphene lattice reveals to be strongly distorted. Extensive ab initio calculations supported by Scanning Tunneling Microscopy experiments, demonstrate here that the substrate indeed induces a strong nanostructuration of the interface carbon layer. It propagates to the above C layer where it generates incommensurate ripples in the honeycomb lattice. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.3394v1.pdf"}
{"id": "0712.3982", "abstract": "  Cosmic acceleration is explained quantitatively, as an apparent effect due to gravitational energy differences that arise in the decoupling of bound systems from the global expansion of the universe. \"Dark energy\" is a misidentification of those aspects of gravitational energy which by virtue of the equivalence principle cannot be localised, namely gradients in the energy due to the expansion of space and spatial curvature variations in an inhomogeneous universe. A new scheme for cosmological averaging is proposed which solves the Sandage-de Vaucouleurs paradox. Concordance parameters fit supernovae luminosity distances, the angular scale of the sound horizon in the CMB anisotropies, and the effective comoving baryon acoustic oscillation scale seen in galaxy clustering statistics. Key observational anomalies are potentially resolved, and unique predictions made, including a quantifiable variance in the Hubble flow below the scale of apparent homogeneity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.3982v1.pdf"}
{"id": "0801.0638", "abstract": "  Recent astronomical observations have indicated that the Universe is in the phase of accelerated expansion. While there are many cosmological models which try to explain this phenomenon, we focus on the interacting ΛCDM model where the interaction between the dark energy and dark matter sectors takes place. This model is compared to its simpler alternative—the ΛCDM model. To choose between these models the likelihood ratio test was applied as well as the model comparison methods (employing Occam's principle): the Akaike information criterion (AIC), the Bayesian information criterion (BIC) and the Bayesian evidence. Using the current astronomical data: SNIa (Union2.1), h(z), BAO, Alcock–Paczynski test and CMB we evaluated both models. The analyses based on the AIC indicated that there is less support for the interacting ΛCDM model when compared to the ΛCDM model, while those based on the BIC indicated that there is the strong evidence against it in favor the ΛCDM model. Given the weak or almost none support for the interacting ΛCDM model and bearing in mind Occam's razor we are inclined to reject this model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.0638v3.pdf"}
{"id": "0801.0965", "abstract": "  As part of a large survey of halo and thick disc stars, we found one halo star, HD 106038, exceptionally overabundant in beryllium. In spite of its low metallicity, [Fe/H] = -1.26, the star has log(Be/H) = -10.60, which is similar to the solar meteoritic abundance, log(Be/H) = -10.58. This abundance is more than ten times higher the abundance of stars with similar metallicity and cannot be explained by models of chemical evolution of the Galaxy that include the standard theory of cosmic-ray spallation. No other halo star exhibiting such a beryllium overabundance is known. In addition, overabundances of Li, Si, Ni, Y, and Ba are also observed. We suggest that all these chemical peculiarities, but the Ba abundance, can be simultaneously explained if the star was formed in the vicinity of a hypernova. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.0965v1.pdf"}
{"id": "0801.1517", "abstract": "  In the synchrotron radiation model, the polarization property depends on both the configuration of the magnetic field and the geometry of the visible emitting region. Some peculiar behaviors in the X-ray afterglows of Swift gamma-ray bursts (GRBs), such as energetic flares and the plateau followed by a sharp drop, might by highly linearly-polarized because the outflows powering these behaviors may be Poynting-flux dominated. Furthermore, the broken-down of the symmetry of the visible emitting region may be hiding in current X-ray data and will give rise to interesting polarization signatures. In this work we focus on the polarization accompanying the very early sharp decline of GRB X-ray afterglows. We show that strong polarization evolution is possible in both the high latitude emission model and the dying central engine model which are used to interpret this sharp X-ray decline. It is thus not easy to efficiently probe the physical origin of the very early X-ray sharp decline with future polarimetry. Strong polarization evolution is also possible in the decline phase of X-ray flares and in the shallow decline phase of X-ray light curves characterized by chromatic X-ray VS. Optical breaks. An XRT-like detector but with polarization capability on board a Swift-like satellite would be suitable to test our predictions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.1517v2.pdf"}
{"id": "0801.1914", "abstract": "  We give a closer look at the Central Limit Theorem (CLT) behavior in quasi-stationary states of the Hamiltonian Mean Field model, a paradigmatic one for long-range-interacting classical many-body systems. We present new calculations which show that, following their time evolution, we can observe and classify three kinds of long-standing quasi-stationary states (QSS) with different correlations. The frequency of occurrence of each class depends on the size of the system. The different microsocopic nature of the QSS leads to different dynamical correlations and therefore to different results for the observed CLT behavior. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.1914v2.pdf"}
{"id": "0801.2324", "abstract": "  Spin propagation in systems of one-dimensional interacting fermions at finite temperature is intrinsically diffusive. The spreading rate of a spin packet is controlled by a transport coefficient termed \"spin drag\" relaxation time τ_ sd. In this paper we present both numerical and analytical calculations of τ_ sd for a two-component spin-polarized cold Fermi gas trapped inside a tight atomic waveguide. At low temperatures we find an activation law for τ_ sd, in agreement with earlier calculations of Coulomb drag between slightly asymmetric quantum wires, but with a different and much stronger temperature dependence of the prefactor. Our results provide a fundamental input for microscopic time-dependent spin-density functional theory calculations of spin transport in 1D inhomogeneous systems of interacting fermions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.2324v1.pdf"}
{"id": "0801.2927", "abstract": "  We consider collisions of particles advected in a fluid. As already pointed out by Smoluchowski [Z. f. physik. Chemie XCII, 129-168, (1917)], macroscopic motion of the fluid can significantly enhance the frequency of collisions between the suspended particles. This effect was invoked by Saffman and Turner [J. Fluid Mech. 1, 16-30, (1956)] to estimate collision rates of small water droplets in turbulent rain clouds, the macroscopic motion being caused by turbulence. Here we show that the Saffman-Turner theory is unsatisfactory because it describes an initial transient only. The reason for this failure is that the local flow in the vicinity of a particle is treated as if it were a steady hyperbolic flow, whereas in reality it must fluctuate. We derive exact expressions for the steady-state collision rate for particles suspended in rapidly fluctuating random flows and compute how this steady state is approached. For incompressible flows, the Saffman-Turner expression is an upper bound. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.2927v1.pdf"}
{"id": "0801.3234", "abstract": "  We present a method to include stereoscopic information about the three dimensional structure of flux tubes into the reconstruction of the coronal magnetic field. Due to the low plasma beta in the corona we can assume a force free magnetic field, with the current density parallel to the magnetic field lines. Here we use linear force free fields for simplicity. The method uses the line of sight magnetic field on the photosphere as observational input. The value of α is determined iteratively by comparing the reconstructed magnetic field with the observed structures. The final configuration is the optimal linear force solution constrained by both the photospheric magnetogram and the observed plasma structures. As an example we apply our method to SOHO MDI/EIT data of an active region. In the future it is planned to apply the method to analyse data from the SECCHI instrument aboard the STEREO mission. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.3234v2.pdf"}
{"id": "0801.3437", "abstract": "  We investigate both experimentally and theoretically disorder induced damping of Bloch oscillations of Bose-Einstein condensates in optical lattices. The spatially inhomogeneous force responsible for the damping is realised by a combination of a disordered optical and a magnetic gradient potential. We show that the inhomogeneity of this force results in a broadening of the quasimomentum spectrum, which in turn causes damping of the centre-of-mass oscillation. We quantitatively compare the obtained damping rates to the simulations using the Gross-Pitaevskii equation. Our results are relevant for high precision experiments on very small forces, which require the observation of a large number of oscillation cycles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.3437v2.pdf"}
{"id": "0801.4091", "abstract": "  We have conducted an optical and infrared imaging in the neighbourhoods of 4 triplets of quasars. R, z', J and Ks images were obtained with MOSAIC II and ISPI at Cerro Tololo Interamerican Observatory. Accurate relative photometry and astrometry were obtained from these images for subsequent use in deriving photometric redshifts. We analyzed the homogeneity and depth of the photometric catalog by comparing with results coming from the literature. The good agreement shows that our magnitudes are reliable to study large scale structure reaching limiting magnitudes of R = 24.5, z' = 22.5, J = 20.5 and Ks = 19.0. With this catalog we can study the neighbourhoods of the triplets of quasars searching for galaxy overdensities such as groups and galaxy clusters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.4091v1.pdf"}
{"id": "0801.4454", "abstract": "  We study the sudden expansion of strongly correlated fermions in a one-dimensional lattice, utilizing the time-dependent density-matrix renormalization group method. Our focus is on the behavior of experimental observables such as the density, the momentum distribution function, and the density and spin structure factors. As our main result, we show that correlations in the transient regime can be accurately described by equilibrium reference systems. In addition, we find that the expansion from a Mott insulator produces distinctive peaks in the momentum distribution function at |k|   pi/2, accompanied by the onset of power-law correlations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.4454v3.pdf"}
{"id": "0801.4612", "abstract": "  The results from a Hubble Space Telescope (HST) snapshot survey of post-AGB objects are shown. The aim of the survey is to complement existing HST images of PPN and to connect various types of nebulosities with physical and chemical properties of their central stars. Nebulosities are detected in 15 of 33 sources. Images and photometric and geometric measurements are presented. For sources with nebulosities we see a morphological bifurcation into two groups, DUPLEX and SOLE, as previous studies have found. We find further support to the previous results suggesting that this dichotomy is caused by a difference in optical thickness of the dust shell. The remaining 18 sources are classified as stellar post-AGB objects, because our observations indicate a lack of nebulosity. We show that some stellar sources may in fact be DUPLEX or SOLE based on their infrared colors. The cause of the differences among the groups are investigated. We discuss some evidence suggesting that high progenitor-mass AGB stars tend to become DUPLEX post-AGB objects. Intermediate progenitor-mass AGB stars tend to be SOLE post-AGB objects. Most of the stellar sources probably have low mass progenitors and do not seem to develop nebulosities during the post-AGB phase and therefore do not become planetary nebulae. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.4612v1.pdf"}
{"id": "0801.4859", "abstract": "  A new model of population dynamics on lattices is proposed. The model consists of players on lattice points, each of which plays the RSP game with neighboring players. Each player copies the next hand from the hand of the neighbouring player with the maximum point. The model exhibits a steady pattern with pairs of vortices and sinks on the triangular lattice. It is shown that the stationary vortex is due to the frustrations on the triangular lattice. A frustration is the three-sided situation where each of the three players around a triangle chooses the rock, the scissors and the paper, respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.4859v1.pdf"}
{"id": "0802.0627", "abstract": "  Vastly different time and length scales are a common problem in numerical simulations of astrophysical phenomena. Here, we present an approach to numerical modeling of such objects on the example of Type Ia supernova simulations. The evolution towards the explosion proceeds on much longer time scales than the explosion process itself. The physical length scales relevant in the explosion process cover 11 orders of magnitude and turbulent effects dominate the physical mechanism. Despite these challenges, three-dimensional simulations of Type Ia supernova explosions have recently become possible and pave the way to a better understanding of these important astrophysical objects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.0627v1.pdf"}
{"id": "0802.1716", "abstract": "  Strong-Field Electrodynamics (SFE) is Maxwell theory with a certain Lorentz-covariant Ohm's law which uses only the electromagnetic degrees of freedom. We show that SFE is semi-dissipative: while the dissipation rate of the electromagnetic energy is non-negative, it can be exactly zero for non-trivial electromagnetic fields.   It appears that SFE is well-defined for arbitrary electromagnetic fields. It should be possible to calculate the dissipative pulsar magnetosphere and resolve the magnetic separatrix using SFE.   We show that SFE reduces to Force-Free Electrodynamics (FFE) in the large conductivity limit. In the regions where the ideal FFE 4-current is space-like, SFE predicts small dissipative corrections. In the regions where the ideal FFE 4-current is time-like, SFE predicts a zero correction. This indicates that bright pulsars radiate primarily from the magnetic separatrix. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.1716v1.pdf"}
{"id": "0802.1746", "abstract": "  I discuss some observational properties of aspherical nebulae around massive stars, and conclusions inferred for how they may have formed. Whether or not these ideas are applicable to the shaping of planetary nebulae is uncertain, but the observed similarities between some PNe and bipolar nebulae around massive stars is compelling. In the well-observed case of Eta Carinae, several lines of observational evidence point to a scenario where the shape of its bipolar nebula resulted from an intrinsically bipolar explosive ejection event rather than an interacting winds scenario occurring after ejection from teh star. A similar conclusion has been inferred for some planetary nebulae. I also briefly mention bipolar nebulae around some other massive stars, such as the progenitor of SN 1987A and related blue supergiants. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.1746v1.pdf"}
{"id": "0802.2543", "abstract": "  Unexpected increases in demand and most of all flash crowds are considered the bane of every web application as they may cause intolerable delays or even service unavailability. Proper quality of service policies must guarantee rapid reactivity and responsiveness even in such critical situations. Previous solutions fail to meet common performance requirements when the system has to face sudden and unpredictable surges of traffic. Indeed they often rely on a proper setting of key parameters which requires laborious manual tuning, preventing a fast adaptation of the control policies. We contribute an original Self-* Overload Control (SOC) policy. This allows the system to self-configure a dynamic constraint on the rate of admitted sessions in order to respect service level agreements and maximize the resource utilization at the same time. Our policy does not require any prior information on the incoming traffic or manual configuration of key parameters. We ran extensive simulations under a wide range of operating conditions, showing that SOC rapidly adapts to time varying traffic and self-optimizes the resource utilization. It admits as many new sessions as possible in observance of the agreements, even under intense workload variations. We compared our algorithm to previously proposed approaches highlighting a more stable behavior and a better performance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.2543v2.pdf"}
{"id": "0802.2853", "abstract": "  This paper presents a formalized proof of a discrete form of the Jordan Curve Theorem. It is based on a hypermap model of planar subdivisions, formal specifications and proofs assisted by the Coq system. Fundamental properties are proven by structural or noetherian induction: Genus Theorem, Euler's Formula, constructive planarity criteria. A notion of ring of faces is inductively defined and a Jordan Curve Theorem is stated and proven for any planar hypermap. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.2853v1.pdf"}
{"id": "0802.3808", "abstract": "  We analyze the scattering and bound state physics of a pair of atoms in a one-dimensional optical lattice interacting via a narrow Feshbach resonance. The lattice provides a structured continuum allowing for the existence of bound dimer states both below and above the continuum bands, with pairs above the continuum stabilized by either repulsive interactions or their center of mass motion. Inside the band the Feshbach coupling to a closed channel bound state leads to a Fano resonance profile for the transmission, which may be mapped out by RF- or photodissociative spectroscopy. We generalize the scattering length concept to the one-dimensional lattice, where a scattering length may be defined at both the lower and the upper continuum thresholds. As a function of the applied magnetic field the scattering length at either band edge exhibits the usual Feshbach divergence when a bound state enters or exits the continuum. Near the scattering length divergences the binding energy and wavefunction of the weakly bound dimer state acquires a universal form reminiscent of those of free-space Feshbach molecules. We give numerical examples of our analytic results for a specific Feshbach resonance, which has been studied experimentally. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.3808v2.pdf"}
{"id": "0802.4442", "abstract": "  We investigate strong mechanical feedback for the single-electron tunneling device coupled to an underdamped harmonic oscillator in the high-frequency case, when the mechanical energy of the oscillator exceeds the tunnel rate, and for weak coupling. In the strong feedback regime, the mechanical oscillations oscillated by the telegraph signal from the SET in their turn modify the electric current. In contrast to the earlier results for the low frequencies, the current noise in not enhanced above the Poisson value. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.4442v1.pdf"}
{"id": "0803.0061", "abstract": "  We consider meson radiative decays within the framework of U_0(1)× U(1)× SU(2) gauge symmetry. This approach is based on the linear sigma-model extended by the gauge and quark-meson interactions. Physical content and parameters of the model are discussed. Theoretical predictions for some radiative decays of vector mesons are in a good agreement with the experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.0061v2.pdf"}
{"id": "0803.0904", "abstract": "  We present an algorithm to approximate the solutions to variational problems where set of admissible functions consists of convex functions. The main motivator behind this numerical method is estimating solutions to Adverse Selection problems within a Principal-Agent framework. Problems such as product lines design, optimal taxation, structured derivatives design, etc. can be studied through the scope of these models. We develop a method to estimate their optimal pricing schedules. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.0904v1.pdf"}
{"id": "0803.1128", "abstract": "  We investigate energy transport in several two-level atom or spin-1/2 models by a direct coupling to heat baths of different temperatures. The analysis is carried out on the basis of a recently derived quantum master equation which describes the nonequilibrium properties of internally weakly coupled systems appropriately. For the computation of the stationary state of the dynamical equations, we employ a Monte Carlo wave-function approach. The analysis directly indicates normal diffusive or ballistic transport in finite models and hints toward an extrapolation of the transport behavior of infinite models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.1128v1.pdf"}
{"id": "0803.1725", "abstract": "  Quantitative constraints on the wind clumping of massive stars can be obtained from the study of the hard X-ray variability of SFXTs. In these systems, a large fraction of the hard X-ray emission is emitted in the form of flares with typical duration of 3 ksec, frequency of 7 days and luminosity of 10^36 ergs/s. Such flares are most probably emitted by the interaction of a compact object orbiting at ∼10 R_* with wind clumps (10^22-23 g). The density ratio between the clumps and the inter-clump medium is 10^2-4 . The parameters of the clumps and of the inter-clump medium are in good agreement with macro-clumping scenario and line-driven instability simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.1725v1.pdf"}
{"id": "0803.2049", "abstract": "  We study the transport properties of a long non-uniform quantum wire where the electron-electron interactions and the density vary smoothly at large length scales. We show that these inhomogeneities lead to a finite resistivity of the wire, due to a weak violation of momentum conservation in the collisions between electrons. Estimating the rate of change of momentum associated with non-momentum-conserving scattering processes, we derive the expression for the resistivity of the wire in the regime of weakly interacting electrons and find a contribution linear in temperature for a broad range of temperatures below the Fermi energy. By estimating the energy dissipated throughout the wire by low-energy excitations, we then develop a different method for deriving the resistivity of the wire, which can be combined with the bosonization formalism. This allows us to compare our results with previous works relying on an extension of the Tomonaga-Luttinger model to inhomogeneous systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.2049v1.pdf"}
{"id": "0803.2252", "abstract": "  We study resonances of nonlinear systems of differential equations, including but not limited to the equations of motion of a particle moving in a potential. We use the calculus of variations to determine the minimal additive forcing function that induces a desired terminal response, such as an energy in the case of a physical system. We include the additional constraint that only select degrees of freedom be forced, corresponding to a very general class of problems in which not all of the degrees of freedom in an experimental system are accessible to forcing. We find that certain Lagrange multipliers take on a fundamental physical role as the effective forcing experienced by the degrees of freedom which are not forced directly. Furthermore, we find that the product of the displacement of nearby trajectories and the effective total forcing function is a conserved quantity. We demonstrate the efficacy of this methodology with several examples. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.2252v1.pdf"}
{"id": "0803.2693", "abstract": "  Recent theoretical work has pointed out that the transition layer between a jet an the medium surrounding it may be more complex than previously thought. Under physically realizable conditions, the transverse profile of the Lorentz factor in the boundary layer can be non-monotonic, displaying the absolute maximum where the flow is faster than at the jet spine, followed by an steep fall off. Likewise, the rest-mass density, reaches an absolute minimum (coincident with the maximum in Lorentz factor) and then grows until it reaches the external medium value. Such a behavior is in contrast to the standard monotonic decline of the Lorentz factor (from a maximum value at the jet central spine) and the corresponding increase of the rest-mass density (from the minimum reached at the jet core). We study the emission properties of the aforementioned anomalous shear layer structures in kiloparsec-scale jets aiming to show observable differences with respect to conventional monotonic and smooth boundary layers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.2693v1.pdf"}
{"id": "0804.0072", "abstract": "  We have quantified the average filamentarity of the galaxy distribution in seven nearly two dimensional strips from the SDSS DR5 using a volume limited sample in the absolute magnitude range -21 < M_r < -20. The average filamentarity of star forming (SF) galaxies, which are predominantly blue, is found to be more than that of other galaxies which are predominantly red. This difference is possibly an outcome of the fact that blue galaxies have a more filamentary distribution. Comparing the SF galaxies with only the blue other galaxies, we find that the two show nearly equal filamentarity. Separately analyzing the galaxies with high star formation rates (SFR) and low SFR, we find that the latter has a more filamentary distribution. We interpret this in terms of two effects (1.) A correlation between the SFR and individual galaxy properties like luminosity with the high SFR galaxies being more luminous (2.) A relation between the SFR and environmental effects like the density with the high SFR galaxies preferentially occurring in high density regions. These two effects are possibly not independent and are operating simultaneously. We do not find any difference in the filamentarity of SF galaxies and AGNs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.0072v2.pdf"}
{"id": "0804.0244", "abstract": "  We give a brief account of the recent progresses in super Yang-Mills theories based in particular on the application of Nekrasov's instanton technology to the case of N=1 supersymmetry. We have developed a first-principle formalism from which any chiral observable in the theory can be computed, including in strongly coupled confining vacua. The correlators are first expressed in terms of some external variables as sums over colored partitions. The external variables are then fixed to their physical values by extremizing the microscopic quantum superpotential. Remarquably, the results can be shown to coincide with the Dijkgraaf-Vafa matrix model approach, which uses a totally different mathematical framework. These results clarify many important properties of N=1 theories, related in particular to generalized Konishi anomaly equations and to Veneziano-Yankielowicz terms in the glueball superpotentials. The proof of the equivalence between the formalisms based on colored partitions and on matrices is also a proof of the open/closed string duality in the chiral sector of the theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.0244v1.pdf"}
{"id": "0804.0765", "abstract": "  In the framework of an extended Nambu–Jona-Lasinio model we are studying pion condensation in quark matter with an asymmetric isospin composition in a gravitational field of the static Einstein universe at finite temperature and chemical potential. This particular choice of the gravitational field configuration enables us to investigate phase transitions of the system with exact consideration of the role of this field in the formation of quark and pion condensates and to point out its influence on the phase portraits. We demonstrate the effect of oscillations of the thermodynamic quantities as functions of the curvature and also refer to a certain similarity between the behavior of these quantities as functions of curvature and finite temperature. Finally, the role of quantum fluctuations for spontaneous symmetry breaking in the case of a finite volume of the universe is shortly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.0765v1.pdf"}
{"id": "0804.1075", "abstract": "  Gravitational waveforms and fluxes from extreme mass–ratio inspirals can be computed using time–domain methods with accuracy that is fast approaching that of frequency–domain methods. We study in detail the computational efficiency of these methods for equatorial orbits of fast spinning Kerr black holes, and find the number of modes needed in either method –as functions of the orbital parameters– in order to achieve a desired accuracy level. We then estimate the total computation time and argue that for high eccentricity orbits the time–domain approach is more efficient computationally. We suggest that in practice low–m modes are computed using the frequency–domain approach, and high–m modes are computed using the time–domain approach, where m is the azimuthal mode number. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.1075v1.pdf"}
{"id": "0804.1090", "abstract": "  Using space-, time- and phase-resolved Brillouin light scattering spectroscopy we investigate the difference in phase of the two counterpropagating spin waves excited by the same microwave microstrip transducer. These studies are performed both for backward volume magnetostatic waves and magnetostatic surface waves in an in-plane magnetized yttrium iron garnet film. The experiments show that for the backward volume magnetostatic spin waves (which are reciprocal and excited symmetrically in amplitude) there is a phase difference of π associated with the excitation process and thus the phase symmetry is distorted. On the contrary, for the magnetostatic surface spin waves (which are non-reciprocal and unsymmetrical in amplitude) the phase symmetry is preserved (there is no phase difference between the two waves associated with the excitation). Theoretical analysis confirms this effect. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.1090v1.pdf"}
{"id": "0804.1110", "abstract": "  Can one understand the statistics of wins and losses of baseball teams? Are their consecutive-game winning and losing streaks self-reinforcing or can they be described statistically? We apply the Bradley-Terry model, which incorporates the heterogeneity of team strengths in a minimalist way, to answer these questions. Excellent agreement is found between the predictions of the Bradley-Terry model and the rank dependence of the average number team wins and losses in major-league baseball over the past century when the distribution of team strengths is taken to be uniformly distributed over a finite range. Using this uniform strength distribution, we also find very good agreement between model predictions and the observed distribution of consecutive-game team winning and losing streaks over the last half-century; however, the agreement is less good for the previous half-century. The behavior of the last half-century supports the hypothesis that long streaks are primarily statistical in origin with little self-reinforcing component. The data further show that the past half-century of baseball has been more competitive than the preceding half-century. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.1110v2.pdf"}
{"id": "0804.1301", "abstract": "  We derive the generalized Fokker-Planck equation associated with a Langevin equation driven by arbitrary additive white noise. We apply our result to study the distribution of symmetric and asymmetric Lévy flights in an infinitely deep potential well. The fractional Fokker-Planck equation for Lévy flights is derived and solved analytically in the steady state. It is shown that Lévy flights are distributed according to the beta distribution, whose probability density becomes singular at the boundaries of the well. The origin of the preferred concentration of flying objects near the boundaries in nonequilibrium systems is clarified. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.1301v2.pdf"}
{"id": "0804.2876", "abstract": "  Calculations are carried out for the scattering of heavy rare gas atoms with surfaces using a recently developed classical theory that can track particles trapped in the physisorption potential well and follow them until ultimate desorption. Comparisons are made with recent experimental data for xenon scattering from molten gallium and indium, systems for which the rare gas is heavier than the surface atoms. The good agreement with the data obtained for both time-of-flight energy-resolved spectra and for total scattered angular distributions yields an estimate of the physisorption well depths for the two systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.2876v1.pdf"}
{"id": "0804.2998", "abstract": "  Recently Li and Xia have proposed a transmission scheme for wireless relay networks based on the Alamouti space time code and orthogonal frequency division multiplexing to combat the effect of timing errors at the relay nodes. This transmission scheme is amazingly simple and achieves a diversity order of two for any number of relays. Motivated by its simplicity, this scheme is extended to a more general transmission scheme that can achieve full cooperative diversity for any number of relays. The conditions on the distributed space time block code (DSTBC) structure that admit its application in the proposed transmission scheme are identified and it is pointed out that the recently proposed full diversity four group decodable DSTBCs from precoded co-ordinate interleaved orthogonal designs and extended Clifford algebras satisfy these conditions. It is then shown how differential encoding at the source can be combined with the proposed transmission scheme to arrive at a new transmission scheme that can achieve full cooperative diversity in asynchronous wireless relay networks with no channel information and also no timing error knowledge at the destination node. Finally, four group decodable distributed differential space time block codes applicable in this new transmission scheme for power of two number of relays are also provided. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.2998v2.pdf"}
{"id": "0804.3981", "abstract": "  Generating nonclassical light offers a benchmark tool for the fundamental research and potential applications in quantum optics. Conventionally, it has become a standard technique to produce the nonclassical light through the nonlinear optical processes occurring in nonlinear crystals. In this review we describe using cold atomic-gas media to generate such nonclassical light, especially focusing on narrow-band biphoton generation. Compared with the standard procedure, the new biphoton source has such properties as long coherence time, long coherence length, high spectral brightness, and high conversion efficiency. In this paper we concentrate on the theoretical aspect of the entangled two-photon state produced from the four-wave mixing in a multilevel atomic ensemble. We show that both linear and nonlinear optical responses to the generated fields play an important role in determining the biphoton waveform and, consequently on the two-photon temporal correlation. There are two characteristic regimes determined by whether the linear or nonlinear coherence time is dominant. In addition, our model provides a clear physical picture that brings insight into understanding biphoton optics with this new source. We apply our model to recent work on generating narrow-band (and even subnatural linewidth) paired photons using the technique of electromagnetically induced transparency and slow-light effect in cold atoms, and find good agreements with experimental results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.3981v1.pdf"}
{"id": "0804.4118", "abstract": "  We show that any number of parties can coherently exchange any one pure quantum state for another, without communication, given prior shared entanglement. Two applications of this fact to the study of multi-prover quantum interactive proof systems are given. First, we prove that there exists a one-round two-prover quantum interactive proof system for which no finite amount of shared entanglement allows the provers to implement an optimal strategy. More specifically, for every fixed input string, there exists a sequence of strategies for the provers, with each strategy requiring more entanglement than the last, for which the probability for the provers to convince the verifier to accept approaches 1. It is not possible, however, for the provers to convince the verifier to accept with certainty with a finite amount of shared entanglement. The second application is a simple proof that multi-prover quantum interactive proofs can be transformed to have near-perfect completeness by the addition of one round of communication. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.4118v2.pdf"}
{"id": "0804.4212", "abstract": "  We investigate the role of the boundary in the symmetric simple exclusion process with competing nonlocal and local hopping events. With open boundaries, the system undergoes a first order phase transition from a finite density phase to an empty road phase as the nonlocal hopping rate increases. Using a cluster stability analysis, we determine the location of such an abrupt nonequilibrium phase transition, which agrees well with numerical results. Our cluster analysis provides a physical insight into the mechanism behind this transition. We also explain why the transition becomes discontinuous in contrast to the case with periodic boundary conditions, in which the continuous phase transition has been observed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.4212v2.pdf"}
{"id": "0804.4525", "abstract": "  We study the problem of generating a test sequence that achieves maximal coverage for a reactive system under test. We formulate the problem as a repeated game between the tester and the system, where the system state space is partitioned according to some coverage criterion and the objective of the tester is to maximize the set of partitions (or coverage goals) visited during the game. We show the complexity of the maximal coverage problem for non-deterministic systems is PSPACE-complete, but is NP-complete for deterministic systems. For the special case of non-deterministic systems with a re-initializing “reset” action, which represent running a new test input on a re-initialized system, we show that the complexity is again co-NP-complete. Our proof technique for reset games uses randomized testing strategies that circumvent the exponentially large memory requirement in the deterministic case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.4525v1.pdf"}
{"id": "0805.0138", "abstract": "  We compute the average luminosity of X-ray flares as a function of time, for a sample of 10 long-duration gamma-ray burst afterglows. The mean luminosity, averaged over a timescale longer than the duration of the individual flares, declines as a power-law in time with index  -1.5. We elaborate on the properties of the central engine that can produce such a decline. Assuming that the engine is an accreting compact object, and for a standard conversion factor between accretion rate and jet luminosity, the switch between a neutrino-cooled thin disk and a non-cooled thick disk takes place at the transition from the prompt to the flaring phase. We discuss the implications of this coincidence under different scenarios for the powering of the GRB outflow. We also show that the interaction of the outflow with the envelope of the progenitor star cannot produce flares out of a continuous relativistic flow, and conclude that it is the dynamics of the disk or the jet-launching mechanism that generates an intrinsically unsteady outflow on timescales much longer than the dynamical timescale of the system. This is consistent with the fact that X-ray flares are observed in short-duration GRBs as well as in long-duration ones. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.0138v1.pdf"}
{"id": "0805.1837", "abstract": "  We use symbolic dynamics to study discrete-time dynamical systems with multiple time delays. We exploit the concept of avoiding sets, which arise from specific non-generating partitions of the phase space and restrict the occurrence of certain symbol sequences related to the characteristics of the dynamics. In particular, we show that the resulting forbidden sequences are closely related to the time delays in the system. We present two applications to coupled map lattices, namely (1) detecting synchronization and (2) determining unknown values of the transmission delays in networks with possibly directed and weighted connections and measurement noise. The method is applicable to multi-dimensional as well as set-valued maps, and to networks with time-varying delays and connection structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.1837v2.pdf"}
{"id": "0805.1883", "abstract": "  Current helicity quantifies the location of twisted and sheared non-potential structures in a magnetic field. We simulate the evolution of magnetic fields in the solar atmosphere in response to flux emergence and shearing by photospheric motions. In our global-scale simulation over many solar rotations the latitudinal distribution of current helicity develops a clear statistical pattern, matching the observed hemispheric sign at active latitudes. In agreement with observations there is significant scatter and intermixing of both signs of helicity, where we find local values of current helicity density that are much higher than those predicted by linear force-free extrapolations. Forthcoming full-disk vector magnetograms from Solar Dynamics Observatory will provide an ideal opportunity to test our theoretical results on the evolution and distribution of current helicity, both globally and in single active regions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.1883v1.pdf"}
{"id": "0805.2310", "abstract": "  The estimation of the correlation between time series is often hampered by the asynchronicity of the signals. Cumulating data within a time window suppresses this source of noise but weakens the statistics. We present a method to estimate correlations without applying long time windows. We decompose the correlations of data cumulated over a long window using decay of lagged correlations as calculated from short window data. This increases the accuracy of the estimated correlation significantly and decreases the necessary efforts of calculations both in real and computer experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.2310v3.pdf"}
{"id": "0805.2522", "abstract": "  This paper describes an Artificial Embryology method (called “Epigenetic Tracking”) to generate predefined arbitrarily shaped 2-dimensional arrays of cells by means of evolutionary techniques. It is based on a model of development, whose key features are: i) the distinction bewteen “normal” and “driver” cells, being the latter able to receive guidance from the genome, ii) the implementation of the proliferation/apoptosis events in such a way that many cells are created/deleted at once, in order to speed-up the morphogenetic process. iii) the presence in driver cells of an epigenetic memory, that holds the position of the cell in the cell lineage tree and represents the source of differentiation during development. The experiments performed with a number of 100x100 black and white and colour target shapes (the horse, the couple, the hand, the dolphin, the map of Britain, the foot, the frog, the baby, the stomach, the french flag, the head) bring to the conclusion that the method described is able to generate any target shape, outperforming any other known method in terms of size and variety of the generated shapes. The interpretation of the proposed method as a model of embryogenesis and its biological implications are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.2522v1.pdf"}
{"id": "0805.2532", "abstract": "  The correlation dimension, that is, the dimension obtained by computing the correlation function of pairs of points of a trajectory in phase space, is a numerical technique introduced in the field of nonlinear dynamics in order to compute the dimension of the manifold in which an orbit moves, without the need of knowing the actual equations of motion that give rise to the trajectory. This technique has been proposed in the past as a method to measure the dimension of stellar orbits in astronomical potentials, i.e., the number of isolating integrals of motion the orbits obey. Although the algorithm can in principle yield that number, some care has to be taken in order to obtain good results. We studied the relevant parameters of the technique, found their optimal values, and tested the validity of the method on a number of potentials previously studied in the literature, using the SALI, Lyapunov exponents and spectral dynamics as gauges. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.2532v1.pdf"}
{"id": "0805.2689", "abstract": "  Data clustering, including problems such as finding network communities, can be put into a systematic framework by means of a Bayesian approach. The application of Bayesian approaches to real problems can be, however, quite challenging. In most cases the solution is explored via Monte Carlo sampling or variational methods. Here we work further on the application of variational methods to clustering problems. We introduce generative models based on a hidden group structure and prior distributions. We extend previous attends by Jaynes, and derive the prior distributions based on symmetry arguments. As a case study we address the problems of two-sides clustering real value data and clustering data represented by a hypergraph or bipartite graph. From the variational calculations, and depending on the starting statistical model for the data, we derive a variational Bayes algorithm, a generalized version of the expectation maximization algorithm with a built in penalization for model complexity or bias. We demonstrate the good performance of the variational Bayes algorithm using test examples. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.2689v3.pdf"}
{"id": "0805.3094", "abstract": "  Point defects such as interstitials, vacancies, and impurities in otherwise perfect crystals induce complex displacement fields that are of long-range nature. In the present paper we study numerically the response of a two-dimensional colloidal crystal on a triangular lattice to the introduction of an interstitial particle. While far from the defect position the resulting displacement field is accurately described by linear elasticity theory, lattice effects dominate in the vicinity of the defect. In comparing the results of particle based simulations with continuum theory, it is crucial to employ corresponding boundary conditions in both cases. For the periodic boundary condition used here, the equations of elasticity theory can be solved in a consistent way with the technique of Ewald summation familiar from the electrostatics of periodically replicated systems of charges and dipoles. Very good agreement of the displacement fields calculated in this way with those determined in particle simulations is observed for distances of more than about 10 lattice constants. Closer to the interstitial, strongly anisotropic displacement fields with exponential behavior can occur for certain defect configurations. Here we rationalize this behavior with a simple bead-spring that relates the exponential decay constant to the elastic constants of the crystal. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.3094v1.pdf"}
{"id": "0805.3226", "abstract": "  Thermodynamic properties of an ultracold Fermi gas in a harmonic trap are calculated within a local density approximation, using a conserving many-body formalism for the BCS to BEC crossover problem, which has been developed by Haussmann et al. [Phys. Rev. A 75, 023610 (2007)]. We focus on the unitary regime near a Feshbach resonance and determine the local density and entropy profiles and the global entropy S(E) as a function of the total energy E. Our results are in good agreement with both experimental data and previous analytical and numerical results for the thermodynamics of the unitary Fermi gas. The value of the Bertsch parameter at T=0 and the superfluid transition temperature, however, differ appreciably. We show that, well in the superfluid regime, removal of atoms near the cloud edge enables cooling far below temperatures that have been reached so far. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.3226v4.pdf"}
{"id": "0805.3733", "abstract": "  An interesting feature of the giant planets of our solar system is the existence of regions around these objects where no irregular satellites are observed. Surveys have shown that, around Jupiter, such a region extends from the outermost regular satellite Callisto, to the vicinity of Themisto, the innermost irregular satellite. To understand the reason for the existence of such a satellite-void region, we have studied the dynamical evolution of Jovian irregulars by numerically integrating the orbits of several hundred test particles, distributed in a region between 30 and 80 Jupiter-radii, for different values of their semimajor axes, orbital eccentricities, and inclinations. As expected, our simulations indicate that objects in or close to the influence zones of the Galilean satellites become unstable because of interactions with Ganymede and Callisto. However, these perturbations cannot account for the lack of irregular satellites in the entire region between Callisto and Themisto. It is suggested that at distances between 60 and 80 Jupiter-radii, Ganymede and Callisto may have long-term perturbative effects, which may require the integrations to be extended to times much longer than 10 Myr. The interactions of irregular satellites with protosatellites of Jupiter at the time of the formation of Jovian regulars may also be a destabilizing mechanism in this region. We present the results of our numerical simulations and discuss their applicability to similar satellite void-regions around other giant planets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.3733v1.pdf"}
{"id": "0805.4554", "abstract": "  A four-dimensional static black hole solution of Einstein equation conformally coupled to a massive and self interacting scalar field is obtained. A nontrivial scalar solution proposes a weak scalar hair. A dressed black hole shows a trace of scalar charge in the metric signalling the presence of scalar hair. A number of metrics with regular horizons and temperatures are also proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.4554v1.pdf"}
{"id": "0806.0136", "abstract": "  Monte Carlo(MC) simulations produce evidence that annealed copolymers incorporating two interconverting monomers, P and H, adsorb as homopolymers with an effective adsorption energy per monomer, ϵ_eff, that depends on the PH equilibrium constants in the bulk and at the surface. The cross-over exponent, Φ, is unmodified. The MC results on the overall PH ratio, the PH ratio at the surface and in the bulk as well as the number of adsorbed monomers are in quantitative agreement with this hypothesis and the theoretically derived ϵ_eff. The evidence suggests that the form of surface potential does not affect Φ but does influence the PH equilibrium. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.0136v2.pdf"}
{"id": "0806.1419", "abstract": "  We present a detailed optical study of the ultra-compact X-ray binary 4U0614+091. We have used 63 hrs of time-resolved optical photometry taken with three different telescopes (IAC80, NOT and SPM) to search for optical modulations. The power spectra of each dataset reveals sinusoidal modulations with different periods, which are not always present. The strongest modulation has a period of 51.3 mins, a semi-amplitude of 4.6 mmags, and is present in the IAC80 data. The SPM and NOT data show periods of 42 mins and 64 mins respectively, but with much weaker amplitudes, 2.6 mags and 1.3 mmags respectively. These modulations arise from either X-ray irradiation of the inner face of the secondary star and/or a superhump modulation from the accretion disc, or quasi-periodic modulations in the accretion disc. It is unclear whether these periods/quasi-periodic modulations are related to the orbital period, however, the strongest period of 51.3 mins is close to earlier tentative orbital periods. Further observations taken over a long base-line are encouraged. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.1419v1.pdf"}
{"id": "0806.1953", "abstract": "  We investigate multi-field inflationary scenarios with fields that drop out of the model in a staggered fashion. This feature is natural in certain multi-field inflationary setups within string theory; for instance, it can manifest itself when fields are related to tachyons that condense, or inter-brane distances that become meaningless when branes annihilate. Considering a separable potential, and promoting the number of fields to a smooth time-dependent function, we derive the formalism to deal with these models at the background and perturbed level, providing general expressions for the scalar spectral index and the running. We recover known results of e.g. a dynamically relaxing cosmological constant in the appropriate limits. We further show that isocurvature perturbations are suppressed during inflation, so that perturbations are adiabatic and nearly Gaussian. The resulting setup might be interpreted as a novel type of warm inflation, readily implemented within string theory and without many of the shortcomings associated with warm inflation.   To exemplify the applicability of the formalism we consider three concrete models: assisted inflation with exponential potentials as a simple toy model (a graceful exit becomes possible), inflation from multiple tachyons (a constant decay rate of the number of fields and negligible slow roll contributions turns out to be in good agreement with observations) and inflation from multiple M5-branes within M-theory (a narrow stacking of branes yields a consistent scenario). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.1953v3.pdf"}
{"id": "0806.3460", "abstract": "  We present the results of a numerical study on the effects of metal enrichment and metal cooling on galaxy formation and cosmic star formation (SF) history using cosmological hydrodynamic simulations. We find following differences in the simulation with metal cooling when compared to the run without it: (1) the cosmic star formation rate (SFR) is enhanced by about 50     20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.3460v2.pdf"}
{"id": "0806.3473", "abstract": "  We present a radial velocity study of the rapidly rotating B-star Regulus that indicates the star is a single-lined spectroscopic binary. The orbital period (40.11 d) and probable semimajor axis (0.35 AU) are large enough that the system is not interacting at present. However, the mass function suggests that the secondary has a low mass (M_2 > 0.30 M_sun), and we argue that the companion may be a white dwarf. Such a star would be the remnant of a former mass donor that was the source of the large spin angular momentum of Regulus itself. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.3473v1.pdf"}
{"id": "0806.3537", "abstract": "  Statistical learning theory chiefly studies restricted hypothesis classes, particularly those with finite Vapnik-Chervonenkis (VC) dimension. The fundamental quantity of interest is the sample complexity: the number of samples required to learn to a specified level of accuracy. Here we consider learning over the set of all computable labeling functions. Since the VC-dimension is infinite and a priori (uniform) bounds on the number of samples are impossible, we let the learning algorithm decide when it has seen sufficient samples to have learned. We first show that learning in this setting is indeed possible, and develop a learning algorithm. We then show, however, that bounding sample complexity independently of the distribution is impossible. Notably, this impossibility is entirely due to the requirement that the learning algorithm be computable, and not due to the statistical nature of the problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.3537v2.pdf"}
{"id": "0806.4325", "abstract": "  We consider a classical, two-dimensional system of identical particles which interact via a finite-ranged, repulsive pair potential. We assume that the system is in a crystalline phase. We calculate the normal vibrational modes of a two-dimensional square Bravais lattice, first analytically within the nearest-neighbour approximation, and then numerically, relaxing the preceding hypothesis. We show that, in the harmonic approximation, the excitation of a transverse vibrational mode leads to the breakdown of the square lattice. We next study the case of the hexagonal Bravais lattice and we show that it can be stable with respect to lattice vibrations. We give a criterion determining whether or not it is stable in the nearest-neighbour approximation. Finally, we apply our results to a two-dimensional system of composite bosons and infer that the crystalline phase of such a system, if it exists, corresponds to a hexagonal lattice. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.4325v1.pdf"}
{"id": "0806.4536", "abstract": "  We present the results of numerical simulations of continuum-driven winds of stars that exceed the Eddington limit and compare these against predictions from earlier analytical solutions. Our models are based on the assumption that the stellar atmosphere consists of clumped matter, where the individual clumps have a much larger optical thickness than the matter between the clumps. This `porosity' of the stellar atmosphere reduces the coupling between radiation and matter, since photons tend to escape through the more tenuous gas between the clumps. This allows a star that formally exceeds the Eddington limit to remain stable, yet produce a steady outflow from the region where the clumps become optically thin. We have made a parameter study of wind models for a variety of input conditions in order to explore the properties of continuum-driven winds.   The results show that the numerical simulations reproduce quite closely the analytical scalings. The mass loss rates produced in our models are much larger than can be achieved by line driving. This makes continuum driving a good mechanism to explain the large mass loss and flow speeds of giant outbursts, as observed in eta Carinae and other luminous blue variable (LBV) stars. Continuum driving may also be important in population III stars, since line driving becomes ineffective at low metalicities. We also explore the effect of photon tiring and the limits it places on the wind parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.4536v1.pdf"}
{"id": "0807.0145", "abstract": "  We analyze a systematic algorithm for the exact computation of the current cumulants in stochastic nonequilibrium systems, recently discussed in the framework of full counting statistics for mesoscopic systems. This method is based on identifying the current cumulants from a Rayleigh-Schrodinger perturbation expansion for the generating function. Here it is derived from a simple path-distribution identity and extended to the joint statistics of multiple currents. For a possible thermodynamical interpretation, we compare this approach to a generalized Onsager-Machlup formalism. We present calculations for a boundary driven Kawasaki dynamics on a one-dimensional chain, both for attractive and repulsive particle interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.0145v2.pdf"}
{"id": "0807.0200", "abstract": "  We study the properties of strange quark matter in equilibrium with normal nuclear matter. Instead of using the conventional bag model in quark sector, we achieve the confinement by a density-dependent quark mass derived from in-medium chiral condensates. In nuclear matter, we adopt the equation of state from the Brueckner-Bethe-Goldstone approach with three-body forces. It is found that the mixed phase can occur, for a reasonable confinement parameter, near the normal nuclear saturation density, and goes over into pure quark matter at about 5 times the saturation. The onset of mixed and quark phases is compatible with the observed class of low-mass neutron stars, but it hinders the occurrence of kaon condensation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.0200v1.pdf"}
{"id": "0807.1118", "abstract": "  We study strategies for establishing long-distance entanglement in quantum networks. Specifically, we consider networks consisting of regular lattices of nodes, in which the nearest neighbors share a pure, but non-maximally entangled pair of qubits. We look for strategies that use local operations and classical communication. We compare the classical entanglement percolation protocol, in which every network connection is converted with a certain probability to a singlet, with protocols in which classical entanglement percolation is preceded by measurements designed to transform the lattice structure in a way that enhances entanglement percolation. We analyze five examples of such comparisons between protocols and point out certain rules and regularities in their performance as a function of degree of entanglement and choice of operations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.1118v4.pdf"}
{"id": "0807.1249", "abstract": "  We study the behavior of simple principal pivoting methods for the P-matrix linear complementarity problem (P-LCP). We solve an open problem of Morris by showing that Murty's least-index pivot rule (under any fixed index order) leads to a quadratic number of iterations on Morris's highly cyclic P-LCP examples. We then show that on K-matrix LCP instances, all pivot rules require only a linear number of iterations. As the main tool, we employ unique-sink orientations of cubes, a useful combinatorial abstraction of the P-LCP. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.1249v2.pdf"}
{"id": "0807.1383", "abstract": "  The classical model of an oscillator linearly coupled to a string captures, for a low price in technique, many general features of more realistic models for describing a particle interacting with a field or an atom in a electromagnetic cavity. The scattering matrix and the asymptotic in and out waves on the string can be computed exactly and the phenomenon of resonant scattering can be introduced in the simplest way. The dissipation induced by the coupling of the oscillator to the string can be studied completely. In the case of a d'Alembert string, the backreaction leads to an Abraham-Lorentz-Dirac-like equation. In the case of a Klein-Gordon string, one can see explicitely how radiation governs the (meta)stability of the (quasi)bounded mode. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.1383v1.pdf"}
{"id": "0807.1390", "abstract": "  We computed potentials between static color sources from the six lowest representations of G(2) lattice gauge theory, in numerical simulations with the Wilson action on asymmetric lattices with nonperturbatively estimated values of the bare anisotropy. We present evidence for (approximate) Casimir scaling of the obtained intermediate string tensions. The agreement with the Casimir-scaling prediction improves by increasing the coupling beta in the weak-coupling region above the crossover observed in G(2) gauge theory. The result naturally fits into confinement models with magnetic disorder and vacuum domain structure, but may represent a challenge for other approaches. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.1390v2.pdf"}
{"id": "0807.1622", "abstract": "  We present an exact many-body theory of ultracold fermionic gases for the Bose-Einstein condensation (BEC) regime of the BEC-BCS crossover. This is a purely fermionic approach which treats explicitely and systematically the dimers formed in the BEC regime as made of two fermions. We consider specifically the zero temperature case and calculate the first terms of the expansion of the chemical potential in powers of the density n. We derive first the mean-field contribution, which has the expected standard expression when it is written in terms of the dimer-dimer scattering length a_M. We go next in the expansion to the Lee-Huang-Yang order, proportional to n^3/2. We find the far less obvious result that it retains also the same expression in terms of a_M as for elementary bosons. The composite nature of the dimers appears only in the next term proportional to n^2. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.1622v1.pdf"}
{"id": "0807.1813", "abstract": "  The aim of this paper is to provide a logic-based conceptual analysis of the twin paradox (TwP) theorem within a first-order logic framework. A geometrical characterization of TwP and its variants is given. It is shown that TwP is not logically equivalent to the assumption of the slowing down of moving clocks, and the lack of TwP is not logically equivalent to the Newtonian assumption of absolute time. The logical connection between TwP and a symmetry axiom of special relativity is also studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.1813v2.pdf"}
{"id": "0807.2342", "abstract": "  We study the reduced dynamics of interacting spins, each coupled to its own bath of bosons. We derive the solution in analytic form in the white-noise limit and analyze the rich behaviors in diverse limits ranging from weak coupling and/or low temperature to strong coupling and/or high temperature. We also view the one spin as being coupled to a spin-boson environment and consider the regimes in which it is effectively nonlinear, and in which it can be regarded as a resonant bosonic environment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.2342v1.pdf"}
{"id": "0807.3773", "abstract": "  H.E.S.S. observed TeV blazar PKS 2155–304 in a strong flare state in 2006 July. The TeV flux varied on timescale as short as a few minutes, which sets strong constraints on the properties of the emission region. By use of the synchrotron self-Compton model, we found that models with the bulk Lorentz factor ∼ 100, the size of the emission region ∼ 10^15 cm, and magnetic field ∼ 0.1 G explain the observed spectral energy distribution and the flare timescale ∼ a few minutes. This model with a large value of Γ accounts for the emission spectrum not only in the TeV band but also in the X-ray band. The major cooling process of electrons/positrons in the jet is inverse Compton scattering off synchrotron photons. The energy content of the jet is highly dominated by particle kinetic energy over magnetic energy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.3773v1.pdf"}
{"id": "0807.4538", "abstract": "  We report a comprehensive analysis of the ground state properties of axisymmetric toroidal crystals based on the elastic theory of defects on curved substrates. The ground state is analyzed as a function of the aspect ratio of the torus, which provides a non-local measure of the underlying Gaussian curvature, and the ratio of the defect core-energy to the Young modulus. Several structural features are discussed,including a spectacular example of curvature-driven amorphization in the limit of the aspect ratio approaching one. The outcome of the elastic theory is then compared with the results of a numerical study of a system of point-like particles constrained on the surface of a torus and interacting via a short range potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.4538v1.pdf"}
{"id": "0808.0042", "abstract": "  We present two efficient quantum key distribution schemes over two different collective-noise channels. The accepted hypothesis of collective noise is that photons travel inside a time window small compared to the variation of noise. Noiseless subspaces are made up of two Bell states and the spatial degree of freedom is introduced to form two nonorthogonal bases. Although these protocols resort to entangled states for encoding the key bit, the receiver is only required to perform single-particle product measurements and there is no basis mismatch. Moreover, the detection is passive as the receiver does not switch his measurements between two conjugate measurement bases to get the key. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.0042v3.pdf"}
{"id": "0808.0400", "abstract": "  We discuss the non-anticommutative (N=1/2) supersymmetric Wess-Zumino model in four dimensions. Firstly we introduce differential operators which implement the non-anticommutative supersymmetry algebra acting on the component fields and action. Then we perform the renormalisation of the model up to two-loop order, including the complete set of terms necessary for renormalisability. We show that (at least up to this order) the results obtained when we eliminate the auxiliary field after renormalisation are equivalent to those obtained when we eliminate the auxiliary fields before quantisation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.0400v3.pdf"}
{"id": "0808.1203", "abstract": "  Defects in crystalline silicon consisting of a silicon self-interstitial atom and one, two, three, or four hydrogen atoms are studied within density-functional theory (DFT). We search for low-energy defects by starting from an ensemble of structures in which the atomic positions in the defect region have been randomized. We then relax each structure to a minimum in the energy. We find a new defect consisting of a self-interstitial and one hydrogen atom (denoted by I,H) which has a higher symmetry and a lower energy than previously reported structures. We recover the I,H_2 defect found in previous studies and confirm that it is the most stable such defect. Our best I,H_3 defect has a slightly different structure and lower energy than the one previously reported, and our lowest energy I,H_4 defect is different to those of previous studies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.1203v1.pdf"}
{"id": "0808.2186", "abstract": "  We introduce a \"Hamiltonian\"-like function, called the volume function, indispensable to describe the ensemble of jammed matter such as granular materials and emulsions from a geometrical point of view. The volume function represents the available volume of each particle in the jammed systems. At the microscopic level, we show that the volume function is the Voronoi volume associated to each particle and in turn we provide an analytical formula for the Voronoi volume in terms of the contact network, valid for any dimension. We then develop a statistical theory for the probability distribution of the volumes in 3d to calculate an average volume function coarse-grained at a mesoscopic level. The salient result is the discovery of a mesoscopic volume function inversely proportional to the coordination number. Our analysis is the first step toward the calculation of macroscopic observables and equations of state using the statistical mechanics of jammed matter, when supplemented by the condition of mechanical equilibrium of jamming that properly defines jammed matter at the ensemble level. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.2186v2.pdf"}
{"id": "0808.2220", "abstract": "  We prove that every computably enumerable (c.e.) random real is provable in Peano Arithmetic (PA) to be c.e. random. A major step in the proof is to show that the theorem stating that \"a real is c.e. and random iff it is the halting probability of a universal prefix-free Turing machine\" can be proven in PA. Our proof, which is simpler than the standard one, can also be used for the original theorem.   Our positive result can be contrasted with the case of computable functions, where not every computable function is provably computable in PA, or even more interestingly, with the fact that almost all random finite strings are not provably random in PA.   We also prove two negative results: a) there exists a universal machine whose universality cannot be proved in PA, b) there exists a universal machine U such that, based on U, PA cannot prove the randomness of its halting probability.   The paper also includes a sharper form of the Kraft-Chaitin Theorem, as well as a formal proof of this theorem written with the proof assistant Isabelle. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.2220v5.pdf"}
{"id": "0808.4033", "abstract": "  The anisotropy parameter of two-dimensional equilibrium clusters of site percolation process in long-range self-affine correlated structures are studied numerically. We use a fractional Brownian Motion(FBM) statistic to produce both persistent and anti-persistent long-range correlations in 2-D models. It is seen that self affinity makes the shape of percolation clusters slightly more isotropic. Moreover, we find that the sign of correction to scaling term is determined by the nature of correlation. For persistent correlation the correction to scaling term adds a negative contribution to the anisotropy of percolation clusters, while for the anti-persistent case it is positive. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.4033v1.pdf"}
{"id": "0808.4160", "abstract": "  We develop a maximum relative entropy formalism to generate optimal approximations to probability distributions. The central results consist in (a) justifying the use of relative entropy as the uniquely natural criterion to select a preferred approximation from within a family of trial parameterized distributions, and (b) to obtain the optimal approximation by marginalizing over parameters using the method of maximum entropy and information geometry. As an illustration we apply our method to simple fluids. The \"exact\" canonical distribution is approximated by that of a fluid of hard spheres. The proposed method first determines the preferred value of the hard-sphere diameter, and then obtains an optimal hard-sphere approximation by a suitably weighed average over different hard-sphere diameters. This leads to a considerable improvement in accounting for the soft-core nature of the interatomic potential. As a numerical demonstration, the radial distribution function and the equation of state for a Lennard-Jones fluid (argon) are compared with results from molecular dynamics simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.4160v1.pdf"}
{"id": "0809.0187", "abstract": "  We present a preliminary analysis of the photospheric activity of CoRoT-Exo-2a, a young G7V star accompanied by a transiting hot Jupiter recently discovered by CoRoT. We apply spot modelling techniques developed for the analysis of the Sun as a star and capable to extract from CoRoT high precision light curves information on the variation of the total spotted area and the longitude of active regions along the 142 days of the observations. This preliminary analysis shows that the active regions form within two active longitudes separated by about 180 degrees and rotating with periods of 4.5221 and 4.5543 days, respectively, and that the total spotted area oscillates with a period of about 28.9 days. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.0187v1.pdf"}
{"id": "0809.0901", "abstract": "  N-body simulations have unveiled several apparently universal properties of dark matter halos, including a cusped density profile, a power-law pseudo phase-space density ρ/σ_r^3, and a linear β-γ relation between the density slope and the velocity anisotropy. We present a family of self-consistent phase-space distribution functions F(E,L), based on the Dehnen-McLaughlin Jeans models, that incorporate these universal properties very accurately. These distribution functions, derived using a quadratic programming technique, are analytical, positive and smooth over the entire phase space and are able to generate four-parameter velocity anisotropy profiles β(r) with arbitrary asymptotic values β_0 and β_∞. We discuss the orbital structure of six radially anisotropic systems in detail and argue that, apart from its use for generating initial conditions for N-body studies, our dynamical modeling provides a valuable complementary approach to understand the processes involved in the formation of dark matter halos. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.0901v1.pdf"}
{"id": "0809.2615", "abstract": "  We study the steady state of the abelian sandpile models with stochastic toppling rules. The particle addition operators commute with each other, but in general these operators need not be diagonalizable. We use their abelian algebra to determine their eigenvalues, and the Jordan block structure. These are then used to determine the probability of different configurations in the steady state. We illustrate this procedure by explicitly determining the numerically exact steady state for a one dimensional example, for systems of size ≤12, and also study the density profile in the steady state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.2615v1.pdf"}
{"id": "0809.3524", "abstract": "  We discuss a new analytical approach to real-time evolution in quantum many-body systems. Our approach extends the framework of continuous unitary transformations such that it amounts to a novel solution method for the Heisenberg equations of motion for an operator. It is our purpose to illustrate the accuracy of this approach by studying dissipative quantum systems on all time scales. In particular, we obtain results for non-equilibrium correlation functions for general initial conditions. We illustrate our ideas for the exactly solvable dissipative oscillator, and, as a non-trivial model, for the dissipative two-state system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.3524v2.pdf"}
{"id": "0809.4539", "abstract": "  We investigate correlations between the direction of the optical linear polarization and the orientation of the host galaxy/extended emission for type1 and type2 radio-loud and radio-quiet quasars. We have used high resolution Hubble Space Telescope data and a deconvolution process to obtain a good determination of the host galaxy/extended emission (EE) position angle. With these new measurements and a compilation of data from the literature, we find a significant correlation, different for type1 and type2 objects, between the linear polarization position angle and the orientation of the EE, suggesting scattering by an extended UV/blue region in both types of objects. Our observations support the extension of the Unification Model to the higher luminosity AGNs like the quasars, assuming a two component scattering model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.4539v1.pdf"}
{"id": "0809.4639", "abstract": "  DNA adsorption on solid or liquid surfaces is a topic of broad fundamental and applied interest. Here we study by x-ray reflectivity the adsorption of monodisperse double-stranded DNA molecules a positively-charged surface, obtained through chemical grafting of a homogeneous organicmonomolecular layer of N-(2-aminoethyl) dodecanamide on an oxide-free monocrystalline Si(111) wafer. The adsorbed dsDNA is found to embed into the soft monolayer which is deformed in the process. The surface coverage is very high and this adsorbed layer is expected to display 2D nematic ordering. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.4639v1.pdf"}
{"id": "0809.4820", "abstract": "  Transient radio emission from X-ray binaries is associated with synchrotron emission from collimated jets that escape the system, and accreting millisecond X-ray pulsars (AMXPs) are no exception. Although jets from black hole X-ray binaries are well-studied, those from neutron star systems appear much fainter, for reasons yet uncertain. Jets are usually undetectable at higher frequencies because of the relative brightness of other components such as the accretion disc. AMXPs generally have small orbital separations compared with other X-ray binaries and as such their discs are relatively faint. Here, I present data that imply jets in fact dominate the radio-to-optical spectrum of outbursting AMXPs. They therefore may provide the best opportunity to study the behaviour of jets produced by accreting neutron stars, and compare them to those produced by black hole systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.4820v1.pdf"}
{"id": "0810.0582", "abstract": "  We use previously-published moderate-resolution spectra in combination with stellar atmosphere models to derive the first measured chemical abundance ratios in the Leo II dSph galaxy. We find that for spectra with SNR > 24, we are able to measure abundances from weak Ti, Fe and Mg lines located near the calcium infrared triplet (CaT). We also quantify and discuss discrepancies between the metallicities measured from Fe I lines and those estimated from the CaT features. We find that while the most metal-poor ([Fe/H] <-2.0]) Leo II stars have Ca and Ti abundance ratios similar to those of Galactic globular clusters, the more metal-rich stars show a gradual decline of Ti, Mg and Ca abundance ratio with increasing metallicity. Finding these trends in this distant and apparently dynamically stable dSph galaxy supports the hypothesis that the slow chemical enrichment histories of the dSph galaxies is universal, independent of any interaction with the Milky Way. Combining our spectroscopic abundances with published broadband photometry and updated isochrones, we are able to approximate stellar ages for our bright RGB stars to a relative precision of 2-3 Gyr. While the derived age-metallicity relationship of Leo II hints at some amount of slow enrichment, the data are still statistically consistent with no enrichment over the history of Leo II. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.0582v1.pdf"}
{"id": "0810.1619", "abstract": "  In this paper we elaborate on the structure of the semigroup tree and the regularities on the number of descendants of each node observed earlier. These regularites admit two different types of behavior and in this work we investigate which of the two types takes place in particular for well-known classes of semigroups. Also we study the question of what kind of chains appear in the tree and characterize the properties (like being (in)finite) thereof. We conclude with some thoughts that show how this study of the semigroup tree may help in solving the conjecture of Fibonacci-like behavior of the number of semigroups with given genus. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.1619v1.pdf"}
{"id": "0810.1788", "abstract": "  We discuss the properties of a strongly interacting spin-charge separated one dimensional system coupled to ferromagnets and/or superconductors. Our results are valid for arbitrary temperatures with respect to the spin energy, but require temperature be small compared to the charge energy. We focus mainly on the spin-incoherent regime where temperature is large compared to the spin energy, but small compared to the charge energy. In the case of a ferromagnet we study spin pumping and the renormalized dynamics of a precessing magnetic order parameter. We find the interaction-dependent temperature dependence of the spin pumping can be qualitatively different in the spin-incoherent regime from the Luttinger liquid regime, allowing an identification of the former. Likewise, the temperature dependence of the renormlized magnetization dynamics can be used to identify spin-incoherent physics. For the case of a spin-incoherent Luttinger liquid coupled to two superconductors, we compute the ac and dc Josephson current for a wire geometry in the limit of tunnel coupled superconductors. Both the ac and dc response contain \"smoking gun\" signatures that can be used to identify spin-incoherent behavior. Experimental requirements for the observation of these effects are laid out. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.1788v1.pdf"}
{"id": "0810.3281", "abstract": "  The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the mass of electron neutrinos from beta-decay of tritium with an unprecedented sensitivity of 0.2 eV/c^2 improving present limits by one order of magnitude. The decay electrons will originate from a 10 m long windowless, gaseous tritium source. Super-conducting magnets guide the electrons through differential and cryogenic pumping sections to the electro-static tandem spectrometer (MAC-E-filter), where the kinetic energy will be measured. The experiment is presently being built at the Forschungszentrum Karlsruhe by an international collaboration of more than 120 scientists. The largest component, the 1240 m^3 main spectrometer, was delivered end of 2006 and first commissioning tests have been performed. This presentation describes the goals and technological challenges of the experiment and reports on the progress in commissioning first major components. The start of first measurements is expected in 2012. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.3281v1.pdf"}
{"id": "0810.3556", "abstract": "  We report on X-ray and soft gamma-ray observations of the black-hole candidate GX 339-4 during its 2007 outburst, performed with the RXTE and INTEGRAL satellites. The hardness-intensity diagram of all RXTE/PCA data combined shows a q-shaped track similar to that observed in previous outbursts.The evolution in the diagram suggested that a transition from hard-intermediate state to soft-intermediate state occurred, simultaneously with INTEGRAL observations performed in March. The transition is confirmed by the timing analysis presented in this work, which reveals that a weak type-A quasi-periodic oscillation (QPO) replaces a strong type-C QPO. At the same time, spectral analysis shows that the flux of the high-energy component shows a significant decrease in its flux. However, we observe a delay (roughly one day) between variations of the spectral parameters of the high-energy component and changes in the flux and timing properties. The changes in the high-energy component can be explained either in terms the high-energy cut-off or in terms of a variations in the reflection component. We compare our results with those from a similar transition during the 2004 outburst of GX 339-4. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.3556v1.pdf"}
{"id": "0810.3674", "abstract": "  Diffuse 511 keV line emission, from the annihilation of cold positrons, has been observed in the direction of the Galactic Centre for more than 30 years. The latest high-resolution maps of this emission produced by the SPI instrument on INTEGRAL suggest at least one component of the emission is spatially coincident with the distribution of  70 luminous, low-mass X-ray binaries detected in the soft gamma-ray band. The X-ray band, however, is generally a more sensitive probe of X-ray binary populations. Recent X-ray surveys of the Galactic Centre have discovered a much larger population (>4000) of faint, hard X-ray point sources. We investigate the possibility that the positrons observed in the direction of the Galactic Centre originate in pair-dominated jets generated by this population of fainter accretion-powered X-ray binaries. We also consider briefly whether such sources could account for unexplained diffuse emission associated with the Galactic Centre in the microwave (the WMAP `haze') and at other wavelengths. Finally, we point out several unresolved problems in associating Galactic Centre 511 keV emission with the brightest X-ray binaries. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.3674v1.pdf"}
{"id": "0810.4945", "abstract": "  Digital synoptic sky surveys pose several new object classification challenges. In surveys where real-time detection and classification of transient events is a science driver, there is a need for an effective elimination of instrument-related artifacts which can masquerade as transient sources in the detection pipeline, e.g., unremoved large cosmic rays, saturation trails, reflections, crosstalk artifacts, etc. We have implemented such an Artifact Filter, using a supervised neural network, for the real-time processing pipeline in the Palomar-Quest (PQ) survey. After the training phase, for each object it takes as input a set of measured morphological parameters and returns the probability of it being a real object. Despite the relatively low number of training cases for many kinds of artifacts, the overall artifact classification rate is around 90", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.4945v1.pdf"}
{"id": "0810.4983", "abstract": "  Motivated by recent experiments on rotating Bose-Einstein condensates, we investigate a rotating, polarized Fermi gas trapped in an anharmonic potential. We apply a semiclassical expansion of the density of states in order to determine how the thermodynamic properties depend on the rotation frequency. The accuracy of the semiclassical approximation is tested and shown to be sufficient for describing typical experiments. At zero temperature, rotating the gas above a given frequency Ω_ DO leads to a `donut'-shaped cloud which is analogous to the hole found in two-dimensional Bose-Einstein condensates. The free expansion of the gas after suddenly turning off the trap is considered and characterized by the time and rotation frequency dependence of the aspect ratio. Temperature effects are also taken into account and both low- and high-temperature expansions are presented for the relevant thermodynamical quantities. In the high-temperature regime a virial theorem approach is used to study the delicate interplay between rotation and anharmonicity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.4983v2.pdf"}
{"id": "0810.4989", "abstract": "  Viable models of modified gravity which satisfy both local as well as cosmological tests are investigated. It is demonstrated that some versions of such highly non-linear models exhibit multiply de Sitter universe solutions, which often appear in pairs, being one of them stable and the other unstable. It is explicitly shown that, for some values of the parameters, it is possible to find several de Sitter spaces   (as a rule, numerically); one of them may serve for the inflationary stage, while the other can be used for the description of the dark energy epoch. The numerical evolution of the effective equation of state parameter is also presented, showing that these models can be considered as natural candidates for the unification of early-time inflation with late-time acceleration through dS critical points. Moreover, based on the de Sitter solutions, multiply SdS universes are constructed which might also appear at the (pre-)inflationary stage. Their thermodynamics are studied and free energies are compared. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.4989v2.pdf"}
{"id": "0810.5543", "abstract": "  We study the distribution of the time-integrated current in an exactly-solvable toy model of heat conduction, both analytically and numerically. The simplicity of the model allows us to derive the full current large deviation function and the system statistics during a large deviation event. In this way we unveil a relation between system statistics at the end of a large deviation event and for intermediate times. Midtime statistics is independent of the sign of the current, a reflection of the time-reversal symmetry of microscopic dynamics, while endtime statistics do depend on the current sign, and also on its microscopic definition. We compare our exact results with simulations based on the direct evaluation of large deviation functions, analyzing the finite-size corrections of this simulation method and deriving detailed bounds for its applicability. We also show how the Gallavotti-Cohen fluctuation theorem can be used to determine the range of validity of simulation results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.5543v3.pdf"}
{"id": "0810.5661", "abstract": "  There have been attempts to fit the abundance patterns of extremely metal-poor stars with supernova nucleosynthesis models for the lighter elements than Zn. On the other hand, observations have revealed that the presence of EMP stars with peculiarly high ratio of \"weak r-process elements\" Sr, Y and Zr. Although several possible processes were suggested for the origin of these elements, the complete solution for reproducing those ratios is not found yet. In order to reproduce the abundance patterns of such stars, we investigate a model with neutron rich matter ejection from the inner region of the conventional mass-cut. We find that explosive nucleosynthesis in a high energy supernova (or \"hypernova\") can reproduce the high abundances of Sr, Y and Zr but that the enhancements of Sr, Y and Zr are not achieved by nucleosynthesis in a normal supernova. Our results imply that, if these elements are ejected from a normal supernova, nucleosynthesis in higher entropy flow than that of the supernova shock is required. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.5661v1.pdf"}
{"id": "0811.0443", "abstract": "  Lac OB1 is a nearby OB association in its final stage of star formation. While the member stars suggest an expansion time scale of tens of Myr, the latest star formation episode, as manifested by the existence of massive and pre-main sequence stars, took place no more than a few Myr ago. The remnant molecular clouds in the region provide evidence of starbirth triggered by massive stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.0443v1.pdf"}
{"id": "0811.0751", "abstract": "  We introduce and investigate the ribbon groupoid associated with a Garside group. Under a technical hypothesis, we prove that this category is a Garside groupoid. We decompose this groupoid into a semi-direct product of two of its parabolic subgroupoids and provide a groupoid presentation. In order to established the latter result, we describe quasi-centralizers in Garside groups. All results hold in the particular case of Artin-Tits groups of spherical type. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.0751v1.pdf"}
{"id": "0811.1071", "abstract": "  The geometric phases of a two-level atom interacting with non-Markovian environments are calculated and the non-Markovian effects on the geometric phases are discussed in this paper. Three kinds of methods that describe the non-Markovian process, projection superoperator technique, memory kernel master equation and post-Markovian master equation, are used in the discussions. The results show that when the dissipation rate is large, the non-Markovian effects change the geometric phase more strikingly than the small one. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.1071v1.pdf"}
{"id": "0811.1250", "abstract": "  We develop the concept of ABC-Boost (Adaptive Base Class Boost) for multi-class classification and present ABC-MART, a concrete implementation of ABC-Boost. The original MART (Multiple Additive Regression Trees) algorithm has been very successful in large-scale applications. For binary classification, ABC-MART recovers MART. For multi-class classification, ABC-MART considerably improves MART, as evaluated on several public data sets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.1250v1.pdf"}
{"id": "0811.1596", "abstract": "  We discuss the various manifestations of quantum decoherence in the forms of dephasing, entanglement with the environment, and revelation of \"which-path\" information. As a specific example, we consider an electron interference experiment. The coupling of the coherent electrons to the quantized electromagnetic field illustrates all of these versions of decoherence. This decoherence has two equivalent interpretations, in terms of photon emission or in terms of Aharonov-Bohm phase fluctuations. We consider the case when the coherent electrons are coupled to photons in a squeezed vacuum state. The time-averaged result is increased decoherence. However, if only electrons which are emitted during selected periods are counted, the decoherence can be suppressed below the level for the photon vacuum. This is the phenomenon of recoherence. This effect is closely related to the quantum violations of the weak energy condition, and is restricted by similar inequalities. We give some estimates of the magnitude of the recoherence effect and discuss prospects for observing it in an electron interferometry experiment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.1596v1.pdf"}
{"id": "0811.2723", "abstract": "  We develop a description of diffusion limited growth in solid-solid transformations, which are strongly influenced by elastic effects. Density differences and structural transformations provoke stresses at interfaces, which affect the phase equilibrium conditions. We formulate equations for the interface kinetics similar to dendritic growth and study the growth of a stable phase from a metastable solid in both a channel geometry and in free space. We perform sharp interface calculations based on Green's function methods and phase field simulations, supplemented by analytical investigations. For pure dilatational transformations we find a single growing finger with symmetry breaking at higher driving forces, whereas for shear transformations the emergence of twin structures can be favorable. We predict the steady state shapes and propagation velocities, which can be higher than in conventional dendritic growth. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.2723v1.pdf"}
{"id": "0811.2945", "abstract": "  The electron-electron correlations in a many-electron (Ne = 1, 2,..., 5) quantum dot confined by a parabolic potential is investigated in the presence of a single magnetic ion and a perpendicular magnetic field. We obtained the energy spectrum and calculated the addition energy which exhibits cusps as function of the magnetic field. The vortex properties of the many-particle wave function of the ground state are studied and for large magnetic fields are related to composite fermions. The position of the impurity influences strongly the spin pair correlation function when the external field is large. In small applied magnetic field, the spin exchange energy together with the Zeeman terms leads to a ferromagnetic-antiferromagnetic(FM-AFM) transition. When the magnetic ion is shifted away from the center of the quantum dot a remarkable re-entrant AFM-FM-AFM transition is found as function of the strength of the Coulomb interaction. Thermodynamic quantities as the heat capacity, the magnetization, and the susceptibility are also studied. Cusps in the energy levels show up as peaks in the heat capacity and the susceptibility. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.2945v1.pdf"}
{"id": "0811.2992", "abstract": "  Star formation in the Local spiral arm in the direction of the Galactic longitudes 132–158 deg is reviewed. Recent star-forming activity in this Milky Way direction is evidenced by the presence here of the Cam OB1 association and dense dust and molecular clouds containing Hα emission stars, young irregular variables and infrared stellar objects. The clouds of the Local arm concentrate in two layers at 150-300 pc and at about 900 pc from the Sun. The Perseus arm objects in this direction are at a distance of about 2 kpc. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.2992v1.pdf"}
{"id": "0811.3297", "abstract": "  We propose two Fabry-Perot cavities, each pumped through both the mirrors, positioned in line as a toy model of the gravitational-wave (GW) detector free from displacement noise of the test masses. It is demonstrated that the displacement noise of cavity mirrors as well as laser noise can be completely excluded in a proper linear combination of the cavities output signals. We show that in low-frequency approximation (gravitational wave length λ-gw is much greater than distance L between mirrors λ_gw≫ L) the decrease of response signal is about (L/λ_gw)^2, i.e. signal is stronger than the one of the interferometer recently proposed by S. Kawamura and Y. Chen. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.3297v1.pdf"}
{"id": "0811.3874", "abstract": "  We implement self-consistent microscopic calculations in order to describe out-of-equilibrium non-local transport in normal metal-superconductor-normal metal hybrid structures in the presence of a magnetic field and for arbitrary interface transparencies. A four terminal setup simulating usual experimental situations is described by means of a tight-binding model. We present results for the self-consistent order parameter and current profiles within the sample. These profiles illustrate a crossover from a quasi-equilibrium to a strong non-equilibrium situation when increasing the interface transparencies and the applied voltages. We analyze in detail the behavior of the non-local conductance in these two different regimes. While in quasi-equilibrium conditions this can be expressed as the difference between elastic cotunneling and crossed Andreev transmission coefficients, in a general situation additional contributions due to the voltage dependence of the self-consistent order parameter have to be taken into account. The present results provide a first step towards a self-consistent theory of non-local transport including non-equilibrium effects and describe qualitatively a recent experiment [Phys. Rev. Lett. 97, 237003 (2006)]. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.3874v3.pdf"}
{"id": "0812.0197", "abstract": "  We describe a new methodology for studying persistence of topological features across a family of spaces or point-cloud data sets, called zigzag persistence. Building on classical results about quiver representations, zigzag persistence generalises the highly successful theory of persistent homology and addresses several situations which are not covered by that theory. In this paper we develop theoretical and algorithmic foundations with a view towards applications in topological statistics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.0197v1.pdf"}
{"id": "0812.0698", "abstract": "  A distributed classification paradigm known as collaborative tagging has been widely adopted in new Web applications designed to manage and share online resources. Users of these applications organize resources (Web pages, digital photographs, academic papers) by associating with them freely chosen text labels, or tags. Here we leverage the social aspects of collaborative tagging and introduce a notion of resource distance based on the collective tagging activity of users. We collect data from a popular system and perform experiments showing that our definition of distance can be used to build a weighted network of resources with a detectable community structure. We show that this community structure clearly exposes the semantic relations among resources. The communities of resources that we observe are a genuinely emergent feature, resulting from the uncoordinated activity of a large number of users, and their detection paves the way for mapping emergent semantics in social tagging systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.0698v1.pdf"}
{"id": "0812.0876", "abstract": "  The statistical entropy of a scalar field on the warped AdS_3 black hole in the cosmological topologically massive gravity is calculated based on the brick-wall method, which is different from the Wald's entropy formula giving the modified area law due to the higher-derivative corrections in that the entropy still satisfies the area law. It means that the entropy for scalar excitations on this background is independent of higher-order derivative terms or the conventional brick wall method has some limitations to take into account the higher-derivative terms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.0876v3.pdf"}
{"id": "0812.1128", "abstract": "  We consider a regular random network where each node has exactly three neighbours. Ising spins at the network nodes interact antiferromagnetically along the links. The clustering coefficient C is tuned from zero to 1/3 by adding new links. At the same time, the density of geometrically frustrated links increases. We calculate the magnetic specific heat, the spin susceptibility and the Edwards-Anderson order parameter q by means of the heat-bath Monte Carlo simulations. The aim is the transition temperature T_x dependence on the clustering coefficient C. The results are compared with the predictions of the Bethe approximation. At C=0, the network is bipartite and the low temperature phase is antiferromagnetic. When C increases, the critical temperature falls down towards the values which are close to the theoretical predictions for the spin-glass phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.1128v2.pdf"}
{"id": "0812.2209", "abstract": "  The Casimir force is calculated between Au thin films that are described by a Drude model with a frequency dependent damping function. The model parameters are obtained from available experimental data for Au thin films. Two cases are considered; annealed and nonannealed films that have a different damping function. Compared with the calculations using a Drude model with a constant damping parameter, we observe changes in the Casimir force of a few percent. This behavior is only observed in films of no more than 300 Å thick. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.2209v1.pdf"}
{"id": "0812.2514", "abstract": "  We experimentally analyze a Bessel beam produced with a conical mirror, paying particular attention to its superluminal and diffraction-free properties. We spatially characterized the beam in the radial and on-axis dimensions, and verified that the central peak does not spread over a propagation distance of 73 cm. In addition, we measured the superluminal phase and group velocities of the beam in free space. Both spatial and temporal measurements show good agreement with the theoretical predictions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.2514v1.pdf"}
{"id": "0812.3088", "abstract": "  We develop a complete theoretical description of photoassociative Stimulated Raman Adiabatic Passage (STIRAP) near a Feshbach resonance in a thermal atomic gas. We show that it is possible to use low intensity laser pulses to directly excite the continuum at a Feshbach resonance and transfer nearly the entire atomic population to the lowest rovibrational level in the molecular ground state. In case of a broad resonance, commonly found in several diatomic alkali molecules, our model predicts a transfer efficiency η up to 97", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3088v1.pdf"}
{"id": "0812.3356", "abstract": "  A new heuristic method for the evaluation of definite integrals is presented. This method of brackets has its origin in methods developed for theevaluation of Feynman diagrams. We describe the operational rules and illustrate the method with several examples. The method of brackets reduces the evaluation of a large class of definite integrals to the solution of a linear system of equations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3356v1.pdf"}
{"id": "0812.3581", "abstract": "  The finite element computation of structures such as waveguides can lead to heavy computations when the length of the structure is large compared to the wavelength. Such waveguides can in fact be seen as one-dimensional periodic structures. In this paper a simple recursive method is presented to compute the global dynamic stiffness matrix of finite periodic structures. This allows to get frequency response functions with a small amount of computations. Examples are presented to show that the computing time is of order log_2 N where N is the number of periods of the waveguide. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3581v1.pdf"}
{"id": "0812.3869", "abstract": "  The possibility of physics in multiple time dimensions is investigated. Drawing on recent work by Walter Craig and myself, I show that, contrary to conventional wisdom, there is a well-posed initial value problem–deterministic, stable evolution–for theories in multiple time dimensions. Though similar in many ways to ordinary, single-time theories, multi-time theories have some rather intriguing properties which suggest new directions for the understanding of fundamental physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3869v1.pdf"}
{"id": "0812.3874", "abstract": "  No-scale supersymmetry or gaugino mediation augmented with large negative Higgs soft masses at the input scale provides a simple solution to the supersymmetric flavor problem while giving rise to a neutralino LSP. However, to obtain a neutralino LSP it is often necessary to have tachyonic input Higgs soft masses that can give rise to charge-and-color-breaking (CCB) minima and unbounded-from-below (UFB) directions in the low energy theory. We investigate the vacuum structure in these theories to determine when such problematic features are present. When the standard electroweak vacuum is only metastable, we compute its lifetime under vacuum tunneling. We find that vacuum metastability leads to severe restrictions on the parameter space for larger tanβ∼ 30, while for smaller tanβ∼ 10, only minor restrictions are found. Along the way, we derive an exact bounce solution for tunneling through an inverted parabolic potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3874v1.pdf"}
{"id": "0812.4512", "abstract": "  I sketch what it is supposed to mean to quantize gauge theory, and how this can be made more concrete in perturbation theory and also by starting with a finite-dimensional lattice approximation. Based on real experiments and computer simulations, quantum gauge theory in four dimensions is believed to have a mass gap. This is one of the most fundamental facts that makes the Universe the way it is. This article is the written form of a lecture presented at the conference \"Geometric Analysis: Past and Future\" (Harvard University, August 27-September 1, 2008), in honor of the 60th birthday of S.-T. Yau. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.4512v3.pdf"}
{"id": "0812.4611", "abstract": "  We show the existence of gap-Townes solitons for the multidimensional Gross-Pitaeviskii equation with attractive interactions and in two- and three-dimensional optical lattices. In absence of the periodic potential the solution reduces to the known Townes solitons of the multi-dimensional nonlinear Schrödinger equation, sharing with these the propriety of being unstable against small norm (number of atoms) variations. We show that in the presence of the optical lattice the solution separates stable localized solutions (gap-solitons) from decaying ones, characterizing the delocalizing transition occurring in the multidimensional case. The link between these higher dimensional solutions and the ones of one dimensional nonlinear Schrödinger equation with higher order nonlinearities is also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.4611v1.pdf"}
{"id": "0901.0535", "abstract": "  Two major advantages of the STAR detector - uniform azimuthal acceptance complementing extended pseudo-rapidity coverage, and the ability to identify a wide variety of the hadron species in almost all kinematic ranges - have allowed us to address successfully a set of key physics topics at RHIC. We report here selected recent results from the STAR experiment, including insights on system size effects on medium properties, hadronization mechanisms, and partonic energy loss from triggered and non-triggered probes. In conclusion, we present an outlook on the STAR new physics program in upcoming years. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.0535v1.pdf"}
{"id": "0901.1215", "abstract": "  We consider the interaction between dark matter and dark energy in the framework of holographic dark energy, and propose a natural and physically plausible form of interaction, in which the interacting term is proportional to the product of the powers of the dark matter and dark energy densities. We investigate the cosmic evolution in such models. The impact of the coupling on the dark matter and dark energy components may be asymmetric. While the dark energy decouples from the dark matter at late time, just as other components of the cosmic fluid become decoupled as the universe expands, interestingly, the dark matter may actually become coupled to the dark energy at late time. We shall name such a phenomenon as \"incoupling\". We use the latest type Ia supernovae data from the SCP team, baryon acoustics oscillation data from SDSS and 2dF surveys, and the position of the first peak of the CMB angular power spectrum to constrain the model. We find that the interaction term which is proportional to the the first power product of the dark energy and dark matter densities gives excellent fit to the current data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.1215v5.pdf"}
{"id": "0901.1624", "abstract": "  As technological advances allow us to fabricate smaller autonomous self-propelled devices, it is clear that at some point directed propulsion could not come from pre-specified deterministic periodic deformation of the swimmer's body and we need to develop strategies to extract a net directed motion from a series of random transitions in the conformation space of the swimmer. We present a theoretical formulation to describe the \"stochastic motor\" that drives the motion of low Reynolds number swimmers based on this concept, and use it to study the propulsion of a simple low Reynolds number swimmer, namely, the three-sphere swimmer model. When the detailed-balanced is broken and the motor is driven out of equilibrium, it can propel the swimmer in the required direction. The formulation can be used to study optimal design strategies for molecular-scale low Reynolds number swimmers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.1624v1.pdf"}
{"id": "0901.3929", "abstract": "  The ideals of the eighteenth century's Age of Enlightenment are the foundation of modern democracies. The era was characterized by thinkers who promoted progressive social reforms that opposed the long-established aristocracies and monarchies of the time. Prominent examples of such reforms include the establishment of inalienable human rights, self-governing republics, and market capitalism. Twenty-first century democratic nations can benefit from revisiting the systems developed during the Enlightenment and reframing them within the techno-social context of the Information Age. This article explores the application of social algorithms that make use of Thomas Paine's (English: 1737–1809) representatives, Adam Smith's (Scottish: 1723–1790) self-interested actors, and Marquis de Condorcet's (French: 1743–1794) optimal decision making groups. It is posited that technology-enabled social algorithms can better realize the ideals articulated during the Enlightenment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.3929v2.pdf"}
{"id": "0901.4354", "abstract": "  We introduce a new class of models describing the quark mass hierarchy. In this class, the dynamics primarily responsible for electroweak symmetry breaking (EWSB) leads to the mass spectrum of quarks with no (or weak) isospin violation. Moreover, the values of these masses are of the order of the observed masses of the down-type quarks. Then, strong (although subcritical) horizontal diagonal interactions for the t quark plus horizontal flavor-changing neutral interactions between different families lead (with no fine tuning) to a realistic quark mass spectrum. In this scenario, many composite Higgs bosons occur. A concrete model with the dynamical EWSB with the fourth family is described in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.4354v2.pdf"}
{"id": "0901.4583", "abstract": "  We consider a Georgi-Glashow model conformally coupled to gravity. The conformally invariant action includes a triplet of scalar fields and SO(3) non-Abelian gauge fields. However, the usual mass term μ^2 ϕ^2 is forbidden by the symmetry and this role is now played by the conformal coupling of the Ricci scalar to the scalar fields. Spontaneous symmetry breaking occurs via gravitation. The spherically symmetric solutions correspond to localized solitons (magnetic monopoles) in asymptotically anti-de-Sitter (AdS) space-time and the metric outside the core of the monopole is found to be Schwarzschild-AdS. Though conformal symmetry excludes the Einstein-Hilbert term in the original action, it emerges in the effective action after spontaneous symmetry breaking and dominates the low-energy/long-distance regime outside the core of the monopole. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.4583v1.pdf"}
{"id": "0901.4601", "abstract": "  The epsilon-near-zero (ENZ) tunneling phenomenon allows full transmission of waves through a narrow channel even in the presence of a strong geometric mismatch. Here we experimentally demonstrate nonlinear control of the ENZ tunneling by an external field, as well as self-modulation of the transmission resonance due to the incident wave. Using a waveguide section near cut-off frequency as the ENZ system, we introduce a diode with tunable and nonlinear capacitance to demonstrate both of these effects. Our results confirm earlier theoretical ideas on using an ENZ channel for dielectric sensing, and their potential applications for tunable slow-light structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.4601v2.pdf"}
{"id": "0902.0588", "abstract": "  MUSE, a 2nd generation VLT instrument, will become the world's largest integral field spectrograph. It will be an AO assisted instrument which, in a single exposure, covers the wavelength range from 465 to 930 nm with an average resolution of 3000 over a field of view of 1'x1' with 0.2” spatial sampling. Both the complexity and the rate of the data are a challenge for the data processing of this instrument.   We will give an overview of the data processing scheme that has been designed for MUSE. Specifically, we will use only a single resampling step from the raw data to the reduced data product. This allows us to improve data quality, accurately propagate variance, and minimize spreading of artifacts and correlated noise. This approach necessitates changes to the standard way in which reduction steps like wavelength calibration and sky subtraction are carried out, but can be expanded to include combination of multiple exposures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.0588v2.pdf"}
{"id": "0903.0046", "abstract": "  This review summarizes the state of the art in searches for supersymmetry at colliders on the eve of the LHC era. Supersymmetry is unique among extensions of the standard model in being motivated by naturalness, dark matter, and force unification, both with and without gravity. At the same time, weak-scale supersymmetry encompasses a wide range of experimental signals that are also found in many other frameworks. We recall the motivations for supersymmetry and review the various models and their distinctive features. We then comprehensively summarize searches for neutral and charged Higgs bosons and standard model superpartners at the high energy frontier, considering both canonical and non-canonical supersymmetric models, and including results from LEP, HERA, and the Tevatron. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.0046v2.pdf"}
{"id": "0903.1487", "abstract": "  We report the three-dimensional (3-D) momentum-resolved soft x-ray photoemission spectroscopy of the Fermi liquid LaNiO_3. The out-of-plane and in-plane cuts of the 3-D electron- and hole-Fermi surfaces (FSs) are observed by energy- and angle- dependent photoemission measurements. The energy bands forming the electron FS suggest an ω^2 dependence of the imaginary part of the self-energy and a `correlation kink' at an energy scale of 0.25 eV. In contrast, the bands which form nesting character hole FSs do not show kinks and match local density approximation calculations. The results indicate a momentum-dependent mass renormalization, leading to electron-hole asymmetry in strongly correlated LaNiO_3. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.1487v1.pdf"}
{"id": "0903.1786", "abstract": "  We calculate the inelastic scattering probabilities in the wide band limit of a local polaron model with quadratic coupling to bosons. The central object is a two-particle Green function which is calculated exactly using a purely algebraic approach. Compared with the usual linear interaction term a quadratic interaction term gives higher probabilities for inelastic scattering involving a large number of bosons. As an application we consider the problem hot electron mediated energy transfer at surfaces and use the delta self-consistent field extension of density functional theory to calculate and compare coupling parameters and probabilities for exciting different vibrational modes of CO adsorbed on a Cu(100) surface. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.1786v1.pdf"}
{"id": "0903.1836", "abstract": "  Some dynamical properties of a bouncing ball model under the presence of an external force modeled by two nonlinear terms are studied. The description of the model is made by use of a two dimensional nonlinear measure preserving map on the variables velocity of the particle and time. We show that raising the straight of a control parameter which controls one of the nonlinearities, the positive Lyapunov exponent decreases in the average and suffers abrupt changes. We also show that for a specific range of control parameters, the model exhibits the phenomenon of Fermi acceleration. The explanation of both behaviours is given in terms of the shape of the external force and due to a discontinuity of the moving wall's velocity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.1836v1.pdf"}
{"id": "0903.2623", "abstract": "  We calculate the absorption efficiency of the composite grains, made up of host silicate spheroids and inclusions of ices/graphites/or voids, in the spectral region 7.0-14.0μm The absorption efficiencies of the composite spheroidal grains for three axial ratios are computed using the discrete dipole approximation (DDA) as well as using the effective medium approximation     T-Matrix (EMT-Tmatrix) ap proach. We study the absorption as a function of the volume fraction of the inclusions and porosity. In particular, we study the variation in the 10.0μm feature with the volume fraction of the inclusions and porosity. We then calculate the infrared fluxes for these composite grains and compare the model curves with the average observed IRAS-LRS curve, obtained for several circumstellar dust shells around stars. These results on the composite grains show that the wavelength of the peak absorption shifts and the width of the 10.0μm feature varies with the variation in the volume fraction of the inclusions. The model curves for composite grains with axial ratios not very large (AR∼1.3) and volume fractions of inclusions with f=0.20, and dust temperature of about 250-300^∘K, fit the observed emission curves reasonably well. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.2623v1.pdf"}
{"id": "0903.3229", "abstract": "  The radiative recombination of a free electron into an excited state of a bare, high-Z ion is studied, together with its subsequent decay, within the framework of the density matrix theory and Dirac's relativistic equation. Special attention is paid to the polarization and angular correlations between the recombination and the decay photons. In order to perform a systematic analysis of these correlations the general expression for the double-differential recombination cross section is obtained by making use of the resonance approximation. Based on this expression, detailed computations for the linear polarization of x-ray photons emitted in the (e, 2γ) two-step recombination of uranium ions U^92+ are carried out for a wide range of projectile energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.3229v3.pdf"}
{"id": "0903.4204", "abstract": "  A parallel dispersive finite-difference time-domain (FDTD) method for the modeling of three-dimensional (3-D) electromagnetic cloaking structures is presented in this paper. The permittivity and permeability of the cloak are mapped to the Drude dispersion model and taken into account in FDTD simulations using an auxiliary differential equation (ADE) method. It is shown that the correction of numerical material parameters and the slow switching-on of source are necessary to ensure stable and convergent single-frequency simulations. Numerical results from wideband simulations demonstrate that waves passing through a three-dimensional cloak experience considerable delay comparing with the free space propagations, as well as pulse broadening and blue-shift effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.4204v1.pdf"}
{"id": "0903.4463", "abstract": "  It is demonstrated that strong laser pulses can introduce torsional motion in the axially chiral molecule 3,5-diflouro-3',5'-dibromo-biphenyl (DFDBrBPh). A nanosecond laser pulse spatially aligns the stereogenic carbon-carbon (C-C) bond axis allowing a perpendicularly polarized, intense femtosecond pulse to initiate torsional motion accompanied by a rotation about the fixed axis. We monitor the induced motion by femtosecond time-resolved Coulomb explosion imaging. Our theoretical analysis corroborates the experimental findings and on the basis of these results we discuss future applications of laser induced torsion, viz., time-resolved studies of de-racemization and laser controlled molecular junctions based on molecules with torsion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.4463v1.pdf"}
{"id": "0903.4716", "abstract": "  I review here some of the physics we are learning and expect to learn in the near future through the observation of cosmic rays. The study of cosmic rays involves a combination of data from accelerators, ground arrays, atmospheric fluorescence detectors and balloon and satellite experiments. I will discuss the data of the Pierre Auger Observatory, PAMELA, ATIC and FST among other experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.4716v1.pdf"}
{"id": "0904.0111", "abstract": "  The mitotic spindle is an important intermediate structure in eukaryotic cell division, in which each of a pair of duplicated chromosomes is attached through microtubules to centrosomal bodies located close to the two poles of the dividing cell. Several mechanisms are at work towards the formation of the spindle, one of which is the `capture' of chromosome pairs, held together by kinetochores, by randomly searching microtubules. Although the entire cell cycle can be up to 24 hours long, the mitotic phase typically takes only less than an hour. How does the cell keep the duration of mitosis within this limit? Previous theoretical studies have suggested that the chromosome search and capture is optimized by tuning the microtubule dynamic parameters to minimize the search time. In this paper, we examine this conjecture. We compute the mean search time for a single target by microtubules from a single nucleating site, using a systematic and rigorous theoretical approach, for arbitrary kinetic parameters. The result is extended to multiple targets and nucleating sites by physical arguments. Estimates of mitotic time scales are then obtained for different cells using experimental data. In yeast and mammalian cells, the observed changes in microtubule kinetics between interphase and mitosis are beneficial in reducing the search time. In Xenopus extracts, by contrast, the opposite effect is observed, in agreement with the current understanding that large cells use additional mechanisms to regulate the duration of the mitotic phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.0111v3.pdf"}
{"id": "0904.0399", "abstract": "  The structural and electronic properties of Si(335)-Au surface decorated with Pb atoms are studied by means of density-functional theory. The resulting structural model features Pb atoms bonded to neighboring Si and Au surface atoms, forming monoatomic chain located 0.2 nm above the surface. The presence of Pb chain leads to a strong rebonding of Si atoms at the step edge. The fact that Pb atoms occupy positions in the middle of terrace is consistent with STM data, and also confirmed by simulated STM images. The calculated band structure clearly shows one-dimensional metallic character. The calculated electronic bands remain in very good agreement with photoemission data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.0399v1.pdf"}
{"id": "0904.0983", "abstract": "  We present new calculations for the Stark broadening of the hydrogen line profiles in the dense atmospheres of white dwarf stars. Our improved model is based on the unified theory of Stark broadening from Vidal, Cooper     Smith, but it also includes non-ideal gas effects from the Hummer     Mihalas occupation probability formalism directly inside the line profile calculations. This approach improves upon previous calculations that relied on the use of an ad-hoc free parameter to describe the dissolution of the line wing opacity in the presence of high electric microfields in the plasma. We present here the first grid of model spectra for hot Teff >  12,000 K DA white dwarfs that has no free parameters. The atmospheric parameters obtained from optical and UV spectroscopic observations using these improved models are shown to differ substantially from those published in previous studies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.0983v1.pdf"}
{"id": "0904.0989", "abstract": "  Background: If biology is modular then clusters, or communities, of proteins derived using only protein interaction network structure should define protein modules with similar biological roles. We investigate the link between biological modules and network communities in yeast and its relationship to the scale at which we probe the network.   Results: Our results demonstrate that the functional homogeneity of communities depends on the scale selected, and that almost all proteins lie in a functionally homogeneous community at some scale. We judge functional homogeneity using a novel test and three independent characterizations of protein function, and find a high degree of overlap between these measures. We show that a high mean clustering coefficient of a community can be used to identify those that are functionally homogeneous. By tracing the community membership of a protein through multiple scales we demonstrate how our approach could be useful to biologists focusing on a particular protein.   Conclusions: We show that there is no one scale of interest in the community structure of the yeast protein interaction network, but we can identify the range of resolution parameters that yield the most functionally coherent communities, and predict which communities are most likely to be functionally homogeneous. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.0989v3.pdf"}
{"id": "0904.1795", "abstract": "  The theory of planetary dynamos and its applications to observed phenomena of planetary magnetism are outlined. It is generally accepted that convection flows driven by thermal or compositional buoyancy are the most likely source for the sustenance of global planetary magnetic fields. While the existence of dynamos in electrically conducting fluid planetary cores provides constraints on properties of the latter, the lack of knowledge about time dependences of the magnetic fields and about their toroidal components together with the restricted parameter regions accessible to theory have prevented so far a full understanding of the phenomena of planetary magnetism. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.1795v1.pdf"}
{"id": "0904.2409", "abstract": "  We revisit the problem of the critical velocity of a clean one-dimensional superconductor. At the level of mean-field theory, we find that the zero-temperature value of the critical velocity–the uniform velocity of the superfluid condensate at which the superconducting state becomes unstable–is a factor of √(2) smaller than the Landau critical velocity. This is in contrast to a prior finding, which held that the critical velocity is equal to the Landau critical velocity. The smaller value of the critical velocity, which our analysis yields, is the result of a pre-emptive Clogston-Chandrasekhar–like discontinuous phase transition, and is an analog of the threshold value of the uniform exchange-field of a superconductor, previously investigated by Sarma and by Maki and Tsuneto. We also consider the impact of nonzero temperature, study critical currents, and examine metastability and its limits in the temperature versus flow-velocity phase diagram. In addition, we comment on the effects of electron scattering by impurities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.2409v2.pdf"}
{"id": "0904.3224", "abstract": "  In four space-time dimensions, there are good theoretical reasons for believing that General Relativity is the correct geometrical theory of gravity, at least at the classical level. If one admits the possibility of extra space-time dimensions, what would we expect classical gravity to be like? It is often stated that the most natural generalisation is Lovelock's theory, which shares many physical properties with GR. But there are also key differences and problems. A potentially serious problem is the breakdown of determinism, which can occur when the matrix of coefficients of second time derivatives of the metric degenerates. This can be avoided by imposing inequalities on the curvature. Here it is argued that such inequalities occur naturally if the Lovelock action is obtained from Weyl's formulae for the volume and surface area of a tube. Part of the purpose of this article is to give a treatment of the Weyl tube formula in terminology familiar to relativists and to give an appropriate (straightforward) generalisation to a tube embedded in Minkowski space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.3224v2.pdf"}
{"id": "0904.4220", "abstract": "  Using a sheaf-theoretic extension of conventional principal bundle theory, the Dirac monopole is formulated as a spherically symmetric model free of singularities outside the origin such that the charge may assume arbitrary real values. For integral charges, the construction effectively coincides with the usual model. Spin structures and Dirac operators are also generalised by the same technique. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.4220v2.pdf"}
{"id": "0904.4682", "abstract": "  We report on the Suzaku observation of neutron star low-mass X-ray binary Cygnus X-2 which reveals a presence of the iron K_alpha emission line. The line profile shows a significant red wing. This discovery increases the number of neutron star sources where red-skewed iron lines were observed and strongly suggests that this phenomenon is common not only in black holes but also in other types of accreting compact objects. We examine the line profile in terms of models which attribute its production to the relativistic effects due to reflection of X-ray radiation from a cold accretion disk and also as a result of the line formation in the extended wind/outflow configuration. Both models are able to adequately represent the observed line profile. We consider the results of line modeling in the context of subsecond variability. While we were unable to conclusively disqualify one of the models, we find that the wind paradigm has several advantages over the relativistic disk reflection model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.4682v1.pdf"}
{"id": "0905.0114", "abstract": "  We propose a quantum feedback scheme for the preparation and protection of photon number states of light trapped in a high-Q microwave cavity. A quantum non-demolition measurement of the cavity field provides information on the photon number distribution. The feedback loop is closed by injecting into the cavity a coherent pulse adjusted to increase the probability of the target photon number. The efficiency and reliability of the closed-loop state stabilization is assessed by quantum Monte-Carlo simulations. We show that, in realistic experimental conditions, Fock states are efficiently produced and protected against decoherence. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.0114v1.pdf"}
{"id": "0905.1032", "abstract": "  We give an arithmetical proof of the strong normalization of the λ-calculus (and also of the λμ-calculus) where the type system is the one of simple types with recursive equations on types. The proof using candidates of reducibility is an easy extension of the one without equations but this proof cannot be formalized in Peano arithmetic. The strength of the system needed for such a proof was not known. Our proof shows that it is not more than Peano arithmetic. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.1032v1.pdf"}
{"id": "0905.1796", "abstract": "  We describe the endomorphism rings of maximal rigid objects in the cluster categories of tubes. Moreover, we show that they are gentle and have Gorenstein dimension 1. We analyse their representation theory and prove that they are of finite type. Finally, we study the relationship between the module category and the cluster tube via the Hom-functor. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.1796v1.pdf"}
{"id": "0905.2196", "abstract": "  We present self-consistent cosmological magnetohydrodynamic (MHD) simulations that simultaneously follow the formation of a galaxy cluster and the magnetic field ejection by an active galactic nucleus (AGN). We find that the magnetic fields ejected by the AGNs, though initially distributed in relatively small volumes, can be transported throughout the cluster and be further amplified by the intra-cluster medium (ICM) turbulence during the cluster formation process. The ICM turbulence is shown to be generated and sustained by the frequent mergers of smaller halos. Furthermore, a cluster-wide dynamo process is shown to exist in the ICM and amplify the magnetic field energy and flux. The total magnetic energy in the cluster can reach ∼ 10^61 ergs while micro Gauss (μG) fields can distribute over ∼ Mpc scales throughout the whole cluster. This finding shows that magnetic fields from AGNs, being further amplified by the ICM turbulence through small-scale dynamo processes, can be the origin of cluster-wide magnetic fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.2196v1.pdf"}
{"id": "0905.2268", "abstract": "  We propose to use the large-scale structure of the universe as a cosmic standard ruler, based on the fact that the pattern of galaxy distribution should be maintained in the course of time on large scales. By examining the scale-dependence of the pattern in different redshift intervals it is possible to reconstruct the expansion history of the universe, and thus to measure the cosmological parameters governing the expansion of the universe. The features in the galaxy distribution that can be used as standard rulers include the topology of large-scale structure and the overall shapes of galaxy power spectrum and correlation function. The genus, being an intrinsic topology measure, is resistant against the non-linear gravitational evolution, galaxy biasing, and redshift-space distortion effects, and thus is ideal for quantifying the primordial topology of the large-scale structure. The expansion history of the universe can be constrained by comparing among the genus measured at different redshifts. In the case of initially Gaussian fluctuations the genus accurately recovers the slope of the primordial power spectrum near the smoothing scale, and the expansion history can be constrained by comparing between the predicted and measured genus. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.2268v1.pdf"}
{"id": "0905.2961", "abstract": "  Conversion of microwave radiation into the optical range has been predicted to reach unity quantum efficiency in whispering gallery resonators made from an optically nonlinear crystal and supporting microwave and optical modes simultaneously. In this work we theoretically explore and experimentally demonstrate a resonator geometry that can provide the required phase matching for such a conversion at any desired frequency in the sub-THz range. We show that such a ring-shaped resonator not only allows for the phase matching, but also maximizes the overlap of the interacting fields. As a result, unity-efficient conversion is expected in a resonator with feasible parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.2961v2.pdf"}
{"id": "0905.3547", "abstract": "  We develop a complete analytical description of the time evolution of squeezed states of a charged particle under the Fock-Darwin Hamiltonian and a time-dependent electric field. This result generalises a relation obtained by Infeld and Plebański for states of the one-dimensional harmonic oscillator. We relate the evolution of a state-vector subjected to squeezing to that of state which is not subjected to squeezing and for which the time-evolution under the simple harmonic oscillator dynamics is known (e.g. an eigenstate of the Hamiltonian). A corresponding relation is also established for the Wigner functions of the states, in view of their utility in the analysis of cold-ion experiments. In an appendix, we compute the response functions of the FD Hamiltonian to an external electric field, using the same techniques as in the main text. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.3547v1.pdf"}
{"id": "0905.3757", "abstract": "  We show that tools from circuit complexity can be used to study decompositions of global constraints. In particular, we study decompositions of global constraints into conjunctive normal form with the property that unit propagation on the decomposition enforces the same level of consistency as a specialized propagation algorithm. We prove that a constraint propagator has a a polynomial size decomposition if and only if it can be computed by a polynomial size monotone Boolean circuit. Lower bounds on the size of monotone Boolean circuits thus translate to lower bounds on the size of decompositions of global constraints. For instance, we prove that there is no polynomial sized decomposition of the domain consistency propagator for the ALLDIFFERENT constraint. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.3757v1.pdf"}
{"id": "0905.4283", "abstract": "  We study the dynamics of the Magellanic Clouds in a model for the Local Group whose mass is constrained using the timing argument/two-body limit of the action principle. The goal is to evaluate the role of M31 in generating the high angular momentum orbit of the Clouds, a puzzle that has only been exacerbated by the latest HST proper motion measurements. We study the effects of varying the total Local Group mass, the relative mass of the Milky Way and M31, the proper motion of M31, and the proper motion of the LMC on this problem. Over a large part of this parameter-space we find that tides from M31 are insignificant. For a range of LMC proper motions approximately 3σ higher than the mean and total Local Group mass > 3.5× 10^12 M_⊙, M31 can provide a significant torque to the LMC orbit. However, if the LMC is bound to the MW, then M31 is found to have negligible effect on its motion and the origin of the high angular momentum of the system remains a puzzle. Finally, we use the timing argument to calculate the total mass of the MW-LMC system based on the assumption that they are encountering each other for the first time, their previous perigalacticon being a Hubble time ago, obtaining M_ MW + M_ LMC = (8.7 ± 0.8) × 10^11 M_⊙. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.4283v1.pdf"}
{"id": "0906.0480", "abstract": "  We analyze structure of the world foreign currency exchange (FX) market viewed as a network of interacting currencies. We analyze daily time series of FX data for a set of 63 currencies, including gold, silver and platinum. We group together all the exchange rates with a common base currency and study each group separately. By applying the methods of filtered correlation matrix we identify clusters of closely related currencies. The clusters are formed typically according to the economical and geographical factors. We also study topology of weighted minimal spanning trees for different network representations (i.e., for different base currencies) and find that in a majority of representations the network has a hierarchical scale-free structure. In addition, we analyze the temporal evolution of the network and detect that its structure is not stable over time. A medium-term trend can be identified which affects the USD node by decreasing its centrality. Our analysis shows also an increasing role of euro in the world's currency market. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.0480v1.pdf"}
{"id": "0906.1686", "abstract": "  We examine particle entanglement, characterized by pseudo-spin squeezing, of spin-1 bosonic atoms with coupled ground states in a one-dimensional optical lattice. Both the superfluid and Mott-insulator phases are investigated separately for ferromagnetic and antiferromagnetic interactions. Mode entanglement is also discussed in the Mott insulating phase. The role of a small but nonzero angle between the polarization vectors of counter-propagating lasers forming the optical lattice on quantum correlations is investigated as well. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.1686v2.pdf"}
{"id": "0906.1747", "abstract": "  The discovery of high-T_c superconductivity in the pnictides, materials with a Fermi surface determined by several bands, highlights the need to understand how superconductivity arises in multiband systems. In this effort, using symmetry considerations and mean-field approximations, we discuss how strong hybridization among orbitals may lead to both intra and interband pairing, and we present calculations of the spectral functions to guide the experimental search for this kind of state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.1747v2.pdf"}
{"id": "0906.2365", "abstract": "  The observations of the total electronic component and the positron fraction in cosmic rays by the FERMI, HESS, ATIC, and PAMELA instruments are studied with analytical propagation models, both for a set of discrete sources and for a spatially smooth source distribution. The positron fraction over the entire energy range of  1-100 GeV is shown to fit with the nested leaky box model. We derive the spectrum of electrons in cosmic rays arising from direct acceleration by the sources and discuss the narrow spectral feature in the spectrum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.2365v1.pdf"}
{"id": "0906.3185", "abstract": "  We have developed a stellar wind model for OB supergiants to investigate the effects of accretion from a clumpy wind on the luminosity and variability properties of High Mass X-ray Binaries. Assuming that the clumps are confined by ram pressure of the ambient gas and exploring different distributions for their mass and radii, we computed the expected X-ray light curves in the framework of the Bondi-Hoyle accretion theory, modified to take into account the presence of clumps. The resulting variability properties are found to depend not only on the assumed orbital parameters but also on the wind characteristics. We have then applied this model to reproduce the X-ray light curves of three representative High Mass X-ray Binaries: two persistent supergiant systems (VelaX-1 and 4U1700-377) and the Supergiant Fast X-ray Transient IGRJ11215-5952. The model can reproduce well the observed light curves, but requiring in all cases an overall mass loss from the supergiant about a factor 3-10 smaller than the values inferred from UV lines studies that assume a homogeneous wind. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.3185v1.pdf"}
{"id": "0906.4230", "abstract": "  Some recent investigations of spectropolarimetric observations of the Zeeman effect in the Fe I lines at 630 nm carried out with the Hinode solar space telescope have concluded that the strength of the magnetic field vector in the internetwork regions of the quiet Sun is in the hG regime and that its inclination is predominantly horizontal. We critically reconsider the analysis of such observations and carry out a complete Bayesian analysis with the aim of extracting as much information as possible from them, including error bars. We apply the recently developed BayesME code that carries out a complete Bayesian inference for Milne-Eddington atmospheres. The sampling of the posterior distribution function is obtained with a Markov Chain Monte Carlo scheme and the marginal distributions are analyzed in detail. The Kullback-Leibler divergence is used to study the extent to which the observations introduce new information in the inference process resulting in sufficiently constrained parameters. Our analysis clearly shows that only upper limits to the magnetic field strength can be inferred with fields in the kG regime completely discarded. Furthermore, the noise level present in the analyzed Hinode observations induces a substantial loss of information for constraining the azimuth of the magnetic field. Concerning the inclination of the field, we demonstrate that some information is available to constrain it for those pixels with the largest polarimetric signal. The results also point out that the field in pixels with small polarimetric signals can be nicely reproduced in terms of a quasi-isotropic distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.4230v1.pdf"}
{"id": "0906.4448", "abstract": "  Spiral galaxies are studied using a simple global disc model as a means for approximate determination of mass profiles. Based on rotation curves and the amount of gas (HI+He), we find global surface mass densities consistent with measurements and compare them with B-band surface brightness profiles. As a result we obtain mass-to-light ratio profiles. We give some arguments for why our approach is reliable and sometimes better than those assuming ad hoc the presence of a massive non-baryonic dark matter halo. Using this model, we study galaxies NGC 7793, 1365, 6946 and UGC 6446. Based on a rotation curve from The HI Nearby Galaxy Survey (THINGS) we also study galaxy NGC 4536 and compare the results with those we published elsewhere for the same galaxy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.4448v3.pdf"}
{"id": "0907.0409", "abstract": "  Experiments measuring cosmic rays above an energy of 10^14 eV deduce the energy and mass of the primary cosmic ray particles from air-shower simulations. We investigate the importance of hadronic interactions at low and high energies on the distributions of muons and electrons in showers on ground. In air shower simulation programs, hadronic interactions below an energy threshold in the range from 80 GeV to 500 GeV are simulated by low energy interaction models, like Fluka or Gheisha, and above that energy by high energy interaction models, e.g. Sibyll or QGJSJet. We find that the impact on shower development obtained by switching the transition energy from 80 GeV to 500 GeV is comparable to the difference obtained by switching between Fluka and Gheisha. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.0409v1.pdf"}
{"id": "0907.0783", "abstract": "  We learn multiple hypotheses for related tasks under a latent hierarchical relationship between tasks. We exploit the intuition that for domain adaptation, we wish to share classifier structure, but for multitask learning, we wish to share covariance structure. Our hierarchical model is seen to subsume several previously proposed multitask learning models and performs well on three distinct real-world data sets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.0783v1.pdf"}
{"id": "0907.1012", "abstract": "  Ant Colony Optimization (ACO) has time complexity O(t*m*N*N), and its typical application is to solve Traveling Salesman Problem (TSP), where t, m, and N denotes the iteration number, number of ants, number of cities respectively. Cutting down running time is one of study focuses, and one way is to decrease parameter t and N, especially N. For this focus, the following method is presented in this paper. Firstly, design a novel clustering algorithm named Special Local Clustering algorithm (SLC), then apply it to classify all cities into compact classes, where compact class is the class that all cities in this class cluster tightly in a small region. Secondly, let ACO act on every class to get a local TSP route. Thirdly, all local TSP routes are jointed to form solution. Fourthly, the inaccuracy of solution caused by clustering is eliminated. Simulation shows that the presented method improves the running speed of ACO by 200 factors at least. And this high speed is benefit from two factors. One is that class has small size and parameter N is cut down. The route length at every iteration step is convergent when ACO acts on compact class. The other factor is that, using the convergence of route length as termination criterion of ACO and parameter t is cut down. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.1012v2.pdf"}
{"id": "0907.1040", "abstract": "  We present an analytical theory for the gate electrostatics and the classical and quantum capacitance of the graphene nanoribbons (GNRs) and compare it with the exact self-consistent numerical calculations based on the tight-binding p-orbital Hamiltonian within the Hartree approximation. We demonstrate that the analytical theory is in a good qualitative (and in some aspects quantitative) agreement with the exact calculations. There are however some important discrepancies. In order to understand the origin of these discrepancies we investigate the self-consistent electronic structure and charge density distribution in the nanoribbons and relate the above discrepancy to the inability of the simple electrostatic model to capture the classical gate electrostatics of the GNRs. In turn, the failure of the classical electrostatics is traced to the quantum mechanical effects leading to the significant modification of the self-consistent charge distribution in comparison to the non-interacting electron description. The role of electron-electron interaction in the electronic structure and the capacitance of the GNRs is discussed. Our exact numerical calculations show that the density distribution and the potential profile in the GNRs are qualitatively different from those in conventional split-gate quantum wires; at the same time, the electron distribution and the potential profile in the GNRs show qualitatively similar features to those in the cleaved-edge overgrown quantum wires. Finally, we discuss an experimental extraction of the quantum capacitance from experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.1040v1.pdf"}
{"id": "0907.1225", "abstract": "  We provide evidence that indicate the star cluster Pfleiderer 2, which is projected in a rich field, as a newly identified Galactic globular cluster. Since it is located in a crowded field, core extraction and decontamination tools were applied to reveal the cluster sequences in B, V and I Color-Magnitude Diagrams (CMDs). The main CMD features of Pfleiderer 2 are a tilted Red Giant Branch, and a red Horizontal Branch, indicating a high metallicity around solar. The reddening is E(B-V)=1.01. The globular cluster is located at a distance from the Sun d_⊙ = 16±2 kpc.   The cluster is located at 2.7 kpc above the Galactic plane and at a distance from the Galactic center of R_ GC=9.7 kpc, which is unusual for a metal-rich globular cluster. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.1225v1.pdf"}
{"id": "0907.2782", "abstract": "  The present knowledge of the structure of the photon is presented based on results obtained by measurements of photon structure functions at e+e- collider. Results are presented both for the QED structure of the photon as well as for the hadronic structure, where the data are also compared to recent parametrisations of the hadronic structure function F2gamma(x,Q^2). Prospects of future photon structure function measurements, especially at an International Linear Collider are outlined. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.2782v1.pdf"}
{"id": "0907.3041", "abstract": "  In quantum dots or molecules with vibrational degrees of freedom the electron-vibron coupling renormalizes the electronic charging energy. For sufficiently strong coupling, the renormalized charging energy can become negative. Here, we discuss an instability towards adding or removing an arbitrary number of electrons when the magnitude of the renormalized charging energy exceeds the single-particle level spacing. We show that the instability is regularized by the anharmonic contribution to the vibron energy. The resulting effective charging energy as a function of the electron number has a double-well structure causing a variety of novel features in the Coulomb blockade properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.3041v1.pdf"}
{"id": "0907.3251", "abstract": "  For random walks on networks (graphs), it is a theoretical challenge to explicitly determine the mean first-passage time (MFPT) between two nodes averaged over all pairs. In this paper, we study the MFPT of random walks in the famous T-graph, linking this important quantity to the resistance distance in electronic networks. We obtain an exact formula for the MFPT that is confirmed by extensive numerical calculations. The interesting quantity is derived through the recurrence relations resulting from the self-similar structure of the T-graph. The obtained closed-form expression exhibits that the MFPT approximately increases as a power-law function of the number of nodes, with the exponent lying between 1 and 2. Our research may shed light on the deeper understanding of random walks on the T-graph. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.3251v2.pdf"}
{"id": "0907.4446", "abstract": "  Erupting filaments are sometimes observed to undergo a rotation about the vertical direction as they rise. This rotation of the filament axis is generally interpreted as a conversion of twist into writhe in a kink-unstable magnetic flux rope. Consistent with this interpretation, the rotation is usually found to be clockwise (as viewed from above) if the post-eruption arcade has right-handed helicity, but counterclockwise if it has left-handed helicity. Here, we describe two non–active-region filament events recorded with the Extreme-Ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO), in which the sense of rotation appears to be opposite to that expected from the helicity of the post-event arcade. Based on these observations, we suggest that the rotation of the filament axis is in general determined by the net helicity of the erupting system, and that the axially aligned core of the filament can have the opposite helicity sign to the surrounding field. In most cases, the surrounding field provides the main contribution to the net helicity. In the events reported here, however, the helicity associated with the filament “barbs” is opposite in sign to and dominates that of the overlying arcade. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.4446v1.pdf"}
{"id": "0907.4721", "abstract": "  Purpose: Manipulation of the radio-sensitivity of the nucleotide-base driven by the spin blockade mechanism of diffusive free radicals against ionizing radiation.   Materials and methods: We theoretically propose a mechanism which uses the simultaneous application of circularly polarized light and an external magnetic field to control the polarization of the free radicals and create S=1 electron-hole spin excitations (excitons) on nucleotide-base. We deploy an ab-initio molecular dynamics model to calculate the characteristic parameters of the light needed for optical transitions.   Results: As a specific example, we present the numerical results calculated for a Guanine, in the presence of an OH free radical. To increase the radio-resistivity of this system, a blue light source for the optical pumping and induction of excitons on guanine can be used.   Conclusions: The effect of spin-injection on the formation of a free energy barrier in diffusion controlled chemical reaction pathways leads to the control of radiation-induced base damage. The proposed method allows us to manipulate and partially suppress the damage induced by ionizing radiation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.4721v1.pdf"}
{"id": "0908.0239", "abstract": "  The sort transform (ST) is a modification of the Burrows-Wheeler transform (BWT). Both transformations map an arbitrary word of length n to a pair consisting of a word of length n and an index between 1 and n. The BWT sorts all rotation conjugates of the input word, whereas the ST of order k only uses the first k letters for sorting all such conjugates. If two conjugates start with the same prefix of length k, then the indices of the rotations are used for tie-breaking. Both transforms output the sequence of the last letters of the sorted list and the index of the input within the sorted list. In this paper, we discuss a bijective variant of the BWT (due to Scott), proving its correctness and relations to other results due to Gessel and Reutenauer (1993) and Crochemore, Desarmenien, and Perrin (2005). Further, we present a novel bijective variant of the ST. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.0239v1.pdf"}
{"id": "0908.0502", "abstract": "  In the Minimal Supersymmetric Standard Model (MSSM) with three generations of fermions, there is a stringent upper bound on the mass of the lightest neutral Higgs h, and the mass of the charged Higgs H^+, must be close (within tens of GeV) to the heavier neutral Higgs, H, and the pseudoscalar Higgs A. In this Brief Report, we show that in the four generation MSSM, the upper bound on the h mass is much higher, as high as 400 GeV, and H^+ is generally much heavier than the A, allowing the H^+ -> A W^+ decay, potentially changing search strategies for both the charged Higgs and the pseudoscalar. The H mass, on the other hand, remains within tens of GeV of the charged Higgs mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.0502v2.pdf"}
{"id": "0908.1410", "abstract": "  Gamma-rays provide a powerful insight into the non-thermal universe and perhaps a unique probe for new physics beyond the standard model. Current experiments are already giving results in the physics of acceleration of cosmic rays in supernova remnants, pulsar and active galactic nuclei with almost a hundred sources detected at very-high-energies so far. Despite its relatively recent appearance, very high-energy gamma-ray astronomy has proven to have reached a mature technology with fast assembling, relatively cheap and reliable telescopes. The goal of future installation is to increase the sensitivity by a factor ten compared to current installations, and enlarge the energy domain from few tens of GeV to a hundred TeV. Gamma-ray spectra of astrophysical origin are rather soft thus hardly one single size telescope can cover more than 1.5 decades in energy, therefore an array of telescopes of 2,3 different sizes is required. Hereafter, we present design considerations for a Cherenkov Telescope Array (CTA), a project for a new generation of highly automated telescopes for gamma-ray astronomy. The status of the project, technical solutions and an insight in the involved physics will be presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.1410v1.pdf"}
{"id": "0908.1499", "abstract": "  The notion of q-grading on the enveloping algebra generated by products of q-deformed Heisenberg algebras is introduced for q complex number in the unit disc. Within this formulation, we consider the extension of the notion of supersymmetry in the enveloping algebra. We recover the ordinary ℤ_2 grading or Grassmann parity for associative superalgebra, and a modified version of the usual supersymmetry. As a specific problem, we focus on the interesting limit q→ -1 for which the Arik and Coon deformation of the Heisenberg algebra allows to map fermionic modes to bosonic ones in a modified sense. Different algebraic consequences are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.1499v1.pdf"}
{"id": "0908.2938", "abstract": "  A compact, quasi-4pi position sensitive silicon array, TIARA, designed to study direct reactions induced by radioactive beams in inverse kinematics is described here. The Transfer and Inelastic All-angle Reaction Array (TIARA) consists of 8 resistive charge division detectors forming an octagonal barrel around the target and a set of double-sided silicon-strip annular detectors positioned at each end of the barrel. The detector was coupled to the -ray array EXOGAM and the spectrometer VAMOS at the GANIL Laboratory to demonstrate the potential of such an apparatus with radioactive beams. The 14N(d,p)15N reaction, well known in direct kinematics, has been carried out in inverse kinematics for that purpose. The observation of the 15N ground state and excited states at 7.16 and 7.86 MeV is presented here as well as the comparison of the measured proton angular distributions with DWBA calculations. Transferred l-values are in very good agreement with both theoretical calculations and previous experimental results obtained in direct kinematics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.2938v2.pdf"}
{"id": "0908.4142", "abstract": "  An efficient implementation of the nonequilibrium Green function (NEGF) method combined with the density functional theory (DFT) using localized pseudo-atomic orbitals (PAOs) is presented for electronic transport calculations of a system connected with two leads under a finite bias voltage. In the implementation, accurate and efficient methods are developed especially for evaluation of the density matrix and treatment of boundaries between the scattering region and the leads. Equilibrium and nonequilibrium contributions in the density matrix are evaluated with very high precision by a contour integration with a continued fraction representation of the Fermi-Dirac function and by a simple quadratureon the real axis with a small imaginary part, respectively. The Hartree potential is computed efficiently by a combination of the two dimensional fast Fourier transform (FFT) and a finite difference method, and the charge density near the boundaries is constructed with a careful treatment to avoid the spurious scattering at the boundaries. The efficiency of the implementation is demonstrated by rapid convergence properties of the density matrix. In addition, as an illustration, our method is applied for zigzag graphene nanoribbons, a Fe/MgO/Fe tunneling junction, and a LaMnO_3/SrMnO_3 superlattice, demonstrating its applicability to a wide variety of systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.4142v1.pdf"}
{"id": "0908.4179", "abstract": "  We propose an algorithm for the reconstruction of the signal induced by cosmic strings in the cosmic microwave background (CMB), from radio-interferometric data at arcminute resolution. Radio interferometry provides incomplete and noisy Fourier measurements of the string signal, which exhibits sparse or compressible magnitude of the gradient due to the Kaiser-Stebbins (KS) effect. In this context the versatile framework of compressed sensing naturally applies for solving the corresponding inverse problem. Our algorithm notably takes advantage of a model of the prior statistical distribution of the signal fitted on the basis of realistic simulations. Enhanced performance relative to the standard CLEAN algorithm is demonstrated by simulated observations under noise conditions including primary and secondary CMB anisotropies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.4179v2.pdf"}
{"id": "0909.0213", "abstract": "  We perform kinetic Monte Carlo simulations of flow-induced nucleation in polymer melts with an algorithm that is tractable even at low undercooling. The configuration of the non-crystallized chains under flow is computed with a recent non-linear tube model. Our simulations predict both enhanced nucleation and the growth of shish-like elongated nuclei for sufficiently fast flows. The simulations predict several experimental phenomena and theoretically justify a previously empirical result for the flow-enhanced nucleation rate. The simulations are highly pertinent to both the fundamental understanding and process modeling of flow-induced crystallization in polymer melts. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.0213v1.pdf"}
{"id": "0909.0306", "abstract": "  A short gamma-ray burst GRB 090510 detected by Fermi shows an extra spectral component between 10 MeV and 30 GeV, an addition to a more usual low-energy (<10 MeV) Band component. In general, such an extra component could originate from accelerated protons. In particular, inverse Compton emission from secondary electron-positron pairs and proton synchrotron emission are competitive models for reproducing the hard spectrum of the extra component in GRB 090510. Here, using Monte Carlo simulations, we test the hadronic scenarios against the observed properties. To reproduce the extra component around GeV with these models, the proton injection isotropic-equivalent luminosity is required to be larger than 10^55 erg/s. Such large proton luminosities are a challenge for the hadronic models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.0306v2.pdf"}
{"id": "0909.0592", "abstract": "  Dynamical friction arises from the interaction of a perturber and the gravitational wake it excites in the ambient medium. This interaction is usually derived assuming that the perturber has a constant velocity. In realistic situations, motion is accelerated as for instance by dynamical friction itself. Here, we study the effect of acceleration on the dynamical friction force. We characterize the density enhancement associated with a constantly accelerating perturber with rectilinear motion in an infinite homogeneous gaseous medium and show that dynamical friction is not a local force and that its amplitude may depend on the perturber's initial velocity. The force on an accelerating perturber is maximal between Mach 1 and Mach 2, where it is smaller than the corresponding uniform motion friction. In the limit where the perturber's size is much smaller than the distance needed to change the Mach number by unity through acceleration, a subsonic perturber feels a force similar to uniform motion friction only if its past history does not include supersonic episodes. Once an accelerating perturber reaches large supersonic speeds, accelerated motion friction is marginally stronger than uniform motion friction. The force on a decelerating supersonic perturber is weaker than uniform motion friction as the velocity decreases to a few times the sound speed. Dynamical friction on a decelerating subsonic perturber with an initial Mach number larger than 2 is much larger than uniform motion friction and tends to a finite value as the velocity vanishes in contrast to uniform motion friction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.0592v2.pdf"}
{"id": "0909.0860", "abstract": "  We present a few–mode Galerkin model for convection in binary fluid layers subject to an approximation to realistic horizontal boundary conditions at positive separation ratios. The model exhibits convection patterns in form of rolls and squares. The stable squares at onset develop into stable rolls at higher thermal driving. In between, a regime of a so-called crossroll structure is found. The results of our few–mode model are in good agreement with both experiments and numerical multi–mode simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.0860v1.pdf"}
{"id": "0909.0904", "abstract": "  In this work we discuss a theory for entanglement generation, characterization and detection in fermionic two-particle interferometers at finite temperature. The motivation for our work is provided by the recent experiment by the Heiblum group, Neder et al, Nature 448, 333 (2007), realizing the two particle interferometer proposed by Samuelsson, Sukhorukov, and Buttiker, Phys. Rev. Lett. 92, 026805 (2004). The experiment displayed a clear two-particle Aharonov-Bohm effect, however with an amplitude suppressed due to finite temperature and dephasing. This raised qualitative as well quantitative questions about entanglement production and detection in mesoscopic conductors at finite temperature. As a response to these questions, in our recent work, Samuelsson, Neder, and Buttiker, Phys. Rev. Lett. 102, 106804 (2009) we presented a general theory for finite temperature entanglement in mesoscopic conductors. Applied to the two-particle interferometer we showed that the emitted two-particle state in the experiment was clearly entangled. Moreover, we demonstrated that the entanglement of the reduced two-particle state, reconstructed from measurements of average currents and current cross correlations, constitutes a lower bound to the entanglement of the emitted state. The present work provides an extended and more detailed discussion of these findings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.0904v1.pdf"}
{"id": "0909.2699", "abstract": "  We study the onset of patterns in vertically oscillated layers of frictionless dissipative particles. Using both numerical solutions of continuum equations to Navier-Stokes order and molecular dynamics (MD) simulations, we find that standing waves form stripe patterns above a critical acceleration of the cell. Changing the frequency of oscillation of the cell changes the wavelength of the resulting pattern; MD and continuum simulations both yield wavelengths in accord with previous experimental results. The value of the critical acceleration for ordered standing waves is approximately 10", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.2699v1.pdf"}
{"id": "0909.3592", "abstract": "  We report on our theoretical investigation considering the widths of quantized Hall plateaus (QHPs) depending on the density asymmetry induced by the large current within the out-of-linear response regime. We solve the Schrodinger equation within the Hartree type mean field approximation using Thomas Fermi Poisson nonlinear screening theory. We observe that the two dimensional electron system splits into compressible and incompressible regions for certain magnetic field intervals, where the Hall resistance is quantized and the longitudinal resistance vanishes, if an external current is imposed. We found that the strong current imposed, induces an asymmetry on the IS width depending linearly on the current intensity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.3592v2.pdf"}
{"id": "0909.3986", "abstract": "  Recently, Horava proposed a power counting renormalizable theory for (3+1)-dimensional quantum gravity, which reduces to Einstein gravity with a non-vanishing cosmological constant in IR, but possesses improved UV behaviors. In this work, we analyze the stability of the Einstein static universe by considering linear homogeneous perturbations in the context of an IR modification of Horava gravity, which implies a `soft' breaking of the `detailed balance' condition. The stability regions of the Einstein static universe are parameterized by the linear equation of state parameter w=p/ρand the parameters appearing in the Horava theory, and it is shown that a large class of stable solutions exists in the respective parameter space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.3986v2.pdf"}
{"id": "0909.4394", "abstract": "  A pair of two-level systems initially prepared in different thermal states and coupled to an external reversible work source, do not in general reach a common temperature at the end of a unitary work extraction process. We define an effective temperature for the final nonequilibrium but passive state of the bipartite quantum system and analyse its properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.4394v1.pdf"}
{"id": "0909.4928", "abstract": "  We discuss the origin of the runaway early B-type star HD271791 and show that its extremely high velocity (≃530-920 km/s) cannot be explained within the framework of the binary-supernova ejection scenario. Instead, we suggest that HD271791 attained its peculiar velocity in the course of a strong dynamical encounter between two hard massive binaries or via an exchange encounter between a hard massive binary and a very massive star, formed through runaway mergers of ordinary massive stars in the dense core of a young massive star cluster. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.4928v1.pdf"}
{"id": "0909.5317", "abstract": "  We calculate the transmission of electrons and holes between two normal-metal electrodes (N), separated over a distance L by an impurity-free superconductor (S) with d-wave symmetry of the order parameter. Nodal lines of vanishing excitation gap form ballistic conduction channels for coupled electron-hole excitations, described by an anisotropic two-dimensional Dirac equation. We find that the transmitted electrical and thermal currents, at zero energy, both have the pseudodiffusive 1/L scaling characteristic of massless Dirac fermions - regardless of the presence of tunnel barriers at the NS interfaces. Tunnel barriers reduce the slope of the 1/L scaling in the case of the electrical current, while leaving the thermal current unaffected. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.5317v1.pdf"}
{"id": "0909.5469", "abstract": "  The full Super-Kamiokande-III data-taking period, which ran from August of 2006 through August of 2008, yielded 298 live days worth of solar neutrino data with a lower total energy threshold of 4.5 MeV. During this period we made many improvements to the experiment's hardware and software, with particular emphasis on its water purification system and Monte Carlo simulations. As a result of these efforts, we have significantly reduced the low energy backgrounds as compared to earlier periods of detector operation, cut the systematic errors by nearly a factor of two, and achieved a 4.5 MeV energy threshold for the solar neutrino analysis. In this presentation, I will present the preliminary SK-III solar neutrino measurement results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.5469v4.pdf"}
{"id": "0909.5525", "abstract": "  We show that, under rather general assumptions, the phase diagram of a quasi-one-dimensional repulsive Fermi system consists of two ordered phases: the density wave, spin or charge, and the superconductivity. It is demonstrated that the symmetry of the superconducting order parameter is a non-universal property sensitive to microscopic details of the model. Three potentially stable superconducting states are identified: they are triplet f-wave, singlet d_x^2-y^2-wave, and d_xy-wave. Presence of multiple competing superconducting states implies that for a real material this symmetry is difficult to predict theoretically and hard to probe experimentally, since artifacts of theoretical approximations or variations in experimental conditions could tip the balance between the superconducting phases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.5525v1.pdf"}
{"id": "0910.0026", "abstract": "  Starting from the second law of thermodynamics applied to an isolated system consisting of the system surrounded by an extremely large medium, we formulate a general non-equilibrium thermodynamic description of the system when it is out of equilibrium. We then apply it to study the structural relaxation in glasses and establish the phenomenology behind the concept of the fictive temperature and of the empirical Tool-Narayanaswamy equation on firmer theoretical foundation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.0026v1.pdf"}
{"id": "0910.0426", "abstract": "  We consider lattice gas diffusive dynamics with creation-annihilation in the bulk and maintained out of equilibrium by two reservoirs at the boundaries. This stochastic particle system can be viewed as a toy model for granular gases where the energy is injected at the boundary and dissipated in the bulk. The large deviation functional for the particle currents flowing through the system is computed and some physical consequences are discussed: the mechanism for local current fluctuations, dynamical phase transitions, the fluctuation-relation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.0426v1.pdf"}
{"id": "0910.0847", "abstract": "  The ATLAS pixel detector is the innermost detector of the ATLAS experiment at the Large Hadron Collider at CERN. With approximately 80 million readout channels, the ATLAS silicon pixel detector is a high-acceptance, high-resolution, low-noise tracking device. Providing the desired refinement in charged track pattern recognition capability in order to meet the stringent track reconstruction requirements, the pixel detector largely defines the ability of ATLAS to effectively resolve primary and secondary vertices and perform efficient flavor tagging essential for discovery of new physics.   Being the last sub-system installed in ATLAS by July 2007, the pixel detector was successfully connected, commissioned, and tested in situ while meeting an extremely tight schedule, and was ready to take data upon the projected turn-on of the LHC. Since fall 2008, the pixel detector has been included in the combined ATLAS detector operation, collecting cosmic muon data. Details from the pixel detector installation and commissioning, as well as details on calibration procedures and the results obtained with collected cosmic data, are presented along with a summary of the detector status. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.0847v3.pdf"}
{"id": "0910.0964", "abstract": "  Grover's algorithm for quantum search can also be applied to classical energy transfer. The procedure takes a system in which the total energy is equally distributed among N subsystems and transfers most of the it to one marked subsystem. We show that in a relativistic setting the efficiency of this procedure can be improved. We will consider the transfer of relativistic kinetic energy in a series of elastic collisions. In this case, the number of steps of the energy transfer procedure approaches 1 as the initial velocities of the objects become closer to the speed of light. This is a consequence of introducing non-linearities in the procedure. However, the maximum attainable transfer will depend on the particular combination of speed and number of objects. In the procedure, we will use N elements, like in the classical case, instead of the log_2(N) states of the quantum algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.0964v1.pdf"}
{"id": "0910.1024", "abstract": "  A proof that continuous time quantum walks are universal for quantum computation, using unweighted graphs of low degree, has recently been presented by Childs [PRL 102 180501 (2009)]. We present a version based instead on the discrete time quantum walk. We show the discrete time quantum walk is able to implement the same universal gate set and thus both discrete and continuous time quantum walks are computational primitives. Additionally we give a set of components on which the discrete time quantum walk provides perfect state transfer. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.1024v3.pdf"}
{"id": "0910.1062", "abstract": "  We study the emergence and dynamics of pointer states in the motion of a quantum test particle affected by collisional decoherence. These environmentally distinguished states are shown to be exponentially localized solitonic wave functions which evolve according to the classical equations of motion. We explain their formation using the orthogonal unraveling of the master equation, and we demonstrate that the statistical weights of the arising mixture are given by projections of the initial state onto the pointer basis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.1062v2.pdf"}
{"id": "0910.1530", "abstract": "  We discuss convergence and coupling of Markov chains, and present general relations between the transfer matrices describing these two processes. We then analyze a recently developed local-patch algorithm, which computes rigorous upper bound for the coupling time of a Markov chain for non-trivial statistical-mechanics models. Using the coupling from the past protocol, this allows one to exactly sample the underlying equilibrium distribution. For spin glasses in two and three spatial dimensions, the local-patch algorithm works at lower temperatures than previous exact-sampling methods. We discuss variants of the algorithm which might allow one to reach, in three dimensions, the spin-glass transition temperature. The algorithm can be adapted to hard-sphere models. For two-dimensional hard disks, the algorithm allows us to draw exact samples at higher densities than previously possible. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.1530v1.pdf"}
{"id": "0910.1646", "abstract": "  A unified treatment of mass varying dark matter coupled to cosmon-like dark energy is shown to result in effective generalized Chaplygin gas (GCG) scenarios. The mass varying mechanism is treated as a cosmon field inherent effect. Coupling dark matter with dark energy allows for reproducing the conditions for the present cosmic acceleration and for recovering the stability resulted from a positive squared speed of sound c_s^, as in the GCG scenario. The scalar field mediates the nontrivial coupling between the dark matter sector and the sector responsible for the accelerated expansion of the universe. The equation of state of perturbations is the same as that of the background cosmology so that all the effective results from the GCG paradigm are maintained. Our results suggest the mass varying mechanism, when obtained from an exactly soluble field theory, as the right responsible for the stability issue and for the cosmic acceleration of the universe. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.1646v2.pdf"}
{"id": "0910.2333", "abstract": "  We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. The field equations admit two types of singularities, and their local asymptotic structure is investigated. One of these singularities is found to develop, as a spacelike singularity, inside the black hole. We then study the internal structure of the evaporating black hole from the horizon to the singularity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.2333v2.pdf"}
{"id": "0910.2450", "abstract": "  Antiferromagnetism of ultracold fermions in an optical lattice can be detected by Bragg diffraction of light, in analogy to the diffraction of neutrons from solid state materials. A finite sublattice magnetization will lead to a Bragg peak from the (1/2 1/2 1/2) crystal plane with an intensity depending on details of the atomic states, the frequency and polarization of the probe beam, the direction and magnitude of the sublattice magnetization, and the finite optical density of the sample. Accounting for these effects we make quantitative predictions about the scattering intensity and find that with experimentally feasible parameters the signal can be readily measured with a CCD camera or a photodiode and used to detect antiferromagnetic order. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.2450v1.pdf"}
{"id": "0910.2637", "abstract": "  In microfluidics, varying wetting properties, expressed in terms of the local slip length, can be used to influence the flow of a liquid through a device. We study flow past surfaces on which the slip length is modulated in stripes. We find that the effective slip length for such a flow can be expressed as a function of the individual slip lengths on the stripes. The angle dependence of the effective slip is in excellent agreement with a recent theory describing the slip length as a tensorial quantity. This tensorial nature allows to induce a transverse flow, which can be used in micro mixers to drive a vortex. In our simulations of a flow through a square channel with patterned surfaces we see a homogeneous rotation about the direction of the flow. We investigate the influence of patterns of cosine shaped varying local slip on the flow field depending on the orientation of the pattern and find the largest effective slip length for periods of stripes parallel to the flow direction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.2637v2.pdf"}
{"id": "0910.3200", "abstract": "  Quantum cosmology offers a unique stage to address questions of time related to its underlying (and perhaps truly quantum dynamical) meaning as well as its origin. Some of these issues can be analyzed with a general scheme of quantum cosmology, others are best seen in loop quantum cosmology. The latter's status is still incomplete, and so no full scenario has yet emerged. Nevertheless, using properties that have a potential of pervading more complicated and realistic models, a vague picture shall be sketched here. It suggests the possibility of deriving a beginning within a beginningless theory, by applying cosmic forgetfulness to an early history of the universe. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.3200v1.pdf"}
{"id": "0910.3230", "abstract": "  A new class of solutions to the coupled, spherically symmetric Einstein-Maxwell equations for a compact material source is constructed. Some of these solutions can be made to satisfy a number of requirements for being physically relevant, including having a causal speed of sound. In the case of vanishing charge these solutions reduce to those found by Bayin and Tolman. Only the latter can be considered as having physically realistic properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.3230v1.pdf"}
{"id": "0910.3250", "abstract": "  An accurate geometric distortion solution for the Hubble Space Telescope UVIS-channel of Wide Field Camera 3 is the first step towards its use for high precision astrometry. In this work we present an average correction that enables a relative astrometric accuracy of  1 mas (in each axis for well exposed stars) in three broad-band ultraviolet filters (F225W, F275W, and F336W). More data and a better understanding of the instrument are required to constrain the solution to a higher level of accuracy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.3250v1.pdf"}
{"id": "0910.3435", "abstract": "  We provide an analytical description of the dynamics of an atom in an optical lattice using the method of perturbative adiabatic expansion. A precise understanding of the lattice-atom interaction is essential to taking full advantage of the promising applications that optical lattices offer in the field of atom interferometry. One such application is the implementation of Large Momentum Transfer (LMT) beam splitters that can potentially provide multiple order of magnitude increases in momentum space separations over current technology. We also propose interferometer geometries where optical lattices are used as waveguides for the atoms throughout the duration of the interferometer sequence. Such a technique could simultaneously provide a multiple order of magnitude increase in sensitivity and a multiple order of magnitude decrease in interferometer size for many applications as compared to current state-of-the-art atom interferometers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.3435v2.pdf"}
{"id": "0910.4017", "abstract": "  We present strong arguments that the deep structure of the quantum vacuum contains a web of microscopic wormholes or short-cuts. We develop the concept of wormhole spaces and show that this web of wormholes generate a peculiar array of long-range correlations in the patterns of vacuum fluctuations on the Planck scale. We conclude that this translocal structure represents the common cause for both the BH-entropy-area law, the more general holographic principle and the entanglement phenomena in quantum theory. In so far our approach exhibits a common structure which underlies both gravity and quantum theory on a microscopic scale. A central place in our analysis is occupied by a quantitative derivation of the distribution laws of microscopic wormholes in the quantum vacuum. This makes it possible to address a number of open questions and controversial topics in the field of quantum gravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.4017v1.pdf"}
{"id": "0910.4693", "abstract": "  In the context of Born-Infeld determinantal gravity formulated in a n-dimensional spacetime with absolute parallelism, we found an exact 3-dimensional vacuum circular symmetric solution without cosmological constant consisting in a rotating spacetime with non singular behavior. The space behaves at infinity as the conical geometry typical of 3-dimensional General Relativity without cosmological constant. However, the solution has no conical singularity because the space ends at a minimal circle that no freely falling particle can ever reach in a finite proper time. The space is curved, but no divergences happen since the curvature invariants vanish at both asymptotic limits. Remarkably, this very mechanism also forbids the existence of closed timelike curves in such a spacetime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.4693v2.pdf"}
{"id": "0910.5643", "abstract": "  In this paper we study the optimal placement and optimal number of active relay nodes through the traffic density in mobile sensor ad-hoc networks. We consider a setting in which a set of mobile sensor sources is creating data and a set of mobile sensor destinations receiving that data. We make the assumption that the network is massively dense, i.e., there are so many sources, destinations, and relay nodes, that it is best to describe the network in terms of macroscopic parameters, such as their spatial density, rather than in terms of microscopic parameters, such as their individual placements.   We focus on a particular physical layer model that is characterized by the following assumptions: i) the nodes must only transport the data from the sources to the destinations, and do not need to sense the data at the sources, or deliver them at the destinations once the data arrive at their physical locations, and ii) the nodes have limited bandwidth available to them, but they use it optimally to locally achieve the network capacity.   In this setting, the optimal distribution of nodes induces a traffic density that resembles the electric displacement that will be created if we substitute the sources and destinations with positive and negative charges respectively. The analogy between the two settings is very tight and have a direct interpretation in wireless sensor networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.5643v1.pdf"}
{"id": "0911.1008", "abstract": "  This paper presents a novel framework for track fitting which is usable in a wide range of experiments, independent of the specific event topology, detector setup, or magnetic field arrangement. This goal is achieved through a completely modular design. Fitting algorithms are implemented as interchangeable modules. At present, the framework contains a validated Kalman filter. Track parameterizations and the routines required to extrapolate the track parameters and their covariance matrices through the experiment are also implemented as interchangeable modules. Different track parameterizations and extrapolation routines can be used simultaneously for fitting of the same physical track. Representations of detector hits are the third modular ingredient to the framework. The hit dimensionality and orientation of planar tracking detectors are not restricted. Tracking information from detectors which do not measure the passage of particles in a fixed physical detector plane, e.g. drift chambers or TPCs, is used without any simplifications. The concept is implemented in a light-weight C++ library called GENFIT, which is available as free software. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.1008v3.pdf"}
{"id": "0911.1134", "abstract": "  If SUSY provides a solution to the hierarchy problem then supersymmetric states should not be too heavy. This requirement is quantified by a fine tuning measure that provides a quantitative test of SUSY as a solution to the hierarchy problem. The measure is useful in correlating the impact of the various experimental measurements relevant to the search for supersymmetry and also in identifying the most sensitive measurements for testing SUSY. In this paper we apply the measure to the CMSSM, computing it to two-loop order and taking account of current experimental limits and the constraint on dark matter abundance. Using this we determine the present limits on the CMSSM parameter space and identify the measurements at the LHC that are most significant in covering the remaining parameter space. Without imposing the LEP Higgs mass bound we show that the smallest fine tuning (1:13) consistent with a relic density within the WMAP bound corresponds to a Higgs mass of 114±2 GeV. Fine tuning rises rapidly for heavier Higgs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.1134v2.pdf"}
{"id": "0911.1170", "abstract": "  This paper gives a summary of the author's works concerning the emergent general relativity in a particular class of tensor models, which possess Gaussian classical solutions. In general, a classical solution in a tensor model may be physically regarded as a background space, and small fluctuations about the solution as emergent fields on the space. The numerical analyses of the tensor models possessing Gaussian classical background solutions have shown that the low-lying long-wavelength fluctuations around the backgrounds are in one-to-one correspondence with the geometric fluctuations on flat spaces in the general relativity. It has also been shown that part of the orthogonal symmetry of the tensor model spontaneously broken by the backgrounds can be identified with the local translation symmetry of the general relativity. Thus the tensor model provides an interesting model of simultaneous emergence of space, the general relativity, and its local gauge symmetry of translation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.1170v1.pdf"}
{"id": "0911.1302", "abstract": "  We study a sudden interaction quench in the weak-coupling regime of the quantum sine-Gordon model. The real time dynamics of the bosonic mode occupation numbers is calculated using the flow equation method. While we cannot prove results for the asymptotic long time limit, we can establish the existence of an extended regime in time where the mode occupation numbers relax to twice their equilibrium values. This factor two indicates a non-equilibrium distribution and is a universal feature of weak interaction quenches. The weak-coupling quantum sine-Gordon model therefore turns out to be on the borderline between thermalization and non-thermalization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.1302v2.pdf"}
{"id": "0911.2335", "abstract": "  We study the collective excitation of a gas of highly excited atoms confined to a large spacing ring lattice, where the ground and the excited states are coupled resonantly via a laser field. Our attention is focused on the regime where the interaction between the highly excited atoms is very weak in comparison to the Rabi frequency of the laser. We demonstrate that in this case the many-body excitations of the system can be expressed in terms of free spinless fermions. The complex many-particle states arising in this regime are characterized and their properties, e.g. their correlation functions, are studied. In addition we investigate how one can actually experimentally access some of these many-particle states by a temporal variation of the laser parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2335v1.pdf"}
{"id": "0911.2468", "abstract": "  We analyse the potential migration of massive planets forming far away from an inner planetary system. For this, we follow the dynamical evolution of the orbital elements of a massive planet undergoing a dissipative process with a gas disc centred around the central sun. We use a new method for post-Newtonian, high-precision integration of planetary systems containing a central sun by splitting the forces on a particle between a dominant central force and additional perturbations. In this treatment, which allows us to integrate with a very high-accuracy close encounters, all gravitational forces are integrated directly, without resorting to any simplifying approach. After traversing the disc a number of times, the planet is finally trapped into the disc with a non-negligible eccentricity ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2468v1.pdf"}
{"id": "0911.2488", "abstract": "  Klein-Gordon and Dirac equations are the motion equations for relativistic particles with spin 0 (so-called scalar particles) and 1/2 (electron/positron) respectively. For a free particle, the Dirac equation is derived from the Klein-Gordon equation by taking its square root in a bi-quaternionic formalism fully justified by the first principles of the scale relativity theory. This is no more true when an external electro-magnetic field comes into play. If one tries to derive the electro-magnetic Dirac equation in a manner analogous to the one used when this field is absent, one obtains an additional term which is the relativistic analogue of the spin-magnetic field coupling term encountered in the Pauli equation, valid for a non-relativistic particle with spin 1/2. There is however a method to recover the standard form of the electro-magnetic Dirac equation, with no additional term, which amounts modifying the way both covariances involved here, quantum and scale, are implemented. Without going into technical details, it will be shown how these results suggest this last method is based on more profound roots of the scale relativity theory since it encompasses naturally the spin-charge coupling. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2488v1.pdf"}
{"id": "0911.2615", "abstract": "  The solid-liquid interface free energy γsl is a key parameter controlling nucleation and growth during solidification and other phenomena. There are intrinsic difficulties in obtaining accurate experimental values, and the previous approaches to compute γsl with atomistic simulations are computationally demanding. We propose a new approach, which is to obtain γsl from a free energy map of the phase transition reconstructed by metadynamics. We apply this to the benchmark case of a Lennard-Jones potential and the results confirm the most reliable data obtained previously. We demonstrate several advantages of our new approach: it is simple to implement, robust and free of hysteresis problems, it allows a rigorous and unbiased estimate of the statistical uncertainty and it returns a good estimate of of the thermodynamic limit with system sizes of a just a few hundred atoms. It is therefore attractive for using with more realistic and specific models of interatomic forces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2615v3.pdf"}
{"id": "0911.2652", "abstract": "  An artificial neural network (ANN) is investigated as a tool for estimating rate coefficients for the collisional excitation of molecules. The performance of such a tool can be evaluated by testing it on a dataset of collisionally-induced transitions for which rate coefficients are already known: the network is trained on a subset of that dataset and tested on the remainder. Results obtained by this method are typically accurate to within a factor   2.1 (median value) for transitions with low excitation rates and   1.7 for those with medium or high excitation rates, although 4", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2652v1.pdf"}
{"id": "0911.2700", "abstract": "  We make an inventory of the baryonic and gravitating mass in structures ranging from the smallest galaxies to rich clusters of galaxies. We find that the fraction of baryons converted to stars reaches a maximum between M500 = 1E12 and 1E13 Msun, suggesting that star formation is most efficient in bright galaxies in groups. The fraction of baryons detected in all forms deviates monotonically from the cosmic baryon fraction as a function of mass. On the largest scales of clusters, most of the expected baryons are detected, while in the smallest dwarf galaxies, fewer than 1", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2700v1.pdf"}
{"id": "0911.2838", "abstract": "  The statefinder diagnosic is a useful method for distinguishing different dark energy models. In this paper, we investigate the new agegraphic dark energy model with interaction between dark energy and matter component by using statefinder parameter pair {r, s} and study its cosmological evolution. We plot the trajectories of the new agegraphic dark energy model for different interaction cases in the statefinder plane. As a result, the influence of the interaction on the evolution of the universe is shown in the statefinder diagrams. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2838v2.pdf"}
{"id": "0911.2997", "abstract": "  By means of a semiclassical analysis we show that the trace anomaly does not affect the cosmological constant. We calculate the evolution of the Hubble parameter in quasi de Sitter spacetime, where the Hubble parameter varies slowly in time, and in FLRW spacetimes. We show dynamically that a Universe consisting of matter with a constant equation of state, a cosmological constant and the quantum trace anomaly evolves either to the classical de Sitter attractor or to a quantum trace anomaly driven one. There is no dynamical effect that influences the effective value of the cosmological constant. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2997v1.pdf"}
{"id": "0911.3854", "abstract": "  We consider the Casimir interaction between a ferromagnetic and a non-magnetic mirror, and show how the Casimir effect gives rise to a magnetic anisotropy in the ferromagnetic layer. The anisotropy is out-of-plane if the non-magnetic plate is optically isotropic. If the non-magnetic plate shows a uniaxial optical anisotropy (with optical axis in the plate plane), we find an in-plane magnetic anisotropy. In both cases, the energetically most favorable magnetization orientation is given by the competition between polar, longitudinal and transverse contributions to the magneto-optical Kerr effect, and will therefore depend on the interplate distance. Numerical results will be presented for a magnetic plate made out of iron, and non-magnetic plates of gold (optically isotropic), quartz, calcite and barium titanate (all uniaxially birefringent). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.3854v1.pdf"}
{"id": "0911.4430", "abstract": "  The framed little 2-discs operad is homotopy equivalent to the Kimura-Stasheff-Voronov cyclic operad of moduli spaces of genus zero stable curves with tangent rays at the marked points and nodes. We show that this cyclic operad is formal, meaning that its chains and its homology (the Batalin-Vilkovisky operad) are quasi-isomorphic cyclic operads. To prove this we introduce a new complex of graphs in which the differential is a combination of edge deletion and contraction, and we show that this complex resolves BV as a cyclic operad. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.4430v2.pdf"}
{"id": "0911.4577", "abstract": "  We have proposed a new minimal extension of the Standard Model with a heavy Majorana fermion triplet(Σ) and an extra scalar doublet(η) so that the seesaw mechanism is radiative and can be accessible at upcoming accelerators. The origin of neutrino mass via the famous seesaw mechanism through the heavy Majorana fermion triplet has been discussed. We have proposed a mechanism of leptogenesis by the decay of the lightest neutral component of the fermion triplet into a Standard Model lepton doublet and an extra Higgs doublet. The important thing is that the leptogenesis scenario discussed in this letter can be of TeV scale and hence can be testable at Large Hadron Collider(LHC). We have also discussed a possible dark matter scenario in our model and the possible phenomenology of the fermion field Σ. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.4577v2.pdf"}
{"id": "0911.5153", "abstract": "  Towards employing low complexity transceivers for signal reception in Ultra-Wideband (UWB) systems, Transmitted Reference (TR) and Differential TR (DTR) schemes have attracted researchers attention. In this letter, we introduce an alternative, less complex scheme, called Self Reference (SR) UWB transceiver, which uses a modified replica of the received signal itself as reference pulse, resulting in double data rates compared to TR schemes. Moreover, SR eliminates the need for delay lines at the receiver side, which constitute a major drawback of the conventional TR and DTR schemes, while it also requires no channel estimations, resulting in lower complexity implementations and power savings. The performance of the SR scheme is investigated in high-frequency (HF) channels, showing that it offers a better or comparable performance to that of DTR, depending on the channel conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.5153v5.pdf"}
{"id": "0911.5185", "abstract": "  We propose a way of generating optical lattices embedded in photonic crystals. By setting up extended modes in photonic crystals, ultracold atoms can be mounted in different types of field intensity distributions. This novel way of constructing optical lattices can be used to produce more elaborate periodic potentials by manufacturing appropriate geometries of photonic crystals. We exemplify this with a square lattice and comment on the possibility of using geometries with defects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.5185v1.pdf"}
{"id": "0912.2939", "abstract": "  We model the light-curves from radiation-driven clouds near an accreting black hole. Taking into account the multiple images due to strong gravitational lensing, we find that sharp spikes can significantly enhance the observed flux. Following our previous work (Horak     Karas 2006a,b) we assume that scattering of ambient light takes place in a cloud that is in radial motion under a combined influence of black hole gravity and the radiation field. The retro-lensed photons give rise to peaks in the observed signal that follow with a characteristic time lag after the direct-image photons. Duration of these features is very short and the predicted polarization varies abruptly on the time-scale comparable with the light-crossing time of the system – a signature of the photon orbit. We also consider the polarization properties of scattered light. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.2939v2.pdf"}
{"id": "0912.3254", "abstract": "  The time evolution of magnons subject to a time-dependent microwave field is usually described within the so-called \"S-theory\", where kinetic equations for the distribution function are obtained within the time-dependent Hartree-Fock approximation. To explain the recent observation of \"Bose-Einstein condensation of magnons\" in an external microwave field [Demokritov et al., Nature 443, 430 (2006)], we extend the \"S-theory\" to include the Gross-Pitaevskii equation for the time-dependent expectation values of the magnon creation and annihilation operators. We explicitly solve the resulting coupled equations within a simple approximation where only a single condensed mode is retained. We also re-examine the usual derivation of an effective boson model from a realistic spin model for yttrium-iron garnet films and argue that in the parallel pumping geometry (where both the static and the time-dependent magnetic field are parallel to the macroscopic magnetization) the time-dependent Zeemann energy cannot give rise to magnon condensation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.3254v2.pdf"}
{"id": "0912.3828", "abstract": "  The Galactic Center region is expected to host the largest density of Dark Matter (DM) particles within the Milky Way. Then a relatively large gamma-ray signal would be expected from the possible DM particles annihilation (or decay). We are searching for the DM gamma-ray signal from the Galactic Center, which is also rich in bright discrete gamma-ray sources. Furthermore intense diffuse gamma-ray emission due to cosmic-ray interactions with interstellar gas and radiation is detected from the same direction. A preliminary analysis of the data, taken during the first 11 months of the Fermi satellite operations, is reported. The diffuse gamma-ray backgrounds and discrete sources, as we know them today, can account for the large majority of the detected gamma-ray emission from the Galactic Center. Nevertheless a residual emission is left, not accounted for by the above models. An improved model of the Galactic diffuse emission and a careful evaluation of new (possibly unresolved) sources (or source populations) will improve the sensitivity for a DM search. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.3828v1.pdf"}
{"id": "0912.3850", "abstract": "  Radio galaxies are the only non-blazar AGN detected in the VHE (E > 100 GeV) band. These objects enable the investigation of the main substructures of the AGN, in particular the core, the jet and its interaction with the intergalactic environment. VERITAS observations have included exposures on a number of radio galaxies. Recently, the discovery by Fermi of GeV emission from the radio galaxy NGC 1275 triggered VERITAS observations of this source. Results from the VERITAS observations of radio galaxies and future plans are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.3850v1.pdf"}
{"id": "0912.4469", "abstract": "  In this work it is studied the Hopfield fermionic spin glass model which allows interpolating from trivial randomness to a highly frustrated regime. Therefore, it is possible to investigate whether or not frustration is an essential ingredient which would allow this magnetic disordered model to present naturally inverse freezing by comparing the two limits, trivial randomness and highly frustrated regime and how different levels of frustration could affect such unconventional phase transition. The problem is expressed in the path integral formalism where the spin operators are represented by bilinear combinations of Grassmann variables. The Grand Canonical Potential is obtained within the static approximation and one-step replica symmetry breaking scheme. As a result, phase diagrams temperature versus the chemical potential are obtained for several levels of frustration. Particularly, when the level of frustration is diminished, the reentrance related to the inverse freezing is gradually suppressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.4469v2.pdf"}
{"id": "0912.4801", "abstract": "  Bianchi type V string cosmological models with bulk viscosity for massive string are investigated. The bulk viscosity is assumed to vary with time in such a manner that it is related to simple power function of the energy density. Using generation technique (Camci et al., 2001), it is shown that Einstein's field equations are solvable for any arbitrary cosmic scale function. Solution for particular form of cosmic scale functions are also obtained. It is found that solutions based on generation technique are relevant to the observational results. Some physical and geometrical aspect of the models are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.4801v2.pdf"}
{"id": "0912.5139", "abstract": "  For scalar and electromagnetic fields we evaluate the vacuum expectation value of the energy-momentum tensor induced by a curved boundary in the Robertson–Walker spacetime with negative spatial curvature. In order to generate the vacuum densities we use the conformal relation between the Robertson-Walker and Rindler spacetimes and the corresponding results for a plate moving by uniform proper acceleration through the Fulling–Rindler vacuum. For the general case of the scale factor the vacuum energy-momentum tensor is presented as the sum of the boundary free and boundary induced parts. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.5139v1.pdf"}
{"id": "1001.0106", "abstract": "  The structural profiles and electronic properties of pentacene (C_22H_14) multilayers on Ag(111) surface has been studied within the density functional theory (DFT) framework. We have performed first-principle total energy calculations based on the projector augmented wave (PAW) method to investigate the initial growth patterns of pentacene (Pn) on Ag(111) surface. In its bulk phase, pentacene crystallizes with a triclinic symmetry while a thin film phase having an orthorhombic unit cell is energetically less favorable by 0.12 eV/cell. Pentacene prefers to stay planar on Ag(111) surface and aligns perfectly along silver rows without any molecular deformation at a height of 3.9 Å. At one monolayer (ML) coverage the separation between the molecular layer and the surface plane extends to 4.1 Å due to intermolecular interactions weakening surface–pentacene attraction. While the first ML remains flat, the molecules on a second full pentacene layer deposited on the surface rearrange so that they become skewed with respect to each other. This adsorption mode is energetically more preferable than the one for which the molecules form a flat pentacene layer by an energy difference similar to that obtained for bulk and thin film phases. Moreover, as new layers added, pentacenes assemble to maintain this tilting for 3 and 4 ML similar to its bulk phase while the contact layer always remains planar. Therefore, our calculations indicate bulk-like initial stages for the growth pattern. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.0106v1.pdf"}
{"id": "1001.0256", "abstract": "  The Kepler Mission seeks to detect Earth-size planets transiting solar-like stars in its  115 deg^2 field of view over the course of its 3.5 year primary mission by monitoring the brightness of each of  156,000 Long Cadence stellar targets with a time resolution of 29.4 minutes. We discuss the photometric precision achieved on timescales relevant to transit detection for data obtained in the 33.5-day long Quarter 1 (Q1) observations that ended 2009 June 15. The lower envelope of the photometric precision obtained at various timescales is consistent with expected random noise sources, indicating that Kepler has the capability to fulfill its mission. The Kepler light curves exhibit high precision over a large dynamic range, which will surely permit their use for a large variety of investigations in addition to finding and characterizing planets. We discuss the temporal characteristics of both the raw flux time series and the systematic error-corrected flux time series produced by the Kepler Science Pipeline, and give examples illustrating Kepler's large dynamic range and the variety of light curves obtained from the Q1 observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.0256v1.pdf"}
{"id": "1001.0309", "abstract": "  Antal et al. [Phys. Rev. E 72, 036121 (2005)] have studied the balance dynamics on the social networks. In this paper, based on the model proposed by Antal et al., we improve it and generalize the binary social networks to the ternary social networks. When the social networks get dynamically balanced, we obtain the distributions of each relation and the time needed for dynamic balance. Besides, we study the self-organized criticality on the ternary social networks based on our model. For the ternary social networks evolving to the sensitive state, any small disturbance may result in an avalanche. The occurrence of the avalanche satisfies the power-law form both spatially and temporally. Numerical results verify our theoretical expectations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.0309v1.pdf"}
{"id": "1001.0959", "abstract": "  We present a general self-consistent lepto/hadronic jet model for the non-thermal electromagnetic emission of microquasars. The model is applied to the low-mass microquasar (LMMQ) GX 339-4 and predicts its high-energy features. We assume that both leptons and hadrons are accelerated up to relativistic energies by diffusive shock acceleration, and calculate their contribution to the electromagnetic spectrum through all main radiative processes. The radiative contribution of secondary particles (pions, muons and electron-positron pairs) is included. We use a set of simultaneous observations in radio and X-rays to constrain the model parameters and find the best fit to the data. We obtain different spectral energy distributions that can explain the observations, and make predictions for the high-energy emission. Observations with gamma-ray instruments like Fermi can be used to test the model and determine the proton content of the jets. Finally, we estimate the positron injection in the surrounding medium. Our findings support the suggested association between LMMQs and the observed distribution of the 511 keV line flux observed by INTEGRAL. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.0959v1.pdf"}
{"id": "1001.1190", "abstract": "  Here we have studied first and second-order intertwining approach to generate isospectral partner potentials of position-dependent (effective) mass Schroedinger equation. The second-order intertwiner is constructed directly by taking it as second order linear differential operator with position depndent coefficients and the system of equations arising from the intertwining relationship is solved for the coefficients by taking an ansatz. A complete scheme for obtaining general solution is obtained which is valid for any arbitrary potential and mass function. The proposed technique allows us to generate isospectral potentials with the following spectral modifications: (i) to add new bound state(s), (ii) to remove bound state(s) and (iii) to leave the spectrum unaffected. To explain our findings with the help of an illustration, we have used point canonical transformation (PCT) to obtain the general solution of the position dependent mass Schrodinger equation corresponding to a potential and mass function. It is shown that our results are consistent with the formulation of type A N-fold supersymmetry [14,18] for the particular case N = 1 and N = 2 respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.1190v2.pdf"}
{"id": "1001.1331", "abstract": "  Adiabatic techniques are well known tools in multi-level electron systems to transfer population between different states with high fidelity. Recently it has been realised that these ideas can also be used in ultra-cold atom systems to achieve coherent manipulation of the atomic centre-of-mass states. Here we present an investigation into a realistic setup using three atomic waveguides created on top of an atom chip and show that such systems hold large potential for the observation of adiabatic phenomena in experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.1331v1.pdf"}
{"id": "1001.1969", "abstract": "  In this paper, we present measurements of the ortho-positronium emission energy in vacuum from mesoporous films using the time of flight technique. We show evidence of quantum mechanical confinement in the mesopores that defines the minimal energy of the emitted Ps. Two samples with different effective pore sizes, measured with positron annihilation lifetime spectroscopy, are compared for the data collected in the temperature range 50-400 K. The sample with smaller pore size exhibits a higher minimal energy (73±5 meV), compared to the sample with bigger pores (48±5 meV), due to the stronger confinement. The dependence of the emission energy with the temperature of the target is modeled as ortho-positronium being confined in rectangular boxes in thermodynamic equilibrium with the sample. We also measured that the yield of positronium emitted in vacuum is not affected by the temperature of the target. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.1969v3.pdf"}
{"id": "1001.2527", "abstract": "  Bloch oscillations appear for a particle in a weakly tilted periodic potential. The intrinsic spin Hall effect is an outcome of a spin-orbit coupling. We demonstrate that both these phenomena can be realized simultaneously in a gas of weakly interacting ultracold atoms exposed to a tilted optical lattice and to a set of spatially dependent light fields inducing an effective spin-orbit coupling. It is found that both the spin Hall as well as the Bloch oscillation effects may coexist, showing, however, a strong correlation between the two. These correlations are manifested as a transverse spin current oscillating in-phase with the Bloch oscillations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.2527v2.pdf"}
{"id": "1001.2595", "abstract": "  We compute that extrasolar minor planets can retain much of their internal H_2O during their host star's red giant evolution. The eventual accretion of a water-rich body or bodies onto a helium white dwarf might supply an observable amount of atmospheric hydrogen, as seems likely for GD 362. More generally, if hydrogen pollution in helium white dwarfs typically results from accretion of large parent bodies rather than interstellar gas as previously supposed, then H_2O probably constitutes at least 10", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.2595v2.pdf"}
{"id": "1001.4515", "abstract": "  We present extensive first principles density functional theory (DFT) calculations dedicated to analyze the magnetic and electronic properties of small V_n clusters (n=1,2,3,4,5,6) embedded in a Cu fcc matrix. We consider different cluster structures such as: i) a single V impurity, ii) several V_2 dimers having different interatomic distance and varying local atomic environment, iii) V_3 and iv) V_4 clusters for which we assume compact as well as 2- and 1-dimensional atomic configurations and finally, in the case of the v) V_5 and vi) V_6 structures we consider a square pyramid and a square bipyramid together with linear arrays, respectively. In all cases, the V atoms are embedded as substitutional impurities in the Cu network. In general, and as in the free standing case, we have found that the V clusters tend to form compact atomic arrays within the cooper matrix. Our calculated non spin-polarized density of states at the V sites shows a complex peaked structure around the Fermi level that strongly changes as a function of both the interatomic distance and local atomic environment, a result that anticipates a non trivial magnetic behavior. In fact, our DFT calculations reveal, in each one of our clusters systems, the existence of different magnetic solutions (ferromagnetic, ferrimagnetic, and antiferromagnetic) with very small energy differences among them, a result that could lead to the existence of complex finite-temperature magnetic properties. Finally, we compare our results with recent experimental measurements. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.4515v1.pdf"}
{"id": "1001.4718", "abstract": "  There are only a few sources that are definitely known to be gamma-ray binaries. Two of these are listed as associations in the Fermi LAT Bright Source List. We are developing novel techniques to extract high signal-to-noise light curves of all cataloged Fermi sources and to search for periodic variability using appropriately weighted power spectra. The detection of periodic variability would be strong evidence for the detection of a new gamma-ray binary. The LAT's sensitivity provides the opportunity to open up completely new discovery space for additional binary systems, potentially involving novel astrophysics. We present here demonstrations of the sensitivity gains obtained through the use of these techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.4718v1.pdf"}
{"id": "1001.5197", "abstract": "  Stars in the solar neighbourhood do not have a smooth distribution of velocities. Instead, the distribution of velocity components in the Galactic plane manifests a great deal of kinematic substructure. Here I present an analysis in action-angle variables of the Geneva-Copenhagen survey of  14,000 nearby F     G dwarfs with distances and full space motions. I show that stars in the so-called \"Hyades stream\" have both angle and action variables characteristic of their having been scattered at an inner Lindblad resonance of a rotating disturbance potential. This discovery seems to favour spiral patterns as recurrent, short-lived instabilities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.5197v2.pdf"}
{"id": "1002.1132", "abstract": "  The existence of a minimal and fundamental length scale, say, the Planck length, is a characteristic feature of almost all the models of quantum gravity. The presence of the fundamental length is expected to lead to an improved ultra-violet behavior of the semi-classical propagators. The hypothesis of path integral duality provides a prescription to evaluate the modified propagator of a free, quantum scalar field in a given spacetime, taking into account the existence of the fundamental length in a locally Lorentz invariant manner. We use this prescription to compute the quantum gravitational modifications to the propagators in spacetimes with constant curvature, and show that: (i) the modified propagators are ultra-violet finite, and (ii) the modifications are non-perturbative in the Planck length. We discuss the implications of our results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.1132v1.pdf"}
{"id": "1002.2271", "abstract": "  This paper studies network information theory problems where the external noise is Gaussian distributed. In particular, the Gaussian broadcast channel with coherent fading and the Gaussian interference channel are investigated. It is shown that in these problems, non-Gaussian code ensembles can achieve higher rates than the Gaussian ones. It is also shown that the strong Shamai-Laroia conjecture on the Gaussian ISI channel does not hold. In order to analyze non-Gaussian code ensembles over Gaussian networks, a geometrical tool using the Hermite polynomials is proposed. This tool provides a coordinate system to analyze a class of non-Gaussian input distributions that are invariant over Gaussian networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.2271v1.pdf"}
{"id": "1002.3107", "abstract": "  We propose and test a wavelet transform modulus maxima method for the au- tomated detection and extraction of coronal loops in extreme ultraviolet images of the solar corona. This method decomposes an image into a number of size scales and tracks enhanced power along each ridge corresponding to a coronal loop at each scale. We compare the results across scales and suggest the optimum set of parameters to maximise completeness while minimising detection of noise. For a test coronal image, we compare the global statistics (e.g., number of loops at each length) to previous automated coronal-loop detection algorithms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.3107v1.pdf"}
{"id": "1002.3293", "abstract": "  On the basis of an extensive new spectroscopic survey of Galactic O stars, we introduce the Ofc category, which consists of normal spectra with C III λλ4647-4650-4652 emission lines of comparable intensity to those of the Of defining lines N III λλ4634-4640-4642. The former feature is strongly peaked to spectral type O5, at all luminosity classes, but preferentially in some associations or clusters and not others. The relationships of this phenomenon to the selective C III λ5696 emission throughout the normal Of domain, and to the peculiar, variable Of?p category, for which strong C III λλ4647-4650-4652 emission is a defining characteristic, are discussed. Magnetic fields have recently been detected on two members of the latter category. We also present two new extreme Of?p stars, NGC 1624-2 and CPD -28^∘2561, bringing the number known in the Galaxy to five. Modeling of the behavior of these spectral features can be expected to better define the physical parameters of both normal and peculiar objects, as well as the atomic physics involved. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.3293v1.pdf"}
{"id": "1002.3965", "abstract": "  We calculate Root Mean Square (RMS) deviations from equilibrium for atoms in a two dimensional crystal with local (e.g. covalent) bonding between close neighbors. Large scale Monte Carlo calculations are in good agreement with analytical results obtained in the harmonic approximation. When motion is restricted to the plane, we find a slow (logarithmic) increase in fluctuations of the atoms about their equilibrium positions as the crystals are made larger and larger. We take into account fluctuations perpendicular to the lattice plane, manifest as undulating ripples, by examining dual layer systems with coupling between the layers to impart local rigidly (i.e. as in sheets of graphene made stiff by their finite thickness). Surprisingly, we find a rapid divergence with increasing system size in the vertical mean square deviations, independent of the strength of the interplanar coupling. We consider an attractive coupling to a flat substrate, finding that even a weak attraction significantly limits the amplitude and average wavelength of the ripples. We verify our results are generic by examining a variety of distinct geometries, obtaining the same phenomena in each case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.3965v1.pdf"}
{"id": "1002.3988", "abstract": "  We study the dynamics of a quench-prepared domain wall state released into a system whose unitary time evolution is dictated by the Hamiltonian of the Heisenberg spin-1/2 gapped antiferromagnetic chain. Using exact wavefunctions and their overlaps with the domain wall state allows us to describe the release dynamics to high accuracy, up to the long-time limit, for finite as well as infinite systems. The results for the infinite system allow us to rigorously prove that the system in the gapped regime (Δ >1) cannot thermalize in the strict sense. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.3988v1.pdf"}
{"id": "1002.4691", "abstract": "  Accurate mass determination of clusters of galaxies is crucial if they are to be used as cosmological probes. However, there are some discrepancies between cluster masses determined based on gravitational lensing, and X-ray observations assuming strict hydrostatic equilibirium (i.e., the equilibrium gas pressure is provided entirely by thermal pressure). Cosmological simulations suggest that turbulent gas motions remaining from hierarchical structure formation may provide a significant contribution to the equilibrium pressure in clusters. We analyze a sample of massive clusters of galaxies drawn from high resolution cosmological simulations, and find a significant contribution (20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.4691v2.pdf"}
{"id": "1003.0510", "abstract": "  The dynamical response of the Abrikosov vortex lattice in the presence of an oscillating driving field is calculated by constructing an analytical solution of the time-dependent Ginzburg-Landau equation. The solution is steady-state, and work done by the input signal is dissipated through vortex cores, mainly by scattering with phonons. The response is nonlinear in the input signal, and is verified for consistency within the theory. The existence of well-defined parameters to control nonlinear effects is important for any practical application in electronics, and a normalised distance from the normal-superconducting phase-transition boundary is found to be such a parameter to which the response is sensitive. Favourable comparison with NbN experimental data in the optical region is made, where the effect is in the linear regime. Predictions are put forward regarding the suppression of heating and also the lattice configuration at high frequency. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.0510v2.pdf"}
{"id": "1003.1726", "abstract": "  We examine the effective counterion-mediated electrostatic interaction between two like-charged dielectric cylinders immersed in a continuous dielectric medium containing neutralizing mobile counterions. We focus on the effects of image charges induced as a result of the dielectric mismatch between the cylindrical cores and the surrounding dielectric medium and investigate the counterion-mediated electrostatic interaction between the cylinders in both limits of weak and strong electrostatic couplings (corresponding, e.g., to systems with monovalent and multivalent counterions, respectively). The results are compared with extensive Monte-Carlo simulations exhibiting good agreement with the limiting weak and strong coupling results in their respective regime of validity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.1726v1.pdf"}
{"id": "1003.2007", "abstract": "  We study quantum entanglement in the ground state of the Affleck-Kennedy-Lieb-Tasaki (AKLT) model defined on two-dimensional graphs with reflection and/or inversion symmetry. The ground state of this spin model is known as the valence-bond-solid state. We investigate the properties of reduced density matrix of a subsystem which is a mirror image of the other one. Thanks to the reflection symmetry, the eigenvalues of the reduced density matrix can be obtained by numerically diagonalizing a real symmetric matrix whose elements are calculated by Monte Carlo integration. We calculate the von Neumann entropy of the reduced density matrix. The obtained results indicate that there is some deviation from the naive expectation that the von Neumann entropy per valence bond on the boundary between the subsystems is ln 2. This deviation is interpreted in terms of the hidden spin chain along the boundary between the subsystems. In some cases where graphs are on ladders, the numerical results are analytically or algebraically confirmed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.2007v2.pdf"}
{"id": "1003.3140", "abstract": "  We investigate the Ruderman-Kittel-Kasuya-Yosida oscillations of the itinerant carrier spin density in a system where those oscillations appear only due to a finite distribution of a localized spin. The system represents a half-infinite one-dimensional quantum wire with a magnetic impurity located at its edge. In contrast to the conventional model of a point-like exchange interaction the itinerant carrier spin density oscillations in this system exist. We analytically demonstrate that when the radius of the exchange interaction is less than the wave length of the itinerant carriers living on the Fermi surface, the long range behavior of the oscillations is identical to the one taking place in the zero radius limit of the same exchange interaction but for an infinite one-dimensional quantum wire where, in comparison with the original half-infinite system, the mass of the itinerant carriers is strongly modified by the exchange interaction radius. On the basis of our analysis we make a suggestion on directionality of surface Ruderman-Kittel-Kasuya-Yosida interaction shown in recent experiments: we believe that in general the anisotropy of the Ruderman-Kittel-Kasuya-Yosida interaction could result not only from the anisotropy of the Fermi surface of itinerant carriers but also from the anisotropy of the spin carrying atomic orbitals of magnetic impurities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.3140v2.pdf"}
{"id": "1003.3290", "abstract": "  We study the dynamics of the photon entanglement, E_N(t), for the two-mode Jaynes-Cummings model in the few-photon case. The atomic transitions associated with the photons with different polarizations are assumed to be independent and, hence, the evolution of the \"+\"- and \"-\"-polarized photons is formally separable. However, due to the photons indistinguishability such interaction still leads to entanglement of initially disentangled states owing to the non-linear dependence of the characteristic frequencies on the photon population numbers. The time dependence of entanglement is the result of superimposing oscillations with incommensurate frequencies. Therefore, E_N(t) is a quasi-periodic function of time with the complex profile strongly depending on the number of photons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.3290v1.pdf"}
{"id": "1003.3378", "abstract": "  The interplay between the coupling of an interacting quantum dot to a conduction band and its connection to localized levels has been studied in a triple quantum dot arrangement. The electronic Dicke effect, resulting from quasi-resonant states of two side-coupled non-interacting quantum dots, is found to produce important effects on the Kondo resonance of the interacting dot. We study in detail the Kondo regime of the system by applying a numerical renormalization group analysis to a finite-U multi-impurity Anderson Hamiltonian model. We find an extreme narrowing of the Kondo resonance, as the single-particle levels of the side dots are tuned towards the Fermi level and \"squeeze\" the Kondo resonance, accompanied by a strong drop in the Kondo temperature, due to the presence of a supertunneling state. Further, we show that the Kondo temperature vanishes in the limit of the Dicke effect of the structure. By analyzing the magnetic moment and entropy of the three-dot cluster versus temperature, we identify a different local singlet that competes with the Kondo state, resulting in the eventual suppression of the Kondo temperature and strongly affecting the spin correlations of the structure. We further show that system asymmetries in couplings, level structure or due to Coulomb interactions, result in interesting changes in the spectral function near the Fermi level. These strongly affect the Kondo temperature and the linear conductance of the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.3378v2.pdf"}
{"id": "1003.3562", "abstract": "  We investigate how well the one-dimensional Hubbard model describes the entanglement of particles trapped in a string of quantum wells. We calculate the average single-site entanglement for two particles interacting via a contact interaction and consider the effect of varying the interaction strength and the interwell distance. We compare the results with the ones obtained within the one-dimensional Hubbard model with on-site interaction. We suggest an upper bound for the average single-site entanglement for two electrons in M wells and discuss analytical limits for very large repulsive and attractive interactions. We investigate how the interplay between interaction and potential shape in the quantum well system dictates the position and size of the entanglement maxima and the agreement with the theoretical limits. Finally we calculate the spatial entanglement for the quantum well system and compare it to its average single-site entanglement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.3562v1.pdf"}
{"id": "1003.3890", "abstract": "  We report on the study of the intensities of several gamma lines emitted after the inelastic scattering of neutrons in ^56Fe. Neutrons were produced by cosmic muons passing the 20t massive iron cube placed at the Earth's surface and used as a passive shield for the HPGe detector. Relative intensities of detected gamma lines are compared with the results collected in the same iron shield by the use of ^252Cf neutrons. Assessment against the published data from neutron scattering experiments at energies up to 14 MeV is also provided. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.3890v1.pdf"}
{"id": "1003.5966", "abstract": "  Linear receivers are often used to reduce the implementation complexity of multiple-antenna systems. In a traditional linear receiver architecture, the receive antennas are used to separate out the codewords sent by each transmit antenna, which can then be decoded individually. Although easy to implement, this approach can be highly suboptimal when the channel matrix is near singular. This paper develops a new linear receiver architecture that uses the receive antennas to create an effective channel matrix with integer-valued entries. Rather than attempting to recover transmitted codewords directly, the decoder recovers integer combinations of the codewords according to the entries of the effective channel matrix. The codewords are all generated using the same linear code which guarantees that these integer combinations are themselves codewords. Provided that the effective channel is full rank, these integer combinations can then be digitally solved for the original codewords. This paper focuses on the special case where there is no coding across transmit antennas and no channel state information at the transmitter(s), which corresponds either to a multi-user uplink scenario or to single-user V-BLAST encoding. In this setting, the proposed integer-forcing linear receiver significantly outperforms conventional linear architectures such as the zero-forcing and linear MMSE receiver. In the high SNR regime, the proposed receiver attains the optimal diversity-multiplexing tradeoff for the standard MIMO channel with no coding across transmit antennas. It is further shown that in an extended MIMO model with interference, the integer-forcing linear receiver achieves the optimal generalized degrees-of-freedom. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.5966v4.pdf"}
{"id": "1004.0001", "abstract": "  As some of the first known objects to exist in the Universe, Lyman alpha emitting galaxies (LAEs) naturally draw a lot of interest. First discovered over a decade ago, they have allowed us to probe the early Universe, as their strong emission line compensates for their faint continuum light. While initially thought to be indicative of the first galaxies forming in the Universe, recent studies have shown them to be increasingly complex, as some fraction appear evolved, and many LAEs appear to be dusty, which one would not expect from primordial galaxies. Presently, much interest resides in discovering not only the highest redshift galaxies to constrain theories of reionization, but also pushing closer to home, as previous ground-based studies have only found LAEs at z > 3 due to observational limitations. In this review talk I will cover everything from the first theoretical predictions of LAEs, to their future prospects for study, including the HETDEX survey here in Texas. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.0001v1.pdf"}
{"id": "1004.0056", "abstract": "  This paper defines a class of labeled stratified order structures that characterizes exactly the notion of combined traces (i.e., comtraces) proposed by Janicki and Koutny in 1995. Our main technical contributions are the representation theorems showing that comtrace quotient monoid, combined dependency graph (Kleijn and Koutny 2008) and our labeled stratified order structure characterization are three different and yet equivalent ways to represent comtraces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.0056v2.pdf"}
{"id": "1004.0948", "abstract": "  We present a statistical characterization of the carbon-star to M-giant (C/M) ratio in the halo of M31. Based on application of pseudo-filter band passes to our Keck/DEIMOS spectra we measure the 81-77-color index of 1288 stars in the giant stellar stream and in halo fields out to large distances. From this well-established narrow-band system, supplemented by V-I colors, we find only a low number (five in total) of C-star candidates. The resulting low C/M ratio of 10", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.0948v1.pdf"}
{"id": "1004.1332", "abstract": "  Grain boundaries are topological defects that often have a disordered character. Disorder implies that understanding general trends is more important than accurate investigations of individual grain boundaries. Here we present trends in the grain boundaries of graphene. We use density-functional tight-binding method to calculate trends in energy, atomic structure (polygon composition), chemical reactivity (dangling bond density), corrugation heights (inflection angles), and dynamical properties (vibrations), as a function of lattice orientation mismatch. The observed trends and their mutual interrelations are plausibly explained by structure, and supported by past experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.1332v1.pdf"}
{"id": "1004.1378", "abstract": "  Network epidemiology often assumes that the relationships defining the social network of a population are static. The dynamics of relationships is only taken indirectly into account, by assuming that the relevant information to study epidemic spread is encoded in the network obtained by considering numbers of partners accumulated over periods of time roughly proportional to the infectious period of the disease at hand. On the other hand, models explicitly including social dynamics are often too schematic to provide a reasonable representation of a real population, or so detailed that no general conclusions can be drawn from them. Here we present a model of social dynamics that is general enough that its parameters can be obtained by fitting data from surveys about sexual behaviour, but that can still be studied analytically, using mean field techniques. This allows us to obtain some general results about epidemic spreading. We show that using accumulated network data to estimate the static epidemic threshold leads to a significant underestimation of it. We also show that, for a dynamic network, the relative epidemic threshold is an increasing function of the infectious period of the disease, implying that the static value is a lower bound to the real threshold. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.1378v1.pdf"}
{"id": "1004.1504", "abstract": "  A theory of the anomalous Hall conductivity based on the properties of single site orbitals is presented. Effect of the finite electron life time is modeled by energy fluctuations of atomic-like orbitals. Transition from the ideal Bloch system for which the conductivity is determined by the Berry phase curvatures to the case of strong disorder for which the conductivity becomes dependent on the relaxation time is analyzed. Presented tight-binding model gives by the unified way experimentally observed qualitative features of the anomalous conductivity in the so called good metal regime and that called as bad metal or hopping regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.1504v1.pdf"}
{"id": "1004.1813", "abstract": "  We study an optomechanical system in which the collective density excitations (Bogoliubov modes) of a Bose Einstein condensate (BEC) is coupled to a cavity field. We show that the optical force changes the frequency and the damping constant of the collective density excitations of the BEC. We further analyze the occurrence of normal mode splitting (NMS) due to mixing of the fluctuations of the cavity field and the fluctuations of the condensate with finite atomic two-body interaction. The NMS is found to vanish for small values of the two-body interaction. We further show that the density excitations of the condensate can be used to squeeze the output quantum fluctuations of the light beam. This system may serve as an optomechanical control of quantum fluctuations using a Bose Einstein condensate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.1813v1.pdf"}
{"id": "1004.1944", "abstract": "  The characterization of physical systems requires a comprehensive understanding of quantum effects. One aspect is a proper quantification of the strength of such quantum phenomena. Here, a general convex ordering of quantum states will be introduced which is based on the algebraic definition of classical states. This definition resolves the ambiguity of the quantumness quantification using topological distance measures. Classical operations on quantum states will be considered to further generalize the ordering prescription. Our technique can be used for a natural and unambiguous quantification of general quantum properties whose classical reference has a convex structure. We apply this method to typical scenarios in quantum optics and quantum information theory to study measures which are based on the fundamental quantum superposition principle. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.1944v2.pdf"}
{"id": "1004.3066", "abstract": "  We present theoretical studies of the influence of spin orbit coupling on the spin wave excitations of the Fe monolayer and bilayer on the W(110) surface. The Dzyaloshinskii-Moriya interaction is active in such films, by virtue of the absence of reflection symmetry in the plane of the film. When the magnetization is in plane, this leads to a linear term in the spin wave dispersion relation for propagation across the magnetization. The dispersion relation thus assumes a form similar to that of an energy band of an electron trapped on a semiconductor surfaces with Rashba coupling active. We also show SPEELS response functions that illustrate the role of spin orbit coupling in such measurements. In addition to the modifications of the dispersion relations for spin waves, the presence of spin orbit coupling in the W substrate leads to a substantial increase in the linewidth of the spin wave modes. The formalism we have developed applies to a wide range of systems, and the particular system explored in the numerical calculations provides us with an illustration of phenomena which will be present in other ultrathin ferromagnet/substrate combinations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.3066v1.pdf"}
{"id": "1004.3519", "abstract": "  The main goal of the IceCube Deep Core Array is to search for neutrinos of astrophysical origins. Atmospheric neutrinos are commonly considered as a background for these searches. We show here that cascade measurements in the Ice Cube Deep Core Array can provide strong evidence for tau neutrino appearance in atmospheric neutrino oscillations. A careful study of these tau neutrinos is crucial, since they constitute an irreducible background for astrophysical neutrino detection. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.3519v1.pdf"}
{"id": "1004.3682", "abstract": "  Graphene research is currently one of the largest fields in condensed matter. Due to its unusual electronic spectrum with Dirac-like quasiparticles, and the fact that it is a unique example of a metallic membrane, graphene has properties that have no match in standard solid state textbooks. In these lecture notes, I discuss some of these properties that are not covered in detail in recent reviews. We study the particular aspects of the physics/chemistry of carbon that influence the properties of graphene; the basic features of graphene's band structure including the pi and sigma bands; the phonon spectra in free floating graphene; the effects of a substrate on the structural properties of graphene; and the effect of deformations in the propagation of electrons. The objective of these notes is not to provide an unabridged theoretical description of graphene but to point out some of the peculiar aspects of this material. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.3682v1.pdf"}
{"id": "1004.3774", "abstract": "  In this article, new regular incidence structures are presented. They arise from sets of conics in the affine plane blown-up at its rational points. The LDPC codes given by these incidence matrices are studied. These sparse incidence matrices turn out to be redundant, which means that their number of rows exceeds their rank. Such a feature is absent from random LDPC codes and is in general interesting for the efficiency of iterative decoding. The performance of some codes under iterative decoding is tested. Some of them turn out to perform better than regular Gallager codes having similar rate and row weight. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.3774v3.pdf"}
{"id": "1004.3971", "abstract": "  The uncertainty in the absolute value of the fluorescence yield is still one of the main contributions to the total error in the reconstruction of the primary energy of ultra-energetic air showers using the fluorescence technique. A significant number of experimental values of the fluorescence yield have been published in the last years, however reported results are given very often in different units (photons/MeV or photons/m) and for different wavelength intervals. In this work we present a comparison of available results normalized to its value in photons/MeV for the 337 nm band at 800 hPa and 293 K. The conversion of photons/m to photons/MeV requires an accurate determination of the energy deposited by the electrons in the field of view of the experimental setup. We have calculated the energy deposition for each experiment by means of a detailed Monte Carlo simulation including when possible the geometrical details of the particular setup. Our predictions on deposited energy, as well as on some geometrical factors, have been compared with those reported by the authors of the corresponding experiments and possible corrections to the fluorescence yields are proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.3971v2.pdf"}
{"id": "1004.4052", "abstract": "  We use a non-Markovian generalized master equation (GME) to describe the time-dependent charge transfer through a parabolically confined quantum wire of a finite length coupled to semi-infinite quasi two-dimensional leads. The quantum wire and the leads are in a perpendicular external magnetic field. The contacts to the left and right leads depend on time and are kept out of phase to model a quantum turnstile of finite size. The effects of the driving period of the turnstile, the external magnetic field, the character of the contacts, and the chemical potential bias on the effectiveness of the charge transfer of the turnstile are examined, both in the absence and in the presence of the magnetic field. The interplay between the strength of the coupling and the strength of the magnetic field is also discussed. We observe how the edge states created in the presence of the magnetic field contribute to the pumped charge. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.4052v1.pdf"}
{"id": "1004.4831", "abstract": "  Based on a mesoscopic theory we investigate the non-equilibrium dynamics of a sheared nematic liquid, with the control parameter being the shear stress σ_xy (rather than the usual shear rate, γ̇). To this end we supplement the equations of motion for the orientational order parameters by an equation for γ̇, which then becomes time-dependent. Shearing the system from an isotropic state, the stress- controlled flow properties turn out to be essentially identical to those at fixed γ̇. Pronounced differences when the equilibrium state is nematic. Here, shearing at controlled γ̇ yields several non-equilibrium transitions between different dynamic states, including chaotic regimes. The corresponding stress-controlled system has only one transition from a regular periodic into a stationary (shear-aligned) state. The position of this transition in the σ_xy-γ̇ plane turns out to be tunable by the delay time entering our control scheme for σ_xy. Moreover, a sudden change of the control method can stabilize the chaotic states appearing at fixed γ̇. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.4831v2.pdf"}
{"id": "1004.4993", "abstract": "  We carry out a comparative study of electronic properties of 2D electron gas (2DEG) in a magnetic field of an infinitesimally thin solenoid with relativistic dispersion as in graphene and quadratic dispersion as in semiconducting heterostructures. The problem of ambiguity of the zero mode solutions of the Dirac equation is treated by considering of a finite radius flux tube which allows to select unique solutions associated with each 𝐊 point of graphene's Brillouin zone. Then this radius is allowed to go to zero. On the base of the obtained in this case analytical solutions in the Aharonov-Bohm potential the local and total density of states (DOS) are calculated. It is shown that in the case of graphene there is an excess of LDOS near the vortex, while in 2DEG the LDOS is depleted. This results in excess of the induced by the vortex DOS in graphene and in its depletion in 2DEG. We discuss the application of the results for the local density of states for the scanning tunneling spectroscopy done on graphene. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.4993v2.pdf"}
{"id": "1004.5157", "abstract": "  Low-density parity-check (LDPC) convolutional codes are capable of achieving excellent performance with low encoding and decoding complexity. In this paper we discuss several graph-cover-based methods for deriving families of time-invariant and time-varying LDPC convolutional codes from LDPC block codes and show how earlier proposed LDPC convolutional code constructions can be presented within this framework. Some of the constructed convolutional codes significantly outperform the underlying LDPC block codes. We investigate some possible reasons for this \"convolutional gain,\" and we also discuss the — mostly moderate — decoder cost increase that is incurred by going from LDPC block to LDPC convolutional codes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.5157v3.pdf"}
{"id": "1005.0226", "abstract": "  We study a model of opinion formation where the collective decision of group is said to happen if the fraction of agents having the most common opinion exceeds a threshold value, a critical mass. We find that there exists a unique, non-trivial critical mass giving the most efficient convergence to consensus. In addition, we observe that for small critical masses, the characteristic time scale for the relaxation to consensus splits into two. The shorter time scale corresponds to a direct relaxation and the longer can be explained by the existence of intermediate, metastable states similar to those found in [P. Chen and S. Redner, Phys. Rev. E 71, 036101 (2005)]. This longer time-scale is dependent on the precise condition for consensus—with a modification of the condition it can go away. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.0226v1.pdf"}
{"id": "1005.0340", "abstract": "  This paper presents a method for automated healing as part of off-line automated troubleshooting. The method combines statistical learning with constraint optimization. The automated healing aims at locally optimizing radio resource management (RRM) or system parameters of cells with poor performance in an iterative manner. The statistical learning processes the data using Logistic Regression (LR) to extract closed form (functional) relations between Key Performance Indicators (KPIs) and Radio Resource Management (RRM) parameters. These functional relations are then processed by an optimization engine which proposes new parameter values. The advantage of the proposed formulation is the small number of iterations required by the automated healing method to converge, making it suitable for off-line implementation. The proposed method is applied to heal an Inter-Cell Interference Coordination (ICIC) process in a 3G Long Term Evolution (LTE) network which is based on soft-frequency reuse scheme. Numerical simulations illustrate the benefits of the proposed approach. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.0340v1.pdf"}
{"id": "1005.0508", "abstract": "  A detailed and systematic density-functional theory (DFT) study of a series of early transition-metal carbides (TMC's) in the NaCl structure is presented. The focus is on the trends in the electronic structure and nature of bonding, which are essential for the understanding of the reactivity of TMC's. The employed approach is based on a thorough complementary analysis of the electron density differences, the density of states (DOS), the band structure, and the real-space wave functions to gain insight into the bonding of this class of materials and get a more detailed picture of it than previously achieved, as the trend study allows for a systematic identification of the bond character along the different bands. Our approach confirms the presence of both the well-known TM–C and TM–TM bonds and, more importantly, it shows the existence and significance of direct C–C bonds in all investigated TMC's, which are frequently neglected but have been recently identified in some cases [Solid State Commun. 121, 411 (2002); Phys. Rev. B 75, 235438 (2007)]. New information on the spatial extent of the bonds, their k-space location within the band structure, and their importance for the bulk cohesion is provided. Trends in covalency and ionicity are presented. The resulting electron-structural trends are analyzed and discussed within a two-level model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.0508v1.pdf"}
{"id": "1005.1225", "abstract": "  Errors in numerical simulations of gravitating systems can be magnified exponentially over short periods of time. Numerical shadowing provides a way of demonstrating that the dynamics represented by numerical simulations are representative of true dynamics. Using the Sitnikov Problem as an example, it is demonstrated that unstable orbits of the 3-body problem can be shadowed for long periods of time. In addition, it is shown that the stretching of phase space near escape and capture regions is a cause for the failure of the shadowing refinement procedure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.1225v1.pdf"}
{"id": "1005.3489", "abstract": "  Iron, the Universe's most abundant refractory element, is highly depleted in both circumstellar and interstellar environments, meaning it exists in solid form. The nature of this solid is unknown. In this Letter, we provide evidence that metallic iron grains are present around oxygen-rich AGB stars, where it is observationally manifest as a featureless mid-infrared excess. This identification is made using Spitzer Space Telescope observations of evolved globular cluster stars, where iron dust production appears ubiquitous and in some cases can be modelled as the only observed dust product. In this context, FeO is examined as the likely carrier for the 20-micron feature observed in some of these stars. Metallic iron appears to be an important part of the dust condensation sequence at low metallicity, and subsequently plays an influential role in the interstellar medium. We explore the stellar metallicities and luminosities at which iron formation is observed, and how the presence of iron affects the outflow and its chemistry. The conditions under which iron can provide sufficient opacity to drive a wind remain unclear. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.3489v1.pdf"}
{"id": "1005.3734", "abstract": "  In May 2008, the Antares collaboration has completed the construction of the first deep sea neutrino telescope in the Northern hemisphere. Antares is a 3D array of 900 photomultipliers held in the sea by twelve mooring lines anchored at a depth of 2500 m in the Mediterranean Sea 40 km off the southern French coast. The detection principle is based on the observation of Cerenkov light induced by charged particles produced in neutrino interactions in the matter surrounding the detector. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.3734v1.pdf"}
{"id": "1005.4294", "abstract": "  We compute the Casimir interaction between a plane and a sphere, the configuration employed in the most precise experiments. The scattering formula is developed by taking a suitably chosen plane-wave and multipole basis and is valid for arbitrary values of the sphere radius, inter-plate distance, temperature and arbitrary dielectric functions for both sphere and plate. Our analytical and numerical results for metallic surfaces show a non-trivial interplay between the effects of curvature, temperature, finite conductivity and dissipation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.4294v1.pdf"}
{"id": "1005.4778", "abstract": "  Suppose we are given the free product V of a finite family of finite or countable sets. We consider a transient random walk on the free product arising naturally from a convex combination of random walks on the free factors. We prove the existence of the asymptotic entropy and present three different, equivalent formulas, which are derived by three different techniques. In particular, we will show that the entropy is the rate of escape with respect to the Greenian metric. Moreover, we link asymptotic entropy with the rate of escape and volume growth resulting in two inequalities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.4778v4.pdf"}
{"id": "1006.1331", "abstract": "  We study the possibility of testing experimentally signatures of P-odd effects related with the vorticity of the medium. The Chiral Vortaic Effect is generalized to the case of conserved charges different from the electric one. In the case of baryonic charge and chemical potential such effect should manifest itself in neutron asymmetries at the NICA accelerator complex measured by the MPD detector. The required accuracy may be achieved in a few months of accelerator running. We also discuss polarization of the hyperons and P-odd correlations of particle momenta (handedness) as probes of vorticity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.1331v2.pdf"}
{"id": "1006.1805", "abstract": "  We investigate the dynamics of quantum and classical correlations in a system of two qubits under local colored-noise dephasing channels. The time evolution of a single qubit interacting with its own environment is described by a memory kernel non-Markovian master equation. The memory effects of the non-Markovian reservoirs introduce new features in the dynamics of quantum and classical correlations compared to the white noise Markovian case. Depending on the geometry of the initial state, the system can exhibit frozen discord and multiple sudden transitions between classical and quantum decoherence [L. Mazzola, J. Piilo and S. Maniscalco, Phys. Rev. Lett. 104 (2010) 200401]. We provide a geometric interpretation of those phenomena in terms of the distance of the state under investigation to its closest classical state in the Hilbert space of the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.1805v2.pdf"}
{"id": "1006.1854", "abstract": "  We demonstrate that the modulation instability of the zone boundary mode in a finite (periodic) Fermi-Pasta-Ulam chain is the necessary but not sufficient condition for the efficient energy transfer by localized excitations. This transfer results from the exclusion of complete energy exchange between spatially different parts of the chain, and the excitation level corresponding to that turns out to be twice more than threshold of zone boundary mode's instability. To obtain this result one needs in far going extension of the beating concept to a wide class of finite oscillatory chains. In turn, such an extension leads to description of energy exchange and transition to energy localization and transfer in terms of 'effective particles' and Limiting Phase Trajectories. The 'effective particles' appear naturally when the frequency spectrum crowding ensures the resonance interaction between zone boundary and two nearby nonlinear normal modes, but there are no additional resonances. We show that the Limiting Phase Trajectories corresponding to the most intensive energy exchange between 'effective particles' can be considered as an alternative to Nonlinear Normal Modes, which describe the stationary process. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.1854v1.pdf"}
{"id": "1006.2581", "abstract": "  We investigate the formation process of planetesimals from the dust layer by the gravitational instability in the gas disk using local N-body simulations. The gas is modeled as a background laminar flow. We study the formation process of planetesimals and its dependence on the strength of the gas drag. Our simulation results show that the formation process is divided into three stages qualitatively: the formation of wake-like density structures, the creation of planetesimal seeds, and their collisional growth. The linear analysis of the dissipative gravitational instability shows that the dust layer is secularly unstable although Toomre's Q value is larger than unity. However, in the initial stage, the growth time of the gravitational instability is longer than that of the dust sedimentation and the decrease in the velocity dispersion. Thus, the velocity dispersion decreases and the disk shrinks vertically. As the velocity dispersion becomes sufficiently small, the gravitational instability finally becomes dominant. Then wake-like density structures are formed by the gravitational instability. These structures fragment into planetesimal seeds. The seeds grow rapidly owing to mutual collisions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.2581v2.pdf"}
{"id": "1006.3328", "abstract": "  A problem of finding stationary states of open quantum systems is addressed. We focus our attention on a generic type of open system: a qubit coupled to its environment. We apply the theory of block operator matrices and find stationary states of two–level open quantum systems under certain conditions applied both on the qubit and the surrounding. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.3328v4.pdf"}
{"id": "1006.3734", "abstract": "  Using the high granular CALICE analog hadron calorimeter (AHCal) a tracking algorithm capable of identifying MIP-like tracks within hadronic showers is presented. Such an algorithm provides excellent tools for detector calibration and for studies of the substructure of hadronic showers. The properties of the identified tracks are used as observables for a Monte-Carlo to data comparison. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.3734v1.pdf"}
{"id": "1006.4288", "abstract": "  A joint characterisation of the observability and controllability of a particular kind of discrete system has been developed. The key idea of the procedure can be reduced to a correct choice of the sampling sequence. This freedom, owing to the arbitrary choice of the sampling instants, is used to improve the sensitivity of system observability and controllability, by exploiting an adequate geometric structure. Some qualitative examples are presented for illustrative purposes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.4288v1.pdf"}
{"id": "1006.4826", "abstract": "  We overview the status of the studies on neutrino oscillations with accelerators at the present running experiments. Past and present results enlighten the path towards the observation of massive neutrinos and the settling of their oscillations. The very near future may still have addiction from the outcome of the on-going experiments. OPERA is chosen as a relevant example justified by the very recent results released. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.4826v1.pdf"}
{"id": "1007.0827", "abstract": "  We propose an experimental scheme to cool and measure the three-dimensional (3D) motion of an optically trapped nanosphere in a cavity. Driven by three lasers on TEM00, TEM01, and TEM10 modes, a single cavity can cool a trapped nanosphere to the quantum ground states in all three dimensions under the resolved-sideband condition. Our scheme can also detect an individual collision between a single molecule and a cooled nanosphere efficiently. Such ability can be used to measure the mass of molecules and the surface temperature of the nanosphere. We also discuss the heating induced by the intensity fluctuation, pointing instability, and the phase noise of lasers, and justify the feasibility of our scheme under current experimental conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.0827v2.pdf"}
{"id": "1007.1352", "abstract": "  The normal modes of a three-dimensional Yukawa plasma in an isotropic, harmonic confinement are investigated by solving the linearized cold fluid equations. The eigenmodes are found analytically and expressed in terms of hypergeometric functions. It is found that the mode frequencies solely depend on the dimensionless plasma parameter ξ=κ R, where R is the plasma radius and κ the inverse screening length. The eigenfrequencies increase monotonically with ξ and saturate in the limit ξ→∞. Compared with the results in the Coulomb limit [D. H. E. Dubin, Phys. Rev. Lett. 66, 2076 (1991)], we find a new class of modes characterized by the number n which determines the number of radial nodes in the perturbed potential. These modes originate from the degenerate bulk modes of the Coulomb system. Analytical formulas for the eigenfrequencies are derived for limiting cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.1352v1.pdf"}
{"id": "1007.1495", "abstract": "  Density functional calculations were performed to systematically study a series of finite and infinite cluster-assembled silicon nanotubes (SiNTs). One-dimensional SiNTs can be prepared by proper assembly of hydrogenated cage-like silicon clusters to form semiconductors with a large band gap, and their electronic properties can be accurately tuned by transition metal doping in the center of the tubes. Specifically, doping with Fe made the SiNTs metallic and magnetic materials. More interestingly, a metal to half-metal transition was observed with increasing tube radius in Fe-doped SiNTs, which demonstrates that SiNTs doped with magnetic elements may find important applications in spintronics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.1495v1.pdf"}
{"id": "1007.2164", "abstract": "  The determination of the Ba abundance in globular cluster (GC) stars is a very powerful test to address several issues in the framework of multiple population scenarios. We measured the Ba content for a sample of more than 1200 stars in 15 Galactic GCs, using high-resolution FLAMES/Giraffe spectra. We found no variation in [Ba/Fe] ratios for different stellar populations within each cluster; this means that low-mass asymptotic giant branch stars do not significantly contribute to the intra-cluster pollution. Very interestingly, we obtained that the fraction of Ba-stars in first generation (FG) stars is close to the values derived for field stars (∼2%); on the other hand, second generation (SG) stars present a significant lower fraction. An independent and successful test, based on radial velocity variations among giant stars in NGC 6121, confirms our finding: the binary fraction among FG stars is about ∼12% to be compared with ∼1% of SG stars. This is an evidence that SG stars formed in a denser environment, where infant mortality of binary systems was particularly efficient. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2164v3.pdf"}
{"id": "1007.2789", "abstract": "  In this paper, we continue the work begun in a previous article. We compute, in the formalism of local composite operators, the value of the asymmetry in the dimension two condensate for finite temperatures. We find a positive value for the asymmetry, which disappears when the temperature is increased. We also compute the value of the full dimension two condensate for higher temperatures, and we find that it decreases in absolute value, finally disappearing for sufficiently high temperature. We also comment on the temperature dependence of the electric and magnetic components of the condensate separately. We compare our results with the corresponding lattice date found by Chernodub and Ilgenfritz. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2789v1.pdf"}
{"id": "1007.2858", "abstract": "  A field in the vacuum state, which is in principle separable, can evolve to an entangled state in a dynamical gravitational collapse. We will study, quantify, and discuss the origin of this entanglement, showing that it could even reach the maximal entanglement limit for low frequencies or very small black holes, with consequences in micro-black hole formation and the final stages of evaporating black holes. This entanglement provides quantum information resources between the modes in the asymptotic future (thermal Hawking radiation) and those which fall to the event horizon. We will also show that fermions are more sensitive than bosons to this quantum entanglement generation. This fact could be helpful in finding experimental evidence of the genuine quantum Hawking effect in analog models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2858v2.pdf"}
{"id": "1007.2935", "abstract": "  The behavior of persistent current in a mesoscopic cylinder threaded by an Aharonov-Bohm flux ϕ is carefully investigated within a Hartree-Fock mean field approach. We examine the combined effect of second-neighbor hopping integral and Hubbard correlation on the enhancement of persistent current in presence of disorder. A significant change in current amplitude is observed compared to the traditional nearest-neighbor hopping model and the current amplitude becomes quite comparable to experimental realizations. Our analysis is found to exhibit several interesting results which have so far remained unaddressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2935v2.pdf"}
{"id": "1007.4453", "abstract": "  Most of us must have been fascinated by the eye catching displays of collectively moving animals. Schools of fish can move in a rather orderly fashion and then change direction amazingly abruptly. There are a huge number of further examples both from the living and the non-living world for phenomena during which the many interacting, permanently moving units seem to arrive at a common behavioural pattern taking place in a short time. As a paradigm of this type of phenomena we consider the problem of how birds arrive at a decision resulting in their synchronized landing. We introduce a simple model to interpret this process. Collective motion prior to landing is modelled using a simple self-propelled particle (SPP) system with a new kind of boundary condition, while the tendency and the sudden propagation of the intention of landing is introduced through rules analogous to the random field Ising model in an external field. We show that our approach is capable of capturing the most relevant features of collective decision making in a system of units with a variance of individual intentions and being under an increasing level of pressure to switch states. We find that as a function of the few parameters of our model the collective switching from the flying to the landing state is indeed much sharper than the distribution of the individual landing intentions. The transition is accompanied by a number of interesting features discussed in this report. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.4453v1.pdf"}
{"id": "1007.5356", "abstract": "  The entanglement entropy of the integer Quantum Hall states satisfies the area law for smooth domains with a vanishing topological term. In this paper we consider polygonal domains for which the area law acquires a constant term that only depends on the angles of the vertices and we give a general expression for it. We study also the dependence of the entanglement spectrum on the geometry and give it a simple physical interpretation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.5356v1.pdf"}
{"id": "1008.0174", "abstract": "  One of the most discussed peculiarities of Einstein's theory of relativity is the twin paradox, the fact that the time between two events in space-time appears to depend on the path between these events. We show that this time discrepancy results only from faulty assumptions in the transition from one reference system to another. The twin paradox does not exist. But the Lorentz invariance of the theory has strong consequences, if we assume that it is valid not only locally, but also on cosmic scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.0174v1.pdf"}
{"id": "1008.0768", "abstract": "  We have investigated the fluctuations and the higher order susceptibilities of quark number, isospin number, electric charge and strangeness at vanishing chemical potential for 2+1 flavor Polyakov loop extended Nambu–Jona-Lasinio model. The calculations are performed for the bound effective potential in the quark sector requiring up to eight quark interaction terms. These have been contrasted to the lattice results which currently have somewhat heavier quarks in the light flavor sector. The results show sufficient qualitative agreement. For comparison we also present the results obtained with the conventional effective potential containing upto six quark interaction terms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.0768v3.pdf"}
{"id": "1008.1063", "abstract": "  Evolutionary 2 × 2 games are studied with players located on a square lattice. During the evolution the randomly chosen neighboring players try to maximize their collective income by adopting a random strategy pair with a probability dependent on the difference of their summed payoffs between the final and initial state assuming quenched strategies in their neighborhood. In the case of the anti-coordination game this system behaves alike an anti-ferromagnetic kinetic Ising model. Within a wide region of social dilemmas this dynamical rule supports the formation of similar spatial arrangement of the cooperators and defectors ensuring the optimum total payoff if the temptation to choose defection exceeds a threshold value dependent on the sucker's payoff. The comparison of the results with those achieved for pairwise imitation and myopic strategy updates has indicated the relevant advantage of pairwise collective strategy update in the maintenance of cooperation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.1063v1.pdf"}
{"id": "1008.1198", "abstract": "  We consider the Kuramoto model of globally coupled phase oscillators with time-delayed interactions, that is subject to the Ornstein-Uhlenbeck (Gaussian) colored or the non-Gaussian colored noise. We investigate numerically the interplay between the influences of the finite correlation time of noise τ and the time delay τ_d on the onset of the synchronization process. Both cases for identical and nonidentical oscillators had been considered. Among the obtained results for identical oscillators is a large increase of the synchronization threshold as a function of time delay for the colored non-Gaussian noise compared to the case of the colored Gaussian noise at low noise correlation time τ. However, the difference reduces remarkably for large noise correlation times. For the case of nonidentical oscillators, the incoherent state may become unstable around the maximum value of the threshold (as a function of time delay) even at lower coupling strength values in the presence of colored noise as compared to the noiseless case. We had studied the dependence of the critical value of the coupling strength (the threshold of synchronization) on given parameters of the stochastic Kuramoto model in great details and presented results for possible cases of colored Gaussian and non-Gaussian noises. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.1198v1.pdf"}
{"id": "1008.2619", "abstract": "  Motivated by a recent experiment directly measuring the current-phase relation (CPR) in graphene under the influence of a superconducting proximity effect, we here study the temperature dependence of the CPR in ballistic graphene SNS Josephson junctions within the the self-consistent tight-binding Bogoliubov-de Gennes (BdG) formalism. By comparing these results with the standard Dirac-BdG method, where rigid boundary conditions are assumed at the SN interfaces, we show on a crucial importance of both proximity effect and depairing by current for the CPR. The proximity effect grows with temperature and reduces the skewness of the CPR towards the harmonic result. In short junctions (L<ξ) current depairing is also important and gives rise to a critical phase ϕ_c<π/2 over a wide range of temperatures and doping levels. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.2619v2.pdf"}
{"id": "1008.2948", "abstract": "  Niobium-based Superconducting Radio Frequency (SRF) cavity performance is sensitive to localized defects that give rise to quenches at high accelerating gradients. In order to identify these material defects on bulk Nb surfaces at their operating frequency and temperature, it is important to develop a new kind of wide bandwidth microwave microscopy with localized and strong RF magnetic fields. By taking advantage of write head technology widely used in the magnetic recording industry, one can obtain  200 mT RF magnetic fields, which is on the order of the thermodynamic critical field of Nb, on submicron length scales on the surface of the superconductor. We have successfully induced the nonlinear Meissner effect via this magnetic write head probe on a variety of superconductors. This design should have a high spatial resolution and is a promising candidate to find localized defects on bulk Nb surfaces and thin film coatings of interest for accelerator applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.2948v1.pdf"}
{"id": "1008.3463", "abstract": "  We study entropy production and fluctuation relations in the restricted solid-on-solid growth model, which is a microscopic realization of the KPZ equation. Solving the one dimensional model exactly on a particular line of the phase diagram we demonstrate that entropy production quantifies the distance from equilibrium. Moreover, as an example of a physically relevant current different from the entropy, we study the symmetry of the large deviation function associated with the interface height. In a special case of a system of length L=4 we find that the probability distribution of the variation of height has a symmetric large deviation function, displaying a symmetry different from the Gallavotti-Cohen symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.3463v1.pdf"}
{"id": "1008.3609", "abstract": "  We report on the first detection of ionospheric disturbances caused by short repeated gamma-ray bursts from the magnetar SGR J1550-5418. Very low frequency (VLF) radio wave data obtained in South America clearly show sudden amplitude and phase changes at the corresponding times of eight SGR bursts. Maximum amplitude and phase changes of the VLF signals appear to be correlated with the gamma-ray fluence. On the other hand, VLF recovery timescales do not show any significant correlation with the fluence, possibly suggesting that the bursts' spectra are not similar to each other. In summary, the Earth's ionosphere can be used as a very large gamma-ray detector and the VLF observations provide us with a new method to monitor high energy astrophysical phenomena without interruption such as Earth Occultation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.3609v1.pdf"}
{"id": "1008.5008", "abstract": "  In this article, we explore the kinematics of timelike geodesic congruences in warped five dimensional bulk spacetimes, with and without thick or thin branes. Beginning with geodesic flows in the Randall–Sundrum AdS (Anti de Sitter) geometry without and with branes we find analytical expressions for the expansion scalar and comment on the effects of including thin branes on its evolution. Later, we move on to congruences in more general warped bulk geometries with a cosmological thick brane and a time-dependent extra dimensional scale. Using analytical expressions for the velocity field, we interpret the expansion, shear and rotation (ESR) along the flows, as functions of the extra dimensional coordinate. The evolution of a cross-sectional area orthogonal to the congruence, as seen from a local observer's point of view, is also shown graphically. Finally, the Raychaudhuri and geodesic equations in backgrounds with a thick brane are solved numerically in order to figure out the role of initial conditions (prescribed on the ESR) and spacetime curvature on the evolution of the ESR. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.5008v3.pdf"}
{"id": "1008.5395", "abstract": "  I point to an interesting similarity in the radio and the soft X-ray light curves between the November 2009 outburst of the X-ray binary Aquila X-1 and some solar flares. The ratio of the soft X-ray and radio luminosities of Aquila X-1 in that outburst is also similar to some weak solar flares, and so is the radio spectrum near 8 GHz. Based on these, as well as on some other recent studies that point to some similar properties of accretion disk coronae and stellar flares, such as ratio of radio to X-ray luminosities (Laor     Behar 2008), I speculate that the soft X-ray outburst of Aquila X-1 was related to a huge magnetic flare from its disk corona. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.5395v1.pdf"}
{"id": "1009.0712", "abstract": "  Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the Universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of a shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone not be used to do convergence map reconstruction, even on small scales. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.0712v1.pdf"}
{"id": "1009.1172", "abstract": "  We consider the transition from quark to hadronic matter which may result during the cooling/expansion of the quark-gluon plasma formed in energetic collisions of weakly isospin-asymmetric ions. This transition involves the energy density of u and d quark matter and the one of nearly isospin-symmetric nuclear matter. Within bag models, the former entails knowledge of the bag pressure, a poorly constrained quantity. The bag pressure at high density can be fixed imposing equality of quark and nucleonic energy densities at the (assumed known) transition point. We find this value to be very model dependent. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.1172v1.pdf"}
{"id": "1009.1734", "abstract": "  We revisit the scattering of surface plasmons by shallow surface defects for both protrusions and indentations of various lengths, which are deemed infinite in one-dimension parallel to the surface. Subwavelength protrusions and indentations of equal shape present different scattering coefficients when their height and width are comparable. In this case, a protrusion scatters plasmons like a vertical point-dipole on a plane, while an indentation scatters like a horizontal point-dipole on a plane. We corroborate that long and shallow asymmetrically-shaped surface defects have very similar scattering, as already found with approximate methods. In the transition from short shallow scatterers to long shallow scatterers the radiation can be understood in terms of interference between a vertical and a horizontal dipole. The results attained numerically are exact and accounted for with analytical models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.1734v1.pdf"}
{"id": "1009.5384", "abstract": "  The existence of stable magnetic configurations in white dwarfs, neutron stars and various non-convective stellar regions is now well recognized. It has recently been shown numerically that various families of equilibria, including axisymmetric mixed poloidal-toroidal configurations, are stable. Here we test the stability of an analytically-derived non force-free magnetic equilibrium, using three-dimensional magnetohydrodynamic simulations: the mixed configuration is compared with the dynamical evolution of its purely poloidal and purely toroidal components, both known to be unstable. The mixed equilibrium shows no sign of instability under white noise perturbations. This configuration therefore provides a good description of magnetic equilibrium topology inside non-convective stellar objects and will be useful to initialize magneto-rotational transport in stellar evolution codes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.5384v1.pdf"}
{"id": "1010.0264", "abstract": "  The upper main sequence magnetic chemically peculiar (Ap) stars exhibit a non-uniform distribution of chemical elements across their surfaces and with height in their atmospheres. These inhomogeneities, responsible for the conspicuous photometric and spectroscopic variation of Ap stars, are believed to be produced by atomic diffusion operating in the stellar atmospheres stabilized by multi-kG magnetic fields. Here I present an overview of the current state-of-the-art in understanding Ap-star spots and their relation to magnetic fields. In particular, I highlight recent 3-D chemical spot structure studies and summarize magnetic field mapping results based on the inversion of the full Stokes vector spectropolarimetric observations. I also discuss a puzzling new type of spotted stars, HgMn stars, in which the formation and evolution of heavy element spots is driven by a poorly understood mechanism, apparently unrelated to magnetic fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.0264v1.pdf"}
{"id": "1010.0827", "abstract": "  At low volume fraction, disordered arrangements of frictionless spheres are found in un–jammed states unable to support applied stresses, while at high volume fraction they are found in jammed states with mechanical strength. Here we show, focusing on the hard sphere zero pressure limit, that the transition between un-jammed and jammed states does not occur at a single value of the volume fraction, but in a whole volume fraction range. This result is obtained via the direct numerical construction of disordered jammed states with a volume fraction varying between two limits, 0.636 and 0.646. We identify these limits with the random loose packing volume fraction  and the random close packing volume fraction  of frictionless spheres, respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.0827v1.pdf"}
{"id": "1010.2364", "abstract": "  The asymmetric shape of the nebula around η-Carinae (Homunculus) can be explained by a spherical expansion in a non-homogeneous medium. Two models are analyzed: an exponential and an inverse power law dependence for the density as a function of distance from the equatorial plane. The presence of a medium with variable density along the polar direction progressively converts the original spherical shell into a bipolar nebula. In the case of the nebula around η-Carinae, we know the time elapsed since the great outburst in 1840. An exact match between observed radii and velocities can be obtained by fine tuning the parameters involved, such as initial radius, initial velocity and the typical scale that characterizes the gradient in density. The observed radius and velocity of the Homunculus as a function of the polar angle in spherical coordinates can be compared with the corresponding simulated data by introducing the efficiency in a single or multiple directions. Once the 3D spatial structure of the Homunculus is obtained, we can compose the image by integrating along the line of sight. In order to simulate the observed image, we have considered a bipolar nebula with constant thickness and an optically thin emitting layer. Some simulated cuts of the relative intensity are reported and may represent a useful reference for the astronomical cuts. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.2364v1.pdf"}
{"id": "1010.3730", "abstract": "  Ground-based gamma-ray astronomy has experienced a major breakthrough in the last decade thanks to the advent of new generation instruments such as H.E.S.S., MAGIC, Milagro and VERITAS. A large variety of cosmic particle accelerators has been unveiled, comprising supermassive black holes in the centres of active galaxies, nearby star forming galaxies, Galactic supernova remnants and pulsar wind nebulae, and stellar binary systems housing a compact object. While current instruments revealed the tips of the non-thermal icebergs in our Universe, a factor of 10 increase in sensitivity, improved angular resolution and an extended energy coverage is required to fully explore and understand the physics of cosmic particle acceleration. The Cherenkov Telescope Array (CTA) will provide these performances, by deploying two arrays of Cherenkov telescopes in the northern and southern hemispheres, allowing full-sky coverage. In this paper we summarize the project status and present the science prospects of the CTA observatory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.3730v2.pdf"}
{"id": "1010.4389", "abstract": "  Brown Dwarf and extrasolar planet atmospheres form clouds which strongly influence the local chemistry and physics. These clouds are globally neutral obeying dust-gas charge equilibrium which is, on short time scales, inconsistent with the observation of stochastic ionisation events of the solar system planets. We argue that a significant volume of the clouds in Brown Dwarfs and extrasolar planets is susceptible to local discharge events. These are electron avalanches triggered by charged dust grains. Such intra-cloud discharges occur on time scales shorter than the time needed to neutralise the dust grains by collisional processes. An ensemble of discharges is likely to produce enough free charges to suggest a partial and stochastic coupling of the atmosphere to a large-scale magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.4389v1.pdf"}
{"id": "1010.5619", "abstract": "  We study the full counting statistics (FCS) in a single-molecule magnet (SMM) with finite Coulomb interaction U. For finite U the FCS, differing from U→∞, shows a symmetric gate-voltage-dependence when the coupling strengths with two electrodes are interchanged, which can be observed experimentally just by reversing the bias-voltages. Moreover, we find that the effect of finite U on shot noise depends on the internal level structure of the SMM and the coupling asymmetry of the SMM with two electrodes as well. When the coupling of the SMM with the incident-electrode is stronger than that with the outgoing-electrode, the super-Poissonian shot noise in the sequential tunneling regime appears under relatively small gate-voltage and relatively large finite U, and dose not for U→∞; while it occurs at relatively large gate-voltage for the opposite coupling case. The formation mechanism of super-Poissonian shot noise can be qualitatively attributed to the competition between fast and slow transport channels. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.5619v3.pdf"}
{"id": "1011.0014", "abstract": "  Many different programs are the implementation of the same algorithm. The collection of programs can be partitioned into different classes corresponding to the algorithms they implement. This makes the collection of algorithms a quotient of the collection of programs. Similarly, there are many different algorithms that implement the same computable function. The collection of algorithms can be partitioned into different classes corresponding to what computable function they implement. This makes the collection of computable functions into a quotient of the collection of algorithms. Algorithms are intermediate between programs and functions:   Programs ↠ Algorithms ↠ Functions.   Galois theory investigates the way that a subobject sits inside an object. We investigate how a quotient object sits inside an object. By looking at the Galois group of programs, we study the intermediate types of algorithms possible and the types of structures these algorithms can have. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.0014v2.pdf"}
{"id": "1011.0439", "abstract": "  Transiting planet discoveries have largely been restricted to the short-period or low-periastron distance regimes due to the bias inherent in the geometric transit probability. Through the refinement of planetary orbital parameters, and hence reducing the size of transit windows, long-period planets become feasible targets for photometric follow-up. Here we describe the TERMS project that is monitoring these host stars at predicted transit times. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.0439v1.pdf"}
{"id": "1011.1753", "abstract": "  A model for network panel data is discussed, based on the assumption that the observed data are discrete observations of a continuous-time Markov process on the space of all directed graphs on a given node set, in which changes in tie variables are independent conditional on the current graph. The model for tie changes is parametric and designed for applications to social network analysis, where the network dynamics can be interpreted as being generated by choices made by the social actors represented by the nodes of the graph. An algorithm for calculating the Maximum Likelihood estimator is presented, based on data augmentation and stochastic approximation. An application to an evolving friendship network is given and a small simulation study is presented which suggests that for small data sets the Maximum Likelihood estimator is more efficient than the earlier proposed Method of Moments estimator. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.1753v1.pdf"}
{"id": "1011.2070", "abstract": "  Stellar light from an AGB star is scattered by the circumstellar dust and polarized in the direction perpendicular to the source. Therefore, images of circumstellar envelopes around AGB stars in polarized light traces the dust distribution and can be used to search for asymmetries, and to achieve a better understanding of the mechanisms at play when AGB stars are transformed into planetary nebulae. The PolCor instrument is a combined imager, polarimeter, and coronograph providing images with an angular resolution down to 0.2\". We have used it to map the dust distribution around three AGB stars: W Aql, and the detached shell sources DR Ser, and U Cam. W Aql is a binary and we find indications of a bi-polar dust distribution around the star. The observations of the latter two sources clearly reveal the detached shells, likely the result of a brief, strongly enhanced mass-loss rate during the late evolution of these stars. Mapping the detached shells gives us clues to the symmetry of the mass loss and important evolutionary processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2070v1.pdf"}
{"id": "1011.2449", "abstract": "  We study CP violation in the two-body decay of a scalar tau into a neutralino and a tau, which should be probed at the LHC and ILC. From the normal tau polarization, a CP asymmetry is defined which is sensitive to the CP phases of the trilinear scalar coupling parameter A_τ, the gaugino mass parameter M_1, and the higgsino mass parameter μ in the stau-neutralino sector of the Minimal Supersymmetric Standard Model. Asymmetries of more than 70", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2449v2.pdf"}
{"id": "1011.2741", "abstract": "  Around the world, several scientific projects share the interest of a global network of small Cherenkov telescopes for monitoring observations of the brightest blazars - the DWARF network. A small, ground based, imaging atmospheric Cherenkov telescope of last generation is intended to be installed and operated in Romania as a component of the DWARF network. To prepare the construction of the observatory, two support projects have been initiated. Within the framework of these projects, we have assessed a number of possible sites where to settle the observatory. In this paper we submit a brief report on the general characteristics of the best four sites selected after the local infrastructure, the nearby facilities and the social impact criteria have been applied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2741v1.pdf"}
{"id": "1011.3732", "abstract": "  Microwave cavities with high quality factors enable coherent coupling of distant quantum systems. Virtual photons lead to a transverse exchange interaction between qubits, when they are non-resonant with the cavity but resonant with each other. We experimentally probe the inverse scaling of the inter-qubit coupling with the detuning from a cavity mode and its proportionality to the qubit-cavity interaction strength. We demonstrate that the enhanced coupling at higher frequencies is mediated by multiple higher-harmonic cavity modes. Moreover, in the case of resonant qubits, the symmetry properties of the system lead to an allowed two-photon transition to the doubly excited qubit state and the formation of a dark state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.3732v1.pdf"}
{"id": "1011.4951", "abstract": "  A first adiabatic core is a transient object formed in the early phase of star formation. The observation of a first core is believed to be difficult because of its short lifetime and low luminosity. On the basis of radiation hydrodynamic simulations, we propose a novel theoretical model of first cores, Exposed Long-lifetime First core (ELF). In the very low-mass molecular core, the first core evolves slowly and lives longer than 10,000 years because the accretion rate is considerably low. The evolution of ELFs is different from that of ordinary first cores because radiation cooling has a significant effect there. We also carry out radiation transfer calculation of dust-continuum emission from ELFs to predict their observational properties. ELFs have slightly fainter but similar SEDs to ordinary first cores in radio wavelengths, therefore they can be observed. Although the probabilities that such low mass cores become gravitationally unstable and start to collapse are low, we still can expect that a considerable number of ELFs can be formed because there are many low-mass molecular cloud cores in star-forming regions that can be progenitors of ELFs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.4951v2.pdf"}
{"id": "1011.4966", "abstract": "  The parameters of the p-mode oscillations vary with solar activity. Such temporal variations provide insights for the study of the structural and dynamical changes occurring in the Sun's interior throughout the solar cycle. We present here a complete picture of the temporal variations of the global p-mode parameters (excitation, damping, frequency, peak asymmetry, and rotational splitting) over the entire solar cycle 23 and the beginning of cycle 24 as observed by the space-based, Sun-as-a-star helioseismic GOLF and VIRGO instruments onboard SoHO. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.4966v1.pdf"}
{"id": "1011.5062", "abstract": "  In this paper, we study the weak convergence of the integrated periodogram indexed by classes of functions for linear processes with symmetric α-stable innovations. Under suitable summability conditions on the series of the Fourier coefficients of the index functions, we show that the weak limits constitute α-stable processes which have representations as infinite Fourier series with i.i.d. α-stable coefficients. The cases α∈(0,1) and α∈[1,2) are dealt with by rather different methods and under different assumptions on the classes of functions. For example, in contrast to the case α∈(0,1), entropy conditions are needed for α∈[1,2) to ensure the tightness of the sequence of integrated periodograms indexed by functions. The results of this paper are of additional interest since they provide limit results for infinite mean random quadratic forms with particular Toeplitz coefficient matrices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.5062v1.pdf"}
{"id": "1011.5454", "abstract": "  A long-range soliton interaction is discussed whereby two or more dark solitons interact in an inhomogeneous atomic condensate, modifying their respective dynamics via the exchange of sound waves without ever coming into direct contact. An idealized double well geometry is shown to yield perfect energy transfer and complete periodic identity reversal of the two solitons. Two experimentally relevant geometries are analyzed which should enable the observation of this long-range interaction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.5454v1.pdf"}
{"id": "1011.6206", "abstract": "  We have conducted a spectroscopic survey of the inner regions of the Sagittarius (Sgr) dwarf galaxy using the AAOmega spectrograph on the Anglo-Australian Telescope. We determine radial velocities for over 1800 Sgr star members in 6 fields that cover an area 18.84 deg^2, with a typical accuracy of  2 km/s. Motivated by recent numerical models of the Sgr tidal stream that predict a substantial amount of rotation in the dwarf remnant core, we compare the kinematic data against N-body models that simulate the stream progenitor as (i) a pressure-supported, mass-follows-light system, and (ii) a late-type, rotating disc galaxy embedded in an extended dark matter halo. We find that the models with little, or no intrinsic rotation clearly yield a better match to the mean line-of-sight velocity in all surveyed fields, but fail to reproduce the shape of the line-of-sight velocity distribution. This result rules out models wherein the prominent bifurcation observed in the leading tail of the Sgr stream was caused by a transfer from intrinsic angular momentum from the progenitor satellite into the tidal stream. It also implies that the trajectory of the young tidal tails has not been affected by internal rotation in the progenitor system. Our finding indicates that new, more elaborate dynamical models, in which the dark and luminous components are treated independently, are necessary for simultaneously reproducing both the internal kinematics of the Sgr dwarf and the available data for the associated tidal stream. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.6206v1.pdf"}
{"id": "1011.6613", "abstract": "  In this work we study an ultrastrong coupled qubit-cavity system subjected to slow repeated measurements. We demonstrate that even under a few imperfect measurements it is possible to detect transitions of the qubit from its free ground state to the excited state. The excitation probability grows exponentially fast in analogy with the quantum anti-Zeno effect. The dynamics and physics described in this paper is accessible to current superconducting circuit technology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.6613v2.pdf"}
{"id": "1012.1395", "abstract": "  A statistical scenario is proposed to explain the γ-ray variability and flares of the Crab nebula, which were observed recently by the Fermi/LAT. In this scenario electrons are accelerated in a series of knots, whose sizes follow a power-law distribution. These knots presumably move outwards from the pulsar and have a distribution in the Doppler boost factor. The maximal electron energy is assumed to be proportional to the size of the knot. Fluctuations at the highest energy end of the overall electron distribution will result in variable γ-ray emission via the synchrotron process in the ∼ 100 MeV range. Since highly boosted larger knots are rarer than smaller knots, the model predicts that the variability of the synchrotron emission increases with the photon energy. We realize such a scenario with a Monte-Carlo simulation and find that the model can reproduce both the two γ-ray flares over a period of ∼ year and the monthly scale γ-ray flux fluctuations as observed by the Fermi/LAT. The observed γ-ray spectra in both the steady and flaring states are also well reproduced. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.1395v2.pdf"}
{"id": "1012.2110", "abstract": "  New results of a search for the ultra-rare decay μ→ e γ by the MEG collaboration are reported in this contribution. The data were taken during 2009 and correspond to approximately 6.5 10^13 muon stopped on target. A maximum likelihood analysis sets an upper limit at 90% C.L. on the branching ratio, BF(μ→ e γ) <1.5 10^-11. The results presented here are preliminary. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.2110v1.pdf"}
{"id": "1012.2360", "abstract": "  We discuss the recent detection of a strong, organized magnetic field in the bright, broad-line B2V star, HR 5907, using the ESPaDOnS spectropolarimeter on the CFHT as part of the Magnetism in Massive Stars (MiMeS) survey. We find a rotational period of 0.50833 days, making it the fastest-rotating, non-degenerate magnetic star ever detected. Like the previous rapid-rotation record holder HR 7355 (also discovered by MiMeS: Oksala et al. 2010, Rivinius et al. 2010), this star shows emission line variability that is diagnostic of a structured magnetosphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.2360v1.pdf"}
{"id": "1012.3476", "abstract": "  Restricted Boltzmann Machines (RBM) have attracted a lot of attention of late, as one the principle building blocks of deep networks. Training RBMs remains problematic however, because of the intractibility of their partition function. The maximum likelihood gradient requires a very robust sampler which can accurately sample from the model despite the loss of ergodicity often incurred during learning. While using Parallel Tempering in the negative phase of Stochastic Maximum Likelihood (SML-PT) helps address the issue, it imposes a trade-off between computational complexity and high ergodicity, and requires careful hand-tuning of the temperatures. In this paper, we show that this trade-off is unnecessary. The choice of optimal temperatures can be automated by minimizing average return time (a concept first proposed by [Katzgraber et al., 2006]) while chains can be spawned dynamically, as needed, thus minimizing the computational overhead. We show on a synthetic dataset, that this results in better likelihood scores. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.3476v1.pdf"}
{"id": "1012.3965", "abstract": "  We present a theory of single-magnet flowmeter for liquid metals and compare it with experimental results. The flowmeter consists of a freely rotating permanent magnet, which is magnetized perpendicularly to the axle it is mounted on. When such a magnet is placed close to a tube carrying liquid metal flow, it rotates so that the driving torque due to the eddy currents induced by the flow is balanced by the braking torque induced by the rotation itself. The equilibrium rotation rate, which varies directly with the flow velocity and inversely with the distance between the magnet and the layer, is affected neither by the electrical conductivity of the metal nor by the magnet strength. We obtain simple analytical solutions for the force and torque on slowly moving and rotating magnets due to eddy currents in a layer of infinite horizontal extent. The predicted equilibrium rotation rates qualitatively agree with the magnet rotation rate measured on a liquid sodium flow in stainless steel duct. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.3965v2.pdf"}
{"id": "1012.4348", "abstract": "  After close to 20 years of preparation, the dedicated heavy ion experiment ALICE took first data with proton collisions at the LHC at the end of 2009. This article recalls the main design choices made for the detector and summarizes initial operation and performance of ALICE at the LHC; first physics results are covered elsewhere in these proceedings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.4348v1.pdf"}
{"id": "1012.4595", "abstract": "  The late-time behaviour of the Einstein-dust system is well understood for homogeneous spacetimes. For the case of Bianchi I we have been able to show that the late-time behaviour of the Einstein-Vlasov system is well approximated by the Einstein-dust system assuming that one is close to the unique stationary solution which is the attractor of the Einstein-dust system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.4595v1.pdf"}
{"id": "1012.4662", "abstract": "  We generalize the notion of quasi-local charges, introduced by P. Tod for Yang–Mills fields with unitary groups, to non-Abelian gauge theories with arbitrary gauge group, and calculate its small sphere and large sphere limits both at spatial and null infinity. We show that for semisimple gauge groups no reasonable definition yield conserved total charges and Newman–Penrose (NP) type quantities at null infinity in generic, radiative configurations. The conditions of their conservation, both in terms of the field configurations and the structure of the gauge group, are clarified. We also calculate the NP quantities for stationary, asymptotic solutions of the field equations with vanishing magnetic charges, and illustrate these by explicit solutions with various gauge groups. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.4662v2.pdf"}
{"id": "1012.5021", "abstract": "  We calculate the bi-photon state generated by spontaneous parametric down conversion in a thin crystal and under collinear phase matching conditions using a pump consisting of any superposition of Laguerre-Gauss modes. The result has no restrictions on the angular or radial momenta or, in particular, on the width of the pump, signal and idler modes. We demonstrate the strong effect of the pump to signal/idler width ratio on the composition of the down-converted entangled fields. Knowledge of the pump to signal/idler width ratio is shown to be essential when calculating the maximally entangled states that can be produced using pumps with a complex spatial profile. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.5021v1.pdf"}
{"id": "1012.5811", "abstract": "  The far-ultraviolet (FUV) channel of the Cosmic Origins Spectrograph (COS) is designed to operate between 1130Å and 1850Å, limited at shorter wavelengths by the reflectivity of the MgF2 protected aluminum reflective surfaces on the Optical Telescope Assembly and on the COS FUV diffraction gratings. However, because the detector for the FUV channel is windowless, it was recognized early in the design phase that there was the possibility that COS would retain some sensitivity at shorter wavelengths due to the first surface reflection from the MgF2 coated optics. Preflight testing of the flight spare G140L grating revealed  5", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.5811v1.pdf"}
{"id": "1101.0603", "abstract": "  We present single-epoch radio afterglow observations of 24 long-duration gamma-ray burst (GRB) on a timescale of >100 d after the burst. These observations trace the afterglow evolution when the blastwave has decelerated to mildly- or non-relativistic velocities and has roughly isotropized. We infer beaming-independent kinetic energies using the Sedov-Taylor self-similar solution, and find a median value for the sample of detected bursts of about 7x10^51 erg, with a 90", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.0603v1.pdf"}
{"id": "1101.3189", "abstract": "  We study nano-pattern formation in a stochastic model for adsorption-desorption processes with interacting adsorbate and hyperbolic transport caused by memory effects. It is shown that at early stages the system manifests pattern selection processes. Stationary stable patterns of nano-size are analyzed. It was found that multiplicative noise satisfying fluctuation-dissipation relation can induce re-entrant pattern formation related to non-equilibrium transitions. According to obtained Fokker-Planck equation kinetics of island sizes in a quasi-stationary limit is discussed. Analytical results are compared with computer simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.3189v1.pdf"}
{"id": "1101.3490", "abstract": "  We present a simple mathematical framework for the description of the dynamics of glassy systems in terms of a random walk in a complex energy landscape pictured as a network of minima. We show how to use the tools developed for the study of dynamical processes on complex networks, in order to go beyond mean-field models that consider that all minima are connected to each other. We consider several possibilities for the transition rates between minima, and show that in all cases the existence of a glassy phase depends on a delicate interplay between the network's topology and the relationship between energy and degree of a minimum. Interestingly, the network's degree correlations and the details of the transition rates do not play any role in the existence (nor in the value) of the transition temperature, but have an impact only on more involved properties. For Glauber or Metropolis rates in particular, we find that the low-temperature phase can be further divided into two regions with different scaling properties of the average trapping time. Overall, our results rationalize and link the empirical findings about correlations between the energy of the minima and their degree, and should stimulate further investigations on this issue. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.3490v2.pdf"}
{"id": "1101.3617", "abstract": "  We propose a stochastic map model of economic dynamics. In the last decade, an array of observations in economics has been investigated in the econophysics literature, a major example being the universal features of inequality in terms of income and wealth. Another area of inquiry is the formation of opinion in a society. The proposed model attempts to produce positively skewed distributions and the power law distributions as has been observed in the real data of income and wealth. Also, it shows a non-trivial phase transition in the opinion of a society (opinion formation). A number of physical models also generates similar results. In particular, the kinetic exchange models have been especially successful in this regard. Therefore, we compare the results obtained from these two approaches and discuss a number of new features and drawbacks of this model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.3617v2.pdf"}
{"id": "1101.3717", "abstract": "  We consider the problem of a single level quantum dot coupled to the edge of a one-dimensional Luttinger liquid wire by both a hopping term and electron-electron interactions. Using bosonization and Coulomb gas mapping of the Anderson-Yuval type we show that thermodynamic properties of the level, in particular, its occupation, depend on the various interactions in the system only through a single quantity — the corresponding Fermi edge singularity exponent. However, dynamical properties, such as the level density of states, depend in a different way on each type of interaction. Hence, we can construct different models, with and without interactions in the wire, with equal Fermi edge singularity exponents, which have identical population curves, although they originate from very different level densities of states. The latter may either be regular or show a power-law suppression or enhancement at the Fermi energy. These predictions are verified to a high degree of accuracy using the density matrix renormalization group algorithm to calculate the dot occupation, and classical Monte Carlo simulations on the corresponding Coulomb gas model to extract the level density of states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.3717v1.pdf"}
{"id": "1101.3731", "abstract": "  We examine the local density of states of an impurity level or a quantum dot coupled to a fractional quantum Hall edge, or to the end of a single one-dimensional Luttinger-liquid lead. Effects of an Ohmic dissipative bath are also taken into account. Using both analytical and numerical techniques we show that, in general, the density of states exhibits power-law frequency dependence near the Fermi energy. In a substantial region of the parameter space it simply reflects the behavior of the tunneling density of states at the end of a Luttinger-liquid, and is insensitive either to the value of the dot-lead interaction or to the strength of dissipation; otherwise it depends on these couplings too. This behavior should be contrasted with the thermodynamic properties of the level, in particular, its occupancy, which were previously shown to depend on the various interactions in the system only through the corresponding Fermi edge singularity exponent, and thus cannot display any Luttinger-liquid specific power-law. Hence, we can construct different models, some with and some without interactions in the wire (but with equal Fermi edge singularity exponents), which would have very different level densities of states, although they all result in the same level population vs. energy curves. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.3731v1.pdf"}
{"id": "1101.3973", "abstract": "  The subject of this work is the patrolling of an environment with the aid of a team of autonomous agents. We consider both the design of open-loop trajectories with optimal properties, and of distributed control laws converging to optimal trajectories. As performance criteria, the refresh time and the latency are considered, i.e., respectively, time gap between any two visits of the same region, and the time necessary to inform every agent about an event occurred in the environment. We associate a graph with the environment, and we study separately the case of a chain, tree, and cyclic graph. For the case of chain graph, we first describe a minimum refresh time and latency team trajectory, and we propose a polynomial time algorithm for its computation. Then, we describe a distributed procedure that steers the robots toward an optimal trajectory. For the case of tree graph, a polynomial time algorithm is developed for the minimum refresh time problem, under the technical assumption of a constant number of robots involved in the patrolling task. Finally, we show that the design of a minimum refresh time trajectory for a cyclic graph is NP-hard, and we develop a constant factor approximation algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.3973v3.pdf"}
{"id": "1101.4146", "abstract": "  Irradiation with high energy photons (10.2 - 11.8 eV) was applied to small diamondoids isolated in solid rare gas matrices at low temperature. The photoproducts were traced via UV absorption spectroscopy. We found that upon ionization the smallest of these species lose a peripheral H atom to form a stable closed-shell cation. This process is also likely to occur under astrophysical conditions for gas phase diamondoids and it opens the possibility to detect diamond-like molecules using their rotational spectrum since the dehydrogenated cations possess strong permanent dipole moments. The lowest-energy electronic features of these species in the UV were found to be rather broad, shifting to longer wavelengths with increasing molecular size. Calculations using time-dependent density functional theory support our experimental findings and extend the absorption curves further into the vacuum ultraviolet. The complete sigma - sigma* spectrum displays surprisingly strong similarities to meteoritic nanodiamonds containing 50 times more C atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.4146v4.pdf"}
{"id": "1101.4815", "abstract": "  This paper investigates the optimum source transmission strategy to maximize the capacity of a multiple-input single-output (MISO) amplify-and-forward relay channel, assuming source-relay channel mean feedback at the source. The challenge here is that relaying introduces a nonconvex structure in the objective function, thereby excluding the possible use of previous methods dealing with mean feedback that generally rely on the concavity of the objective function. A novel method is employed, which divides the feasible set into two subsets and establishes the optimum from one of them by comparison. As such, the optimization is transformed into the comparison of two nonnegative random variables in the Laplace transform order, which is one of the important stochastic orders. It turns out that the optimum transmission strategy is to transmit along the known channel mean and its orthogonal eigenchannels. The condition for rank-one precoding (beamforming) to achieve capacity is also determined. Our results subsume those for traditional MISO precoding with mean feedback. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.4815v1.pdf"}
{"id": "1101.5002", "abstract": "  The abstract framework of quantum mechanics (QM) causes the well-known weirdness, which leads to the field of foundation of QM. We constructed the new concept, i.e., scope, to lay the foundation of quantum coherence and openness, also the principles of superposition and entanglement. We studied analytically and quantitatively the quantum correlations and information, also we discussed the physical essence of the existed entanglement measures. We compared with several other approaches to the foundation of QM, and we stated that the concept of scope is unique and has not been demonstrated before. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.5002v2.pdf"}
{"id": "1101.5048", "abstract": "  In social systems, people communicate with each other and form groups based on their interests. The pattern of interactions, the network, and the ideas that flow on the network naturally evolve together. Researchers use simple models to capture the feedback between changing network patterns and ideas on the network, but little is understood about the role of past events in the feedback process. Here we introduce a simple agent-based model to study the coupling between peoples' ideas and social networks, and better understand the role of history in dynamic social networks. We measure how information about ideas can be recovered from information about network structure and, the other way around, how information about network structure can be recovered from information about ideas. We find that it is in general easier to recover ideas from the network structure than vice versa. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.5048v1.pdf"}
{"id": "1101.5174", "abstract": "  In this paper, we propose a masked photocathode inside a photoinjector for generating high brightness electron beam. Instead of mounting the photocathode onto an electrode, an electrode with small hole is used as a mask to shield the photocathode from the accelerating vacuum chamber. Using such a masked photocathode will make the replacement of photocathode material easy by rotating the photocathode behind the electrode into the hole. Furthermore, this helps reduce the dark current or secondary electron emission from the photocathode material. The masked photocathode also provides transverse cut-off to a Gaussian laser beam that reduces electron beam emittance growth from nonlinear space-charge effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.5174v2.pdf"}
{"id": "1101.6042", "abstract": "  An interpretation of the beam spin azimuthal asymmetries measured at JLAB in deep exclusive electroproduction of charged and neutral pions is presented. The model combines a Regge pole approach with the effect of nucleon resonances. The s- and u-channel contributions are described using a dual Bloom-Gilman connection between the exclusive form factors and inclusive deep inelastic structure functions. The results are in agreement with data provided the excitations of nucleon resonances are taken into account. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.6042v1.pdf"}
{"id": "1102.0067", "abstract": "  A nonlocal coupling mechanism to directly transfer the energy from large-scale Magnetohydrodynamic(MHD) Alfven waves to small-scale kinetic Alfven waves is presented. It is shown that the interaction between a MHD Alfven wave and a reversely propagating kinetic Alfven wave can generate another kinetic Alfven wave, and this interaction exists in the plasmas where the thermal to magnetic pressure ratio is larger than the electron to ion mass ratio. The proposed nonlocal interaction may have a potential application to account for the observed electron scale kinetic Alfven waves in the solar wind and solar corona plasmas. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.0067v2.pdf"}
{"id": "1102.0704", "abstract": "  We discuss the feasibility of seeing a Higgs boson which decays to four partons through a pair of (pseudo-)scalars at the LHC. We restrict our search to Higgs bosons produced in association with a W/Z boson at high transverse momentum. We argue that subjet analysis techniques are a good discriminant between such events and W/Z plus jets and top-antitop production. For light scalar masses (below 30 GeV), we find evidence that a flavor-independent search for such a non-standard Higgs boson is plausible with 100 fb^-1 of data, while a Higgs decaying to heavier scalars is only likely to be visible in models where scalar decays to b quarks dominate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.0704v1.pdf"}
{"id": "1102.0976", "abstract": "  The role of long range badly screened Coulomb interactions in a one-dimensional chain of Josephson junctions is studied. Correlation functions for the phase correlator are obtained as a function of the Josephson coupling energy, the short range part of Coulomb repulsion and its long range component. Though quasi-long range order is no longer possible and the usual Kosterlitz-Thouless transition no longer exists, there are remnants of it. As an application, we calculate the I-V curves for Andreev reflexion when a normal metal is placed in contact with the chain. Formally, there is always an offset voltage V_0 below which no current can flow, however, in some regimes V_0 can be negligible. Contrary to what happens without long-range interactions, the Andreev current, as a function of applied voltage, increases faster than any power law. Signatures of long range interactions and phase slips appear in the I-V curves. Possible application for quasi one-dimensional thin superconducting wires is outlined. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.0976v1.pdf"}
{"id": "1102.1020", "abstract": "  The question \"what is the observable electromagnetic (EM) signature of a compact binary merger?\" is an intriguing one with crucial consequences to the quest for gravitational waves (GW). Compact binary mergers are prime sources of GW, targeted by current and next generation detectors. Numerical simulations have demonstrated that these mergers eject energetic sub-relativistic (or even relativistic) outflows. This is certainly the case if the mergers produce short GRBs, but even if not, significant outflows are expected. The interaction of such outflows with the surround matter inevitably leads to a long lasting radio signal. We calculate the expected signal from these outflows (our calculations are also applicable to short GRB orphan afterglows) and we discuss their detectability. We show that the optimal search for such signal should, conveniently, take place around 1.4 GHz. Realistic estimates of the outflow parameters yield signals of a few hundred μJy, lasting a few weeks, from sources at the detection horizon of advanced GW detectors. Followup radio observations, triggered by GW detection, could reveal the radio remnant even under unfavorable conditions. Upcoming all sky surveys can detect a few dozen, and possibly even thousands, merger remnants at any give time, thereby providing robust merger rate estimates even before the advanced GW detectors become operational. In fact, the radio transient RT 19870422 fits well the overall properties predicted by our model and we suggest that its most probable origin is a compact binary merger radio remnant. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.1020v1.pdf"}
{"id": "1102.3206", "abstract": "  We set the first limits on the ultra-high energy (UHE) neutrino fluence at energies greater than 10^9 GeV from gamma-ray bursts (GRBs) based on data from the second flight of the ANtarctic Impulsive Transient Antenna (ANITA). During the 31 day flight of ANITA-II, 26 GRBs were recorded by Swift or Fermi. Of these, we analyzed the 12 GRBs which occurred during quiet periods when the payload was away from anthropogenic activity. In a blind analysis, we observe 0 events on a total background of 0.0044 events in the combined prompt window for all 12 low-background bursts. We also observe 0 events from the remaining 14 bursts. We place a 90", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.3206v1.pdf"}
{"id": "1102.5738", "abstract": "  The momentum distribution is one of the most important quantities which provides information about interactions in many-body systems. At the same time it is a quantity that can easily be accessed in experiments on ultracold atoms. In this paper, we consider mixtures of light and heavy fermionic atoms in an optical lattice described effectively by the Falicov-Kimball model. Using a Monte Carlo method, we study how different ordered density-wave phases can be detected by measurement of the momentum distribution of the light atoms. We also demonstrate that ordered phases can be seen in Bragg scattering experiments. Our results indicate that the main factor that determines the momentum distribution of the light atoms is the trap confinement. On the other hand, the pattern formed by the heavy atoms seen in the Bragg scattering experiments is very sensitive to the temperature and possibly can be used in low-temperature thermometry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.5738v1.pdf"}
{"id": "1103.0489", "abstract": "  Based on a simple model for spin-polarized scanning tunneling spectroscopy (SP-STS) we study how tip magnetization and electronic structure affects the differential conductance (dI/dV) tunneling spectrum of an Fe(001) surface. We take into account energy dependence of the vacuum decay of electron states, and tip electronic structure either using an ideal model or based on ab initio electronic structure calculation. In the STS approach, topographic and magnetic contributions to dI/dV can clearly be distinguished and analyzed separately. Our results suggest that the sensitivity of STS on a magnetic sample can be tuned and even enhanced by choosing the appropriate magnetic tip and bias setpoint, and the effect is governed by the effective spin-polarization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.0489v2.pdf"}
{"id": "1103.1222", "abstract": "  We present a numerical study on an interacting monomer-dimer model with nearest neighbor repulsion on a square lattice, which possesses two symmetric absorbing states. The model is observed to exhibit two nearby continuous transitions: the Z_2 symmetry-breaking order-disorder transition and the absorbing transition with directed percolation criticality. We find that the symmetry-breaking transition shows a non-Ising critical behavior, and that the absorbing phase becomes critical, in the sense that the critical decay of the dimer density observed at the absorbing transition persists even within the absorbing phase. Our findings call for further studies on the microscopic models and corresponding continuum description belonging to the generalized voter universality class. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.1222v3.pdf"}
{"id": "1103.1287", "abstract": "  Optimized, necessary and sufficient conditions for the identification of the Schmidt number will be derived in terms of general Hermitian operators. These conditions apply to arbitrary mixed quantum states. The optimization procedure delivers equations similar to the eigenvalue problem of an operator. The properties of the solution of these equations will be studied. We solve these equations for classes of operators. The solutions will be applied to phase randomized two-mode squeezed-vacuum states in continuous variable systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.1287v1.pdf"}
{"id": "1103.1383", "abstract": "  We discuss two phenomenological descriptions of low-current transport in bilayer quantum Hall system with exciton condensates, one based on a Landauer-Buttiker description of Andreev scattering at contacts to coherent bilayers and one based on a simplified single-parameter p-ology description of the weak to strong interlayer coupling crossover. The Andreev scattering phenomenology in intended to apply when the condensate is well developed and is used to predict current-voltage relationships for a variety of two contact geometries. We also apply this formalism to circumstances in which the tunnel current exceeds its critical value and the condensate is time-dependent. The p-ology approach is used to establish the universal development of large longitudinal drags, even in homogenous coherent samples, as the condensate weakens and the Hall drag is reduced. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.1383v1.pdf"}
{"id": "1103.4863", "abstract": "  We present three-dimensional hydrodynamic models of radio galaxies interacting with initially relaxed hot atmospheres and explore the significant off-axis radio lobe structures which result under certain conditions. With a focus on the \"winged\" and \"X-shaped\" radio galaxy population, we confirm the importance of observed trends such as the connection of wing formation with jets co-aligned with the major axis of the surrounding atmosphere. These wings are formed substantially by the deflection of lobe plasma flowing back from the hot spots (backflow) and develop in two stages: supersonic expansion of an overpressured cocoon at early times followed by buoyant expansion at later times. We explore a limited parameter space of jet and atmosphere properties and find that the most prominent wings are produced when a decaying jet is injected into a small, dense, highly elliptical atmosphere. On the basis of this search, we argue that the deflection of backflow by gradients in the hot atmosphere is a strong candidate for forming observed wings but must work in tandem with some other mechanism for forming the initial wing channels. Our models indicate that lobe interaction with the hot atmosphere may play a dominant role in shaping the morphology of radio galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.4863v1.pdf"}
{"id": "1103.4988", "abstract": "  The free parameters of a flat accelerating model without dark energy are constrained by using Supernovae type Ia and observational H(z) data. Instead of the vacuum dominance, the present accelerating stage in this modified Einstein-de Sitter cosmology is a consequence of the gravitationally-induced particle production of cold dark matter. The model present a transition from a decelerating to an accelerating regime at low redshifts, and is also able to harmonize a cold dark matter picture with the latest measurements of the Hubble constant H_0, the Supernovae observations (Constitution sample), and the H(z) data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.4988v1.pdf"}
{"id": "1103.5269", "abstract": "  We investigate a prototypical agent-based model, the Naming Game, on two-dimensional random geometric networks. The Naming Game [A. Baronchelli et al., J. Stat. Mech.: Theory Exp. (2006) P06014.] is a minimal model, employing local communications that captures the emergence of shared communication schemes (languages) in a population of autonomous semiotic agents. Implementing the Naming Games with local broadcasts on random geometric graphs, serves as a model for agreement dynamics in large-scale, autonomously operating wireless sensor networks. Further, it captures essential features of the scaling properties of the agreement process for spatially-embedded autonomous agents. Among the relevant observables capturing the temporal properties of the agreement process, we investigate the cluster-size distribution and the distribution of the agreement times, both exhibiting dynamic scaling. We also present results for the case when a small density of long-range communication links are added on top of the random geometric graph, resulting in a \"small-world\"-like network and yielding a significantly reduced time to reach global agreement. We construct a finite-size scaling analysis for the agreement times in this case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.5269v1.pdf"}
{"id": "1103.5545", "abstract": "  We investigate one-dimensional (1D) discrete time quantum walks (QWs) with spatially or temporally random defects as a consequence of interactions with random environments. We focus on the QWs with chiral symmetry in a topological phase, and reveal that chiral symmetry together with bipartite nature of the QWs brings about intriguing behaviors such as coexistence of topologically protected edge states at zero energy and Anderson transitions in the 1D chiral class at non-zero energy in their dynamics. Contrary to the previous studies, therefore, the spatially disordered QWs can avoid complete localization due to the Anderson transition. It is further confirmed that the edge states are robust for spatial disorder but not for temporal disorder. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.5545v3.pdf"}
{"id": "1104.0608", "abstract": "  Improved results using a method similar to the Munn-Silbey approach have been obtained on the temperature dependence of transport properties of an extended Holstein model incorporating simultaneous diagonal and off-diagonal exciton-phonon coupling. The Hamiltonian is partially diagonalized by a canonical transformation, and optimal transformation coefficients are determined in a self-consistent manner. Calculated transport properties exhibit substantial corrections on those obtained previously by Munn and Silbey for a wide range of temperatures thanks to a numerically exact evaluation and an added momentum-dependence of the transformation matrix. Results on the diffusion coefficient in the moderate and weak coupling regime show distinct band-like and hopping-like transport features as a function of temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.0608v3.pdf"}
{"id": "1104.0955", "abstract": "  We present an analytic derivation of the temporal dependence of the perpendicular transport coefficient of charged particles in magnetostatic turbulence, for times smaller than the time needed to charged particles to travel the turbulence correlation length. This time window is left unexplored in most transport models. In our analysis all magnetic scales are taken to be much larger than the particle gyroradius, so that perpendicular transport is assumed to be dominated by the guiding center motion. Particle drift from the local magnetic field lines and magnetic field lines random walk are evaluated separately for slab and 3D isotropic turbulence. Contributions of wavelength scales shorter and longer than the turbulence coherence length are compared. In contrast to slab case, particles in 3D isotropic turbulence unexpectedly diffuse from local magnetic field lines; this result questions the common assumption that particle magnetization is independent on turbulence geometry. Extensions of this model will allow for a study of solar wind anisotropies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.0955v1.pdf"}
{"id": "1104.1002", "abstract": "  Hadron collider signatures of new physics are investigated in which a primary resonance is produced that decays to a secondary resonance by emitting a W-boson, with the secondary resonance decaying to two jets. This topology can arise in supersymmetric theories with R-parity violation where the lightest supersymmetric particles are either a pair of squarks, or a slepton - sneutrino pair. The resulting signal can have a cross section consistent with the Wjj observation reported by the CDF collaboration, while remaining consistent with earlier constraints. Other observables that can be used to confirm this scenario include a significant charge asymmetry in the same channel at the LHC. With strongly interacting resonances such as squarks, pair production topologies additionally give rise to 4 jet and WW + 4 jet signatures, each with two equal-mass dijet resonances within the 4 jets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.1002v3.pdf"}
{"id": "1104.1824", "abstract": "  We present in this paper our work regarding simulating a type of P system known as a spiking neural P system (SNP system) using graphics processing units (GPUs). GPUs, because of their architectural optimization for parallel computations, are well-suited for highly parallelizable problems. Due to the advent of general purpose GPU computing in recent years, GPUs are not limited to graphics and video processing alone, but include computationally intensive scientific and mathematical applications as well. Moreover P systems, including SNP systems, are inherently and maximally parallel computing models whose inspirations are taken from the functioning and dynamics of a living cell. In particular, SNP systems try to give a modest but formal representation of a special type of cell known as the neuron and their interactions with one another. The nature of SNP systems allowed their representation as matrices, which is a crucial step in simulating them on highly parallel devices such as GPUs. The highly parallel nature of SNP systems necessitate the use of hardware intended for parallel computations. The simulation algorithms, design considerations, and implementation are presented. Finally, simulation results, observations, and analyses using an SNP system that generates all numbers in ℕ - 1 are discussed, as well as recommendations for future work. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.1824v1.pdf"}
{"id": "1104.3184", "abstract": "  We introduce and study random bipartite networks with hidden variables. Nodes in these networks are characterized by hidden variables which control the appearance of links between node pairs. We derive analytic expressions for the degree distribution, degree correlations, the distribution of the number of common neighbors, and the bipartite clustering coefficient in these networks. We also establish the relationship between degrees of nodes in original bipartite networks and in their unipartite projections. We further demonstrate how hidden variable formalism can be applied to analyze topological properties of networks in certain bipartite network models, and verify our analytical results in numerical simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.3184v2.pdf"}
{"id": "1104.3540", "abstract": "  Velocity errors in particle tracking velocimetry (PTV) are studied. When using high-speed video cameras, the velocity error may increase at a high camera frame rate. This increase in velocity error is due to particle-position uncertainty, which is one of two sources of velocity errors studied here. The other source of error is particle acceleration, which has the opposite trend of diminishing at higher frame rates. Both kinds of errors can propagate into quantities calculated from velocity, such as the kinetic temperature of particles or correlation functions. As demonstrated in a dusty plasma experiment, the kinetic temperature of particles has no unique value when measured using PTV, but depends on the sampling time interval or frame rate. It is also shown that an artifact appears in an autocorrelation function computed from particle positions and velocities, and it becomes more severe when a small sampling-time interval is used. Schemes to reduce these errors are demonstrated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.3540v1.pdf"}
{"id": "1104.3689", "abstract": "  We study discrete conjugate nets whose Laplace sequence is of period four. Corresponding points of opposite nets in this cyclic sequence have equal osculating planes in different net directions, that is, they correspond in an asymptotic transformation. We show that this implies that the connecting lines of corresponding points form a discrete W-congruence. We derive some properties of discrete Laplace cycles of period four and describe two explicit methods for their construction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.3689v1.pdf"}
{"id": "1104.3941", "abstract": "  An interacting boson model Hamiltonian determined from Hartree-Fock-Bogoliubov calculations with the new microscopic Gogny energy density functional D1M, is applied to the spectroscopic analysis of neutron-rich Yb, Hf, W, Os and Pt isotopes with mass A∼ 180-200. Excitation energies and transition rates for the relevant low-lying quadrupole collective states are calculated by this method. Transitions from prolate to oblate ground-state shapes are analyzed as a function of neutron number N in a given isotopic chain by calculating excitation energies, B(E2) ratios, and correlation energies in the ground state. It is shown that such transitions tend to occur more rapidly for the isotopes with lower proton number Z, when departing from the proton shell closure Z=82. The triaxial degrees of freedom turn out to play an important role in describing the considered mass region. Predicted low-lying spectra for the neutron-rich exotic Hf and Yb isotopes are presented. The approximations used in the model and the possibilities to refine its predictive power are addressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.3941v3.pdf"}
{"id": "1104.4371", "abstract": "  We develop a simple and efficient theoretical model to understand the quantum properties of broadband continuous variable quantum teleportation. We show that, if stated properly, the problem of multimode teleportation can be simplified to teleportation of a single effective mode that describes the input state temporal characteristic. Using that model, we show how the finite bandwidth of squeezing and external noise in the classical channel affect the output teleported quantum field. We choose an approach that is especially relevant for the case of non-Gaussian non-classical quantum states and we finally back-test our model with recent experimental results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.4371v2.pdf"}
{"id": "1105.0485", "abstract": "  We report a 3D magnetohydrodynamics simulation that studies the formation of dipolarization fronts during magnetotail reconnection. The crucial new feature uncovered in the present 3D simulation is that the process of reconnection produces flux ropes developing within the reconnection region. These flux ropes are unstable to the kink mode and introduce a spontaneous structure in the dawn-dusk direction. The dipolarization fronts forming downstream of reconnection are strongly affected by the kinking ropes. At the fronts, a density gradient is present with opposite direction to that of the acceleration field and leads to an interchange instability. We present evidence for a causal link where the perturbations of the kinking flux ropes with their natural and well defined scales drive and select the scales for the interchange mode in the dipolarization fronts. The results of the simulation are validated against measured structures observed by the Themis mission. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.0485v1.pdf"}
{"id": "1105.1172", "abstract": "  We argue that the Isham-Storey exact solution to bigravity does not describe black holes because the horizon is a singular surface. However, this is not a generic property of bigravity, but a property of a particular potential. More general potentials do accept regular black holes. For regular black holes, we compute the total energy and thermodynamical parameters. Phase transitions occur for certain critical temperatures. We also find a novel region on phase space describing up to 4 allowed states for a given temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.1172v3.pdf"}
{"id": "1105.1510", "abstract": "  We establish the existence of fixed points for certain gauge theories candidate to be magnetic duals of QCD with one adjoint Weyl fermion. In the perturbative regime of the magnetic theory the existence of a very large number of fixed points is unveiled. We classify them by analyzing their basin of attraction. The existence of several nonsupersymmetric fixed points for the magnetic gauge theory lends further support towards the existence of gauge-gauge duality beyond supersymmetry. We also discover that among these very many fixed points there are supersymmetric ones emerging from a generic nonsupersymmetric renormalization group flow. We therefore conclude that supersymmetry naturally emerges as a fixed point theory from a nonsupersymmetric Lagrangian without the need for fine-tuning of the bare couplings. Our results suggest that supersymmetry can be viewed as an emergent phenomenon in field theory. In particular there should be no need for fine-tuning the bare couplings when performing Lattice simulations aimed to investigate supersymmetry on the Lattice. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.1510v1.pdf"}
{"id": "1105.1669", "abstract": "  We conduct a systematic investigation of the nuclear collective dynamics that emerges in systems with random two-body interactions. We explore the development of the mean field and study its geometry. We investigate multipole collectivities in the many-body spectra and their dependence on the underlying two-body interaction Hamiltonian. The quadrupole-quadrupole interaction component appears to be dynamically dominating in two-body random ensembles. This quadrupole coherence leads to rotational spectral features and thus suggests the formation of the deformed mean-field of a specific geometry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.1669v1.pdf"}
{"id": "1105.2222", "abstract": "  We have studied the dynamics of quantum correlations such as entanglement, Bell-nonlocality and quantum discord between identical as well as unidentical atoms interacting with a single-mode cavity field and subject to cavity decay. The effect of single atom detuning, cavity decay rate and initial preparation of the atoms on the corresponding correlation measures have been investigated. It is found that even under strong dissipation, time evolution can create high quantum discord while entanglement and Bell nonlocality stay zero for an initially separable state. Quantum discord increases while entanglement decreases in a certain time period under dissipation for the initial state that both atoms are in the excited state if the qubits are identical. For some type of initial states, cavity decay is shown to drive the system to a stationary state with high entanglement and quantum discord. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.2222v3.pdf"}
{"id": "1105.3151", "abstract": "  We use the clump giants of the disk as standard candles calibrated from Hipparcos parallaxes in order to map their distribution with two new near-IR surveys of the Galactic plane: UKIDSS-GPS and VVV. We explore different selection cuts of clump giants. We conclude that there is an edge of the stellar disk of the Milky Way at R=13.9+/-0.5kpc along various lines of sight across the galaxy. The effect of the warp is considered, taking fields at different longitudes and above and below the plane. We demonstrate that the edge of the stellar disk of the Milky Way can now be mapped in the near infrared in order to test different models, and to establish our own place within the galaxy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.3151v1.pdf"}
{"id": "1105.3724", "abstract": "  We consider the k=1 Friedman-Robertson-Walker (FRW) model within loop quantum cosmology, paying special attention to the existence of an ambiguity in the quantization process. In spatially non-flat anisotropic models such as Bianchi II and IX, the standard method of defining the curvature through closed holonomies is not admissible. Instead, one has to implement the quantum constraints by approximating the connection via open holonomies. In the case of flat k=0 FRW and Bianchi I models, these two quantization methods coincide, but in the case of the closed k=1 FRW model they might yield different quantum theories. In this manuscript we explore these two quantizations and the different effective descriptions they provide of the bouncing cyclic universe. In particular, as we show in detail, the most dramatic difference is that in the theory defined by the new quantization method, there is not one, but two different bounces through which the cyclic universe alternates. We show that for a `large' universe, these two bounces are very similar and, therefore, practically indistinguishable, approaching the dynamics of the holonomy based quantum theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.3724v1.pdf"}
{"id": "1105.4241", "abstract": "  Van der Waals-Casimir dispersion interactions between two apposed graphene layers, a graphene layer and a substrate, and in a multilamellar graphene system are analyzed within the framework of the Lifshitz theory. This formulation hinges on a known form of the dielectric response function of an undoped or doped graphene sheet, assumed to be of a random phase approximation form. In the geometry of two apposed layers the separation dependence of the van der Waals-Casimir interaction for both types of graphene sheets is determined and compared with some well known limiting cases. In a multilamellar array the many-body effects are quantified and shown to increase the magnitude of the van der Waals-Casimir interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.4241v1.pdf"}
{"id": "1105.4546", "abstract": "  We investigate baryogenesis via leptogenesis and generation of neutrino masses and mixings through the Type I plus Type III seesaw plus an one-loop mechanism in the context of Renormalizable Adjoint SU(5) theory. One light neutrino remains massless, because the contributions of three heavy Majorana fermions ρ_0, ρ_3 and ρ_8 to the neutrino mass matrix are not linearly independent. However none of these heavy fermions is decoupled from the generation of neutrino masses. This opens a new range in parameter space for successful leptogenesis, in particular, allows for inverted hierarchy of the neutrino masses. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.4546v3.pdf"}
{"id": "1105.4695", "abstract": "  Lattice molecule models are proposed in order to study statistical mechanics of glass transition in finite dimensions. Molecules in the models are represented by hard Wang tiles and their density is controlled by a chemical potential. An infinite series of irregular ground states are constructed theoretically. By defining a glass order parameter as a collection of the overlap with each ground state, a thermodynamic transition to a glass phase is found in a stratified Wang tiles model on a cubic lattice. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.4695v1.pdf"}
{"id": "1105.4782", "abstract": "  We present a study of the effects of the tensor-isospin term of the effective interaction in Hartree-Fock and Random Phase Approximation calculations. We used finite-range forces of Gogny type, and we added to them a tensor-isospin term which behaves, at large internucleonic distances, as the analogous term of the microscopic interactions. The strength of this tensor force has been chosen to reproduce the experimental energy of the lowest 0^- excited state in ^16O, which shows large sensitivity to this term of the interaction. With these finite-range interactions, we have studied the effects of the tensor-isospin force in ground and excited states of carbon, oxygen, calcium, nickel, zirconium, tin and lead isotopes. Our results show that the tensor force affects mainly the nucleon single particle energies. However, we found some interesting cases where also bulk nuclear properties are sensitive to the tensor interaction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.4782v1.pdf"}
{"id": "1105.5151", "abstract": "  Generating entanglement by simply cooling a system into a stationary state which is highly entangled has many advantages. Schemes based on this idea are robust against parameter fluctuations, tolerate relatively large spontaneous decay rates, and achieve high fidelities independent of their initial state. A possible implementation of this idea in atom-cavity systems has recently been proposed by Kastoryano et al. [Phys. Rev. Lett. 106, 090502 (2011)]. Here we propose an improved entanglement cooling scheme for two atoms inside an optical cavity which achieves higher fidelities for comparable single-atom cooperativity parameters C. For example, we predict fidelities above 90", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.5151v1.pdf"}
{"id": "1105.5266", "abstract": "  We study spatial self-organisation and dynamical phase-space compression of a dilute cold gas of laser-illuminated polarisable particles in an optical resonator. Deriving a non-linear Fokker–Planck equation for the particles' phase-space density allows us to treat arbitrarily large ensembles in the far-detuning limit and explicitly calculate friction forces, momentum diffusion and steady-state temperatures. In addition, we calculate the self-organisation threshold in a self-consistent analytic form. For a homogeneous ensemble below threshold the cooling rate for fixed laser power is largely independent of the particle number. Cooling leads to a q-Gaussian velocity distribution with a steady-state temperature determined by the cavity linewidth. Numerical simulations using large ensembles of particles confirm the analytical threshold condition for the appearance of an ordered state, where the particles are trapped in a periodic pattern and can be cooled to temperatures close to a single vibrational excitation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.5266v2.pdf"}
{"id": "1106.1046", "abstract": "  The Lagrangian dynamics of the velocity gradient tensor A in isotropic and homogeneous turbulence depend on the joint action of the self-streching term and the pressure Hessian. Existing closures for pressure effects in terms of A are unable to reproduce one important statistical role played by the anisotropic part of the pressure Hessian, namely the redistribution of the probabilities towards enstrophy production dominated regions. As a step towards elucidating the required properties of closures, we study several synthetic velocity fields and how well they reproduce anisotropic pressure effects. It is found that synthetic (i) Gaussian, (ii) Multifractal and (iii) Minimal Turnover Lagrangian Map (MTLM) incompressible velocity fields reproduce many features of real pressure fields that are obtained from numerical simulations of the Navier Stokes equations, including the redistribution towards enstrophy-production regions. The synthetic fields include both spatially local, and nonlocal, anisotropic pressure effects. However, we show that the local effects appear to be the most important ones: by assuming that the pressure Hessian is local in space, an expression in terms of the Hessian of the second invariant Q of the velocity gradient tensor can be obtained. This term is found to be well correlated with the true pressure Hessian both in terms of eigenvalue magnitudes and eigenvector alignments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.1046v2.pdf"}
{"id": "1106.1254", "abstract": "  The only evidence we have for a discrete reality comes from quantum measurements; without invoking these measurements, quantum theory describes continuous entities. This seeming contradiction can be resolved via analysis that treats measurements as boundary constraints. It is well-known that boundaries can induce apparently-discrete behavior in continuous systems, and strong analogies can be drawn to the case of quantum measurement. If quantum discreteness arises in this manner, this would not only indicate an analog reality, but would also offer a solution to the so-called \"measurement problem\". ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.1254v1.pdf"}
{"id": "1106.2249", "abstract": "  The coherent radiation spectrum of two-level polar molecules with UV transition is studied at the multiphoton resonant excitation by a moderately strong laser field. The spectrum corresponding to harmonic generation and low-frequency radiation is investigated both analytically and numerically. Specifically, a mechanism for generation of intense smoothly tunable terahertz radiation by two-level molecular configurations (with dynamic Stark shifts) possessing permanent dipole moments, is considered. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.2249v1.pdf"}
{"id": "1106.3455", "abstract": "  The paper presents instructive interdisciplinary applications of constrained mechanics calculus in economics on a level appropriate for the undergraduate physics education. The aim of the paper is: 1. to meet the demand for illustrative examples suitable for presenting the background of the highly expanding research field of econophysics even on the undergraduate level and 2. to enable the students to understand deeper the principles and methods routinely used in mechanics by looking at the well known methodology from the different perspective of economics. Two constrained dynamic economic problems are presented using the economic terminology in an intuitive way. First, the Phillips model of business cycle is presented as a system of forced oscillations and the general problem of two interacting economies is solved by the nonholonomic dynamics approach. Second, the Cass-Koopmans-Ramsey model of economical growth is solved as a variational problem with a velocity dependent constraint using the vakonomic approach. The specifics of the solution interpretation in economics compared to mechanics is discussed in detail, a discussion of the nonholonomic and vakonomic approaches to constrained problems in mechanics and economics is provided and an economic interpretation of the Lagrange multipliers (possibly surprising for the students of physics) is carefully explained. The paper can be used by the undergraduate students of physics interested in interdisciplinary physics applications to get in touch with current scientific approach to economics based on a physical background or by university teachers as an attractive supplement to the classical mechanics lessons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.3455v1.pdf"}
{"id": "1106.4526", "abstract": "  We report two nearby high proper motion dwarfs of special interest identified using the Preliminary Data Release of the Wide-field Infrared Survey Explorer (WISE) and the Two Micron All-Sky Survey (2MASS). WISEP J191239.91-361516.4 has a motion of 2.1 arcseconds per year. Photometry identifies it as a mid-M dwarf. WISEP J190648.47+401106.8 is a spectroscopically confirmed L1 dwarf in the Kepler Mission field with a motion of 0.48 arcseconds per year. The estimated distance is 17 parsecs. Both lie at relatively low galactic latitudes and demonstrate the possibility of discovering proper motion stars independently of the historic photographic sky surveys. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.4526v1.pdf"}
{"id": "1106.5783", "abstract": "  We use the S-matrix formalism of bound-state QED to study the photon-atom scattering. We find that the internal lines in Feynman diagrams which describing the propagation of off-shell bound electrons provide the off-shell amplitudes of photons' propagation in atoms phenomenally. Our work set up the connection between the property of Feynman propagators in bound-state QED and the superluminal but casual propagating behavior of light in atomic media. We also studied the relation between the bound-state QED and the widely used light-atom interacting model in quantum optics, and give the experimental condition where only the bound-state QED is valid. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.5783v3.pdf"}
{"id": "1107.0358", "abstract": "  The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers. The differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest drift velocity monitoring results are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.0358v1.pdf"}
{"id": "1107.0754", "abstract": "  We consider new-physics (NP) contributions to the decay t -> b b̅ c. We parameterize the NP couplings by an effective Lagrangian consisting of 10 Lorentz structures. We show that the presence of NP can be detected through the measurement of the partial width. A partial identification of the NP can be achieved through the measurements of a forward-backward-like asymmetry, a top-quark-spin-dependent asymmetry, the partial rate asymmetry, and a triple-product asymmetry. These observables, which vanish in the standard model, can all take values in the 10-20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.0754v2.pdf"}
{"id": "1107.0800", "abstract": "  Using our recently improved understanding of star cluster physics, we are now within reach of answering a number of fundamental questions in contemporary astrophysics. Star cluster physics has immediate bearing on questions ranging from the physical basis of the stellar initial mass function - Do any O-type stars form in isolation? What is the relative importance of stochastic (random) star formation versus competitive accretion? - to the build-up of the most massive clusters - Does the cluster mass function differ in different types of galaxies? How and why do the most massive star clusters form in small dwarf galaxies and what does that imply for the build-up of larger cluster samples? What are the main observables one could (or should) use to try and distinguish among the various star- and cluster-formation scenarios? Newly emerging theoretical insights, novel high-quality observational data and the advent of the next generation of observational facilities offer significant promise to reach satisfactory and robust answers to the key outstanding questions in this field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.0800v1.pdf"}
{"id": "1107.1264", "abstract": "  We study dynamical effects in proton breakup from a weakly bound state in an exotic nucleus on a heavy target. The Coulomb interactions between the proton and the core and the proton and the target are treated to all orders, including also the full multipole expansion of the Coulomb potential. The dynamics of proton nuclear and Coulomb breakup is compared to that of an equiva- lent neutron of larger binding energy in order to elucidate the differences with the well understood neutron breakup mechanism. A number of experimentally measurable observables such as parallel momentum distributions, proton angular distributions and total breakup cross sections are calculated. With respect to nuclear breakup it is found that a proton behaves exactly as a neutron of larger binding energy. The extra 'effective energy' is due to the combined core-target Coulomb barrier. In Coulomb breakup we distinguish the effect of the core-target Coulomb potential (called recoil effect), with respect to which the proton behaves again as a more bound neutron, from the direct proton-target Coulomb potential. The latter gives cross sections about an order of magnitude larger than the recoil term. The two effects give rise to complicated interferences in the parallel momentum distributions. They are instead easily separable in the proton angular distributions which are therefore suggested as a very useful observable for future experimental studies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.1264v1.pdf"}
{"id": "1107.3749", "abstract": "  We investigate here the genericity and stability aspects for naked singularities and black holes that arise as the final states for a complete gravitational collapse of a spherical massive matter cloud. The form of the matter considered is a general Type I matter field, which includes most of the physically reasonable matter fields such as dust, perfect fluids and such other physically interesting forms of matter widely used in gravitation theory. We first study here in some detail the effects of small pressure perturbations in an otherwise pressure-free collapse scenario, and examine how a collapse evolution that was going to the black hole endstate would be modified and go to a naked singularity, once small pressures are introduced in the initial data. This allows us to understand the distribution of black holes and naked singularities in the initial data space. Collapse is examined in terms of the evolutions allowed by Einstein equations, under suitable physical conditions and as evolving from a regular initial data. We then show that both black holes and naked singularities are generic outcomes of a complete collapse, when genericity is defined in a suitable sense in an appropriate space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.3749v2.pdf"}
{"id": "1107.5052", "abstract": "  Electronic nematicity, proposed to exist in a number of transition metal materials, can have different microscopic origins. In particular, the anisotropic resistivity and meta-magnetic jumps observed in Sr3Ru2O7 are consistent with an earlier proposal that the isotropic-nematic transition is generically first order and accompanied by meta-magnetism when tuned by a magnetic field. However, additional striking experimental features such as a non-Fermi liquid resistivity and critical thermodynamic behavior imply the presence of an unidentified quantum critical point (QCP). Here we show that orbital degrees of freedom play an essential role in revealing a nematic QCP, even though it is overshadowed by a nearby meta-nematic transition at low temperature. We further present a finite temperature phase diagram including the entropy landscape and discuss our findings in light of the phenomena observed in Sr3Ru2O7. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.5052v5.pdf"}
{"id": "1107.5450", "abstract": "  Quantum confinement of the perpendicular motion of electrons in single-crystalline metallic superconducting nanofilms splits the conduction band into a series of single-electron subbands. A distinctive feature of such a nanoscale multi-band superconductor is that the energetic position of each subband can vary significantly with changing nanofilm thickness, substrate material, protection cover and other details of the fabrication process. It can occur that the bottom of one of the available subbands is situated in the vicinity of the Fermi level. We demonstrate that the character of the superconducting pairing in such a subband changes dramatically and exhibits a clear molecule-like trend, which is very similar to the well-known crossover from the Bardeen-Cooper-Schrieffer regime to Bose-Einstein condensation (BCS-BEC) observed in trapped ultracold fermions. For Pb nanofilms with thickness of 4 and 5 monolayers (ML) this will lead to a spectacular scenario: up to half of all the Cooper pairs nearly collapse, shrinking in the lateral size (parallel to the nanofilm) down to a few nanometers. As a result, the superconducting condensate will be a coherent mixture of almost molecule-like fermionic pairs with ordinary, extended Cooper pairs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.5450v1.pdf"}
{"id": "1107.5578", "abstract": "  Diffraction calculations, such as the angular spectrum method, and Fresnel diffractions, are used for calculating scalar light propagation. The calculations are used in wide-ranging optics fields: for example, computer generated holograms (CGHs), digital holography, diffractive optical elements, microscopy, image encryption and decryption, three-dimensional analysis for optical devices and so on. However, increasing demands made by large-scale diffraction calculations have rendered the computational power of recent computers insufficient. We have already developed a numerical library for diffraction calculations using a graphic processing unit (GPU), which was named the GWO library. However, this GWO library is not user-friendly, since it is based on C language and was also run only on a GPU. In this paper, we develop a new C++ class library for diffraction and CGH calculations, which is referred as to a CWO++ library, running on a CPU and GPU. We also describe the structure, performance, and usage examples of the CWO++ library. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.5578v1.pdf"}
{"id": "1107.5711", "abstract": "  We report the experimental study of the degassing dynamics through a thin layer of shear-thinning viscoelastic fluid (CTAB/NaSal solution), when a constant air flow is imposed at its bottom. Over a large range of parameters, the air is periodically released through series of successive bubbles, hereafter named cascades. Each cascade is followed by a continuous degassing, lasting for several seconds, corresponding to an open channel crossing the fluid layer. The periodicity between two cascades does not depend on the injected flow-rate. Inside one cascade, the properties of the overpressure signal associated with the successive bubbles vary continuously. The pressure threshold above which the fluid starts flowing, fluid deformation and pressure drop due to degassing through the thin fluid layer can be simply described by a Maxwell model. We point out that monitoring the evolution inside the cascades provides a direct access to the characteristic relaxation time associated with the fluid rheology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.5711v1.pdf"}
{"id": "1107.5998", "abstract": "  A Ginzburg-Landau model for the macroscopic behaviour of a shape memory alloy is proposed. The model is one-dimensional in essence, in that we consider the effect of the martensitic phase transition in terms of a uniaxial deformation along a fixed direction and we use a scalar order parameter whose equilibrium values describe the austenitic phase and the two martensitic variants. The model relies on a Ginzburg-Landau free energy defined as a function of macroscopically measurable quantities, and accounts for thermal effects; couplings between the various relevant physical aspects are established according to thermodynamic consistency. The theoretical model has been implemented within a finite-element framework and a number of numerical tests are presented which investigate the mechanical behaviour of the model under different conditions; the results obtained are analysed in relation to experimental evidences available in literature. In particular, the influence of the strain-rate and of the ambient conditions on the response of the model is highlighted. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.5998v1.pdf"}
{"id": "1108.0997", "abstract": "  A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their models to describe the radial distribution of stars in `nebulae'. This article reviews the progress since then, providing both an historical perspective and a contemporary review of the stellar structure of bulges, discs and elliptical galaxies. The quantification of galaxy nuclei, such as central mass deficits and excess nuclear light, plus the structure of dark matter halos and cD galaxy envelopes, are discussed. Issues pertaining to spiral galaxies including dust, bulge-to-disc ratios, bulgeless galaxies, bars and the identification of pseudobulges are also reviewed. An array of modern scaling relations involving sizes, luminosities, surface brightnesses and stellar concentrations are presented, many of which are shown to be curved. These 'redshift zero' relations not only quantify the behavior and nature of galaxies in the Universe today, but are the modern benchmark for evolutionary studies of galaxies, whether based on observations, N-body-simulations or semi-analytical modelling. For example, it is shown that some of the recently discovered compact elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.0997v1.pdf"}
{"id": "1108.2537", "abstract": "  We show the planned upgrade of a cavity QED experimental apparatus. The system consists of an optical cavity and an ensemble of ultracold ^85Rb atoms coupled to its mode. We propose enhancements to both. First, we document the building process for a new cavity, with a planned finesse of ∼20000. We address problems of maintaining mirror integrity during mounting and improving vibration isolation. Second, we propose improvements to the cold atom source in order to achieve better optical pumping and control over the flux of atoms. We consider a 2-D optical molasses for atomic beam deflection, and show computer simulation results for evaluating the design. We also examine the possibility of all-optical atomic beam focusing, but find that it requires unreasonable experimental parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.2537v2.pdf"}
{"id": "1108.3492", "abstract": "  The Galactic X-ray transient XTE J1752-223 was shown to have properties of black hole binary candidates. As reported in our previous paper, we identified transient and decelerating ejecta in multi-epoch Very Long Baseline Interferometry (VLBI) observations with the European VLBI Network (EVN) and the NRAO Very Long Baseline Array (VLBA). Here we present new EVN and VLBA data in which a new transient ejection event and later a stationary component are identified. The latter is interpreted as a reappearance of the radio core/compact jet during the transition from soft to hard X-ray state. This component appears to be highly variable in brightness although effects of tropospheric instabilities might play a role too. We also re-analyze the earlier VLBI data and find that the transient ejecta closer to the core position has significantly higher proper motion, further strengthening the case for strongly decelerating ejecta on the scale of several hundred milli-arcsecond, never observed in X-ray binaries before. Although the distance of the source is not well constrained, it is clear that these ejectas are at least mildly relativistic at the early stages. Moreover, we show the large scale environment of the transient from the Westerbork synthesis array data recorded in parallel during the EVN run. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.3492v1.pdf"}
{"id": "1108.4926", "abstract": "  We find that imposing the crossing symmetry in the iteration process considerably extends the range of convergence for solutions of the parquet equations for the Hubbard model. When the crossing symmetry is not imposed, the convergence of both simple iteration and more complicated continuous loading (homotopy) methods are limited to high temperatures and weak interactions. We modify the algorithm to impose the crossing symmetry without increasing the computational complexity. We also imposed time reversal and a subset of the point group symmetries, but they did not further improve the convergence. We elaborate the details of the latency hiding scheme which can significantly improve the performance in the computational implementation. With these modifications, stable solutions for the parquet equations can be obtained by iteration more quickly even for values of the interaction that are a significant fraction of the bandwidth and for temperatures that are much smaller than the bandwidth. This may represent a crucial step towards the solution of two-particle field theories for correlated electron models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.4926v2.pdf"}
{"id": "1108.5675", "abstract": "  We study the binary fraction of the globular cluster M10 (NGC 6254) as a function of radius from the cluster core to the outskirts, by means of a quan- titative analysis of the color distribution of stars relative to the fiducial main sequence. By taking advantage of two data-sets, acquired with the Advanced Camera for Survey and the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we have studied both the core and the external regions of the cluster. The binary fraction is found to decrease from 14", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.5675v1.pdf"}
{"id": "1109.0147", "abstract": "  We investigate system-environment correlations based on the exact dynamics of a qubit and its environment in the framework of pure decoherence (phase damping). We focus on the relation of decoherence and the build-up of system-reservoir entanglement for an arbitrary (possibly mixed) initial qubit state. In the commonly employed regime where the qubit dynamics can be described by a Markov master equation of Lindblad type, we find that for almost all qubit initial states inside the Bloch sphere, decoherence is complete while the total state is still separable - no entanglement is involved. In general, both \"separable\" and \"entangling\" decoherence occurs, depending on temperature and initial qubit state. Moreover, we find situations where classical and quantum correlations periodically alternate as a function of time in the regime of low temperatures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.0147v4.pdf"}
{"id": "1109.0884", "abstract": "  Edge reconstruction modifies the electronic properties of finite graphene samples. We formulate a low-energy theory of the reconstructed zigzag edge by deriving the modified boundary condition to the Dirac equation. If the unit cell size of the reconstructed edge is not a multiple of three with respect to the zigzag unit cell, valleys remain uncoupled and the edge reconstruction is accounted for by a single angular parameter ϑ. Dispersive edge states exist generically, unless |ϑ| = π/2. We compute ϑ from a microscopic model for the \"reczag\" reconstruction (conversion of two hexagons into a pentagon-heptagon pair) and show that it can be measured via the local density of states. In a magnetic field there appear three distinct edge modes in the lowest Landau level, two of which are counterpropagating. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.0884v3.pdf"}
{"id": "1109.1847", "abstract": "  Propagation of dressed solitary excitations are studied in a partially degenerate quantum plasma in the framework of quantum-hydrodynamics (QHD) model using multiple scales technique. The evolution equation together with a linear inhomogeneous differential equation is solved using Kodama-Taniuti renormalizing technique. It is shown that the type of solitary excitations (bright or dark) is defined by two critical plasma parameter values. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.1847v1.pdf"}
{"id": "1109.2474", "abstract": "  Perhaps the most compelling evidence for the role of magnetic reconnection in solar flares comes from the supra-arcade downflows that have been observed above many post-flare loop arcades. These downflows are thought to be related to highly non-potential field lines that have reconnected and are propagating away from the current sheet. We present new observations of supra-arcade downflows taken with the Atmospheric Imagining Assembly (AIA) on the Solar Dynamics Observatory (SDO). The morphology and dynamics of the downflows observed with AIA provide new evidence for the role of magnetic reconnection in solar flares. With these new observations we are able to measure downflows originating at much larger heights than in previous studies. We find, however, that the initial velocities measured here (∼144 km s^-1) are well below the Alfvén speed expected in the lower corona, and consistent with previous results. We also find no evidence that the downflows brighten with time, as would be expected from chromospheric evaporation. These observations suggest that simple two-dimensional models cannot explain the detailed observations of solar flares. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.2474v1.pdf"}
{"id": "1109.2570", "abstract": "  I consider the generic situation where a finite number of identical test systems in varying (possibly unknown) initial states are subjected independently to the same unknown process. I show how one can infer from the output data alone whether or not the process in question induces thermalization, and if so, which constants of the motion characterize the final equilibrium states. In case thermalization does occur and there is no evidence for constants of the motion other than energy, I further show how the same output data can be used to estimate the test systems' effective Hamiltonian. For both inference tasks I devise a statistical framework inspired by the generic techniques of factor and principal component analysis. I illustrate its use in the simple example of qubits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.2570v1.pdf"}
{"id": "1109.4038", "abstract": "  According to the Harrison-Zel'dovich prescription, the amplitude of matter density perturbations at horizon crossing is the same at all scales. Based on this prescription, we show how to construct the matter power spectrum of generic dark energy models from the power spectrum of a ΛCDM model without the need of solving in full the dynamical equations describing the evolution of all energy density perturbations. Our approach allows to make model predictions of observables that can be expressed in terms of the matter power spectrum alone, such as the amplitude of matter fluctuations, peculiar velocities, cosmic microwave background temperature anisotropies on large angular scales or the weak lensing convergence spectrum. Then, models that have been tested only at the background level using the rate of the expansion of the Universe can now be tested using data on gravitational clustering and on large scale structure. This method can save a lot of effort in checking the validity of dark energy models. As an example of the accurateness of the approximation used, we compute the power spectrum of different dark energy models with constant equation of state parameter (w_DE=-0.1, -0.5 and -0.8, ruled out by observations but easy to compare to numerical solutions) using our methodology and discuss the constraints imposed by the low multipoles of the cosmic microwave background. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.4038v3.pdf"}
{"id": "1109.4168", "abstract": "  We consider pricing weather derivatives for use as protection against weather extremes. The method described utilizes results from spatial statistics and extreme value theory to first model extremes in the weather as a max-stable process, and then use these models to simulate payments for a general collection of weather derivatives. These simulations capture the spatial dependence of payments. Incorporating results from catastrophe ratemaking, we show how this method can be used to compute risk loads and premiums for weather derivatives which are renewal-additive. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.4168v1.pdf"}
{"id": "1109.4238", "abstract": "  The early evolution of planetary systems is expected to depend on various periods of disk matter accretion onto the central star, which may include the accretion of metal-rich matter after the star settles on the main sequence. When this happens, the accreted material is rapidly mixed within the surface convective zone and induces an inverse mean-molecular-weight gradient, unstable for thermohaline convection. The induced mixing, which dilutes the metal excess, may also have important consequences on the light elements abundances. We model and analyze this process, and present the results according to various possible accretion scenarios. We give a detailed discussion of the different ways of treating thermohaline mixing, as proposed by previous authors, and we converge on a consistent view, including the most recent numerical simulations. We show how the observations of light elements in stars can be used as tracers of such events. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.4238v2.pdf"}
{"id": "1109.4263", "abstract": "  Interface states at a boundary between regions with different spin-orbit interactions (SOIs) in two-dimensional (2D) electron systems are investigated within the one-band effective mass method with generalized boundary conditions for envelope functions. We have found that the interface states unexpectedly exist even if the effective interface potential equals zero. Depending on the system parameters, the energy of these states can lie in either or both forbidden and conduction bands of bulk states. The interface states have chiral spin texture similar to that of the edge states in 2D topological insulators. However, their energy spectrum is more sensitive to the interfacial potential, the largest effect being produced by the spin-dependent component of the interfacial potential. We have also studied the size quantization of the interface states in a strip of 2D electron gas with SOI and found an unusual (non-monotonic) dependence of the quantization energy on the strip width. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.4263v1.pdf"}
{"id": "1109.4368", "abstract": "  We investigate the quantum statistical properties of the light emitted by a quantum well interacting with squeezed light from a degenerate subthreshold optical parametric oscillator. We obtain analytical solutions for the pertinent quantum Langevin equations in the strong coupling and low excitation regimes. Using these solutions we calculate the intensity spectrum, autocorrelation function, quadrature squeezing for the fluorescent light. We show that the fluorescent light exhibits bunching and quadrature squeezing. We also show that the squeezed light leads to narrowing of the width of the spectrum of the fluorescent light. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.4368v1.pdf"}
{"id": "1109.4533", "abstract": "  We are interested in the estimation and prediction of a parametric model on a short dataset upon which it is expected to overfit and perform badly. To overcome the lack of data (relatively to the dimension of the model) we propose the construction of an informative hierarchical Bayesian prior based upon another longer dataset which is assumed to share some similarities with the original, short dataset. We illustrate the performance of our prior on simulated dataset from three standard models. Then we apply the methodology to a working model for the electricity load forecasting on real datasets, where it leads to a substantial improvement of the quality of the predictions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.4533v5.pdf"}
{"id": "1109.4577", "abstract": "  We derive general results for the mass shift of bound states with angular momentum l >= 1 in a periodic cubic box in two and three spatial dimensions. Our results have applications to lattice simulations of hadronic molecules, halo nuclei, and Feshbach molecules. The sign of the mass shift can be related to the symmetry properties of the state under consideration. We verify our analytical results with explicit numerical calculations. Moreover, we comment on the relations connecting the effective range parameter, the binding momentum of a given state and the asymptotic normalization coefficient of the corresponding wave function. We give explicit expressions for this relation in the shallow binding limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.4577v1.pdf"}
{"id": "1109.4957", "abstract": "  It is straightforward to determine the size of the Earth and the distance to the Moon without making use of a telescope. The methods have been known since the 3rd century BC. However, few amateur or professional astronomers have worked this out from data they themselves have taken. Here we use a gnomon to determine the latitude and longitude of South Bend, Indiana, and College Station, Texas, and determine a value of the radius of the Earth of 6290 km, only 1.4 percent smaller than the true value. We use the method of Aristarchus and the size of the Earth's shadow during the lunar eclipse of 2011 June 15 to derive an estimate of the distance to the Moon (62.3 R_Earth), some 3.3 percent greater than the true mean value. We use measurements of the angular motion of the Moon against the background stars over the course of two nights, using a simple cross staff device, to estimate the Moon's distance at perigee and apogee. Finally, we use simultaneous CCD observations of asteroid 1996 HW1 obtained with small telescopes in Socorro, New Mexico, and Ojai, California, to derive a value of the Astronomical Unit of (1.59 +/- 0.19) X 10^8 km, about 6 percent too large. The data and methods presented here can easily become part of a beginning astronomy lab class. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.4957v2.pdf"}
{"id": "1109.6081", "abstract": "  A unified model of electron penetration into linear plasma wakefields is formulated and studied. The optimum angle for side injection of electrons is found. At smaller angles, all electrons are reflected radially. At larger angles, electrons enter the wakefield with superfluous transverse momentum that is unfavorable for trapping. Separation of incident electrons into penetrated and reflected fractions occur in the outer region of the wakefield at some \"reflection\" radius that depends on the electron energy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.6081v1.pdf"}
{"id": "1109.6875", "abstract": "  We present the first investigation of the Blue Straggler star (BSS) population in two isolated dwarf spheroidal galaxies of the Local Group, Cetus and Tucana. Deep HST/ACS photometry allowed us to identify samples of 940 and 1214 candidates, respectively. The analysis of the star formation histories of the two galaxies suggests that both host a population of BSSs. Specifically, if the BSS candidates are interpreted as young main sequence stars, they do not conform to their galaxy's age-metallicity relationship. The analysis of the luminosity function and the radial distributions support this conclusion, and suggest a non-collisional mechanism for the BSS formation, from the evolution of primordial binaries. This scenario is also supported by the results of new dynamical simulations presented here. Both galaxies coincide with the relationship between the BSS frequency and the absolute visual magnitude Mv found by Momany et al (2007). If this relationship is confirmed by larger sample, then it could be a valuable tool to discriminate between the presence of BSSs and galaxies hosting truly young populations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.6875v1.pdf"}
{"id": "1110.1160", "abstract": "  We have measured the thermopower across the metamagnetic transition of the heavy fermion compound CeRu2Si2 at temperatures down to 0.1K and magnetic fields up to 11.5T. We find a large negative enhancement of the thermopower on crossing the metamagnetic field, as well as a sudden change in slope. We argue that this is consistent with the Zeeman-driven deformation of the Fermi surface through a topological transition. The field dependence of the thermopower highlights the discrepancy between thermodynamic and transport properties across the metamagnetic transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.1160v2.pdf"}
{"id": "1110.2357", "abstract": "  Two models for the calculation of ionization cross sections by electron impact on atoms, the Binary-Encouter-Bethe and the Deutsch-Maerk models, have been implemented; they are intended to extend and improve Geant4 simulation capabilities in the energy range below 1 keV. The physics features of the implementation of the models are described, and their differences with respect to the original formulations are discussed. Results of the verification with respect to the original theoretical sources and of extensive validation with respect to experimental data are reported. The validation process also concerns the ionization cross sections included in the Evaluated Electron Data Library used by Geant4 for low energy electron transport. Among the three cross section options, the Deutsch-Maerk model is identified as the most accurate at reproducing experimental data over the energy range subject to test. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.2357v1.pdf"}
{"id": "1110.2853", "abstract": "  We study the chemical bonds of small palladium clusters Pd_n (n=2-9) saturated by hydrogen atoms using electronic stress tensor. Our calculation includes bond orders which are recently proposed based on the stress tensor. It is shown that our bond orders can classify the different types of chemical bonds in those clusters. In particular, we discuss Pd-H bonds associated with the H atoms with high coordination numbers and the difference of H-H bonds in the different Pd clusters from viewpoint of the electronic stress tensor. The notion of \"pseudo-spindle structure\" is proposed as the region between two atoms where the largest eigenvalue of the electronic stress tensor is negative and corresponding eigenvectors forming a pattern which connects them. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.2853v1.pdf"}
{"id": "1110.2906", "abstract": "  Many natural and engineered complex networks have intricate mesoscopic organization, e.g., the clustering of the constituent nodes into several communities or modules. Often, such modularity is manifested at several different hierarchical levels, where the clusters defined at one level appear as elementary entities at the next higher level. Using a simple model of a hierarchical modular network, we show that such a topological structure gives rise to characteristic time-scale separation between dynamics occurring at different levels of the hierarchy. This generalizes our earlier result for simple modular networks, where fast intra-modular and slow inter-modular processes were clearly distinguished. Investigating the process of synchronization of oscillators in a hierarchical modular network, we show the existence of as many distinct time-scales as there are hierarchical levels in the system. This suggests a possible functional role of such mesoscopic organization principle in natural systems, viz., in the dynamical separation of events occurring at different spatial scales. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.2906v1.pdf"}
{"id": "1110.2997", "abstract": "  In this paper we present an algorithm for rapid Bayesian analysis that combines the benefits of nested sampling and artificial neural networks. The blind accelerated multimodal Bayesian inference (BAMBI) algorithm implements the MultiNest package for nested sampling as well as the training of an artificial neural network (NN) to learn the likelihood function. In the case of computationally expensive likelihoods, this allows the substitution of a much more rapid approximation in order to increase significantly the speed of the analysis. We begin by demonstrating, with a few toy examples, the ability of a NN to learn complicated likelihood surfaces. BAMBI's ability to decrease running time for Bayesian inference is then demonstrated in the context of estimating cosmological parameters from Wilkinson Microwave Anisotropy Probe and other observations. We show that valuable speed increases are achieved in addition to obtaining NNs trained on the likelihood functions for the different model and data combinations. These NNs can then be used for an even faster follow-up analysis using the same likelihood and different priors. This is a fully general algorithm that can be applied, without any pre-processing, to other problems with computationally expensive likelihood functions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.2997v2.pdf"}
{"id": "1110.3412", "abstract": "  The origin of a chemical reaction between two reactant atoms is associated to the activation energy, with the assumption that, high-energy collisions between these atoms, are the ones that overcome the activation energy. Here, we (i) show that a stronger attractive van der Waals (vdW) and electron-ion Coulomb interactions between two polarized atoms are responsible to initiate a chemical reaction, either before or after the collision. We derive this stronger vdW attraction formula exactly using the quasi one-dimensional Drude model within the ionization energy theory and the energy-level spacing renormalization group method. Along the way, we (ii) expose the precise physical mechanism responsible for the existence of a stronger vdW interaction for both long and short distances, and also show how to technically avoid the electron-electron Coulomb repulsion between polarized electrons from these two reactant atoms. Finally, we properly and correctly associate the existence of this stronger attraction to Ramachandran's 'normal limits' (distance shorter than what is allowed by the standard vdW bond) between chemically nonbonded atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.3412v6.pdf"}
{"id": "1110.3919", "abstract": "  In this lecture I give a brief review of low-dimensional few-body problems recently encountered in attempting a quantitative description of ultracold atoms and molecules confined in 2D and 1D optical lattices. Multi-channel nature of these processes has required the development of special computational methods and algorithms which I discuss here as well as the most interesting results obtained with the offered computational technique and future perspectives. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.3919v2.pdf"}
{"id": "1110.5280", "abstract": "  We introduce a growing network evolution model with nodal attributes. The model describes the interactions between potentially violent V and non-violent N agents who have different affinities in establishing connections within their own population versus between the populations. The model is able to generate all stable triads observed in real social systems. In the framework of rate equations theory, we employ the mean-field approximation to derive analytical expressions of the degree distribution and the local clustering coefficient for each type of nodes. Analytical derivations agree well with numerical simulation results. The assortativity of the potentially violent network qualitatively resembles the connectivity pattern in terrorist networks that was recently reported. The assortativity of the network driven by aggression shows clearly different behavior than the assortativity of the networks with connections of non-aggressive nature in agreement with recent empirical results of an online social system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.5280v1.pdf"}
{"id": "1110.5471", "abstract": "  The Earth's density distribution can be approximately considered piecewise continuous at the scale of two-flavor oscillations of neutrinos with energies about 1 MeV. This quite general assumption appears to be enough to analytically calculate the day-night asymmetry factor. Using the explicit time averaging procedure, we show that, within the leading-order approximation, this factor is determined by the electron density immediately before the detector, i.e. in the Earth's crust. Within the approximation chosen, the resulting asymmetry factor does not depend either on the properties of the inner Earth's layers or on the substance and the dimensions of the detector. For beryllium neutrinos, we arrive at the asymmetry factor estimation of about -4 × 10^-4, which is at least one order of magnitude beyond the present experimental resolution, including that of the Borexino experiment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.5471v3.pdf"}
{"id": "1110.5500", "abstract": "  We apply the nonperturbative functional renormalization group (NP-FRG) in the superfield formalism that we have developed in the preceding paper to study long-standing issues concerning the critical behavior of the random field Ising model. Through the introduction of an appropriate regulator and a supersymmetry-compatible nonperturbative approximation, we are able to follow the supersymmetry, more specifically the superrotational invariance first unveiled by Parisi and Sourlas [Phys. Rev. Lett. 43, 744 (1979)], and its spontaneous breaking along the RG flow. Breaking occurs below a critical dimension dDR ≃5.1, and the supersymmetry-broken fixed point that controls the critical behavior then leads to a breakdown of the \"dimensional reduction\" property. We solve the NP-FRG flow equations numerically and determine the critical exponents as a function of dimension down to d < 3, with a good agreement in d = 3 and d = 4 with the existing numerical estimates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.5500v1.pdf"}
{"id": "1110.6056", "abstract": "  Recently, Chen et al. [New J. Phys. 13 (2011) 083018] presented experimental results, accompanied by quantum-mechanical analysis, showing that the quantum interference behavior of Bell states could be simulated in a modified Mach-Zehnder interferometer whose inputs are pseudothermal light beams obtained by passing laser light through a rotating ground-glass diffuser. Their experiments and their theory presumed low-flux operation in which the simulated quantum interference is observed via photon-coincidence counting. We first show that the Chen et al. photon-coincidence counting experiments can be fully explained with semiclassical photodetection theory, in which light is taken to be a classical electromagnetic wave, and the discreteness of the electron charge leads to shot noise as the fundamental photodetection noise. We then use semiclassical photodetection theory to show that the same simulated quantum interference pattern can be observed in high-flux operation, when photocurrent cross-correlation is used instead of photon-coincidence counting. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.6056v2.pdf"}
{"id": "1111.0169", "abstract": "  The properties of the thermal Abelian color-magnetic monopoles in the maximally Abelian gauge are studied in the deconfinement phase of the lattice SU(2) gluodynamics. To check universality of the monopole properties we employ the tadpole improved Symanzik action. The simulated annealing algorithm combined with multiple gauge copies is applied for fixing the maximally Abelian gauge to avoid effects of Gribov copies. We compute the density, interaction parameters, thermal mass and chemical potential of the thermal Abelian monopoles in the temperature range between Tc and 3Tc. In comparison with earlier findings our results for these quantities are improved either with respect to effects of Gribov copies or with respect to lattice artifacts. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.0169v2.pdf"}
{"id": "1111.0206", "abstract": "  In this paper the structure properties of asymmetrical nuclear matter has been calculated employing AV18 potential for different values of proton to neutron ratio. These calculations have been also made for the case of symmetrical nuclear matter with UV14, AV14 and AV18 potentials. In our calculations, we use the lowest order constrained variational (LOCV) method to compute the correlation function of the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.0206v1.pdf"}
{"id": "1111.0918", "abstract": "  Although the framework for oscillations of the three neutrino flavors in the Standard Model has been convincingly established, indications persist that it may be incomplete. Challenges are coming from the LSND and MiniBooNe short-baseline experiments, from the neutrino sources used in the Gallex and Sage solar neutrino experiments and, more recently,from an a-posteriori analysis of reactor neutrino experiments. One way to accommodate the reported \"anomalies\", if real, is to introduce one or more sterile neutrinos in the mass range δ m^2 ∼ 1 eV^2. TeV atmospheric neutrinos propagating through the Earth undergo resonant oscillations in the presence of sterile neutrinos; a clear signature in a neutrino telescope like IceCube is the the change in shape of the zenith-energy distribution of the atmospheric neutrinos. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.0918v1.pdf"}
{"id": "1111.1174", "abstract": "  Spectroscopy of nuclei in the mass range A=76 to A=130, participating in double beta decay processes are studied in the framework of the self-consistent deformed Hartree-Fock (HF) and angular momentum (J) projection model. Spectra of ground bands have been studied and compared with available experimental results for even-even parent and daughter as well as for intermediate odd-odd nuclei. To test the reliability of the wave functions we have also calculated the reduced E2 transition matrix elements, electric quadrupole moments and magnetic dipole moments for these nuclei. The calculated results are compared with the experimental findings and substantial agreement is achieved. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.1174v1.pdf"}
{"id": "1111.1241", "abstract": "  We numerically study dynamical behaviors of the quasiperiodically forced Hodgkin-Huxley neuron and compare the dynamical responses with those for the case of periodic stimulus. In the periodically forced case, a transition from a periodic to a chaotic oscillation was found to occur via period doublings in previous numerical and experimental works. We investigate the effect of the quasiperiodic forcing on this period-doubling route to chaotic oscillation. In contrast to the case of periodic forcing, new type of strange nonchaotic (SN) oscillating states (that are geometrically strange but have no positive Lyapunov exponents) are found to exist between the regular and chaotic oscillating states as intermediate ones. Their strange fractal geometry leads to aperiodic \"complex\" spikings. Various dynamical routes to SN oscillations are identified, as in the quasiperiodically forced logistic map. These SN spikings are expected to be observed in experiments of the quasiperiodically forced squid giant axon. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.1241v1.pdf"}
{"id": "1111.2228", "abstract": "  This work explores fundamental modeling and algorithmic issues arising in the well-established MapReduce framework. First, we formally specify a computational model for MapReduce which captures the functional flavor of the paradigm by allowing for a flexible use of parallelism. Indeed, the model diverges from a traditional processor-centric view by featuring parameters which embody only global and local memory constraints, thus favoring a more data-centric view. Second, we apply the model to the fundamental computation task of matrix multiplication presenting upper and lower bounds for both dense and sparse matrix multiplication, which highlight interesting tradeoffs between space and round complexity. Finally, building on the matrix multiplication results, we derive further space-round tradeoffs on matrix inversion and matching. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.2228v1.pdf"}
{"id": "1111.2856", "abstract": "  Giant radio haloes in galaxy clusters are the primary evidence for the existence of relativistic particles (cosmic rays) and magnetic fields over Mpc scales. Observational tests for the different theoretical models explaining their powering mechanism have so far been obtained through X-ray selection of clusters, e.g. by comparing cluster X-ray luminosities with radio halo power. Here we present the first global scaling relations between radio halo power and integrated Sunyaev-Zel'dovich (SZ) effect measurements, using the Planck all-sky cluster catalog and published radio data. The correlation agrees well with previous scaling measurements based on X-ray data, and offers a more direct probe into the mass dependence inside radio haloes. However, we find no strong indication for a bi-modal cluster population split between radio halo and radio quiet objects. We discuss the possible causes for this apparent lack of bi-modality, and compare the observed slope of the radio-SZ correlation with competing theoretical models of radio halo origin. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.2856v3.pdf"}
{"id": "1111.2900", "abstract": "  We investigate the emergence of hyperons in black-hole-forming failed supernovae, which are caused by the dynamical collapse of nonrotating massive stars. We perform neutrino-radiation hydrodynamical simulations in general relativity adopting realistic hyperonic equation-of-state (EOS). Attractive and repulsive cases are examined for the potential of Σ hyperons. Since hyperons soften the EOS, they shorten the time interval from the bounce to black hole formation, which corresponds to the duration of neutrino emission. This effect is larger for the attractive case than the repulsive case because Σ hyperons appear more easily. In addition, we investigate the impacts of pions to find that they also promotes the recollapse towards the black hole formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.2900v1.pdf"}
{"id": "1111.3167", "abstract": "  In this work, one shows that a specific non-minimal coupling between the scalar curvature and matter can mimic the dark matter component of galaxy clusters. For this purpose, one assesses the Abell cluster A586, a massive nearby relaxed cluster of galaxies in virial equilibrium, where direct mass estimates and strong-lensing determinations are possible. One then extends the dark matter mimicking to a large sample of galaxy clusters whose density profiles are obtained from the Chandra high quality data, also in virial equilibrium. The total density, which generally follows a cusped profile and reveals a very small baryonic component, can be effectively described within this framework. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.3167v2.pdf"}
{"id": "1111.4466", "abstract": "  We investigate the use of a logarithmic density variable in estimating the Lagrangian displacement field, motivated by the success of a logarithmic transformation in restoring information to the matter power spectrum. The logarithmic relation is an extension of the linear relation, motivated by the continuity equation, in which the density field is assumed to be proportional to the divergence of the displacement field; we compare the linear and logarithmic relations by measuring both of these fields directly in a cosmological N-body simulation. The relative success of the logarithmic and linear relations depends on the scale at which the density field is smoothed. Thus we explore several ways of measuring the density field, including Cloud-In-Cell smoothing, adaptive smoothing, and the (scale-independent) Delaunay tessellation, and we use both a Fourier space and a geometrical tessellation approach to measuring the divergence. We find that the relation between the divergence of the displacement field and the density is significantly tighter with a logarithmic density variable, especially at low redshifts and for very small ( 2 Mpc/h) smoothing scales. We find that the grid-based methods are more reliable than the tessellation-based method of calculating both the density and the divergence fields, though in both cases the logarithmic relation works better in the appropriate regime, which corresponds to nonlinear scales for the grid-based methods and low densities for the tessellation-based method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.4466v2.pdf"}
{"id": "1111.4868", "abstract": "  We present the AGILE gamma-ray observations in the energy range 50 MeV - 10 GeV of the supernova remnant (SNR) W44, one of the most interesting systems for studying cosmic-ray production. W44 is an intermediate-age SNR (20, 000 years) and its ejecta expand in a dense medium as shown by a prominent radio shell, nearby molecular clouds, and bright [SII] emitting regions. We extend our gamma-ray analysis to energies substantially lower than previous measurements which could not conclusively establish the nature of the radiation. We find that gamma-ray emission matches remarkably well both the position and shape of the inner SNR shocked plasma. Furthermore, the gamma-ray spectrum shows a prominent peak near 1 GeV with a clear decrement at energies below a few hundreds of MeV as expected from neutral pion decay. Here we demonstrate that: (1) hadron-dominated models are consistent with all W44 multiwavelength constraints derived from radio, optical, X-ray, and gamma-ray observations; (2) ad hoc lepton-dominated models fail to explain simultaneously the well-constrained gamma-ray and radio spectra, and require a circumstellar density much larger than the value derived from observations; (3) the hadron energy spectrum is well described by a power-law (with index s = 3.0 ±0.1) and a low-energy cut-off at Ec = 6 ±1 GeV. Direct evidence for pion emission is then established in an SNR for the first time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.4868v1.pdf"}
{"id": "1111.6127", "abstract": "  Nonthermal fixed points of the dynamics of a dilute degenerate Bose gas far from thermal equilibrium are analyzed in two and three spatial dimensions. Universal power-law distributions, previously found within a nonperturbative quantum-field theoretical approach and recently shown to be related to vortical dynamics and superfluid turbulence [Phys. Rev. B 84, 020506(R) (2011)], are studied in detail. The results imply an interpretation of the scaling behavior in terms of independent vortex excitations of the superfluid and show that the statistics of topological excitations can be described in the framework of wave turbulence. The particular scaling exponents observed in the single-particle momentum distributions are found to be consistent with irreversibility as well as conservation laws obeyed by the wave interactions. Moreover, long-wavelength acoustic excitations of the vortex-bearing condensate, driven by vortex annihilations, are found to follow a nonthermal power law. Considering vortex correlations in a statistical model, the long-time departure from the nonthermal fixed point is related to vortex-antivortex pairing. The studied nonthermal fixed points are accessible in cold-gas experiments. The results shed light on fundamental aspects of superfluid turbulence and have strong potential implications for related phenomena, e.g., in early-universe inflation or quark-gluon plasma dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.6127v2.pdf"}
{"id": "1111.6650", "abstract": "  Existing optimal control protocols for mitigating the effects of relaxation and/or RF inhomogeneity on broadband pulse performance are extended to the more difficult problem of designing robust, refocused, frequency selective excitation pulses. For the demanding case of T1 and T2 equal to the pulse length, anticipated signal losses can be significantly reduced while achieving nearly ideal frequency selectivity. Improvements in performance are the result of allowing residual unrefocused magnetization after applying relaxation-compensated selective excitation by optimized pulses (RC-SEBOP). We demonstrate simple pulse sequence elements for eliminating this unwanted residual signal. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.6650v1.pdf"}
{"id": "1111.6803", "abstract": "  The Fermi Flare Advocate (also known as Gamma-ray Sky Watcher, FA-GSW) service provides for a daily quicklook analysis and review of the high-energy gamma-ray sky seen by the Fermi Gamma-ray Space Telescope. The duty offers alerts for potentially new gamma-ray sources, interesting transients and relevant flares. A public weekly digest containing the main highlights about the GeV gamma-ray sky is published in the web-based Fermi Sky Blog. During the first 3 years of all-sky survey, more than 150 Astronomical Telegrams, several alerts to the TeV Cherenkov telescopes, and targets of opportunity to Swift and other observatories have been realized. This increased the rate of simultaneous multi-frequency observing campaigns and the level of international cooperation. Many gamma-ray flares from blazars (like extraordinary outbursts of 3C 454.3, intense flares of PKS 1510-089, 4C 21.35, PKS 1830-211, AO 0235+164, PKS 1502+106, 3C 279, 3C 273, PKS 1622-253), short/long flux duty cycles, unidentified transients near the Galactic plane (like J0910-5041, J0109+6134, the Galactic center region), flares associated to Galactic sources (like the Crab nebula, the nova V407 Cyg, the microquasar Cyg X-3), emission of the quiet and active sun, were observed by Fermi and communicated by FA-GSWs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.6803v2.pdf"}
{"id": "1111.7063", "abstract": "  We study the prospects of probing large extra dimension model at the LHC through neutral triple gauge boson production processes. In theories with extra dimensions these processes result from the exchange of a tower of massive graviton modes between the SM particles. We consider γγγ, γγZ, γZ Z and ZZZ production processes, and present our results for various kinematic distributions at the LHC for √(S)=14 TeV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.7063v2.pdf"}
{"id": "1112.0219", "abstract": "  We discuss the scenario of light neutralino dark matter in the minimal supersymmetric standard model, which is motivated by the results of some of the direct detection experiments — DAMA, CoGENT, and CRESST. We update our previous analysis with the latest results of the LHC. We show that new LHC constraints disfavour the parameter region that can reproduce the results of DAMA and CoGENT. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.0219v2.pdf"}
{"id": "1112.0533", "abstract": "  The galactic neighborhood, extending from the Milky Way to redshifts of about 0.1, is our unique local laboratory for detailed study of galaxies and their interplay with the environment. Such study provides a foundation of knowledge for interpreting observations of more distant galaxies and their environment. The Astro 2010 Science Frontier Galactic Neighborhood Panel identified four key scientific questions: 1) What are the flows of matter and energy in the circumgalactic medium? 2) What controls the mass-energy-chemical cycles within galaxies? 3) What is the fossil record of galaxy assembly from first stars to present? 4) What are the connections between dark and luminous matter? These questions, essential to the understanding of galaxies as interconnected complexes, can be addressed most effectively and/or uniquely in the galactic neighborhood. The panel also highlighted the discovery potential of time-domain astronomy and astrometry with powerful new techniques and facilities to greatly advance our understanding of the precise connections among stars, galaxies, and newly discovered transient events. The relevant needs for laboratory astrophysics will be emphasized, especially in the context of supporting NASA missions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.0533v1.pdf"}
{"id": "1112.4388", "abstract": "  Gravitational wave detectors from the advanced generation onwards are expected to be limited in sensitivity by thermal noise of the optics, making the reduction of this noise a key factor in the success of such detectors. A proposed method for reducing the impact of this noise is to use higher-order Laguerre-Gauss (LG) modes for the readout beam, as opposed to the currently used fundamental mode. We present here a synopsis of the research program undertaken by the University of Birmingham into the suitability of LG mode technology for future gravitational wave detectors. This will cover our previous and current work on this topic, from initial simulations and table-top LG mode experiments up to implementation in a prototype scale suspended cavity and high-power laser bench. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.4388v1.pdf"}
{"id": "1112.4509", "abstract": "  We investigate Lipatov's QCD effective action for the QCD high energy limit and propose a pole prescription for higher order induced vertices. The latter can be used in the evaluation of loop corrections to high energy factorized matrix elements within the effective action approach. The proposed prescription respects the symmetry properties of the unregulated vertices. Explicit results are presented up to third order in the gauge coupling, while an iterative procedure for higher orders is proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.4509v1.pdf"}
{"id": "1112.4826", "abstract": "  Previous research has highlighted the importance of strong heterogeneity for the successful evolution of cooperation in games governed by pairwise interactions. Here we determine to what extent this is true for games governed by group interactions. We therefore study the evolution of cooperation in the public goods game on the square lattice, the triangular lattice and the random regular graph, whereby the payoffs are distributed either uniformly or exponentially amongst the players by assigning to them individual scaling factors that determine the share of the public good they will receive. We find that uniformly distributed public goods are more successful in maintaining high levels of cooperation than exponentially distributed public goods. This is not in agreement with previous results on games governed by pairwise interactions, indicating that group interactions may be less susceptible to the promotion of cooperation by means of strong heterogeneity as originally assumed, and that the role of strongly heterogeneous states should be reexamined for other types of games. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.4826v1.pdf"}
{"id": "1112.5604", "abstract": "  Cells are constantly exposed to fluctuating environmental conditions. External signals are sensed, processed and integrated by cellular signal transduction networks, which translate input signals into specific cellular responses by means of biochemical reactions. These networks have a complex nature, and we are still far from having a complete characterization of the process through which they integrate information, specially given the noisy environment in which that information is embedded. Guided by the many instances of constructive influences of noise that have been reported in the physical sciences in the last decades, here we explore how multiple signals are integrated in an eukaryotic cell in the presence of background noise, or chatter. To that end, we use a Boolean model of a typical human signal transduction network. Despite its complexity, we find that the network is able to display simple patterns of signal integration. Furthermore, our computational analysis shows that these integration patterns depend on the levels of fluctuating background activity carried by other cell inputs. Taken together, our results indicate that signal integration is sensitive to environmental fluctuations, and that this background noise effectively determines the information integration capabilities of the cell. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.5604v1.pdf"}
{"id": "1201.1744", "abstract": "  We report on the long-term evolution of the spin period of the symbiotic X-ray pulsar GX 1+4 and a possible interpretation within a model of quasi-spherical accretion. New period measurements from BeppoSAX, INTEGRAL and Fermi observations have been combined with previously published data from four decades of observations. During the 1970s GX 1+4 was spinning up with the fastest rate among the known X-ray pulsars at the time. In the mid 1980s it underwent a change during a period of low X-ray ux and started to spin down with a rate similar in magnitude to the previous spin up rate. The spin period has changed from  110 s to  160 s within the last three decades. Our results demonstrate that the overall spin down trend continues and is stronger than ever. We compare the observations with predictions from a model assuming quasi-spherical accretion from the slow wind of the M giant companion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.1744v1.pdf"}
{"id": "1201.1918", "abstract": "  We study coherent transport through a semiconductor nanowire in the presence of spin-orbit coupling and Zeeman splitting due to an applied magnetic field. By employing analytical and numerical techniques we develop a theory for the Josephson effect in the superconductor-semiconductor nanowire-superconductor structure. We show that Josephson current through the clean semiconductor nanowire exhibits a number of interesting features due to the interplay between the Zeeman splitting and spin-orbit coupling. We also study effect how disorder in the nanowire affects Andreev bound-state energy spectrum and calculate local density of states at the junction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.1918v2.pdf"}
{"id": "1201.2389", "abstract": "  Ultrafast synchrotron microtomography has been used to study in-situ and in real time the initial stages of silicate glass melt formation from crystalline granular raw materials. Significant and unexpected rearrangements of grains occur below the nominal eutectic temperature, and several drastically different solid-state reactions are observed to take place at different types of intergranular contacts. These reactions have a profound influence on the formation and the composition of the liquids produced, and control the formation of defects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.2389v1.pdf"}
{"id": "1201.2720", "abstract": "  We demonstrate how the Fundamental Manifold (FM) can be used to cross-calibrate distance estimators even when those \"standard candles\" are not found in the same galaxy. Such an approach greatly increases the number of distance measurements that can be utilized to check for systematic distance errors and the types of estimators that can be compared. Here we compare distances obtained using SN Ia, Cepheids, surface brightness fluctuations, the luminosity of the tip of the red giant branch, circumnuclear masers, eclipsing binaries, RR Lyrae stars, and the planetary nebulae luminosity functions. We find no significant discrepancies (differences are < 2 sigma) between distance methods, although differences at the  10", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.2720v1.pdf"}
{"id": "1201.2802", "abstract": "  We present the energy eigenvalues of a quantum bouncer in the framework of the Generalized (Gravitational) Uncertainty Principle (GUP) via quantum mechanical and semiclassical schemes. In this paper, we use two equivalent nonperturbative representations of a deformed commutation relation in the form [X,P]=iħ(1+βP^2) where βis the GUP parameter. The new representation is formally self-adjoint and preserves the ordinary nature of the position operator. We show that both representations result in the same modified semiclassical energy spectrum and agrees well with the quantum mechanical description. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.2802v1.pdf"}
{"id": "1201.3244", "abstract": "  We present a mechanism for amplitude death in coupled nonlinear dynamical systems on a complex network having interactions with a common environment-like external system. We develop a general stability analysis that is valid for any network topology and obtain the threshold values of coupling constants for the onset of amplitude death. An important outcome of our study is a universal relation between the critical coupling strength and the largest non-zero eigenvalue of the coupling matrix. Our results are fully supported by the detailed numerical analysis for different network topologies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.3244v2.pdf"}
{"id": "1201.3968", "abstract": "  We show that quadratic divergences in top-quark condensation are cancelled when the tadpoles cancel. This latter cancellation is naturally implemented as the cancellation among the top-quark, Goldstone and Higgs contributions. We also calculate the bosonic correction terms to Gribov's mass formula for the Higgs boson. These reduce the prediction for M_H from 167 GeV to 132 GeV. The tadpole cancellation condition by itself is an independent condition on the mass of the Higgs boson which, in Gribov's U(1)_Y scenario, yields M_H ≈117 GeV with large theoretical uncertainty. More generally, we are able to obtain all three masses, M_W, m_t and M_H, in 100 MeV to 10 TeV energy range as a function of the cut-off scale and the gauge couplings only. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.3968v3.pdf"}
{"id": "1201.4525", "abstract": "  Starting from the pioneering work of G. S. Agarwal [Zeitschrift für Physik 252, 25 (1972)], we present a unified derivation of a number of modified fluctuation-dissipation relations (MFDR) that relate response to small perturbations around non-equilibrium steady states to steady-state correlations. Using this formalism we show the equivalence of velocity forms of MFDR derived using continuum Langevin and discrete master equation dynamics. The resulting additive correction to the Einstein relation is exemplified using a flashing ratchet model of molecular motors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.4525v1.pdf"}
{"id": "1201.5424", "abstract": "  We present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically-associated transiting planets. Binary stars provide the primary source of false positives among Kepler planet candidates, implying that false positives should be nearly randomly-distributed among Kepler targets. In contrast, true transiting planets would appear clustered around a smaller number of Kepler targets if detectable planets tend to come in systems and/or if the orbital planes of planets encircling the same star are correlated. There are more than one hundred times as many Kepler planet candidates in multi-candidate systems as would be predicted from a random distribution of candidates, implying that the vast majority are true planets. Most of these multis are multiple planet systems orbiting the Kepler target star, but there are likely cases where (a) the planetary system orbits a fainter star, and the planets are thus significantly larger than has been estimated, or (b) the planets orbit different stars within a binary/multiple star system. We use the low overall false positive rate among Kepler multis, together with analysis of Kepler spacecraft and ground-based data, to validate the closely-packed Kepler-33 planetary system, which orbits a star that has evolved somewhat off of the main sequence. Kepler-33 hosts five transiting planets with periods ranging from 5.67 to 41 days. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.5424v1.pdf"}
{"id": "1201.5662", "abstract": "  Precision cosmology studies based on wide-field surveys of galaxy clusters benefit from constraints on intrinsic scatter in mass-observable relationships. In principle, two-parameter models combining direct measurements of galaxy cluster structural variation with mass proxies such as X-ray luminosity and temperature can be used to constrain scatter in the relationship between the mass proxy and the cluster's halo mass and to measure the redshift evolution of that scatter. One candidate for quantifying cluster substructure is the ICM temperature inhomogeneity inferred from X-ray spectral properties, an example of which is T_HBR, the ratio of hardband to broadband spectral-fit temperatures. In this paper we test the effectiveness of T_HBR as an indicator of scatter in the mass-temperature relation using 118 galaxy clusters simulated with radiative cooling and feedback. We find that, while T_HBR is correlated with clusters' departures δlnT_X from the mean M-T_X relation, the effect is modest. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.5662v1.pdf"}
{"id": "1201.5760", "abstract": "  Interaction of domain walls (DWs) in ferromagnetic stripes is studied with relevance to the formation of stable complexes of many domains. Two DW system is described with the Landau-Lifshitz-Gilbert equation including regimes of narrow and wide stripes which correspond the presence of transverse and vortex DWs. The DWs of both kinds are characterized with their chiralities (the direction of the magnetization rotation in the stripe plane) and polarities (the magnetization orientation in the center of a vortex and/or halfvortices), hence, their interactions are analyzed with dependence on these properties. In particular, pairs of the DWs of opposite or like both chiralities and polarities are investigated as well as pairs of opposite (like) chiralities and of like (opposite) polarities. Conditions of the creation of stationary magnetic bubbles built of two interacting DWs are formulated with relevance to the situations of presence and absence of the external magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.5760v3.pdf"}
{"id": "1202.0304", "abstract": "  We implement Slow Roll Reconstruction – an optimal solution to the inverse problem for inflationary cosmology – within ModeCode, a publicly available solver for the inflationary dynamics. We obtain up-to-date constraints on the reconstructed inflationary potential, derived from the WMAP 7-year dataset and South Pole Telescope observations, combined with large scale structure data derived from SDSS Data Release 7. Using ModeCode in conjunction with the MultiNest sampler, we compute Bayesian evidence for the reconstructed potential at each order in the truncated slow roll hierarchy. We find that the data are well-described by the first two slow roll parameters, ϵand η, and that there is no need to include a nontrivial ξparameter. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.0304v3.pdf"}
{"id": "1202.0461", "abstract": "  High-field magnetic white dwarfs have been long suspected to be the result of stellar mergers. However, the nature of the coalescing stars and the precise mechanism that produces the magnetic field are still unknown. Here we show that the hot, convective, differentially rotating corona present in the outer layers of the remnant of the merger of two degenerate cores is able to produce magnetic fields of the required strength that do not decay for long timescales. We also show, using an state-of-the-art Monte Carlo simulator, that the expected number of high-field magnetic white dwarfs produced in this way is consistent with that found in the Solar neighborhood. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.0461v1.pdf"}
{"id": "1202.0624", "abstract": "  Calorimetry at future linear colliders could be based on a particle flow approach where granularity is the key to high jet energy resolution. Among different technologies, Micromegas chambers with 1 cm2 pad segmentation are studied for the active medium of a hadronic calorimeter. A chamber of 1 m2 with 9216 channels read out by a low noise front-end ASIC called MICROROC has recently been constructed and tested. Chamber design, ASIC circuitry and preliminary test beam results are reported. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.0624v1.pdf"}
{"id": "1202.0858", "abstract": "  We demonstrate the implementation of a simple time-of-flight (ToF) mass spectrometer with medium-mass resolution (m/Δ m∼50) geared towards the demands of atomic, molecular, and chemical physics experiments. By utilizing a novel radial ion extraction scheme from a linear quadrupole trap, a device with large trap capacity and high optical access is realized without sacrificing mass resolution. Here we describe the construction and implementation of the device as well as present representative ToF spectra. We conclude by demonstrating the flexibility of the device with proof-of-principle experiments that include the observation of molecular-ion photodissociation and the measurement of trapped-ion chemical reaction rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.0858v1.pdf"}
{"id": "1202.1018", "abstract": "  Using scattering theory, we investigate interferometers composed of chiral Majorana fermion modes coupled to normal metal leads. We advance an approach in which also the basis states in the normal leads are written in terms of Majorana modes. Thus each pair of electron-hole states is associated with a pair of Majorana modes. Only one lead Majorana mode couples to the intrinsic Majorana mode whereas its partner is completely reflected. Similarly the remaining Majorana modes are completely reflected but in general mix pair-wise. We demonstrate that the charge current can also be expressed in terms of interference between pairs of Majorana modes. These two basic facts permit a treatment and understanding of current and noise signatures of chiral Majorana fermion interferometry in an especially elegant way. As a particular example of applications, in Fabry-Perot-type interferometers where chiral Majorana modes form loops, resonances (anti-resonances) from such loops always lead to peaked (suppressed) Andreev differential conductances, and negative (positive) cross-correlations that originate purely from two-Majorana-fermion exchange. These investigations are intimately related to current and noise signatures of Majorana bound states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.1018v1.pdf"}
{"id": "1202.1396", "abstract": "  Despite decades of dedicated efforts there are still basic questions to answer with regard to Supernova progenitor systems and explosion mechanisms. In particular, in the last years a number of exceptionally bright objects and extremely faint events have demonstrated an unexpected large Supernova variety. The large number of Supernovae candidates at different redshifts provided by the next generation surveys, from ground and space, will allow to reach a better insight of the Supernova events in all their flavours. In particular it will be the possible to assess the systematics of type Ia Supernovae as distance indicator at any redshift. The Gaia astrometric mission is expected to discover a huge number of transient events, including Supernovae, which will be immediately disseminated to the astronomical community by a transients alert system for a suitable follow up. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.1396v2.pdf"}
{"id": "1202.1688", "abstract": "  In this paper we propose several models that describe the dynamics of liquid films which are covered by a high concentration layer of insoluble surfactant. First, we briefly review the 'classical' hydrodynamic form of the coupled evolution equations for the film height and surfactant concentration that are well established for small concentrations. Then we re-formulate the basic model as a gradient dynamics based on an underlying free energy functional that accounts for wettability and capillarity. Based on this re-formulation in the framework of nonequilibrium thermodynamics, we propose extensions of the basic hydrodynamic model that account for (i) nonlinear equations of state, (ii) surfactant-dependent wettability, (iii) surfactant phase transitions, and (iv) substrate-mediated condensation. In passing, we discuss important differences to most of the models found in the literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.1688v1.pdf"}
{"id": "1202.1981", "abstract": "  The Hierarchical Reference Theory (HRT) of fluids is a general framework for the description of phase transitions in microscopic models of classical and quantum statistical physics. The foundations of HRT are briefly reviewed in a self-consistent formulation which includes both the original sharp cut-off procedure and the smooth cut-off implementation, which has been recently investigated. The critical properties of HRT are summarized, together with the behavior of the theory at first order phase transitions. However, the emphasis of this presentation is on the close relationship between HRT and non perturbative renormalization group methods, as well as on recent generalizations of HRT to microscopic models of interest in soft matter and quantum many body physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.1981v1.pdf"}
{"id": "1202.2459", "abstract": "  The expansion of an initially unmagnetized planar rarefaction wave has recently been shown to trigger a thermal anisotropy-driven Weibel instability (TAWI), which can generate magnetic fields from noise levels. It is examined here if the TAWI can also grow in a curved rarefaction wave. The expansion of an initially unmagnetized circular plasma cloud, which consists of protons and hot electrons, into a vacuum is modelled for this purpose with a two-dimensional particle-in-cell (PIC) simulation. It is shown that the momentum transfer from the electrons to the radially accelerating protons can indeed trigger a TAWI. Radial current channels form and the aperiodic growth of a magnetowave is observed, which has a magnetic field that is oriented orthogonal to the simulation plane. The induced electric field implies that the electron density gradient is no longer parallel to the electric field. Evidence is presented here for that this electric field modification triggers a second magnetic instability, which results in a rotational low-frequency magnetowave. The relevance of the TAWI is discussed for the growth of small-scale magnetic fields in astrophysical environments, which are needed to explain the electromagnetic emissions by astrophysical jets. It is outlined how this instability could be examined experimentally. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.2459v1.pdf"}
{"id": "1202.3986", "abstract": "  The pairing Hamiltonian constitutes an important approximation in many- body systems, it is exactly soluble and quantum integrable. On the other hand, the continuum single particle level density (CSPLD) contains information about the continuum energy spectrum. The question whether one can use the Hamiltonian with constant pairing strength for correlations in the continuum is still unanswered. In this paper we generalize the Richardson exact solution for the pairing Hamiltonian including correlations in the continuum. The resonant and non-resonant continuum are included through the CSPLD. The resonant correlations are made explicit by using the Cauchy theorem. Low lying states with seniority zero and two are calculated for the even Carbon isotopes. We conclude that energy levels can indeed be calculated with constant pairing in the continuum using the CSPLD. It is found that the nucleus ^24C is unbound. The real and complex energy representation of the continuum is developed and their differences are shown. The trajectory of the pair energies in the continuum for the nucleus ^28C is shown. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.3986v2.pdf"}
{"id": "1202.4055", "abstract": "  A more extended low density region of coexisting uniform antiferromagnetism and d-wave superconductivity has been reported in multilayer cuprates, when compared to single or bilayer cuprates. This coexistence could be due to the enhanced screening of random potential modulations in inner layers or to the interlayer Heisenberg and Josephson couplings. A theoretical analysis using a renormalized mean field theory, favors the former explanation. The potential for an improved determination of the antiferromagnetic and superconducting order parameters in an ideal single layer from zero field NMR and infrared Josephson plasma resonances in multilayer cuprates is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.4055v1.pdf"}
{"id": "1202.4796", "abstract": "  We use our recently proposed accelerated dynamics algorithm (Tiwary     van de Walle, 2011) to calculate temperature and stress dependence of activation free energy for surface nucleation of dislocations in pristine Gold nanopillars under realistic loads. While maintaining fully atomistic resolution, we achieve the fraction of a second time-scale regime. We find that the activation free energy depends significantly on the driving force (stress or strain) and temperature, leading to very high activation entropies. We also perform compression tests on Gold nanopillars for strain rates varying between 7 orders of magnitudes, reaching as low as 10^3/s. Our calculations show the quantitative effects on the yield point of unrealistic strain-rate Molecular Dynamics calculations: we find that while the failure mechanism for <001> compression of Gold nanopillars remains the same across the entire strain-rate range, the elastic limit (defined as stress for nucleation of the first dislocation) depends significantly on the strain-rate. We also propose a new methodology that overcomes some of the limits in our original accelerated dynamics scheme (and accelerated dynamics methods in general). We lay out our methods in sufficient details so as to be used for understanding and predicting deformation mechanism under realistic driving forces for various problems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.4796v2.pdf"}
{"id": "1202.5163", "abstract": "  In the original holographic dark energy (HDE) model, the dark energy density is proposed to be ρ_de = 3c^2M^2_plL^-2, with c is a dimensionless constant characterizing the properties of the HDE. In this work, we propose the generalized holographic dark energy (GHDE) model by considering the parameter c as a redshift-dependent function c(z). We derive all the physical quantities of the GHDE model analytically, and fit the c(z) by trying four kinds of parametrizations. The cosmological constraints of the c(z) are obtained from the joint analysis of the present SNLS3+BAO+CMB+H_0 data. We find that, compared with the original HDE model, the GHDE models can provide a better fit to the data. For example, the GHDE model with JBP-type c(z) can reduce the χ^2_min of the HDE model by 2.16. We also find that, unlike the original HDE model with a phantom-like behavior in the future, the GHDE models can present many more different possibilities, i.e., it allows the GHDE in the future to be either quintessence like, cosmological constant like, or phantom like, depending on the forms of c(z). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.5163v3.pdf"}
{"id": "1202.5197", "abstract": "  We present an extension of the Allen-Cahn/Cahn-Hilliard system which incorporates a geometrically linear ansatz for the elastic energy of the precipitates. The model contains both the elastic Allen-Cahn system and the elastic Cahn-Hilliard system as special cases and accounts for the microstructures on the microscopic scale. We prove the existence of weak solutions to the new model for a general class of energy functionals. We then give several examples of functionals that belong to this class. This includes the energy of geometrically linear elastic materials for D<3. Moreover we show this for D=3 in the setting of scalar-valued deformations, which corresponds to the case of anti-plane shear. All this is based on explicit formulas for relaxed energy functionals newly derived in this article for D=1 and D=3. In these cases we can also prove uniqueness of the weak solutions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.5197v2.pdf"}
{"id": "1202.6468", "abstract": "  It has been alleged in several papers that the so called delayed continuous-time random walks (DCTRWs) provide a model for the one-dimensional telegraph equation at microscopic level. This conclusion, being widespread now, is strange, since the telegraph equation describes phenomena with finite propagation speed, while the velocity of the motion of particles in the DCTRWs is infinite. In this paper we investigate how accurate are the approximations to the DCTRWs provided by the telegraph equation. We show that the diffusion equation, being the correct limit of the DCTRWs, gives better approximations in L_2 norm to the DCTRWs than the telegraph equation. We conclude therefore that, first, the DCTRWs do not provide any correct microscopic interpretation of the one-dimensional telegraph equation, and second, the kinetic (exact) model of the telegraph equation is different from the model based on the DCTRWs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.6468v1.pdf"}
{"id": "1203.4732", "abstract": "  In this extended abstract we provide a unifying framework that can be used to characterize and compare the expressive power of query languages for different data base models. The framework is based upon the new idea of valid partition, that is a partition of the elements of a given data base, where each class of the partition is composed by elements that cannot be separated (distinguished) according to some level of information contained in the data base. We describe two applications of this new framework, first by deriving a new syntactic characterization of the expressive power of relational algebra which is equivalent to the one given by Paredaens, and subsequently by studying the expressive power of a simple graph-based data model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.4732v1.pdf"}
{"id": "1203.6573", "abstract": "  The temperature dependence of the thermodynamic potential of quantum chromodynamics (QCD), the specific heat, and the quark effective mass are calculated for imbalanced quark matter in the limit of a large number of quark flavors (large-N_F), which corresponds to the random phase approximation. Also a generalization of the relativistic Landau effective-mass relation in the imbalanced case is given, which is then applied to this thermodynamic potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.6573v1.pdf"}
{"id": "1204.0369", "abstract": "  We revisit the problem of phantom behaviour of effective dark energy in scalar-tensor gravity. The main focus is on the properties of the functions defining the model. We find that models with the present phantom behavior can be made consistent with all constraints, but one of these functions must have rather contrived shape, and the initial data must be strongly fine-tuned. Also, the phantom stage must have begun fairly recently, at z≲ 1. All this disfavors the effective phantom behaviour in the scalar-tensor gravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.0369v1.pdf"}
{"id": "1204.2150", "abstract": "  We consider a communication scenario where a source communicates with a destination over a directed layered relay network. Each relay performs analog network coding where it scales and forwards the signals received at its input. In this scenario, we address the question: What portion of the maximum end-to-end achievable rate can be maintained if only a fraction of relay nodes available at each layer are used?   We consider, in particular, the Gaussian diamond network (layered network with a single layer of relay nodes) and a class of symmetric layered networks. For these networks we show that each relay layer increases the additive gap between the optimal analog network coding performance with and without network simplification (using k instead of N relays in each layer, k < N) by no more than log(N/k)^2 bits and the corresponding multiplicative gap by no more than a factor of (N/k)^2, asymptotically (in source power). To the best of our knowledge, this work offers the first characterization of the performance of network simplification in general layered amplify-and-forward relay networks. Further, unlike most of the current approximation results that attempt to bound optimal rates either within an additive gap or a multiplicative gap, our results suggest a new rate approximation scheme that allows for the simultaneous computation of additive and multiplicative gaps. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.2150v2.pdf"}
{"id": "1204.2211", "abstract": "  Evidence from numerical simulations suggest that the nature of dynamo transition changes from supercritical to subcritical as the magnetic Prandtl number is decreased. To explore this interesting crossover we first use direct numerical simulations to investigate the hysteresis zone of a subcritical Taylor-Green dynamo. We establish that a well defined boundary exists in this hysteresis region which separates dynamo states from the purely hydrodynamic solution. We then propose simple dynamo models which show similar crossover from supercritical to subcritical dynamo transition as a function of the magnetic Prandtl number. Our models show that the change in the nature of dynamo transition is connected to the stabilizing or de-stabilizing influence of governing non-linearities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.2211v3.pdf"}
{"id": "1204.2949", "abstract": "  We consider two interacting Bose-Einstein condensates (BEC's) with different kind of the potential energy of interaction of the condensates: (a) the standard potential; (b) the potential has a positive three-body and a negative two-body scattering terms and (c) the potential has a positive four-body and a negative three-body scattering terms for the first BEC and a positive three-body and a negative two-body scattering terms for the second BEC. It is shown that in these cases there exist regular spherically symmetric solutions. Physically such solution is either a defect or a droplet created by the condensates. The defect is a cavity filled with one BEC on the background of another BEC. The droplet is an object on the background of the empty space. For (a) and (b) cases the obtained objects are supported by a constant external trapping potential and for (c) case the droplet is a self-maintaining object without any external potential. The possibility of construction of an elementary logic qubit device on the basis of this droplet is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.2949v3.pdf"}
{"id": "1204.3723", "abstract": "  Charge equilibration has been recognized as a dominant process at the early stage of low-energy heavy-ion reactions. The production of exotic nuclei is suppressed under the appearance of charge equilibration, in which the proton-neutron ratios of the final reaction products are inevitably averaged. Therefore charge equilibration plays one of the most crucial roles in the synthesis of chemical elements. Focusing on how and when the charge equilibration takes place, the zero-sound propagation in femto-scale quantum liquids is explained. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.3723v1.pdf"}
{"id": "1204.4095", "abstract": "  Exciton-polariton condensates display a variety of intriguing pattern-forming behaviors, particularly when confined in potential traps. It has previously been predicted that triangular lattices of vortices of the same sign will form spontaneously as the result of surface instabilities in a harmonic trap. However, natural disorder, deviation of the external potential from circular symmetry, or higher-order terms modifying the dynamical equations may all have detrimental effects and destabilize the circular trajectories of vortices. Here we address these issues, by characterizing the robustness of the vortex lattice against disorder and deformations of the trapping potential. Since most experiments use time integrated measurements it would be hard to observe directly the rotating vortex lattices or distinguish them from vortex-free states. We suggest how these difficulties can be overcome and present an experimentally viable interference-imaging scheme that would allow the detection of rotating vortex lattices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.4095v1.pdf"}
{"id": "1204.4099", "abstract": "  We consider a Hubble expansion law modified in the infra-red by distance-dependent terms, and attempt to enforce homogeneity upon it. As a warm-up, we re-derive the basic kinematics of a Friedman Robertson Walker universe without using standard general relativistic tools: we describe the expansion with a `Hubble velocity field' rather than with a four dimensional metric. Then we extend this analysis to the modified Hubble expansion and impose a transformation for velocities that makes it identical for all comoving observers, and therefore homogeneous. We derive the modified equation for light ray trajectories and other geometrical properties that are incompatible with the general relativistic description. We speculate that this extended framework could help addressing cosmological problems which are normally explained with accelerating expansions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.4099v1.pdf"}
{"id": "1204.4356", "abstract": "  A soap film, or a flexible membrane without bending and torsional stiffness, that is confined in a cylinder is shown to be susceptible to a surface-tension-driven instability when it is stretched or twisted. This leads to its breakdown and places an upper limit on the aspect ratio of such structures. A simple analysis confirms the values for the critical aspect ratio of the stretched film found in both simulations and experiments on soap films, and this threshold decreases with increasing twist of the film. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.4356v2.pdf"}
{"id": "1204.6101", "abstract": "  We present a large bank of chemical profiles and pulsation periods suited for asteroseismological studies of ZZ Ceti (or DAV) variable stars. Our background equilibrium DA white dwarf models are the result of fully evolutionary computations that take into account the complete history of the progenitor stars from the ZAMS. The models are characterized by self-consistent chemical structures from the centre to the surface, and cover a wide range of stellar masses, effective temperatures, and H envelope thicknesses. We present dipole and quadrupole pulsation g-mode periods comfortably covering the interval of periods observed in ZZ Ceti stars. Complete tabulations of chemical profiles and pulsation periods to be used in asteroseismological period fits, as well as other quantities of interest, can be freely downloaded from our website (<http://www.fcaglp.unlp.edu.ar/evolgroup> ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.6101v1.pdf"}
{"id": "1204.6309", "abstract": "  We simultaneously analyze vector and axial-vector spectral functions in vacuum using hadronic models constrained by experimental data and the requirement that Weinberg-type sum rules are satisfied. Upon explicit inclusion of an excited vector state, viz. rho', and the requirement that the perturbative continua are degenerate in vector and axial-vector channels, we deduce the existence of an excited axial-vector resonance state, a1', in order that the Weinberg sum rules are satisfied. The resulting spectral functions are further tested with QCD sum rules. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.6309v2.pdf"}
{"id": "1204.6440", "abstract": "  The Zaklan model had been proposed and studied recently using the equilibrium Ising model on Square Lattices (SL) by Zaklan et al (2008), near the critica temperature of the Ising model presenting a well-defined phase transition; but on normal and modified Apollonian networks (ANs), Andrade et al. (2005, 2009) studied the equilibrium Ising model. They showed the equilibrium Ising model not to present on ANs a phase transition of the type for the 2D Ising model. Here, using agent-based Monte-Carlo simulations, we study the Zaklan model with the well-known majority-vote model (MVM) with noise and apply it to tax evasion on ANs, to show that differently from the Ising model the MVM on ANs presents a well defined phase transition. To control the tax evasion in the economics model proposed by Zaklan et al, MVM is applied in the neighborhood of the critical noise q_c to the Zaklan model. Here we show that the Zaklan model is robust because this can be studied besides using equilibrium dynamics of Ising model also through the nonequilibrium MVM and on various topologies giving the same behavior regardless of dynamic or topology used here. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.6440v2.pdf"}
{"id": "1205.0146", "abstract": "  Gravity can be thought as an emergent phenomenon and it has a nice \"thermodynamic\" structure. In this context, it is then possible to study the thermodynamics without knowing the details of the underlying microscopic degrees of freedom. Here, based on the ordinary thermodynamics, we investigate the phase transition of the static, spherically symmetric charged black hole solution with arbitrary scalar curvature 2k in Hořava-Lifshitz gravity at the Lifshitz point z=3. The analysis is done using the canonical ensemble frame work; i.e. the charge is kept fixed. We find (a) for both k=0 and k=1, there is no phase transition, (b) while k=-1 case exhibits the second order phase transition within the physical region of the black hole. The critical point of second order phase transition is obtained by the divergence of the heat capacity at constant charge. Near the critical point, we find the various critical exponents. It is also observed that they satisfy the usual thermodynamic scaling laws. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.0146v2.pdf"}
{"id": "1205.0389", "abstract": "  We consider the embedding method of the superconformal group in four dimensions in the case of extended supersymmetry, hence generalizing the recent work of Goldberger, Skiba and Son which was restricted at N=1. Moreover, we work out explicitly the case of N=2 chiral superfields in four dimensions, putting the component fields in correspondence with Pascal's pyramid at layer N. This correspondence is a generic property of the N-extended chiral sector. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.0389v2.pdf"}
{"id": "1205.1387", "abstract": "  By taking into account the local energy balance per unit volume between the viscous heating and the advective cooling plus the radiative cooling, we investigate the vertical structure of radiation pressure-supported accretion disks in spherical coordinates. Our solutions show that the photosphere of the disk is close to the polar axis and therefore the disk seems to be extremely thick. However, the profile of density implies that most of the accreted matter exists in a moderate range around the equatorial plane. We show that the well-known polytropic relation between the pressure and the density is unsuitable for describing the vertical structure of radiation pressure-supported disks. More importantly, we find that the energy advection is significant even for slightly sub-Eddington accretion disks. We argue that the non-negligible advection may help to understand why the standard thin disk model is likely to be inaccurate above ∼0.3 Eddington luminosity, which was found by some works on the black hole spin measurement. Furthermore, the solutions satisfy the Solberg-Hoiland conditions, which indicates the disk to be convectively stable. In addition, we discuss the possible link between our disk model and ultraluminous X-ray sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.1387v2.pdf"}
{"id": "1205.1393", "abstract": "  Coherent diffraction imaging (CDI) of single molecules at atomic resolution is a major goal for the x-ray free electron lasers (XFELs). However, during an imaging pulse, the fast laser-induced ionization may strongly affect the recorded diffraction pattern of the irradiated sample. The radiation tolerance of the imaged molecule should then be investigated 'a priori' with a dedicated simulation tool. The continuum approach is a powerful tool for modeling the evolution of irradiated large systems consisting of more than a few hundred thousand atoms. However, this method follows the evolution of average single-particle densities, and the experimentally recorded intensities reflect the spatial two-particle correlations. The information on these correlations is then inherently not accessible within the continuum approach. In this paper we analyze this limitation of continuum models and discuss the applicability of continuum models for imaging studies. We propose a formula to calculate scattered intensities (including both elastic and inelastic scattering) from the estimates obtained with a single-particle continuum model. We derive this formula for systems under conditions typical for CDI studies with XFELs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.1393v1.pdf"}
{"id": "1205.1744", "abstract": "  In this work,we study the Kondo effect of a quantum dot (QD) connected to leads and to a discrete set of one particle states provided by a quantum box represented by a quantum ring (QR) pierced by a magnetic flux side attached to the QD. The interplay between the bulk Kondo effect and the so called Kondo box regime is studied. In this system the QR energies can be continuously modified by the application of the magnetic field. The crossover between these two regimes is analyzed by changing the connection of the QD to the QR from the weak to the strong coupling regime. In the weak coupling regime, the differential conductance develops a sequence of Fano-Kondo antiresonances due to destructive interferences between the discrete quantum ring levels and the conducting Kondo channel provided by the leads. In the strong coupling regime the differential conductance has very sharp resonances when one of the Kondo discrete sub-level characterizing the Kondo box is tunned by the applied potential. The conductance, the current fluctuations and the Fano coefficient result to be the relevant physical magnitudes to be analyzed to reveal the physical properties of these two Kondo regimes and the crossover region between them. The results were obtained by using the Slave Boson Mean Field Theory (SBMFT). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.1744v3.pdf"}
{"id": "1205.2395", "abstract": "  While the connection between Long Gamma-Ray Bursts (GRBs) and Type Ib/c Supernovae (SNe Ib/c) from stripped stars has been well-established, one key outstanding question is what conditions and factors lead to each kind of explosion in massive stripped stars. One promising line of attack is to investigate what sets apart SNe Ib/c with GRBs from those without GRBs. Here, I briefly present two observational studies that probe the SN properties and the environmental metallicities of SNe Ib/c (specifically broad-lined SNe Ic) with and without GRBs. I present an analysis of expansion velocities based on published spectra and on the homogeneous spectroscopic CfA data set of over 70 SNe of Types IIb, Ib, Ic and Ic-bl, which triples the world supply of well-observed Stripped SNe. Moreover, I demonstrate that a meta-analysis of the three published SN Ib/c metallicity data sets, when including only values at the SN positions to probe natal oxygen abundances, indicates at very high significance that indeed SNe Ic erupt from more metal-rich environments than SNe Ib, while SNe Ic-bl with GRBs still prefer, on average, more metal-poor sites than those without GRBs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.2395v1.pdf"}
{"id": "1205.2801", "abstract": "  Photonic quantum simulators are promising candidates for providing insight into other small- to medium-sized quantum systems. The available photonic quantum technology is reaching the state where significant advantages arise for the quantum simulation of interesting questions in Heisenberg spin systems. Here we experimentally simulate such spin systems with single photons and linear optics. The effective Heisenberg-type interactions among individual single photons are realized by quantum interference at the tunable direction coupler followed by the measurement process. The effective interactions are characterized by comparing the entanglement dynamics using pairwise concurrence of a four-photon quantum system. We further show that photonic quantum simulations of generalized Heisenberg interactions on a four-site square lattice and a six-site checkerboard lattice are in reach of current technology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.2801v1.pdf"}
{"id": "1205.2813", "abstract": "  We study properties of a trapped dipolar Bose-Einstein condensate (BEC) in a circular ring or a spherical shell using the mean-field Gross-Pitaevskii equation. In the case of the ring-shaped trap we consider different orientations of the ring with respect to the polarization direction of the dipoles. In the presence of long-range anisotropic dipolar and short-range contact interactions, the anisotropic density distribution of the dipolar BEC in both traps is discussed in detail. The stability condition of the dipolar BEC in both traps is illustrated in phase plot of dipolar and contact interactions. We also study and discuss the properties of a vortex dipolar BEC in these traps. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.2813v1.pdf"}
{"id": "1205.4304", "abstract": "  There has been a lively debate in many fields, including statistics and related applied fields such as psychology and biomedical research, on possible reforms of the scholarly publishing system. Currently, referees contribute so much to improve scientific papers, both directly through constructive criticism and indirectly through the threat of rejection. We discuss ways in which new approaches to journal publication could continue to make use of the valuable efforts of peer reviewers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.4304v1.pdf"}
{"id": "1205.4819", "abstract": "  We have carried out electron energy-loss investigations of the lowest singlet excitons in pentacene at 20 K. Our studies allow to determine the full exciton band structure in the a*,b* reciprocal lattice plane. The lowest singlet exciton can move coherently within this plane, and the resulting exciton dispersion is highly anisotropic. The analysis of the energetically following (satellite) features indicates a strong admixture of charge transfer excitations to the exciton wave function. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.4819v1.pdf"}
{"id": "1205.5806", "abstract": "  Mergers of two carbon-oxygen white dwarfs have long been suspected to be progenitors of Type Ia Supernovae. Here we present our modifications to the cosmological smoothed particle hydrodynamics code Gadget to apply it to stellar physics including but not limited to mergers of white dwarfs. We demonstrate a new method to map a one-dimensional profile of an object in hydrostatic equilibrium to a stable particle distribution. We use the code to study the effect of initial conditions and resolution on the properties of the merger of two white dwarfs. We compare mergers with approximate and exact binary initial conditions and find that exact binary initial conditions lead to a much more stable binary system but there is no difference in the properties of the actual merger. In contrast, we find that resolution is a critical issue for simulations of white dwarf mergers. Carbon burning hotspots which may lead to a detonation in the so-called violent merger scenario emerge only in simulations with sufficient resolution but independent of the type of binary initial conditions. We conclude that simulations of white dwarf mergers which attempt to investigate their potential for Type Ia supernovae should be carried out with at least 10^6 particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.5806v1.pdf"}
{"id": "1205.6466", "abstract": "  The first Search for Extra-Terrestrial Intelligence (SETI) conducted with Very Long Baseline Interferometry (VLBI) is presented. By consideration of the basic principles of interferometry, we show that VLBI is efficient at discriminating between SETI signals and human generated radio frequency interference (RFI). The target for this study was the star Gliese 581, thought to have two planets within its habitable zone. On 2007 June 19, Gliese 581 was observed for 8 hours at 1230-1544 with the Australian Long Baseline Array. The dataset was searched for signals appearing on all interferometer baselines above five times the noise limit. A total of 222 potential SETI signals were detected and by using automated data analysis techniques, were ruled out as originating from the Gliese 581 system. From our results we place an upper limit of 7 MW/Hz on the power output of any isotropic emitter located in the Gliese 581 system, within this frequency range. This study shows that VLBI is ideal for targeted SETI, including follow-up observations. The techniques presented are equally applicable to next-generation interferometers, such as the long baselines of the Square Kilometre Array (SKA). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.6466v1.pdf"}
{"id": "1205.6495", "abstract": "  We present data from our investigation of the anomalous orange-colored afterglow that was seen in the GammeV Chameleon Afterglow Search (CHASE). These data includes information about the broad band color of the observed glow, the relationship between the glow and the temperature of the apparatus, and other data taken prior to and during the science operations of CHASE. While differing in several details, the generic properties of the afterglow from CHASE are similar to luminescence seen in some vacuum compounds. Contamination from this, or similar, luminescent signatures will likely impact the design of implementation of future experiments involving single photon detectors and high intensity light sources in a cryogenic environment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.6495v1.pdf"}
{"id": "1205.6970", "abstract": "  This paper describes our large reformed introductory physics course at UC Davis, which bioscience students have been taking since 1996. The central feature of this course is a focus on sense-making by the students during the five hours per week discussion/labs in which the students take part in activities emphasizing peer-peer discussions, argumentation, and presentations of ideas. The course differs in many fundamental ways from traditionally taught introductory physics courses. After discussing the unique features of CLASP and its implementation at UC Davis, various student outcome measures are presented showing increased performance by students who took the CLASP course compared to students who took a traditionally taught introductory physics course. Measures we use include upper-division GPAs, MCAT scores, FCI gains, and MPEX-II scores. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.6970v2.pdf"}
{"id": "1206.0941", "abstract": "  We present new constraints on the star formation histories of the ultra-faint dwarf (UFD) galaxies, using deep photometry obtained with the Hubble Space Telescope (HST). A galaxy class recently discovered in the Sloan Digital Sky Survey, the UFDs appear to be an extension of the classical dwarf spheroidals to low luminosities, offering a new front in efforts to understand the missing satellite problem. They are the least luminous, most dark-matter dominated, and least chemically-evolved galaxies known. Our HST survey of six UFDs seeks to determine if these galaxies are true fossils from the early universe. We present here the preliminary analysis of three UFD galaxies: Hercules, Leo IV, and Ursa Major I. Classical dwarf spheroidals of the Local Group exhibit extended star formation histories, but these three Milky Way satellites are at least as old as the ancient globular cluster M92, with no evidence for intermediate-age populations. Their ages also appear to be synchronized to within  1 Gyr of each other, as might be expected if their star formation was truncated by a global event, such as reionization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.0941v1.pdf"}
{"id": "1206.1461", "abstract": "  Simple broadband microwave interconnects are needed for increasing the size of focal plane heterodyne radiometer arrays. We have measured loss and cross-talk for arrays of microstrip transmission lines in flex circuit technology at 297 and 77 K, finding good performance to at least 20 GHz. The dielectric constant of Kapton substrates changes very little from 297 to 77 K, and the electrical loss drops. The small cross-sectional area of metal in a printed circuit structure yields overall thermal conductivities similar to stainless steel coaxial cable. Operationally, the main performance tradeoffs are between crosstalk and thermal conductivity. We tested a patterned ground plane to reduce heat flux. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.1461v1.pdf"}
{"id": "1206.1701", "abstract": "  We study the melting of a K^- condensate in hot and neutrino-trapped protoneutron stars. In this connection, we adopt relativistic field theoretical models to describe the hadronic and condensed phases. It is observed that the critical temperature of antikaon condensation is enhanced as baryon density increases. For a fixed baryon density, the critical temperature of antikaon condensation in a protoneutron star is smaller than that of a neutron star. We also exhibit the phase diagram of a protoneutron star with a K^- condensate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.1701v1.pdf"}
{"id": "1206.5688", "abstract": "  For a gas trapped in a harmonic potential, the sloshing (or Kohn) mode is undamped and its frequency coincides with the trap frequency, independently of the statistics, interaction and temperature of the gas. However, experimental trap potentials have usually Gaussian shape and anharmonicity effects appear as the temperature and, in the case of Fermions, the filling of the trap are increased. We study the sloshing mode of a degenerate Fermi gas in an anharmonic trap within the Boltzmann equation, including in-medium effects in both the transport and collision terms. The calculated frequency shifts and damping rates of the sloshing mode due to the trap anharmonicity are in satisfactory agreement with the available experimental data. We also discuss higher-order dipole, octupole, and bending modes and show that the damping of the sloshing mode is caused by its coupling to these modes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.5688v2.pdf"}
{"id": "1206.6067", "abstract": "  We report the first Chandra detection of emission out to the virial radius in the cluster Abell 1835 at z=0.253. Our analysis of the soft X-ray surface brightness shows that emission is present out to a radial distance of 10 arcmin or 2.4 Mpc, and the temperature profile has a factor of ten drop from the peak temperature of 10 keV to the value at the virial radius. We model the Chandra data from the core to the virial radius and show that the steep temperature profile is not compatible with hydrostatic equilibrium of the hot gas, and that the gas is convectively unstable at the outskirts. A possible interpretation of the Chandra data is the presence of a second phase of warm-hot gas near the cluster's virial radius that is not in hydrostatic equilibrium with the cluster's potential. The observations are also consistent with an alternative scenario in which the gas is significantly clumped at large radii. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.6067v3.pdf"}
{"id": "1207.0046", "abstract": "  The Gottesman-Knill theorem allows for the efficient simulation of stabilizer-based quantum error-correction circuits. Errors in these circuits are commonly modeled as depolarizing channels by using Monte Carlo methods to insert Pauli gates randomly throughout the circuit. Although convenient, these channels are poor approximations of common, realistic channels like amplitude damping. Here we analyze a larger set of efficiently simulable error channels by allowing the random insertion of any one-qubit gate or measurement that can be efficiently simulated within the stabilizer formalism. Our new error channels are shown to be a viable method for accurately approximating real error channels. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.0046v2.pdf"}
{"id": "1207.0783", "abstract": "  Semi-supervised template update systems allow to automatically take into account the intra-class variability of the biometric data over time. Such systems can be inefficient by including too many impostor's samples or skipping too many genuine's samples. In the first case, the biometric reference drifts from the real biometric data and attracts more often impostors. In the second case, the biometric reference does not evolve quickly enough and also progressively drifts from the real biometric data. We propose a hybrid system using several biometric sub-references in order to increase per- formance of self-update systems by reducing the previously cited errors. The proposition is validated for a keystroke- dynamics authentication system (this modality suffers of high variability over time) on two consequent datasets from the state of the art. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.0783v1.pdf"}
{"id": "1207.1100", "abstract": "  We perform spherically-symmetric general-relativistic simulations of core collapse and the postbounce preexplosion phase in 32 presupernova stellar models of solar metallicity with zero-age-main-sequence masses of 12 M_sun to 120 M_sun. Using energy-dependent three-species neutrino transport in the two-moment approximation with an analytic closure, we show that the emitted neutrino luminosities and spectra follow very systematic trends that are correlated with the compactness ( M/R) of the progenitor star's inner regions via the accretion rate in the preexplosion phase. We find that these qualitative trends depend only weakly on the nuclear equation of state, but quantitative observational statements will require independent constraints on the equation of state and the rotation rate of the core as well as a more complete understanding of neutrino oscillations. We investigate the simulated response of water Cherenkov detectors to the electron antineutrino fluxes from our models and find that the large statistics of a galactic core collapse event may allow robust conclusions on the inner structure of the progenitor star. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.1100v2.pdf"}
{"id": "1207.1485", "abstract": "  We test models for the evolution of neutron star (NS) magnetic fields (B). Our model for the evolution of the NS spin is taken from an analysis of pulsar timing noise presented by Hobbs et al. (2010). We first test the standard model of a pulsar's magnetosphere in which B does not change with time and magnetic dipole radiation is assumed to dominate the pulsar's spin-down. We find this model fails to predict both the magnitudes and signs of the second derivatives of the spin frequencies (ν̈). We then construct a phenomenological model of the evolution of B, which contains a long term decay (LTD) modulated by short term oscillations (STO); a pulsar's spin is thus modified by its B-evolution. We find that an exponential LTD is not favored by the observed statistical properties of ν̈ for young pulsars and fails to explain the fact that ν̈ is negative for roughly half of the old pulsars. A simple power-law LTD can explain all the observed statistical properties of ν̈. Finally we discuss some physical implications of our results to models of the B-decay of NSs and suggest reliable determination of the true ages of many young NSs is needed, in order to constrain further the physical mechanisms of their B-decay. Our model can be further tested with the measured evolutions of ν̇ and ν̈ for an individual pulsar; the decay index, oscillation amplitude and period can also be determined this way for the pulsar. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.1485v3.pdf"}
{"id": "1207.1936", "abstract": "  The universal secure network coding presented by Silva et al. realizes secure and reliable transmission of a secret message over any underlying network code, by using maximum rank distance codes. Inspired by their result, this paper considers the secure network coding based on arbitrary linear codes, and investigates its security performance and error correction capability that are guaranteed independently of the underlying network code. The security performance and error correction capability are said to be universal when they are independent of underlying network codes. This paper introduces new code parameters, the relative dimension/intersection profile (RDIP) and the relative generalized rank weight (RGRW) of linear codes. We reveal that the universal security performance and universal error correction capability of secure network coding are expressed in terms of the RDIP and RGRW of linear codes. The security and error correction of existing schemes are also analyzed as applications of the RDIP and RGRW. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.1936v2.pdf"}
{"id": "1207.2475", "abstract": "  Given two distributions F and G on the nonnegative integers we propose an algorithm to construct in- and out-degree sequences from samples of i.i.d. observations from F and G, respectively, that with high probability will be graphical, that is, from which a simple directed graph can be drawn. We then analyze a directed version of the configuration model and show that, provided that F and G have finite variance, the probability of obtaining a simple graph is bounded away from zero as the number of nodes grows. We show that conditional on the resulting graph being simple, the in- and out-degree distributions are (approximately) F and G for large size graphs. Moreover, when the degree distributions have only finite mean we show that the elimination of self-loops and multiple edges does not significantly change the degree distributions in the resulting simple graph. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.2475v1.pdf"}
{"id": "1207.2859", "abstract": "  We construct and discuss a toy model of the population of numerous non-identical extragalactic sources of ultra-high-energy cosmic rays. In the model, cosmic-ray particles are accelerated in magnetospheres of supermassive black holes in galactic nuclei, the key parameter of acceleration being the black-hole mass. We use astrophysical data on the redshift-dependent black-hole mass function to describe the population of these cosmic-ray accelerators, from weak to powerful, and confront the model with cosmic-ray data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.2859v1.pdf"}
{"id": "1207.3700", "abstract": "  We investigate the equilibration and thermalization properties of quantum systems interacting with a finite dimensional environment. By exploiting the concept of time averaged states, we introduce a completely positive map which allows to describe in a quantitative way the dependence of the equilibrium state on the initial condition. Our results show that the thermalization of quantum systems is favored if the dynamics induces small system-environment correlations, as well as small changes in the environment, as measured by the trace distance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.3700v1.pdf"}
{"id": "1207.4047", "abstract": "  This paper addresses the problem of determining the symmetries of a plane or space curve defined by a rational parametrization. We provide effective methods to compute the involution and rotation symmetries for the planar case. As for space curves, our method finds the involutions in all cases, and all the rotation symmetries in the particular case of Pythagorean-hodograph curves. Our algorithms solve these problems without converting to implicit form. Instead, we make use of a relationship between two proper parametrizations of the same curve, which leads to algorithms that involve only univariate polynomials. These algorithms have been implemented and tested in the Sage system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.4047v7.pdf"}
{"id": "1207.4248", "abstract": "  Magneto-convection can produce an active region without an initial coherent flux tube. A simulation was performed where uniform, untwisted, horizontal magnetic field of 1 kG strenght was advected into the bottom of a computational domain 48 Mm wide by 20 Mm deep. The up and down convective motions produce a hierarchy of magnetic loops with a wide range of scales, with smaller loops riding \"piggy back\" in a serpentine fashion on larger loops. When a large loop approaches the surface it produces an small active region with a compact leading spot and more diffuse following spots. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.4248v1.pdf"}
{"id": "1207.5539", "abstract": "  A general constructive procedure is presented for analyzing magnetic instabilities in two-dimensional materials, in terms of [predominantly] double nesting, and applied to Hartree-Fock HF+RPA and Gutzwiller approximation GA+RPA calculations of the Hubbard model. Applied to the cuprates, it is found that competing magnetic interactions are present only for hole doping, between half filling and the Van Hove singularity. While HF+RPA instabilities are present at all dopings (for sufficiently large Hubbard U), in a Gutzwiller approximation they are restricted to a doping range close to the range of relevance for the physical cuprates. The same model would hold for charge instabilities, except that the interaction is more likely to be q-dependent. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.5539v1.pdf"}
{"id": "1207.5817", "abstract": "  Fullerenes have recently been identified in space and they may play a significant role in the gas and dust budget of various astrophysical objects including planetary nebulae (PNe), reflection nebulae (RNe) and H II regions. The tenuous nature of the gas in these environments precludes the formation of fullerene materials following known vaporization or combustion synthesis routes even on astronomical timescales. We have studied the processing of hydrogenated amorphous carbon (a-C:H or HAC) nano-particles and their specific derivative structures, which we name \"arophatics\", in the circumstellar environments of young, carbon-rich PNe. We find that UV-irradiation of such particles can result in the formation of fullerenes, consistent with the known physical conditions in PNe and with available timescales. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.5817v2.pdf"}
{"id": "1207.6119", "abstract": "  A phenomenological formalism is presented in which the apparent acceleration of the universe is generated by cosmic structure formation, without resort to Dark Energy, modifications to gravity, or a local void. The observed acceleration results from the combined effect of innumerable local perturbations due to individually virializing systems, overlapping together in a smoothly-inhomogeneous adjustment of the FRW metric, in a process governed by the causal flow of inhomogeneity information outward from each clumped system. After noting how common arguments claiming to limit backreaction are physically unrealistic, models are presented which fit the supernova luminosity distance data essentially as well as ΛCDM, while bringing several important cosmological parameters to a new Concordance. These goals are all achieved with a second-generation version of our formalism that accounts for the negative feedback of Causal Backreaction upon itself due to the slowed propagation of gravitational inhomogeneity information. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.6119v1.pdf"}
{"id": "1207.6354", "abstract": "  We consider utility maximization in networks where the sources do not employ flow control and may consequently overload the network. In the absence of flow control at the sources, some packets will inevitably have to be dropped when the network is in overload. To that end, we first develop a distributed, threshold-based packet dropping policy that maximizes the weighted sum throughput. Next, we consider utility maximization and develop a receiver-based flow control scheme that, when combined with threshold-based packet dropping, achieves the optimal utility. The flow control scheme creates virtual queues at the receivers as a push-back mechanism to optimize the amount of data delivered to the destinations via back-pressure routing. A novel feature of our scheme is that a utility function can be assigned to a collection of flows, generalizing the traditional approach of optimizing per-flow utilities. Our control policies use finite-buffer queues and are independent of arrival statistics. Their near-optimal performance is proved and further supported by simulation results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.6354v1.pdf"}
{"id": "1207.6443", "abstract": "  To describe neutrino oscillations in the sense of quantum mechanics and quantum field theory, we propose to use an off-diagonal neutrino-Higgs (mass) interaction, as discussed originally in a family gauge theory and in the extended Standard Model. For neutrino oscillations which take place presumably between point-like Dirac particles, the proposed description would be unique in the quantum mechanics sense. This may help us to resolve a few outstanding puzzles - the question of why there are only three generations, the question of why the masses of neutrinos are so tiny, the question of why neutrinos oscillate, and the question of why the dark-matter world is so huge (25", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.6443v2.pdf"}
{"id": "1208.1400", "abstract": "  In the asymptotic theory of quantum hypothesis testing, the minimal error probability of the first kind jumps sharply from zero to one when the error exponent of the second kind passes by the point of the relative entropy of the two states in an increasing way. This is well known as the direct part and strong converse of quantum Stein's lemma. Here we look into the behavior of this sudden change and have make it clear how the error of first kind grows smoothly according to a lower order of the error exponent of the second kind, and hence we obtain the second-order asymptotics for quantum hypothesis testing. This actually implies quantum Stein's lemma as a special case. Meanwhile, our analysis also yields tight bounds for the case of finite sample size. These results have potential applications in quantum information theory. Our method is elementary, based on basic linear algebra and probability theory. It deals with the achievability part and the optimality part in a unified fashion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.1400v3.pdf"}
{"id": "1208.1531", "abstract": "  The Heterodyne Instrument for the Far Infrared (HIFI) aboard the Herschel Space Observatory has acquired high-resolution broadband molecular spectra of star-forming regions in a wavelength range that is mostly inaccessible from ground-based astronomical observatories. These spectral surveys provide new insight into the chemical composition and physical properties of molecular clouds. In this manuscript, we present initial results from the HIFI spectral survey of the Sagittarius B2(N) molecular cloud, which contains spectral features assigned to at least 40 different molecules in a range of physical environments. While extensive line blending is observed due to the chemical complexity of this region, reliable molecular line identifications can be made, down to the noise floor, due to the large number of transitions detected for each species in the 1.2 THz survey bandwidth. This allows for the extraction of new weakly emitting species from the line forest. These HIFI surveys will be an invaluable archival resource for future investigations into interstellar chemistry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.1531v1.pdf"}
{"id": "1208.1767", "abstract": "  There are only a few tracers available to probe the kinematics of individual early-type galaxies beyond one effective radius. Here we directly compare a sample of planetary nebulae (PNe), globular clusters (GCs) and galaxy starlight velocities out to  4 effective radii, in the S0 galaxy NGC 2768. Using a bulge-to-disk decomposition of a K-band image we assign PNe and starlight to either the disk or the bulge. We show that the bulge PNe and bulge starlight follow the same radial density distribution as the red subpopulation of GCs, whereas the disk PNe and disk starlight are distinct components. We find good kinematic agreement between the three tracers to several effective radii (and with stellar data in the inner regions). Further support for the distinct nature of the two galaxy components come from our kinematic analysis. After separating the tracers into bulge and disk components we find the bulge to be a slowly rotating pressure-supported system, whereas the disk reveals a rapidly rising rotation curve with a declining velocity dispersion profile. The resulting V/sigma ratio for the disk resembles that of a spiral galaxy and hints at an origin for NGC 2768 as a transformed late-type galaxy. A two-component kinematic analysis for a sample of S0s will help to elucidate the nature of this class of galaxy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.1767v1.pdf"}
{"id": "1208.3037", "abstract": "  The dynamic shape relaxation of the two-layer-vesicle is calculated. In additional to the undulation relaxation where the two bilayers move in the same direction, the squeezing mode appears when the gap between the two bilayers is small. At large gap, the inner vesicle relaxes much faster, whereas the slow mode is mainly due to the outer layer relaxation. We have calculated the viscoelasticity of the dilute two-layer-vesicle suspension. It is found that for small gap, the applied shear drives the undulation mode strongly while the slow squeezing mode is not much excited. In this limit the complex viscosity is dominated by the fast mode contribution. On the other hand, the slow mode is strongly driven by shear for larger gap. We have determined the crossover gap which depends on the interaction between the two bilayers. For a series of samples where the gap is changed systematically, it is possible to observe the two amplitude switchings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.3037v1.pdf"}
{"id": "1208.4025", "abstract": "  We demonstrate experimentally the resonant extinction of THz radiation by a single plasmonic bowtie antenna, formed by two n-doped Si monomers with a triangular shape and facing apexes. This demonstration is achieved by placing the antenna at the output aperture of a conically tapered waveguide, which enhances the intensity of the incident THz field at the antenna position by a factor 10. The waveguide also suppresses the background radiation that otherwise is transmitted without being scattered by the antenna. Bowtie antennas, supporting localized surface plasmon polaritons, are relevant due to their ability of resonantly enhancing the field intensity at the gap separating the two triangular elements. This gap has subwavelength dimensions, which allows the concentration of THz radiation beyond the diffraction limit. The combination of a bowtie plasmonic antenna and a conical waveguide may serve as a platform for far-field THz time-domain spectroscopy of single nanostructures placed in the gap. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.4025v1.pdf"}
{"id": "1208.4738", "abstract": "  Extrinsic multiferroic hybrid structures consisting of ferromagnetic and ferroelectric layers elastically coupled to each other are promising due to their robust magnetoelectric effects even at room temperature. For a quantitative analysis of these magnetoelectric effects, a detailed knowledge of the piezoelectric and magnetoelastic behavior of both constituents as well as their mutual elastic coupling is mandatory. We here report on a theoretical and experimental study of the magnetic behavior of BaTiO3-based extrinsic multiferroic structures. An excellent agreement between molecular dynamics simulations and the experiments was found for Fe50Co50/BaTiO3 and Ni/BaTiO3 hybrid structures. This demonstrates that the magnetic behavior of extrinsic multiferroic hybrid structures can be determined by means of ab-initio calculations, allowing for the design of novel multiferroic hybrids. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.4738v1.pdf"}
{"id": "1208.5474", "abstract": "  Structure-preserving numerical schemes for a nonlinear parabolic fourth-order equation, modeling the electron transport in quantum semiconductors, with periodic boundary conditions are analyzed. First, a two-step backward differentiation formula (BDF) semi-discretization in time is investigated. The scheme preserves the nonnegativity of the solution, is entropy stable and dissipates a modified entropy functional. The existence of a weak semi-discrete solution and, in a particular case, its temporal second-order convergence to the continuous solution is proved. The proofs employ an algebraic relation which implies the G-stability of the two-step BDF. Second, an implicit Euler and q-step BDF discrete variational derivative method are considered. This scheme, which exploits the variational structure of the equation, dissipates the discrete Fisher information (or energy). Numerical experiments show that the discrete (relative) entropies and Fisher information decay even exponentially fast to zero. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.5474v1.pdf"}
{"id": "1209.0132", "abstract": "  We present calculated spectral properties and lattice parameters for cerium pnictides (CeN, CeP, CeAs, CeSb, CeBi) and gamma-Ce, within the LDA/GGA+DMFT (local density approximation/generalized gradient approximation + dynamical mean field theory) approach. The effective impurity model arising in the DMFT is solved by using the spin-polarized T-matrix fluctuation-exchange (SPTF) solver for CeN compound, and the Hubbard I (HI) solver for CeP, CeAs, CeSb, and CeBi. For all the addressed compounds the calculated spectral properties are in reasonable agreement with measured photoelectron spectra at high binding energies. At low binding energies the HI approximation does not manage to capture the Kondo-like peak observed for several of the Ce-pnictides. Nevertheless, the calculated lattice constants are in a good agreement with available experimental data, showing that the such a peak does not play a major role on the bonding properties. Furthermore, the HI calculations are compared to a simpler treatment of the Ce 4f electron as core-like in LDA/GGA for CeP, CeAs, CeSb, and CeBi, and the two approaches are found to give similar results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.0132v1.pdf"}
{"id": "1209.0162", "abstract": "  A theoretical approach for a non-perturbative dynamical description of two interacting atoms in an optical lattice potential is introduced. The approach builds upon the stationary eigenstates found by a procedure described in Grishkevich et al. [Phys. Rev. A 84, 062710 (2011)]. It allows presently to treat any time-dependent external perturbation of the lattice potential up to quadratic order. Example calculations of the experimentally relevant cases of an acceleration of the lattice and the turning-on of an additional harmonic confinement are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.0162v1.pdf"}
{"id": "1209.0346", "abstract": "  In this paper we develop a quantum field approach to reveal the thermodynamic properties of the trapped BEC with the equal Rashba and Dresselhaus spin-orbit couplings. In the experimentally-feasible regime, the phase transition from the separate phase to the single minimum phase can be well driven by the tunable temperature. Moreover, the critical temperature, which is independent of the trapped potential, can be derived exactly. At the critical point, the specific heat has a large jump and can be thus regarded as a promising candidate to detect this temperature-driven phase transition. In addition, we obtain the analytical expressions for the specific heat and the entropy in the different phases. In the single minimum phase, the specific heat as well as the entropy are governed only by the Rabi frequency. However, in the separate phase with lower temperature, we find that they are determined only by the strength of spin-orbit coupling. Finally, the effect of the effective atom interaction is also addressed. In the separate phase, this effective atom interaction affects dramatically on the critical temperature and the corresponding thermodynamic properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.0346v1.pdf"}
{"id": "1209.0500", "abstract": "  The exact superposition of a central static black hole with surrounding thin disk in presence of a magnetic field is investigated. We consider two models of disk, one of infinite extension based on a Kuzmin-Chazy-Curzon metric and other finite based on the first Morgan-Morgan disk. We also analyze a simple model of active galactic nuclei consisting of black hole, a Kuzmin-Chazy-Curzon disk and two rods representing jets, in presence of magnetic field. To explain the stability of the disks we consider the matter of the disk made of two pressureless streams of counterrotating charged particles (counterrotating model) moving along electrogeodesic. Using the Rayleigh criterion we derivate for circular orbits the stability conditions of the particles of the streams. The influence of the magnetic field on the matter properties of the disk and on its stability are also analyzed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.0500v4.pdf"}
{"id": "1209.1169", "abstract": "  We report the results from a detailed analysis of an archival XMM-Newton observation of the X-ray source XGPS-I J183251-100106, which has been suggested as a promising magnetic cataclysmic variable candidate based on its optical properties. A single periodic signal of 1.5 hrs is detected from all EPIC cameras on board XMM-Newton. The phase-averaged X-ray spectrum can be well-modeled with a thermal bremsstrahlung of a temperature kT 50 keV. Both X-ray spectral and temporal behavior of this system suggest it as a eclipsing cataclysmic variable of AM Herculis (or polar) type. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.1169v1.pdf"}
{"id": "1209.1381", "abstract": "  We consider methods to identify the classical ground state for an exchange-coupled Heisenberg antiferromagnet on a non-Bravais lattice with interactions J_ij to several neighbor distances. Here we apply this to the unusual \"octahedral\" lattice in which spins sit on the edge midpoints of a simple cubic lattice. Our approach is informed by the eigenvectors of J_ij with largest eigenvalues. We discovered two families of non-coplanar states: (i) two kinds of commensurate state with cubic symmetry, each having twelve sublattices with spins pointing in (1,1,0) directions in spin space (modulo a global rotation); (ii) varieties of incommensurate conic spiral. The latter family is addressed by projecting the three-dimensional lattice to a one-dimensional chain, with a basis of two (or more) sites per unit cell. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.1381v2.pdf"}
{"id": "1209.1614", "abstract": "  The high-energy QCD factorization for Deep Inelastic Scattering and for proton-nucleus collisions using Wilson line formalism and factorization in rapidity is discussed. We show that in DIS the factorization in rapidity reduces to the k_ T-factorization when the 2-gluon approximation is applied, provided that the composite Wilson line operator is used in the high-energy Operator Product Expansion. We then show that the inclusive forward cross-section in proton-nucleus collisions factorizes in parton distribution functions, fragmentation functions and dipole gluon distribution function at one-loop level. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.1614v1.pdf"}
{"id": "1209.1862", "abstract": "  We present our new photometry of DV Psc obtained in 2010 and 2011, and new spectroscopic observation on Feb. 14, 2012. During our observations, three flare-like events might be detected firstly in one period on DV Psc. The flare rate of DV Psc is about 0.017 flares per hour. Using Wilson-Devinney program, we derived the preliminary starspot parameters. Moreover, the magnetic cycle is 9.26(+/-0.78) year analyzed by variabilities of Max.I - Max.II. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.1862v1.pdf"}
{"id": "1209.4770", "abstract": "  We study adiabatic pumping through a two-level quantum dot with spin-orbit coupling. Using a diagrammatic real-time approach, we calculate both the pumped charge and spin for a periodic variation of the dot's energy levels in the limit of weak tunnel coupling. Thereby, we compare the two limits of vanishing and infinitely large charging energy on the quantum dot. We discuss the dependence of the pumped charge and pumped spin on gate voltages, the symmetry in the tunnel-matrix elements and spin-orbit coupling strength. We identify the possibility to generate pure spin currents in the absence of charge currents. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.4770v2.pdf"}
{"id": "1209.4881", "abstract": "  We study general stochastic birth and death processes including delay. We develop several approaches for the analytical treatment of these non-Markovian systems, valid, not only for constant delays, but also for stochastic delays with arbitrary probability distributions. The interplay between stochasticity and delay and, in particular, the effects of delay in the fluctuations and time correlations are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.4881v1.pdf"}
{"id": "1209.5794", "abstract": "  We present preliminary diameters and albedos for 13511 MBAs that were observed during the 3-Band Cryo phase of the WISE survey (after the outer cryogen tank was exhausted) and as part of the NEOWISE Post-Cryo Survey (after the inner cryogen tank was exhausted). With a reduced or complete loss of sensitivity in the two long wavelength channels of WISE, the uncertainty in our fitted diameters and albedos is increased to  20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.5794v1.pdf"}
{"id": "1209.5999", "abstract": "  The Statistical Toolkit is an open source system specialized in the statistical comparison of distributions. It addresses requirements common to different experimental domains, such as simulation validation (e.g. comparison of experimental and simulated distributions), regression testing in the course of the software development process, and detector performance monitoring. Various sets of statistical tests have been added to the existing collection to deal with the one sample problem (i.e. the comparison of a data distribution to a function, including tests for normality, categorical analysis and the estimate of randomness). Improved algorithms and software design contribute to the robustness of the results. A simple user layer dealing with primitive data types facilitates the use of the toolkit both in standalone analyses and in large scale experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.5999v1.pdf"}
{"id": "1209.6547", "abstract": "  In an emergency situation, imitation of strategies of neighbours can lead to an order-disorder phase transition, where spatial clusters of pedestrians adopt the same strategy. We assume that there are two strategies, cooperating and competitive, which correspond to a smaller or larger desired velocity. The results of our simulations within the Social Force Model indicate that the ordered phase can be detected as an increase of spatial order of positions of the pedestrians in the crowd. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.6547v1.pdf"}
{"id": "1210.0015", "abstract": "  In this paper we study the geometry and the thermodynamics of a holographic screen in the framework of the ultraviolet self-complete quantum gravity. To achieve this goal we construct a new static, neutral, non-rotating black hole metric, whose outer (event) horizon coincides with the surface of the screen. The space-time admits an extremal configuration corresponding to the minimal holographic screen and having both mass and radius equalling the Planck units. We identify this object as the space-time fundamental building block, whose interior is physically unaccessible and cannot be probed even during the Hawking evaporation terminal phase. In agreement with the holographic principle, relevant processes take place on the screen surface. The area quantization leads to a discrete mass spectrum. An analysis of the entropy shows that the minimal holographic screen can store only one byte of information while in the thermodynamic limit the area law is corrected by a logarithmic term. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.0015v3.pdf"}
{"id": "1210.0235", "abstract": "  We develop a model for visible matter-dark matter interaction based on the exchange of a massive gray boson called herein the Mulato. Our model hinges on the assumption that all known particles in the visible matter have their counterparts in the dark matter. We postulate six families of particles five of which are dark. This leads to the unavoidable postulation of six parallel worlds, the visible one and five invisible worlds. A close study of big bang nucleosynthesis (BBN), baryon asymmetries, cosmic microwave background (CMB) bounds, galaxy dynamics, together with the Standard Model assumptions, help us to set a limit on the mass and width of the new gauge boson. Modification of the statistics underlying the kinetic energy distribution of particles during the BBN is also discussed. The changes in reaction rates during the BBN due to a departure from the Debye-Hueckel electron screening model is also investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.0235v1.pdf"}
{"id": "1210.1932", "abstract": "  Multipersistence homology modules were introduced by G.Carlsson and A.Zomorodian which gave, together with G.Singh, an algorithm to compute their Groebner bases. Although their algorithm has polynomial complexity when the chain modules are free, i.e. in the one-critical case, it might be exponential in general. We give a new presentation of multipersistence homology modules, which allows us to design an algorithm to compute their Groebner bases always in polynomial time by avoiding the mapping telescope. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.1932v1.pdf"}
{"id": "1210.2908", "abstract": "  Complex networks have been shown to be robust against random structural perturbations, but vulnerable against targeted attacks. Robustness analysis usually simulates the removal of individual or sets of nodes, followed by the assessment of the inflicted damage. For complex metabolic networks, it has been suggested that evolutionary pressure may favor robustness against reaction removal. However, the removal of a reaction and its impact on the network may as well be interpreted as selective regulation of pathway activities, suggesting a tradeoff between the efficiency of regulation and vulnerability. Here, we employ a cascading failure algorithm to simulate the removal of single and pairs of reactions from the metabolic networks of two organisms, and estimate the significance of the results using two different null models: degree preserving and mass-balanced randomization. Our analysis suggests that evolutionary pressure promotes larger cascades of non-viable reactions, and thus favors the ability of efficient metabolic regulation at the expense of robustness. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.2908v1.pdf"}
{"id": "1210.3985", "abstract": "  This first part of Special Session 5 explored the current status of infrared-based observations of obscured and distant stellar clusters in the Milky Way galaxy. Recent infrared surveys, either serendipitously or using targeted searches, have uncovered a rich population of young and massive clusters. However, cluster characterization is more challenging as it must be obtained often entirely in the infrared due to high line-of-sight extinction. Despite this, much is to be gained through the identification and careful analysis of these clusters, as they allow for the early evolution of massive stars to be better constrained. Further, they act as beacons delineating the Milky Way's structure and as nearby, resolved analogues to the distant unresolved massive clusters studied in distant galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.3985v1.pdf"}
{"id": "1210.5213", "abstract": "  The clumping of massive star winds is an established paradigm, which is confirmed by multiple lines of evidence and is supported by stellar wind theory. We use the results from time-dependent hydrodynamical models of the instability in the line-driven wind of a massive supergiant star to derive the time-dependent accretion rate on to a compact object in the Bondi-Hoyle-Lyttleton approximation. The strong density and velocity fluctuations in the wind result in strong variability of the synthetic X-ray light curves. Photoionization of inhomogeneous winds is different from the photoinization of smooth winds. The degree of ionization is affected by the wind clumping. The wind clumping must also be taken into account when comparing the observed and model spectra of the photoionized stellar wind. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.5213v1.pdf"}
{"id": "1210.6025", "abstract": "  We experimentally investigate the phenomenon of a quantum ratchet created by exposing a Bose-Einstein Condensate to short pulses of a potential which is periodic in both space and time. Such a ratchet is manifested by a directed current of particles, even though there is an absence of a net bias force. We confirm a recent theoretical prediction [M. Sadgrove and S. Wimberger, New J. Phys. 11, 083027 (2009)] that the current direction can be controlled by experimental parameters which leave the underlying symmetries of the system unchanged. We demonstrate that this behavior can be understood using a single variable containing many of the experimental parameters and thus the ratchet current is describable using a single universal scaling law. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.6025v1.pdf"}
{"id": "1210.6311", "abstract": "  The description of the hadron production at very forward rapidities and low transverse momentum is usually made using phenomenological models based on nonperturbative physics. However, at high energies and large rapidities the wave function of one of the projectiles is probed at very small Bjorken x, being characterized by a large number of gluons. In this kinematical regime, a new state of matter - the Color Glass Condensate (CGC) - is expected to be formed. One the main characteristics of such system is the presence of a new dynamical momentum scale, the saturation scale Q_s, which can assume values very larger than the QCD confinement scale Λ_QCD and give the scale of the running coupling constant. In this paper we assume that in particular kinematical region probed by LHC forward (LHCf) experiment the saturation scale can be considered the hard momentum scale present in the process and calculate the forward neutral pion production at very low-p_T using a perturbative approach. We demonstrate that the CGC formalism is able to successfully describe the LHCf data, which can be considered as a compelling indication of the presence of non-linear QCD effects at LHC energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.6311v2.pdf"}
{"id": "1210.6583", "abstract": "  A kinetic-rate equation approach in a thermally expanding medium is employed to calculate the evolution of charmonium and bottomonium distributions in heavy-ion collisions. The equilibrium properties of the quarkonia are taken from in-medium spectral functions which are schematically constrained by euclidean correlators from lattice QCD. The initial conditions for the rate equation (heavy-flavor cross sections, nuclear absorption) and the thermal evolution are constrained by data as available. After fixing two free parameters to describe charmonium data at SPS and RHIC, the predictions for LHC are discussed in light of recent data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.6583v1.pdf"}
{"id": "1210.6717", "abstract": "  The recently discovered high-energy transient Sw J1644+57 is thought to arise from the tidal disruption of a passing star by a dormant massive black hole. The long-term, bright radio emission of Sw J1644+57 is believed to result from the synchrotron emission of the blast wave produced by an outflow expanding into the surrounding medium. Using the detailed multi-epoch radio spectral data, we are able to determine the total number of radiating electrons in the outflow at different times, and further the evolution of the cross section of the outflow with time. We find that the outflow gradually transits from a conical jet to a cylindrical one at later times. The transition may be due to collimation of the outflow by the pressure of the shocked jet cocoon that forms while the outflow is propagating in the ambient medium. Since cylindrical jets usually exist in AGNs and extragalactic jets, this may provide independent evidence that Sw J1644+57 signals the onset of an AGN. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.6717v1.pdf"}
{"id": "1210.6949", "abstract": "  The public goods game is one of the most famous models for studying the evolution of cooperation in sizable groups. The multiplication factor in this game can characterize the investment return from the public good, which may be variable depending on the interactive environment in realistic situations. Instead of using the same universal value, here we consider that the multiplication factor in each group is updated based on the differences between the local and global interactive environments in the spatial public goods game, but meanwhile limited to within a certain range. We find that the adaptive and bounded investment returns can significantly promote cooperation. In particular, full cooperation can be achieved for high feedback strength when appropriate limitation is set for the investment return. Also, we show that the fraction of cooperators in the whole population can become larger if the lower and upper limits of the multiplication factor are increased. Furthermore, in comparison to the traditionally spatial public goods game where the multiplication factor in each group is identical and fixed, we find that cooperation can be better promoted if the multiplication factor is constrained to adjust between one and the group size in our model. Our results highlight the importance of the locally adaptive and bounded investment returns for the emergence and dominance of cooperative behavior in structured populations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.6949v1.pdf"}
{"id": "1210.7210", "abstract": "  We analyze QCD and Weinberg-type sum rules in a low-temperature pion gas using vector and axial-vector spectral functions following from the model-independent chiral-mixing scheme. Toward this end we employ recently constructed vacuum spectral functions with ground and first-excited states in both channels and a universal perturbative continuum; they quantitatively describe hadronic tau-decay data and satisfy vacuum sum rules. These features facilitate the implementation of chiral mixing without further assumptions, and lead to in-medium spectral functions which exhibit a mutual tendency of compensating resonance and dip structures, suggestive for an approach toward structureless distributions. In the sum rule analysis, we account for pion mass corrections, which turn out to be significant. While the Weinberg sum rules remain satisfied even at high temperatures, the numerical evaluation of the QCD sum rules for vector and axial-vector channels reveals significant deviations setting in for temperatures beyond  140 MeV, suggestive of additional physics beyond low-energy chiral pion dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.7210v2.pdf"}
{"id": "1210.7757", "abstract": "  The existence of planets born in environments highly perturbed by a stellar companion represents a major challenge to the paradigm of planet formation. In numerical simulations, the presence of a close binary companion stirs up the relative velocity between planetesimals, which is fundamental in determining the balance between accretion and erosion. However, the recent discovery of circumbinary planets by Kepler establishes that planet formation in binary systems is clearly viable. We perform N-body simulations of planetesimals embedded in a protoplanetary disk, where planetesimal phasing is frustrated by the presence of stochastic torques, modeling the expected perturbations of turbulence driven by the magnetorotational instability (MRI). We examine perturbation amplitudes relevant to dead zones in the midplane (conducive to planet formation in single stars), and find that planetesimal accretion can be inhibited even in the outer disk (4-10 AU) far from the central binary, a location previously thought to be a plausible starting point for the formation of circumbinary planets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.7757v1.pdf"}
{"id": "1210.7826", "abstract": "  Topological singularities occur in a broad range of physical systems, including collapsing stars and pinching fluid interfaces. They are important for being able to concentrate energy into a small region. Underwater air bubbles in particular appear in many practical applications, including new technologies to reduce skin drag on cargo ships. Previous theories show that just before an air bubble pinches off, the neck looks like a cylinder at its very smallest point. Unusually, however, the neck approaches this shape so gradually that the theoretical cylinder solution is not reached in practice; the singularity spends its entire lifetime in a transient phase. Therefore, in order to understand the evolution, we study the transient effects in detail. This paper details the simulation results of bubbles with initial conditions far from the cylindrical solution: squat, up–down asymmetric neck shapes, with imposed vertical flow. We find that the asymmetry is transient: the neck quickly shifts vertically to become up–down symmetric. Importantly, we find that the resulting symmetric singularity is a blend of the initial top and bottom sides, with a weighting factor that is tunable by adjusting the airflow through the neck. This effect should have implications for the later stages of evolution, including the generation of satellite bubbles and the formation of the Worthington jet. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.7826v2.pdf"}
{"id": "1211.0183", "abstract": "  We define thermodynamic configurations and identify two primitives of discrete quantum processes between configurations for which heat and work can be defined in a natural way. This allows us to uncover a general second law for any discrete trajectory that consists of a sequence of these primitives, linking both equilibrium and non-equilibrium configurations. Moreover, in the limit of a discrete trajectory that passes through an infinite number of configurations, i.e. in the reversible limit, we recover the saturation of the second law. Finally, we show that for a discrete Carnot cycle operating between four configurations one recovers Carnot's thermal efficiency. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.0183v1.pdf"}
{"id": "1211.2694", "abstract": "  We reconsider the structure-based route to coarse graining in which the coarse-grained model is defined in such a way to reproduce some distributions functions of the original system as accurately as possible. We consider standard expressions for pressure and chemical potential applied to this family of coarse-grained models with density-dependent interactions and show that they only provide approximations to the pressure and chemical potential of the underlying original system. These approximations are then carefully compared in two cases: we consider a generic microscopic system in the low-density regime and polymer solutions under good-solvent conditions. Moreover, we show that the state-dependent potentials depend on the ensemble in which they have been derived. Therefore, care must be used in applying canonical state-dependent potentials to predict phase lines, which is typically performed in other ensembles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.2694v3.pdf"}
{"id": "1211.4123", "abstract": "  Following established tradition, software engineering today is rooted in a conceptually centralized way of thinking. The primary SE artifact is a specification of a machine – a computational artifact – that would meet the (elicited and) stated requirements. Therein lies a fundamental mismatch with (open) sociotechnical systems, which involve multiple autonomous social participants or principals who interact with each other to further their individual goals. No central machine governs the behaviors of the various principals.   We introduce Interaction-Oriented Software Engineering (IOSE) as an approach expressly suited to the needs of open sociotechnical systems. In IOSE, specifying a system amounts to specifying the interactions among the principals as protocols. IOSE reinterprets the classical software engineering principles of modularity, abstraction, separation of concerns, and encapsulation in a manner that accords with the realities of sociotechnical systems. To highlight the novelty of IOSE, we show where well-known SE methodologies, especially those that explicitly aim to address either sociotechnical systems or the modeling of interactions among autonomous principals, fail to satisfy the IOSE principles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.4123v1.pdf"}
{"id": "1211.4764", "abstract": "  We describe a simple experiment for measuring the thermal expansion coefficient of a metal wire and discuss how the experiment can be used as a tool for exploring the interplay of measurement uncertainty and scientific models. In particular, we probe the regimes of applicability of three models of the wire: stiff and massless, elastic and massless, and elastic and massive. Using both analytical and empirical techniques, we present the conditions under which the wire's mass and elasticity can be neglected. By accounting for these effects, we measure nichrome's thermal expansion coefficient to be 17.1(1.3) ppm/K, which is consistent with the accepted value at the 8", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.4764v2.pdf"}
{"id": "1211.5850", "abstract": "  Over the past few years it has been discovered that an \"observable\" can be set up on the lattice which obeys the discrete Cauchy-Riemann equations. The ensuing condition of discrete holomorphicity leads to a system of linear equations which can be solved to yield the Boltzmann weights of the underlying lattice model. Surprisingly, these are the well known Boltzmann weights which satisfy the star-triangle or Yang-Baxter equations at criticality. This connection has been observed for a number of exactly solved models. I briefly review these developments and discuss how this connection can be made explicit in the context of the Z_N model. I also discuss how discrete holomorphicity has been used in recent breakthroughs in the rigorous proof of some key results in the theory of planar self-avoiding walks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.5850v2.pdf"}
{"id": "1211.6790", "abstract": "  We study a quantum thermal engine model for which the heat transfer law is determined by Einstein's theory of radiation. The working substance of the quantum engine is assumed to be a two-level quantum systems of which the constituent particles obey Maxwell-Boltzmann(M.B.), Fermi-Dirac(F.D.) or Bose-einstein(B.E.) distributions respectively at equilibrium. The thermal efficiency and its bounds at maximum power of these models are derived and discussed in the long and short thermal contact time limits. The similarity and difference between these models are discussed. We also compare the efficiency bounds of this quantum thermal engine to those of its classical counterpart. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.6790v1.pdf"}
{"id": "1212.0129", "abstract": "  We consider the interacting holographic dark energy with new infrared cutoff (involving Hubble parameter and its derivative) in non-flat universe. In this context, we obtain the equation of state parameter which evolutes the universe from vacuum dark energy region towards quintessence region for particular values of constant parameters. It is found that this model always remains unstable against small perturbations. Further, we establish the correspondence of this model having quintessential behavior with quintessence, tachyon, K-essence and dilaton scalar field models. The dynamics of scalar fields and potentials indicate accelerated expansion of the universe which is consistent with the current observations. Finally, we discuss the validity of the generalized second law of thermodynamics in this scenario. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.0129v1.pdf"}
{"id": "1212.0162", "abstract": "  We study theoretically the spatiotemporal response of a lipid membrane submitted to a local chemical change of its environment, taking into account the time-dependent profile of the reagent concentration due to diffusion in the solution above the membrane. We show that the effect of the evolution of the reagent concentration profile becomes negligible after some time. It then becomes possible to extract interesting properties of the membrane response to the chemical modification. We find that a local density asymmetry between the two monolayers relaxes by spreading diffusively in the whole membrane. This behavior is driven by intermonolayer friction. Moreover, we show how the ratio of the spontaneous curvature change to the equilibrium density change induced by the chemical modification can be extracted from the dynamics of the local membrane deformation. Such information cannot be obtained by analyzing the equilibrium vesicle shapes that exist in different membrane environments in light of the area-difference elasticity model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.0162v1.pdf"}
{"id": "1212.0354", "abstract": "  Different variants of MFDFA technique are applied in order to investigate various (artificial and real-world) time series. Our analysis shows that the calculated singularity spectra are very sensitive to the order of the detrending polynomial used within the MFDFA method. The relation between the width of the multifractal spectrum (as well as the Hurst exponent) and the order of the polynomial used in calculation is evident. Furthermore, type of this relation itself depends on the kind of analyzed signal. Therefore, such an analysis can give us some extra information about the correlative structure of the time series being studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.0354v1.pdf"}
{"id": "1212.1028", "abstract": "  The antiferromagnetic correlation plays an important role in high-T_c superconductors. Considering this effect, the magnetic excitations in n-type cuprates near the optimal doping are studied within the spin density wave description. The magnetic excitations are commensurate in the low energy regime and further develop into spin wave-like dispersion at higher energy, well consistent with the inelastic neutron scattering measurements. We clearly demonstrate that the commensurability originates from the band splitting and Fermi surface topology. The commensurability is a normal state property, and has nothing to do with d-wave superconductivity. The distinct behaviors of magnetic excitation between the n-type and p-type cuprates are further discussed. Our results strongly suggest the essential role of antiferromagnetic correlations in the cuprates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.1028v1.pdf"}
{"id": "1212.1161", "abstract": "  We consider bosonic atoms in an optical lattice at integer filling, tuned to the superfluid-Mott insulator critical point, and coupled to a single, mobile impurity atom of a different species. This setup is inspired by current experiments with quantum gas microscopes, which enable tracking of the impurity motion. We describe the evolution of the impurity motion from quantum wave packet spread at short times, to Brownian diffusion at long times. This dynamics is controlled by the interplay between dangerously irrelevant perturbations at the strongly-interacting field theory describing the superfluid-insulator transition in two spatial dimensions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.1161v2.pdf"}
{"id": "1212.3027", "abstract": "  We study thermodynamics of the 3D Hubbard model at half filling on approach to the Néel transition by means of large-scale unbiased Diagrammatic Determinant Monte Carlo simulations. We obtain the transition temperature in the strongly correlated regime, as well as temperature dependence of energy, entropy, double occupancy, and the nearest-neighbor spin correlation function. Our results improve the accuracy of previous unbiased studies and present accurate benchmarks in the ongoing effort to realize the antiferromagnetic state of matter with ultracold atoms in optical lattices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.3027v2.pdf"}
{"id": "1212.4264", "abstract": "  We use the Busca et al. (2012) measurement of the Hubble parameter at redshift z = 2.3 in conjunction with 21 lower z measurements, from Simon et al. (2005), Gaztanaga et al. (2009), Stern et al. (2010), and Moresco et al. (2012), to place constraints on model parameters of constant and time-evolving dark energy cosmological models. The inclusion of the new Busca et al. (2012) measurement results in H(z) constraints significantly more restrictive than those derived by Farooq et al. (2012). These H(z) constraints are now more restrictive than those that follow from current Type Ia supernova (SNIa) apparent magnitude measurements (Suzuki et al. 2012). The H(z) constraints by themselves require an accelerating cosmological expansion at about 2-sigma confidence level, depending on cosmological model and Hubble constant prior used in the analysis. A joint analysis of H(z), baryon acoustic oscillation peak length scale, and SNIa data favors a spatially-flat cosmological model currently dominated by a time-independent cosmological constant but does not exclude slowly-evolving dark energy density. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.4264v1.pdf"}
{"id": "1212.4953", "abstract": "  Electronic realizations of neurons are of great interest as building blocks for neuromorphic computation. Electronic neurons should send signals into the input and output lines when subject to an input signal exceeding a given threshold, in such a way that they may affect all other parts of a neural network. Here, we propose a design for a neuron that is based on molecular-electronics components and thus promises a very high level of integration. We employ the Monte Carlo technique to simulate typical time evolutions of this system and thereby show that it indeed functions as a neuron. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.4953v1.pdf"}
{"id": "1212.5314", "abstract": "  Lognormality was found experimentally for coarse-grained squared turbulence velocity and velocity increment when the coarsening scale is comparable to the correlation scale of the velocity (Mouri et al. Phys. Fluids 21, 065107, 2009). We investigate this large-scale lognormality by using a simple stochastic process with correlation, the Ornstein-Uhlenbeck (OU) process. It is shown that the OU process has a similar large-scale lognormality, which is studied numerically and analytically. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.5314v2.pdf"}
{"id": "1212.5615", "abstract": "  We introduce in this paper a new four-parameter generalized version of the linear failure rate (LFR) distribution which is called Beta-linear failure rate (BLFR) distribution. The new distribution is quite flexible and can be used effectively in modeling survival data and reliability problems. It can have a constant, decreasing, increasing, upside-down bathtub (unimodal) and bathtub-shaped failure rate function depending on its parameters. It includes some well-known lifetime distributions as special submodels. We provide a comprehensive account of the mathematical properties of the new distributions. In particular, A closed-form expressions for the density, cumulative distribution and hazard rate function of the BLFR is given. Also, the rth order moment of this distribution is derived. We discuss maximum likelihood estimation of the unknown parameters of the new model for complete sample and obtain an expression for Fishers information matrix. In the end, to show the flexibility of this distribution and illustrative purposes, an application using a real data set is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.5615v1.pdf"}
{"id": "1212.6146", "abstract": "  We propose an efficient strategy to infer sparse Hopfield network based on magnetizations and pairwise correlations measured through Glauber samplings. This strategy incorporates the ℓ_1 regularization into the Bethe approximation by a quadratic approximation to the log-likelihood, and is able to further reduce the inference error of the Bethe approximation without the regularization. The optimal regularization parameter is observed to be of the order of M^-ν where M is the number of independent samples. The value of the scaling exponent depends on the performance measure. ν≃0.5001 for root mean squared error measure while ν≃0.2743 for misclassification rate measure. The efficiency of this strategy is demonstrated for the sparse Hopfield model, but the method is generally applicable to other diluted mean field models. In particular, it is simple in implementation without heavy computational cost. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.6146v4.pdf"}
{"id": "1301.1809", "abstract": "  Chemically induced dynamic nuclear polarization is a signature of spin order appearing in many photosynthetic reaction centers. Such polarization, significantly enhanced above thermal equilibrium, is known to result from the nuclear spin sorting inherent in the radical pair mechanism underlying long-lived charge-separated states in photosynthetic reaction centers. We will here show that the recently understood fundamental quantum dynamics of radical-ion-pair reactions open up a new and completely unexpected venue towards obtaining CIDNP signals. The fundamental decoherence mechanism inherent in the recombination process of radical pairs is shown to produce nuclear spin polarizations on the order of 10^4 times or more higher than the thermal equilibrium value at earth's magnetic field relevant to natural photosynthesis. This opens up the possibility of a fundamentally new exploration of the biological significance of high nuclear polarizations in photosynthesis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.1809v2.pdf"}
{"id": "1301.1874", "abstract": "  Transporting solids of different sizes is an essential process in the evolution of protoplanetary disks and planet formation. Large solids are supposed to drift inward; high-temperature minerals found in comets are assumed to have been transported outward. From low-gravity experiments on parabolic flights we studied the light-induced erosion of dusty bodies caused by a solid-state greenhouse effect and photophoresis within a dust bed's upper layers. The gravity levels studied were 0.16g, 0.38g, 1g, and 1.7g. The light flux during the experiments was 12 +/- 2 kW/m^2 and the ambient pressure was 6 +/- 0.9 mbar. Light-induced erosion is strongly gravity dependent, which is in agreement with a developed model. In particular for small dusty bodies ((sub)-planetesimals), efficient erosion is possible at the optically thin inner edges of protoplanetary disks. Light-induced erosion prevents significant parts of a larger body from moving too close to the host star and be being subsequently accreted. The small dust produced continues to be subject to photophoresis and is partially transported upward and outward over the surface of the disk; the resulting small dust particles observed over the disk's lifetime. The fraction of eroded dust participates in subsequent cycles of growth during planetesimal formation. Another fraction of dust might be collected by a body of planetary size if this body is already present close to the disk edge. Either way, light induced erosion is an efficient recycling process in protoplanetary disks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.1874v1.pdf"}
{"id": "1301.2132", "abstract": "  CoREAS is a Monte Carlo code for the simulation of radio emission from extensive air showers. It implements the endpoint formalism for the calculation of electromagnetic radiation directly in CORSIKA. As such, it is parameter-free, makes no assumptions on the emission mechanism for the radio signals, and takes into account the complete complexity of the electron and positron distributions as simulated by CORSIKA. In this article, we illustrate the capabilities of CoREAS with simulations carried out in different frequency ranges from tens of MHz up to GHz frequencies, and describe in particular the emission characteristics at high frequencies due to Cherenkov effects arising from the varying refractive index of the atmosphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.2132v1.pdf"}
{"id": "1301.2920", "abstract": "  The impact of a sessile droplet with a moving meniscus, as encountered in processes such as dip-coating, generically leads to the entrapment of small air bubbles. Here we experimentally study this process of bubble formation by looking through the liquid using high-speed imaging. Our central finding is that the size of the entrapped bubble crucially depends on the location where coalescence between the drop and the moving meniscus is initiated: (i) at a finite height above the substrate, or (ii) exactly at the contact line. In the first case, we typically find bubble sizes of the order of a few microns, independent of the size and speed of the impacting drop. By contrast, the bubbles that are formed when coalescence starts at the contact line become increasingly large, as the size or the velocity of the impacting drop is increased. We show how these observations can be explained from a balance between the lubrication pressure in the air layer and the capillary pressure of the drop. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.2920v1.pdf"}
{"id": "1301.3141", "abstract": "  The heating of the Sun's chromosphere remains poorly understood. While progress has been made on understanding what drives the quiet Sun internetwork chromosphere, chromospheric heating in strong magnetic field regions continues to present a difficult challenge, mostly because of a lack of observational constraints. We use high-resolution spectropolarimetric data from the Swedish 1-m Solar Telescope to identify the location and spatio-temporal properties of heating in the magnetic chromosphere. In particular, we report the existence of raised-core spectral line profiles in the Ca II 8542 line. These profiles are characterized by the absence of an absorption line core, showing a quasi-flat profile between +/- 0.5 Å, and are abundant close to magnetic bright-points and plage. Comparison with 3D MHD simulations indicates that such profiles occur when the line-of-sight goes through an \"elevated temperature canopy\" associated with the expansion with height of the magnetic field of flux concentrations. This temperature canopy in the simulations is caused by ohmic dissipation where there are strong magnetic field gradients. The raised-core profiles are thus indicators of locations of increased chromospheric heating. We characterize the location and temporal and spatial properties of such profiles in our observations, thus providing much stricter constraints on theoretical models of chromospheric heating mechanisms than before. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.3141v2.pdf"}
{"id": "1301.3150", "abstract": "  We consider the problem of consumption of stars by a supermassive black hole (SBH) at the center of an axisymmetric galaxy. Inside the SBH sphere of influence, motion of stars in the mean field is regular and can be described analytically in terms of three integrals of motion: the energy E, the z-component of angular momentum L_z, and the secular Hamiltonian H. There exist two classes of orbits, tubes and saucers; saucers occupy the low-angular-momentum parts of phase space and their fraction is proportional to the degree of flattening of the nucleus. Perturbations due to gravitational encounters lead to diffusion of stars in integral space, which can be described using the Fokker-Planck equation. We calculate the diffusion coefficients and solve this equation in the two-dimensional phase space (L_z, H), for various values of the capture radius and the degree of flattening. Capture rates are found to be modestly higher than in the spherical case, up to a factor of a few, and most captures take place from saucer orbits. We also carry out a set of collisional N-body simulations to confirm the predictions of the Fokker-Planck models. We discuss the implications of our results for rates of tidal disruption and capture in the Milky Way and external galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.3150v2.pdf"}
{"id": "1301.3238", "abstract": "  The Rock-Paper-Scissors (RPS) game is a widely used model system in game theory. Evolutionary game theory predicts the existence of persistent cycles in the evolutionary trajectories of the RPS game, but experimental evidence has remained to be rather weak. In this work we performed laboratory experiments on the RPS game and analyzed the social-state evolutionary trajectories of twelve populations of N=6 players. We found strong evidence supporting the existence of persistent cycles. The mean cycling frequency was measured to be 0.029 ± 0.009 period per experimental round. Our experimental observations can be quantitatively explained by a simple non-equilibrium model, namely the discrete-time logit dynamical process with a noise parameter. Our work therefore favors the evolutionary game theory over the classical game theory for describing the dynamical behavior of the RPS game. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.3238v3.pdf"}
{"id": "1301.4097", "abstract": "  The nondetection of neutrinos coming from Gamma Ray Bursts (GRBs) by the IceCube experiment has raised serious questions on our understanding of GRB's and the mechanism of neutrino flux production in them. Motivated by this and the need for a precise calculation for GRB neutrino flux, here we study the effects of beyond standard model physics on the GRB neutrino flux. In the internal shock model of GRB, high energy neutrinos are expected from muon, pion and kaon decays. Using the latest best fit neutrino oscillation parameters, we compute the expected flux on earth for standard as well as non-standard oscillation scenarios. Among the non-standard scenarios, we consider neutrino decay, pseudo-dirac nature of neutrinos and presence of one eV scale light sterile neutrino. Incorporating other experimental bounds on these new physics scenarios, we show that neutrino decay scenario can significantly alter the neutrino flux on earth from the expected ones whereas the corresponding changes for pseudo-dirac and sterile neutrino cases are moderate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.4097v1.pdf"}
{"id": "1301.4182", "abstract": "  We analyze the transport properties of a semiconductor based bilayer system under non-equilibrium conditions with special emphasis on the charge transfer statistics in the regime dominated by the exciton transport. We consider two different models. In one of them the transport occurs incoherently and is dominated by incoherent tunneling processes of individual excitons, while in the other system no disorder is present and transport processes are fully coherent. We find that the strength of cross correlations of currents in different layers is only insignificantly affected by the disorder and shows up similar behaviour in both systems. We discuss possible experimental realizations and make predictions for measurable quantities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.4182v1.pdf"}
{"id": "1301.4648", "abstract": "  The geological systems such as petroleum reservoirs is investigated by the entropy introduced by Tsallis and multiplicative hierarchical cascade model. When non-Gaussianity appears, it is sign of uncertainty and phase transition, which could be sign of existence of petroleum reservoirs. Two important parameters which describe a system at any scale are determined; the non-Gaussian degree, q, announced in entropy and the intermittency, λ^2, which explains a critical behavior in the system. There exist some petrophysical indicators in order to characterize a reservoir, but there is vacancy to measure scaling information contain in comparison with together, yet. In this article, we compare the non-Gaussianity in three selected indicators in various scales. The quantities investigated in this article includes Gamma emission (GR), sonic transient time (DT) and Neutron porosity (NPHI). It is observed that GR has a fat tailed PDF at all scales which is a sign of phase transition in the system which indicates high q and λ^2. This results in the availability of valuable information about this quantity. NPHI displays a scale dependence of PDF which converges to a Gaussian at large scales. This is a sign of a separated and uncorrelated porosity at large scales. For the DT series, small λ^2 and q at all scales are a hallmark of local correlations in this quantity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.4648v1.pdf"}
{"id": "1301.5109", "abstract": "  The source-coding problem with side information at the decoder is studied subject to a constraint that the encoder—to whom the side information is unavailable—be able to compute the decoder's reconstruction sequence to within some distortion. For discrete memoryless sources and finite single-letter distortion measures, an expression is given for the minimal description rate as a function of the joint law of the source and side information and of the allowed distortions at the encoder and at the decoder. The minimal description rate is also computed for a memoryless Gaussian source with squared-error distortion measures. A solution is also provided to a more general problem where there are more than two distortion constraints and each distortion function may be a function of three arguments: the source symbol, the encoder's reconstruction symbol, and the decoder's reconstruction symbol. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.5109v1.pdf"}
{"id": "1301.5210", "abstract": "  In the following we stress the advantages of the NICA research programme in the context of studying the spectator-induced electromagnetic phenomena present in proton-nucleus and heavy ion collisions. We point at the specific interest of using these phenomena as a new, independent source of information on the space-time evolution of the reaction and of the non-perturbative process of particle production. We propose an extended series of measurements of well-defined observables to be performed in different types of nuclear reactions and in the whole range of collision energies available to NICA. We expect these measurements to bring very valuable new insight into the mechanism of non-perturbative strong interactions, complementary to the studies made at the SPS at CERN, RHIC at BNL, and the LHC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.5210v1.pdf"}
{"id": "1301.5334", "abstract": "  A broadcast network is a classical network with all source messages collocated at a single source node. For broadcast networks, the standard cut-set bounds, which are known to be loose in general, are closely related to union as a specific set operation to combine the basic cuts of the network. This paper provides a new set of network coding bounds for general broadcast networks. These bounds combine the basic cuts of the network via a variety of set operations (not just the union) and are established via only the submodularity of Shannon entropy. The tightness of these bounds are demonstrated via applications to combination networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.5334v1.pdf"}
{"id": "1301.5773", "abstract": "  Among the distinguishing characteristics of the remarkable hot R Coronae Borealis star DY Cen, which was recently found to be a spectroscopic binary, is the presence of nebular forbidden lines in its optical spectrum. A compilation of photometry from 1970 to the present suggests that the star has evolved to higher effective temperatures. Comparison of spectra from 2010 with earlier spectra show that between 2003 and 2010, the 6717 and 6730 A emission lines of [S II] underwent a dramatic change in their fluxes suggesting an increase in the nebula's electron density of 290 cm-3 to 3140 cm-3 from 1989 to 2010 while the stellar temperature increased from 19500 K to 25000 K. The nebular radius is about 0.02 pc, 60000 times bigger than the semimajor axis of DY Cen binary system. Rapid changes of stellar temperature and its response by the nebula demonstrate stellar evolution in action. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.5773v1.pdf"}
{"id": "1301.5981", "abstract": "  Treated beyond the single-mode approximation, Measurement-Induced-Nonlocality (MIN) is investigated for both Dirac and Bosonic fields in non-inertial frames. Two distinctly differences between the Dirac and Bosonic fields are: (i) the MIN for Dirac fields persists for any acceleration, while the quantity for Bosonic fields does decay to zero in the infinite acceleration limit; (ii) the dynamic behaviors of the MIN for Dirac fields is quite different from the Bosonic fields case. Besides, we also study the nonlocality for Dirac fields and find that the MIN is more general than the quantum nonlocality related to violation of Bell's inequalities. Meanwhile some discussions of geometric discord are presented too. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.5981v1.pdf"}
{"id": "1301.6133", "abstract": "  Based on the generalized uncertainty principle (GUP), proposed by some approaches to quantum gravity such as string theory and doubly special relativity theories, we investigate the effect of GUP on the thermodynamic properties of compact stars with two different components. We note that the existence of quantum gravity correction tends to resist the collapse of stars if the GUP parameter α is taking values between Planck scale and electroweak scale. Comparing with approaches, it is found that the radii of compact stars are found smaller. Increasing energy almost exponentially decreases the radii of compact stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.6133v1.pdf"}
{"id": "1301.6456", "abstract": "  In this paper, we derive a Singleton bound for lattice schemes and obtain Singleton bounds known for binary codes and subspace codes as special cases. It is shown that the modular structure affects the strength of the Singleton bound. We also obtain a new upper bound on the code size for non-constant dimension codes. The plots of this bound along with plots of the code sizes of known non-constant dimension codes in the literature reveal that our bound is tight for certain parameters of the code. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.6456v4.pdf"}
{"id": "1301.7239", "abstract": "  We analyze the response of a nanomechanical resonator to an external drive when it is also coupled to a single-electron transistor (SET). The interaction between the SET electrons and the mechanical resonator depends on the amplitude of the mechanical motion leading to a strongly non-linear response to the drive which is similar to that of a Duffing oscillator. We show that the average dynamics of the resonator is well-described by a simple effective model which incorporates damping and frequency renormalization terms which are amplitude dependent. We also find that for a certain range of parameters the system displays interesting bistable dynamics in which noise arising from charge fluctuations causes the resonator to switch slowly between different dynamical states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.7239v2.pdf"}
{"id": "1302.0255", "abstract": "  Understanding models which represent the invasion of network-based systems by infectious agents can give important insights into many real-world situations, including the prevention and control of infectious diseases and computer viruses. Here we consider Markovian susceptible-infectious-susceptible (SIS) dynamics on finite strongly connected networks, applicable to several sexually transmitted diseases and computer viruses. In this context, a theoretical definition of endemic prevalence is easily obtained via the quasi-stationary distribution (QSD). By representing the model as a percolation process and utilising the property of duality, we also provide a theoretical definition of invasion probability. We then show that, for undirected networks, the probability of invasion from any given individual is equal to the (probabilistic) endemic prevalence, following successful invasion, at the individual (we also provide a relationship for the directed case). The total (fractional) endemic prevalence in the population is thus equal to the average invasion probability (across all individuals). Consequently, for such systems, the regions or individuals already supporting a high level of infection are likely to be the source of a successful invasion by another infectious agent. This could be used to inform targeted interventions when there is a threat from an emerging infectious disease. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.0255v2.pdf"}
{"id": "1302.1962", "abstract": "  We propose a computational procedure for creating a stable equilibrium triple junction (TJ) with controlled grain misorientations. We apply this procedure to construct a TJ between a Σ5(210) grain boundary (GB) and two general high-angle GBs in copper, and calculate the diffusion coefficients along the TJ and the GBs using molecular dynamics with an embedded-atom potential. The TJ diffusion is only a factor of two faster than diffusion in the Σ5 GB but significantly faster than diffusion in the general GBs. Both the GBs and the TJ studied here show a premelting behavior near the bulk melting point, where their diffusivities converge to the diffusivity of bulk liquid. Although our results are consistent with the common assumption that TJ diffusion is generally faster than GB diffusion, the difference between the two diffusivities does not appear to be large enough to ensure a significant contribution of TJs to diffusional creep in polycrystals at high temperatures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.1962v1.pdf"}
{"id": "1302.3336", "abstract": "  In this report we present the temperature evolution of magnetic coercivity of graphene oxide (GO) and reduced graphene oxide (RGO). We report an anamolous decrease in coercivity of GO and RGO with decreasing temperature. We could explain this anamolous behavior invoking the inherent presence of ripple in graphene. We observe antiferromagnetic and ferromagnetic behavior at room temperature for GO and RGO respectively, but at low temperatures both shows paramagnetic behavior. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.3336v1.pdf"}
{"id": "1302.3387", "abstract": "  A remarkable number of different numerical algorithms can be understood and analyzed using the concepts of symmetric spaces and Lie triple systems, which are well known in differential geometry from the study of spaces of constant curvature and their tangents. This theory can be used to unify a range of different topics, such as polar-type matrix decompositions, splitting methods for computation of the matrix exponential, composition of selfadjoint numerical integrators and dynamical systems with symmetries and reversing symmetries. The thread of this paper is the following: involutive automorphisms on groups induce a factorization at a group level, and a splitting at the algebra level. In this paper we will give an introduction to the mathematical theory behind these constructions, and review recent results. Furthermore, we present a new Yoshida-like technique, for self-adjoint numerical schemes, that allows to increase the order of preservation of symmetries by two units. Since all the time-steps are positive, the technique is particularly suited to stiff problems, where a negative time-step can cause instabilities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.3387v1.pdf"}
{"id": "1302.3746", "abstract": "  Ab initio calculations within the density-functional theory formalism are performed to investigate the chemical functionalization of a graphene-like monolayer of silicon - silicene - with B, N, Al or P atoms. The structural, electronic, magnetic and vibrational properties are reported. The most preferable adsorption sites are found to be valley, bridge, valley and hill site for B, N, Al and P adatoms, respectively. All the relaxed systems with adsorbed/substituted atoms exhibit metallic behaviour with strongly bonded B, N, Al, and P atoms accompanied by an appreciable electron transfer from silicene to the B, N and P adatom/substituent. The Al atoms exhibit opposite charge transfer, with n-type doping of silicene and weaker bonding. The adatoms/substituents induce characteristic branches in the phonon spectrum of silicene, which can be probed by Raman measurements. Using molecular dynamics we found that the systems under study are stable up to at least T = 500 K. Our results demonstrate that silicene has a very reactive and functionalizable surface. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.3746v1.pdf"}
{"id": "1302.3915", "abstract": "  We have performed an in-depth concept study of a gravitational wave data analysis method which targets repeated long quasi-monochromatic transients (triggers) from cosmic sources. The algorithm concept can be applied to multi-trigger data sets in which the detector-source orientation and the statistical properties of the data stream change with time, and does not require the assumption that the data is Gaussian. Reconstructing or limiting the energetics of potential gravitational wave emissions associated with quasi-periodic oscillations (QPOs) observed in the X-ray lightcurve tails of soft gamma repeater flares might be an interesting endeavour of the future. Therefore we chose this in a simplified form to illustrate the flow, capabilities, and performance of the method. We investigate performance aspects of a multi-trigger based data analysis approach by using O(100 s) long stretches of mock data in coincidence with the times of observed QPOs, and by using the known sky location of the source. We analytically derive the PDF of the background distribution and compare to the results obtained by applying the concept to simulated Gaussian noise, as well as off-source playground data collected by the 4-km Hanford detector (H1) during LIGO's fifth science run (S5). We show that the transient glitch rejection and adaptive differential energy comparison methods we apply succeed in rejecting outliers in the S5 background data. Finally, we discuss how to extend the method to a network containing multiple detectors, and as an example, tune the method to maximize sensitivity to SGR 1806-20 flare times. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.3915v1.pdf"}
{"id": "1302.4020", "abstract": "  The topological interference management problem refers to the study of the capacity of partially connected linear (wired and wireless) communication networks with no channel state information at the transmitters (no CSIT) beyond the network topology, i.e., a knowledge of which channel coefficients are zero (weaker than the noise floor in the wireless case). While the problem is originally studied with fixed topology, in this work we explore the implications of varying connectivity, through a series of simple and conceptually representative examples. Specifically, we highlight the synergistic benefits of coding across alternating topologies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.4020v1.pdf"}
{"id": "1302.4501", "abstract": "  Events of giant conductance and anomalies of the phase transmission time for holes, are theoretically investigated within the multicomponent scattering approach. Based on this model, new analytical expressions for unitarity relations in the uncoupled hole transport are obtained and directly applied to study the behavior of the conductance and the phase transmission time in a double barrier resonant tunneling (DBRT) and a superlattice GaAs-cladding layer/(AlAs/GaAs)^n/GaAs-cladding layer. Clear-signature evidences of giant conductance phenomena for hole transmission without valence-band mixing through a DBRT and a superlattice were found. The giant conductance effect losses robustness by manipulating the number of superlattice layers and by including the valence-band particles coupling as well. Phase time through the heterostructure exhibits extremal dependencies in the gaps and in the barriers, as those reported before for electrons. We have detected an earlier arrival phase time for the propagation of both flavors of holes within the barrier, in the order of few tenths of picoseconds. An appealing filter-like effect is presented, whenever a selective confinement strength arises independently for both flavors of holes in the uncoupled regime. Our results also prescribe noticeable evidences for both uncoupled and coupled hole fluxes, similar to those foretold by Hartman, upon transmission of electrons through opaque barriers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.4501v1.pdf"}
{"id": "1302.4563", "abstract": "  The transport properties of molten LiF-YF3 mixtures have been studied by pulsed field gradient nuclear magnetic resonance spectroscopy, potentiometric experiments, and molecular dynamics simulations. The calculated diffusion coefficients and electric conductivities compare very well with the measurements accross a wide composition range. We then extract static (radial distribution functions, coordination numbers distributions) and dynamic (cage correlation functions) quantities from the simulations. Then, we discuss the interplay between the microscopic structure of the molten salts and their dynamic properties. It is often considered that variations in the diffusion coefficient of the anions are mainly driven by the evolution of its coordination with the metallic ion (Y3+ here). We compare this system with fluorozirconate melts and demonstrate that the coordination number is a poor indicator of the evolution of the diffusion coefficient. Instead, we propose to use the ionic bonds lifetime. We show that the weak Y-F ionic bonds in LiF-YF3 do not induce the expected tendency of the fluoride diffusion coefficient to converge toward the one of yttrium cation when the content in YF3 increases. Implications on the validity of the Nernst-Einstein relation for estimating the electrical conductivity are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.4563v2.pdf"}
{"id": "1302.4662", "abstract": "  We study the phase diagram of the Kondo-lattice model with nearest-neighbor hopping in the square lattice by means of the variational Monte Carlo technique. Specifically, we analyze a wide class of variational wave functions that allow magnetic and superconducting order parameters, so to assess the possibility that superconductivity might emerge close to the magnetic instability, as often observed in heavy fermion systems. Indeed, we do find evidence of d-wave superconductivity in the paramagnetic sector, i.e., when magnetic order is not allowed in the variational wave function. However, when magnetism is allowed, it completely covers the superconducting region, which thus disappears from the phase diagram. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.4662v1.pdf"}
{"id": "1302.5601", "abstract": "  We discuss physical implications of the explicit method in numerical analysis. Numerical methods have there own condition for causality, known as the Courant-Friedrichs-Lewy condition. It is proposed that numerical causality merges with physical causality as the grid interval size approaches zero. We discuss the implications of this proposition on the numerical analysis of the wave equation. We also show that, insisting on physical causality, the numerical analysis of Schrodinger's equation implies that the minimum space interval should satisfy Δ x ≥ a_0 λ_c, where λ_c is the reduced Compton wavelength and a_0 is a constant of the order unity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.5601v1.pdf"}
{"id": "1302.5694", "abstract": "  We analyze the extent to which the LHC and Tevatron results as of the end of 2012 constrain invisible (or undetected) decays of the Higgs boson-like state at   125 GeV. To this end we perform global fits for several cases: 1) a Higgs boson with Standard Model (SM) couplings but additional invisible decay modes; 2) SM couplings to fermions and vector bosons, but allowing for additional new particles modifying the effective Higgs couplings to gluons and photons; 3) no new particles in the loops but tree-level Higgs couplings to the up-quarks, down-quarks and vector bosons, relative to the SM, treated as free parameters. We find that in the three cases invisible decay rates of 23", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.5694v3.pdf"}
{"id": "1302.6062", "abstract": "  A systematic method of calculating the dynamical conductivity tensor in a general multiband electronic model with strong boson-mediated electron-electron interactions is described. The theory is based on the exact semiclassical expression for the coupling between valence electrons and electromagnetic fields and on the self-consistent Bethe–Salpeter equations for the electron-hole propagators. The general diagrammatic perturbation expressions for the intraband and interband single-particle conductivity are determined. The relations between the intraband Bethe–Salpeter equation, the quantum transport equation and the ordinary transport equation are briefly discussed within the memory-function approximation. The effects of the Lorentz dipole-dipole interactions on the dynamical conductivity of low-dimensional sp_α models are described in the same approximation. Such formalism proves useful in studies of different (pseudo)gapped states of quasi-one-dimensional systems with the metal-to-insulator phase transitions and can be easily extended to underdoped two-dimensional high-T_c superconductors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.6062v1.pdf"}
{"id": "1302.6350", "abstract": "  We report on the discovery of an infrared cometary nebula around PSR J1549-4848 in our Spitzer survey of a few middle-aged radio pulsars. Following the discovery, multi-wavelength imaging and spectroscopic observations of the nebula were carried out. We detected the nebula in Spitzer IRAC 8.0, MIPS 24 and 70 μm imaging and in Spitzer IRS 7.5–14.4 μm spectroscopic observations, and also in the WISE all-sky survey at 12 and 22 μm.These data were analyzed in detail, and we find that the nebula can be described with a standard bow-shock shape, and that its spectrum contains polycyclic aromatic hydrocarbon and H_2 emission features. However, it is not certain which object drives the nebula. We analyze the field stars and conclude that none of them can be the associated object because stars with a strong wind or mass ejection that usually produce bow shocks are much brighter than the field stars. The pulsar is approximately 15 away from the region in which the associated object is expected to be located. In order to resolve the discrepancy, we suggest that a highly collimated wind could be emitted from the pulsar and produce the bow shock. X-ray imaging to detect the interaction of the wind with the ambient medium and high-spatial resolution radio imaging to determine the proper motion of the pulsar should be carried out, which will help verify the association of the pulsar with the bow shock nebula. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.6350v2.pdf"}
{"id": "1302.6884", "abstract": "  The effects of both elliptical shape and stage of emergence of the coronal loop on the resonant absorption of standing kink oscillations are studied. To do so, a typical coronal loop is modeled as a zero-beta longitudinally stratified cylindrical magnetic flux tube. We developed the connection formulae for the resonant absorption of standing transversal oscillations of a coronal loop with an elliptical shape, at various stages of its emergence. Using the connection formulae, the dispersion relation is derived and solved numerically to obtain the frequencies and damping rates of the fundamental and first-overtone kink modes. Our numerical results show that both the elliptical shape and stage of emergence of the loop alter the frequencies and damping rates of the tube as well as the ratio of frequencies of the fundamental and its first-overtone modes. However, the ratio of the oscillation frequency to the damping rate is not affected by the tube shape and stage of its emergence and also is independent of the density stratification parameter. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.6884v1.pdf"}
{"id": "1302.7034", "abstract": "  It has recently been pointed out that the geometric quantum discord, as defined by the Hilbert-Schmidt norm (2-norm), is not a good measure of quantum correlations, since it may increase under local reversible operations on the unmeasured subsystem. Here, we revisit the geometric discord by considering general Schatten p-norms, explicitly showing that the 1-norm is the only p-norm able to define a consistent quantum correlation measure. In addition, by restricting the optimization to the tetrahedron of two-qubit Bell-diagonal states, we provide an analytical expression for the 1-norm geometric discord, which turns out to be equivalent to the negativity of quantumness. We illustrate the measure by analyzing its monotonicity properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.7034v3.pdf"}
{"id": "1303.0058", "abstract": "  A multiple access relay channel (MARC) is considered in which an analogue-like network coding is implemented in the relay node. This analogue coding is a simple addition of the received signals at the relay node. Using \"nulling detection\" structure employed in V-BLAST receiver, we propose a detection scheme in the destination which is able to provide a diversity order of two for all users. We analytically evaluate the performance of our proposed scheme for the MARC with two users where tight upper bounds for both uncoded and Convolutionally coded transmission blocks are provided. We verify our analytical evaluations by simulations and compare the results with those of noncooperative transmission and Alamouti's scheme for the same power and rate transmission. Our results indicate that while our proposed scheme shows a comparable performance compared to the Alamouti's scheme, it substantially outperforms the non-cooperate transmission. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.0058v2.pdf"}
{"id": "1303.1354", "abstract": "  This work aims at combining adaptive protocol design, utility maximization and stochastic geometry. We focus on a spatial adaptation of Aloha within the framework of ad hoc networks. We consider quasi-static networks in which mobiles learn the local topology and incorporate this information to adapt their medium access probability (MAP) selection to their local environment. We consider the cases where nodes cooperate in a distributed way to maximize the global throughput or to achieve either proportional fair or max-min fair medium access. In the proportional fair case, we show that nodes can compute their optimal MAPs as solutions to certain fixed point equations. In the maximum throughput case, the optimal MAPs are obtained through a Gibbs Sampling based algorithm. In the max min case, these are obtained as the solution of a convex optimization problem. The main performance analysis result of the paper is that this type of distributed adaptation can be analyzed using stochastic geometry in the proportional fair case. In this case, we show that, when the nodes form a homogeneous Poisson point process in the Euclidean plane, the distribution of the optimal MAP can be obtained from that of a certain shot noise process w.r.t. the node Poisson point process and that the mean utility can also be derived from this distribution. We discuss the difficulties to be faced for analyzing the performance of the other cases (maximum throughput and max-min fairness). Numerical results illustrate our findings and quantify the gains brought by spatial adaptation in such networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.1354v1.pdf"}
{"id": "1303.2309", "abstract": "  Establishing bounds on the accuracy achievable by localization techniques represents a fundamental technical issue. Bounds on localization accuracy have been derived for cases in which the position of an agent is estimated on the basis of a set of observations and, possibly, of some a priori information related to them (e.g., information about anchor positions and properties of the communication channel). In this manuscript new bounds are derived under the assumption that the localization system is map-aware, i.e., it can benefit not only from the availability of observations, but also from the a priori knowledge provided by the map of the environment where it operates. Our results show that: a) map-aware estimation accuracy can be related to some features of the map (e.g., its shape and area) even though, in general, the relation is complicated; b) maps are really useful in the presence of some combination of low signal-to-noise ratios and specific geometrical features of the map (e.g., the size of obstructions); c) in most cases, there is no need of refined maps since additional details do not improve estimation accuracy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.2309v1.pdf"}
{"id": "1303.3100", "abstract": "  We propose new ergodic interference alignment techniques for K-user interference channels with delayed feedback. Two delayed feedback scenarios are considered – delayed channel information at transmitter (CIT) and delayed output feedback. It is proved that the proposed techniques achieve total 2K/(K+2) DoF which is higher than that by the retrospective interference alignment for the delayed feedback scenarios. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.3100v1.pdf"}
{"id": "1303.3111", "abstract": "  One of the important factors governing the growth morphology of materials is the interface kinetic coefficient μ, which is the proportionality constant between the velocity of solid-liquid interface and undercooling. We employ Ginzburg-Landau (GL) free energy functional to derive an analytical expression of kinetic coefficients. The anisotropy of kinetic coefficients naturally arise from the broken symmetry at the solid-liquid interface for various crystalline orientations. The analytical expression of kinetic coefficients is compared to Mikheev-Chernov theory [J. Cryst. Growth 112, 591 (1991)] derived from hydrodynamic equations. In addition, we use equilibrium density wave profiles to evaluate kinetic coefficients and compare them with that from MD simulations. Our results are in good agreement with Mikheev-Chernov theory and MD simulations and shed lights on a possible origin of anisotropy of interfacial kinetics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.3111v1.pdf"}
{"id": "1303.3179", "abstract": "  From the viewpoint of the SU(2) coherent states (CS) and their path integrals (PI) labeled by a full set of Euler angles (ϕ, θ, ψ) which we developed in the previous paper, we study the relations between gauge symmetries of Lagrangians and allowed quantum states; we investigate permissible types of fiducial vectors (FV) in the full quantum dynamics in terms of SU(2) coherent states for typical Lagrangians. We propose a general framework for a Lagrangian having a certain gauge symmetry with respect to one of the Euler angles ψ. We find that for the case fiducial vectors are so restricted that they belong to the eigenstates of Ŝ_3 or to the orbits of them under the action of the SU(2); and the strength of a fictitious monopole, which appears in the Lagrangian, is a multiple of 1/2. In this case Dirac strings are permitted. Our formulations and results deepen those of the preceding work by Stone that has piloted us; we illustrate the relation between the two methods. The reasoning here does not work for a Lagrangian without the gauge symmetry. This suggests a new possibility about monopole charge quantization. Besides analogies to field theory and entanglements in quantum information (QI) are briefly mentioned. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.3179v2.pdf"}
{"id": "1303.4041", "abstract": "  We propose that viewing angle expansion of the holographic image can be realized by using high-order diffraction beams caused by the pixel structure sampling the hologram data. The diffractive beam propagating to new optical axis direction plays a role in a modulated carrier similar to a carrier signal of the off-axis holography, which makes new viewing zone of the reconstruction image. The reconstructed image in the Fresnel hologram is deformed along new viewing direction, whereas the Fourier hologram enables to retrieve three-dimensional image with other perspective. High resolution hologram fringe is imaged on the image plane through an imaging system, and thus, only collection of diffracted beams increases a viewing zone angle. We verify our proposal through the numerical analysis for the sampled hologram showing high-order diffraction beams with various viewing zones. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.4041v3.pdf"}
{"id": "1303.4766", "abstract": "  We used -0.1 nm and magnetic field (at 1.56μ) data obtained with the New Solar Telescope to study the origin of the disk counterparts to type II spicules, so-called rapid blueshifted excursions (RBEs). The high time cadence of our chromospheric (10 s) and magnetic field (45 s) data allowed us to generate x-t plots using slits parallel to the spines of the RBEs. These plots, along with potential field extrapolation, led us to suggest that the occurrence of RBEs is generally correlated with the appearance of new, mixed or unipolar fields in close proximity to network fields. RBEs show a tendency to occur at the interface between large-scale fields and small-scale dynamic magnetic loops and thus are likely to be associated with existence of a magnetic canopy. Detection of kinked and/or inverse \"Y\" shaped RBEs further confirm this conclusion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.4766v1.pdf"}
{"id": "1303.5110", "abstract": "  Geometric quantum discord is a well-defined measure of quantum correlation if Schatten 1-norm (trace norm) is adopted as a distance measure. Here, we analytically investigate the dynamical behavior of the 1-norm geometric quantum discord under the effect of decoherence. By starting from arbitrary Bell-diagonal mixed states under Markovian local noise, we provide the decays of the quantum correlation as a function of the decoherence parameters. In particular, we show that the 1-norm geometric discord exhibits the possibility of double sudden changes and freezing behavior during its evolution. For non-trivial Bell-diagonal states under simple Markovian channels, these are new features that are in contrast with the Schatten 2-norm (Hilbert-Schmidt) geometric discord. The necessary and sufficient conditions for double sudden changes as well as their exact locations in terms of decoherence probabilities are provided. Moreover, we illustrate our results by investigating decoherence in quantum spin chains in the thermodynamic limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.5110v2.pdf"}
{"id": "1303.5240", "abstract": "  Wireless Sensor Networks (WSNs) with their dynamic applications gained a tremendous attention of researchers. Constant monitoring of critical situations attracted researchers to utilize WSNs at vast platforms. The main focus in WSNs is to enhance network life-time as much as one could, for efficient and optimal utilization of resources. Different approaches based upon clustering are proposed for optimum functionality. Network life-time is always related with energy of sensor nodes deployed at remote areas for constant and fault tolerant monitoring. In this work, we propose Quadrature-LEACH (Q-LEACH) for homogenous networks which enhances stability period, network life-time and throughput quiet significantly. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.5240v1.pdf"}
{"id": "1303.6653", "abstract": "  We perform a detailed study of a specific Two Higgs Doublet Model (2HDM) with a U(1) gauge symmetry, instead of a typical Z2 discrete symmetry, containing a very light gauge boson Z' (GeV scale or below). The Standard Model (SM) fermions do not carry U(1) charges, but induced couplings to the Z' (called the dark Z) are generated through mixing with the SM neutral gauge bosons. Such a light Z' could explain some astrophysical anomalies as well as the muon g-2 deviation, and has been the subject of great experimental interest. We consider the scenario in which the 125 GeV SM-like Higgs (H) is the heavier scalar state, and focus on the lighter neutral state (h) as well as charged Higgs. We analyze the constraints on the model from various experiments and predict novel channels to search for these Higgs scalars at the LHC. In particular, experiments looking for lepton-jets are among potentially important searches. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.6653v3.pdf"}
{"id": "1303.7474", "abstract": "  Recently, an extension of independent component analysis (ICA) from one to multiple datasets, termed independent vector analysis (IVA), has been the subject of significant research interest. IVA has also been shown to be a generalization of Hotelling's canonical correlation analysis. In this paper, we provide the identification conditions for a general IVA formulation, which accounts for linear, nonlinear, and sample-to-sample dependencies. The identification conditions are a generalization of previous results for ICA and for IVA when samples are independently and identically distributed. Furthermore, a principal aim of IVA is the identification of dependent sources between datasets. Thus, we provide the additional conditions for when the arbitrary ordering of the sources within each dataset is common. Performance bounds in terms of the Cramer-Rao lower bound are also provided for the demixing matrices and interference to source ratio. The performance of two IVA algorithms are compared to the theoretical bounds. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.7474v1.pdf"}
{"id": "1304.0795", "abstract": "  Gas accreting onto a galaxy will be of low metallicity while halo gas due to a galactic fountain will be of near-solar metallicity. We test these predictions by measuring the metal absorption line properties of halo gas 5 kpc above the plane of the edge-on galaxy NGC 891, using observations taken with HST/STIS toward a bright background quasar. Metal absorption lines of Fe II, Mg II, and Mg I in the halo of NGC 891 are clearly seen, and when combined with recent deep H I observations, we are able to place constraints on the metallicity of the halo gas for the first time. The H I line width defines the line broadening, from which we model opacity effects in these metal lines, assuming the absorbing gas is continuously distributed in the halo. The gas-phase metallicities are [Fe/H] = -1.18 +/- 0.07 and [Mg/H] = -0.23 +0.36/-0.27 (statistical errors) and this difference is probably due to differential depletion onto grains. When corrected for such depletion using Galactic gas as a guide, both elements have approximately solar or even supersolar abundances. This suggests that the gas is from the galaxy disk, probably expelled into the halo by a galactic fountain, rather than from accretion of intergalactic gas, which would have a low metallicity. The abundances would be raised by significant amounts if the absorbing gas lies in a few clouds with thermal widths smaller than the rotational velocity of the halo. If this is the case, both the abundances and [Mg/Fe] would be supersolar. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.0795v1.pdf"}
{"id": "1304.0812", "abstract": "  We report the detection and observed characteristics of giant pulses from the Crab Nebula pulsar (B0531+21) in four frequency bands covering 20-84 MHz using the recently-completed Long Wavelength Array Station 1 (LWA1) radio telescope. In 10 hours of observations distributed over a 72-day period in Fall of 2012, 33 giant pulses having peak flux densities between 400 Jy and 2000 Jy were detected. Twenty-two of these pulses were detected simultaneously in channels of 16 MHz bandwidth centered at 44 MHz, 60 MHz, and 76 MHz, including one pulse which was also detected in a channel centered at 28 MHz. We quantify statistics of pulse amplitude and pulse shape characteristics, including pulse broadening. Amplitude statistics are consistent with expectations based on extrapolations from previous work at higher and lower frequencies. Pulse broadening is found to be relatively high, but not significantly greater than expected. We present procedures that have been found to be effective for observing giant pulses in this frequency range. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.0812v1.pdf"}
{"id": "1304.0960", "abstract": "  We use numerical modeling to study the features of parametric (quasi-Cherenkov) cooperative radiation arising when an electron bunch passes through a crystal (natural or artificial) under the conditions of dynamical diffraction of electromagnetic waves in the presence of shot noise. It is shown that in both Laue and Bragg diffraction cases, parametric radiation consists of two strong pulses: one emitted at small angles with respect to the particle velocity direction and the other emitted at large angles to it. Under Bragg diffraction conditions, the intensity of parametric radiation emitted at small angles to the particle velocity direction reaches saturation at sufficiently smaller number of particles than the intensity of parametric radiation emitted at large angles. Under Laue diffraction conditions, every pulse contains two strong peaks, which are associated with the emission of electromagnetic waves at the front and back ends of the bunch. The presence of noise causes a chaotic signal in the interval between the two peaks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.0960v1.pdf"}
{"id": "1304.1640", "abstract": "  A two-step measurement protocol of a quantum system, known as weak value (WV), has been introduced more than two decades ago by Aharonov et al. [1], and has since been studied in various contexts. Here we discuss another two-step measurement protocol which we dub null weak value (NWV). The protocol consists of a partial-collapse measurement followed by quantum manipulation on the system and finally a strong measurement. The first step is a strong measurement which takes place with small probability. The second strong measurement is used as postselection on the outcome of the earlier step. Not being measured in the partial-collapse stage (null outcome) leads to a non-trivial correlation between the two measurements. The NVW protocol, first defined for a two-level system [2], is generalized to a multi-level system, and compared to the standard-WV protocol. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.1640v1.pdf"}
{"id": "1304.2201", "abstract": "  We propose a dissipative method to prepare the ground state of the isotropic XY spin Hamiltonian in a transverse field. Our model consists of a spin chain with nearest-neighbour interactions and an additional collective coupling of the spins to a damped harmonic oscillator. The latter provides an effective environment with a Lorentzian spectral density and can be used to drive the chain asymptotically towards its multipartite-entangled ground state at a rate that depends on the degree of non-Markovianity of the evolution. We also present a detailed proposal for the experimental implementation with a chain of trapped ions. The protocol does not require individual addressing, concatenated pulses, or multi-particle jump operators, and is capable of generating the desired target state in small ion chains with very high fidelities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.2201v2.pdf"}
{"id": "1304.2824", "abstract": "  We set up the general formalism to model polytropic Newtonian stars with anisotropic pressure. We obtain the corresponding Lane-Emden equation. A heuristic model based on an ansatz to obtain anisotropic matter solutions from known solutions for isotropic matter is adopted to illustrate the effects of the pressure anisotropy on the structure of the star. In particular, we calculate the Chandrasekhar mass for a white dwarf. It is clearly displayed how the Chandrasekhar mass limit changes depending on the anisotropy. Prospective astrophysical applications of the proposed approach are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.2824v2.pdf"}
{"id": "1304.3994", "abstract": "  In this letter, we focus on the performance of a worst-case mobile user (MU) in the downlink cellular network. We derive the coverage probability and the spectral efficiency of the worst-case MU using stochastic geometry. Through analytical and numerical results, we draw out interesting insights that the coverage probability and the spectral efficiency of the worst-case MU decrease down to 23", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.3994v3.pdf"}
{"id": "1304.4248", "abstract": "  We present the discovery of 17 low mass white dwarfs (WDs) in short-period P<1 day binaries. Our sample includes four objects with remarkable log(g) 5 surface gravities and orbital solutions that require them to be double degenerate binaries. All of the lowest surface gravity WDs have metal lines in their spectra implying long gravitational settling times or on-going accretion. Notably, six of the WDs in our sample have binary merger times <10 Gyr. Four have >=0.9 Msun companions. If the companions are massive WDs, these four binaries will evolve into stable mass transfer AM CVn systems and possibly explode as underluminous supernovae. If the companions are neutron stars, then these may be milli-second pulsar binaries. These discoveries increase the number of detached, double degenerate binaries in the ELM Survey to 54; 31 of these binaries will merge within a Hubble time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.4248v1.pdf"}
{"id": "1304.4269", "abstract": "  Electron transport in electric-field-driven tight-binding lattice coupled to fermion baths is comprehensively studied. We reformulate the problem by using the scattering state method within the Coulomb gauge. Calculations show that the formulation justifies direct access to the steady-state bypassing the time-transient calculations, which then makes the steady-state methods developed for quantum dot theories applicable to lattice models. We show that the effective temperature of the hot-electron induced by a DC electric field behaves as T_ eff=Cγ(Ω/Γ) with a numerical constant C, tight-binding parameter γ, the Bloch oscillation frequency Ω and the damping parameter Γ. In the small damping limit Γ/Ω→ 0, the steady-state has a singular property with the electron becoming extremely hot in an analogy to the short-circuit effect. This leads to the conclusion that the dissipation mechanism cannot be considered as an implicit process, as treated in equilibrium theories. Finally, using the energy flux relation, we derive a steady-state current for interacting models where only on-site Green's functions are necessary. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.4269v1.pdf"}
{"id": "1304.4999", "abstract": "  The performance of the GlueX Forward Calorimeter was studied using a small version of the detector and a variable energy electron beam derived from the Hall B tagger at Jefferson Lab. For electron energies from 110 MeV to 260 MeV, which are near the lower-limits of the design sensitivity, the fractional energy resolution was measured to range from 20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.4999v1.pdf"}
{"id": "1304.5674", "abstract": "  Cable theory has been developed over the last decades, usually assuming that the extracellular space around membranes is a perfect resistor. However, extracellular media may display more complex electrical properties due to various phenomena, such as polarization, ionic diffusion or capacitive effects, but their impact on cable properties is not known. In this paper, we generalize cable theory for membranes embedded in arbitrarily complex extracellular media. We outline the generalized cable equations, then consider specific cases. The simplest case is a resistive medium, in which case the equations recover the traditional cable equations. We show that for more complex media, for example in the presence of ionic diffusion, the impact on cable properties such as voltage attenuation can be significant. We illustrate this numerically always by comparing the generalized cable to the traditional cable. We conclude that the nature of intracellular and extracellular media may have a strong influence on cable filtering as well as on the passive integrative properties of neurons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.5674v3.pdf"}
{"id": "1304.6568", "abstract": "  It is well known experimentally that well-quenched amorphous solids exhibit a plastic instability in the form of a catastrophic shear localization at a well defined value of the external strain. The instability may develop to a shear-band that in some cases is followed by a fracture. It is also known that the values of the yield-strain (and yield-stress), as well as the direction of the shear band with respect to the principal stress axis, vary considerably with variations in the external loading conditions. In this paper we present a microscopic theory of these phenomena for 2-dimensional athermal amorphous solids that are strained quasi-statically. We present analytic formulae for the yield-strains for different loading conditions, and well as for the angles of the shear bands. We explain that the external loading conditions determine the eigenvalues of the quadrupolar Eshelby inclusions which model the non-affine displacement field. These inclusions model elementary plastic events and determine both the yield-strain and the direction of the shear-band. We show that the angles of the shear bands with respect to the principal stress axis are limited theoretically between 30^o and 60^o. Available experimental data conform to this prediction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.6568v1.pdf"}
{"id": "1304.6695", "abstract": "  The Group for the development of neutron and gamma detectors in the Central Institute of Engineering, Electronics and Analytics (ZEA-2) at Forschungszentrum Juelich (FZJ) has developed, in collaboration with European institutes, an Anger Camera prototype for improving the impact point reconstruction of neutron tracks. The detector is a chamber filled with ^3He+CF_4 gas for neutron capture and subsequent production of a tritium and a proton. The energy deposition by the ions gives rise to drifting electrons with an avalanche amplification as they approach a micro-strip anode structure. The scintillating light, generated during the electron drift and avalanche stage, is collected by four vacuum photomultipliers. The position reconstruction is performed via software algorithms. The JUDIDT readout electronics was modified at ZEA-2 to cope with the data acquisition requirements of the prototype. The results of the commissioning of the electronics are here presented and commented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.6695v1.pdf"}
{"id": "1304.7167", "abstract": "  Nano–particles are of great interest in fundamental and applied research. However, their accurate visualization is often difficult and the interpretation of the obtained images can be complicated. We present a comparative scanning electron microscopy and helium ion microscopy study of cetyltrimethylammonium–bromide (CTAB) coated gold nano–rods. Using both methods we show how the gold core as well as the surrounding thin CTAB shell can selectively be visualized. This allows for a quantitative determination of the dimensions of the gold core or the CTAB shell. The obtained CTAB shell thickness of 1.0 nm–1.5 nm is in excellent agreement with earlier results using more demanding and reciprocal space techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.7167v3.pdf"}
{"id": "1305.0364", "abstract": "  In this paper, we present surface brightness profiles for 79 globular clusters in M31, using images observed with Hubble Space Telescope, some of which are from new observations. The structural and dynamical parameters are derived from fitting the profiles to several different models for the first time. The results show that in the majority of cases, King models fit the M31 clusters as well as Wilson models, and better than Sérsic models. However, there are 11 clusters best fitted by Sérsic models with the Sérsic index n>2, meaning that they have cuspy central density profiles. These clusters may be the well-known core-collapsed candidates. There is a bimodality in the size distribution of M31 clusters at large radii, which is different from their Galactic counterparts. In general, the properties of clusters in M31 and the Milky Way fall in the same regions of parameter spaces. The tight correlations of cluster properties indicate a \"fundamental plane\" for clusters, which reflects some universal physical conditions and processes operating at the epoch of cluster formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.0364v1.pdf"}
{"id": "1305.2007", "abstract": "  Large-scale faint structure detected by the recent observations in the halo of the Andromeda galaxy (M31) provides an attractive window to explore the structure of outer cold dark matter (CDM) halo in M31. Using an N-body simulation of the interaction between an accreting satellite galaxy and M31, we investigate the mass density profile of the CDM halo. We find the sufficient condition of the outer density profile of CDM halo in M31 to reproduce the Andromeda giant stream and the shells at the east and west sides of M31. The result indicates that the density profile of the outer dark matter halo of M31 is a steeper than the prediction of the theory of the structure formation based on the CDM model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.2007v1.pdf"}
{"id": "1305.2239", "abstract": "  We present squeezing and anti-squeezing spectra of the output from a degenerate optical parametric oscillator (OPO) network arranged in different coherent quantum feedback configurations. One OPO serves as a quantum plant, the other as a quantum controller. The addition of coherent feedback enables shaping of the output squeezing spectrum of the plant, and is found to be capable of pushing the frequency of maximum squeezing away from the optical driving frequency and broadening the spectrum over a wider frequency band. The experimental results are in excellent agreement with the developed theory, and illustrate the use of coherent quantum feedback to engineer the quantum-optical properties of the plant OPO output. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.2239v1.pdf"}
{"id": "1305.3116", "abstract": "  We prove for an infinite array of globally coupled overdamped anharmonic oscillators subject to additive Gaussian white noise the existence of a well-behaved critical manifold in the parameter space which separates a symmetric phase from a symmetry broken phase. Given two of the system parameters there is an unique critical value of the third. The proof exploits that the critical control parameter a_c is bounded by its limit values for weak and for strong noise. In these limits the mechanism of symmetry breaking differs. For weak noise the distribution is Gaussian and the symmetry is broken as the whole distribution is shifted in either the positive or the negative direction. For strong noise there is a symmetric double-peak distribution and the symmetry is broken as the weights of the peaks become different. We derive an ordinary differential equation whose solution describes the critical manifold. Using a series ansatz to solve this differential equation we determine the critical manifold for weak and for strong noise and compare it to numerical results. We derive analytic expressions for the order parameter and the susceptibility close to the critical manifold. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.3116v2.pdf"}
{"id": "1305.3887", "abstract": "  In this work we propose schemes for joint model-order and step-size adaptation of reduced-rank adaptive filters. The proposed schemes employ reduced-rank adaptive filters in parallel operating with different orders and step sizes, which are exploited by convex combination strategies. The reduced-rank adaptive filters used in the proposed schemes are based on a joint and iterative decimation and interpolation (JIDF) method recently proposed. The unique feature of the JIDF method is that it can substantially reduce the number of coefficients for adaptation, thereby making feasible the use of multiple reduced-rank filters in parallel. We investigate the performance of the proposed schemes in an interference suppression application for CDMA systems. Simulation results show that the proposed schemes can significantly improve the performance of the existing reduced-rank adaptive filters based on the JIDF method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.3887v1.pdf"}
{"id": "1305.5678", "abstract": "  We study the dynamics of polariton condensate wave trains that propagate along a quasi one-dimensional waveguide. Through the application of tuneable potential barriers the propagation can be reflected and multiple reflections used to confine and store a propagating state. Energy-relaxation processes allow the delayed relaxation into a long-living coherent ground state. Aside the potential routing of polariton condensate signals, the system forms an AND-type logic gate compatible with incoherent inputs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.5678v3.pdf"}
{"id": "1305.5680", "abstract": "  We develop a theory of spin-dependent phenomena in the streaming regime characterized by ballistic acceleration of electrons in the moderate electric field until they achieve the optical phonon energy and abruptly emit the phonons. It is shown that the Dyakonov-Perel spin relaxation is drastically modified in this regime, the current-induced spin orientation remarkably increases, reaches a high value  2", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.5680v1.pdf"}
{"id": "1306.0363", "abstract": "  We study a model for the observed phenomenon of electron spin resonance (ESR) at the Zeeman frequency as seen by a scanning tunneling microscope (STM) via its current noise. The model for this ESR-STM phenomenon allows the STM current to flow in two arms of a nanoscopic interferometer, one arm has direct tunneling from the tip to the substrate while the second arm has tunneling through two spin states. We evaluate analytically the noise spectrum for non-polarized leads, as relevant to the experimental setup. We show that spin-orbit interactions allow for an interference of two tunneling paths resulting in a resonance effect. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.0363v1.pdf"}
{"id": "1306.0447", "abstract": "  This paper studies secure multiparty quantum computation (SMQC) without nonlocal measurements. Firstly, this task is reduced to secure two-party quantum computation of nonlocal controlled-NOT (NL-CNOT) gate. Then, in the passive adversaries model, the secure computation of NL-CNOT is reduced to bit commitment. Thus, a SMQC scheme can be constructed based on bit commitment. This scheme does not depend on trusted third party, and is secure in the passive adversaries model. It is also pointed out that a vulnerability exists in any secure two-party quantum computation protocol of NL-CNOT gate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.0447v2.pdf"}
{"id": "1306.0627", "abstract": "  Symplectic integration methods based on operator splitting are well established in many branches of science. For Hamiltonian systems which split in more than two parts, symplectic methods of higher order have been studied in detail only for a few special cases. In this work, we present and compare different ways to construct high order symplectic schemes for general Hamiltonian systems that can be split in three integrable parts. We use these techniques to numerically solve the equations of motion for a simple toy model, as well as the disordered discrete nonlinear Schrödinger equation. We thereby compare the efficiency of symplectic and non-symplectic integration methods. Our results show that the new symplectic schemes are superior to the other tested methods, with respect to both long term energy conservation and computational time requirements. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.0627v1.pdf"}
{"id": "1306.1664", "abstract": "  The boundary sheath of a low temperature plasma comprises typically only a small fraction of its volume but is responsible for many aspects of the macroscopic behavior. A thorough understanding of the sheath dynamics is therefore of theoretical and practical importance. This work focusses on the so-called \"algebraic\" approach which strives to describe the electrical behavior of RF modulated boundary sheaths in closed analytical form, i.e., without the need to solve differential equations. A mathematically simple, analytical expression for the charge-voltage relation of a sheath is presented which holds for all excitation wave forms and amplitudes and covers all regimes from the collision-less motion at low gas pressure to the collision dominated motion at gas high pressure. A comparison with the results of self-consistent particle-in-cell simulations is also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.1664v1.pdf"}
{"id": "1306.1760", "abstract": "  We present an exact analytic class of solutions for a system of two membranes in eleven-dimensional supergravity. One brane in the system is completely localized along the overall and relative transverse coordinates while the other brane in the system is localized only along the overall transverse coordinates. The membrane configuration preserves four supersymmetries. Moreover we find some approximate solutions for the system of two membranes with a Bianchi space as the overall transverse space to both membranes. All supergravity solutions preserve 1/8 of the supersymmetry. Upon dimensional reduction, the solutions provide intersecting configurations of three D-branes in type IIA supergravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.1760v1.pdf"}
{"id": "1306.3401", "abstract": "  The Susceptible-Infected-Susceptible (SIS) model is one of the simplest memoryless system for describing information/epidemic spreading phenomena with competing creation and spontaneous annihilation reactions. The effect of quenched disorder on the dynamical behavior has recently been compared to quenched mean-field (QMF) approximations in scale-free networks. QMF can take into account topological heterogeneity and clustering effects of the activity in the steady state by spectral decomposition analysis of the adjacency matrix. Therefore, it can provide predictions on possible rare-region effects, thus on the occurrence of slow dynamics. I compare QMF results of SIS with simulations on various large dimensional graphs. In particular, I show that for Erdős-Rényi graphs this method predicts correctly the epidemic threshold and the rare-region effects. Griffiths Phases emerge if the graph is fragmented or if we apply strong, exponentially suppressing weighting scheme on the edges. The latter model describes the connection time distributions in the face-to-face experiments. In case of generalized Barabási-Albert type of networks with aging connections strong rare-region effects and numerical evidence for Griffiths Phase dynamics are shown. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.3401v1.pdf"}
{"id": "1306.3924", "abstract": "  The archetypal system demonstrating stochastic resonance is nothing more than a threshold triggered device. It consists of a periodic modulated input and noise. Every time an output crosses the threshold the signal is recorded. Such a digitally filtered signal is sensitive to the noise intensity. There exist the optimal value of the noise intensity resulting in the \"most\" periodic output. Here, we explore properties of the non-dynamical stochastic resonance in non-equilibrium situations, i.e. when the Gaussian noise is replaced by an α-stable noise. We demonstrate that non-equilibrium α-stable noises, depending on noise parameters, can either weaken or enhance the non-dynamical stochastic resonance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.3924v1.pdf"}
{"id": "1306.4187", "abstract": "  We report on ab initio time-dependent spin dynamics simulations for a two-center magnetic molecular complex based on time-dependent non-collinear spin density functional theory. In particular, we discuss how the dynamical behavior of the ab initio spin-density in the time-domain can be mapped onto a model Hamiltonian based on the classical Heisenberg spin-spin interaction JS_1·S_2. By analyzing individual localized-spin trajectories, extracted from the spin-density evolution, we demonstrate a novel method for evaluating the effective Heisenberg exchange coupling constant, J, from first principles simulations. We find that J, extracted in such a new dynamical way, agrees quantitatively to that calculated by the standard density functional theory broken-symmetry scheme. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.4187v1.pdf"}
{"id": "1306.5201", "abstract": "  A system of two masses connected with a weightless rod (called dumbbell in this paper) interacting with a flat boundary is considered. The sharp bound on the number of collisions with the boundary is found using billiard techniques. In case, the ratio of masses is large and the dumbbell rotates fast, an adiabatic invariant is obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.5201v1.pdf"}
{"id": "1306.5603", "abstract": "  We consider the asymptotic consistency of maximum likelihood parameter estimation for dynamical systems observed with noise. Under suitable conditions on the dynamical systems and the observations, we show that maximum likelihood parameter estimation is consistent. Our proof involves ideas from both information theory and dynamical systems. Furthermore, we show how some well-studied properties of dynamical systems imply the general statistical properties related to maximum likelihood estimation. Finally, we exhibit classical families of dynamical systems for which maximum likelihood estimation is consistent. Examples include shifts of finite type with Gibbs measures and Axiom A attractors with SRB measures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.5603v2.pdf"}
{"id": "1306.5812", "abstract": "  The inhomogeneous fluctuations that underlie structure formation - galaxies and CMB hotspots - might have been seeded by quantum cosmological fluctuations, as magnified by some inflationary mechanism. The Halliwell-Hawking model for these, as a lower-energy semiclassical limit, is expected to be shared by many theories. E.g. an O((H/m_pl)^2) suppression of power at large scales results from this. This model contains/suppresses very many terms; we want a qualitative understanding of the meaning of these terms and of different regimes resulting from different combinations of them. I study this with toy models that have tractable mathematics: minisuperspace and, especially, relational particle mechanics. In the present Seminar, I consider in particular averaged terms with some lessons from Hartree-Fock approach to Atomic and Molecular Physics. One needs to anchor this on variational principles; treating the subsequent equations is a numerical venture. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.5812v2.pdf"}
{"id": "1307.0240", "abstract": "  This paper presents the development of a new continuous forest fire model implemented as a weighted local small-world network approach. This new approach was designed to simulate fire patterns in real, heterogeneous landscapes. The wildland fire spread is simulated on a square lattice in which each cell represents an area of the land's surface. The interaction between burning and non-burning cells, in the present work induced by flame radiation, may be extended well beyond nearest neighbors. It depends on local conditions of topography and vegetation types. An approach based on a solid flame model is used to predict the radiative heat flux from the flame generated by the burning of each site towards its neighbors. The weighting procedure takes into account the self-degradation of the tree and the ignition processes of a combustible cell through time. The model is tested on a field presenting a range of slopes and with data collected from a real wildfire scenario. The critical behavior of the spreading process is investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.0240v1.pdf"}
{"id": "1307.0856", "abstract": "  Using a set of zoomed-in cosmological simulations of high-redshift progenitors of massive galaxies, we isolate and trace the history of gas that is accreted by central supermassive black holes. We determine the origins of the accreted gas, in terms of whether it entered the galaxy during a merger event or was smoothly accreted. Furthermore, we designate whether the smoothly accreted gas is accreted via a cold flow or is shocked upon entry into the halo. For moderate-mass (10^6 - 10^7 Msun) black holes at z   4, there is a preference to accrete cold flow gas than gas of shocked or merger origin. However, this result is a consequence of the fact that the entire galaxy has a higher fraction of gas from cold flows. In general, each black hole tends to accrete the same fractions of smooth- and merger-accreted gas as is contained in its host galaxy, suggesting that once gas enters a halo it becomes well-mixed, and its origins are erased. We find that the angular momentum of the gas upon halo entry is a more important factor; black holes preferentially accrete gas that had low angular momentum when it entered the galaxy, regardless of whether it was accreted smoothly or through mergers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.0856v2.pdf"}
{"id": "1307.1190", "abstract": "  The microbunching instability usually exists in the LINAC of a free electron laser (FEL) facility. In many cases, the longitudinal space charge (LSC) is a dominant factor that generates the instability. For the highly bright electron beams, the plasma effect is found to be non-trivial in the development of the instability. In this paper, starting from the Vlasov and Poisson equations in the multiple-dimensional phase space, we perform the straightforward analysis of the microbunching instability based on the explicit formula of the longitudinal electric field introduced by the density perturbation in the longitudinal direction, in such a way to be highly comparable to the well-developed method for higher energy beams. This method generally applies in both the cases with and without acceleration and independent of lattice components. The results show that for a electron beam with small transverse emittance at low energies, which is always the case in the injector of a free electron laser device, the plasma effect results in the oscillation of the longitudinal electric field in the modified plasma frequency that depends on the transverse size of the beam, and the Landau damping effect in the longitudinal electric field due to the uncorrelated longitudinal velocity spread during the beam transportation. These two effects both play important roles in the development of the instability. As the result, the energy modulation driven by the LSC impedance differs from the regular value significantly and the discrepancy leads to the noticeable change of the final gain of the instability. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.1190v3.pdf"}
{"id": "1307.1498", "abstract": "  A universal quantum simulator would enable efficient simulation of quantum dynamics by implementing quantum-simulation algorithms on a quantum computer. Specifically the quantum simulator would efficiently generate qubit-string states that closely approximate physical states obtained from a broad class of dynamical evolutions. I provide an overview of theoretical research into universal quantum simulators and the strategies for minimizing computational space and time costs. Applications to simulating many-body quantum simulation and solving linear equations are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.1498v1.pdf"}
{"id": "1307.2064", "abstract": "  In this communication, a simple mechanism in the optional public goods game is experimentally investigated using two experimental settings; and first time, the cyclic strategy pattern in full state space is demonstrated by means of velocity. It is, furthermore, elaborated that the strategies of cooperation, defection and nonparticipant form a Rock-Paper-Scissors type cycle, and the cycle of three strategies are persistent over 200 rounds. This cycle is very similar to the cycle given by evolutionary dynamics e.g. replicator dynamics. The mechanism that nonparticipant can sustain cooperation is driven by the Rock-Paper-Scissors type of cyclic dominance in the three strategies. That is, if the cycle is existent, the cooperation will always sustain. Meanwhile, the distribution of social states changes in the state space and from cooperation as the most frequent strategy to defection and, from defection to nonparticipant, forms a clear rotation path in a long run. These results seem to implicate that the evolutionary dynamics has ability to capture the real dynamics applying not only on biosphere, but also on human society. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.2064v2.pdf"}
{"id": "1307.2235", "abstract": "  The effect of environment on the circumgalactic medium (CGM) is investigated through a comparison of Lya absorption line data in the Virgo Cluster and the field. This Letter uses the first systematic survey of background QSOs in and around the Virgo Cluster and large existing surveys of galaxies at low redshift. While previous studies found denser gas (higher equivalent width) closer to a galaxy (lower impact parameter), this correlation disappears in the Virgo environment. In addition, the covering fraction of the CGM is lower in the cluster environment than in the circumcluster environment and field. The results indicate that the CGM is suppressed for cluster galaxies while galaxies in the circumcluster environment have abundant CGM. The truncation of the CGM may result in the quenching of star formation through starvation. Our results also show that CGM surveys must consider the role of environment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.2235v3.pdf"}
{"id": "1307.3897", "abstract": "  Recently the most general static self-consistent multi-soliton solutions in Bogoliubov-de Gennes and chiral Gross-Neveu systems are derived by the present authors [D. A. Takahashi and M. Nitta, Phys. Rev. Lett. 110, 131601 (2013)]. Here we show a few complementary results, which were absent in the previous our work. We prove directly from the gap equation that the self-consistent solutions need to have reflectionless potentials. We also give the self-consistent condition for the system consisting of only right-movers, which is more used in high-energy physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.3897v1.pdf"}
{"id": "1307.4240", "abstract": "  Until now, just a few extrasolar planets ( 30 out of 860) have been found through the direct imaging method. This number should greatly improve when the next generation of High Contrast Instruments like Gemini Planet Imager (GPI) at Gemini South Telescope or SPHERE at VLT will became operative at the end of this year. In particular, the Integral Field Spectrograph (IFS), one of the SPHERE subsystems, should allow a first characterization of the spectral type of the found extrasolar planets. Here we present the results of the last performance tests that we have done on the IFS instrument at the Institut de Planetologie et d'Astrophysique de Grenoble (IPAG) in condition as similar as possible to the ones that we will find at the telescope. We have found that we should be able to reach contrast down to 5x10^-7 and make astrometry at sub-mas level with the instrument in the actual conditions. A number of critical issues have been identified. The resolution of these problems could allow to further improve the performance of the instrument. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.4240v2.pdf"}
{"id": "1307.4542", "abstract": "  The WMAP and Planck observations show that the quadrupole and octopole orientations of the CMB might align with each other. We reveal that the quadrupole–octopole alignment is a natural implication of the primordial power spectrum in an anisotropic spacetime. The primordial power spectrum is presented with a dipolar modulation. We obtain the privileged plane by employing the “power tensor” technique. At this plane, there is the maximum correlation between quadrupole and octopole. The probability for the alignment is much larger than what in the isotropic universe. We find that this model would lead to deviations from the statistical isotropy only for low–ℓ multipoles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.4542v2.pdf"}
{"id": "1307.5385", "abstract": "  Protecting quantum correlation from decoherence is one of the crucial issues in quantum information processing. It has been commonly recognized that any initial quantum correlation of a composite system diminishes asymptotically or abruptly to zero under local Markovian decoherence. Here we show that, contrary to this recognition, a noticeable Gaussian quantum discord of a continuous-variable bipartite system can be frozen in the steady state in the non-Markovian dynamics if each of the subsystems forms a localized mode with its local reservoir. The condition for this frozen quantum discord can be reached by appropriately engineering the structure of the reservoirs. The possible realization of our results in a coupled cavity array system formed by a photonic crystal is proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.5385v2.pdf"}
{"id": "1307.5680", "abstract": "  We analyze the depolarization of ultracold neutrons confined in a magnetic field configuration similar to those used in existing or proposed magneto-gravitational storage experiments aiming at a precise measurement of the neutron lifetime. We use an extension of the semi-classical Majorana approach as well as an approximate quantum mechanical analysis, both pioneered by Walstrom et al. [Nucl. Instr. Meth. Phys. Res. A 599, 82 (2009)]. In contrast with this previous work we do not restrict the analysis to purely vertical modes of neutron motion. The lateral motion is shown to cause the predominant depolarization loss in a magnetic storage trap. The system studied also allowed us to estimate the depolarization loss suffered by ultracold neutrons totally reflected on a non-magnetic mirror immersed in a magnetic field. This problem is of preeminent importance in polarized neutron decay studies such as the measurement of the asymmetry parameter A using ultracold neutrons, and it may limit the efficiency of ultracold neutron polarizers based on passage through a high magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.5680v1.pdf"}
{"id": "1307.6047", "abstract": "  We provide a systematic analysis of a prototypical nonlinear oscillator system respecting PT-symmetry i.e., one of them has gain and the other an equal and opposite amount of loss. Starting from the linear limit of the system, we extend considerations to the nonlinear case for both soft and hard cubic nonlinearities identifying symmetric and anti-symmetric breather solutions, as well as symmetry breaking variants thereof. We propose a reduction of the system to a Schrödinger type PT-symmetric dimer, whose detailed earlier understanding can explain many of the phenomena observed herein, including the PT phase transition. Nevertheless, there are also significant parametric as well as phenomenological potential differences between the two models and we discuss where these arise and where they are most pronounced. Finally, we also provide examples of the evolution dynamics of the different states in their regimes of instability. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.6047v1.pdf"}
{"id": "1307.6339", "abstract": "  We simulate SU(2) gauge theory at temperatures ranging from slightly below T_c to roughly 2T_c for two different values of the gauge coupling. Using a histogram method, we extract the effective potential for the Polyakov loop and for the phases of the eigenvalues of the thermal Wilson loop, in both the fundamental and adjoint representations. We show that the classical potential of the fundamental loop can be parametrized within a simple model which includes a Vandermonde potential and terms linear and quadratic in the Polyakov loop. We discuss how parametrizations for the other cases can be obtained from this model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.6339v1.pdf"}
{"id": "1307.6607", "abstract": "  Using the gauge-gravity duality, we argue that for a certain class of out-of-equilibrium steady-state systems in contact with a thermal background at a given temperature, the macroscopic physics can be captured by an effective thermodynamic description. The steady-state is obtained by applying a constant electric field that results in a stationary current flow. Within holography, we consider generic probe systems where an open string equivalence principle and an open string metric govern the effective thermodynamics. This description comes equipped with an effective temperature, which is larger than the background temperature, and a corresponding effective entropy. For conformal or scale-invariant theories, certain scaling behaviours follow immediately. In general, in the large electric field limit, this effective temperature is also observed to obey generic relations with various physical parameters in the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.6607v2.pdf"}
{"id": "1307.6680", "abstract": "  In this paper, we use Bell inequality and nonlocality to study the bipartite correlation in an exactly soluble two-dimensional mixed spin system. Bell inequality turns out to be a valuable detector for phase transitions in this model. It can detect not only the quantum phase transition, but also the thermal phase transitions, of the system. The property of bipartite correlation in the system is also analyzed. In the quantum anti-ferromagnetic phase, the Bell inequality is violated thus nonlocality is present. It is interesting that the nonlocality is enhanced by thermal fluctuation, and similar results have not been observed in anti-ferromagnetic phase. In the ferromagnetic phase, the quantum correlation turns out to be very novel, which cannot be captured by entanglement or nonlocality. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.6680v1.pdf"}
{"id": "1307.7024", "abstract": "  We propose a new approach, multi-view Laplacian support vector machines (SVMs), for semi-supervised learning under the multi-view scenario. It integrates manifold regularization and multi-view regularization into the usual formulation of SVMs and is a natural extension of SVMs from supervised learning to multi-view semi-supervised learning. The function optimization problem in a reproducing kernel Hilbert space is converted to an optimization in a finite-dimensional Euclidean space. After providing a theoretical bound for the generalization performance of the proposed method, we further give a formulation of the empirical Rademacher complexity which affects the bound significantly. From this bound and the empirical Rademacher complexity, we can gain insights into the roles played by different regularization terms to the generalization performance. Experimental results on synthetic and real-world data sets are presented, which validate the effectiveness of the proposed multi-view Laplacian SVMs approach. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.7024v1.pdf"}
{"id": "1307.7427", "abstract": "  The magnetization dynamics of spin torque oscillator (STO) consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer was studied by solving the Landau-Lifshitz-Gilbert equation. We derived the analytical formula of the relation between the current and the oscillation frequency of the STO by analyzing the energy balance between the work done by the spin torque and the energy dissipation due to the damping. We also found that the field-like torque breaks the energy balance, and change the oscillation frequency. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.7427v1.pdf"}
{"id": "1307.7981", "abstract": "  Prior-weighted logistic regression has become a standard tool for calibration in speaker recognition. Logistic regression is the optimization of the expected value of the logarithmic scoring rule. We generalize this via a parametric family of proper scoring rules. Our theoretical analysis shows how different members of this family induce different relative weightings over a spectrum of applications of which the decision thresholds range from low to high. Special attention is given to the interaction between prior weighting and proper scoring rule parameters. Experiments on NIST SRE'12 suggest that for applications with low false-alarm rate requirements, scoring rules tailored to emphasize higher score thresholds may give better accuracy than logistic regression. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.7981v1.pdf"}
{"id": "1307.8147", "abstract": "  Recently there has been great interest around quantum relativistic models for plasmas. In particular striking advances have been obtained by means of the Klein-Gordon-Maxwell system, which provides a first order approach to the relativistic regimes of quantum plasmas. It is a reliable method as long as the plasma spin dynamics is not a fundamental aspect, to be addressed using more refined (and heavier) models involving the Pauli-Schrödinger or Dirac equations. In this work a further simplification is considered, tracing back to the early days of relativistic quantum theory. Namely, we revisit the square-root Klein-Gordon-Poisson system, where the positive branch of the relativistic energy-momentum relation is mapped to a quantum wave equation. The associated linear wave propagation is analyzed and compared to the results in the literature. We determine physical parameters where the simultaneous quantum and relativistic effects can be noticeable in weakly coupled electrostatic plasmas. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.8147v1.pdf"}
{"id": "1308.0584", "abstract": "  The current status of flavored dark matter is reviewed. We discuss the main experimental constraints on models of flavored dark matter and survey some possible considerations which are relevant for the constructions of models. We then review the application of existing flavor principles to dark matter, with an emphasis on minimal flavor violation, and discuss implications of flavored dark matter on collider phenomenology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.0584v1.pdf"}
{"id": "1308.0620", "abstract": "  We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.0620v1.pdf"}
{"id": "1308.1378", "abstract": "  The problem of optimally discriminating between two completely unknown qubit states is generalized by allowing an error margin. It is visualized as a device—the programmable discriminator—with one data and two program ports, each fed with a number of identically prepared qubits—the data and the programs. The device aims at correctly identifying the data state with one of the two program states. This scheme has the unambiguous and the minimum-error schemes as extremal cases, when the error margin is set to zero or it is sufficiently large, respectively. Analytical results are given in the two situations where the margin is imposed on the average error probability—weak condition—or it is imposed separately on the two probabilities of assigning the state of the data to the wrong program—strong condition. It is a general feature of our scheme that the success probability rises sharply as soon as a small error margin is allowed, thus providing a significant gain over the unambiguous scheme while still having high confidence results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.1378v2.pdf"}
{"id": "1308.1740", "abstract": "  The standard technique for measurement of random uncertainties of star formation histories (SFHs) is the bootstrap Monte Carlo, in which the color-magnitude diagram (CMD) is repeatedly resampled. The variation in SFHs measured from the resampled CMDs is assumed to represent the random uncertainty in the SFH measured from the original data. However, this technique systematically and significantly underestimates the uncertainties for times in which the measured star formation rate is low or zero, leading to overly (and incorrectly) high confidence in that measurement. This study proposes an alternative technique, the Markov Chain Monte Carlo (MCMC), which samples the probability distribution of the parameters used in the original solution to directly estimate confidence intervals. While the most commonly used MCMC algorithms are incapable of adequately sampling a probability distribution that can involve thousands of highly correlated dimensions, the Hybrid Monte Carlo algorithm is shown to be extremely effective and efficient for this particular task. Several implementation details, such as the handling of implicit priors created by parameterization of the SFH, are discussed in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.1740v1.pdf"}
{"id": "1308.2273", "abstract": "  We investigate evolutionary dynamics of two-strategy matrix games with zealots in finite populations. Zealots are assumed to take either strategy regardless of the fitness. When the strategy selected by the zealots is the same, the fixation of the strategy selected by the zealots is a trivial outcome. We study fixation time in this scenario. We show that the fixation time is divided into three main regimes, in one of which the fixation time is short, and in the other two the fixation time is exponentially long in terms of the population size. Different from the case without zealots, there is a threshold selection intensity below which the fixation is fast for an arbitrary payoff matrix. We illustrate our results with examples of various social dilemma games. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.2273v2.pdf"}
{"id": "1308.2924", "abstract": "  In this paper, we describe the design, construction and performance of an apparatus installed in the Aberdeen Tunnel laboratory in Hong Kong for studying spallation neutrons induced by cosmic-ray muons under a vertical rock overburden of 611 meter water equivalent (m.w.e.). The apparatus comprises of six horizontal layers of plastic-scintillator hodoscopes for determining the direction and position of the incident cosmic-ray muons. Sandwiched between the hodoscope planes is a neutron detector filled with 650 kg of liquid scintillator doped with about 0.06", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.2924v1.pdf"}
{"id": "1308.3663", "abstract": "  A novel model of thermal regulation of homoeothermic animals has been implemented. The model is based on a non-equilibrium thermodynamic approach which introduces entropy balance and the rate of entropy generation as a formulation of The Second Law. The model explains linear correlation between an animals skin and environment temperatures using the first principles and demonstrates the role of blood circulation in the thermoregulation of homoeothermic animals. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.3663v1.pdf"}
{"id": "1308.5107", "abstract": "  A double quantum dot coupled to an s-wave superconductor and subject to an inhomogeneous magnetic field can host a pair of zero-energy Majorana fermions when the dot properties are tuned appropriately. Here, we demonstrate the possibility to generate a fractional 4-pi Josephson effect in two such double dots tunnel-coupled to each other. We discuss the robustness of this effect with respect to perturbations away from the special point in parameter space where the uncoupled double dots host Majorana fermions. We demonstrate the possibility to generate Josephson effects with a period of 8-pi and 12-pi in strongly-coupled double dots. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.5107v1.pdf"}
{"id": "1308.5960", "abstract": "  We study the effects of strong coupling of a localized state charge to one-dimensional electronic channels out of equilibrium. While the state of this charge and the coupling strengths determine the scattering phase shifts in the channels, the nonequilibrium partitioning noise induces the tunneling transitions to the localized state. The strong coupling leads to a nonperturbative backaction effect which is manifested in the orthogonality catastrophe and the Fermi-edge singularity in the transition rates. We predict an unusually pronounced manifestation of the non-Gaussian component of noise that breaks the charge symmetry, resulting in a nontrivial shape, and a shift of the position of the tunneling resonance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.5960v3.pdf"}
{"id": "1308.6338", "abstract": "  We consider a minimal classically scale-invariant extension of the Standard Model. In this theory, the Higgs mechanism is triggered and the electroweak symmetry breaking is generated radiatively by the Coleman-Weinberg sector which is coupled to the SM Higgs. We extend the Higgs portal interactions of the theory to include an additional singlet which is also non-minimally coupled to gravity. This generates a single-field slow-roll inflation mechanism in the effective field theory formulation which is robust up to Planck scales. Our approach does not require integrating in any additional new physics degrees of freedom to unitarise the theory in the sub-Planckian regime where inflation happens. As a result, no large threshold corrections appear in our approach to inflation so that the electroweak scale and the SM Higgs mass are not affected. The singlet field responsible for inflation also gives a viable dark matter candidate in our model. We also discuss the relation between classical scale-invariance of the effective theory and the possible local scale invariance of the full theory and comment on the naturalness of the electroweak scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.6338v2.pdf"}
{"id": "1308.6418", "abstract": "  We investigate the applicability of a random-matrix model to the description of non-collective excitations in heavy-ion reactions around the Coulomb barrier. To this end, we study fusion in the reaction ^16O + ^208Pb, taking account of the known non-collective excitations in the ^208Pb nucleus. We show that the random-matrix model for the corresponding couplings reproduces reasonably well the exact calculations, obtained using empirical deformation parameters. This implies that the model may provide a powerful method for systems in which the non-collective couplings are not so well known. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.6418v1.pdf"}
{"id": "1309.0258", "abstract": "  We consider the quasi-one dimensional system realized by an array of weakly coupled parallel one-dimensional \"tubes\" in a two-dimensional lattice which permits free motion of atoms in an axial direction in the presence of a Zeeman field, Rashba type spin orbit coupling (SOC), and an s-wave attractive interaction, while the radial motion is tightly confined. We solve the zero-temperature (T=0) Bogoliubov-de Gennes (BdG) equations for the quasi-1D Fermi gas with the dispersion modified by tunneling between the tubes, and show that the T=0 phase diagram hosts the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase with non-zero center of mass momentum Cooper pairs for small values of the SOC while for larger values of the SOC and high Zeeman fields the uniform superfluid phase with zero center of mass momentum Cooper pairs has an instability towards the topological uniform superfluid phase with Majorana fermions at the tube ends. Also, we show that tuning the two-dimensional optical lattice strength in this model allows one to explore the crossover behaviors of the phases during the transition between the 3D and the 1D system and in general the FFLO (for small SOC) and the topological uniform superfluid phase (for large SOC) are favored as the system becomes more one-dimensional. We also find evidence of the existence of a Zeeman tuned topological quantum phase transition (TQPT) within the FFLO phase itself and for large values of the Zeeman field and small SOC the TQPT gives rise to a topologically distinct FFLO phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.0258v1.pdf"}
{"id": "1309.0656", "abstract": "  We explore the use of the resource of intra-particle entanglement for secure quantum key distribution in the device-independent scenario. By virtue of the local nature of such entanglement, Bell tests must be implemented locally, which leads to a natural decoupling of device errors from channel errors. We consider a side channel attack on the sender's state preparation device, for which the intra-particle-entanglement based scheme is shown to be more secure than the one that uses separable states. Of practical relevance is the fact that such entanglement can be easily generated using linear optics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.0656v4.pdf"}
{"id": "1309.2429", "abstract": "  3C 66A was monitored by the BATC(Beijing-Arizona-Taipei-Connecticut) telescope from 2005 to 2008,1994 observations were obtained on 89 nights. Detailed research and analysis was performed on these observations in this paper. A long term burst occurred in the whole light curve. No intra-day variability was claimed in our campaign by intra-night light curve analysis. Time lag of shorter wavelenth preceding longer wavelength was shown by correlation analysis. The results showed that the optical spectral shape turned flatter when the source brightened, and the spectral variability indicator was bigger on shorter time-scale as determined by the color indices variation analysis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.2429v1.pdf"}
{"id": "1309.2825", "abstract": "  We searched for periodic and quasiperiodic signal in the prompt emission of a sample of 44 bright short gamma-ray bursts detected with Fermi/GBM, Swift/BAT, and CGRO/BATSE. The aim was to look for the observational signature of quasiperiodic jet precession which is expected from black hole-neutron star mergers, but not from double neutron star systems. Thus, this kind of search holds the key to identify the progenitor systems of short GRBs and, in the wait for gravitational wave detection, represents the only direct way to constrain the progenitors. We tailored our search to the nature of the expected signal by properly stretching the observed light curves by an increasing factor with time, after calibrating the technique on synthetic curves. In none of the GRBs of our sample we found evidence for periodic or quasiperiodic signals. In particular, for the 7 unambiguously short GRBs with best S/N we obtained significant upper limits to the amplitude of the possible oscillations. This result suggests that BH-NS systems do not dominate the population of short GRB progenitors as described by the kinematic model of Stone, Loeb,     Berger (2013). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.2825v2.pdf"}
{"id": "1309.3063", "abstract": "  A solar-type dynamo model in a spherical shell is developed with allowance for random dependence of the poloidal field generation mechanism on time and latitude. The model shows repeatable epochs of strongly decreased amplitude of magnetic cycles similar to the Maunder minimum of solar activity. Random dependence of dynamo-parameters on latitude brakes the equatorial symmetry of generated fields. The model shows the correlation of the occurrence of grand minima with deviations in the dynamo-field from dipolar parity. An increased north-south asymmetry of magnetic activity can, therefore, be an indicator of transitions to grand minima. Qualitative interpretation of this correlation is suggested. Statistics of grand minima in the model are close to the Poisson random process indicating that the onset of a grand minimum is statistically independent of preceding minima. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.3063v2.pdf"}
{"id": "1309.3366", "abstract": "  We propose and analyze a model for phase transitions in an inhomogeneous fluid membrane, that couples local composition with curvature nonlinearly. For asymmetric membranes, our model shows generic non-Ising behavior and the ensuing phase diagram displays either a first- or a second-order phase transition through a critical point (CP) or a tricritical point (TP), depending upon the bending modulus. It predicts generic nontrivial enhancement in fluctuations of asymmetric membranes that scales with system size in a power law fashion at the CP and TP in two dimensions, not observed in symmetric membranes. It also yields two-dimensional Ising universality class for symmetric membranes, in agreement with experimental results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.3366v1.pdf"}
{"id": "1309.3455", "abstract": "  Convergent infinite products, indexed by all natural numbers, in which each factor is a rational function of the index, can always be evaluated in terms of finite products of gamma functions. This goes back to Euler. A purpose of this note is to demonstrate the usefulness of this fact through a number of diverse applications involving multiplicative partitions, entries in Ramanujan's notebooks, the Chowla–Selberg formula, and the Thue–Morse sequence. In addition, we propose a numerical method for efficiently evaluating more general infinite series such as the slowly convergent Kepler–Bouwkamp constant. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.3455v1.pdf"}
{"id": "1309.3531", "abstract": "  Eukaryotic adaptation pathways operate within wide-ranging environmental conditions without stimulus saturation. Despite numerous differences in the adaptation mechanisms employed by bacteria and eukaryotes, all require energy consumption. Here, we present two minimal models showing that expenditure of energy by the cell is not essential for adaptation. Both models share important features with large eukaryotic cells: they employ small diffusible molecules and involve receptor subunits resembling highly conserved G-protein cascades. Analyzing the drawbacks of these models helps us understand the benefits of energy consumption, in terms of adjustability of response and adaptation times as well as separation of cell-external sensing and cell-internal signaling. Our work thus sheds new light on the evolution of adaptation mechanisms in complex systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.3531v1.pdf"}
{"id": "1309.3865", "abstract": "  In this work, we have used an Effective Field Theory (EFT) framework based on Heavy Quark Spin (HQSS), Heavy Flavour (HFS) and Heavy Antiquark-Diquark symmetries (HADS). Using a standard lagrangian for the heavy meson-heavy antimeson system, we fit the counter-terms of the model to predict some promising experimental data that can be interpreted as heavy meson-heavy antimeson molecules, that is, the X(3872) and the Z_b(10610)/Z'_b(10650). Next, and, taking advantage of HADS, we use the same lagrangian to explore the consequences for heavy meson-doubly heavy baryon molecules, which can also be interpreted as triply heavy pentaquarks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.3865v1.pdf"}
{"id": "1309.4115", "abstract": "  Both pulsation and mass loss are commonly observed in stars and are important ingredients for understanding stellar evolution and structure, especially for massive stars. There is a growing body of evidence that pulsation can also drive and enhance mass loss in massive stars and that pulsation-driven mass loss is important for stellar evolution. In this review, I will discuss recent advances in understanding pulsation driven mass loss in massive main sequence stars, classical Cepheids and red supergiants and present some challenges remaining. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.4115v2.pdf"}
{"id": "1309.4216", "abstract": "  We demonstrate an information transfer mechanism between two dissimilar remote InAs/GaAs quantum dots weakly coupled to a common photonic crystal microcavity. Bichromatic excitation in the s-state of one of the dots leads to the formation of dressed states due to the coherent coupling to the laser field, in resonance with the quantum dot. Information on the resulting dressed structure is read out through the photo-luminescence spectrum of the other quantum dot, as well as the cavity mode. The effect is also observed upon exchange of the excitation and detection quantum dots. This quantum dot inter-talk is interpreted in terms of a cavity-mediated coupling involving acoustic phonons. A master equation for a three level system coherently pumped by the two lasers quantitatively describes the behavior of our system. Our results present an important step towards scalable solid-state quantum networking based on coupled multi-quantum-dot-cavity systems, without the need of using identical quantum emitters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.4216v1.pdf"}
{"id": "1309.4752", "abstract": "  A century of coherent experimental and theoretical investigations have uncovered the laws of nature that underly nuclear physics. The standard model of strong and electroweak interactions, with its modest number of input parameters, dictates the dynamics of the quarks and gluons - the underlying building blocks of protons, neutrons, and nuclei. While the analytic techniques of quantum field theory have played a key role in understanding the dynamics of matter in high energy processes, they encounter difficulties when applied to low-energy nuclear structure and reactions, and dense systems. Expected increases in computational resources into the exa-scale during the next decade will provide the ability to numerically compute a range of important strong interaction processes directly from QCD with quantifiable uncertainties using the technique of Lattice QCD. These calculations will refine the chiral nuclear forces that are used as input into nuclear many-body calculations, including the three- and four-nucleon interactions. I discuss the state-of-the-art Lattice QCD calculations of quantities of interest in nuclear physics, progress that is expected in the near future, and the impact upon nuclear physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.4752v1.pdf"}
{"id": "1309.6234", "abstract": "  We discuss two Higgs doublet models with a softly-broken discrete 𝕊_3 symmery, where the mass matrix for charged-leptons is predicted as the diagonal form in the weak eigenbasis of lepton fields. Similar to an introduction of ℤ_2 symmetry, the tree level flavor changing neutral current can be forbidden by imposing the 𝕊_3 symmetry to the model. Under the 𝕊_3 symmetry, there are four types of Yukawa interactions depending on the 𝕊_3 charge assignment to right-handed fermions. We find that extra Higgs bosons can be muon and electron specific in one of four types of the Yukawa interaction. This property does not appear in any other two Higgs doublet models with a softly-broken ℤ_2 symmetry. We discuss the phenomenology of the muon and electron specific Higgs bosons at the Large Hadron Collider; namely we evaluate allowed parameter regions from the current Higgs boson search data and discovery potential of such a Higgs boson at the 14 TeV run. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.6234v4.pdf"}
{"id": "1309.6981", "abstract": "  We present a computational scheme for extracting the energy level alignment of a metal/molecule interface, based on constrained density functional theory and local exchange and correlation functionals. The method, applied here to benzene on Li(100), allows us to evaluate charge transfer energies, as well as the spatial distribution of the image charge induced on the metal surface. We systematically study the energies for charge transfer from the molecule to the substrate as function of the molecule-substrate distance, and investigate the effects arising from image charge confinement and local charge neutrality violation. For benzene on Li(100) we find that the image charge plane is located at about 1.8 Åabove the Li surface, and that our calculated charge transfer energies compare perfectly with those obtained with a classical electrostatic model having the image plane located at the same position. The methodology outlined here can be applied to study any metal/organic interface in the weak coupling limit at the computational cost of a total energy calculation. Most importantly, as the scheme is based on total energies and not on correcting the Kohn-Sham quasiparticle spectrum, accurate results can be obtained with local/semi-local exchange and correlation functionals. This enables a systematic approach to convergence. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.6981v1.pdf"}
{"id": "1309.7463", "abstract": "  Social media, regarded as two-layer networks consisting of users and items, turn out to be the most important channels for access to massive information in the era of Web 2.0. The dynamics of human activity and item popularity is a crucial issue in social media networks. In this paper, by analyzing the growth of user activity and item popularity in four empirical social media networks, i.e., Amazon, Flickr, Delicious and Wikipedia, it is found that cross links between users and items are more likely to be created by active users and to be acquired by popular items, where user activity and item popularity are measured by the number of cross links associated with users and items. This indicates that users generally trace popular items, overall. However, it is found that the inactive users more severely trace popular items than the active users. Inspired by empirical analysis, we propose an evolving model for such networks, in which the evolution is driven only by two-step random walk. Numerical experiments verified that the model can qualitatively reproduce the distributions of user activity and item popularity observed in empirical networks. These results might shed light on the understandings of micro dynamics of activity and popularity in social media networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.7463v2.pdf"}
{"id": "1309.7902", "abstract": "  Analysis of the properties of resonant modes in a reentrant cavity structure comprising of a post and a ring was undertaken and verified experimentally. In particular we show the existence of higher order reentrant cavity modes in such a structure. Results show that the new cavity has two re-entrant modes, one which has a better displacement sensitivity than the single post resonator and the other with a reduced sensitivity. The more sensitive mode is better than the single post resonator by a factor of 2 to 1.5 when the gap spacing is below 100 μm. This type of cavity has the potential to operate as a highly sensitive transducer for a variety of precision measurement applications, in particular applications which require coupling to more than one sensitive transducer mode. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.7902v3.pdf"}
{"id": "1309.7963", "abstract": "  Monte Carlo simulations of the transport of protons in human tissue have been deployed on graphics processing units (GPUs) with impressive results. To provide a more complete treatment of non-elastic nuclear interactions in these simulations, we developed a fast intranuclear cascade-evaporation simulation for the GPU. This can be used to model non-elastic proton collisions on any therapeutically relevant nuclei at incident energies between 20 and 250 MeV. Predictions are in good agreement with Geant4.9.6p2. It takes approximately 2 s to calculate 1× 10^6 200 MeV proton-^16O interactions on a NVIDIA GTX680 GPU. A speed-up factor of ∼20 relative to one Intel i7-3820 core processor thread was achieved. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.7963v2.pdf"}
{"id": "1310.0043", "abstract": "  Attractive colloidal particles can form a disordered elastic solid or gel when quenched into a two-phase region, if the volume fraction is sufficiently large. When the interactions are comparable to thermal energies the stress-bearing network within the gel restructures over time as individual particle bonds break and reform. Typically, under gravity such weak gels show a prolonged period of either no or very slow settling, followed by a sudden and rapid collapse - a phenomenon known as delayed collapse. The link between local bond breaking events and the macroscopic process of delayed collapse is not well understood. Here we summarize the main features of delayed collapse and discuss the microscopic processes which cause it. We present a plausible model which connects the kinetics of bond breaking to gel collapse and test the model by exploring the effect of an applied external force on the stability of a gel. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.0043v2.pdf"}
{"id": "1310.0051", "abstract": "  Several variants of the recently proposed Density Matrix Embedding Theory (DMET) [G. Knizia and G. K-L. Chan, Phys. Rev. Lett. 109, 186404 (2012)] are formulated and tested. We show that spin symmetry breaking of the lattice mean-field allows precise control of the lattice and fragment filling while providing very good agreement between predicted properties and exact results. We present a rigorous proof that at convergence this method is guaranteed to preserve lattice and fragment filling. Differences arising from fitting the fragment one-particle density matrix alone versus fitting fragment plus bath are scrutinized. We argue that it is important to restrict the density matrix fitting to solely the fragment. Furthermore, in the proposed broken symmetry formalism, it is possible to substantially simplify the embedding procedure without sacrificing its accuracy by resorting to density instead of density matrix fitting. This simplified Density Embedding Theory (DET) greatly improves the convergence properties of the algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.0051v2.pdf"}
{"id": "1310.0861", "abstract": "  In this paper we perform an assessment of the 2880 Earth impact risk for asteroid (29075) 1950 DA. To obtain reliable predictions we analyze the contribution of the observational dataset and the astrometric treatment, the numerical error in the long-term integration, and the different accelerations acting on the asteroid. The main source of uncertainty is the Yarkovsky effect, which we statistically model starting from 1950 DA's available physical characterization, astrometry, and dynamical properties. Before the release of 2012 radar data, this modeling suggests that 1950 DA has 99", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.0861v2.pdf"}
{"id": "1310.0913", "abstract": "  The appearance of quark matter in the core of hybrid stars is a fundamental issue in such compact stars. The central density of these stars is sufficiently high such that nuclear matter undergoes a further change into other exotic phases that consist of hyperons and quarks. However, the equation of state (EOS) for the high-density matter is still not clear and several recent observations have indicated the limitations of the EOSs; theoretical studies should try to elucidate the EOSs. It is believed that the inner regions of the stars should consist of a mixed hadron-quark phase. We study the mixed hadron-quark phase, taking into account finite-size effects, and find that that the mixed phase should be restricted to a narrower region. Therefore, a quark matter phase should appear in the central region. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.0913v1.pdf"}
{"id": "1310.1110", "abstract": "  Quantum properties of correlations have a key role in disparate fields of physics, from quantum information processing, to quantum foundations, to strongly correlated systems. We tackle a specific aspect of the fundamental quantum marginal problem: we address the issue of deducing the global properties of correlations of tripartite quantum states based on the knowledge of their bipartite reductions, focusing on relating specific properties of bipartite correlations to global correlation properties. We prove that strictly classical bipartite correlations may still require global entanglement and that unentangled—albeit not strictly classical—reductions may require global genuine multipartite entanglement, rather than simple entanglement. On the other hand, for three qubits, the strict classicality of the bipartite reductions rules out the need for genuine multipartite entanglement. Our work sheds new light on the relation between local and global properties of quantum states, and on the interplay between classical and quantum properties of correlations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.1110v3.pdf"}
{"id": "1310.3095", "abstract": "  We review the Bogoliubov theory in the context of recent experiments, where atoms are scattered from a Bose-Einstein Condensate into two well-separated regions. We find the full dynamics of the pair-production process, calculate the first and second order correlation functions and show that the system is ideally number-squeezed. We calculate the Fisher information to show how the entanglement between the atoms from the two regions changes in time. We also provide a simple expression for the lower bound of the useful entanglement in the system in terms of the average number of scattered atoms and the number of modes they occupy. We then apply our theory to a recent \"twin-beam\" experiment [R. Bücker et al., Nat. Phys. 7, 608 (2011)]. The only numerical step of our semi-analytical description can be easily solved and does not require implementation of any stochastic methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.3095v1.pdf"}
{"id": "1310.3183", "abstract": "  We present radiative one-loop neutrino mass model with hypercharge zero scalar triplet in conjunction with another charged singlet scalar and an additional vectorlike lepton doublet. We study three variants of this mass model: the first one without additional beyond-SM symmetry, the second with imposed DM-stabilizing discrete Z_2 symmetry, and the third in which this Z_2 symmetry is promoted to the gauge symmetry U(1)_D. The two latter cases are scotogenic, with a neutral component of the scalar triplet as a dark matter candidate. In first scotogenic model the Z_2-odd dark matter candidate is at the multi-TeV mass scale, so that all new degrees of freedom are beyond the direct reach of the LHC. In second scotogenic setup, with broken U(1)_D symmetry the model may have LHC signatures or be relevant to astrophysical observations, depending on the scale of U(1)_D breaking. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.3183v2.pdf"}
{"id": "1310.4315", "abstract": "  We compare our pion production results with recent MiniBooNE data measured in mineral oil. Our total cross sections lie below experimental data for neutrino energies above 1 GeV. Differential cross sections show our model produces too few high energy pions in the forward direction as compared to data. The agreement with experiment improves by artificially removing pion final state interaction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.4315v1.pdf"}
{"id": "1310.4511", "abstract": "  Confluent with the single dimension of time, breach of time-reversal symmetry is usually perceived as a one-dimensional concept. In its ultimate realization–the one-way guiding device–it allows optical propagation in one direction, say +z, and forbids it in the opposite direction, -z. Hence, in studies of time-reversal asymmetry the mapping t↦ -t is naturally associated with z↦ -z. However, strongly non-reciprocal or one-way nano-scale threads can be used to weave meta-surfaces thus adding dimensions to this concept. In this new family of surfaces the aforementioned association cannot be made. An example of appropriate threads are the planar one-way particle chains based on the two-type rotation principle. The resulting surfaces–the meta-weaves–posses generalized non-reciprocity such as \"sector-way\" propagation, and offer new possibilities for controlling light in thin surfaces. We study several meta-weave designs and their asymmetries in the wave-vector space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.4511v3.pdf"}
{"id": "1310.4660", "abstract": "  Within the framework of Boltzmann transport equation with a Bhatnagar-Gross-Krook (BGK) collisional kernel, we study the wake potential induced by fast partons traveling through the high-temperature QCD plasma which is anisotropic in momentum-space. We calculate the dielectric response function of a collisional anisotropic quark-gluon plasma (AQGP) for small ξ (anisotropic parameter) limit. Using this, the wake potential for various combinations of the anisotropy parameter (ξ) and the collision rate (ν) is evaluated both for parallel and perpendicular directions of motion of the fast parton. It is seen that the inclusion of the collision modifies the wake potential and the amount as well as the nature of the potential depends on the combinations of ξ and ν ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.4660v1.pdf"}
{"id": "1310.4752", "abstract": "  The space-borne missions CoRoT and Kepler have opened a new era in stellar physics, especially for evolved stars, with precise asteroseismic measurements that help determine precise stellar parameters and perform ensemble astero seismology. This paper deals with the quality of the information that we can retrieve from the oscillations. It focusses on the conditions for obtaining the most accurate measurement of the radial and non-radial oscillation patterns. This accuracy is a prerequisite for making the best with asteroseismic data. From radial modes, we derive proxies of the stellar mass and radii with an unprecedented accuracy for field stars. For dozens of subgiants and thousands of red giants, the identification of mixed modes (corresponding to gravity waves propagating in the core coupled to pressure waves propagating in the envelope) indicates unambiguously their evolutionary status. As probes of the stellar core, these mixed modes also reveal the internal differential rotation and show the spinning down of the core rotation of stars ascending the red giant branch. A toy model of the coupling of waves constructing mixed modes is exposed, for illustrating many of their features. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.4752v1.pdf"}
{"id": "1310.5200", "abstract": "  We consider the one-dimensional scattering of two identical blocks of mass M that exchange energy and momentum via elastic collisions with an intermediary ball of mass m=α M. Initially, one block is incident upon the ball with the other block at rest. For α<1, the three objects will make multiple collisions with one another. In our analysis, we construct a Euclidean vector V_n whose components are proportional to the velocities of the objects. Energy-momentum conservation then requires a covariant recurrence relation for V_n that transforms like a pure rotation in three dimensions. The analytic solutions of the terminal velocities result in a remarkable prediction for values of α, in cases where the initial energy and momentum of the incident block are completely transferred to the scattered block. We call these values for α \"magic mass ratios.\" ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.5200v2.pdf"}
{"id": "1310.5970", "abstract": "  Quantum vacuum forces dictate the interaction between individual atoms and dielectric surfaces at nanoscale distances. For example, their large strengths typically overwhelm externally applied forces, which makes it challenging to controllably interface cold atoms with nearby nanophotonic systems. Here, we show that it is possible to tailor the vacuum forces themselves to provide strong trapping potentials. The trapping scheme takes advantage of the attractive ground state potential and adiabatic dressing with an excited state whose potential is engineered to be resonantly enhanced and repulsive. This procedure yields a strong metastable trap, with the fraction of excited state population scaling inversely with the quality factor of the resonance of the dielectric structure. We analyze realistic limitations to the trap lifetime and discuss possible applications that might emerge from the large trap depths and nanoscale confinement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.5970v1.pdf"}
{"id": "1310.5989", "abstract": "  Screening is one of the fundamental concepts in solid state physics. It has a great impact on the electronic properties of graphene where huge mobilities were observed in spite of the large concentration of charged impurities. While static screening has successfully explained DC mobilities, screening properties can be significantly changed at infrared or optical frequencies. In this paper we discuss the influence of dynamical screening on the optical absorption of graphene and other 2D electron systems like metallic monolayers. This research is motivated by recent experimental results which pointed out that graphene plasmon linewidths and optical scattering rates can be much larger than scattering rates determined by DC mobilities. Specifically we discuss a process where a photon incident on a graphene plane can excite a plasmon by scattering from an impurity, or surface optical phonon of the substrate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.5989v2.pdf"}
{"id": "1310.6681", "abstract": "  At measurements of gamma-radiation spectra from ultra-relativistic electrons in periodic structures, pileup of events in the calorimeter may cause significant deviation of the detector signal from the classically evaluated spectrum. That requires appropriate resummation of multiphoton contributions. We describe the resummation procedure for the photon spectral intensity and for the photon multiplicity spectrum, and apply it to the study of spectra of coherent radiation with an admixture of incoherent component. Impact of multiphoton effects on the shape of the radiation spectrum is investigated. The limit of high photon multiplicity for coherent radiation is explored. A method for reconstruction of the underlying single-photon spectrum from the multiphoton one is proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.6681v1.pdf"}
{"id": "1310.7019", "abstract": "  We simulate scanning probe imaging of the local density of states related to scattering Fermi level wave functions inside a resonant cavity. We calculate potential landscape within the cavity taking into account the Coulomb charge of the probe and its screening by deformation of the two-dimensional electron gas using the local density approximation. Approximation of the tip potential by a Lorentz function is discussed. The electron transfer problem is solved with a finite difference approach. We look for stable work points for the extraction of the local density of states from conductance maps. We find that conductance maps are highly correlated with the local density of states when the Fermi energy level enters into Fano resonance with states localized within the cavity. Generally outside resonances the correlation between the local density of states and conductance maps is low. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.7019v1.pdf"}
{"id": "1310.7283", "abstract": "  We consider the effect of contact interaction in a prototypical quantum spin Hall system of pseudo-spin-1/2 particles. A strong effective magnetic field with opposite directions for the two spin states restricts two-dimensional particle motion to the lowest Landau level. While interaction between same-spin particles leads to incompressible correlated states at fractional filling factors as known from the fractional quantum Hall effect, these states are destabilized by interactions between opposite spin particles. Exact results for two particles with opposite spin reveal a quasi-continuous spectrum of extended states with a large density of states at low energy. This has implications for the prospects of realizing the fractional quantum spin Hall effect in electronic or ultra-cold atom systems. Numerical diagonalization is used to extend the two-particle results to many bosonic particles and trapped systems. The interplay between an external trapping potential and spin-dependent interactions is shown to open up new possibilities for engineering exotic correlated many-particle states with ultra-cold atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.7283v2.pdf"}
{"id": "1311.0005", "abstract": "  We study ground-state properties in a hard-core Bose-Hubbard model on a layered triangular lattice. Combining cluster mean-field theory with the density matrix renormalization group method, we discuss the effect of the interlayer coupling on the supersolid states realized in a single layered model. By examining the distributions for the particle density and superfluid order parameter, the rich phase diagram of the system is obtained. We find that the supersolid states are widely stabilized at a commensurate filling, in contrast to the case of the single layered model. The nature of the supersolid states is also addressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.0005v1.pdf"}
{"id": "1311.0068", "abstract": "  The pre-neutron-emission mass distributions for reaction ^232Th(n, f) up to 60 MeV are systematically studied with an empirical fission potential model. The energy dependences of the peaks and valleys of the pre-neutron-emission mass distributions are described by the exponential expressions based on the newly measured data. The energy dependence of evaporation neutrons before scission, which plays a crucial role for the reasonable description of the mass distribution, is also considered. Both the double-humped and triple-humped shape of the measured pre-neutron-emission mass distributions for reaction ^232Th(n, f) are reasonably well reproduced at incident energies up to 60 MeV. The mass distributions at unmeasured energies and the critical energies at which the humped pre-neutron-emission mass distributions are transformed into each other are also predicted. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.0068v1.pdf"}
{"id": "1311.0791", "abstract": "  We show that, nonlinear optical processes of nanoparticles can be controlled by the presence of interactions with a molecule or a quantum dot. By choosing the appropriate level spacing for the quantum emitter, one can either suppress or enhance the nonlinear frequency conversion. We reveal the underlying mechanism for this effect, which is already observed in recent experiments: (i) Suppression occurs simply because transparency induced by Fano resonance does not allow an excitation at the converted frequency. (ii) Enhancement emerges since nonlinear process can be brought to resonance. Path interference effect cancels the nonresonant frequency terms. We demonstrate the underlying physics using a simplified model, and we show that the predictions of the model are in good agreement with the 3-dimensional boundary element method (MNPBEM toolbox) simulations. Here, we consider the second harmonic generation in a plasmonic converter as an example to demonstrate the control mechanism. The phenomenon is the semi-classical analog of nonlinearity enhancement via electromagnetically induced transparency. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.0791v4.pdf"}
{"id": "1311.2313", "abstract": "  Amorphous solids, and many disordered lattices, exhibit a remarkable qualitative and quantitative universality in their acoustic properties at temperature ≲ 3K. This phenomenon is attributed to the existence of tunneling two level systems (TTLSs), characterized by a homogenous density of states (DOS) at energies much lower than the disorder energy (≈ 0.1eV). Here we calculate numerically, from first principles, the DOS of KBr:CN glass, the archetypal disordered lattice showing universality. In contrast to the standard tunneling model, we find that the DOS diminishes abruptly at ≈ 3 K, and that tunneling states differ essentially by their symmetry under inversion. This structure of the TTLSs dictates the low temperature below which universality is observed, and the quantitative universality of the acoustic properties in glasses. Consequences to the properties of glasses at intermediate temperatures, as well as to the microscopic structure of amorphous solids, are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.2313v3.pdf"}
{"id": "1311.4506", "abstract": "  In neutrino oscillation experiments, neutrino interactions at the detector are simulated using event generators which attempt to reflect our understanding of nuclear physics. We study the impact of different neutrino interactions and nuclear models on the determination of neutrino oscillation parameters. We use two independent neutrino event generators, GENIE and GiBUU, and apply them to a setup with a conventional neutrino beam aiming at a water Čerenkov detector, for which only the QE-like sample is selected. Subsequently, we perform a fit to the oscillation parameters in the ν_μ disappearance channel. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.4506v3.pdf"}
{"id": "1311.4973", "abstract": "  We propose a new method of measuring the third and fourth moments of return distribution based on quadratic variation method when the return process is assumed to have zero drift. The realized third and fourth moments variations computed from high frequency return series are good approximations to corresponding actual moments of the return distribution. An investor holding an asset with skewed or fat-tailed distribution is able to hedge the tail risk by contracting the third or fourth moment swap under which the float leg of realized variation and the predetermined fixed leg are exchanged. Thus constructed portfolio follows more Gaussian-like distribution and hence the investor effectively hedge the tail risk. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.4973v1.pdf"}
{"id": "1311.5890", "abstract": "  The ability to post-select the outcomes of an experiment is a useful theoretical concept and experimental tool. In the context of weak measurements post-selection can lead to surprising results such as complex weak values outside the range of eigenvalues. Usually post-selection is realized by a projective measurement, which is hard to implement in ensemble systems such as NMR. We demonstrate the first experiment of a weak measurement with post-selection on an NMR quantum information processor. Our setup is used for measuring complex weak values and weak values outside the range of eigenvalues. The scheme for overcoming the problem of post-selection in an ensemble quantum computer is general and can be applied to any circuit-based implementation. This experiment paves the way for studying and exploiting post-selection and weak measurements in systems where projective measurements are hard to realize experimentally. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.5890v2.pdf"}
{"id": "1311.6778", "abstract": "  The optical and near-IR emission from some classes of supernovae (SNe), including Type IIn and possibly some super-luminous SNe, is likely powered by a collision between the SN ejecta and dense circumstellar material (CSM). We argue that for a range of CSM masses and their radii, a collisionless shock can form, allowing for efficient cosmic-ray (CR) acceleration. We show that pp collisions between these newly accelerated CRs and the CSM leads to not only gamma rays but also secondary electrons and positrons that radiate synchrotron photons in the high-frequency radio bands. Our estimates imply that various facilities including the Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) may observe such SNe at Gpc distances by followup observations in months-to-years, although the detectability strongly depends on the CSM density as well as observed frequency. Detecting this signal would give us a unique probe of CR acceleration at early times, and even non-detections can put interesting limits on the possibility of CR ion acceleration. Following our previous work, we also show that GeV gamma rays can escape from the system without severe attenuation, encouraging point-source and stacking analyses with Fermi. We provide recipes for diagnosing interaction-powered SN scenario with multi-messenger (neutrino and gamma-ray) observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.6778v2.pdf"}
{"id": "1311.7272", "abstract": "  An algorithm for imaginary time evolution of a fermionic projected entangled pair state (PEPS) with ancillas from infinite temperature down to a finite temperature state is presented. As a benchmark application, it is applied to spinless fermions hopping on a square lattice subject to p-wave pairing interactions. With a tiny bias it allows to evolve the system across a high-temperature continuous symmetry-breaking phase transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.7272v2.pdf"}
{"id": "1312.0230", "abstract": "  Given a locally consistent set of reduced density matrices, we construct approximate density matrices which are globally consistent with the local density matrices we started from when the trial density matrix has a tree structure. We employ the cavity method of statistical physics to find the optimal density matrix representation by slowly decreasing the temperature in an annealing algorithm, or by minimizing an approximate Bethe free energy depending on the reduced density matrices and some cavity messages originated from the Bethe approximation of the entropy. We obtain the classical Bethe expression for the entropy within a naive (mean-field) approximation of the cavity messages, which is expected to work well at high temperatures. In the next order of the approximation, we obtain another expression for the Bethe entropy depending only on the diagonal elements of the reduced density matrices. In principle, we can improve the entropy approximation by considering more accurate cavity messages in the Bethe approximation of the entropy. We compare the annealing algorithm and the naive approximation of the Bethe entropy with exact and approximate numerical simulations for small and large samples of the random transverse Ising model on random regular graphs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.0230v4.pdf"}
{"id": "1312.0570", "abstract": "  The standard approach to analyzing 16S tag sequence data, which relies on clustering reads by sequence similarity into Operational Taxonomic Units (OTUs), underexploits the accuracy of modern sequencing technology. We present a clustering-free approach to multi-sample Illumina datasets that can identify independent bacterial subpopulations regardless of the similarity of their 16S tag sequences. Using published data from a longitudinal time-series study of human tongue microbiota, we are able to resolve within standard 97", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.0570v2.pdf"}
{"id": "1312.2105", "abstract": "  In this paper we will look at the phenomenon of Microwave Amplification by Stimulated Emission of Radiation (a maser system). We begin by deriving amplification by stimulated emission using time-dependent perturbation theory, in which the perturbation provided by external radiation. When this perturbation is applied to an ensemble of particles exhibiting a population inversion, the result is stimulated microwave radiation. We will explore both unsaturated and saturated masers and compare their properties. By understanding their gain, as well as the effect of line broadening, astronomers are to identify astrophysical masers. By studying such masers, we gain new insight into poorly understood physical environments, particularly those around young and old stars, and compact stellar bodies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.2105v1.pdf"}
{"id": "1312.2215", "abstract": "  The onset of spiral structure in galaxies appears to occur between redshifts 1.4 and 1.8 when disks have developed a cool stellar component, rotation dominates over turbulent motions in the gas, and massive clumps become less frequent. During the transition from clumpy to spiral disks, two unusual types of spirals are found in the Hubble Ultra Deep Field that are massive, clumpy and irregular like their predecessor clumpy disks, yet spiral-like or sheared like their descendants. One type is “woolly” with massive clumpy arms all over the disk and is brighter than other disk galaxies at the same redshift, while another type has irregular multiple arms with high pitch angles, star formation knots and no inner symmetry like today's multiple-arm galaxies. The common types of spirals seen locally are also present in a redshift range around z 1, namely grand design with two symmetric arms, multiple arm with symmetry in the inner parts and several long, thin arms in the outer parts, and flocculent, with short, irregular and patchy arms that are mostly from star formation. Normal multiple arm galaxies are found only closer than z 0.6 in the UDF. Grand design galaxies extend furthest to z 1.8, presumably because interactions can drive a two-arm spiral in a disk that would otherwise have a more irregular structure. The difference between these types is understandable in terms of the usual stability parameters for gas and stars, and the ratio of the velocity dispersion to rotation speed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.2215v1.pdf"}
{"id": "1312.2943", "abstract": "  In this article we summarise on-going work on the so-called Gaia FGK Benchmark Stars. This work consists of the determination of their atmospheric parameters and of the construction of a high-resolution spectral library. The definition of such a set of reference stars has become crucial in the current era of large spectroscopic surveys. Only with homogeneous and well documented stellar parameters can one exploit these surveys consistently and understand the structure and history of the Milky Way and therefore other of galaxies in the Universe. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.2943v1.pdf"}
{"id": "1312.3483", "abstract": "  The AMS-02 experiment confirms the excess of positrons in cosmic rays (CRs) for energy above 10 GeV with respect to the secondary production of positrons in the interstellar medium. This is interpreted as evidence of the existence of a primary source of these particles. Possible candidates are dark matter or astrophysical sources. In this work we discuss the possible contribution due to pulsars and their nebulae. Our key assumption is that the primary spectrum of electrons and positrons at the source is the same of the well known photon spectrum observed from gamma-rays telescopes. Using a diffusion model in the Galaxy we propagate the source spectra up to the Solar System. We compare our results with the recent experiments and with the LIS model ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.3483v1.pdf"}
{"id": "1312.3655", "abstract": "  When a harmonic oscillator is under the influence of a Gaussian process such as linear damping, parametric gain, and linear coupling to a thermal environment, its coherent states are transformed into states with Gaussian Wigner function. Qubit states can be encoded in the |0> and |1> Fock states of a quantum harmonic oscillator, and it is relevant to know the fidelity of the output qubit state after a Gaussian process on the oscillator. In this paper we present a general expression for the average qubit fidelity in terms of the first and second moments of the output from input coherent states subjected to Gaussian processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.3655v1.pdf"}
{"id": "1312.3726", "abstract": "  A direct WIMP (Weakly Interacting Massive Particle) detector with a neutron veto system is designed to better reject neutrons. An experimental configuration is studied in the present paper: a WIMP detectors with CsI(Na) target is placed inside a reactor neutrino detector. The neutrino detector is used as a neutron veto device. The neutron background for the experimental design has been estimated using the Geant4 simulation. The results show that the neutron background can decrease to O(0.01) events per year per tonne of CsI(Na). We calculate the sensitivity to spin-independent WIMP-nucleon elastic scattering. An exposure of one tonne × year could reach a cross-section of about 3×10^-11 pb. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.3726v2.pdf"}
{"id": "1312.4011", "abstract": "  Synthetic spin-orbit coupling in ultracold atomic gases can be taken to extremes rarely found in solids. We study a two dimensional Hubbard model of bosons in an optical lattice in the presence of spin-orbit coupling strong enough to drive direct transitions from Mott insulators to superfluids. Here we find phase-modulated superfluids with finite momentum that are generated entirely by spin-orbit coupling. We investigate the rich phase patterns of the superfluids, which may be directly probed using time-of-flight imaging of the spin-dependent momentum distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.4011v2.pdf"}
{"id": "1312.4231", "abstract": "  Attribute reduction is a basic issue in knowledge representation and data mining. Rough sets provide a theoretical foundation for the issue. Matroids generalized from matrices have been widely used in many fields, particularly greedy algorithm design, which plays an important role in attribute reduction. Therefore, it is meaningful to combine matroids with rough sets to solve the optimization problems. In this paper, we introduce an existing algebraic structure called dependence space to study the reduction problem in terms of matroids. First, a dependence space of matroids is constructed. Second, the characterizations for the space such as consistent sets and reducts are studied through matroids. Finally, we investigate matroids by the means of the space and present two expressions for their bases. In a word, this paper provides new approaches to study attribute reduction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.4231v2.pdf"}
{"id": "1312.4362", "abstract": "  The effect of magnetic field on the structure properties of hot spin polarized strange quark stars has been investigated. For this purpose, we use the MIT bag model with a density dependent bag constant to calculate the thermodynamic properties of spin polarized strange quark matter such as energy and equation of state. We see that the energy and equation of state of strange quark matter changes significantly in a strong magnetic field. Finally, using our equation of state, we compute the structure of spin polarized strange quark star at different temperatures and magnetic fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.4362v1.pdf"}
{"id": "1312.4604", "abstract": "  We summarize the recent theoretical and numerical works on spin turbulence (ST) in spin-1 spinor Bose-Einstein condensates. When the system is excited from the ground state, it goes through hy- drodynamic instability to ST in which the spin density vector has various disordered direction. The properties of ST depend on whether the spin-dependent interaction is ferromagnetic or antiferro- magnetic. ST has some characteristics different from other kinds of turbulence in quantum fluids. Firstly, the spectrum of the spin-dependent interaction energy exhibits the characteristic power law different from the usual Kolmogorov -5/3 law. Secondly, ST can show the spin-glass-like behavior; the spin density vectors are spatially random but temporally frozen. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.4604v1.pdf"}
{"id": "1312.4733", "abstract": "  We selected and studied 180 pairs with dV < 800 km/s and Dp < 60 kpc containing Markarian (MRK) galaxies to investigate the dependence of galaxies' integral parameters, star-formation (SF) and active galactic nuclei (AGN) properties on kinematics of pairs, their structure and large-scale environments. Projected radial separation Dp and perturbation level P are better measures of interaction strength than dV. The latter correlates with the density of large-scale environment and with the morphologies of galaxies. Both galaxies in a pair are of the same nature, the only difference is that MRK galaxies are usually righter than their neighbors. Specific star formation rates (SSFR) of galaxies in pairs with smaller Dp or dV is in average 0.5 dex higher than that of galaxies in pairs with larger Dp or dV. Closeness of a neighbor with the same and later morphological type increases the SSFR, while earlier-type neighbors do not increase SSFR. Major interactions/mergers trigger SF and AGN more effectively than minor ones. The fraction of AGNs is higher in more perturbed pairs and pairs with smaller Dp. AGNs typically are in stronger interacting systems than star-forming and passive galaxies. There are correlations of both SSFRs and spectral properties of nuclei between pair members. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.4733v2.pdf"}
{"id": "1312.5311", "abstract": "  We present new X-ray (Chandra) and radio (JVLA) observations of the nearby cluster Abell 3744. It hosts two prominent radio galaxies with powers in the range critical for radio-mode feedback. The radio emission from these galaxies terminates in buoyant tendrils reaching the cluster's outer edge, and the radio-emitting plasma clearly influences the cluster's X-ray-emitting atmosphere. The cluster's average gas temperature, of kT=3.5 keV, is high for its bolometric luminosity of 3.2 ×10^43 ergs s^-1, but the 100 kpc-scale cavity carved out by radio-emitting plasma shows evidence of less than 2 per cent of the excess enthalpy. We suggest instead that a high-velocity encounter with a galaxy group is responsible for dispersing and increasing the entropy of the gas in this non-cool-core cluster. We see no evidence for shocks, or established isobaric gas motions (sloshing), but there is much sub-structure associated with a dynamically active central region that encompasses the brightest radio emission. Gas heating is evident in directions perpendicular to the inferred line of encounter between the infalling group and cluster. The radio-emitting tendrils run along boundaries between gas of different temperature, apparently lubricating the gas flows and inhibiting heat transfer. The first stages of the encounter may have helped trigger the radio galaxies into their current phase of activity, where we see X-rays from the nuclei, jets, and hotspots. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.5311v1.pdf"}
{"id": "1312.5480", "abstract": "  A radio tomographic imaging (RTI) system uses the received signal strength (RSS) measured by RF sensors in a static wireless network to localize people in the deployment area, without having them to carry or wear an electronic device. This paper addresses the fact that small-scale changes in the position and orientation of the antenna of each RF sensor can dramatically affect imaging and localization performance of an RTI system. However, the best placement for a sensor is unknown at the time of deployment. Improving performance in a deployed RTI system requires the deployer to iteratively \"guess-and-retest\", i.e., pick a sensor to move and then re-run a calibration experiment to determine if the localization performance had improved or degraded. We present an RTI system of servo-nodes, RF sensors equipped with servo motors which autonomously \"dial it in\", i.e., change position and orientation to optimize the RSS on links of the network. By doing so, the localization accuracy of the RTI system is quickly improved, without requiring any calibration experiment from the deployer. Experiments conducted in three indoor environments demonstrate that the servo-nodes system reduces localization error on average by 32", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.5480v1.pdf"}
{"id": "1312.5613", "abstract": "  The evaporation residue of Barium isotopes are investigated in a microscopic study using relativistic mean field theory. The investigation includes the isotopes of Barium from the valley of stability to exotic proton-rich region. The ground as well as neck configurations for these nuclei are generated from their total nucleonic density distributions of the corresponding state. We have estimated the constituents (number of nucleons) in the elongated neck region of the fission state. We found the α-particle as the constituent of neck of Ba-isotopes, referred to as the evaporated residue in heavy-ion reaction studies. A strong correlation between the neutron and proton is observed throughout the isotopic chain. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.5613v1.pdf"}
{"id": "1312.6804", "abstract": "  I show the equivalence between a model of financial contagion and the threshold model of global cascades proposed by Watts (2002). The model financial network comprises banks that hold risky external assets as well as interbank assets. It is shown that a simple threshold model can replicate the size and the frequency of financial contagion without using information about individual balance sheets. Keywords: financial network, cascades, financial contagion, systemic risk. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.6804v2.pdf"}
{"id": "1312.6985", "abstract": "  We investigate the in-plane spin relaxation of electrons due to the D'yakonov-Perel' and Elliot-Yafet mechanisms including the intra- and inter-valley processes in monolayer MoS_2. We construct the effective Hamiltonian for the conduction band using the Löwdin partition method from the anisotropic two-band Hamiltonian with the intrinsic spin-orbit coupling of the conduction band included. The spin-orbit coupling of the conduction band induces the intra- and inter-valley D'yakonov-Perel' spin relaxation. In addition, the Elliot-Yafet spin relaxation also takes place due to the interband spin mixing. We find that the D'yakonov-Perel' mechanism dominates the in-plane spin relaxation. In the framework of this mechanism, the intravalley process is shown to play a more important role at low temperature whereas the intervalley one becomes more important at high temperature. At the temperature in between, the leading process of the in-plane spin relaxation changes from the intervalley to intravalley one as the electron density increases. Moreover, we find that the intravalley process is dominated by the electron-electron Coulomb scattering even with high impurity density since the dominant term in the spin-orbit coupling is isotropic, which does not lead to the spin relaxation together with the electron-impurity scattering. This is very different from the previous studies in semiconductors and graphene. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.6985v1.pdf"}
{"id": "1401.0276", "abstract": "  Whether or not space-time is fundamentally discrete is of central importance for the development of the theory of quantum gravity. If the fundamental description of space-time is discrete, typically represented in terms of a graph or network, then the apparent smoothness of geometry on large scales should be imperfect – it should have defects. Here, we review a model for space-time defects and summarize the constraints on the prevalence of these defects that can be derived from observation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.0276v1.pdf"}
{"id": "1401.0290", "abstract": "  We propose here a first-principles, parameter free, real space method for the study of disordered extended defects in solids. We shall illustrate the power of the technique with an application to graphene sheets with randomly placed Stone-Wales defects and shall examine the signature of such random defects on the density of states as a function of their concentration. The technique is general enough to be applied to a whole class of systems with lattice translational symmetry broken not only locally but by extended defects and defect clusters. The real space approach will allow us to distinguish signatures of specific defects and defect clusters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.0290v2.pdf"}
{"id": "1401.1228", "abstract": "  There is an ever-growing need for predictive models for the elasto-viscoplastic deformation of solids. Our goal in this paper is to incorporate recently developed out-of-equilibrium statistical concepts into a thermodynamically consistent, finite-deformation, continuum framework for deforming amorphous solids. The basic premise is that the configurational degrees of freedom of the material — the part of the internal energy/entropy that corresponds to mechanically stable microscopic configurations — are characterized by a configurational temperature that might differ from that of the vibrational degrees of freedom, which equilibrate rapidly with an external heat bath. This results in an approximate internal energy decomposition into weakly interacting configurational and vibrational subsystems, which exchange energy following a Fourier-like law, leading to a thermomechanical framework permitting two well-defined temperatures. In this framework, internal variables that carry information about the state of the material equilibrate with the configurational subsystem, are explicitly associated with energy and entropy of their own, and couple to a viscoplastic flow rule. The coefficients that determine the rate of flow of entropy and heat between different internal systems are proposed to explicitly depend on the rate of irreversible deformation. As an application of this framework, we discuss two constitutive models for the response of glassy materials, a simple phenomenological model and a model related to the concept of Shear-Transformation-Zones as the basis for internal variables. The models account for several salient features of glassy deformation phenomenology. Directions for future investigation are briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.1228v1.pdf"}
{"id": "1401.2564", "abstract": "  We report on constraints on the lifetime of decaying gravitino dark matter in models with bilinear R-parity violation derived from observations of cosmic-ray antiprotons with the PAMELA experiment. Performing a scan over a viable set of cosmic-ray propagation parameters we find lower limits ranging from 8× 10^28s to 6× 10^28s for gravitino masses from roughly 100 GeV to 10 TeV. Comparing these limits to constraints derived from gamma-ray and neutrino observations we conclude that the presented antiproton limits are currently the strongest and most robust limits on the gravitino lifetime in the considered mass range. These constraints correspond to upper limits on the size of the bilinear R-parity breaking parameter in the range of 10^-8 to 8× 10^-13. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.2564v1.pdf"}
{"id": "1401.3279", "abstract": "  This work presents a general formalism to analyze a generic bulk scalar field in a multiple warped extra-dimensional model with arbitrary number of extra dimensions. The Kaluza-Klein mass modes along with the self-interaction couplings are determined and the possibility of having lowest lying KK mode masses near TeV scale are discussed. Also some numerical values for low-lying KK modes has been presented showing explicit localization around TeV scale. It is argued that the appearance of large number of closely spaced KK modes with enhanced coupling may prompt possible new signatures in collider physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.3279v2.pdf"}
{"id": "1401.3663", "abstract": "  We show that the geometry of the Wilson lines, entering the operator definition of the transverse-momentum dependent parton distributions and that of the soft factor, follows from the kinematics of the underlying physical process in conjunction with the gauge invariance of the QCD Lagrangian. We demonstrate our method in terms of concrete examples and determine the paths of the associated Wilson lines. The validation of the factorization theorem in our approach is postponed to future work. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.3663v2.pdf"}
{"id": "1401.4918", "abstract": "  We present a numerical method for calculating piecewise smooth spectral functions of correlated quantum systems in the thermodynamic limit from the spectra of finite systems computed using the dynamical or correction-vector density-matrix renormalization group method. The key idea is to consider this problem as a blind deconvolution with an unknown kernel which causes both a broadening and finite-size corrections of the spectrum. In practice, the method reduces to a least-square optimization under non-linear constraints which enforce the positivity and piecewise smoothness of spectral functions. The method is demonstrated on the single-particle density of states of one-dimensional paramagnetic Mott insulators represented by the half-filled Hubbard model on an open chain. Our results confirm that the density of states has a step-like shape but no square-root singularity at the spectrum onset. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.4918v2.pdf"}
{"id": "1401.4926", "abstract": "  We propose a multilevel quantum heat engine with a working medium described by a generalized Rabi model which consists of a two-level system coupled to a single mode bosonic field. The model is constructed to be a continuum limit of a quantum biological description of light harvesting complexes so that it can amplify quantum coherence by a mechanism which is a quantum analog of classical Huygen's clocks. The engine operates in quantum Otto cycle where the working medium is coupled to classical heat baths in the isochoric processes of the four stroke cycle; while either the coupling strength or the resonance frequency is changed in the adiabatic stages. We found that such an engine can produce work with an efficiency close to Carnot bound when it operates at low temperatures and in the ultrastrong coupling regime. Interplay of quantum coherence and quantum correlations on the engine performance is discussed in terms of second order coherence, quantum mutual information and logarithmic negativity of entanglement. We point out that the proposed quantum Otto engine can be implemented experimentally with the modern circuit quantum electrodynamic systems where flux qubits can be coupled ultrastrongly to superconducting transmission line resonators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.4926v2.pdf"}
{"id": "1401.5192", "abstract": "  Motivated by the InSb nanowire superconductor system, we investigate a system where one-dimensional topological superconductors are placed in parallel. It would be simulated well by a ladder of the Kitaev chains. The system undergoes multiple topological phase transitions, where the number of Majorana fermions changes as a function of the interchain superconducting pairings. We analytically determine the topological phase diagram by explicitly calculating the topological number and the band structure. They show even-odd effects with respect to the number of legs of the ladder. When the relative phase between the inter- and intrachain superconducting pairings is 0 or π, the system belongs to the class BDI characterized by the ℤ index, and otherwise it belongs to the class D characterized by the ℤ_2 index. This topological class change would be caused by applying the Josephson current or an external magnetic field, and could be observed by measuring the zero-bias differential conductance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5192v4.pdf"}
{"id": "1401.5475", "abstract": "  We suggest that the hysteretic cycle of black hole state transitions arises from two established properties of accretion disks: the increase in turbulent stress in disks threaded by a net magnetic field and the ability of thick (but not thin) disks to advect such a field radially. During quiescence, magnetic field loops are generated by the magnetorotational instability at the interface between the inner hot flow and outer thin disk. Vertical flux is advected into and accumulates stochastically within the inner flow, where it stimulates the turbulence so that α∼ 1. The transition to a geometrically thin inner disk occurs when L ∼α^2 L_ Edd∼ L_ Edd, and the first \"thin\" disk to form is itself moderately thick, strongly magnetized, and able to advect field inward. These properties favor episodic jet production. As the accretion rate declines magnetic flux escapes, α decreases to α∼ 0.01 - 0.1, and a hot inner flow is not re-established until L ≪ L_ Edd. We discuss possible observational consequences of our scenario. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5475v1.pdf"}
{"id": "1401.5645", "abstract": "  We present the C III λ977, O VI λλ1032, 1038 and N IV] λ1486 emission line maps of the Cygnus Loop, obtained with the newly processed data of Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR; also known as FIMS) mission. In addition, the Si IV+O IV] line complexes around 1400 Å are resolved into two separate emission lines, whose intensity demonstrates a relatively high Si IV region predicted in the previous study. The morphological similarity between the O VI and X-ray images, as well as a comparison of the O VI intensity with the value expected from the X-ray results, indicates that large portions of the observed O VI emissions could be produced from X-ray emitting gas. Comparisons of the far-ultraviolet (FUV) images with the optical and H I 21 cm images, reveal spatial variations of shock-velocity populations and high FUV extinction in the direction of a previously identified H I cloud. By calculating the FUV line ratios for several subregions of the Cygnus Loop, we investigate the spatial variation of the population of radiative shock velocities; and the effects of resonance scattering, X-ray emitting gas, and non-radiative shocks. The FUV and X-ray luminosity comparisons between the Cygnus Loop and the Vela supernova remnant suggest that the fraction of shocks in the early evolutionary stages is much larger in the Cygnus Loop. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5645v1.pdf"}
{"id": "1401.5758", "abstract": "  We present AGNfitter: a Markov Chain Monte Carlo algorithm developed to fit the spectral energy distributions (SEDs) of active galactic nuclei (AGN) with different physical models of AGN components. This code is well suited to determine in a robust way multiple parameters and their uncertainties, which quantify the physical processes responsible for the panchromatic nature of active galaxies and quasars. We describe the technicalities of the code and test its capabilities in the context of X-ray selected obscured AGN using multiwavelength data from the XMM-COSMOS survey. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5758v1.pdf"}
{"id": "1401.5879", "abstract": "  A double-crystal diamond (111) monochromator recently implemented at the Linac Coherent Light Source (LCLS) enables splitting of the primary X-ray beam into a pink (transmitted) and a monochromatic (reflected) branch. The first monochromator crystal with a thickness of 100 um provides sufficient X-ray transmittance to enable simultaneous operation of two beamlines. Here we report on the design, fabrication, and X-ray characterization of the first and second (300-um-thick) crystals utilized in the monochromator and the optical assemblies holding these crystals. Each crystal plate has a region of about 5 X 2 mm2 with low defect concentration, sufficient for use in X-ray optics at the LCLS. The optical assemblies holding the crystals were designed to provide mounting on a rigid substrate and to minimize mounting-induced crystal strain. The induced strain was evaluated using double-crystal X-ray topography and was found to be small over the 5 X 2 mm2 working regions of the crystals. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5879v1.pdf"}
{"id": "1401.6669", "abstract": "  This paper describes a model for nonlinear acoustic wave propagation through absorbing and weakly dispersive media, and its numerical solution by means of finite differences in time domain method (FDTD). The attenuation is based on multiple relaxation processes, and provides frequency dependent absorption and dispersion without using computational expensive convolutional operators. In this way, by using an optimization algorithm the coefficients for the relaxation processes can be obtained in order to fit a frequency power law that agrees the experimentally measured attenuation data for heterogeneous media over the typical frequency range for ultrasound medical applications. Our results show that two relaxation processes are enough to fit attenuation data for most soft tissues in this frequency range including the fundamental and the first ten harmonics. Furthermore, this model can fit experimental attenuation data that do not follow exactly a frequency power law over the frequency range of interest. The main advantage of the proposed method is that only one auxiliary field per relaxation process is needed, which implies less computational resources compared with time-domain fractional derivatives solvers based on convolutional operators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.6669v1.pdf"}
{"id": "1401.6758", "abstract": "  We investigate the dynamics and afterglow light curves of gamma-ray burst (GRB) blast waves that encounter various density structures (such as bumps, voids, or steps) in the surrounding ambient medium. We present and explain the characteristic response features that each type of density structures in the medium leaves on the forward shock (FS) and reverse shock (RS) dynamics, for blast waves with either a long-lived or short-lived RS. We show that, when the ambient medium density drops, the blast waves exhibit in some cases a period of an actual acceleration (even during their deceleration stage), due to adiabatic cooling of blast waves. Comparing numerical examples that have different shapes of bumps or voids, we propose a number of consistency tests that correct modeling of blast waves needs to satisfy. Our model results successfully pass these tests. Employing a Lagrangian description of blast waves, we perform a sophisticated calculation of afterglow emission. We show that, as a response to density structures in the ambient medium, the RS light curves produce more significant variations than the FS light curves. Some observed features (such as re-brightenings, dips, or slow wiggles) can be more easily explained within the RS model. We also discuss on the origin of these different features imprinted on the FS and RS light curves. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.6758v2.pdf"}
{"id": "1401.6886", "abstract": "  The comparison studies of theoretical approaches to the description of the Casimir interaction in layered systems including graphene is performed. It is shown that at zero temperature the approach using the polarization tensor leads to the same results as the approach using the longitudinal density-density correlation function of graphene. An explicit expression for the zero-temperature transverse density-density correlation function of graphene is provided. We further show that the computational results for the Casimir free energy of graphene-graphene and graphene-Au plate interactions at room temperature, obtained using the temperature-dependent polarization tensor, deviate significantly from those using the longitudinal density-density correlation function defined at zero temperature. We derive both the longitudinal and transverse density-density correlation functions of graphene at nonzero temperature. The Casimir free energy in layered structures including graphene, computed using the temperature-dependent correlation functions, is exactly equal to that found using the polarization tensor. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.6886v2.pdf"}
{"id": "1401.7348", "abstract": "  We have investigated the mass accretion rate implied by published surface abundances of Si and C in the white dwarf component of the 3.62 hr period pre-cataclysmic binary and planet host candidate QS Vir (DA+M2-4). Diffusion timescales for gravitational settling imply Ṁ∼ 10^-16M_⊙ yr^-1 for the 1999 epoch of the observations, which is three orders of magnitude lower than measured from a 2006 XMM-Newton observation. This is the first time that large accretion rate variations have been seen in a detached pre-CV. A third body in a 14 yr eccentric orbit suggested in a recent eclipse timing study is too distant to perturb the central binary sufficiently to influence accretion. A hypothetical coronal mass ejection just prior to the XMM-Newton observation might explain the higher accretion rate, but the implied size and frequency of such events appear too great. We suggest accretion is most likely modulated by a magnetic cycle on the secondary acting as a wind \"accretion switch\", a mechanism that can be tested by X-ray and ultraviolet monitoring. If so, QS Vir and similar pre-CVs could provide powerful insights into hitherto inscrutable cataclysmic variable and M dwarf magnetospheres, and mass and angular momentum loss rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.7348v1.pdf"}
{"id": "1401.7602", "abstract": "  We present a generative probabilistic model for a tidal stream and demonstrate how this model is used to constrain the Galactic potential. The model takes advantage of the simple structure of a stream in angle and frequency space for the correct potential. We investigate how the method performs on full 6D mock stream data, and mock data with outliers included. As currently formulated the technique is computationally costly when applied to data with large observational errors, but we describe several modifications that promise to make the technique computationally tractable. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.7602v2.pdf"}
{"id": "1402.0291", "abstract": "  The bright gamma-ray quasar 4C +55.17 is a distant source (z = 0.896) with a hard spectrum at GeV energies as observed by the Large Area Telescope (LAT) on board the Fermi satellite. This source is identified as a good source candidate for very-high-energy (VHE; > 30 GeV) gamma rays. In general VHE gamma rays from distant sources provide an unique opportunity to study the extragalactic background light (EBL) and underlying astrophysics. The flux intensity of this source in the VHE range is investigated. Then, constraints on the EBL are derived from the attenuation of gamma-ray photons coming from the distant blazar. We searched for a gamma-ray signal from this object using the 35-hour observations taken by the MAGIC telescopes between November 2010 and January 2011. No significant VHE gamma-ray signal was detected. We computed the upper limits of the integrated gamma-ray flux at 95% confidence level of 9.4 × 10^-12 cm^-2 s^-1 and 2.5 × 10^-12 cm^-2 s^-1 above 100 GeV and 200 GeV, respectively. The differential upper limits in four energy bins in the range from 80 GeV to 500 GeV are also derived. The upper limits are consistent with the attenuation predicted by low-flux EBL models on the assumption of a simple power-law spectrum extrapolated from LAT data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.0291v1.pdf"}
{"id": "1402.0873", "abstract": "  We propose to detect quadrupole interactions of neutral ultra-cold atoms via their induced mean-field shift. We consider a Mott insulator state of spin-polarized atoms in a two-dimensional optical square lattice. The quadrupole moments of the atoms are aligned by an external magnetic field. As the alignment angle is varied, the mean-field shift shows a characteristic angular dependence, which constitutes the defining signature of the quadrupole interaction. For the ^3P_2 states of Yb and Sr atoms, we find a frequency shift of the order of tens of Hertz, which can be realistically detected in experiment with current technology. We compare our results to the mean-field shift of a spin-polarized quasi-2D Fermi gas in continuum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.0873v1.pdf"}
{"id": "1402.1179", "abstract": "  Imaging Atmosphere Cherenkov Telescopes (IACT) are arrays of very large optical telescopes that are well-suited for rapid photometry of bright sources. I investigate their potential in observing stellar occultations by small objects in the outer Solar System, Transjovian Objects (TJOs). These occultations cast diffraction patterns on the Earth. Current IACT arrays are capable of detecting objects smaller than 100 metres in radius in the Kuiper Belt and 1 km radius out to 5000 AU. The future Cherenkov Telescope Array (CTA) will have even greater capabilities. Because the arrays include several telescopes, they can potentially measure the speeds of TJOs without degeneracies, and the sizes of the TJOs and background stars. I estimate the achievable precision using a Fisher matrix analysis. With CTA, the precisions of these parameter estimations will be as good as a few percent. I consider how often detectable occultations occur by members of different TJO populations, including Centaurs, Kuiper Belt Objects (KBOs), Oort cloud objects, and satellites and Trojans of Uranus and Neptune. The great sensitivity of IACT arrays means that they likely detect KBO occultations once every O(10) hours when looking near the ecliptic. IACTs can also set useful limits on many other TJO populations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.1179v2.pdf"}
{"id": "1402.3066", "abstract": "  The Logic of Proofs, LP, and its successor, Justification Logic, is a refinement of the modal logic approach to epistemology in which proofs/justifications are taken into account. In 2000 Kuznets showed that satisfiability for LP is in the second level of the polynomial hierarchy, a result which has been successfully repeated for all other one-agent justification logics whose complexity is known.   We introduce a family of multi-agent justification logics with interactions between the agents' justifications, by extending and generalizing the two-agent versions of the Logic of Proofs introduced by Yavorskaya in 2008. Known concepts and tools from the single-agent justification setting are adjusted for this multiple agent case. We present tableau rules and some preliminary complexity results. In several cases the satisfiability problem for these logics remains in the second level of the polynomial hierarchy, while for others it is PSPACE or EXP-hard. Furthermore, this problem becomes PSPACE-hard even for certain two-agent logics, while there are EXP-hard logics of three agents. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.3066v2.pdf"}
{"id": "1402.4543", "abstract": "  This paper provides a solution to a critical issue in large-scale Multi-User Multiple-Input Multiple-Output (MU-MIMO) communication systems: how to estimate the Signal-to-Interference-plus-Noise-Ratios (SINRs) and their expectations in MU-MIMO mode at the Base Station (BS) side when only the Channel Quality Information (CQI) in Single-User MIMO (SU-MIMO) mode and non-ideal Channel State Information (CSI) are known? A solution to this problem would be very beneficial for the BS to predict the capacity of MU-MIMO and choose the proper modulation and channel coding for MU-MIMO. To that end, this paper derives a normalized volume formula of a hyperball based on the probability density function of the canonical angle between any two points in a complex Grassmann manifold, and shows that this formula provides a solution to the aforementioned issue. It enables the capability of a BS to predict the capacity loss due to non-ideal CSI, group users in MU-MIMO mode, choose the proper modulation and channel coding, and adaptively switch between SU-MIMO and MU-MIMO modes, as well as between Conjugate Beamforming (CB) and Zero-Forcing (ZF) precoding. Numerical results are provided to verify the validity and accuracy of the solution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.4543v1.pdf"}
{"id": "1403.0498", "abstract": "  We extend the taming techniques for explicit Euler approximations of stochastic differential equations (SDEs) driven by Lévy noise with super-linearly growing drift coefficients. Strong convergence results are presented for the case of locally Lipschitz coefficients. Moreover, rate of convergence results are obtained in agreement with classical literature when the local Lipschitz continuity assumptions are replaced by global and, in addition, the drift coefficients satisfy polynomial Lipschitz continuity. Finally, we further extend these techniques to the case of delay equations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.0498v2.pdf"}
{"id": "1403.0800", "abstract": "  A suffix tree is able to efficiently locate a pattern in an indexed string, but not in general the most recent copy of the pattern in an online stream, which is desirable in some applications. We study the most general version of the problem of locating a most recent match: supporting queries for arbitrary patterns, at each step of processing an online stream. We present augmentations to Ukkonen's suffix tree construction algorithm for optimal-time queries, maintaining indexing time within a logarithmic factor in the size of the indexed string. We show that the algorithm is applicable to sliding-window indexing, and sketch a possible optimization for use in the special case of Lempel-Ziv compression. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.0800v3.pdf"}
{"id": "1403.0953", "abstract": "  A scheme is proposed to construct integer and fractional topological quantum states of fermions in two spatial dimensions. We devise models for such states by coupling wires of non-chiral Luttinger liquids of electrons, that are arranged in a periodic array. Which inter-wire couplings are allowed is dictated by symmetry and the compatibility criterion that they can simultaneously acquire a finite expectation value, opening a spectral gap between the ground state(s) and all excited states in the bulk. First, with these criteria at hand, we reproduce the tenfold classification table of integer topological insulators, where their stability against interactions becomes immediately transparent in the Luttinger liquid description. Second, we construct an example of a strongly interacting fermionic topological phase of matter with short-range entanglement that lies outside of the tenfold classification. Third, we expand the table to long-range entangled topological phases with intrinsic topological order and fractional excitations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.0953v3.pdf"}
{"id": "1403.0956", "abstract": "  The observations of jet breaks in the afterglows of short gamma-ray bursts (SGRBs) indicate that the jet has a small opening angle of < 10. The collimation mechanism of the jet is a longstanding theoretical problem. We numerically analyze the jet propagation in the material ejected by double neutron star merger, and demonstrate that if the ejecta mass is > 10^-2 M_sun, the jet is well confined by the cocoon and emerges from the ejecta with the required collimation angle. Our results also suggest that there are some populations of choked (failed) SGRBs or low-luminous new types of event. By constructing a model for SGRB 130603B, which is associated with the first kilonova/macronova can- didate, we infer that the equation-of-state of neutron stars would be soft enough to provide sufficient ejecta to collimate the jet, if this event was associated with a double neutron star merger. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.0956v1.pdf"}
{"id": "1403.1326", "abstract": "  We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path ℓ is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than ℓ, even when the surface is fairly smooth, 5-10 nm rms, and the peak thermal wavelength is 0.6 μm. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order ℓ, the conductance is dominated by ballistic transport and is effectively set by the beam area. We have demonstrated a uniformity of ±8", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.1326v1.pdf"}
{"id": "1403.1676", "abstract": "  We present a study of site and bond percolation on periodic lattices with (on average) fewer than three nearest neighbors per site. We have studied this issue in two contexts: By simulating oxides with a mixture of 2-coordinated and higher-coordinated sites, and by mapping site-bond percolation results onto a site model with mixed coordination number. Our results show that a conjectured power-law relationship between coordination number and site percolation threshold holds approximately if the coordination number is defined as the average number of connections available between high-coordinated sites, and suggest that the conjectured power-law relationship reflects a real phenomenon requiring further study. The solution may be to modify the power-law relationship to be an implicit formula for percolation threshold, one that takes into account aspects of the lattice beyond spatial dimension and average coordination number. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.1676v1.pdf"}
{"id": "1403.1779", "abstract": "  We analyze a 1-d ring structure composed of many two-level systems, in the limit where only one excitation is present. The two-level systems are coupled to a common environment, where the excitation can be lost, which induces super and subradiant behavior, an example of cooperative quantum coherent effect. We consider time-independent random fluctuations of the excitation energies. This static disorder, also called inhomogeneous broadening in literature, induces Anderson localization and is able to quench Superradiance. We identify two different regimes: i) weak opening, in which Superradiance is quenched at the same critical disorder at which the states of the closed system localize; ii) strong opening, with a critical disorder strength proportional to both the system size and the degree of opening, displaying robustness of cooperativity to disorder. Relevance to photosynthetic complexes is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.1779v3.pdf"}
{"id": "1403.2389", "abstract": "  In a recent contribution, Bahl & Baumgardt investigated the incidence of planar alignments of satellite galaxies in the Millennium-II simulation, and concluded that vast thin planes of dwarf galaxies, similar to that observed in the Andromeda galaxy (M31), occur frequently by chance in Λ-Cold Dark Matter cosmology. However, their analysis did not capture the essential fact that the observed alignment is simultaneously radially extended, yet thin, and kinematically unusual. With the caveat that the Millennium-II simulation may not have sufficient mass resolution to identify confidently simulacra of low-luminosity dwarf galaxies, we re-examine that simulation for planar structures, using the same method as employed by Ibata et al. (2013) on the real M31 satellites. We find that 0.04% of host galaxies display satellite alignments that are at least as extreme as the observations, when we consider their extent, thickness and number of members rotating in the same sense. We further investigate the angular momentum properties of the co-planar satellites, and find that the median of the specific angular momentum derived from the line of sight velocities in the real M31 structure (1.3×10^4 km/s kpc) is very high compared to systems drawn from the simulations. This analysis confirms that it is highly unlikely that the observed structure around the Andromeda galaxy is due to a chance occurrence. Interestingly, the few extreme systems that are similar to M31 arise from the accretion of a massive sub-halo with its own spatially-concentrated entourage of orphan satellites. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.2389v1.pdf"}
{"id": "1403.2744", "abstract": "  The essential quantum many-body physics of an ultracold quantum gas relies on the single-particle Green's functions. We demonstrate that it can be extracted by the spectrum of electromagnetically induced transparency (EIT). The single-particle Green's function can be reconstructed by the measurements of frequency moments in EIT spectroscopy. This optical measurement provides an efficient and nondestructive method to reveal the many-body properties, and we propose an experimental setup to realize it. Finite temperature and finite size effects are discussed, and we demonstrate the reconstruction steps of Green's function for the examples of three-dimensional Mott-insulator phase and one-dimensional Luttinger liquid. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.2744v2.pdf"}
{"id": "1403.2903", "abstract": "  Self-assembly of nanoparticles is an important tool in nanotechnology, with numerous applications including thin films, electronics, and drug delivery. We study the deposition of ionic nanoparticles on a glass substrate both experimentally and theoretically. Our theoretical model consists of a stochastic cooperative adsorption and evaporation process on a two-dimensional lattice. By exploring the relationship between the initial concentration of nanoparticles in the colloidal solution and the density of particles deposited on the substrate, we relate the deposition rate of our theoretical model to the concentration. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.2903v2.pdf"}
{"id": "1403.2939", "abstract": "  Multipartite quantum correlations are important resources for the development of quantum information and computation protocols. However, the resourcefulness of multipartite quantum correlations in practical settings is limited by its fragility under decoherence due to environmental interactions. Though there exist protocols to protect bipartite entanglement under decoherence, the implementation of such protocols for multipartite quantum correlations has not been sufficiently explored. Here, we study the effect of local amplitude damping channel on the generalized Greenberger-Horne-Zeilinger state, and use a protocol of optimal reversal quantum weak measurement to protect the multipartite quantum correlations. We observe that the weak measurement reversal protocol enhances the robustness of multipartite quantum correlations. Further it increases the critical damping value that corresponds to entanglement sudden death. To emphasize the efficacy of the technique in protection of multipartite quantum correlation, we investigate two proximately related quantum communication tasks, namely, quantum teleportation in a one sender, many receivers setting and multiparty quantum information splitting, through a local amplitude damping channel. We observe an increase in the average fidelity of both the quantum communication tasks under the weak measurement reversal protocol. The method may prove beneficial, for combating external interactions, in other quantum information tasks using multipartite resources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.2939v1.pdf"}
{"id": "1403.3523", "abstract": "  The charge transported when a quantum pump is adiabatically driven by time-dependent external forces in presence of dissipation is given by the line integral of a pumping field 𝐅. We give a general expression of 𝐅 in terms of quantum correlation functions evaluated at fixed external forces. Hence, an advantage of our method is that it transforms the original time-dependent problem into an autonomous one. Yet another advantage is that the curl of 𝐅 gives immediate visual information about the geometric structures governing dissipative quantum pumping. This can be used in a wide range of experimental cases, including electron pumps based on quantum dots and Cooper-pair pumps based on superconducting devices. Applied to a Cooper-pair sluice, we find an intriguing dissipation-induced enhancement of charge pumping, reversals of current, and emergence of asymmetries. This geometric method thus enables one to unveil a plethora of beneficial, dissipation-assisted operation protocols. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.3523v2.pdf"}
{"id": "1403.4316", "abstract": "  The total kinetic energy release in the neutron induced fission of ^235U was measured (using white spectrum neutrons from LANSCE) for neutron energies from E_n = 3.2 to 50 MeV. In this energy range the average post-neutron total kinetic energy release drops from 167.4 ± 0.7 to 162.1 ± 0.8 MeV, exhibiting a local dip near the second chance fission threshold. The values and the slope of the TKE vs. E_n agree with previous measurements but do disagree (in magnitude) with systematics. The variances of the TKE distributions are larger than expected and apart from structure near the second chance fission threshold, are invariant for the neutron energy range from 11 to 50 MeV. We also report the dependence of the total excitation energy in fission, TXE, on neutron energy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.4316v1.pdf"}
{"id": "1403.4538", "abstract": "  We study the connection between the cumulants of a time-integrated observable of a quantum system and the PT-symmetry properties of the non-Hermitian deformation of the Hamiltonian from which the generating function of these cumulants is obtained. This non-Hermitian Hamiltonian can display regimes of broken and of unbroken PT-symmetry, depending on the parameters of the problem and on the counting field that sets the strength of the non-Hermitian perturbation. This in turn determines the analytic structure of the long-time cumulant generating function (CGF) for the time-integrated observable. We consider in particular the case of the time-integrated (longitudinal) magnetisation in the one-dimensional Ising model in a transverse field. We show that its long-time CGF is singular on a curve in the magnetic field/counting field plane that delimits a regime where PT-symmetry is spontaneously broken (which includes the static ferromagnetic phase), from one where it is preserved (which includes the static paramagnetic phase). In the paramagnetic phase, conservation of PT -symmetry implies that all cumulants are sub-linear in time, a behaviour usually associated to the absence of decorrelation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.4538v1.pdf"}
{"id": "1403.5358", "abstract": "  We explicitly build a generalized local-density approximation (GLDA) correlation functional based on one-dimensional (1D) uniform electron gases (UEGs). The fundamental parameters of the GLDA —a generalization of the widely-known local-density approximation (LDA) used in density-functional theory (DFT) —are the electronic density ρ and a newly-defined two-electron local parameter called the hole curvature η. The UEGs considered in this study are finite versions of the conventional infinite homogeneous electron gas and consist of n electrons on a infinitely thin wire with periodic boundary conditions. We perform a comprehensive study of these finite UEGs at high, intermediate and low densities using perturbation theory and quantum Monte Carlo calculations. We show that the present GLDA functional yields accurate estimates of the correlation energy for both weakly and strongly correlated one-dimensional systems and can be easily generalized to higher-dimensional systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.5358v2.pdf"}
{"id": "1403.5741", "abstract": "  We analyze the possibility of defining infinite-dimensional manifolds as ringed spaces. More precisely, we consider three definitions of manifolds modeled on locally convex spaces: in terms of charts and atlases, in terms of ringed spaces, and in terms of functored spaces, as introduced by Douady in his thesis. It is shown that for large classes of locally convex model spaces (containing Fréchet spaces and duals of Fréchet-Schwartz spaces), the three definitions are actually equivalent. The equivalence of the definition via charts with the definition via ringed spaces is based on the fact that for the classes of model spaces under consideration, smoothness of maps turns out to be equivalent to their scalarwise smoothness (that is, the smoothness of their composition with smooth real-valued functions). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.5741v2.pdf"}
{"id": "1403.6276", "abstract": "  Stellar abundances of beryllium are useful in different areas of astrophysics, including studies of the Galactic chemical evolution, of stellar evolution, and of the formation of globular clusters. Determining Be abundances in stars is, however, a challenging endeavor. The two Be II resonance lines useful for abundance analyses are in the near UV, a region strongly affected by atmospheric extinction. CUBES is a new spectrograph planned for the VLT that will be more sensitive than current instruments in the near UV spectral region. It will allow the observation of fainter stars, expanding the number of targets where Be abundances can be determined. Here, a brief review of stellar abundances of Be is presented together with a discussion of science cases for CUBES. In particular, preliminary simulations of CUBES spectra are presented, highlighting its possible impact in investigations of Be abundances of extremely metal-poor stars and of stars in globular clusters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.6276v1.pdf"}
{"id": "1403.6679", "abstract": "  Driven surface diffusion occurs, for example, in molecular beam epitaxy when particles are deposited under an oblique angle. Elastic phase transitions happen when normal modes in crystals become soft due to the vanishing of certain elastic constants. We show that these seemingly entirely disparate systems fall under appropriate conditions into the same universality class. We derive the field theoretic Hamiltonian for this universality class, and we use renormalized field theory to calculate critical exponents and logarithmic corrections for several experimentally relevant quantities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.6679v2.pdf"}
{"id": "1403.6855", "abstract": "  The 2x3 channel pseudo Vertex Position Detector (pVPD) in the STAR experiment at RHIC has been upgraded to a 2x19 channel detector in the same acceptance, called the Vertex Position Detector (VPD). This detector is fully integrated into the STAR trigger system and provides the primary input to the minimum-bias trigger in Au+Au collisions. The information from the detector is used both in the STAR Level-0 trigger and offline to measure the location of the primary collision vertex along the beam pipe and the event \"start time\" needed by other fast-timing detectors in STAR. The offline timing resolution of single detector channels in full-energy Au+Au collisions is  100 ps, resulting in a start time resolution of a few tens of picoseconds and a resolution on the primary vertex location of  1 cm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.6855v1.pdf"}
{"id": "1403.7221", "abstract": "  DIRAC (Distributed Infrastructure with Remote Agent Control) is a general framework for the management of tasks over distributed heterogeneous computing environments. It has been originally developed to support the production activities of the LHCb (Large Hadron Collider Beauty) experiment and today is extensively used by several particle physics and biology communities. Current (Fermi Large Area Telescope – LAT) and planned (Cherenkov Telescope Array – CTA) new generation astrophysical/cosmological experiments, with very large processing and storage needs, are currently investigating the usability of DIRAC in this context. Each of these use cases has some peculiarities: Fermi-LAT will interface DIRAC to its own workflow system to allow the access to the grid resources, while CTA is using DIRAC as workflow management system for Monte Carlo production and analysis on the grid. We describe the prototype effort that we lead toward deploying a DIRAC solution for some aspects of Fermi-LAT and CTA needs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.7221v1.pdf"}
{"id": "1403.7771", "abstract": "  In many non-integrable open systems in physics and mathematics resonances have been found to be surprisingly ordered along curved lines in the complex plane. In this article we provide a unifying approach to these resonance chains by generalizing dynamical zeta functions. By means of a detailed numerical study we show that these generalized zeta functions explain the mechanism that creates the chains of quantum resonance and classical Ruelle resonances for 3-disk systems as well as geometric resonances on Schottky surfaces. We also present a direct system-intrinsic definition of the continuous lines on which the resonances are strung together as a projection of an analytic variety. Additionally, this approach shows that the existence of resonance chains is directly related to a clustering of the classical length spectrum on multiples of a base length. Finally, this link is used to construct new examples where several different structures of resonance chains coexist. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.7771v2.pdf"}
{"id": "1404.0136", "abstract": "  We experimentally study the velocity scaling of granular convection which is a possible mechanism of the regolith migration on the surface of small asteroids. In order to evaluate the contribution of granular convection to the regolith migration, the velocity of granular convection under the microgravity condition has to be revealed. Although it is hard to control the gravitational acceleration in laboratory experiments, scaling relations involving the gravitational effect can be evaluated by systematic experiments. Therefore, we perform such a systematic experiment of the vibration-induced granular convection. From the experimental data, a scaling form for the granular convective velocity is obtained. The obtained scaling form implies that the granular convective velocity can be decomposed into two characteristic velocity components: vibrational and gravitational velocities. In addition, the system size dependence is also scaled. According to the scaling form, the granular convective velocity v depends on the gravitational acceleration g as v ∝ g^0.97 when the normalized vibrational acceleration is fixed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.0136v2.pdf"}
{"id": "1404.0794", "abstract": "  We study the causal structure of the minimal surface of the four-gluon scattering, and find a world-sheet wormhole parametrized by Mandelstam variables, thereby demonstrate the EPR = ER relation for gluon scattering. We also propose that scattering amplitude is the change of the entanglement entropy by generalizing the holographic entanglement entropy of Ryu-Takayanagi to the case where two regions are divided in space-time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.0794v2.pdf"}
{"id": "1404.1061", "abstract": "  The genotype-fitness map plays a fundamental role in shaping the dynamics of evolution. However, it is difficult to directly measure a fitness landscape in practice, because the number of possible genotypes is astronomical. One approach is to sample as many genotypes as possible, measure their fitnesses, and fit a statistical model of the landscape that includes additive and pairwise interactive effects between loci. Here we elucidate the pitfalls of using such regressions, by studying artificial but mathematically convenient fitness landscapes. We identify two sources of bias inherent in these regression procedures that each tends to under-estimate high fitnesses and over-estimate low fitnesses. We characterize these biases for random sampling of genotypes, as well as for samples drawn from a population under selection in the Wright-Fisher model of evolutionary dynamics. We show that common measures of epistasis, such as the number of monotonically increasing paths between ancestral and derived genotypes, the prevalence of sign epistasis, and the number of local fitness maxima, are distorted in the inferred landscape. As a result, the inferred landscape will provide systematically biased predictions for the dynamics of adaptation. We identify the same biases in a computational RNA-folding landscape, as well as in regulatory sequence binding data, treated with the same fitting procedure. Finally, we present a method that may ameliorate these biases in some cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.1061v1.pdf"}
{"id": "1404.1655", "abstract": "  Intrinsic bilayer graphene is a gapless semimetal. Under the application of a bias field it becomes a semiconductor with a direct band gap that is proportional to the applied field. Under a layer-asymmetric strain (where the upper layer undergoes compression and lower layer tension or visa-versa) we find that the band gap of a biased bilayer graphene ribbon becomes indirect and, for higher strains, becomes negative returning the material its original semimetal state. As a result, the conductivity of the ribbon increases and can be almost an order of magnitude larger that of the intrinsic unbiased material - a change that can be induced with a strain of only  2-3", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.1655v2.pdf"}
{"id": "1404.3356", "abstract": "  We study the stochastic behavior of heterogeneous diffusion processes with the power-law dependence D(x)∼|x|^α of the generalized diffusion coefficient encompassing sub- and superdiffusive anomalous diffusion. Based on statistical measures such as the amplitude scatter of the time averaged mean squared displacement of individual realizations, the ergodicity breaking and non-Gaussianity parameters, as well as the probability density function P(x,t) we analyze the weakly non-ergodic character of the heterogeneous diffusion process and, particularly, the degree of irreproducibility of individual realization. As we show, the fluctuations between individual realizations increase with growing modulus |α| of the scaling exponent. The fluctuations appear to diverge when the critical value α=2 is approached, while for even larger α the fluctuations decrease, again. At criticality, the power-law behavior of the mean squared displacement changes to an exponentially fast growth, and the fluctuations of the time averaged mean squared displacement do not seem to converge for increasing number of realizations. From a systematic comparison we observe some striking similarities of the heterogeneous diffusion process with the familiar subdiffusive continuous time random walk process with power-law waiting time distribution and diverging characteristic waiting time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.3356v1.pdf"}
{"id": "1404.4244", "abstract": "  The issue of using informative priors for estimation of mixtures at multiple time points is examined. Several different informative priors and an independent prior are compared using samples of actual and simulated aerosol particle size distribution (PSD) data. Measurements of aerosol PSDs refer to the concentration of aerosol particles in terms of their size, which is typically multimodal in nature and collected at frequent time intervals. The use of informative priors is found to better identify component parameters at each time point and more clearly establish patterns in the parameters over time. Some caveats to this finding are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.4244v1.pdf"}
{"id": "1404.4522", "abstract": "  Confinement has generally the effect of suppressing order in condensed matter. Indeed, phase transitions such as freezing, or the superfluid transition in liquid helium, occur at lower temperatures in confinement than they do in the bulk. We provide here an illustration of a physical setting in which the opposite takes place. Specifically, the enhancement of the superfluid response of parahydrogen confined to nanoscale size cavities is demonstrated by means of first principle computer simulations. Prospects to stabilize and observe the long sought but yet elusive bulk superfluid phase of parahydrogen in purposefully designed porous media are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.4522v2.pdf"}
{"id": "1404.5170", "abstract": "  Tadpole Galaxies look like a star forming head with a tail structure to the side. They are also named cometaries. In a series of recent works we have discovered a number of issues that lead us to consider them extremely interesting targets. First, from images, they are disks with a lopsided starburst. This result is firmly established with long slit spectroscopy in a nearby representative sample. They rotate with the head following the rotation pattern but displaced from the rotation center. Moreover, in a search for extremely metal poor (XMP) galaxies, we identified tadpoles as the dominant shapes in the sample- nearly 80", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.5170v1.pdf"}
{"id": "1404.5495", "abstract": "  While the motion of particles near a rotating, electrically-neutral (Kerr), and charged (Kerr–Newman) black hole is always strictly regular, a perturbation in the gravitational or the electromagnetic field generally leads to chaos. The transition from regular to chaotic dynamics is relatively gradual if the system preserves axial symmetry, whereas non-axisymmetry induces chaos more efficiently. Here we study the development of chaos in an oblique (electro-vacuum) magnetosphere of a magnetized black hole. Besides the strong gravity of the massive source represented by the Kerr metric we consider the presence of a weak, ordered, large-scale magnetic field. An axially-symmetric model consisting of a rotating black hole embedded in an aligned magnetic field is generalized by allowing an oblique direction of the field having a general inclination, with respect to the rotation axis of the system. The inclination of the field acts as an additional perturbation to the motion of charged particles as it breaks the axial symmetry of the system and cancels the related integral of motion. The axial component of angular momentum is no longer conserved and the resulting system thus has three degrees of freedom. Our primary concern within this contribution is to find out how sensitive the system of bound particles is to the inclination of the field. We employ the method of the maximal Lyapunov exponent to distinguish between regular and chaotic orbits and to quantify their chaoticity. We find that even a small misalignment induces chaotic motion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.5495v2.pdf"}
{"id": "1404.6406", "abstract": "  We consider the diffusion of markers in a layered medium, with the lateral diffusion coefficient being the function of hight. We show that the probability density of the lateral displacements follows one-dimensional Batchelor's equation with time-dependent diffusion coefficient governed by the particles' redistribution in height. For the film of a finite thickness the resulting mean squared displacement exhibits superdiffusion at short times and crosses over to normal diffusion at long times. The approach is used for description of experimental results on inhomogeneous molecular diffusion in thin liquid films deposited on solid surfaces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.6406v1.pdf"}
{"id": "1404.7321", "abstract": "  We study here the curious particle dynamics resulting from electro-osmotic flow around a microchannel junction corner whose dielectric walls are weakly polarizable. The hydrodynamic velocity field is obtained via superposition of a linear irrotational term associated with the equilibrium zeta potentials of both the microchannel and particle surfaces and the non-linear induced-charge electro-osmotic flow which originates from the interaction of the externally applied electric field on the charge cloud it induces at the solid-liquid interface. The particle dynamics are analyzed by considering dielectrophoretic forces via the addition of a mobility term to the flow field in the limit of Stokes drag law. The former, non-divergence free term is responsible for migration of particles towards the sharp microchannel junction corner, where they can potentially accumulate. Experimental observations of particle trapping for various applied electric fields and microparticle size are rationalized in terms of the growing relative importance of the dielectrophoretic force and induced-charge contributions to the global velocity field with increasing intensity of the externally applied electric field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.7321v1.pdf"}
{"id": "1405.0180", "abstract": "  The continued observations of Sw J1644+57 in X-ray and radio bands accumulated a rich data set to study the relativistic jet launched in this tidal disruption event. The X-ray light curve of Sw J1644+57 from 5-30 days presents two kinds of quasi-periodic variations: a 200 second quasi-periodic oscillation (QPO) and a 2.7-day quasi-periodic variation. The latter has been interpreted by a precessing jet launched near the Bardeen-Petterson radius of a warped disk. Here we suggest that the ∼ 200s QPO could be associated with a second, narrower jet sweeping the observer line-of-sight periodically, which is launched from a spinning black hole in the misaligned direction with respect to the black hole's angular momentum. In addition, we show that this two-component jet model can interpret the radio light curve of the event, especially the re-brightening feature starting ∼ 100 days after the trigger. From the data we infer that inner jet may have a Lorentz factor of Γ_ j∼ 5.5 and a kinetic energy of E_ k,iso∼ 3.0 × 10^52 erg, while the outer jet may have a Lorentz factor of Γ_ j∼ 2.5 and a kinetic energy of E_ k,iso∼ 3.0 × 10^53 erg. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.0180v1.pdf"}
{"id": "1405.3770", "abstract": "  A Langevin process diffusing in a periodic potential landscape has a time dependent diffusion constant which means that its average mean squared displacement (MSD) only becomes linear at late times. The long time, or effective diffusion constant, can be estimated from the slope of a linear fit of the MSD at late times. Due to the cross over between a short time microscopic diffusion constant, which is independent of the potential, to the effective late time diffusion constant, a linear fit of the MSD will not in general pass through the origin and will have a non-zero constant term. Here we address how to compute the constant term and provide explicit results for Brownian particles in one dimension in periodic potentials. We show that the constant is always positive and that at low temperatures it depends on the curvature of the minimum of the potential. For comparison we also consider the same question for the simpler problem of a symmetric continuous time random walk in discrete space. Here the constant can be positive or negative and can be used to determine the variance of the hopping time distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.3770v1.pdf"}
{"id": "1405.5912", "abstract": "  We present analysis of C7.0 solar flare of Febrary 17, 2013, revealing a strong helioseismic response (sunquake) caused by a very compact impact in the photosphere. This is the weakest known C-class flare generating a sunquake event. To investigate possible mechanisms of this event, and to understand the role of accelerated charged particles and photospheric electric currents, we use data from three space observatories: Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Solar Dynamics Observatory (SDO) and Geostationary Operational Environmental Satellite (GOES). We find that the photospheric flare impact does not spatially correspond to the strongest HXR emission source, but both of these events are parts of the same energy release. Our analysis reveals a close association of the flare energy release with a rapid increase of the electric currents, and suggests that the sunquake initiation is unlikely to be explained by the impact of high-energy electrons but may be associated with a rapid current dissipation or a localized impulsive Lorentz force. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.5912v2.pdf"}
{"id": "1405.6255", "abstract": "  We propose a scheme for generating atomic NOON states via adiabatic passage. In the scheme, a double Λ-type three-level atom is trapped in a bimodal cavity and two sets of Λ-type three-level atoms are translated into and outside of two single mode cavities respectively. The three cavities connected by optical fibres are always in vacuum states. After a series of operations and suitable interaction time, we can obtain arbitrary large-n NOON states of two sets of Λ-type three-level atoms in distant cavities by performing a single projective measurement on the double Λ-type three-level atom. Due to adiabatic elimination of atomic excited states and the application of adiabatic passage, our scheme is robust against the spontaneous emissions of atoms, the decays of fibres and cavities photon leakage. So the scheme has a high fidelity and feasibility under the current available techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.6255v1.pdf"}
{"id": "1405.7133", "abstract": "  A general algorithm for handling the energy dependence of meson-nucleon amplitudes in the nuclear medium has been recently applied to antikaons and to eta mesons. Here we test this approach on π N amplitudes in pionic atoms where direct comparison can be made with ample experimental results. Applying this algorithm to a large-scale fit of 100 pionic-atom data points across the periodic table, which also include the `deeply-bound' states in Sn and Pb, reaffirms earlier conclusions on the density-dependent renormalization of the π N threshold isovector amplitude b_1, or equivalently the renormalization of the pion decay constant f_π in the nuclear medium. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.7133v2.pdf"}
{"id": "1405.7200", "abstract": "  Theoretical, numerical and experimental results examining thermoviscous losses in sonic crystals are presented in this work, enabling the fabrication and characterization of an acoustic metamaterial absorber with complex-valued anisotropic inertia. The formulations developed can be written with no unknown or empirical coefficients, due to the structured lattice of the sonic crystals and organized layering scheme, and it is shown that higher filling fraction arrangements can be used to provide a large enhancement in the loss factor. To accurately describe these structures in a realizable experimental configuration, confining structures are needed which modify the effective properties, due to the thermal and viscous boundary layer effects within the sonic crystal lattice. Theoretical formulations are presented which describe the effects of these confined sonic crystals, both individually and as part of an acoustic metamaterial structure, and is demonstrated experimentally in an acoustic impedance tube. It is observed that confined sonic crystals demonstrate an increase in the viscous losses and a reduction in the effective bulk modulus, enabling better acoustic absorber performance through improved impedance matching and enhanced absorption. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.7200v1.pdf"}
{"id": "1405.7440", "abstract": "  The rate maximization for the K-user interference channels (ICs) has been investigated extensively in the literature. However, the dual problem of minimizing the error probability with given signal modulations and/or data rates of the users is less exploited. In this paper, by utilizing the additional degrees of freedom attained from the improper signaling (versus the conventional proper signaling), we optimize the precoding matrices for the K-user single-input single-output (SISO) ICs to achieve minimal pair-wise error probability (PEP) and symbol error rate (SER) with two proposed algorithms, respectively. Compared to conventional proper signaling as well as other state-of-the-art improper signaling designs, our proposed improper signaling schemes achieve notable SER improvement in SISO-ICs under both additive white Gaussian noise (AWGN) channel and cellular system setups. Our study provides another viewpoint for optimizing transmissions in ICs and further justifies the practical benefit of improper signaling in interference-limited communication systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.7440v1.pdf"}
{"id": "1405.7893", "abstract": "  We show that, independently of the scalar field potential and of specific asymptotic properties of the spacetime (asymptotically flat, de Sitter or anti-de Sitter), any static, spherically symmetric or planar, black hole or soliton solution of the Einstein theory minimally coupled to a real scalar field with a general potential is mode stable under linear odd-parity perturbations. To this end, we generalize the Regge-Wheeler equation for a generic self-interacting scalar field, and show that the potential of the relevant Schrödinger operator can be mapped, by the so-called S-deformation, to a semi-positively defined potential. With these results at hand we study the existence of slowly rotating configurations. The frame dragging effect is compared with the Kerr black hole. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.7893v1.pdf"}
{"id": "1406.1856", "abstract": "  We provide a general mechanism to design online learning algorithms based on a minimax analysis within a drifting-games framework. Different online learning settings (Hedge, multi-armed bandit problems and online convex optimization) are studied by converting into various kinds of drifting games. The original minimax analysis for drifting games is then used and generalized by applying a series of relaxations, starting from choosing a convex surrogate of the 0-1 loss function. With different choices of surrogates, we not only recover existing algorithms, but also propose new algorithms that are totally parameter-free and enjoy other useful properties. Moreover, our drifting-games framework naturally allows us to study high probability bounds without resorting to any concentration results, and also a generalized notion of regret that measures how good the algorithm is compared to all but the top small fraction of candidates. Finally, we translate our new Hedge algorithm into a new adaptive boosting algorithm that is computationally faster as shown in experiments, since it ignores a large number of examples on each round. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.1856v2.pdf"}
{"id": "1406.2176", "abstract": "  Interactions are known to have dramatic effects on bosonic gases in one dimension (1D). Not only does the ground state transform from a condensate-like state to an effective Fermi sea, but new fundamental excitations, which do not have any higher-dimensional equivalents, are predicted to appear. In this work, we trace these elusive excitations via their effects on the dynamical structure factor of 1D strongly-interacting Bose gases at low temperature. An array of 1D Bose gases is obtained by loading a ^87Rb condensate in a 2D lattice potential. The dynamical structure factor of the system is probed by energy deposition through low-momentum Bragg excitations. The experimental signals are compared to recent theoretical predictions for the dynamical structure factor of the Lieb-Liniger model at T > 0. Our results demonstrate that the main contribution to the spectral widths stems from the dynamics of the interaction-induced excitations in the gas, which cannot be described by the Luttinger liquid theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.2176v3.pdf"}
{"id": "1406.2248", "abstract": "  A general theory is presented to describe optomechanical interactions of acoustic phonons, having extremely long lifetimes in superfluid ^4He, with optical photons in the medium placed in a suitable electromagnetic cavity. The acoustic nonlinearity in the fluid motion is included to consider processes beyond the usual linear process involving absorption or emission of one phonon at a time. We first apply our formulation to the simplest one-phonon process involving the usual resonant anti-Stokes upconversion of an incident optical mode. However, when the allowed optical cavity modes are such that there is no single-phonon mode in the superfluid which can give rise to a resonant allowed anti-Stokes mode, we must consider the possibility of two phonon upconversion. For such a case, we show that the two step two phonon process could be dominant. We present arguments for large two step process and negligible single step two phonon contribution. The two step process also shows interesting quantum interference among different transition pathways. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.2248v2.pdf"}
{"id": "1406.3138", "abstract": "  Integrability of a square billiard is spontaneously broken as it rotates about one of its corners. The system becomes quasi-integrable where the invariant tori are broken with respect to a certain parameter, λ = 2E/ω^2 where E is the energy of the particle inside the billiard and ω is the angular frequency of rotation of billiard. We study the system classically and quantum mechanically in view of obtaining a correspondence in the two descriptions. Classical phase space in Poincaré surface of section shows transition from regular to chaotic motion as the parameter λ is decreased. In the Quantum counterpart, the spectral statistics shows a transition from Poisson to Wigner distribution as the system turns chaotic with decrease in λ. The wavefunction statistics however show breakdown of time-reversal symmetry as λ decreases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.3138v1.pdf"}
{"id": "1406.4676", "abstract": "  Classification is an important task in many fields including biomedical research and machine learning. Traditionally, a classification rule is constructed based a bunch of labeled data. Recently, due to technological innovation and automatic data collection schemes, we easily encounter with data sets containing large amounts of unlabeled samples. Because to label each of them is usually costly and inefficient, how to utilize these unlabeled data in a classifier construction process becomes an important problem. In machine learning literature, active learning or semi-supervised learning are popular concepts discussed under this situation, where classification algorithms recruit new unlabeled subjects sequentially based on the information learned from previous stages of its learning process, and these new subjects are then labeled and included as new training samples. From a statistical aspect, these methods can be recognized as a hybrid of the sequential design and stochastic approximation procedure. In this paper, we study sequential learning procedures for building efficient and effective classifiers, where only the selected subjects are labeled and included in its learning stage. The proposed algorithm combines the ideas of Bayesian sequential optimal design and uncertainty sampling. Computational issues of the algorithm are discussed. Numerical results using both synthesized data and real examples are reported. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.4676v1.pdf"}
{"id": "1406.4961", "abstract": "  The measurement of 1.97 ± 0.04 M_solar for PSR J1614-2230 and 2.01 ± 0.04M_solar for PSR J0348+0432 puts a strong constraint on the neutron star equation of state and its exotic composition at higher densities. In this paper, we investigate the possibility of exotic equation of state within the observational mass constraint of 2M_solar in the framework of relativistic mean field model with density-dependent couplings. We particularly study the effect of antikaon condensates in the presence of hyperons on the mass-radius relationship of the neutron star. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.4961v1.pdf"}
{"id": "1406.5114", "abstract": "  The thermal properties of the three-dimensional Dirac oscillator are considered. The canonical partition function is determined, and the high-temperature limit is assessed. The degeneracy of energy levels and their physical implications on the main thermodynamic functions are analyzed, revealing that these functions assume values greater than the one-dimensional case. So that at high temperatures, the limit value of the specific heat is three times bigger. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.5114v2.pdf"}
{"id": "1406.5888", "abstract": "  In this paper a hidden extra symmetry of conformally invariant Lagrangians occuring in physics is pointed out. This symmetry is most apparent in a metric independent, i.e. in a Palatini-like presentation of the variational problem. In such presentation, the usual conformal weight of fields can be encoded as local dilatation group gauge charges. The conventional conformal invariance of Lagrangians is then equivalent to dilatation gauge invariance. The claim of the paper is, that the most commonly occurring conformally invariant Lagrangians turning up in physics are not only invariant to local dilatation gauge transformations, but they are also invariant to any change of the dilatation gauge connection, meaning an additional algebraic symmetry property. In terms of dimensional analysis and differential geometry, this additional symmetry means complete insensitivity of the Lagrangian to the choice of the parallel transport rule of local measurement units throughout spacetime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.5888v3.pdf"}
{"id": "1406.5932", "abstract": "  The dynamics of Bose-Einstein condensation in a three-dimensional harmonic trap is studied explicitly including the Bogoliubov approximation for temperatures below the critical one. To model the evolution towards equilibrium at each cooling step, we derive quantum kinetic equations that describe the dynamics of the gas for temperatures above and below the transition temperature. These equations, valid in the Born and Markov approximations, consider the essential role of the chemical potential as the main parameter that signals the transition. The kinetic equation that describes the growth of the condensate below the transition temperature is derived within the Bogoliubov approximation. To illustrate our results we propose an energetic cooling protocol and simulate the whole sequence of the formation of a condensate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.5932v1.pdf"}
{"id": "1406.6707", "abstract": "  Sharp chemical discontinuities can occur in protoplanetary discs, particularly at `snow-lines' where a gas-phase species freezes out to form ice grains. Such sharp discontinuities will diffuse out due to the turbulence suspected to drive angular momentum transport in accretion discs. We demonstrate that the concentration gradient - in the vicinity of the snow-line - of a species present outside a snow-line but destroyed inside is strongly sensitive to the level of turbulent diffusion (provided the chemical and transport time-scales are decoupled) and provides a direct measurement of the radial `Schmidt number' (the ratio of the angular momentum transport to radial turbulent diffusion). Taking as an example the tracer species N_2H^+, which is expected to be destroyed inside the CO snow-line (as recently observed in TW Hya) we show that ALMA observations possess significant angular resolution to constrain the Schmidt number. Since different turbulent driving mechanisms predict different Schmidt numbers, a direct measurement of the Schmidt number in accretion discs would allow inferences about the nature of the turbulence to be made. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.6707v1.pdf"}
{"id": "1406.6846", "abstract": "  We study bond-order parameters for generalized t-J models on a square lattice. Using the plane-wave limit the considered order parameters form basis functions for irreducible representations of the symmetry transformations of the point group and of time reversal. We show that for instability wave vectors along the diagonals all possible basis functions are either fine-tuned (i.e., obey restrictions beyond the requirements of symmetry) or break time reversal symmetry and thus describe flux states. For instability wave vectors along the crystalline axes, corresponding to the observed case in underdoped cuprates, there are only three representations with A_1, B_1, and E symmetry which do not break time reversal symmetry in the general case. We suggest that one of them has recently been observed in resonant elastic X-ray scattering. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.6846v2.pdf"}
{"id": "1406.7754", "abstract": "  Under certain conditions, Hg(Cd)Te quantum wells (QWs) are known to realize a time-reversal symmetric, two-dimensional topological insulator phase. Its low-energy excitations are well-described by the phenomenological Bernevig-Hughes-Zhang (BHZ) model that interpolates between Schrödinger and Dirac fermion physics. We study the polarization function of this model in random phase approximation (RPA) in the intrinsic limit and at finite doping. While the polarization properties in RPA of Dirac and Schrödinger particles are two comprehensively studied problems, our analysis of the BHZ model bridges the gap between these two limits, shedding light on systems with intermediate properties. We gain insight into the screening properties of the system and on its characteristic plasma oscillations. Interestingly, we discover two different kinds of plasmons that are related to the presence of intra- and interband excitations. Observable signatures of these plasmons are carefully analyzed in a variety of distinct parameter regimes, including the experimentally relevant ones for Hg(Cd)Te QWs. We conclude that the discovered plasmons are observable by Raman or electron loss spectroscopy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.7754v2.pdf"}
{"id": "1407.0126", "abstract": "  We present a review and discussions on characterizations and quantifications of macroscopic quantum states as well as their implementations and applications in optical systems. We compare and criticize different measures proposed to define and quantify macroscopic quantum superpositions and extend such comparisons to several types of optical quantum states actively considered for experimental implementations within recent research topics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.0126v3.pdf"}
{"id": "1407.1693", "abstract": "  Among the most spectacular variable stars are the Luminous Blue Variables (LBVs), which can show three types of variability. The LBV phase of evolution is poorly understood, and the driving mechanisms for the variability are not known. The most common type of variability, the S Dor instability, occurs on timescales of tens of years. During an S Dor outburst, the visual magnitude of the star increases, while the bolometric magnitude stays approximately constant. In this work, we investigate pulsation as a possible trigger for the S Dor type outbursts. We calculate the pulsations of envelope models using a nonlinear hydrodynamics code including a time-dependent convection treatment. We initialize the pulsation in the hydrodynamic model based on linear non-adiabatic calculations. Pulsation properties for a full grid of models from 20 to 85 M_⊙ were calculated, and in this paper we focus on the few models that show either long-period pulsations or outburst-like behaviour, with photospheric radial velocities reaching 70-80 km/s. At the present time, our models cannot follow mass loss, so once the outburst event begins, our simulations are terminated. Our results show that pulsations alone are not able to drive enough surface expansion to eject the outer layers. However, the outbursts and long-period pulsations discussed here produce large variations in effective temperature and luminosity, which are expected to produce large variations in the radiatively driven mass-loss rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.1693v2.pdf"}
{"id": "1407.2104", "abstract": "  This paper investigates the problem of decomposition with respect to outputs for Boolean control networks (BCNs). First, with the linear expression of BCNs and the matrix semi-tensor product, some algebraic equivalent conditions for the decomposition are obtained. Second, a necessary and sufficient graphical condition for the decomposition with respect to outputs is given. Third, an effective method is proposed to reduce the computational burden in the realization of the decomposition. Finally, some examples are addressed to validate the effectiveness of the proposed method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.2104v1.pdf"}
{"id": "1407.2701", "abstract": "  We construct higher order rogue wave solutions and breather profiles for the quasi-one-dimensional Gross-Pitaevskii equation with a time-dependent interatomic interaction and external trap through the similarity transformation technique. We consider three different forms of traps, namely (i) time-independent expulsive trap, (ii) time-dependent monotonous trap and (iii) time-dependent periodic trap. Our results show that when we change a parameter appearing in the time-independent or time-dependent trap the second and third-order rogue waves transform into the first-order like rogue waves. We also analyze the density profiles of breather solutions. Here also we show that the shapes of the breathers change when we tune the strength of trap parameter. Our results may help to manage rogue waves experimentally in a BEC system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.2701v2.pdf"}
{"id": "1407.5686", "abstract": "  The Milky Way can act as a large-scale weak gravitational lens of the cosmic microwave background (CMB). We study this effect using a photon ray-tracing code and a Galactic mass distribution with disk, bulge and halo components. For an observer at the Sun's coordinates in the Galaxy, the bending of CMB photon paths is limited to less than one arcsecond, and only for rays that pass within a few degrees of the Galactic Center. However, the entire sky is affected, resulting in global distortions of the CMB on large angular scales. These distortions can cause the low-order multipoles of a spherical harmonic expansion of the CMB sky temperature to leak into higher-order modes. Thus the component of the CMB dipole that results from the Local Group's motion relative to the local cosmic frame of rest contributes to higher-order moments for an observer in the solar system. With our ray-tracing code we show that the phenomenon is not sensitive to the specific choice of Galactic potential. We also quantitatively rule it out as a contributor to CMB anomalies such as power asymmetry or correlated alignment of low-order multipole moments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.5686v1.pdf"}
{"id": "1407.6430", "abstract": "  GRB 120308A, a long duration γ-ray burst detected by Swift, was distinguished by a highly-polarized early optical afterglow emission that strongly suggests an ordered magnetic field component in the emitting region. In this work we model the optical and X-ray emission in the reverse and forward shock scenario and show that the strength of the magnetic field in reverse shock region is ∼ 10 times stronger than that in the forward shock region. Consequently the outflow powering the highly-polarized reverse shock optical emission was mildly-magnetized at a degree σ∼ a few percent. Considering the plausible magnetic energy dissipation in both the acceleration and prompt emission phases of the Gamma-ray Burst (GRB) outflow, the afterglow data of GRB 120308A provides us the compelling evidence that at least for some GRBs a non-ignorable fraction of the energy was released in the form of Poynting-flux, confirming the finding firstly made in the reverse-forward shock emission modeling of the optical afterglow of GRB 990123 (Fan et al. 2002; Zhang et al. 2003). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.6430v1.pdf"}
{"id": "1407.6780", "abstract": "  Phase diagram based on the mean square displacement (MSD) and the distribution of diffusion coefficients of the time-averaged MSD for the stored-energy-driven Lévy flight (SEDLF) is presented. In the SEDLF, a random walker cannot move while storing energy, and it jumps by the stored energy. The SEDLF shows a whole spectrum of anomalous diffusions including subdiffusion and superdiffusion, depending on the coupling parameter between storing time (trapping time) and stored energy. This stochastic process can be investigated analytically with the aid of renewal theory. Here, we consider two different renewal processes, i.e., ordinary renewal process and equilibrium renewal process, when the mean trapping time does not diverge. We analytically show the phase diagram according to the coupling parameter and the power exponent in the trapping-time distribution. In particular, we find that distributional behavior of time-averaged MSD intrinsically appears in superdiffusive as well as normal diffusive regime even when the mean trapping time does not diverge. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.6780v1.pdf"}
{"id": "1407.7536", "abstract": "  IceCube have observed neutrinos which are presumably of extra-galactic origin. Since specific sources have not yet been identified, we discuss what could be learned from the conceptual point of view. We use a simple model for neutrino production from the interactions between nuclei and matter, and we focus on the description of the spectral shape and flavor composition observed by IceCube. Our main parameters are spectral index, maximal energy, magnetic field, and composition of the accelerated nuclei. We show that a cutoff at PeV energies can be achieved by soft enough spectra, a cutoff of the primary energy, or strong enough magnetic fields. These options, however, are difficult to reconcile with the hypothesis that these neutrinos originate from the same sources as the ultra-high energy cosmic rays. We demonstrate that heavier nuclei accelerated in the sources may be a possible way out if the maximal energy scales appropriately with the mass number of the nuclei. In this scenario, neutrino observations can actually be used to test the UHECR acceleration mechanism. We also emphasize the need for a volume upgrade of the IceCube detector for future precision physics, for which the flavor information becomes a statistical meaningful model discriminator as qualitatively new ingredient. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.7536v2.pdf"}
{"id": "1407.8172", "abstract": "  Feedback control of quantum systems via continuous measurement involves complex nonlinear dynamics. Except in very special cases, even for a single qubit optimal feedback protocols are unknown. Not even do intuitive candidates exist for choosing the measurement basis, which is the primary non-trivial ingredient in the feedback control of a qubit. Here we present a series of arguments that suggest a particular form for the optimal protocol for a broad class of noise sources in the regime of good control. This regime is defined as that in which the control is strong enough to keep the system close to the desired state. With the assumption of this form the remaining parameters can be determined via a numerical search. The result is a non-trivial feedback protocol valid for all feedback strengths in the regime of good control. We conjecture that this protocol is optimal to leading order in the small parameters that define this regime. The protocol can be described relatively simply, and as a notable feature contains a discontinuity as a function of the feedback strength. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.8172v1.pdf"}
{"id": "1407.8341", "abstract": "  The Spherical Hecke central (SHc) algebra has been shown to act on the Nekrasov instanton partition functions of 𝒩=2 gauge theories. Its presence accounts for both integrability and AGT correspondence. On the other hand, a specific limit of the Omega background, introduced by Nekrasov and Shatashvili (NS), leads to the appearance of TBA and Bethe like equations. To unify these two points of view, we study the NS limit of the SHc algebra. We provide an expression of the instanton partition function in terms of Bethe roots, and define a set of operators that generates infinitesimal variations of the roots. These operators obey the commutation relations defining the SHc algebra at first order in the equivariant parameter ϵ_2. Furthermore, their action on the bifundamental contributions reproduces the Kanno-Matsuo-Zhang transformation. We also discuss the connections with the Mayer cluster expansion approach that leads to TBA-like equations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.8341v3.pdf"}
{"id": "1407.8420", "abstract": "  We study a modified Ramsey spectroscopy technique employing slowly decaying states for quantum metrology applications using dense ensembles. While closely positioned atoms exhibit superradiant collective decay and dipole-dipole induced frequency shifts, recent results [Ostermann, Ritsch and Genes, Phys. Rev. Lett. 111, 123601 (2013)] suggest the possibility to suppress such detrimental effects and achieve an even better scaling of the frequency sensitivity with interrogation time than for noninteracting particles. Here we present an in-depth analysis of this 'protected subspace Ramsey technique' using improved analytical modeling and numerical simulations including larger 3D samples. Surprisingly we find that using sub-radiant states of N particles to encode the atomic coherence yields a scaling of the optimal sensitivity better than 1/√(N). Applied to ultracold atoms in 3D optical lattices we predict a precision beyond the single atom linewidth. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.8420v2.pdf"}
{"id": "1408.0390", "abstract": "  We describe the coherent manipulation of harmonic oscillator and qubit modes using resonant trains of single flux quantum pulses in place of microwaves. We show that coherent rotations are obtained for pulse-to-pulse spacing equal to the period of the oscillator. We consider a protocol for preparing bright and dark harmonic oscillator pointer states. Next we analyze rotations of a two-state qubit system. We calculate gate errors due to timing jitter of the single flux quantum pulses and due to weak anharmonicity of the qubit. We show that gate fidelities in excess of 99.9", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.0390v1.pdf"}
{"id": "1408.0396", "abstract": "  Single layer core/shell structures consisting of graphene as core and hexagonal boron nitride as shell are studied using first-principles plane wave method within density functional theory. Electronic energy level structure is analysed as a function of the size of both core and shell. It is found that the confinement of electrons in two dimensional graphene quantum dot is reduced by the presence of boron nitride shell. The energy gap is determined by the graphene states. Comparison of round, hexagonal, rectangular and triangular core/shell structures reveals that their electronic and magnetic states are strongly affected by their geometrical shapes. The energy level structure, energy gap and magnetic states can be modified by external charging. The core part acts as a two-dimensional quantum dot for both electrons and holes. The capacity of extra electron intake of these quantum dots is shown to be limited by the Coulomb blockade in two-dimension. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.0396v1.pdf"}
{"id": "1408.0870", "abstract": "  We have developed a procedure for the classification of eclipsing binaries from their light-curve parameters and spectral type. The procedure was tested on more than 1000 systems with known classification, and its efficiency was estimated for every evolutionary status we use. The procedure was applied to about 4700 binaries with no classification, and the vast majority of them was classified successfully. Systems of relatively rare evolutionary classes were detected in that process, as well as systems with unusual and/or contradictory parameters. Also, for 50 previously unclassified cluster binaries evolutionary classes were identified. These stars can serve as tracers for age and distance estimation of their parent stellar systems. The procedure proved itself as fast, flexible and effective enough to be applied to large ground based and space born surveys, containing tens of thousands of eclipsing binaries. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.0870v2.pdf"}
{"id": "1408.1162", "abstract": "  Deep architecture such as hierarchical semi-Markov models is an important class of models for nested sequential data. Current exact inference schemes either cost cubic time in sequence length, or exponential time in model depth. These costs are prohibitive for large-scale problems with arbitrary length and depth. In this contribution, we propose a new approximation technique that may have the potential to achieve sub-cubic time complexity in length and linear time depth, at the cost of some loss of quality. The idea is based on two well-known methods: Gibbs sampling and Rao-Blackwellisation. We provide some simulation-based evaluation of the quality of the RGBS with respect to run time and sequence length. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.1162v1.pdf"}
{"id": "1408.1220", "abstract": "  In this paper, we present a reduced basis method for pricing European and American options based on the Black-Scholes and Heston model. To tackle each model numerically, we formulate the problem in terms of a time dependent variational equality or inequality. We apply a suitable reduced basis approach for both types of options. The characteristic ingredients used in the method are a combined POD-Greedy and Angle-Greedy procedure for the construction of the primal and dual reduced spaces. Analytically, we prove the reproduction property of the reduced scheme and derive a posteriori error estimators. Numerical examples are provided, illustrating the approximation quality and convergence of our approach for the different option pricing models. Also, we investigate the reliability and effectivity of the error estimators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.1220v1.pdf"}
{"id": "1408.2337", "abstract": "  This is the second in a series of papers reporting on a large reverberation mapping (RM) campaign to measure black hole (BH) mass in high accretion rate active galactic nuclei (AGNs). The goal is to identify super-Eddington accreting massive black holes (SEAMBHs) and to use their unique properties to construct a new method for measuring cosmological distances. Based on theoretical models, the saturated bolometric luminosity of such sources is proportional to the BH mass which can be used to obtain their distance. Here we report on five new RM measurements and show that in four of the cases we can measure the BH mass and three of these sources are SEAMBHs. Together with the three sources from our earlier work, we now have six new sources of this type. We use a novel method based on a minimal radiation efficiency to identify nine additional SEAMBHs from earlier RM-based mass measurements. We use a Bayesian analysis to determine the parameters of the new distance expression, and the method uncertainties, from the observed properties of the objects in the sample. The ratio of the newly measured distances to the standard cosmological ones has a mean scatter of 0.14 dex, indicating that SEAMBHs can be use as cosmological distance probes. With their high luminosity, long period of activity and large numbers at high redshifts, SEAMBHs have a potential to extend the cosmic distance ladder beyond the range now explored by type Ia supernovae. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.2337v1.pdf"}
{"id": "1408.2392", "abstract": "  The electronic properties of the novel two dimensional (2D) material silicene are strongly influenced by the application of a perpendicular electric field E_z and of an exchange field M due to adatoms positioned on the surface or a ferromagnetic substrate. Within the random phase approximation, we investigate how electron-electron interactions are affected by these fields and present analytical and numerical results for the dispersion of plasmons, their lifetime, and their oscillator strength. We find that the combination of the fields E_z and M brings a spin and valley texture to the particle-hole excitation spectrum and allows the formation of spin- and valley-polarized plasmons. When the Fermi level lies in the gap of one spin in one valley, the intraband region of the corresponding spectrum disappears. For zero E_z and finite M the spin symmetry is broken and spin polarization is possible. The lifetime and oscillator strength of the plasmons are shown to depend strongly on the number of spin and valley type electrons that form the electron-hole pairs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.2392v1.pdf"}
{"id": "1408.3063", "abstract": "  The emission from young stellar objects (YSOs) in the mid-IR is dominated by the inner rim of their circumstellar disks. We present an IR-monitoring survey of about 800 objects in the direction of the Lynds 1688 (L1688) star forming region over four visibility windows spanning 1.6 years using the Spitzer space telescope in its warm mission phase. Among all lightcurves, 57 sources are cluster members identified based on their spectral-energy distribution and X-ray emission. Almost all cluster members show significant variability. The amplitude of the variability is larger in more embedded YSOs. Ten out of 57 cluster members have periodic variations in the lightcurves with periods typically between three and seven days, but even for those sources, significant variability in addition to the periodic signal can be seen. No period is stable over 1.6 years. Non-periodic lightcurves often still show a preferred timescale of variability which is longer for more embedded sources. About half of all sources exhibit redder colors in a fainter state. This is compatible with time-variable absorption towards the YSO. The other half becomes bluer when fainter. These colors can only be explained with significant changes in the structure of the inner disk. No relation between mid-IR variability and stellar effective temperature or X-ray spectrum is found. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.3063v1.pdf"}
{"id": "1408.3223", "abstract": "  The successful deployment of LTE heterogeneous networks (HetNets) depends crucially on the inter-cell interference (ICI) management. Among ICI coordination schemes, fractional frequency reuse (FFR) is considered as an efficient technique well-suited to OFDMA-based HetNets. Two coupled questions in this context are: 1) how to associate users to appropriate base-stations considering the long list of available candidate cells, and 2) how to allocate frequency resources among multiple cells. In this paper, we treat the multi-cell frequency allocation as frequency partitioning among multiple reuse patterns, and develop a novel algorithm to solve these two coupled questions in a joint manner. We also provide practical criterion to select the set of essential candidate patterns from all possible patterns. Results show that the proposed joint strategy improves both the cell-edge user and overall network throughput. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.3223v1.pdf"}
{"id": "1408.5320", "abstract": "  All swarm-intelligence-based optimization algorithms use some stochastic components to increase the diversity of solutions during the search process. Such randomization is often represented in terms of random walks. However, it is not yet clear why some randomization techniques (and thus why some algorithms) may perform better than others for a given set of problems. In this work, we analyze these randomization methods in the context of nature-inspired algorithms. We also use eagle strategy to provide basic observations and relate step sizes and search efficiency using Markov theory. Then, we apply our analysis and observations to solve four design benchmarks, including the designs of a pressure vessel, a speed reducer, a PID controller and a heat exchanger. Our results demonstrate that eagle strategy with Lévy flights can perform extremely well in reducing the overall computational efforts. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.5320v1.pdf"}
{"id": "1408.6088", "abstract": "  We study critical Casimir forces between planar walls and geometrically structured substrates within mean-field theory. As substrate structures, crenellated surfaces consisting of periodic arrays of rectangular crenels and merlons are considered. Within the widely used proximity force approximation, both the top surfaces of the merlons and the bottom surfaces of the crenels contribute to the critical Casimir force. However, for such systems the full, numerically determined critical Casimir forces deviate significantly fromthe pairwise addition formalismunderlying the proximity force approximation. A first-order correction to the proximity force approximation is presented in terms of a step contribution arising from the critical Casimir interaction between a planar substrate and the right-angled steps of the merlons consisting of their upper and lower edges as well as their sidewalls. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.6088v1.pdf"}
{"id": "1408.6924", "abstract": "  Joint optimization of nonlinear precoders and receive filters is studied for both the uplink and downlink in a cellular system. For the uplink, the base transceiver station (BTS) receiver implements successive interference cancellation, and for the downlink, the BTS station pre-compensates for the interference with Tomlinson-Harashima precoding (THP). Convergence of alternating optimization of receivers and transmitters in a single cell is established when filters are updated according to a minimum mean squared error (MMSE) criterion, subject to appropriate power constraints. Adaptive algorithms are then introduced for updating the precoders and receivers in the absence of channel state information, assuming time-division duplex transmissions with channel reciprocity. Instead of estimating the channels, the filters are directly estimated according to a least squares criterion via bi-directional training: Uplink pilots are used to update the feedforward and feedback filters, which are then used as interference pre-compensation filters for downlink training of the mobile receivers. Numerical results show that nonlinear filters can provide substantial gains relative to linear filters with limited forward-backward iterations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.6924v1.pdf"}
{"id": "1409.0369", "abstract": "  For nearly two centuries the dynamics of chains have offered examples of paradoxical theoretical predictions. Here we propose a theory for the dissipative dynamics of one-dimensional continua with singularities which provides a unified treatment for chain problems that have suffered from paradoxical solutions. These problems are duly solved within the present theory and their paradoxes removed—we hope. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.0369v1.pdf"}
{"id": "1409.0511", "abstract": "  Cosmology and particle physics come across a tight connection in the attempt to reproduce and understand quantitatively the results of experimental findings. Indeed, the quark gluon plasma (QGP) found at colliders and the baryon asymmetry provided by the WMAP collaboration are examples where to apply field theoretical techniques in issues relevant for Cosmology. In the simplest leptogenesis framework, heavy Majorana neutrinos are at the origin of the baryon asymmetry. The non-relativistic regime appears to be relevant during the lepton asymmetry generation where the interactions among particles occur in a thermal medium. We discuss the development of an effective field theory (EFT) for non-relativistic Majorana particles to address calculations at finite temperature. We show an application of such a method to the case of a heavy Majorana neutrino decaying in a hot and dense plasma of Standard Model (SM) particles. These techniques are analogous to those widely used for the investigation of heavy-ion collisions at colliders by exploiting hard probes. Finally we sketch some commonalities between Majorana neutrinos and bound state of heavy quarks in medium. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.0511v1.pdf"}
{"id": "1409.0773", "abstract": "  By using a simple relativistic model, we compute the glueball and gluelump spectra and relate these quantities, respectively, to the trace anomaly and Polyakov loop in the adjoint representation of gluodynamics. This spectroscopic description of thermodynamics is extended with the inclusion of quarks. The relation between the hadron resonance gas and the Polyakov loop in the fundamental and higher representations is addressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.0773v1.pdf"}
{"id": "1409.0973", "abstract": "  A Path Relinking algorithm is proposed for the Bandwidth Coloring problem and the Bandwidth MultiColoring problem. It combines a population based relinking method and a tabu search based local search procedure. The proposed algorithm is assessed on two sets of 66 benchmark instances commonly used in the literature. Computational results demonstrate that the proposed algorithm is highly competitive in terms of both solution quality and efficiency compared to the best performing algorithms in the literature. Specifically, it improves the previous best known results for 15 out of 66 instances, while matching the previous best known results for 47 cases. Some key elements of the proposed algorithm are investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.0973v1.pdf"}
{"id": "1409.1276", "abstract": "  In this paper, we present a novel approach to model the fluid/solid interaction forces in a direct solver of the Navier-Stokes equations based on the volume of fluid interface tracking method. The key ingredient of the model is the explicit inclusion of the fluid/solid interaction forces into the governing equations. We show that the interaction forces lead to a partial wetting condition and in particular to a natural definition of the equilibrium contact angle. We present two numerical methods to discretize the interaction forces that enter the model; these two approaches differ in complexity and convergence. To validate the computational framework, we consider the application of these models to simulate two-dimensional drops at equilibrium, as well as drop spreading. We demonstrate that the model, by including the underlying physics, captures contact line dynamics for arbitrary contact angles. More generally, the approach permits novel means to study contact lines, as well as a diverse range of phenomena that previously could not be addressed in direct simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.1276v2.pdf"}
{"id": "1409.1766", "abstract": "  We consider the metastable dynamics of a flattened dipolar condensate. We develop an analytic model that quantifies the energy barrier to the system undergoing local collapse to form a density spike. We also develop a stochastic Gross-Pitaevskii equation (SGPE) theory for a flatted dipolar condensate, which we use to perform finite temperature simulations verifying the local collapse scenario. We predict that local collapses play a significant role in the regime where rotons are predicted to exist, and will be an important consideration for experiments looking to detect these excitations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.1766v1.pdf"}
{"id": "1409.2326", "abstract": "  The exact formulation of multi-configuration density-functional theory (DFT) is discussed in this work. As an alternative to range-separated methods, where electron correlation effects are split in the coordinate space, the combination of Configuration Interaction methods with orbital occupation functionals is explored at the formal level through the separation of correlation effects in the orbital space. When applied to model Hamiltonians, this approach leads to an exact Site-Occupation Embedding Theory (SOET). An adiabatic connection expression is derived for the complementary bath functional and a comparison with Density Matrix Embedding Theory (DMET) is made. Illustrative results are given for the simple two-site Hubbard model. SOET is then applied to a quantum chemical Hamiltonian, thus leading to an exact Complete Active Space Site-Occupation Functional Theory (CASSOFT) where active electrons are correlated explicitly within the CAS and the remaining contributions to the correlation energy are described with an orbital occupation functional. The computational implementation of SOET and CASSOFT as well as the development of approximate functionals are left for future work. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.2326v2.pdf"}
{"id": "1409.3248", "abstract": "  Timing of high-count rate sources with the NuSTAR Small Explorer Mission requires specialized analysis techniques. NuSTAR was primarily designed for spectroscopic observations of sources with relatively low count-rates rather than for timing analysis of bright objects. The instrumental dead time per event is relatively long ( 2.5 msec), and varies by a few percent event-to-event. The most obvious effect is a distortion of the white noise level in the power density spectrum (PDS) that cannot be modeled easily with the standard techniques due to the variable nature of the dead time. In this paper, we show that it is possible to exploit the presence of two completely independent focal planes and use the cross power density spectrum to obtain a good proxy of the white noise-subtracted PDS. Thereafter, one can use a Monte Carlo approach to estimate the remaining effects of dead time, namely a frequency-dependent modulation of the variance and a frequency-independent drop of the sensitivity to variability. In this way, most of the standard timing analysis can be performed, albeit with a sacrifice in signal to noise relative to what would be achieved using more standard techniques. We apply this technique to NuSTAR observations of the black hole binaries GX 339-4, Cyg X-1 and GRS 1915+105. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.3248v1.pdf"}
{"id": "1409.4404", "abstract": "  The paper concerns two interacting consumer-resource pairs based on chemostat-like equations under the assumption that the dynamics of the resource is considerably slower than that of the consumer. The presence of two different time scales enables to carry out a fairly complete analysis of the problem. This is done by treating consumers and resources in the coupled system as fast-scale and slow-scale variables respectively and subsequently considering developments in phase planes of these variables, fast and slow, as if they are independent. When uncoupled, each pair has unique asymptotically stable steady state and no self-sustained oscillatory behavior (although damped oscillations about the equilibrium are admitted). When the consumer-resource pairs are weakly coupled through direct reciprocal inhibition of consumers, the whole system exhibits self-sustained relaxation oscillations with a period that can be significantly longer than intrinsic relaxation time of either pair. It is shown that the model equations adequately describe locally linked consumer-resource systems of quite different nature: living populations under interspecific interference competition and lasers coupled via their cavity losses. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.4404v1.pdf"}
{"id": "1409.8638", "abstract": "  This is comment to preprint arXiv:1409.7459 by Y. Tada, Wenxing Nie and M. Oshikawa \"Orbital angular momentum and spectral flow in two dimensional chiral superfluids\", where the effect of spectral flow along the edge states on the magnitude of the orbital angular momentum is discussed. The general conclusion of the preprint on the essential reduction of the angular momentum for the higher values of chirality, |ν|>1, is confirmed. However, we show that if parity is violated, the reduction of the angular momentum takes place also for the p-wave superfluids with |ν|=1. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.8638v3.pdf"}
{"id": "1410.0135", "abstract": "  We study the temporal and energy spectral characteristics of the persistent black hole X-ray binary LMC X-1 using two XMM-Newton and a Suzaku observation. We report the discovery of low frequency (  26-29 mHz) quasi-periodic oscillations (QPOs). We also report the variablity of the broad iron K-alpha line studied earlier with Suzaku. The QPOs are found to be weak with fractional rms amplitude in the   1-2 ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.0135v2.pdf"}
{"id": "1410.0966", "abstract": "  A macronova (kilonova) was discovered with a short gamma-ray burst, GRB 130603B, which is widely believed to be powered by the radioactivity of r-process elements synthesized in the ejecta of a neutron star binary merger. As an alternative, we propose that macronovae are energized by the central engine, i.e., a black hole or neutron star, and the injected energy is emitted after the adiabatic expansion of ejecta. This engine model is motivated by extended emission of short GRBs. In order to compare the theoretical models with observations, we develop analytical formulae for the light curves of macronovae. The engine model allows a wider parameter range, especially smaller ejecta mass, and better fit to observations than the r-process model. Future observations of electromagnetic counterparts of gravitational waves should distinguish energy sources and constrain the activity of central engine and the r-process nucleosynthesis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.0966v3.pdf"}
{"id": "1410.2696", "abstract": "  The main theoretical tool to provide precise predictions for scattering cross sections of strongly interacting particles is perturbative QCD. Starting at next-to-leading order (NLO) the calculation suffers from unphysical IR-divergences that cancel in the final result. At NLO there exist general subtraction algorithms to treat these divergences during a calculation. Since the LHC demands for more precise theoretical predictions, general subtraction methods at next-to-next-to-leading order (NNLO) are needed. This proceeding outlines the four-dimensional formulation of the sector improved residue subtraction. The subtraction scheme STRIPPER and in particular its extension to arbitrary multiplicities is explained. Therefore, it furnishes a general framework for the calculation of NNLO cross sections in perturbative QCD. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.2696v1.pdf"}
{"id": "1410.2723", "abstract": "  The counterfactuality of the recently proposed protocols for direct quantum communication is analyzed. It is argued that the protocols can be counterfactual only for one value of the transmitted bit. The protocols achieve a reduced probability of detection of the particle in the transmission channel by increasing the number of paths in the channel. However, this probability is not lower than the probability of detecting a particle actually passing through such a multi-path channel, which was found to be surprisingly small. The relation between security and counterfactuality of the protocols is discussed. An analysis of counterfactuality of the protocols in the framework of the Bohmian interpretation is performed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.2723v3.pdf"}
{"id": "1410.2749", "abstract": "  Directional detection of WIMPs, in which the energies and directions of the recoiling nuclei are measured, currently presents the only prospect for probing the local velocity distribution of Galactic dark matter. We investigate the extent to which future directional detectors would be capable of probing dark matter substructure in the form of streams. We analyse the signal expected from a Sagittarius-like stream and also explore the full parameter space of stream speed, direction, dispersion and density. Using a combination of non-parametric directional statistics, a profile likelihood ratio test and Bayesian parameter inference we find that within acceptable exposure times (O(10) kg yr for cross sections just below the current exclusion limits) future directional detectors will be sensitive to a wide range of stream velocities and densities. We also examine and discuss the importance of the energy window of the detector. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.2749v2.pdf"}
{"id": "1410.3099", "abstract": "  The motion of a test particle in the gravitational field of a non-spherical source endowed with both mass and mass quadrupole moment is investigated when a test radiation field is also present. The background is described by the Erez-Rosen solution, which is a static spacetime belonging to the Weyl class of solutions to the vacuum Einstein's field equations, and reduces to the familiar Schwarzschild solution when the quadrupole parameter vanishes. The radiation flux has a fixed but arbitrary (non-zero) angular momentum. The interaction with the radiation field is assumed to be Thomson-like, i.e., the particles absorb and re-emit radiation, thus suffering for a friction-like drag force. Such an additional force is responsible for the Poynting-Robertson effect, which is well established in the framework of Newtonian gravity and has been recently extended to the general theory of relativity. The balance between gravitational attraction, centrifugal force and radiation drag leads to the occurrence of equilibrium circular orbits which are attractors for the surrounding matter for every fixed value of the interaction strength. The presence of the quadrupolar structure of the source introduces a further degree of freedom: there exists a whole family of equilibrium orbits parametrized by the quadrupole parameter, generalizing previous works. This scenario is expected to play a role in the context of accretion matter around compact objects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.3099v1.pdf"}
{"id": "1410.3203", "abstract": "  We determine the character of orbits of stars moving in the meridional plane (R,z) of an axially symmetric time-independent disk galaxy model with a spherical central nucleus. In particular, we try to reveal the influence of the value of the angular momentum on the different families of orbits of stars, by monitoring how the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families evolve when angular momentum varies. The smaller alignment index (SALI) was computed by numerically integrating the equations of motion as well as the variational equations to extensive samples of orbits in order to distinguish safely between ordered and chaotic motion. In addition, a method based on the concept of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used to identify the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. Our investigation takes place both in the physical (R,z) and the phase (R,Ṙ) space for a better understanding of the orbital properties of the system. Our numerical computations reveal that low angular momentum stars are most likely to move in chaotic orbits, while on the other hand, the vast majority of high angular momentum stars perform regular orbits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.3203v1.pdf"}
{"id": "1410.3252", "abstract": "  Higher order corrections in perturbative quantum field theory are required for precise theoretical analysis to investigate new physics beyond the Standard Model. This indicates that we need to evaluate Feynman loop diagram with multi-loop integral which may require multi-precision calculation. We developed a dedicated accelerator system for multi-precision calculation (GRAPE9-MPX). We present performance results of our system for the case of Feynman two-loop box and three-loop selfenergy diagrams with multi-precision. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.3252v2.pdf"}
{"id": "1410.3989", "abstract": "  This note reexamines the data from a weight-judging competition described in an article by Francis Galton published in 1907. Following the correction of some errors, it is shown that this forecasting competition is an interesting precursor of two more recent developments in the statistical forecasting literature. One is forecast combination, with the mean forecast here exactly coinciding with the outcome, and the second is the use of two-piece frequency and probability distributions to describe asymmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.3989v1.pdf"}
{"id": "1410.4285", "abstract": "  We propose a scheme to characterize the non-Markovian dynamics and quantify the non-Markovianity via the non-classicality measured by the negativity of quantumness. By considering a qubit in contact with a critical Ising spin bath and introducing an ancilla, we show that revivals of negativity of quantumness indicate the non-Markovian dynamics. Furthermore, a normalized measure of non-Markovianity based on the negativity of quantumness is introduced and the influences of bath criticality, bath temperature and bath size on the non-Markovianity are discussed. It is shown that, at the critical point, the decay of non-Markovianity versus the size of spin bath is fastest and the non-Markovianity is exactly zero only in the thermodynamic limit. Besides, non-trivial behaviours of negativity of quantumness such as sudden change, double sudden changes and keeping constant are found for different relations between parameters of the initial state. Finally, how the non-classicality of the system is affected by a series of bang-bang pulses is also examined. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.4285v1.pdf"}
{"id": "1410.4768", "abstract": "  We present an extension of the spin-adapted configuration-interaction method for the computation of four electrons in a quasi two-dimensional quantum dot. By a group-theoretical decomposition of the basis set and working with relative and center-of-mass coordinates we obtain an analytical identification of all spurious center-of-mass states of the Coulomb-interacting electrons. We find a substantial reduction in the basis set used for numerical computations. At the same time we increase the accuracy compared to the standard spin-adapted configuration-interaction method (SACI) due to the absence of distortions caused by an unbalanced cut-off of center-of-mass excitations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.4768v2.pdf"}
{"id": "1410.5443", "abstract": "  The eigenvalue structure of the quantum transfer matrix is known to encode essential information about the elementary excitations. Here we study transfer matrices of quantum states in a topological phase using the tensor network formalism. We demonstrate that topological quantum order requires a particular type of `symmetry breaking' for the fixed point subspace of the transfer matrix, and relate physical anyon excitations to domain wall excitations at the level of the transfer matrix. A topological phase transition to a trivial phase triggers a change in the fixed point subspace to either a larger or smaller symmetry and we explain how this relates to a condensation or confinement of the corresponding anyon sectors. The tensor network formalism enables us to determine the structure of the topological sectors in two-dimensional gapped phases very efficiently, therefore opening novel avenues for studying fundamental open questions related to anyon condensation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.5443v2.pdf"}
{"id": "1410.5711", "abstract": "  Magnetic tunnel junction (MTJ) spin torque oscillators (STO) have shown the potential to be used in a wide range of microwave and sensing applications. To evaluate potential uses of MTJ STO technology in various applications, an analytical model that can capture MTJ STO's characteristics, while enabling system- and circuit-level designs, is of great importance. An analytical model based on macrospin approximation is necessary for these designs since it allows implementation in hardware description languages. This paper presents a new macrospin-based, comprehensive and compact MTJ STO model, which can be used for various MTJ STOs to estimate the performance of MTJ STOs together with their application-specific integrated circuits. To adequately present the complete model, this paper is divided into two parts. In Part I, the analytical model is introduced and verified by comparing it against measured data of three different MTJ STOs, varying the angle and magnitude of the magnetic field, as well as the DC biasing current. The proposed analytical model is suitable for being implemented in Verilog-A and used for efficient simulations at device-, circuit- and system-levels. In Part II, the full Verilog-A implementation of the analytical model with accurate phase noise generation is presented and verified by simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.5711v3.pdf"}
{"id": "1410.6788", "abstract": "  We re-examine the question of condensed neutrino objects (de- generate neutrino matter) based on new calculations. The potential show-stopper issue of free-streaming light neutrinos inhibiting galaxy formation is addressed. We compute the period associated with sim- ple harmonic motion (SHM) of galaxies embedded within condensed neutrino objects. For observational consequences, we examine the ro- tational velocities of embedded galaxies using Hickson 88A (N6978) as the prototype. Finally, we point out that degenerate neutrino objects repel each other in overlap and we compute directly the repulsive force between two interesting and relevant configurations. An outstanding issue is whether the accompanying tidal forces generated by condensed neutrino matter on embedded galaxies give rise to galactic bulges and halos. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.6788v1.pdf"}
{"id": "1410.7361", "abstract": "  To make a useful STT-MRAM (spin-transfer torque magnetoresistive random-access memory) device, it is necessary to be able to calculate switching rates, which determine the error rates of the device. In a single-macrospin model, one can use a Fokker-Planck equation to obtain a low-current thermally activated rate ∝exp(-E_eff/k_B T). Here the effective energy barrier E_eff scales with the single-macrospin energy barrier KV, where K is the effective anisotropy energy density and V the volume. A long-standing paradox in this field is that the actual energy barrier appears to be much smaller than this. It has been suggested that incoherent motions may lower the barrier, but this has proved difficult to quantify. In the present paper, we show that the coherent precession has a magnetostatic instability, which allows quantitative estimation of the energy barrier and may resolve the paradox. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.7361v1.pdf"}
{"id": "1410.8046", "abstract": "  Phase-squeezed light can enhance the precision of optical phase estimation. The larger the photon numbers are and the stronger the squeezing is, the better the precision will be. We propose an experimental scheme for generating phase-squeezed light pulses with large coherent amplitudes. In our scheme, one arm of a single-photon Mach-Zehnder interferometer interacts with coherent light via a non-linear optical Kerr medium to generate a coherent superposition state. Post-selecting the single photon by properly tuning a variable beam splitter in the interferometer yields a phase-squeezed output. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.8046v3.pdf"}
{"id": "1411.1587", "abstract": "  We present a novel approach for the optical manipulation of neutral atoms in annular light structures produced by the phenomenon of conical refraction occurring in biaxial optical crystals. For a beam focused to a plane behind the crystal, the focal plane exhibits two concentric bright rings enclosing a ring of null intensity called the Poggendorff ring. We demonstrate both theoretically and experimentally that the Poggendorff dark ring of conical refraction is confined in three dimensions by regions of higher intensity. We derive the positions of the confining intensity maxima and minima and discuss the application of the Poggendorff ring for trapping ultra-cold atoms using the repulsive dipole force of blue-detuned light. We give analytical expressions for the trapping frequencies and potential depths along both the radial and the axial directions. Finally, we present realistic numerical simulations of the dynamics of a ^87Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.1587v2.pdf"}
{"id": "1411.2193", "abstract": "  We consider three-dimensional gravity based on torsion. Specifically, we consider an extension of the so-called Teleparallel Equivalent of General Relativity in the presence of a scalar field with a self-interacting potential, where the scalar field is non-minimally coupled with the torsion scalar. Then, we find asymptotically AdS hairy black hole solutions, which are characterized by a scalar field with a power-law behavior, being regular outside the event horizon and null at spatial infinity and by a self-interacting potential, which tends to an effective cosmological constant at spatial infinity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.2193v2.pdf"}
{"id": "1411.2448", "abstract": "  Structural and physical properties determined by measurements on large single crystals of the anisotropic ferromagnet MnBi are reported. The findings support the importance of magneto-elastic effects in this material. X-ray diffraction reveals a structural phase transition at the spin reorientation temperature T_SR = 90 K. The distortion is driven by magneto-elastic coupling, and upon cooling transforms the structure from hexagonal to orthorhombic. Heat capacity measurements show a thermal anomaly at the crystallographic transition, which is suppressed rapidly by applied magnetic fields. Effects on the transport and anisotropic magnetic properties of the single crystals are also presented. Increasing anisotropy of the atomic displacement parameters for Bi with increasing temperature above T_SR is revealed by neutron diffraction measurements. It is likely that this is directly related to the anisotropic thermal expansion in MnBi, which plays a key role in the spin reorientation and magnetocrystalline anisotropy. The identification of the true ground state crystal structure reported here may be important for future experimental and theoretical studies of this permanent magnet material, which have to date been performed and interpreted using only the high temperature structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.2448v1.pdf"}
{"id": "1411.3881", "abstract": "  Based on the measurement of quantum correlation functions, the quantum statistical properties of spectral measurements are studied for broadband radiation fields. The spectral filtering of light before its detection is compared with the direct detection followed by the spectral analysis of the recorded photocurrents. As an example, the squeezing spectra of the atomic resonance fluorescence are studied for both types of filtering procedures. The conditions for which the detection of the nonclassical signatures of the radiation is possible are analyzed. For the considered example, photocurrent filtering appears to be the superior option to detect nonclassicality, due to the vacuum-noise effects in the optical filtering. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.3881v1.pdf"}
{"id": "1411.4401", "abstract": "  We consider the nonlinear energy conditions and their quantum extensions. These new energy conditions behave much better than the usual pointwise energy conditions in the presence of semiclassical quantum effects. Analogous quantum extensions for the linear energy conditions are not always satisfied as one enters the quantum realm, but they can be used to constrain the violation of the classical conditions. Thus, the existence of wormholes supported by a fluid which violates the null energy condition in a controlled way is of particular interest. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.4401v1.pdf"}
{"id": "1411.4472", "abstract": "  The ability to extract public opinion from web portals such as review sites, social networks and blogs will enable companies and individuals to form a view, an attitude and make decisions without having to do lengthy and costly researches and surveys. In this paper machine learning techniques are used for determining the polarity of forum posts on kajgana which are written in Macedonian language. The posts are classified as being positive, negative or neutral. We test different feature metrics and classifiers and provide detailed evaluation of their participation in improving the overall performance on a manually generated dataset. By achieving 92", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.4472v1.pdf"}
{"id": "1411.4828", "abstract": "  We elaborate the possibility for a deformed extra space to be considered as the dark matter candidate. To perform calculations a class of two-dimensional extra metrics was considered in the framework of the multidimensional gravity. It was shown that there exists a family of stationary metrics of the extra space possessing point-like defect. Estimation of cross section of scattering of a particle of the ordinary matter on a spatial domain with deformed extra space is in agreement with the observational constraints. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.4828v2.pdf"}
{"id": "1411.6779", "abstract": "  In this paper we provide a unified treatment of some convex minimization problems, which allows for a better understanding and, in some cases, improvement of results in this direction proved recently in spaces of curvature bounded above. For this purpose, we analyze the asymptotic behavior of compositions of finitely many firmly nonexpansive mappings in the setting of p-uniformly convex geodesic spaces focusing on asymptotic regularity and convergence results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.6779v1.pdf"}
{"id": "1412.0332", "abstract": "  We investigate the exact dynamics of trace distance discord by considering two qubits under dephasing whose states belong to a class of X states beyond Bell diagonal form. The necessary condition for the occurrence of freezing trace distance discord is found and compared with that of entropic discord. For an illustration, we consider two interacting qubits coupled to independent reservoirs and demonstrate these dynamical properties of trace distance discord. It is interesting to find that the freezing trace distance discord exists even for X states without maximally mixed marginals and can be tuned by dipole-dipole coupling of two qubits. Moreover, we consider the initial extended Werner-like states and investigate the differences between trace distance discord and entanglement. The influences of initial state and the dipole-dipole coupling of the two qubits on the dynamics of nonclassical correlations are explored. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.0332v1.pdf"}
{"id": "1412.0749", "abstract": "  In the framework of first-principles calculations, we investigate the structural and electronic properties of graphene in contact with as well as sandwiched between WS_2 and WSe_2 monolayers. We report the modification of the band characteristics due to the interaction at the interface and demonstrate that the presence of the dichalcogenides results in quantum spin Hall states in the absence of a magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.0749v1.pdf"}
{"id": "1412.1717", "abstract": "  A challenging problem in computational mathematics is to compute roots of a high-degree univariate random polynomial. We combine an efficient multiprecision implementation for solving high-degree random polynomials with two certification methods, namely Smale's α-theory and one based on Gerschgorin's theorem, for showing that a given numerical approximation is in the quadratic convergence region of Newton's method of some exact solution. With this combination, we can certifiably count the number of real roots of random polynomials. We quantify the difference between the two certification procedures and list the salient features of both of them. After benchmarking on random polynomials where the coefficients are drawn from the Gaussian distribution, we obtain novel experimental results for the Cauchy distribution case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.1717v1.pdf"}
{"id": "1412.3015", "abstract": "  We present solution of the equations for relativistic static spherically symmetric stars (SSSS) in the model of minimal dilatonic gravity (MDG) using the polytropic equation of state. A polytropic equation of state, which has a good fitting with a more realistic one, is used. Results are obtained for all variables of a single neutron star in the model of MDG. The maximum mass about two solar masses is in accordance with the latest observations of pulsars. Several new effects are observed for the variables related with the dilaton Φ and the cosmological constant Λ. The mass-radius relation is also obtained. Special attention is paid to the behavior of the quantities which describe the effects analogous to those of dark energy and dark matter in MDG. The results of the present paper confirm the conclusion that the dilaton Φ is able to play simultaneously the role of dark energy and dark matter. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.3015v2.pdf"}
{"id": "1412.3166", "abstract": "  We consider the rotation of neutrally buoyant axisymmetric particles suspended in isotropic turbulence. Using laboratory experiments as well as numerical and analytical calculations, we explore how particle rotation depends upon particle shape. We find that shape strongly affects orientational trajectories, but that it has negligible effect on the variance of the particle angular velocity. Previous work has shown that shape significantly affects the variance of the tumbling rate of axisymmetric particles. It follows that shape affects the spinning rate in a way that is, on average, complementary to the shape-dependence of the tumbling rate. We confirm this relationship using direct numerical simulations, showing how tumbling rate and spinning rate variances show complementary trends for rod-shaped and disk-shaped particles. We also consider a random but non-turbulent flow. This allows us to explore which of the features observed for rotation in turbulent flow are due to the effects of particle alignment in vortex tubes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.3166v1.pdf"}
{"id": "1412.4070", "abstract": "  We address the question on how weak perturbations, that are quite ineffective in small many-body systems, can lead to decoherence and hence to irreversibility when they proliferate as the system size increases. This question is at the heart of solid state NMR. There, an initially local polarization spreads all over due to spin-spin interactions that conserve the total spin projection, leading to an equilibration of the polarization. In principle, this quantum dynamics can be reversed by changing the sign of the Hamiltonian. However, the reversal is usually perturbed by non reversible interactions that act as a decoherence source. The fraction of the local excitation recovered defines the Loschmidt echo (LE), here evaluated in a series of closed N spin systems with all-to-all interactions. The most remarkable regime of the LE decay occurs when the perturbation induces proliferated effective interactions. We show that if this perturbation exceeds some lower bound, the decay is ruled by an effective Fermi golden rule (FGR). Such a lower bound shrinks as N increases, becoming the leading mechanism for LE decay in the thermodynamic limit. Once the polarization stayed equilibrated longer than the FGR time, it remains equilibrated in spite of the reversal procedure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.4070v3.pdf"}
{"id": "1412.4083", "abstract": "  We investigate the neutral pion photoproduction on the proton near threshold in covariant chiral perturbation theory with the explicit inclusion of Delta degrees of freedom. This channel is specially sensitive to chiral dynamics and the advent of very precise data from the Mainz microtron has shown the limits of the convergence of the chiral series for both the heavy baryon and the covariant approaches. We show that the inclusion of the Delta resonance substantially improves the convergence leading to a good agreement with data for a wider range of energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.4083v2.pdf"}
{"id": "1412.4693", "abstract": "  The recent analysis on noncommutative geometry, showing quantization of the volume for the Riemannian manifold entering the geometry, can support a view of quantum mechanics as arising by a stochastic process on it. A class of stochastic processes can be devised, arising as fractional powers of an ordinary Wiener process, that reproduce in a proper way a stochastic process on a noncommutative geometry. These processes are characterized by producing complex values and so, the corresponding Fokker-Planck equation resembles the Schroedinger equation. Indeed, by a direct numerical check, one can recover the kernel of the Schroedinger equation starting by an ordinary Brownian motion. This class of stochastic processes needs a Clifford algebra to exist. In four dimensions, the full set of Dirac matrices is needed and the corresponding stochastic process in a noncommutative geometry is easily recovered as is the Dirac equation in the Klein-Gordon form being it the Fokker–Planck equation of the process. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.4693v4.pdf"}
{"id": "1412.5405", "abstract": "  Making use of a generalized quantum theory of paraxial light propagation where the radiation-axis and the temporal coordinates play exchanged roles, we discuss the potential of bulk nonlinear optical media in cavityless configurations for quantum statistical mechanics studies of the conservative many-body dynamics of a gas of interacting photons. To illustrate the general features of this point of view, we investigate the response of the fluid of light to the quantum quenches in the photon-photon interaction constant experienced at the front and the back faces of a finite slab of weakly nonlinear material. Extending the standard Bogoliubov theory of dilute Bose-Einstein condensates, peculiar features are predicted for the statistical properties of the light emerging from the nonlinear medium. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.5405v3.pdf"}
{"id": "1412.6246", "abstract": "  The one-dimensional free Fermi gas is a prototype conformally invariant system, whose entanglement properties are well-understood. In this work, the effects of a single impurity on one dimensional free fermion entanglement entropy are studied both analytically and numerically. Such an impurity represents an exactly marginal perturbation to the bulk conformally invariant fixed point. We find that the impurity leads to sub-leading contributions to the entanglement entropy that scale inversely with the subsystem size. The origin of such contributions are identified. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6246v2.pdf"}
{"id": "1412.6261", "abstract": "  The scheme of the XUV/X-ray free electron laser based on the optical undulator created by two overlapped transverse laser beams is analyzed. A kinetic theoretical description and an ad hoc numerical model are developed to account for the finite energy spread, angular divergence and the spectral properties of the electron beam in the optical lattice. The theoretical findings are compared to the results of the one- and three-dimensional numerical modeling with the spectral free electron laser code PLARES. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6261v1.pdf"}
{"id": "1412.6338", "abstract": "  A graphene antidot lattice, created by a regular perforation of a graphene sheet, can exhibit a considerable band gap required by many electronics devices. However, deviations from perfect periodicity are always present in real experimental setups and can destroy the band gap. Our numerical simulations, using an efficient linear-scaling quantum transport simulation method implemented on graphics processing units, show that disorder that destroys the band gap can give rise to a transport gap caused by Anderson localization. The size of the defect induced transport gap is found to be proportional to the radius of the antidots and inversely proportional to the square of the lattice periodicity. Furthermore, randomness in the positions of the antidots is found to be more detrimental than randomness in the antidot radius. The charge carrier mobilities are found to be very small compared to values found in pristine graphene, in accordance with recent experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6338v2.pdf"}
{"id": "1412.6524", "abstract": "  The DAMA/LIBRA-phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles) give evidence at 9.3 σ C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(Tl) target. Results and comparisons will be shortly addressed as well as perspectives of the presently running DAMA/LIBRA-phase2. Finally, some arguments arisen in the discussion section of this workshop are mentioned in the Appendix. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6524v1.pdf"}
{"id": "1501.01534", "abstract": "  The pulsar wind model is updated by considering the effect of particle density and pulsar death. It can describe both the short term and long term rotational evolution of pulsars consistently. It is applied to model the rotational evolution of the Crab pulsar. The pulsar is spun down by a combination of magnetic dipole radiation and particle wind. The parameters of the Crab pulsar, including magnetic field, inclination angle, and particle density are calculated. The primary particle density in acceleration region is about 10^3 times the Goldreich-Julian charge density. The lower braking index between glitches is due to a larger outflowing particle density. This may be glitch induced magnetospheric activities in normal pulsars. Evolution of braking index and the Crab pulsar in P-Pdot diagram are calculated. The Crab pulsar will evolve from magnetic dipole radiation dominated case towards particle wind dominated case. Considering the effect of pulsar \"death\", the Crab pulsar (and other normal pulsars) will not evolve to the cluster of magnetars but downwards to the death valley. Different acceleration models are also considered. Applications to other sources are also discussed, including pulsars with braking index measured, and the magnetar population. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.01534v2.pdf"}
{"id": "1501.02946", "abstract": "  To obtain the initial pressure from the collected data on a planar sensor arrangement in Photoacoustic tomography, there exists an exact analytic frequency domain reconstruction formula. An efficient realization of this formula needs to cope with the evaluation of the datas Fourier transform on a non-equispaced mesh. In this paper, we use the non-uniform fast Fourier transform to handle this issue and show its feasibility in 3D experiments. This is done in comparison to the standard approach that uses polynomial interpolation. Moreover, we investigate the effect and the utility of flexible sensor location on the quality of photoacoustic image reconstruction. The computational realization is accomplished by the use of a multi-dimensional non-uniform fast Fourier algorithm, where non-uniform data sampling is performed both in frequency and spatial domain. We show that with appropriate sampling the imaging quality can be significantly improved. Reconstructions with synthetic and real data show the superiority of this method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.02946v1.pdf"}
{"id": "1501.04449", "abstract": "  We discovered fine-scale structure within the scattering disk of PSR B0329+54 in observations with the RadioAstron ground-space radio interferometer. Here, we describe this phenomenon, characterize it with averages and correlation functions, and interpret it as the result of decorrelation of the impulse-response function of interstellar scattering between the widely-separated antennas. This instrument included the 10-m Space Radio Telescope, the 110-m Green Bank Telescope, the 14x25-m Westerbork Synthesis Radio Telescope, and the 64-m Kalyazin Radio Telescope. The observations were performed at 324 MHz, on baselines of up to 235,000 km in November 2012 and January 2014. In the delay domain, on long baselines the interferometric visibility consists of many discrete spikes within a limited range of delays. On short baselines it consists of a sharp spike surrounded by lower spikes. The average envelope of correlations of the visibility function show two exponential scales, with characteristic delays of τ_1=4.1± 0.3 μ s and τ_2=23± 3 μ s, indicating the presence of two scales of scattering in the interstellar medium. These two scales are present in the pulse-broadening function. The longer scale contains 0.38 times the scattered power of the shorter one. We suggest that the longer tail arises from highly-scattered paths, possibly from anisotropic scattering or from substructure at large angles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.04449v3.pdf"}
{"id": "1501.04759", "abstract": "  In the context of agent based modeling and network theory, we focus on the problem of recovering behavior-related choice information from origin-destination type data, a topic also known under the name of network tomography. As a basis for predicting agents' choices we emphasize the connection between adaptive intelligent behavior, causal entropy maximization and self-organized behavior in an open dynamic system. We cast this problem in the form of binary and weighted networks and suggest information theoretic entropy-driven methods to recover estimates of the unknown behavioral flow parameters. Our objective is to recover the unknown behavioral values across the ensemble analytically, without explicitly sampling the configuration space. In order to do so, we consider the Cressie-Read family of entropic functionals, enlarging the set of estimators commonly employed to make optimal use of the available information. More specifically, we explicitly work out two cases of particular interest: Shannon functional and the likelihood functional. We then employ them for the analysis of both univariate and bivariate data sets, comparing their accuracy in reproducing the observed trends. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.04759v3.pdf"}
{"id": "1501.05218", "abstract": "  In this paper, we introduce the counterterms that remove the non-logarithmic divergences of the action in third order Lovelock gravity for static spacetimes. We do this by defining the cosmological constant in such a way that the asymptotic form of the metric have the same form in Lovelock and Einstein gravities. Thus, we employ the counterterms of Einstein gravity and show that the power law divergences of the action of Lovelock gravity for static spacetimes can be removed by suitable choice of coefficients. We find that the dependence of these coefficients on the dimension in Lovelock gravity is the same as in Einstein gravity. We also introduce the finite energy-momentum tensor and employ these counterterms to calculate the finite action and mass of static black hole solutions of third order Lovelock gravity. Next, we calculate the thermodynamic quantities and show that the entropy calculated through the use of Gibbs-Duhem relation is consistent with the obtained entropy by Wald's formula. Furthermore, we find that in contrast to Einstein gravity in which there exists no uncharged extreme black hole, third order Lovelock gravity can have these kind of black holes. Finally, we investigate the stability of static charged black holes of Lovelock gravity in canonical ensemble and find that small black holes show a phase transition between very small and small black holes, while the large ones are stable. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.05218v2.pdf"}
{"id": "1501.06071", "abstract": "  We introduce an information heat engine that is autonomous (i.e., without any time-dependent parameter) but has separated measurement and feedback processes. This model serves as a bridge between the other types of information heat engines inspired by Maxwell's demon; from the original Szilard-engine type systems to the autonomous demonic setups. By analyzing our model on the basis of a general framework introduced in our previous paper [N. Shiraishi and T. Sagawa, Phys. Rev. E 91, 012130 (2015).], we clarify the role of the separation of measurement and feedback in the integral fluctuation theorems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.06071v2.pdf"}
{"id": "1501.06222", "abstract": "  We study the discrimination of multipartite quantum states by local operations and classical communication. We derive that any optimal discrimination of quantum states spanning a two-dimensional Hilbert space in which each party's space is finite dimensional is possible by local operations and one-way classical communication, regardless of the optimality criterion used and how entangled the states are. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.06222v1.pdf"}
{"id": "1501.06436", "abstract": "  We study a model of particle acceleration coupled with an MHD model of magnetic reconnection in unstable twisted coronal loops. The kink instability leads to the formation of helical currents with strong parallel electric fields resulting in electron acceleration. The motion of electrons in the electric and magnetic fields of the reconnecting loop is investigated using a test-particle approach taking into account collisional scattering. We discuss the effects of Coulomb collisions and magnetic convergence near loop footpoints on the spatial distribution and energy spectra of high-energy electron populations and possible implications on the hard X-ray emission in solar flares. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.06436v1.pdf"}
{"id": "1501.06661", "abstract": "  In Compressed Sensing the matrices that satisfy the Restricted Isometry Property (RIP) play an important role. But to date, very few results for designing such matrices are available. For applications such as multiplier-less data compression, binary sensing matrices are of interest. The present work constructs deterministic and binary sensing matrices using Euler Squares. In particular, given a positive integer m different from p, p^2 for a prime p, we show that it is possible to construct a binary sensing matrix of size m × c (mμ)^2, where μ is the coherence parameter of the matrix and c ∈ [1,2). The matrices that we construct have smaller density (that is, percentage of nonzero entries in the matrix is small) with no function evaluation in their construction, which support algorithms with low computational complexity. Through experimental work, we show that our binary sensing matrices can be used for such applications as content based image retrieval. Our simulation results demonstrate that the Euler Square based CS matrices give better performance than their Gaussian counterparts. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.06661v2.pdf"}
{"id": "1501.07601", "abstract": "  We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822, obtained with the new VLT-KMOS instrument. From comparisons with model spectra in the J-band we determine the metallicity of 11 RSGs, finding a mean value of [Z] = -0.52 ± 0.21 which agrees well with previous abundance studies of young stars and HII regions. We also find an indication for a low-significance abundance gradient within the central 1 kpc. We compare our results with those derived from older stellar populations and investigate the difference using a simple chemical evolution model. By comparing the physical properties determined for RSGs in NGC 6822 with those derived using the same technique in the Galaxy and the Magellanic Clouds, we show that there appears to be no significant temperature variation of RSGs with respect to metallicity, in contrast with recent evolutionary models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.07601v1.pdf"}
{"id": "1501.07722", "abstract": "  By applying density functional theory (DFT) approximations, we present a first-principles investigation of elastic properties for the experimentally verified phases of a metallic perovskite LaNiO_3. In order to improve the accuracy of calculations, at first we select the most appropriate DFT approaches according to their performance in reproducing the low-temperature crystalline structure and the electronic density of states observed for the bulk LaNiO_3. Then, we continue with the single-crystal elastic constants and mechanical stability for the most common rhombohedral as well as high-temperature cubic and strain-induced monoclinic phases. Together with the calculated single-crystal elastic constants, the deduced polycrystalline properties, including bulk, shear, and Young's moduli, Poisson's ratio, Vickers hardness, sound velocities, Debye temperature, and anisotropy indexes, remedy the existing gap of knowledge about the elastic and mechanical behaviour of LaNiO_3, at least from a theoretical standpoint. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.07722v1.pdf"}
{"id": "1501.07758", "abstract": "  Gibbs-ringing is a well known artifact which manifests itself as spurious oscillations in the vicinity of sharp image transients, e.g. at tissue boundaries. The origin can be seen in the truncation of k-space during MRI data-acquisition. Consequently, correction techniques like Gegenbauer reconstruction or extrapolation methods aim at recovering these missing data. Here, we present a simple and robust method which exploits a different view on the Gibbs-phenomena. The truncation in k-space can be interpreted as a convolution with a sinc-function in image space. Hence, the severity of the artifacts depends on how the sinc-function is sampled. We propose to re-interpolate the image based on local, subvoxel shifts to sample the ringing pattern at the zero-crossings of the oscillating sinc-function. With this, the artifact can effectively and robustly be removed with a minimal amount of smoothing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.07758v1.pdf"}
{"id": "1502.00977", "abstract": "  Extended f(R) theories of gravity have been investigated from the symmetry point of view. We briefly has been investigated Noether symmetry of two types of extended f(R) theories: f(R,T) theory, in which curvature is coupled non minimally to the trace of energy momentum tensor T_μν and mimetic f (R) gravity, a theory with a scalar field degree of freedom, but ghost-free and with internal conformal symmetry. In both cases we write point -like Lagrangian for flat Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological background in the presence of ordinary matter. We have been shown that some classes of models existed with Noether symmetry in these viable extensions of f(R) gravity. As a motivated idea, we have been investigating the stability of the solutions and the bouncing and ΛCDM models using the Noether symmetries. We have been shown that in mimetic f(R) gravity bouncing and ΛCDM solutions are possible. Also a class of solutions with future singularities has been investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.00977v2.pdf"}
{"id": "1502.01358", "abstract": "  Distant regions close to the plane of our Galaxy are largely unexplored by optical surveys as they are hidden by dust. We have used near-infrared data (that minimizes dust obscuration) from the ESO Public survey VISTA Variables of the Via Lactea (VVV) (Minniti et al. 2011; Saito et al. 2012; henceforth S12) to search for distant stars at low latitudes. We have discovered four Cepheid variables within an angular extent of one degree centered at Galactic longitude of l = -27.4^∘ and Galactic latitude of b = -1.08 ^∘. We use the tightly constrained period-luminosity relationship that these pulsating stars obey (Persson et al. 2004; Matsunaga et al. 2011) to derive distances. We infer an average distance to these Cepheid variables of 90 kpc. The Cepheid variables are highly clustered in angle (within one degree) and in distance (the standard deviation of the distances is 12 kpc). They are at an average distance of ∼ 2  kpc from the plane and their maximum projected separation is ∼ 1  kpc. These young (∼ 100 Myr old), pulsating stars (Bono et al. 2005) are unexpected at such large distances from the Galactic disk, which terminates at ∼ 15 kpc (Minniti et al. 2011). The highly clustered nature in distance and angle of the Cepheid variables suggests that the stars may be associated with a dwarf galaxy, one that was earlier predicted by a dynamical analysis (Chakrabarti & Blitz 2009). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.01358v1.pdf"}
{"id": "1502.01767", "abstract": "  We have designed a realistic simulation of astronomical observing using a relatively low-cost commercial CCD camera and a microcontroller-based circuit that drives LEDs inside a light-tight box with time-varying intensities. As part of a laboratory experiment, students can acquire sequences of images using the camera, and then perform data analysis using a language such as MATLAB or Python to: (a) extract the intensity of the imaged LEDs, (b) perform basic calibrations on the time-series data, and (c) convert their data into the frequency domain where they can then identify the frequency structure. The primary focus is on studying light curves produced by the pulsating white dwarf stars. The exercise provides an introduction to CCD observing, a framework for teaching concepts in numerical data analysis and Fourier techniques, and connections with the physics of white dwarf stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.01767v1.pdf"}
{"id": "1502.02565", "abstract": "  In this work, the quantum confinement effect is proposed as the cause of the displacement of the vibrational spectrum of molecular groups that involve hydrogen bonds. In this approach the hydrogen bond imposes a space barrier to hydrogen and constrains its oscillatory motion. We studied the vibrational transitions through the Morse potential, for the NH and OH molecular groups inside macromolecules in situation of confinement (when hydrogen bonding is formed) and non-confinement (when there is no hydrogen bonding). The energies were obtained through the variational method with the trial wave functions obtained from Supersymmetric Quantum Mechanics (SQM) formalism. The results indicate that it is possible to distinguish the emission peaks related to the existence of the hydrogen bonds. These analytical results were satisfactorily compared with experimental results obtained from infrared spectroscopy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.02565v1.pdf"}
{"id": "1502.02928", "abstract": "  Open neutrino physics issues require precision studies, both theoretical and experimental ones, and towards this aim coherent neutral current neutrino-nucleus scattering events are expected to be observed soon. In this work, we explore ν-nucleus processes from a nuclear theory point of view and obtain results with high confidence level based on accurate nuclear structure cross sections calculations. Besides cross sections, the present study includes simulated signals expected to be recorded by nuclear detectors, differential event rates as well as total number of events predicted to be measured. Our original cross sections calculations are focused on measurable rates for the Standard Model process, but we also perform calculations for various channels of the non-standard neutrino-nucleus reactions and come out with promising results within the current upper limits of the corresponding exotic parameters. We concentrate on the possibility of detecting (i) supernova neutrinos by using massive detectors like those of the GERDA and SuperCDMS dark matter experiments and (ii) laboratory neutrinos produced near the spallation neutron source facilities (at Oak Ridge National Lab) by the COHERENT experiment. Our nuclear calculations take advantage of the relevant experimental sensitivity and employ the severe bounds extracted for the exotic parameters entering the Lagrangians of various particle physics models and specifically those resulting from the charged lepton flavour violating μ^-→ e^- experiments (Mu2e and COMET experiments). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.02928v1.pdf"}
{"id": "1502.03254", "abstract": "  We study the mass at the origin in the uncorrelated SABR stochastic volatility model, and derive several tractable expressions, in particular when time becomes small or large. As an application–in fact the original motivation for this paper–we derive small-strike expansions for the implied volatility when the maturity becomes short or large. These formulae, by definition arbitrage free, allow us to quantify the impact of the mass at zero on existing implied volatility approximations, and in particular how correct/erroneous these approximations become. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.03254v2.pdf"}
{"id": "1502.04529", "abstract": "  We study the characteristics of the light generated by few emitters in a cavity at strong light-matter coupling. By means of the Glauber g^(2)-function we can identify clearly distinguished parameter regimes with super-Poissonian and sub-Poissonian photon statistics. We establish a relation between the emission characteristics for one and multiple emitters, and explain its origin in terms of the photon-dressed emitter states. Cooperative effects lead to the generation of nonclassical light already at reduced light-matter coupling if the number of emitters is increased. Our results are obtained with a full input-output formalism and master equation valid also at strong light-matter coupling. We compare the behavior obtained with and without counter-rotating light-matter interaction terms in the Hamiltonian, and find that the generation of nonclassical light is robust against such modifications. Finally, we contrast our findings with the predictions of the quantum optical master equation and find that it fails entirely at predicting regimes with different photon statistics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.04529v2.pdf"}
{"id": "1502.06492", "abstract": "  We present a user-friendly, but powerful interface for the data mining of scientific repositories. We present the tool in use with actual astronomy data and show how it may be used to achieve many different types of powerful semantic queries. The tool itself hides the gory details of query formulation, and data retrieval from the user, and allows the user to create workflows which may be used to transform the data into a convenient form. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.06492v1.pdf"}
{"id": "1502.06718", "abstract": "  The polarization measure is the probability that among 3 individuals chosen at random from a finite population exactly 2 come from the same class. This index is maximum at the midpoints of the edges of the probability simplex. We compute the gradient flow of this index that is the differential equation whose solutions are the curves of steepest ascent. Tools from Information Geometry are extensively used. In a time series, a comparison of the estimated velocity of variation with the direction of the gradient field should be a better index than the simple variation of the index. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.06718v2.pdf"}
{"id": "1502.07055", "abstract": "  Fast Fourier transform (FFT) of large number of samples requires huge hardware resources of field programmable gate arrays (FPGA), which needs more area and power. In this paper, we present an area efficient architecture of FFT processor that reuses the butterfly elements several times. The FFT processor is simulated using VHDL and the results are validated on a Virtex-6 FPGA. The proposed architecture outperforms the conventional architecture of a N-point FFT processor in terms of area which is reduced by a factor of log_N 2 with negligible increase in processing time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.07055v1.pdf"}
{"id": "1502.07984", "abstract": "  In this work we analyze the temporal dynamics of a system comprising an optical cavity filled with a nonlinear Kerr medium, whose frequency is allowed to change during time evolution. By exactly solving the corresponding time-dependent anharmonic-oscillator Hamiltonian, we demonstrate that squeezed coherent-state superpositions can be generated within the optical cavity. Moreover, we show that the squeezing degree of the produced states may be tuned by properly controlling the frequency shift of the cavity, a feature that might lead to interesting studies in the field of quantum state engineering. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.07984v2.pdf"}
{"id": "1503.00959", "abstract": "  Single linear polymer chains in dilute solutions under good solvent conditions are studied by Monte Carlo simulations with the pruned-enriched Rosenbluth method up to the chain length N ∼ O(10^4). Based on the standard simple cubic lattice model (SCLM) with fixed bond length and the bond fluctuation model (BFM) with bond lengths in a range between 2 and √(10), we investigate the conformations of polymer chains described by self-avoiding walks (SAWs) on the simple cubic lattice, and by random walks (RWs) and non-reversible random walks (NRRWs) in the absence of excluded volume (EV) interactions. In addition to flexible chains, we also extend our study to semiflexible chains for different stiffness controlled by a bending potential. The persistence lengths of chains extracted from the orientational correlations are estimated for all cases. We show that chains based on the BFM are more flexible than those based on the SCLM for a fixed bending energy. The microscopic differences between these two lattice models are discussed and the theoretical predictions of scaling laws given in the literature are checked and verified. Our simulations clarify that a different mapping ratio between the coarse-grained models and the atomistically realistic description of polymers is required in a coarse-graining approach due to the different crossovers to the asymptotic behavior. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.00959v1.pdf"}
{"id": "1503.01627", "abstract": "  We investigate scaling of work and efficiency of a photonic Carnot engine with the number of quantum coherent resources. Specifically, we consider a generalization of the \"phaseonium fuel\" for the photonic Carnot engine, which was first introduced as a three-level atom with two lower states in a quantum coherent superposition by [M. O. Scully, M. Suhail Zubairy, G. S. Agarwal, and H. Walther, Science 299, 862 (2003)], to the case of N+1 level atoms with N coherent lower levels. We take into account atomic relaxation and dephasing as well as the cavity loss and derive a coarse grained master equation to evaluate the work and efficiency, analytically. Analytical results are verified by microscopic numerical examination of the thermalization dynamics. We find that efficiency and work scale quadratically with the number of quantum coherent levels. Quantum coherence boost to the specific energy (work output per unit mass of the resource) is a profound fundamental difference of quantum fuel from classical resources. We consider typical modern resonator set ups and conclude that multilevel phaseonium fuel can be utilized to overcome the decoherence in available systems. Preparation of the atomic coherences and the associated cost of coherence are analyzed and the engine operation within the bounds of the second law is verified. Our results bring the photonic Carnot engines much closer to the capabilities of current resonator technologies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.01627v4.pdf"}
{"id": "1503.01917", "abstract": "  The geometrically frustrated spin-1/2 Ising-Heisenberg model on triangulated Husimi lattices is exactly solved by combining the generalized star-triangle transformation with the method of exact recursion relations. The ground-state and finite-temperature phase diagrams are rigorously calculated along with both sublattice magnetizations of the Ising and Heisenberg spins. It is evidenced that the Ising-Heisenberg model on triangulated Husimi lattices with two or three inter-connected triangles-in-triangles units displays in a highly frustrated region a quantum disorder irrespective of temperature, whereas the same model on triangulated Husimi lattices with a greater connectivity of triangles-in-triangles units exhibits at low enough temperatures an outstanding quantum order due to the order-by-disorder mechanism. The quantum reduction of both sublattice magnetizations in the peculiar quantum ordered state gradually diminishes with increasing the coordination number of underlying Husimi lattice. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.01917v1.pdf"}
{"id": "1503.03313", "abstract": "  A Linear Boltzmann Transport model within perturbative QCD is developed for the study of parton propagation inside the quark-gluon plasma. Both leading partons and thermal recoil partons are tracked so that one can also study jet-induced medium excitations. In this study, we implement the complete set of elastic parton scattering processes and investigate elastic parton energy loss, transverse momentum broadening and their nontrivial energy and length dependence. We further investigate medium modifications of the jet shape and fragmentation functions of reconstructed jets. Contributions from thermal recoil partons are found to have significant influences on jet shape, fragmentation functions and angular distribution of reconstructed jets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.03313v3.pdf"}
{"id": "1503.03375", "abstract": "  We introduce new methods for robust high-precision photometry from well-sampled images of a non-crowded field with a strongly varying point-spread function. For this work, we used archival imaging data of the open cluster M37 taken by MMT 6.5m telescope. We find that the archival light curves from the original image subtraction procedure exhibit many unusual outliers, and more than 20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.03375v1.pdf"}
{"id": "1503.04234", "abstract": "  A new class of pattern forming systems is identified and investigated: anisotropic systems that are spatially inhomogeneous along the direction perpendicular to the preferred one. By studying the generic amplitude equation of this new class and a model equation, we show that branched stripe patterns emerge, which for a given parameter set are stable within a band of different wavenumbers and different numbers of branching points (defects). Moreover, the branched patterns and unbranched ones (defect-free stripes) coexist over a finite parameter range. We propose two systems where this generic scenario can be found experimentally, surface wrinkling on elastic substrates and electroconvection in nematic liquid crystals, and relate them to the findings from the amplitude equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.04234v2.pdf"}
{"id": "1503.04345", "abstract": "  We introduce a model of a dual-core optical waveguide with opposite signs of the group-velocity-dispersion (GVD) in the two cores, and a phase-velocity mismatch between them. The coupler is embedded into an active host medium, which provides for the linear coupling of a gain-loss type between the two cores. The same system can be derived, without phenomenological assumptions, by considering the three-wave propagation in a medium with the quadratic nonlinearity, provided that the depletion of the second-harmonic pump is negligible. This linear system offers an optical realization of the charge-parity (𝒞𝒫) symmetry, while the addition of the intra-core cubic nonlinearity breaks the symmetry. By means of direct simulations and analytical approximations, it is demonstrated that the linear system generates expanding Gaussian states, while the nonlinear one gives rise to broad oscillating solitons, as well as a general family of stable stationary gap solitons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.04345v1.pdf"}
{"id": "1503.04434", "abstract": "  In the present article we have obtained new set of exact solutions of Einstein field equations for anisotropic fluid spheres by using the Herrera et al.[1] algorithm. The anisotropic fluid solution so obtained join continuously to Schwarzschild exterior solution across the pressure free boundary. It is observed that most of the new anisotropic solutions are well behaved and utilized to construct the super-dense star models such as neutron star and pulsars. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.04434v2.pdf"}
{"id": "1503.05091", "abstract": "  Competition between the Kondo effect and Ruderman-Kittel-Kasuya-Yosida interaction in the two-impurity Kondo problem can be phenomenologically described by the Rasul-Schlottmann spin model. We revisit this model from the quantum entanglement perspective by calculating both the inter-impurity entanglement and the local Kondo entanglement, the latter being the entanglement between a local magnetic impurity and its spatially nearby conduction electron. A groundstate phase diagram is derived and a discontinuous breakdown of the local Kondo entanglement is found at the singular point, associated concomitantly with a jump in the inter-impurity entanglement. An entanglement monogamy holds in the whole phase diagram. Our results identify the important role of the frustrated cross-coupling and demonstrate the local characteristic of the quantum phase transition in the two-impurity Kondo problem. The implications of these results for Kondo lattices and quantum information processing are also briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.05091v1.pdf"}
{"id": "1503.06077", "abstract": "  The LHCb collaboration has recently reported on some anomalies in b→ s transitions. In addition to discrepancies with the Standard Model (SM) predictions in some angular observables and branching ratios, an intriguing hint for lepton universality violation was found. Here we propose a simple model that extends the SM with a dark sector charged under an additional U(1) gauge symmetry. The spontaneous breaking of this symmetry gives rise to a massive Z^' boson, which communicates the SM particles with a valid dark matter candidate, while solving the b→ s anomalies with contributions to the relevant observables. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.06077v2.pdf"}
{"id": "1503.06174", "abstract": "  We study the spread of stochastic SIR (Susceptible → Infectious → Recovered) epidemics in two types of structured populations, both consisting of schools and households. In each of the types, every individual is part of one school and one household. In the independent partition model, the partitions of the population into schools and households are independent of each other. This model corresponds to the well-studied household-workplace model. In the hierarchical model which we introduce here, members of the same household are also members of the same school.   We introduce computable branching process approximations for both types of populations and use these to compare the probabilities of a large outbreak. The branching process approximation in the hierarchical model is novel and of independent interest. We prove by a coupling argument that if all households and schools have the same size, an epidemic spreads easier (in the sense that the number of individuals infected is stochastically larger) in the independent partition model. We also show by example that this result does not necessarily hold if households and/or schools do not all have the same size. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.06174v1.pdf"}
{"id": "1503.06481", "abstract": "  We study analytic surfaces in 3-dimensional Euclidean space containing two circular arcs through each point. The problem of finding such surfaces traces back to the works of Darboux from XIXth century. We reduce finding all such surfaces to the algebraic problem of finding all Pythagorean 6-tuples of polynomials. The reduction is based on the Schicho parametrization of surfaces containing two conics through each point and a new approach using quaternionic rational parametrization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.06481v2.pdf"}
{"id": "1503.06841", "abstract": "  The high-mass star-forming site G009.62+00.20E hosts the 6.7 GHz methanol maser source with the greatest flux density in the Galaxy which has been flaring periodically over the last ten years. We performed high-resolution astrometric measurements of the CH3OH, H2O, and OH maser emission and 7 mm continuum in the region. The radio continuum emission was resolved in two sources separated by 1300 AU. The CH3OH maser cloudlets are distributed along two north-south ridges of emission to the east and west of the strongest radio continuum component. This component likely pinpoints a massive young stellar object which heats up its dusty envelope, providing a constant IR pumping for the Class II CH3OH maser transitions. We suggest that the periodic maser activity may be accounted for by an independent, pulsating, IR radiation field provided by a bloated protostar in the vicinity of the brightest masers. We also report about the discovery of an elliptical distribution of CH3OH maser emission in the region of periodic variability. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.06841v2.pdf"}
{"id": "1503.07200", "abstract": "  We consider a nonlinear kinetic equation of Boltzmann type which takes into account the influence of conviction during the formation of opinion in a system of agents which interact through the binary exchanges introduced in [G. Toscani, Commun. Math. Sci. 4, 481 (2006)]. The original exchange mechanism, which is based on the human tendency to compromise and change of opinion through self-thinking, is here modified in the parameters of the compromise and diffusion terms, which now are assumed to depend on the personal degree of conviction. The numerical simulations show that the presence of conviction has the potential to break symmetry, and to produce clusters of opinions. The model is partially inspired by the recent work [L. Pareschi, G. Toscani, Phil. Trans. R. Soc. A 372, 20130396 (2014)], in which the role of knowledge in the formation of wealth distribution has been investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.07200v1.pdf"}
{"id": "1503.08453", "abstract": "  We consider an special dynamics of a quantum walk (QW) on a line. Initially, the walker localized at the origin of the line with arbitrary chirality, evolves to an asymptotic stationary state. In this stationary state a measurement is performed and the state resulting from this measurement is used to start a second QW evolution to achieve a second asymptotic stationary state. In previous works, we developed the thermodynamics associated with the entanglement between the coin and position degrees of freedom in the QW. Here we study the application of the first and second laws of thermodynamics to the process between the two stationary states mentioned above. We show that: i) the entropy change has upper and lower bounds that are obtained analytically as a function of the initial conditions. ii) the energy change is associated to a heat-transfer process. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.08453v1.pdf"}
{"id": "1503.08946", "abstract": "  Traditional databases are not equipped with the adequate functionality to handle the volume and variety of \"Big Data\". Strict schema definition and data loading are prerequisites even for the most primitive query session. Raw data processing has been proposed as a schema-on-demand alternative that provides instant access to the data. When loading is an option, it is driven exclusively by the current-running query, resulting in sub-optimal performance across a query workload. In this paper, we investigate the problem of workload-driven raw data processing with partial loading. We model loading as fully-replicated binary vertical partitioning. We provide a linear mixed integer programming optimization formulation that we prove to be NP-hard. We design a two-stage heuristic that comes within close range of the optimal solution in a fraction of the time. We extend the optimization formulation and the heuristic to pipelined raw data processing, scenario in which data access and extraction are executed concurrently. We provide three case-studies over real data formats that confirm the accuracy of the model when implemented in a state-of-the-art pipelined operator for raw data processing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.08946v2.pdf"}
{"id": "1504.00404", "abstract": "  The Radial Velocity Experiment (RAVE) is a large wide-field spectroscopic stellar survey of the Milky Way. Over the period 2003-2013, 574,630 spectra for 483,330 stars have been amassed at a resolution of R=7500 in the Ca-triplet region of 8410-8795Å. Wavelength coverage and resolution are thus comparable to that anticipated from the Gaia RVS. Derived data products of RAVE include radial velocities, stellar parameters, chemicals abundances for Mg, Al, Si, Ca, Ti, Fe, and Ni, and absorption measures based on the diffuse interstellar bands (DIB) at 8620Å. Since more than 290000 RAVE targets are drawn from the Tycho-2 catalogue, RAVE will be an interesting prototype for the anticipated full Gaia data releases, in particular when combined with the early Gaia data releases, which contain astrometry but not yet stellar parameters and abundances. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.00404v1.pdf"}
{"id": "1504.00590", "abstract": "  The mesoscopic organization of complex systems, from financial markets to the brain, is an intermediate between the microscopic dynamics of individual units (stocks or neurons, in the mentioned cases), and the macroscopic dynamics of the system as a whole. The organization is determined by \"communities\" of units whose dynamics, represented by time series of activity, is more strongly correlated internally than with the rest of the system. Recent studies have shown that the binary projections of various financial and neural time series exhibit nontrivial dynamical features that resemble those of the original data. This implies that a significant piece of information is encoded into the binary projection (i.e. the sign) of such increments. Here, we explore whether the binary signatures of multiple time series can replicate the same complex community organization of the financial market, as the original weighted time series. We adopt a method that has been specifically designed to detect communities from cross-correlation matrices of time series data. Our analysis shows that the simpler binary representation leads to a community structure that is almost identical with that obtained using the full weighted representation. These results confirm that binary projections of financial time series contain significant structural information. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.00590v1.pdf"}
{"id": "1504.01096", "abstract": "  We carry out the harmonic analysis on four Platonic spherical three-manifolds with different topologies. Starting out from the homotopies (Everitt 2004), we convert them into deck operations, acting on the simply connected three-sphere as the cover, and obtain the corresponding variety of deck groups. For each topology, the three-sphere is tiled into copies of a fundamental domain under the corresponding deck group. We employ the point symmetry of each Platonic manifold to construct its fundamental domain as a spherical orbifold. While the three-sphere supports an orthonormal complete basis for harmonic analysis formed by Wigner polynomials, a given spherical orbifold leads to a selection of a specific subbasis. The resulting selection rules find applications in cosmic topology, probed by the cosmic microwave background. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.01096v1.pdf"}
{"id": "1504.01205", "abstract": "  Type Ib/c supernovae (SNe Ib/c) mark the deaths of hydrogen-deficient massive stars. The evolutionary scenarios for SNe Ib/c progenitors involve many important physical processes including mass loss by winds and its metallicity dependence, stellar rotation, and binary interactions. This makes SNe Ib/c an excellent test bed for stellar evolution theory. We review the main results of evolutionary models for SN Ib/c progenitors available in the literature and their confrontation with recent observations. We argue that the nature of SN Ib/c progenitors can be significantly different for single and binary systems, and that binary evolution models can explain the ejecta masses derived from SN Ib/c light curves, the distribution of SN Ib/c sites in their host galaxies, and the optical magnitudes of the tentative progenitor candidate of iPTF13bvn. We emphasize the importance of early-time observations of light curves and spectra, accurate measurements of helium mass in SN Ib/c ejecta, and systematic studies about the metallicity dependence of SN Ib/c properties, to better constrain theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.01205v2.pdf"}
{"id": "1504.02189", "abstract": "  We present a technique to construct a spectropolarimetrically accurate magneto-hydrostatic model of a large-scale solar magnetic field concentration, mimicking a sunspot. Using the constructed model we perform a simulation of acoustic wave propagation, conversion and absorption in the solar interior and photosphere with the sunspot embedded into it. With the 6173Å magnetically sensitive photospheric absorption line of neutral iron, we calculate observable quantities such as continuum intensities, Doppler velocities, as well as full Stokes vector for the simulation at various positions at the solar disk, and analyse the influence of non-locality of radiative transport in the solar photosphere on helioseismic measurements. Bisector shapes were used to perform multi-height observations. The differences in acoustic power at different heights within the line formation region at different positions at the solar disk were simulated and characterised. An increase in acoustic power in the simulated observations of the sunspot umbra away from the solar disk centre was confirmed as the slow magneto-acoustic wave. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.02189v1.pdf"}
{"id": "1504.02299", "abstract": "  We provide the solution of the classical theory for the Higgs sector of the Standard Model obtaining the exact Green function for the broken phase. Solving the Dyson-Schwinger equations for the Higgs field we show that the propagator coincides with that of the classical theory confirming the spectrum also at the quantum level. In this way we obtain a proof of triviality using the Källen-Lehman representation. This has as a consequence that higher excited states must exist for the Higgs particle, representing an internal spectrum for it. Higher excited states have exponentially smaller amplitudes and so, their production rates are significantly depressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.02299v3.pdf"}
{"id": "1504.03834", "abstract": "  We compare the capability of wavelet functions used for noise removal in preprocessing step of a QRS detection algorithm in the electrocardiogram (ECG) signal. The QRS signal to noise ratio enhancement and the detection accuracy of each wavelet function are evaluated using three measures: (1) the ratio of the maximum beat amplitude to the minimum beat amplitude (RMM), (2) the mean of absolute of time error (MATE), and (3) the figure of merit (FOM). Three wavelet functions from previous well-known publications are explored, i.e., Bior1.3, Db10, and Mexican hat wavelet functions. Results evaluated with the ECG signal from MIT-BIH arrhythmia database show that the Mexican hat wavelet function is better than the others. While the scale 8 of Mexican hat wavelet function can provide the best enhancement in QRS signal to noise ratio, the scale 4 of Mexican hat wavelet function can provide the best detection accuracy. These results may be combined and may enable the use of a single fixed threshold for all ECG records leading to the reduction in computational complexity of the QRS detection algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.03834v2.pdf"}
{"id": "1504.05710", "abstract": "  It has been pointed out that the null energy condition can be violated stably in some non-canonical scalar-field theories. This allows us to consider the Galilean Genesis scenario in which the universe starts expanding from Minkowski spacetime and hence is free from the initial singularity. We use this scenario to study the early-time completion of inflation, pushing forward the recent idea of Pirtskhalava et al. We present a generic form of the Lagrangian governing the background and perturbation dynamics in the Genesis phase, the subsequent inflationary phase, and the graceful exit from inflation, as opposed to employing the effective field theory approach. Our Lagrangian belongs to a more general class of scalar-tensor theories than the Horndeski theory and Gleyzes-Langlois-Piazza-Vernizzi generalization, but still has the same number of the propagating degrees of freedom, and thus can avoid Ostrogradski instabilities. We investigate the generation and evolution of primordial perturbations in this scenario and show that one can indeed construct a stable model of inflation preceded by (generalized) Galilean Genesis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.05710v2.pdf"}
{"id": "1504.06350", "abstract": "  In this paper, we give a characterization of the visibility graphs of pseudo-polygons. We first identify some key combinatorial properties of pseudo-polygons, and we then give a set of five necessary conditions based off our identified properties. We then prove that these necessary conditions are also sufficient via a reduction to a characterization of vertex-edge visibility graphs given by O'Rourke and Streinu. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.06350v1.pdf"}
{"id": "1504.06412", "abstract": "  Self-steepening of optical pulses arises due the dispersive contribution of the χ^(3)(ω) Kerr nonlinearity. In typical structures this response is on the order of a few femtoseconds with a fixed frequency response. In contrast, the effective χ^(3) Kerr nonlinearity in photonic crystal waveguides (PhCWGs) is largely determined by the geometrical parameters of the structure and is consequently tunable over a wide range. Here we show self-steepening based on group-velocity (group-index) modulation for the first time, giving rise to a new physical mechanism for generating this effect. Further, we demonstrate that periodic media such as PhCWGS can exhibit self-steepening coefficients two orders of magnitude larger than typical systems. At these magnitudes the self-steepening strongly affects the nonlinear pulse dynamics even for picosecond pulses. Due to interaction with additional higher-order nonlinearities in the semiconductor materials under consideration, we employ a generalized nonlinear Schrödinger equation numerical model to describe the impact of self-steepening on the temporal and spectral properties of the optical pulses in practical systems, including new figures of merit. These results provide a theoretical description for recent experimental results presented in [Scientific Reports 3, 1100 (2013) and Phys. Rev. A 87, 041802 (2013)]. More generally, these observations apply to all periodic media due to the rapid group-velocity variation characteristic of these structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.06412v1.pdf"}
{"id": "1504.07085", "abstract": "  We extend the Balancing Domain Decomposition by Constraints (BDDC) method to flows in porous media discretised by mixed-hybrid finite elements with combined mesh dimensions. Such discretisations appear when major geological fractures are modelled by 1D or 2D elements inside three-dimensional domains. In this set-up, the global problem as well as the substructure problems have a symmetric saddle-point structure, containing a `penalty' block due to the combination of meshes. We show that the problem can be reduced by means of iterative substructuring to an interface problem, which is symmetric and positive definite. The interface problem can thus be solved by conjugate gradients with the BDDC method as a preconditioner. A parallel implementation of this algorithm is incorporated into an existing software package for subsurface flow simulations. We study the performance of the iterative solver on several academic and real-world problems. Numerical experiments illustrate its efficiency and scalability. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.07085v1.pdf"}
{"id": "1504.07970", "abstract": "  We propose a fundamental theory whose low-energy effective theory provides a phenomenological description of electroweak baryogenesis, radiative neutrino mass generation, and dark matter. The model is based on SUSY SU(2)_H gauge theory with confinement, and the model contains new Z_2 discrete symmetry and Z_2-odd right-handed neutrino superfields. The Higgs sector in the low energy effective theory of this model below confinement scale is described by fifteen mesonic superfields of fundamental SU(2)_H doublets. We present a benchmark scenario of this model, where all the constraints from the current neutrino, dark matter, lepton flavour violation and LHC data are satisfied. We also discuss how to test the scenario by the future collider experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.07970v1.pdf"}
{"id": "1505.00872", "abstract": "  This paper introduces a new optimal control model to describe and control the dynamics of infectious diseases. In the present model, the average time of isolation (i.e. hospitalization) of infectious population is the main time-dependent parameter that defines the spread of infection. All the preventive measures aim to decrease the average time of isolation under given constraints. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.00872v1.pdf"}
{"id": "1505.02207", "abstract": "  To clarify the origin of a charge-density wave (CDW) phase in 1T-TiSe_2, we study the ground state property of a half-filled two-band Hubbard model in a triangular lattice including electron-phonon interaction. By using the variational Monte Carlo method, the electronic and lattice degrees of freedom are both treated quantum mechanically on an equal footing beyond the mean-field approximation. We find that the cooperation between Coulomb interaction and electron-phonon interaction is essential to induce the CDW phase. We show that the \"pure\" exciton condensation without lattice distortion is difficult to realize under the poor nesting condition of the underlying Fermi surface. Furthermore, by systematically calculating the momentum resolved hybridization between the two bands, we examine the character of electron-hole pairing from the viewpoint of BCS-BEC crossover within the CDW phase and find that the strong-coupling BEC-like pairing dominates. We therefore propose that the CDW phase observed in 1T-TiSe_2 originates from a BEC-like electron-hole pairing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.02207v2.pdf"}
{"id": "1505.02210", "abstract": "  We model the multi-wavelength emission in the southern hotspot of the radio quasar 4C74.26. The synchrotron radio emission is resolved near the shock with the MERLIN radio-interferometer, and the rapid decay of this emission behind the shock is interpreted as the decay of the amplified downstream magnetic field as expected for small scale turbulence. Electrons are accelerated to only 0.3 TeV, consistent with a diffusion coefficient many orders of magnitude greater than in the Bohm regime. If the same diffusion coefficient applies to the protons, their maximum energy is only  100 TeV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.02210v2.pdf"}
{"id": "1505.02762", "abstract": "  We propose a novel mechanism for the protection against spin gapped states in doped antiferromagnets. It requires the presence of a Chern-Simons term that can be generated by a coupling between spin and an insulator. We first demonstrate that in the presence of this term the vortex loop excitations of the spin sector behave as anyons with fractional statistics. To generate such term, the fermions should have massive Dirac spectrum coupled to the emergent spin field of the spin sector. The Dirac spectrum can be realized by a planar spin configuration arising as the lowest-energy configuration of a square lattice antiferromagnet Hamiltonian involving a Dzyaloshinskii-Moriya interaction. The mass is provided by a combination of dimerization and staggered chemical potential. We finally show that for realistic parameters, anyonic vortex loop condensation will likely never occur and thus the spin gapped state is prevented. We also propose real magnetic materials for an experimental verification of our theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.02762v2.pdf"}
{"id": "1505.03933", "abstract": "  We report the measurement of the directed flow (v_1) for charged kaons in Au+Au collisions at √(s_NN) =7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV as a function of rapidity and compare these results for pions, protons and antiprotons. These new kaon results may help to constrain the medium properties and collision dynamics including the in-medium kaon potential and baryon number transport in these collisions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.03933v1.pdf"}
{"id": "1505.05378", "abstract": "  The stationary thermionic electron emission currents from heated metals are compared against an analytical expression derived using a non equilibrium quantum Kappa energy distribution for the electrons. This later depends on the temperature decreasing parameter κ(T) which can be estimated from the raw experimental data and characterizes the departure of the electron energy spectrum from the equilibrium Fermi-Dirac statistics. The calculations accurately predict the measured thermionic emission currents for both high and moderate temperature ranges. The Richardson-Dushman law governs the electron emission for large values of Kappa or equivalently, for moderate metal temperatures. The high energy tail in the electron energy distribution function which develops at higher temperatures or lower Kappa parameters, increases the emission currents well over the predictions of the classical expression. This analysis also permits the quantitative estimation of the departure of the metal electrons from the equilibrium Fermi-Dirac statistics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.05378v1.pdf"}
{"id": "1505.05445", "abstract": "  We present a scheme for locking optical cavities with arbitrary detuning many line widths from resonance using an electro-optic modulator that can provide arbitrary ratios of amplitude to phase modulation. We demonstrate our scheme on a Fabry-Perot cavity, and show that a well-behaved linear error signal can be obtained by demodulating the reflected light from a cavity that is detuned by several line widths. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.05445v1.pdf"}
{"id": "1505.05640", "abstract": "  We investigate the possibility that the broken spatial inversion symmetry by a trap potential induces a spin-triplet Cooper-pair amplitude in an s-wave superfluid Fermi gas. Being based on symmetry considerations, we clarify that this phenomenon may occur, when a spin rotation symmetry of the system is also broken. We also numerically confirm that a triplet pair amplitude is really induced under this condition, using a simple model. Our results imply that this phenomenon is already present in a trapped s-wave superfluid Fermi gas with spin imbalance. As an interesting application of this phenomenon, we point out that one may produce a p-wave superfluid Fermi gas, by suddenly changing the s-wave pairing interaction to a p-wave one by using the Feshbach resonance technique. Since a Cooper pair is usually classified into the spin-singlet (and even-parity) state and the spin-triplet (and odd-parity) state, our results would be useful in considering how to mix them with each other in a superfluid Fermi gas. Such admixture has recently attracted much attention in the field of non-centrosymmetric superconductivity, so that our results would also contribute to the further development of this research field, on the viewpoint of cold Fermi gas physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.05640v1.pdf"}
{"id": "1505.05961", "abstract": "  We study the effects of hadronic rescattering on hadron distributions in high-energy nuclear collisions by using an integrated dynamical approach. This approach is based on a hybrid model combining (3+1)-dimensional ideal hydrodynamics for the quark gluon plasma (QGP), and a transport model for the hadron resonance gas. Since the hadron distributions are the result of the entire expansion history of the system, understanding the QGP properties requires investigating how rescattering during the hadronic stage affects the final distributions of hadrons. We include multistrange hadrons in our study, and quantify the effects of hadronic rescattering on their mean transverse momenta and elliptic flow. We find that multistrange hadrons scatter less during the hadronic stage than nonstrange particles, and thus their distributions reflect the properties of the system in an earlier stage than the distributions of nonstrange particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.05961v2.pdf"}
{"id": "1505.06073", "abstract": "  This paper aims to validate the β-Ginibre point process as a model for the distribution of base station locations in a cellular network. The β-Ginibre is a repulsive point process in which repulsion is controlled by the β parameter. When β tends to zero, the point process converges in law towards a Poisson point process. If β equals to one it becomes a Ginibre point process. Simulations on real data collected in Paris (France) show that base station locations can be fitted with a β-Ginibre point process. Moreover we prove that their superposition tends to a Poisson point process as it can be seen from real data. Qualitative interpretations on deployment strategies are derived from the model fitting of the raw data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.06073v1.pdf"}
{"id": "1505.06628", "abstract": "  We introduce the notion of π-cosupport as a new tool for the stable module category of a finite group scheme. In the case of a finite group, we use this to give a new proof of the classification of tensor ideal localising subcategories. In a sequel to this paper, we carry out the corresponding classification for finite group schemes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.06628v2.pdf"}
{"id": "1505.07943", "abstract": "  We investigate the properties in finite magnetic field of an extended anisotropic XXZ spin-1/2 model on the Kagome lattice, originally introduced by Balents, Fisher, and Girvin [Phys. Rev. B, 65, 224412 (2002)]. The magnetization curve displays plateaus at magnetization m=1/6 and 1/3 when the anisotropy is large. Using low-energy effective constrained models (quantum loop and quantum dimer models), we discuss the nature of the plateau phases, found to be crystals that break discrete rotation and/or translation symmetries. Large-scale quantum Monte-Carlo simulations were carried out in particular for the m=1/6 plateau. We first map out the phase diagram of the effective quantum loop model with an additional loop-loop interaction to find stripe order around the point relevant for the original model as well as a topological Z2 spin liquid. The existence of a stripe crystalline phase is further evidenced by measuring both standard structure factor and entanglement entropy of the original microscopic model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.07943v2.pdf"}
{"id": "1506.00282", "abstract": "  The stability, electronic and optical properties of single-walled carbon nanotubes (CNTs) and graphene noncovalently functionalized with free-base tetraphenylporphyrin (TPP) molecules is addressed by density functional theory calculations, including corrections to dispersive interactions. We study the TPP physisorption on 42 CNT species, particularly those with chiral indices (n,m), where 5 ≤ n ≤ 12 and 0≤ m≤ n. Our results show a quite strong π-π interaction between TPP and the CNT surface, with binding energies ranging from 1.1 to 1.8 eV, where higher energies can be associated with increasing CNT diameters. We also find that the TPP optical absorptions would not be affected by the CNT diameter or chirality. Results for the TPP physisorption on graphene show a remarkable stability with binding energy of 3.2 eV, inducing a small redshift on the π-stacked TPP absorption bands. The strong graphene-TPP interaction also induces a charge transfer from TPP to graphene, indicating a n-type doping mechanism without compromising the graphene structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.00282v1.pdf"}
{"id": "1506.00902", "abstract": "  We propose a novel method to constrain the spatial extent of dust around galaxies through the measurement of dust temperature. Our method combines the dust emission of galaxies from far-infrared (FIR) image stacking analysis and the quasar reddening due to the dust absorption around galaxies. As a specific application of our method, we use the stacked FIR emission profiles of SDSS photometric galaxies over the IRAS 100μm map, and the recent measurement of the SDSS galaxy-quasar cross-correlation. If we adopt a single-temperature dust model, the resulting temperature is around 18K, which is consistent with a typical dust temperature for a central part of galaxies. If we assume an additional dust component with much lower temperature, the current data imply the temperature of the galactic dust needs to be higher, 20K to 30K. Since the model of the density and temperature distribution of dust adopted in the current paper is very simple, we cannot draw any strong conclusion at this point. Nevertheless our novel method with the elaborated theoretical model and multi-band measurement of dust will offer an interesting constraint on the statistical nature of galactic dust. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.00902v1.pdf"}
{"id": "1506.01252", "abstract": "  The robust effect of curvature on spin polarization is reported in a three-terminal bridge system where the bridging material is subjected to Rashba spin-orbit interaction. The results are examined considering two different geometric configurations, ring- and linear-like, of the material which is coupled to one input and two output leads. Our results exhibit absolute zero spin polarization for the linear sample, while finite polarization is obtained in output leads for the ring-like sample. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.01252v1.pdf"}
{"id": "1506.02040", "abstract": "  We present an algorithm that computes the multipole coefficients of the galaxy three-point correlation function (3PCF) without explicitly considering triplets of galaxies. Rather, centering on each galaxy in the survey, it expands the radially-binned density field in spherical harmonics and combines these to form the multipoles without ever requiring the relative angle between a pair about the central. This approach scales with number and number density in the same way as the two-point correlation function, allowing runtimes that are comparable, and 500 times faster than a naive triplet count. It is exact in angle and easily handles edge correction. We demonstrate the algorithm on the LasDamas SDSS-DR7 mock catalogs, computing an edge corrected 3PCF out to 90  Mpc/h in under an hour on modest computing resources. We expect this algorithm will render it possible to obtain the large-scale 3PCF for upcoming surveys such as Euclid, LSST, and DESI. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.02040v2.pdf"}
{"id": "1506.02456", "abstract": "  The percolation threshold and wrapping probability R_∞ for the two-dimensional problem of continuum percolation on the surface of a Klein bottle have been calculated by the Monte Carlo method with the Newman–Ziff algorithm for completely permeable disks. It has been shown that the percolation threshold of disks on the Klein bottle coincides with the percolation threshold of disks on the surface of a torus, indicating that this threshold is topologically invariant. The scaling exponents determining corrections to the wrapping probability and critical concentration owing to the finite-size effects are also topologically invariant. At the same time, the quantities R_∞ are different for percolation on the torus and Klein bottle and are apparently determined by the topology of the surface. Furthermore, the difference between the R_∞ values for the torus and Klein bottle means that at least one of the percolation clusters is degenerate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.02456v1.pdf"}
{"id": "1506.03326", "abstract": "  We present Suzaku XIS observation of V2491 Cyg (Nova Cyg 2008 No. 2) obtained in quiescence, more than two years after the outburst. The nova was detected as a very luminous source in a wide spectral range from soft to hard X-rays. A very soft blackbody-like component peaking at 0.5 keV indicates that either we observe remaining, localized hydrogen burning on the surface of the white dwarf, or accretion onto a magnetized polar cap. In the second case, V2491 Cyg is a candidate \"soft intermediate polar\". We obtained the best fit for the X-ray spectra with several components: two of thermal plasma, a blackbody and a complex absorber. The later is typical of intermediate polars. The X-ray light-curve shows a modulation with a ∼38 min period. The amplitude of this modulation is strongly energy dependent and reaches maximum in the 0.8–2.0 keV range. We discuss the origin of the X-ray emission and pulsations, and the likelihood of the intermediate polar scenario. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.03326v1.pdf"}
{"id": "1506.04169", "abstract": "  Three identical bosons or fermions are considered in the limit of zero-range interactions and finite effective range. By using a two channel model, we show that these systems are not integrable and that the wave function verifies specific continuity conditions at the contact of three particles. This last feature permits us to solve a contradiction brought by the contact model which can lead to an opposite result concerning the integrability issue. For fermions, the vicinity of integrability is characterized by large deviations with respect to the predictions of the Bethe ansatz. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.04169v2.pdf"}
{"id": "1506.05718", "abstract": "  The results of speckle interferometric observations at the SOAR telescope in 2014 are given. A total of 1641 observations were taken, yielding 1636 measurements of 1218 resolved binary and multiple stars and 577 non-resolutions of 441 targets. We resolved for the first time 56 pairs, including some nearby astrometric or spectroscopic binaries and ten new subsystems in previously known visual binaries. The calibration of the data is checked by linear fits to the positions of 41 wide binaries observed at SOAR over several seasons. The typical calibration accuracy is 0.1deg in angle and 0.3", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.05718v1.pdf"}
{"id": "1506.06147", "abstract": "  We consider estimating the parameter associated with the qubit depolarizing channel when the available initial states that might be employed are mixed. We use quantum Fisher information as a measure of the accuracy of estimation to compare protocols which use collections of qubits in product states to one in which the qubits are in a correlated state. We show that, for certain parameter values and initial states, the correlated state protocol can yield a greater accuracy per channel invocation than the product state protocols. We show that, for some parameters and initial states, using more than two qubits and channel invocations is advantageous. These results stand in contrast to the known optimal case that uses pure initial states and a single channel invocation on a pair of entangled qubits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.06147v1.pdf"}
{"id": "1506.06613", "abstract": "  Contraction theory is a powerful tool for proving asymptotic properties of nonlinear dynamical systems including convergence to an attractor and entrainment to a periodic excitation. We consider three generalizations of contraction with respect to a norm that allow contraction to take place after small transients in time and/or amplitude. These generalized contractive systems (GCSs) are useful for several reasons. First, we show that there exist simple and checkable conditions guaranteeing that a system is a GCS, and demonstrate their usefulness using several models from systems biology. Second, allowing small transients does not destroy the important asymptotic properties of contractive systems like convergence to a unique equilibrium point, if it exists, and entrainment to a periodic excitation. Third, in some cases as we change the parameters in a contractive system it becomes a GCS just before it looses contractivity with respect to a norm. In this respect, generalized contractivity is the analogue of marginal stability in Lyapunov stability theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.06613v1.pdf"}
{"id": "1506.06731", "abstract": "  Description of a nuclear system in its ground state and at low excitations based on the equation of state (EoS) around normal density is presented. In the expansion of the EoS around the saturation point additional spin polarization terms are taken into account. These terms, together with the standard symmetry term, are responsible for appearance of the α-like clusters in the ground state configurations of the N=Z even-even nuclei. At the nuclear surface these clusters can be identified as alpha particles. A correction for the surface effects is introduced for atomic nuclei. Taking into account an additional interaction between clusters the binding energies and sizes of the considered nuclei are very accurately described. The limits of the EoS parameters are established from the properties of the α, ^3He and t particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.06731v3.pdf"}
{"id": "1506.07185", "abstract": "  What intrinsic properties shape the light curves of Type II supernovae (SNe)? To address this question we derive observational measures that are robust (i.e., insensitive to detailed radiative transfer) and constrain the contribution from ^56Ni, as well as a combination of the envelope mass, progenitor radius, and explosion energy. By applying our methods to a sample of type II SNe from the literature we find that ^56Ni contribution is often significant. In our sample its contribution to the time weighted integrated luminosity during the photospheric phase ranges between 8", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.07185v2.pdf"}
{"id": "1506.08974", "abstract": "  Starting from a microscopic model, we investigate the optical spectra of molecules in strongly-coupled organic microcavities examining how they might self-consistently adapt their coupling to light. We consider both rotational and vibrational degrees of freedom, focusing on features which can be seen in the peak in the center of the spectrum at the bare excitonic frequency. In both cases we find that the matter-light coupling can lead to a self-consistent change of the molecular states, with consequent temperature-dependent signatures in the absorption spectrum. However, for typical parameters, these effects are much too weak to explain recent measurements. We show that another mechanism which naturally arises from our model of vibrationally dressed polaritons has the right magnitude and temperature dependence to be at the origin of the observed data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.08974v2.pdf"}
{"id": "1507.00069", "abstract": "  We propose a quantum processor for the scalable quantum computation on microwave photons in distant one-dimensional superconducting resonators. It is composed of a common resonator R acting as a quantum bus and some distant resonators r_j coupled to the bus in different positions assisted by superconducting quantum interferometer devices (SQUID), different from previous processors. R is coupled to one transmon qutrit, and the coupling strengths between r_j and R can be fully tuned by the external flux through the SQUID. To show the processor can be used to achieve universal quantum computation effectively, we present a scheme to complete the high-fidelity quantum state transfer between two distant microwave-photon resonators and another one for the high-fidelity controlled-phase gate on them. By using the technique for catching and releasing the microwave photons from resonators, our processor may play an important role in quantum communication as well. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.00069v2.pdf"}
{"id": "1507.00203", "abstract": "  We analyze the dynamics of model supercooled liquids in a temperature regime where predictions of mode coupling theory (MCT) are known to be valid qualitatively. In this regime, the Adam-Gibbs (AG) relation, based on an activation picture of dynamics also describes the dynamics satisfactorily, and we explore the mutual consistency and interrelation of these descriptions. Although entropy and dynamics are related via phenomenological theories, the connection between MCT and entropy has not been argued for. In this work we explore this connection and provide a microscopic derivation of the phenomenological Rosenfeld theory. At low temperatures the overlap between MCT power law regime and AG relation implies that the AG relation predicts an avoided divergence at T_c, the origin of which is traced back to the vanishing of pair configurational entropy, which we find occurs at the same temperature. We also show that the residual multiparticle entropy plays an important role in describing the relaxation time ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.00203v1.pdf"}
{"id": "1507.00272", "abstract": "  Hidden-variable resultant methods are a class of algorithms for solving multidimensional polynomial rootfinding problems. In two dimensions, when significant care is taken, they are competitive practical rootfinders. However, in higher dimensions they are known to miss zeros, calculate roots to low precision, and introduce spurious solutions. We show that the hidden variable resultant method based on the Cayley (Dixon or Bézout) matrix is inherently and spectacularly numerically unstable by a factor that grows exponentially with the dimension. We also show that the Sylvester matrix for solving bivariate polynomial systems can square the condition number of the problem. In other words, two popular hidden variable resultant methods are numerically unstable, and this mathematically explains the difficulties that are frequently reported by practitioners. Regardless of how the constructed polynomial eigenvalue problem is solved, severe numerical difficulties will be present. Along the way, we prove that the Cayley resultant is a generalization of Cramer's rule for solving linear systems and generalize Clenshaw's algorithm to an evaluation scheme for polynomials expressed in a degree-graded polynomial basis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.00272v3.pdf"}
{"id": "1507.00766", "abstract": "  The Berry phase has found applications in building topological order parameters for certain condensed matter systems. The question whether some geometric phase for mixed states can serve the same purpose has been raised, and proposals are on the table. We analyze the intricate behaviour of Uhlmann's geometric phase in the Kitaev chain at finite temperature, and then argue that it captures quite different physics from that intended. We also analyze the behaviour of a geometric phase introduced in the context of interferometry. For the Kitaev chain, this phase closely mirrors that of the Berry phase, and we argue that it merits further investigation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.00766v2.pdf"}
{"id": "1507.01820", "abstract": "  Recently I proposed a simple dynamical network model for discrete space-time which self-organizes as a graph with Hausdorff dimension d_H=4. The model has a geometric quantum phase transition with disorder parameter (d_H-d_s) where d_s is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.01820v2.pdf"}
{"id": "1507.01901", "abstract": "  We use bank-level balance sheet data from 2005 to 2010 to study interactions within the banking system of five emerging countries: Argentina, Brazil, Mexico, South Africa, and Taiwan. For each country we construct a financial network based on the leverage ratio dependence between each pair of banks, and find results that are comparable across countries. Banks present a variety of leverage ratio behaviors. This leverage diversity produces financial networks that exhibit a modular structure characterized by one large bank community, some small ones and isolated banks. There exist compact structures that have synchronized dynamics. Many groups of banks merge together creating a financial network topology that converges to a unique big cluster at a relatively low leverage dependence level. Finally, we propose a model that includes corporate and interbank loans for studying the banking system. This model generates networks similar to the empirical ones. Moreover, we find that faster-growing banks tend to be more highly interconnected between them, and this is also observed in empirical data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.01901v1.pdf"}
{"id": "1507.02143", "abstract": "  Gamma-ray bursts (GRBs) are believed to be powered by the electromagnetic extraction of spin energy from a black hole endowed with a magnetic field supported by electric currents in a surrounding disk (Blandford     Znajek 1977). A generic feature of this mechanism is that, under certain fairly general assumptions, the energy loss rate decays exponentially. In this work, we are looking precisely for such exponential decay in the lightcurves of long duration GRBs observed with the XRT instrument on the Swift satellite. We found out that almost 30 ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.02143v1.pdf"}
{"id": "1507.02831", "abstract": "  It has long been proposed that low frequency QPOs in stellar mass black holes or their equivalents in super massive black holes are results of resonances between infall and cooling time scales. We explicitly compute these two time scales in a generic situation to show that resonances are easily achieved. During an outburst of a transient black hole candidate (BHC), the accretion rate of the Keplerian disk as well as the geometry of the Comptonizing cloud change very rapidly. During some period, resonance condition between the cooling time scale (predominantly by Comptonization) and the infall time scale of the Comptonizing cloud is roughly satisfied. This leads to low frequency quasi-periodic oscillations (LFQPOs) of the Compton cloud and the consequent oscillation of hard X-rays. In this paper, we explicitly follow the BHC H 1743-322 during its 2010 outburst. We compute Compton cooling time and infall time on several days and show that QPOs take place when these two roughly agree within  50", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.02831v1.pdf"}
{"id": "1507.04082", "abstract": "  We investigate the location of the radio jet bases (\"radio cores\") of blazars in radio images, and their stationarity by means of dense very long baseline interferometry (VLBI) observations. In order to measure the position of a radio core, we conducted 12 epoch astrometric observation of the blazar Markarian 421 with the VLBI Exploration of Radio Astrometry at 22 GHz immediately after a large X-ray flare, which occurred in the middle of 2011 September. For the first time, we find that the radio core is not stationary but rather changes its location toward 0.5 mas downstream. This angular scale corresponds to the de-projected length of a scale of 10^5 Schwarzschild radii (Rs) at the distance of Markarian 421. This radio-core wandering may be a new type of manifestation associated with the phenomena of large X-ray flares. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.04082v1.pdf"}
{"id": "1507.04930", "abstract": "  Folksonomies - large databases arising from collaborative tagging of items by independent users - are becoming an increasingly important way of categorizing information. In these systems users can tag items with free words, resulting in a tripartite item-tag-user network. Although there are no prescribed relations between tags, the way users think about the different categories presumably has some built in hierarchy, in which more special concepts are descendants of some more general categories. Several applications would benefit from the knowledge of this hierarchy. Here we apply a recent method to check the differences and similarities of hierarchies resulting from tags given by independent individuals and from tags given by a centrally managed repository system. The results from out method showed substantial differences between the lower part of the hierarchies, and in contrast, a relatively high similarity at the top of the hierarchies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.04930v1.pdf"}
{"id": "1507.05466", "abstract": "  Quantum electrodynamics under conditions of distinguishability of interacting matter entities, and of controlled actions and back-actions between them, is considered. Such \"mesoscopic quantum electrodynamics\" is shown to share its dynamical structure with the classical stochastic electrodynamics. In formal terms, we demonstrate that all general relations of the mesoscopic quantum electrodynamics may be recast in a form lacking Planck's constant. Mesoscopic quantum electrodynamics is therefore subject to \"doing quantum electrodynamics while thinking classically,\" allowing one to substitute essentally classical considerations for quantum ones without any loss in generality. Implications of these results for the quantum measurement theory are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.05466v1.pdf"}
{"id": "1507.06845", "abstract": "  In this note we explain the method how to find the resonance condition on quantum graphs, which is called pseudo orbit expansion. In three examples with standard coupling we show in detail how to obtain the resonance condition. We focus on non-Weyl graphs, i.e. the graphs which have fewer resonances than expected. For these graphs we explain benefits of the method of \"deleting edges\" for simplifying the graph. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.06845v2.pdf"}
{"id": "1507.07115", "abstract": "  Consider a multi-input multi-output (MIMO) downlink multi-user channel. A well-studied problem in such system is the design of linear beamformers for power minimization with the quality of service (QoS) constraints. The most representative algorithms for solving this class of problems are the so-called MMSE-SOCP algorithm [11-12] and the UDD algorithm [9]. The former is based on alternating optimization of the transmit and receive beamformers, while the latter is based on the well-known uplink-dowlink duality theory. Despite their wide applicability, the convergence (to KKT solutions) of both algorithms is still open in the literature. In this paper, we rigorously establish the convergence of these algorithms for QoS-constrained power minimization (QCPM) problem with both single stream and multiple streams per user cases. Key to our analysis is the development and analysis of a new MMSE-DUAL algorithm, which connects the MMSE-SOCP and the UDD algorithm. Our numerical experiments show that 1) all these algorithms can almost always reach points with the same objective value irrespective of initialization, 2) the MMSE-SOCP/MMSE-DUAL algorithm works well while the UDD algorithm may fail with an infeasible initialization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.07115v1.pdf"}
{"id": "1507.07341", "abstract": "  The interaction of competing agents is described by classical game theory. It is now well known that this can be extended to the quantum domain, where agents obey the rules of quantum mechanics. This is of emerging interest for exploring quantum foundations, quantum protocols, quantum auctions, quantum cryptography, and the dynamics of quantum cryptocurrency, for example. In this paper, we investigate two-player games in which a strategy pair can exist as a Nash equilibrium when the games obey the rules of quantum mechanics. Using a generalized Einstein-Podolsky-Rosen (EPR) setting for two-player quantum games, and considering a particular strategy pair, we identify sets of games for which the pair can exist as a Nash equilibrium only when Bell's inequality is violated. We thus determine specific games for which the Nash inequality becomes equivalent to Bell's inequality for the considered strategy pair. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.07341v6.pdf"}
{"id": "1507.07714", "abstract": "  Hydrogen adatoms are one of the most the promising proposals for the functionalization of graphene. Hydrogen induces narrow resonances near the Dirac energy, which lead to the formation of magnetic moments. Furthermore, they also create local lattice distortions which enhance the spin-orbit coupling. The combination of magnetism and spin-orbit coupling allows for a rich variety of phases, some of which have non trivial topological features. We analyze the interplay between magnetism and spin-orbit coupling in ordered arrays of hydrogen on graphene monolayers, and classify the different phases that may arise. We extend our model to consider arrays of adsorbates in graphene-like crystals with stronger intrinsic spin-orbit couplings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.07714v2.pdf"}
{"id": "1507.08009", "abstract": "  We investigate the electrical control of the exchange coupling (J) between donor bound electrons in silicon with a detuning gate bias, crucial for the implementation of the two-qubit gate in a silicon quantum computer. We find the asymmetric 2P-1P system provides a highly tunable exchange-curve with mitigated J-oscillation, in which 5 orders of magnitude change in the exchange energy can be achieved using a modest range of electric field for 15 nm qubit separation. Compared to the barrier gate control of exchange in the Kane qubit, the detuning gate design reduces the demanding constraints of precise donor separation, gate width, density and location, as a range of J spanning over a few orders of magnitude can be engineered for various donor separations. We have combined a large-scale full band atomistic tight-binding method with a full configuration interaction technique to capture the full two-electron spectrum of gated donors, providing state-of-the-art calculations of exchange energy in 1P-1P and 2P-1P qubits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.08009v1.pdf"}
{"id": "1508.00453", "abstract": "  The dielectric engineered tunnel field-effect transistor (DE-TFET) as a high performance steep transistor is proposed. In this device, a combination of high-k and low-k dielectrics results in a high electric field at the tunnel junction. As a result a record ON-current of about 1000 uA/um and a subthreshold swing (SS) below 20mV/dec are predicted for WTe2 DE-TFET. The proposed TFET works based on a homojunction channel and electrically doped contacts both of which are immune to interface states, dopant fluctuations, and dopant states in the band gap which typically deteriorate the OFF-state performance and SS in conventional TFETs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.00453v1.pdf"}
{"id": "1508.02740", "abstract": "  Specific heat measurements have been successfully used to probe unconventional superconducting phases in one-band heavy-fermion and organic superconductors. We extend the method to study successive phase transitions in multi-band materials such as iron based superconductors. The signatures are multiple peaks in the specific heat, at low temperatures and high magnetic field, which can lead the experimental verification of unconventional superconducting states with non-zero total momentum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.02740v2.pdf"}
{"id": "1508.03304", "abstract": "  We generalize the kinetic theory of fluids, in which the description of fluids is based on the geodesic motion of particles, to spacetimes modeled by Finsler geometry. Our results show that Finsler spacetimes are a suitable background for fluid dynamics and that the equation of motion for a collisionless fluid is given by the Liouville equation, as it is also the case for a metric background geometry. We finally apply this model to collisionless dust and a general fluid with cosmological symmetry and derive the corresponding equations of motion. It turns out that the equation of motion for a dust fluid is a simple generalization of the well-known Euler equations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.03304v1.pdf"}
{"id": "1508.04303", "abstract": "  The purpose of the present study is to compare the predictions of different models of star formation rate (SFR) history in the universe with the upper limit of Super Kamiokande for the neutrino background. To this aim we have calculated the expected neutrino density for the most popular models of SFR history, Hogg et al. ,Glazebrook et al., Cole et al., Yuksel et al., Hernquist et al. and Kaplinghat et al. Differerent from previous studies we have used the ΛCDM model with Ω_Λ = 0.7. We have assumed that the detector used for the detection the neutrino flux is SuperK and also we have assumed that the electron neutrinos produced in the Supernovae oscillate equally to the three standard model flavors. By these assumptions all models stay below the upper limit of SuperK on the event rate and the detection of the supernova relic neutrino background (SRNB) remains undetected. Future neutrino detectors such as KM3Net will be able to detect the SRNB and distinguish between the models of the SFR history. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.04303v2.pdf"}
{"id": "1508.04412", "abstract": "  We present methods for efficient characterization of an optical coherent state |α⟩. We choose measurement settings adaptively and stochastically, based on data while it is collected. Our algorithm divides the estimation into two distinct steps: (i) before the first detection of a vacuum state, the probability of choosing a measurement setting is proportional to detecting vacuum with the setting, which makes using too similar measurement settings twice unlikely; and (ii) after the first detection of vacuum, we focus measurements in the region where vacuum is most likely to be detected. In step (i) [(ii)] the detection of vacuum (a photon) has a significantly larger effect on the shape of the posterior probability distribution of α. Compared to nonadaptive schemes, our method makes the number of measurement shots required to achieve a certain level of accuracy smaller approximately by a factor proportional to the area describing the initial uncertainty of α in phase space. While this algorithm is not directly robust against readout errors, we make it such by introducing repeated measurements in step (i). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.04412v2.pdf"}
{"id": "1508.04680", "abstract": "  We present a new approach to calculate excited states with the full configuration interaction quantum Monte Carlo (FCIQMC) method. The approach uses a Gram-Schmidt procedure, instantaneously applied to the stochastically evolving distributions of walkers, to orthogonalize higher energy states against lower energy ones. It can thus be used to study several of the lowest-energy states of a system within the same symmetry. This additional step is particularly simple and computationally inexpensive, requiring only a small change to the underlying FCIQMC algorithm. No trial wave functions or partitioning of the space is needed. The approach should allow excited states to be studied for systems similar to those accessible to the ground-state method, due to a comparable computational cost. As a first application we consider the carbon dimer in basis sets up to quadruple-zeta quality, and compare to existing results where available. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.04680v2.pdf"}
{"id": "1508.06528", "abstract": "  It is now reasonably clear that disc fragmentation can only operate in the outer parts of protostellar discs (r > 50 au). It is also expected that any object that forms via disc fragmentation will have an initial mass greater than that of Jupiter. However, whether or not such a process actually operates, or can play a significant role in the formation of planetary-mass objects, is still unclear. We do have a few examples of directly imaged objects that may have formed in this way, but we have yet to constrain how often disc fragmentation may actually form such objects. What we want to consider here is whether or not we can constrain the likely population of planetary-mass objects formed via disc fragmentation by considering how a population of objects at large radii (a > 50) au - if they do exist - would evolve under perturbations from more distant stellar companions. We find that there is a specific region of parameter space to which such objects would be scattered and show that the known exoplanets in that region have properties more consistent with that of the bulk exoplanet population, than with having been formed via disc fragmentation at large radii. Along with the scarcity of directly-imaged objects at large radii, our results provide a similar, but independent, constraint on the frequency of objects formed via disc fragmentation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.06528v1.pdf"}
{"id": "1508.07138", "abstract": "  We have investigated spin reorientation phenomena and interaction driven effects under the presence of applied strains on the (001) surface of Pb_1-xSn_x(Te, Se) topological crystalline insulators, which host multiple Dirac cones. Our analysis is based on a four-band k· p model, which captures the spin and orbital textures of the surface states at low energies around the X̅ and Y̅ points, including the Lifshitz transition. Even without breaking the time-reversal symmetry, we find that certain strains which break the mirror symmetry can induce hedgehog-like spin texture associated with gap formation at the Dirac points. The Chern number of the gapped surface ground state is shown to be tunable through the interplay of strains and a perpendicular Zeeman field. We also consider effects of strain in the presence of interactions in driving competing orders, and obtain the associated phase diagram at the mean-field level. Potential applications of our results for low power consuming electronics are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.07138v2.pdf"}
{"id": "1509.00579", "abstract": "  The potential capabilities of resonators based on two dimensional arrays of re-entrant posts is demonstrated. Such posts may be regarded as magnetically-coupled lumped element microwave harmonic oscillators, arranged in a 2D lattices structure, which is enclosed in a 3D cavity. By arranging these elements in certain 2D patterns, we demonstrate how to achieve certain requirements with respect to field localisation and device spectra. Special attention is paid to symmetries of the lattices, mechanical tuning, design of areas of high localisation of magnetic energy, which in turn creates unique discrete mode spectra. We demonstrate analogies between systems designed on the proposed platform and well known physical phenomena such as polarisation, frustration and Whispering Gallery Modes. The mechanical tunability of the cavity with multiple posts is analysed and its consequences to optomechanical applications is calculated. One particular application to quantum memory is demonstrated with a cavity design consisting of separate resonators analogous to discrete Fabry-Pérot resonators. Finally, we propose a generalised approach to a microwave system design based on the concept of Programmable Cavity Arrays. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.00579v2.pdf"}
{"id": "1509.00645", "abstract": "  In this article, we propose an improved multiple feedback successive interference cancellation (IMF-SIC) algorithm for symbol vector detection in multiple-input multiple-output (MIMO) spatial multiplexing systems. The multiple feedback (MF) strategy in successive interference cancellation (SIC) is based on the concept of shadow area constraint (SAC) where, if the decision falls in the shadow region multiple neighboring constellation points will be used in the decision feedback loop followed by the conventional SIC. The best candidate symbol from multiple neighboring symbols is selected using the maximum likelihood (ML) criteria. However, while deciding the best symbol from multiple neighboring symbols, the SAC condition may occur in subsequent layers which results in inaccurate decision. In order to overcome this limitation, in the proposed algorithm, SAC criteria is checked recursively for each layer. This results in successful mitigation of error propagation thus significantly improving the bit error rate (BER) performance. Further, we also propose an ordered IMF-SIC (OIMF-SIC) where we use log likelihood ratio (LLR) based dynamic ordering of the detection sequence. In OIMF-SIC, we use the term dynamic ordering in the sense that the detection order is updated after every successful decision. Simulation results show that the proposed algorithms outperform the existing detectors such as conventional SIC and MF-SIC in terms of BER, and achieves a near ML performance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.00645v1.pdf"}
{"id": "1509.01712", "abstract": "  We demonstrate the existence of complex solitary wave and periodic solutions of the Kortweg de-vries (KdV) and modified Kortweg de-Vries (mKdV) equations. The solutions of the KdV (mKdV) equation appear in complex-conjugate pairs and are even (odd) under the simultaneous actions of parity (P) and time-reversal (T) operations. The corresponding localized solitons are hydrodynamic analogs of Bloch soliton in magnetic system, with asymptotically vanishing intensity. The PT-odd complex soliton solution is shown to be iso-spectrally connected to the fundamental sech^2 solution through supersymmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.01712v1.pdf"}
{"id": "1509.01744", "abstract": "  We investigate the effective interaction between two randomly charged but otherwise net-neutral, planar dielectric slabs immersed in an asymmetric Coulomb fluid containing a mixture of mobile monovalent and multivalent ions. The presence of charge disorder on the apposed bounding surfaces of the slabs leads to substantial qualitative changes in the way they interact, as compared with the standard picture provided by the van der Waals and image-induced, ion-depletion interactions. While, the latter predict purely attractive interactions between strictly neutral slabs, we show that the combined effects from surface charge disorder, image depletion, Debye (or salt) screening and also, in particular, their coupling with multivalent ions, give rise to a more diverse behavior for the effective interaction between net-neutral slabs. Disorder effects show large variation depending on the properly quantified strength of disorder, leading either to non-monotonic effective interaction with both repulsive and attractive branches when the surface charges are weakly disordered (small disorder variance) or to a dominating attractive interaction that is larger both in its range and magnitude than what is predicted from the van der Waals and image-induced, ion-depletion interactions, when the surfaces are strongly disordered (large disorder variance). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.01744v1.pdf"}
{"id": "1509.02248", "abstract": "  A frequentist asymptotic expansion method for error estimation is employed for a network of gravitational wave detectors to assess the amount of information that can be extracted from gravitational wave observations. Mathematically we derive lower bounds in the errors that any parameter estimator will have in the absence of prior knowledge to distinguish between the post-Einsteinian (ppE) description of coalescing binary systems and that of general relativity. When such errors are smaller than the parameter value, there is possibility to detect these violations from GR. A parameter space with inclusion of dominant dephasing ppE parameters (β, b) is used for a study of first- and second-order (co)variance expansions, focusing on the inspiral stage of a nonspinning binary system of zero eccentricity detectible through Adv. LIGO and Adv. Virgo. Our procedure is an improvement of the Cramér-Rao Lower Bound. When Bayesian errors are lower than our bound it means that they depend critically on the priors. The analysis indicates the possibility of constraining deviations from GR in inspiral SNR (ρ∼ 15-17) regimes that are achievable in upcoming scientific runs (GW150914 had an inspiral SNR ∼ 12). The errors on β also increase errors of other parameters such as the chirp mass ℳ and symmetric mass ratio η. Application is done to existing alternative theories of gravity, which include modified dispersion relation of the waveform, non-spinning models of quadratic modified gravity, and dipole gravitational radiation (i.e., Brans-Dicke type) modifications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.02248v2.pdf"}
{"id": "1509.02511", "abstract": "  In this paper we review some results on time-homogeneous birth-death processes. Specifically, for truncated birth-death processes with two absorbing or two reflecting endpoints, we recall the necessary and sufficient conditions on the transition rates such that the transition probabilities satisfy a spatial symmetry relation. The latter leads to simple expressions for first-passage-time densities and avoiding transition probabilities. This approach is thus thoroughly extended to the case of bilateral birth-death processes, even in the presence of catastrophes, and to the case of a two-dimensional birth-death process with constant rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.02511v1.pdf"}
{"id": "1509.02993", "abstract": "  Coherently driven atomic gases inside optical cavities hold great promise for generating rich dynamics and exotic states of matter. It was shown recently that an exotic topological superradiant state exists in a two-component degenerate Fermi gas coupled to a cavity, where local order parameters coexist with global topological invariants. In this work, we characterize in detail various properties of this exotic state, focusing on the feedback interactions between the atoms and the cavity field. In particular, we demonstrate that cavity-induced interband coupling plays a crucial role in inducing the topological phase transition between the conventional and topological superradiant states. We analyze the interesting signatures in the cavity field left by the closing and reopening of the atomic bulk gap across the topological phase boundary and discuss the robustness of the topological superradiant state by investigating the steady-state phase diagram under various conditions. Furthermore, we consider the interaction effect and discuss the interplay between the pairing order in atomic ensembles and the superradiance of the cavity mode. Our work provides many valuable insights into the unique cavity–atom hybrid system under study and is helpful for future experimental exploration of the topological superradiant state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.02993v2.pdf"}
{"id": "1509.03179", "abstract": "  The so-called \"early activity\" of comet 67P/Churyumov-Gerasimenko has been observed to originate mostly in parts of the concave region or \"neck\" between its two lobes. Since activity is driven by the sublimation of volatiles, this is a puzzling result because this area is less exposed to the Sun and is therefore expected to be cooler on average (Sierks et al. 2015).   We used a thermophysical model that takes into account thermal inertia, global self-heating, and shadowing, to compute surface temperatures of the comet. We found that, for every rotation in the August–December 2014 period, some parts of the neck region undergo the fastest temperature variations of the comet's surface precisely because they are shadowed by their surrounding terrains. Our work suggests that these fast temperature changes are correlated to the early activity of the comet, and we put forward the hypothesis that erosion related to thermal cracking is operating at a high rate on the neck region due to these rapid temperature variations. This may explain why the neck contains some ice –as opposed to most other parts of the surface (Capaccioni et al. 2015)– and why it is the main source of the comet's early activity (Sierks et al. 2015).   In a broader context, these results indicate that thermal cracking can operate faster on atmosphereless bodies with significant concavities than implied by currently available estimates (Delbo' et al. 2014). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.03179v1.pdf"}
{"id": "1509.03596", "abstract": "  We consider a central system which is coupled via dephasing to an open system, i.e. an intermediate system which in turn is coupled to another environment. Considering intermediate and far environment as one composite system, the coherences in the central system are given in the form of fidelity amplitudes for a certain perturbed echo dynamics in the composite environment. On the basis of the Born-Markov approximation, we derive a master equation for the reduction of that dynamics to the intermediate system alone. In distinction to an earlier paper [arXiv: 1502.04143 (2015)] where we discussed the stabilizing effect of the far environment on the decoherence in the central system, we focus here on the possibility to use the measurable coherences in the central system for probing the open quantum dynamics in the intermediate system. We illustrate our results for the case of chaotic dynamics in the near environment, where we compare random matrix simulations with our analytical result. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.03596v1.pdf"}
{"id": "1509.03955", "abstract": "  The effects of reservoir squeezing on the precision of parameter estimation are investigated analytically based on non-perturbation procedures. The exact analytic quantum Fisher information (QFI) is obtained. It is shown that the QFI depends on the estimated parameter and its decay could be reduced by the squeezed reservoir compared with thermal (vacuum) reservoir, in particular, if the squeezing phase matching is satisfied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.03955v1.pdf"}
{"id": "1509.05110", "abstract": "  We study the geodesic motion of massive and massless test particles in the background of a particular class of multiple charge black holes in gauged supergravity theories in D = 4. We have analysed the horizon structure along with the nature of the effective potentials for the case of four equal charges. In view of the corresponding effective potentials, we have discussed all the possible orbits in detail for different values of energy and angular momentum of the incoming test particles. The periods for one complete revolution of circular orbits and the advance of perihelion of the planetary orbit have also been investigated in greater detail for massive test particles. We have also discussed the time period of unstable circular motion and cone of avoidance of massless test particles in detail. All the corresponding results obtained for massive and massless test particles are then compared accordingly. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.05110v1.pdf"}
{"id": "1509.05915", "abstract": "  While theoretical models and simulations of magnetic reconnection often assume symmetry such that the magnetic null point when present is co-located with a flow stagnation point, the introduction of asymmetry typically leads to non-ideal flows across the null point. To understand this behavior, we present exact expressions for the motion of three-dimensional linear null points. The most general expression shows that linear null points move in the direction along which the vector field and its time derivative are antiparallel. Null point motion in resistive magnetohydrodynamics results from advection by the bulk plasma flow and resistive diffusion of the magnetic field, which allows non-ideal flows across topological boundaries. Null point motion is described intrinsically by parameters evaluated locally; however, global dynamics help set the local conditions at the null point. During a bifurcation of a degenerate null point into a null-null pair or the reverse, the instantaneous velocity of separation or convergence of the null-null pair will typically be infinite along the null space of the Jacobian matrix of the magnetic field, but with finite components in the directions orthogonal to the null space. Not all bifurcating null-null pairs are connected by a separator. Furthermore, except under special circumstances, there will not exist a straight line separator connecting a bifurcating null-null pair. The motion of separators cannot be described using solely local parameters, because the identification of a particular field line as a separator may change as a result of non-ideal behavior elsewhere along the field line. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.05915v1.pdf"}
{"id": "1509.07149", "abstract": "  In baseball games, the coefficient of restitution of baseballs strongly affects the flying distance of batted balls, which determines the home-run probability. In Japan, the range of the coefficient of restitution of official baseballs has changed frequently over the past five years, causing the the number of home runs to vary drastically. We analyzed data from Japanese baseball games played in 2014 to investigate the statistical properties of pitched balls. In addition, we used the analysis results to develop a baseball-batting simulator for determining the home-run probability as a function of the coefficient of restitution. Our simulation results are explained by a simple theoretical argument. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.07149v2.pdf"}
{"id": "1509.07239", "abstract": "  We investigate the short-term dynamical evolution of stellar grand-design spiral arms in barred spiral galaxies using a three-dimensional (3D) N-body/hydrodynamic simulation. Similar to previous numerical simulations of unbarred, multiple-arm spirals, we find that grand-design spiral arms in barred galaxies are not stationary, but rather dynamic. This means that the amplitudes, pitch angles, and rotational frequencies of the spiral arms are not constant, but change within a few hundred million years (i.e. the typical rotational period of a galaxy). We also find that the clear grand-design spirals in barred galaxies appear it only when the spirals connect with the ends of the bar. Furthermore, we find that the short-term behaviour of spiral arms in the outer regions (R> 1.5–2 bar radius) can be explained by the swing amplification theory and that the effects of the bar are not negligible in the inner regions (R< 1.5–2 bar radius). These results suggest that, although grand-design spiral arms in barred galaxies are affected by the stellar bar, the grand-design spiral arms essentially originate not as bar-driven stationary density waves, but rather as self-excited dynamic patterns. We imply that a rigidly rotating grand-design spiral could not be a reasonable dynamical model for investigating gas flows and cloud formation even in barred spiral galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.07239v2.pdf"}
{"id": "1509.07291", "abstract": "  We report characterization and magnetic studies of mixtures of micrometer-size ribbons of Mn_12 acetate and micrometer-size particles of YBaCuO superconductor. Extremely narrow zero-field spin-tunneling resonance has been observed in the mixtures, pointing to the absence of the inhomogeneous dipolar broadening. It is attributed to the screening of the internal magnetic fields in the magnetic particles by Josephson currents between superconducting grains surrounding the particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.07291v1.pdf"}
{"id": "1509.07825", "abstract": "  In this work, we formulate a Non-Commutative (NC) extension of AdS-CFT correspondence that is manifested in the modification of behavior of a holographic superconductor. The noncommutativity is introduced in the model through the NC corrected AdS charged black hole metric developed by Nicolini, Smailagic and Spallucci. First of all we discuss thermodynamic properties of this black hole in Euclidean formalism. In particular, we compute trace of the boundary energy-momentum tensor which, as expected, is non-zero due to the NC scale introduced in the model. Our findings indicate that the non-commutative effects tend to work against the black hole hair formation. This, in turn, has an adverse effect on the holographic superconductor by making the superconducting phase more fragile. This is reflected in the reduced value of the critical magnetic field and critical temperature. Finally, we comment on a qualitative agreement between our (holographic superconductor) result and that obtained for a conventional superconductor in NC space in a purely condensed matter scenario. In both cases noncommutativity tends to oppose the superconducting phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.07825v4.pdf"}
{"id": "1509.08264", "abstract": "  We investigate the imprint of reheating on the gravitational wave spectrum produced by self-ordering of multi-component scalar fields after a global phase transition. The equation of state of the Universe during reheating, which usually has different behaviour from that of a radiation-dominated Universe, affects the evolution of gravitational waves through the Hubble expansion term in the equations of motion. This gives rise to a different power-law behavior of frequency in the gravitational wave spectrum. The reheating history is therefore imprinted in the shape of the spectrum. We perform 512^3 lattice simulations to investigate how the ordering scalar field reacts to the change of the Hubble expansion and how the reheating effect arises in the spectrum. We also compare the result with inflation-produced gravitational waves, which has a similar spectral shape, and discuss whether it is possible to distinguish the origin between inflation and global phase transition by detecting the shape with future direct detection gravitational wave experiments such as DECIGO. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.08264v1.pdf"}
{"id": "1509.08710", "abstract": "  The current paradigm foresees that relativistic jets are launched as magnetically dominated flows, whose magnetic power is progressively converted to kinetic power of of the matter of the jet, until equipartition is reached. Therefore, at the end of the acceleration phase, the jet should still carry a substantial fraction (≈ half) of its power in the form of a Poynting flux. It has been also argued that, in these conditions, the best candidate particle acceleration mechanism is efficient reconnection of magnetic field lines, for which it is predicted that magnetic field and accelerated relativistic electron energy densities are in equipartition.Through the modeling of the jet non–thermal emission, we explore if equipartition is indeed possible in BL Lac objects, i.e. low-power blazars with weak or absent broad emission lines. We find that one-zone models (for which only one region is involved in the production of the radiation we observe) the particle energy density is largely dominating (by 1-2 orders of magnitude) over the magnetic one. As a consequence, the jet kinetic power largely exceeds the magnetic power. Instead, if the jet is structured (i.e. made by a fast spine surrounded by a slower layer), the amplification of the IC emission due to the radiative interplay between the two components allows us to reproduce the emission in equipartition conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.08710v2.pdf"}
{"id": "1510.00798", "abstract": "  Renewable energy powered cognitive radio (CR) network has gained much attention due to its combination of the CR's spectrum efficiency and the renewable energy's \"green\" nature. In the paper, we investigate the delay-optimal data transmission in the renewable energy aided CR networks. Specifically, a primary user (PU) and a secondary user (SU) share the same frequency in an area. The SU's interference to the PU is controlled by interference-signal-ratio (ISR) constraint, which means that the ISR at the PU receiver (Rx) should be less than a threshold. Under this constraint, the renewable energy powered SU aims to minimize the average data buffer delay by scheduling the renewable allocations in each slot. A constrained stochastic optimization problem is formulated when the randomness of the renewable arrival, the uncertainty of the SU's data generation, and the variability of the fading channel are taken into account. By analyzing the formulated problem, we propose two practical algorithms that is optimal for two special scenarios. And the two algorithms respectively give an upper and a lower bound for the general scenario. In addition, the availability of the PU's private information at the SU is discussed. Finally, numerical simulations verify the effectiveness of the proposed algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.00798v1.pdf"}
{"id": "1510.01256", "abstract": "  Transmission of terahertz waves through a thin layer of the superconductor NbN deposited on an anisotropic R-cut sapphire substrate is studied as a function of temperature in a magnetic field oriented parallel with the sample. A significant difference is found between transmitted intensities of beams linearly polarized parallel with and perpendicular to the direction of applied magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.01256v1.pdf"}
{"id": "1510.01456", "abstract": "  The conditions of local thermodynamic equilibrium of baryons (non-strange, strange) and mesons (strange) are presented for central Au + Au collisions at FAIR energies using the microscopic transport model UrQMD. The net particle density, longitudinal-to-transverse pressure anisotropy and inverse slope parameters of the energy spectra of non-strange and strange hadrons are calculated inside a cell in the central region within rapidity window |y| < 1.0 at different time steps after the collision. We observed that the strangeness content is dominated by baryons at all energies, however contribution from mesons become significant at higher energies. The time scale obtained from local pressure (momentum) isotropization and thermalization of energy spectra are nearly equal and found to decrease with increase in laboratory energy. The equilibrium thermodynamic properties of the system are obtained with statistical thermal model. The time evolution of the entropy densities at FAIR energies are found very similar with the ideal hydrodynamic behaviour at top RHIC energy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.01456v2.pdf"}
{"id": "1510.01535", "abstract": "  A stochastic second-order wave model is applied to assess the statistical properties of wave orbital velocity in random sea states below the water surface. Directional spreading effects as well as the dependency of the water depth are investigated by means of a Monte-Carlo approach. Unlike for the surface elevation, sub-harmonics dominate the second-order contribution to orbital velocity. We show that a notable set-down occurs for the most energetic and steepest groups. This engenders a negative skewness in the temporal evolution of the orbital velocity. A substantial deviation of the upper and lower tails of the probability density function from the Gaussian distribution is noticed, velocities are faster below the wave trough and slower below the wave crest when compared with linear theory predictions. Second-order nonlinearity effects strengthen with reducing the water depth, while weaken with the broadening of the wave spectrum. The results are confirmed by laboratory data. Corresponding experiments have been conducted in a large wave basin taking into account the directionality of the wave field. As shown, laboratory data are in very good agreement with the numerical prediction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.01535v1.pdf"}
{"id": "1510.01734", "abstract": "  It has recently been demonstrated that self-consistent particle-in-cell simulations of low-obliquity pulsar magnetospheres in flat spacetime show weak particle acceleration and no pair production near the poles. We investigate the validity of this conclusion in a more realistic spacetime geometry via general-relativistic particle-in-cell simulations of the aligned pulsar magnetospheres with pair formation. We find that the addition of frame-dragging effect makes local current density along the magnetic field larger than the Goldreich-Julian value, which leads to unscreened parallel electric fields and the ignition of a pair cascade. When pair production is active, we observe field oscillations in the open field bundle which could be related to pulsar radio emission. We conclude that general relativistic effects are essential for the existence of pulsar mechanism in low obliquity rotators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.01734v1.pdf"}
{"id": "1510.01870", "abstract": "  Nonreciprocal effective interaction forces can occur between mesoscopic particles in colloidal suspensions that are driven out of equilibrium. These forces violate Newton's third law actio=reactio on coarse-grained length and time scales. Here we explore the statistical mechanics of Brownian particles with nonreciprocal effective interactions. Our model system is a binary fluid mixture of spherically symmetric, diffusiophoretic mesoscopic particles, and we focus on the time-averaged particle pair- and triplet-correlation functions. Based on the many-body Smoluchowski equation we develop a microscopic statistical theory for the particle correlations and test it by computer simulations. For model systems in two and three spatial dimensions, we show that nonreciprocity induces distinct nonequilibrium pair correlations. Our predictions can be tested in experiments with chemotactic colloidal suspensions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.01870v2.pdf"}
{"id": "1510.02206", "abstract": "  We compare and contrast the entangling properties of a three-well Bose-Hubbard model and an optical beamsplitter. The coupling between the different modes is linear in both cases, and we may identify two output modes. Obvious differences are that our Bose-Hubbard model, with only the middle well initially occupied, does not have a vacuum input port, there is no equivalent of a collisional, χ^(3) nonlinearity with the beamsplitter, and the results of the Bose-Hubbard model show a time-dependence. In the non-interacting case, we obtain analytic solutions and show that, like a beamsplitter, the Bose-Hubbard system will not produce entanglement for classical initial states. We also show that whether inseparability or entanglement are detected depends sensitively on the criteria measured, with different criteria giving contradictory predictions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.02206v1.pdf"}
{"id": "1510.02869", "abstract": "  We study stochastic acceleration models for the Fermi bubbles. Turbulence is excited just behind the shock front via Kelvin–Helmholtz, Rayleigh–Taylor, or Richtmyer–Meshkov instabilities, and plasma particles are continuously accelerated by the interaction with the turbulence. The turbulence gradually decays as it goes away from the shock fronts. Adopting a phenomenological model for the stochastic acceleration, we explicitly solve the temporal evolution of the particle energy distribution in the turbulence. Our results show that the spatial distribution of high-energy particles is different from those for a steady solution. We also show that the contribution of electrons that escaped from the acceleration regions significantly softens the photon spectrum. The photon spectrum and surface brightness profile are reproduced by our models. If the escape efficiency is very high, the radio flux from the escaped low-energy electrons can be comparable to that of the WMAP haze. We also demonstrate hadronic models with the stochastic acceleration, but they are unlikely in the viewpoint of the energy budget. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.02869v2.pdf"}
{"id": "1510.03589", "abstract": "  I present a new FITS viewer designed to explore 3D spectral line data (in particular HI) and assist with visual source extraction and analysis. Using the artistic software Blender, FRELLED can visualise even large ( 600^3 voxels) data sets at high frame rates (10 f.p.s.) in 3D. Blender's interface enables easy navigation within the 3D environment, and the FRELLED scripts support world coordinate systems. A variety of tools are included to aid source extraction and analysis, including interactively masking data (using 3D polyhedra of arbitrary complexity), querying NED, calculating the flux in specified volumes, generating contour plots and overlaying optical data. It includes tools to overlay n-body particle data, and multi-volume rendering is supported. The interface is designed to make cataloguing sources as easy as possible and I show that this can be as much as a factor of 50 times faster than using other viewers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.03589v1.pdf"}
{"id": "1510.04337", "abstract": "  We explore the adsorption of MoS2 on a range of metal substrates by means of first-principles density functional theory calculations. Including van der Waals forces in the density functional is essential to capture the interaction between MoS2 and a metal surface, and obtain reliable interface potential steps and Schottky barriers. Special care is taken to construct interface structures that have a mismatch between the MoS2 and the metal lattices of <1", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.04337v2.pdf"}
{"id": "1510.04742", "abstract": "  The compressibility of molecular cloud (MC) turbulence plays a crucial role in star formation models, because it controls the amplitude and distribution of density fluctuations. The relation between the compressive ratio (the ratio of powers in compressive and solenoidal motions) and the statistics of turbulence has been previously studied systematically only in idealized simulations with random external forces. In this work, we analyze a simulation of large-scale turbulence (250 pc) driven by supernova (SN) explosions that has been shown to yield realistic MC properties. We demonstrate that SN driving results in MC turbulence with a broad lognormal distribution of the compressive ratio, with a mean value ≈ 0.3, lower than the equilibrium value of ≈ 0.5 found in the inertial range of isothermal simulations with random solenoidal driving. We also find that the compressibility of the turbulence is not noticeably affected by gravity, nor are the mean cloud radial (expansion or contraction) and solid-body rotation velocities. Furthermore, the clouds follow a general relation between the rms density and the rms Mach number similar to that of supersonic isothermal turbulence, though with a large scatter, and their average gas density PDF is described well by a lognormal distribution, with the addition of a high-density power-law tail when self-gravity is included. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.04742v2.pdf"}
{"id": "1510.05530", "abstract": "  An evolution of luminosity of galaxies in emission lines or wavelength ranges in which they are sensitive to the star formation process is caused by burning out of the most massive O-class stars during a few million years after a starburst. We study the impact of this effect on the luminosity function (LF) of a sample of star-forming galaxies.   We introduce several types of LFs: an initial LF after a starburst, current, time-averaged and sample ones. We find the relations between them in general and specify them in the case of the luminosity evolution law proposed for the luminous compact galaxies. We obtain the sample LF for the cases the initial one is described by the pure Schechter function or the log-normal distribution and analyze the properties of these LFs. As a result we get two new types of LFs to fit the LF of a sample of star-forming galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.05530v1.pdf"}
{"id": "1510.06887", "abstract": "  In this paper we determine the phase diagrams (for T=0 as well as T>0) of the Penson-Kolb-Hubbard model for two dimensional square lattice within Hartree-Fock mean-field theory focusing on investigation of superconducting phases and possibility of the occurrence of the phase separation. We obtain that the phase separation, which is a state of coexistence of two different superconducting phases (with s-wave and η-wave symmetries), occurs in define range of the electron concentration. In addition, increasing temperature can change the symmetry of the superconducting order parameter (from η-wave into s-wave). The system considered exhibits also an interesting multicritical behaviour including bicritical points. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.06887v3.pdf"}
{"id": "1510.07671", "abstract": "  We investigate the thermal evolution of comet 67P/Churyumov-Gerasimenko's subsurface in the Seth_01 region, where active pits have been observed by the ESA/Rosetta mission. Our simulations show that clathrate destabilization and amorphous ice crystallization can occur at depths corresponding to those of the observed pits in a timescale shorter than 67P/Churyumov-Gerasimenko's lifetime in the comet's activity zone in the inner solar system. Sublimation of crystalline ice down to such depths is possible only in the absence of a dust mantle, which requires the presence of dust grains in the matrix small enough to be dragged out by gas from the pores. Our results are consistent with both pits formation via sinkholes or subsequent to outbursts, the dominant process depending on the status of the subsurface porosity. A sealed dust mantle would favor episodic and disruptive outgassing as a result of an increasing gas pressure in the pores, while a high porosity should allow the formation of large voids in the subsurface due to the continuous escape of volatiles. We finally conclude that the subsurface of 67P/Churyumov-Gerasimenko is not uniform at a spatial scale of 100-200 m. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.07671v1.pdf"}
{"id": "1510.07834", "abstract": "  A view of the Galactic bulge by means of their globular clusters is necessary for a deep understanding of its formation and evolution. Connections between the globular cluster and field star properties in terms of kinematics, orbits, chemical abundances and ages should shed light on different stellar population components. Based on spatial distribution and metallicity, we define a probable best list of bulge clusters, containing 43 entries. Future work on newly discovered objects, mostly from the VVV survey, is suggested. These candidates might alleviate the issue of missing clusters on the far side of the bulge. We discuss the reddening law affecting the cluster distances towards the center of the Galaxy, and conclude that the most suitable total-to-selective absorption value appears to be R_ V=3.2, in agreement with recent analyses. An update of elemental abundances for bulge clusters is provided. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.07834v1.pdf"}
{"id": "1510.07927", "abstract": "  Loyal buyer-seller relationships can arise by design, e.g. when a seller tailors a product to a specific market niche to accomplish the best possible returns, and buyers respond to the dedicated efforts the seller makes to meet their needs. We ask whether it is possible, instead, for loyalty to arise spontaneously, and in particular as a consequence of repeated interaction and co-adaptation among the agents in a market. We devise a stylized model of double auction markets and adaptive traders that incorporates these features. Traders choose where to trade (which market) and how to trade (to buy or to sell) based on their previous experience. We find that when the typical scale of market returns (or, at fixed scale of returns, the intensity of choice) become higher than some threshold, the preferred state of the system is segregated: both buyers and sellers are segmented into subgroups that are persistently loyal to one market over another. We characterize the segregated state analytically in the limit of large markets: it is stabilized by some agents acting cooperatively to enable trade, and provides higher rewards than its unsegregated counterpart both for individual traders and the population as a whole. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.07927v2.pdf"}
{"id": "1510.08567", "abstract": "  We propose a location-based beamforming scheme for wiretap channels, where a source communicates with a legitimate receiver in the presence of an eavesdropper. We assume that the source and the eavesdropper are equipped with multiple antennas, while the legitimate receiver is equipped with a single antenna. We also assume that all channels are in a Rician fading environment, the channel state information from the legitimate receiver is perfectly known at the source, and that the only information on the eavesdropper available at the source is her location. We first describe how the beamforming vector that minimizes the secrecy outage probability of the system is obtained, illustrating its dependence on the eavesdropper's location. We then derive an easy-to-compute expression for the secrecy outage probability when our proposed location-based beamforming is adopted. Finally, we investigate the impact location uncertainty has on the secrecy outage probability, showing how our proposed solution can still allow for secrecy even when the source has limited information on the eavesdropper's location. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.08567v1.pdf"}
{"id": "1511.00006", "abstract": "  We present a study of spatial variations in the metallicity of old red giant branch stars in the Andromeda galaxy. Photometric metallicity estimates are derived by interpolating isochrones for over seven million stars in the Panchromatic Hubble Andromeda Treasury (PHAT) survey. This is the first systematic study of stellar metallicities over the inner 20 kpc of Andromeda's galactic disk. We see a clear metallicity gradient of -0.020±0.004 dex/kpc from ∼4-20 kpc assuming a constant RGB age. This metallicity gradient is derived after correcting for the effects of photometric bias and completeness and dust extinction and is quite insensitive to these effects. The unknown age gradient in M31's disk creates the dominant systematic uncertainty in our derived metallicity gradient. However, spectroscopic analyses of galaxies similar to M31 show that they typically have small age gradients that make this systematic error comparable to the 1σ error on our metallicity gradient measurement. In addition to the metallicity gradient, we observe an asymmetric local enhancement in metallicity at radii of 3-6 kpc that appears to be associated with Andromeda's elongated bar. This same region also appears to have an enhanced stellar density and velocity dispersion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.00006v1.pdf"}
{"id": "1511.00831", "abstract": "  Dimensionality reduction methods are very common in the field of high dimensional data analysis. Typically, algorithms for dimensionality reduction are computationally expensive. Therefore, their applications for the analysis of massive amounts of data are impractical. For example, repeated computations due to accumulated data are computationally prohibitive. In this paper, an out-of-sample extension scheme, which is used as a complementary method for dimensionality reduction, is presented. We describe an algorithm which performs an out-of-sample extension to newly-arrived data points. Unlike other extension algorithms such as Nyström algorithm, the proposed algorithm uses the intrinsic geometry of the data and properties for dimensionality reduction map. We prove that the error of the proposed algorithm is bounded. Additionally to the out-of-sample extension, the algorithm provides a degree of the abnormality of any newly-arrived data point. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.00831v1.pdf"}
{"id": "1511.01658", "abstract": "  Ordinary differential equations (ODEs) are widely used to model biological, (bio-)chemical and technical processes. The parameters of these ODEs are often estimated from experimental data using ODE-constrained optimisation. This article proposes a simple simulation-based approach for solving optimisation problems with steady state constraints relying on an ODE. This simulation-based optimisation method is tailored to the problem structure and exploits the local geometry of the steady state manifold and its stability properties. A parameterisation of the steady state manifold is not required. We prove local convergence of the method for locally strictly convex objective functions. Effciency and reliability of the proposed method are demonstrated in two examples. The proposed method demonstrated better convergence properties than existing general purpose methods and a significantly higher number of converged starts per time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.01658v1.pdf"}
{"id": "1511.02932", "abstract": "  The baryon Dirac form factor is computed at one-loop order in large-N_c baryon chiral perturbation theory, where N_c is the number of color charges. Loop graphs with octet and decuplet intermediate states are systematically incorporated into the analysis and the effects of the decuplet-octet mass difference are accounted for. There are large-N_c cancellations between different one-loop graphs as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. As a byproduct, the mean-square charge radius is also computed through a detailed numerical analysis. The predictions of large-N_c baryon chiral perturbation theory are in very good agreement both with the expectations from the 1/N_c expansion and with the experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.02932v1.pdf"}
{"id": "1511.03705", "abstract": "  This paper studies secrecy transmission with the aid of a group of wireless energy harvesting (WEH)-enabled amplify-and-forward (AF) relays performing cooperative jamming (CJ) and relaying. The source node in the network does simultaneous wireless information and power transfer (SWIPT) with each relay employing a power splitting (PS) receiver in the first phase; each relay further divides its harvested power for forwarding the received signal and generating artificial noise (AN) for jamming the eavesdroppers in the second transmission phase. In the centralized case with global channel state information (CSI), we provide closed-form expressions for the optimal and/or suboptimal AF-relay beamforming vectors to maximize the achievable secrecy rate subject to individual power constraints of the relays, using the technique of semidefinite relaxation (SDR), which is proved to be tight. A fully distributed algorithm utilizing only local CSI at each relay is also proposed as a performance benchmark. Simulation results validate the effectiveness of the proposed multi-AF relaying with CJ over other suboptimal designs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.03705v1.pdf"}
{"id": "1511.04733", "abstract": "  Motivated by the importance of non-collinear and non-coplanar magnetic phases in determining various electrical properties of magnetic materials, we investigate the phase diagrams of the extended Hubbard model on anisotropic triangular lattice. We make use of a mean-field scheme that treats collinear, non-collinear and non-coplanar phases on equal footing. In addition to the ferromagnetic and 120 antiferromagnetic phases, we find the four-sublattice flux, the 3Q non-coplanar and the non-collinear charge-ordered states to be stable at specific values of filling fraction n. Inter-site Coulomb repulsion leads to intriguing spin-charge ordered phases. Most notable of these are the collinear and non-collinear magnetic states at n=2/3, which occur together with a pinball-liquid-like charge order. Our results demonstrate that the elementary single-orbital extended Hubbard model on a triangular lattice hosts unconventional spin-charge ordered phases, which have been reported in more complex and material-specific electronic Hamiltonians relevant to layered triangular systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.04733v1.pdf"}
{"id": "1511.04872", "abstract": "  We explore the orbital dynamics of a realistic three dimensional model describing the properties of a disk galaxy with a spherically symmetric central dense nucleus and a triaxial dark matter halo component. Regions of phase space with regular and chaotic motion are identified depending on the parameter values for triaxiality of the dark matter halo and for breaking the rotational symmetry. The four dimensional Poincaré map of the three degrees of freedom system is analyzed by a study of its restriction to various two dimensional invariant subsets of its domain. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.04872v1.pdf"}
{"id": "1511.05686", "abstract": "  Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.05686v3.pdf"}
{"id": "1511.07514", "abstract": "  We present a suite of extragalactic explorations of the origins and nature of globular clusters (GCs) and ultra-compact dwarfs (UCDs), and the connections between them. An example of GC metallicity bimodality is shown to reflect underlying, distinct metal-poor and metal-rich stellar halo populations. Metallicity-matching methods are used to trace the birth sites and epochs of GCs in giant E/S0s, pointing to clumpy disk galaxies at z   3 for the metal-rich GCs, and to a combination of accreted and in-situ formation modes at z   5-6 for the metal-poor GCs. An increasingly diverse zoo of compact stellar systems is being discovered, including objects that bridge the gaps between UCDs and faint fuzzies, and between UCDs and compact ellipticals. Many of these have properties pointing to origins as the stripped nuclei of larger galaxies, and a smoking-gun example is presented of an omega Cen-like star cluster embedded in a tidal stream. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.07514v1.pdf"}
{"id": "1511.08648", "abstract": "  This paper presents a mechanism for the coexistence of hyperbolic and non-hyperbolic dynamics arising in a neighbourhood of a conservative Bykov cycle where trajectories turn in opposite directions near the two saddle-foci. We show that within the class of divergence-free vector fields that preserve the cycle, tangencies of the invariant manifolds of two hyperbolic saddle-foci densely occur. The global dynamics is persistently dominated by heteroclinic tangencies and by the existence of infinitely many elliptic points coexisting with suspended hyperbolic horseshoes. A generalized version of the Cocoon bifurcations for conservative systems is obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.08648v1.pdf"}
{"id": "1511.09068", "abstract": "  One potential star-planet interaction mechanism for hot Jupiters involves planetary heating via currents set up by interactions between the stellar wind and planetary magnetosphere. Early modeling results indicate that such currents, which are analogous to the terrestrial global electric circuit (GEC), have the potential to provide sufficient heating to account for the additional radius inflation seen in some hot Jupiters. Here we present a more detailed model of this phenomenon, exploring the scale of the effect, the circumstances under which it is likely to be significant, implications for the planetary magnetospheric structure, and observational signatures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.09068v1.pdf"}
{"id": "1512.00344", "abstract": "  This paper is concerned with stochastic SIR and SEIR epidemic models on random networks in which individuals may rewire away from infected neighbors at some rate ω (and reconnect to non-infectious individuals with probability α or else simply drop the edge if α=0), so-called preventive rewiring. The models are denoted SIR-ω and SEIR-ω, and we focus attention on the early stages of an outbreak, where we derive expression for the basic reproduction number R_0 and the expected degree of the infectious nodes E(D_I) using two different approximation approaches. The first approach approximates the early spread of an epidemic by a branching process, whereas the second one uses pair approximation. The expressions are compared with the corresponding empirical means obtained from stochastic simulations of SIR-ω and SEIR-ω epidemics on Poisson and scale-free networks. Without rewiring of exposed nodes, the two approaches predict the same epidemic threshold and the same E(D_I) for both types of epidemics, the latter being very close to the mean degree obtained from simulated epidemics over Poisson networks. Above the epidemic threshold, pairwise models overestimate the value of R_0 computed from simulations, which turns out to be very close to the one predicted by the branching process approximation. When exposed individuals also rewire with α > 0 (perhaps unaware of being infected), the two approaches give different epidemic thresholds, with the branching process approximation being more in agreement with simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.00344v3.pdf"}
{"id": "1512.02039", "abstract": "  We discuss constraints on the formation of multiple populations in globular clusters (GCs) imposed by their present-day kinematics (velocity dispersion and anisotropy) and spatial distribution. We argue that the observational evidence collected so far in the outer parts of clusters is generally consistent with an enriched population forming more centrally concentrated compared to the primordial population, in agreement with all the scenarios proposed to date (in some cases by design), but not sufficient to favour a particular scenario. We highlight that the differential rotation of subpopulations is a signature that may provide crucial new constraints and allow us to distinguish between various scenarios. Finally, we discuss the spatial distribution of subpopulations in the central regions of GCs and speculate that mass segregation between subpopulations may be due to a difference in their binary fraction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.02039v1.pdf"}
{"id": "1512.02653", "abstract": "  We consider new regular exact spherically symmetric solutions of a nonminimal Einstein–Yang-Mills theory with a cosmological constant and a gauge field of magnetic Wu-Yang type. The most interesting solutions found are black holes with metric and curvature invariants that are regular everywhere, i.e., regular black holes. We set up a classification of the solutions according to the number and type of horizons. The structure of these regular black holes is characterized by four specific features: a small cavity in the neighborhood of the center, a repulsion barrier off the small cavity, a distant equilibrium point, in which the metric function has a minimum, and a region of Newtonian attraction. Depending on the sign and value of the cosmological constant the solutions are asymptotically de Sitter (dS), asymptotically flat, or asymptotically anti-de Sitter (AdS). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.02653v2.pdf"}
{"id": "1512.02833", "abstract": "  The present study is the first such attempt to examine rigorously and comprehensively the spectral properties of a three-dimensional ultracold atom when both the spin-orbit interaction and the Zeeman field are taken into account. The model operator is the Rashba spin-orbit coupled operator in dimension three. The self-adjoint extensions are constructed using the theory of singular perturbations, where regularized rank two perturbations describe spin-dependent contact interactions. The spectrum of self-adjoint extensions is investigated in detail laying emphasis on the effects due to spin-orbit coupling. When the spin-orbit-coupling strength is small enough, the asymptotics of eigenvalues is obtained. The conditions for the existence of eigenvalues above the threshold are discussed in particular. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.02833v1.pdf"}
{"id": "1512.02957", "abstract": "  Binary quantum information can be fault tolerantly encoded in states defined in infinite dimensional Hilbert spaces. Such states define a computational basis, and permit a perfect equivalence between continuous and discrete universal operations. The drawback of this encoding is that the corresponding logical states are unphysical, meaning infinitely localized in phase space. We use the modular variables formalism to show that, in a number of protocols relevant for quantum information and for the realization of fundamental tests of quantum mechanics, it is possible to loosen the requirements on the logical subspace without jeopardizing their usefulness or their successful implementation. Such protocols involve measurements of appropriately chosen modular observables that permit the readout of the encoded discrete quantum information from the corresponding logical states. Finally, we demonstrate the experimental feasibility of our approach by applying it to the transverse degrees of freedom of single photons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.02957v2.pdf"}
{"id": "1512.04782", "abstract": "  Critical software systems face stringent requirements in safety, security, and reliability due to the circumstances surrounding their operation. Safety and security have progressively gained importance over the years due to the integration of hardware with software-intensive deployments that introduce additional sources of errors. It is, then, necessary to follow high-quality exhaustive software development processes that besides the needed development activities to increase safety and security also integrate techniques to increase the reliability of the software development process itself. In practice, the use of automated techniques for the verification of the verification process is, however, not sufficiently wide spread. This is mainly due to the high cost of the required techniques and to their degree of complexity when adjusting to the different norms and regulations. This work presents an approach for comprehensive management of the verification processes; the approach allows engineers to monitor and control the project status regarding the applicable standards. This approach has been validated through its implementation in a tool and its application to real projects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.04782v1.pdf"}
{"id": "1512.05350", "abstract": "  The broad-band variability of many accreting systems displays characteristic structure; log-normal flux distributions, RMS-flux relations, and long inter-band lags. These characteristics are usually interpreted as inward propagating fluctuations in an accretion disk driven by stochasticity of the angular momentum transport mechanism. We present the first analysis of propagating fluctuations in a long-duration, high-resolution, global three-dimensional magnetohydrodynamic (MHD) simulation of a geometrically-thin (h/r≈0.1) accretion disk around a black hole. While the dynamical-timescale turbulent fluctuations in the Maxwell stresses are too rapid to drive radially-coherent fluctuations in the accretion rate, we find that the low-frequency quasi-periodic dynamo action introduces low-frequency fluctuations in the Maxwell stresses which then drive the propagating fluctuations. Examining both the mass accretion rate and emission proxies, we recover log-normality, linear RMS-flux relations, and radial coherence that would produce inter-band lags. Hence, we successful relate and connect the phenomenology of propagating fluctuations to modern MHD accretion disk theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.05350v1.pdf"}
{"id": "1512.05829", "abstract": "  It is generally considered that an atomic nucleus is always compact. Based on the isospin-dependent Boltzmann nuclear transport model, here I show that large block nuclear matter or excited nuclear matter may both be hollow. And the size of inner bubble in these matter is affected by the charge number of nuclear matter. Existence of hollow nuclear matter may have many implications in nuclear or atomic physics or astrophysics as well as some practical applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.05829v1.pdf"}
{"id": "1512.05866", "abstract": "  We investigate the f(R) theory of gravity with broken diffeomorphism due to the change of the coefficient in front of the total divergence term in the (3+1)-decomposition of the scalar curvature. We perform the canonical analysis of this theory and show that its consistent, i.e. with no unphysical degrees of freedom, form is equivalent to the low-energy limit of the non-projectable f(R) Horava-Lifshitz theory of gravity. We also analyze its cosmological solutions and show that the de Sitter solution can be obtained also in the case of this broken symmetry. The consequences of the proposed theory on the asymptotic solutions of a few specific models in the cosmological context are also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.05866v3.pdf"}
{"id": "1512.05981", "abstract": "  We introduce a semi-classical wavefunction (SCWF) model for strong-field physics and attosecond science. When applied to high harmonic generation (HHG), this formalism allows one to show that the natural time-domain separation of the contribution of ionization, propagation and recollisions to the HHG process leads to a frequency-domain factorization of the harmonic yield into these same contributions, for any choice of atomic or molecular potential. We first derive the factorization from the natural expression of the dipole signal in the temporal domain by using a reference system, as in the quantitative rescattering (QRS) formalism [J. Phys. B. 43, 122001 (2010)]. Alternatively, we show how the trajectory component of the SCWF can be used to express the factorization, which also allows one to attribute individual contributions to the spectrum to the underlying trajectories. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.05981v1.pdf"}
{"id": "1512.06456", "abstract": "  We investigate the dynamics of a quantum system coupled linearly to Gaussian white noise using functional methods. By performing the integration over the noisy field in the evolution operator, we get an equivalent non-Hermitian Hamiltonian, which evolves the quantum state with a dissipative dynamics. We also show that if the integration over the noisy field is done for the time evolution of the density matrix, a gain contribution from the fluctuations, can be accessed in addition to the loss one from the non-hermitian Hamiltonian dynamics. We illustrate our study by computing analytically the effective non-Hermitian Hamiltonian, which we found to be the complex frequency harmonic oscillator, with a known evolution operator. It leads to space and time localisation, a common feature of noisy quantum systems in general applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.06456v1.pdf"}
{"id": "1512.06553", "abstract": "  The transition metal dichalcogenide (TMD) 1T-TaS_2 exhibits a rich set of charge density wave (CDW) orders. Recent investigations suggested that using light or electric field can manipulate the commensurate (C) CDW ground state. Such manipulations are considered to be determined by the charge carrier doping. Here we simulate by first-principles calculations the carrier doping effect on CCDW in 1T-TaS_2. We investigate the charge doping effects on the electronic structures and phonon instabilities of 1T structure and analyze the doping induced energy and distortion ratio variations in CCDW structure. We found that both in bulk and monolayer 1T-TaS_2, CCDW is stable upon electron doping, while hole doping can significantly suppress the CCDW, implying different mechanisms of such reported manipulations. Light or positive perpendicular electric field induced hole doping increases the energy of CCDW, so that the system transforms to NCCDW or similar metastable state. On the other hand, even the CCDW distortion is more stable upon in-plain electric field induced electron injection, some accompanied effects can drive the system to cross over the energy barrier from CCDW to nearly commensurate (NC) CDW or similar metastable state. We also estimate that hole doping can introduce potential superconductivity with T_c of 6∼7 K. Controllable switching of different states such as CCDW/Mott insulating state, metallic state, and even the superconducting state can be realized in 1T-TaS_2, which makes the novel material have very promising applications in the future electronic devices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.06553v3.pdf"}
{"id": "1512.06925", "abstract": "  The success of product quantization (PQ) for fast nearest neighbor search depends on the exponentially reduced complexities of both storage and computation with respect to the codebook size. Recent efforts have been focused on employing sophisticated optimization strategies, or seeking more effective models. Residual quantization (RQ) is such an alternative that holds the same property as PQ in terms of the aforementioned complexities. In addition to being a direct replacement of PQ, hybrids of PQ and RQ can yield more gains for approximate nearest neighbor search. This motivated us to propose a novel approach to optimizing RQ and the related hybrid models. With an observation of the general randomness increase in a residual space, we propose a new strategy that jointly learns a local transformation per residual cluster with an ultimate goal to reduce overall quantization errors. We have shown that our approach can achieve significantly better accuracy on nearest neighbor search than both the original and the optimized PQ on several very large scale benchmarks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.06925v1.pdf"}
{"id": "1512.07208", "abstract": "  We use a simple machine learning model, logistically-weighted regularized linear least squares regression, in order to predict baseball, basketball, football, and hockey games. We do so using only the thirty-year record of which visiting teams played which home teams, on what date, and what the final score was. No real \"statistics\" are used. The method works best in basketball, likely because it is high-scoring and has long seasons. It works better in football and hockey than in baseball, but in baseball the predictions are closer to a theoretical optimum. The football predictions, while good, can in principle be made much better, and the hockey predictions can be made somewhat better. These findings tells us that in basketball, most statistics are subsumed by the scores of the games, whereas in football, further study of game and player statistics is necessary to predict games as well as can be done. Baseball and hockey lie somewhere in between. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.07208v2.pdf"}
{"id": "1512.07686", "abstract": "  We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics and current-induced vibrational instabilities using a simplified eigen-mode analysis.Our study shows that the armchair nanoribbon serves as a possible testbed for probing the current-induced forces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.07686v1.pdf"}
{"id": "1512.07738", "abstract": "  Current acceleration of the cosmic expansion leads to coincidence as well as fine-tuning issues in the framework of general relativity. Dynamical scalar fields have been introduced in response of these problems, some of them invoking screening mechanisms for passing local tests of gravity. Recent lab experiments based on atom interferometry in a vacuum chamber have been proposed for testing modified gravity models. So far only analytical computations have been used to provide forecasts. We derive numerical solutions for chameleon models that take into account the effect of the vacuum chamber wall and its environment. With this realistic profile of the chameleon field in the chamber, we refine the forecasts that were derived analytically. We finally highlight specific effects due to the vacuum chamber that are potentially interesting for future experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.07738v1.pdf"}
{"id": "1601.00251", "abstract": "  A high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave green laser (532 nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064 nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO_3 crystal. The maximum achieved green power at 5 W IR pump power is 1.74 W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7 kW with a corresponding enhancement of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.0 GeV and 50 μA. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.00251v2.pdf"}
{"id": "1601.00801", "abstract": "  We consider Friedel oscillation in the two-dimensional Dirac materials when Fermi level is near the van Hove singularity. Twisted graphene bilayer and the surface state of topological crystalline insulator are the representative materials which show low-energy saddle points that are feasible to probe by gating. We approximate the Fermi surface near saddle point with a hyperbola and calculate the static Lindhard response function. Employing a theorem of Lighthill, the induced charge density δ n due to an impurity is obtained and the algebraic decay of δ n is determined by the singularity of the static response function. Although a hyperbolic Fermi surface is rather different from a circular one, the static Lindhard response function in the present case shows a singularity similar with the response function associated with circular Fermi surface, which leads to the δ n∝ R^-2 at large distance R. The dependences of charge density on the Fermi energy are different. Consequently, it is possible to observe in twisted graphene bilayer the evolution that δ n∝ R^-3 near Dirac point changes to δ n∝ R^-2 above the saddle point. Measurements using scanning tunnelling microscopy around the impurity sites could verify the prediction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.00801v1.pdf"}
{"id": "1601.02255", "abstract": "  We study the thermoelectrical transports for an interacting dot attached to two graphene electrodes. Graphene band structure shows a pseudogap density of states that affects strongly the transport properties. In this work, we focus on the Coulomb blockade regime and derive the expression for Onsager matrix O_ij that relates the electrical and heat currents with electrical and thermal biases in the linear response regime. Our findings show double peak structures for the electrical and thermal conductances versus the dot level in accordance with the Coulom blockade phenomenon. Remarkably, however, the thermal conductance is much smaller than the electrical conductance, resulting in high figure of merit value for some gate voltage. Finally, we report a large departure from the Wiedemann-Franz law caused mainly by the pseudogap density of states in the contacts and weakly affected by interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.02255v1.pdf"}
{"id": "1601.03429", "abstract": "  Topological insulators (TIs) are a new quantum state of matter discovered recently, which are characterized by unconventional bulk topological invariants. Proposals for practical applications of the TIs are mostly based upon their metallic surface or edge states. Here, we report the theoretical discovery of a bulk quantum pumping effect in a two-dimensional TI electrically modulated in adiabatic cycles. In each cycle, an amount of spin proportional to the sample width can be pumped into a nonmagnetic electrode, which is attributed to nonzero spin Chern numbers C_±. Moreover, by using a half-metallic electrode, universal quantized charge pumping conductivities -C_±e^2/h can be measured. This discovery paves the way for direct investigation of the robust topological properties of the TIs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.03429v1.pdf"}
{"id": "1601.04806", "abstract": "  Some developments of nuclear-structure physics uniquely related to Copenhagen School are sketched based on theoretical considerations versus experimental findings and one-particle versus collective aspects. Based on my personal overview I pick up the following topics; (1) Study of vibration in terms of particle-vibration coupling; (2) One-particle motion in deformed and rotating potentials, and yrast spectroscopy in high-spin physics; (3) Triaxial shape in nuclei: wobbling motion and chiral bands; (4) Nuclear structure of drip line nuclei: in particular, shell-structure (or magic numbers) change and spherical or deformed halo phenomena; (5) shell structure in oblate deformation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.04806v1.pdf"}
{"id": "1601.05680", "abstract": "  A weak Galerkin (WG) finite element method for solving the stationary Stokes equations in two- or three- dimensional spaces by using discontinuous piecewise polynomials is developed and analyzed. The variational form we considered is based on two gradient operators which is different from the usual gradient-divergence operators. The WG method is highly flexible by allowing the use of discontinuous functions on arbitrary polygons or polyhedra with certain shape regularity. Optimal-order error estimates are established for the corresponding WG finite element solutions in various norms. Numerical results are presented to illustrate the theoretical analysis of the new WG finite element scheme for Stokes problems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.05680v1.pdf"}
{"id": "1601.08132", "abstract": "  Future multi-tier communication networks will require enhanced network capacity and reduced overhead. In the absence of Channel State Information (CSI) at the transmitters, Blind Interference Alignment (BIA) and Topological Interference Management (TIM) can achieve optimal Degrees of Freedom (DoF), minimising network's overhead. In addition, Non-Orthogonal Multiple Access (NOMA) can increase the sum rate of the network, compared to orthogonal radio access techniques currently adopted by 4G networks. Our contribution is two interference management schemes, BIA and a hybrid TIM-NOMA scheme, employed in heterogeneous networks by applying user-pairing and Kronecker Product representation. BIA manages inter- and intra-cell interference by antenna selection and appropriate message scheduling. The hybrid scheme manages intra-cell interference based on NOMA and inter-cell interference based on TIM. We show that both schemes achieve at least double the rate of TDMA. The hybrid scheme always outperforms TDMA and BIA in terms of Degrees of Freedom (DoF). Comparing the two proposed schemes, BIA achieves more DoF than TDMA under certain restrictions, and provides better Bit-Error-Rate (BER) and sum rate performance to macrocell users, whereas the hybrid scheme improves the performance of femtocell users. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.08132v1.pdf"}
{"id": "1602.01998", "abstract": "  Based on the quantum technique of weak measurement, we propose a scheme to protect the entanglement from correlated amplitude damping decoherence. In contrast to the results of memoryless amplitude damping channel, we show that the memory effects play a significant role in the suppression of entanglement sudden death and protection of entanglement under severe decoherence. Moreover, we find that the initial entanglement could be drastically amplified by the combination of weak measurement and quantum measurement reversal even under the correlated amplitude damping channel. The underlying mechanism can be attributed to the probabilistic nature of weak measurements. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.01998v1.pdf"}
{"id": "1602.02153", "abstract": "  Winner-take-all phenomena are observed in various competitive systems. We find similar phenomena in replicator models with randomly fluctuating growth rates. The disparity between winners and losers increases indefinitely, even if all elements are statistically equivalent. A lognormal distribution describes well the nonstationary time evolution. If a nonlinear load corresponding to progressive taxation is introduced, a stationary distribution is obtained and disparity widening is suppressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.02153v1.pdf"}
{"id": "1602.02604", "abstract": "  The process of capture of a molecular enesemble into rotational resonance in the optical centrifuge is investigated. The adiabaticity and phase space incompressibility are used to find the resonant capture probability in terms of two dimensionless parameters P1,P2 characterising the driving strength and the nonlinearity, and related to three characteristic time scales in the problem. The analysis is based on the transformation to action-angle variables and the single resonance approximation, yielding reduction of the three-dimensional rotation problem to one degree of freedom. The analytic results for capture probability are in a good agreement with simulations. The existing experiments satisfy the validity conditions of the theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.02604v1.pdf"}
{"id": "1602.02832", "abstract": "  We present an implementation of the hierarchical tree algorithm on the individual timestep algorithm (the Hermite scheme) for collisional N-body simulations, running on GRAPE-9 system, a special-purpose hardware accelerator for gravitational many-body simulations. Such combination of the tree algorithm and the individual timestep algorithm was not easy on the previous GRAPE system mainly because its memory addressing scheme was limited only to sequential access to a full set of particle data. The present GRAPE-9 system has an indirect memory addressing unit and a particle memory large enough to store all particles data and also tree nodes data. The indirect memory addressing unit stores interaction lists for the tree algorithm, which is constructed on host computer, and, according to the interaction lists, force pipelines calculate only the interactions necessary. In our implementation, the interaction calculations are significantly reduced compared to direct N^2 summation in the original Hermite scheme. For example, we can archive about a factor 30 of speedup (equivalent to about 17 teraflops) against the Hermite scheme for a simulation of N=10^6 system, using hardware of a peak speed of 0.6 teraflops for the Hermite scheme. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.02832v1.pdf"}
{"id": "1602.03402", "abstract": "  Consider the problem of pricing options on forwards in energy markets, when spot prices follow a geometric multi-factor model in which several rates of mean reversion appear. In this paper we investigate the role played by slow mean reversion when pricing and hedging options. In particular, we determine both upper and lower bounds for the error one makes neglecting low rates of mean reversion in the spot price dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.03402v1.pdf"}
{"id": "1602.03983", "abstract": "  We investigate light dark matter production associated with a heavy quarkonium at B factories in a model-independent way by adopting the effective field theory approach for the interaction of dark matter with standard model particles. We consider the effective operators for the dark matter-heavy quark interaction, which are relevant to the production of dark matter associated with a heavy quarkonium. We calculate the cross sections for dark matter production associated with a J/psi or eta_c to compare with the standard model backgrounds. We set bounds on the energy scale of new physics for various effective operators and also obtain the corresponding limits for the dark matter-nucleon scattering cross sections for light dark matter with mass of the order of a few GeV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.03983v2.pdf"}
{"id": "1602.04153", "abstract": "  The glass transition remains one of the great unsolved mysteries of contemporary condensed matter physics. When crystallization is bypassed by rapid cooling, a supercooled liquid, retaining amorphous particle arrangment, results. The physical phenomenology of supercooled liquids is as vast as it is interesting. Most significant, the viscosity of the supercooled liquid displays an incredible increase over a narrow temperature range. Eventually, the supercooled liquid ceases to flow, becomes a glass, and gains rigidity and solid-like behaviors. Understanding what underpins the monumental growth of viscosity, and how rigidity results without long range order is a long-sought goal. Many theories of the glassy slowdown require the growth of static lengthscale related to structure with lowering of the temperature. To that end, we have proposed a new, natural lengthscale- \"the shear penetration depth\". This lengthscale quantifies the structural connectivity of the supercooled liquid. The shear penetration depth is defined as the distance up to which a shear perturbation applied to the boundary propagates into the liquid. We provide numerical data, based on the simulations of NiZr_2, illustrating that this length scale exhibits dramatic growth and eventual divergence upon approach to the glass transition. We further discuss this in relation to percolating structural connectivity and a new theory of the glass transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.04153v1.pdf"}
{"id": "1602.04433", "abstract": "  The recent success of deep neural networks relies on massive amounts of labeled data. For a target task where labeled data is unavailable, domain adaptation can transfer a learner from a different source domain. In this paper, we propose a new approach to domain adaptation in deep networks that can jointly learn adaptive classifiers and transferable features from labeled data in the source domain and unlabeled data in the target domain. We relax a shared-classifier assumption made by previous methods and assume that the source classifier and target classifier differ by a residual function. We enable classifier adaptation by plugging several layers into deep network to explicitly learn the residual function with reference to the target classifier. We fuse features of multiple layers with tensor product and embed them into reproducing kernel Hilbert spaces to match distributions for feature adaptation. The adaptation can be achieved in most feed-forward models by extending them with new residual layers and loss functions, which can be trained efficiently via back-propagation. Empirical evidence shows that the new approach outperforms state of the art methods on standard domain adaptation benchmarks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.04433v2.pdf"}
{"id": "1602.04803", "abstract": "  In interferometers, the more information about the quanta's path available in an ancillary quantum system (AQS), the less visibility the interference has. By use of Shannon entropy, we try to compare the amount of which-phase information with the amount of which-way information stored in the AQS of two-path interferometers with symmetric beam merging. We show that the former is lower than or equal the latter if the bipartite system of the single-quanta and the AQS is initially prepared in a pure state and the interaction between the two parts is unitary. Especially when there exists symmetry, the equality holds. No which-way information is obtained by the measurement that we use for extracting the which-phase information and vice versa. In order to verify the results experimentally, we propose assembling a new single-photon interferometer. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.04803v3.pdf"}
{"id": "1602.05130", "abstract": "  In this paper we present an algorithm to compute risk averse policies in Markov Decision Processes (MDP) when the total cost criterion is used together with the average value at risk (AVaR) metric. Risk averse policies are needed when large deviations from the expected behavior may have detrimental effects, and conventional MDP algorithms usually ignore this aspect. We provide conditions for the structure of the underlying MDP ensuring that approximations for the exact problem can be derived and solved efficiently. Our findings are novel inasmuch as average value at risk has not previously been considered in association with the total cost criterion. Our method is demonstrated in a rapid deployment scenario, whereby a robot is tasked with the objective of reaching a target location within a temporal deadline where increased speed is associated with increased probability of failure. We demonstrate that the proposed algorithm not only produces a risk averse policy reducing the probability of exceeding the expected temporal deadline, but also provides the statistical distribution of costs, thus offering a valuable analysis tool. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.05130v1.pdf"}
{"id": "1602.05214", "abstract": "  We present status of simulations used to design a novel device for the detection of hazardous substances in the aquatic environment using neutron activation. Unlike the other considered methods based on this technique we propose to use guides for neutron and gamma quanta which speeds up and simplifies identification. First preliminary results show that both the neutron guide and the γ ray guide increase the performance of underwater threats detection. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.05214v1.pdf"}
{"id": "1602.05429", "abstract": "  We present a construction of invariants for links using an isomorphism theorem for affine Yokonuma–Hecke algebras. The isomorphism relates affine Yokonuma–Hecke algebras with usual affine Hecke algebras. We use it to construct a large class of Markov traces on affine Yokonuma–Hecke algebras, and in turn, to produce invariants for links in the solid torus. By restriction, this construction contains the construction of invariants for classical links from classical Yokonuma–Hecke algebras. In general, the obtained invariants form an infinite family of 3-variables polynomials. As a consequence of the construction via the isomorphism, we reduce the number of invariants to study, given the number of connected components of a link. In particular, if the link is a classical link with N components, we show that N invariants generate the whole family. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.05429v1.pdf"}
{"id": "1602.05898", "abstract": "  The popular, stable, robust and computationally inexpensive cubic spline interpolation algorithm is adopted and used for finite temperature Green's function calculations of realistic systems. We demonstrate that with appropriate modifications the temperature dependence can be preserved while the Green's function grid size can be reduced by about two orders of magnitude by replacing the standard Matsubara frequency grid with a sparser grid and a set of interpolation coefficients. We benchmarked the accuracy of our algorithm as a function of a single parameter sensitive to the shape of the Green's function. Through numerous examples, we confirmed that our algorithm can be utilized in a systematically improvable, controlled, and black-box manner and highly accurate one- and two-body energies and one-particle density matrices can be obtained using only around 5", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.05898v1.pdf"}
{"id": "1602.05964", "abstract": "  We develop a theory for light-induced superconductivity in underdoped cuprates in which the competing bond-density wave order is suppressed by driving phonons with light. Close to a bond-density wave instability in a system with a small Fermi surface, such as a fractionalized Fermi liquid, we show that the coupling of electrons to phonons is strongly enhanced at the bond-density wave ordering wavevectors, leading to a strong softening of phonons at these wavevectors. For a model of classical phonons with anharmonic couplings, we show that the combination of strong softening and driving can lead to large phonon oscillations. When coupled to a phenomenological model describing the competition between bond-density wave order and superconductivity, these phonon oscillations melt bond-density wave order, thereby enhancing pairing correlations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.05964v2.pdf"}
{"id": "1602.08063", "abstract": "  Voting rules allow multiple agents to aggregate their preferences in order to reach joint decisions. Perhaps one of the most important desirable properties in this context is Condorcet-consistency, which requires that a voting rule should return an alternative that is preferred to any other alternative by some majority of voters. Another desirable property is participation, which requires that no voter should be worse off by joining an electorate. A seminal result in social choice theory by Moulin (1998) has shown that Condorcet-consistency and participation are incompatible whenever there are at least 4 alternatives and 25 voters. We leverage SAT solving to obtain an elegant human-readable proof of Moulin's result that requires only 12 voters. Moreover, the SAT solver is able to construct a Condorcet-consistent voting rule that satisfies participation as well as a number of other desirable properties for up to 11 voters, proving the optimality of the above bound. We also obtain tight results for set-valued and probabilistic voting rules, which complement and significantly improve existing theorems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.08063v1.pdf"}
{"id": "1602.08441", "abstract": "  Prompt neutrino fluxes due to the interactions of high-energy cosmic rays with the Earth's atmosphere are backgrounds in the search for high-energy neutrinos of galactic or extra-galactic origin performed by Very Large Volume Neutrino Telescopes. We summarize our predictions for prompt neutrinos, showing their basic features as emerging from the calculation in a QCD framework capable of describing recent charm data from the Large Hadron Collider. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.08441v1.pdf"}
{"id": "1602.08758", "abstract": "  We examine a regime in which a linearly-polarized laser pulse with relativistic intensity irradiates a sub-critical plasma for much longer than the characteristic electron response time. A steady-state channel is formed in the plasma in this case with quasi-static transverse and longitudinal electric fields. These relatively weak fields significantly alter the electron dynamics. The longitudinal electric field reduces the longitudinal dephasing between the electron and the wave, leading to an enhancement of the electron energy gain from the pulse. The energy gain in this regime is ultimately limited by the superluminosity of the wave fronts induced by the plasma in the channel. The transverse electric field alters the oscillations of the transverse electron velocity, allowing it to remain anti-parallel to laser electric field and leading to a significant energy gain. The energy enhancement is accompanied by development of significant oscillations perpendicular to the plane of the driven motion, making trajectories of energetic electrons three-dimensional. Proper electron injection into the laser beam can further boost the electron energy gain. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.08758v1.pdf"}
{"id": "1602.09092", "abstract": "  In this paper, a reconstruction method for the spatially distributed dielectric constant of a medium from the back scattering wave field in the frequency domain is considered. Our approach is to propose a globally convergent algorithm, which does not require any knowledge of a small neighborhood of the solution of the inverse problem in advance. The Quasi-Reversibility Method (QRM) is used in the algorithm. The convergence of the QRM is proved via a Carleman estimate. The method is tested on both computationally simulated and experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.09092v1.pdf"}
{"id": "1603.00357", "abstract": "  In this paper the duality correspondence between fermion-antifermion and difermion interaction channels is established in two (2+1)-dimensional Gross-Neveu type models with a fermion number chemical potential μ and a chiral chemical potential μ_5. The role and influence of this property on the phase structure of the models are investigated. In particular, it is shown that the chemical potential μ_5 promotes the appearance of dynamical chiral symmetry breaking, whereas the chemical potential μ contributes to the emergence of superconductivity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.00357v2.pdf"}
{"id": "1603.00487", "abstract": "  A historical problem for indirect exoplanet detection has been contending with the intrinsic variability of the host star. If the variability is periodic, it can easily mimic various exoplanet signatures, such as radial velocity variations that originate with the stellar surface rather than the presence of a planet. Here we present an update for the HD 99492 planetary system, using new radial velocity and photometric measurements from the Transit Ephemeris Refinement and Monitoring Survey (TERMS). Our extended time series and subsequent analyses of the Ca II H&K emission lines show that the host star has an activity cycle of ∼13 years. The activity cycle correlates with the purported orbital period of the outer planet, the signature of which is thus likely due to the host star activity. We further include a revised Keplerian orbital solution for the remaining planet, along with a new transit ephemeris. Our transit-search observations were inconclusive. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.00487v2.pdf"}
{"id": "1603.01966", "abstract": "  We propose a tight-binding model to investigate electronic transport properties of single helical protein molecules incorporating both the helical symmetry and the possibility of multiple charge transfer pathways. Our study reveals that due to existence of both the multiple charge transfer pathways and helical symmetry, the transport properties are quite rigid under influence of envi- ronmental fluctuations which indicates that these biomolecules can serve as better alternatives in nanoelectronic devices than its other biological counterparts e.g., single-stranded DNA. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.01966v1.pdf"}
{"id": "1603.02427", "abstract": "  A numerical investigation of two locally applied drag reducing control schemes is carried out in the configuration of a spatially developing turbulent boundary layer (TBL). One control is designed to damp near-wall turbulence and the other induces constant mass flux in the wall-normal direction. Both control schemes yield similar local drag reduction rates within the control region. However, the flow development downstream of the control significantly differs: persistent drag reduction is found for the uniform blowing case whereas drag increase is found for the turbulence damping case. In order to account for this difference the formulation of a global drag reduction rate is suggested. It represents the reduction of the streamwise force exerted by the fluid on a finite length plate. Furthermore, it is shown that the far downstream development of the TBL after the control region can be described by a single quantity, namely a streamwise shift of the uncontrolled boundary layer, i.e. a changed virtual origin. Based on this result, a simple model is developed that allows relating for the local drag reduction rate to the global one without the need of conducting expensive simulations or measurements far downstream of the control region. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.02427v2.pdf"}
{"id": "1603.04417", "abstract": "  The advent of quantum devices, which exploit the two essential elements of quantum physics, coherence and entanglement, has sparked renewed interest in the control of open quantum systems. Successful implementations face the challenge to preserve the relevant nonclassical features at the level of device operation. A major obstacle is decoherence which is caused by interaction with the environment. Optimal control theory is a tool that can be used to identify control strategies in the presence of decoherence. We review here recent advances in optimal control methodology that allow for tackling typical tasks in device operation for open quantum systems and discuss examples of relaxation-optimized dynamics. Optimal control theory is also a useful tool to exploit the environment for control. We discuss examples and point out possible future extensions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.04417v2.pdf"}
{"id": "1603.05397", "abstract": "  Solar prominences are long-lived cool and dense plasma curtains in the hot and rarefied outer solar atmosphere or corona. The physical mechanism responsible for their formation and especially for their internal plasma circulation has been uncertain for decades. The observed ubiquitous down flows in quiescent prominences are difficult to interpret as plasma with high conductivity seems to move across horizontal magnetic field lines. Here we present three-dimensional numerical simulations of prominence formation and evolution in an elongated magnetic flux rope as a result of in-situ plasma condensations fueled by continuous plasma evaporation from the solar chromosphere. The prominence is born and maintained in a fragmented, highly dynamic state with continuous reappearance of multiple blobs and thread structures that move mainly downward dragging along mass-loaded field lines. The prominence plasma circulation is characterized by the dynamic balance between the drainage of prominence plasma back to the chromosphere and the formation of prominence plasma via continuous condensation. Plasma evaporates from the chromosphere, condenses into the prominence in the corona, and drains back to the chromosphere, establishing a stable chromosphere-corona plasma cycle. Synthetic images of the modeled prominence with the Solar Dynamics Observatory Atmospheric Imaging Assembly closely resemble actual observations, with many dynamical threads underlying an elliptical coronal cavity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.05397v1.pdf"}
{"id": "1603.06020", "abstract": "  Quandle 2-cocycles define invariants of classical and virtual knots, and extensions of quandles. We show that the quandle 2-cocycle invariant with respect to a non-trivial 2-cocycle is constant, or takes some other restricted form, for classical knots when the corresponding extensions satisfy certain algebraic conditions. In particular, if an abelian extension is a conjugation quandle, then the corresponding cocycle invariant is constant. Specific examples are presented from the list of connected quandles of order less than 48. Relations among various quandle epimorphisms involved are also examined. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.06020v1.pdf"}
{"id": "1603.06097", "abstract": "  The detachment of a semi-ordered monolayer of polystyrene microspheres adhered to an aluminum-coated glass substrate is studied using a laser-induced spallation technique. The microsphere-substrate adhesion force is estimated from substrate surface displacement measurements obtained using optical interferometry, and a rigid-body model that accounts for the inertia of the microspheres. The estimated adhesion force is compared with estimates obtained from interferometric measurement of the out-of-plane microsphere contact resonance. Reasonable agreement is found between the two experiments. Scanning electron microscope images of detached monolayer regions reveal a unique morphology, namely, partially detached monolayer flakes composed of single hexagonal close packed crystalline domains. This work contributes to an improved understanding of microsphere adhesion and demonstrates a unique monolayer delamination morphology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.06097v1.pdf"}
{"id": "1603.06218", "abstract": "  A less well known variant of the Nambu–Jona-Lasinio model with Nc colors and U(2)L X U(2)R chiral symmetry is studied in 1+1 dimensions. Using semi-classical methods appropriate for the large Nc limit, we determine the vacuum manifold, the meson spectrum, massless and massive multi-fermion bound states and the phase diagram as a function of temperature, chemical potential and isospin chemical potential. An important tool to understand soliton dynamics is the generalization of the time-dependent Hartree-Fock approach to two flavors along the lines recently developed by Takahashi in the context of unconventional fermionic superfluids and superconductors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.06218v4.pdf"}
{"id": "1603.06446", "abstract": "  We propose a new Eulerian numerical approach for constructing the forward flow maps in continuous dynamical systems. The new algorithm improves the original formulation developed in [23, 24] so that the associated partial differential equations (PDEs) are solved forward in time and, therefore, the forward flow map can now be determined on the fly. Due to the simplicity in the implementations, we are now able to efficiently compute the unstable coherent structures in the flow based on quantities like the finite time Lyapunov exponent (FTLE), the finite size Lyapunov exponent (FSLE) and also a related infinitesimal size Lyapunov exponent (ISLE). When applied to the ISLE computations, the Eulerian method is in particularly computationally efficient. For each separation factor r in the definition of the ISLE, typical Lagrangian methods require to shoot and monitor an individual set of ray trajectories. If the scale factor in the definition is changed, these methods have to restart the whole computations all over again. The proposed Eulerian method, however, requires to extract only an isosurface of a volumetric data for an individual value of r which can be easily done using any well-developed efficient interpolation method or simply an isosurface extraction algorithm. Moreover, we provide a theoretical link between the FTLE and the ISLE fields which explains the similarity in these solutions observed in various applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.06446v2.pdf"}
{"id": "1603.09618", "abstract": "  Hard-soft bilayers are analogous to prototype exchange-biased ferromagnetic -antiferromagnetic systems as the minor loop of the soft layer is biased by the hard and furthermore they offer bias layer tunability. In sputtered CoPt/Co hard-soft bilayers we demonstrate that the exchange bias field shows a linear dependence on the hard layer magnetization, while the coercivity shows a quadratic dependence. Analysis of the minor hysteresis loop features supported by Monte-Carlo simulations provide clear evidence that the coercivity of the soft layer is mainly determined by the tunable randomness of the domain state of the hard layer. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.09618v1.pdf"}
{"id": "1604.00070", "abstract": "  Radiation pressure dominated accretion discs around compact objects may have turbulent velocities that greatly exceed the electron thermal velocities within the disc. Bulk Comptonization by the turbulence may therefore dominate over thermal Comptonization in determining the emergent spectrum. Bulk Comptonization by divergenceless turbulence is due to radiation viscous dissipation only. It can be treated as thermal Comptonization by solving the Kompaneets equation with an equivalent \"wave\" temperature, which is a weighted sum over the power present at each scale in the turbulent cascade. Bulk Comptonization by turbulence with non-zero divergence is due to both pressure work and radiation viscous dissipation. Pressure work has negligible effect on photon spectra in the limit of optically thin turbulence, and in this limit radiation viscous dissipation alone can be treated as thermal Comptonization with a temperature equivalent to the full turbulent power. In the limit of extremely optically thick turbulence, radiation viscous dissipation is suppressed, and the evolution of local photon spectra can be understood in terms of compression and expansion of the strongly coupled photon and gas fluids. We discuss the consequences of these effects for self-consistently resolving and interpreting turbulent Comptonization in spectral calculations in radiation MHD simulations of high luminosity accretion flows. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.00070v2.pdf"}
{"id": "1604.00344", "abstract": "  It is not fully understood how electromagnetic waves propagate through plasma density fluctuations when the size of the fluctuations is comparable with the wavelength of the incident radiation. In this paper, the perturbing effect of a turbulent plasma density layer on a traversing microwave beam is simulated with full-wave simulations. The deterioration of the microwave beam is calculated as a function of the characteristic turbulence structure size, the turbulence amplitude, the depth of the interaction zone and the size of the waist of the incident beam. The maximum scattering is observed for a structure size on the order of half the vacuum wavelength. The scattering and beam broadening was found to increase linearly with the depth of the turbulence layer and quadratically with the fluctuation strength. Consequences for experiments and 3D effects are considered. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.00344v2.pdf"}
{"id": "1604.01082", "abstract": "  By introducing a temporal change timescale τ_A(t) for the time-dependent system Hamiltonian, a general formulation of the Markovian quantum master equation is given to go well beyond the adiabatic regime. In appropriate situations, the framework is well justified even if τ_A(t) is faster than the decay timescale of the bath correlation function. An application to the dissipative Landau-Zener model demonstrates this general result. The findings are applicable to a wide range of fields, providing a basis for quantum control beyond the adiabatic regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.01082v3.pdf"}
{"id": "1604.01594", "abstract": "  The huge and increasing demand of data connectivity motivates the development of new and effective power line communication (PLC) channel models, which are able to faithfully describe a real communication scenario. This is of fundamental importance since a good model represents a quick evaluation tool for new standards or devices, allowing a considerable saving in time and costs. The aim of this paper is to discuss a novel top-down MIMO PLC synthetic channel model, able to numerically emulate a real PLC environment. First, the most common channel modeling strategies are briefly described, highlighting strengths and weaknesses. Afterwards, the basic model approach is described considering the SISO scenario. The implementation strategy is then extended to the MIMO case. The validity of the proposed model is proved making a comparison between the simulated channels and channels obtained with measurements in terms of both performance and statistical metrics. The focus is on the broadband frequency spectrum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.01594v1.pdf"}
{"id": "1604.01920", "abstract": "  This report deals with the preparation of a clean Ta(110) surface, investigated by means of scanning tunneling microscopy/spectroscopy as well as by low-energy electron diffraction and Auger electron spectroscopy. The surface initially exhibits a surface reconstruction induced by oxygen contamination. This reconstruction can be removed by annealing at high temperatures under ultrahigh vacuum conditions. The reconstruction-free surface reveals a surface resonance at a bias voltage of about -500 mV. The stages of the transformation are presented and discussed. In a next step, Fe islands were grown on top of Ta(110) and investigated subsequently. An intermixing regime was identified for annealing temperatures of (550 - 590) K. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.01920v2.pdf"}
{"id": "1604.02140", "abstract": "  We investigate quasinormal modes (QNMs) and Hawking radiation of a Reissner-Nordström black hole sur-rounded by quintessence. The Wentzel-Kramers-Brillouin (WKB) method is used to evaluate the QNMs and the rate of radiation. The results show that due to the interaction of the quintessence with the background metric, the QNMs of the black hole damp more slowly when increasing the density of quintessence and the black hole radiates at slower rate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.02140v1.pdf"}
{"id": "1604.02316", "abstract": "  Recently, vision-based Advanced Driver Assist Systems have gained broad interest. In this work, we investigate free-space detection, for which we propose to employ a Fully Convolutional Network (FCN). We show that this FCN can be trained in a self-supervised manner and achieve similar results compared to training on manually annotated data, thereby reducing the need for large manually annotated training sets. To this end, our self-supervised training relies on a stereo-vision disparity system, to automatically generate (weak) training labels for the color-based FCN. Additionally, our self-supervised training facilitates online training of the FCN instead of offline. Consequently, given that the applied FCN is relatively small, the free-space analysis becomes highly adaptive to any traffic scene that the vehicle encounters. We have validated our algorithm using publicly available data and on a new challenging benchmark dataset that is released with this paper. Experiments show that the online training boosts performance with 5", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.02316v2.pdf"}
{"id": "1604.02511", "abstract": "  With the development of wireless communication, industrial wireless sensor networks (IWSNs) plays an important role in monitoring and control systems. In this paper, we extend the application of IWSNs into High Frequency Surface-Wave Radar (HFSWR) system. The traditional antenna is replaced by mobile IWSNs. In combination of the application precondition of super-directivity in HF band and circular topology of IWSNs, a super-directivity synthesis method is presented for designing super-directivity array. In this method, the dominance of external noise is ensured by constraining the Ratio of External to Internal Noise (REIN) of the array, and the desired side lobe level is achieved by implementing linear constraint. By using this method, the highest directivity will be achieved in certain conditions. Using the designed super directive circular array as sub-arrays, the compact receive antenna array is constructed, the purpose of miniaturization is achieved. Simulation verifies that the proposed method is correct and effective, the validity of the proposed method has been proved. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.02511v1.pdf"}
{"id": "1604.03868", "abstract": "  This study addresses the mitigation of a nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA), is introduced in this paper. An unconventional aspect of the NLTVA is that the mathematical form of its restoring force is tailored according to the nonlinear restoring force of the primary system. The NLTVA parameters are then determined using a nonlinear generalization of Den Hartog's equal-peak method. The mitigation of the resonant vibrations of a Duffing oscillator is considered to illustrate the proposed developments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.03868v1.pdf"}
{"id": "1604.04088", "abstract": "  Amorphous solids yield in strain-controlled protocols at a critical value of the strain. For larger strains the stress and energy display a generic complex serrated signal with elastic segments punctuated by sharp energy and stress plastic drops having a wide range of magnitudes. Here we provide a theory of the scaling properties of such serrated signals taking into account the system-size dependence. We show that the statistics are not homogeneous - they separate sharply to a regime of `small' and `large' drops, each endowed with its own scaling properties. A scaling theory is first derived solely by data analysis, showing a somewhat complex picture. But after considering the physical interpretation one discovers that the scaling behavior and the scaling exponents are in fact very simple and universal. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.04088v1.pdf"}
{"id": "1604.04590", "abstract": "  The motion of a collisionless plasma - a high-temperature, low-density, ionized gas - is described by the Vlasov-Maxwell (VM) system. These equations are considered in one space dimension and two momentum dimensions without the assumption of relativistic velocity corrections. The main results are bounds on the spatial and velocity supports of the particle distribution function and uniform estimates on derivatives of this function away from the critical velocity | v_1 | = 1. Additionally, for initial particle distributions that are even in the second velocity argument v_2, the global-in-time existence of solutions is shown. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.04590v1.pdf"}
{"id": "1604.05061", "abstract": "  We overview a series of recent works addressing numerical simulations of partial differential equations in the presence of some elements of randomness. The specific equations manipulated are linear elliptic, and arise in the context of multiscale problems, but the purpose is more general. On a set of prototypical situations, we investigate two critical issues present in many settings: variance reduction techniques to obtain sufficiently accurate results at a limited computational cost when solving PDEs with random coefficients, and finite element techniques that are sufficiently flexible to carry over to geometries with random fluctuations. Some elements of theoretical analysis and numerical analysis are briefly mentioned. Numerical experiments, although simple, provide convincing evidence of the efficiency of the approaches. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.05061v1.pdf"}
{"id": "1604.05380", "abstract": "  We study flare processes in the lower solar atmosphere using observational data for a M1-class flare of June 12, 2014, obtained by New Solar Telescope (NST/BBSO) and Helioseismic Magnetic Imager (HMI/SDO). The main goal is to understand triggers and manifestations of the flare energy release in the lower layers of the solar atmosphere (the photosphere and chromosphere) using high-resolution optical observations and magnetic field measurements. We analyze optical images, HMI Dopplergrams and vector magnetograms, and use Non-Linear Force-Free Field (NLFFF) extrapolations for reconstruction of the magnetic topology. The NLFFF modelling reveals interaction of oppositely directed magnetic flux-tubes in the PIL. These two interacting magnetic flux tubes are observed as a compact sheared arcade along the PIL in the high-resolution broad-band continuum images from NST. In the vicinity of the PIL, the NST H alpha observations reveal formation of a thin three-ribbon structure corresponding to the small-scale photospheric magnetic arcade. Presented observational results evidence in favor of location of the primary energy release site in the dense chromosphere where plasma is partially ionized in the region of strong electric currents concentrated near the polarity inversion line. Magnetic reconnection may be triggered by two interacting magnetic flux tubes with forming current sheet elongated along the PIL. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.05380v1.pdf"}
{"id": "1604.05476", "abstract": "  In this paper, we investigate detectability and identifiability of attacks on linear dynamical systems that are subjected to external disturbances. We generalize a concept for a security index, which was previously introduced for static systems. The generalized index exactly quantifies the resources necessary for targeted attacks to be undetectable and unidentifiable in the presence of disturbances. This information is useful for both risk assessment and for the design of anomaly detectors. Finally, we show how techniques from the fault detection literature can be used to decouple disturbances and to identify attacks, under certain sparsity constraints. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.05476v1.pdf"}
{"id": "1604.05580", "abstract": "  We present a deterministic scheme for generating large-scale atomic W states in cavity QED system via a simple expansion mechanism, which is realized only by a detuned interaction between two identical atoms and a vacuum cavity mode. With the presented scheme, a W-type Bell pair can be created and an n-atom W state can be expanded to a 2n-atom W state with a unit probability of success in principle. No multi-atom gates, quantum memories or quantum non-demolition measurements are required, greatly simplifying the experimental realization of the scheme. The feasibility analysis shows that our expansion scheme can be implemented with state-of-the-art technologies. Our scheme enables advances not only in quantum information and communication but also in quantum thermodynamics, where atomic W states plays a crucial role. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.05580v1.pdf"}
{"id": "1604.05667", "abstract": "  Oscillation amplitudes are generally smaller within magnetically active regions like sunspots and plage, when compared to their surroundings. Such magnetic features, when viewed in spatially-resolved powermaps, appear as regions of suppressed power due to reductions in the oscillation amplitudes. Employing high spatial- and temporal-resolution observations from the Dunn Solar Telescope (DST) in New Mexico, we study the power suppression in a region of evolving magnetic fields adjacent to a pore. By utilising wavelet analysis, we study for the first time, how the oscillatory properties in this region change as the magnetic field evolves with time. Image sequences taken in the blue continuum, G-band, Ca ii K and Hα filters were used in this study. It is observed that the suppression found in the chromosphere occupies a relatively larger area confirming previous findings. Also, the suppression is extended to structures directly connected to the magnetic region and is found to get enhanced as the magnetic field strength increased with time. The dependence of the suppression on the magnetic field strength is greater at longer periods and higher formation heights. Furthermore, the dominant periodicity in the chromosphere was found to be anti-correlated with increases in the magnetic field strength. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.05667v1.pdf"}
{"id": "1604.06127", "abstract": "  It is well known that any link can be represented by the closure of a braid. The minimum number of strings needed in a braid whose closure represents a given link is called the braid index of the link and the well known Morton-Frank-Williams inequality reveals a close relationship between the HOMFLY polynomial of a link and its braid index. In the case that a link is already presented in a closed braid form, Jaeger derived a special formulation of the HOMFLY polynomial. In this paper, we prove a variant of Jaeger's result as well as a dual version of it. Unlike Jaeger's original reasoning, which relies on representation theory, our proof uses only elementary geometric and combinatorial observations. Using our variant and its dual version, we provide a direct and elementary proof of the fact that the braid index of a link that has an n-string closed braid diagram that is also reduced and alternating, is exactly n. Until know this fact was only known as a consequence of a result due to Murasugi on fibered links that are star products of elementary torus links and of the fact that alternating braids are fibered. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.06127v3.pdf"}
{"id": "1604.06187", "abstract": "  Evolutionary algorithms have been widely studied from a theoretical perspective. In particular, the area of runtime analysis has contributed significantly to a theoretical understanding and provided insights into the working behaviour of these algorithms. We study how these insights into evolutionary processes can be used for evolutionary art. We introduce the notion of evolutionary image transition which transfers a given starting image into a target image through an evolutionary process. Combining standard mutation effects known from the optimization of the classical benchmark function OneMax and different variants of random walks, we present ways of performing evolutionary image transition with different artistic effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.06187v1.pdf"}
{"id": "1604.06640", "abstract": "  We evaluate the next-to-leading order correction to the Nambu-Jona-Lasinio model starting from quantum chromodynamics. We show that a systematic expansion exists, starting from a given set of exact classical solutions, so that higher order corrections could in principle be computed at any order. In this way, we are able to fix the constants of the Nambu-Jona-Lasinio model from quantum chromodynamics and analyze the behavior of strong interactions at low energies. The technique is to expand in powers of currents of the generating functional. We apply it to a simple Yukawa model with self-interaction showing how this has a Nambu-Jona-Lasinio model and its higher order corrections as a low-energy limit. The same is shown to happen for quantum chromodynamics in the chiral limit with two quarks. We prove stability of the NJL model so obtained. Then, we prove that the correction term we obtained does not change the critical temperature of the chiral transition of the Nambu-Jona-Lasinio model at zero chemical potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.06640v2.pdf"}
{"id": "1604.07145", "abstract": "  We show that the 750 GeV diphoton excess can be explained by introducing vector-like quarks and hidden fermions charged under a hidden U(1) gauge symmetry, which has a relatively large coupling constant as well as a significant kinetic mixing with U(1)_Y. With the large kinetic mixing, the standard model gauge couplings unify around 10^17 GeV, suggesting the grand unified theory without too rapid proton decay. Our scenario predicts events with a photon and missing transverse momentum, and its cross section is related to that for the diphoton excess through the kinetic mixing. We also discuss other possible collider signatures and cosmology, including various ways to evade constraints on exotic stable charged particles. In some cases where the 750 GeV diphoton excess is due to diaxion decays, our scenario also predicts triphoton and tetraphoton signals. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.07145v3.pdf"}
{"id": "1604.08243", "abstract": "  Recent years have witnessed several initiatives on enabling Internet access to the next three billion people. Access to the Internet necessarily translates to access to its services. This means that the goal of providing Internet access requires ac- cess to its critical service infrastructure, which are currently hosted in the cloud. However, recent works have pointed out that the current cloud centric nature of the Internet is a fundamental barrier for Internet access in rural/remote areas as well as in developing regions. It is important to explore (low cost) solutions such as micro cloud infrastructures that can provide services at the edge of the network (potentially on demand), right near the users. In this paper, we present Cloudrone- a preliminary idea of deploying a lightweight micro cloud infrastructure in the sky using indigenously built low cost drones, single board computers and lightweight Operating System virtualization technologies. Our paper lays out the preliminary ideas on such a system that can be instantaneously deployed on demand. We describe an initial design of the Cloudrone and provide a preliminary evaluation of the proposed system mainly focussed on the scalability issues of supporting multiple services and users. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.08243v1.pdf"}
{"id": "1604.08268", "abstract": "  The formalism of quantum theory in Hilbert space has been applied with success to the modeling and explanation of several cognitive phenomena, whereas traditional cognitive approaches were problematical. However, this 'quantum cognition paradigm' was recently challenged by its proven impossibility to simultaneously model 'question order effects' and 'response replicability'. In Part I of this paper we describe sequential dichotomic measurements within an operational and realistic framework for human cognition elaborated by ourselves, and represent them in a quantum-like 'extended Bloch representation' where the Born rule of quantum probability does not necessarily hold. In Part II we apply this mathematical framework to successfully model question order effects, response replicability and unpacking effects, thus opening the way toward quantum cognition beyond Hilbert space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.08268v1.pdf"}
{"id": "1605.00733", "abstract": "  Accurate molecular crystal structure prediction is a fundamental goal in academic and industrial condensed matter research and polymorphism is arguably the biggest obstacle on the way. We tackle this challenge in the difficult case of the repeatedly studied, abundantly used aminoacid Glycine that hosts still little-known phase transitions and we illustrate the current state of the field through this example. We demonstrate that the combination of recent progress in structure search algorithms with the latest advances in the description of van der Waals interactions in Density Functional Theory, supported by data-mining analysis, enables a leap in predictive power: we resolve, without prior empirical input, all known phases of glycine, as well as the structure of the previously unresolved ζ phase after a decade of its experimental observation [Boldyreva et al. Z. Kristallogr. 2005, 220, 50-57]. The search for the well-established α phase instead reveals the remaining challenges in exploring a polymorphic landscape. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.00733v1.pdf"}
{"id": "1605.01864", "abstract": "  We consider two minimal models of active fluid droplets that exhibit complex dynamics including steady motion, deformation, rotation and oscillating motion. First we consider a droplet with a concentration of active contractile matter adsorbed to its boundary. We analytically predict activity driven instabilities in the concentration profile, and compare them to the dynamics we find from simulations. Secondly, we consider a droplet of active polar fluid of constant concentration. In this system we predict, motion and deformation of the droplets in certain activity ranges due to instabilities in the polarisation field. Both these systems show spontaneous transitions to motility and deformation which resemble dynamics of the cell cytoskeleton in animal cells. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.01864v4.pdf"}
{"id": "1605.04149", "abstract": "  The charge-current-induced spin polarization is a key property of topological insulators for their applications in spintronics. However, topological surface states are expected to give rise to only one type of spin polarization for a given current direction, which has been a limiting factor for spin manipulations. Here we report that in devices based on the bulk-insulating topological insulator BiSbTeSe2, an unexpected switching of spin polarization was observed upon changing the chemical potential. The spin polarization expected from the topological surface states was detected in a heavily electron-doped device, whereas the opposite polarization was reproducibly observed in devices with low carrier densities. We propose that the latter type of spin polarization stems from topologically-trivial two-dimensional states with a large Rashba spin splitting, which are caused by a strong band bending at the surface of BiSbTeSe2 beneath the ferromagnetic electrode used as a spin detector. This finding paves the way for realizing the \"spin transistor\" operation in future topological spintronic devices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.04149v2.pdf"}
{"id": "1605.04272", "abstract": "  Electron beam induced current (EBIC) is a powerful characterization technique which offers the high spatial resolution needed to study polycrystalline solar cells. Current models of EBIC assume that excitations in the p-n junction depletion region result in perfect charge collection efficiency. However we find that in CdTe and Si samples prepared by focused ion beam (FIB) milling, there is a reduced and nonuniform EBIC lineshape for excitations in the depletion region. Motivated by this, we present a model of the EBIC response for excitations in the depletion region which includes the effects of surface recombination from both charge-neutral and charged surfaces. For neutral surfaces we present a simple analytical formula which describes the numerical data well, while the charged surface response depends qualitatively on the location of the surface Fermi level relative to the bulk Fermi level. We find the experimental data on FIB-prepared Si solar cells is most consistent with a charged surface, and discuss the implications for EBIC experiments on polycrystalline materials. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.04272v2.pdf"}
{"id": "1605.04604", "abstract": "  We propose a Dynamical generalized Polynomial Chaos (DgPC) method to solve time-dependent stochastic partial differential equations (SPDEs) with white noise forcing. The long-time simulation of SPDE solutions by Polynomial Chaos (PC) methods is notoriously difficult as the dimension of the stochastic variables increases linearly with time. Exploiting the markovian property of white noise, DgPC [1] implements a restart procedure that allows us to expand solutions at future times in terms of orthogonal polynomials of the measure describing the solution at a given time and the future white noise. The dimension of the representation is kept minimal by application of a Karhunen–Loeve (KL) expansion. Using frequent restarts and low degree polynomials on sparse multi-index sets, the method allows us to perform long time simulations, including the calculation of invariant measures for systems which possess one. We apply the method to the numerical simulation of stochastic Burgers and Navier–Stokes equations with white noise forcing. Our method also allows us to incorporate time-independent random coefficients such as a random viscosity. We propose several numerical simulations and show that the algorithm compares favorably with standard Monte Carlo methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.04604v2.pdf"}
{"id": "1605.05846", "abstract": "  The nonlocal properties of the W states are investigated under particle loss. By removing all but two particles from an N-qubit W state, the resulting two-qubit state is still entangled. Hence, the W state has high persistency of entanglement. We ask an analogous question regarding the persistency of nonlocality introduced in [Phys. Rev. A 86, 042113]. Namely, we inquire what is the minimal number of particles that must be removed from the W state so that the resulting state becomes local. We bound this value in function of N qubits by considering Bell nonlocality tests with two alternative settings per site. In particular, we find that this value is between 2N/5 and N/2 for large N. We also develop a framework to establish bounds for more than two settings per site. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.05846v1.pdf"}
{"id": "1605.06560", "abstract": "  As the complexity of deep neural networks (DNNs) trend to grow to absorb the increasing sizes of data, memory and energy consumption has been receiving more and more attentions for industrial applications, especially on mobile devices. This paper presents a novel structure based on functional hashing to compress DNNs, namely FunHashNN. For each entry in a deep net, FunHashNN uses multiple low-cost hash functions to fetch values in the compression space, and then employs a small reconstruction network to recover that entry. The reconstruction network is plugged into the whole network and trained jointly. FunHashNN includes the recently proposed HashedNets as a degenerated case, and benefits from larger value capacity and less reconstruction loss. We further discuss extensions with dual space hashing and multi-hops. On several benchmark datasets, FunHashNN demonstrates high compression ratios with little loss on prediction accuracy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.06560v1.pdf"}
{"id": "1605.06743", "abstract": "  Our formal understanding of the inductive bias that drives the success of convolutional networks on computer vision tasks is limited. In particular, it is unclear what makes hypotheses spaces born from convolution and pooling operations so suitable for natural images. In this paper we study the ability of convolutional networks to model correlations among regions of their input. We theoretically analyze convolutional arithmetic circuits, and empirically validate our findings on other types of convolutional networks as well. Correlations are formalized through the notion of separation rank, which for a given partition of the input, measures how far a function is from being separable. We show that a polynomially sized deep network supports exponentially high separation ranks for certain input partitions, while being limited to polynomial separation ranks for others. The network's pooling geometry effectively determines which input partitions are favored, thus serves as a means for controlling the inductive bias. Contiguous pooling windows as commonly employed in practice favor interleaved partitions over coarse ones, orienting the inductive bias towards the statistics of natural images. Other pooling schemes lead to different preferences, and this allows tailoring the network to data that departs from the usual domain of natural imagery. In addition to analyzing deep networks, we show that shallow ones support only linear separation ranks, and by this gain insight into the benefit of functions brought forth by depth - they are able to efficiently model strong correlation under favored partitions of the input. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.06743v4.pdf"}
{"id": "1605.07080", "abstract": "  We consider a hypothetical substance, where interaction between (within) structural elements of condensed matter (molecules, nanoparticles, clusters, layers, wires etc.) depends on state of Cooper pairs: an additional work must be made against this interaction to break a pair. Such a system can be described by BCS Hamiltonian with the external pair potential term. In this model the potential essentially renormalizes the order parameter: if the pairing lowers energy of the structure the energy gap is slightly enlarged at zero temperature and asymptotically tends to zero as temperature rises. Thus the critical temperature of such a superconductor is equal to infinity formally. For this case the effective Ginzburg-Landau theory is formulated, where the coherence length decreases as temperature rises, the GL parameter and the second critical field are increasing functions of temperature unlike the standard theory. If the pairing enlarges energy of the structure then suppression of superconductivity and the first order phase transition occur. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.07080v8.pdf"}
{"id": "1605.07208", "abstract": "  In this paper, a plasmonic absorber consisting of a metal-dielectric-metal stack with a top layer of Sierpinski nanocarpet is theoretically investigated. Such compact absorber depicts broadband angle-independent behavior over a wide optical wavelength range (400-700 nm) and a broad range of angles of light incidence (0-80^∘). Including several feature sizes, such fractal-like structure shows widely strong extinction (85-99", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.07208v2.pdf"}
{"id": "1606.00048", "abstract": "  Protein aggregation is of great importance in biology, e.g., in amyloid fibrillation. The aggregation processes that occur at the cellular scale must be highly stochastic in nature because of the statistical number fluctuations that arise on account of the small system size at the cellular scale. We study the nucleated reversible self-assembly of monomeric building blocks into polymer-like aggregates using the method of kinetic Monte Carlo. Kinetic Monte Carlo, being inherently stochastic, allows us to study the impact of fluctuations on the polymerisation reactions. One of the most important characteristic features in this kind of problem is the existence of a lag phase before self-assembly takes off, which is what we focus attention on. We study the associated lag time as a function of the system size and kinetic pathway. We find that the leading order stochastic contribution to the lag time before polymerisation commences is inversely proportional to the system volume for large-enough system size for all nine reaction pathways tested. Finite-size corrections to this do depend on the kinetic pathway. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.00048v1.pdf"}
{"id": "1606.01105", "abstract": "  Two decades after the discovery of 51 Peg b, the formation processes and atmospheres of short-period gas giants remain poorly understood. Observations of eccentric systems provide key insights on those topics as they can illuminate how a planet's atmosphere responds to changes in incident flux. We report here the analysis of multi-day multi-channel photometry of the eccentric (e  0.93) hot Jupiter HD 80606 b obtained with the Spitzer Space Telescope. The planet's extreme eccentricity combined with the long coverage and exquisite precision of new periastron-passage observations allow us to break the degeneracy between the radiative and dynamical timescales of HD 80606 b's atmosphere and constrain its global thermal response. Our analysis reveals that the atmospheric layers probed heat rapidly ( 4 hr radiative timescale) from 500 to 1400 K as they absorb   20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.01105v1.pdf"}
{"id": "1606.03268", "abstract": "  In graph modification problems, one is given a graph G and the goal is to apply a minimum number of modification operations (such as edge deletions) to G such that the resulting graph fulfills a certain property. For example, the Cluster Deletion problem asks to delete as few edges as possible such that the resulting graph is a disjoint union of cliques. Graph modification problems appear in numerous applications, including the analysis of biological and social networks. Typically, graph modification problems are NP-hard, making them natural candidates for parameterized complexity studies. We discuss several fruitful interactions between the development of fixed-parameter algorithms and the design of heuristics for graph modification problems, featuring quite different aspects of mutual benefits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.03268v1.pdf"}
{"id": "1606.04270", "abstract": "  Gamma-ray bursts (GRBs) are cosmological explosions which carry valuable information from the distant past of the expanding universe. One of the greatest discoveries in modern cosmology is the finding of the accelerated expansion of the universe using Type Ia supernovae (SN Ia) as standard candles. However, due to the interstellar extinction SN Ia can be seen only up to a redshift z∼ 1.5. GRBs are considered as the potential alternative to push this limit to as high as z∼ 10, a redshift regime corresponding to an epoch when the universe just started to form the first structures. There exist several correlations between the energy and an observable of a GRB which can be used to derive luminosity distance. In recent works, we have studied spectral evolution within the individual pulses and obtained such correlations within the pulses. Here we summarize our results of the pulse-wise GRB correlation study. It is worth mentioning that all GRB correlations are still empirical, and we cannot use them in cosmology unless we understand the basic physics of GRBs. To this end, we need to investigate the prompt emission spectrum which is so far generally described by the empirical Band function. We shall discuss our current understanding of the radiation process particularly the finding of two blackbodies and a powerlaw (the 2BBPL model) as the generic spectral model and its implication. This is a work in progress and we expect to obtain the most fundamental GRB correlation based on our improved spectral model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.04270v1.pdf"}
{"id": "1606.04302", "abstract": "  Using a Direct Simulation Monte Carlo technique, we have studied the time evolution of a cold atom cloud interacting with a time dependent radio frequency (rf) dressed state potential. Exposure of a cloud of ^87Rb atoms, trapped in a quadrupole magnetic trap, to a time dependent rf-field with increasing amplitude and decreasing frequency, shows a variation in the number of trapped atoms and the overall shape of the atom cloud. It is shown by simulations that, initially at lower rf-field strength, the rf-field results in ejection of atoms from the trap, leading to evaporative cooling of the atom cloud. Later, at higher rf-field strength, the atoms undergo the non-adiabatic Landau-Zener (LZ) transitions, which leads to their trapping in an rf-dressed state potential of toroidal shape. The results of simulations explain the experimentally observed results. The simulations can be useful to predict the atom cloud dynamics and trapping geometries with other forms of the potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.04302v2.pdf"}
{"id": "1606.04972", "abstract": "  Statistics of article page views is useful for measuring the impact of individual articles. Analyzing the temporal evolution of article page views, we find that article page views usually decay over time after reaching a peak, especially exhibiting relaxation with nonexponentiality. This finding suggests that relaxation in article page views resembles physical aging as frequently found in complex systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.04972v1.pdf"}
{"id": "1606.05547", "abstract": "  We investigate percolation in binary and ternary mixtures of patchy colloidal particles theoretically and using Monte Carlo simulations. Each particle has three identical patches, with distinct species having different types of patch. Theoretically we assume tree-like clusters and calculate the bonding probabilities using Wertheim's first-order perturbation theory for association. For ternary mixtures we find up to eight fundamentally different percolated states. The states differ in terms of the species and pairs of species that have percolated. The strongest gel is a trigel or tricontinuous gel, in which each of the three species has percolated. The weakest gel is a mixed gel in which all of the particles have percolated, but none of the species percolates by itself. The competition between entropy of mixing and internal energy of bonding determines the stability of each state. Theoretical and simulation results are in very good agreement. The only significant difference is the temperature at the percolation threshold, which is overestimated by the theory due to the absence of closed loops in the theoretical description. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.05547v1.pdf"}
{"id": "1606.06538", "abstract": "  The ratios of off-diagonal and diagonal susceptibilities of conserved charges are studied using a hadron resonance gas (HRG) model with an emphasis towards providing a proper baseline for comparison to the corresponding future experimental measurements. We have studied the effect of kinematic acceptances, transverse momentum (p_T) and pseudorapidity (η), and different charged states on the ratios of the calculated susceptibilities. We find that the effect of p_T and η acceptance on the ratio of the susceptibilities are small relative to their dependence on the beam energy or the charged states of the used particles. We also present a HRG based calculation for various combinations of cumulant ratios of protons and pions, recently proposed as robust observables (with no theoretical uncertainties) for critical point search in the experiments. These results which increase as a function of collision energy will provide a better baseline for non-critical point physics compared to Poisson expectation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.06538v2.pdf"}
{"id": "1606.08470", "abstract": "  We theoretically investigate the supercurrent-induced magnetization dynamics of a two-dimensional lattice of ferromagnetically ordered spins placed on a conventional superconductor with broken spatial inversion symmetry and strong spin-orbit coupling. We develop a phenomenological description of the coupled dynamics of the superconducting condensate and the spin system, and demonstrate that supercurrents produce a reactive spin-orbit torque on the magnetization. By performing a microscopic self-consistent calculation, we show that the spin-orbit torque originates from a spin-polarization of the Cooper pairs due to current-induced spin-triplet correlations. Interestingly, we find that there exists an intrinsic limitation for the maximum achievable spin-orbit torque, which is determined by the coupling strength between the condensate and the spin system. In proximitized hole-doped semiconductors, the maximum achievable spin-orbit torque field is estimated to be on the order of 0.16 mT, which is comparable to the critical field for current-induced magnetization switching in ferromagnetic semiconductors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.08470v1.pdf"}
{"id": "1606.08929", "abstract": "  We propose a scheme to modulate the entanglement between two oscillators separated in space via the squeezing cavity field generated by the optical parametric amplifier instead of injecting the squeezing field directly with the assistance of Coulomb interaction. We show that the Coulomb interaction between the oscillators is the essential reason for the existence of entanglement. Due to the gain of the optical parametric amplifier and the phase of the pump driving the optical parametric amplifier can simultaneously modulate the squeezing cavity field, the radiation pressure interaction between the cavity field and the oscillator is modulated accordingly. We find that there is competing effect between the radiation pressure interaction and the Coulomb interaction for the oscillator which these two interactions act on simultaneously. Therefore, the modulation of entanglement can be achieved with the assistance of Coulomb interaction. The results of numerical simulation show that the present scheme has stronger robustness against the temperature of environment compared with previous schemes in experimentally feasible regimes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.08929v1.pdf"}
{"id": "1607.00231", "abstract": "  We employ density-functional theory (DFT) in the generalized gradient approximation (GGA) and its extensions GGA+U and GGA+Gutzwiller to calculate the magnetic exchange couplings between pairs of Mn ions substituting Cd in a CdTe crystal at very small doping. DFT(GGA) overestimates the exchange couplings by a factor of three because it underestimates the charge-transfer gap in Mn-doped II-VI semiconductors. Fixing the nearest-neighbor coupling J_1 to its experimental value in GGA+U, in GGA+Gutzwiller, or by a simple scaling of the DFT(GGA) results provides acceptable values for the exchange couplings at 2nd, 3rd, and 4th neighbor distances in Cd(Mn)Te, Zn(Mn)Te, Zn(Mn)Se, and Zn(Mn)S. In particular, we recover the experimentally observed relation J_4>J_2,J_3. The filling of the Mn 3d-shell is not integer which puts the underlying Heisenberg description into question. However, using a few-ion toy model the picture of a slightly extended local moment emerges so that an integer 3d-shell filling is not a prerequisite for equidistant magnetization plateaus, as seen in experiment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.00231v1.pdf"}
{"id": "1607.00244", "abstract": "  We present a class of left-right symmetric models where Dirac as well as Majorana mass terms of neutrinos can arise at one-loop level in a scotogenic fashion: with dark matter particles going inside the loop. We show the possibility of naturally light right handed neutrinos that can have interesting implications at neutrinoless double beta decay experiments as well as cosmology. Apart from a stable dark matter candidate stabilised by a remnant Z_2 symmetry, one can also have a long lived keV sterile neutrino dark matter in these models. This class of models can have very different collider signatures compared to the conventional left-right models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.00244v2.pdf"}
{"id": "1607.00490", "abstract": "  We consider the following network computation problem. In an acyclic network, there are multiple source nodes, each generating multiple messages, and there are multiple sink nodes, each demanding a function of the source messages. The network coding problem corresponds to the case in which every demand function is equal to some source message, i.e., each sink demands some source message. Connections between network coding problems and matroids have been well studied. In this work, we establish a relation between network computation problems and representable matroids. We show that a network computation problem in which the sinks demand linear functions of source messages admits a scalar linear solution if and only if it is matroidal with respect to a representable matroid whose representation fulfills certain constraints dictated by the network computation problem. Next, we obtain a connection between network computation problems and functional dependency relations (FD-relations) and show that FD-relations can be used to characterize network computation problem with arbitrary (not necessarily linear) function demands as well as nonlinear network codes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.00490v1.pdf"}
{"id": "1607.01400", "abstract": "  We propose a clustering-based iterative algorithm to solve certain optimization problems in machine learning, where we start the algorithm by aggregating the original data, solving the problem on aggregated data, and then in subsequent steps gradually disaggregate the aggregated data. We apply the algorithm to common machine learning problems such as the least absolute deviation regression problem, support vector machines, and semi-supervised support vector machines. We derive model-specific data aggregation and disaggregation procedures. We also show optimality, convergence, and the optimality gap of the approximated solution in each iteration. A computational study is provided. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.01400v1.pdf"}
{"id": "1607.01645", "abstract": "  We investigate two recent parameterizations of the galactic magnetic field with respect to their impact on cosmic nuclei traversing the field. We present a comprehensive study of the size of angular deflections, dispersion in the arrival probability distributions, multiplicity in the images of arrival on Earth, variance in field transparency, and influence of the turbulent field components. To remain restricted to ballistic deflections, a cosmic nucleus with energy E and charge Z should have a rigidity above E/Z=6 EV. In view of the differences resulting from the two field parameterizations as a measure of current knowledge in the galactic field, this rigidity threshold may have to be increased. For a point source search with E/Z>60 EV, field uncertainties increase the required signal events for discovery moderately for sources in the northern and southern regions, but substantially for sources near the galactic disk. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.01645v2.pdf"}
{"id": "1607.01868", "abstract": "  Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the laser energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The predicted improved characteristics of laser-driven proton beams would be critical for a number of applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.01868v1.pdf"}
{"id": "1607.02113", "abstract": "  We study pattern formation in a complex Swift Hohenberg equation with phase-sensitive (parametric) gain. Such an equation serves as a universal order parameter equation describing the onset of spontaneous oscillations in extended systems submitted to a kind of forcing dubbed rocking when the instability is towards long wavelengths. Applications include two-level lasers and photorefractive oscillators. Under rocking, the original continuous phase symmetry of the system is replaced by a discrete one, so that phase bistability emerges. This leads to the spontaneous formation of phase-locked spatial structures like phase domains and dark-ring (phase-) cavity solitons. Stability of the homogeneous solutions is studied and numerical simulations are made covering all the dynamical regimes of the model, which turn out to be very rich. Formal derivations of the rocked complex Swift-Hohenberg equation, using multiple scale techniques, are given for the two-level laser and the photorefractive oscillator. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.02113v2.pdf"}
{"id": "1607.02249", "abstract": "  Noncontiguous transmission schemes combined with high power-efficiency requirements pose big challenges for radio transmitter and power amplifier (PA) design and implementation. Due to the nonlinear nature of the PA, severe unwanted emissions can occur, which can potentially interfere with neighboring channel signals or even desensitize the own receiver in frequency division duplexing (FDD) transceivers. In this article, to suppress such unwanted emissions, a low-complexity sub-band DPD solution, specifically tailored for spectrally noncontiguous transmission schemes in low-cost devices, is proposed. The proposed technique aims at mitigating only the selected spurious intermodulation distortion components at the PA output, hence allowing for substantially reduced processing complexity compared to classical linearization solutions. Furthermore, novel decorrelation based parameter learning solutions are also proposed and formulated, which offer reduced computing complexity in parameter estimation as well as the ability to track time-varying features adaptively. Comprehensive simulation and RF measurement results are provided, using a commercial LTE-Advanced mobile PA, to evaluate and validate the effectiveness of the proposed solution in real world scenarios. The obtained results demonstrate that highly efficient spurious component suppression can be obtained using the proposed solutions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.02249v2.pdf"}
{"id": "1607.02952", "abstract": "  In this paper, we are analyzing the interactivity time, defined as the duration between two consecutive tasks such as sending emails, collecting friends and followers and writing comments in online social networks (OSNs). The distributions of these times are heavy tailed and often described by a power-law distribution. However, power-law distributions usually only fit the heavy tail of empirical data and ignore the information in the smaller value range. Here, we argue that the durations between writing emails or comments, adding friends and receiving followers are likely to follow a lognormal distribution.   We discuss the similarities between power-law and lognormal distributions, show that binning of data can deform a lognormal to a power-law distribution and propose an explanation for the appearance of lognormal interactivity times. The historical debate of similarities between lognormal and power-law distributions is reviewed by illustrating the resemblance of measurements in this paper with the historical problem of income and city size distributions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.02952v1.pdf"}
{"id": "1607.04483", "abstract": "  Complex structures on a material surface can significantly reduce total secondary electron emission from that surface. A velvet is a surface that consists of an array of vertically standing whiskers. The reduction occurs due to the capture of low-energy, true secondary electrons emitted at the bottom of the structure and on the sides of the velvet whiskers. We performed numerical simulations and developed an approximate analytical model that calculates the net secondary electron emission yield from a velvet surface as a function of the velvet whisker length and packing density, and the angle of incidence of primary electrons. We found that to suppress secondary electrons, the following condition on dimensionless parameters must be met: π/2 DA tan θ >> 1 where θ is the angle of incidence of the primary electron from the normal, D is the fraction of surface area taken up by the velvet whisker bases, and A is the aspect ratio, A ≡ h/r, the ratio of height to radius of the velvet whiskers. We find that velvets available today can reduce the secondary electron yield by 90", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.04483v3.pdf"}
{"id": "1607.05367", "abstract": "  With the recent development of optomechanics, the vibration in solids, involving collective motion of trillions of atoms, gradually enters into the realm of quantum control. Built on the recent remarkable progress in optical control of motional states of diamonds, here we report an experimental demonstration of quantum teleportation from light beams to vibrational states of a macroscopic diamond under ambient conditions. Through quantum process tomography, we demonstrate average teleportation fidelity (90.6+/- 1.0)", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.05367v1.pdf"}
{"id": "1607.06807", "abstract": "  We introduce a new matrix function for studying graphs and real-world networks based on a double-factorial penalization of walks between nodes in a graph. This new matrix function is based on the matrix error function. We find a very good approximation of this function using a matrix hyperbolic tangent function. We derive a communicability function, a subgraph centrality and a double-factorial Estrada index based on this new matrix function. We obtain upper and lower bounds for the double-factorial Estrada index of graphs, showing that they are similar to those of the single-factorial Estrada index. We then compare these indices with the single-factorial one for simple graphs and real-world networks. We conclude that for networks containing chordless cycles—holes—the two penalization schemes produce significantly different results. In particular, we study two series of real-world networks representing urban street networks, and protein residue networks. We observe that the subgraph centrality based on both indices produce significantly different ranking of the nodes. The use of the double factorial penalization of walks opens new possibilities for studying important structural properties of real-world networks where long-walks play a fundamental role, such as the cases of networks containing chordless cycles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.06807v3.pdf"}
{"id": "1607.07042", "abstract": "  The Paul Scherrer Institut in Switzerland operates the high intensity proton accelerator facility HIPA. A 590 MeV kinetic energy proton beam of presently up to 2.4 mA is sent to target stations producing pions, muons and neutrons for fundamental and applied physics. The beam power of 1.4 MW provides the world's highest intensities of low momentum muons which can be stopped in low mass targets. Rates of surface muons of up to about 10^8/s are being provided to various unique precision particle physics experiments. Two feasibility studies are ongoing to considerably improve the available muon beams. The high intensity muon beamline, HiMB, could deliver on the order of 10^10/s surface muons and the stopped muon cooler, muCool, aims at a gain factor of 10^10 in phase space quality while sacrificing only less than 3 orders of magnitude in intensity for low energy μ^+. These beams will allow a new generation of precision physics experiments with stopped muons and muonium atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.07042v1.pdf"}
{"id": "1607.07558", "abstract": "  Monocular SLAM refers to using a single camera to estimate robot ego motion while building a map of the environment. While Monocular SLAM is a well studied problem, automating Monocular SLAM by integrating it with trajectory planning frameworks is particularly challenging. This paper presents a novel formulation based on Reinforcement Learning (RL) that generates fail safe trajectories wherein the SLAM generated outputs do not deviate largely from their true values. Quintessentially, the RL framework successfully learns the otherwise complex relation between perceptual inputs and motor actions and uses this knowledge to generate trajectories that do not cause failure of SLAM. We show systematically in simulations how the quality of the SLAM dramatically improves when trajectories are computed using RL. Our method scales effectively across Monocular SLAM frameworks in both simulation and in real world experiments with a mobile robot. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.07558v5.pdf"}
{"id": "1607.07642", "abstract": "  The usage of x-ray free electron laser (XFEL) in femtosecond nanocrystallography involves sequential illumination of many small crystals of arbitrary orientation. Hence a wide radiation bandwidth will be useful in order to obtain and to index a larger number of Bragg peaks used for determination of the crystal orientation. Considering the baseline configuration of the European XFEL in Hamburg, and based on beam dynamics simulations, we demonstrate here that the usage of corrugated structures allows for a considerable increase in radiation bandwidth. Data collection with a 3", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.07642v1.pdf"}
{"id": "1607.08617", "abstract": "  We use an external spin as a dynamical probe of many body localization. The probe spin is coupled to an interacting and disordered environment described by a Heisenberg spin chain in a random field. The spin-chain environment can be tuned between a thermalizing delocalized phase and non-thermalizing localized phase, both in its ground- and high-energy states. We study the decoherence of the probe spin when it couples to the environment prepared in three states: the ground state, the infinite temperature state and a high energy Néel state. In the non-thermalizing many body localized regime, the coherence shows scaling behaviour in the disorder strength. The long-time dynamics of the probe spin shows a logarithmic dephasing in analogy with the logarithmic growth of entanglement entropy for a bi-partition of a many-body localized system. In summary, we show that decoherence of the probe spin provides clear signatures of many-body localization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.08617v2.pdf"}
{"id": "1608.01739", "abstract": "  This paper considers the quantile regression approach for partially linear spatial autoregressive models with possibly varying coefficients. B-spline is employed for the approximation of varying coefficients. The instrumental variable quantile regression approach is employed for parameter estimation. The rank score tests are developed for hypotheses on the coefficients, including the hypotheses on the non-varying coefficients and the constancy of the varying coefficients. The asymptotic properties of the proposed estimators and test statistics are both established. Monte Carlo simulations are conducted to study the finite sample performance of the proposed method. Analysis of a real data example is presented for illustration. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.01739v1.pdf"}
{"id": "1608.03618", "abstract": "  The two dimensional incompressible viscous flow past a flapping foil immersed in a uniform stream is studied numerically. Numerical simulations were performed using a Lattice-Boltzmann model for moderate Reynolds numbers. The computation of the hydrodynamic force on the foil is related to the the wake structure. In particular, when the foil's centre of mass is fixed in space, numerical results suggest a relation between drag coefficient behaviour and the flapping frequency which determines the transition from the von Kármán (vKm) to the inverted von Kármán wake. Beyond the inverted vKm transition the foil was released. Upstream swimming was observed at high enough flapping frequencies. Computed hydrodynamic forces suggest the propulsion mechanism for the swimming foil. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.03618v1.pdf"}
{"id": "1608.04623", "abstract": "  We propose wave and ray approaches for modelling mid- and high- frequency structural vibrations through smoothed joints on thin shell cylindrical ridges. The models both emerge from a simplified classical shell theory setting. The ray model is analysed via an appropriate phase-plane analysis, from which the fixed points can be interpreted in terms of the reflection and transmission properties. The corresponding full wave scattering model is studied using the finite difference method to investigate the scattering properties of an incident plane wave. Through both models we uncover the scattering properties of smoothed joints in the interesting mid-frequency region close to the ring frequency, where there is a qualitative change in the dynamics from anisotropic to simple geodesic propagation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.04623v1.pdf"}
{"id": "1608.04638", "abstract": "  According to Dyson's three fold way, from the viewpoint of global time reversal symmetry there are three circular ensembles of unitary random matrices relevant to the study of chaotic spectra in quantum mechanics. These are the circular orthogonal, unitary and symplectic ensembles, denoted COE, CUE and CSE respectively. For each of these three ensembles and their thinned versions, whereby each eigenvalue is deleted independently with probability 1-ξ, we take up the problem of calculating the first two terms in the scaled large N expansion of the spacing distributions. It is well known that the leading term admits a characterisation in terms of both Fredholm determinants and Painlevé transcendents. We show that modifications of these characterisations also remain valid for the next to leading term, and that they provide schemes for high precision numerical computations. In the case of the CUE there is an application to the analysis of Odlyzko's data set for the Riemann zeros, and in that case some further statistics are similarly analysed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.04638v4.pdf"}
{"id": "1608.04889", "abstract": "  In this paper we study efficiency of particle acceleration in the magnetospheres of stellar mass black holes. For this purpose we consider the linearized set of the Euler equation, continuity equation and Poisson equation respectively. After introducing the varying relativistic centrifugal force, we show that the charge separation undergoes the parametric instability, leading to generation of centrifugally excited Langmuir waves. It is shown that these waves, via the Langmuir collapse damp by means of the Landau damping, as a result energy transfers to particles accelerating them to energies of the order of 10^16eV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.04889v1.pdf"}
{"id": "1608.04915", "abstract": "  Breakup of water jets under gravity is a common-place phenomenon. The role of surface tension in the instability of water jets was recognized by Rayleigh and the theory propounded goes by the name of Plateau-Rayleigh theory. The necks and bulges down along the jet-length that are created by perturbation waves of wavelengths larger than a certain value keep growing with time and ultimately cause the jet to breakup into drops. The effect of perturbation waves have been investigated experimentally and found to confirm the essentials of the theory. However, there is no unanimity about the origin of these perturbation waves. Recently, the idea of recoil capillary waves as an important source of the perturbation waves has been emphasized. The recoil of the end point of the remaining continuous jet at its breakup point is considered to travel upward as a recoil capillary wave which gets reflected at the mouth of the nozzle from which the jet originates. The reflected capillary wave travels along the jet downward with its Doppler shifted wavelength as a perturbation wave. We set up an experiment to directly verify the existence and effect of the recoil capillary waves and present some preliminary results of our experiment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.04915v1.pdf"}
{"id": "1608.05158", "abstract": "  Gas-grain and gas-phase reactions dominate the formation of molecules in the interstellar medium (ISM). Gas-grain reactions require a substrate (e.g. a dust or ice grain) on which the reaction is able to occur. The formation of molecular hydrogen (H_2) in the ISM is the prototypical example of a gas-grain reaction. In these reactions, an atom of hydrogen will strike a surface, stick to it, and diffuse across it. When it encounters another adsorbed hydrogen atom, the two can react to form molecular hydrogen and then be ejected from the surface by the energy released in the reaction. We perform in-depth classical molecular dynamics (MD) simulations of hydrogen atoms interacting with an amorphous water-ice surface. This study focuses on the first step in the formation process; the sticking of the hydrogen atom to the substrate. We find that careful attention must be paid in dealing with the ambiguities in defining a sticking event. The technical definition of a sticking event will affect the computed sticking probabilities and coefficients. Here, using our new definition of a sticking event, we report sticking probabilities and sticking coefficients for nine different incident kinetic energies of hydrogen atoms [5 K - 400 K] across seven different temperatures of dust grains [10 K - 70 K]. We find that probabilities and coefficients vary both as a function of grain temperature and incident kinetic energy over the range of 0.99 - 0.22. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.05158v1.pdf"}
{"id": "1608.05790", "abstract": "  In this article, we report negative thermal expansion and spin frustration in hexagonal GdInO_3. Rietveld refinement of the XRD patterns reveal that the negative thermal expansion in the temperature range of 50-100K stems from the triangular lattice of Gd^3+ ions. At low temperature, the downward deviation of the inverse susceptibility (χ^-1) vs. T plot from the Curie-Weiss law indicates spin frustration which inhibits long-range magnetic ordering down to 2K. Magnetostriction measurements clearly demonstrate a strong spin-lattice coupling. Low temperature anomalous phonon softening, as obtained from temperature dependent Raman measurements, also reveals the same. Our experimental observations are supported by first principles density functional theory calculations of the electronic and phonon dispersion of GdInO_3. The calculations suggest that the GdInO_3 lattice is highly frustrated at low temperature. Further, the calculated normal mode frequencies of the Gd related Γ point phonons are found to depend on the magnetic structure of the lattice, suggesting significant magneto-elastic coupling. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.05790v1.pdf"}
{"id": "1608.05837", "abstract": "  Coherent spin transport through bilayer graphene (BLG) nanoflakes sandwiched between two electrodes made of single-layer zigzag graphene nanoribbon was investigated by means of Landauer-Buttiker formalism. Application of a magnetic field only on BLG structure as a channel produces a perfect spin polarization in a large energy region. Moreover, the conductance could be strongly modulated by magnetization of the zigzag edge of AB-stacked BLG, and the junction, entirely made of carbon, produces a giant magnetoresistance (GMR) up to 10^6%. Intestinally, GMR and spin polarization could be tuned by varying BLG width and length. Generally, MR in a AB-stacked BLG strongly increases (decreases) with length (width). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.05837v1.pdf"}
{"id": "1608.06446", "abstract": "  We study intermittency as a departure from self-similarity of the solar wind magnetic turbulence and investigate the evolution with the heliocentric distance and latitude. We use data from the Ulysses spacecraft measured during two solar minima (1997-1998 and 2007-2008) and one solar maximum (1999-2001). In particular, by modeling a multifractal spectrum, we revealed the intermittent character of turbulence in the small-scale fluctuations of the magnetic field embedded in the slow and fast solar wind. Generally, at small distances from the Sun, in both the slow and fast solar wind, we observe the high degree of multifractality (intermittency) that decreases somewhat slowly with distance and slowly with latitude. The obtained results seem to suggest that generally intermittency in the solar wind has a solar origin. However, the fast and slow streams, shocks, and other nonlinear interactions can only be considered as the drivers of the intermittent turbulence. It seems that analysis shows that turbulence beyond the ecliptic plane evolves too slowly to maintain the intermittency with the distance and latitude. Moreover, we confirm that the multifractality and intermittency are at a lower level than in the ecliptic, as well as the existence of symmetry with respect to the ecliptic plane, suggesting that there are similar turbulent properties observed in the two hemispheres. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.06446v1.pdf"}
{"id": "1608.06803", "abstract": "  We study the effects that ripples induce on the electrical and magnetic properties of graphene. The variation of the interatomic distance created by the ripples translates in a modulation of the hopping parameter between carbon atoms. A tight binding Hamiltonian including a Hubbard interaction term is solved self consistently for ripples with different amplitudes and periods. We find that, for values of the Hubbard interaction U above a critical value U_C, the system displays a superposition of local ferromagnetic and antiferromagnetic ordered states. Nonetheless the global ferromagnetic order parameter is zero. The U_C depends only on the product of the period and hopping amplitude modulation. When the Hubbard interaction is close to the critical value of the antiferromagnetic transition in pristine graphene, the antiferromagnetic order parameter becomes much larger than the ferromagnetic one, being the ground state similar to that of flat graphene. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.06803v1.pdf"}
{"id": "1608.07075", "abstract": "  We use the renormalization group method to study model E of critical dynamics in the presence of velocity fluctuations arising in accordance with the stochastic Navier-Stokes equation. Using Martin-Siggia-Rose theorem, we obtain a field- theoretical model that allows a perturbative renormalization group analysis. By direct power counting and an analysis of ultraviolet divergences, we show that the model is multiplicatively renormalizable, and we use a two-parameter expansion in ε and δ to calculate renormalization constants. Here, ε is a deviation from the critical dimension four, and δ is a deviation from the Kolmogorov regime. We present the results of the one-loop approximation and part of the fixed-point structure. We briefly discuss the possible effect of velocity fluctuations on the large-scale behavior of the model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.07075v1.pdf"}
{"id": "1608.07749", "abstract": "  When dealing with symmetry properties of mathematical objects, one of the fundamental questions is to determine their full automorphism group. In this paper this question is considered in the context of even/odd permutations dichotomy. More precisely: when is it that existence of automorphisms acting as even permutations on the vertex set of a graph, called even automorphisms, forces existence of automorphisms that act as odd permutations, called odd automorphisms. As a first step towards resolving the above question, a complete information on existence of odd automorphisms in cubic symmetric graphs is given. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.07749v1.pdf"}
{"id": "1608.07766", "abstract": "  We investigate two coupled nonlinear cavities that are coherently driven in a dissipative environment. We perform semiclassical, numerical and analytical quantum studies of this dimer model when both cavities are symmetrically driven. In the semiclassical analysis, we find steady-state solutions with different photon occupations in two cavities. Such states can be considered analogs of the closed system double well symmetry breaking states. We analyze the occurrence and properties of these localized states in the system parameter space and examine how the symmetry breaking states, in form of a bistable pair, are associated to the single cavity bistable behavior. In a full quantum calculation of the master equation dynamics that includes quantum fluctuations, the symmetry breaking states and bistability disappear due to the quantum fluctuations. In quantum trajectory picture, we observe enhanced quantum jumps and switching which indicate the presence of the underlying semiclassical symmetry breaking states. Finally, we present a set of analytical solutions for the steady state correlation functions using the complex P-representation and discuss its regime of validity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.07766v2.pdf"}
{"id": "1608.08214", "abstract": "  We explore dynamics of cosmological models with bounce solutions evolving on a spatially flat Friedmann-Lemaitre-Robertson-Walker background. We consider cosmological models that contain the Hilbert-Einstein curvature term, the induced gravity term with a negative coupled constant, and even polynomial potentials of the scalar field. Bounce solutions with non-monotonic Hubble parameters have been obtained and analyzed. The case when the scalar field has the conformal coupling and the Higgs-like potential with an opposite sign is studied in detail. In this model the evolution of the Hubble parameter of the bounce solution essentially depends on the sign of the cosmological constant. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.08214v3.pdf"}
{"id": "1608.08245", "abstract": "  Sequence A000975 in the Online Encyclopedia of Integer Sequences (OEIS) starts out 1, 2, 5, 10, 21, 42, 85, ... . As of July 1, 2016, the description in the OEIS lists several characterizations of this sequence and numerous examples of instances where this sequence occurs. It also presents a \"not yet proved\" result, a conjecture, and an unanswered question concerning this sequence. In this paper we show that all of these proposed results are in fact true. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.08245v1.pdf"}
{"id": "1609.00216", "abstract": "  We describe a surface structure consisting of a metal-air interface where the metallic part consists of two metallic segments with a periodic modulation of the interface between them. Such a structure possesses a different transmissivity for a surface plasmon polariton incident on it from one side of it than it has for a surface plasmon polariton incident on it from the opposite side. This asymmetric transmission of a surface plasmon polariton is based on the suppression of the zero-order Bragg beam which, for a certain value of the modulation depth, is not transmitted through the structure, while the diffraction efficiencies of the +1 and -1 Bragg beams can be modified by varying the period of grating and/or the angle of incidence. For a certain range of the incidence angle one can observe asymmetry in transmittance for the -1 mode while the +1 mode is completely suppressed. By varying the material and geometrical parameters of the diffractive structure one can control the contrast transmission that characterizes the degree of the asymmetry. This property of the structure is demonstrated by the results of computer simulation calculations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.00216v1.pdf"}
{"id": "1609.00258", "abstract": "  Future neutrino-oscillation experiments are expected to bring definite answers to the questions of neutrino-mass hierarchy and violation of charge-parity symmetry in the lepton sector. To realize this ambitious program it is necessary to ensure a significant reduction of uncertainties, particularly those related to neutrino-energy reconstruction. In this paper, we discuss different sources of systematic uncertainties, paying special attention to those arising from nuclear effects and detector response. By analyzing nuclear effects we show the importance of developing accurate theoretical models, capable to provide quantitative description of neutrino cross sections, together with the relevance of their implementation in Monte Carlo generators and extensive testing against lepton-scattering data. We also point out the fundamental role of efforts aiming to determine detector responses in test-beam exposures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.00258v3.pdf"}
{"id": "1609.00569", "abstract": "  The distribution of the sunspot group size (area) and its dependence on the level of solar activity is studied. It is shown that the fraction of small groups is not constant but decreases with the level of solar activity so that high solar activity is largely defined by big groups. We study the possible influence of solar activity on the ability of a realistic observer to see and report the daily number of sunspot groups. It is shown that the relation between the number of sunspot groups as seen by different observers with different observational acuity thresholds is strongly non-linear and cannot be approximated by the traditionally used linear scaling (k-factors). The observational acuity threshold [A_ th] is considered to quantify the quality of each observer, instead of the traditional relative k-factor. A nonlinear c-factor based on A_ th is proposed, which can be used to correct each observer to the reference conditions. The method is tested on a pair of principal solar observers, Wolf and Wolfer, and it is shown that the traditional linear correction, with the constant k-factor of 1.66 to scale Wolf to Wolfer, leads to an overestimate of solar activity around solar maxima. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.00569v1.pdf"}
{"id": "1609.01258", "abstract": "  The conditional entropy of glueball states is calculated using a holographic description. Glueball states are represented by a supergravity dual picture, consisting of a 5-dimensional graviton-dilaton action of a dynamical holographic AdS/QCD model. The conditional entropy is studied as a function of the glueball spin and of the mass, providing information about the stability of the glueball states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.01258v1.pdf"}
{"id": "1609.01637", "abstract": "  We investigate theoretically the morphology of a thin nematic film adsorbed at flat substrate patterned by stripes with alternating aligning properties, normal and tangential respectively. We construct a simple \"exactly-solvable\" effective interfacial model where the liquid crystal distortions are accounted for via an effective interface potential. We find that chemically patterned substrates can strongly deform the nematic-air interface. The amplitude of this substrate-induced undulations increases with decreasing average film thickness and with increasing surface pattern pitch. We find a regime where the interfacial deformation may be described in terms of a material-independent universal scaling function. Surprisingly, the predictions of the effective interfacial model agree semi-quantitatively with the results of the numerical solution of a full model based on the Landau-de Gennes theory coupled to a square-gradient phase field free energy functional for a two phase system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.01637v1.pdf"}
{"id": "1609.01693", "abstract": "  This work advocates Eulerian motion representation learning over the current standard Lagrangian optical flow model. Eulerian motion is well captured by using phase, as obtained by decomposing the image through a complex-steerable pyramid. We discuss the gain of Eulerian motion in a set of practical use cases: (i) action recognition, (ii) motion prediction in static images, (iii) motion transfer in static images and, (iv) motion transfer in video. For each task we motivate the phase-based direction and provide a possible approach. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.01693v2.pdf"}
{"id": "1609.02230", "abstract": "  We investigate energy transfer by the radiation from a cavity quantum electrodynamics (QED) system in the context of quantum thermodynamics. We propose a method of decomposing it into work and heat within the framework of quantum master equations. We find that the work and heat correspond respectively to the coherent and incoherent parts of the radiation. In the derivation of the method, it is crucial to investigate the dynamics of the system that receives the radiation from the cavity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.02230v2.pdf"}
{"id": "1609.02428", "abstract": "  We compare the time evolution of entanglement measures after local operator excitation in the critical Ising model with predictions from conformal field theory. For the spin operator and its descendants we find that Renyi entropies of a block of spins increase by a constant that matches the logarithm of the quantum dimension of the conformal family. However, for the energy operator we find a small constant contribution that differs from the conformal field theory answer equal to zero. We argue that the mismatch is caused by the subtleties in the identification between the local operators in conformal field theory and their lattice counterpart. Our results indicate that evolution of entanglement measures in locally excited states not only constraints this identification, but also can be used to extract non-trivial data about the conformal field theory that governs the critical point. We generalize our analysis to the Ising model away from the critical point, states with multiple local excitations, as well as the evolution of the relative entropy after local operator excitation and discuss universal features that emerge from numerics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.02428v2.pdf"}
{"id": "1609.02541", "abstract": "  We consider importance sampling (IS) type weighted estimators based on Markov chain Monte Carlo (MCMC) targeting an approximate marginal of the target distribution. In the context of Bayesian latent variable models, the MCMC typically operates on the hyperparameters, and the subsequent weighting may be based on IS or sequential Monte Carlo (SMC), but allows for multilevel techniques as well. The IS approach provides a natural alternative to delayed acceptance (DA) pseudo-marginal/particle MCMC, and has many advantages over DA, including a straightforward parallelisation and additional flexibility in MCMC implementation. We detail minimal conditions which ensure strong consistency of the suggested estimators, and provide central limit theorems with expressions for asymptotic variances. We demonstrate how our method can make use of SMC in the state space models context, using Laplace approximations and time-discretised diffusions. Our experimental results are promising and show that the IS type approach can provide substantial gains relative to an analogous DA scheme, and is often competitive even without parallelisation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.02541v6.pdf"}
{"id": "1609.02702", "abstract": "  In this paper we build the structure equations and the integrable systems for a discrete centroaffine indefinite surface in ^3. At the same time, some centroaffine invariants are obtained according to the structure equations. Using these centroaffine invariants, we study the Laplacian operator and the convexity of a discrete centroaffine indefinite surface. Furthermore, some interest examples are provided. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.02702v1.pdf"}
{"id": "1609.02758", "abstract": "  We study a simple model describing superradiance in a system of two-level atoms interacting with a single-mode bosonic field. The model permits a continuous crossover between integrable and partially chaotic regimes and shows a complex thermodynamic and quantum phase structure. Several types of excited-state quantum phase transitions separate quantum phases that are characterized by specific energy dependences of various observables and by different atom-field and atom-atom entanglement properties. We observe an approximate revival of some states from the weak atom-field coupling limit in the strong coupling regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.02758v2.pdf"}
{"id": "1609.02933", "abstract": "  We demonstrate an optical fiber fault location method based on the frequency response of the modulated fiber optical backscattered signal in a steady state low-frequency step regime. Careful calibration and measurement allows for the reconstruction of the fiber transfer function, which, associated to its mathematical model, is capable of extracting the fiber characteristics. The technique is capable of identifying non-reflective fault events in an optical fiber link and is perfectly compatible with previous methods that focus on the reflective events. The fact that the recuperation of the complex signal is performed in the frequency domain and not via a Fourier Transform enables the measurements to overcome the spatial resolution limitation of Fourier Transform incoherent-OFDR measurements even with frequency sweep ranges down to 100-100000 Hz. This result is backed up by a less than 10 meters difference in fault location when compared to standard OTDR measurements. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.02933v1.pdf"}
{"id": "1609.03234", "abstract": "  Counterfactual Regret Minimization (CFR) is the most popular iterative algorithm for solving zero-sum imperfect-information games. Regret-Based Pruning (RBP) is an improvement that allows poorly-performing actions to be temporarily pruned, thus speeding up CFR. We introduce Total RBP, a new form of RBP that reduces the space requirements of CFR as actions are pruned. We prove that in zero-sum games it asymptotically prunes any action that is not part of a best response to some Nash equilibrium. This leads to provably faster convergence and lower space requirements. Experiments show that Total RBP results in an order of magnitude reduction in space, and the reduction factor increases with game size. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.03234v1.pdf"}
{"id": "1609.05004", "abstract": "  We use molecular dynamics simulations to investigate the tracer diffusion in a sea of polymers with specific binding zones for the tracer. These binding zones act as traps. Our simulations show that the tracer can undergo normal yet non-Gaussian diffusion under certain circumstances, e.g, when the polymers with traps are frozen in space and the volume fraction and the binding strength of the traps are moderate. In this case, as the tracer moves, it experiences a heterogeneous environment and exhibits confined continuous time random walk (CTRW) like motion resulting a non-Gaussian behavior. Also the long time dynamics becomes subdiffusive as the number or the binding strength of the traps increases. However, if the polymers are mobile then the tracer dynamics is Gaussian but could be normal or subdiffusive depending on the number and the binding strength of the traps. In addition, with increasing binding strength and the number of the polymer traps, the probability of the tracer being trapped increases. On the other hand, removing the binding zones does not result trapping, even at comparatively high crowding. Our simulations also show that the trapping probability increases with the increasing size of the tracer and for a bigger tracer with the frozen polymer background the dynamics is only weakly non-Gaussian but highly subdiffusive. Our observations are in the same spirit as found in many recent experiments on tracer diffusion in polymeric materials and questions the validity of Gaussian theory to describe diffusion in crowded environment in general. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.05004v1.pdf"}
{"id": "1609.05506", "abstract": "  Various novel transport phenomena in chiral systems result from the interplay of quantum anomalies with magnetic field and vorticity in high-energy heavy-ion collisions, and could survive the expansion of the fireball and be detected in experiments. Among them are the chiral magnetic effect, the chiral vortical effect and the chiral magnetic wave, the experimental searches for which have aroused extensive interest. The goal of this review is to describe the current status of experimental studies at Relativistic Heavy Ion Collider at BNL and the Large Hadron Collider at CERN, and to outline the future work in experiment needed to eliminate the existing uncertainties in the interpretation of the data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.05506v1.pdf"}
{"id": "1609.05887", "abstract": "  We give a mathematical framework for weighted ensemble (WE) sampling, a binning and resampling technique for efficiently computing probabilities in molecular dynamics. We prove that WE sampling is unbiased in a very general setting that includes adaptive binning. We show that when WE is used for stationary calculations in tandem with a coarse model, the coarse model can be used to optimize the allocation of replicas in the bins. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.05887v3.pdf"}
{"id": "1609.07406", "abstract": "  Understanding decoherence in cryogenically-cooled rare-earth-ion doped glass fibers is of fundamental interest and a prerequisite for applications of these material in quantum information applications. Here we study the coherence properties in a weakly doped erbium silica glass fiber motivated by our recent observation of efficient and long-lived Zeeman sublevel storage in this material and by its potential for applications at telecommunication wavelengths. We analyze photon echo decays as well as the potential mechanisms of spectral diffusion that can be caused by coupling with dynamic disorder modes that are characteristic for glassy hosts, and by the magnetic dipole-dipole interactions between Er^3+ ions. We also investigate the effective linewidth as a function of magnetic field, temperature and time, and then present a model that describes these experimental observations. We highlight that the operating conditions (0.6 K and 0.05 T) at which we previously observed efficient spectral hole burning coincide with those for narrow linewidths (1 MHz)  an important property for applications that has not been reported before for a rare-earth-ion doped glass. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.07406v2.pdf"}
{"id": "1609.08984", "abstract": "  A study of the dynamics of the positive charges in liquid argon has been carried out in the context of the future massive time projection chambers proposed for dark matter and neutrino physics. Given their small mobility coefficient in liquid argon, the ions spend a considerably longer time in the active volume with respect to the electrons. The positive charge density can be additionally increased by the injection, in the liquid volume, of the ions produced by the electron multiplying devices located in gas argon. The impact of the ion current on the uniformity of the field has been evaluated as well as the probability of the charge signal quenching due to the electron-ion recombination along the drift. The study results show some potential concerns for massive detectors with drift of many meters operated on surface. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.08984v3.pdf"}
{"id": "1609.09009", "abstract": "  The non-Markovian dynamics of open quantum systems is still a challenging task, particularly in the non-perturbative regime at low temperatures. While the Stochastic Liouville-von Neumann equation (SLN) provides a formally exact tool to tackle this problem for both discrete and continuous degrees of freedom, its performance deteriorates for long times due to an inherently non-unitary propagator. Here we present a scheme which combines the SLN with projector operator techniques based on finite dephasing times, gaining substantial improvements in terms of memory storage and statistics. The approach allows for systematic convergence and is applicable in regions of parameter space where perturbative methods fail, up to the long time domain. Findings are applied to the coherent and incoherent quantum dynamics of two- and three-level systems. In the long time domain sequential and super-exchange transfer rates are extracted and compared to perturbative predictions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.09009v1.pdf"}
{"id": "1609.09137", "abstract": "  We study the asymptotic behavior of the spectral gap of simple barrier tunneling problems, which are related to using quantum annealing to find the global optimum of cost functions defined over n bits. Specifically we look at the problem of having an n qubit system tunnel through a barrier of width and height proportional to n^a. We show that with these quantum annealing problems, the asymptotic, n→∞, behavior of the spectral gap does not accurately describe the behavior of the gap at finite n until extremely large values of n (n>10^12). We prove that this deficiency of the asymptotic expression is a feature of simple one-dimensional tunneling problems themselves, casting doubt on whether asymptotic analysis is an appropriate tool for studying tunneling problems in quantum annealing for reasonably sized systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.09137v1.pdf"}
{"id": "1609.09303", "abstract": "  Recently ATLAS reported a 3.3σ excess in the stop search with ℓ+jets+E_T^miss channel. We try to interpret the signal by a light stop pair production in the MSSM. We find: (1) simple models where stop decays into a higgsino or a bino are not favored. (2) an extension of them can explain the data at 2σ level without conflicting with the other search channels. A surviving possibility includes a light stop and a light higgsino, which is expected in a natural SUSY scenario. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.09303v1.pdf"}
{"id": "1610.00151", "abstract": "  A k-submodular function is a generalization of submodular and bisubmodular functions. This paper establishes a compact representation for minimizers of a k-submodular function by a poset with inconsistent pairs (PIP). This is a generalization of Ando-Fujishige's signed poset representation for minimizers of a bisubmodular function. We completely characterize the class of PIPs (elementary PIPs) arising from k-submodular functions. We give algorithms to construct the elementary PIP of minimizers of a k-submodular function f for three cases: (i) a minimizing oracle of f is available, (ii) f is network-representable, and (iii) f arises from a Potts energy function. Furthermore, we provide an efficient enumeration algorithm for all maximal minimizers of a Potts k-submodular function. Our results are applicable to obtain all maximal persistent labelings in actual computer vision problems. We present experimental results for real vision instances. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.00151v2.pdf"}
{"id": "1610.00315", "abstract": "  Bayesian inference provides a principled way of estimating the parameters of a stochastic process that is observed discretely in time. The overdamped Brownian motion of a particle confined in an optical trap is generally modelled by the Ornstein-Uhlenbeck process and can be observed directly in experiment. Here we present Bayesian methods for inferring the parameters of this process, the trap stiffness and the particle diffusion coefficient, that use exact likelihoods and sufficient statistics to arrive at simple expressions for the maximum a posteriori estimates. This obviates the need for Monte Carlo sampling and yields methods that are both fast and accurate. We apply these to experimental data and demonstrate their advantage over commonly used non-Bayesian fitting methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.00315v2.pdf"}
{"id": "1610.00508", "abstract": "  The recent measurement of the differential γ+c-jet cross section, performed at the Tevatron collider in Run II by the D0 collaboration, is studied in a next-to-leading order (NLO) global QCD analysis to assess its impact on the proton parton distribution functions (PDFs). We show that these data lead to a significant change on the gluon and charm quark distributions. We demonstrate also that there is an inconsistency between the new high precision HERA I+II combined data and Tevatron measurement. Moreover, in this study we investigate the impact of older EMC measurements of charm structure function F_c^2 on the PDFs and compare the results with those gaining from the analysis of Tevatron data. We show that both of them have a same impact on PDFs, and thus can be recognized as same evidences for inefficiency of perturbative QCD in dealing with the charm production in some kinematic regions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.00508v1.pdf"}
{"id": "1610.01214", "abstract": "  By making use of a simple model that captures the key features of the anomalous Maxwell equations, we study the role of inhomogeneities on the evolution of magnetic fields in a chiral plasma. We find that inhomogeneities of the chiral asymmetry by themselves do not prevent the anomaly-driven inverse cascade and, as in the homogeneous case, the magnetic helicity is transferred from shorter to longer wavelength helical modes of the magnetic field. However, we also find that the evolution appears to be sensitive to the effects of diffusion. In the case when diffusion is negligible, the inverse cascade slows down considerably compared to the homogeneous scenario. In the case of the primordial plasma, though, we find that the diffusion is substantial and efficiently suppresses chiral asymmetry inhomogeneities. As a result, the inverse cascade proceeds practically in the same way as in the chirally homogeneous model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.01214v1.pdf"}
{"id": "1610.02217", "abstract": "  The linear hydrodynamic stability of a model for confined quasi-two-dimensional granular gases is analyzed. The system exhibits homogeneous hydrodynamics, i.e. there are macroscopic evolution equations for homogeneous states. The stability analysis is carried out around all these states and not only the homogeneous steady state reached eventually by the system. It is shown that in some cases the linear analysis is not enough to reach a definite conclusion on the stability, and molecular dynamics simulation results are presented to elucidate these cases. The analysis shows the relevance of nonlinear hydrodynamic contributions to describe the behavior of spontaneous fluctuations occurring in the system, that lead even to the transitory formation of clusters of particles. The conclusion is that the system is always stable. The relevance of the results for describing the instabilities of confined granular gases observed experimentally is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.02217v1.pdf"}
{"id": "1610.03058", "abstract": "  We study the intrinsic, disorder-induced decoherence of an isolated quantum system under its own dynamics. Specifically, we investigate the characteristic time scale (i.e., the decoherence time) associated with an interacting many-body system losing the memory of its initial state. To characterize the erasure of the initial state memory, we define a time scale, the intrinsic decoherence time, by thresholding the gradual decay of the disorder-averaged return probability. We demonstrate the system-size independence of the intrinsic decoherence time in different models, and we study its dependence on the disorder strength. We find that the intrinsic decoherence time increases monotonically as the disorder strength increases in accordance with the relaxation of locally measurable quantities. We investigate several interacting spin (e.g., Ising and Heisenberg) and fermion (e.g., Anderson and Aubry-André) models to obtain the intrinsic decoherence time as a function of disorder and interaction strength. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.03058v2.pdf"}
{"id": "1610.04809", "abstract": "  \"Net neutrality\" often refers to the policy dictating that an Internet service provider (ISP) cannot charge content providers (CPs) for delivering their content to consumers. Many past quantitative models designed to determine whether net neutrality is a good idea have been rather equivocal in their conclusions. Here we propose a very simple two-sided market model, in which the types of the consumers and the CPs are power-law distributed — a kind of distribution known to often arise precisely in connection with Internet-related phenomena. We derive mostly analytical, closed-form results for several regimes: (a) Net neutrality, (b) social optimum, (c) maximum revenue by the ISP, or (d) maximum ISP revenue under quality differentiation. One unexpected conclusion is that (a) and (b) will differ significantly, unless average CP productivity is very high. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.04809v1.pdf"}
{"id": "1610.05219", "abstract": "  The maximum synchrotron burnoff limit of 160 MeV represents a fundamental limit to radiation resulting from electromagnetic particle acceleration in one-zone ideal plasmas. In magnetic reconnection, however, particle acceleration and radiation are decoupled because the electric field is larger than the magnetic field in the diffusion region. We carry out two-dimensional particle-in-cell simulations to determine the extent to which magnetic reconnection can produce synchrotron radiation above the burnoff limit. We use the test particle comparison (TPC) method to isolate the effects of cooling by comparing the trajectories and acceleration efficiencies of test particles incident on such a reconnection region with and without cooling them. We find that the cooled and uncooled particle trajectories are typically similar during acceleration in the reconnection region, and derive an effective limit on particle acceleration that is inversely proportional to the average magnetic field experienced by the particle during acceleration. Using the calculated distribution of this average magnetic field as a function of uncooled final particle energy, we find analytically that cooling does not affect power-law particle energy spectra except at energies far above the synchrotron burnoff limit. Finally, we compare fully cooled and uncooled simulations of reconnection, confirming that the synchrotron burnoff limit does not produce a cutoff in the particle energy spectrum. Our results indicate that the TPC method accurately predicts the effects of cooling on particle acceleration in relativistic reconnection, and that even far above the burnoff limit, the synchrotron energy of radiation produced in reconnection is not limited by cooling. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.05219v1.pdf"}
{"id": "1610.05388", "abstract": "  Neutrino oscillations are at the forefront of advances in Physics beyond the Standard Model. Increasing accuracy in measurements of the neutrino mixing matrix is an important challenge in current experiments. It depends on parameters that do not directly correspond to observables of the neutrino system. This type of estimation problem is handled by Quantum Estimation Theory (QET) via the Fisher Information (FI) and the Quantum Fisher Information (QFI). In this work, we analyze two-flavor neutrino oscillations within the framework of QET. We compute the QFI for the mixing angle θ and show that mass measurements are the ones that achieve optimal precision. We also study the FI associated with flavor measurements and show that they are optimized at specific neutrino times-of-flight. Therefore, although the usual population measurement does not realize the precision limit set by the QFI, it can in principle be implemented with the best possible sensitivity to θ. We study how these quantifiers relate to the single-particle, mode entanglement. We demonstrate that this form of entanglement does not enhance neither of them. In particular, this shows that in single-particle settings, entanglement is not directly connected with the optimal precision in metrological tasks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.05388v2.pdf"}
{"id": "1610.05665", "abstract": "  Tapered and dispersion managed (DM) silicon nanophotonic waveguides are investigated for the generation of optimal ultra broadband supercontinuum (SC). DM waveguides are structures showing a longitudinally dependent group velocity dispersion that results from the variation of the waveguide width with the propagation distance. For the generation of optimal SC, a genetic algorithm has been used to find the best dispersion map. This allows for the generation of highly coherent supercontinuums that span over 1.14 octaves from 1300 nm to 2860 nm and 1.25 octaves from 1200 nm to 2870 nm at -20 dB level for the tapered and DM waveguides respectively, for a 2 μm, 200 fs and 6.4 pJ input pulse. The comparison of these two structures with the usually considered optimal fixed width waveguide shows that the SC is broader and flatter in the more elaborated DM waveguide, while the high coherence is ensured by the varying dispersion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.05665v2.pdf"}
{"id": "1610.05668", "abstract": "  Applications of variational methods are typically restricted to conservative systems. Some extensions to dissipative systems have been reported too but require ad hoc techniques such as the artificial doubling of the dynamical variables. Here, a different approach is proposed. We show that, for a broad class of dissipative systems of practical interest, variational principles can be formulated using constant Lagrange multipliers and Lagrangians nonlocal in time, which allow treating reversible and irreversible dynamics on the same footing. A general variational theory of linear dispersion is formulated as an example. In particular, we present a variational formulation for linear geometrical optics in a general dissipative medium, which is allowed to be nonstationary, inhomogeneous, nonisotropic, and exhibit both temporal and spatial dispersion simultaneously. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.05668v2.pdf"}
{"id": "1610.05752", "abstract": "  Recent experimental results have confirmed a possible reduction in the GT_+ strengths of pf-shell nuclei. These proton-rich nuclei are of relevance in the deflagration and explosive burning phases of Type Ia supernovae. While prior GT strengths result in nucleosynthesis predictions with a lower-than-expected electron fraction, a reduction in the GT_+ strength can result in an slightly increased electron fraction compared to previous shell model predictions, though the enhancement is not as large as previous enhancements in going from rates computed by Fuller, Fowler, and Newman based on an independent particle model. A shell model parametrization has been developed which more closely matches experimental GT strengths. The resultant electron-capture rates are used in nucleosynthesis calculations for carbon deflagration and explosion phases of Type Ia supernovae, and the final mass fractions are compared to those obtained using more commonly-used rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.05752v2.pdf"}
{"id": "1610.07013", "abstract": "  A discrete Boltzmann model (DBM) is proposed to probe the Rayleigh-Taylor instability (RTI) in two-component compressible flows. Each species has a flexible specific heat ratio and is described by one discrete Boltzmann equation (DBE). Independent discrete velocities are adopted for the two DBEs. The collision and force terms in the DBE account for the molecular collision and external force, respectively. Two types of force terms are exploited. In addition to recovering the modified Navier-Stokes equations in the hydrodynamic limit, the DBM has the capability of capturing detailed nonequilibrium effects. Furthermore, we use the DBM to investigate the dynamic process of the RTI. The invariants of tensors for nonequilibrium effects are presented and studied. For low Reynolds numbers, both global nonequilibrium manifestations and the growth rate of the entropy of mixing show three stages (i.e., the reducing, increasing, and then decreasing trends) in the evolution of the RTI. On the other hand, the early reducing tendency is suppressed and even eliminated for high Reynolds numbers. Relevant physical mechanisms are analyzed and discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.07013v3.pdf"}
{"id": "1610.07859", "abstract": "  The compositions of nascent planets depend on the compositions of their birth disks. In particular, the elemental compositions of Gas Giant gaseous envelopes depend on the elemental composition of the disk gas from which the envelope is accreted. Previous models demonstrated that sequential freeze-out of O and C-bearing volatiles in disks will result in an supersolar C/O ratios and subsolar C/H ratios in the gas between water and CO snowlines. This result does not take into account, however, the expected grain growth and radial drift of pebbles in disks, and the accompanying re-distribution of volatiles from the outer to the inner disk. Using a toy model we demonstrate that when drift is considered, CO is enhanced between the water and CO snowline, resulting in both supersolar C/O and C/H ratios in the disk gas in the Gas Giant formation zone. This result appears robust to the details of the disk model as long as there is substantial pebble drift across the CO snowline, and the efficiency of CO vapor diffusion is limited. Gas Giants that accrete their gaseous envelopes exterior to the water snowline and do not experience substantial core-envelope mixing, may thus present both superstellar C/O and C/H ratios in their atmospheres. Pebble drift will also affect the nitrogen and noble gas abundances in the planet forming zones, which may explain some of Jupiter's peculiar abundance patterns. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.07859v1.pdf"}
{"id": "1610.07990", "abstract": "  In this paper, we analyse the effect of the expansion of the universe on the clustering of galaxies. We evaluate the configurational integral for interacting system of galaxies in an expanding universe by including effects produced by the cosmological constant. The gravitational partition function is obtained using this configuration integral. Thermodynamic quantities, specifically, Helmholtz free energy, entropy, internal energy, pressure and chemical potential are also derived for this system. It is observed that they depend on the modified clustering parameter for this system of galaxies. It is also demonstrated that these thermodynamical quantities get corrected because of the cosmological constant. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.07990v1.pdf"}
{"id": "1610.08040", "abstract": "  The electrical conductivity of graphene with a nonzero mass-gap parameter is investigated starting from the first principles of quantum electrodynamics in (2+1)-dimensional space-time at any temperature. The formalism of the polarization tensor defined over the entire plane of complex frequency is used. At zero temperature we reproduce the results for both real and imaginary parts of the conductivity, obtained previously in the local approximation, and generalize them taking into account the effects of nonlocality. At nonzero temperature the exact analytic expressions for real and imaginary parts of the longitudinal and transverse conductivities of gapped graphene are derived, as well as their local limits and approximate expressions in several asymptotic regimes. Specifically, a simple local result for the real part of conductivity of gapped graphene valid at any temperature is obtained. According to our results, the real part of the conductivity is not equal to zero for frequencies exceeding the width of the gap and goes to the universal conductivity with increasing frequency. The imaginary part of conductivity of gapped graphene varies from infinity at zero frequency to minus infinity at the frequency defined by the gap parameter and then goes to zero with further increase of frequency. The analytic expressions are accompanied by the results of numerical computations. Possible future generalization of the used formalism is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.08040v2.pdf"}
{"id": "1610.09463", "abstract": "  In this paper, we propose majority voting neural networks for sparse signal recovery in binary compressed sensing. The majority voting neural network is composed of several independently trained feedforward neural networks employing the sigmoid function as an activation function. Our empirical study shows that a choice of a loss function used in training processes for the network is of prime importance. We found a loss function suitable for sparse signal recovery, which includes a cross entropy-like term and an L_1 regularized term. From the experimental results, we observed that the majority voting neural network achieves excellent recovery performance, which is approaching the optimal performance as the number of component nets grows. The simple architecture of the majority voting neural networks would be beneficial for both software and hardware implementations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.09463v1.pdf"}
{"id": "1610.09932", "abstract": "  We review the concept of support vector machines (SVMs) and discuss examples of their use. One of the benefits of SVM algorithms, compared with neural networks and decision trees is that they can be less susceptible to over fitting than those other algorithms are to over training. This issue is related to the generalisation of a multivariate algorithm (MVA); a problem that has often been overlooked in particle physics. We discuss cross validation and how this can be used to improve the generalisation of a MVA in the context of High Energy Physics analyses. The examples presented use the Toolkit for Multivariate Analysis (TMVA) based on ROOT and describe our improvements to the SVM functionality and new tools introduced for cross validation within this framework. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.09932v1.pdf"}
{"id": "1611.00225", "abstract": "  Very recently quasi two-dimensional (2D) systems made of attractive fermionic alkali-metal atoms with a widely tunable interaction due to Fano-Feshbach resonances have been realized. In this way it has been achieved the 2D crossover from the Bardeen-Cooper-Schrieffer regime of weakly-interacting Cooper pairs to the Bose-Einstein condensate regime strongly bound dimers. These experiments pave the way to the investigation of 2D strongly-interacting attractive fermions during the Berezinskii-Kosterlitz-Thouless (BKT) transition from a low-temperature superfluid phase characterized by quasi-condensation to a high-temperature normal phase, where vortex proliferation driven by quantum and thermal fluctuations completely destroys superfluidity. In this paper we discuss our preliminar theoretical results on the behavior of the BKT critical temperature across the crossover. Our microscopic calculations are based on functional integration taking into account renormalized Gaussian fluctuations and the crucial 2D effect of vortex-antivortex unbinding. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.00225v1.pdf"}
{"id": "1611.01028", "abstract": "  Energy level spectrum of protactinium atom (Pa, Z=91) is simulated with a CI calculation. Levels belonging to the separate manifolds of a given total angular momentum and parity J^π exhibit distinct properties of many-body quantum chaos. Moreover, an extremely strong enhancement of small perturbations takes place. As an example, effective three-electron interaction is investigated and found to play a significant role in the system. Chaotic properties of the eigenstates allow one to develop a statistical theory and predict probabilities of different processes in chaotic systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.01028v1.pdf"}
{"id": "1611.02262", "abstract": "  The Mathematization project investigates students' use of mathematical tools across the undergraduate physics curriculum. As a part of this project, we look at intermediate mechanics students' written homework solutions to understand how they use these tools in approaching traditional mechanics problems. We use a modified version of the ACER (Activation-Construction-Execution-Reflection) framework to analyze students' solutions and to identify patterns of mathematical skills used on traditional problems. We apply techniques borrowed from network analysis and the Resources Framework to build a \"fingerprint\" of students' mathematical tool use. In this paper, we present preliminary findings on patterns that we identified in students' problem solving. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.02262v4.pdf"}
{"id": "1611.02697", "abstract": "  The contribution of crossed gluon fields in flux tubes connecting quarks to the proton spin is calculated. The calculations are performed following non-perturbative Heisenberg's quantization technique. In our approach a proton is considered as consisting of three quarks connected by three flux tubes. The flux tubes contain color longitudinal electric and transversal electric and magnetic fields. The transversal fields causes the appearance of the angular momentum density. The dimensionless relation between the angular momentum and the mass of the gluon fields is obtained. The contribution to proton spin from rotating quarks and flux tubes connecting quarks is estimated. Simple numerical relation between the proton mass, the speed of light and the proton radius, which is of the same order as the Planck constant, is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.02697v3.pdf"}
{"id": "1611.04404", "abstract": "  We report total-energy calculations based on the density-functional theory that clarify microscopic mechanisms of initial stage of graphene formation on the SiC(0001) surface. We explore favorable reactions for desorption of either Si or C atoms from the stepped surface by determining the desorption and the subsequent migration pathways and calculating the corresponding energy barriers for the first time. We find that the energy barrier for the desorption of an Si atom at the step edge and the subsequent migration toward stable terrace sites are lower than that of a C atom by 0.75 eV, indicative of the selective desorption of Si from the SiC surface. We also find that the subsequent Si desorption is an exothermic reaction. This exothermicity comes from the energy gain due to the bond formation of C atoms being left near the step edges. This is certainly a seed of graphene flakes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.04404v2.pdf"}
{"id": "1611.04542", "abstract": "  Grover's search algorithm is the optimal quantum algorithm that can search an unstructured database quadratically faster than any known classical algorithm. The role of entanglement and correlations in the search algorithm have been studied in great detail and it is known that entanglement between the qubits is necessary to gain a quadratic speedup, for pure state implementation of the Grover search algorithm. Here, we systematically investigate the behavior of quantum coherence and monogamy of entanglement in the discrete analogue of the analog analogue of Grover search algorithm. The analog analogue of Grover search is a continuous time quantum algorithm based on the adiabatic Hamiltonian evolution that gives a quadratic speedup, similar to the original Grover search algorithm. We show that the decrease of quantum coherence, quantified using various coherence monotones, is a clear signature of attaining the maximum success probability in the analog Grover search. We also show that for any two qubit reduced density matrix of the system, the concurrence evolves in close vicinity to the increasing rate of success probability. Furthermore, we show that the system satisfies a n-party monogamy inequality for arbitrary times, hence bounding the amount of n-qubit entanglement during the quantum search. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.04542v1.pdf"}
{"id": "1611.05207", "abstract": "  Optical fibers confine and guide light almost unattenuated and thus convey light forces to polarizable nano-particles over very long distances. Radiation pressure forces arise from scattering of guided photons into free space while gradient forces are based on coherent scattering between different fiber modes or propagation directions. Interestingly, even scattering between co-propagating modes induces longitudinal forces as the transverse confinement of the light modes creates mode dependent longitudinal wave-vectors and photon momenta. We generalize a proven scattering matrix based approach to calculate single as well as inter-particle forces to include several forward and backward propagating modes. We show that an injection of the higher order mode only in a two mode fiber will induce a stationary tractor force against the injection direction, when the mode coupling to the lower order mode dominates against backscattering and free space losses. Generically this arises for non-absorbing particles at the center of a waveguide. The model also gives improved predictions for inter-particle forces in evanescent nanofiber fields as experimentally observed recently. Surprisingly strong tractor forces can also act on whole optically bound arrays. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.05207v1.pdf"}
{"id": "1611.06686", "abstract": "  In stochastic optimization, the population risk is generally approximated by the empirical risk. However, in the large-scale setting, minimization of the empirical risk may be computationally restrictive. In this paper, we design an efficient algorithm to approximate the population risk minimizer in generalized linear problems such as binary classification with surrogate losses and generalized linear regression models. We focus on large-scale problems, where the iterative minimization of the empirical risk is computationally intractable, i.e., the number of observations n is much larger than the dimension of the parameter p, i.e. n ≫ p ≫ 1. We show that under random sub-Gaussian design, the true minimizer of the population risk is approximately proportional to the corresponding ordinary least squares (OLS) estimator. Using this relation, we design an algorithm that achieves the same accuracy as the empirical risk minimizer through iterations that attain up to a cubic convergence rate, and that are cheaper than any batch optimization algorithm by at least a factor of 𝒪(p). We provide theoretical guarantees for our algorithm, and analyze the convergence behavior in terms of data dimensions. Finally, we demonstrate the performance of our algorithm on well-known classification and regression problems, through extensive numerical studies on large-scale datasets, and show that it achieves the highest performance compared to several other widely used and specialized optimization algorithms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.06686v1.pdf"}
{"id": "1611.07649", "abstract": "  Security and distributed infrastructure are two of the most common requirements for big data software. But the security features of the big data platforms are still premature. It is critical to identify, modify, test and execute some of the existing security mechanisms before using them in the big data world. In this paper, we propose a novel intrusion detection technique that understands and works according to the needs of big data systems. Our proposed technique identifies program level anomalies using two methods - a profiling method that models application behavior by creating process signatures from control-flow graphs; and a matching method that checks for coherence among the replica nodes of a big data system by matching the process signatures. The profiling method creates a process signature by reducing the control-flow graph of a process to a set of minimum spanning trees and then creates a hash of that set. The matching method first checks for similarity in process behavior by matching the received process signature with the local signature and then shares the result with all replica datanodes for consensus. Experimental results show only 0.8", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.07649v1.pdf"}
{"id": "1611.08580", "abstract": "  We introduce a new approximate multiresolution analysis (MRA) using a single Gaussian as the scaling function, which we call Gaussian MRA (GMRA). As an initial application, we employ this new tool to accurately and efficiently compute the probability density function (PDF) of the product of independent random variables. In contrast with Monte-Carlo (MC) type methods (the only other universal approach known to address this problem), our method not only achieves accuracies beyond the reach of MC but also produces a PDF expressed as a Gaussian mixture, thus allowing for further efficient computations. We also show that an exact MRA corresponding to our GMRA can be constructed for a matching user-selected accuracy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.08580v2.pdf"}
{"id": "1611.09093", "abstract": "  The wetting properties of graphene have proven controversial and difficult to assess. The presence of a graphene layer on top of a substrate does not significantly change the wetting properties of the solid substrate, suggesting that a single graphene layer does not affect the adhesion between the wetting phase and the substrate. However, wetting experiments of water on graphene show contact angles that imply a large amount of adhesion. Here, we investigate the wetting of graphene by measuring the mass of water vapor adsorbing to graphene flakes of different thickness at different relative humidities. Our experiments unambiguously show that the thinnest of graphene flakes do not adsorb water, from which it follows that the contact angle of water on these flakes is  180o. Thicker flakes of graphene nanopowder, on the other hand, do adsorb water. A calculation of the van der Waals (vdW) interactions that dominate the adsorption in this system confirms that the adhesive interactions between a single atomic layer of graphene and water are so weak that graphene is superhydrophobic. The observations are confirmed in an independent experiment on graphene-coated water droplets that shows that it is impossible to make liquid 'marbles' with molecularly thin graphene. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.09093v3.pdf"}
{"id": "1611.09916", "abstract": "  We introduce a set of Bell inequalities for a three-qubit system. Each inequality within this set is violated by all generalized GHZ states. More entangled a generalized GHZ state is, more will be the violation. This establishes a relation between nonlocality and entanglement for this class of states. Certain inequalities within this set are violated by pure biseparable states. We also provide numerical evidence that at least one of these Bell inequalities is violated by a pure genuinely entangled state. These Bell inequalities can distinguish between separable, biseparable and genuinely entangled pure three-qubit states. We also generalize this set to n-qubit systems and may be suitable to characterize the entanglement of n-qubit pure states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.09916v3.pdf"}
{"id": "1612.00454", "abstract": "  We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [Ca II] emission. A striking feature of both transients is their host environments: PTF12bho is an intra-cluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset  150 kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out an underlying host system to a limit of M_R > -8.0 mag, while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. We show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for Type Ia supernovae or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require larger kick velocities and/or longer merger times than sGRBs. We also show that almost all Ca-rich gap transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intra-group/intra-cluster light following galaxy-galaxy interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.00454v2.pdf"}
{"id": "1612.00493", "abstract": "  Fractional nonlinear differential equations present an interplay between two common and important effective descriptions used to simplify high dimensional or more complicated theories: nonlinearity and fractional derivatives. These effective descriptions thus appear commonly in physical and mathematical modeling. We present a new series method providing systematic controlled accuracy for solutions of fractional nonlinear differential equations. The method relies on spatially iterative use of power series expansions. Our approach permits an arbitrarily large radius of convergence and thus solves the typical divergence problem endemic to power series approaches. We apply our method to the fractional nonlinear Schrödinger equation and its imaginary time rotation, the fractional nonlinear diffusion equation. For the fractional nonlinear Schrödinger equation we find fractional generalizations of cnoidal waves of Jacobi elliptic functions as well as a fractional bright soliton. For the fractional nonlinear diffusion equation we find the combination of fractional and nonlinear effects results in a more strongly localized solution which nevertheless still exhibits power law tails, albeit at a much lower density. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.00493v1.pdf"}
{"id": "1612.00615", "abstract": "  Multiple Sclerosis is a degenerative condition of the central nervous system that affects nearly 2.5 million of individuals in terms of their physical, cognitive, psychological and social capabilities. Researchers are currently investigating on the use of patient reported outcome measures for the assessment of impact and evolution of the disease on the life of the patients. To date, a clear understanding on the use of such measures to predict the evolution of the disease is still lacking. In this work we resort to regularized machine learning methods for binary classification and multiple output regression. We propose a pipeline that can be used to predict the disease progression from patient reported measures. The obtained model is tested on a data set collected from an ongoing clinical research project. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.00615v1.pdf"}
{"id": "1612.01305", "abstract": "  Gravitational wave astronomy has become a reality after the historical detections accomplished during the first observing run of the two advanced LIGO detectors. In the following years, the number of detections is expected to increase significantly with the full commissioning of the advanced LIGO, advanced Virgo and KAGRA detectors. The development of sophisticated data analysis techniques to improve the opportunities of detection for low signal-to-noise-ratio events is hence a most crucial effort. We present in this paper one such technique, dictionary-learning algorithms, which have been extensively developed in the last few years and successfully applied mostly in the context of image processing. However, to the best of our knowledge, such algorithms have not yet been employed to denoise gravitational wave signals. By building dictionaries from numerical relativity templates of both, binary black holes mergers and bursts of rotational core collapse, we show how machine-learning algorithms based on dictionaries can be also successfully applied for gravitational wave denoising. We use a subset of signals from both catalogs, embedded in non-white Gaussian noise, to assess our techniques with a large sample of tests and to find the best model parameters. The application of our method to the actual signal GW150914 shows promising results. Dictionary-learning algorithms could be a complementary addition to the gravitational wave data analysis toolkit. They may be used to extract signals from noise and to infer physical parameters if the data are in good enough agreement with the morphology of the dictionary atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.01305v1.pdf"}
{"id": "1612.02711", "abstract": "  Electrical currents at the surface or edge of a topological insulator are intrinsically spin-polarized. We show that such surface/edge currents can be used to switch the orientation of a molecular magnet weakly coupled to the surface or edge of a topological insulator. For the edge of a two-dimensional topological insulator as well as for the surface of a three-dimensional topological insulator the application of a well-chosen surface/edge current can lead to a complete polarization of the molecule if the molecule's magnetic anisotropy axis is appropriately aligned with the current direction. For a generic orientation of the molecule a nonzero but incomplete polarization is obtained. We calculate the probability distribution of the magnetic states and the switching rates as a function of the applied current. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.02711v1.pdf"}
{"id": "1612.03051", "abstract": "  We study the statics and dynamics of a stable, mobile, three-dimensional matter-wave spherical quantum ball created in the presence of an attractive two-body and a very small repulsive three-body interaction. The quantum ball can propagate with a constant velocity in any direction in free space and its stability under a small perturbation is established numerically and variationally. In frontal head-on and angular collisions at large velocities two quantum balls behave like quantum solitons. Such collision is found to be quasi elastic and the quantum balls emerge after collision without any change of direction of motion and velocity and with practically no deformation in shape. When reflected by a hard impenetrable plane, the quantum ball bounces off like a wave obeying the law of reflection without any change of shape or speed. However, in a collision at small velocities two quantum balls coalesce to form a larger ball which we call a quantum-ball breather. We point out the similarity and difference between the collision of two quantum and classical balls. The present study is based on an analytic variational approximation and a full numerical solution of the mean-field Gross-Pitaevskii equation using the parameters of ^7Li atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.03051v3.pdf"}
{"id": "1612.03137", "abstract": "  While the idea of using the operator product expansion (OPE) to extract the strong coupling from hadronic τ decay data is not new, there is an ongoing controversy over how to include quark-hadron \"duality violations\" (i.e., resonance effects) which are not described by the OPE. One approach attempts to suppress duality violations enough that they might become negligible, but pays the price of an uncontrolled OPE truncation. We critically examine a recent analysis using this approach and show that it fails to properly account for non-perturbative effects, making the resulting determination of the strong coupling unreliable. In a different approach duality violations are taken into account with a model, avoiding the OPE truncation. This second approach provides a self-consistent determination of the strong coupling from τ decays. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.03137v1.pdf"}
{"id": "1612.04049", "abstract": "  We propose a numerical approach to study the invasion fitness of a mutant and to determine evolutionary singular strategies in evolutionary structured models in which the competitive exclusion principle holds. Our approach is based on a dual representation, which consists of the modelling of the small size mutant population by a stochastic model and the computation of its corresponding deterministic model. The use of the deterministic model greatly facilitates the numerical determination of the feasibility of invasion as well as the convergence-stability of the evolutionary singular strategy. Our approach combines standard adaptive dynamics with the link between the mutant survival criterion in the stochastic model and the sign of the eigenvalue in the corresponding deterministic model. We present our method in the context of a mass-structured individual-based chemostat model. We exploit a previously derived mathematical relationship between stochastic and deterministic representations of the mutant population in the chemostat model to derive a general numerical method for analyzing the invasion fitness in the stochastic models. Our method can be applied to the broad class of evolutionary models for which a link between the stochastic and deterministic invasion fitnesses can be established. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.04049v2.pdf"}
{"id": "1612.05351", "abstract": "  We propose the possibility of a new phenomenon affecting the settling of dust grains at the terrestrial region in early protoplanetary disks. Sinking dust grains evaporate in a hot inner region during the early stage of disk evolution, and the effects of condensation and evaporation on vertical dust settling can be significant. A 1-D dust settling model considering both physical and chemical aspects is presented in this paper. Modeling results show that dust grains evaporate as they descend into the hotter interior and form a \"condensation front,\" above which dust-composing major elements, Mg, Si, and Fe, accumulate, creating a large temperature gradient. Repeated evaporation at the front inhibits grain growth, and small grain sizes elevate the opacity away from the mid-plane. Self-consistent calculations including radiative heat transfer and condensation theory suggest that the mid-disk temperature could be high enough for silicates to remain evaporated longer than previous estimates. The formation of a condensation front leads to contrasting settling behaviors between highly refractory elements, such as Al and Ca, and moderately refractory elements, such as Mg, Si, and Fe, suggesting that elemental abundance in planetesimals may not be a simple function of volatility. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.05351v4.pdf"}
{"id": "1612.05700", "abstract": "  In this paper we lay out a simple set of relationships connecting the dynamics of fast plasma jets to the dynamical state of their ambient media. The objective is to provide a tool kit that can be used to connect the morphologies of radio AGNs in galaxy clusters to the dynamical state of the local ICM. The formalism is intended to apply to jets whether they are relativistic or non-relativistic. Special attention is paid to interactions involving ICM shocks, although the results can be applied more broadly. Our formalism emphasizes the importance of the relative Mach number of the impacting ICM flow and the internal Mach number of the AGN jet in determining how the AGN outflows evolve. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.05700v1.pdf"}
{"id": "1612.07039", "abstract": "  The galactic cosmic rays are the main source of ionization in the Earth stratosphere and troposphere. The induced by primary cosmic ray particles ionization is important in various processes related to atmospheric physics and chemistry, specifically the minor constituents. The ion production in the atmosphere is enhanced compared to the average following major solar energetic particles events, specifically over the polar caps. During the solar cycle 23 we observed several strong ground level enhancements, one of the strongest among them been the Bastille day event on 14 July 2000. In the work presented here we apply a full Monte Carlo 3-D model in order to compute the cosmic ray induced ionization. The model is based on atmospheric shower simulation with the PLANETOCOSMICS code and the ion production rate is considered as a superposition of cosmic rays with galactic and solar origin. The ion production rate is computed as a function of the altitude above the sea level and the short, mid and long term ionization effect relative to the average due to galactic cosmic rays is computed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.07039v1.pdf"}
{"id": "1612.08006", "abstract": "  Displacements of atoms and molecules away from lattice sites in helium and parahydrogen solids at low temperature have been studied by means of Quantum Monte Carlo simulations. In the bcc phases of He-3 and He-4, atomic displacements are largely quantum-mechanical in character, even at melting. The computed Lindemann ratio at melting is found to be in good agreement with experimental results for He-4. Unlike the case of helium, in solid parahydrogen there exists near melting a significant thermal contribution to molecular vibrations, accounting for roughly half of the total effect. Although the Lindemann ratio at melting is in quantitative agreement with experiment, computed molecular mean square fluctuations feature a clear temperature dependence, in disagreement with recent experimental observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.08006v2.pdf"}
{"id": "1612.08250", "abstract": "  Compact objects with a light sphere such as black holes and wormholes can reflect light rays like a mirror. This gravitational lensing phenomenon is called retrolensing and it is an interesting tool to survey dark and compact objects with a light sphere near the solar system. In this paper, we calculate the deflection angle analytically in the strong deflection limit in the Reissner-Nordstrom spacetime without Taylor expanding it in the power of the electric charge. Using the obtained deflection angle in the strong deflection limit, we investigate the retrolensing light curves and the separation of double images by the light sphere of Reissner-Nordstrom black holes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.08250v2.pdf"}
{"id": "1612.09019", "abstract": "  Magnetic electric effects in ferromagnetic metals are discussed from the viewpoint of effective spin electromagnetic field that couples to conduction electron spin. The effective field in the adiabatic limit is the spin Berry's phase in space and time, and it leads to spin motive force (voltage generated by magnetization dynamics) and topological Hall effect due to spin chirality. Its gauge coupling to spin current describes the spin transfer effect, where magnetization structure is driven by an applied spin current. The idea of effective gauge field can be extended to include spin relaxation and Rashba spin-orbit interaction. Voltage generation by the inverse Edelstein effect in junctions is interpreted as due to the electric component of Rashba-induced spin gauge field. The spin gauge field arising from the Rashba interaction turns out to coincides with troidal moment, and causes asymmetric light propagation (directional dichroism) as a result of the Doppler shift. Rashba conductor without magnetization is shown to be natural metamaterial exhibiting negative refraction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.09019v1.pdf"}
{"id": "1701.01424", "abstract": "  We present a study of diffusion enhancement of underdamped Brownian particles in 1D symmetric space-periodic potential due to external symmetric time-periodic forcing with zero mean. We show that the diffusivity can be enhanced by many orders of magnitude at appropriate choice of the forcing amplitude and frequency. The diffusivity demonstrates TAD, abnormal (decreasing) temperature dependence at forcing amplitudes exceeding certain value. At any fixed forcing frequency Ω normal temperature dependence of the diffusivity is restored at low enough temperatures, T<T_TAD(Ω) — in contrast with the problem with constant external forcing. At fixed temperature at small forcing frequency the diffusivity either slowly decreases with Ω, or (at stronger forcing) goes through a maximum near Ω_2, reciprocal superdiffusion stage duration. At high frequencies, between Ω_2 and a fraction of the oscillation frequency at the potential minimum, the diffusivity is shown to decrease with Ω according to a power law, with exponent related to the transient superdiffusion exponent. This behavior is found similar for the cases of sinusoidal in time and piecewise constant periodic (\"square\") forcing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.01424v2.pdf"}
{"id": "1701.02012", "abstract": "  We study chemical reaction networks with discrete state spaces, such as the standard continuous time Markov chain model, and present sufficient conditions on the structure of the network that guarantee the system exhibits an extinction event. The conditions we derive involve creating a modified chemical reaction network called a domination-expanded reaction network and then checking properties of this network. We apply the results to several networks including an EnvZ-OmpR signaling pathway in Escherichia coli. This analysis produces a system of equalities and inequalities which, in contrast to previous results on extinction events, allows algorithmic implementation. Such an implementation will be investigated in a companion paper where the results are applied to 458 models from the European Bioinformatics Institute's BioModels database. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.02012v2.pdf"}
{"id": "1701.02430", "abstract": "  We study the motion of magnetic skyrmions in a nanowire induced by a spin-wave current J flowing out of a driving layer close to the edge of the wire. By applying micromagnetic simulation and an analysis of the effective Thiele equation, we find that the skyrmion trajectory is governed by an interplay of both forces due to the magnon current and the wire boundary. The skyrmion is attracted to the driving layer and is accelerated by the repulsive force due to the wire boundary. We consider both cases of a driving longitudinal and transverse to the nanowire, but a steady-state motion of the skyrmion is only obtained for a transverse magnon current. For the latter case, we find in the limit of low current densities J the velocity-current relation v ∼ J/α where v is the skyrmion velocity and α is the Gilbert damping. For large J in case of strong driving, the skyrmion is pushed into the driving layer resulting in a drop of the skyrmion velocity and, eventually, the destruction of the skyrmion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.02430v2.pdf"}
{"id": "1701.02895", "abstract": "  The range resolution in conventional continuous time frequency modulation (CTFM) is inversely proportional to the signal bandwidth. The dual-demodulator continuous time frequency modulation (DD-CTFM) processing technique was proposed by Gough et al [1] as a method to increase the range resolution by making the output of DD-CTFM truly continuous. However, it has been found that in practice the range resolution is still limited by the signal bandwidth. The limitation of DD-CTFM has been explained using simulations and mathematically in this paper. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.02895v1.pdf"}
{"id": "1701.03292", "abstract": "  We study how large functional networks can grow stably under possible cascading overload failures and evaluated the maximum stable network size above which even a small-scale failure would cause a fatal breakdown of the network. Employing a model of cascading failures induced by temporally fluctuating loads, the maximum stable size n_max has been calculated as a function of the load reduction parameter r that characterizes how quickly the total load is reduced during the cascade. If we reduce the total load sufficiently fast (r≥ r_c), the network can grow infinitely. Otherwise, n_max is finite and increases with r. For a fixed r (<r_c), n_max for a scale-free network is larger than that for an exponential network with the same average degree. We also discuss how one detects and avoids the crisis of a fatal breakdown of the network from the relation between the sizes of the initial network and the largest component after an ordinarily occurring cascading failure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.03292v1.pdf"}
{"id": "1701.03572", "abstract": "  This paper describes the development of a novel algorithm to tackle the problem of real-time video stabilization for unmanned aerial vehicles (UAVs). There are two main components in the algorithm: (1) By designing a suitable model for the global motion of UAV, the proposed algorithm avoids the necessity of estimating the most general motion model, projective transformation, and considers simpler motion models, such as rigid transformation and similarity transformation. (2) To achieve a high processing speed, optical-flow based tracking is employed in lieu of conventional tracking and matching methods used by state-of-the-art algorithms. These two new ideas resulted in a real-time stabilization algorithm, developed over two phases. Stage I considers processing the whole sequence of frames in the video while achieving an average processing speed of 50fps on several publicly available benchmark videos. Next, Stage II undertakes the task of real-time video stabilization using a multi-threading implementation of the algorithm designed in Stage I. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.03572v1.pdf"}
{"id": "1701.03966", "abstract": "  Thermal expansion in materials can be accurately modeled with careful anharmonic phonon calculations within density functional theory. However, because of interest in controlling thermal expansion and the time consumed evaluating thermal expansion properties of candidate materials, either theoretically or experimentally, an approach to rapidly identifying materials with desirable thermal expansion properties would be of great utility. When the ionic bonding is important in a material, we show that the fraction of crystal volume occupied by ions, (based upon ionic radii), the mean bond coordination, and the deviation of bond coordination are descriptors that correlate with the room-temperature coefficient of thermal expansion for these materials found in widely accessible databases. Correlation is greatly improved by combining these descriptors in a multi-dimensional fit. This fit reinforces the physical interpretation that open space combined with low mean coordination and a variety of local bond coordinations leads to materials with lower coefficients of thermal expansion, materials with single-valued local coordination and less open space have the highest coefficients of thermal expansion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.03966v2.pdf"}
{"id": "1701.04037", "abstract": "  The observation and imaging of hundreds or thousands of radio sources with the technique of very long baseline interferometry (VLBI) is a computationally intensive task. However, these surveys allow us to conduct statistical investigations of large source samples, and also to discover new phenomena or types of objects. The field of view of these high-resolution VLBI imaging observations is typically a few arcseconds at cm wavelengths. For practical reasons, often a much smaller fraction of the field, the central region is imaged only. With an automated process we imaged the  1.5-arcsec radius fields around more than 1000 radio sources, and found a variety of extended radio structures. Some of them are yet unknown in the literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.04037v1.pdf"}
{"id": "1701.06186", "abstract": "  We investigate the influence of spatial dispersion on atom-surface quantum friction. We show that for atom-surface separations shorter than the carrier's mean free path within the material, the frictional force can be several orders of magnitude larger than that predicted by local optics. In addition, when taking into account spatial dispersion effects, we show that the commonly used local thermal equilibrium approximation underestimates by approximately 95", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.06186v2.pdf"}
{"id": "1701.06230", "abstract": "  We compare classical versus quantum electron transport in recently investigated magnetic focusing devices [S. Bhandari et al., Nano Lett. 16, 1690 (2016)] exposed to the perturbing potential of a scanning gate microscope (SGM). Using the Landauer-Büttiker formalism for a multi-terminal device, we calculate resistance maps that are obtained as the SGM tip is scanned over the sample. There are three unique regimes in which the scanning tip can operate (focusing, repelling, and mixed regime) which are investigated. Tip interacts mostly with electrons with cyclotron trajectories passing directly underneath it, leaving a trail of modified current density behind it. Other (indirect) trajectories become relevant when the tip is placed near the edges of the sample, and current is scattered between the tip and the edge. We also discuss possible explanations for spatial asymmetry of experimentally measured resistance maps, and connect it with specific configurations of the measuring probes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.06230v1.pdf"}
{"id": "1701.06332", "abstract": "  We report on the modeling, simulation and experimental demonstration of complete mode crossings of Fano resonances within chip-integrated microresonators. The continuous reshaping of resonant lineshapes is achieved via nonlinear thermo-optical tuning when the cavity-coupled optical pump is partially absorbed by the material. The locally generated heat then produces a thermal field, which influences the spatially overlapping optical modes, allowing thus to alter the relative spectral separation of resonances. Furthermore, we exploit such tunability to probe continuously the coupling between different families of quasi-degenerate modes that exhibit asymmetric Fano-interactions. As a particular case, we demonstrate for the first time a complete disappearance of one of the modal features in the transmission spectrum as predicted by U. Fano [Phys. Rev. 124, 1866 (1961)]. The phenomenon is modeled as a third order non-linearity with a spatial distribution that depends on the stored optical field and the thermal diffusion within the resonator. The performed non-linear numerical simulations are in excellent agreement with the experimental results, which confirm the validity of the developed theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.06332v1.pdf"}
{"id": "1701.07834", "abstract": "  By exploiting two ACS/HST datasets separated by a temporal baseline of  7 years, we have determined the relative stellar proper motions (providing membership) and the absolute proper motion of the Galactic globular cluster M71. The absolute proper motion has been used to reconstruct the cluster orbit within a Galactic, three-component, axisymmetric potential. M71 turns out to be in a low latitude disk-like orbit inside the Galactic disk, further supporting the scenario in which it lost a significant fraction of its initial mass. Since large differential reddening is known to affect this system, we took advantage of near-infrared, ground-based observations to re-determine the cluster center and density profile from direct star counts. The new structural parameters turn out to be significantly different from the ones quoted in the literature. In particular, M71 has a core and a half-mass radii almost 50", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.07834v1.pdf"}
{"id": "1701.07884", "abstract": "  Recent experimental advances in using strain engineering to significantly alter the band structure of moderately correlated systems offer opportunities and challenges to weak-coupling renormalization group (RG) analysis approaches for predicting superconducting instabilities. On one hand, the RG approach can provide theoretical guidance. On the other hand, it is now imperative to better understand how the predictions of the RG approach depends on microscopic and non-universal model details. Here we focus on the effect of band-selective mass-renormalization often observed in angle resolved photoemission spectroscopy. Focusing on a specific example of uniaxially strained Sr_2RuO_4 we carry out the weak-coupling RG analysis from two sets of band structures as starting points: one is based on density functional theory (DFT) calculations and the other is based on angle-resolved photoemission spectroscopy (ARPES) measurements. Despite good agreement between the Fermi surfaces of the the two band structures we find the two sets of band structures to predict qualitatively different trends in the strain dependence of the superconducting transition temperature T_c as well as the dominant channel. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.07884v1.pdf"}
{"id": "1702.01860", "abstract": "  We report on the implementation of a novel optical setup for generating high-resolution customizable potentials to address ultracold bosonic atoms in two dimensions. Two key features are developed for this purpose. The customizable potential is produced with a direct image of a spatial light modulator, conducted with an in-vacuum imaging system of high numerical aperture. Custom potentials are drawn over an area of 600 × 400 μm with a resolution of 0.9 μm. The second development is a two-dimensional planar trap for atoms with an aspect ratio of 900 and spatial extent of Rayleigh range 1.6 × 1.6 mm, providing near-ballistic in-planar movement. We characterize the setup and present a brief catalog of experiments to highlight the versatility of the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.01860v2.pdf"}
{"id": "1702.02094", "abstract": "  Recent works on planetary migration show that the orbital structure of the Kuiper belt can be very well reproduced if before the onset of the planetary instability Neptune underwent a long-range planetesimal-driven migration up to ∼28 au. However, considering that all giant planets should have been captured in mean motion resonances among themselves during the gas-disk phase, it is not clear whether such a very specific evolution for Neptune is possible, nor whether the instability could have happened at late times. Here, we first investigate which initial resonant configuration of the giant planets can be compatible with Neptune being extracted from the resonant chain and migrating to ∼28 au before that the planetary instability happened. We address the late instability issue by investigating the conditions where the planets can stay in resonance for about 400 My. Our results indicate that this can happen only in the case where the planetesimal disk is beyond a specific minimum distance δ_stab from Neptune. Then, if there is a sufficient amount of dust produced in the planetesimal disk, that drifts inwards, Neptune can enter in a slow dust-driven migration phase for hundreds of Mys until it reaches a critical distance δ_mig from the disk. From that point, faster planetesimal-driven migration takes over and Neptune continues migrating outward until the instability happens. We conclude that, although an early instability reproduces more easily the evolution of Neptune required to explain the structure of the Kuiper belt, such evolution is also compatible with a late instability. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.02094v1.pdf"}
{"id": "1702.02117", "abstract": "  The baryon asymmetry, together with a dark matter asymmetry, may be produced during a first order phase transition in a generative sector. We study the possibility of a gravitational wave signal in a model realising such a scenario. We identify areas of parameter space with strong phase transitions which can be probed by future, space based, gravitational wave detectors. Other signals of this scenario include collider signatures of a Z', DM self interactions, a contribution to Δ N_ eff and nuclear recoils at direct detection experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.02117v3.pdf"}
{"id": "1702.03156", "abstract": "  Broad-lined type Ic supernovae (SNe Ic-BL) are a subclass of rare core collapse SNe whose energy source is debated in the literature. Recently a series of investigations on SNe Ic-BL with the magnetar (plus 56Ni) model were carried out. Evidence for magnetar formation was found for the well-observed SNe Ic-BL 1998bw and 2002ap. In this paper we systematically study a large sample of SNe Ic-BL not associated with gamma-ray bursts. We use photospheric velocity data determined in a homogeneous way. We find that the magnetar+56Ni model provides a good description of the light curves and velocity evolution of our sample of SNe Ic-BL, although some SNe (not all) can also be described by the pure-magnetar model or by the two-component pure-56Ni model (3 out of 12 are unlikely explained by two-component model). In the magnetar+56Ni model, the amount of 56Ni required to explain their luminosity is significantly reduced, and the derived initial explosion energy is, in general, in accordance with neutrino heating. Some correlations between different physical parameters are evaluated and their implications regarding magnetic field amplification and the total energy reservoir are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.03156v2.pdf"}
{"id": "1702.04045", "abstract": "  Motivated by the recently proposed parallel orbital-updating approach in real space method, we propose a parallel orbital-updating based plane-wave basis method for electronic structure calculations, for solving the corresponding eigenvalue problems. In addition, we propose two new modified parallel orbital-updating methods. Compared to the traditional plane-wave methods, our methods allow for two-level parallelization, which is particularly interesting for large scale parallelization. Numerical experiments show that these new methods are more reliable and efficient for large scale calculations on modern supercomputers ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.04045v1.pdf"}
{"id": "1702.04864", "abstract": "  We demonstrate that 4-body real space Jastrow factors are, with the right type of Jastrow basis function, capable of performing successful wave function stenciling to remove unwanted ionic terms from an overabundant fermionic reference without unduly modifying the remaining components. In addition to greatly improving size consistency (restoring it exactly in the case of a geminal power), real-space wave function stenciling is, unlike its Hilbert space predecessors, immediately compatible with diffusion Monte Carlo, allowing it to be used in the pursuit of compact, strongly correlated trial functions with reliable nodal surfaces. We demonstrate the efficacy of this approach in the context of a double bond dissociation by using it to extract a qualitatively correct nodal surface despite being paired with a restricted Slater determinant, that, due to ionic term errors, produces a ground state with a qualitatively incorrect nodal surface when used in the absence of the Jastrow. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.04864v1.pdf"}
{"id": "1702.04923", "abstract": "  We present a time-dependent solution of the Maxwell equations in the Einstein universe, whose electric and magnetic fields, as seen by the stationary observers, are aligned with the Clifford parallels of the 3-sphere S^3. The conformal equivalence between Minkowski's spacetime and (a region of) the Einstein cylinder is then exploited in order to obtain a knotted, finite energy, radiating solution of the Maxwell equations in flat spacetime. We also discuss similar electromagnetic fields in expanding closed Friedmann models, and compute the matter content of such configurations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.04923v2.pdf"}
{"id": "1702.05862", "abstract": "  The modification of hard jets in the Quark Gluon Plasma (QGP) is studied using the MATTER event generator. Based on the higher twist formalism of energy loss, the MATTER event generator simulates the evolution of highly virtual partons through a medium. These partons sampled from an underlying PYTHIA kernel undergo splitting through a combination of vacuum and medium induced emission. The momentum exchange with the medium is simulated via the jet transport coefficient q̂, which is assumed to scale with the entropy density at a given location in the medium. The entropy density is obtained from a relativistic viscous fluid dynamics simulation (VISH2+1D) in 2+1 space time dimensions. Results for jet and hadron observables are presented using an independent fragmentation model. These proceedings will focus on the physics input and simulation details of the MATTER event generator as compared to a variety of test observables. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.05862v2.pdf"}
{"id": "1702.06159", "abstract": "  Personal sensory data is used by context-aware mobile applications to provide utility. However, the same data can also be used by an adversary to make sensitive inferences about a user thereby violating her privacy.   We present DEEProtect, a framework that enables a novel form of inference control, in which mobile apps with access to sensor data are limited (provably) in their ability to make inferences about user's sensitive data and behavior. DEEProtect adopts a two-layered privacy strategy. First, it leverages novel autoencoder techniques to perform data minimization and limits the amount of information being shared; the learning network is used to derive a compact representation of sensor data consisting only of features relevant to authorized utility-providing inferences. Second, DEEProtect obfuscates the previously learnt features, thereby providing an additional layer of protection against sensitive inferences. Our framework supports both conventional as well as a novel relaxed notion of local differential privacy that enhances utility. Through theoretical analysis and extensive experiments using real-world datasets, we demonstrate that when compared to existing approaches DEEProtect provides provable privacy guarantees with up to 8x improvement in utility. Finally, DEEProtect shares obfuscated but raw sensor data reconstructed from the perturbed features, thus requiring no changes to the existing app interfaces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.06159v2.pdf"}
{"id": "1702.06275", "abstract": "  A spectrogram of a ship wake is a heat map that visualises the time-dependent frequency spectrum of surface height measurements taken at a single point as the ship travels by. Spectrograms are easy to compute and, if properly interpreted, have the potential to provide crucial information about various properties of the ship in question. Here we use geometrical arguments and analysis of an idealised mathematical model to identify features of spectrograms, concentrating on the effects of a finite-depth channel. Our results depend heavily on whether the flow regime is subcritical or supercritical. To support our theoretical predictions, we compare with data taken from experiments we conducted in a model test basin using a variety of realistic ship hulls. Finally, we note that vessels with a high aspect ratio appear to produce spectrogram data that contains periodic patterns. We can reproduce this behaviour in our mathematical model by using a so-called two-point wavemaker. These results highlight the role of wave interference effects in spectrograms of ship wakes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.06275v2.pdf"}
{"id": "1702.06621", "abstract": "  The ALICE detector has excellent Particle IDentification (PID) capabilities in the central barrel (|η| < 0.9). This allows identified hadron production to be measured over a wide transverse momentum (p_T) range, using different sub-detectors and techniques: their specific energy loss (dE/dx), the velocity determination via time-of-flight measurement, the Cherenkov angle or their characteristic weak decay topology. Results on identified light flavour hadron production at mid-rapidity measured by ALICE in proton-proton collisions at √(s) = 13 TeV are presented and compared with previous measurements performed at lower energies. The results cover a wide range of particle species including long-lived hadrons, resonances and multi-strange baryons over the p_T range from 150 MeV/c up to 20 GeV/c, depending on the particle species. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.06621v1.pdf"}
{"id": "1702.06663", "abstract": "  Real-time monitoring and responses to emerging public health threats rely on the availability of timely surveillance data. During the early stages of an epidemic, the ready availability of line lists with detailed tabular information about laboratory-confirmed cases can assist epidemiologists in making reliable inferences and forecasts. Such inferences are crucial to understand the epidemiology of a specific disease early enough to stop or control the outbreak. However, construction of such line lists requires considerable human supervision and therefore, difficult to generate in real-time. In this paper, we motivate Guided Deep List, the first tool for building automated line lists (in near real-time) from open source reports of emerging disease outbreaks. Specifically, we focus on deriving epidemiological characteristics of an emerging disease and the affected population from reports of illness. Guided Deep List uses distributed vector representations (ala word2vec) to discover a set of indicators for each line list feature. This discovery of indicators is followed by the use of dependency parsing based techniques for final extraction in tabular form. We evaluate the performance of Guided Deep List against a human annotated line list provided by HealthMap corresponding to MERS outbreaks in Saudi Arabia. We demonstrate that Guided Deep List extracts line list features with increased accuracy compared to a baseline method. We further show how these automatically extracted line list features can be used for making epidemiological inferences, such as inferring demographics and symptoms-to-hospitalization period of affected individuals. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.06663v1.pdf"}
{"id": "1702.06681", "abstract": "  We present gas kinematics based on the [OIII] λ5007 line and their connection to galaxy gravitational potential, active galactic nucleus (AGN) energetics, and star formation, using a large sample of  110,000 AGNs and star-forming (SF) galaxies at z<0.3. Gas and stellar velocity dispersions are comparable to each other in SF galaxies, indicating that the ionized gas kinematics can be accounted by the gravitational potential of host galaxies. In contrast, AGNs clearly show non-gravitational kinematics, which is comparable to or stronger than the virial motion caused by the gravitational potential. The [OIII] velocity-velocity dispersion (VVD) diagram dramatically expands toward high values as a function of AGN luminosity, implying that the outflows are AGN-driven, while SF galaxies do not show such a trend. We find that the fraction of AGNs with a signature of outflow kinematics, steeply increases with AGN luminosity and Eddington ratio. In particular, the majority of luminous AGNs presents strong non-gravitational kinematics in the [OIII] profile. AGNs with strong outflow signatures show on average similar specific star formation rate (SSFR) to that of starforming galaxies. In contrast, AGNs with weak or no outflows have an order of magnitude lower SSFR, suggesting that AGNs with current strong outflows do now show any negative AGN feedback and that it may take the order of a dynamical time to impact on star formation over galactic scales. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.06681v2.pdf"}
{"id": "1702.07385", "abstract": "  In this paper we construct the complete evolution of the universe driven by the mass dimension one dark spinor called Elko, starting with inflation, passing by the matter dominated era and finishing with the recent accelerated expansion. The dynamic of the fermionic Elko field with a symmetry breaking type potential can reproduce all phases of the universe in a natural and elegant way. The dynamical equations in general case and slow roll conditions in the limit H≪ m_pl are also presented for the Elko system. Numerical analysis for the number of e-foldings during inflation, energy density after inflation and for present time and also the actual size of the universe are in good agreement with the standard model of cosmology. An interpretation of the inflationary phase as a result of Pauli exclusion principle is also possible if the Elko field is treated as an average value of its quantum analogue. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.07385v3.pdf"}
{"id": "1702.07614", "abstract": "  In recent years the scintillation mechanism of inorganic crystals has been extensively investigated in different studies. The main issues are the non-proportionality mechanism of the light response versus energy and its connection with the shaping time used for the scintillation signals. In this study the Compton coincidence technique has been used to measure the relative non-proportionality of three crystals: CdWO_4, BGO, and NaI(Tl). To test the non-proportionality dependence on shaping time, the preamplified scintillator pulses have been digitized and shaped with a digital trapezoidal filter. Since no analogic shaping occurs the majority of the scintillation components are digitized, thus avoiding major information losses. The obtained results suggest the existence of a correlation between the time constant of the scintillation emission and light yield. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.07614v2.pdf"}
{"id": "1703.00134", "abstract": "  We define a multiaccess communication scheme that effectively eliminates interference and resolves collisions in many-to-one and many-to-many communication scenarios. Each transmitter is uniquely identified by a steering vector. All signals issued from a specific transmitter will be steered into the same single-dimensional or double-dimensional subspace at all receivers hearing this transmission. This subspace is orthogonal to the noise subspace at a receiver and the signals within the subspace can be extracted using the root-MUSIC method. At high SNR, local channel knowledge and strict synchronization, the algorithm asymptotically achieves full network capacity on condition that a channel remains constant within a single time slot. Without synchronization, the worst case asymptotic performance is still greater than the 50% throughput achieved by collision resolution algorithms and interference management techniques like interference alignment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.00134v1.pdf"}
{"id": "1703.00385", "abstract": "  We present chemical abundances for 17 elements in a sample of 11 red giant branch stars in NGC 6362 from UVES spectra. NGC 6362 is one of the least massive globulars where multiple populations have been detected, yet its detailed chemical composition has not been investigated so far. NGC 6362 turns out to be a metal-intermediate ([Fe/H]=-1.07±0.01 dex) cluster, with its α- and Fe-peak elements content compatible with that observed in clusters with similar metallicity. It also displays an enhancement in its s-process element abundances. Among the light elements involved in the multiple populations phenomenon, only [Na/Fe] shows star-to-star variations, while [Al/Fe] and [Mg/Fe] do not show any evidence for abundance spreads. A differential comparison with M4, a globular cluster with similar mass and metallicity, reveals that the two clusters share the same chemical composition. This finding suggests that NGC 6362 is indeed a regular cluster, formed from gas that has experienced the same chemical enrichment of other clusters with similar metallicity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.00385v1.pdf"}
{"id": "1703.01346", "abstract": "  Plasma proteins such as fibrinogen induce the aggregation of red blood cells (RBC) into rouleaux, which are responsible for the pronounced shear thinning behavior of blood, control the erythro- cyte sedimentation rate (ESR) a common hematological test and are involved in many situations of physiological relevance such as structuration of blood in the microcirculation or clot formation in pathological situations. Confocal microscopy is used to characterize the shape of RBCs within rouleaux at equilibrium as a function of macromolecular concentration, revealing the diversity of contact zone morphology. Three different configurations that have only been partly predicted before are identified, namely parachute, male-female and sigmoid shapes, and quantitatively recovered by numerical simulations. A detailed experimental and theoretical analysis of clusters of two cells shows that the deformation increases nonlinearly with the interaction energy. Models indicate a forward bifurcation in which the contacting membrane undergoes a buckling instability from a flat to a de- formed contact zone at a critical value of the interaction energy. These results are not only relevant for the understanding of the morphology and stability of RBC aggregates, but also for a whole class of interacting soft deformable objects such as vesicles, capsules or cells in tissues. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.01346v1.pdf"}
{"id": "1703.02024", "abstract": "  We investigate the superfluid behavior of a two-dimensional (2D) Bose gas of ^87Rb atoms using classical field dynamics. In the experiment by R. Desbuquois et al., Nat. Phys. 8, 645 (2012), a 2D quasicondensate in a trap is stirred by a blue-detuned laser beam along a circular path around the trap center. Here, we study this experiment from a theoretical perspective. The heating induced by stirring increases rapidly above a velocity v_c, which we define as the critical velocity. We identify the superfluid, the crossover, and the thermal regime by a finite, a sharply decreasing, and a vanishing critical velocity, respectively. We demonstrate that the onset of heating occurs due to the creation of vortex-antivortex pairs. A direct comparison of our numerical results to the experimental ones shows good agreement, if a systematic shift of the critical phase-space density is included. We relate this shift to the absence of thermal equilibrium between the condensate and the thermal wings, which were used in the experiment to extract the temperature. We expand on this observation by studying the full relaxation dynamics between the condensate and the thermal cloud. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.02024v1.pdf"}
{"id": "1703.02627", "abstract": "  This work provides a comprehensive scaling law based performance analysis for multi-cell multi-user massive multiple-input-multiple-output (MIMO) downlink systems. Imperfect channel state information (CSI), pilot contamination, and channel spatial correlation are all considered. First, a sum- rate lower bound is derived by exploiting the asymptotically deterministic property of the received signal power, while keeping the random nature of other components in the signal-to-interference-plus-noise-ratio (SINR) intact. Via a general scaling model on important network parameters, including the number of users, the channel training energy and the data transmission power, with respect to the number of base station antennas, the asymptotic scaling law of the effective SINR is obtained, which reveals quantitatively the tradeoff of the network parameters. More importantly, pilot contamination and pilot contamination elimination (PCE) are considered in the analytical framework. In addition, the applicability of the derived asymptotic scaling law in practical systems with large but finite antenna numbers are discussed. Finally, sufficient conditions on the parameter scalings for the SINR to be asymptotically deterministic in the sense of mean square convergence are provided, which covers existing results on such analysis as special cases and shows the effect of PCE explicitly. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.02627v2.pdf"}
{"id": "1703.03833", "abstract": "  Quantum oscillations in the binary antiferromagnetic metal FeAs are presented and compared to theoretical predictions for the electronic band structure in the anomalous spin density wave state of this material. Demonstrating a new method for growing single crystals out of Bi flux, we utilize the highest quality FeAs to perform torque magnetometry experiments up to 35 T, using rotations of field angle in two planes to provide evidence for one electron and one hole band in the magnetically ordered state. The resulting picture agrees with previous experimental evidence for multiple carriers at low temperatures, but the exact Fermi surface shape differs from predictions, suggesting that correlations play a role in deviation from ab initio theory and cause up to a four-fold enhancement in the effective carrier mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.03833v2.pdf"}
{"id": "1703.03916", "abstract": "  Axioms can be used to model derived predicates in domain- independent planning models. Formulating models which use axioms can sometimes result in problems with much smaller search spaces and shorter plans than the original model. Previous work on axiom-aware planners focused solely on state- space search planners. We propose axiom-aware planners based on answer set programming and integer programming. We evaluate them on PDDL domains with axioms and show that they can exploit additional expressivity of axioms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.03916v2.pdf"}
{"id": "1703.05591", "abstract": "  The analysis of clouds in the earth's atmosphere is important for a variety of applications, viz. weather reporting, climate forecasting, and solar energy generation. In this paper, we focus our attention on the impact of cloud on the total solar irradiance reaching the earth's surface. We use weather station to record the total solar irradiance. Moreover, we employ collocated ground-based sky camera to automatically compute the instantaneous cloud coverage. We analyze the relationship between measured solar irradiance and computed cloud coverage value, and conclude that higher cloud coverage greatly impacts the total solar irradiance. Such studies will immensely help in solar energy generation and forecasting. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.05591v1.pdf"}
{"id": "1703.06897", "abstract": "  In this paper we study centrifugal acceleration of particles moving along a prescribed rotating curved trajectories. We consider the physical system embedded in an isotropic photon field and study the influence of the photon drag force on the acceleration process. For this purpose we study three major configurations of the field lines: the straight line; the Archimede's spiral and the dipolar field line configuration. By analysing dynamics of particles sliding along the field lines in the equatorial plane we have found several interesting features of motion. In particular, it has been shown that for rectilinear field lines the particles reach the light cylinder (area where the linear velocity of rotation exactly equals the speed of light) zone relatively slowly for bigger drag forces. Considering the Archimede's spiral, we have found that in cases when the field lines lag behind the rotation, the particles achieve the force-free regime of dynamics regardless of the drag force. Unlike this scenario, when the spiral is screwed up in an opposite direction there the particles do not reach the force free regime, but tend to stable equilibrium locations. Such a behaviour has been found for straight field lines as well. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.06897v2.pdf"}
{"id": "1703.07043", "abstract": "  In this paper, energy efficient power control for the uplink two-tier networks where a macrocell tier with a massive multiple-input multiple-output (MIMO) base station is overlaid with a small cell tier is investigated. We propose a distributed energy efficient power control algorithm which allows each user in the two-tier network taking individual decisions to optimize its own energy efficiency (EE) for the multi-user and multi-cell scenario. The distributed power control algorithm is implemented by decoupling the EE optimization problem into two steps. In the first step, we propose to assign the users on the same resource into the same group and each group can optimize its own EE, respectively. In the second step, multiple power control games based on evolutionary game theory (EGT) are formulated for each group, which allows each user optimizing its own EE. In the EGT-based power control games, each player selects a strategy giving a higher payoff than the average payoff, which can improve the fairness among the users. The proposed algorithm has a linear complexity with respect to the number of subcarriers and the number of cells in comparison with the brute force approach which has an exponential complexity. Simulation results show the remarkable improvements in terms of fairness by using the proposed algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.07043v1.pdf"}
{"id": "1703.07110", "abstract": "  We present a frequency-renormalized multipolaron expansion method to explore the ground state of quantum Rabi model (QRM). The main idea is to take polaron as starting point to expand the ground state of QRM. The polarons are deformed and displaced oscillator states with variationally determined frequency-renormalization and displacement parameters. This method is an extension of the previously proposed polaron concept and the coherent state expansion used in the literature, which shows high efficiency in describing the physics of the QRM. The proposed method is expected to be useful for solving other more complicated light-matter interaction models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.07110v1.pdf"}
{"id": "1703.07781", "abstract": "  This letter presents a revised radiative transfer model for the infrared (IR) emission of active galactic nuclei (AGN). While current models assume that the IR is emitted from a dusty torus in the equatorial plane of the AGN, spatially resolved observations indicate that the majority of the IR emission from 100 pc in many AGN originates from the polar region, contradicting classical torus models. The new model CAT3D-WIND builds upon the suggestion that the dusty gas around the AGN consists of an inflowing disk and an outflowing wind. Here, it is demonstrated that (1) such disk+wind models cover overall a similar parameter range of observed spectral features in the IR as classical clumpy torus models, e.g. the silicate feature strengths and mid-IR spectral slopes, (2) they reproduce the 3-5μm bump observed in many type 1 AGN unlike torus models, and (3) they are able to explain polar emission features seen in IR interferometry, even for type 1 AGN at relatively low inclination, as demonstrated for NGC3783. These characteristics make it possible to reconcile radiative transfer models with observations and provide further evidence of a two-component parsec-scaled dusty medium around AGN: the disk gives rise to the 3-5μm near-IR component, while the wind produces the mid-IR emission. The model SEDs will be made available for download. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.07781v1.pdf"}
{"id": "1703.07822", "abstract": "  We consider the problem of a robot learning the mechanical properties of objects through physical interaction with the object, and introduce a practical, data-efficient approach for identifying the motion models of these objects. The proposed method utilizes a physics engine, where the robot seeks to identify the inertial and friction parameters of the object by simulating its motion under different values of the parameters and identifying those that result in a simulation which matches the observed real motions. The problem is solved in a Bayesian optimization framework. The same framework is used for both identifying the model of an object online and searching for a policy that would minimize a given cost function according to the identified model. Experimental results both in simulation and using a real robot indicate that the proposed method outperforms state-of-the-art model-free reinforcement learning approaches. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.07822v1.pdf"}
{"id": "1703.08498", "abstract": "  We propose an alternative method to generate samples of a spatially correlated random field with applications to large-scale problems for forward propagation of uncertainty. A classical approach for generating these samples is the Karhunen-Loève (KL) decomposition. However, the KL expansion requires solving a dense eigenvalue problem and is therefore computationally infeasible for large-scale problems. Sampling methods based on stochastic partial differential equations provide a highly scalable way to sample Gaussian fields, but the resulting parametrization is mesh dependent. We propose a multilevel decomposition of the stochastic field to allow for scalable, hierarchical sampling based on solving a mixed finite element formulation of a stochastic reaction-diffusion equation with a random, white noise source function. Numerical experiments are presented to demonstrate the scalability of the sampling method as well as numerical results of multilevel Monte Carlo simulations for a subsurface porous media flow application using the proposed sampling method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.08498v1.pdf"}
{"id": "1703.08767", "abstract": "  The polynomial eigenvalue problem arises in many applications and has received a great deal of attention over the last decade. The use of root-finding methods to solve the polynomial eigenvalue problem dates back to the work of Kublanovskaya (1969, 1970) and has received a resurgence due to the work of Bini and Noferini (2013). In this paper, we present a method which uses Laguerre iteration for computing the eigenvalues of a matrix polynomial. An effective method based on the numerical range is presented for computing initial estimates to the eigenvalues of a matrix polynomial. A detailed explanation of the stopping criteria is given, and it is shown that under suitable conditions we can guarantee the backward stability of the eigenvalues computed by our method. Then, robust methods are provided for computing both the right and left eigenvectors and the condition number of each eigenpair. Applications for Hessenberg and tridiagonal matrix polynomials are given and we show that both structures benefit from substantial computational savings. Finally, we present several numerical experiments to verify the accuracy of our method and its competitiveness for solving the roots of a polynomial and the tridiagonal eigenvalue problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.08767v1.pdf"}
{"id": "1703.10604", "abstract": "  We present theoretical and experimental evidence of a universal mechanism through which temporal cavity solitons of externally-driven, passive, Kerr resonators can form robust long-range bound states. These bound states, sometime also referred to as multi-soliton states or soliton crystals in microresonators, require perturbations to the strict Lugiato-Lefever mean field description of temporal cavity solitons. Binding occurs when the perturbation excites a narrowband resonance in the soliton spectrum, which gives long oscillatory tails to the solitons. Those tails can then interlock for a discrete set of temporal separations between the solitons. The universality of this mechanism is demonstrated in fiber ring cavities by providing experimental observations of long-range bound states ensuing from three different perturbations: third-order dispersion (dispersive wave generation), the periodic nature of the cavity (Kelly sidebands), and the random birefringence of the resonator. Sub-picosecond resolution of bound state separations and their dynamics are obtained by using the dispersive Fourier transform technique. Good agreement with theoretical models, including a new vector mean-field model, is also reported. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.10604v1.pdf"}
{"id": "adap-org9911006", "abstract": "  We propose a stochastic dynamic model of migration and economic aggregation in a system of employed (immobile) and unemployed (mobile) agents which respond to local wage gradients. Dependent on the local economic situation, described by a production function which includes cooperative effects, employed agents can become unemployed and vice versa. The spatio-temporal distribution of employed and unemployed agents is investigated both analytically and by means of stochastic computer simulations. We find the establishment of distinct economic centers out of a random initial distribution. The evolution of these centers occurs in two different stages: (i) small economic centers are formed based on the positive feedback of mutual stimulation/cooperation among the agents, (ii) some of the small centers grow at the expense of others, which finally leads to the concentration of the labor force in different extended economic regions. This crossover to large-scale production is accompanied by an increase in the unemployment rate. We observe a stable coexistence between these regions, although they exist in an internal quasistationary non-equilibrium state and still follow a stochastic eigendynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/adap-org/pdf/9911/9911006v1.pdf"}
{"id": "astro-ph0001157", "abstract": "  We present near infrared J, H, and K images and K-band spectroscopy in the giant HII region W42. A massive star cluster is revealed; the color-color plot and K-band spectroscopic morphology of two of the brighter objects suggest the presence of young stellar objects. The spectrum of the bright central star is similar to unobscured stars with MK spectral types of O5-O6.5. If this star is on the zero age main sequence, then the derived spectrophotometric distance is considerably smaller than previous estimates. The Lyman continuum luminosity of the cluster is a few times that of the Trapezium. The slope of the K-band luminosity function is similar to that for the Trapezium cluster and significantly steeper than that for the massive star cluster in M17 or the Arches cluster near the Galactic center. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0001/0001157v1.pdf"}
{"id": "astro-ph0001407", "abstract": "  Results of a 1997 September 9-10 BeppoSAX observation of the 5.57 hr low-mass X-ray binary (LMXRB) X1822-371 are presented. The 0.3-40 keV spectrum is unusually complex and cannot be fit by any of the standard models applied to other LMXRB. At least two components are required. One component has a shape consistent with that expected from the Comptonization of an input soft (Wein) spectrum while the other, contributing  40", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0001/0001407v1.pdf"}
{"id": "astro-ph0002065", "abstract": "  We have detected an X-ray flare on the very low mass star VB 10 (GL 752 B; M8 V) using the ROSAT High Resolution Imager. VB 10 is the latest type (lowest mass) main sequence star known to exhibit coronal activity. X-rays were detected from the star during a single 1.1-ksec segment of an observation which lasted 22 ksec in total. The energy released by this flare is on the order of 10^27 ergs/sec. This is at least two orders of magnitude greater than the quiescent X-ray luminosity of VB 10, which has yet to be measured. This X-ray flare is very similar in nature to the far ultraviolet flare which was observed by Linsky et al. (1995) using the Goddard High Resolution Spectrograph onboard Hubble Space Telescope. We discuss reasons for the extreme difference between the flare and quiescent X-ray luminosities, including the possibility that VB 10 has no quiescent (10^6 K) coronal plasma at all. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0002/0002065v1.pdf"}
{"id": "astro-ph0003048", "abstract": "  We present new radio and optical observations of the colliding-wind system WR146 aimed at understanding the nature of the companion to the Wolf-Rayet star and the collision of their winds. The radio observations reveal emission from three components: the WR stellar wind, the non-thermal wind-wind interaction region and, for the first time, the stellar wind of the OB companion. This provides the unique possibility of determining the mass-loss rate and terminal wind velocity ratios of the two winds, independent of distance. Respectively, these ratios are determined to be 0.20+/-0.06 and 0.56+/-0.17 for the OB-companion star relative to the WR star. A new optical spectrum indicates that the system is more luminous than had been believed previously. We deduce that the “companion” cannot be a single, low luminosity O8 star as previously suggested, but is either a high luminosity O8 star, or possibly an O8+WC binary system. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0003/0003048v1.pdf"}
{"id": "astro-ph0003291", "abstract": "  We report the detection of Hα emission in the T dwarf (methane brown dwarf) 2MASSW J1237392+652615 over three days using the Keck Low Resolution Imaging Spectrograph. The measured line flux, log(L_Hα/L_bol) = -4.3, is roughly consistent with early M dwarf activity levels and inconsistent with decreasing activity trends in late M and L dwarfs. Similar emission is not seen in two other T dwarfs. We speculate on several mechanisms that may be responsible for emission, including a strong magnetic field, continuous flaring, acoustic heat generation, and a close (a ∼ 4 - 20 R_Jup) interacting binary, with the cooler component overflowing its Roche lobe. We suggest that the M9.5Ve PC 0025+0447 could be a warm analogue to 2MASS J1237+65, and may be powered by the latter mechanism. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0003/0003291v1.pdf"}
{"id": "astro-ph0003452", "abstract": "  We suggest a new mechanism to account for the loss of angular momentum in binaries with non-conservative mass exchange. It is shown that in some cases the loss of matter can result in increase of the orbital angular momentum of a binary. If included into consideration in evolutionary calculations, this mechanism appreciably extends the range of mass ratios of components for which mass exchange in binaries is stable. It becomes possible to explain the existence of some observed cataclysmic binaries with high donor/accretor mass ratio, which was prohibited in conservative evolution models. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0003/0003452v1.pdf"}
{"id": "astro-ph0004395", "abstract": "  A continuous stochastic background of gravitational waves (GWs) for burst sources is produced if the mean time interval between the occurrence of bursts is smaller than the average time duration of a single burst at the emission, i.e., the so called duty cycle must be greater than one. To evaluate the background of GWs produced by an ensemble of sources, during their formation, for example, one needs to know the average energy flux emitted during the formation of a single object and the formation rate of such objects as well. In many cases the energy flux emitted during an event of production of GWs is not known in detail, only characteristic values for the dimensionless amplitude and frequencies are known. Here we present a shortcut to calculate stochastic backgrounds of GWs produced from cosmological sources. For this approach it is not necessary to know in detail the energy flux emitted at each frequency. Knowing the characteristic values for the “lumped” dimensionless amplitude and frequency we show that it is possible to calculate the stochastic background of GWs produced by an ensemble of sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0004/0004395v1.pdf"}
{"id": "astro-ph0005183", "abstract": "  We have simulated the evolution of a large sample of X-ray clusters in a Lambda-CDM universe at high spatial resolution using adaptive mesh refinement and placed the results in an online archive for public access. The Simulated Cluster Archive website http://sca.ncsa.uiuc.edu provides tools for interactive 2D and 3D analysis of gas and dark matter fields, X-ray and SZ imaging, and data export. We encourage community use and solicit their feedback. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0005/0005183v1.pdf"}
{"id": "astro-ph0005445", "abstract": "  We investigate the dynamical importance of a newly recognized possible source of significant feedback generated during structure formation; namely cosmic ray (CR) pressure. We present evidence for the existence of numerous shocks in the hot gas of galaxy clusters (GCs). We employ for the first time an explicit numerical treatment of CR acceleration and transport in hydro simulations of structure formation. According to our results, CRs provide an important fraction of the total pressure inside GCs, up to several tenths. This was true even at high redshift (z=2), meaning that such non-thermal component could affect the evolution of structure formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0005/0005445v1.pdf"}
{"id": "astro-ph0006286", "abstract": "  Several different approximations and techniques have been developed for the calculation of atomic structure, ionization, and excitation of atoms and ions. These techniques have been used to compute large amounts of spectroscopic data of various levels of accuracy. This paper presents a review of these theoretical methods to help non-experts in atomic physics to better understand the qualities and limitations of various data sources and assess how reliable are spectral models based on those data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0006/0006286v1.pdf"}
{"id": "astro-ph0007110", "abstract": "  A very high activity of Cygnus X-1 on 1999 April 19-21 was recorded by BATSE Large Area Detectors onboard the Compton Gamma-Ray Observatory. The peak luminosity was one order of magnitude higher than the normal luminosity of Cyg X-1. This fact can be critical for models of the hard state of Cyg X-1. The longest outburst lasted  1000 s and demonstrated very unusual temporal and spectral behavior which indicates the presence of two emission components. One component is relatively soft (with a cutoff below 100 keV) and highly variable, and the other one is hard (extending above 100 keV), with much slower variability. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0007/0007110v2.pdf"}
{"id": "astro-ph0007477", "abstract": "  In this paper the Stewart-Lyth inverse problem is introduced. It consists of solving two non-linear differential equations for the first slow-roll parameter and finding the inflaton potential. The equations are derived from the Stewart–Lyth equations for the scalar and tensorial perturbations produced during the inflationary period. The geometry of the phase planes transverse to the trajectories is analyzed, and conclusions about the possible behaviour for general solutions are drawn. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0007/0007477v3.pdf"}
{"id": "astro-ph0008159", "abstract": "  We have shown that the Sun's shadow by high energy cosmic rays moves year by year and its behavior is correlated with a time variation of the large-scale structure of the solar and interplanetary magnetic fields. The solar activity was near minimum in the period from 1996 through 1997. Using the data obtained with the Tibet air shower array, we examined the shadowing of cosmic rays by the Sun in this quiet phase of solar cycle, and found that the Sun's shadow was just in the apparent direction of the Sun, though it was observed at the position considerably away from the Sun to the south-west in the period between 1990 and 1993. It is known that the magnetic pole of equivalent solar dipole was reversed during the previous active phase, and near solar minimum the dipole was aligned with the rotating axis, preserving its N-pole on the north pole side of the Sun. This causes the solar magnetic field to shift the Sun's shadow to the east. Thus, the observed results suggest that the shift of the Sun's shadow due to the solar magnetic field was pushed back by the effect of the geomagnetic field, since the geomagnetic field always make the shadow shift to the west. We discuss the Sun's shadow observed during the period near solar minimum in 1996-1997 and compare it with the simulation results. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0008/0008159v1.pdf"}
{"id": "astro-ph0008446", "abstract": "  We perform a likelihood analysis of the recently released BOOMERanG and MAXIMA data, allowing for the possibility of a time-varying fine-structure constant. We find that in general this data prefers a value of α that was smaller in the past (which is in agreement with measurements of α from quasar observations). However, there are some interesting degeneracies in the problem which imply that strong statements about α can not be made using this method until independent accurate determinations of Ω_b h^2 and H_0 are available.   We also show that a preferred lower value of α comes mainly from the data points around the first Doppler peak, whereas the main effect of the high-ℓ data points is to increase the preferred value for Ω_b h^2 (while also tightening the constraints on Ω_0 and H_0). We comment on some implications of our results. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0008/0008446v1.pdf"}
{"id": "astro-ph0009136", "abstract": "  Circumstances are described in which symmetry breaking during the formation of our three-dimensional brane within a higher-dimensional space in the early universe excites mesoscopic classical radion or brane-displacement degrees of freedom and produces a detectable stochastic background of gravitational radiation. The spectrum of the background is related to the unification energy scale and the the sizes and numbers of large extra dimensions. It is shown that properties of the background observable by gravitational-wave observatories at frequencies f≈ 10^-4 Hz to 10^3 Hz contain information about unification on energy scales from 1 to 10^10 TeV, gravity propagating through extra-dimension sizes from 1 mm to 10^-18mm, and the dynamical history and stabilization of from one to seven extra dimensions. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0009/0009136v1.pdf"}
{"id": "astro-ph0009386", "abstract": "  After a short history of the Λ-term it is explained why the (effective) cosmological constant is expected to obtain contributions from short-distance physics, corresponding to an energy at least as large as the Fermi scale. The actual tiny value of the cosmological constant by particle physics standards represents, therefore, one of the deepest mysteries of present-day fundamental physics. Recent proposals of an approach to the cosmological constant problem which make use of (large) extra dimensions are briefly discussed. Cosmological models with a dynamical Λ, which attempt to avoid the disturbing cosmic coincidence problem, are also reviewed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0009/0009386v1.pdf"}
{"id": "astro-ph0011013", "abstract": "  We present a semi-empirical model for the evolving far-infrared to ultraviolet diffuse background produced by stars in galaxies. The model is designed to reproduce the results of deep galaxy surveys, and therefore may be considered as a cosmology-independent lower limit to the extragalactic background light. Using this model and recent HEGRA data, we infer the intrinsic spectrum at multi-TeV gamma-ray energies for Mkn501 and find that it is consistent with a power law of spectral index 2.49+-0.04. In turn, this finding renders it rather unlikely that the present-day infrared background has an intensity as high as claimed by Finkbeiner et al. (2000). Future 10GeV to TeV observations could be used to either constrain the ultraviolet-to-infrared background model at high redshifts or cosmological parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011013v1.pdf"}
{"id": "astro-ph0011254", "abstract": "  We report the first wide-field mapping of the kinematics and stellar populations in the E3 galaxy NGC 4365. The velocity maps extend previous long-slit work. They show two independent kinematic subsystems: the central 300 x 700 pc rotates about the projected minor axis, and the main body of the galaxy, 3 x 4 kpc, rotates almost at right angles to this. The line-strength maps show that the metallicity of the stellar population decreases from a central value greater than solar, to one-half solar at a radius of 2 kpc. The decoupled core and main body of the galaxy have the same luminosity-weighted age, of  14 Gyr, and the same elevated magnesium-to-iron ratio. The two kinematically distinct components have thus shared a common star formation history. We infer that the galaxy underwent a sequence of mergers associated with dissipative star formation that ended >12 Gyr ago. The misalignment between the photometric and kinematic axes of the main body is unambiguous evidence of triaxiality. The similarity of the stellar populations in the two components suggests that the observed kinematic structure has not changed substantially in 12 Gyr. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011254v1.pdf"}
{"id": "astro-ph0011405", "abstract": "  We carry out ray tracing through five high resolution simulations of a galaxy cluster to study how its ability to produce giant gravitationally lensed arcs is influenced by the collision cross-section of its dark matter. In three cases typical dark matter particles in the cluster core undergo between 1 and 100 collisions per Hubble time; two more explore the long (“collisionless”) and short (“fluid”) mean free path limits. We study the size and shape distributions of arcs and compute the cross-section for producing “extreme” arcs of various sizes. Even a few collisions per particle modify the core structure enough to destroy the cluster's ability to produce long, thin arcs. For larger collision frequencies the cluster must be scaled up to unrealistically large masses before it regains the ability to produce giant arcs. None of our models with self-interacting dark matter (except the “fluid” limit) is able to produce radial arcs; even the case with the smallest scattering cross-section must be scaled to the upper limit of observed cluster masses before it produces radial arcs. Apparently the elastic collision cross-section of dark matter in clusters must be very small, below 0.1 cm^2 g^-1, to be compatible with the observed ability of clusters to produce both radial arcs and giant arcs. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011405v2.pdf"}
{"id": "astro-ph0011557", "abstract": "  We outline here the next generation of cluster-finding algorithms. We show how advances in Computer Science and Statistics have helped develop robust, fast algorithms for finding clusters of galaxies in large multi-dimensional astronomical databases like the Sloan Digital Sky Survey (SDSS). Specifically, this paper presents four new advances: (1) A new semi-parametric algorithm - nicknamed “C4” - for jointly finding clusters of galaxies in the SDSS and ROSAT All-Sky Survey databases; (2) The introduction of the False Discovery Rate into Astronomy; (3) The role of kernel shape in optimizing cluster detection; (4) A new determination of the X-ray Cluster Luminosity Function which has bearing on the existence of a “deficit” of high redshift, high luminosity clusters. This research is part of our “Computational AstroStatistics” collaboration (see Nichol et al. 2000) and the algorithms and techniques discussed herein will form part of the “Virtual Observatory” analysis toolkit. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011557v1.pdf"}
{"id": "astro-ph0012121", "abstract": "  The issue of a starburst-AGN connection in local and distant galaxies is relevant for understanding galaxy formation and evolution, the star formation and metal enrichment history of the universe, the origin of the extragalactic background at low and high energies, and the origin of nuclear activity in galaxies. Here I review some of the observational evidence recently brought forward in favor of a connection between the starburst and AGN phenomena. I conclude by raising a number of questions concerning the exact nature of this connection. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0012/0012121v1.pdf"}
{"id": "astro-ph0012181", "abstract": "  In this work we analyse the role of low- and intermediate-mass stars in contributing to the chemical enrichment of the interstellar medium. First we present new sets of stellar yields basing on the results of updated evolutionary calculations, which extend from the ZAMS up to the end of the AGB phase (Girardi et al. 2000; Marigo et al. 1999a). These new yields, that present a significant dependence on metallicity, are then compared to those of other available sets (Renzini     Voli 1981; van de Hoek     Groenewegen 1997). The resulting differences are explained in terms of different model assumptions – i.e. treatment of convective boundaries, mass loss, dredge-up, hot-bottom burning –, and further discussed on the basis of important empirical constraints which should be reproduced by theory – i.e. the initial-final mass relation, white dwarf mass distribution, carbon star luminosity function, and chemical abundances of planetary nebulae. We show that present models are able to reproduce such constraints in a satisfactory way. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0012/0012181v1.pdf"}
{"id": "astro-ph0012389", "abstract": "  We present colour-magnitude diagrams for two rich ( 10^4 Msun) Large Magellanic Cloud star clusters with ages  10^7 years, constructed from optical and near-infrared data obtained with the Hubble Space Telescope. These data are part of an HST project to study LMC clusters with a range of ages. In this paper we investigate the massive star content of the young clusters, and determine the cluster ages and metallicities, paying particular attention to Be star and blue straggler populations and evidence of age spreads. We compare our data to detailed stellar population simulations to investigate the turn-off structure of  25 Myr stellar systems, highlighting the complexity of the blue straggler phenomenon. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0012/0012389v1.pdf"}
{"id": "astro-ph0101021", "abstract": "  Early data taken during commissioning of the SDSS have resulted in the discovery of a very cool white dwarf. It appears to have stronger collision induced absorption from molecular hydrogen than any other known white dwarf, suggesting it has a cooler temperature than any other. While its distance is presently unknown, it has a surprisingly small proper motion, making it unlikely to be a halo star. An analysis of white dwarf cooling times suggests that this object may be a low-mass star with a helium core. The SDSS imaging and spectroscopy also recovered LHS 3250, the coolest previously known white dwarf, indicating that the SDSS will be an effective tool for identifying these extreme objects. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0101/0101021v1.pdf"}
{"id": "astro-ph0101083", "abstract": "  We analyze the effects of lepton asymmetry on neutrino oscillations and on cosmological nucleosynthesis with active-sterile oscillating neutrinos. It is shown that small lepton asymmetries, L < 0.01, whose direct kinetic effect on nucleosynthesis is negligible, still effect nucleosynthesis considerably through their influence on oscillating neutrinos. Two different cases of lepton asymmetry are discussed: an initially present and a dynamically generated in oscillations. Dynamically generated in resonant oscillations asymmetry at small mixing angles suppresses oscillations, hence, the nucleosynthesis bounds on neutrino mass differences at small mixings are relaxed. Initially present asymmetry may suppress or enhance oscillations. The enhancement is a result of interchanging resonances between neutrino and antineutrino ensembles due to resonance waves passing through the neutrino and antineutrino spectrum. Updated nucleosynthesis bounds on neutrino oscillation parameters accounting for lepton asymmetry are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0101/0101083v1.pdf"}
{"id": "astro-ph0102251", "abstract": "  Collisionless N-body simulations of merging disk-galaxies with mass ratios (η) of 1:1, 2:1, 3:1, and 4:1 have been performed using direct summation with the special purpose hardware GRAPE. The simulations are used to examine whether the formation of elliptical galaxies can be explained in the context of the merger scenario. The photometric, kinematical and isophotal properties of the merger remnants are investigated and turn out to be in very good agreement with observations of giant elliptical galaxies. We conclude that equal mass mergers lead to slowly rotating, anisotropic remnants having predominantly boxy isophotes. Mergers with a mass ratio of 3:1 and 4:1, on the other hand, are fast isotropic rotators with disky isophotes. Projection effects can explain the observed scatter in the kinematical and isophotal properties of elliptical galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0102/0102251v1.pdf"}
{"id": "astro-ph0102390", "abstract": "  We discuss recent developments in the study of primordial black holes, focussing particularly on their formation and quantum evaporation. Such studies can place important constraints on models of the early Universe. An especially interesting development has been the realization that such constraints may be severely modified if the value of the gravitational \"constant\" G varies with cosmological epoch, a possibility which arises in many scenarios for the early Universe. The nature of the modification depends upon whether the value of G near a black hole maintains the value it had at its formation epoch (corresponding to gravitational memory) or whether it tracks the background cosmological value. This is still uncertain but we discuss various approaches which might help to resolve the issue. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0102/0102390v2.pdf"}
{"id": "astro-ph0103054", "abstract": "  We present the optical (V, R, and I) photometry for BL Lacertae, which was observed from 1997 through 1999, with the 1.56-m telescope at the Shanghai astronomical observatory (SHAO). After the 1997 outburst, it dimmed to a low state and then brightened again. During the period JD 2450701 to JD 2450701.5, variations of 0.40mag, 0.27mag, and 0.21mag over a time scale of 100 minutes were found for V, R, and I bands, suggesting that the variations were decreasing with wavelength.   The correlation between V, R, and I is also analyzed using the   DCF (Discrete Correlation Function) method. This shows that the variability in the V, R, and I bands are correlated with no time delay longer than 0.2 day. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0103/0103054v1.pdf"}
{"id": "astro-ph0104117", "abstract": "  Neutral hydrogen VLA D-array observations of the dwarf irregular galaxy HoII, a prototype galaxy for studies of shell formation and self-propagating star formation, are presented. The large-scale HI morphology is reminiscent of ram pressure and is unlikely caused by interactions. A case is made for intragroup gas in poor and compact groups similar to the M81 group, to which HoII belongs. Numerous shortcomings of the supernova explosions and stellar winds scenario to create the shells in HoII are highlighted, and it is suggested that ram pressure may be able to reconcile the numerous observations available. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0104/0104117v1.pdf"}
{"id": "astro-ph0105542", "abstract": "  We examine the early angular momentum history of stars in young clusters via 197 photometric periods in the Orion Flanking Fields, 83 photometric periods in NGC 2264, and 256 measurements of v sin i in the ONC. We show that PMS stars, even those without observable disks, apparently do not conserve stellar angular momentum as they evolve down their convective tracks, but instead evolve at nearly constant angular velocity. This result is inconsistent with expectations that convective stars lacking disks should spin up as they contract, but paradoxically consistent with disk-locking models. We briefly explore possible resolutions, including disk locking, birthline effects, stellar winds, and planetary companions. We have found no plausible explanations for this paradox. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0105/0105542v1.pdf"}
{"id": "astro-ph0107193", "abstract": "  The capture and gradual inspiral of stellar mass objects by a massive black hole at the centre of a galaxy has been proposed as one of the most promising source of gravitational radiation to be detected by LISA. Unfortunately rate estimates for this process suffer from many uncertainties. Here we report on the use of our newly developed Monte Carlo stellar dynamics code to tackle this problem. We present results from simple galactic nuclei models that demonstrate the high potential of our approach and point out the aspects of the problem where an improved treatment seems desirable. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0107/0107193v1.pdf"}
{"id": "astro-ph0107315", "abstract": "  Protostellar jets and winds are probably driven magnetocentrifugally from the surface of accretion disks close to the central stellar objects. The exact launching conditions on the disk, such as the distributions of magnetic flux and mass ejection rate, are poorly unknown. They could be constrained from observations at large distances, provided that a robust model is available to link the observable properties of the jets and winds at the large distances to the conditions at the base of the flow. We discuss the difficulties in constructing such large-scale wind models, and describe a novel technique which enables us to numerically follow the acceleration and propagation of the wind from the disk surface to arbitrarily large distances and the collimation of part of the wind into a dense, narrow “jet” around the rotation axis. Special attention is paid to the shape of the jet and its mass flux relative to that of the whole wind. The mass flux ratio is a measure of the jet formation efficiency. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0107/0107315v1.pdf"}
{"id": "astro-ph0107569", "abstract": "  The orientation of a massive binary undergoes a random walk due to gravitational encounters with field stars. The rotational diffusion coefficient for a circular-orbit binary is derived via scattering experiments. The binary is shown to reorient itself by an angle of order (m/M)^1/2 during the time that its semi-major axis shrinks appreciably, where M is the binary mass and m the perturber mass. Implications for the orientations of rotating black holes are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0107/0107569v2.pdf"}
{"id": "astro-ph0108385", "abstract": "  The main inference from the experiments of the '80s that the time-averaged energy spectra of pulsars had to steepen in the GeV-TeV energy region has been reinforced in the '90s from experiments with higher sensitivities. However, results from several experiments from the past and the more sensitive experiments at present can be reconciled by invoking a possibly different component arising in the TeV region. The results of the preliminary analysis of the data being collected with the PACT array will be presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0108/0108385v1.pdf"}
{"id": "astro-ph0108425", "abstract": "  Tunable imaging filters have been used for a variety of science programmes on the Anglo-Australian and William Herschel Telescopes during the last five years. This contribution describes these novel devices and reviews the science (both Galactic and extragalactic) done with them. Possible strategies for implementing a tunable filter at the VLT are also discussed. Significant scientific potential exists for a tunable filter on the VLT, particularly in the years before such capability becomes available on 8 – 10 m-class telescopes elsewhere. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0108/0108425v1.pdf"}
{"id": "astro-ph0109209", "abstract": "  Weak magnetism increases antineutrino mean free paths in core collapse supernovae. The parity violating interference between axial and vector currents makes antineutrino-nucleon cross sections smaller then those for neutrinos. We calculate simple, exact correction factors to include recoil and weak magnetism in supernova simulations. Weak magnetism may significantly increase the neutrino energy flux. We calculate, in a diffusion approximation, an increase of order 15", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0109/0109209v2.pdf"}
{"id": "astro-ph0109268", "abstract": "  XMM-Newton has been performing comprehensive studies of X-ray bright RS CVn binaries in its Calibration and Guaranteed Time programs. We present results from ongoing investigations in the context of a systematic study of coronal emission from RS CVns. We concentrate in this paper on coronal abundances and investigate the abundance pattern in RS CVn binaries as a function of activity and average temperature. A transition from an Inverse First Ionization Potential (FIP) effect towards an absence of a clear trend is found in intermediately active RS CVn systems. This scheme corresponds well into the long-term evolution from an IFIP to a FIP effect found in solar analogs. We further study variations in the elemental abundances during a large flare. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0109/0109268v1.pdf"}
{"id": "astro-ph0109344", "abstract": "  We describe systematic changes in the centroid frequencies and the splitting coefficients as found using data from MDI on board SOHO, covering cycle 23. The data allow us to construct a seismic map of the evolving solar activity – covering all latitudes. At lower latitudes, the temporal evolution closely tracks that of butterfly diagram. The additional information from higher latitudes in the map is of a significant activity in the polar region, peaking at activity minimum in 1996. The most plausible source of solar oscillation frequency changes over the solar cycle is the evolution of the radial component of the small-scale magnetic field. The amplitude of the required mean field changes is about 100 G at the photosphere, and increasing going inward. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0109/0109344v1.pdf"}
{"id": "astro-ph0109501", "abstract": "  We study an effect of inhomogeneity of density distribution of the Universe. We propose a new Lagrangian perturbation theory with a backreaction effect by inhomogeneity. The inhomogeneity affects the expansion rate in a local domain and its own growing rate. We numerically analyze a one-dimensional plane-symmetric model, and calculate the probability distribution functions (PDFs) of several observed variables to discuss those statistical properties. We find that the PDF of pairwise peculiar velocity shows an effective difference from the conventional Lagrangian approach, i.e. even in one-dimensional plane symmetric case, the PDF approaches an exponential form in a small relative-velocity region, which agree with the N-body simulation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0109/0109501v1.pdf"}
{"id": "astro-ph0110033", "abstract": "  We present a new method of image cleaning for imaging atmospheric Cherenkov telescopes. The method is based on the utilization of wavelets to identify noise pixels in images of gamma-ray and hadronic induced air showers. This method selects more signal pixels with Cherenkov photons than traditional image processing techniques. In addition, the method is equally efficient at rejecting pixels with noise alone. The inclusion of more signal pixels in an image of an air shower allows for a more accurate reconstruction, especially at lower gamma-ray energies that produce low levels of light. We present the results of Monte Carlo simulations of gamma-ray and hadronic air showers which show improved angular resolution using this cleaning procedure. Data from the Whipple Observatory's 10-m telescope are utilized to show the efficacy of the method for extracting a gamma-ray signal from the background of hadronic generated images. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0110/0110033v1.pdf"}
{"id": "astro-ph0110151", "abstract": "  We report the detection of a new radio transient source, GCRT J1746-2757, located only 1.1 degrees north of the Galactic center. Consistent with other radio transients toward the Galactic center, this source brightened and faded on a time scale of a few months. No X-ray counterpart was detected. We also report new 0.33 GHz measurements of the radio counterpart to the X-ray transient source, XTE J1748-288, previously detected and monitored at higher radio frequencies. We show that the spectrum of XTE J1748-288 steepened considerably during a period of a few months after its peak. We also discuss the need for a more efficient means of finding additional radio transients. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0110/0110151v1.pdf"}
{"id": "astro-ph0110290", "abstract": "  Comparison of the observed evolution of the Ly-alpha transmitted flux in the spectra of four highest redshift quasars discovered by SLOAN survey with the theoretical prediction for this evolution based on the state-of-the-art numerical simulations of cosmological reionization already allows one to constrain the redshift of reionization to z = 6.2 +- 0.1s +- 0.2r, where systematic and random errors are given respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0110/0110290v1.pdf"}
{"id": "astro-ph0110312", "abstract": "  Light curve analysis of decay phase of nova outburst are summarized. Nova duration is determined by the strong wind mass-loss which depends only on the white dwarf mass. Fast novae correspond very massive white dwarfs and very slow novae correspond almost lower mass limit of white dwarfs. This relation is shown in both of classical novae and recurrent novae. Light curves are theoretically reproduced for recurrent novae, U Sco, V394 CrA, CI Aql, V2487 Oph, RS Oph, T CrB, V745 Sco and V3890 Sgr, using binary model composed of a white dwarf, an irradiated accretion disk, and partly irradiated companion which is shadowed by the accretion disk. From the light curve fitting, we conclude that most of these objects contain a very massive white dwarf close to the Chandrasekhar mass limit (1.37 M_for U Sco, V394 CrA T CrB and RS Oph, 1.35 M_for V2487 Oph, V3890 Sgr and V745 Sco). They are strong candidates of type Ia SN progenitors. Population II novae have trends of slow evolution and small expanding velocity compared with disk novae. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0110/0110312v1.pdf"}
{"id": "astro-ph0110619", "abstract": "  We report the discovery of possible infrared counterparts to SGR 1806-20. We use archival Chandra observations to determine the location of SGR 1806-20 to <1 accuracy. We then locate 2 infrared objects within this error circle in K-band (2.2 μm) images of this field. Based on the X-ray absorption towards SGR 1806-20 and the extinction towards the nearby star cluster, we discuss the likelihood of association for the possible counterparts, and the implications for SGR 1806-20's physical properties and origins. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0110/0110619v1.pdf"}
{"id": "astro-ph0111045", "abstract": "  We review what has been learned recently using N-body simulations about the evolution of globular clusters. While simulations of star clusters have become more realistic, and now include the evolution of single and binary stars, the prospect of reaching large enough N is still a distant one. Nevertheless more restricted kinds of simulations have recently brought valuable progress for certain problems of current observational interest, including the origin and structure of tidal tails of globular clusters. In addition, such simulations have forced us to rethink some basic aspects of stellar dynamics, including, in particular, the process of escape. Finally we turn to faster, approximate methods for studying star cluster dynamics, where the role of N-body simulations is one of calibration. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0111/0111045v1.pdf"}
{"id": "astro-ph0111103", "abstract": "  Our knowledge of the initial conditions and early stages of high mass star formation is very limited. We will review recent surveys of regions in the early stages of massive star formation using molecular tracers of high density and dust continuum emission and consider the status of evolutionary schemes. Comparison to the situation for low mass, relatively isolated star formation will be used to illustrate the outstanding issues in massive star formation. The problem of initial conditions is particularly acute because there is a lack of observational evidence for regions capable of forming massive stars BEFORE star formation actually begins. By analogy with the Pre-Protostellar Cores (PPCs) studied for low-mass star formation, one might call such regions Pre-Proto-cluster Cores (PPclCs). We will conclude with some speculation about what such cores might look like and possibilities for their detection. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0111/0111103v1.pdf"}
{"id": "astro-ph0111453", "abstract": "  We present numerical simulations of gravito-inertial waves propagating in radiative zones of rapidly rotating stars. A first model, using the Boussinesq approximation, allows us to study the oscillations of a quasi-incompressible stratified fluid embedded in a rapidly rotating sphere or spherical shell. In a second step, we investigate the case of a Gamma-Doradus star using the anelastic approximation. Some fascinating features of rapidly rotating fluids, such as wave attractors, appear in both cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0111/0111453v1.pdf"}
{"id": "astro-ph0111464", "abstract": "  Using the Chandra High Energy Transmission Grating Spectrometer (HETGS), we have found significant absorption features in the X-ray spectrum of Cyg X-1 taken in the continuous clocking mode. These features include resonance lines of He-like ions of S, Si, and Mg; the Ly alpha lines of H-like S, Si, Mg, and Ne; and several lower ionization lines of Fe XX, XXII, and XXIV. Preliminary analysis shows that the lines are resolved in many cases, giving line widths of order 300 km/s and are redshifted by 460 +/- 10 km/s. These features are interpreted in the context of an accreting stellar wind model that is ionized by the X-ray source. In addition, there are clear absorption features due to neutral Mg, Fe, and O in the interstellar medium. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0111/0111464v1.pdf"}
{"id": "astro-ph0111497", "abstract": "  The spectra of disc accreting neutron stars generally show complex curvature, and individual components from the disc, boundary layer and neutron star surface cannot be uniquely identified. Here we show that much of the confusion over the spectral form derives from inadequate approximations for comptonization and for the iron line. There is an intrinsic low energy cutoff in comptonised spectra at the seed photon energy. It is very important to model this correctly in neutron star systems as these have expected seed photon temperatures (from either the neutron star surface, inner disc or self-absorbed cyclotron) of  1 keV, clearly within the observed X-ray energy band. There is also reflected continuum emission which must accompany the observed iron line, which distorts the higher energy spectrum. We illustrate these points by a reanalysis of the GINGA spectra of Cyg X-2 at all points along its Z track, and show that the spectrum can be well fit by models in which the low energy spectrum is dominated by the disc, while the higher energy spectrum is dominated by comptonised emission from the boundary layer, together with its reflected spectrum from a relativistically smeared, ionised disc. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0111/0111497v1.pdf"}
{"id": "astro-ph0112124", "abstract": "  If a gravitational microlensing event is caused by a widely separated binary lens and the source approaches both lens components, the source flux is successively magnified by the individual lenses: double microlensing events. If events are observed astrometrically, double lensing events are expected to occur with an increased frequency due to the long range astrometric effect of the companion. We find that although the trajectory of the source star image centroid shifts of an astrometric double lensing event has a distorted shape from both of the elliptical ones induced by the individual single lens components, event duplication can be readily identified by the characteristic loop in the trajectory formed during the source's passage close to the companion. We determine and compare the probabilities of detecting double lensing events from both photometric and astrometric lensing observations by deriving analytic expressions for the relations between binary lensing parameters to become double lensing events. From this determination, we find that for a given set of the binary separation and the mass ratio the astrometric probability is roughly an order higher than the photometric probability. Therefore, we predict that a significant fraction of events that will be followed up by using future high precision interferometeric instruments will be identified as double lensing events. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0112/0112124v1.pdf"}
{"id": "astro-ph0112171", "abstract": "  In this talk I will present a model for primordial galaxy formation. In particular, I will review the feedback effects that regulate the process: (i) radiative (i.e. ionizing and H_2-photodissociating photons) and (ii) stellar (i.e. SN explosions) feedback produced by massive stars. I will show the results of a model for galaxy formation and IGM reionization, which includes a self-consistent treatment of the above feedback effects. Finally, I will describe a Monte Carlo method for the radiative transfer of ionizing photons through the IGM and discuss its application to the IGM reionization problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0112/0112171v1.pdf"}
{"id": "astro-ph0112218", "abstract": "  We examine linear and quasi-liner stages of Cherenkov-drift instability in the relativistic magnetized electron-positron plasma. The external magnetic field lines are assumed to be slightly curved. In this case the curvature drift of relativistic beam particles plays decisive role in the development of the instability. Quasi-linear relaxation of the relativistic beam leads to diffusion of the resonant particles in the momenta space. The expressions for diffusion coefficients of Cherenkov-drift instability are obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0112/0112218v1.pdf"}
{"id": "astro-ph0112415", "abstract": "  Recent observational results obtained with SCUBA, COBE and ISO have greatly improved our knowledge of the infrared and sub-mm background radiation. These limits become constraining given the realization that most AGNs are heavily obscured and must reradiate strongly in the IR/sub-mm. Here we predict the contribution of AGNs to the IR/sub-mm background, starting from measurements of the hard X-ray background. We show that an application of what we know of AGN Spectral Energy Distributions (SEDs) and the IR background requires that a significant fraction of the 10-150 micron background comes from AGNs. This conclusion can only be avoided if obscured AGNs are intrinsically brighter in the X-rays (with respect to the optical-UV) than unobscured AGNs, contrary to “unified schemes” for AGNs, or have a dust to gas ratio much lower (< 0.1) than Galactic. We show that these results are rather robust and not strongly dependent on the details of the modeling. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0112/0112415v1.pdf"}
{"id": "astro-ph0201246", "abstract": "  In October 1997, the Italian and Dutch GRB teams started a collaboration on ESO optical follow-up of rapidly and accurately localized GRBs. Subsequently, starting April 1, 2000, this collaboration was extended to astronomers from other countries, who contributed their expertise for the creation of a Consortium committed to the study of GRB counterparts and host galaxies at optical and near-infrared wavelengths. The collaboration aims at the joint exploitation of the observations taken within an ESO Large Programme approved for the two-year period April 1, 2000 - March 31, 2002. Here we describe history and organization of this Consortium, the goals of the ESO Large Programme, and the main results obtained up to now with ESO telescopes. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0201/0201246v1.pdf"}
{"id": "astro-ph0203261", "abstract": "  We present new results on RR Lyrae stars and anomalous Cepheids in the Draco dwarf spheroidal galaxy. We have increased the number of double-mode RR Lyrae stars and found three new anomalous Cepheids. With period-magnitude and period-amplitude diagrams, we discuss the Oosterhoff classification of Draco. Contradictory results were found in that Draco appears to contain both Oosterhoff I and II type RR Lyrae populations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0203/0203261v1.pdf"}
{"id": "astro-ph0204168", "abstract": "  The VLTI is the ideal instrument for measuring the distances of nearby Cepheids with the Baade-Wesselink method, allowing an accurate recalibration of the Cepheid Period-Luminosity relation. The high accuracy required by such measurement, however, can only be reached taking into account the effects of limb darkening, and its dependence on the Cepheid pulsations. We present here our new method to compute phase- and wavelength-dependent limb darkening profiles, based on hydrodynamic simulation of Classical Cepheid atmospheres. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0204/0204168v1.pdf"}
{"id": "astro-ph0205016", "abstract": "  We derive the pairwise peculiar velocity distribution function of dark matter particles applying the dark matter halo approach. Unlike the previous work, we do not assume a Gaussian velocity distribution function of dark matter in a single halo, but compute it self-consistently with the assumed density profile for dark matter halo. The resulting distribution function is well approximated by an exponential distribution which is consistent with the previous observational, numerical and theoretical results. We also compute the pairwise peculiar velocity dispersion for different density profiles, and provide a practical fitting formula. We apply an empirical biasing scheme into our model and present prediction for pairwise peculiar velocity dispersion of galaxies, and reproduce the previous results of simulations using our semi-analytical method. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0205/0205016v1.pdf"}
{"id": "astro-ph0205033", "abstract": "  AAT/WFI optical images of a candidate extragalactic HI cloud, HIPASS J1712-64, are presented. The g and r-band CCD mosaic camera frames were processed using a new data pipeline recently installed at the AAO. The resultant stacked images reach significantly deeper levels than those of previous published optical imaging of this candidate, providing a detection limit M_g -7 at a distance of 3Mpc, the inferred distance to HIPASS J1712-64. However, detailed analysis of the images fails to uncover any stellar population associated with the HI emission. If this system is a member of the Local Group then it is pathologically different to other members. Hence, our observations reinforce earlier suggestions that this HI cloud is most likely Galactic in origin and not a Local Volume dwarf galaxy. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0205/0205033v1.pdf"}
{"id": "astro-ph0205078", "abstract": "  The use of wide-field multi-object fiber-input spectrographs for large redshift surveys introduces the possibility of variations in the observed signal-to-noise ratio across the survey area due to errors in positioning the fibers with respect to the target image positions, leading to position-dependent errors in the survey catalog. This paper brings together a comprehensive description of the sources of fiber-to-image position errors in different instrument designs, and quantifies their effects on the efficiency with which signal is recorded. For point sources, a function relating a fractional efficiency and an equivalent aperture correction to the fiber-to-image position error, the fiber diameter and the image size is plotted for typical values of fiber and image sizes found in current instruments. The tools required by observers to maximize the efficiency of fiber-spectrographic surveys are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0205/0205078v2.pdf"}
{"id": "astro-ph0205240", "abstract": "  We present a set of cluster models that link the present-day properties of clusters to the processes that govern galaxy formation. These models treat the entropy distribution of the intracluster medium as its most fundamental property. Because convection strives to establish an entropy gradient that rises with radius, the observable properties of a relaxed cluster depend entirely on its dark-matter potential and the entropy distribution of its uncondensed gas. Guided by simulations, we compute the intracluster entropy distribution that arises in the absence of radiative cooling and supernova heating by assuming that the gas-density distribution would be identical to that of the dark matter. The lowest-entropy gas would then fall below a critical entropy threshold at which the cooling time equals a Hubble time. Radiative cooling and whatever feedback is associated with it must modify the entropy of that low-entropy gas, changing the overall entropy distribution function and thereby altering the observable properties of the cluster. Using some phenomenological prescriptions for entropy modification based on the existence of this cooling threshold, we construct a remarkably realistic set of cluster models. The surface-brightness profiles, mass-temperature relation, and luminosity-temperature relation of observed clusters all naturally emerge from these models. By introducing a single adjustable parameter related to the amount of intracluster gas that can cool within a Hubble time, we can also reproduce the observed temperature gradients of clusters and the deviations of cooling-flow clusters from the standard luminosity-temperature relation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0205/0205240v1.pdf"}
{"id": "astro-ph0205433", "abstract": "  We have obtained near-infrared images and spectra of three blue compact dwarf galaxies of intermediate sub-solar metallicity Tol 35, Tol 3 and UM 462. This work is part of a larger project aimed to study the star formation and the stellar populations of low metallicity galaxies in the near-infrared. In this frame work galaxies of intermediate metallicity represent an important step in understanding the most extreme cases filling the gap between solar and very low metallicity galaxies. We have observed HII region like spectra in all three galaxies; in all cases the star formation episodes are only a few Myr old. Consistently with a young age our spectra show no evidence for stellar absorption features typical of supergiants, nor of [FeII] emission typical of supernovae. The K-band gas fraction ranges from 20 to 40 ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0205/0205433v2.pdf"}
{"id": "astro-ph0206021", "abstract": "  The Time-of-Flight (TOF) system of the AMS detector gives the fast trigger to the read out electronics and measures velocity, direction and charge of the crossing particles. The first version of the detector (called AMS-01) has flown in 1998 aboard of the shuttle Discovery for a 10 days test mission, and collected about 10^8 events. The new version (called AMS-02) will be installed on the International Space Station and will operate for at least three years, collecting roughly 10^10 Cosmic Ray (CR) particles. The TOF system of AMS-01 successfully operated during the test mission, obtaining a time resolution of 120 ps for protons and better for other CR ions. The TOF system of AMS-02 will be different due to the strong fringing magnetic field and weight constraints ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0206/0206021v2.pdf"}
{"id": "astro-ph0207232", "abstract": "  We present the follow-up of three medium redshift galaxy clusters from the SHARC survey observed with XMM-Newton. We studied RX J0256.5+0006 which shows two components which are very likely in interaction. The smallest component exhibits a comet-like structure indicating ram pressure stripping as it falls onto the main cluster. The second cluster, RX J2237.0-1516 is an elliptical cluster with a gas temperature of 3.0±0.5 keV. The third cluster, RX J1200.8-0328 seems to be in a relaxed state because its shape is regular and we do not see obvious temperature gradient. Its mean temperature is 5.1^+0.7_-0.5 keV. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0207/0207232v1.pdf"}
{"id": "astro-ph0207336", "abstract": "  I present the latest results from a search for hot molecular cores at mid-infrared wavelengths from the largest optical telescopes available at the present time. Three well-observed hot molecular cores were imaged, G29.96-0.02, G19.61-0.23, and G34.26+0.15. Even though mid-infrared sources have been claimed to be detected previously at the hot molecular core locations of both G19.61-0.23 and G34.26+0.15, only the hot molecular core in G29.96-0.02 resulted in a detection. New upper limits on mid-infrared emission are given for the hot molecular cores that were not detected. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0207/0207336v1.pdf"}
{"id": "astro-ph0208023", "abstract": "  We present predictions for two statistical measures of the hydrogen reionization process at high redshift. The first statistic is the number of neutral segments identified in spectra of high redshift QSOs as a function of their length. The second is the cross-correlation of neutral regions with possible sources of ionizing radiation. These independent probes are sensitive to the topology of the ionized regions. If reionization proceeded from high to low density regions then the cross-correlation will be negative, while if voids were ionized first then we expect a positive correlation and a relatively small number of long neutral segments. We test the sensitivity of these statistics for reionization by stars in high redshift galaxies. The flux of ionizing radiation emitted from stars is estimated by identifying galaxies in an N-body simulation using a semi-analytic galaxy formation model. The spatial distribution of ionized gas is traced in various models for the propagation of the ionization fronts. A model with ionization proceeding from high to low density regions is consistent with the observations of Becker et al. (2001), while models in which ionization begins in the lowest density regions appear to be inconsistent with the present data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0208/0208023v1.pdf"}
{"id": "astro-ph0208053", "abstract": "  Mass segregation in a star cluster is studied in an analytical manner. We consider a two-component cluster, which consists of two types of stars with different masses. Plummer's model is used for the initial condition. We trace the overall behaviors of the probability distribution functions of the two components and obtain the timescale of mass segregation as a simple function of the cluster parameters. The result is used to discuss the origin of a black hole with mass of > 1000 M(sun) found in the starburst galaxy M82. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0208/0208053v1.pdf"}
{"id": "astro-ph0208351", "abstract": "  Weak gravitational lensing provides a direct way to study the mass distribution of clusters of galaxies at large radii. Unfortunately, large scale structure along the line of sight also contributes to the lensing signal, and consequently affects the measurements. We quantify the effect of distant uncorrelated large scale structure on the inferred mass profile of clusters as measured from weak lensing. We consider NFW profiles, and find that large scale structure is a major source of uncertainty for most practical situations, when a model, with the mass M_200 and the concentration parameter c as free parameters, is fit to the observations. We find that the best constraints are found for clusters at intermediate redshifts (z 0.3). For a cluster at z=0.3, optimal results are obtained when the lensing signal is measured out to 10-15 arcminutes. Measurements at larger radii do not improve the accuracy with which the profile can be determined, contrary to what is expected when the contribution from large scale structure is ignored. The true uncertainties in M_200 and the concentration parameter c are  2 times larger than when distant large scale structure is not included in the error budget. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0208/0208351v1.pdf"}
{"id": "astro-ph0209015", "abstract": "  A relativistic version of Pauli paramagnetism for n-p-e system inside a strongly magnetized neutron star has been developed. An analytical expressions for the saturation value of magnetic field strength for each of these constituents at which they are completely polarized have been obtained. From the fully polarized configuration of electronic component, an upper limit for neutron star magnetic field is predicted. It has been concluded that indeed, magnetars, as stronly magnetized young neutron stars can not exist if the constituents are electron, proton and neutron in β-equilibrium. An alternative model has been proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0209/0209015v1.pdf"}
{"id": "astro-ph0209230", "abstract": "  The distant globular cluster Palomar 13 has been found to have a very high mass-to-light ratio and its profile can be well fitted either by a King model with a tail, or with a NFW model. This cluster may be the first case of the many clumps predicted by CDM simulations that would not be disrupted by the galactic halo potential. We make the hypothesis that Pal 13 is made of neutralinos and run the DarkSuspect code to estimate the high-energy photon flux due to the annihilation of neutralinos through various channels in some benchmark scenarios. These low fluxes may be used as targets to be reached in proposals for future ground-based high altitude Cerenkov telescopes. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0209/0209230v1.pdf"}
{"id": "astro-ph0211099", "abstract": "  We report the first measurement of genus curves for the two-dimensional mass map in the neighborhood of rich, X-ray luminous galaxy cluster MS1054-03 at z=0.83, reconstructed from weak lensing data obtained by Suprime-Cam on the prime focus of 8.2m Subaru telescope. We find that the genus curve measured in the whole survey field deviates from that expected from a random Gaussian field. We show that this non-Gaussianity is induced by the rich cluster in this region, and that the genus curve for the region without the cluster is consistent with the prediction for a random Gaussian field. The results demonstrate the feasibility of the genus statistics to examine the non-Gaussianity due to the large scale structures and to probe the statistical properties of the large scale clustering. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0211/0211099v2.pdf"}
{"id": "astro-ph0211101", "abstract": "  We have observed the radio-quiet X-ray pulsar 1E 1207.4-5209 with the high throughput EPIC cameras onboard XMM-Newton. The spectrum of this peculiar source is characterized by two broad absorption features which present significant substructures and show a clear phase-dependence. We believe that these features represent a strong evidence for the presence of a magnetized atmosphere containing heavy elements. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0211/0211101v2.pdf"}
{"id": "astro-ph0211213", "abstract": "  I examine simple tests for the presence of accretion disks in AGN - changes of surface brightness with viewing angle, changes of colour temperature with luminosity, and behaviour during variability. AGN observations pass the first two tests but fail the third, unless there is some previously unobserved source of heating - the “ghost in the machine”. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0211/0211213v1.pdf"}
{"id": "astro-ph0211565", "abstract": "  Emission lines in ionized nebulae can provide strong and useful constraints on the properties of both ionizing and non-ionizing stellar populations in regions with star formation, provided that stellar evolution and stellar atmosphere models can be used in a selfconsistent way. Recently, the application of these techniques has shown important discrepancies between predicted and observed nebular spectra that point to stellar atmosphere models of WR stars which are too energetic and/or to a significant leakageof high energy photons. In this contribution, these two alternatives are analyzed in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0211/0211565v1.pdf"}
{"id": "astro-ph0211632", "abstract": "  The atmospheric muon and neutrino flux have been simulated using the same approach which successfully accounted for the recent secondary proton, electron and positron flux measurements in orbit by the AMS experiment. For the muon flux, a good agreement is obtained with the CAPRICE and HEAT data for altitudes ranging from sea level up to about 38 km. The general features of the calculated atmospheric neutrino flux are reported and discussed. The flux obtained at the Super-Kamiokande experiment location are reported and compared with other calculations. For low neutrino energies the flux obtained is significantly smaller than that used in the data analysis of underground experiment. The simulation results for the SOUDAN experiment site are also reported. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0211/0211632v2.pdf"}
{"id": "astro-ph0212090", "abstract": "  We have developed a timing analysis method to determine the distances of variable galactic X-ray sources based on the method advanced by Trümper and Schönfelder in 1973. The light-curve of the halo produced by the scattering of X-rays off the interstellar dust is delayed and smeared by the dust grains. This method utilizes the differences between the power density spectra of the point source and the halo. We present the details of this method and our first applications of this method to the Chandra data of X-ray binary Cyg X-3. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0212/0212090v1.pdf"}
{"id": "astro-ph0212172", "abstract": "  Millimeter and mid-infrared observations have been made of the dense clumps of dust and gas and of young stellar objects (YSOs) associated with the bright, compact submillimeter source G79.3+0.3 P1 in the relatively nearby MSX infrared-dark cloud G79.3+0.3. The Gemini mid-infrared observations reported here indicate the presence of three YSOs within the cloud. BIMA 3 mm continuum observations show that the brightest of the YSOs is likely to be a Herbig Ae/Be star. High-angular-resolution molecular-line observations suggest that a wind from this star may be triggering collapse in the adjacent molecular cloud. The submillimeter source G79.3+0.3 P1 itself does not contain infrared sources and may represent an earlier stage of star formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0212/0212172v1.pdf"}
{"id": "astro-ph0212208", "abstract": "  The off-axis location of the Advanced Camera for Surveys (ACS) is the chief (but not sole) cause of strong geometric distortion in all detectors: the Wide Field Camera (WFC), High Resolution Camera (HRC), and Solar Blind Camera (SBC). Dithered observations of rich star cluster fields are used to calibrate the distortion. We describe the observations obtained, the algorithms used to perform the calibrations and the accuracy achieved. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0212/0212208v1.pdf"}
{"id": "astro-ph0301370", "abstract": "  Of the known pulsar wind nebulae, 8 are good candidates for being in the early stage of evolution where the wind nebula is interacting with the freely expanding supernova ejecta. Several of these have been identified with historical supernovae. Although the identification of SN 1181 with 3C 58 has been thought to be relatively secure, the large size of the nebula, the amount of swept up mass, and the internal energy indicate a larger age. For G11.2-0.3, the nebular size and internal energy are consistent with the identification with the possible supernova of 386. Although the Crab Nebula appears to have approximate energy equipartition between particles and the magnetic field, the nebulae 3C 58 and MSH 15-52 appear to be particle dominated. The low magnetic field is consistent with models in which the nebulae are created by a shocked pulsar wind. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0301/0301370v2.pdf"}
{"id": "astro-ph0301640", "abstract": "  It is a known fact that a quintessence model with w_q < -1 fits the publicly available Super Nova (SN) type Ia data better than a model with cosmological constant or w_q > -1. Two types of models have this property: Scalar fields with unconventional kinetic term and models with cosmological constant and a slowly decaying Cold Dark Matter (CDM). In this work we investigate the possibility of replacing the cosmological constant in the latter models with gradual condensation of a scalar field produced during the decay of the CDM and present some preliminary results. The advantage of this class of models to the ordinary quintessence is that the evolution of the dark energy and CDM are correlated and cosmological coincidence problem is solved or at least reduced to the fine tuning of the coupling between decaying CDM and quintessence field i.e the Hierarchy problem. Here we show that for part of the parameter space these models are consistent with present estimation of cosmological parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0301/0301640v1.pdf"}
{"id": "astro-ph0302270", "abstract": "  We present Chandra X-ray monitoring of the M87 jet in 2002, which shows that the intensity of HST-1, an optical knot 0.8\" from the core, increased by a factor of two in 116 days and a factor of four in 2 yrs. There was also a significant flux decrease over two months, with suggestive evidence for a softening of the spectrum. From this variability behavior, we argue that the bulk of the X-ray emission of HST-1 comes from synchrotron emission. None of the other conceivable emission processes can match the range of observed characteristics. By estimating synchrotron model parameters for various bulk relativistic velocities, we demonstrate that a model with a Doppler factor, delta, in the range 2 to 5 fits our preliminary estimates of light travel time and synchrotron loss timescales. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0302/0302270v1.pdf"}
{"id": "astro-ph0302343", "abstract": "  Noise is a problem of major concern for N-body simulations of structure formation in the early Universe, of galaxies and plasmas. Here for the first time we use wavelets to remove noise from N-body simulations of disc galaxies, and show that they become equivalent to simulations with two orders of magnitude more particles. We expect a comparable improvement in performance for cosmological and plasma simulations. Our wavelet code will be described in a following paper, and will then be available on request. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0302/0302343v1.pdf"}
{"id": "astro-ph0303149", "abstract": "  With excellent angular resolution, good energy resolution and broad energy band, the Chandra ACIS is the best instrument for studying the X-ray halos around some galactic X-ray point sources caused by the dust scattering of X-rays in the interstellar medium. However, the direct images of bright sources obtained with ACIS usually suffer from severe pile-up. Making use of the fact that an isotropic image could be reconstructed from its projection into any direction, we can reconstruct the images of the X-ray halos from the data obtained with the HETGS and/or in CC mode. These data have no or less serious pile-up and enable us to take full advantage of the excellent angular resolution of Chandra. With the reconstructed high resolution images, we can probe the X-ray halos as close as 1” to their associated point sources. Applying this method to Cygnus X-1 observed with Chandra HETGS in CC mode, we derived an energy dependent radial halo flux distribution and concluded that, in a circular region (2' in radius) centered at the point source: (1) relative to the total intensity, the fractional halo intensity (FHI) is about 15", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0303/0303149v2.pdf"}
{"id": "astro-ph0303482", "abstract": "  We present a general formulation of special-relativistic magnetohydrodynamics and derive exact radially self-similar solutions for axisymmetric outflows from strongly magnetized, rotating compact objects. We generalize previous work by including thermal effects and analyze in detail the various forces that guide, accelerate, and collimate the flow. We demonstrate that, under the assumptions of a quasi-steady poloidal magnetic field and of a highly relativistic poloidal velocity, the equations become effectively time-independent and the motion can be described as a frozen pulse. We concentrate on trans-Alfvenic solutions and consider outflows that are super-Alfvenic throughout in the companion paper. Our results are applicable to relativistic jets in gamma-ray burst (GRB) sources, active galactic nuclei, and microquasars, but our discussion focuses on GRBs. We envision the outflows in this case to initially consist of a hot and optically thick mixture of baryons, electron-positron pairs, and photons. We show that the flow is at first accelerated thermally but that the bulk of the acceleration is magnetic, with the asymptotic Lorentz factor corresponding to a rough equipartition between the Poynting and kinetic-energy fluxes (i.e., 5̃0", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0303/0303482v1.pdf"}
{"id": "astro-ph0304203", "abstract": "  Several measurements of QSO-galaxy correlations have reported signals much larger than predictions of magnification by large-scale structure. We find that the expected signal depends stronly on the properties of the foreground galaxy population. On arcminute scales it can be either larger or smaller by a factor of two for different galaxy types in comparison with a linearly biased version of the mass distribution. Thus the resolution of some of the excess measurements may lie in examining the halo occupation properties of the galaxy population sampled by a given survey; this is also the primary information such measurements will provide.   We use the halo model of clustering and simulations to predict the magnification induced cross-correlations and errors for forthcoming surveys. With the full Sloan Digital Sky Survey the statistical errors will be below 1 percent for the galaxy-galaxy correlations and significantly larger for QSO-galaxy correlations. Thus accurate constraints on parameters of the galaxy halo occupation distribution can be obtained from small scale measurements and on the bias parameter from large scales. Since the lensing induced cross-correlation measures the first moment of the halo occupation number of galaxies, these measurements can provide the basis for interpreting galaxy clustering measurements which measure the second and higher order moments. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0304/0304203v2.pdf"}
{"id": "astro-ph0304506", "abstract": "  An improved way of taking off-source data for background determination in Cherenkov telescope observations is proposed. Generalizing the traditional concept of taking on-source/off-source observations of equal duration (e.g. 30 minutes ON followed by 30 minutes OFF), Faster Background Determination (FBD) permits an off-source observation with the same zenith angle distribution as the on-source observation to be obtained within less time. The method permits the on-source observation time to be maximized without compromising the quality of the background determination. It also increases the signal significance for strong sources. The only modification necessary in the data acquisition is a small change to the tracking algorithm. The only modification necessary in the data analysis is to introduce a time normalization which does not increase the systematic errors. The method could become the normal observing mode for Cherenkov telescopes when observing strong sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0304/0304506v1.pdf"}
{"id": "astro-ph0304522", "abstract": "  We use N-body simulations of star clusters to investigate the possible dynamical origins of the observed spread in core radius among intermediate-age and old star clusters in the Large Magellanic Cloud (LMC). Two effects are considered, a time-varying external tidal field and variations in primordial hard binary fraction. Simulations of clusters orbiting a point-mass galaxy show similar core radius evolution for clusters on both circular and elliptical orbits and we therefore conclude that the tidal field of the LMC has not yet significantly influenced the evolution of the intermediate-age clusters. The presence of large numbers of hard primordial binaries in a cluster leads to core radius expansion; however, the magnitude of the effect is insufficient to explain the observations. Further, the range of binary fractions required to produce significant core radius growth is inconsistent with the observational evidence that all the LMC clusters have similar stellar luminosity functions. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0304/0304522v1.pdf"}
{"id": "astro-ph0305042", "abstract": "  It is suggested that M31 was created by the early merger, and subsequent violent relaxation, of two or more massive metal-rich ancestral galaxies within the core of the Andromeda subgroup of the Local Group. On the other hand the evolution of the main body of the Galaxy appears to have been dominated by the collapse of a single ancestral object, that subsequently evolved by capturing a halo of small metal-poor companions. It remains a mystery why the globular cluster systems surrounding galaxies like M33 and the LMC exhibit such striking differences in evolutionary history. It is argued that the first generation of globular clusters might have been formed nearly simultaneously in all environments by the strong pressure increase that accompanied cosmic reionization. On the other hand subsequent generations of globulars may have formed during starbursts that were triggered by collisions and mergers of gas rich galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0305/0305042v2.pdf"}
{"id": "astro-ph0305373", "abstract": "  In helical hydromagnetic turbulence with an imposed magnetic field (which is constant in space and time) the magnetic helicity of the field within a periodic domain is no longer an invariant of the ideal equations. Alternatively, there is a generalized magnetic helicity that is an invariant of the ideal equations. It is shown that this quantity is not gauge invariant and that it can therefore not be used in practice. Instead, the evolution equation of the magnetic helicity of the field describing the deviation from the imposed field is shown to be a useful tool. It is demonstrated that this tool can determine steady state quenching of the alpha-effect. A simple three-scale model is derived to describe the evolution of the magnetic helicity and to predict its sign as a function of the imposed field strength. The results of the model agree favorably with simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0305/0305373v2.pdf"}
{"id": "astro-ph0306022", "abstract": "  We describe a high speed time-series CCD photometer for the prime focus of the 82-in (2.1 m) telescope at McDonald Observatory, and summarize the observational results we have obtained since it was placed into regular use in February, 2002. We compare this instrument with the three-channel time-series photometers we have previously used in the asteroseismological study of pulsating white dwarf stars, which used photomultiplier tubes (PMT) as the detectors. We find the CCD instrument is about 9 times more sensitive than the PMT instruments used on the same telescope for the same exposure time. We can therefore find and measure variable white dwarf stars some 2.4 magnitudes fainter than before, significantly increasing the number of such objects available for study. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0306/0306022v1.pdf"}
{"id": "astro-ph0306436", "abstract": "  Recent BeppoSAX observations of Arp 299, a powerful far-IR merging starburst system composed of IC 694 and NGC 3690, clearly unveiled for the first time in this system the presence of a strongly absorbed active galactic nucleus (AGN). However the system was not spatially resolved by BeppoSAX. Here we present the analysis of archival Chandra and (for the first time) XMM-Newton observations, which allow us to disentangle the X-ray emission of the two galaxies. The detection of a strong 6.4 keV line in NGC 3690 clearly demonstrates the existence of an AGN in this galaxy, while the presence of a strong 6.7 keV Fe-Kalpha line in the spectrum of IC 694 suggests that also this nucleus might harbor an AGN. This would be the second discovery of two AGNs in a merging system after NGC 6240. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0306/0306436v2.pdf"}
{"id": "astro-ph0306456", "abstract": "  As for other areas in modern astronomy, the SKA will revolutionize the field of pulsar astrophysics. Not only will new science be possible by the shear number of pulsars discovered, but also by the unique timing precision achievable with the SKA. The combination of both will not simply mean a continuation of the successes already achieved by using pulsars as fundamental tools of physics but the SKA will provide a new quality of science. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0306/0306456v1.pdf"}
{"id": "astro-ph0307448", "abstract": "  This paper reports positive detections of surface differential rotation on two rapidly rotating cool stars at several epochs, by using stellar surface features (both cool spots and magnetic regions) as tracers of the large scale latitudinal shear that distorts the convective envelope in this type of stars. We also report definite evidence that this differential rotation is different when estimated from cool spots or magnetic regions, and that it undergoes temporal fluctuations of potentially large amplitude on a time scale of a few years. We consider these results as further evidence that the dynamo processes operating in these stars are distributed throughout the convective zone rather than being confined at its base as in the Sun. By comparing our observations with two very simple models of the differential rotation within the convective zone, we obtain evidence that the internal rotation velocity field of the stars we investigated is not like that of the Sun, and may resemble that we expect for rapid rotators. We speculate that the changes in differential rotation result from the dynamo processes (and from the underlying magnetic cycle) that periodically converts magnetic energy into kinetic energy and vice versa. We emphasise that the technique outlined in this paper corresponds to the first practical method for investigating the large scale rotation velocity field within convective zones of cool active stars, and offers several advantages over asteroseismology for this particular purpose and this specific stellar class. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0307/0307448v1.pdf"}
{"id": "astro-ph0308023", "abstract": "  In the nuclear and particle astrophysics session of CIPANP 2003 we heard talks on a number of topics, focused for the most part into four broad areas. Here we outline the discussions of the standard cosmological model, dark matter searches, cosmic rays, and neutrino astrophysics. The robustness of theoretical and experimental programs in all of these areas is very encouraging, and we expect to have many questions answered, and new ones asked, in time for CIPANP 2006. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0308/0308023v1.pdf"}
{"id": "astro-ph0309073", "abstract": "  We present the first high-resolution N-Body/SPH simulations that follow the evolution of low surface brightness disk satellites in a primary halo containing both dark matter and a hot gas component. Tidal shocks turn the stellar disk into a spheroid with low v/σ and remove most of the outer dark and baryonic mass. In addition, by weakening the potential well of the dwarf, tides enhance the effect of ram pressure, and the gas is stripped down to radius three times smaller than the stellar component A very low gas/stars ratio results after several Gyr, similarly to what seen in dwarf spheroidal satellites of the Milky Way and M31. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0309/0309073v1.pdf"}
{"id": "astro-ph0309152", "abstract": "  This review covers hot cores in the context of high-mass star formation. After giving an overview of chemical processes and diversity during high-mass star formation, it reviews the `warm envelope' phase which probably precedes the formation of hot cores. Some recent determinations of the cosmic-ray ionization rate are discussed, as well as recent evidence for hot cores around low-mass stars. Routes for future hot core research are outlined. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0309/0309152v1.pdf"}
{"id": "astro-ph0309172", "abstract": "  We review several aspects of clusters of galaxies and their application to cosmology. We present first results of numerical simulations of the dynamics of the intra-cluster gas and of different interaction processes between cluster galaxies and the intra-cluster gas. In particular metallicity maps are very useful to determine the importance of the different interaction processes. Also mass determination methods and possible sources for uncertainties in the measurements are shown. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0309/0309172v1.pdf"}
{"id": "astro-ph0309173", "abstract": "  Using the data from the PCA and HEXTE on board the RXTE satellite, we investigate the evolution of the 3-200 keV spectra of the peculiar low mass X-ray binary (LMXB) Cir X-1 along the branches on its hardness-intensity diagram (HID) from the vertical horizontal branch (VHB), through the horizontal horizontal branch (HHB) and normal branch (NB), to the flaring branch (FB). We detect a power-law hard component in the spectra. It is found that the derived photon indices (Γ) of the power-law hard component are correlated with the position on the HID. The power-law component dominates the X-ray emission of Cir X-1 in the energy band higher than ∼ 20 keV. The fluxes of the power-law component are compared with those of the bremsstrahlung component in the spectra. A possible origin of the power-law hard component is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0309/0309173v1.pdf"}
{"id": "astro-ph0309285", "abstract": "  We present the results of a high angular resolution study of the BL Lac object Markarian 501 in the radio band. We consider data taken at 14 different epochs, ranging between 1.6 GHz and 22 GHz in frequency, and including new Space VLBI observations obtained on 2001 March 5 and 6 at 1.6 and 5 GHz. We study the kinematics of the parsec-scale jet and estimate its bulk velocity and orientation with respect to the line of sight. Limb brightened structure in the jet is clearly visible in our data and we discuss its possible origin in terms of velocity gradients in the jet. Quasi-simultaneous multi-wavelength observations allow us to map the spectral index distribution and to compare it to the jet morphology. Finally, we estimate the physical parameters of the parsec-scale jet. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0309/0309285v1.pdf"}
{"id": "astro-ph0310668", "abstract": "  Intrinsic absorbers are significant components of AGN environments that provide valuable information and interesting challenges. We present a very brief (and biased, and sometimes speculative) overview of intrinsic absorbers from the perspective of different absorption line classes. We also discuss ways of addressing and learning from the \"problem\" of partial coverage of the background light source, with some examples based on new high-resolution rest-frame UV spectra of quasars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0310/0310668v2.pdf"}
{"id": "astro-ph0311428", "abstract": "  A satisfactory understanding of the origin of the dependence of galaxy properties on their environment has remained, so far, out of reach. In the light of numerous observational results and substantial theoretical progress obtained for clusters of galaxies in the last years, a primary goal is to understand how the star formation activity depends on cluster substructure, i.e. on the merging/accretion history of a cluster. In this contribution we present a case in which it is possible to identify the cluster environment, and in particular the intracluster medium and the recent infall history of galaxies onto the cluster, as the cause for an abrupt change in the star formation histories of a subset of galaxies in the Coma cluster. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0311/0311428v1.pdf"}
{"id": "astro-ph0312477", "abstract": "  We present time-resolved photometry of two cataclysmic variables whose CCD photometric observations were obtained with the 1m telescope at the South African Astronomical Observatory in October 2002 and August 2003 and with the 1m telescope at Hoher List in Germany. Concerning MCT 2347-3144 we detect for the first time a period of 6.65h. For V1193 Ori the 3.96 h periodicity has for the first time been confirmed through time-resolved photometry. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0312/0312477v1.pdf"}
{"id": "astro-ph0401358", "abstract": "  We present the first contemporaneous 43GHz and 86GHz VLBI images of the v=1 J=2-1 and J=1-0 SiO masers in the Orion-KL nebula. Both maser species exhibit the same general morphology of earlier J=1-0 maser images which appear to trace the edges of a bi-polar conical outflow. Surprisingly, the J=2-1 masers form further from the central protostar than the J=1-0 masers, a fact not readily explained by current SiO maser pumping models. The average magnitude of offsets between corresponding regions of the two masing transitions is approximately 14", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0401/0401358v1.pdf"}
{"id": "astro-ph0401487", "abstract": "  Extending the theory we derived recently for HD209458b to different cases of strongly irradiated gaseous exoplanets, we have calculated the consistent evolution of the new transiting planet, OGLE-TR-56b, for its recently revised mass determination. The theory is shown to successfully reproduce the observed radius, for the proper age of the system. We also examine the dissipation of kinetic energy at the planet's internal adiabat due to atmospheric winds, and place constraints on the efficiency of this process. We show that a fraction ∼ 0.1 – 0.5", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0401/0401487v1.pdf"}
{"id": "astro-ph0402590", "abstract": "  We investigated the time lags and the evolution of the cross spectra of Z source GX 5-1, observed by the Rossi X-ray Timing Explorer (RXTE), when it is in the horizontal branch oscillations. We showed that the time lags of 3 horizontal branch oscillations are related to the position on the hardness intensity diagram. All of the three QPOs were shown to have hard time lags. However on the cross spectra, one is in a `dip', one in a `bump', the other has no so obvious characteristic. The time lags of two of the QPOs decrease with QPO's frequency, while the other has a trend increasing with its frequency. Moreover, in the normal branch, we found no significant time lags in the present observational data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0402/0402590v1.pdf"}
{"id": "astro-ph0403053", "abstract": "  We present the results of qualitative consideration of possible changes occurring during the transition from the hot accretion disc to the cool one. We argue the possible existence of one more type of spiral density waves in the inner part of the disc where gasdynamical perturbations are negligible. The mechanism of formation of such a wave as well as its parameters are considered. We also present the results of 3D gasdynamical simulation of cool accretion discs. These results confirm the hypothesis of possible formation of the spiral wave of a new, \"precessional\" type in the inner regions of the disc. Possible observational manifestations of this wave are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0403/0403053v1.pdf"}
{"id": "astro-ph0403438", "abstract": "  Of all pulsars known Vela has been one of the most productive in terms in understanding pulsars and their characteristics. We present the latest results derived from Australian telescopes. These include a more accurate pulsar distance, a more precise pulsar local space velocity, a new model of the spin up and the association of a radio nebula with the X-ray pulsar wind nebula. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0403/0403438v1.pdf"}
{"id": "astro-ph0404015", "abstract": "  The conditions that lead to self-regulated star formation, star bursts and the formation of massive stellar clusters are discussed. Massive stars have a strong impact on their environment, especially on the evolution of dwarf galaxies which are the building blocks of giant galaxies. Energy input by massive young clusters might help to solve some of the most important puzzles of galaxy formation: the cosmological substructure problem and the angular momentum problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0404/0404015v1.pdf"}
{"id": "astro-ph0404167", "abstract": "  We present three new binary pulsars discovered during a search for pulsations in 56 unidentified mid-latitude EGRET gamma-ray error boxes with the Parkes multibeam receiver. Timing observations of these sources is on-going with both the Parkes and the Green Bank telescopes. We discuss the place of these new systems in the population of binary pulsars and suggest that they are all somewhat atypical systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0404/0404167v1.pdf"}
{"id": "astro-ph0404366", "abstract": "  In the past few years, small scale anisotropy has become a primary focus in the search for source of Ultra-High Energy Cosmic Rays (UHECRs). The Akeno Giant Air Shower Array (AGASA) has reported the presence of clusters of event arrival directions in their highest energy data set. The High Resolution Fly's Eye (HiRes) has accumulated an exposure in one of its monocular eyes at energies above 10^(19.5) eV comparable to that of AGASA. However, monocular events observed with an air fluorescence detector are characterized by highly asymmetric angular resolution. A method is developed for measuring autocorrelation with asymmetric angular resolution. It is concluded that HiRes-I observations are consistent with no autocorrelation and that the sensitivity to clustering of the HiRes-I detector is comparable to that of the reported AGASA data set. Furthermore, we state with a 90", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0404/0404366v2.pdf"}
{"id": "astro-ph0404520", "abstract": "  The transport properties of dense stellar electron-proton plasma is studied following an exact relativistic formalism in presence of strong quantizing magnetic field. The variation of transport coefficients with magnetic field are found to be insensitive for the field strengths ≤ 10^17G, beyond which all of them abruptly go to zero. As a consequence, the electron-proton plasma behaves like a superfluid insulator in presence of ultra-strong magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0404/0404520v1.pdf"}
{"id": "astro-ph0405121", "abstract": "  The SPI anticoincidence shield consists of 91 BGO crystals and is operated as a nearly omnidirectional gamma-ray burst detector above  75 keV. Since the start of the mission 269 gamma-ray burst candidates have been detected. 110 bursts have been confirmed with the instruments included in the 3rd Interplanetary Network. Here we present a preliminary statistical analysis of the SPI-ACS sample of gamma-ray bursts and gamma-ray burst candidates; in particular we discuss the duration distribution of the bursts. A prominent population of short burst candidates (duration <200ms) is found which is discovered to be strongly contaminated by cosmic-ray nuclei interacting in the detectors. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0405/0405121v1.pdf"}
{"id": "astro-ph0405227", "abstract": "  We have obtained deep near-infrared K_s-band William Herschel Telescope observations of a sample of 15 nearby spiral galaxies having a range of Hubble types and apparent bar strengths. The near-infrared light distributions are converted into gravitational potentials, and the maximum relative gravitational torques due to the bars and the spirals are estimated. We find that spiral strength, Q_s, and bar strength, Q_b, correlate well with other measures of spiral arm and bar amplitudes, and that spiral and bar strengths also correlate well with each other. We also find a correlation between the position angle of the end of the bar and the position angle of the inner spiral. These correlations suggest that the bars and spirals grow together with the same rates and pattern speeds. We also show that the strongest bars tend to have the most open spiral patterns. Because open spirals imply high disk-to-halo mass ratios, bars and spirals most likely grow together as a combined disk instability. They stop growing for different reasons, however, giving the observed variation in bar-spiral morphologies. Bar growth stops because of saturation when most of the inner disk is in the bar, and spiral growth stops because of increased stability as the gas leaves and the outer disk heats up. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0405/0405227v1.pdf"}
{"id": "astro-ph0405248", "abstract": "  The high spatial and spectral resolution offered by the new generation of infrared spectrometers at ESO is optimally suited for the observational study of outflows from young stellar objects. Models of interstellar shock waves would benefit from observations of spectrally resolved line profiles. This applies also to attempts of measuring the rotation rates of jets very close to their driving source, which in general suffer considerable extinction. Observations of forbidden lines of ionised iron, [Fe II], could be used to accomplish this. The possibility of using rotational lines of molecular hydrogen, H2, to study the temporal evolution of outflow and disk gas is discussed. Similarly, high resolution IR observations of fluorescent water lines, H2O, open up the possibility to access outflow and disk water. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0405/0405248v1.pdf"}
{"id": "astro-ph0406007", "abstract": "  The HI content of Hickson Compact Groups in the southern hemisphere is measured using data from the HI Parkes All Sky Survey (HIPASS), and dedicated observations using the narrowband filter on the Multibeam instrument on the Parkes telescope. The expected HI mass of these groups was estimated using the luminosity, diameter and morphological types of the member galaxies, calibrated from published data. Taking careful account of non-detection limits, the results show that the compact group population that has been detected by these observations has an HI content similar to that of galaxies in the reference field sample. The upper limits for the undetected groups lie within the normal range; improvement of these limits will require a large increase in sensitivity. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0406/0406007v1.pdf"}
{"id": "astro-ph0406119", "abstract": "  We report for the first time Na and O abundances from high-resolution, high S/N echelle spectra of 20 red giants in NGC 2808, taken as part of the Science Verification program of the FLAMES multi-object spectrograph at the ESO VLT. In these stars, spanning about 3 mag from the red giant branch (RGB) tip, large variations are detected in the abundances of oxygen and sodium, anticorrelated with each other; this is a well known evidence of proton-capture reactions at high temperatures in the ON and NeNa cycles. One star appears super O-poor; if the extension of the Na-O anticorrelation is confirmed, NGC 2808 might reach O depletion levels as large as those of M 13. This result confirms our previous findings based on lower resolution spectra (Carretta et al. 2003) of a large star-to-star scatter in proton capture elements at all positions along the RGB in NGC 2808, with no significant evolutionary contribution. Finally, the average metallicity for NGC 2808 is [Fe/H]= -1.14 +/- 0.01 dex (rms=0.06) from 19 stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0406/0406119v1.pdf"}
{"id": "astro-ph0406200", "abstract": "  We investigate the applicability of inhomogeneous absorber models in the formation of AGN outflow absorption-troughs. The models we explore are limited to monotonic gradients of absorbing column densities in front of a finite emission source. Our main finding is that simple power-law and gaussian distributions are hard pressed to fit the Mrk 279 high-quality UV outflow data. An acceptable fit for the O VI troughs can only be obtained by assuming unrealistic optical depth values (upward of 100). The strongest constraints arise from the attempt to fit the Lyman series troughs. In this case it is evident that even allowing for complete freedom of both the power-law exponent and the optical depth as a function of velocity cannot yield an acceptable fit. In contrast, partial covering models do yield good fits for the Lyman series troughs. We conclude that monotonic inhomogeneous absorber models that do not include a sharp edge in the optical depth distribution across the source are not an adequate physical model to explain the trough formation mechanism for the outflow observed in Mrk 279. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0406/0406200v1.pdf"}
{"id": "astro-ph0406335", "abstract": "  In this paper we briefly comment on the observational status of the possible physical association between unidentified EGRET sources and supernova remnants (SNRs) in our Galaxy. We draw upon recent results presented in the review by Torres et al. (Physics Reports, 2003), concerning molecular gas in the vicinity of all 19 SNRs found to be positionally coincident with EGRET sources at low Galactic latitudes. In addition, we present new results regarding the supernova remnant CTA 1. Our findings disfavor the possibility of a physical connection with the nearby (in projection) EGRET source. There remains possible, however, that the compact object produced in the supernova explosion be related with the observed γ-ray flux. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0406/0406335v2.pdf"}
{"id": "astro-ph0407621", "abstract": "  We investigate the gravitational collapse of rapidly rotating relativistic supermassive stars by means of a 3+1 hydrodynamical simulations in conformally flat spacetime of general relativity. We study the evolution of differentially rotating supermassive stars of q ≡ J/M^2∼ 1 (J is the angular momentum and M is the gravitational mass of the star) from the onset of radial instability at R/M ∼ 65 (R is the circumferential radius of the star) to the point where the conformally flat approximation breaks down. We find that the collapse of the star of q ≳ 1, a radially unstable differentially rotating star form a black hole of q ≲ 1. The main reason to prevent formation of a black hole of q ≳ 1 is that quite a large amount of angular momentum stays at the surface. We also find that most of the mass density collapses coherently to form a supermassive black hole with no appreciable disk nor bar. In the absence of nonaxisymmetric deformation, the collapse of differentially rotating supermassive stars from the onset of radial instability are the promising sources of burst and quasinormal ringing waves in the Laser Interferometer Space Antenna. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0407/0407621v1.pdf"}
{"id": "astro-ph0409149", "abstract": "  Chromospherically active, spotted stars generally become redder as well as fainter when large starspots rotate into view on the stellar disc. However, the RS CVn system UX Ari (a triple-lined system), becomes bluer as it gets fainter. One possible explanation is that hot, bright facular regions accompany the cool, dark photospheric spots of the active component. The bluer flux of the hotter, inactive component does not appear to be sufficient to explain the observed behaviour. We have begun a search for additional chromospherically active stars with a similar relation between colour and brightness, to investigate whether these relations can be explained in the same way. Our results for V711 Tau are presented here, and we conclude that the faculae explanation holds also in this case. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0409/0409149v1.pdf"}
{"id": "astro-ph0409168", "abstract": "  The Square Kilometer Array will have the sensitivity, spatial resolution, and frequency resolution to provide new scientific knowledge of evolved stars. Four basic areas of scientific exploration are enhanced by the construction of the SKA: 1) detection and imaging of photospheric radio continuum emission and position correlation with maser distributions, 2) imaging of thermal dust emission around evolved stars and the detailed structures of their circumstellar winds (again, including comparison with maser distributions), 3) study of cm-wavelength molecular line transitions and the circumstellar chemistry around both O-rich and C-rich evolved stars and 4) the possible observation of polarized emission due to the influence of the magnetic fields of AGB stars. Since this short chapter is not meant to be a review article, a comprehensive reference list has not been generated. I have selected just one or perhaps two references for citations where appropriate. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0409/0409168v1.pdf"}
{"id": "astro-ph0409265", "abstract": "  We report the results of a survey for novae in and between the galaxies of the Fornax cluster. Our survey provides strong evidence that intracluster novae exist and that they provide a useful, independent measure of the intracluster light in Fornax. We discovered six strong nova candidates in six distinct epochs spanning eleven years from 1993 to 2004. The data were taken with the 4m and the 1.5m telescopes at CTIO. The spatial distribution of the nova candidates is consistent with ∼16-41", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0409/0409265v2.pdf"}
{"id": "astro-ph0409375", "abstract": "  We present optical light curves of five Type Ia supernovae (2002er, 2002fk, 2003cg, 2003du, 2003fk). The photometric observations were performed in a set of intermediate-band filters. SNe 2002er, 2003du appear to be normal SN Ia events with similar light curve shapes, while SN 2003kf shows the behavior of a brighter SN Ia with slower decline rate after maximum. The light curves of SN 2003cg is unusual; they show a fast rise and dramatic decline near maximum and do not display secondary peak at longer wavelengths during 15-30 days after maximum light. This suggests that SN 2003cg is likely to be an intrinsically subluminous, 91bg-like SN Ia. Exploration of SN Ia feature lines through intermediate-band photometry is briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0409/0409375v1.pdf"}
{"id": "astro-ph0409626", "abstract": "  We report on a long X-ray observation of the slow-rotating binary pulsar GX 1+4. BeppoSAX observed, in the 0.1-200 keV energy range, an event in which the source flux dropped for almost a day, and then recovered. During this event only the high-energy emission was found to be pulsed and the pulsations were shifted in phase of  0.2 . The spectrum during the event was well fitted by a Compton-reflection model. A broad iron line at  6.55 keV was present outside of the event, where instead two narrow emission lines at  6.47 keV and  7.05 keV were detected. The pulse profile was highly variable as a function of both energy and time. We interpret this low-flux event as an occultation of the direct X-ray emission, due to the increase of a torus-like accretion disk; we then discuss similarities between this source and the recently discovered highly absorbed INTEGRAL sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0409/0409626v3.pdf"}
{"id": "astro-ph0411208", "abstract": "  We searched for eclipses of two millisecond pulsars, PSR J1807-2459 and PSR B1908+00. These pulsars are in very low mass binary systems with orbital parameters similar to those of eclipsing binaries. Observations were made with the GBT at frequencies as low as 575 MHz. No eclipses were detected in either system. Observations of well-established eclipsing binary J2051-0827 found eclipses to be substantially weaker than previously seen, with the pulsar detected throughout the eclipse region at 575 MHz and with an electron column density an order of magnitude smaller than previously measured. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0411/0411208v1.pdf"}
{"id": "astro-ph0411285", "abstract": "  We present results from our ongoing spectroscopic search for giant planets within 1 AU around a well-defined sample of metal-poor stars with HIRES on the Keck 1 telescope. We have achieved an rms radial velocity precision of ∼ 8 m/s over a time-span of 1.5 years. The data collected so far build toward evidence of the absence of very short-period (< 1 month) giant planets. However, about 7", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0411/0411285v1.pdf"}
{"id": "astro-ph0411404", "abstract": "  We report on an on-going analysis of high-resolution UV spectra of hot hydrogen-rich central stars of planetary nebulae (CSPN), obtained with the Hubble Space Telescope and FUSE. Since UV spectra of many CSPN are dominated by Fe and Ni lines, we intend to use them as temperature indicators to check the CSPN temperature scale we have derived earlier from CNO ionization balances. Furthermore, the observed line strengths of heavy metals show large variations between different objects suggesting a possible spread in abundances. We will determine abundances of iron group elements by quantitative spectral analyses with non-LTE model atmospheres. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0411/0411404v1.pdf"}
{"id": "astro-ph0411464", "abstract": "  The fraction of substructures required to account for anomalous flux ratios in gravitational lens systems appears to be higher than that predicted in the standard cold dark matter cosmology. We present a possible alternative route to anomalous flux ratios from lens galaxy environments. We consider the compound lens system such that a lens galaxy lie in a group or cluster, and estimate the contribution of substructures in the group/cluster to the fraction using an analytic model of substructures. We find that the contribution becomes dominant when the impact parameter of the lens is less than  30", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0411/0411464v2.pdf"}
{"id": "astro-ph0411502", "abstract": "  We present results of analysis of a Chandra observation of Cygnus A in which the X-ray hotspots at the ends of the jets are mapped in detail. A hardness map reveals previously unknown structure in the form of outer and inner hard arcs around the hotspots, with hardness significantly enhanced compared with the hotspot central regions. The outer hard arcs may constitute the first detection of the bow shock; the inner hard arcs may reveal where the jets impact on the hotspots. We argue that these features cannot result from electrons radiating by the synchrotron self-Compton process. Instead we consider two possible sources of the hard emission: the outer arcs may be due to thermal radiation of hot intracluster gas compressed at the bow shock. Alternatively, both outer and inner arcs may be due to synchrotron radiation of electrons accelerated in turbulent regions highly perturbed by shocks and shear flows. Comparison of measured hardness ratios with simulations of the hardness ratios resulting from these processes show that it is more diffcult to explain the observations with a thermal model. Although we cannot rule out a thermal model, we argue in favour of the non-thermal explanation. The hard regions in the secondary hotspots suggest that jet activity is still powering these hotspots. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0411/0411502v1.pdf"}
{"id": "astro-ph0412495", "abstract": "  Owing to their isotropy, it is generally believed that ultrahigh energy cosmic rays (UHECRs) are extragalactic in origin. It is then expected that interactions of these cosmic rays with photons of the cosmic background radiation (CBR) should produce a drastic reduction in their flux above and energy of about 5 × 10^19 eV (50 EeV), the so-called “GZK effect”. At present, the existence of this effect is uncertain owing to conflicting observational data and small number statistics. We show here that a small amount of Lorentz invariance violation (LIV), which could turn off photomeson interactions of UHECRs with the CBR, could explain the UHECR spectrum as measured by AGASA which shows an excess of UHECRs at energies above 100 EeV. If new results from the Auger array agree with the AGASA spectrum, this may be interpreted as evidence for a small amount of LIV. If, on the other hand, the new results are consistent with the HiRes results favoring a GZK effect, this would place severe constraints on LIV and, by implication, on some Planck scale quantum gravity models. We also discuss the power requirements needed to explain the UHECR spectrum for a range of assumptions, including source evolution and LIV and show that in all cases our results disfavor a γ-ray burst origin for the UHECRs. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0412/0412495v3.pdf"}
{"id": "astro-ph0412528", "abstract": "  It has been proposed that the global circulation of the atmosphere winds at 200 mb can be used as a criteria to establish the suitability of a site for the development of adaptive optics techniques such as slow wavefront corrugation correction. By using the NOAA NCEP/NCAR Reanalysis data base we analyze the monthly average wind velocity at 200 mb for a 16 year period, for two sites in Mexico: Sierra Negra and San Pedro Mártir. We compare the results with those obtained for Mauna Kea, Paranal and La Silla, with Maidanak in Uzbekistan, and with Gamsberg in Namibia. We show that for all the sites under study there is a yearly wind speed modulation and we model that modulation. Our results show that Sierra Negra and San Pedro Mártir are comparable with the best observatory sites as Mauna Kea and are amongst the most advantageous sites to apply adaptive optics techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0412/0412528v1.pdf"}
{"id": "astro-ph0503123", "abstract": "  The universe with adiabatic matter creation is considered. It is thought that the negative pressure caused by matter creation can play the role of a dark energy component, and drive the accelerating expansion of the universe. Using the Type Ia supernovae (SNe Ia) data, the observational Hubble parameter data, the Cosmic Microwave Background (CMB) data and the Baryonic Acoustic Oscillation (BAO) data, we make constraints on the cosmological parameters, assuming a spatially flat universe. Our results show that the model with matter creation is consistent with the SNe Ia data, while the joint constraints of all these observational data disfavor this model. If the cosmological constant is taken into account, a traditional model without matter creation is favored by the joint observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0503/0503123v2.pdf"}
{"id": "astro-ph0503165", "abstract": "  As the first step in a comprehensive, comparative, direct analysis of the spectra of Type Ia supernovae (SNe Ia), we use the parameterized supernova synthetic-spectrum code, SYNOW, to interpret 26 spectra of the well-observed SN 1994D. Our results are consistent with the traditional view that the composition structure (element abundance fractions versus ejection velocity) is radially stratified. We find that resonance-scattering features due to permitted lines of Ca II, Na I, and Fe II persist to more than 100 days after explosion. The fitting parameters for SN 1994D, together with those to be determined for other SNe Ia, will provide an internally consistent quantification of the spectroscopic diversity among SNe Ia, and shed light on how the various manifestations of observational diversity are related to their physical causes. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0503/0503165v1.pdf"}
{"id": "astro-ph0504017", "abstract": "  We have studied constraints on the equation of state, w, and speed of sound, c_s, of the dark energy from a joint analysis of data from the cosmic microwave background, large scale structure and type-Ia supernovae. We find that current observations have no significant sensitivity to c_s. However, there is a slight difference between models in which there are no dark energy perturbations and models in which dark energy behaves as a fluid. Assuming that there are no dark energy perturbations shifts the allowed region for w to slightly higher values. At present models with and without dark energy perturbations provide roughly equally good fits to observations, but the difference is potentially important for future parameter estimations. Finally, we have also performed error forecasts for future measurements of c_s. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0504/0504017v1.pdf"}
{"id": "astro-ph0504054", "abstract": "  Multidimensional reactive flow models of accreted hydrogen rich envelopes on top of degenerate cold white dwarfs are very effective tools for the study of critical, non spherically symmetric, behaviors during the early stages of nova outbursts. Such models can shed light both on the mechanism responsible for the heavy element enrichment observed to characterize nova envelope matter and on the role of perturbations during the early stages of ignition of the runaway. The complexity of convective reactive flow in multi-dimensions makes the computational model itself complex and sensitive to the details of the numerics. In this study, we demonstrate that the imposed outer boundary condition can have a dramatic effect on the solution. Several commonly used choices for the outer boundary conditions are examined. It is shown that the solutions obtained from Lagrangian simulations, where the envelope is allowed to expand and mass is being conserved, are consistent with spherically symmetric solutions. In Eulerian schemes which utilize an outer boundary condition of free outflow, the outburst can be artificially quenched. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0504/0504054v1.pdf"}
{"id": "astro-ph0505327", "abstract": "  Cyclotron decay and absorption rates have been well studied in the literature, focusing primarily on spectral, angular and polarization dependence. Astrophysical applications usually do not require retention of information on the electron spin state, and these are normally averaged in obtaining the requisite rates. In magnetic fields, higher order quantum processes such as Compton scattering become resonant at the cyclotron frequency and its harmonics, with the resonances being formally divergent. Such divergences are usually eliminated by accounting for the finite lifetimes of excited Landau states. This practice requires the use of spin-dependent cyclotron rates in order to obtain accurate determinations of process rates very near cyclotronic resonances, the phase space domain most relevant for certain applications to pulsar models. This paper develops previous results in the literature to obtain compact analytic expressions for cyclotron decay rates/widths in terms of a series of Legendre functions of the second kind; these expressions can be expediently used in astrophysical models. The rates are derived using two popular eigenstate formalisms, namely that due to Sokolov and Ternov, and that due to Johnson and Lippmann. These constitute two sets of eigenfunctions of the Dirac equation that diagonalize different operators, and accordingly yield different spin-dependent cyclotron rates. This paper illustrates the attractive Lorentz transformation characteristics of the Sokolov and Ternov formulation, which is another reason why it is preferable when electron spin information must be explicitly retained. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0505/0505327v1.pdf"}
{"id": "astro-ph0506303", "abstract": "  High-quality K-band spectra of point sources, deeply embedded in massive star-forming regions, have revealed a population of 20 young massive stars showing no photospheric absorption lines, but only emission lines. The K-band spectra exhibit one or more features commonly associated with massive Young Stellar Objects surrounded by circumstellar material: a very red color (J-K) = 2, CO bandhead emission, hydrogen emission lines (sometimes doubly peaked), and FeII and/or MgII emission lines. The CO emission comes from a relatively dense ( 10^10 cm^(-3)) and hot (T   2000-5000 K) region, sufficiently shielded from the intense UV radiation field of the young massive star. Modeling of the CO-first overtone emission shows that the CO gas is located within 5 AU of the star. The hydrogen emission is produced in an ionized medium exposed to UV radiation. The best geometrical configuration is a dense and neutral circumstellar disk causing the CO bandhead emission, and an ionized upper layer where the hydrogen lines are produced. We argue that the circumstellar disk is likely a remnant of the accretion via a circumstellar disk. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0506/0506303v1.pdf"}
{"id": "astro-ph0507171", "abstract": "  Evidence of azimuthal asymmetries in the time structure and signal size have been found in non-vertical showers at the Pierre Auger Observatory. It has been previously shown that the asymmetry in time distributions offers a new possibility for the determination of the mass composition. New studies have demonstrated that the dependence of the asymmetry parameter in the rise-time and fall-time distributions with sec(theta) shows a clear peak. Both, the position of the peak, X_asymax, and the size of the asymmetry at X_asymax are sensitive to primary mass composition and have a small dependence on energy. In this paper a study of the discriminating power of the new observables to separate primary species is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0507/0507171v1.pdf"}
{"id": "astro-ph0507227", "abstract": "  We explore observational constraints on a cosmological brane-world scenario in which the bulk is not empty. Rather, exchange of mass-energy between the bulk and the bane is allowed. The evolution of matter fields to an observer on the brane is then modified due to new terms in the energy momentum tensor describing this exchange. We investigate the constraints from various cosmological observations on the flow of matter from the bulk into the brane. Interestingly, we show that it is possible to have a Λ = 0 cosmology to an observer in the brane which satisfies standard cosmological constraints including the CMB temperature fluctuations, Type Ia supernovae at high redshift, and the matter power spectrum. This model even accounts for the observed suppression of the CMB power spectrum at low multipoles. In this cosmology, the observed cosmic acceleration is attributable to the flow of matter from the bulk to the brane. A peculiar aspect of this cosmology is that the present dark-matter content of the universe may be significantly larger than that of a ΛCDM cosmology. Its influence, however, is offset by the dark-radiation term. Possible additional observational tests of this new cosmological paradigm are suggested. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0507/0507227v3.pdf"}
{"id": "astro-ph0507425", "abstract": "  We present the observed pulsation spectra of all known non-interacting ZZ Ceti stars (hydrogen atmosphere white dwarf variables; DAVs) and examine changes in their pulsation properties across the instability strip. We confirm the well established trend of increasing pulsation period with decreasing effective temperature across the ZZ Ceti instability strip. We do not find a dramatic order of magnitude increase in the number of observed independent modes in ZZ Ceti stars, traversing from the hot to the cool edge of the instability strip; we find that the cool DAVs have one more mode on average compared to the hot DAVs. We confirm the initial increase in pulsation amplitude at the blue edge, and find strong evidence of a decline in amplitude prior to the red edge. We present the first observational evidence that ZZ Ceti stars lose pulsation energy just before pulsations shut down at the empirical red edge of the instability strip. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0507/0507425v2.pdf"}
{"id": "astro-ph0508376", "abstract": "  This is a report on detailed modeling of young high-mass protostellar candidates during their most embedded and obscured phases. We performed narrowband mid-infrared imaging of three candidate high-mass protostellar objects in G11.94-0.62, G29.96-0.02, and G45.07+0.13 at Gemini Observatory using the Thermal-Region Camera and Spectrograph (T-ReCS). The sources were imaged through up to 11 narrowband filters, sampling their SEDs over the entire 2-25um infrared range. For the first time, we have fit the observed SEDs of massive protostars with models that take into account departures from spherical symmetry in the infalling envelopes. In this way, we have been able to back out of the models detailed physical parameters for these earliest stages of massive stellar life. Our detailed modeling suggests that massive star formation can proceed in a way very similar to the formation of low-mass stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0508/0508376v1.pdf"}
{"id": "astro-ph0508423", "abstract": "  We report on the distribution of metallicities, [Fe/H], for very metal-poor stars in the halo of the Galaxy. Although the primary information on the nature of the Metallicity Distribution Function (MDF) is obtained from the two major recent surveys for metal-poor stars, the HK survey of Beers and collaborators, and the Hamburg/ESO Survey of Christlieb and collaborators, we also discuss the MDF derived from the publicly available database of stellar spectra and photometry contained in the third data release of the Sloan Digital Sky Survey (SDSS DR-3). Even though the SDSS was not originally planned as a stellar survey, significant numbers of stars have been observed to date – DR-3 contains spectroscopy for over 70,000 stars, at least half of which are suitable for abundance determinations. There are as many very metal-poor ([Fe/H] < -2.0) stars in DR-3 as have been obtained from all previous survey efforts combined. We also discuss prospects for significant expansion of the list of metal-poor stars to be obtained from the recently funded extension of the SDSS, which includes the project SEGUE: Sloan Extension for Galactic Understanding and Exploration. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0508/0508423v1.pdf"}
{"id": "astro-ph0509074", "abstract": "  The absolute magnitude and perihelion distributions of long-period comets are derived, using data from the Lincoln Near-Earth Asteroid Research (LINEAR) survey. The results are surprising in three ways. Firstly, the flux of comets through the inner solar system is much lower than some previous estimates. Secondly, the expected rise in comet numbers to larger perihelia is not seen. Thirdly, the number of comets per unit absolute magnitude does not significantly rise to fainter magnitudes. These results imply that the Oort cloud contains many fewer comets than some previous estimates, that small long-period comets collide with the Earth too infrequently to be a plausible source of Tunguska-style impacts, and that some physical process must have prevented small icy planetesmals from reaching the Oort cloud, or have rendered them unobservable. A tight limit is placed on the space density of interstellar comets, but the predicted space density is lower still. The number of long-period comets that will be discovered by telescopes such as SkyMapper, Pan-Starrs and LSST is predicted, and the optimum observing strategy discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0509/0509074v1.pdf"}
{"id": "astro-ph0509126", "abstract": "  Bars in gas-rich spiral galaxies are short-lived. They drive gas inflows through their gravity torques, and at the same time self-regulate their strength. Their robustness has been subject of debate, since it was thought that only the resulting central mass concentrations (CMCs) were weakening bars, and only relatively rare massive CMCs were able to completely destroy them. Through numerical simulations including gas dynamics, we find that with the gas parameters of normal spiral galaxies, the CMC is not sufficient to fully dissolve the bar. But another overlooked mechanism, the transfer of angular momentum from the infalling gas to the stellar bar, can also strongly weaken the bar. In addition, we show that gravity torques are correctly reproduced in simulations, and conclude that bars are transient features, with life-time of 1-2 Gyr in typical Sb-Sc galaxies, because of the combined effects of CMCs and gravity torques, while most existing works had focussed on the CMC effects alone. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0509/0509126v1.pdf"}
{"id": "astro-ph0509498", "abstract": "  The CELESTE atmospheric Cherenkov detector, running until June 2004 at the Themis solar facility, has taken data on compact sources such as pulsars and blazars. We will take stock of the experiment, in particular regarding the latest improvements of the detector simulation and data analysis. These changes provide us with a new analysis of old data with smaller uncertainties. We present here the evidence for a weak signal from Mrk 501 in 2000-2001. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0509/0509498v1.pdf"}
{"id": "astro-ph0510013", "abstract": "  Observation of the H2O megamaser galaxy IC 2560 with the Chandra Observatory reveals a complex spectrum composed of soft X-ray emission due to multi-temperature thermal plasma, and a hard continuum with strong emission lines. The continuum is most likely a Compton reflection (reprocessing) of primary emission that is completely absorbed at least up to 7 keV. The lines can be identified with fluorescence from Si, S and Fe in the lowest ionization stages. The equivalent widths of the Si and S lines are broadly compatible with those anticipated for reprocessing by optically thick cold plasma of Solar abundances, while the large equivalent width of the Fe line requires some overabundance of iron. A contribution to the line from a transmitted component cannot be ruled out, but the limits on the strength of the Compton shoulder make it less likely. From the bolometric luminosity of the nuclear region, we infer that the source radiates at 1 - 10", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0510/0510013v2.pdf"}
{"id": "astro-ph0511302", "abstract": "  We have observed a bright flare of Sgr A* in the near infrared with the adaptive optics assisted integral field spectrometer SINFON. Within the uncertainties, the observed spectrum is featureless and can be described by a power law. Our data suggest that the spectral index is correlated with the instantaneous flux and that both quantities experience significant changes within less than one hour. We argue that the near infrared flares from Sgr A* are due to synchrotron emission of transiently heated electrons, the emission being affected by orbital dynamics and synchrotron cooling, both acting on timescales of  20 minutes. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0511/0511302v2.pdf"}
{"id": "astro-ph0511458", "abstract": "  How to analyse Terabytes of photometric data, and extract knowledge on variable stars? How to detect variable phenomena? How to combine different photometric bands? Which algorithm to search for periods? How to characterize and classify the detected variable objects? Many questions, but certainly no definitive answers yet. We present several aspects which are at the interface of photometric surveys and variable stars. Fully automated analyses of photometric surveys are still not at an optimized level. We will take the example of a future survey, the Gaia mission project of the European Space Agency, to show different steps of a possible automated pipeline scheme. Principal component analysis can be applied to the Gaia photometric bands. We give some illustrative examples of classification methods such as Support Vector Machine, Self-Organising Map, or Bayesian classifier. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0511/0511458v1.pdf"}
{"id": "astro-ph0511544", "abstract": "  We present results from an archival study of 70 medium-redshift QSOs observed with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The QSOs have magnitudes M_V < -23 (total nuclear plus host light) and redshifts 0.06 < z < 0.46.   A close relationship between QSO host and nucleus is found by examining multiple parameters at once. A principal components analysis shows that 3 nuclear and host properties are related in a kind of fundamental plane: nuclear luminosity and the size and effective surface magnitude of the bulge. Using optical nuclear luminosity, this relationship explains 95.9", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0511/0511544v1.pdf"}
{"id": "astro-ph0511557", "abstract": "  Loop quantum cosmology is an application of recent developments for a non-perturbative and background independent quantization of gravity to a cosmological setting. Characteristic properties of the quantization such as discreteness of spatial geometry entail physical consequences for the structure of classical singularities as well as the evolution of the very early universe. While the singularity issue in general requires one to use difference equations for a wave function of the universe, phenomenological scenarios for the evolution are based on effective equations implementing the main quantum modifications. These equations show generic bounces as well as inflation in diverse models, which have been combined to more complicated scenarios. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0511/0511557v1.pdf"}
{"id": "astro-ph0511651", "abstract": "  For a rigid model satellite, Chandrasekhar's dynamical friction formula describes the orbital evolution quite accurately, when the Coulomb logarithm is chosen appropriately. However, it is not known if the orbital evolution of a real satellite with the internal degree of freedom can be described by the dynamical friction formula. We performed N-body simulation of the orbital evolution of a self-consistent satellite galaxy within a self-consistent parent galaxy. We found that the orbital decay of the simulated satellite is significantly faster than the estimate from the dynamical friction formula. The main cause of this discrepancy is that the stars stripped out of the satellite are still close to the satellite, and increase the drag force on the satellite through two mechanisms. One is the direct drag force from particles in the trailing tidal arm, a non-axisymmetric force that slows the satellite down. The other is the indirect effect that is caused by the particles remaining close to the satellite after escape. The force from them enhances the wake caused in the parent galaxy by dynamical friction, and this larger wake in turn slows the satellite down more than expected from the contribution of its bound mass. We found these two have comparable effects, and the combined effect can be as large as 20", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0511/0511651v2.pdf"}
{"id": "astro-ph0512020", "abstract": "  We studied the WMAP temperature anisotropy data using two different methods. The derived signal gradient maps show regions with low mean gradients in structures near the ecliptic poles and higher gradient values in the wide ecliptic equatorial zone, being the result of non-uniform observational time sky coverage. We show that the distinct observational time pattern present in the raw (cleaned) data leaves also its imprints on the composite CMB maps. Next, studying distribution of the signal dispersion we show that the north-south asymmetry of the WMAP signal diminishes with galactic altitude, confirming the earlier conclusions that it possibly reveals galactic foreground effects. As based on these results, one can suspect that the instrumental noise sky distribution and non-removed foregrounds can have affected some of the analyses of the CMB signal. We show that actually the different characteristic axes of the CMB sky distribution derived by numerous authors are preferentially oriented towards some distinguished regions on the sky, defined by the observational time pattern and the galactic plane orientation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0512/0512020v2.pdf"}
{"id": "astro-ph0512216", "abstract": "  We study eigenmodes of acoustic oscillations of high multipolarity l   100 - 1000 and high frequency ( 100 kHz), localized in neutron star envelopes. We show that the oscillation problem is self-similar. Once the oscillation spectrum is calculated for a given equation of state (EOS) in the envelope and given stellar mass M and radius R, it can be rescaled to a star with any M and R (but the same EOS in the envelope). For l>300 the modes can be subdivided into the outer and inner ones. The outer modes are mainly localized in the outer envelope. The inner modes are mostly localized near the neutron drip point, being associated with the softening of the EOS after the neutron drip. We calculate oscillation spectra for the EOSs of cold-catalyzed and accreted matter and show that the spectra of the inner modes are essentially different. A detection and identification of high-frequency pressure modes would allow one to infer M and R and determine also the EOS in the envelope (accreted or ground-state) providing thus a new and simple method to explore the main parameters and internal structure of neutron stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0512/0512216v1.pdf"}
{"id": "astro-ph0512255", "abstract": "  We consider the structure of self-gravitating marginally stable accretion disks in galactic centers in which a small fraction of the disk mass has been converted into proto-stars. We find that proto-stars accrete gaseous disk matter at prodigious rates. Mainly due to the stellar accretion luminosity, the disk heats up and geometrically thickens, shutting off further disk fragmentation. The existing proto-stars however continue to gain mass by gas accretion. As a results, the initial mass function for disk-born stars at distances R   0.03-3 parsec from the super-massive black hole should be top-heavy. The effect is most pronounced at around R   0.1 parsec. We suggest that this result explains observations of rings of young massive stars in our Galaxy and in M31, and predict that more of such rings will be discovered. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0512/0512255v2.pdf"}
{"id": "astro-ph0512344", "abstract": "  Hypervelocity stars have been recently discovered in the outskirts of galaxies, such as the unbound star in the Milky Way halo, or the three anomalously fast intracluster planetary nebulae (ICPNe) in the Virgo Cluster. These may have been ejected by close 3-body interactions with a binary supermassive black hole (SMBBH), where a star which passes within the semimajor axis of the SMBBH can receive enough energy to eject it from the system. Stars ejected by SMBBHs may form a significant sub-population with very different kinematics and mean metallicity than the bulk of the intracluster stars. The number, kinematics, and orientation of the ejected stars may constrain the mass ratio, semimajor axis, and even the orbital plane of the SMBBH. We investigate the evolution of the ejected debris from a SMBBH within a clumpy and time-dependent cluster potential using a high resolution, self-consistent cosmological N-body simulation of a galaxy cluster. We show that the predicted number and kinematic signature of the fast Virgo ICPNe is consistent with 3-body scattering by a SMBBH with a mass ratio 10:1 at the center of M87. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0512/0512344v1.pdf"}
{"id": "astro-ph0601276", "abstract": "  We derive an extended version of the well-known Lyth Bound on the total variation of the inflaton field, incorporating higher order corrections in slow roll. We connect the field variation Δϕ to both the spectral index of scalar perturbations and the amplitude of tensor modes. We then investigate the implications of this bound for “small field” potentials, where the field rolls off a local maximum of the potential. The total field variation during inflation is generically of order m_ Pl, even for potentials with a suppressed tensor/scalar ratio. Much of the total field excursion arises in the last e-fold of inflation and in single field models this problem can only be avoided via fine-tuning or the imposition of a symmetry. Finally, we discuss the implications of this result for inflationary model building in string theory and supergravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0601/0601276v3.pdf"}
{"id": "astro-ph0602345", "abstract": "  It has recently been suggested that collapse of neutron stars induced by a phase transition to quark matter can be a considerable source of gravitational waves with kHz frequencies. We demonstrate that if about one percent of all neutron stars undergo this process, the resulting cosmological gravitational wave background would reach about 10^-10 times the critical density. The background would peak at kHz frequencies and could have an observationally significant tail down to Hz frequencies. It would be comparable or higher than other astrophysical backgrounds, for example, from ordinary core collapse supernovae, from r-mode instabilities in rapidly rotating neutron stars, or from magnetars. The scenario is consistent with cosmological backgrounds in neutrinos and photons. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0602/0602345v1.pdf"}
{"id": "astro-ph0603235", "abstract": "  Torque fluctuations due to magnetorotational turbulence in proto-planetary disks may greatly influence the migration patterns and survival probabilities of nascent planets. Provided that the turbulence is a stationary stochastic process with finite amplitude and correlation time, the resulting diffusive migration can be described with a Fokker-Planck equation, which we reduce to an advection-diffusion equation. We calibrate the coefficients with existing turbulent-disk simulations and mean-migration estimates, and solve the equation both analytically and numerically. Diffusion tends to dominate over advection for planets of low-mass and those in the outer regions of proto-planetary disks, whether they are described by the Minimum Mass Solar Nebula (MMSN) or by T-Tauri alpha disks. Diffusion systematically reduces the lifetime of most planets, yet it allows a declining fraction of them to survive for extended periods of time at large radii. Mean planet lifetimes can even be formally infinite (e.g. in an infinite steady MMSN), though median lifetimes are always finite. Surviving planets may linger near specific radii where the combined effects of advection and diffusion are minimized, or at large radii, depending on model specifics. The stochastic nature of migration in turbulent disks challenges deterministic planet formation scenarios and suggests instead that a wide variety of planetary outcomes are possible from similar initial conditions. This would contribute to the diversity of (extrasolar) planetary systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0603/0603235v2.pdf"}
{"id": "astro-ph0604145", "abstract": "  We report results on an “one-way light path” laser diffraction experiment as a function of the laser beam alignment relative to the Earth's velocity vector obtained by COBE measurements of the Doppler shift in the cosmic microwave background radiation (CMBR). An amplified Doppler shift is observed in the diffraction images, and the effect is compatible with a “dipole” speed of light anisotropy due to Earth's motion relative to the “CMBR rest frame”, with an amplitude of δ c/c̅=0.00123. This amplitude coincides with the value of the dipole temperature anisotropy δ T/T̅=0.00123 of the CMBR obtained by COBE. Our results point out that it is not possible to neglect the preferred frame imposed by the cosmology and they are well described by the Ether Gauge Theory (an extension of the Lorentz's ether theory) and it satisfies the cosmological time boundary condition. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0604/0604145v1.pdf"}
{"id": "astro-ph0604545", "abstract": "  We investigate numerically the hydrodynamic instability of an ionization front (IF) accelerating into a molecular cloud, with imposed initial perturbations of different amplitudes. When the initial amplitude is small, the imposed perturbation is completely stabilized and does not grow. When the initial perturbation amplitude is large enough, roughly the ratio of the initial amplitude to wavelength is greater than 0.02, portions of the IF temporarily separate from the molecular cloud surface, locally decreasing the ablation pressure. This causes the appearance of a large, warm HI region and triggers nonlinear dynamics of the IF. The local difference of the ablation pressure and acceleration enhances the appearance and growth of a multimode perturbation. The stabilization usually seen at the IF in the linear regimes does not work due to the mismatch of the modes of the perturbations at the cloud surface and in density in HII region above the cloud surface. Molecular pillars are observed in the late stages of the large amplitude perturbation case. The velocity gradient in the pillars is in reasonably good agreement with that observed in the Eagle Nebula. The initial perturbation is imposed in three different ways: in density, in incident photon number flux, and in the surface shape. All cases show both stabilization for a small initial perturbation and large growth of the second harmonic by increasing amplitude of the initial perturbation above a critical value. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0604/0604545v1.pdf"}
{"id": "astro-ph0606075", "abstract": "  We report the discovery of XMMXCS J2215.9-1738, a massive galaxy cluster at z =1.45, which was found in the XMM Cluster Survey. The cluster candidate was initially identified as an extended X-ray source in archival XMM data. Optical spectroscopy shows that 6 galaxies within a 60 arcsec diameter region lie at z = 1.45 +/- 0.01. Model fits to the X-ray spectra of the extended emission yield kT = 7.4 (+2.7,-1.8) keV (90 ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0606/0606075v2.pdf"}
{"id": "astro-ph0606202", "abstract": "  We present the first observations of magnetic cataclysmic variables with the Spitzer Space Telescope. We used the Infrared Array Camera to obtain photometry of the polars EF Eri, GG Leo, V347 Pav, and RX J0154.0-5947 at 3.6, 4.5, 5.8, and 8.0 μm. In all of our targets, we detect excess mid-infrared emission over that expected from the component stars alone. We explore the origin of this IR excess by examining bremsstrahlung, cyclotron emission, circumbinary dust, and L/T brown dwarf secondary stars. Bremsstrahlung and cyclotron emission appear unlikely to be significant contributors to the observed fluxes. At present, the most likely candidate for the excess emission is dust that is probably located in a circumbinary disk with an inner temperature near 800 K. However, a simple dust disk plus any reasonable low mass or brown dwarf-like secondary star is unable to fully explain the observed flux densities in the 3–8 μm region. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0606/0606202v1.pdf"}
{"id": "astro-ph0606726", "abstract": "  We follow the contraction and evolution of a typical Jupiter-mass clump created by the disk instability mechanism, and compute the rate of planetesimal capture during this evolution. We show that such a clump has a slow contraction phase lasting  3x10^5 years. By following the trajectories of planetesimals as they pass through the envelope of the protoplanet, we compute the cross-section for planetesimal capture at all stages of the protoplanet's evolution. We show that the protoplanet can capture a large fraction of the solid material in its feeding zone, which will lead to an enrichment of the protoplanet in heavy elements. The exact amount of this enrichment depends upon, but is not very sensitive to the size and random speed of the planetesimals. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0606/0606726v1.pdf"}
{"id": "astro-ph0607318", "abstract": "  Diffuse emission in the mid-infrared shows a wealth of structure, that lends itself to high-resolution structure analysis of the interstellar gas. A large part of the emission comes from polycyclic aromatic hydrocarbons, excited by nearby ultra-violet sources. Can the observed diffuse emission structure be interpreted as column density structure? We discuss this question with the help of a set of model molecular clouds bathed in the radiation field of a nearby O-star. The correlation strength between column density and “observed” flux density strongly depends on the absolute volume density range in the region. Shadowing and irradiation effects may completely alter the appearance of an object. Irradiation introduces additional small-scale structure and it can generate structures resembling shells around HII-regions in objects that do not possess any shell-like structures whatsoever. Nevertheless, structural information about the underlying interstellar medium can be retrieved. In the more diffuse regime (n(HI)≲ 100cm^-3), flux density maps may be used to trace the 3D density structure of the cloud via density gradients. Thus, while caution definitely is in order, mid-infrared surveys such as GLIMPSE will provide quantitative insight into the turbulent structure of the interstellar medium. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0607/0607318v1.pdf"}
{"id": "astro-ph0608007", "abstract": "  Earlier papers introduced a method of accurately estimating the angular cosmic microwave background (CMB) temperature power spectrum based on Gibbs sampling. Here we extend this framework to polarized data. All advantages of the Gibbs sampler still apply, and exact analysis of mega-pixel polarized data sets is thus feasible. These advantages may be even more important for polarization measurements than for temperature measurements. While approximate methods can alias power from the larger E-mode spectrum into the weaker B-mode spectrum, the Gibbs sampler (or equivalently, exact likelihood evaluations) allows for a statistically optimal separation of these modes in terms of power spectra. To demonstrate the method, we analyze two simulated data sets: 1) a hypothetical future CMBPol mission, with the focus on B-mode estimation; and 2) a Planck-like mission, to highlight the computational feasibility of the method. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0608/0608007v2.pdf"}
{"id": "astro-ph0608397", "abstract": "  The Period - metallicity - K band luminosity (PLK) relation for RR Lyrae stars in 15 Galactic globular clusters and in the LMC globular cluster Reticulum has been derived. It is based on accurate near infrared (K) photometry combined with 2MASS and other literature data. The PLK relation has been calibrated and compared with the previous empirical and theoretical determinations in literature. The zero point of the absolute calibration has been obtained from the K magnitude of RR Lyr whose distance modulus has been measured via trigonometric parallax with HST. Using this relation we obtain a distance modulus to the LMC of (m-M)_0 = 18.54 ±0.15 mag, in good agreement with recent determinations based on the analysis of Cepheid variable stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0608/0608397v1.pdf"}
{"id": "astro-ph0608550", "abstract": "  Based on a new approach to the detection of radio transients associated with extensive air showers induced by ultra high energy cosmic rays, the experimental apparatus CODALEMA is in operation, measuring about 1 event per day corresponding to an energy threshold   5. 10^16 eV. Its performance makes possible for the first time the study of radio-signal features on an event-by-event basis. The sampling of the magnitude of the electric field along a 600 meters axis is analyzed. It shows that the electric field lateral spread is around 250 m (FWHM). The possibility to determine with radio both arrival directions and shower core positions is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0608/0608550v1.pdf"}
{"id": "astro-ph0608618", "abstract": "  We present a period-luminosity-amplitude analysis of 5899 red giant and binary stars in the Large Magellanic Cloud, using publicly available observations of the MACHO project. For each star, we determined new periods, which were double-checked in order to exclude aliases and false periods. The period-luminosity relations confirm the existence of a short-period, small-amplitude P-L sequence at periods shortward of Seq. A. We point out that the widely accepted sequence of eclipsing binaries between Seqs. C and D, known as Seq. E, does not exist. The correct position for Seq. E is at periods a factor of two greater, and the few stars genuinely lying between Seq. C and D are under-luminous Mira variables, presumably enshrouded in dust. The true Seq. E overlaps with the sequence of Long Secondary Periods (Seq. D) and their P-L relation is well described by a simple model assuming Roche geometry. The amplitudes of LSPs have properties that are different from both the pulsations and the ellipsoidal variations, but they are more similar to the former than the latter, arguing for pulsation rather than binarity as the origin of the LSP phenomenon. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0608/0608618v1.pdf"}
{"id": "astro-ph0609084", "abstract": "  The winds of stars with very specific temperatures and luminosities are ideal for determining the magnitude and nature of mass loss in OB stars. I identify these stars and analyze their wind lines. The results are discussed within the context of recent findings which appear to indicate that the mass-loss rates of OB stars may as much as an order of magnitude less than commonly accepted values. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0609/0609084v1.pdf"}
{"id": "astro-ph0609481", "abstract": "  The present matter density of the Universe, while highly inhomogeneous on small scales, displays approximate homogeneity on large scales. We propose that whereas it is justified to use the Friedmann-Lemaitre-Robertson-Walker (FLRW) line element (which describes an exactly homogeneous and isotropic universe) as a template to construct luminosity distances in order to compare observations with theory, the evolution of the scale factor in such a construction must be governed not by the standard Einstein equations for the FLRW metric, but by the modified Friedmann equations derived by Buchert [7, 8] in the context of spatial averaging in Cosmology. Furthermore, we argue that this scale factor, defined in the spatially averaged cosmology, will correspond to the effective FLRW metric provided the size of the averaging domain coincides with the scale at which cosmological homogeneity arises. This allows us, in principle, to compare predictions of a spatially averaged cosmology with observations, in the standard manner, for instance by computing the luminosity distance versus red-shift relation. The predictions of the spatially averaged cosmology would in general differ from standard FLRW cosmology, because the scale-factor now obeys the modified FLRW equations. This could help determine, by comparing with observations, whether or not cosmological inhomogeneities are an alternative explanation for the observed cosmic acceleration. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0609/0609481v4.pdf"}
{"id": "astro-ph0609521", "abstract": "  Suzaku has, for the first time, enabled the hard X-ray variability of the Seyfert 1 galaxy MCG-6-30-15 to be measured. The variability in the 14-45 keV band, which is dominated by a strong reflection hump, is quenched relative to that at a few keV. This directly demonstrates that the whole reflection spectrum is much less variable than the power-law continuum. The broadband spectral variability can be decomposed into two components - a highly variable power-law and constant reflection - as previously inferred from other observations in the 2-10 keV band. The strong reflection and high iron abundance give rise to a strong broad iron line, which requires the inner disc radius to be at about 2 gravitational radii. Our results are consistent with the predictions of the light bending model which invokes the very strong gravitational effects expected very close to a rapidly spinning black hole. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0609/0609521v1.pdf"}
{"id": "astro-ph0610026", "abstract": "  This review summarizes recent attempts to reconstruct the expansion history of the Universe and to probe the nature of dark energy. Reconstruction methods can be broadly classified into parametric and non-parametric approaches. It is encouraging that, even with the limited observational data currently available, different approaches give consistent results for the reconstruction of the Hubble parameter H(z) and the effective equation of state w(z) of dark energy. Model independent reconstruction using current data allows for modest evolution of dark energy density with redshift. However, a cosmological constant (= dark energy with a constant energy density) remains an excellent fit to the data. Some pitfalls to be guarded against during cosmological reconstruction are summarized and future directions for the model independent reconstruction of dark energy are explored. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610026v3.pdf"}
{"id": "astro-ph0610046", "abstract": "  We present radio observations of 8 ultracool dwarfs with a narrow spectral type range (M8-M9.5) using the Very Large Array at 8.5 GHz. Only the tight M8 binary LP 349-25 was detected. LP 349-25 is the tenth ultracool dwarf system detected in radio and its trigonometric parallax pi = 67.6 mas, recently measured by Gatewood et al., makes it the furthest ultracool system detected by the Very Large Array to date, and the most radio-luminous outside of obvious flaring activity or variability. With a separation of only 1.8 AU, masses of the components of LP 349-25 can be measured precisely without any theoretical assumptions (Forveille et al.), allowing us to clarify their fully-convective status and hence the kind of magnetic dynamo in these components which may play an important role to explain our detection of radio emission from these objects. This also makes LP 349-25 an excellent target for further studies with better constraints on the correlations between X-ray, radio emission and stellar parameters such as mass, age, temperature, and luminosity in ultracool dwarfs. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610046v2.pdf"}
{"id": "astro-ph0610444", "abstract": "  It is widely accepted that the Doppler deboosting effects exist in counter relativistic jets. However, people often neglect another important fact that both Doppler boosting and deboosting effects could happen in forward relativistic jets. Such effects might be used to explain some strange phenomena, such as the invisible gaps between the inner and outer jets of AGNs, and the rapid initial decays and re-brightening bumps in the light curves of GRBs. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610444v1.pdf"}
{"id": "astro-ph0610480", "abstract": "  We present the results of seven years of K-band monitoring of the low-mass X-ray binary GRS 1915+105. Positive correlations between the infrared flux and the X-ray flux and X-ray hardness are demonstrated. Analysis of the frequency spectrum shows that the orbital period of the system is P_orb= 30.8 ± 0.2 days. The phase and amplitude of the orbital modulation suggests that the modulation is due to the heating of the face of the secondary star. We also report another periodic signature between 31.2 and 31.6 days, most likely due to a superhump resonance. From the superhump period we then obtain a range on the mass ratio of the system, 0.05 < q < 0.12. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610480v2.pdf"}
{"id": "astro-ph0610701", "abstract": "  The space density of white dwarfs is highly uncertain even nearby. This results from the fact that the known sample of white dwarfs is largely incomplete in part because most white dwarfs have been discovered as by-products in non-dedicated surveys. In order to obtain more accurate white dwarf space densities and scale heights we must build up a complete sample of white dwarfs. The European Galactic Plane Surveys (EGAPS) are the best database to search for white dwarfs as they will provide broad band (U, g', r', i') and narrow band (Halpha and HeI) measurements for one per cent of all the stars in the Galaxy. By looking at the Galactic Plane, where most stars are, we ensure that we are obtaining a complete sample. The space densities obtained from EGAPS can then be compared with those found in high latitude surveys such as the Sloan Digital Sky Survey (SDSS). The methods used to identify white dwarfs using the colours available in EGAPS are described and some preliminary results presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610701v1.pdf"}
{"id": "astro-ph0610730", "abstract": "  The detection of bright X-ray flares superimposed on the regular afterglow decay in Swift gamma-ray bursts has triggered theoretical speculations on their origin. We study the temporal properties of flares due to internal dissipation and external shock mechanisms. We first show that at least a sizable fraction of the flares cannot be related to external shock mechanisms, since external shock flares evolve on much longer time scales than observed. We then study flares from internal dissipation, showing that the temporal properties allow us to distinguish the emission of slow early shells from that of late faster shells. We show that, due to the rapid evolution of the detected flares, it is most likely that the flares are produced by relatively fast shells ejected by the central engine shortly before they are observed. This implies that the central engine must be active for, in some cases, as long as one day. We finally discuss the constraints and implications that this observation has on the properties and physics of the inner engine, and we elaborate on possible future observational tests on the flare sample to further understand their origin and physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610730v2.pdf"}
{"id": "astro-ph0610788", "abstract": "  The status of present theoretical description of very high energy hadronic interactions is reviewed. The impact of new results of accelerator and cosmic ray experiments on hadronic interaction model constructions is discussed in detail. Special attention is payed to remaining uncertainties in model extrapolations into the ultra-high energy domain, in particular, concerning model predictions for the muon component of extensive air showers. New promising theoretical approaches are outlined and future experimental prospects are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610788v1.pdf"}
{"id": "astro-ph0610837", "abstract": "  The systematics of OB spectra are reviewed in the optical domain, dominated by photospheric lines, and in the far ultraviolet (both IUE and FUSE ranges), in which the stellar-wind profiles dominate. First, the two-dimensional (temperature, luminosity) trends in normal spectra are surveyed. Then, the normal reference frame having been established, various categories of peculiar objects can be distinguished relative to it, which reveal several phenomena of structural and/or evolutionary significance. Included are CNO anomalies at both early and late O types, three varieties of rapid rotators, hot and cool Of/WN transition objects, and the recently discovered second known magnetic O star. The importance of both optical and UV observations to understand these phenomena is emphasized; for instance, progress in understanding the structure of the new O-type magnetic oblique rotator is hampered by the current lack of a UV spectrograph. While progress in the physical interpretation of these trends and anomalies has been and is being made, increased attention to modeling the systematics would accelerate future progress in this author's opinion. Finally, preliminary results from a Chandra high-resolution survey of OB X-ray spectra (PI W. Waldron) are presented. They provide evidence that, just as emerged earlier in the UV, systematic morphological trends exist in the X-ray domain that are correlated with the optical spectral types, and hence the fundamental stellar parameters, contrary to prevailing opinion. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610837v1.pdf"}
{"id": "astro-ph0611050", "abstract": "  We present data from INTEGRAL and BeppoSAX satellites showing spectral state transitions of the neutron-star, atoll-type, low-mass X-ray binary 1705-44. Its energy spectrum can be described as the sum of one or two blackbody components, a 6.4-keV Fe line, and a component due to thermal Comptonization. In addition, and for the first time in this source, we find a strong signature of Compton reflection, presumably due to illumination of the optically-thick accretion disk by the Comptonization spectrum. The two blackbody components, which the soft-state data require, presumably arise from both the disk and the neutron-star surface. The Comptonization probably takes place in a hot inner flow irradiated by some of the blackbody photons. The spectral transitions are shown to be associated with variations in the bolometric luminosity, most likely proportional to the accretion rate. Indipendentely from the spectral state, we also see changes in the temperature of the Comptonizing electrons and the strength of Compton reflection. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0611/0611050v1.pdf"}
{"id": "astro-ph0611174", "abstract": "  Among the hot Jupiters that transit their parent stars known to date, the two best candidates to be observed with transmission spectroscopy in the mid-infrared (MIR) are HD189733b and HD209458b, due to their combined characteristics of planetary density, orbital parameters and parent star distance and brightness. Here we simulate transmission spectra of these two planets during their primary eclipse in the MIR, and we present sensitivity studies of the spectra to the changes of atmospheric thermal properties, molecular abundances and C/O ratios. Our model predicts that the dominant species absorbing in the MIR on hot Jupiters are water vapor and carbon monoxide, and their relative abundances are determined by the C/O ratio. Since the temperature profile plays a secondary role in the transmission spectra of hot Jupiters compared to molecular abundances, future primary eclipse observations in the MIR of those objects might give an insight on EGP atmospheric chemistry. We find here that the absorption features caused by water vapor and carbon monoxide in a cloud-free atmosphere, are deep enough to be observable by the present and future generation of space-based observatories, such as Spitzer Space Telescope and James Webb Space Telescope. We discuss our results in light of the capabilities of these telescopes. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0611/0611174v1.pdf"}
{"id": "astro-ph0611435", "abstract": "  An exponentially expanding Universe, possibly governed by a cosmological constant, forces gravitationally bound structures to become more and more isolated, eventually becoming causally disconnected from each other and forming so-called \"island universes\". This new scenario reformulates the question about which will be the largest structures that will remain gravitationally bound, together with requiring a systematic tool that can be used to recognize the limits and mass of these structures from observational data, namely redshift surveys of galaxies. Here we present a method, based on the spherical collapse model and N-body simulations, by which we can estimate the limits of bound structures as observed in redshift space. The method is based on a theoretical criterion presented in a previous paper that determines the mean density contrast that a spherical shell must have in order to be marginally bound to the massive structure within it. Understanding the kinematics of the system, we translated the real-space limiting conditions of this \"critical\" shell to redshift space, producing a projected velocity envelope that only depends on the density profile of the structure. From it we created a redshift-space version of the density contrast that we called \"density estimator\", which can be calibrated from N-body simulations for a reasonable projected velocity envelope template, and used to estimate the limits and mass of a structure only from its redshift-space coordinates. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0611/0611435v2.pdf"}
{"id": "astro-ph0611511", "abstract": "  For the last three years we have performed a survey for young (<3 Gyrs) giant planets around nearby white dwarfs with HST, Spitzer, and VLT. Direct HST/NICMOS imaging of the seven white dwarfs in the Hyades gave no evidence for companions down to about 10 Jupiter masses and separations larger than 0.5 arcsec (about 25 AU), while VLT/NACO observations revealed a putative companion to a field white dwarf. Second epoch observations with SINFONI on the VLT, however, showed that it is most probably a background star. With IRAC on Spitzer we also found no indications of cool, very low mass companions in our sample of field white dwarfs. The implications of these non-detections are briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0611/0611511v1.pdf"}
{"id": "astro-ph0611677", "abstract": "  A three-dimensional Monte Carlo code for modelling radiation transport in Type Ia supernovae is described. In addition to tracking Monte Carlo quanta to follow the emission, scattering and deposition of radiative energy, a scheme involving volume-based Monte Carlo estimators is used to allow properties of the emergent radiation field to be extracted for specific viewing angles in a multi-dimensional structure. This eliminates the need to compute spectra or light curves by angular binning of emergent quanta. The code is applied to two test problems to illustrate consequences of multi-dimensional structure on the modelling of light curves. First, elliptical models are used to quantify how large scale asphericity can introduce angular dependence to light curves. Secondly, a model which incorporates complex structural inhomogeneity, as predicted by modern explosion models, is used to investigate how such structure may affect light curve properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0611/0611677v2.pdf"}
{"id": "astro-ph0612146", "abstract": "  We propose to measure the weak cosmic shear using the spatial derivatives of the galaxy surface brightness field. The measurement should be carried out in Fourier space, in which the point spread function (PSF) can be transformed to a desired form with multiplications, and the spatial derivatives can be easily measured. This method is mathematically well defined regardless of the galaxy morphology and the form of the PSF, and involves simple procedures of image processing. Furthermore, with high resolution galaxy images, this approach allows one to probe the shape distortions of galaxy substructures, which can potentially provide much more independent shear measurements than the ellipticities of the whole galaxy. We demonstrate the efficiency of this method using computer-generated mock galaxy images. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0612/0612146v2.pdf"}
{"id": "astro-ph0612210", "abstract": "  Recent observations show that the number of stars with very low metallicities in the dwarf spheroidal satellites of the Milky Way is low, despite the low average metallicities of stars in these systems. We undertake numerical simulations of star formation and metal enrichment of dwarf galaxies in order to verify whether this result can be reproduced with \"standard\" assumptions. The answer is likely to be negative, unless some selection bias against very low metallicity stars is present in the observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0612/0612210v1.pdf"}
{"id": "astro-ph0612374", "abstract": "  I review existing methods for determining mass-loss rates of red giants and red supergiants based on infrared data. The simplest method is based on models for the absorption and emission by dust which forms in the dense outflows from these cool stars. I discuss the parameters and assumptions upon which the method relies, review relationships between the mass-loss rate and infrared colours or far-infrared flux density, and propose a new formula for the mass-loss rate as a function of the visual extinction. I also briefly discuss the use of atomic and molecular transitions at infrared wavelengths. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0612/0612374v1.pdf"}
{"id": "astro-ph0612597", "abstract": "  Special relativistic and strong gravity effects are clearly seen in X-ray energy spectra from AGN. Most important here are the broad profiles of the Fe Kalpha line observed in a large fraction of sources. These indicate that X-ray generation and reprocessing takes place very close to the central black hole. Here we explore consequences of such effects on X-ray variability. We perform computations of a possible quasi-periodic signal from a Keplerian motion of primary X-ray source. We also study in some details the light-bending model of variability of the X-ray reprocessed component, extending previous work on the subject. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0612/0612597v1.pdf"}
{"id": "astro-ph0701173", "abstract": "  A mathematical approach to investigate particle acceleration at shock waves moving at arbitrary speed in a medium with arbitrary scattering properties was first discussed in (Vietri 2003) and (Blasi     Vietri 2005. We use this method and somewhat extend it in order to include the effect of a large scale magnetic field in the upstream plasma, with arbitrary orientation with respect to the direction of motion of the shock. We also use this approach to investigate the effects of anisotropic scattering on spectra and anisotropies of the distribution function of the accelerated particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0701/0701173v1.pdf"}
{"id": "astro-ph0701691", "abstract": "  We study the evolution of nitrogen resulting from a set of spiral and irregular galaxy models computed for a large number of input mass radial distributions and with various star formation efficiencies. We show that our models produce a nitrogen abundance evolution in good agreement with the observational data. In particular, low N/O values for high-redshift objects, such as those obtained for Damped Lyman Alpha galaxies can be obtained with our models simultaneously to higher and constant values of N/O as those observed for irregular and dwarf galaxies, at the same low oxygen abundances 12+log(O/H) ∼ 7 dex. The differences in the star formation histories of the regions and galaxies modeled are essential to reproduce the observational data in the N/O-O/H plane. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0701/0701691v1.pdf"}
{"id": "astro-ph0701912", "abstract": "  Recent studies indicate that Type Ia supernovae (SNe Ia) consist of two groups - a \"prompt\" component whose rates are proportional to the host galaxy star formation rate, whose members have broader lightcurves and are intrinsically more luminous, and a \"delayed\" component whose members take several Gyr to explode, have narrower lightcurves, and are intrinsically fainter. As cosmic star formation density increases with redshift, the prompt component should begin to dominate. We use a two-component model to predict that the average lightcurve width should increase by 6", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0701/0701912v2.pdf"}
{"id": "astro-ph0702051", "abstract": "  The study of stellar oscillations - asteroseismology - has revolutionized our understanding of the physical properties of the Sun, and similar potential for other stars has been demonstrated in recent years. In particular, asteroseismic studies can constrain the stellar size, temperature and composition, which are important parameters to our understanding of planetary structure and evolution. This makes asteroseismology a very powerful tool to complement planetary transits. As an example, the transit measurement alone does not give the radius of the planet unless the radius of the host star is known, which again requires a known distance to the system. Transit measurements will therefore often require additional measurements to establish the radius of the planet. With asteroseismology we can determine the radius of a star to very high precision (2-3", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0702/0702051v2.pdf"}
{"id": "astro-ph0703745", "abstract": "  We investigate the plasma dynamics (outflow speed and turbulence) inside polar plumes. We compare line profiles (mainly of O6) observed by the UVCS instrument on SOHO at the minimum of solar cycle 22-23 with model calculations. We consider Maxwellian velocity distributions with different widths in plume and inter-plume regions. Electron densities are assumed to be enhanced in plumes and to approach inter-plume values with increasing height. Different combinations of the outflow and turbulence velocity in the plume regions are considered. We compute line profiles and total intensities of the H1 Lyα and the O6 doublets. The observed profile shapes and intensities are reproduced best by a small solar wind speed at low altitudes in plumes that increases with height to reach ambient inter-plume values above roughly 3-4 R_ combined with a similar variation of the width of the velocity distribution of the scattering atoms/ions. We also find that plumes very close to the pole give narrow profiles at heights above 2.5 R_, which are not observed. This suggests a tendency for plumes to be located away from the pole. We find that the inclusion of plumes in the model computations provides an improved correspondence with the observations and confirms previous results showing that published UVCS observations in polar coronal holes can be roughly reproduced without the need for large temperature anisotropy. The latitude distributions of plumes and magnetic flux distributions are studied by analyzing data from different instruments on SOHO and with SOLIS. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0703/0703745v1.pdf"}
{"id": "astro-ph9504097", "abstract": "  It is already understood that the increasing observational evidence for an open Universe may be reconciled with inflation if our horizon is contained inside one single huge bubble nucleated during the inflationary phase transition. In the scenario we present here, the Universe consists of infinitely many superhorizon bubbles, like our own, the distribution of which can be made to peak at Ω_0≈ 0.2. Therefore, unlike the existing literature, we do not have to rely upon the anthropic principle nor upon special initial conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9504/9504097v1.pdf"}
{"id": "astro-ph9509125", "abstract": "  We present hybrid maps of the A and B images of 0957+561 from each of four sessions of 6 cm VLBI observations that span the six-year interval 1987-1993. The inner- and outer-jets are clearly detected, and confirm the structures reported previously. There is no evidence of change in the separation between the core and inner-jet components, so the prospect of measuring the time delay using differential proper motions is not promising. The flux density in the core of each image peaked between 1989 and 1992. From the variation in these flux densities, we obtain a time-delay estimate of ∼1 yr. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9509/9509125v1.pdf"}
{"id": "astro-ph9602156", "abstract": "  The conventional picture for the origin of the polarization of a supernova is based on a model of Thomson or resonance scattering of photons traveling through an aspherical supernova atmosphere. Positive detection of intrinsic polarization in SN 1987A is then interpretated as evidence of an asymmetrical supernova atmosphere. We show here a different view based on the scattering of the supernova light by a dusty circumstellar material (CSM), or the “light echo” effect. At a given epoch after the explosion, the observed photons consist of both those propagating directly from the supernova and those scattered by dust particles in the CSM. Polarized light can be produced if the distribution of the dust particles is aspherical. The model can reproduce both the time evolution of the observed broad band polarization of SN 1987A and major features of the polarization spectra. It is also successful in providing a natural model for the early infrared light curve, in particular the observed 30 day delay of the IR maximum compared to the maximum of the bolometric light curve. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9602/9602156v1.pdf"}
{"id": "astro-ph9603017", "abstract": "  The goal of the second flight of the Medium Scale Anisotropy Measurement (MSAM1-94) was to confirm the measurement of cosmic microwave background radiation (CMBR) anisotropy made in the first flight (MSAM1-92). The CMBR anisotropy and interstellar dust emission signals from the two flights are compared by forming the sum and difference of those portions of the data with the same pointings on the sky. The difference data are consistent with a null detection, while the summed data show significant signal. We conclude that MSAM1-92 and MSAM1-94 measured the same celestial signal. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9603/9603017v1.pdf"}
{"id": "astro-ph9603023", "abstract": "  We investigate the evolution of metal deficient stellar structures, presenting H-burning isochrones covering cluster ages from 800 Myr to 7 Gyr. Evolutionary evidences for selection effects in the metallicity distribution of very metal poor H-burning red giants are reported. The evolution of stars during central and shell He burning is further investigated, discussing the occurrence of He burning pulsators as a function of cluster age. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9603/9603023v1.pdf"}
{"id": "astro-ph9605116", "abstract": "  We compare the results of numerical simulations of thin and quasi-spherical (thick) accretion flows with existing analytical solutions. We use a Lagrangian code based on the Smooth Particle Hydrodynamics (SPH) scheme and an Eulerian finite difference code based on the Total Variation Diminishing (TVD) scheme. In one-dimensional thin flows, the results of the simulations, with or without shocks, agree very well with each other and with analytical solutions. In two-dimensional thick flows, the general features, namely the locations and strengths of centrifugal and turbulent pressure supported shocks, centrifugal barriers, and the funnel walls which are expected from analytical models, agree very well, though the details vary. Generally speaking, the locations of the shocks may be better obtained by SPH since the angular momentum is strictly preserved in SPH, but the shocks themselves are better resolved by TVD. The agreement of these code test results with analytical solutions provides us with confidence to apply these codes to more complex problems which we will discuss elsewhere. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9605/9605116v1.pdf"}
{"id": "astro-ph9607110", "abstract": "  We present results of RXTE observations of the low-mass X-ray binary and atoll source 4U 1608-52 made over 9 days during the decline of an X-ray intensity outburst in March 1996. A fast-timing analysis shows a strong and narrow quasi periodic oscillation (QPO) peak at frequencies between 850 and 890 Hz on March 3 and 6, and a broad peak around 690 Hz on March 9. Observations on March 12 show no significant signal. On March 3, the X-ray spectrum of the QPO is quite hard; its strength increases steadily from 5 % at ∼2 to ∼20 % at ∼12 keV. The QPO frequency varies between 850 and 890 Hz on that day, and the peak widens and its rms decreases with centroid frequency in a way very similar to the well-known horizontal branch oscillations (HBO) in Z-sources. We apply the HBO beat frequency model to atoll sources, and suggest that, whereas the model could produce QPOs at the observed frequencies, the lack of correlation we observe between QPO properties and X-ray count rate is hard to reconcile with this model. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9607/9607110v1.pdf"}
{"id": "astro-ph9608143", "abstract": "  We have investigated some statistical properties of integrated spectra of galaxies with principal component analysis. The projection of the spectra onto the plane defined by the first two principal components shows that normal galaxies are in a quasi-linear sequence that we call spectral sequence and is closely related to the Hubble morphological sequence. We verify that the spectral sequence is also an evolutive sequence, with galaxy spectra evolving from later to earlier spectral types. Considering the close correspondence between the spectral and morphological sequences, we speculate that galaxies may evolve morphologically along the Hubble sequence, from Sm/Im to E. If this is the case, the first galaxies were mainly gas rich irregular objects, which evolved later along the morphological sequence as long as mergers and interactions increased their masses and developed their spheroidal components. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9608/9608143v1.pdf"}
{"id": "astro-ph9610101", "abstract": "  We discuss the fragmentation of primordial gas clouds in the universe after decoupling. Comparing the time scale of collapse with that of fragmentation, we obtain the typical mass of a fragment both numerically and analytically. It is shown that the estimated mass gives the minimum mass of a fragment which is formed from the primordial gas cloud and is essentially determined by the Chandrasekhar mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9610/9610101v1.pdf"}
{"id": "astro-ph9701175", "abstract": "  Results from the Arecibo HI Strip Survey, an unbiased extragalactic HI survey, combined with optical and 21cm follow-up observations, determine the HI Mass Function and the cosmological mass density of HI at the present epoch. Both are consistent with earlier estimates, computed for the population of optically selected galaxies. This consistency occurs because, although the distribution of optical central surface brightnesses among galaxies is flat, we fail to find a population of galaxies with central surface brightnesses fainter than 24 B-mag/arcsec^2, even though there is no observational selection against them. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9701/9701175v1.pdf"}
{"id": "astro-ph9701190", "abstract": "  We present radio observations of the black hole candidate X-ray binary GX 339-4 with the Australia Telescope compact array. Mapping of the highest resolution 3.5 cm data reveals a jet-like extension, which if confirmed would be the first detection of a radio jet from a persistent black-hole candidate system. No evidence is found for associated structures such as bow shocks or jet lobes on larger scales. The spectral energy distribution from 22 - 3 cm is relatively flat, suggesting emission is dominated by a compact absorbed core. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9701/9701190v1.pdf"}
{"id": "astro-ph9702128", "abstract": "  Theories of stellar orbit diffusion in disk galaxies predict different rates of increase of the velocity dispersions parallel and perpendicular to the disk plane, and it is therefore of interest to measure the different velocity dispersion components in galactic disks of different types. We show that it is possible to extract the three components of the velocity ellipsoid in an intermediate-inclination disk galaxy from measured line-of-sight velocity dispersions on the major and minor axes. On applying the method to observations of the Sb galaxy NGC 488, we find evidence for a higher ratio of vertical to radial dispersion in NGC 488 than in the solar neighbourhood of the Milky Way (the only other place where this quantity has ever been measured). The difference is qualitatively consistent with the notion that spiral structure has been relatively less important in the dynamical evolution of the disk of NGC 488 than molecular clouds. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9702/9702128v1.pdf"}
{"id": "astro-ph9705106", "abstract": "  We report phase-resolved optical polarimetric, photometric and spectroscopic observations of RX J2115.7-5840 (= EUVE J2115-58.6, Craig 1996) which confirms the system to be a magnetic cataclysmic binary of the polar (AM Herculis) subclass. The optical light curve is sometimes flat and occasionally displays a pronounced bright phase, reminiscent of the self-eclipse of a small accretion spot by the revolving white dwarf, as seen in self-eclipsing polars. Our period search reveals ambiguous results only which can be interpret assuming that the white dwarf is not synchronously rotating with the binary orbit. We find circularly polarized cyclotron radiation with V/I ranging from 0", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9705/9705106v1.pdf"}
{"id": "astro-ph9711092", "abstract": "  The onset of gaseous inflows and central activity in interacting galaxies is driven largely by induced bars in the host galaxies. The stability of galaxies against growing bar modes is a direct function of their structural properties — galaxies with central bulges or low disk surface densities are more stable against central starbursts than are bulgeless or disk-dominated systems. Low surface brightness galaxies prove less prone to bar formation and central starbursts than do normal high surface brightness galaxies. This stability of LSB disks also resolves many of the dynamical pitfalls encountered when attempting to link poststarburst \"E+A\" galaxies to interactions involving normal high surface brightness galaxy progenitors. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9711/9711092v1.pdf"}
{"id": "astro-ph9711152", "abstract": "  We report the discovery of a variable blue straggler in the core of the globular cluster M5, based on a 12-hour long series of images obtained with the Planetary Camera aboard the Hubble Space Telescope. In addition, we present the light curves of 28 previously unknown or poorly studied large-amplitude variable stars (all but one are RR Lyrae) in the cluster core. A (V, U-I) color-magnitude diagram shows 24 blue stragglers within 2 core radii of the cluster center. The blue straggler population is significantly more centrally concentrated than the horizontal branch and red giant stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9711/9711152v1.pdf"}
{"id": "astro-ph9711239", "abstract": "  Various types of expansions in series of Chebyshev-Hermite polynomials currently used in astrophysics for weakly non-normal distributions are compared, namely the Gram-Charlier, Gauss-Hermite and Edgeworth expansions. It is shown that the Gram-Charlier series is most suspect because of its poor convergence properties. The Gauss-Hermite expansion is better but it has no intrinsic measure of accuracy. The best results are achieved with the asymptotic Edgeworth expansion. We draw attention to the form of this expansion found by Petrov for arbitrary order of the asymptotic parameter and present a simple algorithm realizing Petrov's prescription for the Edgeworth expansion. The results are illustrated by examples similar to the problems arising when fitting spectral line profiles of galaxies, supernovae, or other stars, and for the case of approximating the probability distribution of peculiar velocities in the cosmic string model of structure formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9711/9711239v1.pdf"}
{"id": "astro-ph9712045", "abstract": "  Out of about 500 Lithium-rich ROSAT counterparts, which are presumed to be low-mass pre-main sequence stars, 21 stars have been observed by HIPPARCOS. We study their parallaxes, proper motions, and photometric data. For 7 out of 10 Taurus and Lupus stars in our sample, proper motions and parallaxes are not inconsistent with membership to these associations, while most of the stars in Chamaeleon and Scorpius appear to be young foreground stars. Combined with ground based photometry and spectroscopy, HIPPARCOS parallaxes allow us to place 15 stars on an H-R diagram. All these 15 stars are indeed pre-main sequence stars with ages from 1 to 15 Myr. Only two of the stars are located on the Hayashi-tracks, whereas the other 13 are post-T Tauri stars located on radiative tracks. Although this sample is admittedly small, containing only 3", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9712/9712045v2.pdf"}
{"id": "astro-ph9801059", "abstract": "  We have searched the northern sky for pulsars at the low radio frequency of 81.5 MHz, using the 3.6-hectare array at Cambridge, England. The survey covered most of the sky north of declination -20 deg and provided sensitivities of order 200 mJy for pulsars not too close to the galactic plane. A total of 20 pulsars were detected, all of them previously known. The effective post-detection sampling rate was 1.3 kHz, and the sensitivity to low-dispersion millisecond pulsars was sufficient to allow the detection of objects similar to PSR J0437-4715 (period 5.7 ms, dispersion measure 2.6 cm^-3 pc, mean flux density 1 Jy). No such pulsars were found. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9801/9801059v1.pdf"}
{"id": "astro-ph9801150", "abstract": "  We present a list of candidates for high redshift late-type galaxies in the field around the z=3.79 quasar PC1643+4631A. Deep U,V and R imaging has been used to search for objects with a strong Lyman break between U and V, characteristic of galaxies with high hydrogen column densities at z∼ 3. A further study of the red objects detected by Hu     Ridgway (1994) has been done, allowing the temptative identification of many of them as low redshift (z∼ 0.4) elliptical galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9801/9801150v1.pdf"}
{"id": "astro-ph9802085", "abstract": "  A multivariate analysis of gamma-ray burst (GRB) bulk properties is presented to discriminate between distinct classes of GRBs. Several variables representing burst duration, fluence and spectral hardness are considered. Two multivariate clustering procedures are used on a sample of 797 bursts from the Third BATSE Catalog: a nonparametric average linkage hierarchical agglomerative clustering procedure validated with Wilks' Λ^* and other MANOVA tests; and a parametric maximum likelihood model-based clustering procedure assuming multinormal populations calculated with the EM Algorithm and validated with the Bayesian Information Criterion.   The two methods yield very similar results. The BATSE GRB population consists of three classes with the following Duration/Fluence/Spectrum bulk properties: Class I with long/bright/intermediate bursts, Class II with short/hard/faint bursts, and Class III with intermediate/intermediate/soft bursts. One outlier with poor data is also present. Classes I and II correspond to those reported by Kouveliotou et al. (1993), but Class III is clearly defined here for the first time. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9802/9802085v1.pdf"}
{"id": "astro-ph9803235", "abstract": "  We present an unbiased method for evaluating the ranges of ages and metallicities which are allowed by the photometric properties of the stellar populations that dominate the light of early-type galaxies in clusters. The method is based on the analysis of morphologically-classified early-type galaxies in 17 clusters at redshifts 0.3<z<0.9 and in the nearby Coma cluster using recent stellar population synthesis models that span a wide range of metallicities. We confirm that metallicity effects must play a role in the origin of the slope of the color-magnitude relation for cluster early-type galaxies. We show, however, that the small scatter of the color-magnitude relation out to redshifts z=1 does not formally imply a common epoch of major star formation for all early-type galaxies. Instead, it requires that galaxies assembling more recently be on average more metal-rich than older galaxies of similar luminosity. Regardless of the true ages and metallicities of early-type galaxies within the allowed range, their photometric properties and the implied strengths of several commonly used spectral indices are found to be consistent with apparently passive evolution of the stellar populations. Also, the implied dependence of the mass-to-light ratio on galaxy luminosity is consistent with the observed trend. The results of our unbiased analysis define the boundaries in age and metallicity that must be satisfied by theoretical studies aimed at explaining the formation and evolution of early-type galaxies in clusters. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9803/9803235v2.pdf"}
{"id": "astro-ph9806192", "abstract": "  The detection of an afterglow, following a gamma-ray burst (GRB), can be described reasonably well by synchrotron emission from a relativistic spherical expanding blast wave, driven by an expanding fireball. We perform detailed calculations considering the emission from the whole region behind the shock front. We use the Blandford McKee self similar adiabatic solution to describe the fluid behind the shock. Using this detailed model, we derive expressions for the peak flux, and the peak frequency at a given observed time. These expressions provide important numerical corrections to previous, more simplified models. We calculate the observed light curve and spectra for several magnetic field models. We show that both the light curve and the spectra are flat near the peak. This rules out the interpretation of the optical peak of GRB970508 as the peak of the light curve, predicted by the existing fireball models. We calculate the observed image of a GRB afterglow. The observed image is bright near the edge and dimmer at the center, thus creating a ring. The contrast between the edge and the center is larger at high frequencies and the width of the ring is smaller. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9806/9806192v1.pdf"}
{"id": "astro-ph9807146", "abstract": "  I first outline new results on the angular modulation of WIMP dark matter scattering on targets in terrestrial laboratories, based on our uncertainties of the WIMP halo distribution, I then outline an exciting new result which indicates that for the high end of allowed SUSY WIMP scattering cross sections there exists a new distribution of WIMP dark matter in our solar system which could produce a dramatically different signal from halo WIMP dark matter in terrestrial detectors. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9807/9807146v1.pdf"}
{"id": "astro-ph9807233", "abstract": "  We have discovered 20 dwarf Cepheids (DC) in the Carina dSph galaxy from the analysis of individual CCD images obtained for a deep photometric study of the system. These short-period pulsating variable stars are by far the most distant ( 100 kpc) and faintest (V   23.0) DCs known. The Carina DCs obey a well-defined period-luminosity relation, allowing us to readily distinguish between overtone and fundamental pulsators in nearly every case. Unlike RR Lyr stars, the pulsation mode turns out to be uncorrelated with light-curve shape, nor do the overtone pulsators tend towards shorter periods compared to the fundamental pulsators. Using the period-luminosity (PL) relations from Nemec et al. (1994 AJ, 108, 222) and McNamara (1995, AJ, 109, 1751), we derive (m-M)_0 = 20.06 +/- 0.12, for E(B-V) = 0.025 and [Fe/H] = -2.0, in good agreement with recent, independent estimates of the distance/reddening of Carina. The error reflects the uncertainties in the DC distance scale, and in the metallicity and reddening of Carina. The frequency of DCs among upper main sequence stars in Carina is approximately 3", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9807/9807233v1.pdf"}
{"id": "astro-ph9809305", "abstract": "  20 months of observations of the radio emission at 15 GHz from Cygnus X-1, starting in 1996 October, show variations at the binary period of 5.6 days, but with a phase offset from those at X-ray wavelengths. There are also longer-term variations on a time-scale of 150 days which are only loosely related to the soft X-ray flux. The source was in the hard/low X-ray state throughout this period. The mean 15-GHz flux density is 13 mJy, the radio spectrum is flat, and the semi-amplitude of the orbital modulation about 2 mJy. We discuss the possible origins of the modulation and the relationship to the soft X-ray emission. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9809/9809305v1.pdf"}
{"id": "astro-ph9810037", "abstract": "  We apply a simple statistical method (Derenzo     Hildebrand 1969) to estimating the completeness of quasar surveys. It requires that an area has been covered by two or more, preferably different, selection techniques. We use three suitable data sets with separate selections from: variability and UV-excess (170 quasars); objective prism and UV-excess (141 quasars); multicolour and X-ray (ROSAT, 19 quasars). We find that, for selection by UV-excess, the common limit of U-B ≤ -0.35 ± -0.05 leads to losses of ∼ 35", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9810/9810037v1.pdf"}
{"id": "astro-ph9812166", "abstract": "  We report simulations of the gas flow in the gravitational potential of the COBE NIR bulge and disk. These models lead to four–armed spiral structure between corotation of the bar and the Sun, in agreement with the observed spiral arm tangents. The 3-kpc-arm is identified with one of the arms emanating from the ends of the bar. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9812/9812166v1.pdf"}
{"id": "astro-ph9812204", "abstract": "  We investigate the dynamics of the recently proposed model of assisted inflation. In this model an arbitrary number of scalar fields with exponential potentials evolve towards an inflationary scaling solution, even if each of the individual potentials is too steep to support inflation on its own. By choosing an appropriate rotation in field space we can write down explicitly the potential for the weighted mean field along the scaling solution and for fields orthogonal to it. This demonstrates that the potential has a global minimum along the scaling solution. We show that the potential close to this attractor in the rotated field space is analogous to a hybrid inflation model, but with the vacuum energy having an exponential dependence upon a dilaton field. We present analytic solutions describing homogeneous and inhomogeneous perturbations about the attractor solution without resorting to slow-roll approximations. We discuss the curvature and isocurvature perturbation spectra produced from vacuum fluctuations during assisted inflation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9812/9812204v1.pdf"}
{"id": "astro-ph9812215", "abstract": "  We find a very strong correlation between the intrinsic spectral slope in X-rays and the amount of Compton reflection from a cold medium in Seyfert AGNs and in hard state of X-ray binaries with either black holes or weakly-magnetized neutron stars. Objects with soft intrinsic spectra show much stronger reflection than ones with hard spectra. We find that at a given spectral slope, black-hole binaries have similar or more reflection than Seyferts whereas neutron-star binaries in our sample have reflection consistent with that in Seyferts. The existence of the correlation implies a dominant role of the reflecting medium as a source of seed soft photons for thermal Comptonization in the primary X-ray source. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9812/9812215v1.pdf"}
{"id": "astro-ph9812320", "abstract": "  Most luminous infrared galaxies (LIGs) are closely interacting/merging systems rich in molecular gas. We study here the relationship between the stage of the galaxy-galaxy interactions, the molecular gas mass, and the star formation rate as deduced from the infrared luminosity L_IR in LIGs. We find a correlation between the CO(1-0) luminosity (a measure of molecular mass M(H_2)) and the projected separation of merger nuclei (indicator of merging stages) in a sample of 50 LIG mergers, which shows that the molecular gas content decreases as merging advances. The starburst is due to enhanced star formation in pre-existing molecular clouds and not to the formation of more molecular clouds from HI.   The molecular content is being rapidly depleted due to the starbursts as merging progresses. This is further supported by an anti-correlation between L_IR/M(H_2), the global measure of the star formation rate per unit gas mass, and the projected separation implying an enhanced star formation “efficiency” in late stage mergers compared to that of early mergers. This is the first evidence connecting the depletion of molecular gas with starbursts in interacting galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9812/9812320v1.pdf"}
{"id": "astro-ph9812358", "abstract": "  The luminous X-ray binary and black-hole candidate LMC X-1 has been observed with the Rossi X-ray Timing Explorer (RXTE) to search for quasi-periodic oscillations (QPO), previously reported in its high state. The source was observed monthly in a series of nine observations. Analysis of the temporal variations shows no evidence for QPO or other periodic changes, but correlations between the high-energy light curve and hardness of the spectrum are described. Spectral fits with two-component models demonstrate that the hardness variations come from changes in the intensity of the high-energy power-law tail. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9812/9812358v1.pdf"}
{"id": "astro-ph9901035", "abstract": "  This paper uses the caustic crossing events in the microlens data sets to explore the nature and location of the lenses. We conclude that the large majority of lenses, whether they are luminous or dark, are likely to be binaries. Further, we demonstrate that blending is an important feature of all the data sets. An additional interpretation suggested by the data, that the caustic crossing events along the directions to the Magellanic Clouds are due to lenses located in the Clouds, implies that most of the LMC/SMC events to date are due to lenses in the Magellanic Clouds. All of these conclusions can be tested. If they are correct, a large fraction of lenses along the direction to the LMC may be ordinary stellar binary systems, just as are the majority of the lenses along the direction to the Bulge. Thus, a better understanding of the larger-than-anticipated value derived for the Bulge optical depth may allow us to better interpret the large value derived for the optical depth to the LMC. Indeed, binarity and blending in the data sets may illuminate connections among several other puzzles: the dearth of binary-source light curves, the dearth of non-caustic-crossing perturbed binary-lens events, and the dearth of obviously blended point-lens events. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9901/9901035v1.pdf"}
{"id": "astro-ph9901285", "abstract": "  We discuss the interpretation of transient, unpulsed radio emission detected from the unique pulsar/Be-star binary system PSR B1259-63. Extensive monitoring of the 1994 and 1997 periastron passages has shown that the source flares over a 100-day interval around periastron, varying on time-scales as short as a day and peaking at 60 mJy ( 100 times the apastron flux density) at 1.4 GHz. Interpreting the emission as synchrotron radiation, we show that (i) the observed variations in flux density are too large to be caused by the shock interaction between the pulsar wind and an isotropic, radiatively driven, Be-star wind, and (ii) the radio emitting electrons do not originate from the pulsar wind. We argue instead that the radio electrons originate from the circumstellar disk of the Be star and are accelerated at two epochs, one before and one after periastron, when the pulsar passes through the disk. A simple model incorporating two epochs of impulsive acceleration followed by synchrotron cooling reproduces the essential features of the radio light curve and spectrum and is consistent with the system geometry inferred from pulsed radio data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9901/9901285v1.pdf"}
{"id": "astro-ph9902196", "abstract": "  The CCD magnitudes in Johnson BV and Cousins R photometric passbands are determined for the optical transient of GRB 990123. These observations have been taken approximately 12 hours after trigger of the gamma-ray burst. BVR photometric light curves are obtained by combining the published data with the present measurements. They indicate that the flux decay constants in BV and R passbands are almost the same. Its value is 1.1± 0.06. Such decay is quite consistent with the fireball models for the optical transient. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9902/9902196v2.pdf"}
{"id": "astro-ph9902311", "abstract": "  The bulk of the hydrogen in the universe transformed from neutral to ionized somewhere in the redshift interval 5 < z < 40, most likely due to ionizing photons produced by an early generation of stars or mini-quasars. The resulting free electrons, interacting with the CMB photons via Thomson scattering, are a mixed blessing, providing both a probe of the epoch of the first stars and a contaminant to the pristine primary anisotropy. Here we review our current knowledge of reionization with emphasis on inhomogeneities and describe the possible connections to CMB anisotropy. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9902/9902311v2.pdf"}
{"id": "astro-ph9903141", "abstract": "  This paper summarizes the observations which provide the best evidence for the presence of black holes in active galactic nuclei. This includes: X-ray variability; kinematical studies using optical emission lines as well as the distribution of megamaser spots; and the shape of the Fe Kα X-ray emission line. It also presents the current status of our understanding of jet-dominated active galaxies (blazars), and briefly reviews the currently popular AGN “Unification Schemes.” ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9903/9903141v1.pdf"}
{"id": "astro-ph9904240", "abstract": "  This investigation is aimed at clarifying the nature of the interstellar gas seen in absorption against bright O and B stars. Towards this end we have obtained for the first time HI absorption spectra towards radio sources very close to the lines of sight towards 25 bright stars previously studied. In this paper we describe the selection criteria, the details regarding our observations, and finally present the absorption spectra. In the accompanying paper we analyse the results and draw conclusions. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9904/9904240v1.pdf"}
{"id": "astro-ph9904327", "abstract": "  We present measurements of the Fundamental Plane (FP) parameters (the effective radius, the mean effective surface brightness, and the central velocity dispersion) of six field elliptical galaxies at intermediate redshift. The imaging is taken from the Medium Deep Survey of the Hubble Space Telescope, while the kinematical data are obtained from long-slit spectroscopy using the 3.6-m ESO telescope. The Fundamental Plane appears well defined in the field even at redshift ≈ 0.3. The data show a shift in the FP zero point with respect to the local relation, possibly indicating modest evolution, consistent with the result found for intermediate redshift cluster samples. The FP slopes derived for our field data, plus other cluster ellipticals at intermediate redshift taken from the literature, differ from the local ones, but are still consistent with the interpretation of the FP as a result of homology, of the virial theorem and of the existence of a relation between luminosity and mass, L ∝ M^η. We also derive the surface brightness vs. effective radius relation for nine galaxies with redshift up to z ≈0.6, and data from the literature; the evolution that can be inferred is consistent with what is found using the FP. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9904/9904327v1.pdf"}
{"id": "astro-ph9905059", "abstract": "  Realistic 3-dimensional (3D), radiative hydrodynamical surface convection simulations of the metal-poor halo stars HD 140283 and HD 84937 have been performed. Due to the dominance of adiabatic cooling over radiative heating very low atmospheric temperatures are encountered. The lack of spectral lines in these metal-poor stars thus causes much steeper temperature gradients than in classical 1D hydrostatic model atmospheres where the temperature of the optically thin layers is determined by radiative equilibrium. The modified atmospheric structures cause changes in the emergent stellar spectra. In particular, the primordial Li abundances may have been overestimated by 0.2-0.35 dex with 1D model atmospheres. However, we caution that our result assumes local thermodynamic equilibrium (LTE), while the steep temperature gradients may be prone to e.g. over-ionization. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9905/9905059v1.pdf"}
{"id": "astro-ph9905096", "abstract": "  We report on the analysis of high-speed photometry of the dwarf-nova HS1804+67 through its outburst cycle with eclipse mapping techniques. Eclipse maps show evidences of the formation of a spiral structure in the disc at the early stages of the outburst and reveal how the disc expands during the rise until its fills most of the primary Roche lobe at maximum light. During the decline phase, the disc becomes progressively fainter as the cooling front moves inwards from the outer regions, until only a small bright region around the white dwarf is left at minimum light. The variable part of the uneclipsed light is possibly due to emission in a wind emanating from the inner parts of the disc. The emission from this region is sensitive to the mass accretion rate. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9905/9905096v1.pdf"}
{"id": "astro-ph9906050", "abstract": "  This paper presents a quantification of the X-ray variability amplitude for 79 ASCA observations of 36 Seyfert 1 galaxies. We find that consideration of sources with the narrowest permitted lines in the optical band introduces scatter into the established correlation between X-ray variability and nuclear luminosity. Consideration of the X-ray spectral index and variability properties together shows distinct groupings in parameter space for broad and narrow-line Seyfert 1 galaxies, confirming previous studies. A strong correlation is found between hard X-ray variability and FWHM Hbeta. A range of nuclear mass and accretion rate across the Seyfert population can explain the differences observed in X-ray and optical properties. An attractive alternative model, which does not depend on any systematic difference in central mass, is that the circumnuclear gas of NLSy1s is different to BLSy1s in temperature, optical depth, density or geometry. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9906/9906050v2.pdf"}
{"id": "astro-ph9906187", "abstract": "  The effects of differences between the local and global values of the Hubble parameter on the cosmologies consistent with studies of high-redshift Type Ia supernovæare discussed. It is found that with a local Hubble parameter around 10 per cent higher than the global value then open cosmological models (such as Ω_M = 0.3, Ω_Λ=0) are prefered and if the local value is around 20 per cent higher then standard cosmological models (Ω_M = 1, Ω_Λ=0) can be recovered. Even in the case where the Hubble parameter ratio is 1, low Ω_M open cosmologies with Ω_Λ = 0 are not rejected at the 95 per cent confidence level. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9906/9906187v1.pdf"}
{"id": "astro-ph9906217", "abstract": "  The thermal and chemical phases of the cool component of interstellar gas are discussed. Variations with galactocentric radius and from galaxy to galaxy are mostly the result of changes in the ambient interstellar pressure and radiation field. Interstellar structure that is hierarchical or fractal in the cloudy parts and has large and connected empty regions between these clouds is probably the result of turbulence. Such structure opens up the disk to the transmission of OB star light into the halo, and it provides for a diffuse ionized component that tapers away gradually from each dense HII region. Fractal cloud structure may also produce the cloud and clump mass functions, and perhaps even the star cluster mass function. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9906/9906217v1.pdf"}
{"id": "astro-ph9906376", "abstract": "  This paper studies multistep methods for the integration of reversible dynamical systems, with particular emphasis on the planar Kepler problem. It has previously been shown by Cano     Sanz-Serna that reversible linear multisteps for first-order differential equations are generally unstable. Here, we report on a subset of these methods – the zero-growth methods – that evade these instabilities. We provide an algorithm for identifying these rare methods. We find and study all zero-growth, reversible multisteps with six or fewer steps. This select group includes two well-known second-order multisteps (the trapezoidal and explicit midpoint methods), as well as three new fourth-order multisteps – one of which is explicit. Variable timesteps can be readily implemented without spoiling the reversibility. Tests on Keplerian orbits show that these new reversible multisteps work well on orbits with low or moderate eccentricity, although at least 100 steps/radian are required for stability. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9906/9906376v1.pdf"}
{"id": "astro-ph9906491", "abstract": "  The amplitude of jet distortions and accompanying pressure and velocity fluctuations resulting from Kelvin-Helmholtz instability of three dimensional relativistic jets are explored. The effect of instability on jets as they accelerate from sub- to super-Alfvénic speeds is explored and a relativistic stabilization mechanism for trans-Alfvénic jets is proposed. The level to which asymmetric instabilities on supermagnetosonic relativistic jets will grow is predicted theoretically and a Doppler boosted “apparent” emissivity is computed. Effects due to helically twisted filamentary structure produced by asymmetric modes of instability should be readily observable on relativistic jets. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9906/9906491v1.pdf"}
{"id": "astro-ph9907111", "abstract": "  We report on the detection of radio emission from the accretion-powered X-ray millisecond pulsar SAX J1808.4-3658, using the Australia Telescope Compact Array. We detected a  0.8 mJy source at the position of SAX J1808.4-3658 on 1998 April 27, approximately one day after the onset of a rapid decline in the X-ray flux; no such source was seen on the previous day. We consider this emission to be related to the radio emission from other X-ray binaries, and is most likely associated with an ejection of material from the system. No radio emission was detected at later epochs, indicating that if SAX J1808.4-3658 is a radio pulsar during X-ray quiescence then its monochromatic luminosity must be less than L(1.4 GHz)  6 mJy/kpc^2. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9907/9907111v1.pdf"}
{"id": "astro-ph9907250", "abstract": "  The aperture mass has been shown in a series of recent publications to be a useful quantitative tool for weak lensing studies, ranging from cosmic shear to the detection of a mass-selected sample of dark matter haloes. Quantitative analytical predictions for the aperture mass have been based on a number of simplifying assumptions. In this paper, we test the reliability of these assumptions and the quality of the analytic approximations, using ray-tracing simulations through a cosmological density field generated by very large N-body simulations. We find that those analytic predictions which take into account the non-linear evolution of the matter distribution, such as the dispersion of the aperture mass and the halo abundance, are surprisingly accurately reproduced with our numerical results, whereas the predictions for the skewness, based on quasi-linear theory, are rather imprecise. In particular, we verify numerically that the probability distribution of the aperture mass decreases exponentially for values much larger than the rms. Given the good overall agreement, comparisons between the observed distribution of the aperture mass and the theoretical values provide a powerful tool for testing cosmological models. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9907/9907250v2.pdf"}
{"id": "astro-ph9907278", "abstract": "  We have analyzed high velocity resolution HI synthesis observations of the nearly face-on Sc galaxy NGC 1232. The neutral gas distribution extends well beyond the optical extent of the galaxy. As expected, local peaks in the HI column density are associated with the spiral arms. Further, the HI column density drops precipitously near the center of the galaxy. Closed contours in the velocity field suggest either that the system is warped, or that the rotation curve declines. The velocity dispersion is approximately constant throughout the system, with a median value of 9.9 +/- 1.8 km/s. When corrected for rotational broadening, there is no indication of a radial trend in the neutral gas velocity dispersion in this galaxy. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9907/9907278v1.pdf"}
{"id": "astro-ph9907296", "abstract": "  We have analysed in detail the discovery measurements of the X-ray burster SAX J1750.8-2900 by the Wide Field Cameras on board BeppoSAX in spring 1997, at a position  1.2 degrees off the Galactic Centre. The source was in outburst on March 13th when the first observation started and showed X-ray emission for   2 weeks. A total of 9 bursts were detected, with peak intensities varying from   0.4 to 1.0 Crab in the 2-10 keV range. Most bursts showed a fast rise time (  1s), an exponential decay profile with e-folding time of   5s, spectral softening during decay, and a spectrum which is consistent with few keV blackbody radiation. These features identify them as type-I X-ray bursts of thermonuclear origin. The presence of type-I bursts and the source position close to the Galactic Centre favours the classification of this object as a neutron star low mass X-ray binary. X-ray emission from SAX J1750.8-2900 was not detected in the previous and subsequent Galactic bulge monitoring, and the source was never seen bursting again. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9907/9907296v1.pdf"}
{"id": "astro-ph9907403", "abstract": "  Measuring the evolution in the clustering of galaxies over a large redshift range is a challenging problem. For a two-dimensional galaxy catalog, however, we can measure the galaxy-galaxy angular correlation function which provides information on the density distribution of galaxies. By utilizing photometric redshifts, we can measure the angular correlation function in redshift shells (Brunner 1997, Connolly et al. 1998) which minimizes the galaxy projection effect, and allows for a measurement of the evolution in the correlation strength with redshift. In this proceedings, we present some preliminary results which extend our previous work using more accurate photometric redshifts, and also incorporate absolute magnitudes, so that we can measure the evolution of clustering with either redshift or intrinsic luminosity. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9907/9907403v1.pdf"}
{"id": "astro-ph9908229", "abstract": "  We present the ASCA results of imaging spectroscopy of the giant molecular cloud Sgr B2. The X-ray spectrum is found to be very peculiar; it exhibits a strong emission line at 6.4 keV, a low energy cutoff below about 4 keV and a pronounced edge-structure at 7.1 keV. The X-ray image is extended and its peak position is shifted from the core of the molecular cloud toward the Galactic center by about 1–2 arcminute. The X-ray spectrum and the morphology are well reproduced by a scenario that X-rays from an external source located in the Galactic center direction are scattered by the molecular cloud Sgr B2, and come into our line of sight. Thus Sgr B2 may be called an X-ray reflection nebula. Possible implications of the Galactic center activity related to this unique source are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9908/9908229v1.pdf"}
{"id": "astro-ph9909001", "abstract": "  This paper presents color transformations for HST NICMOS camera 2 observations to the ground-based CIT/CTIO photometric system, using observations of nineteen moderately bright, red stars in Baade's window in the color range 0.7 < (J-K) < 1.6. We estimate an extension of the transformation to 0.4 < (J-K) < 3.0 with five standards observed by STScI. Convolving near-IR spectra taken above the atmosphere with different filter transmission profiles, we simulate both NICMOS and ground-based photometry, obtaining results which are consistent with our transformation and its extension. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9909/9909001v1.pdf"}
{"id": "astro-ph9909225", "abstract": "  Recent measurements of type Ia supernovae indicate that distant supernovae are substantially fainter than expected from the standard flat cold dark matter model. One possible explanation is that the energy density in our universe is in fact dominated by a cosmological constant. Another possible solution is that there are large amounts of grey dust in the intergalactic medium. Dust grains can be grey either because they are non-spherical or very large. We have numerically investigated whether grey dust can be emitted from high redshift galaxies without also emitting standard, reddening dust, which would have been visible in the spectra of high redshift objects. Our finding is that grain velocities are almost independent of ellipticity so that if greyness are due to the grains being elongated, it will not be possible to separate grey dust from ordinary dust. We also find that velocities are fairly independent of grain size, but we cannot rule out possible sputtering of small grains, so that large, grey dust grains could be preferentially emitted. Therefore, our conclusion is that grey dust is an unlikely explanation of the data, but we cannot rule it out if the grey dust consists of large, spherical grains. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9909/9909225v1.pdf"}
{"id": "astro-ph9909267", "abstract": "  We show that the mass function of black holes expected from the past quasar activity (both visible and obscured) is consistent with the number of dormant black holes found in the bulges of nearby galaxies. The joint formation of quasars and bulges is addressed by means of an analytical model for galaxy formation, based on the hierarchical clustering of cold dark matter halos. The model is able to reproduce the main statistical properties of both populations under the hypotheses that (i) star formation and quasar shining follow an anti-hierarchical order, and (ii) galaxy morphology and final black hole mass are determined by the same physical process. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9909/9909267v2.pdf"}
{"id": "astro-ph9911087", "abstract": "  We present new evolutionary models for zero-metallicity stars, covering a large range of initial masses (from 0.8 to 100 M_sun). Models are computed with overshooting from stellar cores and convective envelopes, and assuming mass-loss from the most massive stars. We discuss the main evolutionary features of these stars, and provide estimates of the amount of newly-synthesized elements dredged-up to the stellar surface, and possibly lost by stellar winds from the most massive stars. Full details of these models will be given in Marigo et al. (2000, in preparation). ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9911/9911087v1.pdf"}
{"id": "astro-ph9911089", "abstract": "  We investigate the statistical evolution of magnetic neutron stars recycled in Low Mass Binary (LMB) systems, simulating synthetic populations. Irrespective to the details of the physical models, we find to be significant the fraction of neutron stars spinning close to their mass shedding limit relative to the millisecond pulsar population. The simulated neutron stars show a tail in their period distribution at periods shorter than 1.558 ms, the minimum detected so far. Crustal magnetic field decay models predict also the existence of massive rapidly spinning neutron stars with very low magnetic moment. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9911/9911089v1.pdf"}
{"id": "astro-ph9911096", "abstract": "  In a recent letter (ApJ 517, L155) Lenz et al. have shown the evidence of uniform temperature along steady long coronal loops observed by TRACE in two different passbands (171 A and 195 A filters). We propose that such an evidence can be explained by the sub-arcsecond structuring of the loops across the magnetic field lines. In this perspective, we present a model of a bundle of six thin parallel hydrostatic filaments with temperature stratification dictated by detailed energy balance and with temperatures at their apex ranging between 0.8 and 5 MK. If analyzed as a single loop, the bundle would appear isothermal along most of its length. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9911/9911096v1.pdf"}
{"id": "astro-ph9911302", "abstract": "  Recent VLBI observations have identified several compact radio sources which have symmetric structures on parsec scales, and exhibit HI absorption which appears to be associated with the active nucleus. These sources are uniquely well suited to investigations into the physics of the central engines, in particular to studies of the kinematics of the gas within 100 pc of the core. In these compact sources, it is reasonable to assume that this circumnuclear material is accreting onto, and “feeding”, the central engine.   We present results of HI imaging studies of 3 symmetric radio galaxies which show evidence of a circumnuclear torus. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9911/9911302v1.pdf"}
{"id": "astro-ph9912120", "abstract": "  It has recently been suggested that Compton downscattering may give rise to the broad iron lines seen in the X-ray spectra of Seyfert 1 galaxies. This challenges the standard model in which these lines originate from the innermost regions of the black hole accretion disk with Doppler shifts and gravitational redshifts giving rise to the broadened line profile. Here, we apply observational constraints to the Compton downscattering model for MCG-6-30-15 and NGC3516, the two best cases to date of Seyfert galaxies with relativistically broad lines. We show that the continuum source in MCG-6-30-15 required by the constrained model violates the black body limit. In the case of NGC3516, only a very small region of parameter space is compatible with the constraints. Hence, we conclude that the Comptonization model is not a viable one for the broad line seen in these two objects. The accretion disk model remains the best interpretation of these data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9912/9912120v2.pdf"}
{"id": "astro-ph9912259", "abstract": "  Evidence is emerging that the luminous X-ray sources in the cores of globular clusters may often consist of, or perhaps even as a class be dominated by, ultracompact (P < 1 hr) binary stars. To the two such systems already known, in NGC 6624 and NGC 6712, we now add evidence for two more. We detect large amplitude variability in the candidate optical counterpart for the X-ray source in the core of NGC 6652. Although the available observations are relatively brief, the existing Hubble Space Telescope data indicate a strong 43.6 min periodic modulation of the visible flux of semi-amplitude 30", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9912/9912259v1.pdf"}
{"id": "astro-ph9912423", "abstract": "  Optical and near-infrared observations of the GRB990705 error box were carried out with ESO telescopes at La Silla and Paranal in Chile and with the NOAO SPIREX 0.6-meter telescope in Antarctica. We detected the counterpart of this GRB in the near-infrared H band and optical V band. The power-law decline of the near-infrared lightcurve is rather steep with a decay index alpha   1.7 in the first hours, and a possible steepening after one day. Broadband spectral analysis of the optical/near-infrared afterglow suggests that this GRB took place in a high density environment. A deep optical image obtained at Antu (VLT-UT1) about 5 days after the GRB trigger shows at the position of the transient an extended object which might be the host galaxy of GRB990705. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9912/9912423v1.pdf"}
{"id": "astro-ph9912528", "abstract": "  Using the all-sky ROSAT soft X-ray and 408-MHz radio continuum data, we show that the North Polar Spur and its western and southern counter-spurs draw a giant dumbbell-shape necked at the galactic plane. We interpret these features as due to a shock front originating from a starburst 15 million years ago with a total energy of the order of ∼ 10^56 ergs or 10^5 type II supernovae. We simulate all-sky distributions of radio continuum and soft X-ray intensities based on the bipolar-hyper-shell galactic center starburst model. The simulations can well reproduce the radio NPS and related spurs, as well as radio spurs in the tangential directions of spiral arms. Simulated X-ray maps in 0.25, 0.75 and 1.5 keV bands reproduce the ROSAT X-ray NPS, its western and southern counter-spurs, and the absorption layer along the galactic plane. We propose to use the ROSAT all-sky maps to probe the physics of gas in the halo-intergalactic interface, and to directly date and measure the energy of a recent Galactic Center starburst. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9912/9912528v1.pdf"}
{"id": "chao-dyn9710016", "abstract": "  Hierarchic properties of chaotic scattering in a model of satellite encounters, studied first by Petit and Henon, are examined by decomposing the dwell time function and comparing scattering trajectories. The analysis reveals an (approximate) ternary organization in the chaotic set of bounded orbits and the presence of a stable island. The results can open the way for a calculation of global quantities characterizing the scattering process by using tools of the thermodynamic formalism. ", "pdf_url": "gs://arxiv-dataset/arxiv/chao-dyn/pdf/9710/9710016v1.pdf"}
{"id": "chao-dyn9902007", "abstract": "  We study a minimal shell model for the advection of a passive scalar by a Gaussian time correlated velocity field. The anomalous scaling properties of the white noise limit are studied analytically. The effect of the time correlations are investigated using perturbation theory around the white noise limit and non-perturbatively by numerical integration. The time correlation of the velocity field is seen to enhance the intermittency of the passive scalar. ", "pdf_url": "gs://arxiv-dataset/arxiv/chao-dyn/pdf/9902/9902007v3.pdf"}
{"id": "chao-dyn9907023", "abstract": "  The structure of the concentration field of a decaying substance produced by chemical sources and advected by a smooth incompressible two-dimensional flow is investigated. We focus our attention on the non-uniformities of the Hölder exponent of the resulting filamental chemical field. They appear most evidently in the case of open flows where irregularities of the field exhibit strong spatial intermittency as they are restricted to a fractal manifold. Non-uniformities of the Hölder exponent of the chemical field in closed flows appears as a consequence of the non-uniform stretching of the fluid elements. We study how this affects the scaling exponents of the structure functions, displaying anomalous scaling, and relate the scaling exponents to the distribution of finite-time Lyapunov exponents of the advection dynamics. Theoretical predictions are compared with numerical experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/chao-dyn/pdf/9907/9907023v1.pdf"}
{"id": "cond-mat0001229", "abstract": "  We elaborate on several observable consequences of the Quantum-Critical-Point scenario. In particular we show that the strong k-dependent scattering of the quasiparticles with the quasi-critical charge and spin fluctuations reproduces the main features of the low-energy spectral weights and of the observed Fermi surfaces. In the underdoped cuprates the attractive k-dependent charge scattering drives the formation of the pseudogap at the M points below the crossover temperature T^*. In this context we discuss models for pseudogap formation with relevant scattering in the particle-particle and particle-hole channels. The experimental consequences for the pair-fluctuation and for the pseudogap behavior are investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0001/0001229v1.pdf"}
{"id": "cond-mat0002223", "abstract": "  Coherent stochastic resonance is explained in terms of first passage time density functions. Scaling relation between first passage time density functions at resonance for different lengths of the medium is obtained. A formula for first passage time density function at resonance is derived in terms of two universal functions, which demonstrates the universal feature of coherent stochastic resonance. A simple approximate expression for first passage time density function at resonance is proposed which is shown to explain the behavior at resonance fairly accurately. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0002/0002223v1.pdf"}
{"id": "cond-mat0002442", "abstract": "  We explore how the spiral spin(SP) state, a spin singlet known to accompany fully-polarized ferromagnetic (F) states in the Hubbard model, is related with the F state in the thermodynamic limit using the density matrix renormalization group and exact diagonalization. We first obtain an indication that when the F state is the ground state the SP state is also eligible as the ground state in that limit. We then follow the general argument by Koma and Tasaki [J. Stat. Phys. 76, 745 (1994)] to find that: (i) The SP state possesses a kind of order parameter. (ii) Although the SP state does not break the SU(2) symmetry in finite systems, it does so in the thermodynamic limit by making a linear combination with other states that are degenerate in that limit. We also calculate the one-particle spectral function and dynamical spin and charge susceptibilities for various 1D finite-size lattices. We find that the excitation spectrum of the SP state and the F state is almost identical. Our present results suggest that the SP and the F states are equivalent in the thermodynamic limit. These properties may be exploited to determine the magnetic phase diagram from finite-size studies. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0002/0002442v1.pdf"}
{"id": "cond-mat0003322", "abstract": "  We argue that the superconducting state found in high-T_c cuprates is inhomogeneous with a corresponding inhomogeneous superfluid density. We introduce two classes of microscopic models which capture the magnetic and superconducting properties of these strongly correlated materials. We start from a generalized t-J model, in which appropriate inhomogeneous terms mimic stripes. We find that inhomogeneous interactions that break magnetic symmetries are essential to induce substantial pair binding of holes in the thermodynamic limit. We argue that this type of model reproduces the ARPES and neutron scattering data seen experimentally. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0003/0003322v1.pdf"}
{"id": "cond-mat0003444", "abstract": "  By making use of the Langevin dynamics and its generating functional (GF) formulation the influence of the long-range nature of the interaction on the tendency of the glass formation is systematically investigated. In doing so two types of models is considered: (i) the non-disordered model with a pure repulsive type of interaction and (ii) the model with a randomly distributed strength of interaction (a quenched disordered model). The long-ranged potential of interaction is scaled with a number of particles N in such a way as to enable for GF the saddle-point treatment as well as the systematic 1/N - expansion around it. We show that the non-disordered model has no glass transition which is in line with the mean-field limit of the mode - coupling theory (MCT) predictions. On the other hand the model with a long-range interaction which above that has a quenched disorder leads to MC - equations which are generic for the p - spin glass model and polymeric manifold in a random media. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0003/0003444v1.pdf"}
{"id": "cond-mat0004169", "abstract": "  We study a heteropolymer model with random contact interactions introduced some time ago as a simplified model for proteins. The model consists of self-avoiding walks on the simple cubic lattice, with contact interactions between nearest neighbor pairs. For each pair, the interaction energy is an independent Gaussian variable with mean value B and variance ^2. For this model the annealed approximation is expected to become exact for low disorder, at sufficiently high dimension and in the thermodynamic limit. We show that corrections to the annealed approximation in the 3-d high temperature phase are small, but do not vanish in the thermodynamic limit, and are in good agreement with our replica symmetric calculations. Such corrections derive from the fact that the overlap between two typical chains is nonzero. We explain why previous authors had come to the opposite conclusion, and discuss consequences for the thermodynamics of the model. Numerical results were obtained by simulating chains up to length 1400 by means of the recent PERM algorithm, in the coil and molten globular phases, well above the freezing temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0004/0004169v1.pdf"}
{"id": "cond-mat0004210", "abstract": "  Low temperature quantum corrections to the density of states (DOS) and the conductivity are examined for a two-dimensional(2D) square crystal with substitutional impurities. By summing the leading logarithmic corrections to the DOS its energy dependence near half-filling is obtained. It is shown that substitutional impurities do not suppress the van Hove singularity at the middle of the band, however they change its energy dependence strongly. Weak disorder due to substitutional impurities in the three-dimensional simple cubic lattice results in a shallow dip in the center of the band. The calculation of quantum corrections to the conductivity of a 2D lattice shows that the well-known logarithmic localization correction exists for all band fillings. Furthermore the magnitude of the correction increases as half-filling is approached. The evaluation of the obtained analytical results shows evidence for delocalized states in the center of the band of a 2D lattice with substitutional impurities. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0004/0004210v1.pdf"}
{"id": "cond-mat0006229", "abstract": "  We present a numerical method for the investigation of non-ergodic effects in the Coulomb glass. For that, an almost complete set of low-energy many-particle states is obtained by a new algorithm. The dynamics of the sample is mapped to the graph formed by the relevant transitions between these states, that means by transitions with rates larger than the inverse of the duration of the measurement. The formation of isolated clusters in the graph indicates non-ergodicity. We analyze the connectivity of this graph in dependence on temperature, duration of measurement, degree of disorder, and dimensionality, studying how non-ergodicity is reflected in the specific heat. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0006/0006229v1.pdf"}
{"id": "cond-mat0006287", "abstract": "  The permeability of two-dimensional fractures with self-affine fractal roughness is studied via analytic arguments and numerical simulations. The limit where the roughness amplitude is small compared with average fracture aperture is analyzed by a perturbation method, while in the opposite case of narrow aperture, we use heuristic arguments based on lubrication theory. Numerical simulations, using the lattice Boltzmann method, are used to examine the complete range of aperture sizes, and confirm the analytic arguments. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0006/0006287v1.pdf"}
{"id": "cond-mat0006337", "abstract": "  We study the electronic properties of an array of small metallic grains connected by tunnel junctions. Such an array serves as a model for a granular metal. Previous theoretical studies of junction arrays were based on models of quantum dissipation which did not take into account the diffusive motion of electrons within the grains. We demonstrate that these models break down at sufficiently low temperatures: for a correct description of the screening properties of a granular metal at low energies the diffusive nature of the electronic motion within the grains is crucial. We present both a diagrammatic and a functional integral approach to analyse the properties of junction arrays. In particular, a new effective action is obtained which enables us to describe the array at arbitrary temperature. In the low temperature limit, our theory yields the correct, dynamically screened Coulomb interaction of a normal metal, whereas at high temperatures the standard description in terms of quantum dissipation is recovered. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0006/0006337v1.pdf"}
{"id": "cond-mat0011059", "abstract": "  A new formalism to calculate the transmission coefficient t of electrons from a material L into the same material L through a barrier B is presented. The barrier B is arbitrary and can be metallic, semiconducting or insulating. The important feature of this formalism is that it starts from the electronic structure of a periodic L/B superlattice. The electronic stucture of such a superlattice is calculated selfconsistently within a Screened Korringa-Kohn-Rostoker method. The capability of the new method is demonstrated by means of a free electron model. First results for the transmission of Cu electrons through a Co layer are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0011/0011059v1.pdf"}
{"id": "cond-mat0011278", "abstract": "  We present a tight-binding potential based on the moment expansion of the density of states, which includes up to the fifth moment. The potential is fitted to bcc and hcp Zr and it is applied to the computation of vibrational properties of bcc-Zr. In particular, we compute the isothermal elastic constants in the temperature range 1200K < T < 2000K by means of standard Monte Carlo simulation techniques. The agreement with experimental results is satisfactory, especially in the case of the stability of the lattice with respect to the shear associated with C'. However, the temperature decrease of the Cauchy pressure is not reproduced. The T=0K phonon frequencies of bcc-Zr are also computed. The potential predicts several instabilities of the bcc structure, and a crossing of the longitudinal and transverse modes in the (001) direction. This is in agreement with recent ab initio calculations in Sc, Ti, Hf, and La. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0011/0011278v2.pdf"}
{"id": "cond-mat0011323", "abstract": "  A recently developed method [A. Shelankov and M. Ozana, Phys. Rev. B 61, 7077 (2000)] is applied to investigate d-wave superconductors in the vicinity of (rough) surfaces. While this method allows the incorporation of arbitrary interfaces into the quasiclassical technique, we discuss, as examples, diffusive surfaces and boundaries with small tilted mirrors (facets). The properties of the surface enter via the scattering matrix in the boundary condition for the quasiclassical Green's function. The diffusive surface is described by an ensemble of random scattering matrices. We find that the fluctuations of the density of states around the average are small; the zero bias conductance peak broadens with increasing disorder. The faceted surface is described in the model where the scattering matrix couples m in- and m out-trajectories (m>=2). No zero bias conductance peak is found for [100] surfaces; the relation to the model of Fogelstrom et al. [Phys. Rev. Lett. 79, 281 (1997)] is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0011/0011323v2.pdf"}
{"id": "cond-mat0011450", "abstract": "  A simple numerical model is used to simulate the effect of vertical taps on a packing of monodisperse hard spheres. Our results are in agreement with an experimantal work done in Chicago and with other previous models, especially concerning the dynamics of the compaction, the influence of the excitation strength on the compaction efficiency, and some ageing effects. The principal asset of the model is that it allows a local analysis of the packings. Vertical and transverse density profiles are used as well as size and volume distributions of the pores. An interesting result concerns the appearance of a vertical gradient in the density profiles during compaction. Furthermore, the volume distribution of the pores suggests that the smallest pores, ranging in size between a tetrahedral and an octahedral site, are not strongly affected by the tapping process, in contrast to the largest pores which are more sensitive to the compaction of the packing. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0011/0011450v5.pdf"}
{"id": "cond-mat0012012", "abstract": "  We have proposed a qualitative model for the structure of binary systems similar to Pd-Er alloys, which explains their nonmonotonic relaxation after the hydrogen saturation. It is based on the assumption that such a solid solution involves two kind heterogeneities. The former are caused by spinodal decomposition of the initially homogeneous state of the solid solution into the phases enriched and depleted of Er atoms. The latter are crystalline defects that trap an additional amount of Er atoms, which leads also to their local accumulation, changing the defect properties. Hydrogen atoms penetrating into the solid disturb the equilibrium of both the phase separation and the defect saturation with Er atoms, causing redistribution of Er atoms. The diffusion fluxes give rise to the motion of the interface between the two phases that is responsible for time variations, for example, in the relative volume of the enriched phase observed experimentally. We have found the conditions when the interface motion can change the direction during the system relaxation to a new equilibrium state. The latter effect is, from our point of view, the essence of the hydrogen induced nonmonotonic relaxation observed in such systems. The numerical simulation confirms the basic assumptions. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0012/0012012v1.pdf"}
{"id": "cond-mat0012410", "abstract": "  We consider a preferential growth model where particles are added one by one to the system consisting of clusters of particles. A new particle can either form a new cluster (with probability q) or join an already existing cluster with a probability proportional to the size thereof. We calculate exactly the probability _i(k,t) that the size of the i-th cluster at time t is k. We analyze the asymptotics, the scaling properties of the size distribution and of the mean size as well as the relation of our system to recent network models. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0012/0012410v1.pdf"}
{"id": "cond-mat0101162", "abstract": "  The paper deals with the ground and the first excited state of the polaron in the one dimensional Holstein model. Various variational methods are used to investigate both the weak coupling and strong coupling case, as well as the crossover regime between them. Two of the methods, which are presented here for the first time, introduce interesting elements to the understanding of the nature of the polaron. Reliable numerical evidence is found that, in the strong coupling regime, the ground and the first excited state of the self-trapped polaron are well described within the adiabatic limit. The lattice vibration modes associated with the self-trapped polarons are analyzed in detail, and the frequency softening of the vibration mode at the central site of the small polaron is estimated. It is shown that the first excited state of the system in the strong coupling regime corresponds to the excitation of the soft phonon mode within the polaron. In the crossover regime, the ground and the first excited state of the system can be approximated by the anticrossing of the self-trapped and the delocalized polaron state. In this way, the connection between the behavior of the ground and the first excited state is qualitatively explained. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0101/0101162v4.pdf"}
{"id": "cond-mat0102225", "abstract": "  We present a new capacitive sensor for displacement measurement in a Surface Forces Apparatus (SFA) which allows dynamical measurements in the range of 0-100 Hz. This sensor measures the relative displacement between two macroscopic opaque surfaces over periods of time ranging from milliseconds to in principle an indefinite period, at a very low price and down to atomic resolution. It consists of a plane capacitor, a high frequency oscillator, and a high sensitivity frequency to voltage conversion. We use this sensor to study the nanorheological properties of dodecane confined between glass surfaces. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0102/0102225v1.pdf"}
{"id": "cond-mat0102466", "abstract": "  Inverse bicontinuous cubic phases are ubiquitous in lipid-water mixtures and consist of a lipid bilayer forming a cubic minimal surface, thereby dividing space into two cubic networks of water channels. For small hydrocarbon chain lengths, the monolayers can be modeled as parallel surfaces to a minimal midsurface. The bending energy of the cubic phases is determined by the distribution of Gaussian curvature over the minimal midsurfaces which we calculate for seven different structures (G, D, P, I-WP, C(P), S and F-RD). We show that the free-energy densities of the structures G, D and P are considerably lower than those of the other investigated structures due to their narrow distribution of Gaussian curvature. The Bonnet transformation between G, D, and P implies that these phases coexist along a triple line, which also includes an excess water phase. Our model includes thermal membrane undulations. Our qualitative predictions remain unchanged when higher order terms in the curvature energy are included. Calculated phase diagrams agree well with the experimental results for 2:1 lauric acid/dilauroyl phosphatidylcholine and water. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0102/0102466v1.pdf"}
{"id": "cond-mat0103068", "abstract": "  A few characteristic exponents describing power law behaviors of roughness, coherence and persistence in stochastic time series are compared to each other. Relevant techniques for analyzing such time series are recalled in order to distinguish how the various exponents are measured, and what basic differences exist between each one. Financial time series, like the JPY/DEM and USD/DEM exchange rates are used for illustration, but mathematical ones, like (fractional or not) Brownian walks can be used also as indicated. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0103/0103068v2.pdf"}
{"id": "cond-mat0104117", "abstract": "  We examine how the current–voltage characteristics of a doped weakly coupled superlattice depends on temperature. The drift velocity of a discrete drift model of sequential tunneling in a doped GaAs/AlAs superlattice is calculated as a function of temperature. Numerical simulations and theoretical arguments show that increasing temperature favors the appearance of current self-oscillations at the expense of static electric field domain formation. Our findings agree with available experimental evidence. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0104/0104117v1.pdf"}
{"id": "cond-mat0104370", "abstract": "  We study the collective excitations of a neutral atomic Bose-Einstein condensate with gravity-like 1/r interatomic attraction induced by electromagnetic wave. Using the time-dependent variational approach, we derive an analytical spectrum for monopole and quadrupole mode frequencies of a gravity-like self-bound Bose condensed state at zero temperature. We also analyze the excitation frequencies of the Thomas-Fermi-gravity (TF-G) and gravity (G) regimes. Our result agrees excellently with that of Giovanazzi et al. [Europhysics Letters, 56, 1 (2001)], which is obtained within the sum-rule approach. We also consider the vortex state. We estimate the superfluid coherence length and the critical angular frequencies to create a vortex around the z-axis. We find that the TF-G regime can exhibit the superfluid properties more prominently than the G-regime. We find that the monopole mode frequency of the condensate decreases due to the presence of a vortex. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0104/0104370v3.pdf"}
{"id": "cond-mat0104494", "abstract": "  Shear yielding of glassy polymers is usually described in terms of the pressure-dependent Tresca or von Mises yield criteria. We test these criteria against molecular dynamics simulations of deformation in amorphous polymer glasses under triaxial loading conditions that are difficult to realize in experiments. Difficulties and ambiguities in extending several standard definitions of the yield point to triaxial loads are described. Two definitions, the maximum and offset octahedral stresses, are then used to evaluate the yield stress for a wide range of model parameters. In all cases, the onset of shear is consistent with the pressure-modified von Mises criterion, and the pressure coefficient is nearly independent of many parameters. Under triaxial tensile loading, the mode of failure changes to cavitation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0104/0104494v2.pdf"}
{"id": "cond-mat0105304", "abstract": "  The curved actin “comet-tail” of the bacterium Listeria monocytogenes is a visually striking signature of actin polymerization-based motility. Similar actin tails are associated with Shigella flexneri, spotted-fever Rickettsiae, the Vaccinia virus, and vesicles and microspheres in related in vitro systems. We show that the torque required to produce the curvature in the tail can arise from randomly placed actin filaments pushing the bacterium or particle. We find that the curvature magnitude determines the number of actively pushing filaments, independent of viscosity and of the molecular details of force generation. The variation of the curvature with time can be used to infer the dynamics of actin filaments at the bacterial surface. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0105/0105304v1.pdf"}
{"id": "cond-mat0106563", "abstract": "  Energy spectra, electron densities, pair correlation functions and heat capacity of a quantum-dot lithium in zero external magnetic field (a system of three interacting two-dimensional electrons in a parabolic confinement potential) are studied using the exact diagonalization approach. A particular attention is given to a Fermi-liquid – Wigner-solid transition in the ground state of the dot, induced by the intra-dot Coulomb interaction. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0106/0106563v2.pdf"}
{"id": "cond-mat0107210", "abstract": "  The formation of secondary structures by a random RNA sequence is studied as a model system for the sequence-structure problem omnipresent in biopolymers. Several toy energy models are introduced to allow detailed analytical and numerical studies. First, a two-replica calculation is performed. By mapping the two-replica problem to the denaturation of a single homogeneous RNA in 6-dimensional embedding space, we show that sequence disorder is perturbatively irrelevant, i.e., an RNA molecule with weak sequence disorder is in a molten phase where many secondary structures with comparable total energy coexist. A numerical study of various models at high temperature reproduces behaviors characteristic of the molten phase. On the other hand, a scaling argument based on the extremal statistics of rare regions can be constructed to show that the low temperature phase is unstable to sequence disorder. We performed a detailed numerical study of the low temperature phase using the droplet theory as a guide, and characterized the statistics of large-scale, low-energy excitations of the secondary structures from the ground state structure. We find the excitation energy to grow very slowly (i.e., logarithmically) with the length scale of the excitation, suggesting the existence of a marginal glass phase. The transition between the low temperature glass phase and the high temperature molten phase is also characterized numerically. It is revealed by a change in the coefficient of the logarithmic excitation energy, from being disorder dominated to entropy dominated. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0107/0107210v1.pdf"}
{"id": "cond-mat0108114", "abstract": "  A simple model of an atomic Bose-Einstein condensate in a box whose size varies with time is studied to determine the nature of adiabaticity in the nonlinear dynamics obtained within the Gross-Pitaevskii equation (the nonlinear Schrödinger equation). Analytical and numerical methods are used to determine the nature of adiabaticity in this nonlinear quantum system. Criteria for validity of an adiabatic approximation are formulated. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0108/0108114v1.pdf"}
{"id": "cond-mat0109463", "abstract": "  Dynamics of fluctuations in unstable Bose-Einstein condensates is analyzed by the solution of approximate operator equations. In the case of a condensate with a negative scattering length the present treatment describes a delay of collapse, in agreement with recent experiments. In the case of a collision of two condensate wavepackets it is shown that quantum effects lead to a Bose enhancement of elastic-scattering losses. In both cases the noncondensate atoms are formed as entangled pairs in squeezed states. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0109/0109463v2.pdf"}
{"id": "cond-mat0111040", "abstract": "  Tunneling of atoms between two trapped Bose-condensed gases at finite temperatures is explored using a many-body linear response tunneling formalism similar to that used in superconductors. To lowest order, the tunneling currents can be expressed quite generally in terms of the single-particle Green's functions of the isolated Bose gases. A coherent first-order tunneling Josephson current between two atomic Bose-condensates is found, in addition to coherent and dissipative contributions from second-order condensate-noncondensate and noncondensate-noncondensate tunneling. Our work is a generalization of Meier and Zwerger, who recently treated tunneling between uniform atomic Bose gases. We apply our formalism to the analysis of an out-coupling experiment induced by light wave fields, using a simple Bogoliubov-Popov quasiparticle approximation for the trapped Bose gas. For tunneling into the vacuum, we recover the results of Japha, Choi, Burnett and Band, who recently pointed out the usefulness of studying the spectrum of out-coupled atoms. In particular, we show that the small tunneling current of noncondensate atoms from a trapped Bose gas has a broad spectrum of energies, with a characteristic structure associated with the Bogoliubov quasiparticle u^2 and v^2 amplitudes. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0111/0111040v4.pdf"}
{"id": "cond-mat0111147", "abstract": "  The network of Barabasi and Albert, a preferential growth model where a new node is linked to the old ones with a probability proportional to their connectivity, is applied to Brazilian election results. The application of the Sznajd rule, that only agreeing pairs of people can convince their neighbours, gives a vote distribution in good agreement with reality. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0111/0111147v1.pdf"}
{"id": "cond-mat0111237", "abstract": "  An event-driven molecular dynamics simulation of inelastic hard spheres contained in a cylinder and subject to strong vibration reproduces accurately experimental results[1] for a system of vibrofluidized glass beads. In particular, we are able to obtain the velocity field and the density and temperature profiles observed experimentally. In addition, we show that the appearance of convection rolls is strongly influenced by the value of the sidewall-particle restitution coefficient. Suggestions for observing more complex convection patterns are proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0111/0111237v1.pdf"}
{"id": "cond-mat0111284", "abstract": "  We study the double exchange model on two lattice sites with one conduction electron in the limit of an infinite Hund's interaction. While this simple problem is exactly solvable, we present an approximate solution which is valid in the limit of large core spins. This solution is obtained by integrating out charge degrees of freedom. The effective action of two core spins obtained in the result of such an integration resembles the action of two fractional spins. We show that the action obtained via naive gradient expansion is inconsistent. However, a “non-perturbative” treatment leads to an extra term in the effective action which fixes this inconsistency. The obtained “Berry phase term” is geometric in nature. It arises from a geometric constraint on a target space imposed by an adiabatic approximation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0111/0111284v1.pdf"}
{"id": "cond-mat0112216", "abstract": "  We present a novel model to calculate vertical transport properties such as conductance and current in unintentionally disordered double barrier GaAs-Al_xGa_1-xAs heterostructures. The source of disorder comes from interface roughness at the heterojunctions (lateral disorder) as well as spatial inhomogeneities of the Al mole fraction in the barriers (compositional disorder). Both lateral and compositional disorder break translational symmetry along the lateral direction and therefore electrons can be scattered off the growth direction. The model correctly describe channel mixing due to these elastic scattering events. In particular, for realistic degree of disorder, we have found that the effects of compositional disorder on transport properties are negligible as compared to the effects due to lateral disorder. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0112/0112216v1.pdf"}
{"id": "cond-mat0112246", "abstract": "  The force laws governing the extension behavior of homopolypeptides are obtained from a phenomenological free energy capable of describing the helix-coil transition. Just above the melting temperature of the free chains, T*, the plot of force, f, vs. end-to-end distance, R, exhibits two plateaus associated with coexistence of helical and coil domains. The lower plateau is due to tension induced onset of helix-coil transition. The higher plateau corresponds to the melting of the helices by overextension. Just below T* the f-R plot exhibits only the upper plateau. The f-R plots, the helical fraction, the number of domains and their polydispersity are calculated for two models: In one the helical domains are viewed as rigid rods while in the second they are treated as worm like chains. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0112/0112246v1.pdf"}
{"id": "cond-mat0201109", "abstract": "  When sheets of layered material like C, WS_2 or BN are restricted to finite sizes, they generally form single- and multi-walled hollow nanoparticles in order to avoid dangling bonds. Using continuum approaches to model elastic deformation and van der Waals interactions of spherical nanoparticles, we predict the variation of mechanical stability, adhesive properties and phase behavior with radius R and thickness h. We find that mechanical stability is limited by forces in the nN range and pressures in the GPa range. Adhesion energies scale linearly with R, but depend only weakly on h. Deformation due to van der Waals adhesion occurs for single-walled particles for radii of few nm, but is quickly suppressed for increasing thickness. As R is increased, the gas-liquid coexistence disappears from the phase diagram for particle radii in the range of 1-3 nm (depending on wall thickness) since the interaction range decreases like 1/R. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0201/0201109v1.pdf"}
{"id": "cond-mat0202128", "abstract": "  Much insight into the low temperature properties of quantum magnets has been gained by generalizing them to symmetry groups of order N, and then studying the large N limit. In this paper we consider an unusual aspect of their finite temperature behavior–their exhibiting a phase transition between a perfectly paramagetic state and a paramagnetic state with a finite correlation length at N = ∞. We analyze this phenomenon in some detail in the large “spin” (classical) limit of the SU(N) ferromagnet which is also a lattice discretization of the CP^N-1 model. We show that at N = ∞the order of the transition is governed by lattice connectivity. At finite values of N, the transition goes away in one or less dimension but survives on many lattices in two dimensions and higher, for sufficiently large N. The latter conclusion contradicts a recent conjecture of Sokal and Starinets, yet is consistent with the known finite temperature behavior of the SU(2) case. We also report closely related first order paramagnet-ferromagnet transitions at large N and shed light on a violation of Elitzur's theorem at infinite N via the large q limit of the q-state Potts model, reformulated as an Ising gauge theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0202/0202128v2.pdf"}
{"id": "cond-mat0202400", "abstract": "  In a previous paper a method was developed to subtract the interactions due to periodically replicated charges (or other long-range entities) in one spatial dimension. The method constitutes a generalized \"electrostatic layer correction\" (ELC) which adapts any standard 3D summation method to slab-like conditions. Here the implementation of the layer correction is considered in detail for the standard Ewald (EW3DLC) and the PPPM mesh Ewald (PPPMLC) methods. In particular this method offers a strong control on the accuracy and an improved computational complexity of O(N log N) for mesh-based implementations. We derive anisotropic Ewald error formulas and give some fundamental guidelines for optimization. A demonstration of the accuracy, error formulas and computation times for typical systems is also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0202/0202400v2.pdf"}
{"id": "cond-mat0204092", "abstract": "  We propose a new scheme for numerically computing collective-mode spectra for large-size systems, using a reformulation of the Random Phase Approximation. In this study, we apply this method to investigate the spectrum and nature of the spin-waves of a (III,Mn)V Diluted Magnetic Semiconductor. We use an impurity band picture to describe the interaction of the charge carriers with the local Mn spins. The spin-wave spectrum is shown to depend sensitively on the positional disorder of the Mn atoms inside the host semiconductor. Both localized and extended spin-wave modes are found. Unusual spin and charge transport is implied. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0204/0204092v1.pdf"}
{"id": "cond-mat0204224", "abstract": "  We propose a detailed investigation of the schematic mode-coupling approach to experimental data, a method based on the use of simple mode-coupling equations to analyze the dynamics of supercooled liquids. Our aim here is to clarify different aspects of this approach that appeared so far uncontrolled or arbitrary, and to validate the results obtained from previous works. Analyzing the theoretical foundations of the approach, we first identify the parameters of the theory playing a key role and obtain simple requirements to be met by a schematic model for its use in this context. Then we compare the results obtained from the schematic analysis of a given set of experimental data with a variety of models and show that they are all perfectly consistent. A number of potential biases in the method are identified and ruled out by the choice of appropriate models. Finally, reference spectra computed from the mode-coupling theory for a model simple liquid are analyzed along the same lines as experimental data, allowing us to show that, despite the strong simplification in the description of the dynamics it involves, the method is free from spurious artifacts and provides accurate estimates of important parameters of the theory. The only exception is the exponent parameter, the evaluation of which is hindered, as for other methods, by corrections to the asymptotic laws of the theory present when the dynamics is known only in a limited time or frequency range. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0204/0204224v1.pdf"}
{"id": "cond-mat0204631", "abstract": "  The process of heat conduction in one-dimensional lattice with on-site potential is studied by means of numerical simulation. Using discrete Frenkel-Kontorova, ϕ–4 and sinh-Gordon we demonstrate that contrary to previously expressed opinions the sole anharmonicity of the on-site potential is insufficient to ensure the normal heat conductivity in these systems. The character of the heat conduction is determined by the spectrum of nonlinear excitations peculiar for every given model and therefore depends on the concrete potential shape and temperature of the lattice. The reason is that the peculiarities of the nonlinear excitations and their interactions prescribe the energy scattering mechanism in each model. For models sin-Gordon and ϕ–4 phonons are scattered at thermalized lattice of topological solitons; for sinh-Gordon and ϕ–4 - models the phonons are scattered at localized high-frequency breathers (in the case of ϕ–4 the scattering mechanism switches with the growth of the temperature). ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0204/0204631v3.pdf"}
{"id": "cond-mat0205512", "abstract": "  Motivated by recent experiments reporting non-Gaussian velocity distributions in driven dilute granular materials, we study by numerical simulation the properties of inelastic gases as functions of the coefficient of restitution η and concentration ϕ with various heating mechanisms. We show that there are marked, qualitative differences in the behavior for uniform heating (as is frequently assumed theoretically) and for particle systems driven at the boundaries of the container (as is frequently done in experiments). In general, we find Gaussian velocity distributions for uniform heating and non-Gaussian velocity distributions for boundary heating. Furthermore, we demonstrate that the form of the observed velocity distribution is governed primarily by the coefficient of restitution η and q=N_H/N_C, the ratio between the average number of heatings and the average number of collisions in the gas. The differences in distributions we find between uniform and boundary heating can then be understood as different limits of q, for q ≫ 1 and q ≲ 1 respectively. Moreover, we demonstrate that very similar behavior is found for a simple model of a gas of inelastic particles with no spatial degrees of freedom. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0205/0205512v2.pdf"}
{"id": "cond-mat0205559", "abstract": "  We study the relation between α-helix formation and folding for a simple artificial peptide, Ala_10-Gly_5-Ala_10. Our data rely on multicanonical Monte Carlo simulations where the interactions among all atoms are taken into account. The free-energy landscape of the peptide is evaluated for various temperatures. Our data indicate that folding of this peptide is a two-step process: in a first step two α-helices are formed which afterwards re-arrange themselves into a U-like structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0205/0205559v1.pdf"}
{"id": "cond-mat0206417", "abstract": "  Typical properties of glassy materials are shown to be captured by a mean-field free-volume theory. Relaxation processes are supposed to be free-volume activated, and different entropy barriers are associated with density relaxation and shear motion. Free-volume time logarithmic relaxation, Kohlrausch-Williams-Watts, and power law viscosity result from the non-linear dynamics of spatially averaged quantities. The exponents associated with these phenomena are related to a single parameter of the theory. The theory also accounts for coexistence of jamming transitions and non-linear rheology. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0206/0206417v1.pdf"}
{"id": "cond-mat0207135", "abstract": "  We study the ground state properties of a superconductor - ferromagnet - insulator trilayer on the basis of a Hubbard Model featuring exchange splitting in the ferromagnet and electron - electron attraction in the superconductor. We solve the spin - polarized Hartree - Fock - Gorkov equations together with the Maxwell's equation (Ampere's law) fully self-consistently. For certain values of the exchange splitting we find that a spontaneous spin polarized current is generated in the ground state and is intimately related to Andreev bound states at the Fermi level. Moreover, the polarization of the current strongly depends on the band filling. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0207/0207135v1.pdf"}
{"id": "cond-mat0207466", "abstract": "  We investigate growing networks based on Barabasi and Albert's algorithm for generating scale-free networks, but with edges sensitive to overload breakdown. the load is defined through edge betweenness centrality. We focus on the situation where the average number of connections per vertex is, as the number of vertices, linearly increasing in time. After an initial stage of growth, the network undergoes avalanching breakdowns to a fragmented state from which it never recovers. This breakdown is much less violent if the growth is by random rather than preferential attachment (as defines the Barabasi and Albert model). We briefly discuss the case where the average number of connections per vertex is constant. In this case no breakdown avalanches occur. Implications to the growth of real-world communication networks are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0207/0207466v1.pdf"}
{"id": "cond-mat0207556", "abstract": "  We compare predictions of the mean-field theory of superconductivity for nearly antiferromagnetic and nearly ferromagnetic metals for cubic and tetragonal lattices. The calculations are based on the parametrization of an effective interaction arising from the exchange of magnetic fluctuations and assume that a single band is relevant for superconductivity. The results show that for comparable model parameters, the robustness of magnetic pairing increases gradually as one goes from a cubic structure to a more and more anisotropic tetragonal structure either on the border of antiferromagnetism or ferromagnetism. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0207/0207556v1.pdf"}
{"id": "cond-mat0208047", "abstract": "  We study the interaction between low-lying transverse collective oscillations and thermal excitations of an elongated Bose-Einstein condensate by means of perturbation theory. We consider a cylindrically trapped condensate and calculate the transverse elementary excitations at zero temperature by solving the linearized Gross-Pitaevskii equations in two dimensions. We use them to calculate the matrix elements between thermal excited states coupled with the quasi-2D collective modes. The Landau damping of transverse collective modes is investigated as a function of temperature. At low temperatures, the damping rate due to the Landau decay mechanism is in agreement with the experimental data for the decay of the transverse quadrupole mode, but it is too small to explain the slow experimental decay of the transverse breathing mode. The reason for this discrepancy is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0208/0208047v1.pdf"}
{"id": "cond-mat0208461", "abstract": "  To study the coexistence of two liquid states of water within one simulation box, we implement an equilibrium sedimentation method–which involves applying a gravitational field to the system and measuring/calculating the resulting density profile in equilibrium. We simulate a system of particles interacting via the ST2 potential, a model for water. We detect the coexistence of two liquid phases at low temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0208/0208461v1.pdf"}
{"id": "cond-mat0209443", "abstract": "  We calculate the elastic field mediated interaction between macroscopic particles in a columnar hexagonal phase. The interaction is found to be long-ranged and non-central, with both attractive and repulsive parts. We show how the interaction modifies the particle correlations and the column fluctuations. We also calculate the interaction of particles with the topological defects of the columnar phase. The particle-defect interaction reduces the mobility of the defects. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0209/0209443v1.pdf"}
{"id": "cond-mat0209610", "abstract": "  It is shown how Luttinger liquids may be studied using sea-bosons.   The main advantage of the sea-boson method is its ability to provide information about short-wavelength physics in addition to the asymptotics and is naturally generalisable to more than one dimension.   In this article, we solve the Luttinger model and the Calogero-Sutherland model, the latter in the weak-coupling limit.   The anomalous exponent we obtain in the former case is identical to the one obtained by Mattis and Lieb.   We also apply this method to solve the two-dimensional analog of the Luttinger model and show that the system is a Landau Fermi liquid.   Then we solve the model of spinless fermions in one-dimension with long-range   (gauge) interactions and map the Wigner crystal phase of the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0209/0209610v3.pdf"}
{"id": "cond-mat0209637", "abstract": "  We review our version of the classical field approximation to the dynamics of a finite temperature Bose gas. In the case of a periodic box potential, we investigate the role of the high momentum cut-off, essential in the method. In particular, we show that the cut-off going to infinity limit decribes the particle number going to infinity with the scattering length going to zero. In this weak interaction limit, the relative population of the condensate tends to unity. We also show that the cross-over energy, at which the probability distribution of the condensate occupation changes its character, grows with a growing scattering length. In the more physical case of the condensate in the harmonic trap we investigate the dissipative dynamics of a vortex. We compare the decay time and the velocities of the vortex with the available analytic estimates. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0209/0209637v2.pdf"}
{"id": "cond-mat0210100", "abstract": "  Three elastic phases of covalent networks, (I) floppy, (II) isostatically rigid and (III) stressed-rigid have now been identified in glasses at specific degrees of cross-linking (or chemical composition) both in theory and experiments. Here we use size-increasing cluster combinatorics and constraint counting algorithms to study analytically possible consequences of self-organization. In the presence of small rings that can be locally I, II or III, we obtain two transitions instead of the previously reported single percolative transition at the mean coordination number r̅=2.4, one from a floppy to an isostatic rigid phase, and a second one from an isostatic to a stressed rigid phase. The width of the intermediate phase r̅ and the order of the phase transitions depend on the nature of medium range order (relative ring fractions). We compare the results to the Group IV chalcogenides, such as Ge-Se and Si-Se, for which evidence of an intermediate phase has been obtained, and for which estimates of ring fractions can be made from structures of high T crystalline phases. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0210/0210100v1.pdf"}
{"id": "cond-mat0210216", "abstract": "  The first-order irreversible phase transitions (IPT) of the Yaldran-Khan model (Yaldran-Khan, J. Catal. 131, 369, 1991) for the CO+NO reaction is studied using the constant coverage (CC) ensemble and performing epidemic simulations. The CC method allows the study of hysteretic effects close to coexistence as well as the location of both the upper spinodal point and the coexistence point. Epidemic studies show that at coexistence the number of active sites decreases according to a (short-time) power law followed by a (long-time) exponential decay. It is concluded that first-order IPT's share many characteristic of their reversible counterparts, such as the development of short ranged correlations, hysteretic effects, metastabilities, etc. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0210/0210216v1.pdf"}
{"id": "cond-mat0210251", "abstract": "  We investigate the dynamics of two interacting electrons in coupled quantum dots driven by an AC field. We find that the two electrons can be trapped in one of the dots by the AC field, in spite of the strong Coulomb repulsion. In particular, we find that the interaction may enhance the localization effect. We also demonstrate the field excitation procedure to generate the maximally entangled Bell states. The generation time is determined by both analytic and numerical solutions of the time dependent Schrodinger equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0210/0210251v1.pdf"}
{"id": "cond-mat0210255", "abstract": "  We have analyzed the shot noise of electron emission under strong applied electric fields within the Landauer-Buttiker scheme. In contrast to the previous studies of vacuum-tube emitters, we show that in new generation electron emitters, scaled down to the nanometer dimensions, shot noise much smaller than the Schottky noise is observable. Carbon nanotube field emitters are among possible candidates to observe the effect of shot-noise suppression caused by quantum partitioning. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0210/0210255v2.pdf"}
{"id": "cond-mat0212478", "abstract": "  The Saffman-Taylor viscous fingering problem is investigated for the displacement of a non-Newtonian fluid by a Newtonian one in a radial Hele-Shaw cell. We execute a mode-coupling approach to the problem and examine the morphology of the fluid-fluid interface in the weak shear limit. A differential equation describing the early nonlinear evolution of the interface modes is derived in detail. Owing to vorticity arising from our modified Darcy's law, we introduce a vector potential for the velocity in contrast to the conventional scalar potential. Our analytical results address how mode-coupling dynamics relates to tip-splitting and side branching in both shear thinning and shear thickening cases. The development of non-Newtonian interfacial patterns in rectangular Hele-Shaw cells is also analyzed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0212/0212478v1.pdf"}
{"id": "cond-mat0301332", "abstract": "  We study the equilibrium properties of a lattice-gas model of an A + B → 0 catalytic reaction on a one-dimensional chain in contact with a reservoir for the particles. The particles of species A and B are in thermal contact with their vapor phases acting as reservoirs, i.e., they may adsorb onto empty lattice sites and may desorb from the lattice. If adsorbed A and B particles appear at neighboring lattice sites they instantaneously react and both desorb. For this model of a catalytic reaction in the adsorption-controlled limit, we derive analytically the expression of the pressure and present exact results for the mean densities of particles and for the compressibilities of the adsorbate as function of the chemical potentials of the two species. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0301/0301332v1.pdf"}
{"id": "cond-mat0303236", "abstract": "  Transport through molecular devices with strong coupling to a single vibrational mode is considered in the case where the vibration is damped by coupling to the environment. We focus on the weak tunneling limit, for which a rate equation approach is valid. The role of the environment can be characterized by a frictional damping term (ω) and corresponding frequency shift. We consider a molecule that is attached to a substrate, leading to frequency-dependent frictional damping of the single oscillator mode of the molecule, and compare it to a reference model with frequency-independent damping featuring a constant quality factor Q. For large values of Q, the transport is governed by tunneling between displaced oscillator states giving rise to the well-known series of the Frank-Condon steps, while at small Q, there is a crossover to the classical regime with an energy gap given by the classical displacement energy. Using realistic values for the elastic properties of the substrate and the size of the molecule, we calculate I-V curves and find qualitative agreement between our theory and recent experiments on C_60 single-molecule devices. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0303/0303236v3.pdf"}
{"id": "cond-mat0303557", "abstract": "  The Density Matrix Renormalization Group (DMRG) has become a powerful numerical method that can be applied to low-dimensional strongly correlated fermionic and bosonic systems. It allows for a very precise calculation of static, dynamical and thermodynamical properties. Its field of applicability has now extended beyond Condensed Matter, and is successfully used in Statistical Mechanics and High Energy Physics as well. In this article, we briefly review the main aspects of the method. We also comment on some of the most relevant applications so as to give an overview on the scope and possibilities of DMRG and mention the most important extensions of the method such as the calculation of dynamical properties, the application to classical systems, inclusion of temperature, phonons and disorder, field theory, time-dependent properties and the ab initio calculation of electronic states in molecules. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0303/0303557v1.pdf"}
{"id": "cond-mat0304275", "abstract": "  We present a configuration interaction method optimized for Fock-Darwin states of two-dimensional quantum dots with an axially symmetric, parabolic confinement potential subject to a perpendicular magnetic field. The optimization explicitly accounts for geometrical and dynamical symmetries of the Fock-Darwin single-particle states and for many-particle symmetries associated with the center-of-mass motion and with the total spin. This results in a basis set of reduced size and improved accuracy. The numerical results compare well with the quantum Monte Carlo and stochastic variational methods. The method is illustrated by the evolution of a strongly correlated few-electron droplet in a magnetic field in the regime of the fractional quantum Hall effect. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0304/0304275v2.pdf"}
{"id": "cond-mat0304548", "abstract": "  In this paper, properties of a homogeneous Bose gas with a Feshbach resonance are studied in the dilute region at zero temperature. The stationary state contains condensations of atoms and molecules. The ratio of the molecule density to the atom density is π na^3. There are two types of excitations, molecular excitations and atomic excitations. Atomic excitations are gapless, consistent with the traditional theory of a dilute Bose gas. The molecular excitation energy is finite in the long wavelength limit as observed in recent experiments on ^85Rb. In addition, the decay process of the condensate is studied. The coefficient of the three-body recombination rate is about 140 times larger than that of a Bose gas without a Feshbach resonance, in reasonably good agreement with the experiment on ^23Na. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0304/0304548v2.pdf"}
{"id": "cond-mat0305468", "abstract": "  We argue that Poisson statistics in logarithmic time provides an idealized description of non-equilibrium configurational rearrangements in aging glassy systems. The description puts stringent requirements on the geometry of the metastable attractors visited at age t_w. Analytical implications for the residence time distributions as a function of t_w and the correlation functions are derived. These are verified by extensive numerical studies of short range Ising spin glasses. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0305/0305468v3.pdf"}
{"id": "cond-mat0306299", "abstract": "  We consider the effects of doping the S = 1/2 kagome lattice with static impurities. We demonstrate that impurities lower the number of low-lying singlet states, induce dimer-dimer correlations of considerable spatial extent, and do not generate free spin degrees of freedom. Most importantly, they experience a highly unconventional mutual repulsion as a direct consequence of the strong spin frustration. These properties are illustrated by exact diagonalization, and reproduced to semi-quantitative accuracy within a dimer resonating-valence-bond description which affords access to longer length scales. We calculate the local magnetization induced by doped impurities, and consider its implications for nuclear magnetic resonance measurements on known kagome systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0306/0306299v1.pdf"}
{"id": "cond-mat0306559", "abstract": "  Employing the lattice gas model, combined with the linear elasticity theory, a correlation between the equilibrium and transport properties of intercalated species is investigated. It is shown that the major features of the intercalation isotherms and the concentration dependence of the chemical diffusion coefficient can be well understood in terms of the change of the host volume in the course of intercalation. Theoretical predictions are compared to the experimental observations on PdH_x, Li_xWO_3 and Li-graphite systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0306/0306559v1.pdf"}
{"id": "cond-mat0308288", "abstract": "  The Thorup-Zwick (TZ) routing scheme is the first generic stretch-3 routing scheme delivering a nearly optimal local memory upper bound. Using both direct analysis and simulation, we calculate the stretch distribution of this routing scheme on random graphs with power-law node degree distributions, P_k ∼ k^-γ. We find that the average stretch is very low and virtually independent of γ. In particular, for the Internet interdomain graph, γ∼ 2.1, the average stretch is around 1.1, with up to 70", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0308/0308288v1.pdf"}
{"id": "cond-mat0309386", "abstract": "  Motivated by observations of the dynamics of Myxococcus xanthus, we present a self-interacting random walk model that describes the competition between chemokinesis and chemotaxis. Cells are constrained to move in one dimension, but release a chemical chemoattractant at a steady state. The bacteria senses the chemical that it produces. The probability of direction reversals is modeled as a function of both the absolute level of chemoattractant sensed directly under each cell as well as the gradient sensed across the length of the cell. If the chemical does not degrade or diffuse rapidly, the one dimensional trajectory depends on the entire past history of the trajectory. We derive the corresponding Fokker-Planck equations, use an iterative mean field approach that we solve numerically for short times, and perform extensive Monte-Carlo simulations of the model. Cell positional distributions and the associated moments are computed in this feedback system. Average drift and mean squared displacements are found. Crossover behavior among different diffusion regimes are found. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0309/0309386v1.pdf"}
{"id": "cond-mat0309621", "abstract": "  In antiferromagnetically coupled superlattices grown on (001) faces of cubic substrates, e.g. based on materials combinations as Co/Cu, Fe/Si, Co/Cr, or Fe/Cr, the magnetic states evolve under competing influence of bilinear and biquadratic exchange interactions, surface-enhanced four-fold in-plane anisotropy, and specific finite-size effects. Using phenomenological (micromagnetic) theory, a comprehensive survey of the magnetic states and reorientation transitions has been carried out for multilayer systems with even number of ferromagnetic sub-layers and magnetizations in the plane. In two-layer systems (N=2) the phase diagrams in dependence on components of the applied field in the plane include “swallow-tail” type regions of (metastable) multistate co-existence and a number of continuous and discontinuous reorientation transitions induced by radial and transversal components of the applied field. In multilayers (N ≥4) noncollinear states are spatially inhomogeneous with magnetization varying across the multilayer stack. For weak four-fold anisotropy the magnetic states under influence of an applied field evolve by a complex continuous reorientation into the saturated state. At higher anisotropy they transform into various inhomogeneous and asymmetric structures. The discontinuous transitions between the magnetic states in these two-layers and multilayers are characterized by broad ranges of multi-phase coexistence of the (metastable) states and give rise to specific transitional domain structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0309/0309621v1.pdf"}
{"id": "cond-mat0309695", "abstract": "  The effect of an AC perturbation on the shot noise of a fractional quantum Hall fluid is studied both in the weak and the strong backscattering regimes. It is known that the zero-frequency current is linear in the bias voltage, while the noise derivative exhibits steps as a function of bias. In contrast, at Laughlin fractions, the backscattering current and the backscattering noise both exhibit evenly spaced singularities, which are reminiscent of the tunneling density of states singularities for quasiparticles. The spacing is determined by the quasiparticle charge ν e and the ratio of the DC bias with respect to the drive frequency. Photo–assisted transport can thus be considered as a probe for effective charges at such filling factors, and could be used in the study of more complicated fractions of the Hall effect. A non-perturbative method for studying photo–assisted transport at ν=1/2 is developed, using a refermionization procedure. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0309/0309695v3.pdf"}
{"id": "cond-mat0310163", "abstract": "  We report the details and revised analysis of an experiment to measure the specific heat of helium with subnanokelvin temperature resolution near the lambda point. The measurements were made at the vapor pressure spanning the region from 22 mK below the superfluid transition to 4 uK above. The experiment was performed in earth orbit to reduce the rounding of the transition caused by gravitationally induced pressure gradients on earth. Specific heat measurements were made deep in the asymptotic region to within 2 nK of the transition. No evidence of rounding was found to this resolution. The optimum value of the critical exponent describing the specific heat singularity was found to be a = -0.0127+ - 0.0003. This is bracketed by two recent estimates based on renormalization group techniques, but is slightly outside the range of the error of the most recent result. The ratio of the coefficients of the leading order singularity on the two sides of the transition is A+/A- =1.053+ - 0.002, which agrees well with a recent estimate. By combining the specific heat and superfluid density exponents a test of the Josephson scaling relation can be made. Excellent agreement is found based on high precision measurements of the superfluid density made elsewhere. These results represent the most precise tests of theoretical predictions for critical phenomena to date. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0310/0310163v1.pdf"}
{"id": "cond-mat0310617", "abstract": "  We report on electronic transport calculations for self-assembled mono-layers (SAM) of 1,4-phenylene diisocyanide on Au(111) contacts. Experimentally one observes more structure (i.e peaks) within the measured conductance curve for this molecule with two cyanide end-groups, compared to measurements with molecules having thiol end-groups. The calculations are performed on the semi-empiric extended Hückel level using elastic scattering quantum chemistry (ESQC) and we investigate three possible explanations for the experimental findings. Comparing the experimental and theoretical data, we are able to rule out all but one of the scenarios. The observed additional peaks are found to be only reproduced by a mono-layer with additional molecules perturbing the periodicity. It is conjectured that the weaker coupling to Au of cyanide end-groups compared to thiol end-groups might be responsible for such perturbations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0310/0310617v1.pdf"}
{"id": "cond-mat0310743", "abstract": "  Motivated by the problem of sorting, we introduce two simple combinatorial models with distinct Hamiltonians yet identical spectra (and hence partition function) and show that the local dynamics of these models are very different. After a deep quench, one model slowly relaxes to the sorted state whereas the other model becomes blocked by the presence of stable local minima. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0310/0310743v1.pdf"}
{"id": "cond-mat0312319", "abstract": "  The entropy of a polymer confined in a curved surface and the elastic free energy of a membrane consisting of polymers are obtained by scaling analysis. It is found that the elastic free energy of the membrane has the form of the in-plane strain energy plus Helfrich's curvature energy [Z. Naturforsch. C 28, 693 (1973)]. The elastic constants in the free energy are obtained by discussing two simplified models: one is the polymer membrane without in-plane strains and asymmetry between its two sides, which is the counterpart of quantum mechanics in curved surface [Jensen and Koppe, Ann. Phys. 63, 586 (1971)]; another is the planar rubber membrane with homogeneous in-plane strains. The equations to describe equilibrium shape and in-plane strains of the polymer vesicles by osmotic pressure are derived by taking the first order variation of the total free energy containing the elastic free energy, the surface tension energy and the term induced by osmotic pressure. The critical pressure, above which spherical polymer vesicle will lose its stability, is obtained by taking the second order variation of the total free energy. It is found that the in-plane mode also plays important role in the critical pressure because it couples with the out-of-plane mode. Theoretical results reveal that polymer vesicles possess the mechanical properties intermediate between fluid membranes and solid shells. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0312/0312319v6.pdf"}
{"id": "cond-mat0401434", "abstract": "  The spreading of an epidemic is determined by the connectiviy patterns which underlie the population. While it has been noted that a virus spreads more easily on a network in which global distances are small, it remains a great challenge to find approaches that unravel the precise role of local interconnectedness. Such topological properties enter very naturally in the framework of our two-timestep description, also providing a novel approach to tract a probabilistic system. The method is elaborated for SIS-type epidemic processes, leading to a quantitative interpretation of the role of loops up to length 4 in the onset of an epidemic. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0401/0401434v1.pdf"}
{"id": "cond-mat0402079", "abstract": "  Motivated by the MIT experiment [Gorlitz et al., Phys. Rev. Lett. 87, 130402 (2001)], we analytically study the effect of density and phase fluctuations on various observables in a quasi one-dimensional degenerate Bose gases. Quantizing the Gross-Pitaevskii Hamiltonian and diagonalize it in terms of the normal modes associated with the density and phase fluctuations of a quasi-one dimensional Bose gas. We calculate dynamic structure factor S(q,ω) from low-energy condensate density fluctuations and find that there are multiple peaks in S(q,ω) for a given momentum q due to the discrete energy spectrum. These multiple peaks can be resolved by a two-photon Bragg pulse with a long duration which transfer the momentum to the system. We calculate the momentum transferred P_z(t) by using the phase-density representation of the Bose order parameter. We also calculate the single-particle density matrix, phase coherence length, and momentum distribution by taking care of the phase fluctuations upto fourth-order term as well as the density fluctuations. Our studies on coherence properties shows that 1D Bose gases of MIT experiment do not form a true condensate, but it can be obtained by a moderate changes of the current experimental parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0402/0402079v2.pdf"}
{"id": "cond-mat0402182", "abstract": "  We derive within a time-dependent scattering formalism expressions for both the current through ac-driven nanoscale conductors and its fluctuations. The results for the time-dependent current, its time average, and, above all, the driven shot noise properties assume an explicit and serviceable form by relating the propagator to a non-Hermitian Floquet theory. The driven noise cannot be expressed in terms of transmission probabilities. The results are valid for a driving of arbitrary strength and frequency. The connection with commonly known approximation schemes such as the Tien-Gordon approach or a high-frequency approximation is elucidated together with a discussion of the corresponding validity regimes. Within this formalism, we study the coherent suppression of current and noise caused by properly chosen electromagnetic fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0402/0402182v2.pdf"}
{"id": "cond-mat0402578", "abstract": "  A susceptibility function χ(L) is introduced to quantify some aspects of the intermittent stick-slip dynamics of a rough metallic cylinder of length L on a rough metallic incline submitted to small controlled perturbations and maintained below the angle of repose. This problem is studied from the experimental point of view and the observed power-law behavior of χ(L) is justified through the use of a general class of scaling hypotheses. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0402/0402578v1.pdf"}
{"id": "cond-mat0403093", "abstract": "  We present a cluster dynamical mean-field treatment of the Hubbard model on a square lattice to study the evolution of magnetism and quasiparticle properties as the electron filling and interaction strength are varied. Our approach for solving the dynamical mean-field equations is an extension of Potthoff's \"two-site\" method [Phys. Rev. B. 64, 165114 (2001)] where the self-consistent bath is represented by a highly restricted set of states. As well as the expected antiferromagnetism close to half filling, we observe distortions of the Fermi surface. The proximity of a van Hove point and the incipient antiferromagnetism lead to the evolution from an electron-like Fermi surface away from the Mott transition, to a hole-like one near half-filling. Our results also show a gap opening anisotropically around the Fermi surface close to the Mott transition (reminiscent of the pseudogap phenomenon seen in the cuprate high-Tc superconductors). This leaves Fermi arcs which are closed into pockets by lines with very small quasiparticle residue. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0403/0403093v1.pdf"}
{"id": "cond-mat0404328", "abstract": "  We present results on the dynamical correlation functions of the particle-hole symmetric Holstein-Hubbard model at zero temperature, calculated using the dynamical mean field theory which is solved by the numerical renormalization group method. We clarify the competing influences of the electron-electron and electron-phonon interactions particularity at the different metal to insulator transitions. The Coulomb repulsion is found to dominate the behaviour in large parts of the metallic regime. By suppressing charge fluctuations, it effectively decouples electrons from phonons. The phonon propagator shows a characteristic softening near the metal to bipolaronic transition but there is very little softening on the approach to the Mott transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0404/0404328v1.pdf"}
{"id": "cond-mat0404562", "abstract": "  We suppose that the doping of the 2D hard-core boson system away from half-filling may result in the formation of multi-center topological inhomogeneity (defect) such as charge order (CO) bubble domain(s) with Bose superfluid (BS) and extra bosons both localized in domain wall(s), or a topological CO+BS phase separation, rather than an uniform mixed CO+BS supersolid phase. Starting from the classical model we predict the properties of the respective quantum system. The long-wavelength behavior of the system is believed to remind that of granular superconductors, CDW materials, Wigner crystals, and multi-skyrmion system akin in a quantum Hall ferromagnetic state of a 2D electron gas. To elucidate the role played by quantum effects and that of the lattice discreteness we have addressed the simplest nanoscopic counterpart of the bubble domain in a checkerboard CO phase of 2D hc-BH square lattice. It is shown that the relative magnitude and symmetry of multi-component order parameter are mainly determined by the sign of the nn and nnn transfer integrals. In general, the topologically inhomogeneous phase of the hc-BH system away from the half-filling can exhibit the signatures both of s,d, and p symmetry of the off-diagonal order. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0404/0404562v1.pdf"}
{"id": "cond-mat0404581", "abstract": "  We have studied the single-electron transport spectrum of a quantum dot in GaAs/AlGaAs resonant tunneling device. The measured spectrum has irregularities indicating a broken circular symmetry. We model the system with an external potential consisting of a parabolic confinement and a negatively charged Coulombic impurity placed in the vicinity of the quantum dot. The model leads to a good agreement between the calculated single-electron eigenenergies and the experimental spectrum. Furthermore, we use the spin-density-functional theory to study the energies and angular momenta when the system contains many interacting electrons. In the high magnetic field regime the increasing electron number is shown to reduce the distortion induced by the impurity. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0404/0404581v1.pdf"}
{"id": "cond-mat0404722", "abstract": "  We develop a strong coupling approach for a general lattice problem. We argue that this strong coupling perspective represents the natural framework for a generalization of the dynamical mean field theory (DMFT). The main result of this analysis is twofold: 1) It provides the tools for a unified treatment of any non-local contribution to the Hamiltonian. Within our scheme, non-local terms such as hopping terms, spin-spin interactions, or non-local Coulomb interactions are treated on equal footing. 2) By performing a detailed strong-coupling analysis of a generalized lattice problem, we establish the basis for possible clean and systematic extensions beyond DMFT. To this end, we study the problem using three different perspectives. First, we develop a generalized expansion around the atomic limit in terms of the coupling constants for the non-local contributions to the Hamiltonian. By analyzing the diagrammatics associated with this expansion, we establish the equations for a generalized dynamical mean-field theory (G-DMFT). Second, we formulate the theory in terms of a generalized strong coupling version of the Baym-Kadanoff functional. Third, following Pairault, Senechal, and Tremblay, we present our scheme in the language of a perturbation theory for canonical fermionic and bosonic fields and we establish the interpretation of various strong coupling quantities within a standard perturbative picture. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0404/0404722v2.pdf"}
{"id": "cond-mat0405111", "abstract": "  New, superfluid specific additive integral of motion is found. This facilitates investigation of general thermodynamic equilibrium conditions for superfluid. The analysis is performed in an extended space of thermodynamic variables containing (along with the usual thermodynamic coordinates such as pressure and temperature) superfluid velocity and momentum density. The equilibrium stability conditions lead to thermodynamic inequalities which replace the Landau superfluidity criterion at finite temperatures. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0405/0405111v1.pdf"}
{"id": "cond-mat0405393", "abstract": "  Rotational Brownian motion of colloidal magnetic particles in ferrofluids under the influence of an oscillating external magnetic field is investigated. It is shown that for a suitable time dependence of the magnetic field, a noise induced rotation of the ferromagnetic particles due to rectification of thermal fluctuations takes place. Via viscous coupling, the associated angular momentum is transferred from the magnetic nano-particles to the carrier liquid and can then be measured as macroscopic torque on the fluid sample. A thorough theoretical analysis of the effect in terms of symmetry considerations, analytical approximations, and numerical solutions is given which is in accordance with recent experimental findings. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0405/0405393v1.pdf"}
{"id": "cond-mat0406210", "abstract": "  We present a detailed finite-temperature Hartree-Fock-Bogoliubov (HFB) treatment of the two-dimensional trapped Bose gas. We highlight the numerical methods required to obtain solutions to the HFB equations within the Popov approximation, the derivation of which we outline. This method has previously been applied successfully to the three-dimensional case and we focus on the unique features of the system which are due to its reduced dimensionality. These can be found in the spectrum of low-lying excitations and in the coherence properties. We calculate the Bragg response and the coherence length within the condensate in analogy with experiments performed in the quasi-one-dimensional regime [Richard et al., Phys. Rev. Lett. 91, 010405 (2003)] and compare to results calculated for the one-dimensional case. We then make predictions for the experimental observation of the quasicondensate phase via Bragg spectroscopy in the quasi-two-dimensional regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0406/0406210v1.pdf"}
{"id": "cond-mat0406342", "abstract": "  We derive the quantum trajectory or stochastic (conditional) master equation for a single superconducting Cooper-pair box (SCB) charge qubit measured by a single-electron transistor (SET) detector. This stochastic master equation describes the random evolution of the measured SCB qubit density matrix which both conditions and is conditioned on a particular realization of the measured electron tunneling events through the SET junctions. Hence it can be regarded as a Monte Carlo method that allows us to simulate the continuous quantum measurement process. We show that the master equation for the \"partially\" reduced density matrix [Y. Makhlin et.al., Phys. Rev. Lett. 85, 4578 (2000)] can be obtained when a \"partial\" average is taken on the stochastic master equation over the fine grained measurement records of the tunneling events in the SET. Finally, we present some Monte Carlo simulation results for the SCB/SET measurement process. We also analyze the probability distribution P(m,t) of finding m electrons that have tunneled into the drain of the SET in time t to demonstrate the connection between the quantum trajectory approach and the \"partially\" reduced density matrix approach. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0406/0406342v1.pdf"}
{"id": "cond-mat0406388", "abstract": "  In this work we investigate the dynamics of random walk processes on scale-free networks in a short to moderate time scale. We perform extensive simulations for the calculation of the mean squared displacement, the network coverage and the survival probability on a network with a concentration c of static traps. We show that the random walkers remain close to their origin, but cover a large part of the network at the same time. This behavior is markedly different than usual random walk processes in the literature. For the trapping problem we numerically compute Φ(n,c), the survival probability of mobile species at time n, as a function of the concentration of trap nodes, c. Comparison of our results to the Rosenstock approximation indicate that this is an adequate description for networks with 2<γ<3 and yield an exponential decay. For γ>3 the behavior is more complicated and one needs to employ a truncated cumulant expansion. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0406/0406388v1.pdf"}
{"id": "cond-mat0406481", "abstract": "  The dynamics of the one-tangle and the concurrence is analyzed in the Lipkin-Meshkov-Glick model which describes many physical systems such as the two-mode Bose-Einstein condensates. We consider two different initial states which are physically relevant and show that their entanglement dynamics are very different. A semiclassical analysis is used to compute the one-tangle which measures the entanglement of one spin with all the others, whereas the frozen-spin approximation allows us to compute the concurrence using its mapping onto the spin squeezing parameter. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0406/0406481v2.pdf"}
{"id": "cond-mat0406543", "abstract": "  Using a non-thermal local search, called Extremal Optimization (EO), in conjunction with a recently developed scheme for classifying the valley structure of complex systems, we analyze a short-range spin glass. In comparison with earlier studies using a thermal algorithm with detailed balance, we determine which features of the landscape are algorithm dependent and which are inherently geometrical. Apparently a characteristic for any local search in complex energy landscapes, the time series of successive energy records found by EO also is characterized approximately by a log-Poisson statistics. Differences in the results provide additional insights into the performance of EO. In contrast with a thermal search, the extremal search visits dramatically higher energies while returning to more widely separated low-energy configurations. Two important properties of the energy landscape are independent of either algorithm: first, to find lower energy records, progressively higher energy barriers need to be overcome. Second, the Hamming distance between two consecutive low-energy records is linearly related to the height of the intervening barrier. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0406/0406543v2.pdf"}
{"id": "cond-mat0406768", "abstract": "  We use first principles density functional theory to calculate the electronic structure of the phenylthiolate (S-C_6H_5) self-assembled monolayer (SAM) on Cu(111) and Au(111) substrates. We find significant lateral dispersion of the SAM molecular states and discuss its implications for transport properties of the molecular wire array. We calculate the two photon photoemission spectra and the work function of the SAM on Cu(111) and compare them with the available experimental data. Our results are used to discuss assignments of the observed spectral data and yield predictions for new electronic states due to the monolayer not yet accessed experimentally. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0406/0406768v2.pdf"}
{"id": "cond-mat0407115", "abstract": "  We calculate all multipoint correlation functions of all local bond modifications in the two-dimensional Abelian sandpile model, both at the critical point, and in the model with dissipation. The set of local bond modifications includes, as the most physically interesting case, all weakly allowed cluster variables. The correlation functions show that all local bond modifications have scaling dimension two, and can be written as linear combinations of operators in the central charge -2 logarithmic conformal field theory, in agreement with a form conjectured earlier by Mahieu and Ruelle in Phys. Rev. E 64, 066130 (2001). We find closed form expressions for the coefficients of the operators, and describe methods that allow their rapid calculation. We determine the fields associated with adding or removing bonds, both in the bulk, and along open and closed boundaries; some bond defects have scaling dimension two, while others have scaling dimension four. We also determine the corrections to bulk probabilities for local bond modifications near open and closed boundaries. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0407/0407115v2.pdf"}
{"id": "cond-mat0408253", "abstract": "  In this paper we report results for magnetic observables of finite spin clusters composed of S=1/2 ions. We consider clusters of two, three and four spins in distinct spatial arrangements, with isotropic Heisenberg interactions of various strengths between ion pairs. In addition to the complete set of energy eigenvalues and eigenvectors, specific heat and magnetic susceptibility, we also quote results for the single crystal and powder average inelastic neutron scattering structure factors. Examples of the application of these results to experimental systems are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0408/0408253v2.pdf"}
{"id": "cond-mat0408557", "abstract": "  We study, both numerically and analytically, a Binary-Agent-Resource (B-A-R) model consisting of N agents who compete for a limited resource 1/2<L/N <1, where L is the maximum available resource per turn for all N agents. As L increases, the system exhibits well-defined plateaux regions in the success rate which are separated from each other by abrupt transitions. Both the maximum and the mean success rates over each plateau are 'quantized' – for example, the maximum success rate forms a well-defined sequence of simple fractions as L increases. We present an analytic theory which explains these surprising phenomena both qualitatively and quantitatively. The underlying cause of this complex behavior is an interesting self-organized phenomenon in which the system, in response to the global resource level, effectively avoids particular patterns of historical outcomes. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0408/0408557v1.pdf"}
{"id": "cond-mat0408655", "abstract": "  Movements of molecular motors on cytoskeletal filaments are described by directed walks on a line. Detachment from this line is allowed to occur with a small probability. Motion in the surrounding fluid is described by symmetric random walks. Effects of detachment and reattachment are calculated by an analytical solution of the master equation. Results are obtained for the fraction of bound motors, their average velocity and displacement. Enclosing the system in a finite geometry (tube, slab) leads to an experimentally realizable problem, that is studied in a continuum description and also numerically in a lattice simulation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0408/0408655v1.pdf"}
{"id": "cond-mat0408675", "abstract": "  We address theoretically the optical parametric oscillator based on semiconductor cavity exciton-polaritons under a pulsed excitation. A \"hyperspin\" formalism is developed which allows, in the case of large number of polaritons, to reduce quantum dynamics of the parametric oscillator wavefunction to the Liouville equation for the classical probability distribution. Implications for the statistics of polariton ensembles are analyzed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0408/0408675v3.pdf"}
{"id": "cond-mat0409078", "abstract": "  Using the Green's function formalism, an ab initio theory for band structures of crystals is derived starting from the Hartree-Fock approximation. It is based on the algebraic diagrammatic construction scheme for the self-energy which is formulated for crystal orbitals (CO-ADC). In this approach, the poles of the Green's function are determined by solving a suitable Hermitian eigenvalue problem. The method is not only applicable to the outer valence and conduction bands, it is also stable for inner valence bands where strong electron correlations are effective. The key to the proposed scheme is to evaluate the self-energy in terms of Wannier orbitals before transforming it to a crystal momentum representation. Exploiting the fact that electron correlations are mainly local, one can truncate the lattice summations by an appropriate configuration selection scheme. This yields a flat configuration space; i.e., its size scales only linearly with the number of atoms per unit cell for large systems and, under certain conditions, the computational effort to determine band structures also scales linearly. As a first application of the new formalism, a lithium fluoride crystal has been chosen. A minimal basis set description is studied, and a satisfactory agreement with previous theoretical and experimental results for the fundamental band gap and the width of the F 2p valence band complex is obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0409/0409078v2.pdf"}
{"id": "cond-mat0410076", "abstract": "  We numerically study the three-dimensional generalization of the kinetically constrained East model, the North-or-East-or-Front (NEF) model. We characterize the equilibrium behaviour of the NEF model in detail, measuring the temperature dependence of several quantities: alpha-relaxation time, distributions of relaxation times, dynamic susceptibility, dynamic correlation length, and four-point susceptibility. We show that the NEF model describes quantitatively experimental observations over an exceptionally wide range of timescales. We illustrate this by fitting experimental data obtained both in the mildly supercooled regime by optical Kerr effect, and close to the glass transition by dielectric spectroscopy. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0410/0410076v2.pdf"}
{"id": "cond-mat0410379", "abstract": "  We introduce a growing network model in which a new node attaches to a randomly-selected node, as well as to all ancestors of the target node. This mechanism produces a sparse, ultra-small network where the average node degree grows logarithmically with network size while the network diameter equals 2. We determine basic geometrical network properties, such as the size dependence of the number of links and the in- and out-degree distributions. We also compare our predictions with real networks where the node degree also grows slowly with time – the Internet and the citation network of all Physical Review papers. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0410/0410379v3.pdf"}
{"id": "cond-mat0410587", "abstract": "  We develop a phenomenological model of superconductivity near a domain wall in a ferromagnet. In addition to the electromagnetic interaction of the order parameter with the ferromagnetic magnetization, we take into account the possibility of a local enhancement or suppression of superconducting pairing in the vicinity of the wall, and also a non-perfect transparency of the wall to electrons. It is found that the critical temperature of superconductivity near the domain wall might be substantially higher than in the bulk. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0410/0410587v1.pdf"}
{"id": "cond-mat0411218", "abstract": "  A grid-based real-space implementation of the Projector Augmented Wave (PAW) method of P. E. Blochl [Phys. Rev. B 50, 17953 (1994)] for Density Functional Theory (DFT) calculations is presented. The use of uniform 3D real-space grids for representing wave functions, densities and potentials allows for flexible boundary conditions, efficient multigrid algorithms for solving Poisson and Kohn-Sham equations, and efficient parallelization using simple real-space domain-decomposition. We use the PAW method to perform all-electron calculations in the frozen core approximation, with smooth valence wave functions that can be represented on relatively coarse grids. We demonstrate the accuracy of the method by calculating the atomization energies of twenty small molecules, and the bulk modulus and lattice constants of bulk aluminum. We show that the approach in terms of computational efficiency is comparable to standard plane-wave methods, but the memory requirements are higher. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0411/0411218v1.pdf"}
{"id": "cond-mat0411370", "abstract": "  We present a model for microwave photoconductivity in two-dimensional electron systems (2DESs) in a magnetic field at the microwave frequencies lower that the electron cyclotron frequency when the intra-Landau level (LL) transitions dominate. Using this model, we explain the effect of decrease in the 2DES dissipative conductivity (and resistivity) and smearing of its Shubnikov – de Haas oscillations by microwave radiation observed recently <cit.>. The model invokes the concept of suppression of elastic impurity scattering of electrons by the microwave electric field. We calculated the dependence of the 2DES conductivity associated with intra-LL transitions as a function of the radiation and cyclotron frequencies and microwave power. The obtained dependences are consistent with the results of recent experimental observations <cit.>. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0411/0411370v1.pdf"}
{"id": "cond-mat0411600", "abstract": "  We investigate spin-charge mixing effect on resonant tunneling in spin-polarized Tomonaga-Luttinger liquid with double impurities. The mixing arises from Fermi velocity difference between two spin species due to Zeeman effect. Zero bias conductance is calculated as a function of gate voltage V_ g, gate magnetic field B_ g, temperature and magnetic field applied to the system. Mixing effect is shown to cause rotation of the lattice pattern of the conductance peaks in (V_ g,B_ g) plane, which can be observed in experiments. At low temperatures, the contour shapes are classified into three types, reflecting the fact that effective barrier potential is renormalized towards “perfect reflection”, “perfect transmission” and magnetic field induced “spin-filtering”, respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0411/0411600v3.pdf"}
{"id": "cond-mat0412095", "abstract": "  We report a simple method for the fabrication of Niobium superconducting (SC) tips for scanning tunnelling microscopy which allow atomic resolution. The tips, formed in-situ by the mechanical breaking of a niobium wire, reveal a clear SC gap of 1.5 meV and a critical temperature Tc=9.2+-0.3 K as deduced from Superconductor Insulator Normal metal (NIS) and Superconductor Insulator Superconductor (SIS) spectra. These match the values of bulk Nb samples. We systematically find an enhanced value of the critical magnetic field in which superconductivity in the tip is destroyed (around 1 T for some tips) up to five times larger than the critical field of bulk Nb (0.21 T). Such enhancement is attributed to a size effect at the tip apex ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0412/0412095v1.pdf"}
{"id": "cond-mat0412190", "abstract": "  We study decoherence of a quantum dot charge qubit due to coupling to piezoelectric acoustic phonons in the Born-Markov approximation. After including appropriate form factors, we find that phonon decoherence rates are one to two orders of magnitude weaker than was previously predicted. We calculate the dependence of the Q-factor on lattice temperature, quantum dot size, and interdot coupling. Our results suggest that mechanisms other than phonon decoherence play a more significant role in current experimental setups. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0412/0412190v2.pdf"}
{"id": "cond-mat0501009", "abstract": "  We study the motion of kinks in a two-lane model of the totally asymmetric simple exclusion process with open boundaries. We analytically study the motion of the kinks by a decoupling approximation. In terms of the decoupling approximation, we find that the positions of the kinks become synchronised,though the difference in the number of particles between lanes remains non-zero when the rate of lane change is asymmetric. The validity of this result is confirmed for small asymmetric cases through the Monte Carlo simulation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0501/0501009v3.pdf"}
{"id": "cond-mat0501384", "abstract": "  We consider unstable attractors; Milnor attractors A such that, for some neighbourhood U of A, almost all initial conditions leave U. Previous research strongly suggests that unstable attractors exist and even occur robustly (i.e. for open sets of parameter values) in a system modelling biological phenomena, namely in globally coupled oscillators with delayed pulse interactions.   In the first part of this paper we give a rigorous definition of unstable attractors for general dynamical systems. We classify unstable attractors into two types, depending on whether or not there is a neighbourhood of the attractor that intersects the basin in a set of positive measure. We give examples of both types of unstable attractor; these examples have non-invertible dynamics that collapse certain open sets onto stable manifolds of saddle orbits.   In the second part we give the first rigorous demonstration of existence and robust occurrence of unstable attractors in a network of oscillators with delayed pulse coupling. Although such systems are technically hybrid systems of delay differential equations with discontinuous `firing' events, we show that their dynamics reduces to a finite dimensional hybrid system system after a finite time and hence we can discuss Milnor attractors for this reduced finite dimensional system. We prove that for an open set of phase resetting functions there are saddle periodic orbits that are unstable attractors. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0501/0501384v1.pdf"}
{"id": "cond-mat0501516", "abstract": "  Optically detected cyclotron resonance of two-dimensional electrons has been studied in nominally undoped CdTe/(Cd,Mn)Te quantum wells. The enhancement of carrier quantum confinement results in an increase of the electron cyclotron mass from 0.099m_0 to 0.112m_0 with well width decreasing from 30 down to 3.6 nm. Model calculations of the electron effective mass have been performed for this material system and good agreement with experimental data is achieved for an electron-phonon coupling constant α=0.32. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0501/0501516v1.pdf"}
{"id": "cond-mat0502286", "abstract": "  We consider the analytically solvable model of a Gaussian pulse tunneling through a transmission resonance with a general Fano characteristic. It is demonstrated that the transmitted pulse contains enough information to determine uniquely all parameters defining the Fano resonance. This is in contrast to the measurement of the static conductance. Our analytical model is in agreement with numerical data published recently for the limit of a Breit-Wigner resonance. We identify two opposite pulse propagation regimes: if the resonance is broad compared to the energetic width of the incident Gaussian pulse a weakly deformed and slightly delayed transmitted Gaussian pulse is found. In the opposite limit of a narrow resonance the dying out of the transmitted pulse is dominated by the slow exponential decay characteristic of a quasi-bound state with a long life time. In this regime we find characteristic interference oscillations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0502/0502286v1.pdf"}
{"id": "cond-mat0503217", "abstract": "  Using the nonequilibrium theory of superconductivity with the tunnel Hamiltonian, we consider a mesoscopic NISINISIN heterostructure, i.e., a structure consisting of five intermittent normal-metal (N) and superconducting (S) regions separated by insulating tunnel barriers (I). Applying the bias voltage between the outer normal electrodes one can drive the central N island very far from equilibrium. Depending on the resistance ratio of outer and inner tunnel junctions, one can realize either effective electron cooling in the central N island or create highly nonequilibrium energy distributions of electrons in both S and N islands. These distributions exhibit multiple peaks at a distance of integer multiples of the superconducting chemical potential. In the latter case the superconducting gap in the S islands is strongly suppressed as compared to its equilibrium value. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0503/0503217v1.pdf"}
{"id": "cond-mat0503508", "abstract": "  We create collectively jammed (CJ) packings of 50-50 bidisperse mixtures of smooth disks in 2d using an algorithm in which we successively compress or expand soft particles and minimize the total energy at each step until the particles are just at contact. We focus on small systems in 2d and thus are able to find nearly all of the collectively jammed states at each system size. We decompose the probability P(ϕ) for obtaining a collectively jammed state at a particular packing fraction ϕ into two composite functions: 1) the density of CJ packing fractions ρ(ϕ), which only depends on geometry and 2) the frequency distribution β(ϕ), which depends on the particular algorithm used to create them. We find that the function ρ(ϕ) is sharply peaked and that β(ϕ) depends exponentially on ϕ. We predict that in the infinite system-size limit the behavior of P(ϕ) in these systems is controlled by the density of CJ packing fractions–not the frequency distribution. These results suggest that the location of the peak in P(ϕ) when N →∞ can be used as a protocol-independent definition of random close packing. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0503/0503508v1.pdf"}
{"id": "cond-mat0503713", "abstract": "  Based on first-principles electron structure calculations and employing the frozen-magnon approximation we study the exchange interactions in a series of transition-metal binary alloys crystallizing in the zinc-blende structure and calculate the Curie temperature within both the mean-field approximation (MFA) and random-phase approximation (RPA). We study two Cr compounds, CrAs and CrSe, and four Mn compounds: MnSi, MnGe, MnAs and MnC. MnC, MnSi and MnGe are isovalent to CrAs and MnAs is isoelectronic with CrSe. Ferromagnetism is particular stable for CrAs, MnSi and MnGe: All three compounds show Curie temperatures around 1000 K. On the other hand, CrSe and MnAs show a tendency to antiferromagnetism when compressing the lattice. In MnC the half-metallic gap is located in the majority-spin channel contrary to the other five compounds. The large half-metallic gaps, very high Curie temperatures, the stability of the ferromagnetism with respect to the variation of the lattice parameter and a coherent growth on semiconductors make MnSi and CrAs most promising candidates for the use in spintronics devises. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0503/0503713v1.pdf"}
{"id": "cond-mat0504568", "abstract": "  We present a Monte Carlo study of a lattice gas driven out of equilibrium by a local hopping bias. Sites can be empty or occupied by one of two types of particles, which are distinguished by their response to the hopping bias. All particles interact via excluded volume and a nearest-neighbor attractive force. The main result is a phase diagram with three phases: a homogeneous phase, and two distinct ordered phases. Continuous boundaries separate the homogeneous phase from the ordered phases, and a first-order line separates the two ordered phases. The three lines merge in a nonequilibrium bicritical point. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0504/0504568v1.pdf"}
{"id": "cond-mat0505125", "abstract": "  We show how to switch on and off the ratchet potential of a collective Brownian motor, depending only on the position of the particles, in order to attain a current higher than or at least equal to that induced by any periodic flashing. Maximization of instant velocity turns out to be the optimal protocol for one particle but is nevertheless defeated by a periodic switching when a sufficiently large ensemble of particles is considered. The protocol presented in this article, although not the optimal one, yields approximately the same current as the optimal protocol for one particle and as the optimal periodic switching for an infinite number of them. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0505/0505125v2.pdf"}
{"id": "cond-mat0505427", "abstract": "  The Roth's two-pole approximation has been used by the present authors to investigate the role of d-p hybridization in the superconducting properties of an extended d-p Hubbard model. Superconductivity with singlet d_x^2-y^2-wave pairing is treated by following Beenen and Edwards formalism. In this work, the Coulomb interaction, the temperature and the superconductivity have been considered in the calculation of some relevant correlation functions present in the Roth's band shift. The behavior of the order parameter associated with temperature, hybridization, Coulomb interaction and the Roth's band shift effects on superconductivity are studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0505/0505427v1.pdf"}
{"id": "cond-mat0506278", "abstract": "  Properties of the self-adjusted Monte Carlo algorithm applied to 2d Ising ferromagnet are studied numerically. The endogenous feedback form expressed in terms of the instant running averages is suggested in order to generate a biased random walk of the temperature that converges to criticality without an external tuning. The robustness of a stationary regime with respect to partial accessibility of the information is demonstrated. Several statistical and scaling aspects have been identified which allow to establish an alternative spin lattice model of the financial market. It turns out that our model alike model suggested by S. Bornholdt, Int. J. Mod. Phys. C 12 (2001) 667, may be described by Lévy-type stationary distribution of feedback variations with unique exponent α_1 ∼ 3.3. However, the differences reflected by Hurst exponents suggest that resemblances between the studied models seem to be nontrivial. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0506/0506278v1.pdf"}
{"id": "cond-mat0507681", "abstract": "  Starting from a set of coupled Boltzmann equations, we investigate the thermalization of a two-species cold atomic gas confined either in a box or in an isotropic harmonic trap. We show that the thermalization times, by contrast to the collision rate, depend on the interferences between scattering partial waves. The dynamics of thermalization in a harmonic trap is also strongly dependent upon the ratio between the collision rate and the trap frequencies. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0507/0507681v2.pdf"}
{"id": "cond-mat0507721", "abstract": "  We consider electronic transport through laterally parallel double open quantum dots embedded in a quantum wire in a perpendicular magnetic field. The coupling modes of the dots are tunable by adjusting the strength of a central barrier and the applied magnetic field. Probability density and electron current density are calculated to demonstrate transport effects including magnetic blocking, magnetic turbulence, and a hole-like quasibound state feature. Fano to dip line-shape crossover in the conductance is found by varying the magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0507/0507721v1.pdf"}
{"id": "cond-mat0509729", "abstract": "  We present a classical analysis of the transient response of Josephson junctions perturbed by microwaves and thermal fluctuations. The results include a specific low frequency modulation in phase and amplitude behavior of a junction in its zero-voltage state. This transient modulation frequency is linked directly to an observed variation in the probability for the system to switch to its non-zero voltage state. Complementing previous work on linking classical analysis to the experimental observations of Rabi-oscillations, this expanded perturbation method also provides closed form analytical results for attenuation of the modulations and the Rabi-type oscillation frequency. Results of perturbation analysis are compared directly (and quantitatively) to numerical simulations of the classical model as well as published experimental data, suggesting that transients to phase-locking are closely related to the observed oscillations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0509/0509729v2.pdf"}
{"id": "cond-mat0510109", "abstract": "  We present a systematic study of the ballistic electron conductance through sp and 3d transition metal atoms attached to copper and palladium crystalline electrodes. We employ the 'ab initio' screened Korringa-Kohn-Rostoker Green's function method to calculate the electronic structure of nanocontacts while the ballistic transmission and conductance eigenchannels were obtained by means of the Kubo approach as formulated by Baranger and Stone. We demonstrate that the conductance of the systems is mainly determined by the electronic properties of the atom bridging the macroscopic leads. We classify the conducting eigenchannels according to the atomic orbitals of the contact atom and the irreducible representations of the symmetry point group of the system that leads to the microscopic understanding of the conductance. We show that if impurity resonances in the density of states of the contact atom appear at the Fermi energy, additional channels of appropriate symmetry could open. On the other hand the transmission of the existing channels could be blocked by impurity scattering. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0510/0510109v1.pdf"}
{"id": "cond-mat0510143", "abstract": "  We consider a Bose-Einstein condensate confined in a “Mexican hat” potential, with a quartic minus quadratic radial dependence. We find conditions under which the ground state is annular in shape, with a hole in the center of the condensate. Rotation leads to the appearance of stable multiply-quantized vortices, giving rise to a superfluid flow around the ring. The collective modes of the system are explored both numerically and analytically using the Gross-Pitaevskii and hydrodynamic equations. Potential experimental schemes to detect vorticity are proposed and evaluated, which include measuring the splitting of collective mode frequencies, observing expansion following release from the trap, and probing the momentum distribution of the condensate. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0510/0510143v1.pdf"}
{"id": "cond-mat0510461", "abstract": "  In this work we give a consistent picture of the thermodynamic properties of bosons in the Mott insulating phase when loaded adiabatically into one-dimensional optical lattices. We find a crucial dependence of the temperature in the optical lattice on the doping level of the Mott insulator. In the undoped case, the temperature is of the order of the large onsite Hubbard interaction. In contrast, at a finite doping level the temperature jumps almost immediately to the order of the small hopping parameter. These two situations are investigated on the one hand by considering limiting cases like the atomic limit and the case of free fermions. On the other hand, they are examined using a quasi-particle conserving continuous unitary transformation extended by an approximate thermodynamics for hardcore particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0510/0510461v1.pdf"}
{"id": "cond-mat0511246", "abstract": "  The finite size effects of the nanoparticles to the atomic pair distribution functions (PDF) are discussed by calculating the radial distribution functions (RDF) on nanoparticles with various shapes, such as sheet, belt, rod, tube and sphere, assuming continua. Their characteristics are shown depending on the shapes and the sizes of the nanoparticles. Alternately, these PDFs can be used to measure the shapes and the sizes of ordered lattice part inside of any materials such as nanoparticles and bulks. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0511/0511246v1.pdf"}
{"id": "cond-mat0512060", "abstract": "  A derivation is given for the Vogel-Fulcher-Tammann thermal activation law for the glassy state of a bulk polymer. Our microscopic considerations involve the entropy of closed polymer molecular chains (i.e. polymer closed strings). For thin film polymer glasses, one obtains open polymer strings in that the boundary surfaces serve as possible string endpoint locations. The Vogel-Fulcher-Tammann thermal activation law thereby holds true for a bulk polymer glass but is modified in the neighborhood of the boundaries of thin film polymers. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0512/0512060v1.pdf"}
{"id": "cond-mat0512214", "abstract": "  Measurements of Lagrangian single-point and multiple-point statistics in a quasi-two-dimensional stratifed layer system are reported. The system consists of a layer of salt water over an immiscible layer of Fluorinert and is forced electromagnetically so that mean-squared vorticity is injected at a well-defined spatial scale. Simultaneous cascades develop in which enstrophy flows predominately to small scales whereas energy cascades, on average, to larger scales. Lagrangian velocity correlations and one- and two-point displacements are measured for random initial conditions and for initial positions within topological centers and saddles. The behavior of these quantities can be understood in terms of the trapping characteristics of long-lived centers, the slow motion near strong saddles, and the rapid fluctuations outside of either centers or saddles. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0512/0512214v1.pdf"}
{"id": "cond-mat0512280", "abstract": "  Phase randomizing processes in mesoscopic systems can be described in a phenomenological way within the Landauer-Büttiker formalism by attaching extra voltage probes to the sample. In this paper, it is shown that a perturbation treatment of this idea allows for the incorporation of such effects without the need of giving up the efficiency of recursive techniques commonly used for calculating the transmission coefficients. The technique is applied to a 4-probe ring, where a Hall effect can be observed that originates from quantum interference rather than a Lorentz force acting on the electrons. The influence of inelastic scattering on both the Hall resistance and the Aharonov-Bohm oscillations in the longitudinal resistance are examined. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0512/0512280v1.pdf"}
{"id": "cond-mat0512326", "abstract": "  The description of electron-electron interactions in transport problems is both analytically and numerically difficult. Here we show that a much simpler description of electron transport in the presence of interactions can be achieved in nanoscale systems. In particular, we show that the electron flow in nanoscale conductors can be described by Navier-Stokes type of equations with an effective electron viscosity, i.e., on a par with the dynamics of a viscous and compressible classical fluid. By using this hydrodynamic approach we derive the conditions for the transition from laminar to turbulent flow in nanoscale systems and discuss possible experimental tests of our predictions. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0512/0512326v3.pdf"}
{"id": "cond-mat0512415", "abstract": "  We investigate the effect of spatial symmetries on phase coherent electronic transport through chaotic quantum dots. For systems which have a spatial symmetry that interchanges the source and drain leads, we find in the framework of random matrix theory that the density of the transmission eigenvalues is indepedent of the number of channels N in the leads. As a consequence, the weak localization correction to the conductance vanishes in these systems, and the shot noise suppression factor F is independent of N. We confirm this prediction by means of numerical calculations for stadium billiards with various lead geometries. These calculations also uncover transport signatures of partially preserved symmetries. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0512/0512415v2.pdf"}
{"id": "cond-mat0602062", "abstract": "  We apply the truncated Wigner method to the process of three-body recombination in ultracold Bose gases. We find that within the validity regime of the Wigner truncation for two-body scattering, three-body recombination can be treated using a set of coupled stochastic differential equations that include diffusion terms, and can be simulated using known numerical methods. As an example we investigate the behaviour of a simple homogeneous Bose gas. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0602/0602062v2.pdf"}
{"id": "cond-mat0603329", "abstract": "  We describe a semi-empirical atomic basis Extended Hückel Theoretical (EHT) technique that can be used to calculate bulk bandstructure, surface density of states, electronic transmission and interfacial chemistry of various materials within the same computational platform. We apply this method to study multiple technologically important systems, starting with carbon-nanotubes (CNT) and their interfaces in this paper, and silicon-based heterostructures in our follow-up paper. We find that when it comes to quantum transport through interesting, complex heterostructures, the Huckel bandstructure offers a fair and practical compromise between orthogonal tight-binding theories (OTB) with limited transferability between environments under large distortion, and density functional theories (DFT) that are computationally quite expensive for the same purpose. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0603/0603329v1.pdf"}
{"id": "cond-mat0603755", "abstract": "  In a thin strip of a two-dimensional semiconductor electronic system, spin-orbit coupling may be induced near both edges of the strip due to the substantial spatial variation of the confining potential in the boundary regions. In this paper we show that, in the presence of boundary-confinement induced spin-orbit coupling, a longitudinal charge current circulating through a 2D semiconductor strip may cause strong non-equilibrium spin accumulation near both edges of the strip. The spins will be polarized along the normal of the 2DEG plane but in opposite directions at both edges of the strip. This phenomenon is essentially a kinetic magnetoelectric effect from the theoretical points of view, but it manifests in a very similar form as was conceived in a spin Hall effect. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0603/0603755v1.pdf"}
{"id": "cond-mat0603829", "abstract": "  We discuss the magnetic excitations of well-ordered stripe and checkerboard phases, including the high energy magnetic excitations of recent interest and possible connections to the \"resonance peak\" in cuprate superconductors. Using a suitably parametrized Heisenberg model and spin wave theory, we study a variety of magnetically ordered configurations, including vertical and diagonal site- and bond-centered stripes and simple checkerboards. We calculate the expected neutron scattering intensities as a function of energy and momentum. At zero frequency, the satellite peaks of even square-wave stripes are suppressed by as much as a factor of 34 below the intensity of the main incommensurate peaks. We further find that at low energy, spin wave cones may not always be resolvable experimentally. Rather, the intensity as a function of position around the cone depends strongly on the coupling across the stripe domain walls. At intermediate energy, we find a saddlepoint at (π,π) for a range of couplings, and discuss its possible connection to the \"resonance peak\" observed in neutron scattering experiments on cuprate superconductors. At high energy, various structures are possible as a function of coupling strength and configuration, including a high energy square-shaped continuum originally attributed to the quantum excitations of spin ladders. On the other hand, we find that simple checkerboard patterns are inconsistent with experimental results from neutron scattering. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0603/0603829v3.pdf"}
{"id": "cond-mat0604073", "abstract": "  We study the Fano effect and the visibility of the Aharonov-Bohm oscillations for a mesoscopic interferometer with an embedded quantum dot in the presence of a nearby second dot. When the electron-electron interaction between the two dots is considered the nearby dot acts as a charge detector. We compute the currents through the interferometer and detector within the Keldysh formalism and the self-energy of the non-equilibrium Green functions is found up to the second order in the interaction strength. The current formula contains a correction to the Landauer-Büẗẗïk̈ër̈ formula. Its contribution to transport and dephasing is discussed. As the bias applied on the detector is increased, the amplitude of both the Fano resonance and Aharonov-Bohm oscillations are considerably reduced due to controlled dephasing. This result is explained by analyzing the behavior of the imaginary part of the self-energy as a function of energy and bias. We investigate as well the role of the ring-dot coupling. Our theoretical results are consistent to the experimental observation of Buks et al. [Nature 391, 871 (1998)]. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0604/0604073v1.pdf"}
{"id": "cond-mat0604134", "abstract": "  We have applied a variational algorithm based on Projected Entangled Pair States (PEPS) to a two dimensional frustrated spin system, the spin-1/2 antiferromagnetic Heisenberg model on the Shastry-Sutherland lattice. We use the class of PEPS with internal tensor dimension D=2, the first step beyond product states (D=1 PEPS). We have found that the D=2 variational PEPS algorithm is able to capture the physics in both the valence-bond crystal and the Neel ordered state. Also the spin-textures giving rise to the magnetization plateaus seen in experiments on SrCu_2(BO_3)_2 are well reproduced. This shows that PEPS with the smallest nontrivial internal dimension, D=2, can provide valuable insights into frustrated spin-systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0604/0604134v1.pdf"}
{"id": "cond-mat0604267", "abstract": "  We investigate how insights from statistical physics, namely survey propagation, can improve decoding of a particular class of sparse error correcting codes. We show that a recently proposed algorithm, time averaged belief propagation, is in fact intimately linked to a specific survey propagation for which Parisi's replica symmetry breaking parameter is set to zero, and that the latter is always superior to belief propagation in the high connectivity limit. We briefly look at further improvements available by going to the second level of replica symmetry breaking. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0604/0604267v1.pdf"}
{"id": "cond-mat0604369", "abstract": "  We present a diagrammatic real-time approach to adiabatic pumping of electrons through interacting quantum dots. Performing a systematic perturbation expansion in the tunnel-coupling strength, we compute the charge pumped through a single-level quantum dot per pumping cycle. The combination of Coulomb interaction and quantum fluctuations, accounted for in contributions of higher order in the tunnel coupling, modifies the pumping characteristics via an interaction-dependent renormalization of the quantum-dot level. The latter is even responsible for the dominant contribution to the pumped charge when pumping via time-dependent tunnel-coupling strengths. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0604/0604369v2.pdf"}
{"id": "cond-mat0605035", "abstract": "  The stochastic dynamics of micron and nanoscale cantilevers immersed in a viscous fluid are quantified. Analytical results are presented for long slender cantilevers driven by Brownian noise. The spectral density of the noise force is not assumed to be white and the frequency dependence is determined from the fluctuation-dissipation theorem. The analytical results are shown to be useful for the micron scale cantilevers that are commonly used in atomic force microscopy. A general thermodynamic approach is developed that is valid for cantilevers of arbitrary geometry as well as for arrays of multiple cantilevers whose stochastic motion is coupled through the fluid. It is shown that the fluctuation-dissipation theorem permits the calculation of stochastic quantities via straightforward deterministic methods. The thermodynamic approach is used with deterministic finite element numerical simulations to quantify the autocorrelation and noise spectrum of cantilever fluctuations for a single micron scale cantilever and the cross-correlations and noise spectra of fluctuations for an array of two experimentally motivated nanoscale cantilevers as a function of cantilever separation. The results are used to quantify the noise reduction possible using correlated measurements with two closely spaced nanoscale cantilevers. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0605/0605035v1.pdf"}
{"id": "cond-mat0605092", "abstract": "  We study certain nonlinear continuous models of opinion formation derived from a kinetic description involving exchange of opinion between individual agents. These models imply that the only possible final opinions are the extremal ones, and are similar to models of pure drift in magnetization. Both analytical and numerical methods allow to recover the final distribution of opinion between the two extremal ones. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0605/0605092v2.pdf"}
{"id": "cond-mat0605260", "abstract": "  We analyze the efficiency of different methods for the calculation of reaction rates in the case of two simple analytical benchmark systems. Two classes of methods are considered: the first are based on the free energy calculation along a reaction coordinate and the calculation of the transmission coefficient, the second on the sampling of dynamical pathways. We give scaling rules for how this efficiency depends on barrier height and width, and we hand out simple optimization rules for the method-specific parameters. We show that the path sampling methods, using the transition interface sampling technique, become exceedingly more efficient than the others when the reaction coordinate is not the optimal one. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0605/0605260v2.pdf"}
{"id": "cond-mat0606140", "abstract": "  We have recently shown that there is a limit to quantum coherence in many-particle spin qubits due to spontaneous symmetry breaking. These results were derived for the Lieb-Mattis spin model. Here we will show that the underlying mechanism of decoherence in systems with spontaneous symmetry breaking is in fact more general. We present here a generic route to finding the decoherence time associated with spontaneous symmetry breaking in many particle qubits, and subsequently we apply this approach to two model systems, indicating how the continuous symmetries in these models are spontaneously broken and discussing the relation of this symmetry breaking to the thin spectrum. We then present in detail the calculations that lead to the limit to quantum coherence, which is due to energy shifts in the thin spectrum. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0606/0606140v1.pdf"}
{"id": "cond-mat0606626", "abstract": "  The evolution of the magnetic moment and various features of the electronic structure of fcc Gd are followed to reduced volume V/Vo = 0.125 using the LDA+U correlated band method. The stability of the moment is substantial; crude estimates of this signature of a possible “Mott transition” in the 4f system suggest a critical pressure Pc 500 GPa. The 4f occupation is found to increase under pressure due to broadening and lowering of the minority states. This trend is consistent with the interpretation of x-ray spectra of Maddox et al. across the volume collapse transition at 59 GPa, and tends to support their suggestion that the delocalization of the 4f states in Gd differs from the original abrupt picture, being instead a process that occurs over an extended range of pressure. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0606/0606626v1.pdf"}
{"id": "cond-mat0607119", "abstract": "  We use a time-dependent dynamical mean-field-hydrodynamic model to study mixing-demixing in a degenerate fermion-fermion mixture (DFFM). It is demonstrated that with the increase of interspecies repulsion and/or trapping frequencies, a mixed state of DFFM could turn into a fully demixed state in both three-dimensional spherically-symmetric as well as quasi-one-dimensional configurations. Such a demixed state of a DFFM could be experimentally realized by varying an external magnetic field near a fermion-fermion Feshbach resonance, which will result in an increase of interspecies fermion-fermion repulsion, and/or by increasing the external trap frequencies. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0607/0607119v1.pdf"}
{"id": "cond-mat0607365", "abstract": "  The silo discharge process is studied by molecular dynamics simulations. The development of the velocity profile and the probability density function for the displacements in the horizontal and vertical axis are obtained. The PDFs obtained at the beginning of the discharge reveal non-Gaussian statistics and superdiffusive behaviors. When the stationary flow is developed, the PDFs at shorter temporal scales are non-Gaussian too. For big orifices a well defined transition between ballistic and diffusive regime is observed. In the case of a small outlet orifice, no well defined transition is observed. We use a nonlinear diffusion equation introduced in the framework of non-extensive thermodynamics in order to describe the movements of the grains. The solution of this equation gives a well defined relationship (γ = 2/(3-q)) between the anomalous diffusion exponent γ and the entropic parameter q introduced by the non-extensive formalism to fit the PDF of the fluctuations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0607/0607365v2.pdf"}
{"id": "cond-mat0608096", "abstract": "  We investigate and compare different optical probes of a condensed state of microcavity polaritons in expected experimental conditions of non-resonant pumping. We show that the energy- and momentum-resolved resonant Rayleigh signal provide a distinctive probe of condensation as compared to, e.g., photoluminescence emission. In particular, the presence of a collective sound mode both above and below the chemical potential can be observed, as well as features directly related to the density of states of particle-hole like excitations. Both resonant Rayleigh response and the absorption and photoluminescence, are affected by the presence of quantum well disorder, which introduces a distribution of oscillator strengths between quantum well excitons at a given energy and cavity photons at a given momentum. As we show, this distribution makes it important that in the condensed regime, scattering by disorder is taken into account to all orders. We show that, in the low density linear limit, this approach correctly describes inhomogeneous broadening of polaritons. In addition, in this limit, we extract a linear blue-shift of the lower polariton versus density, with a coefficient determined by temperature and by a characteristic disorder length. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0608/0608096v2.pdf"}
{"id": "cond-mat0608662", "abstract": "  In this paper we present a very general theoretical framework for addressing fermionic superfluids over the entire range of BCS to Bose Einstein condensation (BEC) crossover in the presence of population imbalance or spin polarization. Our emphasis is on providing a theory which reduces to the standard zero temperature mean field theories in the literature, but necessarily includes pairing fluctuation effects at non-zero temperature within a consistent framework. Physically, these effects are associated with the presence of pre-formed pairs (or a fermionic pseudogap) in the normal phase, and pair excitations of the condensate, in the superfluid phase. We show how this finite T theory of fermionic pair condensates bears many similarities to the condensation of point bosons. In the process we examine three different types of condensate: the usual breached pair or Sarma phase and both the one and two plane wave Larkin- Ovchinnikov, Fulde-Ferrell (LOFF) states. The last of these has been discussed in the literature albeit only within a Landau-Ginzburg formalism, generally valid near T_c. Here we show how to arrive at the two plane wave LOFF state in the ground state as well as at general temperature T. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0608/0608662v1.pdf"}
{"id": "cond-mat0609767", "abstract": "  In indirect resonant inelastic X-ray scattering (RIXS) an intermediate state is created with a core-hole that has a ultrashort lifetime. The core-hole potential therefore acts as a femtosecond pulse on the valence electrons. We show that this fact can be exploited to integrate out the intermediate states from the expressions for the scattering cross section. By this we obtain an effective scattering cross section that only contains the initial and final scattering states. We derive in detail the effective cross section which turns out to be a resonant scattering factor times a linear combination of the charge response function S( q,ω) and the dynamic longitudinal spin density correlation function. This result is asymptotically exact for both strong and weak local core-hole potentials and ultrashort lifetimes. The resonant scattering pre-factor is shown to be weakly temperature dependent. We also derive a sum-rule for the total scattering intensity and generalize the results to multi-band systems. One of the remarkable outcomes is that one can change the relative charge and spin contribution to the inelastic spectral weight by varying the incident photon energy. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0609/0609767v1.pdf"}
{"id": "cond-mat0610661", "abstract": "  The density matrix renormalization group (DMRG) has been extended to study quantum phase transitions on random graphs of fixed connectivity. As a relevant example, we have analysed the random Ising model in a transverse field. If the couplings are random, the number of retained states remains reasonably low even for large sizes. The resulting quantum spin-glass transition has been traced down for a few disorder realizations, through the careful measurement of selected observables: spatial correlations, entanglement entropy, energy gap and spin-glass susceptibility, among others. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0610/0610661v2.pdf"}
{"id": "cond-mat0611403", "abstract": "  We have generated a novel form of shear banding in a 2D foam and measured the relative magnitude of drag forces on soap films at different lubrication layers. We injected air part way along a flowing bubble field in a narrow Hele-Shaw cell. The injected air inflates bubbles as they flow by, and these bubbles form a shear band down the middle of the Hele-Shaw cell. This channel appears to select a height that minimizes the total dissipation. Fitting data to a simple theoretical model, we show that the drag force on a soap film in contact with the wetting layer on a plate of glass is two orders of magnitude larger than the drag on a soap film in contact with another free soap film. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0611/0611403v2.pdf"}
{"id": "cond-mat0611627", "abstract": "  The injection of electrons in the bulk of carbon nanotube which is connected to ideal Fermi liquid leads is considered. While the presence of the leads gives a cancellation of the noise cross-correlations, the auto-correlation noise has a Fano factor which deviates strongly from the Schottky behavior at voltages where finite size effects are expected. Indeed, as the voltage is increased from zero, the noise is first super-poissonian, then sub-poissonian, and eventually it reaches the Schottky limit. These finite size effects are also tested using a diagnosis of photo-assisted transport, where a small AC modulation is superposed to the DC bias voltage between the injection tip and the nanotube. When finite size effects are at play, we obtain a stepwise behavior for the noise derivative, as expected for normal metal systems, whereas in the absence of finite size effects, due to the presence of Coulomb interactions, a smoothed staircase is observed. The present work shows that it is possible to explore finite size effects in nanotube transport via a zero frequency noise measurement. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0611/0611627v2.pdf"}
{"id": "cond-mat0612132", "abstract": "  After removing the double-well potential trapping two initially independent Bose condensates, the density expectation value is calculated when both the exchange symmetry of identical bosons and interatomic interaction are considered. The density expectation value and evolution equations are obtained based on both the first-quantization and second-quantization methods. When the interatomic interaction is considered carefully, after the overlapping of two initially independent condensates, it is shown that there is a nonzero interference term in the density expectation value. It is found that the calculated density expectation value with this model agrees with the interference pattern observed in the experiment by Andrews (Science 275, 637 (1997)). The nonzero interference term in the density expectation value physically arises from the exchange symmetry of identical bosons and interatomic interaction which make two initially independent condensates become coherent after the overlapping. For two initially independent condensates, our researches show that there is an interaction-induced coherence process. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0612/0612132v1.pdf"}
{"id": "cond-mat0612190", "abstract": "  We have investigated random submonolayer films of 3d transition metals on W(001). The tight-binding linear muffin-tin orbital method combined with the coherent potential approximation was employed to calculate the electronic structure of the films. We have estimated local magnetic moments and the stability of different magnetic structures, namely the ferromagnetic order, the disordered local moments and the non-magnetic state, by comparing the total energies of the corresponding systems. It has been found that the magnetic moments of V and Cr decrease and eventually disappear with decreasing coverage. On the other hand, Fe retains approximately the same magnetic moment throughout the whole concentration range from a single impurity to the monolayer coverage. Mn is an intermediate case between Cr and Fe since it is non-magnetic at very low coverages and ferromagnetic otherwise. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0612/0612190v1.pdf"}
{"id": "cond-mat0612305", "abstract": "  Recent theoretical predictions and experimental measurements have demonstrated that equilibrium free energy differences can be obtained from exponential averages of nonequilibrium work values. These results are similar in structure, but not equivalent, to predictions derived nearly three decades ago by Bochkov and Kuzovlev, which are also formulated in terms of exponential averages but do not involve free energy differences. In the present paper the relationship between these two sets of results is elucidated, then illustrated with an undergraduate-level solvable model. The analysis also serves to clarify the physical interpretation of different definitions of work that have been used in the context of thermodynamic systems driven away from equilibrium. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0612/0612305v1.pdf"}
{"id": "cond-mat0701026", "abstract": "  Theoretical studies of the fractional quantum Hall effect (FQHE) in graphene have so far focused on the plausibility and stability of the previously known FQHE states for the interaction matrix elements appropriate for graphene. We consider FQHE for SU(4) symmetry, as appropriate for the situation when all four spin and valley Landau bands are degenerate, and predict new FQHE states that have no analog in GaAs. These result from an essential interplay between the two-fold spin and valley degeneracies at fractions of the form ν=n/(2pn± 1), for n≥ 3. Conditions are outlined for the observation of these states and quantum phase transitions between them; the structure of these states and their excitations is also described. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0701/0701026v2.pdf"}
{"id": "cond-mat0701209", "abstract": "  We report adaptive resolution molecular dynamics simulations of a flexible linear polymer in solution. The solvent, i.e., a liquid of tetrahedral molecules, is represented within a certain radius from the polymer's center of mass with a high level of detail, while a lower coarse-grained resolution is used for the more distant solvent. The high resolution sphere moves with the polymer and freely exchanges molecules with the low resolution region through a transition regime. The solvent molecules change their resolution and number of degrees of freedom on-the-fly. We show that our approach correctly reproduces the static and dynamic properties of the polymer chain and surrounding solvent. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0701/0701209v1.pdf"}
{"id": "cond-mat0701428", "abstract": "  In this paper we give an introduction to the numerical density matrix renormalization group (DMRG) algorithm, from the perspective of the more general matrix product state (MPS) formulation. We cover in detail the differences between the original DMRG formulation and the MPS approach, demonstrating the additional flexibility that arises from constructing both the wavefunction and the Hamiltonian in MPS form. We also show how to make use of global symmetries, for both the Abelian and non-Abelian cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0701/0701428v3.pdf"}
{"id": "cond-mat0702300", "abstract": "  We study the effect of dielectric inhomogeneities on the interaction between two planparallel charged surfaces with oppositely charged mobile charges in between. The dielectric constant between the surfaces is assumed to be different from the dielectric constant of the two semiinfinite regions bounded by the surfaces, giving rise to electrostatic image interactions. We show that on the weak coupling level the image charge effects are generally small, making their mark only in the second order fluctuation term. However, in the strong coupling limit, the image effects are large and fundamental. They modify the interactions between the two surfaces in an essential way. Our calculations are particularly useful in the regime of parameters where computer simulations would be difficult and extremely time consuming due to the complicated nature of the long range image potentials. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0702/0702300v1.pdf"}
{"id": "cond-mat0702453", "abstract": "  This article presents our procedure to measure the quantum state of a dc SQUID within a few nanoseconds, using an adiabatic dc flux pulse. Detection of the ground state is governed by standard macroscopic quantum theory (MQT), with a small correction due to residual noise in the bias current. In the two level limit, where the SQUID constitutes a phase qubit, an observed contrast of 0.54 indicates a significant loss in contrast compared to the MQT prediction. It is attributed to spurious depolarization (loss of excited state occupancy) during the leading edge of the adiabatic flux measurement pulse. We give a simple phenomenological relaxation model which is able to predict the observed contrast of multilevel Rabi oscillations for various microwave amplitudes. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0702/0702453v1.pdf"}
{"id": "cond-mat0702470", "abstract": "  The structural and elastic properties of diamond nanocomposites and ultrananocrystalline diamond films (UNCD) are investigated using both empirical potentials and tight binding schemes. We find that both materials are extremely hard, but their superb diamondlike properties are limited by their sp^2 component. In diamond composites, the sp^2 atoms are found in the matrix and far from the interface with the inclusion, and they are responsible for the softening of the material. In UNCD, the sp^2 atoms are located in the grain boundaries. They offer relaxation mechanisms which relieve the strain but, on the other hand, impose deformations that lead to softening. The higher the sp^2 component the less rigid these materials are. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0702/0702470v1.pdf"}
{"id": "cond-mat0703239", "abstract": "  Solving the Kohn-Sham eigenvalue problem constitutes the most computationally expensive part in self-consistent density functional theory (DFT) calculations. In a previous paper, we have proposed a nonlinear Chebyshev-filtered subspace iteration method, which avoids computing explicit eigenvectors except at the first SCF iteration. The method may be viewed as an approach to solve the original nonlinear Kohn-Sham equation by a nonlinear subspace iteration technique, without emphasizing the intermediate linearized Kohn-Sham eigenvalue problem. It reaches self-consistency within a similar number of SCF iterations as eigensolver-based approaches. However, replacing the standard diagonalization at each SCF iteration by a Chebyshev subspace filtering step results in a significant speedup over methods based on standard diagonalization. Here, we discuss an approach for implementing this method in multi-processor, parallel environment. Numerical results are presented to show that the method enables to perform a class of highly challenging DFT calculations that were not feasible before. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0703/0703239v1.pdf"}
{"id": "cond-mat0703798", "abstract": "  We study experimentally the thermal fluctuations of energy input and dissipation in a harmonic oscillator driven out of equilibrium, and search for Fluctuation Relations. We study transient evolution from the equilibrium state, together with non equilibrium steady states. Fluctuations Relations are obtained experimentally for both the work and the heat, for the stationary and transient evolutions. A Stationary State Fluctuation Theorem is verified for the two time prescriptions of the torque. But a Transient Fluctuation Theorem is satisfied for the work given to the system but not for the heat dissipated by the system in the case of linear forcing. Experimental observations on the statistical and dynamical properties of the fluctuation of the angle, we derive analytical expressions for the probability density function of the work and the heat. We obtain for the first time an analytic expression of the probability density function of the heat. Agreement between experiments and our modeling is excellent. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0703/0703798v1.pdf"}
{"id": "cond-mat9503134", "abstract": "  A crossover from d to d-1, and then back to d-dimensional critical behavior is argued to be a generic feature characterizing ordering in a d-dimensional superlattice composed of atomically thick films of two ferromagnets. The crossover leads to anomalous changes in the amplitudes of critical singularities. In d=3 Heisenberg and XY superlattices large scale critical fluctuations persist over a wide temperature range. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9503/9503134v1.pdf"}
{"id": "cond-mat9510042", "abstract": "  In a previous paper, we have described a method to perform Fixed-Node Quantum Monte Carlo calculations for lattice fermions. In this paper, we present an extension of this method, by which it is possible to find information on the properties of the exact ground-state wave function. We give some further illustrations of the FNMC and the extended methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9510/9510042v1.pdf"}
{"id": "cond-mat9612178", "abstract": "  We present a statistical analysis of spectra of transfer matrices of classical lattice spin models; this continues the work on the eight-vertex model of the preceding paper. We show that the statistical properties of these spectra can serve as a criterion of integrability. It provides also an operational numerical method to locate integrable varieties. In particular, we distinguish the notions of integrability and criticality considering the two examples of the three-dimensional Ising critical point and the two-dimensional three-state Potts critical point. For complex spectra which appear frequently in the context of transfer matrices, we show that the notion of independence of eigenvalues for integrable models still holds. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9612/9612178v1.pdf"}
{"id": "cond-mat9702107", "abstract": "  A recipe for the generalization of the Boltzmann equation to a quantum kinetic equation is given for cases in which only level shift and broadening are considered, while coherence phenomena can be neglected. We also consider a specific problem: Hot luminescence from a quantum wire near the threshold for optical phonon emission. The problem is first discussed within the framework of the Boltzmann equation. After pointing out the failure of this description, the Boltzmann equations are generalized to a set of quantum kinetic equations, which in turn are solved in order to describe the luminescence spectra. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9702/9702107v1.pdf"}
{"id": "cond-mat9707025", "abstract": "  In this paper we consider the application of electromagnetic theory to the analysis of the Scanning Near-field Optical Microscope (SNOM) in order to predict experimentally observable quantities such as the transmission or reflection coefficients for a particular tip-surface configuration. In particular we present the first application of a transfer matrix based calculation to this challenging problem by using an adaptive co-ordinate transformation to accurately model the shape of the SNOM tip.   We also investigate the possibility of increasing the transmitted light through the SNOM tip by introducing a metal wire into the centre of the tip. This converts the tip into a co-axial cable. We show that, in principle, this can dramatically improve the transmission characteristics without having a detrimental effect on the resolution. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9707/9707025v1.pdf"}
{"id": "cond-mat9707237", "abstract": "  On the basis of physical considerations we propose a one-dimensional discrete lattice model for the density relaxation of granular materials under tapping. Solving the difference equation numerically, we find a logarithmic time-dependence of the density relaxation. This is in agreement with experimental results of Knight et al. [Phys. Rev. E 51, 3957(1995)]. The origin of this anomalous relaxation is elucidated analytically by solving the equation of its continuum version asymptotically in time. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9707/9707237v1.pdf"}
{"id": "cond-mat9709175", "abstract": "  It is shown that one can obtain quantitatively accurate values for the superconducting critical temperature within a Hamiltonian framework. This is possible if one uses a renormalized Hamiltonian that contains an attractive electron-electron interaction and renormalized single particle energies. It can be obtained by similarity renormalization or using flow equations for Hamiltonians. We calculate the critical temperature as a function of the coupling using the standard BCS-theory. For small coupling we rederive the McMillan formula for Tc. We compare our results with Eliashberg theory and with experimental data from various materials. The theoretical results agree with the experimental data within 10", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9709/9709175v1.pdf"}
{"id": "cond-mat9710259", "abstract": "  We discuss a few current developments in the use of quantum mechanically coherent systems for information processing. In each of these developments, Rolf Landauer has played a crucial role in nudging us and other workers in the field into asking the right questions, some of which we have been lucky enough to answer. A general overview of the key ideas of quantum error correction is given. We discuss how quantum entanglement is the key to protecting quantum states from decoherence in a manner which, in a theoretical sense, is as effective as the protection of digital data from bit noise. We also discuss five general criteria which must be satisfied to implement a quantum computer in the laboratory, and we illustrate the application of these criteria by discussing our ideas for creating a quantum computer out of the spin states of coupled quantum dots. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9710/9710259v2.pdf"}
{"id": "cond-mat9802230", "abstract": "  In this paper we extend the Gaussian self-consistent method to permit study of the equilibrium and kinetics of conformational transitions for heteropolymers with any given primary sequence. The kinetic equations earlier derived by us are transformed to a form containing only the mean squared distances between pairs of monomers. These equations are further expressed in terms of instantaneous gradients of the variational free energy. The method allowed us to study exhaustively the stability and conformational structure of some periodic and random aperiodic sequences. A typical phase diagram of a fairly long amphiphilic heteropolymer chain is found to contain phases of the extended coil, the homogeneous globule, the micro-phase separated globule, and a large number of frustrated states, which result in conformational phases of the random coil and the frozen globule. We have also found that for a certain class of sequences the frustrated phases are suppressed. The kinetics of folding from the extended coil to the globule proceeds through non-equilibrium states possessing locally compacted, but partially misfolded and frustrated, structure. This results in a rather complicated multistep kinetic process typical of glassy systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9802/9802230v1.pdf"}
{"id": "cond-mat9802255", "abstract": "  A driven system of three species of particle diffusing on a ring is studied in detail. The dynamics is local and conserves the three densities. A simple argument suggesting that the model should phase separate and break the translational symmetry is given. We show that for the special case where the three densities are equal the model obeys detailed balance and the steady-state distribution is governed by a Hamiltonian with asymmetric long-range interactions. This provides an explicit demonstration of a simple mechanism for breaking of ergodicity in one dimension. The steady state of finite-size systems is studied using a generalized matrix product ansatz. The coarsening process leading to phase separation is studied numerically and in a mean-field model. The system exhibits slow dynamics due to trapping in metastable states whose number is exponentially large in the system size. The typical domain size is shown to grow logarithmically in time. Generalizations to a larger number of species are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9802/9802255v1.pdf"}
{"id": "cond-mat9802270", "abstract": "  We calculate the distribution of the current density j in superconducting films along the direction of an external field applied perpendicular to the film plane. Our analysis reveals that in the presence of bulk pinning j is inhomogeneous on a length scale of order the inter vortex distance. This inhomogeneity is significantly enhanced in the presence of surface pinning. We introduce new critical state model, which takes into account the current density variations throughout the film thickness, and show how these variations give rise to the experimentally observed thickness dependence of ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9802/9802270v1.pdf"}
{"id": "cond-mat9804196", "abstract": "  We consider a Ginzburg-Landau model for superconductivity with a Chern-Simons term added. The flow diagram contains two charged fixed points corresponding to the tricritical and infrared stable fixed points. The topological coupling controls the fixed point structure and eventually the region of first order transitions disappears. We compute the critical exponents as a function of the topological coupling. We obtain that the value of the ν exponent does not vary very much from the XY value, ν_XY=0.67. This shows that the Chern-Simons term does not affect considerably the XY scaling of superconductors. We discuss briefly the possible phenomenological applications of this model. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9804/9804196v3.pdf"}
{"id": "cond-mat9804305", "abstract": "  The two-state model of stochastic resonance is extended to a chain of coupled two-state elements governed by the dynamics of Glauber's stochastic Ising model. Appropriate assumptions on the model parameters turn the chain into a prototype system of coupled stochastic resonators. In a weak-signal limit analytical expressions are derived for the spectral power amplification and the signal-to-noise ratio of a two-state element embedded into the chain. The effect of the coupling between the elements on both quantities is analysed and array-enhanced stochastic resonance is established for pure as well as noisy periodic signals. The coupling-induced improvement of the SNR compared to an uncoupled element is shown to be limited by a factor four which is only reached for vanishing input noise. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9804/9804305v1.pdf"}
{"id": "cond-mat9805194", "abstract": "  Related to an idea of Lewin, a mathematical model for behavioral changes under the influence of a social field is developed. The social field reflects public opinion, social norms and trends. It is not only given by external factors (the environment) but also by the interactions of individuals. Two important kinds of interaction processes are distinguished: Imitative and avoidance processes. Variations of individual behavior are taken into account by “diffusion coefficients”. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9805/9805194v1.pdf"}
{"id": "cond-mat9806148", "abstract": "  A thin plate or slab, prepared so that opposite faces have different surface stresses, will bend as a result of the stress difference. We have developed a classical molecular dynamics (MD) formulation where (similar in spirit to constant-pressure MD) the curvature of the slab enters as an additional dynamical degree of freedom. The equations of motion of the atoms have been modified according to a variable metric, and an additional equation of motion for the curvature is introduced. We demonstrate the method to Au surfaces, both clean and covered with Pb adsorbates, using many-body glue potentials. Applications to stepped surfaces, deconstruction and other surface phenomena are under study. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9806/9806148v1.pdf"}
{"id": "cond-mat9809247", "abstract": "  Brownian motion of an array of harmonically coupled particles subject to a periodic substrate potential and driven by an external bias is investigated. In the linear response limit (small bias), the coupling between particles may enhance the diffusion process, depending on the competition between the harmonic chain and the substrate potential. An analytical formula of the diffusion rate for the single-particle case is also obtained. In the nonlinear response regime, the moving kink may become phase-locked to its radiated phonon waves, hence the mobility of the chain may decrease as one increases the external force. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9809/9809247v1.pdf"}
{"id": "cond-mat9810175", "abstract": "  Single-band Hubbard model at criticality of the metal-insulator transition is studied using approximations derived from parquet theory. It is argued that only the electron-hole and interaction two-particle channels in the parquet algebra are relevant. A scheme is proposed how to reduce the parquet equations to a manageable form the complexity of which is comparable with single-channel approximations such as the renormalized RPA. The newly derived approximation, however, contains dynamical vertex corrections, remains self-consistent at the two-particle level and allows only for integrable singularities. A qualitatively new approach for studying two-particle singularities at zero temperature is obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9810/9810175v1.pdf"}
{"id": "cond-mat9811343", "abstract": "  We present a new approach to calculate the attractive long range vortex-vortex interaction of the van der Waals type present in anisotropic and layered superconductors. The mapping of the statistical mechanics of vortex lines onto the imaginary time quantum mechanics of two dimensional charged bosons allows us to define a 2D Casimir problem: Two half-spaces of (dilute) vortex matter separated by a gap of width R are mapped to two dielectric half-planes of charged bosons interacting via a massive gauge field. We determine the attractive Casimir force between the two half-planes and show, that it agrees with the pairwise summation of the van der Waals force between vortices previously found by Blatter and Geshkenbein [Phys. Rev. Lett. 77, 4958 (1996)] ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9811/9811343v1.pdf"}
{"id": "cond-mat9904431", "abstract": "  The elastic constant tensors for the hcp phases of three transition metals (Co, Re, and Fe) are computed as functions of pressure using the Linearized Augmented Plane Wave method with both the local density and generalized gradient approximations. Spin-polarized states are found to be stable for Co (ferromagnetic) and Fe (antiferromagnetic at low pressure). The elastic constants of Co and Re are compared to experimental measurements near ambient conditions and excellent agreement is found. Recent measurements of the lattice strain in high pressure experiments when interpreted in terms of elastic constants for Re and Fe are inconsistent with the calculated moduli. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9904/9904431v1.pdf"}
{"id": "cond-mat9905163", "abstract": "  A Monte Carlo simulation study of the vacancy-assisted domain-growth in asymmetric binary alloys is presented. The system is modeled using a three-state ABV Hamiltonian which includes an asymmetry term, not considered in previous works. Our simulated system is a stoichiometric two-dimensional binary alloy with a single vacancy which evolves according to the vacancy-atom exchange mechanism. We obtain that, compared to the symmetric case, the ordering process slows down dramatically. Concerning the asymptotic behavior it is algebraic and characterized by the Allen-Cahn growth exponent x=1/2. The late stages of the evolution are preceded by a transient regime strongly affected by both the temperature and the degree of asymmetry of the alloy. The results are discussed and compared to those obtained for the symmetric case. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9905/9905163v1.pdf"}
{"id": "cond-mat9906158", "abstract": "  Grand canonical simulations are used to calculate adsorption isotherms of various classical gases on alkali metal and Mg surfaces. Ab initio adsorption potentials and Lennard-Jones gas-gas interactions are used. Depending on the system, the resulting behavior can be nonwetting for all temperatures studied, complete wetting, or (in the intermediate case) exhibit a wetting transition. An unusual variety of wetting transitions at the triple point is found in the case of a specific adsorption potential of intermediate strength. The general threshold for wetting near the triple point is found to be close to that predicted with a heuristic model of Cheng et al. This same conclusion was drawn in a recent experimental and simulation study of Ar on CO_2 by Mistura et al. These results imply that a dimensionless wetting parameter w is useful for predicting whether wetting behavior is present at and above the triple temperature. The nonwetting/wetting crossover value found here is w circa 3.3. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9906/9906158v1.pdf"}
{"id": "cond-mat9906214", "abstract": "  Interaction between collective monopole oscillations of a trapped Bose-Einstein condensate and thermal excitations is investigated by means of perturbation theory. We assume spherical symmetry to calculate the matrix elements by solving the linearized Gross-Pitaevskii equations. We use them to study the resonances of the condensate induced by temperature when an external perturbation of the trapping frequency is applied and to calculate the Landau damping of the oscillations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9906/9906214v1.pdf"}
{"id": "cond-mat9910479", "abstract": "  We calculate the magnetization of the two-dimensional electron gas in a short-period lateral superlattice, with the Coulomb interaction included in Hartree and Hartree-Fock approximations. We compare the results for a finite, mesoscopic system modulated by a periodic potential, with the results for the infinite periodic system. In addition to the expected strong exchange effects, the size of the system, the type and the strength of the lateral modulation leave their fingerprints on the magnetization. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9910/9910479v2.pdf"}
{"id": "cond-mat9910506", "abstract": "  We propose a new method to measure the coherence time of superconducting phase qubits based on the analysis of the magnetic-field dependent dc nonlinear Andreev current across a high-resistance tunnel contact between the qubit and a dirty metal wire and derive a quantitative relation between the subgap I-V characteristic and the internal correlation function of the qubit. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9910/9910506v1.pdf"}
{"id": "cond-mat9912101", "abstract": "  A self-control mechanism for the dynamics of a three-state fully-connected neural network is studied through the introduction of a time-dependent threshold. The self-adapting threshold is a function of both the neural and the pattern activity in the network. The time evolution of the order parameters is obtained on the basis of a recently developed dynamical recursive scheme. In the limit of low activity the mutual information is shown to be the relevant parameter in order to determine the retrieval quality. Due to self-control an improvement of this mutual information content as well as an increase of the storage capacity and an enlargement of the basins of attraction are found. These results are compared with numerical simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9912/9912101v1.pdf"}
{"id": "cond-mat9912241", "abstract": "  The effect of damping of spinwaves in a two-dimensional classical ferromagnetic XY model is considered. The damping rate Γ_q is calculated using the leading diagrams due to the quartic-order deviations from the harmonic spin Hamiltonian. The resulting four-dimensional integrals are evaluated by extending the techniques developed by Gilat and others for spectral density types of integrals. Γ_q is included into the memory function formalism due to Reiter and Solander, and Menezes, to determine the dynamic structure function S(q,ω). For the infinite sized system, the memory function approach is found to give non-divergent spinwave peaks, and a smooth nonzero background intensity (“plateau” or distributed intensity) for the whole range of frequencies below the spinwave peak. The background amplitude relative to the spinwave peak rises with temperature, and eventually becomes higher than the spinwave peak, where it appears as a central peak. For finite-sized systems, there are multiple sequences of weak peaks on both sides of the spinwave peaks whose number and positions depend on the system size and wavevector in integer units of 2π/L. These dynamical finite size effects are explained in the memory function analysis as due to either spinwave difference processes below the spinwave peak or sum processes above the spinwave peak. These features are also found in classical Monte Carlo – Spin-Dynamics simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9912/9912241v1.pdf"}
{"id": "cs0003081", "abstract": "  The rate of occurrence of words is not uniform but varies from document to document. Despite this observation, parameters for conventional n-gram language models are usually derived using the assumption of a constant word rate. In this paper we investigate the use of variable word rate assumption, modelled by a Poisson distribution or a continuous mixture of Poissons. We present an approach to estimating the relative frequencies of words or n-grams taking prior information of their occurrences into account. Discounting and smoothing schemes are also considered. Using the Broadcast News task, the approach demonstrates a reduction of perplexity up to 10", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0003/0003081v1.pdf"}
{"id": "cs0011005", "abstract": "  This paper presents a practical solution for detecting data races in parallel programs. The solution consists of a combination of execution replay (RecPlay) with automatic on-the-fly data race detection. This combination enables us to perform the data race detection on an unaltered execution (almost no probe effect). Furthermore, the usage of multilevel bitmaps and snooped matrix clocks limits the amount of memory used. As the record phase of RecPlay is highly efficient, there is no need to switch it off, hereby eliminating the possibility of Heisenbugs because tracing can be left on all the time. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0011/0011005v1.pdf"}
{"id": "cs0112020", "abstract": "  Concrete computing machines, either sequential or concurrent, rely on an intimate relation between computation and time. We recall the general characteristic properties of physical time and of present realizations of computing systems. We emphasize the role of computing interferences, i.e. the necessity to avoid them in order to give a causal implementation to logical operations. We compare synchronous and asynchronous systems, and make a brief survey of some methods used to deal with computing interferences. Using a graphic representation, we show that synchronous and asynchronous circuits reflect the same opposition as the Newtonian and relativistic causal structures for physical space-time. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0112/0112020v1.pdf"}
{"id": "cs0202032", "abstract": "  Finding optimal solutions for multi-unit combinatorial auctions is a hard problem and finding approximations to the optimal solution is also hard. We investigate the use of Branch-and-Bound techniques: they require both a way to bound from above the value of the best allocation and a good criterion to decide which bids are to be tried first. Different methods for efficiently bounding from above the value of the best allocation are considered. Theoretical original results characterize the best approximation ratio and the ordering criterion that provides it. We suggest to use this criterion. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0202/0202032v1.pdf"}
{"id": "cs0302003", "abstract": "  An overview of some methods of statistical physics applied to the analysis of algorithms for optimization problems (satisfiability of Boolean constraints, vertex cover of graphs, decoding, ...) with distributions of random inputs is proposed. Two types of algorithms are analyzed: complete procedures with backtracking (Davis-Putnam-Loveland-Logeman algorithm) and incomplete, local search procedures (gradient descent, random walksat, ...). The study of complete algorithms makes use of physical concepts such as phase transitions, dynamical renormalization flow, growth processes, ... As for local search procedures, the connection between computational complexity and the structure of the cost function landscape is questioned, with emphasis on the notion of metastability. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0302/0302003v1.pdf"}
{"id": "cs0302017", "abstract": "  Networked communications inherently depend on the ability of the sender of a message to indicate through some token how the message should be delivered to a particular recipient. The tokens that refer messages to recipients are variously known as routes, addresses,handles, and names ordered by their relative nearness to network topology vs. human meaning. All four sorts of token refer in some way to a recipient, but they are controlled by different authorities and their meanings depend on different contextual parameters.   Today's global Internet employs dynamically determined routes, IP addresses, and domain names. Domain names combine the functions of handles and names. The high value of domain names as names leads to substantial social and legal dispute about their assignment, degrading their value as handles. The time has come to provide a distinct open network handle system (ONHS), using handles that are not meaningful in natural language and are therefore not subject to the disputes surrounding the use of names.   A handle service may be deployed easily as a handle domain within the current Domain Name System. In order to minimize the administrative load, and maximize their own autonomy, netizens may use public-key cryptography to assign their own handles. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0302/0302017v1.pdf"}
{"id": "cs0306075", "abstract": "  Every year the PHENIX collaboration deals with increasing volume of data (now about 1/4 PB/year). Apparently the more data the more questions how to process all the data in most efficient way. In recent past many developments in HEP computing were dedicated to the production environment. Now we need more tools to help to obtain physics results from the analysis of distributed simulated and experimental data. Developments in Grid architectures gave many examples how distributed computing facilities can be organized to meet physics analysis needs. We feel that our main task in this area is to try to use already developed systems or system components in PHENIX environment.   We are concentrating here on the followed problems: file/replica catalog which keep names of our files, data moving over WAN, job submission in multicluster environment.   PHENIX is a running experiment and this fact narrowed our ability to test new software on the collaboration computer facilities. We are experimenting with system prototypes at State University of New York at Stony Brook (SUNYSB) where we run midrange computing cluster for physics analysis. The talk is dedicated to discuss some experience with Grid software and achieved results. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0306/0306075v1.pdf"}
{"id": "cs0308004", "abstract": "  We present a new algorithm for fast record retrieval, distribute-probe-gather, or DPG. DPG has important applications both in sorting and in joins. Current main memory sorting algorithms split their work into three phases: extraction of key-pointer pairs; sorting of the key-pointer pairs; and copying of the original records into the destination array according the sorted key-pointer pairs. The copying in the last phase dominates today's sorting time. Hence, the use of DPG in the third phase provides an accelerator for existing sorting algorithms.   DPG also provides two new join methods for foreign key joins: DPG-move join and DPG-sort join. The resulting join methods with DPG are faster because DPG join is cache-efficient and at the same time DPG join avoids the need for sorting or for hashing. The ideas presented for foreign key join can also be extended to faster record pair retrieval for spatial and temporal databases. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0308/0308004v1.pdf"}
{"id": "cs0405022", "abstract": "  We propose a cipher similar to the One Time Pad and McEliece cipher based on a subband coding scheme. The encoding process is an approximation to the One Time Pad encryption scheme. We present results of numerical experiments which suggest that a brute force attack to the proposed scheme does not result in all possible plaintexts, as the One Time Pad does, but still the brute force attack does not compromise the system. However, we demonstrate that the cipher is vulnerable to a chosen-plaintext attack. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0405/0405022v1.pdf"}
{"id": "cs0501067", "abstract": "  Transmission of information over a discrete-time memoryless Rician fading channel is considered where neither the receiver nor the transmitter knows the fading coefficients. The spectral-efficiency/bit-energy tradeoff in the low-power regime is examined when the input has limited peakedness. It is shown that if a fourth moment input constraint is imposed or the input peak-to-average power ratio is limited, then in contrast to the behavior observed in average power limited channels, the minimum bit energy is not always achieved at zero spectral efficiency. The low-power performance is also characterized when there is a fixed peak limit that does not vary with the average power. A new signaling scheme that overlays phase-shift keying on on-off keying is proposed and shown to be optimally efficient in the low-power regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0501/0501067v1.pdf"}
{"id": "cs0612033", "abstract": "  The automatic extraction of acronyms and their meaning from corpora is an important sub-task of text mining. It can be seen as a special case of string alignment, where a text chunk is aligned with an acronym. Alternative alignments have different cost, and ideally the least costly one should give the correct meaning of the acronym. We show how this approach can be implemented by means of a 3-tape weighted finite-state machine (3-WFSM) which reads a text chunk on tape 1 and an acronym on tape 2, and generates all alternative alignments on tape 3. The 3-WFSM can be automatically generated from a simple regular expression. No additional algorithms are required at any stage. Our 3-WFSM has a size of 27 states and 64 transitions, and finds the best analysis of an acronym in a few milliseconds. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0612/0612033v1.pdf"}
{"id": "cs0701180", "abstract": "  We study the notion of hierarchy in the context of visualizing textual data and navigating text collections. A formal framework for “hierarchy” is given by an ultrametric topology. This provides us with a theoretical foundation for concept hierarchy creation. A major objective is scalable annotation or labeling of concept maps. Serendipitously we pursue other objectives such as deriving common word pair (and triplet) phrases, i.e., word 2- and 3-grams. We evaluate our approach using (i) a collection of texts, (ii) a single text subdivided into successive parts (for which we provide an interactive demonstrator), and (iii) a text subdivided at the sentence or line level. While detailing a generic framework, a distinguishing feature of our work is that we focus on locality of hierarchic structure in order to extract semantic information. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0701/0701180v1.pdf"}
{"id": "gr-qc0002089", "abstract": "  We study the evolution of gravitational waves through the preheating era that follows inflation. The oscillating inflaton drives parametric resonant growth of scalar field fluctuations, and although super-Hubble tensor modes are not strongly amplified, they do carry an imprint of preheating. This is clearly seen in the Weyl tensor, which provides a covariant description of gravitational waves. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0002/0002089v1.pdf"}
{"id": "gr-qc0012070", "abstract": "  Detecting binary black holes in interferometer data requires an accurate knowledge of the orbital phase evolution of the system. From the point of view of data analysis one also needs fast algorithms to compute the templates that will employed in searching for black hole binaries. Recently, there has been progress on both these fronts: On the one hand, re-summation techniques have made it possible to accelerate the convergence of poorly convergent asymptotic post-Newtonian series and derive waveforms beyond the conventional adiabatic approximation. We now have a waveform model that extends beyond the inspiral regime into the plunge phase followed by the quasi-normal mode ringing. On the other hand, explicit Fourier domain waveforms have been derived that make the generation of waveforms fast enough so as not to be a burden on the computational resources required in filtering the detector data. These new developments should make it possible to efficiently and reliably search for black hole binaries in data from first interferometers. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0012/0012070v1.pdf"}
{"id": "gr-qc0101015", "abstract": "  In this paper we consider the collision of spinning holes using first order perturbation theory of black holes (Teukolsky formalism). With these results (along with ones, we published in the past) one can predict the properties of the gravitational waves radiated from the late stage inspiral of two spinning, equal mass black holes. Also we note that the energy radiated by the head-on collision of two spinning holes with spins (that are equal and opposite) aligned along the common axis is more than the case in which the spins are perpendicular to the axis of the collision. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0101/0101015v1.pdf"}
{"id": "gr-qc0101115", "abstract": "  We investigate properties of r-modes characterized by regular eigenvalue problem in slowly rotating relativistic polytropes. Our numerical results suggest that discrete r-mode solutions for the regular eigenvalue problem exist only for restricted polytropic models. In particular the r-mode associated with l=m=2, which is considered to be the most important for gravitational radiation driven instability, do not have a discrete mode as solutions of the regular eigenvalue problem for polytropes having the polytropic index N > 1.18 even in the post-Newtonian order. Furthermore for a N=1 polytrope, which is employed as a typical neutron star model, discrete r-mode solutions for regular eigenvalue problem do not exist for stars whose relativistic factor M/R is larger than about 0.1. Here M and R are stellar mass and stellar radius, respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0101/0101115v2.pdf"}
{"id": "gr-qc0104065", "abstract": "  Old and new puzzles of cosmology are reexamined from the point of view of quantum theory of the universe developed here. It is shown that in proposed approach the difficulties of the standard cosmology do not arise. The theory predicts the observed dimensions of the nonhomogeneities of matter density and the amplitude of the fluctuations of the cosmic background radiation temperature in the Universe and points to a new quantum mechanism of their origin. It allows to obtain the value of the deceleration parameter which is in good agreement with the recent SNe Ia measurements. The theory explains the large value of entropy of the Universe and describes other parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0104/0104065v2.pdf"}
{"id": "gr-qc0108020", "abstract": "  The multidimensional gravity on the principal bundle with the SU(2) gauge group is considered. The numerical investigation of the spherically symmetric metrics with the center of symmetry is made. The solution of the gravitational equations depends on the boundary conditions of the “SU(2) gauge potential” (off-diagonal metric components) at the symmetry center and on the type of symmetry (symmetrical or antisymmetrical) of these potentials. In the chosen range of the boundary conditions it is shown that there are two types of solutions: wormhole-like and flux tube. The physical application of such kind of solutions as quantum handles in a spacetime foam is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0108/0108020v2.pdf"}
{"id": "gr-qc0111055", "abstract": "  We consider the quantum vacuum of fermionic field in the presence of a black-hole background as a possible candidate for the stabilized black hole. The stable vacuum state (as well as thermal equilibrium states with arbitrary temperature) can exist if we use the Painlevé-Gullstrand description of the black hole, and the superluminal dispersion of the particle spectrum at high energy, which is introduced in the free-falling frame. Such choice is inspired by the analogy between the quantum vacuum and the ground state of quantum liquid, in which the event horizon for the low-energy fermionic quasiparticles also can arise. The quantum vacuum is characterized by the Fermi surface, which appears behind the event horizon. We do not consider the back reaction, and thus there is no guarantee that the stable black hole exists. But if it does exist, the Fermi surface behind the horizon would be the necessary attribute of its vacuum state. We also consider exact discrete spectrum of fermions inside the horizon which allows us to discuss the problem of fermion zero modes. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0111/0111055v1.pdf"}
{"id": "gr-qc0205063", "abstract": "  This paper is a continuation of our previous analysis (i.e. Turyshev 2002a, 2002b) of the relativistic stellar aberration requirements for the Space Interferometry Mission (SIM). Here we have considered a problem of how the expected astrometric accuracy of parallax determination will constrain the accuracy of the spacecraft navigation. We show that effect of the spacecraft's navigational errors on the accuracy of parallax determination with SIM will be negligible. We discuss the implication of the results obtained for the future mission analysis. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0205/0205063v1.pdf"}
{"id": "gr-qc0304047", "abstract": "  We study several issues related to the different choices of time available for the classical and quantum treatment of linearly polarized cylindrical gravitational waves. We pay especial attention to the time evolution of creation and annihilation operators and the definition of Fock spaces for the different choices of time involved. We discuss also the issue of microcausality and the use of field commutators to extract information about the causal properties of quantum spacetime. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0304/0304047v1.pdf"}
{"id": "gr-qc0304070", "abstract": "  At the threshold of black hole formation in the gravitational collapse of a scalar field a naked singularity is formed through a universal critical solution that is discretely self-similar. We study the global spacetime structure of this solution. It is spherically symmetric, discretely self-similar, regular at the center to the past of the singularity, and regular at the past lightcone of the singularity. At the future lightcone of the singularity, which is also a Cauchy horizon, the curvature is finite and continuous but not differentiable. To the future of the Cauchy horizon the solution is not unique, but depends on a free function (the null data coming out of the naked singularity). There is a unique continuation with a regular center (which is self-similar). All other self-similar continuations have a central timelike singularity with negative mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0304/0304070v1.pdf"}
{"id": "gr-qc0305062", "abstract": "  We study the late time evolution of positively curved FRW models with a scalar field which arises in the conformal frame of the R+α R^2 theory. The resulted three-dimensional dynamical system has two equilibrium solutions corresponding to a de Sitter space and an ever expanding closed universe. We analyze the structure of the first equilibrium with the methods of the center manifold theory and, for the second equilibrium we apply the normal form theory to obtain a simplified system, which we analyze with special phase plane methods. It is shown that an initially expanding closed FRW spacetime avoids recollapse. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0305/0305062v1.pdf"}
{"id": "gr-qc0306124", "abstract": "  The lowest 37000 eigenvalues of the area operator in loop quantum gravity is calculated and studied numerically. We obtain an asymptotical formula for the eigenvalues as a function of their sequential number. The multiplicity of the lowest few hundred eigenvalues is also determined and the smoothed spectral density is calculated. The spectral density is presented for various number of vertices, edges and SU(2) representations. A scaling form of spectral density is found, being a power law for one vertex, while following an exponential for several vertices. The latter case is explained on the basis of the one vertex spectral density. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0306/0306124v1.pdf"}
{"id": "gr-qc0308085", "abstract": "  We consider the general problem of estimating the inflight LISA noise power spectra and cross-spectra, which are needed for detecting and estimating the gravitational wave signals present in the LISA data. For the LISA baseline design and in the long wavelength limit, we bound the error on all spectrum estimators that rely on the use of the fully symmetric Sagnac combination (ζ). This procedure avoids biases in the estimation that would otherwise be introduced by the presence of a strong galactic background in the LISA data. We specialize our discussion to the detection and study of the galactic white dwarf-white dwarf binary stochastic signal. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0308/0308085v1.pdf"}
{"id": "gr-qc0310079", "abstract": "  We consider the possibilities for obtaining information about the equation of state for quark matter by using future direct observational data on gravitational waves. We study the nonradial oscillations of both fluid and spacetime modes of pure quark stars. If we observe the f and the lowest w_ II modes from quark stars, by using the simultaneously obtained radiation radius we can constrain the bag constant B with reasonable accuracy, independently of the s quark mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0310/0310079v2.pdf"}
{"id": "gr-qc0311078", "abstract": "  A method to construct exact general relativistic thick disks that is a simple generalization of the “displace, cut and reflect” method commonly used in Newtonian, as well as, in Einstein theory of gravitation is presented. This generalization consists in the addition of a new step in the above mentioned method. The new method can be pictured as a “displace, cut, fill and reflect” method. In the Newtonian case, the method is illustrated in some detail with the Kuzmin-Toomre disk. We obtain a thick disk with acceptable physical properties. In the relativistic case two solutions of the Weyl equations, the Weyl gamma metric (also known as Zipoy-Voorhees metric) and the Chazy-Curzon metric are used to construct thick disks. Also the Schwarzschild metric in isotropic coordinates is employed to construct another family of thick disks. In all the considered cases we have non trivial ranges of the involved parameter that yield thick disks in which all the energy conditions are satisfied. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0311/0311078v1.pdf"}
{"id": "gr-qc0312119", "abstract": "  We present current theories about the structure of space and time, where the building blocks are some fundamental entities (yes-no experiment, quantum processes, spin net-work, preparticles) that do not presuppose the existence of space and time. The relations among these objects are the base for a pregeometry of discrete character, the continuous limit of which gives rise to the physical properties of the space and time. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0312/0312119v1.pdf"}
{"id": "gr-qc0408025", "abstract": "  We review a recent proposal for the construction of a quantum theory of the gravitational field. The proposal is based on approximating the continuum theory by a discrete theory that has several attractive properties, among them, the fact that in its canonical formulation it is free of constraints. This allows to bypass many of the hard conceptual problems of traditional canonical quantum gravity. In particular the resulting theory implies a fundamental mechanism for decoherence and bypasses the black hole information paradox. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0408/0408025v1.pdf"}
{"id": "gr-qc0501103", "abstract": "  New families of exact general relativistic thick disks are constructed using the “displace, cut, fill and reflect” method. A class of functions used to “fill” the disks is derived imposing conditions on the first and second derivatives to generate physically acceptable disks. The analysis of the function's curvature further restrict the ranges of the free parameters that allow phisically acceptable disks. Then this class of functions together with the Schwarzschild metric is employed to construct thick disks in isotropic, Weyl and Schwarzschild canonical coordinates. In these last coordinates an additional function must be added to one of the metric coefficients to generate exact disks. Disks in isotropic and Weyl coordinates satisfy all energy conditions, but those in Schwarzschild canonical coordinates do not satisfy the dominant energy condition. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0501/0501103v1.pdf"}
{"id": "gr-qc0504067", "abstract": "  LIGO recently conducted its third scientific data run, S3. Here we summarize the veto and data quality studies conducted by the LIGO Scientific Collaboration in connection with the search for binary inspiral signals in the S3 data. LIGO's interferometer channels and physical environmental monitors were monitored, and events in these channels coincident with inspiral triggers were examined. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0504/0504067v1.pdf"}
{"id": "gr-qc0508112", "abstract": "  In this paper we investigate the possibility of measuring the post-Newtonian general relativistic gravitomagnetic Lense-Thirring effect in the Jovian system of its Galilean satellites Io, Europa, Ganymede and Callisto in view of recent developments in processing and modelling their optical observations spanning a large time interval (125 years). The present day best observations have an accuracy between several kilometers to few tens of kilometers, which is just the order of magnitude of the Lense-Thirring shifts of the orbits of the Galilean satellites over almost a century. From a comparison between analytical development and numerical integration it turns out that, unfortunately, most of the secular component of the gravitomagnetic signature is removed in the process of fitting the initial conditions. Indeed, an estimation of the magnitude of the Lense-Thirring effect in the ephemerides residuals is given; the resulting residuals have a maximum magnitude of 20 meters only (over 125 years). ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0508/0508112v2.pdf"}
{"id": "gr-qc0602078", "abstract": "  Numerical results from a study of boson stars under nonspherical perturbations using a fully general relativistic 3D code are presented together with the analysis of emitted gravitational radiation. We have constructed a simulation code suitable for the study of scalar fields in space-times of general symmetry by bringing together components for addressing the initial value problem, the full evolution system and the detection and analysis of gravitational waves. Within a series of numerical simulations, we explicitly extract the Zerilli and Newman-Penrose scalar Ψ_4 gravitational waveforms when the stars are subjected to different types of perturbations. Boson star systems have rapidly decaying nonradial quasinormal modes and thus the complete gravitational waveform could be extracted for all configurations studied. The gravitational waves emitted from stable, critical, and unstable boson star configurations are analyzed and the numerically observed quasinormal mode frequencies are compared with known linear perturbation results. The superposition of the high frequency nonspherical modes on the lower frequency spherical modes was observed in the metric oscillations when perturbations with radial and nonradial components were applied. The collapse of unstable boson stars to black holes was simulated. The apparent horizons were observed to be slightly nonspherical when initially detected and became spherical as the system evolved. The application of nonradial perturbations proportional to spherical harmonics is observed not to affect the collapse time. An unstable star subjected to a large perturbation was observed to migrate to a stable configuration. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0602/0602078v2.pdf"}
{"id": "gr-qc0605053", "abstract": "  The construction of initial data for black-hole binaries usually involves the choice of free parameters that define the spins of the black holes and essentially the eccentricity of the orbit. Such parameters must be chosen carefully to yield initial data with the desired physical properties. In this paper, we examine these choices in detail for the quasiequilibrium method coupled to apparent-horizon/quasiequilibrium boundary conditions. First, we compare two independent criteria for choosing the orbital frequency, the \"Komar-mass condition\" and the \"effective-potential method,\" and find excellent agreement. Second, we implement quasi-local measures of the spin of the individual holes, calibrate these with corotating binaries, and revisit the construction of non-spinning black hole binaries. Higher-order effects, beyond those considered in earlier work, turn out to be important. Without those, supposedly non-spinning black holes have appreciable quasi-local spin; furthermore, the Komar-mass condition and effective potential method agree only when these higher-order effects are taken into account. We compute a new sequence of quasi-circular orbits for non-spinning black-hole binaries, and determine the innermost stable circular orbit of this sequence. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0605/0605053v3.pdf"}
{"id": "gr-qc0608034", "abstract": "  The retarded Green function of the electromagnetic field in spacetime of a straight thin cosmic string is found. It splits into a geodesic part (corresponding to the propagation along null rays) and to the field scattered on the string. With help of the Green function the electric and magnetic fields of simple sources are constructed. It is shown that these sources are influenced by the cosmic string through a self-interaction with their field. The distant field of static sources is studied and it is found that it has a different multipole structure than in Minkowski spacetime. On the other hand, the string suppresses the electric and magnetic field of distant sources–the field is expelled from regions near the string. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0608/0608034v2.pdf"}
{"id": "gr-qc0701028", "abstract": "  Optical reference geometry and related concept of inertial forces are investigated in Kerr-de Sitter spacetimes. Properties of the inertial forces are summarized and their typical behaviour is illustrated. The intuitive 'Newtonian' application of the forces in the relativistic dynamics is demonstrated in the case of the test particle circular motion, static equilibrium positions and perfect fluid toroidal configurations. Features of the optical geometry are illustrated by the embedding diagrams of its equatorial plane. The embedding diagrams do not cover whole the stationary regions of the spacetimes, therefore the limits of embeddability are established. A shape of the embedding diagrams is related to the behaviour of the centrifugal force and it is characterized by the number of turning points of the diagrams. Discussion of the number of embeddable photon circular orbits is also included and the typical embedding diagrams are constructed. The Kerr-de Sitter spacetimes are classified according to the properties of the inertial forces and embedding diagrams. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0701/0701028v1.pdf"}
{"id": "gr-qc9506052", "abstract": "  In this paper the averaged weak (AWEC) and averaged null (ANEC) energy conditions, together with uncertainty principle-type restrictions on negative energy (“quantum inequalities”), are examined in the context of evaporating black hole backgrounds in both two and four dimensions. In particular, integrals over only half-geodesics are studied. We determine the regions of the spacetime in which the averaged energy conditions are violated. In all cases where these conditions fail, there appear to be quantum inequalities which bound the magnitude and extent of the negative energy, and hence the degree of the violation. The possible relevance of these results for the validity of singularity theorems in evaporating black hole spacetimes is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9506/9506052v2.pdf"}
{"id": "gr-qc9610049", "abstract": "  We solve the linearized Einstein equations for a specific oscillating mass distribution and discuss the usual counterarguments against the existence of observable gravitational retardations in the \"near zone\", where d/r << 1 (d = oscillation amplitude of the source, r = distance from the source). We show that they do not apply in the region d/r ≈1, and prove that gravitational forces are retarded in the immediate vicinity of the source. An experiment to measure this retardation is proposed, which may provide the first direct experimental observation of propagating gravitational fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9610/9610049v3.pdf"}
{"id": "gr-qc9710102", "abstract": "  Numerical studies of the plane symmetric, vacuum Gowdy universe on T^3 × R yield strong support for the conjectured asymptotically velocity term dominated (AVTD) behavior of its evolution toward the singularity except, perhaps, at isolated spatial points. A generic solution is characterized by spiky features and apparent “discontinuities” in the wave amplitudes. It is shown that the nonlinear terms in the wave equations drive the system generically to the “small velocity” AVTD regime and that the spiky features are caused by the absence of these terms at isolated spatial points. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9710/9710102v1.pdf"}
{"id": "gr-qc9712047", "abstract": "  We describe a grid generation procedure designed to construct new classes of orthogonal coordinate systems for binary black hole spacetimes. The computed coordinates offer an alternative approach to current methods, in addition to providing a framework for potentially more stable and accurate evolutions of colliding black holes. As a particular example, we apply our procedure to generate appropriate numerical grids to evolve Misner's axisymmetric initial data set representing two equal mass black holes colliding head-on. These new results are compared with previously published calculations, and we find generally good agreement in both the waveform profiles and total radiated energies over the allowable range of separation parameters. Furthermore, because no specialized treatment of the coordinate singularities is required, these new grids are more easily extendible to unequal mass and spinning black hole collisions. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9712/9712047v1.pdf"}
{"id": "gr-qc9812057", "abstract": "  We construct initial data for a particular class of Brill wave metrics using Regge calculus, and compare the results to a corresponding continuum solution, finding excellent agreement. We then search for trapped surfaces in both sets of initial data, and provide an independent verification of the existence of an apparent horizon once a critical gravitational wave amplitude is passed. Our estimate of this critical value, using both the Regge and continuum solutions, supports other recent findings. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9812/9812057v1.pdf"}
{"id": "gr-qc9901040", "abstract": "  Using a metric perturbation method, we study gravitational waves from a test particle scattered by a spherically symmetric relativistic star. We calculate the energy spectrum and the waveform of gravitational waves for axial modes. Since metric perturbations in axial modes do not couple to the matter fluid of the star, emitted waves for a normal neutron star show only one peak in the spectrum, which corresponds to the orbital frequency at the turning point, where the gravitational field is strongest. However, for an ultracompact star (the radius R ≲ 3M), another type of resonant periodic peak appears in the spectrum. This is just because of an excitation by a scattered particle of axial quasinormal modes, which were found by Chandrasekhar and Ferrari. This excitation comes from the existence of the potential minimum inside of a star. We also find for an ultracompact star many small periodic peaks at the frequency region beyond the maximum of the potential, which would be due to a resonance of two waves reflected by two potential barriers (Regge-Wheeler type and one at the center of the star). Such resonant peaks appear neither for a normal neutron star nor for a Schwarzschild black hole. Consequently, even if we analyze the energy spectrum of gravitational waves only for axial modes, it would be possible to distinguish between an ultracompact star and a normal neutron star (or a Schwarzschild black hole). ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9901/9901040v2.pdf"}
{"id": "gr-qc9901079", "abstract": "  Hawking and the author have proposed a class of singular, finite action instantons for defining the initial conditions for inflation. Vilenkin has argued they are unacceptable. He exhibited an analogous class of asymptotically flat instantons which on the face of it lead to an instability of Minkowski space. However, all these instantons must be defined by introducing a constraint into the path integral, which is then integrated over. I show that with a careful definition these instantons do not possess a negative mode. Infinite flat space is therefore stable against decay via singular instantons. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9901/9901079v3.pdf"}
{"id": "gr-qc9906078", "abstract": "  We consider 2+1 dimensional gravity with a cosmological constant, and explore a duality that exists between space-times that have the De Sitter group SO(3,1) as its local isometry group. In particular, the Lorentzian theory with a positive cosmological constant is dual to the Euclidean theory with a negative cosmological constant. We use this duality to construct a mapping between apparently unrelated space-times. More precisely, we exhibit a relation between the Euclidean BTZ family and some T^2-cosmological solutions, and between De-Sitter point particle space-times and the analytic continuations of Anti-De Sitter point particles. We discuss some possible applications for BH and AdS thermodynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9906/9906078v2.pdf"}
{"id": "gr-qc9909054", "abstract": "  We review the derivation of the metric for a spinning body of any shape and composition using linearized general relativity theory, and also obtain the same metric using a transformation argument. The latter derivation makes it clear that the linearized metric contains only the Eddington α and γ parameters, so no new parameter is involved in frame-dragging or Lense-Thirring effects. We then calculate the precession of an orbiting gyroscope in a general weak gravitational field, described by a Newtonian potential (the gravito-electric field) and a vector potential (the gravito-magnetic field). Next we make a multipole analysis of the potentials and the precession equations, giving all of these in terms of the spherical harmonics moments of the density distribution. The analysis is not limited to an axially symmetric source, although the Earth, which is the main application, is very nearly axisymmetric. Finally we analyze the precession in regard to the Gravity Probe B (GP-B) experiment, and find that the effect of the Earth's quadrupole moment (J_2) on the geodetic precession is large enough to be measured by GP-B (a previously known result), but the effect on the Lense-Thirring precession is somewhat beyond the expected GP-B accuracy. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9909/9909054v2.pdf"}
{"id": "gr-qc9911010", "abstract": "  In a companion paper we introduced a kinematical arena for the discussion of the constraints of canonical quantum gravity in the spin network representation based on Vassiliev invariants. In this paper we introduce the Hamiltonian constraint, extend the space of states to non-diffeomorphism invariant “habitats” and check that the off-shell quantum constraint commutator algebra reproduces the classical Poisson algebra of constraints of general relativity without anomalies. One can therefore consider the resulting set of constraints and space of states as a consistent theory of canonical quantum gravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9911/9911010v1.pdf"}
{"id": "hep-ex0002056", "abstract": "  Starting from considerations about meaning and subsequent use of asymmetric uncertainty intervals of experimental results, we review the issue of uncertainty propagation. We show that, using a probabilistic approach (the so-called Bayesian approach), all sources of uncertainty can be included in a logically consistent way. Practical formulae for the first moments of the probability distribution are derived up to second-order approximations. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0002/0002056v1.pdf"}
{"id": "hep-ex0007006", "abstract": "  An S-Matrix ansatz is used to determine the mass and width of the Z boson, as well as the contributions of gamma/Z interference and Z boson exchange to fermion-pair production. For this purpose we use hadron and lepton-pair production cross sections and lepton forward-backward asymmetries that have been measured with the L3 detector at centre-of-mass energies between 87GeV and 189GeV. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0007/0007006v1.pdf"}
{"id": "hep-ex0202030", "abstract": "  The track timing capabilities of a silicon drift detector based tracker for a future linear electron-positron collider are evaluated. We show such a detector can time tracks at the nanosecond, and for high-P_T, sub-nanosecond level. This implies that, even for collider designs with the bunch spacing at 1.4 ns, every track can be assigned to a particular bunch crossing at a confidence level of up to two standard deviations. We suggest a choice for the drift axes in the tracker layers to simultaneously optimize the momentum resolution and track timing. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0202/0202030v1.pdf"}
{"id": "hep-lat0209075", "abstract": "  We perform detailed measurements of the geometrical characteristics of the percolating cluster of the magnetic monopole currents in the confining phase of the lattice SU(2) gluodynamics. The Maximal Abelian projection is used to define the monopoles. The use of the geometrical language is motivated by recent observations that the full non-Abelian action associated with the monopoles corresponds to point-like particles on the currently available lattices. Scaling behavior of various quantities is observed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0209/0209075v1.pdf"}
{"id": "hep-lat0211018", "abstract": "  We study the effective Hamiltonian for strong-coupling lattice QCD in the case of non-zero baryon density. In leading order the effective Hamiltonian is a generalized antiferromagnet. For naive fermions, the symmetry is U(4N_f) and the spins belong to a representation that depends on the local baryon number. Next-nearest-neighbor (nnn) terms in the Hamiltonian break the symmetry to U(N_f) x U(N_f). We transform the quantum problem to a Euclidean sigma model which we analyze in a 1/N_c expansion. In the vacuum sector we recover spontaneous breaking of chiral symmetry for the nearest-neighbor and nnn theories. For non-zero baryon density we study the nearest-neighbor theory only, and show that the pattern of spontaneous symmetry breaking depends on the baryon density. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0211/0211018v2.pdf"}
{"id": "hep-lat0303011", "abstract": "  The Numerical calculations for tadpole-improved U(1) lattice gauge theory in three-dimensions on anisotropic lattices have been performed using standard path integral Monte Carlo techniques. Using average plaquette tadpole renormalization scheme, simulations were done with temporal lattice spacings much smaller than the spatial ones and results were obtained for the string tension, the renormalized anisotropy and scalar glueball masses. We find, by comparing the `regular' and `sideways' potentials, that tadpole improvement results in very little renormalization of the bare anisotropy and reduces the discretization errors in the static quark potential and in the glueball masses. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0303/0303011v3.pdf"}
{"id": "hep-lat0406001", "abstract": "  We present the first investigation of the extrapolation of quenched nucleon magnetic moments in quenched chiral effective field theory. We utilize established techniques in finite-range regularisation and compare with standard dimensional regularisation methods. Finite-volume corrections to the relevant loop integrals are also addressed. Finally, the contributions of dynamical sea quarks to the proton moment are estimated using a recently discovered phenomenological link between quenched and physical QCD. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0406/0406001v2.pdf"}
{"id": "hep-lat0408041", "abstract": "  We investigate critical slowing down in the local updating continuous-time Quantum Monte Carlo method by relating the finite size scaling of Fisher Zeroes to the dynamically generated gap, through the scaling of their respective critical exponents. As we comment, the nonlinear sigma model representation derived through the hamiltonian of our lattice spin model can also be used to give a effective treatment of planar anomalous dimensions in N=4 SYM. We present scaling arguments from our FSS analysis to discuss quantum corrections and recent 2-loop results, and further comment on the prospects of extending this approach for calculating higher twist parton distributions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0408/0408041v1.pdf"}
{"id": "hep-lat0511030", "abstract": "  We compute low-lying eigenmodes of the gauge covariant Laplace operator on the lattice at finite temperature. For classical configurations we show how the lowest mode localizes the monopole constituents inside calorons and that it hops upon changing the boundary conditions. The latter effect we observe for thermalized backgrounds, too, analogously to what is known for fermion zero modes.   We propose a new filter for equilibrium configurations which provides link variables as a truncated sum involving the Laplacian modes. This method not only reproduces classical structures, but also preserves the confining potential, even when only a few modes are used. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0511/0511030v1.pdf"}
{"id": "hep-lat0609032", "abstract": "  We report on the status of our QCD thermodynamics project. It is performed on the QCDOC machine at Brookhaven National Laboratory and the APEnext machine at Bielefeld University. Using a 2+1 flavor formulation of QCD at almost realistic quark masses we calculated several thermodynamical quantities. In this proceeding we show the susceptibilites of the chiral condensate and the Polyakov loop, the static quark potential and the spatial string tension. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0609/0609032v1.pdf"}
{"id": "hep-lat9509083", "abstract": "  We present results for the masses and decay constants of the light mesons in quenched QCD using the standard gluon action and a tadpole–improved SW–clover fermionic action to reduce discretisation errors. The calculation has been carried out at fixed volume and three lattice spacings corresponding to β=5.7, 6.0 and 6.2. We make comparisons with the conventional SW–clover scheme. We use our results to extract continuum limits and to quantify the size of discretisation errors at smaller β-values. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/9509/9509083v1.pdf"}
{"id": "hep-lat9609025", "abstract": "  We calculate the third coefficient of the lattice β function in pure Yang-Mills theory. We make use of a computer code for solving perturbation theory analytically on the lattice. We compute the divergent integrals by using a method based on a Taylor expansion of the integrand in powers of the external momenta in 4 - ϵ dimensions. Our results are in agreement with a previous calculation by M. Lüscher and P. Weisz where the authors used a different technique. We also show how this new coefficient modifies the scaling function on the lattice in both the standard and energy schemes. In particular we show that asymptotic scaling is extremely well achieved in the energy scheme. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/9609/9609025v1.pdf"}
{"id": "hep-lat9811014", "abstract": "  We show that the fermion determinant for 2-D Wilson lattice fermions coupled to an external scalar field is equivalent to self avoiding loops interacting with the external field. In an application of the resulting formula we integrate the scalar field with a Gaussian action to generate the N-component Gross-Neveu model. The loop representation for this model is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/9811/9811014v1.pdf"}
{"id": "hep-lat9909162", "abstract": "  Recent developments on the four dimensional (4d) lattice studies of the finite temperature electroweak phase transition (EWPT) are summarized. The phase diagram is given in the continuum limit. The finite temperature SU(2)-Higgs phase transition is of first order for Higgs-boson masses m_H<66.5 +/- 1.4 GeV. Above this endpoint only a rapid cross-over can be seen. The full 4d result agrees completely with that of the dimensional reduction approximation. The Higgs-boson endpoint mass in the Standard Model (SM) would be 72.1 +/- 1.4 GeV. Taking into account the LEP Higgs-boson mass lower bound excludes any EWPT in the SM. A one-loop calculation of the static potential in the SU(2)-Higgs model enables a precise comparison between lattice simulations and perturbative results. The most popular extension of the SM, the Minimal Supersymmetric SM (MSSM) is also studied on 4d lattices. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/9909/9909162v1.pdf"}
{"id": "hep-lat9912021", "abstract": "  I address the question of how much of QCD in the chiral limit is reproduced by instantons. After reconstructing the instanton content of smoothed Monte Carlo lattice configurations, I compare hadron spectroscopy on this instanton ensemble to the spectroscopy on the original “physical” smoothed configurations using a chirally optimised clover fermion action. By studying the zero mode zone in simple instances I find that the optimised action gives a satisfactory description of it. Through the Banks-Casher formula, instantons by themselves are shown to break chiral symmetry but hadron correlators on the instanton backgrounds are strongly influenced by free quark propagation. This results in unnaturally light hadrons and a small splitting between the vector and the pseudoscalar meson channels. Superimposing a perturbative ensemble of zero momentum gauge field fluctuations (torons) on the instantons is found to be enough to eliminate the free quarks and restore the physical hadron correlators. I argue that the torons that are present only in finite volumes, are probably needed to compensate the unnaturally large finite size effects due to the lack of confinement in the instanton ensemble. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/9912/9912021v1.pdf"}
{"id": "hep-ph0002257", "abstract": "  New physics beyond the electroweak scale may increase weak interaction cross sections beyond the Standard Model predictions. Such cross sections can be expected within theories that solve the hierarchy problem of known interactions with a unification scale in the TeV range. We derive constraints on these cross sections from the flux of neutrinos expected from cosmic ray interactions with the microwave background and the non-observation of horizontal air showers. We also discuss how this limit can be improved by upcoming cosmic ray and neutrino experiments, and how the energy dependence of the new interactions can be probed by these experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0002/0002257v2.pdf"}
{"id": "hep-ph0005228", "abstract": "  We calculate the neutrino mean free path in color superconducting quark matter, and employ it to study the cooling of matter via neutrino diffusion in the superconducting phase as compared to a free quark phase. The cooling process slows when quark matter undergoes a second order phase transition to a superconducting phase at the critical temperature T_c. Cooling subsequently accelerates as the temperature decreases below T_c. This will directly impact the early evolution of a newly born neutron star should its core contain quark matter. Consequently, there may be observable changes in the early neutrino emission which would provide evidence for superconductivity in hot and dense matter. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0005/0005228v1.pdf"}
{"id": "hep-ph0009333", "abstract": "  Considering the low-temperature (T) and high-baryon-number-density (n_B) region of the QCD phase diagram, we present a model for the first-order phase transition between the quark-gluon plasma (QGP) and the recently proposed colour superconducting phase. We study nucleation of a droplet of the superconducting phase within the metastable QGP gas. Numerical results for the activation energy, radius and other physical parameters of the droplets, at various temperatures, densities and gap parameters, are given. We have estimated the latent heat of the phase transition. In the T-n_B plane, we are able to demarcate the region of the superconducting phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0009/0009333v3.pdf"}
{"id": "hep-ph0010221", "abstract": "  A detailed analysis is performed of transverse momentum spectra of several identified hadrons in high energy collisions within the framework of the statistical model of hadronisation. The effect of the decay chain following hadron generation is accurately taken into account. The considered centre-of-mass energies range from   10 to 30 GeV in hadronic collisions (pi+ p, pp and Kp) and from   15 to 45 GeV in e+e- collisions. A clear consistency is found between the temperature parameter extracted from the present analysis and that obtained from fits to average hadron multiplicities in the same collision systems. This finding indicates that in the hadronisation, the production of different particle species and their momentum spectra are two closely related phenomenons governed by one parameter. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0010/0010221v1.pdf"}
{"id": "hep-ph0110173", "abstract": "  We use the POMWIG Monte Carlo generator to predict the cross-sections for double diffractive higgs and di-photon production at the Tevatron and LHC. We find that the higgs production cross-section is too small to be observable at Tevatron energies, and even at the LHC observation would be difficult. Double diffractive di-photon production, however, should be observable within one year of Tevatron Run II. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0110/0110173v2.pdf"}
{"id": "hep-ph0110267", "abstract": "  In this paper we study the effect of finite size on the two-flavour colour superconducting state. As well as restricting the quarks to a box, we project onto states of good baryon number and onto colour singlets, these being necessary restrictions on any observable “quark nuggets”. We find that whereas finite size alone has a significant effect for very small boxes, with the superconducting state often being destroyed, the effect of projection is to restore it again. The infinite-volume limit is a good approximation even for quite small systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0110/0110267v1.pdf"}
{"id": "hep-ph0111155", "abstract": "  We construct hadronic axion models in the framework of the anomaly-mediated supersymmetry breaking scenario. If the Peccei-Quinn symmetry breaking is related to the supersymmetry breaking, mass spectrum of the minimal anomaly-mediated scenario is modified, which may solve the negative slepton mass problem in the minimal anomaly-mediated model. We find several classes of phenomenologically viable models of axion within the framework of the anomaly mediation and, in particular, we point out a new mechanism of stabilizing the axion potential. In this class of models, the Peccei-Quinn scale is related to the messenger scale. We also study phenomenological aspects of this class of models. We will see that, in some case, the lightest particle among the superpartners of the standard-model particles is stau while the lightest superparticle becomes the axino, the superpartner of the axion. With such a unique mass spectrum, conventional studies of the collider physics and cosmology for supersymmetric models should be altered. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0111/0111155v2.pdf"}
{"id": "hep-ph0205087", "abstract": "  Bose-Einstein correlations (BEC) observed between identical bosons produced in high energy multiparticle collisions are regarded as very important tool in investigations of multiparticle production processes. We present here their stochastic feature stressing the fact that they can be regarded as a reflection of correlations of fluctuations present in hadronizing system. We show in particular that such approach allows for simple modelling of BEC in numerical event generators used to describe the multiparticle production processes at high energy collisions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0205/0205087v3.pdf"}
{"id": "hep-ph0205344", "abstract": "  We present four-dimensional gauge theories that describe physics on five-dimensional curved (warped) backgrounds, which includes bulk fields with various spins (vectors, spinors, and scalars). Field theory on the AdS_5 geometry is examined as a simple example of our formulation. Various properties of bulk fields on this background, e.g., the mass spectrum and field localization behavior, can be achieved within a fully four-dimensional framework. Moreover, that gives a localization mechanism for massless vector fields. We also consider supersymmetric cases, and show in particular that the conditions on bulk masses imposed by supersymmetry on warped backgrounds are derived from a four-dimensional supersymmetric theory on the flat background. As a phenomenological application, models are shown to generate hierarchical Yukawa couplings. Finally, we discuss possible underlying mechanisms which dynamically realize the required couplings to generate curved geometries. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0205/0205344v2.pdf"}
{"id": "hep-ph0206113", "abstract": "  The dependence of the nuclear force on standard model parameters plays an important role in bounding time and space variations of fundamental couplings over cosmological time scales. We discuss the quark-mass dependence of deuteron and di-neutron binding in a systematic chiral expansion. The leading quark-mass dependence of the nuclear force arises from one-pion exchange and from local quark-mass dependent four-nucleon operators with coefficients that are presently unknown. By varying these coefficients while leaving nuclear observables at the physical values of the quark masses invariant, we find scenarios where two-nucleon physics depends both weakly and strongly on the quark masses. While the determination of these coefficients is an exciting future opportunity for lattice QCD, we conclude that, at present, bounds on time and space variations of fundamental parameters from the two-nucleon sector are much weaker than previously claimed. This brings into question the reliability of coupling-constant bounds derived from more complex nuclei and nuclear processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0206/0206113v2.pdf"}
{"id": "hep-ph0211215", "abstract": "  We show how methods of continuum perturbation theory can be used to simplify perturbative lattice calculations. We use the technique of asymptotic expansions to expand lattice loop integrals around the continuum limit. After the expansion, all nontrivial dependence on momenta and masses is encoded in continuum loop integrals and the only genuine lattice integrals left are tadpole integrals. Using integration-by-parts relations all of these can be expressed in terms of a small number of master integrals. Four master integrals are needed for bosonic one loop integrals, sixteen in QCD with Wilson or staggered fermions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0211/0211215v1.pdf"}
{"id": "hep-ph0310099", "abstract": "  As an unstable light pure leptonic system, positronium is a very specific probe atom to test bound state QED. In contrast to ordinary QED for free leptons, the bound state QED theory is not so well understood and bound state approaches deserve highly accurate tests. We present a brief overview of precision studies of positronium paying special attention to uncertainties of theory as well as comparison of theory and experiment. We also consider in detail advantages and disadvantages of positronium tests compared to other QED experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0310/0310099v1.pdf"}
{"id": "hep-ph0311198", "abstract": "  A model of quark mass matrices from six dimensions, which is nearly democatic in nature and which is previously constructed by two of us (PQH and MS), is studied in detail in this manuscript. We found that not only it fits all the six quark masses as well as the CKM matrix but also that there exists a region in the allowed parameter space of the model where the constraint on the parameter θ̅ of the Strong CP problem is satisfied. This region itself puts a constraint on the CKM parameters ρ̅ and η̅. As such, through our analysis, there appears to be a deep connection between Strong and Weak CP in this model ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0311/0311198v1.pdf"}
{"id": "hep-ph0402077", "abstract": "  Muon lepton flavor processes are reviewed in connection with search for physics beyond the standard model. Several methods to distinguish different theoretical models are discussed for μ→ e γ, μ→ 3 e, and μ - e conversion processes. New calculation of the μ - e conversion rate is presented including a Higgs boson mediated effect in the supersymmetric seesaw model. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0402/0402077v1.pdf"}
{"id": "hep-ph0403011", "abstract": "  In this work we address the impact of a cubic term addition to the Ginzburg-Landau mean-field potential, and study the consequences on the description of first order phase transitions in superconductors. Constraints are obtained from experiment and used to assess consequences on topological defect creation. No fundamental changes in either the Kibble-Zurek or Hindmarsh-Rajantie predictions are found. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0403/0403011v2.pdf"}
{"id": "hep-ph0404198", "abstract": "  Dark matter may be composed of superWIMPs, superweakly-interacting massive particles produced in the late decays of other particles. We focus on the case of gravitinos produced in the late decays of sleptons or sneutrinos and assume they are produced in sufficient numbers to constitute all of non-baryonic dark matter. At leading order, these late decays are two-body and the accompanying energy is electromagnetic. For natural weak-scale parameters, these decays have been shown to satisfy bounds from Big Bang nucleosynthesis and the cosmic microwave background. However, sleptons and sneutrinos may also decay to three-body final states, producing hadronic energy, which is subject to even more stringent nucleosynthesis bounds. We determine the three-body branching fractions and the resulting hadronic energy release. We find that superWIMP gravitino dark matter is viable and determine the gravitino and slepton/sneutrino masses preferred by this solution to the dark matter problem. In passing, we note that hadronic constraints disfavor the possibility of superWIMPs produced by neutralino decays unless the neutralino is photino-like. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0404/0404198v2.pdf"}
{"id": "hep-ph0404272", "abstract": "  Neutrinos from far-away sources annihilating at the Z resonance on relic neutrinos may give origin to the extreme-energy cosmic rays (EECR). If “Z-bursts” are responsible for the EECR events, then we show that the non-observation of cosmic ray events at energies above 2 x 10^20 eV by the AGASA Collaboration implies a lower bound around 0.3 eV on the relic neutrino mass. Since this mass exceeds the mass-squared differences inferred from oscillation physics, the bound in fact applies to all three neutrino masses. Together with the upper bound provided by comparisons of the CMB anisotropy with large-scale structure, this bound leaves only a small interval for neutrino masses around 0.3 eV, if Z-bursts are to explain the existing EECR events. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0404/0404272v1.pdf"}
{"id": "hep-ph0409038", "abstract": "  While the expansion rate of a homogeneous isotropic Universe is simply proportional to the square-root of the energy density, the expansion rate of an inhomogeneous Universe also depends on the nature of the density inhomogeneities. In this paper we calculate to second order in perturbation variables the expansion rate of an inhomogeneous Universe and demonstrate corrections to the evolution of the expansion rate. While we find that the mean correction is small, the variance of the correction on the scale of the Hubble radius is sensitive to the physical significance of the unknown spectrum of density perturbations beyond the Hubble radius. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0409/0409038v2.pdf"}
{"id": "hep-ph0409072", "abstract": "  We study the competence between chiral symmetry restoration and two flavor color superconductivity (2SC) using a relativistic quark model with covariant nonlocal interactions. We consider two different nonlocal regulators: a Gaussian regulator and a Lorentzian regulator. We find that although the phase diagrams are qualitative similar to those obtained using models with local interactions, in our case the superconducting gaps at medium values of the chemical potential are larger. Consequently, we obtain that in that region the critical temperatures for the disappearance of the 2SC phase might be of the order of 100-120 MeV. We also find that for ratios of the quark-quark and quark-antiquark couplings somewhat above the standard value 3/4, the end point and triple point in the T-μ phase diagram meet and a phase where both the chiral and diquark condensates are non-negligible appears. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0409/0409072v1.pdf"}
{"id": "hep-ph0412183", "abstract": "  The orbital and radial excitations of light-light mesons are studied in the framework of the dominantly orbital state description. The equation of motion is characterized by a relativistic kinematics supplemented by the usual funnel potential with a mixed scalar and vector confinement. The influence of finite quark masses and potential parameters on Regge and vibrational trajectories is discussed. The case of heavy-light mesons is also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0412/0412183v1.pdf"}
{"id": "hep-ph0505002", "abstract": "  This paper gives results for the spectrum, all allowed E1 radiative partial widths (and some important M1 widths) and all open-charm strong decay amplitudes of all 40 c-cbar states expected up to the mass of the 4S multiplet, just above 4.4 GeV. The spectrum and radiative widths are evaluated using two models, the relativized Godfrey-Isgur model and a nonrelativistic potential model. The electromagnetic transitions are evaluated using Coulomb plus linear plus smeared hyperfine wavefunctions, both in a nonrelativistic potential model and in the Godfrey-Isgur model. The open-flavor strong decay amplitudes are determined assuming harmonic oscillator wavefunctions and the 3P0 decay model. This work is intended to motivate future experimental studies of higher-mass charmonia, and may be useful for the analysis of high-statistics data sets to be accumulated by the BES, CLEO and GSI facilities. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0505/0505002v3.pdf"}
{"id": "hep-ph0506011", "abstract": "  Strangeness flavor yield s and the entropy yield S are the observables of the deconfined quark-gluon state of matter which can be studied in the entire available experimental energy range at AGS, SPS, RHIC, and, in near future, at the LHC energy range. We present here a comprehensive analysis of strange, soft hadron production as function of energy and reaction volume. We discuss the physical properties of the final state and argue how evidence about the primordial QGP emerges. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0506/0506011v1.pdf"}
{"id": "hep-ph0507154", "abstract": "  We provide a study of the phenomenology of heterotic orbifold compactifications scenarii within the context of supergravity effective theories. Our investigation focuses on those models where the soft Lagrangian is dominated by loop contributions to the various soft supersymmetry breaking parameters, giving a mixed anomaly-gravity mediation model. We consider the pattern of masses that are governed by these soft terms and investigate the implications of certain indirect constraints on supersymmetric models. In this framework, we point out how the complementarity between direct and indirect detection of a neutralino Dark Matter, and futur accelerator prospects can reduce considerably the parameter space of such models ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0507/0507154v1.pdf"}
{"id": "hep-ph0511010", "abstract": "  We investigate matter effects on highly relativistic neutrinos. The self-energy of neutrinos is determined in an electron or neutrino background taking into account resonance and finite width effects of the gauge bosons. We find minor changes compared to the formerly used formula for the propagator function and large deviations of the effective width from the decay width of the gauge bosons considering higher moments of the electron or neutrino distribution function. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0511/0511010v2.pdf"}
{"id": "hep-ph0512076", "abstract": "  In this paper, we discuss a possibility of studying properties of dark energy in long baseline neutrino oscillation experiments. We consider two types of models of neutrino dark energy. For one type of models the scalar field is taken to be quintessence-like and for the other phantom-like. In these models the scalar fields couple to the neutrinos to give rise to a spatially varying neutrino masses. We will show that the two types of models predict different behaviors of the spatial variation of the neutrino masses inside Earth and consequently result in different signals in long baseline neutrino oscillation experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0512/0512076v1.pdf"}
{"id": "hep-ph0609161", "abstract": "  High energy scattering was recently shown to be similar to a reaction-diffusion process. The latter defines a wide universality class that also contains e.g. some specific population evolution models. The common point of all these models is that their respective dynamics are described by noisy traveling wave equations. This observation has led to a new understanding of QCD in the regime of high energies, and known universal results on reaction-diffusion models could be transposed to obtain quantitative properties of QCD amplitudes. Conversely, new general results for that kind of statistical models have also been derived. Furthermore, an intriguing relationship between noisy traveling wave equations and the theory of spin glasses was found. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0609/0609161v2.pdf"}
{"id": "hep-ph0611111", "abstract": "  Gravitinos and hidden sector fields often cause a cosmological disaster in supersymmetric models. We find that a model with gravitational gauge mediation solves such a problem quite naturally. The mu-problem is also absent in the model. Moreover, the abundance of gravitinos explains correct amount of dark matter of the universe. The dark matter abundance can be calculated without detailed information on the thermal history of the universe such as the reheating temperature after inflation. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0611/0611111v2.pdf"}
{"id": "hep-ph0611284", "abstract": "  We consider a model of dynamical neutrino masses via the see-saw mechanism. Nambu-Goldstone bosons (majorons) arise associated with the formation of the heavy right-handed majorana masses. These bosons then acquire naturally soft masses (become pNGB's) at loop level via the Higgs-Yukawa mass terms. These models, like the original neutrino pNGB quintessence schemes of the 1980's that proceed through the Dirac masses, are natural, have cosmological implications through mass varying neutrinos, long range forces, and provide a soft potential for dark energy. We further argue that these models can explain leptogenesis naturally through the decays of the right-handed neutrinos. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0611/0611284v1.pdf"}
{"id": "hep-ph0612278", "abstract": "  We present a comprehensive update of the bounds on R-Parity violating supersymmetric couplings from lepton-flavour- and lepton-number-violating decay processes. We consider tau and mu decays as well as leptonic and semi-leptonic decays of mesons. We present several new bounds resulting from tau, eta and Kaon decays and correct some results in the literature concerning B-meson decays. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0612/0612278v2.pdf"}
{"id": "hep-ph0701174", "abstract": "  The task of Monte Carlo simulation of the evolution of the parton distributions in QCD and of constructing new parton shower Monte Carlo algorithms requires new way of organizing solutions of the QCD evolution equations, in which quark-gluon transitions on one hand and quark-quark or gluon-gluon transitions (pure gluonstrahlung) on the other hand, are treated separately and differently. This requires certain reorganization of the iterative solutions of the QCD evolution equations and leads to what we refer to as a hierarchic iterative solutions of the evolution equations. We present three formal derivations of such a solution. Results presented here are already used in the other recent works to formulate new MC algorithms for the parton-shower-like implementations of the QCD evolution equations. They are primarily of the non-Markovian type. However, such a solution can be used for the Markovian-type MCs as well. We also comment briefly on the relation of the presented formalism to similar methods used in other branches of physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0701/0701174v1.pdf"}
{"id": "hep-ph9406242", "abstract": "  The damping of a massless fermion coupled to a massless scalar particle at finite temperature is considered using the Braaten-Pisarski resummation technique. First the hard thermal loop diagrams of this theory are extracted and effective Green's functions are constructed. Using these effective Green's functions the damping rate of a soft Yukawa fermion is calculated. This rate provides the most simple example for the damping of a soft particle. To leading order it is proportional to g^2T, whereas the one of a hard fermion is of higher order. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9406/9406242v1.pdf"}
{"id": "hep-ph9407282", "abstract": "  We propose a new method to study transverse flow effects in relativistic nuclear collisions by Fourier analysis of the azimuthal distribution on an event-by-event basis in relatively narrow rapidity windows. The distributions of Fourier coefficients provide direct information on the magnitude and type of flow. Directivity and two dimensional sphericity tensor, widely used to analyze flow, emerge naturally in our approach, since they correspond to the distributions of the first and second harmonic coefficients, respectively. The role of finite particle fluctuations and particle correlations is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9407/9407282v1.pdf"}
{"id": "hep-ph9603205", "abstract": "  Pair production processes of neutral Higgs particles will allow us to study the trilinear Higgs couplings at future high–energy colliders. Several mechanisms give rise to multi–Higgs final states in hadron interactions. In the present paper we investigate Higgs pair production in gluon–gluon collisions. After recapitulating pair production in the Standard Model, the analysis of the cross sections is carried out in detail for the neutral Higgs particles in the minimal supersymmetric extension. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9603/9603205v1.pdf"}
{"id": "hep-ph9611250", "abstract": "  In this paper we continue previous efforts in the literature to determine phenomenological values for the gluon mass by confronting theoretical results obtained in a theory of massive gluons with experimental values or results directly referring to the nontrivial structure of the Yang-Mills vacuum, e.g. to the presence of the gluon condensate. The decays of heavy quarkonia into 3 gluons and 2 gluons + photon are considered in detail as well as the correlators of the electromagnetic current and the scalar glueball current. Based on the analysis for the latter quantities a value for the gluon mass in the range of 500-600 MeV is estimated from the standard SVZ-value of the gluon condensate. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9611/9611250v1.pdf"}
{"id": "hep-ph9702208", "abstract": "  We show how one can measure anomalous WWZ- and WWgamma-couplings with minimal statistical error using integrated observables, without having to assume that the anomalous couplings are small. We propose a parametrisation of these couplings which is well suited for the extraction of both single and many parameters, and which leads to a very simple form of the integrated cross section, from which additional information on the couplings can be obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9702/9702208v1.pdf"}
{"id": "hep-ph9801331", "abstract": "  We discuss the prospect of studying physics at short distances, such as Planck length or GUT scale, using supersymmetry as a probe. Supersymmetry breaking parameters contain information on all physics below the scale where they are induced. We will gain insights into grand unification (or in some cases string theory) and its symmetry breaking pattern combining measurements of gauge coupling constants, gaugino masses and scalar masses. Once the superparticle masses are known, it removes the main uncertainty in the analysis of proton decay, flavor violation and electric dipole moments. We will be able to discuss the consequence of flavor physics at short distances quantitatively. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9801/9801331v1.pdf"}
{"id": "hep-ph9801427", "abstract": "  We report on a new equilibration scenario in relativistic heavy ion collisions, the scenario of the Increasingly Strongly Interacting Parton Plasma, and the effects of this scenario on equilibration and open charm, photon and dilepton production. The parton plasma is shown to be a very special kind of many-body system, which contains new physics concerning the approach towards equilibrium. This is likely to be unique to the parton plasma. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9801/9801427v1.pdf"}
{"id": "hep-ph9803231", "abstract": "  The finite temperature effective potential in the 2+1 dimensional Nambu-Jona-Lasinio model is constructed up to the next to leading order in the large N expansion, where N is the number of flavors in the model. The distinctive feature of the analysis is an inclusion of an additional scalar field, which allows us to circumvent the well known, and otherwise unavoidable problem with the imaginary contribution to the effective potential. In accordance with the Mermin-Wagner-Coleman theorem, applied to the dimensionally reduced subsystem of the zero Matsubara modes of the composite boson fields, the finite temperature effective potential reveals a global minimum at the zero of the composite order parameter. This allows us to conclude that the continuous global symmetry of the NJL model is not broken for any arbitrarily small, finite temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9803/9803231v3.pdf"}
{"id": "hep-ph9810387", "abstract": "  We perform an updated model-independent analysis using the latest solar neutrino data obtained by ^37Cl and ^71Ga radiochemical experiments, and most notably by a large water-Cherenkov detector SuperKamiokande with their 504 days of data taking. We confirm that the astrophysical solutions to the solar neutrino problem are extremely disfavored by the data and a low-temperature modification of the standard solar model is excluded by more than 5 σ. We also propose a new way of illuminating the suppression pattern of various solar neutrino flux without invoking detailed flavor conversion mechanisms. It indicates that the strong suppression of ^7Be neutrinos is no more true when the neutrino flavor conversion is taken into account. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9810/9810387v2.pdf"}
{"id": "hep-ph9903436", "abstract": "  We compute the effects of soft-gluon resummation, at the next-to-leading-logarithmic level, in the fixed-target hadroproduction cross section for prompt photons. We find in general that the corrections to the fixed next-to-leading-order results are large for large renormalization scales, and small for small scales. This leads to a significant reduction of the scale dependence of the results for most experimental configurations of interest. We compare our results to the recent measurements by the E706 and UA6 collaborations. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9903/9903436v1.pdf"}
{"id": "hep-ph9911243", "abstract": "  We revisit the results of recent electroweak baryogenesis calculations and include all allowed large CP-violating supersymmetric phases. If the phases are large, the resulting baryon asymmetry can be considerably larger than the observed value n_B/s ∼ 4 × 10^-11. Much of the asymmetry must therefore be washed out, and we argue that the upper bound on the light Higgs mass is larger than the value reported in previous work. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9911/9911243v1.pdf"}
{"id": "hep-ph9911367", "abstract": "  We study the infrared singularities associated to ultra-soft transverse gluons in the calculation of photon production by a quark-gluon plasma. Despite the fact that the KLN theorem works in this context and provides cancellations of infrared singularities, it does not prevent the production rate of low invariant mass dileptons to be sensitive to the magnetic mass of gluons and therefore the rate to be non perturbative. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9911/9911367v2.pdf"}
{"id": "hep-ph9912428", "abstract": "  The potentials between static sources in various representaions in SU(3) are calculated based on the fat-center-vortices model of Faber, Greensite and Olejnik. At intermediate distances, most distributions of the flux within vortices lead to potentials that are qualitatively in agreement with “Casimir scaling,” which says that the string tension is proportional to the quadratic operator of the representation. However, at the quantitative level, violations of Casimir scaling are generally much larger than those seen in numerical simulations, indicating that additional physical input to the fat-center-vortices model is required. At large distances, screening occurs for zero-triality representations; for the representations with non-zero triality the string tension equals that of the fundamental representation. Some rather “unphysical,” flux distributions can lead to violations of Casimir scaling at intermediate distances and violations of the expected ordering of representations at large distances. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9912/9912428v2.pdf"}
{"id": "hep-th0004051", "abstract": "  We compute the ground state energy of a massive scalar field in the background of a cylindrical shell whose potential is given by a delta function. The zero point energy is expressed in terms of the Jost function of the related scattering problem, the renormalization is performed with the help of the heat kernel expansion. The energy is found to be negative for attractive and for repulsive backgrounds as well. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0004/0004051v1.pdf"}
{"id": "hep-th0010064", "abstract": "  We consider the effect of the (heavy) fundamental quarks on the low energy effective Lagrangian description of nonabelian gauge theories in 2+1 dimensions. We show that in the presence of the fundamental charges, the magnetic Z_N symmetry becomes local. We construct the effective Lagrangian representing this local symmetry in terms of magnetic vortex fields, and discuss its physical consequences. We show that the finite energy states described by this Lagrangian have distinct bag-like structure. The point-like quarks are confined to the region of space where the value of the vortex field is much smaller than in the surrounding vacuum. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0010/0010064v1.pdf"}
{"id": "hep-th0201063", "abstract": "  We consider radion stabilization in hyperbolic brane-world scenarios. We demonstrate that in the context of Einstein gravity, matter fields which stabilize the extra dimensions must violate the null energy condition. This result is shown to hold even allowing for FRW-like expansion on the brane. In particular, we explicitly demonstrate how one putative source of stabilizing matter fails to work, and how others violate the above condition. We speculate on a number of ways in which we may bypass this result, including the effect of Casimir energy in these spaces. A brief discussion of supersymmetry in these backgrounds is also given. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0201/0201063v1.pdf"}
{"id": "hep-th0209006", "abstract": "  A first principle derivation is given of the neutrino damping rate in real-time thermal field theory. Starting from the discontinuity of the neutrino self energy at the two loop level, the damping rate can be expressed as integrals over space phase of amplitudes squared, weighted with statistical factors that account for the possibility of particle absorption or emission from the medium. Specific results for a background composed of neutrinos, leptons, protons and neutrons are given. Additionally, for the real part of the dispersion relation we discuss the relation between the results obtained from the thermal field theory, and those obtained by the thermal average of the forward scattering amplitude. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0209/0209006v1.pdf"}
{"id": "hep-th0209050", "abstract": "  We derive a renormalization group formalism for the Randall-Sundrum scenario, where the renormalization scale is set by a floating compactification radius. While inspired by the AdS/CFT conjecture, our results are derived concretely within higher-dimensional effective field theory. Matching theories with different radii leads to running hidden brane couplings. The hidden brane Lagrangian consists of four-dimensional local operators constructed from the induced value of the bulk fields on the brane. We find hidden Lagrangians which are non-trivial fixed points of the RG flow. Calculations in RS1 can be greatly simplified by “running down” the effective theory to a small radius. We demonstrate these simplifications by studying the Goldberger-Wise stabilization mechanism. In this paper, we focus on the classical and tree-level quantum field theory of bulk scalar fields, which demonstrates the essential features of the RG in the simplest context. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0209/0209050v2.pdf"}
{"id": "hep-th0301076", "abstract": "  We study Born-Infeld type effective action for unstable D3-brane system including a tachyon and an Abelian gauge field, and find the rolling tachyon with constant electric and magnetic fields as the most general homogeneous solution. Tachyonic vacua are characterized by magnitudes of the electric and magnetic fields and the angle between them. Analysis of small fluctuations in this background shows that the obtained configuration may be interpreted as a fluid consisting of string-like objects carrying electric and magnetic fields. They are stretched along one direction and the rolling tachyon move in a perpendicular direction to the strings. Direction of the propagating waves coincides with that of strings with velocity equal to electric field. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0301/0301076v3.pdf"}
{"id": "hep-th0409048", "abstract": "  We introduce the notion of background independent quantum field theory. The distinguishing feature of this theory is that the dynamics can be formulated without recourse to a background metric structure. We show in a simple model how the metric properties of spacetime can be recovered from the dynamics. Background independence is not only conceptually desirable but allows for the resolution of a problem haunting ordinary quantum field theory: the cosmological constant problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0409/0409048v2.pdf"}
{"id": "hep-th0503076", "abstract": "  We illustrate the mass and charge renormalization procedures in quantum field theory using, as an example, a simple model of interacting electrons and photons. It is shown how addition of infinite renormalization counterterms to the Hamiltonian helps to obtain finite and accurate results for the S-matrix. In order to remove the ultraviolet divergences from the Hamiltonian, we apply the Greenberg-Schweber “dressing transformation” and the Glazek-Wilson “similarity renormalization”. The resulting “dressed particle” Hamiltonian is finite in all orders of the perturbation theory and yields accurate S-matrix and bound state energies. The bare and virtual particles are removed from the theory, and physical dressed particles interact via direct action-at-a-distance. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0503/0503076v4.pdf"}
{"id": "hep-th0511170", "abstract": "  The low energy regime of 5D braneworld models with a bulk scalar field is studied. The setup is rather general and includes the Randall-Sundrum and dilatonic braneworlds models as particular cases. We discuss the cosmological evolution of the system and conclude that, in a two brane system, the negative tension brane is generally expected to evolve towards a null warp-factor state. This implies, for late time cosmology, that both branes end up interacting weakly. We also analyze the observational constraints imposed by solar-system and binary-pulsar tests on the braneworld configuration. This is done by considering the small deviations produced by the branes on the 4D gravitational interaction between bodies in the same brane. Using these constraints we show that the geometry around the braneworld is strongly warped, and that both branes must be far apart. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0511/0511170v2.pdf"}
{"id": "hep-th0512084", "abstract": "  We discuss the implications of a model of noncommutative Quantum Mechanics where noncommutativity is extended to the phase space. We analyze how this model affects the problem of the two-dimensional gravitational quantum well and use the latest experimental results for the energy states of neutrons in the Earth's gravitational field to establish an upper bound on the fundamental momentum scale introduced by noncommutativity. We show that the configuration space noncommutativity has, in leading order, no effect on the problem and that in the context of the model, a correction to the presently accepted value of Planck's constant to 1 part in 10^24 arises.   We also study the transition between quantum and classical behaviour of particles in a gravitational quantum well and analyze how an increase in the particles mass turns the energy spectrum into a continuous one. We consider these effects and argue that they could be tested by through experiments with atoms and fullerene-type molecules. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0512/0512084v2.pdf"}
{"id": "hep-th0607226", "abstract": "  D-term inflation is one of the most interesting and versatile models of inflation. It is possible to implement naturally D-term inflation within high energy physics, as for example SUSY GUTs, SUGRA, or string theories. D-term inflation avoids the η-problem, while in its standard form it always ends with the formation of cosmic strings. Given the recent three-year WMAP data on the cosmic microwave background temperature anisotropies, we examine whether D-term inflation can be successfully implemented in non-minimal supergravity theories. We show that for all our choices of Kähler potential, there exists a parameter space for which the predictions of D-term inflation are in agreement with the measurements. The cosmic string contribution on the measured temperature anisotropies is always dominant, unless the superpotential coupling constant is fine tuned; a result already obtained for D-term inflation within minimal supergravity. In conclusion, cosmic strings and their rôle in the angular power spectrum cannot be easily hidden by just considering a non-flat Kähler geometry. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0607/0607226v2.pdf"}
{"id": "hep-th0611214", "abstract": "  We consider two dimensional non linear sigma models on few symmetric superspaces, which are supergroup manifolds of coset type. For those spaces where one loop beta function vanishes, two loop beta function is calculated and is shown to be zero. Vanishing of beta function in all orders of perturbation theory is shown for the principal chiral models on group supermanifolds with zero Killing form. Sigma models on symmetric (super) spaces on supergroup manifold G/H are known to be classically integrable. We investigate a possibility to extend an argument of absence of quantum anomalies in non local current conservation from non super case to the case of supergroup manifolds which are asymptotically free in one loop. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0611/0611214v2.pdf"}
{"id": "hep-th0702181", "abstract": "  The massive spin-2 quantum gauge theory previously developed is applied to calculate gravitational bremsstrahlung. It is shown that this theory is unique and free from defects. In particular, there is no strong coupling if the graviton mass becomes small. The cross sections go over smoothly into the ones of the massless theory in the limit of vanishing graviton mass. The massless cross sections are calculated for the full tensor theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0702/0702181v1.pdf"}
{"id": "hep-th9609016", "abstract": "  We use the four-dimensional N=2 central charge superspace to give a geometrical construction of the Abelian vector-tensor multiplet consisting, under N=1 supersymmetry, of one vector and one linear multiplet. We derive the component field supersymmetry and central charge transformations, and show that there is a super-Lagrangian, the higher components of which are all total derivatives, allowing us to construct superfield and component actions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9609/9609016v1.pdf"}
{"id": "hep-th9705217", "abstract": "  In this work we consider an Abelian O(3) sigma model coupled nonminimally with a gauge field governed by a Maxwell and Chern-Simons terms. Bogomol'nyi equations are constructed for a specific form of the potential and generic nonminimal coupling constant. Furthermore, topological and nontopological self-dual soliton solutions are obtained for a critical value of the nonminimal coupling constant. Some particular static vortex solutions (topological and nontopological) satisfying the Bogomol'nyi bound are numerically solved and presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9705/9705217v2.pdf"}
{"id": "hep-th9805032", "abstract": "  We look for instanton solutions in a class of two scalar field gravity models, which includes the low energy string action in four dimensions. In models where the matter field has a potential with a false vacuum, we find that non-singular instantons exist as long as the Dilaton field found in string theory has a potential with a minimum, and provide an example of such an instanton. The class of singular instanton solutions are also examined, and we find that depending on the parameter values, the volume factor of the Euclidean region does not always vanish fast enough at the singularity to make the action finite. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9805/9805032v2.pdf"}
{"id": "hep-th9902170", "abstract": "  We compute the properties of a class of charged black holes in anti-de Sitter space-time, in diverse dimensions. These black holes are solutions of consistent Einstein-Maxwell truncations of gauged supergravities, which are shown to arise from the inclusion of rotation in the transverse space. We uncover rich thermodynamic phase structures for these systems, which display classic critical phenomena, including structures isomorphic to the van der Waals-Maxwell liquid-gas system. In that case, the phases are controlled by the universal `cusp' and `swallowtail' shapes familiar from catastrophe theory. All of the thermodynamics is consistent with field theory interpretations via holography, where the dual field theories can sometimes be found on the world volumes of coincident rotating branes. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9902/9902170v2.pdf"}
{"id": "hep-th9905116", "abstract": "  The hypothesis that the magnetic catalysis of chiral symmetry breaking is due to interactions of massless fermions in their lowest Landau level is examined in the context of chirally symmetric models with short ranged interactions. It is argued that, when the magnetic field is sufficiently large, even an infinitesimal attractive interaction in the appropriate channel will break chiral symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9905/9905116v2.pdf"}
{"id": "hep-th9911161", "abstract": "  We study brane configurations that give rise to large-N gauge theories with eight supersymmetries and no hypermultiplets. These configurations include a variety of wrapped, fractional, and stretched branes or strings. The corresponding spacetime geometries which we study have a distinct kind of singularity known as a repulson. We find that this singularity is removed by a distinctive mechanism, leaving a smooth geometry with a core having an enhanced gauge symmetry. The spacetime geometry can be related to large-N Seiberg-Witten theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9911/9911161v3.pdf"}
{"id": "math-ph0502037", "abstract": "  We investigate the continuum q-Potts model at its transition point from the disordered to the ordered regime, with particular emphasis on the coexistence of disordered and ordered phases in the high-q case. We argue that occurrence of phase transition can be seen as percolation in the related random cluster representation, similarly to the lattice Potts model, and investigate the typical structure of clusters for high q. We also report on numerical simulations in two dimensions using a continuum version of the Swendsen-Wang algorithm, compare the results with earlier simulations which used the invaded cluster algorithm, and discuss implications on the geometry of clusters in the disordered and ordered phases. ", "pdf_url": "gs://arxiv-dataset/arxiv/math-ph/pdf/0502/0502037v1.pdf"}
{"id": "math-ph0506053", "abstract": "  We investigate Laplacians on supercritical bond-percolation graphs with different boundary conditions at cluster borders. The integrated density of states of the Dirichlet Laplacian is found to exhibit a Lifshits tail at the lower spectral edge, while that of the Neumann Laplacian shows a van Hove asymptotics, which results from the percolating cluster. At the upper spectral edge, the behaviour is reversed. ", "pdf_url": "gs://arxiv-dataset/arxiv/math-ph/pdf/0506/0506053v2.pdf"}
{"id": "math0207302", "abstract": "  In the classical knot theory there is a well-known notion of descending diagram. From an arbitrary diagram one can easily obtain, by some crossing changes, a descending diagram which is a diagram of the unknot or unlink. In this paper the notion of descending diagram for knots and links in the real space is extended to the case of nonoriented knots and links in the projective space. It is also shown that this notion cannot be extended to oriented links. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0207/0207302v2.pdf"}
{"id": "math0512267", "abstract": "  We show a relationship between the non-acyclic Reidemeister torsion and a zero of the acyclic Reidemeister torsion for a lambda-regular SU(2) or SL(2, C)-representation of a knot group. Then we give a method to calculate the non-acyclic Reidemeister torsion of a knot exterior. We calculate a new example and investigate the behavior of the non-acyclic Reidemeister torsion associated to a 2-bridge knot and SU(2)-representations of its knot group. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0512/0512267v6.pdf"}
{"id": "math0601650", "abstract": "  We study the low-bias stabilization of active magnetic bearings (AMBs) subject to voltage saturation based on a recently proposed model for the AMB switching mode of operation. Using a forwarding-like approach, we construct a stabilizing controller of arbitrarily small amplitude and a control-Lyapunov function for the AMB dynamics. We illustrate our construction using a numerical example. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0601/0601650v1.pdf"}
{"id": "math0602376", "abstract": "  We propose a moving mesh adaptive approach for solving time-dependent partial differential equations. The motion of spatial grid points is governed by a moving mesh PDE (MMPDE) in which a mesh relaxation time τis employed as a regularization parameter. Previously reported results on MMPDEs have invariably employed a constant value of the parameter τ. We extend this standard approach by incorporating a variable relaxation time that is calculated adaptively alongside the solution in order to regularize the mesh appropriately throughout a computation. We focus on singular problems involving self-similar blow-up to demonstrate the advantages of using a variable relaxation ime over a fixed one in terms of accuracy, stability and efficiency. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0602/0602376v1.pdf"}
{"id": "math0702017", "abstract": "  What is the optimal shape of a dendrite? Of course, optimality refers to some particular criterion. In this paper, we look at the case of a dendrite sealed at one end and connected at the other end to a soma. The electrical potential in the fiber follows the classical cable equations as established by W. Rall. We are interested in the shape of the dendrite which minimizes either the attenuation in time of the potential or the attenuation in space. In both cases, we prove that the cylindrical shape is optimal. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0702/0702017v2.pdf"}
{"id": "nlin0001040", "abstract": "  Employing the graded versions of the Yang-Baxter equation and the reflection equations, we construct two kinds of integrable impurities for a small-polaron model with general open boundary conditions: (a) we shift the spectral parameter of the local Lax operator at arbitrary sites in the bulk, and (b) we embed the impurity fermion vertex at each boundary of the chain. The Hamiltonians with different types of impurity terms are given explicitly. The Bethe ansatz equations, as well as the eigenvalues of the Hamiltonians, are constructed by means of the quantum inverse scattering method. In addition, we discuss the ground-state properties in the thermodynamic limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0001/0001040v2.pdf"}
{"id": "nlin0107032", "abstract": "  We review the main properties of shell models for magnetohydrodynamic (MHD) turbulence. After a brief account on shell models with nearest neighbour interactions, the paper focuses on the most recent results concerning dynamical properties and intermittency of a model which is a generalization to MHD of the Gledzer-Yamada-Okhitani (GOY) model for hydrodynamic. Applications to astrophysical problems are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0107/0107032v1.pdf"}
{"id": "nlin0111031", "abstract": "  Recently a fingering morphology, resembling the hydrodynamic Saffman-Taylor instability, was identified in the quasi-two-dimensional electrodeposition of copper. We present here measurements of the dispersion relation of the growing front. The instability is accompanied by gravity-driven convection rolls at the electrodes, which are examined using particle image velocimetry. While at the anode the theory presented by Chazalviel et al. describes the convection roll, the flow field at the cathode is more complicated because of the growing deposit. In particular, the analysis of the orientation of the velocity vectors reveals some lag of the development of the convection roll compared to the finger envelope. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0111/0111031v2.pdf"}
{"id": "nlin0205025", "abstract": "  We analyze the self-averaging properties of time-reversed solutions of the paraxial wave equation with random coefficients, which we take to be Markovian in the direction of propagation. This allows us to construct an approximate martingale for the phase space Wigner transform of two wave fields. Using a priori L^2-bounds available in the time-reversal setting, we prove that the Wigner transform in the high frequency limit converges in probability to its deterministic limit, which is the solution of a transport equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0205/0205025v1.pdf"}
{"id": "nlin0301006", "abstract": "  A family of maps or flows depending on a parameter ν which varies in an interval, spans a certain property if along the interval this property depends continuously on the parameter and achieves some asymptotic values along it. We consider families of periodically forced Hamiltonian systems for which the appropriately scaled frequency ω̅(ν) is spanned, namely it covers the semi-infinite line [0,∞). Under some natural assumptions on the family of flows and its adiabatic limit, we construct a convenient labelling scheme for the primary homoclinic orbits which may undergo a countable number of bifurcations along this interval. Using this scheme we prove that a properly defined flux function is C^1 in ν. Combining this proof with previous results of RK and Poje, immediately establishes that the flux function and the size of the chaotic zone depend on the frequency in a non-monotone fashion for a large class of Hamiltonian flows. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0301/0301006v1.pdf"}
{"id": "nlin0309025", "abstract": "  We describe different types of self-trapped optical beams carrying phase dislocations, including vortex solitons and ring-like soliton clusters. We demonstrate numerically how to create such nonlinear singular beams by the interaction of several fundamental optical solitons. Mutual trapping of several solitons can be regarded as a synthesis of `soliton molecules', and it corresponds to a transfer of an initial orbital angular momentum of a system of solitons to a spin momentum of an optical vortex. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0309/0309025v1.pdf"}
{"id": "nlin0312071", "abstract": "  Microscopic flows are almost universally linear, laminar and stationary because Reynolds number, Re, is usually very small. That impedes mixing in micro-fluidic devices, which sometimes limits their performance. Here we show that truly chaotic flow can be generated in a smooth micro-channel of a uniform width at arbitrarily low Re, if a small amount of flexible polymers is added to the working liquid. The chaotic flow regime is characterized by randomly fluctuating three-dimensional velocity field and significant growth of the flow resistance. Although the size of the polymer molecules extended in the flow may become comparable with the micro-channel width, the flow behavior is fully compatible with that in a table-top channel in the regime of elastic turbulence. The chaotic flow leads to quite efficient mixing, which is almost diffusion independent. For macromolecules, mixing time in this microscopic flow can be three to four orders of magnitude shorter than due to molecular diffusion. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0312/0312071v2.pdf"}
{"id": "nlin0402041", "abstract": "  A one-way coupled spatiotemporally chaotic map lattice is used to contruct cryptosystem. With the combinatorial applications of both chaotic computations and conventional algebraic operations, our system has optimal cryptographic properties much better than the separative applications of known chaotic and conventional methods. We have realized experiments to pratice duplex voice secure communications in realistic Wired Public Switched Telephone Network by applying our chaotic system and the system of Advanced Encryption Standard (AES), respectively, for cryptography. Our system can work stably against strong channel noise when AES fails to work. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0402/0402041v1.pdf"}
{"id": "nlin0404054", "abstract": "  In this communication a new algorithm is proposed to produce surrogates for pseudoperiodic time series. By imposing a few constraints on the noise components of pseudoperiodic data sets, we devise an effective method to generate surrogates. Unlike other algorithms, this method properly copes with pseudoperiodic orbits contaminated with linear colored observational noise. We will demonstrate the ability of this algorithm to distinguish chaotic orbits from pseudoperiodic orbits through simulation data sets from theRössler system. As an example of application of this algorithm, we will also employ it to investigate a human electrocardiogram (ECG) record. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0404/0404054v3.pdf"}
{"id": "nlin0407053", "abstract": "  According to the May-Wigner stability theorem, increasing the complexity of a network inevitably leads to its destabilization, such that a small perturbation will be able to disrupt the entire system. One of the principal arguments against this observation is that it is valid only for random networks, and therefore does not apply to real-world networks, which presumably are structured. Here we examine how the introduction of small-world topological structure into networks affect their stability. Our results indicate that, in structured networks, the parameter values at which the stability-instability transition occurs with increasing complexity is identical to that predicted by the May-Wigner criteria. However, the nature of the transition, as measured by the finite-size scaling exponent, appears to change as the network topology transforms from regular to random, with the small-world regime as the cross-over region. This behavior is related to the localization of the largest eigenvalues along the real axis in the eigenvalue plain with increasing regularity in the network. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0407/0407053v1.pdf"}
{"id": "nlin0510002", "abstract": "  We present a detailed analysis of a model for the synchronization of nonlinear oscillators due to reactive coupling and nonlinear frequency pulling. We study the model for the mean field case of all-to-all coupling, deriving results for the initial onset of synchronization as the coupling or nonlinearity increase, and conditions for the existence of the completely synchronized state when all the oscillators evolve with the same frequency. Explicit results are derived for Lorentzian, triangular, and top-hat distributions of oscillator frequencies. Numerical simulations are used to construct complete phase diagrams for these distributions. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0510/0510002v1.pdf"}
{"id": "nlin0603004", "abstract": "  The surrogate data method is widely applied as a data dependent technique to test observed time series against a barrage of hypotheses. However, often the hypotheses one is able to address are not those of greatest interest, particularly for system known to be nonlinear. In the review we focus on techniques which overcome this shortcoming. We summarize a number of recently developed surrogate data methods. While our review of surrogate methods is not exhaustive, we do focus on methods which may be applied to experimental, and potentially nonlinear, data. In each case, the hypothesis being tested is one of the interests to the experimental scientist. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0603/0603004v1.pdf"}
{"id": "nlin0603036", "abstract": "  The relative dispersion process in two-dimensional free convection turbulence is investigated by direct numerical simulation. In the inertial range, the growth of relative separation, r, is expected as <r^2(t)>∝ t^5 according to the Bolgiano-Obukhov scaling. The result supporting the scaling is obtained with exit-time statistics. Detailed investigation of exit-time PDF shows that the PDF is divided into two regions, the Region-I and -II, reflecting two types of separating processes: persistent expansion and random transitions between expansion and compression of relative separation. This is consistent with the physical picture of the self-similar telegraph model. In addition, a method for estimating the parameters of the model are presented. Comparing two turbulence cases, two-dimensional free convection and inverse cascade turbulence, the relation between the drift term of the model and nature of coherent structures is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0603/0603036v1.pdf"}
{"id": "nlin0604025", "abstract": "  The form factor of a quantum graph is a function measuring correlations within the spectrum of the graph. It can be expressed as a double sum over the periodic orbits on the graph. We propose a scheme which allows one to evaluate the periodic orbit sum for a special family of graphs and thus to recover the expression for the form factor predicted by the Random Matrix Theory. The scheme, although producing the expected answer, undercounts orbits of a certain structure, raising doubts about an analogous summation recently proposed for quantum billiards. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0604/0604025v1.pdf"}
{"id": "nlin0606020", "abstract": "  We study the structure and stability of discrete breathers (both pinned and mobile) in two-dimensional nonlinear anisotropic Schrodinger lattices. Starting from a set of identical one-dimensional systems we develop the continuation of the localized pulses from the weakly coupled regime (strongly anisotropic) to the homogeneous one (isotropic). Mobile discrete breathers are seen to be a superposition of a localized mobile core and an extended background of two-dimensional nonlinear plane waves. This structure is in agreement with previous results on onedimensional breather mobility. The study of the stability of both pinned and mobile solutions is performed using standard Floquet analysis. Regimes of quasi-collapse are found for both types of solutions, while another kind of instability (responsible for the discrete breather fission) is found for mobile solutions. The development of such instabilities is studied, examining typical trajectories on the unstable nonlinear manifold. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0606/0606020v1.pdf"}
{"id": "nlin0608031", "abstract": "  We present and discuss isospectral quantum graphs which are not isometric. These graphs are the analogues of the isospectral domains in R2 which were introduced recently and are all based on Sunada's construction of isospectral domains. After presenting some of the properties of these graphs, we discuss a few examples which support the conjecture that by counting the nodal domains of the corresponding eigenfunctions one can resolve the isospectral ambiguity. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0608/0608031v3.pdf"}
{"id": "nlin0703049", "abstract": "  We examine collisions of moving solitons in a fiber Bragg grating with a triplet composed of two closely set repulsive defects of the grating and an attractive one inserted between them. A doublet (dipole), consisting of attractive and repulsive defects with a small distance between them,is considered too. Systematic simulations demonstrate that the triplet provides for superior results, as concerns the capture of a free pulse and creation of a standing optical soliton, in comparison with recently studied traps formed by single and paired defects, as well as the doublet: 2/3 of the energy of the incident soliton can be captured when its velocity attains half the light speed in the fiber (the case most relevant to the experiment), and the captured soliton quickly relaxes to a stationary state. A subsequent collision between another free soliton and the pinned one is examined too, demonstrating that the impinging soliton always bounces back, while the pinned one either remainsin the same state, or is kicked out forward, depending on the collision velocity and phase shift between the solitons. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0703/0703049v1.pdf"}
{"id": "nucl-ex0203008", "abstract": "  The study of near–threshold meson production in pp and pd collisions involving polarized beams and polarized targets offers the rare opportunity to gain insight into short–range features of the nucleon–nucleon interaction. The Cooler Synchrotron COSY at FZ–Jülich is a unique environment to perform such studies. Measurements of polarization observables require a cylindrically symmetrical detector, capable to measure the momenta and the directions of outgoing charged hadrons. The wide energy range of COSY leads to momenta of outgoing protons to be detected in a single meson production reaction between 300 and 2500 MeV/c. Scattering angles of protons to be covered extend to about 45^∘ in the laboratory system. An azimuthal angular coverage of the device around 98", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0203/0203008v1.pdf"}
{"id": "nucl-ex0212023", "abstract": "  Directed and elliptic flow are reported for charged pions and protons as a function of transverse momentum, rapidity, and centrality in 40 and 158 AGeV Pb + Pb collisions. The standard method of correlating particles with an event plane is used. The directed flow of protons is small and shows little variation near to midrapidity, but rises fast towards projectile rapidity in the 40 AGeV data. For most peripheral collisions the flat region becomes negative resulting in v_1 changing sign three times. Elliptic flow doesn't seem to change very much from 40 AGeV to 158 AGeV. The difference is smaller than anticipated from the overall energy dependence from AGS to RHIC. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0212/0212023v1.pdf"}
{"id": "nucl-ex0212027", "abstract": "  A micron-precision optical alignment system (OASys) for the PHENIX muon tracking chambers is developed. To ensure the required mass resolution of vector meson detection, the relative alignment between three tracking station chambers must be monitored with a precision of 25μm. The OASys is a straightness monitoring system comprised of a light source, lens and CCD camera, used for determining the initial placement as well as for monitoring the time dependent movement of the chambers on a micron scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0212/0212027v2.pdf"}
{"id": "nucl-ex0610019", "abstract": "  The density dependence of the symmetry energy in the equation of state of asymmetric nuclear matter (N/Z > 1) is important for understanding the structure of systems as diverse as the atomic nuclei and neutron stars. Due to a proper lack of understanding of the basic nucleon-nucleon interaction for matters that are highly asymmetric and at non-normal nuclear density, this very important quantity has remained largely unconstrained. Recent studies using beams from the Cyclotron Institute of Texas AM University, constraining the density dependence of the symmetry energy, is presented. A dependence of the form E_sym(ρ) = C(ρ/ρ_o)^γ, where C = 31.6 MeV and γ = 0.69, is obtained from the dynamical and statistical model analysis. Their implications to both astrophysical and nuclear physics studies are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0610/0610019v1.pdf"}
{"id": "nucl-ex9610003", "abstract": "  The HADES first level trigger is studied for the system p+Ni at a beam energy of 2 AGeV. The timing properties of the trigger signal are reported. The efficiency loss due to deadtime is specified. A trigger requirement of a time overlap window with the start detector is described. The trigger rates for different overlap windows are given. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/9610/9610003v1.pdf"}
{"id": "nucl-ex9711004", "abstract": "  Experiment NA44 has measured proton and antiproton distributions at mid-rapidity in sulphur and proton collisions with nuclear targets at 200 and 450 GeV/c per nucleon respectively. The inverse slopes of transverse mass distributions increase with system size for both protons and antiprotons but are slightly lower for antiprotons. this could happen if antiprotons are annihilated in the nuclear medium. The antiproton yield increases with system size and centrality and is largest at mid-rapdity. The proton yield also increases with system size and centrality, but decreases from backward rapidity to midrapidity. The stopping of protons at these energies lies between the full stopping and nuclear transparency scenarios. The data are in reasonable agreement with RQMD predictions except for the antiproton yields from sulphur-nucleus collisions. PACS numbers 25.75.-q 13.85.-t 13.60.Rj ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/9711/9711004v2.pdf"}
{"id": "nucl-ex9904003", "abstract": "  We first review previous work on anisotropic flow at the AGS and SPS. Then the physics related to flow is discussed as well as the interaction of flow with other non-flow measurements. From 40k RQMD and 100k HIJING events predictions for anisotropic flow at RHIC are presented. Using the STAR detector acceptance, estimates for the resolution obtainable with STAR are shown. We conclude that it should be possible to obtain good measurements for elliptic flow with either the STAR main TPC or forward TPCs. Anisotropic flow should be easily one of the first results from STAR. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/9904/9904003v1.pdf"}
{"id": "nucl-th0003040", "abstract": "  We investigate the Coulomb breakup of neutron rich nuclei 11Be and (19,17,15)C within a theory developed in the framework of Distorted Wave Born Approximation. Finite range effects are included by a local momentum approximation, which allows incorporation of realistic wave functions for these nuclei in our calculations. Energy and angular as well as parallel momentum distributions of the fragments emitted in the breakup of these nuclei on heavy targets have been calculated using several structure models for their ground state. Comparison with the available experimental data shows that the results are selective about the ground state wave function of the projectile. Our investigations confirm that the nuclei 11Be, 19C and 15C have a one-neutron halo structure in their ground states. However, for 17C such a structure appears to be less likely. Calculations performed within our method have also been compared with those from an adiabatic model and the results are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0003/0003040v2.pdf"}
{"id": "nucl-th0003063", "abstract": "  I compute the gluon self-energy in a color superconductor with three flavors of massless quarks, where condensation of Cooper pairs breaks the color and flavor SU(3)_c x U(3)_V x U(3)_A symmetry of QCD to the diagonal subgroup SU(3)_c+V. At zero temperature, all eight electric gluons obtain a Debye screening mass, and all eight magnetic gluons a Meissner mass. The Debye as well as the Meissner masses are found to be equal for the different gluon colors. These masses determine the coefficients of the kinetic terms in the effective theory for the low-energy degrees of freedom. Their values agree with those obtained by Son and Stephanov. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0003/0003063v1.pdf"}
{"id": "nucl-th0006025", "abstract": "  Earlier attempts to extract parameters of kinetic freeze-out in Pb+Pb collisions at 158AGeV are critically reviewed. Many of these analyses have used approximations which have significant impact on the extracted parameters. Simple estimates are obtained which attempt to avoid the most critical approximations. It is pointed out that constraints based on pion interferometry are less reliable than those from momentum spectra. A universal set of freeze-out parameters from transverse mass spectra would require T > 135 MeV and <beta> < 0.35. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0006/0006025v1.pdf"}
{"id": "nucl-th0006065", "abstract": "  The parity-non-conserving (pnc) asymmetry in n⃗ + p →d+γat thermal energies has recently been calculated using effective field-theory methods. A comparison of this calculation with much more elaborate calculations performed in the 70's is made. This allows one to assess the validity of this new approach as presently used. It is found to overshoot the almost exact calculations by a factor close to 2 for the contribution involving the ^3S_1 component of both the initial and final states. This is much larger than anticipated by the authors. This discrepancy is analyzed and found to originate from the over-simplified description of the deuteron and capture states which underlies the new approach. The claim that earlier determinations of the sign would be in error is also examined. It is found that the sign discrepancy is most probably due, instead, to the fact that the pion-nucleon interaction referred to by the authors corresponds to a parity-non-conserving potential with a sign opposite to what is currently used. Some estimates and constraints relative to the pnc piNN coupling, h^1_π, which the above asymmetry is dependent on, are reviewed. Further details are given in an Appendix. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0006/0006065v1.pdf"}
{"id": "nucl-th0108060", "abstract": "  Progress in the Effective Field Theory of two and three nucleon systems is sketched, concentrating mainly on the low energy version in which pions are integrated out as explicit degrees of freedom. Examples given are: the extraction of nucleon polarisabilities from deuteron Compton scattering at very low energies; the energy dependence of the nucleon polarisabilities; three body forces and the triton; and nd partial waves at momenta below the pion cut. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0108/0108060v1.pdf"}
{"id": "nucl-th0110010", "abstract": "  A recently published highly extrapolatable semiempirical shell model mass equation is shown to describe rather well the energies of several seemingly well identified alpha-decay chains with known end product nuclei observed in superheavy elements research. The equation is also applied to the interpretation problem of some recent hot fusion-evaporation experiments with unknown end products and several conceivable reaction channels. Some plausible interpretations are indicated. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0110/0110010v1.pdf"}
{"id": "nucl-th0201042", "abstract": "  The in-medium properties of the vector mesons are known to be modified significantly in hot and dense hadronic matter due to vacuum polarisation effects from the baryon sector in the Walecka model. The vector meson mass drops significantly in the medium due to the effects of the Dirac sea. In the variational approach adopted in the present paper, these effects are taken into account through a realignment of the ground state with baryon condensates. Such a realignment of the ground state becomes equivalent to summing of the baryonic tadpole diagrams in the relativistic Hartree approximation (RHA). The approximation scheme adopted here goes beyond RHA to include quantum effects from the scalar meson and is nonperturbative and self–consistent. It includes multiloop effects, thus corresponding to a different approximation as compared to the one loop approximation of including scalar field quantum corrections. In the present work, we study the properties of the vector mesons in the hot and dense matter as modified due to such quantum correction effects from the baryon as well as scalar meson sectors. These medium modifications of the properties of the vector mesons are reflected, through the shifting and broadening of the respective peaks, in the low mass dilepton spectra. There is broadening of the peaks due to corrections from scalar meson quantum effects as compared to the relativistic Hartree approximation. It is seen to be rather prominent for the ω meson in the invariant mass plot. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0201/0201042v2.pdf"}
{"id": "nucl-th0202048", "abstract": "  The particle-hole Density Matrix Renormalization Group (p-h DMRG) method is discussed as a possible new approach to large-scale nuclear shell-model calculations. Following a general description of the method, we apply it to a class of problems involving many identical nucleons constrained to move in a single large j-shell and to interact via a pairing plus quadrupole interaction. A single-particle term that splits the shell into degenerate doublets is included so as to accommodate the physics of a Fermi surface in the problem. We apply the p-h DMRG method to this test problem for two j values, one for which the shell model can be solved exactly and one for which the size of the hamiltonian is much too large for exact treatment. In the former case, the method is able to reproduce the exact results for the ground state energy, the energies of low-lying excited states, and other observables with extreme precision. In the latter case, the results exhibit rapid exponential convergence, suggesting the great promise of this new methodology even for more realistic nuclear systems. We also compare the results of the test calculation with those from Hartree-Fock-Bogolyubov approximation and address several other questions about the p-h DMRG method of relevance to its usefulness when treating more realistic nuclear systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0202/0202048v1.pdf"}
{"id": "nucl-th0205080", "abstract": "  In a two-flavor color superconductor, the SU(3)_c gauge symmetry is spontaneously broken by diquark condensation. The Nambu-Goldstone excitations of the diquark condensate mix with the gluons associated with the broken generators of the original gauge group. It is shown how one can decouple these modes with a particular choice of 't Hooft gauge. We then explicitly compute the spectral density for transverse and longitudinal gluons of adjoint color 8. The Nambu-Goldstone excitations give rise to a singularity in the real part of the longitudinal gluon self-energy. This leads to a vanishing gluon spectral density for energies and momenta located on the dispersion branch of the Nambu-Goldstone excitations. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0205/0205080v2.pdf"}
{"id": "nucl-th0301029", "abstract": "  A three-configuration mixing calculation is performed in the context of the interacting boson model with the aim to describe recently observed collective bands built on low-lying 0^+ states in neutron-deficient lead isotopes. The configurations that are included correspond to the regular, spherical states as well as two-particle two-hole and four-particle four-hole excitations across the Z=82 shell gap. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0301/0301029v2.pdf"}
{"id": "nucl-th0302065", "abstract": "  Electromagnetic processes in loosely bound nuclei are investigated using an analytical model. In particular, electromagnetic dissociation of ^8B is studied and the results of our analytical model are compared to numerical calculations based on a three-body picture of the ^8B bound state. The calculation of energy spectra is shown to be strongly model dependent. This is demonstrated by investigating the sensitivity to the rms intercluster distance, the few-body behavior, and the effects of final state interaction. In contrast, the fraction of the energy spectrum which can be attributed to E1 transitions is found to be almost model independent at small relative energies. This finding is of great importance for astrophysical applications as it provides us with a new tool to extract the E1 component from measured energy spectra. An additional, and independent, method is also proposed as it is demonstrated how two sets of experimental data, obtained with different beam energy and/or minimum impact parameter, can be used to extract the E1 component. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0302/0302065v1.pdf"}
{"id": "nucl-th0312007", "abstract": "  According to quantum chromodynamics (QCD), matter at ultra-high densities will take the form of a color-superconducting quark liquid, in which there is a condensate of Cooper pairs of quarks near the Fermi surface. I present a review of the physics of color superconductivity. I give particular attention to the recently proposed gapless CFL (gCFL) phase, which has unusual properties such as quasiquarks with a near-quadratic dispersion relation, and which may well be the favored phase of quark matter in the density range relevant to compact stars. I also discuss the effects of color superconductivity on the mass-radius relationship of compact stars, showing that one would have to fix the bag constant by other measurements in order to see the effects of color superconductivity. An additional parameter in the quark matter equation of state connected with perturbative corrections allows quark matter to imitate nuclear matter over the relevant density range, so that hybrid stars can show a mass-radius relationship very similar to that of nuclear matter, and their masses can reach 1.9 M_solar. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0312/0312007v1.pdf"}
{"id": "nucl-th0312027", "abstract": "  The ground-state properties of Zr and Sn isotopes are studied within the relativistic mean field theory. Zr and Sn isotopes have received tremendous attention due to various reasons, including the predicted giant halos in the neutron-rich Zr isotopes, the unique feature of being robustly spherical in the region of ^100Sn ∼ ^132Sn and the particular interest of Sn isotopes to nuclear astrophysics. Furthermore, four (semi-) magic neutron numbers, 40, 50, 82 and 126, make these two isotopic chains particularly important to test the pairing correlations and the deformations in a microscopic model. In the present work, we carry out a systematic study of Zr and Sn isotopes from the proton drip line to the neutron drip line with deformation effects, pairing correlations and blocking effects for nuclei with odd number of neutrons properly treated. A constrained calculation with quadrupole deformations is performed to find the absolute minimum for each nucleus on the deformation surface. All ground-state properties, including the separation energies, the odd-even staggerings, the nuclear radii, the deformations and the single-particle spectra are analyzed and discussed in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0312/0312027v2.pdf"}
{"id": "nucl-th0407111", "abstract": "  We use the canonical Hartree-Fock-Bogoliubov basis to implement a completely self-consistent quasiparticle-random-phase approximation with arbitrary Skyrme energy density functionals and density-dependent pairing functionals. The point of the approach is to accurately describe multipole strength functions in spherical even-even nuclei, including weakly-bound drip-line systems. We describe the method and carefully test its accuracy, particularly in handling spurious modes. To illustrate our approach, we calculate isoscalar and isovector monopole, dipole, and quadrupole strength functions in several Sn isotopes, both in the stable region and at the drip lines. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0407/0407111v1.pdf"}
{"id": "nucl-th0409003", "abstract": "  Mechanisms for particle production at intermediate pT in nuclear collisions at RHIC are discussed, emphasizing the differences in associated jet-like correlations between color-neutral and colored production. An alternative production mechanism involving both recombination and fragmentation is suggested, which might simultaneously lead to an enhancement of baryons and to jet-like correlations. To gain more insight into the relative importance of different mechanisms a study of constrained distributions of associated multiplicity is proposed. In a simple model it is shown that these multiplicity distributions may change significantly, if the nature of the production mechanism fluctuates from event to event. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0409/0409003v1.pdf"}
{"id": "nucl-th0411107", "abstract": "  Relativistic mean-field theory with δ meson, nonlinear isoscalar self-interactions and isoscalar-isovector cross interaction terms with parametrizations obtained to reproduce Dirac-Brueckner-Hartree-Fock calculations for nuclear matter is used to study asymmetric nuclear matter properties in β-equilibrium, including hyperon degrees of freedom and (hidden) strange mesons. Influence of cross interaction on composition of hyperon matter and electron chemical potential is examined. Softening of nuclear equation of state by the cross interactions results in lowering of hyperonization, although simultaneously enhancing a hyperon-induced decrease of the electron chemical potential, thus indicating further shift of a kaon condensate occurence to higher densities. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0411/0411107v1.pdf"}
{"id": "nucl-th0504006", "abstract": "  We present here a formalism able to generalise to a relativistically covariant scheme the standard nuclear shell model. We show that, using some generalised nuclear Green's functions and their Lehmann representation we can define the relativistic equivalent of the non relativistic single particle wave function (not loosing, however, the physical contribution of other degrees of freedom, like mesons and antinucleons). It is shown that the mass operator associated to the nuclear Green's function can be approximated with the equivalent of a shell-model potential and that the corresponding “single particle wave functions” can be easily derived in a specified frame of reference and then boosted to any other system, thus fully restoring the Lorentz covariance ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0504/0504006v1.pdf"}
{"id": "nucl-th0512053", "abstract": "  Fragment average isospin distributions are investigated within a microcanonical multifragmentation model in different regions of the phase diagram. The results indicate that in the liquid phase <N/Z> versus Z is monotonically increasing, in the phase coexistence region it has a rise and fall shape and in the gas phase it is constant. Deviations from this behavior may manifest at low fragment multiplicity as a consequence of mass/charge conservation. Characterization of the \"free\" and \"bound\" phases function of fragment charge reconfirms the neutron enrichment of the \"free\" phase with respect to the \"bound\" one irrespectively the localization of the multifragmentation event in the phase diagram. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0512/0512053v1.pdf"}
{"id": "nucl-th0603013", "abstract": "  The authors present a relativistic and cross-section factorized framework for computing quasielastic A(p,pN) observables at intermediate and high energies. The model is based on the eikonal approximation and can accomodate both optical potentials and the Glauber method for dealing with the initial- and final-state interactions (IFSI). At lower nucleon energies, the optical-potential philosophy is preferred, whereas at higher energies the Glauber method is more natural. This versatility in dealing with the IFSI allows one to describe A(p,pN) reactions in a wide energy range. Most results presented here use optical potentials as this approach is argued to be the optimum choice for the kinematics of the experiments considered in the present paper. The properties of the IFSI factor, a function wherein the entire effect of the IFSI is contained, are studied in detail. The predictions of the presented framework are compared with two kinematically different experiments. First, differential cross sections for quasielastic proton scattering at 1 GeV off 12C, 16O, and 40Ca target nuclei are computed and compared to data from PNPI. Second, the formalism is applied to the analysis of a 4He(p,2p) experiment at 250 MeV. The optical-potential calculations are found to be in good agreement with the data from both experiments, showing the reliability of the adopted model in a wide energy range. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0603/0603013v3.pdf"}
{"id": "nucl-th0605037", "abstract": "  Particle production in the forward region of heavy-ion collisions is shown to be due to parton recombination without shower partons. The regeneration of soft partons due to momentum degradation through the nuclear medium is considered. The degree of degradation is determined by fitting the p̅/p ratio. The data at √(s)=62.4 GeV and η=3.2 from BRAHMS on the p_T distribution of average charged particles are well reproduced. Large proton-to-pion ratio is predicted. The particles produced at any p_T should have no associated particles above background to manifest any jet structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0605/0605037v4.pdf"}
{"id": "nucl-th0608071", "abstract": "  The proton emission induced by polarized photons is studied in the energy range above the giant resonance region and below the pion emission threshold. Results for the 12C, 16O and 40Ca nuclei are presented. The sensitivity of various observables to final state interaction, meson exchange currents and short range correlations is analyzed. We found relevant effects due to the virtual excitation of the Δ resonance. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0608/0608071v1.pdf"}
{"id": "nucl-th0610037", "abstract": "  We investigate the composition and the equation of state of the kaon condensed phase in neutrino-free and neutrino-trapped star matter within the framework of the Brueckner-Hartree-Fock approach with three-body forces. We find that neutrino trapping shifts the onset density of kaon condensation to a larger baryon density, and reduces considerably the kaon abundance. As a consequence, when kaons are allowed, the equation of state of neutrino-trapped star matter becomes stiffer than the one of neutrino free matter. The effects of different three-body forces are compared and discussed. Neutrino trapping turns out to weaken the role played by the symmetry energy in determining the composition of stellar matter, and thus reduces the difference between the results obtained by using different three-body forces. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0610/0610037v1.pdf"}
{"id": "nucl-th9307002", "abstract": "  Calculations have been performed for the ^16O(γ,pn) and the ^16O(γ,pp) reaction in the photon-energy range E_γ = 60-300 MeV. Besides the contribution from the more common photoabsorption on the pionic degrees of freedom, we have investigated the influence of heavier meson exchange (ρ, σ, ω) and intermediate Δ creation with π and ρ exchange. Whereas the π meson is found to set the main trends, the ρ meson is found not to be discardable in a theoretical description of the (γ,pn) reaction. The incorporation of an energy dependence and a decay width in the Δ propagator is observed to be essential in order to arrive at a more realistic description of (γ,NN) reactions at higher photon energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9307/9307002v2.pdf"}
{"id": "nucl-th9411005", "abstract": "  The influence of short-range correlations on the momentum and energy distribution of nucleons in nuclei is evaluated assuming a realistic meson-exchange potential for the nucleon-nucleon interaction. Using the Green-function approach the calculations are performed directly for the finite nucleus ^16O avoiding the local density approximation and its reference to studies of infinite nuclear matter. The nucleon-nucleon correlations induced by the short-range and tensor components of the interaction yield an enhancement of the momentum distribution at high momenta as compared to the Hartree-Fock description. These high-momentum components should be observed mainly in nucleon knockout reactions like (e,e'p) leaving the final nucleus in a state of high excitation energy. Our analysis also demonstrates that non-negligible contributions to the momentum distribution should be found in partial waves which are unoccupied in the simple shell-model. The treatment of correlations beyond the Brueckner-Hartree-Fock approximation also yields an improvement for the calculated ground-state properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9411/9411005v1.pdf"}
{"id": "nucl-th9411017", "abstract": "  We explore a consistent way to extend the partially conserved axial vector current (PCAC) relationship and corresponding current algebra results in two strongly correlated directions: 1) towards a search for a set of systematic rules for the establishment of PCAC related relationships in a finite low momentum transfer region and for the extrapolation of the momentum transfer q^2 to zero when deriving the low energy PCAC results that can be compared to experimental data and 2) towards taking into account, besides the conventional one, the only other possibility of the spontaneous chiral symmetry breaking, SU(2)_L× SU(2)_R → SU(2)_V, inside a baryonic system by a condensation (in the sense to be specified in the paper) of diquarks. The paper includes investigations of a chiral Ward–Takahashi identity, the explicit chiral symmetry breaking by a finite current quark mass, the modification of the PCAC relationship and its consequences. It is shown that the signals for a hypothetical diquark condensation inside a nucleon and nucleus is observable in high precision experiments despite the fact that they may evade most of the current observations. We briefly discuss how diquark condensation could provide an answer to the question of where about of pions and quark number in a nucleon and a nucleus, which is raised in explaining puzzles in polarized pion nucleus scattering, violation of Gottfried sum rule and EMC effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9411/9411017v3.pdf"}
{"id": "nucl-th9605006", "abstract": "  The effect of projectile shape on cross sections and momentum distributions of fragments from heavy ion reactions is studied. We propose a new approach that implements the underlying symmetries of each isotope with a few parameters directly in the density. Various densities and their nuclear structure are then analyzed in the reactions of ^12C and ^11Li, ^11Be, and ^11C on a carbon target. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9605/9605006v1.pdf"}
{"id": "nucl-th9706058", "abstract": "  We consider pair production in a space-time-dependent background field and derive a source term, i.e., production rate in the one-particle phase space. Such a source term is required in Boltzmann-equation-based models of quark-gluon plasma formation and evolution. We compare the source term derived here with the one that has been used in the literature so far. Significant differences are observed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9706/9706058v1.pdf"}
{"id": "nucl-th9706069", "abstract": "  The present status of our understanding of low mass dilepton production in relativistic heavy ion collisions is discussed. The focus of the discussion will be the sensitivity of dilepton measurements to in medium changes of hadrons and the restoration of chiral symmetry. We will finally discuss how the presence of strong long wavelength pion modes, i.e. disoriented chiral condensates can be seen in the dilepton spectrum. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9706/9706069v1.pdf"}
{"id": "nucl-th9709054", "abstract": "  We investigate the interaction between H-dibaryons employing a quark cluster model with a one-gluon-exchange potential and an effective meson exchange potential (EMEP). A deeply-bound state of two H-dibaryons due to the medium range attraction of the EMEP is obtained. The bound H–H system has a size of about 0.8 ∼ 0.9 fm because of the short-range repulsion generated by the color-magnetic interaction and the Pauli principle. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9709/9709054v1.pdf"}
{"id": "nucl-th9710033", "abstract": "  The role played by the effective residual interaction in the transverse nuclear response for quasi-free electron scattering is discussed. The analysis is done by comparing different calculations performed in the Random–Phase Approximation and Ring Approximation frameworks. The importance of the exchange terms in this energy region is investigated and the changes on the nuclear responses due to the modification of the interaction are evaluated. The calculated quasi-elastic responses show clear indication of their sensibility to the details of the interaction and this imposes the necessity of a more careful study of the role of the different channels of the interaction in this excitation region. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9710/9710033v1.pdf"}
{"id": "nucl-th9804022", "abstract": "  A two phase cascade, LUCIFER II, developed for the treatment of ultra high energy ion-ion collisions is applied to the production of strangeness at SPS energies √(s)=17-20. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons, including strange mesons, by separating the dynamics into two steps, a fast cascade involving only nucleons in the original colliding relativistic ions followed, after an appropriate delay, by multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy ion experiments at the CERN SPS. A byproduct, obtained here in preliminary calculations, is a description of strangeness production in the collision of massive ions. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9804/9804022v1.pdf"}
{"id": "nucl-th9903004", "abstract": "  We compare the properties of three-body systems obtained with two-body potentials with Pauli forbidden states and with the corresponding phase equivalent two-body potentials. In the first case the forbidden states are explicitly excluded in the calculation. Differences arise due to the off-shell properties of these on-shell equivalent potentials. We use the adiabatic hyperspherical method to formulate a practical prescription to exclude Pauli forbidden states in three-body calculations. Schematic as well as realistic potentials are used. Almost indistinguishable results are obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9903/9903004v1.pdf"}
{"id": "nucl-th9903014", "abstract": "  We discuss a few examples of structure functions for polarized, semi-inclusive scattering processes to show the richness of structure. Then we indicate how polarization and particle production can be used to study the quark and gluon structure of hadrons going further than the well-known parton densities and fragmentation functions. We also emphasize how single spin asymmetries in leptoproduction may shed light on explanations for single spin asymmetries in pion production in pp collissions. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9903/9903014v1.pdf"}
{"id": "nucl-th9908015", "abstract": "  In this talk I discuss three related topics based on some of the recent developments in hadron and nuclear physics: one, effective field theory approach to two-nucleon systems; two, an explanation of the flavor singlet axial charge in the proton (i.e., \"proton spin problem\") in terms of a Cheshire Cat phenomenon; and three, the quark-hadron duality in hadronic matter at high density and \"qualitons\" at high density (\"superqualitons\"). The principal common theme in these discussions will be the emergence of the generic feature of the Cheshire Cat Principle. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9908/9908015v1.pdf"}
{"id": "patt-sol9806007", "abstract": "  We present numerical solution of the chlorine dioxide-iodine-malonic acid reaction-diffusion system in two dimensions in a boundary-fed system using a realistic model. The bifurcation diagram for the transition from non-symmetry breaking structures along boundary feed gradients to transverse symmetry breaking patterns in a single layer is numerically determined. We find this transition to be discontinuous. We make connection with earlier results and discuss prospects for future work. ", "pdf_url": "gs://arxiv-dataset/arxiv/patt-sol/pdf/9806/9806007v1.pdf"}
{"id": "physics0008232", "abstract": "  Given a sequence composed of a limit number of characters, we try to \"read\" it as a \"text\". This involves to segment the sequence into \"words\". The difficulty is to distinguish good segmentation from enormous number of random ones.Aiming at revealing the nonrandomness of the sequence as strongly as possible, by applying maximum likelihood method, we find a quantity called Segmentation Entropy that can be used to fulfill the duty. Contrary to commonplace where maximum entropy principle was applied to obtain good solution, we choose to minimize the segmentation entropy to obtain good segmentation. The concept developed in this letter can be used to study the noncoding DNA sequences, e.g., for regulatory elements prediction, in eukaryote genomes. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0008/0008232v1.pdf"}
{"id": "physics0105006", "abstract": "  For a large class of quantum systems the statistical properties of their spectrum show remarkable agreement with random matrix predictions. Recent advances show that the scope of random matrix theory is much wider. In this work, we show that the random matrix approach can be beneficially applied to a completely different classical domain, namely, to the empirical correlation matrices obtained from the analysis of the basic atmospheric parameters that characterise the state of atmosphere. We show that the spectrum of atmospheric correlation matrices satisfy the random matrix prescription. In particular, the eigenmodes of the atmospheric empirical correlation matrices that have physical significance are marked by deviations from the eigenvector distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0105/0105006v1.pdf"}
{"id": "physics0106014", "abstract": "  The effects of passive scalar anisotropy on subgrid-scale (SGS) physics and modeling for Large-Eddy Simulations are studied experimentally. Measurements are performed across a moderate Reynolds number wake flow generated by a heated cylinder, using an array of four X-wire and four cold-wire probes. By varying the separation distance among probes in the array, we obtain filtered and subgrid quantities at three different filter sizes. We compute several terms that comprise the subgrid dissipation tensor of kinetic energy and scalar-variance and test for isotropic behavior, as a function of filter scale. We find that whereas the kinetic energy dissipation tensor tends towards isotropy at small scales, the SGS scalar-variance dissipation remains anisotropic independent of filter scale. The eddy-diffusion model predicts isotropic behavior, whereas the nonlinear (or tensor eddy diffusivity) model reproduces the correct trends, but overestimates the level of scalar dissipation anisotropy. These results provide some support for so-called mixed models but raise new questions about the causes of the observed anisotropy. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0106/0106014v1.pdf"}
{"id": "physics0107063", "abstract": "  We propose a novel clustering method that is based on physical intuition derived from quantum mechanics. Starting with given data points, we construct a scale-space probability function. Viewing the latter as the lowest eigenstate of a Schrodinger equation, we use simple analytic operations to derive a potential function whose minima determine cluster centers. The method has one parameter, determining the scale over which cluster structures are searched. We demonstrate it on data analyzed in two dimensions (chosen from the eigenvectors of the correlation matrix). The method is applicable in higher dimensions by limiting the evaluation of the Schrodinger potential to the locations of data points. In this case the method may be formulated in terms of distances between data points. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0107/0107063v1.pdf"}
{"id": "physics0207124", "abstract": "  The potential profile across a biased molecular junction is calculated within the framework of a simple Thomas-Fermi type screening model. In particular, the relationship between this profile and the lateral molecular cross section is examined. We find that a transition from a linear potential profile to a potential that drops mainly near the molecule-metal contacts occurs with increasing cross section width, in agreement with numerical quantum calculations. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0207/0207124v1.pdf"}
{"id": "physics0211044", "abstract": "  The streamwise and transverse velocities are measured simultaneously in isotropic grid turbulence at relatively high Reynolds numbers, Re(lambda) = 110-330. Using a conditional averaging technique, we extract typical intermittency patterns, which are consistent with velocity profiles of a model for a vortex tube, i.e., Burgers vortex. The radii of the vortex tubes are several of the Kolmogorov length regardless of the Reynolds number. Using the distribution of an interval between successive enhancements of a small-scale velocity increment, we study the spatial distribution of vortex tubes. The vortex tubes tend to cluster together. This tendency is increasingly significant with the Reynolds number. Using statistics of velocity increments, we also study the energetical importance of vortex tubes as a function of the scale. The vortex tubes are important over the background flow at small scales especially below the Taylor microscale. At a fixed scale, the importance is increasingly significant with the Reynolds number. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0211/0211044v1.pdf"}
{"id": "physics0303089", "abstract": "  The possible normal modes of vibration of a nearly spherical virus particle are discussed. Two simple models for the particle are treated, a liquid drop model and an elastic sphere model. Some estimates for the lowest vibrational frequency are given for each model. It is concluded that this frequency is likely to be of the order of a few GHz for particles with a radius of the order of 50 nm. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0303/0303089v1.pdf"}
{"id": "physics0311015", "abstract": "  For several years, periodical arrays of subwavelength cylindrical holes in thin metallic layers have taken a crucial importance in the context of the results reported by Ebbesen et al, on particularly attractive optical transmission experiments. It had been underlined that the zeroth order transmission pattern does not depend on the polarization of the incident light at normal incidence. In the present paper, we show that it is not the case for rectangular holes, by contrast to the case of circular holes. In this context, we suggest a new kind of polarizer that present the advantages brought by the original Ebbesen devices. Assuming the recent technological interest for these kinds of metallic gratings, such a kind of polarizer could lead to new technological applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0311/0311015v2.pdf"}
{"id": "physics0312094", "abstract": "  If the dynamics of an evolutionary differential equation system possess a low-dimensional, attracting, slow manifold, there are many advantages to using this manifold to perform computations for long term dynamics, locating features such as stationary points, limit cycles, or bifurcations. Approximating the slow manifold, however, may be computationally as challenging as the original problem. If the system is defined by a legacy simulation code or a microscopic simulator, it may be impossible to perform the manipulations needed to directly approximate the slow manifold. In this paper we demonstrate that with the knowledge only of a set of “slow” variables that can be used to parameterize the slow manifold, we can conveniently compute, using a legacy simulator, on a nearby manifold. Forward and reverse integration, as well as the location of fixed points are illustrated for a discretization of the Chafee-Infante PDE for parameter values for which an Inertial Manifold is known to exist, and can be used to validate the computational results. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0312/0312094v1.pdf"}
{"id": "physics0403091", "abstract": "  Speden is a computer program that reconstructs the electron density of single particles from their x-ray diffraction patterns, using a single-particle adaptation of the Holographic Method in crystallography. (Szoke, A., Szoke, H., and Somoza, J.R., 1997. Acta Cryst. A53, 291-313.) The method, like its parent, is unique that it does not rely on “back” transformation from the diffraction pattern into real space and on interpolation within measured data. It is designed to deal successfully with sparse, irregular, incomplete and noisy data. It is also designed to use prior information for ensuring sensible results and for reliable convergence. This article describes the theoretical basis for the reconstruction algorithm, its implementation and quantitative results of tests on synthetic and experimentally obtained data. The program could be used for determining the structure of radiation tolerant samples and, eventually, of large biological molecular structures without the need for crystallization. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0403/0403091v1.pdf"}
{"id": "physics0403094", "abstract": "  The distinction between the real positions of moving objects in a single reference frame and the apparent positions of objects at rest in one inertial frame and viewed from another, as predicted by the space-time Lorentz Transformations, is discussed. It is found that in the Rockets-and-String paradox the string remains unstressed and does not break and that the pole in the Barn-and-Pole paradox never actually fits into the barn. The close relationship of the Lorentz-Fitzgerald Contraction and the relativity of simultaneity of Special Relativity is pointed out and an associated paradox, in which causality is apparently violated, is noted. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0403/0403094v3.pdf"}
{"id": "physics0408066", "abstract": "  There is increasing circumstantial evidence that the cuprate superconductors, and correlated-electron materials generally, defy simple materials categorization because of their proximity to one or more continuous zero-temperature phase transitions. This implies that the fifteen-year confusion about the cuprates is not fundamental at all but simply overinterpreted quantum criticality–an effect that seems mysterious by virtue of its hypersensitivity to perturbations, i.e. to sample imperfections in experiment and small modifications of approximation schemes in theoretical modeling, but is really just an unremarkable phase transition of some kind masquerading as something important, a sheep in wolf's clothing. This conclusion is extremely difficult for most physicists even to think about because it requires admitting that an identifiable physical phenomenon might cause the scientific method to fail in some cases. For this reason I have decided to explain the problem in a way that is nonthreatening, easy to read, and fun–as a satire modeled after a similar piece of Lewis Carroll's I once read. My story is humorous fiction. Any similarity of the characters to living persons is accidental. My apologies to Henry W. Longfellow. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0408/0408066v1.pdf"}
{"id": "physics0409129", "abstract": "  We address the common problem of calculating intervals in the presence of systematic uncertainties. We aim to investigate several approaches, but here describe just a Bayesian technique for setting upper limits. The particular example we study is that of inferring the rate of a Poisson process when there are uncertainties on the acceptance and the background. Limit calculating software associated with this work is available in the form of C functions. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0409/0409129v1.pdf"}
{"id": "physics0412075", "abstract": "  The dissociation spectrum of the hydrogen molecular ion by short intense pulses of infrared light is calculated. The time-dependent Schrödinger equation is discretized and integrated in position and momentum space. For few-cycle pulses one can resolve vibrational structure that commonly arises in the experimental preparation of the molecular ion from the neutral molecule. We calculate the corresponding energy spectrum and analyze the dependence on the pulse time-delay, pulse length, and intensity of the laser for λ∼ 790nm. We conclude that the proton spectrum is a both a sensitive probe of the vibrational dynamics and the laser pulse. Finally we compare our results with recent measurements of the proton spectrum for 55 fs pulses using a Ti:Sapphire laser (λ∼ 790nm). Integrating over the laser focal volume, for the intensity I ∼ 3 × 10^15W cm^-2, we find our results are in excellent agreement with these experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0412/0412075v1.pdf"}
{"id": "physics0412101", "abstract": "  The scheme for accurate quantitative treatment of the radiation from a crystalline undulator in presence of the dechanneling and the photon attenuation is presented. The number of emitted photons and the brilliance of electromagnetic radiation generated by ultra-relativistic positrons channeling in a crystalline undulator are calculated for various crystals, positron energies and different bending parameters. It is demonstrated that with the use of high-energy positron beams available at present in modern colliders it is possible to generate the crystalline undulator radiation with energies from hundreds of keV up to tens of MeV region. The brilliance of the undulator radiation within this energy range is comparable to that of conventional light sources of the third generation but for much lower photon energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0412/0412101v1.pdf"}
{"id": "physics0501017", "abstract": "  To study the dynamics of chemical processes, we often adopt rate equations to observe the change in chemical concentrations. However, when the number of the molecules is small, the fluctuations cannot be neglected. We often study the effects of fluctuations with the help of stochastic differential equations.   Chemicals are composed of molecules on a microscopic level. In principle, the number of molecules must be an integer, which must only change discretely. However, in analysis using stochastic differential equations, the fluctuations are regarded as continuous changes. This approximation can only be valid if applied to fluctuations that involve a sufficiently large number of molecules. In the case of extremely rare chemical species, the actual discreteness of the molecules may critically affect the dynamics of the system.   To elucidate the effects of the discreteness, we study an autocatalytic system consisting of several interacting chemical species with a small number of molecules through stochastic particle simulations. We found novel states, which were characterized as an extinction of molecule species, due to the discrete nature of the molecules. We also observed a strong dependence of the chemical concentrations on the size of the system, which was caused by transitions to the novel states. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0501/0501017v1.pdf"}
{"id": "physics0505128", "abstract": "  We study spatial embeddings of random graphs in which nodes are randomly distributed in geographical space. We let the edge probability between any two nodes to be dependent on the spatial distance between them and demonstrate that this model captures many generic properties of social networks, including the “small-world” properties, skewed degree distribution, and most distinctively the existence of community structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0505/0505128v2.pdf"}
{"id": "physics0507208", "abstract": "  To obtain a high degree of long-term length stabilisation of an optical reference cavity, its free-spectral range is locked by means of an accurate and stable frequency synthesizer. The locking scheme is twofold: a laser is locked on the N^th mode of a reference Fabry-Perot cavity and part of the laser light is shifted in frequency to be in resonance with the (N+1)^th mode of the cavity. This shift is generated by an acousto-optical modulator (AOM) mounted in a double-pass scheme, matching half of the free spectral range of the reference cavity. The resulting absolute stabilization of the length of the cavity reaches the 10^-11 level per second, limited by the lock transfer properties and the frequency stability of the AOM control synthesizer. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0507/0507208v2.pdf"}
{"id": "physics0508222", "abstract": "  We investigate the adaptation of the time headways in car-following models as a function of the local velocity variance, which is a measure of the inhomogeneity of traffic flow. We apply this mechanism to several car-following models and simulate traffic breakdowns in open systems with an on-ramp as bottleneck. Single-vehicle data generated by several 'virtual detectors' show a semi-quantitative agreement with microscopic data from the Dutch freeway A9. This includes the observed distributions of the net time headways and times-to-collision for free and congested traffic. While the times-to-collision show a nearly universal distribution in free and congested traffic, the modal value of the time headway distribution is shifted by a factor of about two in congested conditions. Macroscopically, this corresponds to the 'capacity drop' at the transition from free to congested traffic. Finally, we explain the wide scattering of one-minute flow-density data by a self-organized variance-driven process that leads to the spontaneous formation and decay of long-lived platoons even for deterministic dynamics on a single lane. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0508/0508222v1.pdf"}
{"id": "physics0509174", "abstract": "  The LHC experiments have great potential in discovering many possible new particles up to the TeV scale. The significance calculation of an observation of a physics signal with known location and shape is no longer valid when either the location or the shape of the signal is unknown. We find the current LHC significance calculation of new physics is over-estimated and strongly depends on the specifics of the method and the situation it applies to. We describe general procedures for significance calculation and comparing different search schemes. A new method uses maximum likelihood fits with floating parameters and scans the parameter space for the best fit to the entire sample. We find that the new method is significantly more sensitive than current method and is insensitive to the exact location of the new physics signal we search. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0509/0509174v2.pdf"}
{"id": "physics0509260", "abstract": "  An asymptotic theory is developed for a moving drop driven by a wettability gradient. We distinguish the mesoscale where an exact solution is known for the properly simplified problem. This solution is matched at both – the advancing and the receding side – to respective solutions of the problem on the microscale. On the microscale the velocity of movement is used as the small parameter of an asymptotic expansion. Matching gives the droplet shape, velocity of movement as a function of the imposed wettability gradient and droplet volume. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0509/0509260v1.pdf"}
{"id": "physics0510072", "abstract": "  Configuration interaction in many-electron atoms may cause anomalies in the fine structure which make the intervals small and very sensitive to variation of the fine structure constant. Repeated precision measurements of these intervals over long period of time can put strong constrain on possible time variation of the fine structure constant. We consider the 5p^4  ^3P_2,1,0 fine structure multiplet in the ground state of neutral tellurium as an example. Here the effect of change of the fine structure constant is enhanced about one hundred times in the relative change of the small energy interval between the ^3P_1 and ^3P_0 states. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0510/0510072v1.pdf"}
{"id": "physics0511072", "abstract": "  We present a simple method to stabilize the optical path length of an optical fiber to an accuracy of about 1/100 of the laser wavelength. We study the dynamic response of the path length to modulation of an electrically conductive heater layer of the fiber. The path length is measured against the laser wavelength by use of the Pound-Drever-Hall method; negative feedback is applied via the heater. We apply the method in the context of a cryogenic resonator frequency standard. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0511/0511072v2.pdf"}
{"id": "physics0512151", "abstract": "  We have theoretically investigated 3D focusing of a launched cloud of cold atoms using a pair of magnetic lens pulses (the alternate-gradient method). Individual lenses focus radially and defocus axially or vice-versa. The performance of the two possible pulse sequences are compared and found to be ideal for loading both 'pancake' and 'sausage' shaped magnetic/optical microtraps. It is shown that focusing aberrations are considerably smaller for double-impulse magnetic lenses compared to single-impulse magnetic lenses. An analysis of the clouds focused by double-impulse technique is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0512/0512151v2.pdf"}
{"id": "physics0603043", "abstract": "  A rigorous quantum relativistic approach has been used to calculate the relationship between the decay laws of an unstable particle seen from two inertial frames moving with respect to each other. In agreement with experiment, it is found that the usual Einstein's time dilation formula is rather accurate in this case. However, small corrections to this formula were also obtained. Although the observation of these corrections is beyond the resolution of modern experiments, their presence indicates that special relativistic time dilation is not rigorously applicable to particle decays. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0603/0603043v2.pdf"}
{"id": "physics0606095", "abstract": "  Since the introduction of the Black-Scholes model stochastic processes have played an increasingly important role in mathematical finance. In many cases prices, volatility and other quantities can be modeled using stochastic ordinary differential equations. Available methods for solving such equations have until recently been markedly inferior to analogous methods for deterministic ordinary differential equations. Recently, a number of methods which employ variable stepsizes to control local error have been developed which appear to offer greatly improved speed and accuracy. Here we conduct a comparative study of the performance of these algorithms for problems taken from the mathematical finance literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0606/0606095v1.pdf"}
{"id": "physics0607263", "abstract": "  The Rayleigh-Taylor instability of a magnetic fluid superimposed on a non-magnetic liquid of lower density may be suppressed with the help of a spatially homogeneous magnetic field rotating in the plane of the undisturbed interface. Starting from the complete set of Navier-Stokes equations for both liquids a Floquet analysis is performed which consistently takes into account the viscosities of the fluids. Using experimentally relevant values of the parameters we suggest to use this stabilization mechanism to provide controlled initial conditions for an experimental investigation of the Rayleigh-Taylor instability. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0607/0607263v1.pdf"}
{"id": "physics0611243", "abstract": "  We present and discuss the development of an unconditionally stable algorithm used to solve the evolution equations of the Phase Field Crystal (PFC) model. This algorithm allows for an arbitrarily large algorithmic time step. As the basis for our analysis of the accuracy of this algorithm, we determine an effective time step in Fourier space. We then compare our calculations with a set of representative numerical results, and demonstrate that this algorithm is an effective approach for the study of the PFC models, yielding a time step effectively 180 times larger than the Euler algorithm for a representative set of material parameters. As the PFC model is just a simple example of a wide class of density functional theories, we expect this method will have wide applicability to modeling systems of considerable interest to the materials modeling communities. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0611/0611243v2.pdf"}
{"id": "physics0701348", "abstract": "  We study community structure of networks. We have developed a scheme for maximizing the modularity Q based on mean field methods. Further, we have defined a simple family of random networks with community structure; we understand the behavior of these networks analytically. Using these networks, we show how the mean field methods display better performance than previously known deterministic methods for optimization of Q. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0701/0701348v2.pdf"}
{"id": "physics0702182", "abstract": "  The pixel detector is the innermost tracking device of the CMS experiment at the LHC. It is built from two independent sub devices, the pixel barrel and the end disks. The barrel consists of three concentric layers around the beam pipe with mean radii of 4.4, 7.3 and 10.2 cm. There are two end disks on each side of the interaction point at 34.5 cm and 46.5 cm. This article gives an overview of the pixel barrel detector, its mechanical support structure, electronics components, services and its expected performance. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0702/0702182v1.pdf"}
{"id": "physics0702193", "abstract": "  The pixel detector of CMS can be used to reconstruct very low pT charged particles down to about 0.1 GeV/c. This can be achieved with high efficiency, good resolution and a negligible fake rate for elementary collisions. In the case of central PbPb collisions the fake rate can be kept low for pT > 0.4 GeV/c. In addition, the detector can be employed for identification of neutral hadrons (V0s) and converted photons. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0702/0702193v1.pdf"}
{"id": "physics0703165", "abstract": "  We propose a technique of compensating the spurious reflections implied by the multiple-scattering (MS) method, commonly used for analyzing finite photonic crystal (PC) systems, to obtain exact values of characteristic parameters, such as reflection and transmission coefficients, of PC functional elements. Rather than a modification of the MS computational algorithm, our approach involves postprocessing of results obtained by the MS method. We derive analytical formulas for the fields excited in a finite system, taking explicitly into account the spurious reflections occurring at the artificial system boundaries. The intrinsic parameters of the investigated functional element are found by fitting the results of MS simulations to those obtained from the formulas derived. Devices linked with one and two semi-infinite waveguides are analyzed explicitly; possible extensions of the formalism to more complex circuits are discussed as well. The accuracy of the proposed method is tested in a number of systems; the results of our calculations prove to be in good agreement with those obtained independently by other authors. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0703/0703165v1.pdf"}
{"id": "physics9710011", "abstract": "  The possibility is considered that turbulence is described by differential equations for which uniqueness fails maximally, at least in some limit. The inviscid Burgers equation, in the context of Onsager's suggestion that turbulence should be described by a negative absolute temperature, is such a limit. In this picture, the onset of turbulence coincides with the proliferation of singularities which characterizes the failure of uniqueness. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/9710/9710011v1.pdf"}
{"id": "physics9901015", "abstract": "  A quantum-mechanical Gaussian wave-packet approach to the theoretical description of nuclear motions in a condensed-phase environment is developed. General expressions for the time-dependent reduced density matrix are given for a harmonic potential surface, and the exact quantum dynamics is found for a microscopic system-plus-bath model. Particular attention is devoted to the influence of initial correlations between system and bath for the outcome of a pump-probe experiment. We show that the standard factorized preparation, compared to a more realistic correlated preparation, leads to significantly different stimulated emission spectra at high temperatures. Recent experiments for the reaction center are analyzed using this formalism. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/9901/9901015v1.pdf"}
{"id": "physics9903012", "abstract": "  We propose a 2-d computational model-system comprising a mixture of spheres and the objects of some other shapes, interacting via the Lennard-Jones potential. We propose a reliable and efficient numerical algorithm to obtain void statistics. The void distribution, in turn, determines the selective permeability across the system and bears a remarkable similarity with features reported in certain biological experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/9903/9903012v1.pdf"}
{"id": "q-bio0501035", "abstract": "  Motivated by the finding that there is some biological universality in the relationship between school geometry and school biomass of various pelagic fishes in various conditions, I here establish a scaling law for school dimensions: the school diameter increases as a power-law function of school biomass. The power-law exponent is extracted through the data collapse, and is close to 3/5. This value of the exponent implies that the mean packing density decreases as the school biomass increases, and the packing structure displays a mass-fractal dimension of 5/3. By exploiting an analogy between school geometry and polymer chain statistics, I examine the behavioral algorithm governing the swollen conformation of large-sized schools of pelagics, and I explain the value of the exponent. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0501/0501035v2.pdf"}
{"id": "q-bio0604003", "abstract": "  The Yakushevich model of DNA torsion dynamics supports soliton solutions, which are supposed to be of special interest for DNA transcription. In the discussion of the model, one usually adopts the approximation ℓ_0 → 0, where ℓ_0 is a parameter related to the equilibrium distance between bases in a Watson-Crick pair. Here we analyze the Yakushevich model without ℓ_0 → 0. The model still supports soliton solutions indexed by two winding numbers (n,m); we discuss in detail the fundamental solitons, corresponding to winding numbers (1,0) and (0,1) respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0604/0604003v2.pdf"}
{"id": "q-bio0605039", "abstract": "  We present an extremely simplified model of multiple-domains polymer stretching in an atomic force microscopy experiment. We portray each module as a binary set of contacts and decompose the system energy into a harmonic term (the cantilever) and long-range interactions terms inside each domain. Exact equilibrium computations and Monte Carlo simulations qualitatively reproduce the experimental saw-tooth pattern of force-extension profiles, corresponding (in our model) to first-order phase transitions. We study the influence of the coupling induced by the cantilever and the pulling speed on the relative heights of the force peaks. The results suggest that the increasing height of the critical force for subsequent unfolding events is an out-of-equilibrium effect due to a finite pulling speed. The dependence of the average unfolding force on the pulling speed is shown to reproduce the experimental logarithmic law. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0605/0605039v2.pdf"}
{"id": "q-bio0606021", "abstract": "  We study coarse-grained (group-level) alignment dynamics of individual-based animal group models for heterogeneous populations consisting of informed (on preferred directions) and uninformed individuals. The orientation of each individual is characterized by an angle, whose dynamics are nonlinearly coupled with those of all the other individuals, with an explicit dependence on the difference between the individual's orientation and the instantaneous average direction. Choosing convenient coarse-grained variables (suggested by uncertainty quantification methods) that account for rapidly developing correlations during initial transients, we perform efficient computations of coarse-grained steady states and their bifurcation analysis. We circumvent the derivation of coarse-grained governing equations, following an equation-free computational approach. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0606/0606021v2.pdf"}
{"id": "q-bio0611025", "abstract": "  Classical models for competition between two species usually predict exclusion or divergent evolution of resource exploitation. However, recent experimental data show that coexistence is possible for very similar species competing for the same resources without niche partition. Motivated by this experimental challenge to classical competition theory, we propose an individual-based stochastic competition model, which is essentially a modification of a deterministic Lotka-Volterra type model. The proposed model of competition dynamics incorporates the effects of a discrete genotype, which determines the individual's adaptation to the environment, as well as its interaction with the other species. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0611/0611025v1.pdf"}
{"id": "q-bio0612026", "abstract": "  The statistics of steps and dwell times in reversible molecular motors differ from those of cycle completion in enzyme kinetics. The reason is that a step is only one of several transitions in the mechanochemical cycle. As a result, theoretical results for cycle completion in enzyme kinetics do not apply to stepping data. To allow correct parameter estimation, and to guide data analysis and experiment design, a theoretical treatment is needed that takes this observation into account. In this paper, we model the distribution of dwell times and number of forward and backward steps using first passage processes, based on the assumption that forward and backward steps correspond to different directions of the same transition. We extend recent results for systems with a single cycle and consider the full dwell time distributions as well as models with multiple pathways, detectable substeps, and detachments. Our main results are a symmetry relation for the dwell time distributions in reversible motors, and a relation between certain relative step frequencies and the free energy per cycle. We demonstrate our results by analyzing recent stepping data for a bacterial flagellar motor, and discuss the implications for the efficiency and reversibility of the force-generating subunits. Key words: motor proteins; single molecule kinetics; enzyme kinetics; flagellar motor; Markov process; non-equilibrium fluctuations. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0612/0612026v2.pdf"}
{"id": "quant-ph0003049", "abstract": "  We consider the spin 1/2 model coupled to a slowly varying magnetic field in the presence of a weak damping represented by a Lindblad-form operators. We show that Berry's geometrical phase remains unaltered by the two dissipation mechanism considered. Dissipation effects are twofold: a shrinking in the modulus of the Bloch's vector, which characterizes coherence loss and a time dependent (dissipation related) precession angle. We show that the line broadening of the Fourier transformation of the components of magnetization is only due to the presence of dissipation. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0003/0003049v3.pdf"}
{"id": "quant-ph0005024", "abstract": "  Despite the fact that the fundamental physical laws are symmetric in time, most observed processes do not show this symmetry. Especially the phenomenon of decay seems to involve a kind of irreversibility that makes the definition of a microscopic arrow of time possible. Such an intrinsic irreversibility is incorporated within the Rigged Hilbert Space quantum mechanics of the Brussels School, contrasting to the statements of standard quantum mechanics. As shown in this paper, the formalism bears significant advantages in the description of decaying systems, however the breaking of time symmetry can be avoided. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0005/0005024v4.pdf"}
{"id": "quant-ph0012011", "abstract": "  A generalized Noether's theorem and the operational determination of a physical geometry in quantum physics are used to motivate a quantum geometry consisting of relations between quantum states that are defined by a universal group. Making these relations dynamical implies the non local effect of the fundamental interactions on the wave function, as in the Aharonov-Bohm effect and its generalizations to non Abelian gauge fields and gravity. The usual space-time geometry is obtained as the classical limit of this quantum geometry using the quantum state space metric. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0012/0012011v4.pdf"}
{"id": "quant-ph0101127", "abstract": "  For polarization experiments involving photon counting we introduce a quasi-deterministic eigenstate transition model of the analyzer process. Distributions accumulated one photon at a time, provide a deterministic explanation for the law of Malus. We combine this analyzer model with causal polarization coupling to calculate photon-photon correlations, one photon pair at a time. The calculated correlations exceed the Bell limits and show excellent agreement with the measured correlations of [ A. Aspect, P. Grangier and G. Rogers, Phys. Rev. Lett. 49 91 (1982)]. We discuss why this model exceeds the Bell type limits. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0101/0101127v1.pdf"}
{"id": "quant-ph0102079", "abstract": "  Recent experiments to test Bell's inequality using entangled photons and ions aimed at tests of basic quantum mechanical principles. Interesting results have been obtained and many loopholes could be closed. In this paper we want to point out that tests of Bell's inequality also play an important role in verifying atom entanglement schemes. We describe as an example a scheme to prepare arbitrary entangled states of N two-level atoms using a leaky optical cavity and a scheme to entangle atoms inside a photonic crystal. During the state preparation no photons are emitted and observing a violation of Bell's inequality is the only way to test whether a scheme works with a high precision or not. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0102/0102079v1.pdf"}
{"id": "quant-ph0109014", "abstract": "  We consider the environment-affected dynamics of N self-interacting particles living in one-dimensional double wells. Two topics are dealt with. First, we consider the production of entangled states of two-level systems. We show that by adiabatically varying the well biases we may dynamically generate maximally entangled states, starting from initially unentangled product states. Entanglement degradation due to a common type of environmental influence is then computed by solving a master equation. However, we also demonstrate that entanglement production is unaffected if the system-environment coupling is of the type that induces “motional narrowing”. As our second but related topic, we construct a different master equation that seamlessly merges error protection/detection dynamics for quantum information with the environmental couplings responsible for producing the errors in the first place. Adiabatic avoided crossing schemes are used in both topics. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0109/0109014v2.pdf"}
{"id": "quant-ph0109141", "abstract": "  It is shown that different distinguishability measures impose different orderings on ensembles of N pure quantum states. This is demonstrated using ensembles of equally-probable, linearly independent, symmetrical pure states, with the maximum probabilities of correct hypothesis testing and unambiguous state discrimination being the distinguishability measures. This finding implies that there is no absolute scale for comparing the distinguishability of any two ensembles of N quantum states, and that distinguishability comparison is necessarily relative to a particular discrimination strategy. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0109/0109141v3.pdf"}
{"id": "quant-ph0205106", "abstract": "  A two-dimensional electron system interacting with an impurity and placed in crossed magnetic and electric fields is under investigation. Since it is assumed that an impurity center interacts as an attractive δ-like potential a renormalization procedure for the retarded Green's function has to be carried out. For the vanishing electric field we obtain a close analytical expression for the Green's function and we find one bound state localized between Landau levels. It is also shown by numerical investigations that switching on the electric field new long-living resonance states localized in the vicinity of Landau levels can be generated. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0205/0205106v1.pdf"}
{"id": "quant-ph0210165", "abstract": "  The non-resonant interaction between the high-density excitons in a quantum well and a single mode cavity field is investigated. An analytical expression for the physical spectrum of the excitons is obtained. The spectral properties of the excitons, which are initially prepared in the number states or the superposed states of the two different number states by the resonant femtosecond pulse pumping experiment, are studied. Numerical study of the physical spectrum is carried out and a discussion of the detuning effect is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0210/0210165v1.pdf"}
{"id": "quant-ph0210172", "abstract": "  Universal quantum cloning machines (UQCMs), sometimes called quantum cloners, generate many outputs with identical density matrices, with as close a resemblance to the input state as is allowed by the basic principles of quantum mechanics. Any experimental realization of a quantum cloner has to cope with the effects of decoherence which terminate the coherent evolution demanded by a UQCM. We examine how many clones can be generated within a decoherence time. We compare the time that a quantum cloner implemented with trapped ions requires to produce M copies from N identical pure state inputs and the decoherence time during which the probability of spontaneous emission becomes non-negligible. We find a method to construct an N→ M cloning circuit, and estimate the number of elementary logic gates required. It turns out that our circuit is highly vulnerable to spontaneous emission as the number of gates in the circuit is exponential with respect to the number of qubits involved. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0210/0210172v2.pdf"}
{"id": "quant-ph0212012", "abstract": "  We introduce phase operators associated with the algebra su(3), which is the appropriate tool to describe three-level systems. The rather unusual properties of this phase are caused by the small dimension of the system and are explored in detail. When a three-level atom interacts with a quantum field in a cavity, a polynomial deformation of this algebra emerges in a natural way. We also introduce a polar decomposition of the atom-field relative amplitudes that leads to a Hermitian relative-phase operator, whose eigenstates correctly describe the corresponding phase properties. We claim that this is the natural variable to deal with quantum interference effects in atom-field interactions. We find the probability distribution for this variable and study its time evolution in some special cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0212/0212012v1.pdf"}
{"id": "quant-ph0302142", "abstract": "  We present a theoretical study of an ensemble of X-like 4-level atoms placed in an optical cavity driven by a linearly polarized field. We show that the self-rotation (SR) process leads to polarization switching (PS). Below the PS threshold, both the mean field mode and the orthogonal vacuum mode are squeezed. We provide a simple analysis of the phenomena responsible for the squeezing and trace the origin of vacuum squeezing not to SR, but to crossed Kerr effect induced by the mean field. Last, we show that this vacuum squeezing can be interpreted as polarization squeezing. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0302/0302142v1.pdf"}
{"id": "quant-ph0302151", "abstract": "  A system of coherently-driven two-level atoms is analyzed in presence of two independent stochastic perturbations: one due to collisions and a second one due to phase fluctuations of the driving field. The behaviour of the quantum interference induced by the collisional noise is considered in detail. The quantum-trajectory method is utilized to reveal the phase correlations between the dressed states involved in the interfering transition channels. It is shown that the quantum interference induced by the collisional noise is remarkably robust against phase noise. This effect is due to the fact that the phase noise, similarly to collisions, stabilizes the phase-difference between the dressed states. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0302/0302151v1.pdf"}
{"id": "quant-ph0303021", "abstract": "  By using the Green-function concept of quantization of the electromagnetic field in dispersing and absorbing media, the quantized field in the presence of a dispersing and absorbing dielectric multilayer plate is studied. Three-dimensional input-output relations are derived for both amplitude operators in the k-space and the field operators in the coordinate space. The conditions are discussed, under which the input-output relations can be expressed in terms of bosonic operators. The theory applies to both (effectively) free fields and fields, created by active atomic sources inside and/or outside the plate, including also evanescent-field components. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0303/0303021v1.pdf"}
{"id": "quant-ph0307138", "abstract": "  We introduce a convergent iterative algorithm for finding the optimal coding and decoding operations for an arbitrary noisy quantum channel. This algorithm does not require any error syndrome to be corrected completely, and hence also finds codes outside the usual Knill-Laflamme definition of error correcting codes. The iteration is shown to improve the figure of merit \"channel fidelity\" in every step. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0307/0307138v2.pdf"}
{"id": "quant-ph0307226", "abstract": "  We present a theory which can explain the micromaser as well as its optical counterpart, the microlaser, for appropriate values of dissipative parameters. We show that, in both the the cases, the cavity radiation fields can have sub-Poissonian photon statistics. We further analyse if it is possible to attain a Fock state of the radiation field. The microlaser is precluded for such analysics due to the damping of its lasing levels making transitions at optical frequencies. Hence, we focus our attention on the micromaser and our exact simulation of the dynamics shows that it is not possible to generate a Fock state of the cavity radiation field. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0307/0307226v1.pdf"}
{"id": "quant-ph0310009", "abstract": "  We provide optimal measurement schemes for estimating relative parameters of the quantum state of a pair of spin systems. We prove that the optimal measurements are joint measurements on the pair of systems, meaning that they cannot be achieved by local operations and classical communication. We also demonstrate that in the limit where one of the spins becomes macroscopic, our results reproduce those that are obtained by treating that spin as a classical reference direction. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0310/0310009v3.pdf"}
{"id": "quant-ph0312047", "abstract": "  We explore the dynamics of entanglement in classically chaotic systems by considering a multiqubit system that behaves collectively as a spin system obeying the dynamics of the quantum kicked top. In the classical limit, the kicked top exhibits both regular and chaotic dynamics depending on the strength of the chaoticity parameter κ in the Hamiltonian. We show that the entanglement of the multiqubit system, considered for both bipartite and pairwise entanglement, yields a signature of quantum chaos. Whereas bipartite entanglement is enhanced in the chaotic region, pairwise entanglement is suppressed. Furthermore, we define a time-averaged entangling power and show that this entangling power changes markedly as κ moves the system from being predominantly regular to being predominantly chaotic, thus sharply identifying the edge of chaos. When this entangling power is averaged over initial states, it yields a signature of global chaos. The qualitative behavior of this global entangling power is similar to that of the classical Lyapunov exponent. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0312/0312047v1.pdf"}
{"id": "quant-ph0402148", "abstract": "  A key problem in quantum computing is finding a viable technological path toward the creation of a scalable quantum computer. One possible approach toward solving part of this problem is distributed computing, which provides an effective way of utilizing a network of limited capacity quantum computers.   In this paper, we present two primitive operations, cat-entangler and cat-disentangler, which in turn can be used to implement non-local operations, e.g. non-local CNOT and quantum teleportation. We also show how to establish an entangled pair, and use entangled pairs to efficiently create a generalized GHZ state. Furthermore, we present procedures which allow us to reuse channel qubits in a sequence of non-local operations.   These non-local operations work on the principle that a cat-like state, created by cat-entangler, can be used to distribute a control qubit among multiple computers. Using this principle, we show how to efficiently implement non-local control operations in many situation, including a parallel implementation of a certain kind of unitary transformation. Finally, as an example, we present a distributed version of the quantum Fourier transform. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0402/0402148v3.pdf"}
{"id": "quant-ph0403018", "abstract": "  We propose an effective Hamiltonian approach to investigate decoherence of a quantum system in a non-Markovian reservoir, naturally imposing the complete positivity on the reduced dynamics of the system. The formalism is based on the notion of an effective reservoir, i.e., certain collective degrees of freedom in the reservoir that are responsible for the decoherence. As examples for completely positive decoherence, we present three typical decoherence processes for a qubit such as dephasing, depolarizing, and amplitude-damping. The effects of the non-Markovian decoherence are compared to the Markovian decoherence. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0403/0403018v1.pdf"}
{"id": "quant-ph0404002", "abstract": "  Nonlinear dynamics in the fundamental interaction between a two-level atom with recoil and a quantized radiation field in a high-quality cavity is studied. We consider the strongly coupled atom-field system as a quantum-classical hybrid with dynamically coupled quantum and classical degrees of freedom. We show that, even in the absence of any other interaction with environment, the interaction of the purely quantum atom-field system with the external atomic degree of freedom provides the emergence of classical dynamical chaos from quantum electrodynamics. Atomic fractals with self-similar intermittency of smooth and unresolved structures are found in the exit-time scattering function. Tiny interplay between all the degrees of freedom is responsible for dynamical trapping of atoms even in a very short microcavity. Gedanken experiments are proposed to detect manifestations of atomic fractals in cavity quantum electrodynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0404/0404002v2.pdf"}
{"id": "quant-ph0405074", "abstract": "  A recently proposed purification method, in which the Zeno-like measurements of a subsystem can bring about a distillation of another subsystem in interaction with the former, is utilized to yield entangled states between distant systems. It is shown that the measurements of a two-level system locally interacting with other two spatially separated not coupled subsystems, can distill entangled states from the latter irrespectively of the initial states of the two subsystems. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0405/0405074v2.pdf"}
{"id": "quant-ph0407166", "abstract": "  A simple model describing depolarization channels with zero-bandwidth environment is presented and exactly solved. The environment is modelled by Lorentzian, telegraphic and Gaussian zero-bandwidth noises. Such channels can go beyond the standard Markov dynamics and therefore can illustrate the influence of memory effects of the noisy communication channel on the transmitted information. To quantify the disturbance of quantum states the entanglement fidelity between arbitrary input and output states is investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0407/0407166v1.pdf"}
{"id": "quant-ph0408092", "abstract": "  To show the feasibility of a long distance partial Bell-State measurement, a Hong-Ou-Mandel experiment with coherent photons is reported. Pairs of degenerate photons at telecom wavelength are created by parametric down conversion in a periodically poled lithium niobate waveguide. The photon pairs are separated in a beam-splitter and transmitted via two fibers of 25km. The wave-packets are relatively delayed and recombined on a second beam-splitter, forming a large Mach-Zehnder interferometer. Coincidence counts between the photons at the two output modes are registered. The main challenge consists in the trade-off between low count rates due to narrow filtering and length fluctuations of the 25km long arms during the measurement. For balanced paths a Hong-Ou-Mandel dip with a visibility of 47.3", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0408/0408092v3.pdf"}
{"id": "quant-ph0409142", "abstract": "  Twirl operations, which convert impure singlet states into Werner states, play an important role in many schemes for entanglement purification. In this paper we describe strategies for implementing twirl operations, with an emphasis on methods suitable for ensemble quantum information processors such as nuclear magnetic resonance (NMR) quantum computers. We implement our twirl operation on a general two-spin mixed state using liquid state NMR techniques, demonstrating that we can obtain the singlet Werner state with high fidelity. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0409/0409142v1.pdf"}
{"id": "quant-ph0409152", "abstract": "  We treat the problem of normally ordering expressions involving the standard boson operators a, a* where [a,a*]=1. We show that a simple product formula for formal power series - essentially an extension of the Taylor expansion - leads to a double exponential formula which enables a powerful graphical description of the generating functions of the combinatorial sequences associated with such functions - in essence, a combinatorial field theory. We apply these techniques to some examples related to specific physical Hamiltonians. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0409/0409152v1.pdf"}
{"id": "quant-ph0410194", "abstract": "  We address nonlocality of a class of fully inseparable three-mode Gaussian states generated either by bilinear three-mode Hamiltonians or by a sequence of bilinear two-mode Hamiltonians. Two different tests revealing strong nonlocality are considered, in which the dichotomic Bell operator is represented by displaced parity and by pseudospin operator respectively. Three-mode states are also considered as a conditional source of two-mode non Gaussian states, whose nonlocal properties are analyzed. We found that the non Gaussian character of the conditional states allows violation of Bell's inequalities (by parity and pseudospin tests) stronger than with a conventional twin-beam state. However, the non Gaussian character is not sufficient to reveal nonlocality thorough a dichotomized quadrature measurement strategy. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0410/0410194v2.pdf"}
{"id": "quant-ph0411048", "abstract": "  We experimentally demonstrate the entanglement can be created on two distant particles using separate state. We show that two data particles can share some entanglement while one ancilla particle always remains separable from them during the experimental evolution of the system. Our experiment can be viewed as a benchmark to illustrate the idea that no prior entanglement is necessary to create entanglement. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0411/0411048v1.pdf"}
{"id": "quant-ph0503034", "abstract": "  We propose an interferometric method to investigate the non-locality of high-dimensional two-photon orbital angular momentum states generated by spontaneous parametric down conversion. We incorporate two half-integer spiral phase plates and a variable-reflectivity output beam splitter into a Mach-Zehnder interferometer to build an orbital angular momentum analyzer. This setup enables testing the non-locality of high-dimensional two-photon states by repeated use of the Clauser-Horne inequality. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0503/0503034v3.pdf"}
{"id": "quant-ph0505042", "abstract": "  We apply the effective potential analytic continuation (EPAC) method to the calculation of real time quantum correlation functions involving operators nonlinear in the position operator q̂. For a harmonic system the EPAC method provides the exact correlation function at all temperature ranges, while the other quantum dynamics methods, the centroid molecular dynamics and the ring polymer molecular dynamics, become worse at lower temperature. For an asymmetric anharmonic system, the EPAC correlation function is in very good agreement with the exact one at t=0. When the time increases from zero, the EPAC method gives good coincidence with the exact result at lower temperature. Finally, we propose a simplified version of the EPAC method to reduce the computational cost required for the calculation of the standard effective potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0505/0505042v1.pdf"}
{"id": "quant-ph0505092", "abstract": "  We demonstrate that the entropy of entanglement and the distillable entanglement of regions with respect to the rest of a general harmonic lattice system in the ground or a thermal state scale at most as the boundary area of the region. This area law is rigorously proven to hold true in non-critical harmonic lattice system of arbitrary spatial dimension, for general finite-ranged harmonic interactions, regions of arbitrary shape and states of nonzero temperature. For nearest-neighbor interactions - corresponding to the Klein-Gordon case - upper and lower bounds to the degree of entanglement can be stated explicitly for arbitrarily shaped regions, generalizing the findings of [Phys. Rev. Lett. 94, 060503 (2005)]. These higher dimensional analogues of the analysis of block entropies in the one-dimensional case show that under general conditions, one can expect an area law for the entanglement in non-critical harmonic many-body systems. The proofs make use of methods from entanglement theory, as well as of results on matrix functions of block banded matrices. Disordered systems are also considered. We moreover construct a class of examples for which the two-point correlation length diverges, yet still an area law can be proven to hold. We finally consider the scaling of classical correlations in a classical harmonic system and relate it to a quantum lattice system with a modified interaction. We briefly comment on a general relationship between criticality and area laws for the entropy of entanglement. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0505/0505092v3.pdf"}
{"id": "quant-ph0506141", "abstract": "  The closed causal chains arising from backward time travel do not lead to paradoxes if they are self consistent. This raises the question as to how physics ensures that only self-consistent loops are possible. We show that, for one particular case at least, the condition of self consistency is ensured by the interference of quantum mechanical amplitudes associated with the loop. If this can be applied to all loops then we have a mechanism by which inconsistent loops eliminate themselves. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0506/0506141v1.pdf"}
{"id": "quant-ph0508146", "abstract": "  The separability of the continuous-variable EPR state can be tested with Hanbury-Brown and Twiss type interference. The second-order visibility of such interference can provide an experimental test of entanglement. It is shown that time-resolved interference leads to the Hong, Ou and Mandel deep, that provides a signature of quantum non-separability for pure and mixed EPR states. A Hanbury-Brown and Twiss type witness operator can be constructed to test the quantum nature of the EPR entanglement. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0508/0508146v2.pdf"}
{"id": "quant-ph0508208", "abstract": "  By using the concept of negativity, we investigate entanglement in (1/2,1) mixed-spin Heisenberg systems. We obtain the analytical results of entanglement in small isotropic Heisenberg clusters with only nearest-neighbor (NN) interactions up to four spins and in the four-spin Heisenberg model with both NN and next-nearest-neighbor (NNN) interactions. For more spins, we numerically study effects of temperature, magnetic fields, and NNN interactions on entanglement. We study in detail the threshold value of the temperature, after which the negativity vanishes. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0508/0508208v1.pdf"}
{"id": "quant-ph0603269", "abstract": "  We analyze the entanglement between two modes of a free Dirac field as seen by two relatively accelerated parties. The entanglement is degraded by the Unruh effect and asymptotically reaches a non-vanishing minimum value in the infinite acceleration limit. This means that the state always remains entangled to a degree and can be used in quantum information tasks, such as teleportation, between parties in relative uniform acceleration. We analyze our results from the point of view afforded by the phenomenon of entanglement sharing and in terms of recent results in the area of multi-qubit complementarity. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0603/0603269v2.pdf"}
{"id": "quant-ph0604017", "abstract": "  We have developed a rigorous quantum model of spontaneous parametric down-conversion in a nonlinear 1D photonic-band-gap structure based upon expansion of the field into monochromatic plane waves. The model provides a two-photon amplitude of a created photon pair. The spectra of the signal and idler fields, their intensity profiles in the time domain, as well as the coincidence-count interference pattern in a Hong-Ou-Mandel interferometer are determined both for cw and pulsed pumping regimes in terms of the two-photon amplitude. A broad range of parameters characterizing the emitted down-converted fields can be used. As an example, a structure composed of 49 layers of GaN/AlN is analyzed as a suitable source of photon pairs having high efficiency. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0604/0604017v1.pdf"}
{"id": "quant-ph0604101", "abstract": "  1-qubit quantum states form a space called the three-dimensional Bloch ball. To compute Holevo capacity, Voronoi diagrams in the Bloch ball with respect to the quantum divergence have been used as a powerful tool. These diagrams basically treat mixed quantum states corresponding to points in the interior of the Bloch ball. Due to the existence of logarithm in the quantum divergence, the diagrams are not defined on pure quantum states corresponding to points on the two-dimensional sphere. This paper first defines the Voronoi diagrams for pure quantum states on the Bloch sphere by the Fubini-Study distance and the Bures distance. We also introduce other Voronoi diagrams on the sphere obtained by taking a limit of Voronoi diagrams for mixed quantum states by the quantum divergences in the Bloch ball. These diagrams are shown to be equivalent to the ordinary Voronoi diagram on the sphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0604/0604101v1.pdf"}
{"id": "quant-ph0605089", "abstract": "  The influence of the size and shape of a dispersing and absorbing dielectric body on the local-field corrected spontaneous-decay of an excited atom embedded in the body is studied on the basis of the real-cavity model. By means of a Born expansion of the Green tensor of the system it is shown that to linear order in the susceptibility of the body the decay rate exactly follows Tomas's formula found for the special case of an atom at the center of a homogeneous dielectric sphere [Phys. Rev. A 63, 053811 (2001)]. It is further shown that for an atom situated at the interior of an arbitrary dielectric body this formula remains valid beyond the linear order. The case of an atom embedded in a weakly polarizable sphere is discussed in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0605/0605089v2.pdf"}
{"id": "quant-ph0606097", "abstract": "  The experimental observation of quantum phenomena in strongly correlated many particle systems is difficult because of the short length- and timescales involved. Obtaining at the same time detailed control of individual constituents appears even more challenging and thus to date inhibits employing such systems as quantum computing devices. Substantial progress to overcome these problems has been achieved with cold atoms in optical lattices, where a detailed control of collective properties is feasible but it is very difficult to address and hence control or measure individual sites. Here we show, that polaritons, combined atom and photon excitations, in an array of cavities such as a photonic crystal or coupled toroidal micro-cavities, can form a strongly interacting many body system, where individual particles can be controlled and measured. All individual building blocks of the proposed setting have already been experimentally realised, thus demonstrating the potential of this device as a quantum simulator. With the possibility to create attractive on-site potentials the scheme allows for the creation of highly entangled states and a phase with particles much more delocalised than in superfluids. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0606/0606097v2.pdf"}
{"id": "quant-ph0611058", "abstract": "  We analyze the class of single qubit channels with the environment modeled by a one-qubit mixed state. The set of affine transformations for this class of channels is computed analytically, employing the canonical form for the two-qubit unitary operator. We demonstrate that, 3/8 of the generalized depolarizing channels can be simulated by the one-qubit mixed state environment by explicitly obtaining the shape of the volume occupied by this class of channels within the tetrahedron representing the generalized depolarizing channels. Further, as a special case, we show that the two-Pauli Channel cannot be simulated by a one-qubit mixed state environment. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0611/0611058v2.pdf"}
{"id": "quant-ph0611079", "abstract": "  Holonomic gates for quantum computation are commonly considered to be robust against certain kinds of parametric noise, the very motivation of this robustness being the geometric character of the transformation achieved in the adiabatic limit. On the other hand, the effects of decoherence are expected to become more and more relevant when the adiabatic limit is approached. Starting from the system described by Florio et al. [Phys. Rev. A 73, 022327 (2006)], here we discuss the behavior of non ideal holonomic gates at finite operational time, i.e., far before the adiabatic limit is reached. We have considered several models of parametric noise and studied the robustness of finite time gates. The obtained results suggest that the finite time gates present some effects of cancellation of the perturbations introduced by the noise which mimic the geometrical cancellation effect of standard holonomic gates. Nevertheless, a careful analysis of the results leads to the conclusion that these effects are related to a dynamical instead of geometrical feature. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0611/0611079v2.pdf"}
{"id": "quant-ph0611155", "abstract": "  We have analyzed available optical data for Au in the mid-infrared range which is important for a precise prediction of the Casimir force. Significant variation of the data demonstrates genuine sample dependence of the dielectric function. We demonstrate that the Casimir force is largely determined by the material properties in the low frequency domain and argue that therefore the precise values of the Drude parameters are crucial for an accurate evaluation of the force. These parameters can be estimated by two different methods, either by fitting real and imaginary parts of the dielectric function at low frequencies, or via a Kramers-Kronig analysis based on the imaginary part of the dielectric function in the extended frequency range. Both methods lead to very similar results. We show that the variation of the Casimir force calculated with the use of different optical data can be as large as 5", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0611/0611155v1.pdf"}
{"id": "quant-ph0702003", "abstract": "  We show that a system of polaritons - combined atom and photon excitations - in an array of coupled cavities, under an experimental set-up usually considered in electromagnetically induced transparency, is described by the Bose-Hubbard model. This opens up the possibility of using this system as a quantum simulator, allowing for the observation of quantum phase transitions and for the measurement of local properties, such as single site observables. All the basic building blocks of the proposed setting have already been achieved experimentally, showing the feasibility of its realization in the near future. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0702/0702003v1.pdf"}
{"id": "quant-ph0703201", "abstract": "  A space-time symmetric and explicitly Lorentz covariant path integral formalism of relativistic quantum mechanics is proposed, which produces partial locally correlations of quantum processes of massive particles with the velocity of light at low energy limits. A superluminal correlation is also possible if anti-particles that moving along reverse time direction are excited. This provides a new point of view to interpret EPR experiments, also leaks a light of hope for hidden variable theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0703/0703201v1.pdf"}
{"id": "quant-ph9605047", "abstract": "  A model of spontaneous wavefunction collapse, which is explicitly local and Lorentz-invariant, is defined. Some of the predictions of the model for specific experimental situations are derived. It is shown that, although incompatible collapses, e.g. on opposite sides of an EPR-type of experiment, can occur, they will not persist in time and that eventually only compatible results will be obtained. The probabilities of particular results, however, will in general not agree with the predictions of quantum theory. We argue that it is unlikely that the deviations would have been seen in any experiment yet performed. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9605/9605047v1.pdf"}
{"id": "quant-ph9803059", "abstract": "  The temperature dependence of the Casimir effect for the radiation field confined between two conducting plates is analysed. The Casimir energy is shown to decline exponentially with temperature while the Casimir entropy which is defined in the text is shown to approach a limit which depends only on the geometry of the constraining plates. The results are discussed in terms of the relation between the Bose distribution function and the equipartition theorem - a relation based on a study by Einstein and Stern circa 1913. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9803/9803059v2.pdf"}
{"id": "quant-ph9808055", "abstract": "  We show how it is possible to suppress decoherence using tailored external forcing acting as pulses. In the limit of infinitely frequent pulses decoherence and dissipation are completely frozen; however, a significant decoherence suppression is already obtained when the frequency of the pulses is of the order of the reservoir typical frequency scale. This method could be useful in particular to suppress the decoherence of the center-of-mass motion in ion traps. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9808/9808055v5.pdf"}
{"id": "quant-ph9811067", "abstract": "  A recently developed scheme [S. Scheel, L. Knoll, and D.-G. Welsch, Phys. Rev. A 58, 700 (1998)] for quantizing the macroscopic electromagnetic field in linear dispersive and absorbing dielectrics satisfying the Kramers-Kronig relations is used to derive the quantum local-field correction for the standard virtual-sphere-cavity model. The electric and magnetic local-field operators are shown to be consistent with QED only if the polarization noise is fully taken into account. It is shown that the polarization fluctuations in the local field can dramatically change the spontaneous decay rate, compared with the familiar result obtained from the classical local-field correction. In particular, the spontaneous emission rate strongly depends on the radius of the local-field virtual cavity. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9811/9811067v1.pdf"}
{"id": "quant-ph9907071", "abstract": "  We investigate the photon statistics of light transmitted from a driven optical cavity containing one or two atoms interacting with a single mode of the cavity field. We treat arbitrary driving fields with emphasis on departure from previous weak field results. In addition effects of dephasing due to atomic transit through the cavity mode are included using two different models. We find that both models show the nonclassical correlations are quite sensitive to dephasing. The effect of multiple atoms on the system dynamics is investigated by placing two atoms in the cavity mode at different positions, therefore having different coupling strengths. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9907/9907071v2.pdf"}
{"id": "quant-ph9907107", "abstract": "  The interaction of a weakly bound Rydberg electron with an electromagnetic half-cycle pulse (HCP) is described with the help of a multidimensional semiclassical treatment. This approach relates the quantum evolution of the electron to its underlying classical dynamics. The method is nonperturbative and is valid for arbitrary spatial and temporal shapes of the applied HCP. On the basis of this approach angle- and energy-resolved spectra resulting from the ionization of Rydberg atoms by HCPs are analyzed. The different types of spectra obtainable in the sudden-impact approximation are characterized in terms of the appearing semiclassical scattering phenomena. Typical modifications of the spectra originating from finite pulse effects are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9907/9907107v1.pdf"}
{"id": "quant-ph9909023", "abstract": "  We discuss an extension of the theory of spin-orbit pendulum phenomenon given in [1] to relativistic approach. It is done within the so called Dirac Oscillator. Our first results, focusing on circular wave packet motion have been published recently [2]. The scope of this paper is motion of a linear wave packet. In relativistic approach we found Zitterbewegung in spin-orbit motion (in Dirac representation) due to coupling to negative energy states. This effect is washed out in the Foldy-Wouthuysen representation. Another important change with respect to non-relativistic case is the loss of periodicity. The phenomenon reminds the time evolution of population inversion in Jaynes-Cummings model. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9909/9909023v1.pdf"}
{"id": "supr-con9605002", "abstract": "  We investigate by numerical simulations the behavior of the power dissipated in a resistive load capacitively coupled to a Josephson flux flow oscillator and compare the results to those obtained for a d.c. coupled purely resistive load. Assuming realistic values for the parameters R and C, both in the high- and in the low-Tc case the power is large enough to allow the operation of such a device in applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/supr-con/pdf/9605/9605002v1.pdf"}
{"id": "0704.0444", "abstract": "  Katz and Vafa showed how charged matter can arise geometrically by the deformation of ADE-type orbifold singularities in type IIa, M-theory, and F-theory compactifications. In this paper we use those same basic ingredients, used there to geometrically engineer specific matter representations, here to deform the compactification manifold itself in a way which naturally compliments many features of unified model building. We realize this idea explicitly by deforming a manifold engineered to give rise to an SU_5 grand unified model into a one giving rise to the Standard Model. In this framework, the relative local positions of the singularities giving rise to Standard Model fields are specified in terms of the values of a small number of complex structure moduli which deform the original manifold, greatly reducing the arbitrariness of their relative positions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.0444v1.pdf"}
{"id": "0704.1642", "abstract": "  We study ground state properties and excitation spectra for hard-core Bosons on square and triangular lattices, at half filling, using series expansion methods. Nearest-neighbor repulsion between the Bosons leads to the development of short-range density order at the antiferromagnetic wavevector, and simultaneously a roton minima in the density excitation spectra. On the square-lattice, the model maps on to the well studied XXZ model, and the roton gap collapses to zero precisely at the Heisenberg symmetry point, leading to the well known spectra for the Heisenberg antiferromagnet. On the triangular-lattice, the collapse of the roton gap signals the onset of the supersolid phase. Our results suggest that the transition from the superfluid to the supersolid phase maybe weakly first order. We also find several features in the density of states, including two-peaks and a sharp discontinuity, which maybe observable in experimental realization of such systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1642v2.pdf"}
{"id": "0704.2444", "abstract": "  If dark matter decays to electromagnetically-interacting particles, it can inject energy into the baryonic gas and thus affect the processes of recombination and reionization. This leaves an imprint on the cosmic microwave background (CMB): the large-scale polarization is enhanced, and the small-scale temperature fluctuation is damped. We use the WMAP three-year data combined with galaxy surveys to constrain radiatively decaying dark matter. Our new limits to the dark-matter decay width are about ten times stronger than previous limits. For dark-matter lifetimes that exceed the age of the Universe, a limit of ζΓ_χ < 1.7 × 10^-25 s^-1 (95", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.2444v2.pdf"}
{"id": "0705.1722", "abstract": "  This contribution briefly reviews the reverberation mapping technique which leads to determination of black hole masses. I focus on the emerging relation between the broad-line region size and the active galactic nucleus (AGN) luminosity, and on an overview of recent results of reverberation mapping studies which are starting to cover the full AGN luminosity range. Preliminary results and time lag determination from a reverberation mapping program of high-luminosity quasars are also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.1722v1.pdf"}
{"id": "0706.2399", "abstract": "  Models which accelerate the expansion of the universe through the addition of a function of the Ricci scalar f(R) leave a characteristic signature in the large-scale structure of the universe at the Compton wavelength scale of the extra scalar degree of freedom. We search for such a signature in current cosmological data sets: the WMAP cosmic microwave background (CMB) power spectrum, SNLS supernovae distance measures, the SDSS luminous red galaxy power spectrum, and galaxy-CMB angular correlations. Due to theoretical uncertainties in the nonlinear evolution of f(R) models, the galaxy power spectrum conservatively yields only weak constraints on the models despite the strong predicted signature in the linear matter power spectrum. Currently the tightest constraints involve the modification to the integrated Sachs-Wolfe effect from growth of gravitational potentials during the acceleration epoch. This effect is manifest for large Compton wavelengths in enhanced low multipole power in the CMB and anti-correlation between the CMB and tracers of the potential. They place a bound on the Compton wavelength of the field be less than of order the Hubble scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.2399v1.pdf"}
{"id": "0707.4426", "abstract": "  We study the effect of the ferromagnetic (FM) contacts on the spin accumulation in the lateral spin valve system for the collinear magnetization configurations. When an additional FM electrode is introduced in the all-metallic lateral spin-valve system, we find that the transresistance can be fractionally suppressed or very weakly influenced depending on the position of the additional FM electrode, and relative magnitudes of contact resistance and the bulk resistance defined over the spin diffusion length. Nonlocal spin signals such as nonlocal voltage drop and leakage spin currents are independent of the magnetization orientation of the additional FM electrode. Even when the additional contact is nonmagnetic, nonlocal spin signals can be changed by the spin current leaking into the nonmagnetic electrode. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.4426v3.pdf"}
{"id": "0708.1404", "abstract": "  The existence of an unparticle sector, weakly coupled to the standard model, would have a profound impact on supernova (SN) physics. Emission of energy into the unparticle sector from the core of SN1987A would have significantly shortened the observed neutrino burst. The unparticle interaction with nucleons, neutrinos, electrons and muons is constrained to be so weak that it is unlikely to provide any missing-energy signature at colliders. One important exception are models where scale invariance in the hidden sector is broken by the Higgs vacuum expectation value. In this case the SN emission is suppressed by threshold effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.1404v1.pdf"}
{"id": "0708.3197", "abstract": "  First results from a fully self-consistent, temperature-dependent equation of state that spans the whole density range of neutron stars and supernova cores are presented. The equation of state (EoS) is calculated using a mean-field Hartree-Fock method in three dimensions (3D). The nuclear interaction is represented by the phenomenological Skyrme model in this work, but the EoS can be obtained in our framework for any suitable form of the nucleon-nucleon effective interaction. The scheme we employ naturally allows effects such as (i) neutron drip, which results in an external neutron gas, (ii) the variety of exotic nuclear shapes expected for extremely neutron heavy nuclei, and (iii) the subsequent dissolution of these nuclei into nuclear matter. In this way, the equation of state is calculated across phase transitions without recourse to interpolation techniques between density regimes described by different physical models. EoS tables are calculated in the wide range of densities, temperature and proton/neutron ratios on the ORNL NCCS XT3, using up to 2000 processors simultaneously. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.3197v1.pdf"}
{"id": "0709.0135", "abstract": "  Variations in the solar wind density introduce variable delays into pulsar timing observations. Current pulsar timing analysis programs only implement simple models of the solar wind, which not only limit the timing accuracy, but can also affect measurements of pulsar rotational, astrometric and orbital parameters. We describe a new model of the solar wind electron density content which uses observations from the Wilcox Solar Observatory of the solar magnetic field. We have implemented this model into the tempo2 pulsar timing package. We show that this model is more accurate than previous models and that these corrections are necessary for high precision pulsar timing applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.0135v1.pdf"}
{"id": "0709.4612", "abstract": "  The wavelet transform modulus maxima (WTMM) used in the singularity analysis of one fractal function is extended to study the fractal correlation of two multifractal functions. The technique is developed in the framework of joint partition function analysis (JPFA) proposed by Meneveau et al. [1] and is shown to be equally effective. In addition, we show that another leading approach developed for the same purpose, namely, relative multifractal analysis, can be considered as a special case of JPFA at a particular parameter setting. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.4612v1.pdf"}
{"id": "0710.2059", "abstract": "  We summarise applications of Dyson-Schwinger equations to the theory and phenomenology of hadrons. Some exact results for pseudoscalar mesons are highlighted with details relating to the U_A(1) problem. We describe inferences from the gap equation relating to the radius of convergence for expansions of observables in the current-quark mass. We recapitulate upon studies of nucleon electromagnetic form factors, providing a comparison of the ln-weighted ratios of Pauli and Dirac form factors for the neutron and proton. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.2059v1.pdf"}
{"id": "0710.3254", "abstract": "  The influence of hydrodynamic interactions on lane formation of oppositely charged driven colloidal suspensions is investigated using Brownian dynamics computer simulations performed on the Rotne-Prager level of the mobility tensor. Two cases are considered, namely sedimentation and electrophoresis. In the latter case the Oseen contribution to the mobility tensor is screened due to the opposite motion of counterions. The simulation results are compared to that resulting from simple Brownian dynamics where hydrodynamic interactions are neglected. For sedimentation, we find that hydrodynamic interactions strongly disfavor laning. In the steady-state of lanes, a macroscopic phase separation of lanes is observed. This is in marked contrast to the simple Brownian case where a finite size of lanes was obtained in the steady-state. For strong Coulomb interactions between the colloidal particles a lateral square lattice of oppositely driven lanes is stable similar to the simple Brownian dynamics. In an electric field, on the other hand, the behavior is found in qualitative and quantitative accordance with the case of neglected hydrodynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.3254v1.pdf"}
{"id": "0710.5441", "abstract": "  Based on signaling process on complex networks, a method for identification community structure is proposed. For a network with n nodes, every node is assumed to be a system which can send, receive, and record signals. Each node is taken as the initial signal source once to inspire the whole network by exciting its neighbors and then the source node is endowed a nd vector which recording the effects of signaling process. So by this process, the topological relationship of nodes on networks could be transferred into the geometrical structure of vectors in nd Euclidian space. Then the best partition of groups is determined by F-statistic and the final community structure is given by Fuzzy C-means clustering method (FCM). This method can detect community structure both in unweighted and weighted networks without any extra parameters. It has been applied to ad hoc networks and some real networks including Zachary Karate Club network and football team network. The results are compared with that of other approaches and the evidence indicates that the algorithm based on signaling process is effective. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.5441v1.pdf"}
{"id": "0710.5721", "abstract": "  The equation of state for radiation is derived in a canonical formulation of the electromagnetic field. This allows one to include correction terms expected from canonical quantum gravity and to infer implications to the universe evolution in radiation dominated epochs. Corrections implied by quantum geometry can be interpreted in physically appealing ways, relating to the conformal invariance of the classical equations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.5721v1.pdf"}
{"id": "0712.3364", "abstract": "  Spin-polarized attractive Fermi gases in one-dimensional (1D) optical lattices are expected to be remarkably good candidates for the observation of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. We model these systems with an attractive Hubbard model with population imbalance. By means of the density-matrix renormalization-group method we compute the pairing correlations as well as the static spin and charge structure factors in the whole range from weak to strong coupling. We demonstrate that pairing correlations exhibit quasi-long range order and oscillations at the wave number expected from FFLO theory. However, we also show by numerically computing the mixed spin-charge static structure factor that charge and spin degrees of freedom appear to be coupled already for small imbalance. We discuss the consequences of this coupling for the observation of the FFLO phase, as well as for the stabilization of the quasi-long range order into long-range order by coupling many identical 1D systems, as in quasi-1D optical lattices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.3364v1.pdf"}
{"id": "0712.3471", "abstract": "  Cles is an evolution code recently developed to produce stellar models meeting the specific requirements of studies in asteroseismology. It offers the users a lot of choices in the input physics they want in their models and its versatility allows them to tailor the code to their needs and implement easily new features. We describe the features implemented in the current version of the code and the techniques used to solve the equations of stellar structure and evolution. A brief account is given of the use of the program and of a solar calibration realized with it. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.3471v1.pdf"}
{"id": "0712.3712", "abstract": "  We show that nuclear motion of Rydberg atoms can be induced by resonant dipole-dipole interactions that trigger the energy transfer between two energetically close Rydberg states. How and if the atoms move depends on their initial arrangement as well as on the initial electronic excitation. Using a mixed quantum/classical propagation scheme we obtain the trajectories and kinetic energies of atoms, initially arranged in a regular chain and prepared in excitonic eigenstates. The influence of off-diagonal disorder on the motion of the atoms is examined and it is shown that irregularity in the arrangement of the atoms can lead to an acceleration of the nuclear dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.3712v1.pdf"}
{"id": "0801.3042", "abstract": "  Collaborative beamforming enables nodes in a wireless network to transmit a common message over long distances in an energy efficient fashion. However, the process of making available the same message to all collaborating nodes introduces delays. The authors recently proposed a MAC-PHY cross-layer scheme that enables collaborative beamforming with significantly reduced collaboration overhead. The method requires knowledge of node locations and internode channel coefficients. In this paper, the performance of that approach is studied analytically in terms of average beampattern and symbol error probability (SEP) under realistic conditions, i.e., when imperfect channel estimates are used and when there are phase errors in the contributions of the collaborating nodes at the receiver. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.3042v1.pdf"}
{"id": "0801.3903", "abstract": "  A description of mesoscopic fluctuations of the pairing gap in finite-sized quantum systems based on periodic orbit theory is presented. The size of the fluctuations are found to depend on quite general properties. We distinguish between systems where corresponding classical motion is regular or chaotic, and describe in detail fluctuations of the BCS gap as a function of the size of the system. The theory is applied to different mesoscopic systems: atomic nuclei, metallic grains, and ultracold fermionic gases. We also present a detailed description of pairing gap variation with particle number for nuclei based on a deformed cavity potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.3903v1.pdf"}
{"id": "0801.4915", "abstract": "  Observations with the Hinode space observatory led to the discovery of predominantly horizontal magnetic fields in the photosphere of the quiet internetwork region. Here we investigate realistic numerical simulations of the surface layers of the Sun with respect to horizontal magnetic fields and compute the corresponding polarimetric response in the Fe I 630 nm line pair. We find a local maximum in the mean strength of the horizontal field component at a height of around 500 km in the photosphere, where it surpasses the vertical component by a factor of 2.0 or 5.6, depending on the initial and boundary conditions. From the synthesized Stokes profiles we derive a mean horizontal field component that is, respectively, 1.6 and 4.3 times stronger than the vertical component. This is a consequence of both the intrinsically stronger flux density of, and the larger area occupied by the horizontal fields. We find that convective overshooting expels horizontal fields to the upper photosphere, making the Poynting flux positive in the photosphere, while this quantity is negative in the convectively unstable layer below it. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.4915v3.pdf"}
{"id": "0802.1191", "abstract": "  The application of multi-wavelength selection techniques is crucial for discovering a complete and unbiased set of Active Galactic Nuclei (AGNs). Here, we select a sample of 72 AGN candidates in the Extended Groth Strip (EGS) using deep radio and mid-infrared data from the Very Large Array (VLA) and the Spitzer Space Telescope, and analyze their properties across other wavelengths. Only 30", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.1191v1.pdf"}
{"id": "0802.1627", "abstract": "  We study neutrino induced one-pion production off the nucleon in and around the Delta resonance region. Apart from the Delta-pole mechanism we include background terms required by chiral symmetry. These background terms give sizeable contributions in all channels. To better reproduce the ANL q^2-differential cross section data, we make a new fit of the C_5^A(q^2) axial nucleon to Delta form factor. The new result C_5^A(0)=0.867± 0.075 is some 30", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.1627v1.pdf"}
{"id": "0802.1937", "abstract": "  We investigate the effects of scalar and vector unparticles on top quark spin correlations via the process e^+e^-→ t t̅. In addition to the Standard Model diagrams, there is a new contribution to top-antitop quark production process mediated by unparticle in the s-channel. It is shown that scalar and vector unparticle contribution leads to a considerable deviation of the top spin correlations from the Standard Model one. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.1937v1.pdf"}
{"id": "0802.2666", "abstract": "  In this paper, we give a distributed joint source channel coding scheme for arbitrary correlated sources for arbitrary point in the Slepian-Wolf rate region, and arbitrary link capacities using LDPC codes. We consider the Slepian-Wolf setting of two sources and one destination, with one of the sources derived from the other source by some correlation model known at the decoder. Distributed encoding and separate decoding is used for the two sources. We also give a distributed source coding scheme when the source correlation has memory to achieve any point in the Slepian-Wolf rate achievable region. In this setting, we perform separate encoding but joint decoding. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.2666v1.pdf"}
{"id": "0802.4025", "abstract": "  Here I review recent work, by other authors and by myself, on some particular topics related to the regular and chaotic motion in elliptical galaxies. I show that it is quite possible to build highly stable triaxial stellar systems that include large fractions of chaotic orbits and that partially and fully chaotic orbits fill different regions of space, so that it is important not to group them together under the single denomination of chaotic orbits. Partially chaotic orbits should not be confused with weakly fully chaotic orbits either, and their spatial distributions are also different. Slow figure rotation (i.e., rotation in systems with zero angular momentum) seems to be always present in highly flattened models that result from cold collapses, with the rotational velocity diminishing or becoming negligibly small for less flattened models. Finally, I comment on the usefulness and limitation of the classification of regular orbits via frequency analysis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.4025v1.pdf"}
{"id": "0803.0232", "abstract": "  We assume that the noncommutativity starts to be visible continuously from a scale Λ_NC. According to this assumption, a two-loop effective action is derived for noncommutative ϕ^4 and ϕ^3 theories from a Wilsonian point of view. We show that these effective theories are free of UV/IR mixing phenomena. We also investigate the positivity constraint on coefficients of higher dimension operators present in the effective theory. This constraint makes the low energy theory to be UV completion of a full theory. Finally, we discuss noncommutativity and extra dimensions. In our effective theories formulated on noncommutative extra dimensions, if the campactification scale Λ_c is less than the scale Λ_NC, the theory will not suffer from UV/IR mixing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.0232v1.pdf"}
{"id": "0803.0996", "abstract": "  A sequential fourth generation of quarks and leptons is allowed by precision electroweak constraints if the mass splitting between the heavy quarks is between 50 and 80 GeV. Although heavy quarks can be easily detected at the LHC, it is very difficult to detect a sequential heavy charged lepton, L, due to large backgrounds. Should the L mass be above 250 GeV, it can not be pair-produced at a 500 GeV ILC. We calculate the cross section for the one-loop process e+e- -> L tau. Although the cross section is small, it may be detectable. We also consider contributions from the two Higgs doublet model and the Randall-Sundrum model, in which case the cross section can be substantially higher. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.0996v1.pdf"}
{"id": "0804.3460", "abstract": "  Oxygen vacancies at the SnO2(110) and (101) surface and subsurface sites have been studied in the framework of density functional theory by using both all-electron Gaussian and pseudopotential plane-wave methods. The all-electron calculations have been performed using the B3LYP exchange-correlation functional with accurate estimations of energy gaps and density of states. We show that bulk oxygen vacancies are responsible for the appearance of a fully occupied flat energy level lying at about 1 eV above the top valence band, and an empty level resonant with the conduction band. Surface oxygen vacancies strongly modify the surface band structures with the appearance of intragap states covering most of the forbidden energy window, or only a small part of it, depending on the vacancy depth from the surface. Oxygen vacancies can account for electron affinity variations with respect to the stoichiometric surfaces as well. A significant support to the present results is found by comparing them to the available experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.3460v2.pdf"}
{"id": "0805.0255", "abstract": "  Developing a theoretical framework to access quantum phases of itinerant bosons or fermions in two dimensions (2D) that exhibit singular structure along surfaces in momentum space but have no quasi-particle description remains as a central challenge in the field of strongly correlated physics. In this paper we propose that distinctive signatures of such 2D strongly correlated phases will be manifest in quasi-one-dimensional \"N-leg ladder\" systems. Characteristic of each parent 2D quantum liquid would be a precise pattern of 1D gapless modes on the N-leg ladder. These signatures could be potentially exploited to approach the 2D phases from controlled numerical and analytical studies in quasi-1D. As a first step we explore itinerant boson models with a frustrating ring exchange interaction on the 2-leg ladder, searching for signatures of the recently proposed two-dimensional d-wave correlated Bose liquid (DBL) phase. A combination of exact diagonalization, density matrix renormalization group, variational Monte Carlo, and bosonization analysis of a quasi-1D gauge theory, all provide compelling evidence for the existence of a new strong-coupling phase of bosons on the 2-leg ladder which can be understood as a descendant of the two-dimensional DBL. We suggest several generalizations to quantum spin and electron Hamiltonians on ladders which could likewise reveal fingerprints of such 2D non-Fermi liquid phases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.0255v1.pdf"}
{"id": "0805.1334", "abstract": "  In this paper spatial correlations of parallel edge dislocations are studied. After closing a hierarchy of equations for the many-particle density functions by the Kirkwood superposition approximation, we derive evolution equations for the correlation functions. It is found that these resulting equations and those governing the evolution of density fields of total as well as geometrically necessary dislocations around a single edge dislocation are formally the same. The second case corresponds to the already described phenomenon of Debye screening of an individual dislocation. This equivalence of the correlation functions and screened densities is demonstrated also by discrete dislocation dynamics simulation results, which confirm the physical correctness of the applied Kirkwood superposition approximation. Relation of this finding and the linear response theory in thermal systems is also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.1334v2.pdf"}
{"id": "0805.3298", "abstract": "  Blue Compact Dwarf (BCD) galaxies are metal poor systems going through a major starburst that cannot last for long. We have identified galaxies which may be BCDs during quiescence (QBCD), i.e., before the characteristic starburst sets in or when it has faded away. These QBCD galaxies are assumed to be like the BCD host galaxies. The SDSS/DR6 database provides  21500 QBCD candidates. We also select from SDSS/DR6 a complete sample of BCD galaxies to serve as reference. The properties of these two galaxy sets have been computed and compared. The QBCD candidates are thirty times more abundant than the BCDs, with their luminosity functions being very similar except for the scaling factor, and the expected luminosity dimming associated with the end of the starburst. QBCDs are redder than BCDs, and they have larger HII region based oxygen abundance. QBCDs also have lower surface brightness. The BCD candidates turn out to be the QBCD candidates with the largest specific star formation rate (actually, with the largest H_alpha equivalent width). One out of each three dwarf galaxies in the local universe may be a QBCD. The properties of the selected BCDs and QBCDs are consistent with a single sequence in galactic evolution, with the quiescent phase lasting thirty times longer than the starburst phase. The resulting time-averaged star formation rate is low enough to allow this cadence of BCD – QBCD phases during the Hubble time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.3298v1.pdf"}
{"id": "0805.3499", "abstract": "  We present maps of seven sources selected from Klaassen     Wilson (2007a) in SiO (J=8-7) and HCO^+ and H^13CO^+ (J=4-3) which were obtained using HARP-B on the James Clerk Maxwell Telescope. We find that four out of our seven sources have infall signatures based on their HCO^+ emission profiles. From our maps, we have determined the extent of both the outflowing and infalling regions towards these sources, and constrained the amount of infalling and outflowing mass as well as the mass infall rate for each massive star forming region. From our SiO observations, we estimate the source luminosity required to shock the surroundings of these massive star forming regions and find luminosities similar to those of the HII regions themselves. We find that the ratio between our infall and outflow masses is less than one, suggesting high mass entrainment rates in the molecular outflows. We also find that the large scale molecular infall rate towards G10.6-0.4 is comparable to the small scale molecular infall rate found in previous studies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.3499v1.pdf"}
{"id": "0805.4381", "abstract": "  Dielectronic recombination (DR) of few-electron ions has evolved into a sensitive spectroscopic tool for highly charged ions. This is due to technological advances in electron-beam preparation and ion-beam cooling techniques at heavy-ion storage rings. Recent experiments prove unambiguously that DR collision spectroscopy has become sensitive to 2nd order QED and to nuclear effects. This review discusses the most recent developments in high-resolution spectroscopy of low-energy DR resonances, experimental studies of KLL DR of very heavy hydrogenlike ions, isotope shift measurements of DR resonances, and the experimental determination of hyperfine induced decay rates in divalent ions utilizing DR. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.4381v2.pdf"}
{"id": "0806.0199", "abstract": "  A two-dimensional (2D) shock-rest-frame model for particle simulations is developed. Then full kinetic dynamics of a perpendicular collisionless shock is examined by means of a 2D full particle simulation. We found that in the 2D simulation there are fewer nonthermal electrons due to surfing acceleration which was seen in the previous 1D simulations of a high Mach number perpendicular shock in a low-beta and weakly magnetized plasma. This is because the particle motion along the ambient magnetic field disturbs the formation of coherent electrostatic solitary structures which is necessary for electron surfing acceleration. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.0199v2.pdf"}
{"id": "0806.1386", "abstract": "  Massive star clusters observed in galaxy mergers are often suggested to be progenitors of globular clusters. To study this hypothesis, we performed the highest resolution simulation of a gas-rich galaxy merger so far. The formation of massive star clusters of 10^5 to 10^7 Mo, triggered by the galaxy interaction, is directly resolved in this model. We show that these clusters are tightly bound structures with little net rotation, due to evolve into compact long-lived stellar systems. Massive clusters formed in galaxy mergers are thus robust candidates for progenitors of long-lived globular clusters. The simulated cluster mass spectrum is consistent with theory and observations. Tidal dwarf galaxies of 10^8-9 Mo can form at the same time, and appear to be part of a different class of objects, being more extended and rotating. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.1386v1.pdf"}
{"id": "0806.2639", "abstract": "  We present new Spitzer Space Telescope observations of stars in the young  5 Myr gamma Velorum stellar cluster. Combining optical and 2MASS photometry, we have selected 579 stars as candidate members of the cluster. With the addition of the Spitzer mid-infrared data, we have identified 5 debris disks around A-type stars, and 5-6 debris disks around solar-type stars, indicating that the strong radiation field in the cluster does not completely suppress the production of planetesimals in the disks of cluster members. However, we find some evidence that the frequency of circumstellar primordial disks is lower, and the IR flux excesses are smaller than for disks around stellar populations with similar ages. This could be evidence for a relatively fast dissipation of circumstellar dust by the strong radiation field from the highest mass star(s) in the cluster. Another possibility is that gamma Velorum stellar cluster is slightly older than reported ages and the the low frequency of primordial disks reflects the fast disk dissipation observed at  5 Myr. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.2639v1.pdf"}
{"id": "0807.2146", "abstract": "  The connection between the Hamilton and the standard Lagrange formalism is established for a generic Quantum Field Theory with vanishing vacuum expectation values of the fundamental fields. The Effective Actions in both formalisms are the same if and only if the fundamental fields and the momentum fields are related by the stationarity condition. These momentum fields in general differ from the canonical fields as defined via the Effective Action. By means of functional methods a systematic procedure is presented to identify the full correlation functions, which depend on the momentum fields, as functionals of those usually appearing in the standard Lagrange formalism. Whereas Lagrange correlation functions can be decomposed into tree diagrams the decomposition of Hamilton correlation functions involves loop corrections similar to those arising in n-particle effective actions. To demonstrate the method we derive for theories with linearized interactions the propagators of composite auxiliary fields and the ones of the fundamental degrees of freedom. The formalism is then utilized in the case of Coulomb gauge Yang-Mills theory for which the relations between the two-point correlation functions of the transversal and longitudinal components of the conjugate momentum to the ones of the gauge field are given. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.2146v2.pdf"}
{"id": "0807.3949", "abstract": "  The surface magnetic phase transition of a double-exchange model for metallic manganites is studied using a Schwinger-boson mean-field method. About three unit-cells wide surface layers are identified. The magnetic moment in these layers decreases more rapidly than that in the bulk when the temperature is increased. This behavior is consistent with experimental observations. We also discuss the implication of this behavior on the tunneling magnetoresistance effect using manganites and possible improvement of the magnetoresistance effect near the bulk Curie temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.3949v2.pdf"}
{"id": "0809.2122", "abstract": "  A scheme to reduce translational noninvariant quasi-one-dimensional wave guides into singly or multiply connected one-dimensional (1D) lines is proposed. It is meant to simplify the analysis of wave guides, with the low-energy properties of the guides preserved. Guides comprising uniform-cross-sectional sections and discontinuities such as bends and branching junctions are considered. The uniform sections are treated as 1D lines, and the discontinuities are described by equations sets connecting the wave functions on the lines. The procedures to derive the equations and to solve reduced systems are illustrated by examples, and the scheme is found to apply when the discontinuities are distant and the energy is low. When the scheme applies, it may substantially simplify the analysis of a wave guide, and hence the scheme may find uses in the study of related problems, such as quantum wire networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.2122v1.pdf"}
{"id": "0809.2219", "abstract": "  We determine the phase diagrams of conservative diffusive contact processes by means of numerical simulations. These models are versions of the ordinary diffusive single-creation, pair-creation and triplet-creation contact processes in which the particle number is conserved. The transition between the frozen and active states was determined by studying the system in the subcritical regime and the nature of the transition, whether continuous or first order, was determined by looking at the fractal dimension of the critical cluster. For the single-creation model the transition remains continuous for any diffusion rate. For pair- and triplet-creation models, however, the transition becomes first order for high enough diffusion rate. Our results indicate that in the limit of infinite diffusion rate the jump in density equals 2/3 for the pair-creation model and 5/6 for the triplet-creation model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.2219v1.pdf"}
{"id": "0809.4240", "abstract": "  We are designing an all-scintillator Compton gamma imager for use in security investigations and remediation actions involving radioactive threat material. To satisfy requirements for a rugged and portable instrument, we have chosen solid scintillator for the active volumes of both the scatter and absorber detectors. Using the BEAMnrc/EGSnrc Monte Carlo simulation package, we have constructed models using four different materials for the scatter detector: LaBr_3, NaI, CaF_2 and PVT. We have compared the detector performances using angular resolution, efficiency, and image resolution. We find that while PVT provides worse performance than that of the detectors based entirely on inorganic scintillators, all of the materials investigated for the scatter detector have the potential to provide performance adequate for our purposes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.4240v2.pdf"}
{"id": "0809.4792", "abstract": "  We study social cost losses in Facility Location games, where n selfish agents install facilities over a network and connect to them, so as to forward their local demand (expressed by a non-negative weight per agent). Agents using the same facility share fairly its installation cost, but every agent pays individually a (weighted) connection cost to the chosen location. We study the Price of Stability (PoS) of pure Nash equilibria and the Price of Anarchy of strong equilibria (SPoA), that generalize pure equilibria by being resilient to coalitional deviations. A special case of recently studied network design games, Facility Location merits separate study as a classic model with numerous applications and individual characteristics: our analysis for unweighted agents on metric networks reveals constant upper and lower bounds for the PoS, while an O(ln n) upper bound implied by previous work is tight for non-metric networks. Strong equilibria do not always exist, even for the unweighted metric case. We show that e-approximate strong equilibria exist (e=2.718...). The SPoA is generally upper bounded by O(ln W) (W is the sum of agents' weights), which becomes tight Θ(ln n) for unweighted agents. For the unweighted metric case we prove a constant upper bound. We point out several challenging open questions that arise. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.4792v3.pdf"}
{"id": "0809.5161", "abstract": "  It has recently been discovered that for certain rates of mode-exchange collisions analytic solutions can be found for a Hamiltonian describing the two-mode Bose-Einstein condensate. We proceed to study the behavior of the system using perturbation theory if the coupling constants only approximately match these parameter constraints. We find that the model is robust to such perturbations. We study the effects of degeneracy on the perturbations and find that the induced changes differ greatly from the non-degenerate case. We also model inelastic collisions that result in particle loss or condensate decay as external perturbations and use this formalism to examine the effects of three-body recombination and background collisions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.5161v1.pdf"}
{"id": "0810.0739", "abstract": "  We report a numerical study of self-avoiding polymers on the square lattice, including an attractive potential between nonconsecutive monomers. Using Wang-Landau sampling (WLS) with adaptive windows, we obtain the density of states for chains of up to N=300 monomers and associated thermodynamic quantities. The method enables one to simulate accurately the low-temperature regime, which is virtually inaccessible using traditional methods. Instead of defining fixed energy windows, as in usual WLS, this method uses windows with boundaries that depend on the set of energy values on which the histogram is flat at a given stage of the simulation. Shifting the windows each time the modification factor f is reduced, we eliminate border effects that arise in simulations using fixed windows. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.0739v1.pdf"}
{"id": "0810.1871", "abstract": "  The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is the first interferometer dedicated to studying the cosmic microwave background (CMB) radiation at 3mm wavelength. The choice of 3mm was made to minimize the contributions from foreground synchrotron radiation and Galactic dust emission. The initial configuration of seven 0.6m telescopes mounted on a 6-m hexapod platform was dedicated in October 2006 on Mauna Loa, Hawaii. Scientific operations began with the detection of a number of clusters of galaxies via the thermal Sunyaev-Zel'dovich effect. We compare our data with Subaru weak lensing data in order to study the structure of dark matter. We also compare our data with X-ray data in order to derive the Hubble constant. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.1871v2.pdf"}
{"id": "0810.3252", "abstract": "  The INTEGRAL Optical Monitoring Camera, OMC, has detected many high energy sources. We have obtained V-band fluxes and light curves for their counterparts. In the cases of previously unknown counterparts, we have searched for characteristic variations in optical sources around the high-energy target position. Results about the Galactic Bulge Monitoring, INTEGRAL Gamma-Ray sources (IGR), and other high energy sources are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.3252v1.pdf"}
{"id": "0810.4073", "abstract": "  The Generalized Coherent State Model, proposed previously for a unified description of magnetic and electric collective properties of nuclear systems, is used to study the ground state band charge density as well as the E0 transitions from 0^+_β to 0^+_g. The influence of the nuclear deformation and of angular momentum projection on the charge density is investigated. The monopole transition amplitude has been calculated for ten nuclei. The results are compared with some previous theoretical studies and with the available experimental data. Our results concerning angular momentum projection are consistent with those of previous microscopic calculations for the ground state density. The calculations for the E0 transitions agree quite well with the experimental data. Issues like how the shape transitions or shape coexistence are reflected in the ρ(E0) behavior are also addressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.4073v1.pdf"}
{"id": "0810.5324", "abstract": "  For some years now, we have been gathering optical spectra of DA white dwarfs in an effort to study and define the empirical ZZ Ceti instability strip. However, we have recently expanded this survey to include all the DA white dwarfs in the McCook     Sion catalog down to a limiting visual magnitude of V=17.5. We present here a spectroscopic analysis of over 1000 DA white dwarfs from this ongoing survey. We have several specific areas of interest most notably the hot DAO white dwarfs, the ZZ Ceti instability strip, and the DA+dM binary systems. Furthermore, we present a comparison of the ensemble properties of our sample with those of other large surveys of DA white dwarfs, paying particular attention to the distribution of mass as a function of effective temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.5324v1.pdf"}
{"id": "0811.0293", "abstract": "  The parameter fit from a model grid is limited by our capability to reduce the number of models, taking into account the number of parameters and the non linear variation of the models with the parameters. The Local MultiLinear Regression (LMLR) algorithms allow one to fit linearly the data in a local environment. The MATISSE algorithm, developed in the context of the estimation of stellar parameters from the Gaia RVS spectra, is connected to this class of estimators. A two-steps procedure was introduced. A raw parameter estimation is first done in order to localize the parameter environment. The parameters are then estimated by projection on specific vectors computed for an optimal estimation. The MATISSE method is compared to the estimation using the objective analysis. In this framework, the kernel choice plays an important role. The environment needed for the parameter estimation can result from it. The determination of a first parameter set can be also avoided for this analysis. These procedures based on a local projection can be fruitfully applied to non linear parameter estimation if the number of data sets to be fitted is greater than the number of models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.0293v1.pdf"}
{"id": "0812.0398", "abstract": "  Following novel development and adaptation of the Metric Space Technique (MST), a multi-scale morphological analysis of the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) was performed. The technique was adapted to perform a space-scale morphological analysis by filtering the galaxy point distributions with a smoothing Gaussian function, thus giving quantitative structural information on all size scales between 5 and 250 Mpc. The analysis was performed on a dozen slices of a volume of space containing many newly measured galaxies from the SDSS DR5 survey. Using the MST, observational data were compared to galaxy samples taken from N-body simulations with current best estimates of cosmological parameters and from random catalogs. By using the maximal ranking method among MST output functions we also develop a way to quantify the overall similarity of the observed samples with the simulated samples. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.0398v3.pdf"}
{"id": "0812.1937", "abstract": "  A meaning is given to the state of a system that is consistent with the trans-coordinate physics previously proposed by the author. The collapse of such a state is described using the previously proposed q-rules. A Hamiltonian is defined for these states and it is shown that their square modulus is conserved. Keywords: invariance, state reduction, wave collapse. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.1937v7.pdf"}
{"id": "0901.1415", "abstract": "  Feynman's \"no-node\" theorem states that the conventional many-body ground-state wavefunctions of bosons in the coordinate representation is positive-definite. This implies that time-reversal symmetry cannot be spontaneously broken. In this article, we review our progress in studying a class of new states of unconventional Bose-Einstein condensations beyond this paradigm. These states can either be the long-lived metal-stable states of ultra-cold bosons in high orbital bands in optical lattices as a result of the \"orbital-Hund's rule\" interaction, or the ground states of spinful bosons with spin-orbit coupling linearly dependent on momentum. In both cases, Feynman's argument does not apply. The resultant many-body wavefunctions are complex-valued and thus break time-reversal symmetry spontaneously. Exotic phenomena in these states include the Bose-Einstein condensation at non-zero momentum, the ordering of orbital angular momentum moments, the half-quantum vortex, and the spin texture of skyrmions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.1415v2.pdf"}
{"id": "0901.1628", "abstract": "  We study the effectiveness of stationary-phase approximated post-Newtonian waveforms currently used by ground-based gravitational-wave detectors to search for the coalescence of binary black holes by comparing them to an accurate waveform obtained from numerical simulation of an equal-mass non-spinning binary black hole inspiral, merger and ringdown. We perform this study for the Initial- and Advanced-LIGO detectors. We find that overlaps between the templates and signal can be improved by integrating the match filter to higher frequencies than used currently. We propose simple analytic frequency cutoffs for both Initial and Advanced LIGO, which achieve nearly optimal matches, and can easily be extended to unequal-mass, spinning systems. We also find that templates that include terms in the phase evolution up to 3.5 pN order are nearly always better, and rarely significantly worse, than 2.0 pN templates currently in use. For Initial LIGO we recommend a strategy using templates that include a recently introduced pseudo-4.0 pN term in the low-mass (M ≤ 35) region, and 3.5 pN templates allowing unphysical values of the symmetric reduced mass η above this. This strategy always achieves overlaps within 0.3", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.1628v2.pdf"}
{"id": "0901.2113", "abstract": "  We present high resolution simulations on the impact of ionizing radiation of massive O-stars on the surrounding turbulent interstellar medium (ISM). The simulations are performed with the newly developed software iVINE which combines ionization with smoothed particle hydrodynamics (SPH) and gravitational forces. We show that radiation from hot stars penetrates the ISM, efficiently heats cold low density gas and amplifies over-densities seeded by the initial turbulence. The formation of observed pillar-like structures in star forming regions (e.g. in M16) can be explained by this scenario. At the tip of the pillars gravitational collapse can be induced, eventually leading to the formation of low mass stars. Detailed analysis of the evolution of the turbulent spectra shows that UV-radiation of O-stars indeed provides an excellent mechanism to sustain and even drive turbulence in the parental molecular cloud. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.2113v2.pdf"}
{"id": "0901.3335", "abstract": "  Quantum optics with quantum gases represents a new field, where the quantum nature of both light and ultracold matter plays equally important role. Only very recently this ultimate quantum limit of light-matter interaction became feasible experimentally. In traditional quantum optics, the cold atoms are considered classically, whereas, in quantum atom optics, the light is used as an essentially classical axillary tool. On the one hand, the quantization of optical trapping potentials can significantly modify many-body dynamics of atoms, which is well-known only for classical potentials. On the other hand, atomic fluctuations can modify the properties of the scattered light. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.3335v1.pdf"}
{"id": "0902.2069", "abstract": "  The made-to-measure N-body method (Syer     Tremaine 1996) slowly adapts the particle weights of an N-body model, whilst integrating the trajectories in an assumed static potential, until some constraints are satisfied, such as optimal fits to observational data. I propose a novel technique for this adaption procedure, which overcomes several limitations and shortcomings of the original method. The capability of the new technique is demonstrated by generating realistic N-body equilibrium models for dark-matter haloes with prescribed density profile, triaxial shape, and slowly outwardly growing radial velocity anisotropy ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.2069v1.pdf"}
{"id": "0902.2200", "abstract": "  We derive the extension of the Hubbard model to include Rashba spin-orbit coupling that correctly describes Aharonov-Bohm and Aharonov-Casher phases in a ring under applied magnetic and electric fields. When the ring is connected to conducting leads, we develop a formalism that is able to describe both, Kondo and interference effects. We find that in the Kondo regime, the spin-orbit coupling reduces strongly the conductance from the unitary limit. This effect in combination with the magnetic flux, can be used to produce spin polarized carriers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.2200v1.pdf"}
{"id": "0902.3687", "abstract": "  We investigate the conductance statistics of a quantum-chaotic dot–a normal-metal grain–with a superconducting lead attached to it. The cases of one and two normal leads additionally attached to the dot are studied. For these two configurations the complete distribution of the conductance is calculated, within the framework of random matrix theory, as a function of the transparency parameter of the Schottky barrier formed at the interface of the normal-metal and superconducting regions. Our predictions are verified by numerical simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.3687v2.pdf"}
{"id": "0903.3153", "abstract": "  The creation of single collective excitations in atomic ensembles via spontaneous Raman emission plays a key role in several quantum communication protocols, starting with the seminal DLCZ protocol [L.-M.Duan, M.D. Lukin, J.I. Cirac, and P. Zoller, Nature 414, 413 (2001).] This process is usually analyzed theoretically under the assumptions that the write laser pulse inducing the Raman transition is far off-resonance, and that the atomic ensemble is only homogeneously broadened. Here we study the impact of near-resonance excitation for inhomogeneously broadened ensembles on the collective character of the created atomic excitation. Our results are particularly relevant for experiments with hot atomic gases and for potential future solid-state implementations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.3153v1.pdf"}
{"id": "0903.5067", "abstract": "  We present a comparative study of two computer simulation methods to obtain static and dynamic properties of dilute polymer solutions. The first approach is a recently established hybrid algorithm based upon dissipative coupling between Molecular Dynamics and lattice Boltzmann (LB), while the second is standard Brownian Dynamics (BD) with fluctuating hydrodynamic interactions. Applying these methods to the same physical system (a single polymer chain in a good solvent in thermal equilibrium) allows us to draw a detailed and quantitative comparison in terms of both accuracy and efficiency. It is found that the static conformations of the LB model are distorted when the box length L is too small compared to the chain size. Furthermore, some dynamic properties of the LB model are subject to an L^-1 finite size effect, while the BD model directly reproduces the asymptotic L →∞ behavior. Apart from these finite size effects, it is also found that in order to obtain the correct dynamic properties for the LB simulations, it is crucial to properly thermalize all the kinetic modes. Only in this case, the results are in excellent agreement with each other, as expected. Moreover, Brownian Dynamics is found to be much more efficient than lattice Boltzmann as long as the degree of polymerization is not excessively large. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.5067v2.pdf"}
{"id": "0905.0241", "abstract": "  We construct a dark energy model where a scalar field non-minimally coupled to gravity plays the role of the dark component. We compare cosmological consequences of this non-minimal coupling of the scalar field and gravity in the spirit of the dark energy paradigm in Jordan and Einstein frames. Some important issues such as phantom divide line crossing, existence of the bouncing solutions and the stability of the solutions are compared in these two frames. We show that while a non-minimally coupled scalar field in the Jordan frame is a suitable dark energy component with capability to realize phantom divide line crossing, its conformal transformation in the Einstein frame has not this capability. The conformal transformation from Jordan frame to Einstein frame transforms the equation of state parameter of the dark energy component to its minimal form with a redefined scalar field and in this case it is impossible to realize a phantom phase with possible crossing of the phantom divide line. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.0241v1.pdf"}
{"id": "0905.0657", "abstract": "  We derive on the level of quantum optics expressions for the uncertainty of the photocount in a multi-mode multi-frequency setup. The result depends on the quantum correlations of the individual modes and the frequency spectrum of the radiation, the latter leading to a frequency beating sometimes referred to as dynamic laser speckle. When the mode structure of the radiation field is disturbed between source and detector, another contribution to the photocount uncertainty referred to as static speckle appears. To predict the size of this effect, we present a suitable definition of the etendue (or phase space volume) that links the number of modes of a radiation field to macroscopic quantities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.0657v1.pdf"}
{"id": "0906.0452", "abstract": "  Here we show that variations of temperature, even of a few degrees in amplitude, induce the ageing of a granular pile. In particular, we report measurements of physical properties of a granular heap submitted to thermal cycles. Namely, we focus on the evolution of the thermal linear-expansion coefficient and of the thermal conductivity of the pile with the number of cycles. The present contribution nicely supplements a recent article we published elsewhere [Phys. Rev. Lett. 101, 148303 (2008)] and introduces a different and promising method to impose temperature cycles to a granular pile. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.0452v1.pdf"}
{"id": "0906.0913", "abstract": "  We present three-dimensional solutions of the magnetohydrostatic equations in the co-rotating frame of reference outside a magnetized rigidly rotating cylinder. We make no symmetry assumption for the magnetic field, but to be able to make analytical progress we neglect outflows and specify a particular form for the current density. The magnetohydrostatic equations can then be reduced to a single linear partial differential equation for a pseudo-potential U, from which the magnetic field can be calculated by differentiation. The equation for U can be solved by standard methods. The solutions can also be used to determine the plasma pressure, density and temperature as functions of all three spatial coordinates. Despite the obvious limitations of this approach, it can for example be used as a simple tool to create three-dimensional models for the closed field line regions of rotating magnetospheres without rotational symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.0913v1.pdf"}
{"id": "0906.1005", "abstract": "  We review recent numerical work investigating the equilibrium phase diagram, and the dynamics, of the cholesteric blue phases. In equilibrium numerical results confirm the predictions of the classic analytical theories, and extend them to incorporate different values of the elastic constants, or the effects of an applied electric field. There is a striking increase in the stability of blue phase I in systems where the cholesteric undergoes helical sense inversion, and the anomalous electrostriction observed in this phase is reproduced. Solving the equations of motion allows us to present results for the phase transition kinetics of blue phase I under dielectric or flexoelectric coupling to an applied electric field. We also present simulations of the blue phases in a flow field, showing how the disclination network acts to oppose the flow. The results are based on the Landau-de Gennes exapnsion of the liquid crystal free energy: that such a simple and elegant theory can predict such complex and subtle physical behaviour is remarkable. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.1005v1.pdf"}
{"id": "0906.1277", "abstract": "  When a plane shock hits a wedge head on, it experiences a reflection-diffraction process, and then a self-similar reflected shock moves outward as the original shock moves forward in time. The complexity of reflection-diffraction configurations was first reported by Ernst Mach in 1878, and experimental, computational, and asymptotic analysis has shown that various patterns of shock reflection-diffraction configurations may occur, including regular reflection and Mach reflection. In this paper we start with various shock reflection-diffraction phenomena, their fundamental scientific issues, and their theoretical roles as building blocks and asymptotic attractors of general solutions in the mathematical theory of multidimensional hyperbolic systems of conservation laws. Then we describe how the global problem of shock reflection-diffraction by a wedge can be formulated as a free boundary problem for nonlinear conservation laws of mixed-composite hyperbolic-elliptic type. Finally we discuss some recent developments in attacking the shock reflection-diffraction problem, including the existence, stability, and regularity of global regular reflection-diffraction solutions. The approach includes techniques to handle free boundary problems, degenerate elliptic equations, and corner singularities, which is highly motivated by experimental, computational, and asymptotic results. Further trends and open problems in this direction are also addressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.1277v1.pdf"}
{"id": "0906.1535", "abstract": "  We introduce a general range of science drivers for using the Virtual Observatory (VO) and identify some common aspects to these as well as the advantages of VO data access. We then illustrate the use of existing VO tools to tackle multi wavelength science problems. We demonstrate the ease of multi mission data access using the VOExplorer resource browser, as provided by AstroGrid (http://www.astrogrid.org) and show how to pass the various results into any VO enabled tool such as TopCat for catalogue correlation. VOExplorer offers a powerful data-centric visualisation for browsing and filtering the entire VO registry using an iTunes type interface. This allows the user to bookmark their own personalised lists of resources and to run tasks on the selected resources as desired. We introduce an example of how more advanced querying can be performed to access existing X-ray cluster of galaxies catalogues and then select extended only X-ray sources as candidate clusters of galaxies in the 2XMMi catalogue. Finally we introduce scripted access to VO resources using python with AstroGrid and demonstrate how the user can pass on the results of such a search and correlate with e.g. optical datasets such as Sloan. Hence we illustrate the power of enabling large scale data mining of multi wavelength resources in an easily reproducible way using the VO. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.1535v1.pdf"}
{"id": "0906.1933", "abstract": "  The theory of quantum feedback networks has recently been developed with the aim of showing how quantum input-output components may be connected together so as to control, stabilize or enhance the performance of one of the subcomponents. In this paper we show how the degree to which an idealized component (a degenerate parametric amplifier in the strong-coupling regime) can squeeze input fields may be enhanced by placing the component in-loop in a simple feedback mechanism involving a beam splitter. We study the spectral properties of output fields, placing particular emphasis on the elastic and inelastic components of the power density. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.1933v2.pdf"}
{"id": "0906.2490", "abstract": "  Deeply Virtual Compton Scattering (DVCS) in ep collisions has emerged in recent years as a an essential reaction to obtain information on the correlation of partons in the hadron (proton) or on the transverse distribution of these partons. In these proceedings, we examine the lattest data from HERA (at low x_Bj<10^-2) and their impact on models. We analyse in detail what these data imply on the spatial structure of the proton. In particular, the most recent measurements of the Beam Charge Asymmetry by the H1 experiment is discussed in this context. Perspectives are presented for further measurements of DVCS cross sections at CERN, within the COMPASS experiment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.2490v2.pdf"}
{"id": "0906.4139", "abstract": "  In an attempt to look for a viable mechanism leading to a present-day accelerated expansion, we investigate the possibility that the observed cosmic speed up may be recovered in the framework of the Rastall's theory, relying on the non-conservativity of the stress-energy tensor, i.e. T^μ_ν ; μ≠ 0. We derive the modified Friedmann equations and show that they correspond to Cardassian-like equations. We also show that, under suitable assumptions on the equation of state of the matter term sourcing the gravitational field, it is indeed possible to get an accelerated expansion, in agreement with the Hubble diagram of both Type Ia Supernovae (SNeIa) and Gamma Ray Bursts (GRBs). Unfortunately, to achieve such a result one has to postulate a matter density parameter much larger than the typical Ω_M ≃ 0.3 value inferred from cluster gas mass fraction data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.4139v2.pdf"}
{"id": "0906.4229", "abstract": "  We investigate the physical processes in which an electron, upon return to its parent ion, promotes a second electron to an excited state, from which it subsequently tunnels. Employing the strong-field approximation and saddle-point methods, we perform a detailed analysis of the dynamics of the two electrons, in terms of quantum orbits, and delimit constraints for their momentum components parallel to the laser-field polarization. The kinetic energy of the first electron, upon return, exhibits a cutoff slightly lower than 10U_p, where U_p is the ponderomotive energy, as in rescattered above-threshold ionization (ATI). The second electron leaves the excited state in a direct ATI-like process, with the maximal energy of 2U_p. We also compute electron-momentum distributions, whose maxima agree with our estimates and with other methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.4229v1.pdf"}
{"id": "0906.4682", "abstract": "  We study the phase space available to the local stellar distribution using a Galactic potential consistent with several recent observational constraints. We find that the induced phase space structure has several observable consequences. The spiral arm contribution to the kinematic structure in the solar neighborhood may be as important as the one produced by the Galactic bar. We suggest that some of the stellar kinematic groups in the solar neighborhood, like the Hercules structure and the kinematic branches, can be created by the dynamical resonances of self-gravitating spiral arms and not exclusively by the Galactic bar. A structure coincident with the Arcturus kinematic group is developed when a hot stellar disk population is considered, which introduces a new perspective on the interpretation of its extragalactic origin. A bar-related resonant mechanism can modify this kinematic structure.We show that particles in the dark matter disk-like structure predicted by recent LCDM galaxy formation experiments, with similar kinematics to the thick disk, are affected by the same resonances, developing phase space structures or dark kinematic groups that are independent of the Galaxy assembly history and substructure abundance. We discuss the possibility of using the stellar phase space groups as constraints to non-axisymmetric models of the Milky Way structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.4682v2.pdf"}
{"id": "0907.1029", "abstract": "  I report on some theoretical progress concerning the calculation of gluon bremsstrahlung for very high energy particles crossing a weakly-coupled quark-gluon plasma. (i) I advertise that two of the several formalisms used to study this problem, the BDMPS-Zakharov formalism and the AMY formalism (the latter used only for infinite, uniform media), can be made equivalent when appropriately formulated. (ii) A standard technique to simplify calculations is to expand in inverse powers of logarithms ln(E/T). I give an example where such expansions are found to work well for ω/T ≳ 10 where ω is the bremsstrahlung gluon energy. (iii) Finally, I report on perturbative calculations of q̂. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.1029v3.pdf"}
{"id": "0907.1378", "abstract": "  In this paper, a new quantum mechanical method to extract energy from black holes with contracting horizons is proposed. The method is based on a gedanken experiment on quantum energy teleportation (QET), which has been recently proposed in quantum information theory. We consider this QET protocol for N massless fields in near-horizon regions of large-mass black holes with near-horizon geometry described by the Minkowski metric. For each field, a two-level spin is strongly coupled with the local quantum fluctuation outside the horizon during a short time period. After the measurement of N fields, N-bit information is obtained. During the measurement, positive-energy wave packets of the fields form and then fall into the black hole. The amount of excitation energy is independent of the measurement result. After absorption of the wave packets and increase of the black hole mass, a measurement-result-dependent local operation of the N fields is performed outside the horizon. Then, accompanying the extraction of positive energy from the quantum fluctuation by the operation, negative-energy wave packets of the fields form and then fall into the black hole, decreasing the black hole mass. This implies that a part of the absorbed positive energy emitted from the measurement devices is effectively retrieved from the black hole via the measurement results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.1378v3.pdf"}
{"id": "0907.2883", "abstract": "  Recent discoveries have confirmed the existence of a large population of X-ray sources fuelled by accretion from the stellar wind of an OB supergiant. Such systems are powerful laboratories to study many aspects of astrophysics. Over the last decades, the physics of accretion in these systems has been the subject of extensive research, mainly through numerical methods. In spite of this effort, large uncertainties remain in our understanding, reflecting the complexity of the physical situation. A crucial issue that remains open is the possible formation of accretion discs. Though the spin evolution of neutron stars in these systems suggests that angular momentum is, at least occasionally, accreted, and many observational facts seem to require the existence of discs, computational results do not favour this possibility. In this brief review, I will summarise some of the open questions in this area. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.2883v1.pdf"}
{"id": "0909.1504", "abstract": "  Cosmogenic neutrinos are expected from ultrahigh energy cosmic rays undergoing the GZK process and anticipated to be observed by detecting air showers from the decays of tau leptons. We use CORSIKA simulated shower structure to calculate the coherent geosynchrotron radio emissions of the tau decay showers above 10^17eV. We present the pattern and spectrum of radio waves and discuss their detections by radio antennae. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.1504v1.pdf"}
{"id": "0909.1966", "abstract": "  We show that the asymptotic growth rate for the minimal cardinality of a set of simple closed curves on a closed surface of genus g which fill and pairwise intersect at most K≥ 1 times is 2√(g)/√(K) as g →∞ . We then bound from below the cardinality of a filling set of systoles by g/log(g). This illustrates that the topological condition that a set of curves pairwise intersect at most once is quite far from the geometric condition that such a set of curves can arise as systoles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.1966v2.pdf"}
{"id": "0909.3509", "abstract": "  We study the weak Lefschetz property and the Hilbert function of level Artinian monomial almost complete intersections in three variables. Several such families are shown to have the weak Lefschetz property if the characteristic of the base field is zero or greater than the maximal degree of any minimal generator of the ideal. Two of the families have an interesting relation to tilings of hexagons by lozenges. This lends further evidence to a conjecture by Migliore, Miro-Roig, and the second author. Finally, using our results about the weak Lefschetz property, we show that the Hilbert function of each level Artinian monomial almost complete intersection in three variables is peaked strictly unimodal. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.3509v1.pdf"}
{"id": "0909.3879", "abstract": "  Multi-photon states are widely applied in quantum information technology. By the methods presented in this paper, the structure of a multi-photon state in the form of multiple single photon qubit product can be mapped to a single photon qudit, which could also be in separable product with other photons. This makes the possible manipulation of such multi-photon states in the way of processing single photon states. The optical realization of unknown qubit discrimination [B. He, J. A. Bergou, and Y.-H. Ren, Phys. Rev. A 76, 032301 (2007)] is simplified with the transformation methods. Another application is the construction of quantum logic gates, where the inverse transformations back to the input state spaces are also necessary. We especially show that the modified setups to implement the transformations can realize the deterministic multi-control gates (including Toffoli gate) operating directly on the products of single photon qubits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.3879v2.pdf"}
{"id": "0909.4675", "abstract": "  We study light-cone gauge string field theory in noncritical space-time dimensions. Such a theory corresponds to a string theory in a Lorentz noninvariant background. We identify the worldsheet theory for the longitudinal coordinate variables X^± and study its properties. It is a CFT with the right value of Virasoro central charge, using which we propose a BRST invariant formulation of the worldsheet theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.4675v1.pdf"}
{"id": "0910.0826", "abstract": "  Prevalence of cooperation within groups of selfish individuals is puzzling in that it contradicts with the basic premise of natural selection. Favoring players with higher fitness, the latter is key for understanding the challenges faced by cooperators when competing with defectors. Evolutionary game theory provides a competent theoretical framework for addressing the subtleties of cooperation in such situations, which are known as social dilemmas. Recent advances point towards the fact that the evolution of strategies alone may be insufficient to fully exploit the benefits offered by cooperative behavior. Indeed, while spatial structure and heterogeneity, for example, have been recognized as potent promoters of cooperation, coevolutionary rules can extend the potentials of such entities further, and even more importantly, lead to the understanding of their emergence. The introduction of coevolutionary rules to evolutionary games implies, that besides the evolution of strategies, another property may simultaneously be subject to evolution as well. Coevolutionary rules may affect the interaction network, the reproduction capability of players, their reputation, mobility or age. Here we review recent works on evolutionary games incorporating coevolutionary rules, as well as give a didactic description of potential pitfalls and misconceptions associated with the subject. In addition, we briefly outline directions for future research that we feel are promising, thereby particularly focusing on dynamical effects of coevolutionary rules on the evolution of cooperation, which are still widely open to research and thus hold promise of exciting new discoveries. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.0826v1.pdf"}
{"id": "0910.1174", "abstract": "  We consider a model system in which anomalous diffusion is generated by superposition of underlying linear modes with a broad range of relaxation times. In the language of Gaussian polymers, our model corresponds to Rouse (Fourier) modes whose friction coefficients scale as wavenumber to the power 2-z. A single (tagged) monomer then executes subdiffusion over a broad range of time scales, and its mean square displacement increases as t^α with α=1/z. To demonstrate non-trivial aspects of the model, we numerically study the absorption of the tagged particle in one dimension near an absorbing boundary or in the interval between two such boundaries. We obtain absorption probability densities as a function of time, as well as the position-dependent distribution for unabsorbed particles, at several values of α. Each of these properties has features characterized by exponents that depend on α. Characteristic distributions found for different values of α have similar qualitative features, but are not simply related quantitatively. Comparison of the motion of translocation coordinate of a polymer moving through a pore in a membrane with the diffusing tagged monomer with identical α also reveals quantitative differences. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.1174v2.pdf"}
{"id": "0910.3479", "abstract": "  Muon ionization cooling provides the only practical solution for preparing high brightness beams necessary for a neutrino factory or muon collider. The Muon Ionization Cooling Experiment (MICE) is under development at the Rutherford Appleton Laboratory (UK). It comprises a dedicated beam line designed to generate a range of input emittances and momenta with time-of-flight and Cherenkov detectors to select a pure muon beam. A first measurement of emittance is performed in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in liquid hydrogen and acceleration by RF cavities. A second spectrometer identical to the first and another particle identification system provide a measurement of the outgoing emittance. In late 2009, it is expected that the beam and many of the particle identification detectors will be in the final commissioning phase, and the first measurement of input beam emittance will take place in 2010. The steps of commissioning, emittance measurement and cooling will be described. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.3479v1.pdf"}
{"id": "0910.5837", "abstract": "  It has generally been thought that in perturbed Friedmann-Lemaitre-Robertson-Walker models of the Universe, global topology should not have any feedback effects on dynamics. However, a weak-field limit heuristical argument, assuming a finite particle horizon for the transmission of gravitational signals, shows that a residual acceleration effect can occur. The nature of this effect differs algebraically between different constant curvature 3-manifolds. This potentially provides a selection mechanism for the 3-manifold of comoving space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.5837v1.pdf"}
{"id": "0911.4468", "abstract": "  Quasiparticles in semiconductors – such as microcavity polaritons – can form condensates in which the steady-state density profile is set by the balance of pumping and decay. By taking account of the polarization degree of freedom for a polariton condensate, and considering the effects of an applied magnetic field, we theoretically discuss the interplay between polarization dynamics, and the spatial structure of the pumped decaying condensate. If spatial structure is neglected, this dynamics has attractors that are linearly polarized condensates (fixed points), and desynchronized solutions (limit cycles), with a range of bistability. Considering spatial fluctuations about the fixed point, the collective spin modes can either be diffusive, linearly dispersing, or gapped. Including spatial structure, interactions between the spin components can influence the dynamics of vortices; produce stable complexes of vortices and rarefaction pulses with both co- and counter-rotating polarizations; and increase the range of possible limit cycles for the polarization dynamics, with different attractors displaying different spatial structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.4468v1.pdf"}
{"id": "0911.4812", "abstract": "  Far-off-resonant pulsed laser fields produce negligible excitation between two atomic states but may induce considerable phase shifts. The acquired phases are usually calculated by using the adiabatic-elimination approximation. We analyze the accuracy of this approximation and derive the conditions for its applicability to the calculation of the phases. We account for various sources of imperfections, ranging from higher terms in the adiabatic-elimination expansion and irreversible population loss to couplings to additional states. We find that, as far as the phase shifts are concerned, the adiabatic elimination is accurate only for a very large detuning. We show that the adiabatic approximation is a far more accurate method for evaluating the phase shifts, with a vast domain of validity; the accuracy is further enhanced by superadiabatic corrections, which reduce the error well below 10^-4. Moreover, owing to the effect of adiabatic population return, the adiabatic and superadiabatic approximations allow one to calculate the phase shifts even for a moderately large detuning, and even when the peak Rabi frequency is larger than the detuning; in these regimes the adiabatic elimination is completely inapplicable. We also derive several exact expressions for the phases using exactly soluble two-state and three-state analytical models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.4812v1.pdf"}
{"id": "0912.0880", "abstract": "  Accretion onto the massive black hole at the centre of a galaxy can feed energy and momentum into its surroundings via radiation, winds and jets. Feedback due to radiation pressure can lock the mass of the black hole onto the M-sigma relation, and shape the final stellar bulge of the galaxy. Feedback due to the kinetic power of jets can prevent massive galaxies greatly increasing their stellar mass, by heating gas which would otherwise cool radiatively. The mechanisms involved in cosmic feedback are discussed and illustrated with observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.0880v1.pdf"}
{"id": "0912.1992", "abstract": "  Cooperative spontaneous emission of a single photon from a cloud of N atoms modifies substantially the radiation pressure exerted by a far-detuned laser beam exciting the atoms. On one hand, the force induced by photon absorption depends on the collective decay rate of the excited atomic state. On the other hand, directional spontaneous emission counteracts the recoil induced by the absorption. We derive an analytical expression for the radiation pressure in steady-state. For a smooth extended atomic distribution we show that the radiation pressure depends on the atom number via cooperative scattering and that, for certain atom numbers, it can be suppressed or enhanced. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.1992v2.pdf"}
{"id": "0912.4208", "abstract": "  We contrast the impact of Higgs mediated flavor changing neutral currents on epsilon_K in the framework of a warped extra dimension that was recently calculated by Azatov et al. with the older results for Kaluza-Klein gluon induced corrections to that observable. We find that the most stringent constraint on the KK scale for a Higgs field localized on the infrared brane for reasonable additional assumptions comes from KK gluon exchange. In the case of a bulk Higgs field we show that for certain scenarios the Higgs contribution can in fact exceed the KK gluon contribution. In the course of this analysis we also describe in detail the different renormalization procedures that have to be employed in the KK gluon and Higgs cases to relate the new physics at high energies to low energy observables. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.4208v2.pdf"}
{"id": "0912.4225", "abstract": "  We present the results of a multiwavelength campaign searching for young objects in the intragroup medium of seven compact groups of galaxies: HCG 2, 7, 22, 23, 92, 100 and NGC 92. We used Fabry-Perot velocity fields and rotation curves together with GALEX NUV and FUV images, optical R-band and HI maps to evaluate the stage of interaction of each group. We conclude that groups (i) HCG 7 and HCG 23 are in an early stage of interaction, (ii) HCG 2 and HCG 22 are mildly interacting, and (iii) HCG 92, HCG 100 and NGC 92 are in a late stage of evolution. Evolved groups have a population of young objects in their intragroup medium while no such population is found within the less evolved groups. We also report the discovery of a tidal dwarf galaxy candidate in the tail of NGC 92. These three groups, besides containing galaxies which have peculiar velocity fields, also show extended HI tails. Our results indicate that the advanced stage of evolution of a group together with the presence of intragroup HI clouds may lead to star formation in the intragroup medium. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.4225v1.pdf"}
{"id": "0912.4898", "abstract": "  Probability distributions of money, income, and energy consumption per capita are studied for ensembles of economic agents. The principle of entropy maximization for partitioning of a limited resource gives exponential distributions for the investigated variables. A non-equilibrium difference of money temperatures between different systems generates net fluxes of money and population. To describe income distribution, a stochastic process with additive and multiplicative components is introduced. The resultant distribution interpolates between exponential at the low end and power law at the high end, in agreement with the empirical data for USA. We show that the increase of income inequality in USA originates primarily from the increase of the income fraction going to the upper tail, which now exceeds 20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.4898v4.pdf"}
{"id": "1001.0039", "abstract": "  The recently released Chandra Transmission Grating Catalog and Archive, TGCat, presents a fully dynamic on-line catalog allowing users to browse and categorize Chandra gratings observations quickly and easily, generate custom plots of resulting response corrected spectra on-line without the need for special software and to download analysis ready products from multiple observations in one convenient operation. TGCat has been registered as a VO resource with the NVO providing direct access to the catalogs interface. The catalog is supported by a back-end designed to automatically fetch newly public data, process, archive and catalog them, At the same time utilizing an advanced queue system integrated into the archive's MySQL database allowing large processing projects to take advantage of an unlimited number of CPUs across a network for rapid completion. A unique feature of the catalog is that all of the high level functions used to retrieve inputs from the Chandra archive and to generate the final data products are available to the user in an ISIS written library with detailed documentation. Here we present a structural overview of the Systems, Design, and Accessibility features of the catalog and archive. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.0039v1.pdf"}
{"id": "1001.1171", "abstract": "  We present a time-dependent radiative model for the atmosphere of extrasolar planets that takes into account the eccentricity of their orbit. In addition to the modulation of stellar irradiation by the varying planet-star distance, the pseudo-synchronous rotation of the planets may play a significant role. We include both of these time-dependent effects when modeling the planetary thermal structure. We investigate the thermal structure, and spectral characteristics for time-dependent stellar heating for two highly eccentric planets. Finally, we discuss observational aspects for those planets suitable for Spitzer measurements, and investigate the role of the rotation rate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.1171v2.pdf"}
{"id": "1001.1728", "abstract": "  Recent results comparing interacting galaxies to the mass-metallicity relation show that their nuclear oxygen abundances are unexpectedly low. We present analysis of N-body/SPH numerical simulations of equal-mass mergers that confirm the hypothesis that these underabundances are accounted for by radial inflow of low-metallicity gas from the outskirts of the two merging galaxies. The underabundances arise between first and second pericenter, and the simulated abundance dilution is in good agreement with observations. The simulations further predict that the radial metallicity gradients of the disk galaxies flatten shortly after first passage, due to radial mixing of gas. These predictions will be tested by future observations of the radial metallicity distributions in interacting galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.1728v1.pdf"}
{"id": "1002.3109", "abstract": "  Three dimensional electromagnetic gyrofluid simulations of the ideal ballooning mode blowout scenario for tokamak edge localized modes (ELMs) are presented. Special emphasis is placed on energetic diagnosis, examining changes in the growth rate in the linear, overshoot, and decay phases. The saturation process is energy transfer to self generated edge turbulence which exhibits an ion temperature gradient (ITG) mode structure. Convergence in the decay phase is found only if the spectrum reaches the ion gyroradius. The equilibrium is a self consistent background whose evolution is taken into account. Approximately two thirds of the total energy in the edge layer is liberated in the blowout. Parameter dependence with respect to plasma pressure and the ion gyroradius is studied. Despite the violent nature of the short-lived process, the transition to nonlinearity is very similar to that found in generic tokamak edge turbulence. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.3109v1.pdf"}
{"id": "1003.0628", "abstract": "  Text documents are complex high dimensional objects. To effectively visualize such data it is important to reduce its dimensionality and visualize the low dimensional embedding as a 2-D or 3-D scatter plot. In this paper we explore dimensionality reduction methods that draw upon domain knowledge in order to achieve a better low dimensional embedding and visualization of documents. We consider the use of geometries specified manually by an expert, geometries derived automatically from corpus statistics, and geometries computed from linguistic resources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.0628v1.pdf"}
{"id": "1004.0247", "abstract": "  We study, using both theory and molecular dynamics simulations, the relaxation dynamics of a microcanonical two dimensional self-gravitating system. After a sufficiently large time, a gravitational cluster of N particles relaxes to the Maxwell-Boltzmann distribution. The time to reach the thermodynamic equilibrium, however, scales with the number of particles. In the thermodynamic limit, N→∞ at fixed total mass, equilibrium state is never reached and the system becomes trapped in a non-ergodic stationary state. An analytical theory is presented which allows us to quantitatively described this final stationary state, without any adjustable parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.0247v2.pdf"}
{"id": "1004.4775", "abstract": "  It is explained why and how the fireball created in ultrarelativistic nuclear collisions can fragment when passing the phase transition. It can happen at the first-order phase transition but is not excluded even at high collision energies where the smooth crossover is present. Two potential observables sensitive to the appearance of fragmentation are reviewed: event-by-event changes of rapidity distributions and proton correlation in relative rapidity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.4775v1.pdf"}
{"id": "1005.4413", "abstract": "  Recently there has been considerable interest in the properties of carbon nanotori. Such nanotori can be parametrized according to their radii, their chiralities, and the twists that occur upon joining opposite ends of the nanotubes from which they are derived. In this paper, however, we demonstrate that many physically distinct nanotori with wildly different parameters nevertheless share identical band structures, energy spectra, and electrical conductivities. This occurs as a result of certain geometric symmetries known as modular symmetries which are direct consequences of the properties of the compactified graphene sheet. Using these symmetries, we show that there is a dramatic reduction in the number of spectrally distinct carbon nanotori compared with the number of physically distinct carbon nanotori. The existence of these modular symmetries also allows us to demonstrate that many statements in the literature concerning the electronic properties of nanotori are incomplete because they fail to respect the spectral equivalences that follow from these symmetries. We also find that as a result of these modular symmetries, the fraction of spectrally distinct nanotori which are metallic is approximately three times greater than would naively be expected on the basis of standard results in the literature. Finally, we demonstrate that these modular symmetries also extend to cases in which our carbon nanotori enclose non-zero magnetic fluxes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.4413v2.pdf"}
{"id": "1006.1030", "abstract": "  Class prediction is an important application of microarray gene expression data analysis. The high-dimensionality of microarray data, where number of genes (variables) is very large compared to the number of samples (obser- vations), makes the application of many prediction techniques (e.g., logistic regression, discriminant analysis) difficult. An efficient way to solve this prob- lem is by using dimension reduction statistical techniques. Increasingly used in psychology-related applications, Rasch model (RM) provides an appealing framework for handling high-dimensional microarray data. In this paper, we study the potential of RM-based modeling in dimensionality reduction with binarized microarray gene expression data and investigate its prediction ac- curacy in the context of class prediction using linear discriminant analysis. Two different publicly available microarray data sets are used to illustrate a general framework of the approach. Performance of the proposed method is assessed by re-randomization scheme using principal component analysis (PCA) as a benchmark method. Our results show that RM-based dimension reduction is as effective as PCA-based dimension reduction. The method is general and can be applied to the other high-dimensional data problems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.1030v1.pdf"}
{"id": "1007.1070", "abstract": "  The singlet-triplet relaxation in nanowire-based quantum dots induced by confined phonons is investigated theoretically. Due to the quasi-one-dimensional nature of the confined phonons, the singlet-triplet relaxation rates exhibit multi-peaks as function of magnetic field and the relaxation rate between the singlet and the spin up triplet state is found to be enhanced at the vicinity of the singlet-triplet anti-crossing. We compare the effect of the deformation-potential coupling and the piezoelectric coupling and find that the deformation-potential coupling dominates the relaxation rates in most cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.1070v1.pdf"}
{"id": "1007.2687", "abstract": "  We discuss the problem of full counting statistics for periodic pumping. The probability generating function is usually defined on a circle of the \"physical\" values of the counting parameter, with its periodicity corresponding to charge quantization. The extensive part of the generating function can either be an analytic function on this circle or have singularities. These two cases may be interpreted as different thermodynamic phases in time domain. We discuss several examples of phase transitions between these phases for classical and quantum systems. Finally, we prove a criterion for the \"analytic\" phase in the problem of a quantum pump for noninteracting fermions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2687v1.pdf"}
{"id": "1007.2727", "abstract": "  We present simulations of initially stable isothermal clouds exposed to ionizing radiation from a discrete external source, and identify the conditions that lead to radiatively driven implosion and star formation. We use the Smoothed Particle Hydrodynamics code SEREN (Hubber et al. 2010) and the HEALPix-based photoionization algorithm described in Bisbas et al. (2009). We find that the incident ionizing flux is the critical parameter determining the evolution: high fluxes simply disperse the cloud, whereas low fluxes trigger star formation. We find a clear connection between the intensity of the incident flux and the parameters of star formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2727v1.pdf"}
{"id": "1007.2979", "abstract": "  Recent results are reviewed on galaxy dynamics, bar evolution, destruction and re-formation, cold gas accretion, gas radial flows and AGN fueling, minor mergers. Some problems of galaxy evolution are discussed in particular, exchange of angular momentum, radial migration through resonant scattering, and consequences on abundance gradients, the frequency of bulgeless galaxies, and the relative role of secular evolution and hierarchical formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2979v1.pdf"}
{"id": "1007.3077", "abstract": "  The activities towards the fabrication and test of a 1 m3 semi-digital hadronic calorime- ter are reviewed. The prototype sampling planes would consist of 1 m2 Micromegas chambers with 1 cm2 granularity and embedded 2 bits readout suitable for PFA calorime- try at an ILC detector. The design of the 1 m2 chamber is presented first, followed by an overview of the basic performance of small prototypes. The basic units composing the 1 m2 chamber are 32 ×48 cm2 boards with integrated electronics and a micro-mesh. Results of character- ization tests of such boards are shown. Micromegas as a proportional detector is well suited for semi-digital hadronic calorimetry. In order to quantify the gain in perfor- mance when using one or more thresholds, simulation studies are being carried out, some of which will be reported in this contribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.3077v1.pdf"}
{"id": "1007.4904", "abstract": "  The entropy of the Reissner-Nördstrom black hole is studied within the context of a brane-world scenario. Such a black hole is a solution of the Einstein field equations on the brane, possessing a tidal charge which is a reflection of the extra dimension. We use the modified dispersion relation to obtain the entropy of such brane-world black holes. The resulting entropy differs from that of the standard Bekenstein-Hawking's and contains information on the extra dimension. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.4904v1.pdf"}
{"id": "1008.0863", "abstract": "  Adiabatic quantum algorithms are characterized by their run time and accuracy. The relation between the two is essential for quantifying adiabatic algorithmic performance, yet is often poorly understood. We study the dynamics of a continuous time, adiabatic quantum search algorithm, and find rigorous results relating the accuracy and the run time. Proceeding with estimates, we show that under fairly general circumstances the adiabatic algorithmic error exhibits a behavior with two discernible regimes: the error decreases exponentially for short times, then decreases polynomially for longer times. We show that the well known quadratic speedup over classical search is associated only with the exponential error regime. We illustrate the results through examples of evolution paths derived by minimization of the adiabatic error. We also discuss specific strategies for controlling the adiabatic error and run time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.0863v1.pdf"}
{"id": "1008.1742", "abstract": "  The mass density of dust particles that form from asteroids and comets in the interplanetary medium of the solar system is, near 1 AU, comparable to the mass density of the solar wind. It is mainly contained in particles of micrometer size and larger. Dust and larger objects are destroyed by collisions and sublimation and hence feed heavy ions into the solar wind and the solar corona. Small dust particles are present in large number and as a result of their large charge to mass ratio deflected by electromagnetic forces in the solar wind. For nano dust particles of sizes 1 - 10 nm, recent calculations show trapping near the Sun and outside from about 0.15 AU ejection with velocities close to solar wind velocity. The fluxes of ejected nano dust are detected near 1AU with the plasma wave instrument onboard the STEREO spacecraft. Though such electric signals have been observed during dust impacts before, the interpretation depends on several different parameters and data analysis is still in progress. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.1742v1.pdf"}
{"id": "1008.4107", "abstract": "  With an expected ten-fold increase in luminosity in S-LHC, the radiation environment in the tracker volumes will be considerably harsher for silicon-based detectors than the already harsh LHC environment. Since 2006, a group of CMS institutes, using a modified CMS DAQ system, has been exploring the use of Magnetic Czochralski silicon as a detector element for the strip tracker layers in S-LHC experiments. Both p+/n-/n+ and n+/p-/p+ sensors have been characterized, irradiated with proton and neutron sources, assembled into modules, and tested in a CERN beamline. There have been three beam studies to date and results from these suggest that both p+/n-/n+ and n+/p-/p+ Magnetic Czochralski silicon are sufficiently radiation hard for the R>25 cm regions of S-LHC tracker volumes. The group has also explored the use of forward biasing for heavily irradiated detectors, and although this mode requires sensor temperatures less than -50 ^∘C, the charge collection efficiency appears to be promising. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.4107v1.pdf"}
{"id": "1009.0047", "abstract": "  Parametric two-electron reduced-density-matrix (p-2RDM) methods have enjoyed much success in recent years; the methods have been shown to exhibit accuracies greater than coupled cluster with single and double substitutions (CCSD) for both closed- and open-shell ground-state energies, properties, geometric parameters, and harmonic frequencies. The class of methods is herein discussed within the context of the coupled electron pair approximation (CEPA), and several CEPA-like topological factors are presented for use within the p-2RDM framework. The resulting p-2RDM/n methods can be viewed as a density-based generalization of CEPA/n family that are numerically very similar to traditional CEPA methodologies. We cite the important distinction that the obtained energies represent stationary points, facilitating the efficient evaluation of properties and geometric derivatives. The p-2RDM/n formalism is generalized for an equal treatment of exclusion-principle-violating (EPV) diagrams that occur in the occupied and virtual spaces. One of these general topological factors is shown to be identical to that proposed by Kollmar [C. Kollmar, J. Chem. Phys. 125, 084108 (2006)], derived in an effort to approximately enforce the D, Q, and G conditions for N-representability in his size-extensive density matrix functional. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.0047v1.pdf"}
{"id": "1009.3589", "abstract": "  Recent theoretical and empirical work in statistical machine learning has demonstrated the importance of learning algorithms for deep architectures, i.e., function classes obtained by composing multiple non-linear transformations. Self-taught learning (exploiting unlabeled examples or examples from other distributions) has already been applied to deep learners, but mostly to show the advantage of unlabeled examples. Here we explore the advantage brought by out-of-distribution examples. For this purpose we developed a powerful generator of stochastic variations and noise processes for character images, including not only affine transformations but also slant, local elastic deformations, changes in thickness, background images, grey level changes, contrast, occlusion, and various types of noise. The out-of-distribution examples are obtained from these highly distorted images or by including examples of object classes different from those in the target test set. We show that deep learners benefit more from out-of-distribution examples than a corresponding shallow learner, at least in the area of handwritten character recognition. In fact, we show that they beat previously published results and reach human-level performance on both handwritten digit classification and 62-class handwritten character recognition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.3589v1.pdf"}
{"id": "1009.5501", "abstract": "  We analyse the parallel hybrid texture structures in the charged lepton and the neutrino sector. These parallel hybrid texture structures have physical implications as they cannot be obtained from arbitrary lepton mass matrices through weak basis transformations. The total sixty parallel hybrid texture structures can be grouped into twelve classes, and all the hybrid textures in the same class have identical physical implications. We examine all the twelve classes under the assumption of non-factorizable phases in the neutrino mass matrix. Five out of the total twelve classes are found to be phenomenologically disallowed. We study the phenomenological implications of the allowed classes for 1-3 mixing angle, Majorana and Dirac-type CP violating phases. Interesting constraints on effective Majorana mass are obtained for all the allowed classes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.5501v1.pdf"}
{"id": "1010.1172", "abstract": "  I report the discovery of two new Galactic Wolf-Rayet stars in Circinus via detection of their C, N and He Near-Infrared emission lines, using ESO-NTT-SOFI archival data. The H- and K-band spectra of WR67a and WR67b, indicate that they are Wolf-Rayet stars of WN6h and WC8 sub-types, respectively. WR67a presents a weak-lined spectrum probably reminiscent of young hydrogen rich main-sequence stars such as WR25 in Car OB1 and HD97950 in NGC3603. Indeed, this conclusion is reinforced by the close morphological match of the WR67a H- and K-band spectra with that for WR21a, a known extremely massive binary system. WR67b is probably a non-dusty WC8 Wolf-Rayet star that has a estimated heliocentric distance of 2.7(0.9) kpc, which for its Galactic coordinates, puts the star probably in the near portion of the Scutum-Centaurus arm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.1172v1.pdf"}
{"id": "1010.1358", "abstract": "  Motivated by the desirability of universal composability, we analyze in terms of L_1 distinguishability the task of secret key generation from a joint random variable. Under this secrecy criterion, using the Renyi entropy of order 1+s for s in [0,1, we derive a new upper bound of Eve's distinguishability under the application of the universal2 hash functions. It is also shown that this bound gives the tight exponential rate of decrease in the case of independent and identical distributions. The result is applied to the wire-tap channel model and to secret key generation (distillation) by public discussion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.1358v5.pdf"}
{"id": "1010.3689", "abstract": "  Flows around a wedge-shaped bow are simulated with the aim of investigating the wave breaking mechanism and small scale features of ship bow waves. This fluid dynamics video shows the plunging wave breaking process around the wedge including the thin water sheet formation, overturning sheet with surface disturbance, fingering and breaking up into spray, plunging and splashing, and air entrainment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.3689v1.pdf"}
{"id": "1010.4964", "abstract": "  We performed simulations of collapsars with different Kerr parameters a=0, 0.5, 0.9, 0.95. It is shown that a more rapidly rotating black hole is driving a more energetic jet. No jet is seen for the case of Schwartzschild black hole case, while the total energy of the jet is as large as 10^50 erg for a rapidly rotating Kerr black hole case (a=0.95). In order to explain the high luminosity of a GRB, it is concluded that a rapidly rotating black hole is favored ('faster is better'). We also find in the case of a=0.95 that (i) the stagnation region is clearly found in the jet region, (ii) the ordered poloidal field lines are seen in the jet, (iii) the jet region is surrounded by a 'Wall-like' structure that has a higher pressure than the jet region and contains strong vertical magnetic fields, and (iv) the jet is initiated by outgoing Poynting flux from the outer horizon of the black hole (Blandford-Znajek effect). The bulk Lorentz factor of the jet is still of the order of unity. However, energy density of electro-magnetic fields dominates the one of rest-mass in the jet. It can be expected that a relativistic jet will be seen if we perform a simulation for a longer time scale (of the order of 10-100 sec). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.4964v3.pdf"}
{"id": "1010.5395", "abstract": "  We study the effects of decoherence on the entanglement generated by Unruh effect in noninertial frames by using bit flip, phase damping and depolarizing channels. It is shown that decoherence strongly influences the initial state entanglement. The entanglement sudden death can happens irrespective of the acceleration of the noninertial frame under the action of phase flip and phase damping channels. It is investigated that an early sudden death happens for large acceleration under the depolarizing environment. Moreover, the entanglement increases for a highly decohered phase flip channel. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.5395v1.pdf"}
{"id": "1011.0150", "abstract": "  A simple derivation of the optimal state estimation of a quantum bit was obtained by using the no-signaling principle. In particular, the no-signaling principle determines a unique form of the guessing probability independently of figures of merit, such as the fidelity or information gain. This proves that the optimal estimation for a quantum bit can be achieved by the same measurement for almost all figures of merit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.0150v2.pdf"}
{"id": "1011.2351", "abstract": "  We investigate the dynamics of a wave packet in a parity-breaking one-dimensional periodic potential slowly varied in time and perturbed by a linear potential. Parity is broken by considering an asymmetric double well per unit cell. By comparing the prediction of the semiclassical dynamics with the full Schrödinger solution, we show that Bloch oscillations are strongly affected by anomalous velocity corrections related to Berry's phase. We characterize how these effects depend on the degree of parity breaking of the potential and on the modulation parameters. We also discuss how to measure the effects of the anomalous velocity in current experiments with non-interacting Bose-Einstein condensates in bichromatic optical lattices, under the effect of gravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2351v1.pdf"}
{"id": "1011.2718", "abstract": "  The high energy neutrino cross section is a crucial ingredient in the calculation of the event rate in high energy neutrino telescopes. Currently there are several approaches which predict different behaviours for its magnitude for ultrahigh energies. In this paper we present a comparison between the predictions based on linear DGLAP dynamics, non-linear QCD and in the imposition of a Froissart-like behaviour at high energies. In particular, we update the predictions based on the Color Glass Condensate, presenting for the first time the results for σ_ν N using the solution of the running coupling Balitsky-Kovchegov equation. Our results demonstrate that the current theoretical uncertainty for the neutrino-nucleon cross section reaches a factor three for neutrinos energies around 10^11 GeV and increases to a factor five for 10^13 GeV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2718v1.pdf"}
{"id": "1011.2881", "abstract": "  We study a system of an elastic ball moving in the non-relativistic spacetime with a nontrivial causal structure produced by a wormhole-based time machine. For such a system it is possible to formulate a simple model of the so-called `grandfather paradox': for certain `paradoxical' initial conditions the standard straight trajectory of the ball would self-collide inconsistently. We analyze globally consistent solutions of local equations of motion, namely, we find all trajectories with one self-collision. It is demonstrated that all standard initial conditions have a consistent evolution, including those `paradoxical' ones, for which the inconsistent collision-free trajectory is superseded by a special consistent self-colliding trajectory. Moreover, it is shown that for a wide class of initial conditions more than one globally consistent evolution exist. The nontrivial causal structure thus breaks the uniqueness of the classical theory even for locally deterministic physical laws. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2881v1.pdf"}
{"id": "1011.3281", "abstract": "  We study ultrarelativistic encounters of two spinning, equal-mass black holes through simulations in full numerical relativity. Two initial data sequences are studied in detail: one that leads to scattering and one that leads to a grazing collision and merger. In all cases, the initial black hole spins lie in the orbital plane, a configuration that leads to the so-called \"superkicks\". In astrophysical, quasicircular inspirals, such kicks can be as large as  3,000 km/s; here, we find configurations that exceed  15,000 km/s. We find that the maximum recoil is to a good approximation proportional to the total amount of energy radiated in gravitational waves, but largely independent of whether a merger occurs or not. This shows that the mechanism predominantly responsible for the superkick is not related to merger dynamics. Rather, a consistent explanation is that the \"bobbing\" motion of the orbit causes an asymmetric beaming of the radiation produced by the in-plane orbital motion of the binary, and the net asymmetry is balanced by a recoil. We use our results to formulate some conjectures on the ultimate kick achievable in any black hole encounter. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.3281v1.pdf"}
{"id": "1012.1755", "abstract": "  H.E.S.S is an array of atmospheric Cherenkov telescopes dedicated to GeV-TeV gamma-ray astronomy. The original array has been in operation since the beginning of 2004. It is composed of four 12-meter diameter telescopes. The installation of a fifth 28-meter diameter telescope is being completed. This telescope will operate both in stereoscopic mode and in monoscopic mode i.e. without a coincident detection on the smaller telescopes. A second-level trigger system is needed to supress spurious triggers of the 28-meter telescope when operated in monoscopic mode. This paper gives the motivation and principle of the second-level trigger. The principle of operation is illustrated by an example algorithm. The hardware implementation of the second level trigger system of H.E.S.S. phase 2 is described and its expected performances are then evaluated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.1755v1.pdf"}
{"id": "1012.1936", "abstract": "  This paper presents results of comparison between observations of coronal holes in the UV (SOHO EIT) and microwave emission (17, 5.7 GHz, 327 and 150.9 MHz, NoRH, SSRT and Nancy radioheliographs), and solar wind parameters, according to the ACE spacecraft data over the period 12 March–31 May 2007. Increase in the solar wind velocity up to  600 km/s was found to correlate with decrease in the UV flux in the central parts of the solar disk. The connection between parameters of the microwave emission at three different solar atmosphere levels and the solar wind velocity near the Earth's orbit was determined. This connection suggests existence of common mechanisms of solar wind acceleration from chromospheric altitudes to the upper corona. We also suppose existence of two different mechanisms of the solar wind acceleration at altitudes of less and more than one solar radius. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.1936v1.pdf"}
{"id": "1012.3655", "abstract": "  Chemical functionalization of graphene modifies the local electron density of the carbon atoms and hence electron transport. Measuring these changes allows for a closer understanding of the chemical interaction and the influence of functionalization on the graphene lattice. However, not only chemistry, in this case diazonium chemistry, has an effect on the electron transport. Latter is also influenced by defects and dopants resulting from different processing steps. Here, we show that solvents used in the chemical reaction process change the transport properties. In more detail, the investigated combination of isopropanol and heating treatment reduces the doping concentration and significantly increases the mobility of graphene. Furthermore, the isopropanol treatment alone increases the concentration of dopants and introduces an asymmetry between electron and hole transport which might be difficult to distinguish from the effect of functionalization. The results shown in this work demand a closer look on the influence of solvents used for chemical modification in order to understand their influence. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.3655v1.pdf"}
{"id": "1102.1923", "abstract": "  We are developing a 3D radiation hydrodynamics code to simulate the interaction of convection and pulsation in classical variable stars. One key goal is the ability to carry these simulations to full amplitude in order to compare them with observed light and velocity curves. Previous 2D calculations were prevented from doing this because of drift in the radial coordinate system, due to the algorithm defining radial movement of the coordinate system during the pulsation cycle. We remove this difficulty by defining our coordinate system flow algorithm to require that the mass in a spherical shell remain constant throughout the pulsation cycle. We perform adiabatic test calculations to show that large amplitude solutions repeat over more than 150 pulsation periods. We also verify that the computational method conserves the peak kinetic energy per period, as must be true for adiabatic pulsation models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.1923v1.pdf"}
{"id": "1102.2150", "abstract": "  The creation of collective many-body quantum states from a two-dimensional lattice gas of atoms is studied. Our approach relies on the van-der-Waals interaction that is present between alkali metal atoms when laser excited to high-lying Rydberg s-states. We focus on a regime in which the laser driving is strong compared to the interaction between Rydberg atoms. Here energetically low-lying many-particle states can be calculated approximately from a quadratic Hamiltonian. The potential usefulness of these states as a resource for the creation of deterministic single-photon sources is illustrated. The properties of these photon states are determined from the interplay between the particular geometry of the lattice and the interatomic spacing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.2150v1.pdf"}
{"id": "1103.0426", "abstract": "  We present a study of 9 galaxy groups with evidence for non-Gaussianity in their velocity distributions out to 4R200. This sample is taken from 57 groups selected from the 2PIGG catalog of galaxy groups. Statistical analysis indicates that non-Gaussian groups have masses significantly higher than Gaussian groups. We also have found that all non-Gaussian systems seem to be composed of multiple velocity modes. Besides, our results indicate that multimodal groups should be considered as a set of individual units with their own properties. In particular, we have found that the mass distribution of such units are similar to that of Gaussian groups. Our results reinforce the idea of non-Gaussian systems as complex structures in the phase space, likely corresponding to secondary infall aggregations at a stage before virialization. The understanding of these objects is relevant for cosmological studies using groups and clusters through the mass function evolution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.0426v1.pdf"}
{"id": "1103.2808", "abstract": "  Pulsar timing observations are used to place constraints on the rate of coalescence of supermassive black-hole (SMBH) binaries as a function of mass and redshift. In contrast to the indirect constraints obtained from other techniques, pulsar timing observations provide a direct constraint on the black-hole merger rate. This is possible since pulsar timing is sensitive to the gravitational waves (GWs) emitted by these sources in the final stages of their evolution. We find that upper bounds calculated from the recently published Parkes Pulsar Timing Array data are just above theoretical predictions for redshifts below 10. In the future, with improved timing precision and longer data spans, we show that a non-detection of GWs will rule out some of the available parameter space in a particular class of SMBH binary merger models. We also show that if we can time a set of pulsars to 10ns timing accuracy, for example, using the proposed Square Kilometre Array, it should be possible to detect one or more individual SMBH binary systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.2808v1.pdf"}
{"id": "1103.2890", "abstract": "  Different characteristic of matter influencing the evolution of the Universe has been simulated by means of a nonlinear spinor field. Exploiting the spinor description of perfect fluid and dark energy evolution of the Universe given by an anisotropic Bianchi type-VI, VI_0, V, III, I or isotropic Friedmann-Robertson-Walker (FRW) one has been studied. It is shown that due to some restrictions on metric functions, initial anisotropy in the models Bianchi type-VI, VI_0, V and III does not die away, while the anisotropic Bianchi type-I models evolves into the isotropic one. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.2890v1.pdf"}
{"id": "1103.5690", "abstract": "  The field of extrasolar planets is still, in comparison with other astrophysical topics, in its infancy. There have been about 300 or so extrasolar planets detected and their detection has been accomplished by various different techniques. Here we present a simple laboratory experiment to show how planets are detected using the transit technique. Following the simple analysis procedure describe we are able to determine the planetary radius to be 1.27 +/- 0.20 R_J which, within errors agrees with the establish value of 1.32 +/- 0.25 R_J. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.5690v2.pdf"}
{"id": "1103.6074", "abstract": "  The ground-state phases of a spin-orbit (SO) coupled atomic spin-2 Bose-Einstein condensate (BEC) are studied. Interesting density patterns spontaneously formed are widespread due to the competition between SO coupling and spin-dependent interactions like in a SO coupled spin-1 condensate. Unlike the case of spin-1 condensates, which are characterized by either ferromagnetic or polar phase in the absence of SO, spin-2 condensates can take a cyclic phase, where we find the patterns formed due to SO are square or triangular in their spin component densities for axial symmetric SO interaction. Both patterns are found to continuously evolve into striped forms with increased asymmetry of the SO coupling. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.6074v1.pdf"}
{"id": "1104.2977", "abstract": "  The Serpens South embedded cluster, which is located at the constricted part in a long filamentary infrared dark cloud, is believed to be in very early stage of cluster formation. We present results of near-infrared (JHKs) polarization observations toward the filamentary cloud. Our polarization measurements of near-infrared point sources indicate a well-ordered global magnetic field that is perpendicular to the main filament, implying that the magnetic field is likely to have controlled the formation of the main filament. On the other hand, the sub-filaments, which converge on the central part of the cluster, tend to run along the magnetic field. The global magnetic field appears to be curved in the southern part of the main filament. Such morphology is consistent with the idea that the global magnetic field is distorted by gravitational contraction along the main filament toward the northern part that contains larger mass. Applying the Chandrasekhar-Fermi method, the magnetic field strength is roughly estimated to be a few x 100 microgauss, suggesting that the filamentary cloud is close to magnetically critical as a whole. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.2977v1.pdf"}
{"id": "1104.4882", "abstract": "  The European VLBI Network (EVN) has been used at two epochs in 2003 and 2009 to obtain multi-frequency high-resolution images of the merger galaxy NGC6240 in order to study the radio properties of all compact high-brightness components in the galaxy. Our observations at milli-arcsecond resolution detected the northern and southern nuclei and two radio components, which we interpret as long-lived luminous supernovae associated with the circum-nuclear starburst activity at the southern nucleus. The new VLBI data support the presence of an active galactic nucleus (AGN) together with starburst activity at the southern nucleus and provides some evidence for an AGN at the northern nucleus. The two nuclei both display an inverted spectrum at lower GHz frequencies. The spectrum of the southern nucleus indicates thermal free-free absorption on parsec scales, consistent with the presence of an AGN. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.4882v1.pdf"}
{"id": "1104.4926", "abstract": "  We determine numerically the steady-state spectrum for Kelvin waves on a superfluid 4He vortex that is driven by shaking its end points and damped by mutual friction. The relaxation rate towards a steady state is determined by the mutual friction. We have reached the zero temperature limit where the steady-state spectrum and the vortex length become independent of the temperature. Our drive with pointlike pinning sites produces a characteristic spectrum with |w_m|∝ m^-η, where η≈ 1.88. The spatially sharply peaked drive and the fact that we are fixing the oscillation amplitude, not the power, causes that there exists no high k cutoff from mutual friction even when mutual friction is large. This spectrum is generic to the pinned boundary conditions used. Without pinning the spectrum is sensitive to the drive. The spectrum even depends on the amplitude of the initial spectrum if vortex is allowed to relax on its own. Therefore, in real systems the Kelvin spectrum is not unique and depends on external conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.4926v2.pdf"}
{"id": "1104.5183", "abstract": "  The motivation of this work is to illustrate the efficiency of some often overlooked alternatives to deal with optimization problems in systems and control. In particular, we will consider a problem for which an iterative linear matrix inequality algorithm (ILMI) has been proposed recently. As it often happens, this algorithm does not have guaranteed global convergence and therefore many methods may perform better. We will put forward how some general purpose optimization solvers are more suited than the ILMI. This is illustrated with the considered problem and example, but the general observations remain valid for many similar situations in the literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.5183v3.pdf"}
{"id": "1105.0266", "abstract": "  We introduce discrete systems in the form of straight (infinite) and ring-shaped chains, with two symmetrically placed nonlinear sites. The systems can be implemented in nonlinear optics (as waveguiding arrays) and BEC (by means of an optical lattice). A full set of exact analytical solutions for symmetric, asymmetric, and antisymmetric localized modes is found, and their stability is investigated in a numerical form. The symmetry-breaking bifurcation (SBB), through which the asymmetric modes emerge from the symmetric ones, is found to be of the subcritical type. It is transformed into a supercritical bifurcation if the nonlinearity is localized in relatively broad domains around two central sites, and also in the ring of a small size, i.e., in effectively nonlocal settings. The family of antisymmetric modes does not undergo bifurcations, and features both stable and unstable portions. The evolution of unstable localized modes is investigated by means of direct simulations. In particular, unstable asymmetric states, which exist in the case of the subcritical bifurcation, give rise to breathers oscillating between the nonlinear sites, thus restoring an effective dynamical symmetry between them. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.0266v1.pdf"}
{"id": "1105.1987", "abstract": "  We investigate existence, uniqueness, and the asymptotic properties of constant mean curvature (CMC) slicings in vacuum Kantowski-Sachs spacetimes with positive cosmological constant. Since these spacetimes violate the strong energy condition, most of the general theorems on CMC slicings do not apply. Although there are in fact Kantowski-Sachs spacetimes with a unique CMC foliation or CMC time function, we prove that there also exist Kantowski-Sachs spacetimes with an arbitrary number of (families of) CMC slicings. The properties of these slicings are analyzed in some detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.1987v1.pdf"}
{"id": "1105.2448", "abstract": "  X-ray unabsorbed Seyfert 2 galaxies appear to have X-ray absorption column densities that are too low (NH < 10^22 cm-2) to explain the absence of broad emission lines in their optical spectra, challenging the standard AGN unification model. In this paper we report Suzaku exposure on the X-ray unabsorbed Seyfert 2 galaxy IRAS F01475-0740, in which a hidden broad line region was detected through spectropolarimetric observation. The X-ray data show rapid and significant variations on time scales down to 5 ks, indicating that we are viewing its central engine directly. A newly obtained optical spectrum and previous optical/X-ray data suggest that state transition is unlikely in this source. These make IRAS F01475-0740 a very peculiar X-ray unabsorbed Seyfert 2 galaxy which can only be explained by absorption from materials with abnormally high dust-to-gas ratio (by a factor of > 4 larger than Galactic). This is in contrast to most AGNs, which typically show dust-to-gas ratios 3 - 100 times lower than the Galactic. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.2448v2.pdf"}
{"id": "1105.5000", "abstract": "  We investigate the marginally stable modes of the scalar (vector) perturbations in the AdS soliton background coupled to electric field. In the probe limit, we find that the marginally stable modes can reveal the onset of the phase transitions of this model. The critical chemical potentials obtained from this approach are in good agreement with the previous numerical or analytical results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.5000v2.pdf"}
{"id": "1105.5651", "abstract": "  We seek to develop network algorithms for function computation in sensor networks. Specifically, we want dynamic joint aggregation, routing, and scheduling algorithms that have analytically provable performance benefits due to in-network computation as compared to simple data forwarding. To this end, we define a class of functions, the Fully-Multiplexible functions, which includes several functions such as parity, MAX, and k th -order statistics. For such functions we exactly characterize the maximum achievable refresh rate of the network in terms of an underlying graph primitive, the min-mincut. In acyclic wireline networks, we show that the maximum refresh rate is achievable by a simple algorithm that is dynamic, distributed, and only dependent on local information. In the case of wireless networks, we provide a MaxWeight-like algorithm with dynamic flow splitting, which is shown to be throughput-optimal. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.5651v3.pdf"}
{"id": "1105.6185", "abstract": "  We calculate the transverse and time-time components of the instantaneous gluon propagator in Coulomb gauge QCD by using an SU(3) quenched lattice simulation on isotropic and anisotropic lattices. We find that the gluon propagators suffer from strong discretization effects on the isotropic lattice; on the other hand, those on the anisotropic lattices give a better scaling. Moreover, on these two type of lattices the transverse parts are significantly suppressed in the infrared region and have a turnover at about 500 [MeV]. The high resolution to the temporal direction due to the anisotropy yields small discretization errors for the time-time gluon propagators, which also show an infrared enhancement as expected in the Gribov-Zwanziger confinement scenario. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.6185v1.pdf"}
{"id": "1106.1187", "abstract": "  In this article I review the origin and the effects of chirally enhanced loop-corrections in the MSSM based on Refs. [1-3]. Chiral enhancement is related to fermion-Higgs couplings (or self-energies when the Higgs field is replaced by its vev). I describe the resummation of these chirally-enhanced corrections to all orders in perturbation theory and the calculation of the effective fermion-Higgs and gaugino(higgsino)-fermion vertices. As an application a model with radiative flavor-violation is discussed which can solve the SUSY-CP and the SUSY-flavor problem while it is still capable of explaining the observed deviation from the SM in the Bs mixing phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.1187v1.pdf"}
{"id": "1106.1340", "abstract": "  We experimentally realize quantum Hall Mach-Zehnder interferometer which operates far beyond the equilibrium. The operation of the interferometer is based on allowed intra-edge elastic transitions within the same Landau sublevel in the regime of high imbalances between the co-propagating edge states. Since the every edge state is definitely connected with the certain Landau sublevel, the formation of the interference loop can be understood as a splitting and a further reconnection of a single edge state. We observe an Aharonov-Bohm type interference pattern even for low-size interferometers. This novel interference scheme demonstrates high visibility even at millivolt imbalances and survives in a wide temperature range. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.1340v2.pdf"}
{"id": "1106.2239", "abstract": "  High-order harmonic generation (HHG) by hydrogenlike atoms/ions in the uniform periodic electric field, formed by the two linearly polarized counterpropagating laser beams of relativistic intensities, is studied. The relativistic quantum theory of HHG in such fields, at which the impeding factor of relativistic magnetic drift of a strong wave can be eliminated, is presented arising from the Dirac equation. Specifically, a scheme of HHG in underdense plasma with the copropagating ultraintense laser and fast ion beams is proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.2239v1.pdf"}
{"id": "1106.4923", "abstract": "  Resonant dipole-dipole interaction modifies the energy and decay rate of electronic excitations for finite one dimensional chains of ultracold atoms in an optical lattice. We show that collective excited states of the atomic chain can be divided into dark and bright modes, where a superradiant mode with an enhanced collective effective dipole dominates the optical scattering. Studying the generic case of two chain segments of different length and position exhibits an interaction blockade and spatially structured light emission. Ultimately, an extended system of several interfering segments models a long chain with randomly distributed defects of vacant sites. The corresponding emission pattern provides a sensitive tool to study structural and dynamical properties of the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.4923v1.pdf"}
{"id": "1106.5492", "abstract": "  A periodic variation in the pulse timings of the pulsating hot subdwarf B star CS 1246 was recently discovered via the O-C diagram and suggests the presence of a binary companion with an orbital period of two weeks. Fits to this phase variation, when interpreted as orbital reflex motion, imply CS 1246 orbits a barycenter 11 light-seconds away with a velocity of 16.6 km/s. Using the Goodman spectrograph on the SOAR telescope, we decided to confirm this hypothesis by obtaining radial velocity measurements of the system over several months. Our spectra reveal a velocity variation with amplitude, period, and phase in accordance with the O-C diagram predictions. This corroboration demonstrates that the rapid pulsations of hot subdwarf B stars can be adequate clocks for the discovery of binary companions via the pulse timing method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.5492v1.pdf"}
{"id": "1107.3866", "abstract": "  The conventional wisdom for the formation of the first hard binary in core collapse is that three-body interactions of single stars form many soft binaries, most of which are quickly destroyed, but eventually one of them survives. We report on direct N-body simulations to test these ideas, for the first time. We find that both assumptions are often incorrect: 1) quite a few three-body interactions produce a hard binary from scratch; 2) and in many cases there are more than three bodies directly and simultaneously involved in the production of the first binary. The main reason for the discrepancies is that the core of a star cluster, at the first deep collapse, contains typically only five or so stars. Therefore, the homogeneous background assumption, which still would be reasonable for, say, 25 stars, utterly breaks down. There have been some speculations in this direction, but we demonstrate this result here explicitly, for the first time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.3866v1.pdf"}
{"id": "1107.4257", "abstract": "  This article is concerned with the representation of curves by means of integral invariants. In contrast to the classical differential invariants they have the advantage of being less sensitive with respect to noise. The integral invariant most common in use is the circular integral invariant. A major drawback of this curve descriptor, however, is the absence of any uniqueness result for this representation. This article serves as a contribution towards closing this gap by showing that the circular integral invariant is injective in a neighbourhood of the circle. In addition, we provide a stability estimate valid on this neighbourhood. The proof is an application of Riesz-Schauder theory and the implicit function theorem in a Banach space setting. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.4257v3.pdf"}
{"id": "1107.4867", "abstract": "  In this paper we combine the WMAP7 with lookback time and Chandra gas fraction data to constrain the main cosmological parameters and the equation of state for the dark energy. We find that the lookback time is a good measurement that can improve the determination of the equation of state for the dark energy with regard to other external data sets. We conclude that larger lookback time data set will further improve our determination of the cosmological parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.4867v1.pdf"}
{"id": "1108.1039", "abstract": "  We show that the failure of the Delaney-Greer (DG) variational ansatz for transport demonstrated by us in Phys. Rev. B 80, 165301 (2009) (I) is not related to an unsuitable constraint that prevents a broken time-reversal symmetry or to real orbitals, as DG incorrectly claim. The complex orbitals suggested by them as a way-out solution merely represent a particular case of the general case considered by us in I, which do not in the least affect our conclusion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.1039v1.pdf"}
{"id": "1108.3590", "abstract": "  Experimental studies on enzyme evolution show that only a small fraction of all possible mutation trajectories are accessible to evolution. However, these experiments deal with individual enzymes and explore a tiny part of the fitness landscape. We report an exhaustive analysis of fitness landscapes constructed with an off-lattice model of protein folding where fitness is equated with robustness to misfolding. This model mimics the essential features of the interactions between amino acids, is consistent with the key paradigms of protein folding and reproduces the universal distribution of evolutionary rates among orthologous proteins. We introduce mean path divergence as a quantitative measure of the degree to which the starting and ending points determine the path of evolution in fitness landscapes. Global measures of landscape roughness are good predictors of path divergence in all studied landscapes: the mean path divergence is greater in smooth landscapes than in rough ones. The model-derived and experimental landscapes are significantly smoother than random landscapes and resemble additive landscapes perturbed with moderate amounts of noise; thus, these landscapes are substantially robust to mutation. The model landscapes show a deficit of suboptimal peaks even compared with noisy additive landscapes with similar overall roughness. We suggest that smoothness and the substantial deficit of peaks in the fitness landscapes of protein evolution are fundamental consequences of the physics of protein folding. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.3590v1.pdf"}
{"id": "1108.5812", "abstract": "  The phonon thermal conductivity in diamond nanowires (DNW) is studied by molecular dynamics simulation. It is found that the thermal conductivity in narrower DNW is lower and does not show obvious temperature dependence; a very small value (about 2.0 W/m/K) of thermal conductivity is observed in ultra-narrow DNW, which may be of potential applications in thermoelectric devices. These two phenomena are probably due to the dominant surface effect and phonon confinement effect in narrow DNW. Our simulation reveals a high anisotropy in the heat transport of DNW. Specifically, the thermal conductivity in DNW along [110] growth direction is about five times larger than that of [100] and [111] growth directions. The anisotropy is believed to root in the anisotropic group velocity for acoustic phonon modes in DNW along three different growth directions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.5812v1.pdf"}
{"id": "1109.5186", "abstract": "  We describe the generation of single-band point source catalogues from submillimetre Herschel-SPIRE observations taken as part of the Science Demonstration Phase of the Herschel Multi-tiered Extragalactic Survey (HerMES). Flux densities are found by means of peak-finding and the fitting of a Gaussian point-response function. With highly-confused images, careful checks must be made on the completeness and flux density accuracy of the detected sources. This is done by injecting artificial sources into the images and analysing the resulting catalogues. Measured flux densities at which 50 per cent of injected sources result in good detections at (250, 350, 500) μm range from (11.6, 13.2, 13.1) mJy to (25.7, 27.1, 35.8) mJy, depending on the depth of the observation (where a `good' detection is taken to be one with positional offset less than one full-width half-maximum of the point-response function, and with the measured flux density within a factor of 2 of the flux density of the injected source). This paper acts as a reference for the 2010 July HerMES public data release. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.5186v1.pdf"}
{"id": "1110.2027", "abstract": "  One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.2027v1.pdf"}
{"id": "1110.2792", "abstract": "  We present a systematic overview of granular deposits composed of ellipsoidal particles with different particle shapes and size polydispersities. We study the density and anisotropy of such deposits as functions of size polydispersity and two shape parameters that fully describe the shape of a general ellipsoid. Our results show that, while shape influences significantly the macroscopic properties of the deposits, polydispersity plays apparently a secondary role. The density attains a maximum for a particular family of non-symmetrical ellipsoids, larger than the density observed for prolate or oblate ellipsoids. As for anisotropy measures, the contact forces show are increasingly preferred along the vertical direction as the shape of the particles deviates for a sphere. The deposits are constructed by means of an efficient molecular dynamics method, where the contact forces are efficiently and accurately computed. The main results are discussed in the light of applications for porous media models and sedimentation processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.2792v1.pdf"}
{"id": "1110.3723", "abstract": "  Recently, research that focuses on the rigorous understanding of the relation between simulation and/or exact models on graphs and approximate counterparts has gained lots of momentum. This includes revisiting the performance of classic pairwise models with closures at the level of pairs and/or triples as well as effective-degree-type models and those based on the probability generating function formalism. In this paper, for a fully connected graph and the simple SIS (susceptible-infected-susceptible) epidemic model, a novel closure is introduced. This is done via using the equations for the moments of the distribution describing the number of infecteds at all times combined with the empirical observations that this is well described/approximated by a binomial distribution with time dependent parameters. This assumption allows us to express higher order moments in terms of lower order ones and this leads to a new closure. The significant feature of the new closure is that the difference of the exact system, given by the Kolmogorov equations, from the solution of the newly defined approximate system is of order 1/N^2. This is in contrast with the 𝒪(1/N) difference corresponding to the approximate system obtained via the classic triple closure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.3723v1.pdf"}
{"id": "1111.0007", "abstract": "  We report on a re-analysis of archival data from the Very Large Array for a sample of ten long duration radio transients reported by Bower and others. These transients have an implied all-sky rate that would make them the most common radio transient in the sky and yet most have no quiescent counterparts at other wavelengths and therefore no known progenitor (other than Galactic neutron stars). We find that more than half of these transients are due to rare data artifacts. The remaining sources have lower signal-to-noise ratio (SNR) than initially reported by 1 to 1.5-sigma. This lowering of SNR matters greatly since the sources are at the threshold. We are unable to decisively account for the differences. By two orthogonal criteria one source appears to be a good detection. Thus the rate of long duration radio transients without optical counterparts is, at best, comparable to that of the class of recently discovered Swift J1644+57 nuclear radio transients. We revisit the known and expected classes of long duration radio transients and conclude that the dynamic radio sky remains a rich area for further exploration. Informed by the experience of past searches for radio transients, we suggest that future surveys pay closer attention to rare data errors and ensure that a wealth of sensitive multi-wavelength data be available in advance of the radio observations and that the radio searches should have assured follow-up resources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.0007v1.pdf"}
{"id": "1111.3226", "abstract": "  Decameter wavelength radio emission is finely structured in solar bursts. For their research it is very important to use a sufficient sensitivity of antenna systems. In this paper we study an influence of the radiotelescope-antenna effective area on the results of decameter solar radio observations. For this purpose we compared the solar bursts received by the array of 720 ground-based dipoles and the single dipole of the radiotelescope UTR-2. It's shown that a larger effective area of the ground-based antenna allows us to measure a weaker solar emission and to distinguish a fine structure of strong solar events. This feature has been also verified by simultaneous ground- and space-based observations in the overlapping frequency range. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.3226v1.pdf"}
{"id": "1111.3579", "abstract": "  In the present work we study the C8 flare occurred on September 26, 2000 at 19:49 UT and observed by the SOHO/SUMER spectrometer from the beginning of the impulsive phase to well beyond the disappearance in the X-rays. The emission first decayed progressively through equilibrium states until the plasma reached 2-3 MK. Then, a series of cooler lines, i.e. Ca x, Ca vii, Ne vi, O iv and Si iii (formed in the temperature range log T = 4.3 - 6.3 under equilibrium conditions), are emitted at the same time and all evolve in a similar way. Here we show that the simultaneous emission of lines with such a different formation temperature is due to thermal instability occurring in the flaring plasma as soon as it has cooled below   2 MK. We can qualitatively reproduce the relative start time of the light curves of each line in the correct order with a simple (and standard) model of a single flaring loop. The agreement with the observed light curves is greatly improved, and a slower evolution of the line emission is predicted, if we assume that the model loop consists of an ensemble of subloops or strands heated at slightly different times. Our analysis can be useful for flare observations with SDO/EVE. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.3579v1.pdf"}
{"id": "1111.7108", "abstract": "  In this paper, we investigate joint relay and jammer selection in two-way cooperative networks, consisting of two sources, a number of intermediate nodes, and one eavesdropper, with the constraints of physical layer security. Specifically, the proposed algorithms select two or three intermediate nodes to enhance security against the malicious eavesdropper. The first selected node operates in the conventional relay mode and assists the sources to deliver their data to the corresponding destinations using an amplify-and-forward protocol. The second and third nodes are used in different communication phases as jammers in order to create intentional interference upon the eavesdropper node. Firstly, we find that in a topology where the intermediate nodes are randomly and sparsely distributed, the proposed schemes with cooperative jamming outperform the conventional non-jamming schemes within a certain transmitted power regime. We also find that, in the scenario in which the intermediate nodes gather as a close cluster, the jamming schemes may be less effective than their non-jamming counterparts. Therefore, we introduce a hybrid scheme to switch between jamming and non-jamming modes. Simulation results validate our theoretical analysis and show that the hybrid switching scheme further improves the secrecy rate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.7108v1.pdf"}
{"id": "1112.5147", "abstract": "  We use distribution amplitudes of the light Σ baryon and the most general form of the interpolating current for heavy Σ_b baryon to investigate the semileptonic Σ_b→Σ l^+l^- transition in light cone QCD sum rules. We calculate all twelve form factors responsible for this transition and use them to evaluate the branching ratio of the considered channel. The order of branching fraction shows that this channel can be detected at LHC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.5147v1.pdf"}
{"id": "1201.1246", "abstract": "  Supersymmetric models with broken R-parity provide mechanisms that allow to generate Majorana neutrino masses and magnetic moments through virtual particle-sparticle loops. This constitutes an attractive alternative to the see-saw mechanism. In this paper we present a detailed calculation of the transition magnetic moments of a Majorana neutrino in gauge mediated supersymmetry breaking MSSM without R-parity. We base our analysis on the renormalization group evolution of the MSSM parameters, which are unified at the GUT scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.1246v1.pdf"}
{"id": "1201.2818", "abstract": "  Bulges in spiral galaxies have been supposed to be classified into two types: classical bulges or pseudobulges. Classical bulges are thought to form by galactic merger with bursty star formation, whereas pseudobulges are suggested to form by secular evolution. Noguchi (1998, 1999) suggested another bulge formation scenario, `clump-origin bulge'. He demonstrated using a numerical simulation that a galactic disc forms clumpy structures in the early stage of disc formation, then the clumps merge into a single bulge at the centre. I perform a high-resolution N-body/SPH simulation for the formation of the clump-origin bulge in an isolated galaxy model. I find that the clump-origin bulge resembles pseudobulges in dynamical properties, but this bulge consists of old and metal-rich stars. These natures, old metal-rich population but pseudobulge-like structures, mean that the clump-origin bulge can not be simply classified into classical bulges nor pseudobulges. From these results, I discuss similarities of the clump-origin bulge to the Milky Way bulge. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.2818v1.pdf"}
{"id": "1201.2985", "abstract": "  In this paper, we investigate the robust transceiver design for dual-hop amplify-and-forward (AF) MIMO relay systems with Gaussian distributed channel estimation errors. Aiming at maximizing the mutual information under imperfect channel state information (CSI), source precoder at source and forwarding matrix at the relay are jointly optimized. Using some elegant attributes of matrix-monotone functions, the structures of the optimal solutions are derived first. Then based on the derived structure an iterative waterfilling solution is proposed. Several existing algorithms are shown to be special cases of the proposed solution. Finally, the effectiveness of the proposed robust design is demonstrated by simulation results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.2985v1.pdf"}
{"id": "1201.4052", "abstract": "  One of the methods for studying the highest energy cosmic rays is to measure the fluorescence light emitted by the extensive air showers induced by them. To reconstruct a shower cascade curve from measurements of the number of photons arriving from the subsequent shower track elements it is necessary to take into account the multiple scatterings that photons undergo on their way from the shower to the detector. In contrast to the earlier Monte-Carlo work, we present here an analytical method to treat the Rayleigh and Mie scatterings in the atmosphere. The method consists in considering separately the consecutive 'generations' of the scattered light. Starting with a point light source in a uniform medium, we then examine a source in a real atmosphere and finally - a moving source (shower) in it. We calculate the angular distributions of the scattered light superimposed on the not scattered light registered from a shower at a given time. The analytical solutions (although approximate) show how the exact numerical results should be parametrised what we do for the first two generations (the contribution of the higher ones being small). Not allowing for the considered effect may lead to an overestimation of shower primary energy by  15", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.4052v1.pdf"}
{"id": "1201.6546", "abstract": "  We analyze the light curves of the recent solar eclipses measured by the Herzberg channel (200-220 nm) of the Large Yield RAdiometer (LYRA) onboard PROBA-2. The measurements allow us to accurately retrieve the center- to-limb variations (CLV) of the solar brightness. The formation height of the radiation depends on the observing angle so the examination of the CLV provide information about a broad range of heights in the solar atmosphere. We employ the 1D NLTE radiative transfer COde for Solar Irradiance (COSI) to model the measured light curves and corresponding CLV dependencies. The modeling is used to test and constrain the existing 1D models of the solar atmosphere, e.g. the temperature structure of the photosphere and the treatment of the pseudo- continuum opacities in the Herzberg continuum range. We show that COSI can accurately reproduce not only the irradiance from the entire solar disk, but also the measured CLV. It hence can be used as a reliable tool for modeling the variability of the spectral solar irradiance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.6546v1.pdf"}
{"id": "1202.0845", "abstract": "  A unified description of single-pion photoproduction data, together with pion- and eta-hadroproduction data, has been achieved in a Chew-Mandelstam parametrization which is consistent with unitarity at the two-body level. Energy-dependent and single-energy partial wave analyses of pion photoproduction data have been performed and compared to previous SAID fits and multipoles from the Mainz and Bonn-Gatchina groups. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.0845v1.pdf"}
{"id": "1202.0876", "abstract": "  The multicast capacity of a directed network is closely related to the s-t maximum flow, which is equal to the s-t minimum cut capacity due to the max-flow min-cut theorem. If the topology of a network (or link capacities) is dynamically changing or have stochastic nature, it is not so trivial to predict statistical properties on the maximum flow. In this paper, we present a coding theoretic approach for evaluating the accumulate distribution of the minimum cut capacity of weighted random graphs. The main feature of our approach is to utilize the correspondence between the cut space of a graph and a binary LDGM (low-density generator-matrix) code with column weight 2. The graph ensemble treated in the paper is a weighted version of Erdős-Rényi random graph ensemble. The main contribution of our work is a combinatorial lower bound for the accumulate distribution of the minimum cut capacity. From some computer experiments, it is observed that the lower bound derived here reflects the actual statistical behavior of the minimum cut capacity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.0876v1.pdf"}
{"id": "1202.3125", "abstract": "  We present the Suzaku results of the mixed-morphology supernova remnant W28. The X-ray spectra of the central region of W28 exhibit many bright emission lines from highly ionized atoms. An optically thin thermal plasma in collisional ionization equilibrium, either of single-temperature or multi-temperature failed to reproduce the data with line-like and bump-like residuals at the Si Lymanα energy and at 2.4–5.0 keV, respectively. The bumps probably correspond to radiative recombination continua from He-like Si and S. A simple recombining plasma model nicely fit the bump structures, but failed to fit low energy bands. The overall spectra can be fit with a multi-ionization temperature plasma with a common electron temperature. The multi-ionization temperatures are interpreted as elemental difference of ionization and recombination timescales. These results prefer the rarefaction scenario for the origin of the recombining plasma. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.3125v1.pdf"}
{"id": "1202.6507", "abstract": "  We study fundamental optical gap solitons in the model of a fiber Bragg grating (BG), which is subjected to a periodic modulation of the local reflectivity, giving rise to a supergrating. In addition, the local refractive index is also periodically modulated with the same period. It is known that the supergrating opens an infinite system of new bandgaps in the BG's spectrum. We use a combination of analytical and computational methods to show that each emerging bandgap is filled with gap solitons (GSs), including asymmetric ones and bound states of the GSs. In particular, bifurcations of the GSs created by the supergrating are studied in terms of a geometric analysis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.6507v1.pdf"}
{"id": "1203.1711", "abstract": "  The Modulated Wideband Converter (MWC) is a recently proposed analog-to-digital converter (ADC) based on Compressive Sensing (CS) theory. Unlike conventional ADCs, its quantization reference voltage, which is important to the system performance, does not equal the maximum amplitude of original analog signal. In this paper, the quantization reference voltage of the MWC is theoretically analyzed and the conclusion demonstrates that the reference voltage is proportional to the square root of q, which is a trade-off parameter between sampling rate and number of channels. Further discussions and simulation results show that the reference voltage is proportional to the square root of Nq when the signal consists of N narrowband signals. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.1711v1.pdf"}
{"id": "1204.6320", "abstract": "  We present the discovery of three late type (>T4) brown dwarfs, including a probable Y dwarf, in the WFC3 Infrared Spectroscopic Parallels (WISP) Survey. We use the G141 grism spectra to determine the spectral types of the dwarfs and derive distance estimates based on a comparison with nearby T dwarfs with known parallaxes. These are the most distant spectroscopically confirmed T/Y dwarfs, with the farthest at an estimated distance of  400 pc. We compare the number of cold dwarfs found in the WISP survey with simulations of the brown dwarf mass function. The number found is generally consistent with an initial stellar mass function dN/dM ∝M^-α with α= 0.0–0.5, although the identification of a Y dwarf is somewhat surprising and may be indicative of either a flatter absolute magnitude/spectral type relation than previously reported or an upturn in the number of very late type brown dwarfs in the observed volume. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.6320v1.pdf"}
{"id": "1205.2520", "abstract": "  A local exclusion principle is observed for identical particles obeying intermediate/fractional exchange statistics in one and two dimensions, leading to bounds for the kinetic energy in terms of the density. This has implications for models of Lieb-Liniger and Calogero-Sutherland type, and implies a non-trivial lower bound for the energy of the anyon gas whenever the statistics parameter is an odd numerator fraction. We discuss whether this is actually a necessary requirement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.2520v3.pdf"}
{"id": "1205.3361", "abstract": "  The light-quark correlator in the axial-vector channel is used, in conjunction with finite energy QCD sum rules at finite temperature, in order to (a) establish a relation between chiral-symmetry restoration and deconfinement, and (b) determine the temperature behavior of the a_1(1260) width and coupling. Results indicate that deconfinement takes place at a slightly lower temperature than chiral-symmetry restoration, although this difference is not significant given the accuracy of the method. The behaviour of the a_1(1260) parameters is consistent with quark-gluon deconfinement, as the width grows and the coupling decreases with increasing temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.3361v3.pdf"}
{"id": "1205.5127", "abstract": "  We focus on the propagation properties of a single-cycle laser pulse through a two-level medium by numerically solving the full-wave Maxwell-Bloch equations. The counter-rotating terms in the spontaneous emission damping are included such that the equations of motion are slightly different from the conventional Bloch equations. The counter-rotating terms can considerably suppress the broadening of the pulse envelope and the decrease of the group velocity rooted from dispersion. Furthermore, for incident single-cycle pulses with envelope area 4π, the time-delay of the generated soliton pulse from the main pulse depends crucially on the carrier-envelope phase of the incident pulse. This can be utilized to determine the carrier-envelope phase of the single-cycle laser pulse. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.5127v1.pdf"}
{"id": "1206.0005", "abstract": "  The afterglows of gamma-ray bursts (GRBs) have more soft X-ray absorption than expected from the foreground gas column in the Galaxy. While the redshift of the absorption can in general not be constrained from current X-ray observations, it has been assumed that the absorption is due to metals in the host galaxy of the GRB. The large sample of X-ray afterglows and redshifts now available allows the construction of statistically meaningful distributions of the metal column densities. We construct such a sample and show, as found in previous studies, that the typical absorbing column density (N_HX) increases substantially with redshift, with few high column density objects found at low to moderate redshifts. We show, however, that when highly extinguished bursts are included in the sample, using redshifts from their host galaxies, high column density sources are also found at low to moderate redshift. We infer from individual objects in the sample and from observations of blazars, that the increase in column density with redshift is unlikely to be related to metals in the intergalactic medium or intervening absorbers. Instead we show that the origin of the apparent increase with redshift is primarily due to dust extinction bias: GRBs with high X-ray absorption column densities found at z≲4 typically have very high dust extinction column densities, while those found at the highest redshifts do not. It is unclear how such a strongly evolving N_HX/A_V ratio would arise, and based on current data, remains a puzzle. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.0005v1.pdf"}
{"id": "1206.0046", "abstract": "  I describe the computation of energy widths of nuclear states using an integral over the interaction region of ab initio variational Monte Carlo wave functions, and I present calculated widths for many states. I begin by presenting relations that connect certain short-range integrals to widths. I then present predicted widths for 5 <= A <= 9 nuclei, and I compare them against measured widths. They match the data more closely and with less ambiguity than estimates based on spectroscopic factors. I consider the consequences of my results for identification of observed states in ^8B, ^9He, and ^9Li. I also examine failures of the method and conclude that they generally involve broad states and variational wave functions that are not strongly peaked in the interaction region. After examining bound-state overlap functions computed from a similar integral relation, I conclude that overlap calculations can diagnose cases in which computed widths should not be trusted. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.0046v1.pdf"}
{"id": "1206.0432", "abstract": "  I review an extension of the ADHMN construction of monopoles to M-brane models. This extended construction gives a map from solutions to the Basu-Harvey equation to solutions to the self-dual string equation transgressed to loop space. Loop spaces appear in fact quite naturally in M-brane models. This is demonstrated by translating a recently proposed M5-brane model to loop space. Finally, I comment on some recent developments related to the loop space approach to M-brane models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.0432v1.pdf"}
{"id": "1206.4276", "abstract": "  We theoretically study Hawking radiation processes from an analog acoustic black hole in a flowing superfluid of exciton-polaritons in a one-dimensional semiconductor microcavity. Polaritons are coherently injected into the microcavity by a laser pump with a suitably tailored spot profile. An event horizon with a large analog surface gravity is created by inserting a defect in the polariton flow along the cavity plane. Experimentally observable signatures of the analog Hawking radiation are identified in the scattering of phonon wavepackets off the horizon, as well as in the spatial correlation pattern of quantum fluctuations of the polariton density. The potential of these table-top optical systems as analog models of gravitational physics is quantitatively confirmed by numerical calculations using realistic parameters for state-of-the-art devices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.4276v1.pdf"}
{"id": "1206.5470", "abstract": "  We review c-field methods for simulating the non-equilibrium dynamics of degenerate Bose gases beyond the mean-field Gross-Pitaevskii approximation. We describe three separate approaches that utilise similar numerical methods, but have distinct regimes of validity. Systems at finite temperature can be treated with either the closed-system projected Gross-Pitaevskii equation (PGPE), or the open-system stochastic projected Gross-Pitaevskii equation (SPGPE). These are both applicable in quantum degenerate regimes in which thermal fluctuations are significant. At low or zero temperature, the truncated Wigner projected Gross-Pitaevskii equation (TWPGPE) allows for the simulation of systems in which spontaneous collision processes seeded by quantum fluctuations are important. We describe the regimes of validity of each of these methods, and discuss their relationships to one another, and to other simulation techniques for the dynamics of Bose gases. The utility of the SPGPE formalism in modelling non-equilibrium Bose gases is illustrated by its application to the dynamics of spontaneous vortex formation in the growth of a Bose-Einstein condensate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.5470v2.pdf"}
{"id": "1206.5647", "abstract": "  For the first time we have investigated the behavior of fully micro-fabricated low temperature metallic magnetic calorimeters (MMCs) after undergoing an ion-implantation process. This experiment had the aim to show the possibility to perform a high precision calorimetric measurement of the energy spectrum following the electron capture of ^163Ho using MMCs having the radioactive ^163Ho ions implanted in the absorber. The implantation of ^163Ho ions was performed at ISOLDE-CERN. The performance of a detector that underwent an ion-implantation process is compared to the one of a detector without implanted ions. The results show that the implantation dose of ions used in this experiment does not compromise the properties of the detector. In addition an optimized detector design for future ^163Ho experiments is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.5647v1.pdf"}
{"id": "1208.1606", "abstract": "  The light deflection of one component of a binary system due to the gravitational field of the other component is investigated. While this relativistic effect has not been observed thus far, the question arises that whether this effect becomes detectable in view of todays high-precision astrometry which soon will reach the microarcsecond level of accuracy. The effect is studied and its observability is investigated. It turns out, that in total there are about 1000 binaries having orbital parameters such that the light deflection amounts to be at least 1 microarcsecond. Two stringent criteria for the orbital parameters are presented, by means of which one can easily determine the maximal value of light deflection effect for a given binary system. It is found, that for relevant binaries their orbital parameters must take rather extreme values in order to have a light deflection of the order of a few microarcseconds. Only in a very few and rather extreme binary systems the light deflection effect might be detectable by todays astrometry, but their existence is highly improbable. Thus, the detection of this subtle effect of relativity still remains a challenge for future astrometric missions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.1606v1.pdf"}
{"id": "1208.4184", "abstract": "  Myoglobin single-electron transistors were investigated using nanometer- gap platinum electrodes fabricated by electromigration at cryogenic temperatures. Apomyoglobin (myoglobin without heme group) was used as a reference. The results suggest single electron transport is mediated by resonant tunneling with the electronic and vibrational levels of the heme group in a single protein. They also represent a proof-of-principle that proteins with redox centers across nanometer-gap electrodes can be utilized to fabricate single-electron transistors. The protein orientation and conformation may significantly affect the conductance of these devices. Future improvements in device reproducibility and yield will require control of these factors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.4184v1.pdf"}
{"id": "1209.0007", "abstract": "  We show that charged vector mesons cannot be condensed by a magnetic field. Although some hadron models predict the charged vector meson condensation in a strong magnetic field, we prove, by means of the Vafa-Witten theorem, that this is not the case in QCD. We also perform the numerical analysis for the meson mass and condensation in lattice QCD. The lattice QCD data confirm no charged vector meson condensation in a magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.0007v2.pdf"}
{"id": "1209.0599", "abstract": "  This paper presents an efficient algorithm for robust network reconstruction of Linear Time-Invariant (LTI) systems in the presence of noise, estimation errors and unmodelled nonlinearities. The method here builds on previous work on robust reconstruction to provide a practical implementation with polynomial computational complexity. Following the same experimental protocol, the algorithm obtains a set of structurally-related candidate solutions spanning every level of sparsity. We prove the existence of a magnitude bound on the noise, which if satisfied, guarantees that one of these structures is the correct solution. A problem-specific model-selection procedure then selects a single solution from this set and provides a measure of confidence in that solution. Extensive simulations quantify the expected performance for different levels of noise and show that significantly more noise can be tolerated in comparison to the original method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.0599v1.pdf"}
{"id": "1209.1580", "abstract": "  We investigate the spin behavior of close-in rocky planets and the implications for their orbital evolution. Considering that the planet rotation evolves under simultaneous actions of the torque due to the equatorial deformation and the tidal torque, both raised by the central star, we analyze the possibility of temporary captures in spin-orbit resonances. The results of the numerical simulations of the exact equations of motions indicate that, whenever the planet rotation is trapped in a resonant motion, the orbital decay and the eccentricity damping are faster than the ones in which the rotation follows the so-called pseudo-synchronization. Analytical results obtained through the averaged equations of the spin-orbit problem show a good agreement with the numerical simulations. We apply the analysis to the cases of the recently discovered hot super-Earths Kepler-10 b, GJ 3634 b and 55 Cnc e. The simulated dynamical history of these systems indicates the possibility of capture in several spin-orbit resonances; particularly, GJ 3634 b and 55 Cnc e can currently evolve under a non-synchronous resonant motion for suitable values of the parameters. Moreover, 55 Cnc e may avoid a chaotic rotation behavior by evolving towards synchronization through successive temporary resonant trappings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.1580v1.pdf"}
{"id": "1209.2467", "abstract": "  We studied the Bouchaud-Mézard(BM) model, which was introduced to explain Pareto's law in a real economy, on a random network. Using \"adiabatic and independent\" assumptions, we analytically obtained the stationary probability distribution function of wealth. The results shows that wealth-condensation, indicated by the divergence of the variance of wealth, occurs at a larger J than that obtained by the mean-field theory, where J represents the strength of interaction between agents. We compared our results with numerical simulation results and found that they were in good agreement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.2467v1.pdf"}
{"id": "1209.2580", "abstract": "  Silicene is a monolayer of silicon atoms forming a two-dimensional honeycomb lattice. We investigate the topological properties of a silicene superstructure generated by an external periodic potential. The superstructure is a quantum spin-Hall (QSH) insulator if it is topologically connected to silicene. It is remarkable that two inequivalent K and K' points in the silicene Brillouin zone are identified in certain superstructures. In such a case two Dirac cones coexist at the same Dirac point in the momentum space and they are hexagonally warped by the Coulomb interaction. We carry out a numerical analysis by taking an instance of the (3× 3) superstructure on the (4× 4) structure of the Ag substrate. We show that it is a QSH insulator, that there exists no topological phase transition by external electric field, and that the hexagonally warping occurs in the band structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.2580v2.pdf"}
{"id": "1210.0340", "abstract": "  We present a new approach to the minimum-cost integral flow problem for small values of the flow. It reduces the problem to the tests of simple multi-variate polynomials over a finite field of characteristic two for non-identity with zero. In effect, we show that a minimum-cost flow of value k in a network with n vertices, a sink and a source, integral edge capacities and positive integral edge costs polynomially bounded in n can be found by a randomized PRAM, with errors of exponentially small probability in n, running in O(klog(kn)+log^2 (kn)) time and using 2^k(kn)^O(1) processors. Thus, in particular, for the minimum-cost flow of value O(logn), we obtain an RNC^2 algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.0340v1.pdf"}
{"id": "1210.1052", "abstract": "  The detection of electromagnetic pulses from high energy showers is used as a means to search for Ultra-High Energy cosmic ray and neutrino interactions. An approximate formula has been obtained to numerically evaluate the radio pulse emitted by a charged particle that instantaneously accelerates, moves at constant speed along a straight track and halts again instantaneously. The approximate solution is applied to the particle track after dividing it in smaller subintervals. The resulting algorithm (often referred to as the ZHS algorithm) is also the basis for most of the simulations of the electric field produced in high energy showers in dense media. In this work, the electromagnetic pulses as predicted with the ZHS algorithm are compared to those obtained with an exact solution of the electric field produced by a charged particle track. The precise conditions that must apply for the algorithm to be valid are discussed and its accuracy is addressed. This comparison is also made for electromagnetic showers in dense media. The ZHS algorithm is shown to describe Cherenkov radiation and to be valid for most situations of interest concerning detectors searching for Ultra-High Energy neutrinos. The results of this work are also relevant for the simulation of pulses emitted from air showers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.1052v1.pdf"}
{"id": "1210.1449", "abstract": "  Plane-symmetric gravitational waves are considered as gravitational lenses. Numbers of images, frequency shifts, mutual angles, and image distortion parameters are computed exactly in essentially all non-singular plane wave spacetimes. For a fixed observation event in a particular plane wave spacetime, the number of images is found to be the same for almost every source. This number can be any positive integer, including infinity. Wavepackets of finite width are discussed in detail as well as waves which maintain a constant amplitude for all time. Short wavepackets are found to generically produce up to two images of each source which appear (separately) only some time after the wave has passed. They are initially infinitely bright, infinitely blueshifted images of the infinitely distant past. Later, these images become dim and acquire a rapidly-increasing redshift. For sufficiently weak wavepackets, one such \"flash\" almost always exists. The appearance of a second flash requires that the Ricci tensor inside the wave exceed a certain threshold. This might occur if a gravitational plane wave is sourced by, e.g., a sufficiently strong electromagnetic plane wave. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.1449v2.pdf"}
{"id": "1210.1584", "abstract": "  We describe the La Silla-QUEST (LSQ) Variability Survey. LSQ is a dedicated wide-field synoptic survey in the Southern Hemisphere, focussing on the discovery and study of transients ranging from low redshift (z < 0.1) SN Ia, Tidal Disruption events, RR Lyræ variables, CVs, Quasars, TNOs and others. The survey utilizes the 1.0-m Schmidt Telescope of the European Southern Observatory at La Silla, Chile, with the large-area QUEST camera, a mosaic of 112 CCDs with field of view of 9.6 square degrees. The LSQ Survey was commissioned in 2009, and is now regularly covering  1000 square deg per night with a repeat cadence of hours to days. The data are currently processed on a daily basis. We present here a first look at the photometric capabilities of LSQ and we discuss some of the most interesting recent transient detections. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.1584v1.pdf"}
{"id": "1210.3383", "abstract": "  Multiplicative white-noise stochastic processes continuously attract the attention of a wide area of scientific research. The variety of prescriptions available to define it difficults the development of general tools for its characterization. In this work, we study equilibrium properties of Markovian multiplicative white-noise processes. For this, we define the time reversal transformation for this kind of processes, taking into account that the asymptotic stationary probability distribution depends on the prescription. Representing the stochastic process in a functional Grassman formalism, we avoid the necessity of fixing a particular prescription. In this framework, we analyze equilibrium properties and study hidden symmetries of the process. We show that, using a careful definition of equilibrium distribution and taken into account the appropriate time reversal transformation, usual equilibrium properties are satisfied for any prescription. Finally, we present a detailed deduction of a covariant supersymmetric formulation of a multiplicative Markovian white-noise process and study some of the constraints it imposes on correlation functions using Ward-Takahashi identities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.3383v2.pdf"}
{"id": "1210.4989", "abstract": "  We examine the stability of the \"coast\" motion of fish, that is to say, the motion of a neutrally buoyant fish at constant speed in a straight line. The forces and moments acting on the fish body are thus perfectly balanced. The fish motion is said to be unstable if a perturbation in the conditions surrounding the fish results in forces and moments that tend to increase the perturbation and it is stable if these emerging forces tend to reduce the perturbation and return the fish to its original state. Stability may be achieved actively or passively. Active stabilization requires neurological control that activates musculo-skeletal components to compensate for the external perturbations acting against stability. Passive stabilization on the other hand requires no energy input by the fish and is dependent upon the fish morphology, i.e. geometry and elastic properties. In this paper, we use a deformable body consisting of an articulated body equipped with torsional springs at its hinge joints and submerged in an unbounded perfect fluid as a simple model to study passive stability as a function of the body geometry and spring stiffness. We show that for given body dimensions, the spring elasticity, when properly chosen, leads to passive stabilization of the (otherwise unstable) coast motion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.4989v1.pdf"}
{"id": "1210.8450", "abstract": "  We study the dynamics of single photonic and atomic excitations in the Jaynes-Cummings-Hubbard (JCH) model where the cavities are arranged in an Apollonian network (AN). The existence of a gapped field normal frequency spectrum along with strongly localized eigenstates on the AN highlights many of the features provided by the model. By numerically diagonalizing the JCH Hamiltonian in the single excitation subspace, we evaluate the time evolution of fully localized initial states, for many energy regimes. We provide a detailed description of the photonic quantum walk on the AN and also address how an effective Jaynes-Cummings interaction can be achieved at the strong hopping regime. When the hopping rate and the atom-field coupling strength is of the same order, the excitation is relatively allowed to roam between atomic and photonic degrees of freedom as it propagates. However, different cavities will contribute mostly to one of these components, depending on the detuning and initial conditions, in contrast to the strong atom-field coupling regime, where atomic and photonic modes propagate identically. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.8450v2.pdf"}
{"id": "1211.0917", "abstract": "  We study theoretically and experimentally the electronic relaxation of NO2 molecules excited by absorption of one  400 nm pump photon. Semi-classical simulations based on trajectory surface hopping calculations are performed. They predict fast oscillations of the electronic character around the intersection of the ground and first excited diabatic states. An experiment based on high-order harmonic transient grating spectroscopy reveals dynamics occuring on the same timescale. A systematic study of the detected transient is conducted to investigate the possible influence of the pump intensity, pump wavelength, and rotational temperature of the molecules. The quantitative agreement between measured and predicted dynamics shows that, in NO2, high harmonic transient grating spectroscopy encodes vibrational dynamics underlying the electronic relaxation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.0917v1.pdf"}
{"id": "1211.4706", "abstract": "  Many random processes can be simulated as the output of a deterministic model accepting random inputs. Such a model usually describes a complex mathematical or physical stochastic system and the randomness is introduced in the input variables of the model. When the statistics of the output event are known, these input variables have to be chosen in a specific way for the output to have the prescribed statistics. Because the probability distribution of the input random variables is not directly known but dictated implicitly by the statistics of the output random variables, this problem is usually intractable for classical sampling methods. Based on Markov Chain Monte Carlo we propose a novel method to sample random inputs to such models by introducing a modification to the standard Metropolis-Hastings algorithm. As an example we consider a system described by a stochastic differential equation (sde) and demonstrate how sample paths of a random process satisfying this sde can be generated with our technique. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.4706v1.pdf"}
{"id": "1211.5805", "abstract": "  We present and implement a probabilistic (Bayesian) method for producing catalogs from images of stellar fields. The method is capable of inferring the number of sources N in the image and can also handle the challenges introduced by noise, overlapping sources, and an unknown point spread function (PSF). The luminosity function of the stars can also be inferred even when the precise luminosity of each star is uncertain, via the use of a hierarchical Bayesian model. The computational feasibility of the method is demonstrated on two simulated images with different numbers of stars. We find that our method successfully recovers the input parameter values along with principled uncertainties even when the field is crowded. We also compare our results with those obtained from the SExtractor software. While the two approaches largely agree about the fluxes of the bright stars, the Bayesian approach provides more accurate inferences about the faint stars and the number of stars, particularly in the crowded case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.5805v2.pdf"}
{"id": "1212.0959", "abstract": "  Systems with long range interactions present generically the formation of quasi-stationary long-lived non-equilibrium states. These states relax to Boltzmann equilibrium following a dynamics which is not well understood. In this paper we study this process in two-dimensional inhomogeneous self-gravitating systems. Using the Chandrasekhar – or local – approximation we write a simple approximate kinetic equation for the relaxation process, obtaining a Fokker – Planck equation for the velocity distribution with explicit analytical diffusion coefficients. Performing molecular dynamics simulations and comparing them with the evolution predicted by the Fokker – Planck equation, we observe a good agreement with the model for all the duration of the relaxation, from the formation of the quasi-stationary state to thermal equilibrium. We observe however an overestimate or underestimate of the relaxation rate of the particles with the slower or larger velocities respectively. It is due to systematic errors in estimating the velocities of the particles at the moment of the collisions, inherent to the Chandrasekhar approximation when applied to inhomogeneous systems. Theory and simulations give a scaling of the relaxation time proportional to the number of particles in the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.0959v2.pdf"}
{"id": "1212.1994", "abstract": "  The two components of radio emission, above and below 86 GHz respectively, from the Galactic center source-Sgr A* can be naturally explained by the hybrid of thermal and nonthermal electrons in hot accretion flows (e.g., radiatively inefficient accretion flow, RIAF, e.g., Yuan et al. 2003). We further apply this model to a sample of nearby low-luminosity active galactic nuclei (LLAGNs), which are also believed to be powered by the RIAF. We selected the LLAGNs with only compact radio cores according to the high-resolution radio observations, and the sources observed with jets or jet-like features are excluded. We find that the radio emission of LLAGNs is severely underpredicted by pure RIAF model, and can be naturally explained by the RIAF model with a hybrid electron population consisting of both thermal and nonthermal particles. Our model can roughly reproduce the observed anti-correlation between the mass-corrected radio loudness and Eddington ratio for the LLAGNs in our sample. We further model the spectral energy distributions of each source in our sample, and find that roughly all sources can be well fitted if a small fraction of the steady state electron energy is ejected into the nonthermal electrons. The size of radio emission region of our model is around several thousand gravitational radii, which is also roughly consistent with the recent high-resolution VLBI observations for some nearby LLAGNs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.1994v1.pdf"}
{"id": "1302.0164", "abstract": "  Homophily and social influence are the fundamental mechanisms that drive the evolution of attitudes, beliefs and behaviour within social groups. Homophily relates the similarity between pairs of individuals' attitudinal states to their frequency of interaction, and hence structural tie strength, while social influence causes the convergence of individuals' states during interaction. Building on these basic elements, we propose a new mathematical modelling framework to describe the evolution of attitudes within a group of interacting agents. Specifically, our model describes sub-conscious attitudes that have an activator-inhibitor relationship. We consider a homogeneous population using a deterministic, continuous-time dynamical system. Surprisingly, the combined effects of homophily and social influence do not necessarily lead to group consensus or global monoculture. We observe that sub-group formation and polarisation-like effects may be transient, the long-time dynamics being quasi-periodic with sensitive dependence to initial conditions. This is due to the interplay between the evolving interaction network and Turing instability associated with the attitudinal state dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.0164v1.pdf"}
{"id": "1302.2811", "abstract": "  We consider the task of extracting work from quantum systems in the resource theory perspective of thermodynamics, where free states are arbitrary thermal states, and allowed operations are energy conserving unitary transformations. Taking as our work storage system a 'weight' we prove the second law and then present simple protocols which extract average work equal to the free energy change of the system - the same amount as in classical thermodynamics. Crucially, for systems in 'classical' states (mixtures of energy eigenstates) our protocol works on a single copy of the system. This is in sharp contrast to previous results, which showed that in case of almost-deterministic work extraction, collective actions on multiple copies are necessary to extract the free energy. This establishes the fact that free energy is a meaningful notion even for individual systems in classical states. However, for non-classical states, where coherences between energy levels exist, we prove that collective actions are necessary, so long as no external sources of coherence are used. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.2811v1.pdf"}
{"id": "1303.2015", "abstract": "  ANTARES is the largest neutrino telescope in the Northern hemisphere. The main scientific goal is the search for cosmic neutrinos coming from galactic and extragalactic sources. Neutrinos are detected through the Cherenkov light emitted along the path of charged particles produced in neutrino interactions inside or in the vicinity of the detector. ANTARES is sensitive to all flavors though it is optimized for muon neutrinos. The detector has been taking data in its complete configuration since May 2008.   Using data collected in the period 2007-2010, the first analysis devoted to the search for neutrinos from the Fermi Bubbles is presented. The Fermi Bubbles are characterized by gamma emission with a E^-2 spectrum and a relatively constant intensity all over the space. According to a proposed hadronic mechanism for this gamma-ray emission, the Fermi Bubbles can be a source of high-energy neutrinos. No evidence of a neutrino signal is found in the ANTARES data. Therefore upper limits are calculated for neutrino fluxes with different energy cutoffs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.2015v2.pdf"}
{"id": "1303.4256", "abstract": "  There is more than 3 sigma deviation between the experimental and theoretical results of the muon g-2. This suggests that some of the SUSY particles have a mass of order 100 GeV. We study searches for those particles at the LHC with particular attention to the muon g-2. In particular, the recent results on the searches for the non-colored SUSY particles are investigated in the parameter region where the muon g-2 is explained. The analysis is independent of details of the SUSY models. Future prospects of the collider searches are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.4256v1.pdf"}
{"id": "1304.4387", "abstract": "  Coastal transport in the Bay of Palma, a small region in the island of Mallorca, Spain, is characterized in terms of Lagrangian descriptors. The data sets used for this study are the output for two months (one in autumn and one in summer) of a high resolution numerical model, ROMS, forced atmospherically and with a spatial resolution of 300 m. The two months were selected because its different wind regime, which is the main driver of the sea dynamics in this area. Finite-size Lyapunov Exponents (FSLEs) were used to locate semi-persistent Lagrangian coherent structures (LCS) and to understand the different flow regimes in the Bay. The different wind directions and regularity in the two months have a clear impact on the surface Bay dynamics, whereas only topographic features appear clearly in the bottom structures. The fluid interchange between the Bay and the open ocean was tudied by computing particle trajectories and Residence Times (RT) maps. The escape rate of particles out of the Bay is qualitatively different, with a 32", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.4387v4.pdf"}
{"id": "1304.4417", "abstract": "  We apply the frozen density embedding method, using a full relaxation of embedded densities through a freeze-and-thaw procedure, to study the electronic structure of several benchmark ground-state charge-transfer complexes, in order to assess the merits and limitations of the approach for this class of systems. The calculations are performed using both semilocal and hybrid exchange-correlation (XC) functionals. The results show that embedding calculations using semilocal XC functionals yield rather large deviations with respect to the corresponding supermolecular calculations. Due to a large error cancellation effect, however, they can often provide a relatively good description of the electronic structure of charge-transfer complexes, in contrast to supermolecular calculations performed at the same level of theory. On the contrary, when hybrid XC functionals are employed, both embedding and supermolecular calculations agree very well with each other and with the reference benchmark results.   In conclusion, for the study of ground-state charge-transfer complexes via embedding calculations hybrid XC functionals are the method of choice due to their higher reliability and superior performance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.4417v1.pdf"}
{"id": "1305.5163", "abstract": "  The holographic model for a two-dimensional superconductor has been investigated by considering the three-dimensional gravity in the bulk. To find the critical temperature, we used the Sturm-Liouville variational method. Where as the same method is applied for calculating the condensation of the dual operators on the boundary. We included the back reactions on the metric by a combination of the perturbation method of the fields with respect to the small parameter and then applying the variational integrals on the resulting equations of the motion. The critical temperature has been successfully obtained on the backreaction effects, and we showed that it dropped with a rise in the backreaction of the fields, and it makes the condensation harder. We can use our analytical results to support the numerical data which was reported previously. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.5163v1.pdf"}
{"id": "1305.5445", "abstract": "  Estimation of the long-term health effects of air pollution is a challenging task, especially when modelling small-area disease incidence data in an ecological study design. The challenge comes from the unobserved underlying spatial correlation structure in these data, which is accounted for using random effects modelled by a globally smooth conditional autoregressive model. These smooth random effects confound the effects of air pollution, which are also globally smooth. To avoid this collinearity a Bayesian localised conditional autoregressive model is developed for the random effects. This localised model is flexible spatially, in the sense that it is not only able to model step changes in the random effects surface, but also is able to capture areas of spatial smoothness in the study region. This methodological development allows us to improve the estimation performance of the covariate effects, compared to using traditional conditional auto-regressive models. These results are established using a simulation study, and are then illustrated with our motivating study on air pollution and respiratory ill health in Greater Glasgow, Scotland in 2010. The model shows substantial health effects of particulate matter air pollution and income deprivation, whose effects have been consistently attenuated by the currently available globally smooth models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.5445v1.pdf"}
{"id": "1305.5928", "abstract": "  In this note we introduce the (homologically essential) arc complex of a surface as a tool for studying properties of open book decompositions and contact structures. After characterizing destabilizability in terms of the essential translation distance of the monodromy of an open book we given an application of this result to show that there are planer open books of the standard contact structure on the 3-sphere with 5 (or any number larger than 5) boundary components that do not destabilize. We also show that any planar open book with 4 or fewer boundary components does destabilize. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.5928v1.pdf"}
{"id": "1305.7225", "abstract": "  Faraday Rotation (FR) of CMB polarization, as measured through mode-coupling correlations of E and B modes, can be a promising probe of a stochastic primordial magnetic field (PMF). While the existence of a PMF is still hypothetical, there will certainly be a contribution to CMB FR from the magnetic field of the Milky Way. We use existing estimates of the Milky Way rotation measure (RM) to forecast its detectability with upcoming and future CMB experiments. We find that the galactic RM will not be seen in polarization measurements by Planck, but that it will need to be accounted for by CMB experiments capable of detecting the weak lensing contribution to the B-mode. We then discuss prospects for constraining the PMF in the presence of FR due to the galaxy under various assumptions that include partial de-lensing and partial subtraction of the galactic FR. We find that a realistic future sub-orbital experiment, covering a patch of the sky near the galactic poles, can detect a scale-invariant PMF of 0.1 nano-Gauss at better than 95", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.7225v2.pdf"}
{"id": "1306.0151", "abstract": "  We solve for the motion of charged particles in a helical time-periodic ABC (Arnold-Beltrami-Childress) magnetic field. The magnetic field lines of a stationary ABC field with coefficients A=B=C=1 are chaotic, and we show that the motion of a charged particle in such a field is also chaotic at late times with positive Lyapunov exponent. We further show that in time-periodic ABC fields, the kinetic energy of a charged particle can increase indefinitely with time. At late times the mean kinetic energy grows as a power law in time with an exponent that approaches unity. For an initial distribution of particles, whose kinetic energy is uniformly distributed within some interval, the PDF of kinetic energy is, at late times, close to a Gaussian but with steeper tails. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.0151v2.pdf"}
{"id": "1307.7059", "abstract": "  Wireless sensor networks are appearing as an emerging need for mankind. Though, Such networks are still in research phase however, they have high potential to be applied in almost every field of life. Lots of research is done and a lot more is awaiting to be standardized. In this work, cluster based routing in wireless sensor networks is studied precisely. Further, we modify one of the most prominent wireless sensor network's routing protocol \"LEACH\" as modified LEACH (MODLEACH) by introducing efficient cluster head replacement scheme and dual transmitting power levels. Our modified LEACH, in comparison with LEACH out performs it using metrics of cluster head formation, through put and network life. Afterwards, hard and soft thresholds are implemented on modified LEACH (MODLEACH) that boast the performance even more. Finally a brief performance analysis of LEACH, Modified LEACH (MODLEACH), MODLEACH with hard threshold (MODLEACHHT) and MODLEACH with soft threshold (MODLEACHST) is undertaken considering metrics of throughput, network life and cluster head replacements. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.7059v1.pdf"}
{"id": "1308.2630", "abstract": "  This paper reports on a study in which a novel virtual moving sound-based spatial auditory brain-computer interface (BCI) paradigm is developed. Classic auditory BCIs rely on spatially static stimuli, which are often boring and difficult to perceive when subjects have non-uniform spatial hearing perception characteristics. The concept of moving sound proposed and tested in the paper allows for the creation of a P300 oddball paradigm of necessary target and non-target auditory stimuli, which are more interesting and easier to distinguish. We present a report of our study of seven healthy subjects, which proves the concept of moving sound stimuli usability for a novel BCI. We compare online BCI classification results in static and moving sound paradigms yielding similar accuracy results. The subject preference reports suggest that the proposed moving sound protocol is more comfortable and easier to discriminate with the online BCI. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.2630v2.pdf"}
{"id": "1308.4461", "abstract": "  We analyze the effect of color superconductivity in the transition from hot hadron matter to quark matter in the presence of a gas of trapped electron neutrinos. To describe strongly interacting matter we adopt a two-phase picture in which the hadronic phase is described by means of a non-linear Walecka model and just deconfined matter through the MIT bag model including color superconductivity. We impose flavor conservation during the transition in such a way that just deconfined quark matter is transitorily out of equilibrium with respect to weak interactions. Our results show that color superconductivity facilitates the transition for temperatures below T_c. This effect may be strong if the superconducting gap is large enough. As in previous work we find that trapped neutrinos increase the critical density for deconfinement; however, if the just deconfined phase is color superconducting this effect is weaker than if deconfined matter is unpaired. We also explore the effect of different parametrizations of the hadronic equation of state (GM1 and NL3) and the effect of hyperons in the hadronic phase. We compare our results with those previously obtained employing the Nambu-Jona-Lasinio model in the description of just deconfined matter and show that they are in excellent agreement if the bag constant B is properly chosen. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.4461v2.pdf"}
{"id": "1309.2470", "abstract": "  We demonstrate an experimental realization of remote state preparation via the quantum teleportation algorithm, using an entangled photon pair in the polarization degree of freedom as the quantum resource. The input state is encoded on the path of one of the photons from the pair. The improved experimental scheme allows us to control the preparation and teleportation of a state over the entire Bloch sphere with a resolution of the degree of mixture given by the coherence length of the photon pair. Both the preparation of the input state and the implementation of the quantum gates are performed in a pair of chained displaced Sagnac interferometers, which contribute to the overall robustness of the setup. An average fidelity above 0.9 is obtained for the remote state preparation process. This scheme allows for a prepared state to be transmitted on every repetition of the experiment, thus giving an intrinsic success probability of 1. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.2470v1.pdf"}
{"id": "1309.3011", "abstract": "  Curtis-Ingerman-Morrow characterize response matrices for circular planar electrical networks as symmetric square matrices with row sums zero and non-negative circular minors. In this paper, we study this positivity phenomenon more closely, from both algebraic and combinatorial perspectives. Extending work of Postnikov, we introduce electrical positroids, which are the sets of circular minors which can simultaneously be positive in a response matrix. We give a self-contained axiomatic description of these electrical positroids. In the second part of the paper, we discuss a naturally arising example of a Laurent phenomenon algebra, as studied by Lam-Pylyavskyy. We investigate the clusters in this algebra, building off of initial work by Kenyon-Wilson, using an analogue of weak separation, as was originally introduced by Leclerc-Zelevinsky. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.3011v1.pdf"}
{"id": "1309.5994", "abstract": "  We present a nonequilibrium strong-coupling approach to inhomogeneous systems of ultracold atoms in optical lattices. We demonstrate its application to the Mott-insulating phase of a two-dimensional Fermi-Hubbard model in the presence of a trap potential. Since the theory is formulated self-consistently, the numerical implementation relies on a massively parallel evaluation of the self-energy and the Green's function at each lattice site, employing thousands of CPUs. While the computation of the self-energy is straightforward to parallelize, the evaluation of the Green's function requires the inversion of a large sparse 10^d× 10^d matrix, with d > 6. As a crucial ingredient, our solution heavily relies on the smallness of the hopping as compared to the interaction strength and yields a widely scalable realization of a rapidly converging iterative algorithm which evaluates all elements of the Green's function. Results are validated by comparing with the homogeneous case via the local-density approximation. These calculations also show that the local-density approximation is valid in non-equilibrium setups without mass transport. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.5994v1.pdf"}
{"id": "1309.6766", "abstract": "  The style of mathematical models known to probabilists as Interacting Particle Systems and exemplified by the Voter, Exclusion and Contact processes have found use in many academic disciplines. In many such disciplines the underlying conceptual picture is of a social network, where individuals meet pairwise and update their \"state\" (opinion, activity etc) in a way depending on the two previous states. This picture motivates a precise general setup we call Finite Markov Information Exchange (FMIE) processes. We briefly describe a few less familiar models (Averaging, Compulsive Gambler, Deference, Fashionista) suggested by the social network picture, as well as a few familiar ones. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.6766v1.pdf"}
{"id": "1309.7391", "abstract": "  Constructionism is a learning theory that states that we learn more when we construct tangible objects. In the process of building and presenting our work, we make concrete the abstract mental models we've formed, see where they breakdown through the feedback we receive, and revise the models accordingly. Computer programming has long been taught under a constructionist approach using sensory-rich contexts like robots, media, and Logo-style environments. Now, with affordable 3-D printers in the hands of consumers, we have a new medium in which learners may realize their computational ideas. In this demonstration, we share a mobile development environment named Madeup, which empowers its users to navigate 3-D space using a Logo-like imperative and functional language. Every stop in space becomes a vertex in a 3-D model. The generated models may be exported or uploaded to a 3-D printing service. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.7391v1.pdf"}
{"id": "1309.7631", "abstract": "  We study the effect of perpendicular single-ion anisotropy, -As_z^2, on the ground-state structure and finite-temperature properties of a two-dimensional magnetic nanodot in presence of a dipolar interaction of strength D. By a simulated annealing Monte Carlo method, we show that in the ground state a vortex core perpendicular to the nanodot plane emerges already in the range of moderate anisotropy values above a certain threshold level. In the giant-anisotropy regime the vortex structure is superseded by a stripe domain structure with stripes of alternate domains perpendicular to the surface of the sample. We have also observed an intermediate stage between the vortex and stripe structures, with satellite regions of tilted nonzero perpendicular magnetization around the core. At finite temperatures, at small A, we show by Monte Carlo simulations that there is a transition from the the in-plane vortex phase to the disordered phase characterized by a peak in the specific heat and the vanishing vortex order parameter. At stronger A, we observe a discontinuous transition with a large latent heat from the in-plane vortex phase to perpendicular stripe ordering phase before a total disordering at higher temperatures. In the regime of perpendicular stripe domains, namely with giant A, there is no phase transition at finite T: the stripe domains are progressively disordered with increasing T. Finite-size effects are shown and discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.7631v1.pdf"}
{"id": "1310.3455", "abstract": "  Hadrons inclusively produced with large pT in high-energy collisions originate from the jets, whose initial virtuality and energy are of the same order, what leads to an extremely intensive gluon radiation and dissipation of energy at the early stage of hadronization. Besides, these jets have a peculiar structure: the main fraction of the jet energy is carried by a single leading hadron, so such jets are very rare. The constraints imposed by energy conservation enforce an early color neutralization and a cease of gluon radiation. The produced colorless dipole does not dissipate energy anymore and is evolving to form the hadron wave function. The small and medium pT region is dominated by the hydrodynamic mechanisms of hadron production from the created hot medium. The abrupt transition between the hydrodynamic and perturbative QCD mechanisms causes distinct minima in the pT dependence of the suppression factor R_AA and of the azimuthal asymmetry v2. Combination of these mechanisms allows to describe the data through the full range of pT at different collision energies and centralities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.3455v2.pdf"}
{"id": "1310.4790", "abstract": "  We study the dynamics of the entanglement structure of a multipartite system experiencing a dissipative evolution. We characterize the processes leading to a particular form of output system entanglement and provide a recipe for their identification via concatenations of particular linear maps with entanglement-breaking operations. We illustrate the applicability of our approach by considering local and global depolarizing noises acting on general multiqubit states. A difference in the typical entanglement behavior of systems subjected to these noises is observed: the originally genuine entanglement dissociates by splitting off particles one by one in the case of local noise, whereas intermediate stages of entanglement clustering are present in the case of global noise. We also analyze the definitive phase of evolution when the annihilation of the entanglement compound finally takes place. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.4790v2.pdf"}
{"id": "1310.6522", "abstract": "  When a driven oscillator loses phase-locking to a master oscillator via a Hopf bifurcation, it enters a bounded-phase regime in which its average frequency is still equal to the master frequency, but its phase displays temporal oscillations. Here we characterize these two synchronization regimes in a laser experiment, by measuring the spectrum of the phase fluctuations across the bifurcation. We find experimentally, and confirm numerically, that the low frequency phase noise of the driven oscillator is strongly suppressed in both regimes in the same way. Thus the long-term phase stability of the master oscillator is transferred to the driven one, even in the absence of phase-locking. The numerical study of a generic, minimal model suggests that such behavior is universal for any periodically driven oscillator near a Hopf bifurcation point. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.6522v2.pdf"}
{"id": "1310.7494", "abstract": "  After Isaac Newton was knighted by Queen Anne in 1705 he adopted an unusual coat of arms: a pair of human tibiae crossed on a black background, like a pirate flag without the skull. After some general reflections on Newton's monumental scientific achievements and on his enigmatic life, we investigate the story of his coat of arms. We also discuss how its simple design illustrates the concept of chirality, which would later play an important role in the philosophical arguments about Newton's conception of space, as well as in the development of modern chemistry and particle physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.7494v2.pdf"}
{"id": "1310.8116", "abstract": "  Although it is now understood that chaos in complex classical systems is the foundation of thermodynamic behavior, the detailed relations between the microscopic properties of the chaotic dynamics and the macroscopic thermodynamic observations still remain mostly in the dark. In this work, we numerically analyze the probability of chaos in strongly nonlinear Hamiltonian systems and find different scaling properties depending on the nonlinear structure of the model. We argue that these different scaling laws of chaos have definite consequences for the macroscopic diffusive behavior, as chaos is the microscopic mechanism of diffusion. This is compared with previous results on chaotic diffusion [New J. Phys. 15, 053015 (2013)], and a relation between microscopic chaos and macroscopic diffusion is established. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.8116v2.pdf"}
{"id": "1311.4470", "abstract": "  We describe here the first experimental realization of a heat interferometer, thermal counterpart of the well-known superconducting quantum interference device (SQUID). These findings demonstrate, on the first place, the existence of phase-dependent heat transport in Josephson-based superconducting circuits and, on the second place, open the way to novel ways of mastering heat at the nanoscale. Combining the use of external magnetic fields for phase biasing and different Josephson junction architectures we show here that a number of heat interference patterns can be obtained. The experimental realization of these architectures, besides being relevant from a fundamental physics point of view, might find important technological application as building blocks of phase-coherent quantum thermal circuits. In particular, the performance of two different heat rectifying devices is analyzed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.4470v2.pdf"}
{"id": "1311.6276", "abstract": "  We consider the steady-state thermoelectric transport through a vibrating molecular quantum dot that is contacted to macroscopic leads. For moderate electron-phonon interaction strength and comparable electronic and phononic timescales, we investigate the impact of the formation of a local polaron on the thermoelectric properties of the junction. We apply a variational Lang-Firsov transformation and solve the equations of motion in the Kadanoff-Baym formalism up to second order in the dot-lead coupling parameter. We calculate the thermoelectric current and voltage for finite temperature differences in the resonant and inelastic tunneling regimes. For a near resonant dot level, the formation of a local polaron can boost the thermoelectric effect because of the Franck-Condon blockade. The line shape of the thermoelectric voltage signal becomes asymmetrical due to the varying polaronic character of the dot state and in the nonlinear transport regime, vibrational signatures arise. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.6276v2.pdf"}
{"id": "1312.0552", "abstract": "  The Herschel Multi-tiered Extragalactic Survey (HerMES) is the largest Guaranteed Time Key Programme on the Herschel Space Observatory. With a wedding cake survey strategy, it consists of nested fields with varying depth and area totalling  380 deg^2. In this paper, we present deep point source catalogues extracted from Herschel-SPIRE observations of all HerMES fields, except for the later addition of the 270 deg^2 HeLMS field. These catalogues constitute the second Data Release (DR2) made in October 2013. A subset of these catalogues, which consists of bright sources extracted from Herschel-SPIRE observations completed by May 1, 2010 (covering   74 deg^2) were released earlier in the first extensive Data Release (DR1) in March 2012. Two different methods are used to generate the point source catalogues, the SUSSEXtractor (SXT) point source extractor used in two earlier data releases (EDR and EDR2) and a new source detection and photometry method. The latter combines an iterative source detection algorithm, StarFinder (SF), and a De-blended SPIRE Photometry (DESPHOT) algorithm. We use end-to-end Herschel-SPIRE simulations with realistic number counts and clustering properties to characterise basic properties of the point source catalogues, such as the completeness, reliability, photometric and positional accuracy. Over 500, 000 catalogue entries in HerMES fields (except HeLMS) are released to the public through the HeDAM website (http://hedam.oamp.fr/herMES). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.0552v1.pdf"}
{"id": "1312.1597", "abstract": "  We study traveling wave solutions of an equation for surface waves of moderate amplitude arising as a shallow water approximation of the Euler equations for inviscid, incompressible and homogenous fluids. We obtain solitary waves of elevation and depression, including a family of solitary waves with compact support, where the amplitude may increase or decrease with respect to the wave speed. Our approach is based on techniques from dynamical systems and relies on a reformulation of the evolution equation as an autonomous Hamiltonian system which facilitates an explicit expression for bounded orbits in the phase plane to establish existence of the corresponding periodic and solitary traveling wave solutions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.1597v1.pdf"}
{"id": "1312.3597", "abstract": "  In this paper we construct asymptotically locally AdS and flat black holes in the presence of a scalar field whose kinetic term is constructed out from a linear combination of the metric and the Einstein tensor. The field equations as well as the energy-momentum tensor are second order in the metric and the field, therefore the theory belongs to the ones defined by Horndeski. We show that in the presence of a cosmological term in the action, it is possible to have a real scalar field in the region outside the event horizon. The solutions are characterized by a single integration constant, the scalar field vanishes at the horizon and it contributes to the effective cosmological constant at infinity. We extend these results to the topological case. The solution is disconnected from the maximally symmetric AdS background, however, within this family there exits a gravitational soliton which is everywhere regular. This soliton is therefore used as a background to define a finite Euclidean action and to obtain the thermodynamics of the black holes. For a certain region in the space of parameters, the thermodynamic analysis reveals a critical temperature at which a Hawking-Page phase transition between the black hole and the soliton occurs. We extend the solution to arbitrary dimensions grater than four and show that the presence of a cosmological term in the action allows to consider the case in which the standard kinetic term for the scalar it's not present. In such scenario, the solution reduces to an asymptotically flat black hole. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.3597v2.pdf"}
{"id": "1312.4021", "abstract": "  There has been great interest in finding sets of m mutually unbiased bases which are compatible with a given space ℂ^d, specially in physics due to their interesting applications in quantum information theory. Several general results have been obtained so far, but surprising results may occur for definite (m,d)-values. One such case that has remained an open question (the simplest case) is the one regarding the existence of m=4 mutually orthogonal bases for d=6. In the present work we introduce a new approach to the problem by translating it into an optimization procedure for a given pair (m,d). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.4021v3.pdf"}
{"id": "1312.5051", "abstract": "  A computational method based on a first-principles multiscale simulation has been used for calculating the optical response and the ablation threshold of an optical material irradiated with an ultrashort intense laser pulse. The method employs Maxwell's equations to describe laser pulse propagation and time-dependent density functional theory to describe the generation of conduction band electrons in an optical medium. Optical properties, such as reflectance and absorption, were investigated for laser intensities in the range 10^10 W/cm^2 to 2 × 10^15 W/cm^2 based on the theory of generation and spatial distribution of the conduction band electrons. The method was applied to investigate the changes in the optical reflectance of α-quartz bulk, half-wavelength thin-film and quarter-wavelength thin-film and to estimate their ablation thresholds. Despite the adiabatic local density approximation used in calculating the exchange–correlation potential, the reflectance and the ablation threshold obtained from our method agree well with the previous theoretical and experimental results. The method can be applied to estimate the ablation thresholds for optical materials in general. The ablation threshold data can be used to design ultra-broadband high-damage-threshold coating structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.5051v1.pdf"}
{"id": "1312.5398", "abstract": "  In this paper we consider a problem of searching a space of predictive models for a given training data set. We propose an iterative procedure for deriving a sequence of improving models and a corresponding sequence of sets of non-linear features on the original input space. After a finite number of iterations N, the non-linear features become 2^N -degree polynomials on the original space. We show that in a limit of an infinite number of iterations derived non-linear features must form an associative algebra: a product of two features is equal to a linear combination of features from the same feature space for any given input point. Because each iteration consists of solving a series of convex problems that contain all previous solutions, the likelihood of the models in the sequence is increasing with each iteration while the dimension of the model parameter space is set to a limited controlled value. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.5398v2.pdf"}
{"id": "1401.3066", "abstract": "  Iron-base superconductors exhibits features of systems where the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase, a superconducting state with non-zero total momentum of Cooper pairs, is actively sought. Experimental and theoretical evidence points strongly to the FFLO phase in these materials above the Pauli limit. In this article we discuss the ground state of iron-base superconductors near the critical magnetic field and the full h-T phase diagram for pnictides in case of intra-band pairing, in a three-band model with s_± symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.3066v1.pdf"}
{"id": "1401.3396", "abstract": "  Coupling of plasmons in graphene at terahert (THz) frequencies with surface plasmons in a heavily-doped substrate is studied theoretically. We reveal that a huge scattering rate may completely damp out the plasmons, so that proper choices of material and geometrical parameters are essential to suppress the coupling effect and to obtain the minimum damping rate in graphene. Even with the doping concentration 10^19 - 10^20 cm^-3 and the thickness of the dielectric layer between graphene and the substrate 100 nm, which are typical values in real graphene samples with a heavily-doped substrate, the increase in the damping rate is not negligible in comparison with the acoustic-phonon-limited damping rate. Dependence of the damping rate on wavenumber, thicknesses of graphene-to-substrate and gate-to-graphene separation, substrate doping concentration, and dielectric constants of surrounding materials are investigated. It is shown that the damping rate can be much reduced by the gate screening, which suppresses the field spread of the graphene plasmons into the substrate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.3396v1.pdf"}
{"id": "1401.7697", "abstract": "  The paper studies a method for solving elliptic partial differential equations posed on hypersurfaces in ℝ^N, N=2,3. The method allows a surface to be given implicitly as a zero level of a level set function. A surface equation is extended to a narrow-band neighborhood of the surface. The resulting extended equation is a non-degenerate PDE and it is solved on a bulk mesh that is unaligned to the surface. An unfitted finite element method is used to discretize extended equations. Error estimates are proved for finite element solutions in the bulk domain and restricted to the surface. The analysis admits finite elements of a higher order and gives sufficient conditions for archiving the optimal convergence order in the energy norm. Several numerical examples illustrate the properties of the method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.7697v3.pdf"}
{"id": "1402.1595", "abstract": "  NEOs come close to the Earth's orbit so that any dust ejected from them, might be seen as a meteor shower. Orbits evolve rapidly, so that a similarity of orbits at one given time is not suffcient to prove a relationship, orbital evolution over a long time interval also has to be similar. Sporadic meteoroids can not be associated with a single parent body, they can only be classified as cometary or asteroidal. However, by considering one parameter criteria, many sporadics are not classified properly therefore two parameter approach was proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.1595v1.pdf"}
{"id": "1402.3041", "abstract": "  The XMM-Newton spectral-fit database is an ongoing ESA funded project aimed to construct a catalogue of spectral-fitting results for all the sources within the XMM-Newton serendipitous source catalogue for which spectral data products have been pipeline-extracted (  120,000 X-ray source detections). The fundamental goal of this project is to provide the astronomical community with a tool to construct large and representative samples of X-ray sources by allowing source selection according to spectral properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.3041v1.pdf"}
{"id": "1402.3198", "abstract": "  Certain methods of analysis require the knowledge of the spatial distances between entities whose data are stored in a microdata table. For instance, such knowledge is necessary and sufficient to perform data mining tasks such as nearest neighbour searches or clustering. However, when inter-record distances are published in addition to the microdata for research purposes, the risk of identity disclosure has to be taken into consideration again. In order to tackle this problem, we introduce a flexible graph model for microdata in a metric space and propose a linkage attack based on realistic assumptions of a data snooper's background knowledge. This attack is based on the idea of finding a maximum approximate common subgraph of two vertex-labelled and edge-weighted graphs. By adapting a standard argument from algorithmic graph theory to our setup, this task is transformed to the maximum clique detection problem in a corresponding product graph. Using a toy example and experimental results on simulated data show that publishing even approximate distances could increase the risk of identity disclosure unreasonably. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.3198v1.pdf"}
{"id": "1402.3479", "abstract": "  We present a study of age-related spectral signatures observed in 25 young low-mass objects that we have previously determined as possible kinematic members of five young moving groups: the Local Association (Pleiades moving group, age=20 - 150 Myr), the Ursa Major group (Sirius supercluster, age=300 Myr), the Hyades supercluster (age=600 Myr), IC 2391 supercluster (age=35–55 Myr) and the Castor moving group (age=200 Myr).   In this paper we characterize the spectral properties of observed high or low resolution spectra of our kinematic members by fitting theoretical spectral distributions.   We study signatures of youth, such as lithium i 6708 Å, Hα emission and other age-sensitive spectroscopic signatures in order to confirm the kinematic memberships through age constraints.   We find that 21 (84%) targets show spectroscopic signatures of youth in agreement with the age ranges of the moving group to which membership is implied. For two further objects, age-related constraints remain difficult to determine from our analysis. In addition, we confirm two moving group kinematic candidates as brown dwarfs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.3479v1.pdf"}
{"id": "1402.6755", "abstract": "  We have identified spectral features in the late-time X-ray afterglow of the unusually long, slow-decaying GRB 130925A using NuSTAR, Swift-XRT, and Chandra. A spectral component in addition to an absorbed power-law is required at >4σ significance, and its spectral shape varies between two observation epochs at 2×10^5 and 10^6 seconds after the burst. Several models can fit this additional component, each with very different physical implications. A broad, resolved Gaussian absorption feature of several keV width improves the fit, but it is poorly constrained in the second epoch. An additive black body or second power-law component provide better fits. Both are challenging to interpret: the blackbody radius is near the scale of a compact remnant (10^8 cm), while the second powerlaw component requires an unobserved high-energy cutoff in order to be consistent with the non-detection by Fermi-LAT. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.6755v1.pdf"}
{"id": "1403.1125", "abstract": "  The effects of a radiation field (RF) on the interaction process of a relativistic electron beam (REB) with an electron plasma are investigated. The stopping power of the test electron averaged with a period of the RF has been calculated assuming an underdense plasma, ω_0 >ω_p, where ω_0 is the frequency of the RF and ω_p is the plasma frequency. In order to highlight the effect of the radiation field we present a comparison of our analytical and numerical results obtained for nonzero RF with those for vanishing RF. In particular, it has been shown that the weak RF increases the mean energy loss for small angles between the velocity of the REB and the direction of polarization of the RF while decreasing it at large angles. Furthermore, the relative deviation of the energy loss from the field-free value is strongly reduced with increasing the beam energy. Special case of the parallel orientation of the polarization of the RF with respect to the beam velocity has been also considered. At high-intensities of the RF two extreme regimes have been distinguished when the excited harmonics cancel effectively each other reducing strongly the energy loss or increasing it due to the constructive interference. Moreover, it has been demonstrated that the energy loss of the ultrarelativistic electron beam increases systematically with the intensity of the RF exceeding essentially the field-free value. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.1125v1.pdf"}
{"id": "1403.2717", "abstract": "  By using a correlated many body method and using the realistic van der Waals potential we study several statistical measures like the specific heat, transition temperature and the condensate fraction of the interacting Bose gas trapped in an anharmonic potential. As the quadratic plus a quartic confinement makes the trap more tight, the transition temperature increases which makes more favourable condition to achieve Bose-Einstein condensation (BEC) experimentally. BEC in 3D isotropic harmonic potential is also critically studied, the correction to the critical temperature due to finite number of atoms and also the correction due to inter-atomic interaction are calculated by the correlated many-body method. Comparison and discussion with the mean-field results are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.2717v2.pdf"}
{"id": "1404.3476", "abstract": "  We study spreading wave packets in a disordered nonlinear ladder with broken time-reversal symmetry induced by synthetic gauge fields. The model describes the dynamics of interacting bosons in a disordered and driven optical ladder within a mean-field approximation. The second moment of the wave packet m_2 = g t^α grows subdiffusively with the universal exponent α≃ 1/3 similar to the time-reversal case. However the prefactor g is strongly modified by the field strength and shows a non-monotonic dependence. For a weak field, the prefactor increases since time-reversal enhanced backscattering is suppressed. For strong fields the spectrum of the linear wave equation reduces the localization length through the formation of gaps and narrow bands. Consequently the prefactor for the subdiffusive spreading law is suppressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.3476v3.pdf"}
{"id": "1404.4196", "abstract": "  Debris disks are thought to be sculptured by neighboring planets. The same is true for the Edgeworth-Kuiper debris disk, yet no direct observational evidence for signatures of giant planets in the Kuiper belt dust distribution has been found so far. Here we model the dust distribution in the outer solar system to reproduce the dust impact rates onto the dust detector onboard the New Horizons spacecraft measured so far and to predict the rates during the Neptune orbit traverse. To this end, we take a realistic distribution of transneptunian objects to launch a sufficient number of dust grains of different sizes and follow their orbits by including radiation pressure, Poynting-Robertson and stellar wind drag, as well as the perturbations of four giant planets. In a subsequent statistical analysis, we calculate number densities and lifetimes of the dust grains in order to simulate a collisional cascade. In contrast to the previous work, our model not only considers collisional elimination of particles, but also includes production of finer debris. We find that particles captured in the 3:2 resonance with Neptune build clumps that are not removed by collisions, because the depleting effect of collisions is counteracted by production of smaller fragments. Our model successfully reproduces the dust impact rates measured by New Horizons out to  23AU and predicts an increase of the impact rate of about a factor of two or three around the Neptune orbit crossing. This result is robust with respect to the variation of the vaguely known number of dust-producing scattered disk objects, collisional outcomes, and the dust properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.4196v1.pdf"}
{"id": "1405.2408", "abstract": "  Decoherence is one of the main obstacles in long-distance quantum communication. Recently, the theoretical work of Fröwis and W. Dür (Phys. Rev. Lett. 106, 110402 (2011)) and the experiment of Lu et al. (Nat. Photon. 8, 364 (2014)) both showed that the logic qubits entanglement say the concatenated Greenberger-Horne-Zeilinger (C-GHZ) state is more robust under decoherence. In this paper, we describe a protocol for Bell-state analysis for this logic qubits entanglement. This protocol can also be extended to the multipartite C-GHZ state analysis. Also, we discuss its application in the quantum teleportation of a unknown logic qubit and in the entanglement swapping of logic Bell states. As the logic qubits entanglement is more robust under decoherence, our protocol shows that it is possible to realize the long-distance quantum communication based on logic qubits entanglement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.2408v1.pdf"}
{"id": "1405.4690", "abstract": "  When a superconducting sample is submitted to a sufficiently strong external magnetic field, the superconductivity of the material is lost. In this paper we prove that this effect does not, in general, take place at a unique value of the external magnetic field strength. Indeed, for a sample in the shape of a narrow annulus the set of magnetic field strengths for which the sample is superconducting is not an interval. This is a rigorous justification of the Little-Parks effect. We also show that the same oscillation effect can happen for disc-shaped samples if the external magnetic field is non-uniform. In this case the oscillations can even occur repeatedly along arbitrarily large values of the Ginzburg–Landau parameter κ. The analysis is based on an understanding of the underlying spectral theory for a magnetic Schrödinger operator. It is shown that the ground state energy of such an operator is not in general a monotone function of the intensity of the field, even in the limit of strong fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.4690v1.pdf"}
{"id": "1405.6202", "abstract": "  A novel geometry for a sampling calorimeter employing inorganic scintillators as an active medium is presented. To overcome the mechanical challenges of construction, an innovative light collection geometry has been pioneered, that minimises the complexity of construction. First test results are presented, demonstrating a successful signal extraction. The geometry consists of a sampling calorimeter with passive absorber layers interleaved with layers of an active medium made of inorganic scintillating crystals. Wavelength-shifting (WLS) fibres run along the four long, chamfered edges of the stack, transporting the light to photodetectors at the rear. To maximise the amount of scintillation light reaching the WLS fibres, the scintillator chamfers are depolished. It is shown herein that this concept is working for cerium fluoride (CeF_3) as a scintillator. Coupled to it, several different types of materials have been tested as WLS medium. In particular, materials that might be sufficiently resistant to the High-Luminosity Large Hadron Collider radiation environment, such as cerium-doped Lutetium-Yttrium Orthosilicate (LYSO) and cerium-doped quartz, are compared to conventional plastic WLS fibres. Finally, an outlook is presented on the possible optimisation of the different components, and the construction and commissioning of a full calorimeter cell prototype is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.6202v1.pdf"}
{"id": "1405.7514", "abstract": "  Galaxies and massive black holes (BHs) presumably grow via galactic merging events and subsequent BH coalescence. As a case study, we investigate the merging event between the Andromeda galaxy (M31) and a satellite galaxy. We compute the expected observational appearance of the massive BH that was at the center of the satellite galaxy prior to the merger, and is currently wandering in the M31 halo. We demonstrate that a radiatively inefficient accretion flow with a bolometric luminosity of a few tens of solar luminosities develops when Hoyle-Lyttleton accretion onto the BH is assumed. We compute the associated broadband spectrum and show that the radio band (observable with EVLA, ALMA and SKA) is the best frequency range to detect the emission. We also evaluate the mass and the luminosity of the stars bound by the wandering BH and find that such a star cluster is sufficiently luminous that it could correspond to one of the star clusters found by the PAndAS survey. The discovery of a relic massive BH wandering in a galactic halo will provide a direct means to investigate in detail the coevolution of galaxies and BHs. It also means a new population of BHs (off-center massive BHs), and offers targets for clean BH imaging that avoids strong interstellar scattering in the center of galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.7514v1.pdf"}
{"id": "1406.1317", "abstract": "  The tumbling of a rigid rod in a shear flow is analyzed in the high viscosity limit. Following Burgers, the Master Equation is derived for the probability distribution of the orientation of the rod. The equation contains one dimensionless number, the Weissenberg number, which is the ratio of the shear rate and the orientational diffusion constant. The equation is solved for the stationary state distribution for arbitrary Weissenberg numbers, in particular for the limit of high Weissenberg numbers. The stationary state gives an interesting flow pattern for the orientation of the rod, showing the interplay between flow due to the driving shear force and diffusion due to the random thermal forces of the fluid. The average tumbling time and tumbling frequency are calculated as a function of the Weissenberg number. A simple cross-over function is proposed which covers the whole regime from small to large Weissenberg numbers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.1317v1.pdf"}
{"id": "1406.2742", "abstract": "  Fourier-domain Difference Map (FDM) for phase retrieval with two oversampled coded diffraction patterns are proposed. FDM is a 3-parameter family of fixed point algorithms including Fourier-domain Hybrid-Projection-Reflection (FHPR) and Douglas-Rachford (FDR) algorithm. For generic complex objects without any object constraint, FDM yields a unique fixed point, after proper projection back to the object domain, which is the true solution to the phase retrieval problem up to a global phase factor. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.2742v2.pdf"}
{"id": "1406.4411", "abstract": "  Nonlinear optical generation from a crystalline material can reveal the symmetries of both its lattice structure and underlying ordered electronic phases and can therefore be exploited as a complementary technique to diffraction based scattering probes. Although this technique has been successfully used to study the lattice and magnetic structures of systems such as semiconductor surfaces, multiferroic crystals, magnetic thin films and multilayers, challenging technical requirements have prevented its application to the plethora of complex electronic phases found in strongly correlated electron systems. These requirements include an ability to probe small bulk single crystals at the micron length scale, a need for sensitivity to the entire nonlinear optical susceptibility tensor, oblique light incidence reflection geometry and incident light frequency tunability among others. These measurements are further complicated by the need for extreme sample environments such as ultra low temperatures, high magnetic fields or high pressures. In this review we present a novel experimental construction using a rotating light scattering plane that meets all the aforementioned requirements. We demonstrate the efficacy of our scheme by making symmetry measurements on a micron scale facet of a small bulk single crystal of Sr_2IrO_4 using optical second and third harmonic generation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.4411v1.pdf"}
{"id": "1406.6862", "abstract": "  Contracts for Difference (CfDs) are forwards on the spread between an area price and the system price. Together with the system price forwards, these products are used to hedge the area price risk in the Nordic electricity market. The CfDs are typically available for the next two months, three quarters and three years. This is fine, except that CfDs are not traded at NASDAQ OMX Commodities for every Nord Pool Spot price area. We therefore ask the hypothetical question: What would the CfD market price have been, say in the price area NO2, if it had been traded? We build regression models for each observable price area, and use Bayesian elicitation techniques to obtain prior information on how similar the different price areas are to forecast the price in an area where CfDs are not traded. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.6862v1.pdf"}
{"id": "1406.7076", "abstract": "  The dispersion processes of aqueous samples of clay are studied using ultrasound attenuation spectroscopy. The attenuation spectra that are acquired in the frequency range 10-100 MHz are used to determine the particle size distributions (PSDs) for different concentrations and ages of the clay suspensions. Our analysis, using equivalent spherical diameter (ESD) for circular discs under Stokes drag in samples of concentrations greater than 1.5% w/v, shows that a substantial fraction of the aggregates in suspension are actually tactoids that are composed of more than one platelet. This is in contrast to the general belief that clay disperses into individual platelets in the concentration range where their suspensions exhibit glassy behavior. We conclude that the incomplete fragmentation of the clay tactoids arises from the rapid enhancement of the inter-tactoid Coulombic repulsion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.7076v1.pdf"}
{"id": "1406.7269", "abstract": "  We investigate the interference pattern in the spectrum of non-dipole bremsstrahlung on two amorphous foils. Apart from suppression at lowest ω, the spectrum exhibits an enhancement adjacent to it. In classical electrodynamics, the net effect of suppression and enhancement proves to be zero. We study the location and the origin of the spectral features, comparing predictions of full Molière averaging with those of the Gaussian averaging with Coulomb corrections to the rms multiple scattering angle. Comparison with experimental data, and with previous theoretical predictions is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.7269v1.pdf"}
{"id": "1407.0842", "abstract": "  The existence of a star with such a large mass means that the equation of state is stiff enough to provide a high enough pressure up to a fairly large central densities,. Such a stiff equation of state is possible if the ground state has nucleons as its constituents. This further implies that a purely nucleon ground state may exist till about four times nuclear density which indicates that quarks in the nucleon are strongly bound and that the nucleon nucleon potential is strongly repulsive. We find this to be so in a chiral soliton model for the nucleon which has bound state quarks. We point out that this has important implications for the strong interaction μ_B vs T phase diagram. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.0842v1.pdf"}
{"id": "1407.2742", "abstract": "  A new model is formulated of the sociological effect of the spiral of silence, introduced by Elisabeth Noelle-Neumann in 1974. The probability that a new opinion is openly expressed decreases with the difference between this new opinion and the perceived opinion of the majority. We also assume that the system is open, i.e. some people enter and some leave during the process of the opinion formation. An influence of a leader is simulated by a comparison of two runs of the simulation, where the leader has different opinion in each run. The difference of the mean expressed opinions in these two runs persists long after the leader's leave. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.2742v2.pdf"}
{"id": "1407.4715", "abstract": "  We study the transport process of interacting Brownian particles in a tube of varying cross section. To describe this process we introduce a modified Fick-Jacobs equation, considering particles that interact through a hard-core potential. We were able to solve the equation with numerical methods for the case of symmetric and asymmetric cavities. We focused in the concentration of particles along the direction of the tube. We also preformed Monte Carlo simulations to evaluate the accuracy of the results, obtaining good agreement between theory and simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.4715v1.pdf"}
{"id": "1407.6480", "abstract": "  No mixed research of hybrid and fractional-order systems into a cohesive and multifaceted whole can be found in the literature. This paper focuses on such a synergistic approach of the theories of both branches, which is believed to give additional flexibility and help the system designer. It is part II of two companion papers and focuses on fractional-order hybrid control. Specifically, two types of such techniques are reviewed, including robust control of switching systems and different strategies of reset control. Simulations and experimental results are given to show the effectiveness of the proposed strategies. Part I will introduce the fundamentals of fractional-order hybrid systems, in particular, modelling and stability of two kinds of such systems, i.e., fractional-order switching and reset control systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.6480v1.pdf"}
{"id": "1407.7643", "abstract": "  We present results from our Giant Metrewave Radio Telescope (GMRT) HI observations of the interacting pair Arp 202 (NGC 2719 and NGC 2719A). Earlier deep UV(GALEX) observations of this system revealed a tidal tail like extension with a diffuse object towards its end, proposed as a tidal dwarf galaxy (TDG) candidate. We detect HI emission from the Arp 202 system, including HI counterparts for the tidal tail and the TDG candidate. Our GMRT HI morphological and kinematic results clearly link the HI tidal tail and the HI TDG counterparts to the interaction between NGC 2719 and NGC 2719A, thus strengthening the case for the TDG. The Arp 202 TDG candidate belongs to a small group of TDG candidates with extremely blue colours. In order to gain a better understanding of this group we carried out a comparative study of their properties from the available data. We find that HI (and probably stellar) masses of this extremely blue group are similar to the lowest HI mass TDGs in the literature. However the number of such blue TDG candidates examined so far is too small to conclude whether or not their properties justify them to be considered as a subgroup of TDGs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.7643v1.pdf"}
{"id": "1408.0566", "abstract": "  Here the role and influence of aberrations in optical imaging systems employing partially coherent complex scalar fields is studied. Imaging systems require aberrations to yield contrast in the output image. For linear shift-invariant optical systems, we develop an expression for the output cross-spectral density under the space-frequency formulation of statistically stationary partially coherentfields. We also develop expressions for the output crossspectral density and associated spectral density for weak-phase, weak-phase-amplitude, and single-material objects in one transverse spatial dimension. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.0566v3.pdf"}
{"id": "1408.3266", "abstract": "  We introduce a theoretical framework which is suitable for the description of all spatial and time-multiplexed periodic single-photon sources realized or proposed thus far. Our model takes into account all possibly relevant loss mechanisms. This statistical analysis of the known schemes shows that multiplexing systems can be optimized in order to produce maximal single-photon probability for various sets of loss parameters by the appropriate choice of the number of multiplexed units of spatial multiplexers or multiplexed time intervals and the input mean photon pair number, and reveals the physical reasons of the existence of the optimum. We propose a novel time-multiplexed scheme to be realized in bulk optics, which, according to the present analysis, would have promising performance when experimentally realized. It could provide a single-photon probability of 85% with a choice of experimental parameters which are feasible according to the experiments known from the literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.3266v1.pdf"}
{"id": "1408.3534", "abstract": "  Recent studies show that an intermediate mass black hole (IMBH) may develop a dark matter (DM) mini-halo according to some BH formation scenarios. We consider a binary system composed of an IMBH surrounded by a DM mini-spike and a stellar mass object orbiting around the IMBH. The binary evolves due to gravitational pull and dynamical friction from the DM mini-spike and back-reaction from its gravitational wave (GW) radiation which can be detected by future space-borne GW experiments such as eLISA/NGO. We consider a single power-law model for the DM mini-spike which is assumed to consist of non-annihilating DM particles and demonstrate that an eLISA/NGO detection of GW from such a binary enables us to measure the DM mini-spike parameters very accurately. For instance, in our reference case originally advocated by Zhao and Silk (2005) and Bertone et al. (2005), we could determine the power-law index α of the DM mini-spike radial profile with a 1 σ relative error of ± 5× 10^-6 for a GW signal with signal-to-noise-ratio 10 and assuming a 5 year observation with eLISA. We also investigate how accurately the DM parameters can be determined for various DM parameters and the masses of the IMBH-stellar mass object binary surrounded by a DM mini-spike. We find that we can determine the power-law index α at 10 ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.3534v1.pdf"}
{"id": "1408.5385", "abstract": "  Excitation of a model photosynthetic molecular aggregate by incoherent sunlight is systematically examined. For a closed system, the excited state coherence induced by the sunlight oscillates with an average amplitude that is inversely proportional to the excitonic gap, and reaches a stationary amplitude that depends on the temperature and coherence time of the radiation field. For an open system, the light-induced dynamical coherence relaxes to a static coherence determined by the non-canonical thermal distribution resulting from the entanglement with the phonon bath. The decay of the excited state population to the common ground state establishes a non-equilibrium steady-state flux driven by the sunlight, and it defines a time window to observe the transition from dynamical to static coherence. For the parameters relevant to photosynthetic systems, the exciton dynamics initiated by the sunlight exhibits a non-negligible amount of dynamical coherence (quantum beats) on the sub-picosecond timescale; however, this sub-picosecond time-scale is long enough for light-harvesting systems to establish static coherence, which plays a crucial role in efficient energy transfer. Further, a relationship is established between the non-equilibrium steady-state induced by the sunlight and the coherent dynamics initiated from the ground state by a laser δ-pulse, thereby making a direct connection between incoherent sunlight excitation and ultrafast spectroscopy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.5385v1.pdf"}
{"id": "1408.6165", "abstract": "  The kinetic Monte Carlo method is used to model the dynamic properties of proton diffusion in anhydrous proton conductors. The results have been discussed with reference to a two-step process called the Grotthuss mechanism. There is a widespread belief that this mechanism is responsible for fast proton mobility. We showed in detail that the relative frequency of reorientation and diffusion processes is crucial for the conductivity. Moreover, the current dependence on proton concentration has been analyzed. In order to test our microscopic model the proton transport in polymer electrolyte membranes based on benzimidazole C7H6N2 molecules is studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.6165v1.pdf"}
{"id": "1409.3350", "abstract": "  We consider the relation between three physical problems: 2D directed lattice random walks, ensembles of T_n,n+1 torus knots, and instanton ensembles in 5D SQED with one compact dimension in Ω background and with 5D Chern-Simons term at the level one. All these ensembles exhibit the critical behavior typical for the \"area+length+corners\" statistics of grand ensembles of 2D directed paths. Using the combinatorial description, we obtain an explicit expression of the generating function for q-Narayana numbers which amounts to the new critical behavior in the ensemble of T_n,n+1 torus knots and in the ensemble of instantons in 5D SQED. Depending on the number of the nontrivial fugacities, we get either the critical point, or cascade of critical lines and critical surfaces. In the 5D gauge theory the phase transition is of the 3rd order, while in the ensemble of paths and ensemble of knots it is typically of the 1st order. We also discuss the relation with the integrable models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.3350v2.pdf"}
{"id": "1409.3427", "abstract": "  We construct finite volume hyperbolic manifolds with large symmetry groups. The construction makes use of the presentations of finite Coxeter groups provided by Barot and Marsh and involves mutations of quivers and diagrams defined in the theory of cluster algebras. We generalize our construction by assigning to every quiver or diagram of finite or affine type a CW-complex with a proper action of a finite (or affine) Coxeter group. These CW-complexes undergo mutations agreeing with mutations of quivers and diagrams. We also generalize the construction to quivers and diagrams originating from unpunctured surfaces and orbifolds. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.3427v2.pdf"}
{"id": "1409.5423", "abstract": "  In this paper we propose a fast algorithm for trivariate interpolation, which is based on the partition of unity method for constructing a global interpolant by blending local radial basis function interpolants and using locally supported weight functions. The partition of unity algorithm is efficiently implemented and optimized by connecting the method with an effective cube-partition searching procedure. More precisely, we construct a cube structure, which partitions the domain and strictly depends on the size of its subdomains, so that the new searching procedure and, accordingly, the resulting algorithm enable us to efficiently deal with a large number of nodes. Complexity analysis and numerical experiments show high efficiency and accuracy of the proposed interpolation algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.5423v1.pdf"}
{"id": "1409.5509", "abstract": "  We study kinetic representations of flocking models. They arise from agent-based models for self-organized dynamics, such as Cucker-Smale and Motsch-Tadmor models. We prove flocking behavior for the kinetic descriptions of flocking systems, which indicates a concentration in velocity variable in infinite time. We propose a discontinuous Galerkin method to treat the asymptotic δ-singularity, and construct high order positive preserving scheme to solve kinetic flocking systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.5509v1.pdf"}
{"id": "1409.6025", "abstract": "  We report simulations of a frustrated odd-numbered macrospin ring system, with full point dipolar interactions, driven by a rotating uniform applied magnetic field of constant magnitude. The system is designed with equally-spaced radially-aligned macrospins, which must carry a frustrated soliton defect in its ground state. It is shown how correctly tuning the applied field magnitude can allow for non-trivial unidirectional propagation of the soliton, the required directional pressure acquired via the curvature of the ring. Furthermore, the system, which may be employed as a multiple rotation counter, is tested for robustness against quenched disorder as would be present in an experimental realization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.6025v1.pdf"}
{"id": "1409.6370", "abstract": "  We have investigated the motion of vortex domain walls passing across non symmetric triangular notches in single Permalloy nanowires. We have measured hysteresis cycles using the focused magneto-optical Kerr effect before and beyond the notch, which allowed to probe beyond the notch the occurrence probability of clockwise (CW) and counter-clockwise (CCW) walls in tail-to-tail (TT) and head-to-head (HH) configurations. We present experimental evidence of chirality flipping provided by the vortex – notch interaction. With a low exit angle the probability of chirality flipping increases and here with the lowest angle of 15^o the probability of propagation of the energetically favored domain wall configuration (CCW for TT or CW for HH walls) is ≈ 75%. Micromagnetic simulations reveal details of the chirality reversal dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.6370v2.pdf"}
{"id": "1410.1511", "abstract": "  In this paper, we analyse the bosonic current densities induced by a magnetic flux running along an idealized cosmic string in a high-dimensional spacetime, admitting that the coordinate along the string's axis is compactified. Additionally we admit the presence of an magnetic flux enclosed by the compactification axis. In order to develop this analysis we calculate the complete set of normalized bosonic wave-functions obeying a quasiperiodicity condition, with arbitrary phase β, along the compactified dimension. In this context, only azimuthal and axial currents densities take place. As to the azimuthal current, two contributions appear. The first contribution corresponds to the standard azimuthal current in a cosmic string spacetime without compactification, while the second contribution is a new one, induced by the compactification itself. The latter is an even function of the magnetic flux enclosed by the string axis and is an odd function of the magnetic flux along its core with period equal to quantum flux, Φ_0=2π/e. On the other hand, the nonzero axial current density is an even function of the magnetic flux along the core of the string and an odd function of the magnetic flux enclosed by it. We also find that the axial current density vanishes for untwisted and twisted bosonic fields in the absence of the magnetic flux enclosed by the string axis. Some asymptotic expressions for the current density are provided for specific limiting cases of the physical parameter of the model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.1511v4.pdf"}
{"id": "1410.4403", "abstract": "  Investigating the beam-beam limit in the LHC is of great importance, since identifying its source is crucial for the luminosity optimization scenario. Several experiments were carried out to search for this limit and check whether it is dominated by the head-on (HO) or the long-range (LR) interactions. In this paper only the HO collision effects will be considered, tracking the evolution of the maximum tune shift achieved during the dedicated machine developments and the special high pile-up fills. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.4403v1.pdf"}
{"id": "1410.4435", "abstract": "  Electron beam induced current (EBIC) is a powerful technique which measures the charge collection efficiency of photovoltaics with sub-micron spatial resolution. The exciting electron beam results in a high generation rate density of electron-hole pairs, which may drive the system into nonlinear regimes. An analytic model is presented which describes the EBIC response when the total electron-hole pair generation rate exceeds the rate at which carriers are extracted by the photovoltaic cell, and charge accumulation and screening occur. The model provides a simple estimate of the onset of the high injection regime in terms of the material resistivity and thickness, and provides a straightforward way to predict the EBIC lineshape in the high injection regime. The model is verified by comparing its predictions to numerical simulations in 1 and 2 dimensions. Features of the experimental data, such as the magnitude and position of maximum collection efficiency versus electron beam current, are consistent with the 3 dimensional model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.4435v1.pdf"}
{"id": "1410.5282", "abstract": "  Quantum Gaussian states can be considered as the majority of the practical quantum states used in quantum communications and more generally in quantum information. Here we consider their properties in relation with the geometrically uniform symmetry, a property of quantum states that greatly simplifies the derivation of the optimal decision by means of the square root measurements. In a general framework of the N-mode Gaussian states we show the general properties of this symmetry and the application of the optimal quantum measurements. An application example is presented, to quantum communication systems employing pulse position modulation. We prove that the geometrically uniform symmetry can be applied to the general class of multimode Gaussian states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.5282v1.pdf"}
{"id": "1410.5738", "abstract": "  The study of collective decision making system has become the central part of the Swarm- Intelligence Related research in recent years. The most challenging task of modelling a collec- tive decision making system is to develop the macroscopic stochastic equation from its microscopic model. In this report we have investigated the behaviour of a collective decision making system with specified microscopic rules that resemble the chemical reaction and used different group size. Then we ventured to derive a generalized analytical model of a collective-decision system using hyper-geometric distribution.   Index Terms-swarm; collective decision making; noise; group size; hyper-geometric distribution ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.5738v1.pdf"}
{"id": "1410.7714", "abstract": "  We present a scheme for engineering the joint spectrum of photon pairs created via spontaneous parametric down conversion. Our method relies on customizing the poling configuration of a quasi-phase-matched crystal. We use simulated annealing to find an optimized poling configuration which allows almost arbitrary shaping of the crystal's phase-matching function. This has direct application in the creation of pure single photons—currently one of the most important goals of single-photon quantum optics. We describe the general algorithm and provide code, written in C++, that outputs an optimized poling configuration given specific experimental parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.7714v2.pdf"}
{"id": "1410.8662", "abstract": "  We investigate finite-size effects in quantum systems at first-order quantum transitions. For this purpose we consider the one-dimensional q-state Potts models which undergo a first-order quantum transition for any q>4, separating the quantum disordered and ordered phases with a discontinuity in the energy density of the ground state. The low-energy properties around the transition show finite-size scaling, described by general scaling ansatzes with respect to appropriate scaling variables. The size dependence of the scaling variables presents a particular sensitiveness to boundary conditions, which may be considered as a peculiar feature of first-order quantum transitions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.8662v1.pdf"}
{"id": "1411.0062", "abstract": "  The Maximum Agreement Forest (Maf) problem is a well-studied problem in evolutionary biology, which asks for a largest common subforest of a given collection of phylogenetic trees with identical leaf label-set. However, the previous work about the Maf problem are mainly on two binary phylogenetic trees or two general (i.e., binary and non-binary) phylogenetic trees. In this paper, we study the more general version of the problem: the Maf problem on multiple general phylogenetic trees. We present a parameterized algorithm of running time O(3^k n^2m) and a 3-approximation algorithm for the Maf problem on multiple rooted general phylogenetic trees, and a parameterized algorithm of running time O(4^k n^2m) and a 4-approximation algorithm for the Maf problem on multiple unrooted general phylogenetic trees. We also implement the parameterized algorithm and approximation algorithm for the Maf problem on multiple rooted general phylogenetic trees, and test them on simulated data and biological data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.0062v1.pdf"}
{"id": "1411.0635", "abstract": "  We use tools from the theory of dynamical systems with symmetries to stratify Uhlmann's standard purification bundle and derive a new connection for mixed quantum states. For unitarily evolving systems, this connection gives rise to the 'interferometric' geometric phase of Sjöqvist et al. [Phys. Rev. Lett. 85 2845 - 2849 (2000)], and for more generally evolving open systems it gives rise to the generalization of the interferometric geometric phase due to Tong et al. [Phys. Rev. Lett. 93 080405 (2004)]. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.0635v2.pdf"}
{"id": "1411.6131", "abstract": "  Shear localization occurs in various instances of material instability in solid mechanics and is typically associated with Hadamard-instability for an underlying model. While Hadamard instability indicates the catastrophic growth of oscillations around a mean state, it does not by itself explain the formation of coherent structures typically observed in localization. The latter is a nonlinear effect and its analysis is the main objective of this article. We consider a model that captures the main mechanisms observed in high strain-rate deformation of metals, and describes shear motions of temperature dependent non-Newtonian fluids. For a special dependence of the viscosity on the temperature, we carry out a linearized stability analysis around a base state of uniform shearing solutions, and quantitatively assess the effects of the various mechanisms affecting the problem: thermal softening, momentum diffusion and thermal diffusion. Then, we turn to the nonlinear model, and construct localized states - in the form of similarity solutions - that emerge as coherent structures in the localization process. This justifies a scenario for localization that is proposed on the basis of asymptotic analysis in <cit.>. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.6131v3.pdf"}
{"id": "1412.2063", "abstract": "  We present exact solutions of the (0+1)-dimensional kinetic equation for a massive gas in the relaxation time approximation. At first, we analyse the case of classical statistics and argue that the traditional second-order hydrodynamics misses the shear-bulk coupling. In the next step, we include Bose-Einstein and Fermi-Dirac statistics in the calculations and show that they are important for description of the effects connected with bulk viscosity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.2063v2.pdf"}
{"id": "1412.3388", "abstract": "  In this paper we present the experimental realization of a Nb tunnel junction connected to a high-gap superconducting NbTiN embedding circuit. We investigate relaxation of nonequilibrium quasiparticles in a small volume Au layer between the Nb tunnel junction and the NbTiN circuit. We find a saturation in the effective heat-transfer coefficient consistent with a simple theoretical model. This saturation is determined by the thickness of the Au layer. Our findings are important for the design of the ideal Au energy relaxation layer for practical SIS heterodyne mixers and we suggest two geometries, one, using a circular Au layer and, two, using a half-circular Au layer. Our work is concluded with an outlook of our future experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.3388v1.pdf"}
{"id": "1412.3601", "abstract": "  The close vicinity of neutron stars remains poorly constrained by observations. Although plenty of data are available for the peculiar class of pulsars we are still unable to deduce the underlying plasma distribution in their magnetosphere. In the present paper, we try to unravel the magnetospheric structure starting from basic physics principles and reasonable assumptions about the magnetosphere. Beginning with the monopole force-free case, we compute accurate general-relativistic solutions for the electromagnetic field around a slowly rotating magnetized neutron star. Moreover, here we address this problem by including the important effect of plasma screening. This is achieved by solving the time-dependent Maxwell equations in a curved space-time following the 3+1 formalism. We improved our previous numerical code based on pseudo-spectral methods in order to allow for possible discontinuities in the solution. Our algorithm based on a multi-domain decomposition of the simulation box belongs to the discontinuous Galerkin finite element methods. We performed several sets of simulations to look for the general-relativistic force-free monopole and split monopole solutions. Results show that our code is extremely powerful in handling extended domains of hundredth of light-cylinder radii . The code has been validated against known exact analytical monopole solutions in flat space-time. We also present semi-analytical calculations for the general-relativistic vacuum monopole. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.3601v1.pdf"}
{"id": "1412.3650", "abstract": "  Recent results for the QCD phase structure at finite temperature and light-quark chemical potential are summarized, where the cases of N_f = 2 + 1 and N_f = 2+1+1 dynamical quark flavors are considered. Order parameters for the chiral and deconfinement transitions are obtained from solutions of a coupled set of truncated Dyson-Schwinger equations for the quark and gluon propagators of Landau gauge QCD. Based on very good agreement with lattice QCD for zero chemical potential the phase diagram in the whole T-μ-plane and the appearance of a putative critical end-point at large chemical potential are studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.3650v1.pdf"}
{"id": "1412.4366", "abstract": "  We study the bispectrum of the primordial curvature perturbation on uniform-density hypersurfaces generated by a kind of the noncanonical warm inflation, wherein the inflation is provided by a noncanonical scalar inflaton field that is coupled to radiation through a thermal dissipation effect. We obtain an analytic form for the nonlinear parameter f_NL that describes the non-Gaussianity in first-order cosmological perturbation theory and analyse the magnitude of this nonlinear parameter. We make a comparison between our result and those of the standard inflation and the canonical warm inflation. We also discuss when the contribution to the non-Gaussianity due to the second-order perturbation theory becomes more important and what effect can be observed. We take the Dirac-Born-Infeld (DBI) inflation as a concrete example to find how the sound speed and the thermal dissipation strength to decide the non-Gaussianity and to get a lower bound of the sound speed constrained by PLANCK. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.4366v1.pdf"}
{"id": "1412.4387", "abstract": "  The paper discusses the influence of the external in-plane electric and magnetic field on the ground state spin phase diagram of selected monolayer graphene nanostructures. The calculations are performed for triangular graphene nanoflakes with armchair edges as well as for short pieces of armchair graphene nanoribbons with zigzag terminations. The Mean Field Approximation (MFA) is employed to solve the Hubbard model. The total spin for both classes of nanostructures is discussed as a function of external fields for various structure sizes, for charge neutrality conditions as well as for weak charge doping. The variety of nonzero spin states is found and their stability ranges are determined. For some structures, the presence of antiferromagnetic orderings is predicted within the zero-spin phase. The process of magnetization of nanoflakes with magnetic field at constant electric field is also investigated, showing opposite effect of electric field at low and at high magnetic fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.4387v3.pdf"}
{"id": "1412.4875", "abstract": "  Epidemic outbreaks of new pathogens, or known pathogens in new populations, cause a great deal of fear because they are hard to predict. For theoretical models of disease spreading, on the other hand, quantities characterizing the outbreak converge to deterministic functions of time. Our goal in this paper is to shed some light on this apparent discrepancy. We measure the diversity of (and, thus, the predictability of) outbreak sizes and extinction times as functions of time given different scenarios of the amount of information available. Under the assumption of perfect information – i.e., knowing the state of each individual with respect to the disease – the predictability decreases exponentially, or faster, with time. The decay is slowest for intermediate values of the per-contact transmission probability. With a weaker assumption on the information available, assuming that we know only the fraction of currently infectious, recovered, or susceptible individuals, the predictability also decreases exponentially most of the time. There are, however, some peculiar regions in this scenario where the predictability decreases. In other words, to predict its final size with a given accuracy, we would need increasingly more information about the outbreak. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.4875v2.pdf"}
{"id": "1412.6278", "abstract": "  In this paper we present the elementary assumptions of our research on the role of the magnetic field in modelling the quiescence-outbursts cycle in Cataclysmic Variables (CVs). The behaviour of the magnetic field is crucial not only to integrate the disk instability model (Osaki 1974), but also to determine the cause and effect nexus among parameters affecting the behavior of complex systems. On the ground of our interpretation of the results emerging from the literature, we suggest that in models describing DNe outbursts, such as the disk instability model, the secondary instability model (Bath 1973) and the thermonuclear runaway model (Mitrofanov 1978), the role of the magnetic field is at least twofold. On the one hand, it activates a specific dynamic pathway for the accreting matter by channelling it. On the other hand, it could be indirectly responsible for switching a particular outburst modality. In order to represent these two roles of the magnetic field, we need to integrate the disk instability model by looking at the global behaviour of the system under analysis. Stochastic resonance in dynamo models, we believe, is a suitable candidate for accomplishing this task. We shall present the MHD model including this mechanism elsewhere. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6278v1.pdf"}
{"id": "1412.7622", "abstract": "  Luminescence properties of carbon nanotubes are strongly affected by exciton diffusion, which plays an important role in various nonradiative decay processes. Here we perform photoluminescence microscopy on hundreds of individual air-suspended carbon nanotubes to elucidate the interplay between exciton diffusion, end quenching, and exciton-exciton annihilation processes. A model derived from random-walk theory as well as Monte Carlo simulations are utilized to analyze nanotube length dependence and excitation power dependence of emission intensity. We have obtained the values of exciton diffusion length and absorption cross section for different chiralities, and diameter-dependent photoluminescence quantum yield have been observed. The simulations have also revealed the nature of a one-dimensional coalescence process, and an analytical expression for the power dependence of emission intensity is given. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.7622v1.pdf"}
{"id": "1412.8352", "abstract": "  The strategy of constraining the lepton flavor mixing from remnant CP symmetry is investigated in a rather general way. The neutrino mass matrix generally admits four remnant CP transformations which can be derived from the measured lepton mixing matrix in the charged lepton diagonal basis. Conversely, the lepton mixing matrix can be reconstructed from the postulated remnant CP transformations. All mixing angles and CP violating phases can be completely determined by the full set of remnant CP transformations or three of them. When one or two remnant CP transformations are preserved, the resulting lepton mixing matrix would depend on three real parameters or one real parameter respectively in addition to the parameters characterizing the remnant CP, and the concrete form of the mixing matrix is presented. The phenomenological predictions for the mixing parameters are discussed. The conditions leading to vanishing or maximal Dirac CP violation are studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.8352v1.pdf"}
{"id": "1501.03036", "abstract": "  We present new optical observations of the HH 111 Herbig-Haro jet using the Gemini Multi Object Spectrograph in its Integral Field Unit mode. Eight fields of 5\" x 3.5\" have been positioned along and across the HH 111 jet, covering the spatial region from knot E to L in HH 111 (namely, knots E, F, G, H, J, K and L). We present images and velocity channel maps for the [O I] 6300+6360, Halpha, [N II] 6548+6583 and [S II] 6716+6730 lines, as well as for the [S II]6716/6730 line ratio. We find that the HH 111 jet has an inner region with lower excitation and higher radial velocity, surrounded by a broader region of higher excitation and lower radial velocity. Also, we find higher electron densities at lower radial velocities. These results imply that the HH 111 jet has a fast, axial region with lower velocity shocks surrounded by a lower velocity sheath with higher velocity shocks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.03036v1.pdf"}
{"id": "1501.03805", "abstract": "  In this paper, we seek to model the deformation of nucleated cells by single diode-laser bar optical stretchers. We employ a recently developed computational model, the Dynamic Ray-Tracing method, to determine the stress distribution induced by the applied optical forces on a capsule encapsulating a nucleus of different optical properties. These forces are shape dependent and can deform real non-rigid objects; thus resulting in a dynamically changing optical stress distribution with cell and nucleus deformation. Chinese hamster ovary cell is a common biological cell that is of interest to the biomedical community because of their use in recombinant protein therapeutics and is an example of a nucleated cell. To this end, we model chinese hamster ovary cells as two three-dimensional elastic capsules of variable inner capsule size immersed in a fluid where the hydrodynamic forces are calculated using the Immersed Boundary Method. Our results show that the presence of a nucleus has a major effect on the force distribution on the cell surface and the net deformation. Scattering and gradient forces are reported for different nucleus sizes and the effect of nucleus size on the cell deformation is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.03805v1.pdf"}
{"id": "1501.04712", "abstract": "  The article introduces spatial long-range dependent models based on the fractional difference operators associated with the Gegenbauer polynomials. The results on consistency and asymptotic normality of a class of minimum contrast estimators of long-range dependence parameters of the models are obtained. A methodology to verify assumptions for consistency and asymptotic normality of minimum contrast estimators is developed. Numerical results are presented to confirm the theoretical findings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.04712v1.pdf"}
{"id": "1502.02557", "abstract": "  In this paper, we investigate the problem of graph list colouring in the on-line setting. We provide several results on paintability of graphs in the model introduced by Schauz [13] and Zhu [20]. We prove that the on-line version of Ohba's conjecture is true in the class of planar graphs. We also consider several alternate on-line list colouring models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.02557v1.pdf"}
{"id": "1502.04193", "abstract": "  The paper presents the group theory of best localized and symmetry-adapted Wannier functions in a crystal of any given space group G or magnetic group M. Provided that the calculated band structure of the considered material is given and that the symmetry of the Bloch functions at all the points of symmetry in the Brillouin zone is known, the paper details whether or not the Bloch functions of particular energy bands can be unitarily transformed into best localized Wannier functions symmetry-adapted to the space group G, to the magnetic group M, or to a subgroup of G or M. In this context, the paper considers usual as well as spin-dependent Wannier functions, the latter representing the most general definition of Wannier functions. The presented group theory is a review of the theory published by one of the authors in several former papers and is independent of any physical model of magnetism or superconductivity. However, it is suggested to interpret the special symmetry of the best localized Wannier functions in the framework of a nonadiabatic extension of the Heisenberg model, the nonadiabatic Heisenberg model. On the basis of the symmetry of the Wannier functions, this model of strongly correlated localized electrons makes clear predictions whether or not the system can possess superconducting or magnetic eigenstates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.04193v1.pdf"}
{"id": "1502.05489", "abstract": "  We derive first- and second-order piezoelectric coefficients for the zinc-blende III-V semiconductors, Al,Ga,In-N,P,As,Sb. The results are obtained within the Heyd-Scuseria-Ernzerhof hybrid-functional approach in the framework of density functional theory and the Berry-phase theory of electric polarization. To achieve a meaningful interpretation of the results, we build an intuitive phenomenological model based on the description of internal strain and the dynamics of the electronic charge centers. We discuss in detail first- and second-order internal strain effects, together with strain-induced changes in ionicity. This analysis reveals that the relatively large importance in the III-Vs of non-linear piezoelectric effects compared to the linear ones arises because of a delicate balance between the ionic polarization contribution due to internal strain relaxation effects, and the contribution due to the electronic charge redistribution induced by macroscopic and internal strain. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.05489v1.pdf"}
{"id": "1502.05596", "abstract": "  A measure of cluster size heterogeneity (H), introduced by Lee et al [Phys. Rev. E 84, 020101 (2011)] in the context of explosive percolation, was recently applied to random percolation and to domains of parallel spins in the Ising and Potts models. It is defined as the average number of different domain sizes in a given configuration and a new exponent was introduced to explain its scaling with the size of the system. In thermal spin models, however, physical clusters take into account the temperature-dependent correlation between neighboring spins and encode the critical properties of the phase transition. We here extend the measure of H to these clusters and, moreover, present new results for the geometric domains for both d=2 and 3. We show that the heterogeneity associated with geometric domains has a previously unnoticed double peak, thus being able to detect both the thermal and percolative transition. An alternative interpretation for the scaling of H that does not introduce a new exponent is also proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.05596v1.pdf"}
{"id": "1502.05720", "abstract": "  The capture and disruption of stars by supermassive black holes (SMBHs), and the formation and coalescence of binaries, are inevitable consequences of the presence of SMBHs at the cores of galaxies. Pairs of active galactic nuclei (AGN) and binary SMBHs are important stages in the evolution of galaxy mergers, and an intense search for these systems is currently ongoing. In the early and advanced stages of galaxy merging, observations of the triggering of accretion onto one or both BHs inform us about feedback processes and BH growth. Identification of the compact binary SMBHs at parsec and sub-parsec scales provides us with important constraints on the interaction processes that govern the shrinkage of the binary beyond the \"final parsec\". Coalescing binary SMBHs are among the most powerful sources of gravitational waves (GWs) in the universe. Stellar tidal disruption events (TDEs) appear as luminous, transient, accretion flares when part of the stellar material is accreted by the SMBH. About 30 events have been identified by multi-wavelength observations by now, and they will be detected in the thousands in future ground-based or space-based transient surveys. The study of TDEs provides us with a variety of new astrophysical tools and applications, related to fundamental physics or astrophysics. Here, we provide a review of the current status of observations of SMBH pairs and binaries, and TDEs, and discuss astrophysical implications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.05720v2.pdf"}
{"id": "1503.00145", "abstract": "  Despite extensive work on the interplay between traffic dynamics and epidemic spreading, the control of epidemic spreading by routing strategies has not received adequate attention. In this paper, we study the impact of efficient routing protocol on epidemic spreading. In the case of infinite node-delivery capacity, where the traffic is free of congestion, we find that that there exists optimal values of routing parameter, leading to the maximal epidemic threshold. This means that epidemic spreading can be effectively controlled by fine tuning the routing scheme. Moreover, we find that an increase in the average network connectivity and the emergence of traffic congestion can suppress the epidemic outbreak. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.00145v1.pdf"}
{"id": "1503.01231", "abstract": "  We investigate a possibility of estimating mass of an isolated rapidly rotating neutron star (NS) from a continuous gravitational wave (GW) signal emitted by the NS. When the GW passes through the gravitational potential of the NS, the GW takes a slightly longer time to travel to an observer than it does in the absence of the NS. Such a time dilation effect holds also for photons and is often referred to as the gravitational time delay (or the Shapiro time delay). Correspondingly, the phase of the GW from the NS shifts due to the Coulomb type gravitational potential of the NS, and the resulting logarithmic phase shift depends on the mass, the spin frequency of the NS, and the distance to the NS. We show that the NS mass can, in principle, be obtained by making use of the phase shift difference between two modes of the continuous GW such as once and twice spin frequency modes induced by a freely precessing NS or a NS containing a pinned superfluid core. We estimate the measurement accuracy of the NS mass using Monte Carlo simulations and find that the mass of the NS with its ellipticity 10^-6 at 1 kpc is typically measurable with an accuracy 20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.01231v1.pdf"}
{"id": "1503.01301", "abstract": "  In this paper the effect of biaxial and uniaxial strain on the mobility of single-layer MoS_2 for temperatures T > 100 K is investigated. Scattering from intrinsic phonon modes, remote phonon and charged impurities are considered along with static screening. Ab-initio simulations are utilized to investigate the strain induced effects on the electronic bandstructure and the linearized Boltzmann transport equation is used to evaluate the low-field mobility under various strain conditions. The results indicate that the mobility increases with tensile biaxial and tensile uniaxial strain along the armchair direction. Under compressive strain, however, the mobility exhibits a non-monotonic behavior when the strain magnitude is varied. In particular, with a relatively small compressive strain of 1", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.01301v1.pdf"}
{"id": "1504.01725", "abstract": "  In this study, we obtain the approximate analytical solutions of the radial Schrödinger equation for the Deng-Fan diatomic molecular potential by using exact quantization rule approach. The wave functions have been expressed by hypergeometric functions via the functional analysis approach. An extension to rotational-vibrational energy eigenvalues of some diatomic molecules are also presented. It is shown that the calculated energy levels are in good agreement with the ones obtained previously E_nℓ-D (shifted Deng-Fan). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.01725v1.pdf"}
{"id": "1504.03433", "abstract": "  We investigate the influence of photoevaporation of protoplanetary discs on the final distribution of exoplanets semi-major axis distances. We model giant planet migration in viscous discs affected by photoevaporation driven by either pure EUV or soft X-ray radiation (XEUV). We show that the final exoplanet distributions are strongly dependant on the choice of the photoevaporation model. In particular, we find that XEUV is more efficient than pure EUV radiation at parking planets at approximately 1-2 AU distance from their central star, hence roughly reproducing the observed peak in the exoplanets semi-major axis distributions. We note however that a more quantitative comparison with the observations is hindered by the oversimplified treatment of planetary accretion, which severely affects migration rates. For this reason, caution should be used when using these models to constrain details of disc clearing and/or migration from the observations. Nevertheless our results indicate that disc dispersal by photoevaporation may be the main driver of the features in the exoplanets semi-major axis distribution observed by recent surveys. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.03433v1.pdf"}
{"id": "1505.04217", "abstract": "  Projected Entangled Pair States (PEPS) provide a framework for the construction of models where a single tensor gives rise to both Hamiltonian and ground state wavefunction on the same footing. A key problem is to characterize the behavior which emerges in the system in terms of the properties of the tensor, and thus of the Hamiltonian. In this paper, we consider PEPS models with ℤ_2 on-site symmetry and study the occurence of long-range order and spontaneous symmetry breaking. We show how long-range order is connected to a degeneracy in the spectrum of the PEPS transfer operator, and how the latter gives rise to spontaneous symmetry breaking under perturbations. We provide a succinct characterization of the symmetry broken states in terms of the PEPS tensor, and find that using the symmetry broken states we can derive a local entanglement Hamiltonian, thereby restoring locality of the entanglement Hamiltonian for all gapped phases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.04217v2.pdf"}
{"id": "1506.02491", "abstract": "  One possible evolutionary scenario of the dense gluon system produced in an ultrarelativistic heavy ion collision is the bottom-up thermalization scenario, which describes the dynamics of the system shortly after the collision via the decay of originally produced hard gluons to soft ones through QCD branching processes. The soft gluons form a thermal bath that subsequently reaches thermalization and/or equilibration. There is a scaling solution to the bottom-up problem that interpolates between its early stage, which has a highly anisotropic gluon distribution, and its final stage of equilibration which occurs later. Such a solution depends on a single parameter, the so called momentum asymmetry parameter δ. With this scaling solution, the bottom-up scenario gets modified and the evolving parton system, referred to as the m'bottom-up parton system throughout this paper, is described by this modification. The time evolution of the system in the original bottom-up ansatz is driven by the saturation scale, Q_s. However, for the m'bottom-up we generalize the ansatz of the evolution by introducing two additional momentum scales, which give a thermalization time and temperature of the soft gluon bath somewhat different from those obtained when the m'bottom-up matches onto the final stage of the original bottom-up scenario. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.02491v2.pdf"}
{"id": "1506.02746", "abstract": "  In the present work, we conduct large-scale orbital-free DFT calculations to study the energetics of vacancy clustering in aluminum from electronic structure calculations. The simulation domains considered in this study are as large as those containing a million atoms to accurately account for both the electronic structure and long-ranged elastic fields. Our results indicate that vacancy clustering is an energetically favorable mechanisms with positive binding energies for a range of vacancy clusters considered in the present study. In particular, the 19 vacancy hexagonal cluster lying in {111} plane has a very large binding energy with the relaxed atomic structure representative of a prismatic dislocation loop. This suggests that vacancy prismatic loops as small as those formed from 19 vacancies are stable, thus providing insights into the nucleation sizes of these defects in aluminum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.02746v1.pdf"}
{"id": "1506.04055", "abstract": "  The experimental binding energies of single-particle and single-hole neutron states belonging to neutron shells that extend from N = 126 to 184 and 82 to 126 respectively, have been reproduced by solving the Schrödinger equation with a potential that has two components: the generalized Woods-Saxon (GWS) potential and the spin-orbit (SO) coupling term. The GWS potential contains the traditional WS potential plus a term (SU) whose intensity reaches a maximum in the nuclear surface. Our results indicate the existence of a explicit relationship between the strength of the SU potential and the orbital angular momentum quantum number ℓ of the state. This dependence has been used to make reasonable predictions for the excitation energy centroids of states located inside and outside the neutron shells investigated. Comparisons are made with results reported in previous investigations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.04055v2.pdf"}
{"id": "1506.04164", "abstract": "  We study the statistical mechanics of a general Hamiltonian system in the context of symplectic structure of the corresponding phase space. This covariant formalism reveals some interesting correspondences between properties of the phase space and the associated statistical physics. While topology, as a global property, turns out to be related to the total number of microstates, the invariant measure which assigns a priori probability distribution over the microstates, is determined by the local form of the symplectic structure. As an example of a model for which the phase space has a nontrivial topology, we apply our formulation on the Snyder noncommutative space-time with de Sitter four-momentum space and analyze the results. Finally, in the framework of such a setup, we examine our formalism by studying the thermodynamical properties of a harmonic oscillator system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.04164v2.pdf"}
{"id": "1506.06363", "abstract": "  It has been shown that there are not only transverse but also longitudinal couplings between microwave fields and a superconducting qubit with broken inversion symmetry of the potential energy. Using multiphoton processes induced by longitudinal coupling fields and frequency matching conditions, we design a universal algorithm to produce arbitrary superpositions of two-mode photon states of microwave fields in two separated transmission line resonators, which are coupled to a superconducting qubit. Based on our algorithm, we analyze the generation of evenly-populated states and NOON states. Compared to other proposals with only single-photon process, we provide an efficient way to produce entangled microwave states when the interactions between superconducting qubits and microwave fields are in the ultrastrong regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.06363v3.pdf"}
{"id": "1506.06771", "abstract": "  We report rotational periods for 16 young brown dwarfs in the nearby Upper Scorpius association, based on 72 days of high-cadence, high-precision photometry from the Kepler space telescope's K2 mission. The periods range from a few hours to two days (plus one outlier at 5 days), with a median just above one day, confirming that brown dwarfs, except at the very youngest ages, are fast rotators. Interestingly, four of the slowest rotators in our sample exhibit mid-infrared excess emission from disks; at least two also show signs of disk eclipses and accretion in the lightcurves. Comparing these new periods with those for two other young clusters and simple angular momentum evolution tracks, we find little or no rotational braking in brown dwarfs between 1-10 Myr, in contrast to low-mass stars. Our findings show that disk braking, while still at work, is inefficient in the substellar regime, thus provide an important constraint on the mass dependence of the braking mechanism. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.06771v1.pdf"}
{"id": "1506.07914", "abstract": "  The large-scale structure of the magnetic field in the solar corona provides the energy to power large-scale solar eruptive events. Our physical understanding of this structure, and hence our ability to predict these events, is limited by the type of data currently available. It is shown that the multifractal spectrum is a powerful tool to study this structure, by providing a physical connection between the details of photospheric magnetic gradients and current density at all size scales. This uses concepts associated with geometric measure theory and the theory of weakly differentiable functions to compare Ampère's law to the wavelet-transform modulus maximum method. The Hölder exponent provides a direct measure of the rate of change of current density across spatial size scales. As this measure is independent of many features of the data (pixel resolution, data size, data type, presence of quiet-Sun data), it provides a unique approach to studying magnetic-field complexity and hence a potentially powerful tool for a statistical prediction of solar-flare activity. Three specific predictions are provided to test this theory: the multifractal spectra will not be dependent on the data type or quality; quiet-Sun gradients will not persist with time; structures with large current densities at large size scale will be the source of energy storage for solar eruptive events. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.07914v1.pdf"}
{"id": "1506.08092", "abstract": "  Motivated by the energy representation of Riemannian metric, in this paper we study different approaches toward the geometrical concept of black hole thermodynamics. We investigate thermodynamical Ricci scalar of Weinhold, Ruppeiner and Quevedo metrics and show that their number and location of divergences do not coincide with phase transition points arisen from heat capacity. Next, we introduce a new metric to solve these problems. We show that the denominator of the Ricci scalar of the new metric contains terms which coincide with different types of phase transitions. We elaborate the effectiveness of the new metric and shortcomings of the previous metrics with some examples. Furthermore, we find a characteristic behavior of the new thermodynamical Ricci scalar which enables one to distinguish two types of phase transitions. In addition, we generalize the new metric for the cases of more than two extensive parameters and show that in these cases the divergencies of thermodynamical Ricci scalar coincide with phase transition points of the heat capacity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.08092v3.pdf"}
{"id": "1506.08349", "abstract": "  A deep learning approach has been proposed recently to derive speaker identifies (d-vector) by a deep neural network (DNN). This approach has been applied to text-dependent speaker recognition tasks and shows reasonable performance gains when combined with the conventional i-vector approach. Although promising, the existing d-vector implementation still can not compete with the i-vector baseline. This paper presents two improvements for the deep learning approach: a phonedependent DNN structure to normalize phone variation, and a new scoring approach based on dynamic time warping (DTW). Experiments on a text-dependent speaker recognition task demonstrated that the proposed methods can provide considerable performance improvement over the existing d-vector implementation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.08349v1.pdf"}
{"id": "1507.00825", "abstract": "  This paper discusses the effect of hubness in zero-shot learning, when ridge regression is used to find a mapping between the example space to the label space. Contrary to the existing approach, which attempts to find a mapping from the example space to the label space, we show that mapping labels into the example space is desirable to suppress the emergence of hubs in the subsequent nearest neighbor search step. Assuming a simple data model, we prove that the proposed approach indeed reduces hubness. This was verified empirically on the tasks of bilingual lexicon extraction and image labeling: hubness was reduced with both of these tasks and the accuracy was improved accordingly. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.00825v1.pdf"}
{"id": "1507.01840", "abstract": "  The quantum dynamics of quasi-one-dimensional ring with varying electron filling factor is investigated in presence of external electric field. The system is modeled within Hubbard Hamiltonian with attractive Coulomb correlation, which results in superconducting ground state when away from half-filling. The electric field is induced by applying time-dependent Aharonov-Bohm flux in the perpendicular direction. To explore the non-equilibrium phenomena arising from the field, we adopt exact diagonalization and Crank-Nicolson numerical method. With increase in electric field strength, the electron pairs, a signature of superconducting phase, start breaking and the system enters into a metallic phase. However, the strength of the electric field for this quantum phase transition depends on the electronic correlation. This phenomenon has been confirmed by flux-quantization of time-dependent current and pair correlation functions ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.01840v2.pdf"}
{"id": "1507.05845", "abstract": "  The barrel time-of-flight detector for the PANDA experiment at FAIR is foreseen as a Scintillator Tile (SciTil) Hodoscope based on several thousand small plastic scintillator tiles read-out with directly attached Silicon Photomultipliers (SiPMs). The main tasks of the system are an accurate determination of the time origin of particle tracks to avoid event mixing at high collission rates, relative time-of-flight measurements as well as particle identification in the low momentum regime. The main requirements are the use of a minimum material amount and a time resolution of σ < 100 ps. We have performed extensive optimization studies and prototype tests to prove the feasibility of the SciTil design and finalize the R   D phase. In a 2.7 GeV/c proton beam at Forschungszentrum Jülich a time resolution of about 80 ps has been achieved using SiPMs from KETEK and Hamamatsu with an active area of 3×3 mm^2. Employing the Digital Photon Counter from Philips a time resolution of about 30 ps has been reached. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.05845v1.pdf"}
{"id": "1507.06576", "abstract": "  This paper defines the syntax and semantics of the input language of the ASP grounder GRINGO. The definition covers several constructs that were not discussed in earlier work on the semantics of that language, including intervals, pools, division of integers, aggregates with non-numeric values, and lparse-style aggregate expressions. The definition is abstract in the sense that it disregards some details related to representing programs by strings of ASCII characters. It serves as a specification for GRINGO from Version 4.5 on. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.06576v2.pdf"}
{"id": "1509.00785", "abstract": "  We report on a search for hidden photon cold dark matter (HP CDM) using a novel technique with a dish antenna. We constructed two independent apparatus: one is aiming at the detection of the HP with a mass of ∼ eV which employs optical instruments, and the other is for a mass of ∼5×10^-5 eV utilizing a commercially available parabolic antenna facing on a plane reflector. From the result of the measurements, we found no evidence for the existence of HP CDM and set upper limits on the photon-HP mixing parameter χ. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.00785v1.pdf"}
{"id": "1509.05600", "abstract": "  This paper studies the massive MIMO full-duplex relaying (MM-FDR), where multiple source-destination pairs communicate simultaneously with the help of a common full-duplex relay equipped with very large antenna arrays. Different from the traditional MM-FDR protocol, a general model where sources/destinations are allowed to equip with multiple antennas is considered. In contrast to the conventional MIMO system, massive MIMO must be built with low-cost components which are prone to hardware impairments. In this paper, the effect of hardware impairments is taken into consideration, and is modeled using transmit/receive distortion noises. We propose a low complexity hardware impairments aware transceiver scheme (named as HIA scheme) to mitigate the distortion noises by exploiting the statistical knowledge of channels and antenna arrays at sources and destinations. A joint degree of freedom and power optimization algorithm is presented to further optimize the spectral efficiency of HIA based MM-FDR. The results show that the HIA scheme can mitigate the \"ceiling effect\" appears in traditional MM-FDR protocol, if the numbers of antennas at sources and destinations can scale with that at the relay. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.05600v1.pdf"}
{"id": "1509.08756", "abstract": "  In this paper, we have formulated the new exact model of quintessence anisotropic star in f(R) theory of gravity. The dynamical equations in f(R) theory with the anisotropic fluid and quintessence field have been solved by using Krori-Barua solution. In this case, we have used the Starobinsky model of f(R) gravity. We have determined that all the obtained solutions are free from central singularity and potentially stable. The observed values of mass and radius of the different strange stars PSR J 1614-2230, SAXJ1808.4-3658(SS1), 4U1820- 30, PSR J 1614-2230 have been used to calculate the values of unknown constants in Krori and Barua metric. The physical parameters like anisotropy, stability and redshift of the stars have been investigated in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.08756v1.pdf"}
{"id": "1510.00134", "abstract": "  We conducted radio observations searching for OH 18-cm maser emission from a sample of 169 unclassified MIPSGAL compact Galactic bubbles. These sources are thought to be the circumstellar envelopes of different kinds of evolved stars. Our observations were aimed at shedding light on the nature of MIPSGAL bubbles, since their characterisation is a fundamental aid for the development of accurate physical models of stellar and Galaxy evolution. The maser emission is observatively linked to the last stages of the life of low- and intermediate-mass stars, which may constitute a significant fraction of the MIPSGAL bubbles. In particular OH masers are usually observed towards post-AGB stars. Our observations were performed with the Green Bank Telescope and, for each source, produced spectra around the four OH 18-cm transitions. The observations were compared with archive interferometer data in order to exclude possible contamination from nearby sources. The main result is that the OH maser emission is not a common feature among the MIPSGAL bubbles, with only one certain detection. We conclude that among the MIPSGAL bubbles the post-AGB stars could be very rare. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.00134v1.pdf"}
{"id": "1510.01929", "abstract": "  The largest stellar halos in the universe are found in massive galaxy clusters, where interactions and mergers of galaxies, along with the cluster tidal field, all act to strip stars from their host galaxies and feed the diffuse intracluster light (ICL) and extended halos of brightest cluster galaxies (BCGs). Studies of the nearby Virgo Cluster reveal a variety of accretion signatures imprinted in the morphology and stellar populations of its ICL. While simulations suggest the ICL should grow with time, attempts to track this evolution across clusters spanning a range of mass and redshift have proved difficult due to a variety of observational and definitional issues. Meanwhile, studies of nearby galaxy groups reveal the earliest stages of ICL formation: the extremely diffuse tidal streams formed during interactions in the group environment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.01929v1.pdf"}
{"id": "1510.04083", "abstract": "  As social networking takes to the mobile world, smartphone apps provide users with ever-changing ways to interact with each other. Over the past couple of years, an increasing number of apps have entered the market offering end-to-end encryption, self-destructing messages, or some degree of anonymity. However, little work thus far has examined the properties they offer.   To this end, this paper presents a taxonomy of 18 of these apps: we first look at the features they promise in their appeal to broaden their reach and focus on 8 of the more popular ones. We present a technical evaluation, based on static and dynamic analysis, and identify a number of gaps between the claims and reality of their promises. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.04083v3.pdf"}
{"id": "1510.06155", "abstract": "  Peeling, shearing, and sliding are important mechanical phenomena in van der Waals solids. However, theoretically they have been studied mostly using minimal periodic cells and in the context of accurate quantum simulations. Here, we investigate the peeling of large-scale multilayer graphene stacks with varying thicknesses, stackings, and peeling directions by using classical molecular dynamics simulations with a registry-dependent interlayer potential. Simulations show that, while at large scale the peeling proceeds smoothly, at small scale the registry shifts and sliding patterns of the layers are unexpectedly intricate and depend both on the initial stacking and on the peeling direction. These observations indicate that peeling and concomitant kink formations may well transform stacking order and thereby profoundly influence the electronic structures of such multilayer solids. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.06155v1.pdf"}
{"id": "1511.03560", "abstract": "  Two new families of exact solutions to the Einstein equations for a conformastatic spacetime with axial symmetry are presented which describe thin disks of dust immersed in a spheroidal halo. The solutions are obtained by expressing the metric function in terms of an auxiliary function which satisfies the Laplace equation, a characteristic property of the conformastatic spacetimes. The first family of solutions is obtained from the displacement, cut and reflexion method, which introduces a discontinuity in the first z-derivate of the metric tensor across the plane of the disk. The second family of solutions is obtained by using the oblate spheroidal coordinates because they adapt to the shape of the source and introduce naturally a cutting radius for the disk. The energy densities of the disk and the halo are everywhere positive and well behaved and their energy-momentum tensor agrees with all the energy conditions. Some particular solutions for the energy density of the disk and the halo are presented and the rotational curves are obtained by solving the geodesic equation for a particle that moves in circular orbits in the plane of the disk. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.03560v1.pdf"}
{"id": "1511.06543", "abstract": "  As the opening review to the focus meeting “Stellar Behemoths: Red Supergiants across the Local Universe”, I here provide a brief introduction to red supergiants, setting the stage for subsequent contributions. I highlight some recent activity in the field, and identify areas of progress, areas where progress is needed, and how such progress might be achieved. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.06543v1.pdf"}
{"id": "1511.08448", "abstract": "  We propose a scenario for the formation of localized turbulent spots in transition flows, which is known as resulting from the subcritical character of the transition. We show that it is not necessary to add 'by hand\" a term of random noise in the equations, in order to describe the existence of long wavelength fluctuations as soon as the bifurcated state is beyond the Benjamin-Feir instability threshold. We derive the instability threshold for generalized complex Ginzburg-Landau equation which displays subcriticality. Beyond and close to the Benjamin-Feir threshold we show that the dynamics is mainly driven by the phase of the complex amplitude which obeys Kuramoto-Sivashinsky equation while the fluctuations of the modulus are smaller and slaved to the phase (as already proved for the supercritical case). On the opposite, below the Benjamin-Feir instability threshold, the bifurcated state does loose the randomness associated to turbulence so that the transition becomes of the mean-field type as in noiseless reaction-diffusion systems and leads to pulse-like patterns. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.08448v1.pdf"}
{"id": "1512.02111", "abstract": "  The inherently high computational cost of iterative self-consistent-field (SCF) methods proves to be a critical issue delaying visual and haptic feedback in real-time quantum chemistry. In this work, we introduce two schemes for SCF acceleration. They provide a guess for the initial density matrix of the SCF procedure generated by extrapolation techniques. SCF optimizations then converge in fewer iterations, which decreases the execution time of the SCF optimization procedure. To benchmark the proposed propagation schemes, we developed a test bed for performing quantum chemical calculations on sequences of molecular structures mimicking real-time quantum chemical explorations. Explorations of a set of six model reactions employing the semi-empirical methods PM6 and DFTB3 in this testing environment showed that the proposed propagation schemes achieved speedups of up to thirty percent as a consequence of a reduced number of SCF iterations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.02111v1.pdf"}
{"id": "1512.02516", "abstract": "  Various approaches of defining and determining work performed on a quantum system are compared. Any operational definition of work, however, must allow for two facts, first, that work characterizes a process rather than an instantaneous state of a system, and, second, that quantum systems are sensitive to the interactions with a measurement apparatus. We compare different measurement scenarios on the basis of the resulting post-measurement states and the according probabilities for finding a particular work value. In particular, we analyze a recently proposed work-meter for the case of a Gaussian pointer state and compare it with the results obtained by two projective and, alternatively, two Gaussian measurements. In the limit of a strong effective measurement strength the work distribution of projective two energy measurements can be recovered. In the opposite limit the average of work becomes independent of any measurement. Yet the fluctuations about this value diverge. The performance of the work-meter is illustrated by the example of a spin in a suddenly changing magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.02516v1.pdf"}
{"id": "1512.07406", "abstract": "  We have studied the exotic superfluid phases of degenerated Fermi gases with spin-orbit coupling in a mixed dimensional system, where the motion of atoms are free in the x-direction and the tunneling between nearest tubes in the y-direction is permitted. Using the mean-field method, we obtain the phase diagrams of the system during the dimensional crossover between quasi one dimension to quasi two dimension. We find the existence of the topological state and Majorana edge mode in the weak tunneling case, and a rich phase diagram including two kinds of nodal superfluid phase and gapped superfluid phase in the opposite case. Our results show that topological pairing is favoured in quasi one dimension while nodal pairing state is favoured in quasi two dimension. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.07406v2.pdf"}
{"id": "1512.07425", "abstract": "  Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without altering the drift-fluid energy integral. We demonstrate that the inclusion of collisional transport in drift-fluid models gives rise to diffusion of particle density, momentum and pressures in drift-fluid turbulence models and thereby obviate the customary use of artificial diffusion in turbulence simulations. We further derive a computationally efficient, two-dimensional model which can be time integrated for several turbulence de-correlation times using only limited computational resources. The model describes interchange turbulence in a two-dimensional plane perpendicular to the magnetic field located at the outboard midplane of a tokamak. The model domain has two regions modeling open and closed field lines. The model employs a computational expedient model for collisional transport. Numerical simulations show good agreement between the full and the simplified model for collisional transport. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.07425v2.pdf"}
{"id": "1601.00626", "abstract": "  Information hierarchies are organizational structures that often used to organize and present large and complex information as well as provide a mechanism for effective human navigation. Fortunately, many statistical and computational models exist that automatically generate hierarchies; however, the existing approaches do not consider linkages in information networks that are increasingly common in real-world scenarios. Current approaches also tend to present topics as an abstract probably distribution over words, etc rather than as tangible nodes from the original network. Furthermore, the statistical techniques present in many previous works are not yet capable of processing data at Web-scale. In this paper we present the Hierarchical Document Topic Model (HDTM), which uses a distributed vertex-programming process to calculate a nonparametric Bayesian generative model. Experiments on three medium size data sets and the entire Wikipedia dataset show that HDTM can infer accurate hierarchies even over large information networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.00626v1.pdf"}
{"id": "1601.02904", "abstract": "  Social network has become one of the themes of government issues, mainly dealing with the chaos. The use of web is steadily gaining ground in these issues. However, most of the web documents are unstructured and lack of semantic. In this paper we proposed an Information Retrieval driven method for dealing with heterogeneity of features in the web. The proposed solution is to compare some approaches have shown the capacity to extract social relation: strength relations and relations based on online academic database. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.02904v1.pdf"}
{"id": "1601.06689", "abstract": "  An index coding problem with n messages has symmetric rate R if all n messages can be conveyed at rate R. In a recent work, a class of index coding problems for which symmetric rate 1/3 is achievable was characterised using special properties of the side-information available at the receivers. In this paper, we show a larger class of index coding problems (which includes the previous class of problems) for which symmetric rate 1/3 is achievable. In the process, we also obtain a stricter necessary condition for rate 1/3 feasibility than what is known in literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.06689v1.pdf"}
{"id": "1602.01798", "abstract": "  The impact of curvature divergences on physical observers in a black hole space-time which, nonetheless, is geodesically complete is investigated. This space-time is an exact solution of certain extensions of General Relativity coupled to Maxwell's electrodynamics and, roughly speaking, consists on two Reissner-Nordström (or Schwarzschild or Minkowski) geometries connected by a spherical wormhole near the center. We find that, despite the existence of infinite tidal forces, causal contact is never lost among the elements making up the observer. This suggests that curvature divergences may not be as pathological as traditionally thought. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.01798v1.pdf"}
{"id": "1602.03955", "abstract": "  Recent high-resolution infrared space missions have revealed supernova remnants (SNRs) of diverse morphology in infrared (IR) dust emission that is often very different from their X-ray appearance. The observed range of infrared-to-X-ray (IRX) flux ratios of SNRs are also wide. For a sample of 20 Galactic SNRs, we obtain their IR and X-ray properties and investigate the physical causes for such large differences. We find that the observed IRX flux ratios (R_IRX.obs) are related to the IRX morphology, with SNRs with the largest R_IRX,obs showing anticorrelated IRX morphology. By analyzing the relation of R_IRX,obs to X-ray and IR parameters, we show that the R_IRX,obs of some SNRs agree with theoretical ratios of SNR shocks in which dust grains are heated and destroyed by collisions with plasma particles. For the majority of SNRs, however, R_IRX,obs values are either significantly smaller or significantly larger than the theoretical ratios. The latter SNRs have relatively low dust temperatures. We discuss how the natural and/or environmental properties of SNRs could have affected the IRX flux ratios and the IRX morphology of these SNRs. We conclude that the SNRs with largest R_IRX,obs are probably located in dense environment and that their IR emission is from dust heated by shock radiation rather than by collisions. Our result suggests that the IRX flux ratio, together with dust temperature, can be used to infer the nature of unresolved SNRs in external galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.03955v1.pdf"}
{"id": "1602.04039", "abstract": "  We analyze the equilibrium configuration for a modulated beam with sharp boundaries exposed to the fields self-generated by the interaction with a plasma. Through a semi-analytical approach we show the presence of multiple equilibrium configurations and we determine the one more suitable for wakefield excitation. Once pointed out the absence of confinement for the front of the beam and the consequently divergence driven by the emittance, we study the evolution of the equilibrium configuration while propagating in the plasma, discarding all the others time-dependencies. We show the onset of a rigid backward drift of the equilibrium configuration and we provide an explanation in the increasing length of the first bunch. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.04039v1.pdf"}
{"id": "1602.04903", "abstract": "  The perfect absorption of light in subwavelength thickness layers generally relies on exotic materials, metamaterials or thick metallic gratings. Here we demonstrate that total light absorption can be achieved in ultra-thin gratings composed of conventional materials, including relatively weakly-absorbing semiconductors, which are compatible with optoelectronic applications such as photodetectors and optical modulators. We fabricate a 41 nm thick antimony sulphide grating structure that has a measured absorptance of A = 99.3", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.04903v1.pdf"}
{"id": "1602.07463", "abstract": "  We investigate how controlling induced eddy currents in thin film ferromagnet-normal metal (FM/NM) structures can be used to tailor the local microwave (MW) fields in ferromagnetic resonance (FMR) experiments. The MW fields produced by eddy currents will in general have a relative phase shift with respect to the applied MW field which depends on the sample geometry. The induced fields can thus partially compensate the applied MW field, effectively screening the FM in selected parts of the sample. The highly localized fields produced by eddy currents enable the excitation of spin wave modes with non-zero wave vectors, in contrast to the uniform k = 0 mode normally excited in FMR experiments. We find that the orientation of the applied MW field is one of the key parameters controlling the eddy-current effects. The induced currents are maximized when the applied MW field is oriented perpendicular to the sample plane. Increasing the magnitude of the eddy currents results in a stronger induced MW field, enabling a more effective screening of the applied MW field as well as an enhanced excitation of spin wave modes. This investigation underlines that eddy currents can be used to control the magnitude and phase of the local MW fields in thin film structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.07463v2.pdf"}
{"id": "1603.00068", "abstract": "  It is known that the Maximum relative Entropy (MrE) method can be used to both update and approximate probability distributions functions in statistical inference problems. In this manuscript, we apply the MrE method to infer magnetic properties of ferromagnetic materials. In addition to comparing our approach to more traditional methodologies based upon the Ising model and Mean Field Theory, we also test the effectiveness of the MrE method on conventionally unexplored ferromagnetic materials with defects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.00068v2.pdf"}
{"id": "1603.00554", "abstract": "  Photon modes have an important role in characterizing the quantum sources of light. Proper coupling of various photon modes obtained in spontaneous parametric down conversion (SPDC) process in optical fibers is essential to generate an effective source of entangled photons. The two main pre-detection factors affecting the biphoton mode coupling in SPDC are the pump beam focusing parameter and the crystal thickness. We present the numerical and experimental results on the effect of pump focusing on conditional down-converted photon modes for a Type-I BBO crystal. We experimentally verify that biphoton coupling efficiency decreases asymptotically with pump beam focusing parameter. We attribute this behaviour to (a) the asymmetry in the spatial distribution of down-converted photons with the pump beam focusing parameter and (b) the ellipticity of biphoton modes introduced due to the focusing of the pump beam. We also show experimentally the ellipticity as well as quantify the asymmetry with the pump focusing parameter. These results may be useful in selecting optimum conditions in the down-conversion process for generating efficient sources of entangled photons for quantum information applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.00554v1.pdf"}
{"id": "1603.02936", "abstract": "  A new type of the graphene-based three-port circulator is suggested and analysed. The cross-section of the component presents a three-layer structure consisting of a layer of silicon, of silica and of graphene. In-plane figure resembles a common microwave nanostrip circulator with a circular graphene resonator and three waveguides symmetrically connected to it. The graphene is magnetized normally to its plane by a DC magnetic field. The numerical simulation demonstrates the isolation of -15 dB and insertion losses of -2 dB in 6.98 % frequency band with the central frequency 8.23THz. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.02936v1.pdf"}
{"id": "1603.09152", "abstract": "  Inclusive jet production will dominate the high Q^2 final states at the LHC. In this work we try to estimate the up-to-date expectations, for high E_T jets and their expected origin from the various parton-parton scattering processes. For these studies we have used a standard Parton Distribution Function (PDF) and simulated millions of events with the PYTHIA8 event genertor. The results are compared with simulations for center-of-mass energies of 0.9 TeV, 2.36 TeV, 7 TeV and 14 TeV corresponding to existing and future LHC runs. We present some expectations for the relative cross sections of different quark flavours which indicates that eventually we might be able to measure the cross section for b-flavoured jets with reasonable accuracy up to an E_T of a few TeV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.09152v1.pdf"}
{"id": "1604.04621", "abstract": "  We report the discovery of pulsations in three mixed-atmosphere, extremely low-mass white dwarf (ELM WD, M ⩽ 0.3 M_⊙) precursors. Following the recent discoveries of pulsations in both ELM and pre-ELM WDs, we targeted pre-ELM WDs with mixed H/He atmospheres with high-speed photometry. We find significant optical variability in all three observed targets with periods in the range 320–590 s, consistent in timescale with theoretical predictions of p-mode pulsations in mixed-atmosphere ≈ 0.18 M_⊙ He-core pre-ELM WDs. This represents the first empirical evidence that pulsations in pre-ELM WDs can only occur if a significant amount of He is present in the atmosphere. Future, more extensive, time-series photometry of the brightest of the three new pulsators offers an excellent opportunity to constrain the thickness of the surface H layer, which regulates the cooling timescales for ELM WDs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.04621v3.pdf"}
{"id": "1604.04670", "abstract": "  The Fundamental Plane (FP) describes the relation between the stellar mass, size, and velocity dispersion of elliptical galaxies; the Faber-Jackson relation (FJR) is its projection onto mass, velocity space. In this work we redeploy and expand the framework of Desmond     Wechsler (2015) to ask whether abundance matching-based LCDM models that have shown success in matching the spatial distribution of galaxies are also capable of explaining key properties of the FJR and FP, including their scatter. Within our framework, agreement with the normalisation of the FJR requires haloes to expand in response to disc formation. We find that the tilt of the FP may be explained by a combination of the observed non-homology in galaxy structure and the variation in mass-to-light ratio produced by abundance matching with a universal initial mass function (IMF), provided that the anisotropy of stellar motions is taken into account. However, the predicted scatter around the FP is considerably increased by situating galaxies in cosmologically-motivated haloes due to variations in halo properties at fixed stellar mass, and appears to exceed that of the data. This implies that additional correlations between galaxy and halo variables may be required to fully reconcile these models with elliptical galaxy scaling relations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.04670v2.pdf"}
{"id": "1604.06725", "abstract": "  We investigate the effects of ram pressure on the ordered magnetic field of a galaxy hosting a radio halo and strong nuclear outflows. New radio images in total and polarized intensity of the edge-on Virgo galaxy NGC 4388 were obtained within the CHANG-ES EVLA project. The unprecedented noise level reached allows us to detect striking new features of the ordered magnetic field. The nuclear outflow extends far into the halo to about 5 kpc from the center and is spatially correlated with the Hα and X-ray emission. For the first time, the southern outflow is detected. Above and below both spiral arms we find extended blobs of polarized emission with an ordered field oriented perpendicular to the disk. The synchrotron lifetime of the cosmic ray electrons (CREs) in these regions yields a mean outflow velocity of (270±70), in agreement with a galactic wind scenario. The observed symmetry of the polarized halo features in NGC 4388 excludes a compression of the halo gas by the ram pressure of the intra-cluster medium (ICM). The assumption of equilibrium between the halo pressure and the ICM ram pressure yields an estimate of the ICM density that is consistent with both the ICM density derived from X-ray observations and the recent Planck Sunyaev-Zel'dovich measurements. The detection of a faint radio halo around cluster galaxies could thus be used for an estimate of ICM ram pressure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.06725v1.pdf"}
{"id": "1605.00428", "abstract": "  We discuss the hydrodynamics of a wave energy converter consisting of two vertically floating, coaxial cylinders connected by dampers and allowed to heave, sway and roll. This design, viable in deep water and able to extract energy independent of the incident wave direction, is examined for monochromatic waves as well as broad-banded seas described by a Pierson Moskowitz spectrum. Several possible device sizes are considered, and their performance is investigated for a design spectrum, as well as for more severe sea states, with a view towards survivability of the converters. In terms of device motions and captured power, a quantitative assessment of converter design as it relates to survival and operation is provided. Most results are given in dimensionless form to allow for a wide range of applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.00428v1.pdf"}
{"id": "1605.05859", "abstract": "  The AdS/QCD holographic wave function of basis light-front quantization (BLFQ) for vector meson J/ψ is applied in this manuscript. The exclusive production of J/ψ in diffractive process is computed in dipole model with AdS/QCD holographic wave function. We use IP-Sat and IIM model in the calculation of the differential cross section of the dipole scattering off the proton. The prediction of AdS/QCD holographic wave function in BLFQ gives a good agreement to the experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.05859v2.pdf"}
{"id": "1605.06143", "abstract": "  In recent years, an increasing amount of data is collected in different and often, not cooperative, databases. The problem of privacy-preserving, distributed calculations over separated databases and, a relative to it, issue of private data release were intensively investigated. However, despite a considerable progress, computational complexity, due to an increasing size of data, remains a limiting factor in real-world deployments, especially in case of privacy-preserving computations.   In this paper, we present a general method for trade off between performance and accuracy of distributed calculations by performing data sampling. Sampling was a topic of extensive research that recently received a boost of interest. We provide a sampling method targeted at separate, non-collaborating, vertically partitioned datasets. The method is exemplified and tested on approximation of intersection set both without and with privacy-preserving mechanism. An analysis of the bound on error as a function of the sample size is discussed and heuristic algorithm is suggested to further improve the performance. The algorithms were implemented and experimental results confirm the validity of the approach. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.06143v1.pdf"}
{"id": "1605.08513", "abstract": "  In energy harvesting (EH) network, the energy storage devices (i.e., batteries) are usually not perfect. In this paper, we consider a practical battery model with finite battery capacity, energy (dis-)charging loss, and energy dissipation. Taking into account such battery imperfections, we rely on the Lyapunov optimization technique to develop a stochastic online control scheme that aims to maximize the utility of data rates for EH multi-hop wireless networks. It is established that the proposed algorithm can provide a feasible and efficient data admission, power allocation, routing and scheduling solution, without requiring any statistical knowledge of the stochastic channel, data-traffic, and EH processes. Numerical results demonstrate the merit of the proposed scheme. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.08513v1.pdf"}
{"id": "1605.08956", "abstract": "  We report details of single crystal growth of stoichiometric bismuthide PtBi_2 whose structure consists of alternate stacking of Pt layer sandwiched by Bi bilayer along the c-axis. The compound crystallizes in space group P-3 with a hexagonal unit cell of a=b=6.553Å, c=6.165Å. The magnetization data show opposite sign for fields parallel and perpendicular to the Pt layers, respectively. The T-dependent resistivity is typical of a metal and the magnetic response shows clear two types of charge carriers and the validity of the semi-classical Kohler's rule. Its physical properties was discussed in comparison with recently proposed topological superconductor β-PdBi_2. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.08956v2.pdf"}
{"id": "1606.02281", "abstract": "  The electron states in the field of a charged impurity in graphene in a magnetic field are studied numerically. It is shown that a charged impurity removes the degeneracy of Landau levels converting them into bandlike structures. As the charge of impurity grows, the repulsion of sublevels of different Landau levels with the same value of orbital momentum takes place leading to the redistribution of the wave function profiles of these sublevels near the impurity. By studying the polarization effects, it is shown in agreement with the recent experiments that the effective charge of impurity can be very effectively tuned by chemical potential. If the chemical potential is situated inside a Landau level, then the charge of impurity is strongly diminished. In addition, the polarization function in this case has a peak at zero momentum, which leads to the sign-changing oscillations of the screened potential as a function of distance. If the chemical potential lies between the Landau levels, then the screened potential does not change sign, the screening is minimal, and the charged impurity can strongly affect the electron spectrum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.02281v2.pdf"}
{"id": "1606.03656", "abstract": "  Since the discovery of the cuprate high-temperature superconductivity in 1986, a universal phase diagram has been constructed experimentally and numerous theoretical models have been proposed. However, there remains no consensus on the underlying physics thus far. Here, we theoretically investigate the phase diagram of hole-doped cuprates based on an itinerant-localized dual fermion model, with the charge carriers doped on the oxygen sites and localized holes on the copper d_x^2-y^2 orbitals. We analytically demonstrate that the puzzling anomalous normal state or the strange metal could simply stem from a free Fermi gas of carriers bathing in copper antiferromagnetic spin fluctuations. The short-range high-energy spin excitations also act as the `magnetic glue' of carrier Cooper pairs and induce d-wave superconductivity from the underdoped to overdoped regime, distinctly diffrent from the conventional low-frequency magnetic fluctuation mechanism. We further sketch out the characteristic dome-shaped critical temperature T_c versus doping level. The emergence of the pseudogap is ascribed to the localization of partial carriers coupled to the local copper moments or a crossover from the strange metal to a nodal Kondo-like insulator. Our work provides a consistent theoretical framework to understand the typical phase diagram of hole-doped cuprates and paves a distinct way to the studies of both non-Fermi liquid and unconventional superconductivity in strongly correlated systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.03656v5.pdf"}
{"id": "1606.05671", "abstract": "  Nuclear uncertainties in the production of p nuclei in massive stars have been quantified in a Monte Carlo procedure. Bespoke temperature-dependent uncertainties were assigned to different types of reactions involving nuclei from Fe to Bi. Their simultaneous impact was studied in postprocessing explosive trajectories for three different stellar models. It was found that the grid of mass zones in the model of a 25 M_⊙ star, which is widely used for investigations of p nucleosynthesis, is too crude to properly resolve the detailed temperature changes required for describing the production of p nuclei. Using models with finer grids for 15 M_⊙ and 25 M_⊙ stars with initial solar metallicity, it was found that most of the production uncertainties introduced by nuclear reaction uncertainties are smaller than a factor of two. Since a large number of rates were varied at the same time in the Monte Carlo procedure, possible cancellation effects of several uncertainties could be taken into account. Key rates were identified for each p nucleus, which provide the dominant contribution to the production uncertainty. These key rates were found by examining correlations between rate variations and resulting abundance changes. This method is superior to studying flow patterns, especially when the flows are complex, and to individual, sequential variation of a few rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.05671v2.pdf"}
{"id": "1606.06558", "abstract": "  Set of analytic solutions of the geodesic equation in a spherical conformal spacetime is presented. Solutions of this geodesics can be expressed in terms of the Weierstrass ℘ function and the Kleinian σ function. Using conserved energy and angular momentum we can characterize the different orbits. Also, considering parametric diagrams and effective potentials, we plot some possible orbits. Moreover, with the help of analytical solutions, we investigate the light deflection for such an escape orbit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.06558v1.pdf"}
{"id": "1607.00880", "abstract": "  We address the use of maximum distance separable (MDS) codes for distributed storage (DS) to enable efficient content delivery in wireless networks. Content is stored in a number of the mobile devices and can be retrieved from them using device-to-device communication or, alternatively, from the base station (BS). We derive an analytical expression for the download delay in the hypothesis that the reliability state of the network is periodically restored. Our analysis shows that MDS-coded DS can dramatically reduce the download time with respect to the reference scenario where content is always downloaded from the BS. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.00880v2.pdf"}
{"id": "1607.03513", "abstract": "  Derived equivalences between finite dimensional algebras do, in general, not pass to centraliser (or other) subalgebras, nor do they preserve homological invariants of the algebras, such as global or dominant dimension. We show that, however, they do so for large classes of algebras described in this article.   Algebras A of ν-dominant dimension at least one have unique largest non-trivial self-injective centraliser subalgebras H_A. A derived restriction theorem is proved: A derived equivalence between A and B implies a derived equivalence between H_A and H_B.   Two methods are developed to show that global and dominant dimension are preserved by derived equivalences between algebras of ν-dominant dimension at least one with anti-automorphisms preserving simples, and also between almost self-injective algebras. One method is based on identifying particular derived equivalences preserving homological dimensions, while the other method identifies homological dimensions inside certain derived categories.   In particular, derived equivalent cellular algebras have the same global dimension. As an application, the global and dominant dimensions of blocks of quantised Schur algebras with n ≥ r are completely determined. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.03513v1.pdf"}
{"id": "1607.03867", "abstract": "  We analyze extragalactic extinction profiles derived through gamma-ray burst afterglows, using a dust model specifically constructed on the assumption that dust grains are not immutable but respond time-dependently to the local physics. Such a model includes core-mantle spherical particles of mixed chemical composition (silicate core, sp2 and sp3 carbonaceous layers), and an additional molecular component, in the form of free-flying polycyclic aromatic hydrocarbons. We fit most of the observed extinction profiles. Failures occur for lines of sight presenting remarkable rises blueward the bump. We find a tendency in the carbon chemical structure to become more aliphatic with the galactic activity, and to some extent with increasing redshifts. Moreover, the contribution of the moleclar component to the total extinction is more important in younger objects. The results of the fitting procedure (either successes and failures) may be naturally interpreted through an evolutionary prescription based on the carbon cycle in the interstellar medium of galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.03867v1.pdf"}
{"id": "1607.08048", "abstract": "  An approximation to the added mass matrix of an assembly of spheres is constructed on the basis of potential flow theory for situations where one sphere is much larger than the others. In the approximation the flow potential near a small sphere is assumed to be dipolar, but near the large sphere it involves all higher order multipoles. The analysis is based on an exact result for the potential of a magnetic dipole in the presence of a superconducting sphere. Subsequently, the approximate added mass hydrodynamic interactions are used in a calculation of the swimming velocity and rate of dissipation of linear chain structures consisting of a number of small spheres and a single large one, with account also of frictional hydrodynamic interactions. The results derived for periodic swimming on the basis of a kinematic approach are compared with bilinear theory, valid for small amplitude of stroke, and with the numerical solution of the approximate equations of motion. The calculations cover the whole range of scale number between the friction-dominated Stokes limit and the inertia-dominated regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.08048v1.pdf"}
{"id": "1608.01095", "abstract": "  We investigate the charge distributions for the u and d quarks in transverse coordinate space in a light-front quark-diquark model for the nucleons using the overlaps of the wave functions constructed from the soft-wall AdS/QCD prediction. We have also obtained the charge distributions for proton and neutron in transverse coordinate space and compared it with the distributions obtained in impact-parameter space. Further, we study the longitudinal momentum distributions using the wave functions in the transverse coordinate space. We have also shown the explicit fermionic and bosonic contributions for different struck u and d quarks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.01095v2.pdf"}
{"id": "1608.01772", "abstract": "  The main astronomical source of r-process elements has not yet been identified. One plausible site is neutron star mergers (NSMs), but from perspective of the Galactic chemical evolution, it has been pointed out that NSMs cannot reproduce the observed r-process abundance distribution of metal-poor stars at [Fe/H] < -3. Recently, Tsujimoto     Shigeyama (2014) pointed out that NSM ejecta can spread into much larger volume than ejecta from a supernova. We re-examine the enrichment of r-process elements by NSMs considering this difference in propagation using the chemical evolution model under the hierarchical galaxy formation. The observed r-process enhanced stars around [Fe/H] ∼ -3 are reproduced if the star formation efficiency is lower for low-mass galaxies under a realistic delay time distribution for NSMs. We show that a significant fraction of NSM ejecta escape from its host proto-galaxy to pollute intergalactic matter and other proto-galaxies. The propagation of r-process elements over proto-galaxies changes the abundance distribution at [Fe/H] < -3 and obtains distribution compatible with observations of the Milky Way halo stars. In particular, the pre-enrichment of intergalactic medium explains the observed scarcity of EMP stars without Ba and abundance distribution of r-process elements at [Fe/H] ≲ -3.5. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.01772v1.pdf"}
{"id": "1608.02078", "abstract": "  We study the thermal evolution of neutron stars in the presence of hyperons or kaons in the core. Our results indicate that the nucleon and hyperon direct Urca processes play crucial roles for the cooling of neutron stars. The presence of hyperons drives fast cooling mechanisms in two ways: 1) it allows the hyperon direct Urca prior to the nucleon direct Urca, 2) and it makes the nucleon direct Urca more feasible by reducing the neutron Fermi momentum. We found that the neutron star equation of state (EOS) with hyperons can be consistent with both mass and temperature observations. We also found that the neutron star EOS with kaon condensation can be consistent with observations, even though the cooling behavior is seldom useful to identify or isolate the effect of kaon condensation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.02078v1.pdf"}
{"id": "1608.02138", "abstract": "  Using one-dimensional spin-1/2 systems as prototypes of quantum many-body systems, we study the emergence of quantum chaos. The main purpose of this work is to answer the following question: how does the spin-orbit interaction, as a pure quantum interaction, may lead to the onset of quantum chaos? We consider three integrable spin-1/2 systems: the Ising, the XX, and the XXZ limits, and analyze whether quantum chaos develops or not after the addition of the Dzyaloshinskii-Moriya interaction. We find that, depending on the strength of the anisotropy parameter, the answer is positive for the XXZ and Ising models, while no such evidence is observed for the XX model. We also discuss the relationship between quantum chaos and thermalization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.02138v1.pdf"}
{"id": "1609.04759", "abstract": "  In this review, we summarize the theoretical development on the electric dipole moment of light nuclei. We first describe the nucleon level CP violation and its parametrization. We then present the results of calculations of the EDM of light nuclei in the ab initio approach and in the cluster model. The analysis of the effect of several models beyond standard model is presented, together with the prospects for its discovery. The advantage of the electric dipole moment of light nuclei is focused in the point of view of the many-body physics. The evaluations of the nuclear electric dipole moment generated by the θ-term and by the CP phase of the Cabibbo-Kobayashi-Maskawa matrix are also reviewed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.04759v2.pdf"}
{"id": "1609.04762", "abstract": "  Bose-Einstein condensation is a unique phase transition in that it is not driven by inter-particle interactions, but can theoretically occur in an ideal gas, purely as a consequence of quantum statistics. This chapter addresses the question `How is this ideal Bose gas condensation modified in the presence of interactions between the particles?'  This seemingly simple question turns out to be surprisingly difficult to answer. Here we outline the theoretical background to this question and discuss some recent measurements on ultracold atomic Bose gases that have sought to provide some answers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.04762v1.pdf"}
{"id": "1609.09076", "abstract": "  A planet orbiting in the \"habitable zone\" of our closest neighboring star, Proxima Centauri, has recently been discovered, and the next natural question is whether or not Proxima b is \"habitable\". Stellar winds are likely a source of atmospheric erosion that could be particularly severe in the case of M dwarf habitable zone planets that reside close to their parent star. Here we study the stellar wind conditions that Proxima b experiences over its orbit. We construct 3-D MHD models of the wind and magnetic field around Proxima Centauri using a surface magnetic field map for a star of the same spectral type and scaled to match the observed   600 G surface magnetic field strength of Proxima. We examine the wind conditions and dynamic pressure over different plausible orbits that sample the constrained parameters of the orbit of Proxima b. For all the parameter space explored, the planet is subject to stellar wind pressures of more than 2000 times those experienced by Earth from the solar wind. During an orbit, Proxima b is also subject to pressure changes of 1 to 3 orders of magnitude on timescales of a day. Its magnetopause standoff distance consequently undergoes sudden and periodic changes by a factor of 2 to 5. Proxima b will traverse the interplanetary current sheet twice each orbit, and likely crosses into regions of subsonic wind quite frequently. These effects should be taken into account in any physically realistic assessment or prediction of its atmospheric reservoir, characteristics and loss. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.09076v2.pdf"}
{"id": "1610.03613", "abstract": "  In the present contribution, we apply the double exponential Sinc-collocation method (DESCM) to the one-dimensional time independent Schrödinger equation for a class of rational potentials of the form V(x) =p(x)/q(x). This algorithm is based on the discretization of the Hamiltonian of the Schrödinger equation using Sinc expansions. This discretization results in a generalized eigenvalue problem where the eigenvalues correspond to approximations of the energy values of the corresponding Hamiltonian. A systematic numerical study is conducted, beginning with test potentials with known eigenvalues and moving to rational potentials of increasing degree. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.03613v1.pdf"}
{"id": "1610.07986", "abstract": "  Repetitive spatio-temporal propagation patterns are encountered in fields as wide-ranging as climatology, social communication and network science. In neuroscience, perfectly consistent repetitions of the same global propagation pattern are called a synfire pattern. For any recording of sequences of discrete events (in neuroscience terminology: sets of spike trains) the questions arise how closely it resembles such a synfire pattern and which are the spike trains that lead/follow. Here we address these questions and introduce an algorithm built on two new indicators, termed SPIKE-Order and Spike Train Order, that define the Synfire Indicator value, which allows to sort multiple spike trains from leader to follower and to quantify the consistency of the temporal leader-follower relationships for both the original and the optimized sorting. We demonstrate our new approach using artificially generated datasets before we apply it to analyze the consistency of propagation patterns in two real datasets from neuroscience (Giant Depolarized Potentials in mice slices) and climatology (El Ni no sea surface temperature recordings). The new algorithm is distinguished by conceptual and practical simplicity, low computational cost, as well as flexibility and universality. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.07986v4.pdf"}
{"id": "1611.00400", "abstract": "  Sufficient dimension reduction reduces the dimensionality of data while preserving relevant regression information. In this article, we develop Minimum Average Deviance Estimation (MADE) methodology for sufficient dimension reduction. It extends the Minimum Average Variance Estimation (MAVE) approach of Xia et al. (2002) from continuous responses to exponential family distributions to include Binomial and Poisson responses. Local likelihood regression is used to learn the form of the regression function from the data. The main parameter of interest is a dimension reduction subspace which projects the covariates to a lower dimension while preserving their relationship with the outcome. To estimate this parameter within its natural space, we consider an iterative algorithm where one step utilizes a Stiefel manifold optimizer. We empirically evaluate the performance of three prediction methods, two that are intrinsic to local likelihood estimation and one that is based on the Nadaraya-Watson estimator. Initial results show that, as expected, MADE can outperform MAVE when there is a departure from the assumption of additive errors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.00400v1.pdf"}
{"id": "1611.01073", "abstract": "  Using exact Bethe ansatz (BA) solutions, we show that a spin-down fermion immersed into a fully polarized spin-up Fermi sea with a weak attraction is dressed by the surrounding spin-up fermions to form the one-dimensional analog of a polaron. As the attraction becomes strong, the spin-down fermion binds with one spin-up fermion to form a tightly bound molecule. Throughout the whole interaction regime, a crossover from the polaron to a molecule state is fully demonstrated through exact results of the excitation spectrum, the effective mass, binding energy and kinetic energy. Furthermore, a clear distinction between the polaron and molecule is conceived by the probability distribution, single particle reduced density matrix and density-density correlations, which are calculated directly from the Bethe ansatz wave function. Such a polaron-molecule crossover presents a universal nature of an impurity immersed into a fermionic medium with an attraction in one dimension. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.01073v1.pdf"}
{"id": "1611.04300", "abstract": "  We consider the ionisation of atomic hydrogen by a strong infrared field. We extend and study in more depth an existing semi-analytical model. Starting from the time-dependent Schroedinger equation in momentum space and in the velocity gauge we substitute the kernel of the non-local Coulomb potential by a sum of N separable potentials, each of them supporting one hydrogen bound state. This leads to a set of N coupled one-dimensional linear Volterra integral equations to solve. We analyze the gauge problem for the model, the different ways of generating the separable potentials and establish a clear link with the strong field approximation which turns out to be a limiting case of the present model. We calculate electron energy spectra as well as the time evolution of electron wave packets in momentum space. We compare and discuss the results obtained with the model and with the strong field approximation and examine in this context, the role of excited states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.04300v1.pdf"}
{"id": "1611.08540", "abstract": "  The local structure and chemical bonding in two-phase amorphous Cr_1-xC_x nanocomposite thin films are investigated by Cr K-edge (1s) X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies in comparison to theory. By utilizing the computationally efficient stochastic quenching (SQ) technique, we reveal the complexity of different Cr-sites in the transition metal carbides, highlighting the need for large scale averaging to obtain theoretical XANES and EXAFS spectra for comparison with measurements. As shown in this work, it is advantageous to use ab initio theory as an assessment to correctly model and fit experimental spectra and investigate the trends of bond lengths and coordination numbers in complex amorphous materials. With sufficient total carbon content (≥ 30 at%), we find that the short-range coordination in the amorphous carbide phase exhibit similarities to that of a Cr_7C_3±y structure, while excessive carbons assemble in the amorphous carbon phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.08540v1.pdf"}
{"id": "1612.01204", "abstract": "  The phenomenological parameters of eclipsing binary stars, which are the prototypes of the EA, EB and EW systems are determined using the expert complex of computer programs, which realizes the NAV (\"New Algol Variable\") algorithm (Andronov 2010, 2012) and its possible modifications are discussed, as well as constrains for estimates of some physical parameters of the systems in a case of photometric observations only, such as the degree of eclipse, ratio of the mean surface brightnesses of the components. The half-duration of the eclipse is 0.0617(7), 0.1092(18) and 0.1015(7) for Algol, β Lyrae and W UMa, respectively. The brightness ratio is 6.8±1.0, 4.9±1.0 and 1.15±0.13. These results show that the eclipses have distinct begin and end not only in EA (as generally assumed), but also in EB and EW - type systems as well. The algorithm may be applied to classification and study of the newly discovered (or poorly studied) eclipsing variables based on own observations or that obtained using photometric surveys. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.01204v2.pdf"}
{"id": "1612.02341", "abstract": "  Radio observations suggest that 3C 75, located in the dumbbell shaped galaxy NGC 1128 at the center of Abell 400, hosts two colliding jets. Motivated by this source, we perform three-dimensional hydrodynamical simulations using a modified version of the GPU-accelerated Adaptive-MEsh-Refinement hydrodynamical parallel code (𝐺𝐴𝑀𝐸𝑅) to study colliding extragalactic jets. We find that colliding jets can be cast into two categories: 1) bouncing jets, in which case the jets bounce off each other keeping their identities, and 2) merging jets, when only one jet emerges from the collision. Under some conditions the interaction causes the jets to break up into oscillating filaments of opposite helicity, with consequences for their downstream stability. When one jet is significantly faster than the other and the impact parameter is small, the jets merge; the faster jet takes over the slower one. In the case of merging jets, the oscillations of the filaments, in projection, may show a feature which resembles a double helix, similar to the radio image of 3C 75. Thus we interpret the morphology of 3C 75 as a consequence of the collision of two jets with distinctly different speeds at a small impact parameter, with the faster jet breaking up into two oscillating filaments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.02341v1.pdf"}
{"id": "1612.02546", "abstract": "  Hadron-nucleus amplitudes at high energies are studied in the \"toy\" Regge model in zero transverse dimension for finite nuclei, when the standard series of fan diagrams is converted into a finite sum and looses physical sense at quite low energies. Taking into account all the loop contributions by numerical methods we find a physically meaningful amplitudes at all energies. They practically coincide with the amplitudes for infinite nuclei. A surprizing result is that for finite nuclei and small enough triple pomeron coupling the infinite series of fan diagrams describes the amplitude quite well in spite of the fact that in reality the series should be cut and as such deprived of any physical sense at high energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.02546v1.pdf"}
{"id": "1612.05516", "abstract": "  We calculate the radiative heat transfer between two identical metallic one-dimensional lamellar gratings. To this aim we present and exploit a modification to the widely-used Fourier modal method, known as adaptive spatial resolution, based on a stretch of the coordinate associated to the periodicity of the grating. We first show that this technique dramatically improves the rate of convergence when calculating the heat flux, allowing to explore smaller separations. We then present a study of heat flux as a function of the grating height, highlighting a remarkable amplification of the exchanged energy, ascribed to the appearance of spoof-plasmon modes, whose behavior is also spectrally investigated. Differently from previous works, our method allows us to explore a range of grating heights extending over several orders of magnitude. By comparing our results to recent studies we find a consistent quantitative disagreement with some previously obtained results going up to 50%. In some cases, this disagreement is explained in terms of an incorrect connection between the reflection operators of the two gratings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.05516v3.pdf"}
{"id": "1612.06020", "abstract": "  Quantum secure communication provides a new way for protecting the security of information. As an important component of quantum secure communication, remote state preparation (RSP) can securely transmit a quantum state from a sender to a remote receiver. The existence of quantum noise severely affects the security and reliability of quantum communication system. In this paper, we study the method for improving the efficiency of joint RSP (JRSP) subjected to noise with the help of weak measurement and its reversal measurement. Taking a GHZ based deterministic JRSP as an example, we utilize the technique of weak measurement and its reversal to suppress the effect of the amplitude-damping noise firstly. Our study shows that the fidelity of the output state can be improved in the amplitude-damping noise. We also study the effect of weak measurement and its reversal in other three types of noise usually encountered in real-world, namely, the bit-flip, phase-flip (phase-damping) and depolarizing noise. Our results show that the weak measurement has no effect for suppressing the bit-flip and phase-flip (phase-damping) noise, while has slight effect for suppressing the depolarizing noise. Our study is suitable for JRSP and RSP, and will be helpful for improving the efficiency of multiparticle entanglement based quantum secure communication in real implementation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.06020v1.pdf"}
{"id": "1701.02166", "abstract": "  State-of-the-art techniques for 6D object pose recovery depend on occlusion-free point clouds to accurately register objects in 3D space. To deal with this shortcoming, we introduce a novel architecture called Iterative Hough Forest with Histogram of Control Points that is capable of estimating the 6D pose of occluded and cluttered objects given a candidate 2D bounding box. Our Iterative Hough Forest (IHF) is learnt using parts extracted only from the positive samples. These parts are represented with Histogram of Control Points (HoCP), a \"scale-variant\" implicit volumetric description, which we derive from recently introduced Implicit B-Splines (IBS). The rich discriminative information provided by the scale-variant HoCP features is leveraged during inference. An automatic variable size part extraction framework iteratively refines the object's initial pose that is roughly aligned due to the extraction of coarsest parts, the ones occupying the largest area in image pixels. The iterative refinement is accomplished based on finer (smaller) parts that are represented with more discriminative control point descriptors by using our Iterative Hough Forest. Experiments conducted on a publicly available dataset report that our approach show better registration performance than the state-of-the-art methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.02166v1.pdf"}
{"id": "1701.02850", "abstract": "  Epsilon-near-zero (ENZ) materials, including artificial metamaterials, have been advanced to mold laser beams and antenna-mediated radiated waves. Here we propose an efficient method to control Ohmic losses inherent to natural ENZ materials by the assembly of subwavelength structures in a nonperiodic matrix constituting an ENZ metacoating. Implemented over plano-concave transparent substrates whose radius can be of only a few wavelengths, ENZ surface-relief elements demonstrate to adequately shape a plane wave into highly localized fields. Furthermore, our proposal provides an energy efficiency even higher than an ideally-lossless all-ENZ plano-concave lens. Our procedure is satisfactory to generate aberration-free nonparaxial focused waves and accelerating beams in miniaturized spaces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.02850v1.pdf"}
{"id": "1701.03602", "abstract": "  Automatic verification deals with the validation by means of computers of correctness certificates. The related tools, usually called proof assistants or interactive provers, provide an interactive environment for the creation of formal certificates whose correctness can be assessed in a purely automatic way. Such systems have applications both in mathematics, where certificates are proofs of theorems, and in computer science, where certificates testify the correctness of a given software with respect to its specification. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.03602v1.pdf"}
{"id": "1702.01839", "abstract": "  Existing multicasting schemes for massive content delivery do not fully utilize multicasting opportunities in delay tolerant content-oriented applications. In this paper, we propose a novel temporal-spatial aggregation-based multicasting scheme in a large-scale cache-enabled wireless network. The proposed scheme can efficiently exploit multicasting opportunities in asynchronous content requests to improve spectral efficiency. By making use of the delay tolerance of elastic services, the proposed scheme achieves a better energy-throughput-delay tradeoff. Utilizing tools from stochastic geometry, we derive a tractable expression for the successful transmission probability in the general region. Using asymptotic approximations, we derive closed form successful transmission probabilities in the large delay region as well as the large and small user density regions. The asymptotic results reveal that the successful transmission probability increases and the energy consumption decreases at the cost of delay increase in these asymptotic regions. The analysis in this paper provides a new understanding of the energy-throughput-delay tradeoff for massive content delivery in large-scale cache-enabled wireless networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.01839v1.pdf"}
{"id": "1702.02860", "abstract": "  We study homogenization properties of the discrete Laplace operator with random conductances on a large domain in ℤ^d. More precisely, we prove almost-sure homogenization of the discrete Poisson equation and of the top of the Dirichlet spectrum. We assume that the conductances are stationary, ergodic and nearest-neighbor conductances are positive. In contrast to earlier results, we do not require uniform ellipticity but certain integrability conditions on the lower and upper tails of the conductances. We further allow jumps of arbitrary length. Without the long-range connections, the integrability condition on the lower tail is optimal for spectral homogenization. It coincides with a necessary condition for the validity of a local central limit theorem for the random walk among random conductances. As an application of spectral homogenization, we prove a quenched large deviation principle for the normalized and rescaled local times of the random walk in a growing box. Our proofs are based on a compactness result for the Laplacian's Dirichlet energy, Poincare inequalities, Moser iteration and two-scale convergence. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.02860v3.pdf"}
{"id": "1702.03678", "abstract": "  Search of life elsewhere in the galaxy is very fascinating area for planetary scientists and astrobiologists. Earth Similarity Index (ESI) is defined as geometrical mean of four physical parameters (Such as radius, density, escape velocity and surface temperature), which is ranging from 1 (identical to Earth) to 0 (dissimilar to Earth). In this work, ESI is re-defined as six parameters by introducing the two new physical parameters like revolution and surface gravity and is called as New Earth Similarity Index (NESI). The main focus of this paper is to search Tardigrade water-life on exoplanets by varying the temperature parameter in NESI, which is called as Tardigrade Similarity Index (TSI), which is ranging from 1 (Tardigrade can survive) to 0 (Tardigrade Cannot survive). Here the NESI and TSI is cataloged and analyzed for almost 3370 confirmed exoplanets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.03678v1.pdf"}
{"id": "1702.04548", "abstract": "  A few approximate schemes to solve the Hedin equations self-consistently introduced in (Phys. Rev. B 94, 155101 (2016)) are explored and tested for the 3D electron gas at metallic densities. We calculate one electron spectra, dielectric properties, compressibility, and correlation energy. Considerable reduction in the calculated band width (as compared to the self consistent GW result) has been found when vertex correction was used for both polarizability and self energy. Generally, it is advantageous to obtain the diagrammatic representation of polarizability from the definition of this quantity as a functional derivative of the electronic density with respect to the total field (external plus induced). For self energy, the first order vertex correction seems to be sufficient for the range of densities considered. Whenever it is possible, we compare the accuracy of our vertex-corrected schemes with the accuracy of the self-consistent quasi-particle GW approximation (QSGW), which is less expensive computationally. We show that QSGW approach performs poorly and we relate this poor performance with an inaccurate description of the screening in the QSGW method (with an error comprising a factor 2-3 in the physically important range of momenta). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.04548v2.pdf"}
{"id": "1702.06121", "abstract": "  The present paper deals with the discrete inverse problem of reconstructing binary matrices from their row and column sums under additional constraints on the number and pattern of entries in specified minors. While the classical consistency and reconstruction problems for two directions in discrete tomography can be solved in polynomial time, it turns out that these window constraints cause various unexpected complexity jumps back and forth from polynomial-time solvability to ℕℙ-hardness. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.06121v1.pdf"}
{"id": "1702.07193", "abstract": "  In recent years ontologies enjoyed a growing popularity outside specialized AI communities. System engineering is no exception to this trend, with ontologies being proposed as a basis for several tasks in complex industrial implements, including system design, monitoring and diagnosis. In this paper, we consider four different contributions to system engineering wherein ontologies are instrumental to provide enhancements over traditional ad-hoc techniques. For each application, we briefly report the methodologies, the tools and the results obtained with the goal to provide an assessment of merits and limits of ontologies in such domains. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.07193v1.pdf"}
{"id": "1702.07459", "abstract": "  We revisit the Glauber model to study the heavy ion reaction cross sections and elastic scattering angular distributions at low and intermediate energies. The Glauber model takes nucleon-nucleon cross sections and nuclear densities as inputs and has no free parameter and thus can predict the cross sections for unknown systems. The Glauber model works at low energies down to Coulomb barrier with very simple modifications. We present new parametrization of measured total cross sections as well as ratio of real to imaginary parts of the scattering amplitudes for pp and np collisions as a function of nucleon kinetic energy. The nuclear (charge) densities obtained by electron scattering form factors measured in large momentum transfer range are used in the calculations. The heavy ion reaction cross sections are calculated for light and heavy systems and are compared with available data measured over large energy range. The model gives excellent description of the data. The elastic scattering angular distributions are calculated for various systems at different energies. The model gives good description of the data at small momentum transfer but the calculations deviate from the data at large momentum transfer. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.07459v1.pdf"}
{"id": "1703.01519", "abstract": "  In this work, a relation is found between state dependence of bulk observables in the gauge/gravity correspondence and nonperturbative diffeomorphism invariance. Certain bulk constraints, such as the black hole information paradox, appear to obstruct the existence of a linear map from bulk operators to exact CFT operators that is valid over the entire expected range of validity of the bulk effective theory. By formulating the bulk gravitational physics in the Hartle-Hawking framework to address these nonperturbative IR questions, I will demonstrate, in the context of eternal AdS-Schwarzschild, that the problematic operators fail to satisfy the Hamiltonian constraints nonperturbatively. In this way, the map between bulk effective theory Hartle-Hawking wavefunctions and exact CFT states can be linear on the full Hilbert space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.01519v1.pdf"}
{"id": "1703.09441", "abstract": "  We analyze, through resonant photoluminescence, the spin dynamics of an individual magnetic atom (Mn) coupled to a hole in a semiconductor quantum dot. The hybrid Mn-hole spin and the positively charged exciton in a CdTe/ZnTe quantum dot forms an ensemble of Λ systems which can be addressed optically. Auto-correlation of the resonant photoluminescence and resonant optical pumping experiments are used to study the spin relaxation channels in this multilevel spin system. We identified for the hybrid Mn-hole spin an efficient relaxation channel driven by the interplay of the Mn-hole exchange interaction and the coupling to acoustic phonons. We also show that the optical Λ systems are connected through inefficient spin-flips than can be enhanced under weak transverse magnetic field. The dynamics of the resonant photoluminescence in a p-doped magnetic quantum dot is well described by a complete rate equation model. Our results suggest that long lived hybrid Mn-hole spin could be obtained in quantum dot systems with large heavy-hole/light-hole splitting. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.09441v2.pdf"}
{"id": "1703.09448", "abstract": "  The theoretical procedure of supersymmetric quantum mechanics is adopted to generate the resonance state wave functions of the unbound nucleus ^15Be. In this framework, we used a density dependent M3Y microscopic potential and arrived at the energy and width of the 1.8 MeV (5/2^+) resonance state. We did not find any other nearby resonances for ^15Be. It becomes apparent that the present framework is a powerful tool to theoretically complement the increasingly important accelerator based experiments with unbound nuclei. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.09448v2.pdf"}
{"id": "1703.09484", "abstract": "  TUS is the world's first orbital detector of extreme energy cosmic rays (EECRs), which operates as a part of the scientific payload of the Lomonosov satellite since May 19, 2016. TUS employs the nocturnal atmosphere of the Earth to register ultraviolet (UV) fluorescence and Cherenkov radiation from extensive air showers generated by EECRs as well as UV radiation from lightning strikes and transient luminous events, micro-meteors and space debris. The first months of its operation in orbit have demonstrated an unexpectedly rich variety of UV radiation in the atmosphere. We briefly review the design of TUS and present a few examples of events recorded in a mode dedicated to registering EECRs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.09484v3.pdf"}
{"id": "1703.10196", "abstract": "  We present an algorithm capable of identifying a wide variety of human-induced change on the surface of the planet by analyzing matches between local features in time-sequenced remote sensing imagery. We evaluate feature sets, match protocols, and the statistical modeling of feature matches. With application of KAZE features, k-nearest-neighbor descriptor matching, and geometric proximity and bi-directional match consistency checks, average match rates increase more than two-fold over the previous standard. In testing our platform, we developed a small, labeled benchmark dataset expressing large-scale residential, industrial, and civic construction, along with null instances, in California between the years 2010 and 2012. On the benchmark set, our algorithm makes precise, accurate change proposals on two-thirds of scenes. Further, the detection threshold can be tuned so that all or almost all proposed detections are true positives. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.10196v1.pdf"}
{"id": "adap-org9504004", "abstract": "  Surface level instability when tube is injected into vibrating bed of powder, which was originally found in experiments, is investigated numerically. We find that thicker (thiner) tube makes surface level inside tube higher (lower) than surface level outside tube. With fixed acceleration amplitude of vibration, surface level inside tube becomes higher as amplitude of vibration increases, which can be explained by considering the dependence upon strength of convective flow. ", "pdf_url": "gs://arxiv-dataset/arxiv/adap-org/pdf/9504/9504004v1.pdf"}
{"id": "astro-ph0001433", "abstract": "  A short review on theoretical implications of non-thermal emission (radio, extreme ultraviolet, high energy X-ray) from the intra-cluster medium is given. The origin of cluster radio halos and cluster radio relics is discussed within the framework of a network of processes producing a non-thermal electron population. Emphasis is given to the role of old, remnant, presently invisible relativistic plasma released by former radio galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0001/0001433v1.pdf"}
{"id": "astro-ph0002059", "abstract": "  We report results from a program of high-resolution spectral mapping of rotational H_2 emission from bipolar planetary and pre-planetary nebulae. Long-slit spectra obtained with the NOAO Phoenix near-infrared spectrometer allow us to probe the molecular kinematics of these nebulae at moderate spatial resolution. We find strong evidence of a component of rotation in the equatorial H_2 emission from the Egg nebula (RAFGL 2688). In this nebula and in the pre-planetary nebula RAFGL 618, the H_2 kinematics point to the recent emergence of high-velocity polar flows, which likely mark the fairly sudden terminations of the red giant phases of their central stars. The classical bipolar planetary NGC 2346 displays distinct kinematic components, which we interpret as arising in the morphologically distinct equatorial and polar regions of the nebula. The H_2 rings observed in the Phoenix position-velocity maps of this nebula support the hypothesis that ring-like planetaries that display H_2 emission possess bipolar structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0002/0002059v1.pdf"}
{"id": "astro-ph0003254", "abstract": "  Recent studies of galactic nuclei suggest that most galaxies are seeded by super-massive black holes which power the central nucleus. In this picture, the proto-galactic object is likely to have undergone a very active phase during which the surrounding medium was shocked and heated up to very high temperatures. We predict the cosmological effects of this scenario in terms of the thermal and kinetic Sunyaev-Zel'dovich distortions induced on galactic scales by a population of proto-galaxies. These predictions are compared to the observational limit on the mean Compton distortion set by the COBE-FIRAS instrument. This enables us to derive tight constraints on the fraction of proto-galaxies seeded by super-massive black holes as well as on the black hole-to-spheroid mass ratio. Finally, we estimate the contribution of such a population to the angular power spectrum of the Cosmic Microwave Background temperature anisotropies on very small angular scales (l≃ 10^4-10^5). ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0003/0003254v1.pdf"}
{"id": "astro-ph0007177", "abstract": "  We use the CO band at 2.3 micron to constrain the populations of young stars in the central regions of Seyfert galaxies. We report new CO band spectroscopy of 46 Seyfert galaxies. In most cases, the observed CO indices appear diluted by the presence of a non-stellar component (most likely, warm dust surrounding the active nucleus). We used JHKL aperture photometry to estimate the non-stellar contribution at 2.3 micron. We successfully corrected the CO band for the dilution for 16 galaxies which were not dominated by the non-stellar component. Comparing with CO indices measured in elliptical and purely starbursting galaxies, we find no evidence for strong starbursts in the majority of these galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0007/0007177v2.pdf"}
{"id": "astro-ph0007455", "abstract": "  We examined the gravitational contraction of isothermal molecular cloud cores with slow rotation by means of two-dimensional numerical simulations. Applying a sink-cell method, we followed the evolution of the cloud cores up to the stages at which most of the matter accretes onto the central region (i.e., a protostar and a rotationally-supported circumstellar disk). We show that both an infalling disklike envelope and a rotationally-supported disk around the central star are natural outcome of the gravitational contraction of a prolate cloud core with slow rotation. The early evolution of the infalling envelopes resembles sheet models recently proposed by Hartmann and coworkers. In the infalling disklike envelope, the radial profiles of the density, radial velocity, and azimuthal velocity can be approximated by ρ∝ r^-1.5, v_r∝ r^-0.5, and v_ϕ∝ r^-1, respectively. The fate of the infalling envelopes is also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0007/0007455v1.pdf"}
{"id": "astro-ph0008158", "abstract": "  If cluster dark matter is in the form of compact objects it will introduce fluctuations into the light curves of distant sources. Current searches for MACHOs in clusters of galaxies focus on monitoring quasars behind nearby systems. This paper considers the effect of such a compact population on the surface brightness distribution of giant gravitationally lensed arcs. As the microlensing optical depth is significant in these clusters, the expected fluctuations are substantial and are observable. Focusing on the giant arc seen in Abell 370, we demonstrate that several `extreme' events would be visible in a comparison of HST observations at two epochs. Utilizing NGST, long term monitoring should reveal a ubiquitous twinkling of brightness over the surface of the arcs. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0008/0008158v1.pdf"}
{"id": "astro-ph0008288", "abstract": "  We determine the small-scale structure for a large sample of Compact Steep Spectrum (CSS) and Gigahertz Peaked Spectrum (GPS) sources and a sample of larger radio sources at 327 MHz using the technique of Inter-Planetary Scintillation (IPS) with the Ooty Radio Telescope. Our observations provide structural information on angular scales ranging from about 50 to a few hundred milliarcsec. We estimate the size and flux density of the scintillating components from the IPS observations. The fraction of flux density of the hotspots estimated from both the IPS observations as well as from interferometric observations for larger sources from the literature exhibits no significant dependence on either the radio luminosity or linear size for the high-luminosity sources. We examine the collimation of radio jets using the sizes of hotspots from both IPS and interferometric observations. The hotspot sizes do not exhibit a significant dependence on the overall linear size for the larger sources, although the CSS and GPS sources were earlier found to evolve in a self-similar way. The IPS observations show evidence of larger-scale structures compared to the known VLBI-scale structures in 8 CSS and GPS radio sources. We discuss the origin of these structures. We also examine the spectra of compact components in GPS sources using both IPS and interferometric measurements, and attempt to distinguish between different processes for explaining their low-frequency spectra. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0008/0008288v1.pdf"}
{"id": "astro-ph0009370", "abstract": "  The distribution of the stellar and gaseous components in low surface brightness galaxies has been determined directly from optical and HI imaging. The distribution of what might be the dominant mass component, the dark matter, which is inferred from rotation curves, is far harder to determine. Although the rotation curves themselves can be determined fairly accurately from HI synthesis observations, and in particular from Hα spectroscopy, the uncertainty in the mass modeling leaves room for a wide range of possible dark matter distributions, ranging from maximum stellar disks with shallow dark halos to cuspy dark halos with little mass in stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0009/0009370v1.pdf"}
{"id": "astro-ph0011517", "abstract": "  It has been suggested that both X-ray bursters and millisecond radio pulsars may be strange (quark) stars, rather than neutron stars. Confirming (or rejecting) this suggestion may require knowing what role strong-field effects of general relativity play in the accretion flow of the compact X-ray source in low-mass X-ray binaries (LMXBs). We discuss the range of rotational and orbital frequencies, and of masses expected in various models of strange stars, and compare them with observational constraints, suggested by the observed frequencies of kHz QPOs. We explain why future observations of transients (such as SAX J 1808.4-3658) may be crucial to understanding the precise nature of the accreting source. For flattened (e.g., rapidly rotating) distributions of matter, an innermost (marginally) stable orbit may be present even if relativistic effects are negligible. Depending on the stellar rotation rate, the same value of orbital frequency in the innermost stable orbit (say, 0.9 kHz) can correspond to a star of mass equal to 2.4M_⊙, 1.4M_⊙, 0.1M_⊙, 0.01M_⊙, or less. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011517v1.pdf"}
{"id": "astro-ph0011534", "abstract": "  I study the formation of Comptonization spectra in spherically symmetric, fast moving media in a flat spacetime. I analyze the mathematical character of the moments of the transfer equation in the system-frame and describe a numerical method that provides fast solutions of the time-independent radiative transfer problem that are accurate in both the diffusion and free-streaming regimes. I show that even if the flows are mildly relativistic (V 0.1, where V is the electron bulk velocity in units of the speed of light), terms that are second-order in V alter the emerging spectrum both quantitatively and qualitatively. In particular, terms that are second-order in V produce power-law spectral tails, which are the dominant feature at high energies, and therefore cannot be neglected. I further show that photons from a static source are upscattered by the bulk motion of the medium even if the velocity field does not converge. Finally, I discuss these results in the context of radial accretion onto and outflows from compact objects. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011534v2.pdf"}
{"id": "astro-ph0101009", "abstract": "  These lecture notes discuss several topics in the physics of cosmic structure formation starting from the evolution of small-amplitude fluctuations in the radiation-dominated era. The topics include relativistic cosmological perturbation theory with the scalar-vector-tensor decomposition, the evolution of adiabatic and isentropic initial fluctuations, microwave background anisotropy, spatial and angular power spectra, the cold dark matter linear transfer function, Press-Schechter theory, and a brief introduction to numerical simulation methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0101/0101009v1.pdf"}
{"id": "astro-ph0101099", "abstract": "  We have used the IBIS Simulator to produce preliminary response matrices for the ISGRI and PICsIT detectors in order to help understanding their scientific performances before the calibration results are available. The derived matrices, in a format compatible with the XSPEC spectral analysis package, have been tested by fitting simple models and then used to analyze simulations of astrophysical sources with more complex spectra. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0101/0101099v1.pdf"}
{"id": "astro-ph0101342", "abstract": "  About 500d after explosion the light curve of the Type Ia SN1998bu suddenly flattened and at the same time the spectrum changed from the typical nebular emission to a blue continuum with broad absorption and emission features reminiscent of the SN spectrum at early phases. We show that in analogy to SN1991Tbu (Schmidt et al. 1994), this can be explained by the emergence of a light echo from a foreground dust cloud. Based on a simple model we argue that the amount of dust required can consistently explain the extinction which has been estimated by completely independent methods. Because of the similar echo luminosity but much higher optical depth of the dust in SN1998bu compared with SN1991T, we expect that the echo ring size of SN1998bu grows faster than in SN1991T. HST observations have indeed confirmed this prediction. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0101/0101342v1.pdf"}
{"id": "astro-ph0102258", "abstract": "  We investigate the weakly non-linear evolution of cosmic gravitational clustering in phase space by looking at the Zel'dovich solution in the discrete wavelet transform (DWT) representation. We show that if the initial perturbations are Gaussian, the relation between the evolved DWT mode and the initial perturbations in the weakly non-linear regime is quasi-local. That is, the evolved density perturbations are mainly determined by the initial perturbations localized in the same spatial range. Furthermore, we show that the evolved mode is monotonically related to the initial perturbed mode. Thus large (small) perturbed modes statistically correspond to the large (small) initial perturbed modes. We test this prediction by using QSO Lyα absorption samples. The results show that the weakly non-linear features for both the transmitted flux and identified forest lines are quasi-localized. The locality and monotonic properties provide a solid basis for a DWT scale-by-scale Gaussianization reconstruction algorithm proposed by Feng     Fang (Feng     Fang, 2000) for data in the weakly non-linear regime. With the Zel'dovich solution, we find also that the major non-Gaussianity caused by the weakly non-linear evolution is local scale-scale correlations. Therefore, to have a precise recovery of the initial Gaussian mass field, it is essential to remove the scale-scale correlations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0102/0102258v1.pdf"}
{"id": "astro-ph0103052", "abstract": "  Interacting galaxies like the famous Antennae (NGC 4038/4039) or Stephan's Quintet (HCG 92) show considerable star forming activity in their tidal arms. High resolution images (e.g. from HST-observations) indicate that these regions consist of up to hundreds of massive stellar clusters or tidal dwarf galaxies (TDG). In this paper we want to investigate the future fate of these clusters of massive star clusters (in this work called super-clusters). We simulate compact super-clusters in the tidal field of a host-galaxy and investigate the influence of orbital and internal parameters on the rate and timescale of the merging process. We show that it is possible that such configurations merge and build a dwarf galaxy, which could be an important mechanism of how long-lived dwarf satellite galaxies form. A detailed study of the merger object will appear in a follow-up paper. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0103/0103052v2.pdf"}
{"id": "astro-ph0103222", "abstract": "  Abundance observations indicate the presence of rapid-neutron capture (i.e., r-process) elements in old Galactic halo and globular cluster stars. These observations demonstrate that the earliest generations of stars in the Galaxy, responsible for neutron-capture synthesis and the progenitors of the halo stars, were rapidly evolving. Abundance comparisons among several halo stars show that the heaviest neutron-capture elements (including Ba and heavier) are consistent with a scaled solar system r-process abundance distribution, while the lighter such elements do not conform to the solar pattern. These comparisons suggest two r-process sites or at least two different sets of astrophysical conditions. The large star-to-star scatter observed in the neutron-capture/iron ratios at low metallicities – which disappears with increasing [Fe/H] – suggests an early, chemically unmixed and inhomogeneous Galaxy. The stellar abundances indicate a change from the r-process to the slow neutron capture (i.e., s-) process at higher metallicities in the Galaxy. The detection of thorium in halo and globular cluster stars offers a promising, independent age-dating technique that can put lower limits on the age of the Galaxy. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0103/0103222v1.pdf"}
{"id": "astro-ph0104458", "abstract": "  To circumvent the spatial effects of resolution on galaxy classification, the images of 233 objects of known redshift in the Hubble Deep Field (HDF) and its Flanking Fields (FF) that have redshifts in the range 0.20 < z < 1.10 were degraded to the resolution that they would have had if they were all located at a redshift z= 1.00. As in paper XIV of the present series, the effects of shifts in rest wavelength were mitigated by using R-band images for the classification of galaxies with 0.2 < z < 0.6 and I-band images for objects with redshifts 0.6 < z < 1.1. A special effort was made to search for bars in distant galaxies. The present data strongly confirm the previous conclusion that the Hubble tuning fork diagram only provides a satisfactory framework for the classification of galaxies with z  < 0.3. More distant disk galaxies are often difficult to shoehorn into the Hubble classification scheme. The paucity of barred spirals and of grand-design spirals at large redshifts is confirmed. It is concluded that the morphology of disk galaxies observed at look-back times smaller than 3–4 Gyr differs systematically from that of more distant galaxies viewed at look-back times of 4–8 Gyr. The disks of late-type spirals at z >0.5 are seen to be more chaotic than those of their nearer counterparts. Furthermore the spiral structure in distant early-type spirals appears to be less well-developed than it is in nearby early-galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0104/0104458v1.pdf"}
{"id": "astro-ph0105566", "abstract": "  We have made subarcsecond-resolution images of the central 10\" of the Wolf-Rayet dwarf galaxy He 2-10 at 11.7 microns, using the Long Wavelength Spectrometer on the Keck Telescope. The spatial distribution of the infrared emission roughly agrees with that of the rising spectrum radio sources seen by Kobulnicky     Johnson (1999) and confirms that those sources are compact HII regions rather than SNR or other objects. The infrared sources are more extended than the subarcsecond rising spectrum radio sources, although the entire complex is still less than 5\" in extent. On sizescales of 1\" the infrared and radio emission are in excellent agreement, with each source requiring several hundred to a thousand O stars for excitation. The nebulae lie in a flattened disk-like distribution about 240 by 100 pc and provide all of the flux measured by IRAS for the entire galaxy in the 12 micron band; 30", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0105/0105566v1.pdf"}
{"id": "astro-ph0106111", "abstract": "  A set-up is introduced which can be superimposed onto the existing solar flare cellular automata (CA) models, and which specifies the interpretation of the model's variables. It extends the CA models, yielding the magnetic field, the current, and an approximation to the electric field, in a way that is consistent with Maxwell's and the MHD equations. Applications to several solar flare CA models during their natural state (self-organized criticality (SOC)) show, among others, that (1) the magnetic field exhibits characteristic large-scale organization over the entire modeled volume; (2) the magnitude of the current seems spatially dis-organized, with no obvious tendency towards large-scale structures or even local organization; (3) bursts occur at sites with increased current, and after a burst the current is relaxed; (4) by estimating the energy released in individual bursts with the use of the current as Ohmic dissipation, it turns out that the power-law distributions of the released energy persist. The CA models, extended with the set-up, can thus be considered as models for energy-release through current-dissipation. The concepts of power-law loading and anisotropic events (bursts) in CA models are generalized to 3–D vector-field models, and their effect on the magnetic field topology is demonstrated. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0106/0106111v2.pdf"}
{"id": "astro-ph0106284", "abstract": "  Given their proximity and age differences, nearby groups of young stars are valuable laboratories for investigations of disk evolution and diversity. The estimated 10-Myr age of groups like the TW Hydrae Association provides a strong constraint on disk evolution timescales and fills a significant gap in the age sequence between 1-Myr-old T Tauri stars in molecular clouds and 50-Myr-old nearby open clusters. I review the results of recent and on-going studies of dusty disks in three nearby groups –TW Hya, η Cha and MBM 12– that suggest rapid evolution of inner disks. However, it is unlikely that there is a universal evolutionary timescale for protoplanetary disks, especially when the influence of companion stars is taken into account. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0106/0106284v1.pdf"}
{"id": "astro-ph0107595", "abstract": "  The sensitivity of ground-based imaging atmospheric Cherenkov gamma-ray observatories depends critically on the primary particle identification methods which are used to retain photon-initiated events and suppress the spurious background produced by cosmic rays. We suggest a new discrimination technique which utilizes differences in the fluctuations of the light intensity in the images of showers initiated by photons and those initiated by protons or heavier nuclei. The database of simulated events for the proposed VERITAS observatory has been used to evaluate the efficiency of the new technique. Analysis has been performed for both a single VERITAS imaging telescope, and a system of these telescopes. We demonstrate that a discrimination efficiency of > 1.5 - 2.0 can be achieved in addition to traditional background rejection methods based on image shape parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0107/0107595v1.pdf"}
{"id": "astro-ph0108084", "abstract": "  The 1998 outburst of XTE J1550-564 started with a hard X-ray spike, rising in less than a day and declining after 3-4 days; at the same time, the soft X-ray flux was rising with a longer timescale (  10 days). We suggest that the soft and the initial hard X-ray emission are produced by two different components of the accretion flow: a higher angular momentum flow, which forms the disk, and a lower angular momentum flow feeding the hot inner region. Thus, we argue that the onset of the outburst is determined by an increased mass transfer rate from the companion star, but the outburst morphology is also determined by the distribution of specific angular momentum in the accreting matter. In XTE J1550-564, we attribute the initial, impulsive low angular momentum accretion to the breaking down of magnetic confinement by the magnetically active secondary star. We show that a hard X-ray spike is seen at the onset of an outburst in other BHCs. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0108/0108084v1.pdf"}
{"id": "astro-ph0108110", "abstract": "  Relativistic jets carry a significant fraction of the total energy budget of a radio source, rivaling the power that is extracted through accretion. A minor part of this bulk kinetic power is transformed to radiation, possibly through internal shocks if the plasma is accelerated, at the base of the jet, to a velocity which changes in time. In this way we can understand why some radiation is produced all along the jet even if most of it originates at a preferred location, and why the efficiency of conversion of bulk to random energy is small. The recent observations by Chandra of intense jet X-ray emission at large scales suggest that at least the \"spine\" of jets continues to be highly relativistics even up to hundreds of kiloparsecs away from the nucleus and give tight lower limits on the jet bulk kinetic power. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0108/0108110v1.pdf"}
{"id": "astro-ph0108372", "abstract": "  The Crab nebula has proved to be the nearest to a standard candle in VHE γ- ray astronomy. Results on the gamma ray emission from the nebula at various energies have come in the last decade mostly from imaging telescopes. The aim of the new Pachmarhi Atmospheric Cerenkov Telescope (PACT) array has been to use the temporal and spatial distribution of Cerenkov photons in distinguishing between proton and gamma ray showers. The array, with timing information from 175 mirrors, is ideally suited for precise estimation of the arrival direction. Preliminary results from the recent data taken on Crab has shown a 12σ signal with the flux in good agreement with those of the other experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0108/0108372v1.pdf"}
{"id": "astro-ph0109546", "abstract": "  Research on the core of medium and high z clusters of galaxies can derive great benefits from integral field spectroscopy, and a key role in this respect will be played by the Integral Field Unit (IFU) being developed by the VIRMOS Consortium as part of the VIMOS spectrograph. After a brief technical outline of the instrument, some of the problems to be addressed by data reduction techniques are described, and the scientific issues to which VIMOS IFU is likely to give its major contribution are pointed out. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0109/0109546v1.pdf"}
{"id": "astro-ph0110197", "abstract": "  In the first part of this article, we review the observational evidence for spirals in the accretion discs of cataclysmic variables. It is shown that with the increasing amount of data available, spirals appear to be an omnipresent feature of accretion discs in outburst. Spirals seem to live until decline that is, for several tens of orbital periods. We then study the formation of spiral shocks from a theoretical side, using the results of various numerical simulations. We make a comparison between observations and theory and briefly discuss the implications of the presence of spirals in the discs of cataclysmic variables. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0110/0110197v1.pdf"}
{"id": "astro-ph0110690", "abstract": "  Models for the formation and growth of structure in a cold dark matter dominated universe predict that galaxy halos should contain significant substructure. Studies of the Milky Way, however, have yet to identify the expected few hundred sub-halos with masses greater than about 10^6 Msun. Here we propose a test for the presence of sub-halos in the halos of galaxies. We show that the structure of the tidal tails of ancient globular clusters is very sensitive to heating by repeated close encounters with the massive dark sub-halos. We discuss the detection of such an effect in the context of the next generation of astrometric missions, and conclude that it should be easily detectable with the GAIA dataset. The finding of a single extended cold stellar stream from a globular cluster would support alternative theories, such as self-interacting dark matter, that give rise to smoother halos. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0110/0110690v1.pdf"}
{"id": "astro-ph0112247", "abstract": "  We discuss possible distortions of the ionization history of the Universe in the model with small scale baryonic clouds. The corresponding scales of the clouds are much smaller than the typical galactic mass scales. These clouds are considered in a framework of the cosmological model with the isocurvature and adiabatic perturbations. In this model the baryonic clouds do not influence on the cosmic microwave background anisotropy formation directly as an additional sources of perturbations, but due to change of the kinetics of the hydrogen recombination . We also study the corresponding distortions of the anisotropy and polarization power spectra in connection with the launched MAP and future PLANCK missions. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0112/0112247v1.pdf"}
{"id": "astro-ph0204463", "abstract": "  An important aspect of astrophysical MHD turbulence research is developing diagnostics to connect simulations with the observable universe. Turbulent systems are by definition structurally complex in all fluid variables (density, velocity, and magnetic field), such that they must be described statistically. By developing and applying diagnostic tools to simulation data, it is possible to interpret empirical laws for the statistical properties of observed systems in terms of fundamental dynamical processes, and to identify and calibrate robust probes of physical parameters that cannot be measured directly. Using several different examples, I describe how structural diagnostic analyses have already yielded significant insights into the nature of turbulent molecular clouds. I review results from several different groups, and discuss directions for future diagnostics to enhance our understanding of cloud structure and constrain models of the evolutionary course that governs star formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0204/0204463v1.pdf"}
{"id": "astro-ph0205507", "abstract": "  We present optical spectroscopy of all 49 radio galaxies in the 7C-I and 7C-II regions of the 7C Redshift Survey (7CRS). The low-frequency (151 MHz) selected 7CRS sample contains all sources with flux-densities S_151 > 0.5 Jy in three regions of the sky; 7C-I and 7C-II were chosen to overlap with the 5C6 and 5C7 surveys respectively, and cover a total sky area of 0.013 sr. The sample has been completely identified and spectroscopy of the quasars and broad-lined radio galaxies has been presented in Willott et al. (1998). Only seven of the radio galaxies do not have redshift determinations from the spectroscopy, giving a redshift completeness for the sample of >90", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0205/0205507v1.pdf"}
{"id": "astro-ph0206070", "abstract": "  A light echo around SN 1993J was observed 8.2 years after explosion by a HST WFPC2 observation, adding to the small family of supernovae with light echoes. The light echo was formed by supernova light scattered from a dust sheet, which lies 220 parsecs away from the supernova, 50 parsecs thick along the line of sight, as inferred from radius and width of the light echo. The dust inferred from the light echo surface brightness is 1000 times denser than the intercloud dust. The graphite to silicate fraction can not be determined by our BVI photometric measurements, however, a pure graphite model can be excluded based on comparison with the data. With future observations, it will be possible to measure the expansion rate of the light echo, from which an independent distance to M81 can be obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0206/0206070v1.pdf"}
{"id": "astro-ph0207610", "abstract": "  A linear dependence of the amplitude of broadband noise variability on flux for GBHC and AGN has been recently shown by Uttley     McHardy (2001). We present the long term evolution of this rms-flux-relation for Cyg X-1 as monitored from 1998-2002 with RXTE. We confirm the linear relationship in the hard state and analyze the evolution of the correlation for the period of 1996-2002. In the intermediate and the soft state, we find considerable deviations from the otherwise linear relationship. A possible explanation for the rms-flux-relation is a superposition of local mass accretion rate variations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0207/0207610v1.pdf"}
{"id": "astro-ph0211197", "abstract": "  Pulsars provide unique probes for the large-scale interstellar magnetic field in the Galactic disk. The Parkes multibeam pulsar survey has discovered many distant pulsars which enables us for the first time to explore the magnetic field in most of the nearby half of the Galactic disk. The fields are found to be coherent in direction over a linear scale of ∼ 10 kpc between the Carina-Sagittarius and Crux-Scutum arms from l∼45 to l∼305. The coherent spiral structures and field direction reversals, including the newly determined counterclockwise field near the Norma arm, are consistent with bi-symmetric spiral model for the disk field. However, the antisymmetric rotation measure sky from the Galactic halo and the dipole field in the Galactic center suggest that the A0 dynamo is operating there. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0211/0211197v1.pdf"}
{"id": "astro-ph0212156", "abstract": "  Though widely observed to be emanating from a variety of astrophysical sources, the underlying physical mechanism behind the formation of galactic and extragalactic outflows is still enshrouded in a veil of mystery. In addition, it has not been possible to calculate accurately the amount of matter expelled in these events. In this article we present a non-self-similar analytical model, which, for the first time, we believe is able to explain the outflow formation phenomenon as well as compute the mass outflow rate by simultaneously solving the equations governing the exact transonic accretion and outflow. Our model predicts the dependence of this rate on various flow parameters as well as the exact location from where the outflows are launched. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0212/0212156v1.pdf"}
{"id": "astro-ph0301441", "abstract": "  The TexOx-1000 (TOOT) radio source redshift survey is designed to find and study typical radio-loud active galaxies to high redshift. They are typical in the same sense that L* galaxies are typical of galaxies in the optical. Previous surveys have only included the most luminous, rare objects at and beyond the peak of activity at z 2, but in going a factor of 100 fainter than the 3C survey, and in assembling a large sample, TOOT probes for the first time the objects that dominate the radio luminosity density of the universe at high redshift. Here we describe the current status of the TOOT survey and draw preliminary conclusions about the redshift distribution of the radio sources. So far,  520 of the 1000 radio sources have redshifts, with  440 of those in well-defined, complete, sub-regions of the survey. For these we find a median redshift of z=1, but the measured redshift distribution has a deficit of objects with z 2, when compared to predictions based on extrapolating luminosity functions constrained by higher-flux-density samples. These are the more luminous objects that usually show emission lines, and which should not be missed in the survey unless they are heavily reddened. The deficit may be real, but it would not be too surprising to find a population of faint, reddened radio sources at z 2-3 among the TOOT sources yet to have accurate redshifts. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0301/0301441v1.pdf"}
{"id": "astro-ph0302364", "abstract": "  We present results from high-resolution radio and optical observations of PMN J0134-0931, a gravitational lens with a unique radio morphology and an extremely red optical counterpart. Our data support the theory of Keeton     Winn (2003): five of the six observed radio components are multiple images of a single quasar, produced by a pair of lens galaxies. Multi-frequency VLBA maps show that the sixth and faintest component has a different radio spectrum than the others, confirming that it represents a second component of the background source rather than a sixth image. The lens models predict that there should be additional faint images of this second source component, and we find evidence for one of the predicted images. The previously-observed large angular sizes of two of the five bright components are not intrinsic (which would have excluded the possibility that they are lensed images), but are instead due to scatter broadening. Both the extended radio emission observed at low frequencies, and the intrinsic image shapes observed at high frequencies, can be explained by the lens models. The pair of lens galaxies is marginally detected in HST images. The differential extinction of the quasar images suggests that the extreme red color of the quasar is at least partly due to dust in the lens galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0302/0302364v1.pdf"}
{"id": "astro-ph0303368", "abstract": "  A stroboscope designed to observe pulsars in the optical spectrum is presented. The absolute phase of the stroboscope is synchronized to better than 2.5 microseconds with the known radio ephemerides for a given pulsar. The absolute timing is provided by the GPS clock. With such a device phase resolved photometry of pulsars can be performed. We demonstrate the instrument's capabilities with the results of a set of observations of the Crab pulsar, the brightest of the known optical pulsars, with a visual magnitude of 16.5, and a rotational frequency of  29Hz. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0303/0303368v1.pdf"}
{"id": "astro-ph0304102", "abstract": "  The cosmic-ray proton, helium, and muon spectra at small atmospheric depths of 4.5 – 28 g/cm^2 were precisely measured during the slow descending period of the BESS-2001 balloon flight. The variation of atmospheric secondary particle fluxes as a function of atmospheric depth provides fundamental information to study hadronic interactions of the primary cosmic rays with the atmosphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0304/0304102v2.pdf"}
{"id": "astro-ph0306169", "abstract": "  This work studies the optical emission line properties of a sample of 155 low-redshift bright X-ray selected ROSAT Seyfert 1 type AGN for which adequate signal-to-noise ratio spectroscopic observations are available. We measured emission line properties by performing multi-component fits to the emission line profiles, covering the effect of blended iron emission. We also obtained continuum parameters, including 250eV X-ray luminosities derived from the ROSAT database. In addition, the measured properties are gathered for a correlation analysis, which confirms the well-known relations between the strengths of Fe II, [O III] emission and the X-ray slope. We also detect striking correlations between Hβ redshift (or blueshift), flux ratios of Fe `II to Hβ broad component and [O III] to Hβ narrow component. These trends are most likely driven by the Eddington ratio. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0306/0306169v1.pdf"}
{"id": "astro-ph0308058", "abstract": "  The Ultraviolet Coronagraph Spectrometer (UVCS) aboard the SOHO satellite has observed very fast Coronal Mass Ejections (CMEs) associated with X-class flares. These events show spectral signatures different than those seen in most other CMEs in terms of very rapid disruption of the pre-CME streamer, very high Doppler shifts and high temperature plasma visible in the [Fe XVIII] emission line. This paper describes three very similar events on 21 April, 23 July and 24 August 2002 associated with X-class flares. We determine the physical parameters of the pre-CME streamers and discuss the geometrical and physical nature of the streamer blowouts. In the 21 April event, the hot plasma seen as [Fe XVIII] is not related to the structure seen in [Fe XXI] by SUMER at lower heights. It has the form of a rapidly expanding fan, quite likely a current sheet. In the August event, on the other hand, the [Fe XVIII] is probably a bubble of hot plasma formed by reconnection in the wake of the CME. C III emission from the July 23 flare is detected as stray light in the UVCS aperture. It precedes the hard X-ray brightening by about 2 minutes. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0308/0308058v1.pdf"}
{"id": "astro-ph0310565", "abstract": "  We utilize a complete sample of RR Lyrae stars discovered by the QUEST survey using light curves to design selection criteria based on SDSS colors. Thanks to the sensitivity of the u-g color to surface gravity and of g-r color to effective temperature, and to the small photometric errors ( 0.02 mag) delivered by SDSS, RR Lyrae stars can be efficiently and robustly recognized even with single-epoch data. In a 100", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0310/0310565v1.pdf"}
{"id": "astro-ph0311117", "abstract": "  Low Surface Brightness (LSB) galaxies are dominated by dark matter. High-resolution rotation curves suggest that their total mass-density distributions are dominated by constant density cores rather than the steep and cuspy distributions found in Cold Dark Matter (CDM) simulations. The data are best described by a model with a soft core with an inner power-law mass-density slope alpha = 0.2 +/- 0.2. However no single universal halo profile provides an adequate description of the data. The observed mass profiles appear to be inconsistent with LambdaCDM. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0311/0311117v1.pdf"}
{"id": "astro-ph0311339", "abstract": "  This is the first paper about the fragmentation and mass outflow in the molecular cloud by using three-dimensional MHD nested-grid simulations. The binary star formation process is studied paying particular attention to the fragmentation of a rotating magnetized molecular cloud. We assume an isothermal rotating and magnetized cylindrical cloud in hydrostatic balance. Non-axisymmetric as well as axisymmetric perturbations are added to the initial state and the subsequent evolutions are studied. The evolution is characterized by three parameters: the amplitude of the non-axisymmetric perturbations, the rotation speed, and the magnetic field strength. As a result, it is found that non-axisymmetry hardly evolves in the early phase, but begins to grow after the gas contracts and forms a thin disk. Disk formation is strongly promoted by the rotation speed and the magnetic field strength. There are two types of fragmentation: fragmentation from a ring and that from a bar. Thin adiabatic cores fragment if a thickness is smaller than 1/4 of the radius. For the fragments to survive, they should be formed in a heavily elongated barred core or a flat round disk. In the models showing fragmentation, outflows from respective fragments are found as well as those driven by the rotating bar or the disk. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0311/0311339v2.pdf"}
{"id": "astro-ph0312552", "abstract": "  We plan to take advantage of the unprecedented combination of low thermal background and high resolution provided by the 6.5m MMT's adaptive secondary mirror, to target the 3-5 micron atmospheric window where giant planets are expected to be anomalously bright. We are in the process of building a 3-5 micron coronograph that is predicted to be sensitive to planets as close as 0.4 arcsec to the parent star. We expect to be able to detect giant planets down to 5 times Jupiter's mass for a 1 Gyr old system at 10 pc. We plan to carry out a survey which is complementary to the radial velocity detections of planets and constructed to characterize the prevalence and distribution of giant planets around nearby, Sun-like stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0312/0312552v1.pdf"}
{"id": "astro-ph0402373", "abstract": "  We present global 2D and 3D simulations of self-gravitating magnetized tori. We used the 2D calculations to demonstrate that the properties of the MRI are not affected by the presence of self-gravity: MHD turbulence and enhanced angular momentum transport follow the linear growth of the instability. In 3D, we have studied the interaction between an m=2 gravitational instability and MHD turbulence. We found its strength to be significantly decreased by the presence of the latter, showing that both instabilities strongly interact in their non-linear phases. We discuss the consequences of these results. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0402/0402373v1.pdf"}
{"id": "astro-ph0402430", "abstract": "  In this paper we report the results of the first ever time-dependent general relativistic magnetohydrodynamic simulations of the magnetically dominated monopole magnetospheres of black holes. It is found that the numerical solution evolves towards a stable steady-state solution which is very close to the corresponding force-free solution found by Blandford and Znajek. Contrary to the recent claims, the particle inertia does not become dynamically important near the event horizon and the force-free approximation provides a proper framework for magnetically dominated magnetospheres of black holes. For the first time, our numerical simulations show the development of an ultra-relativistic particle wind from a rotating black hole. However, the flow remains Poynting dominated all the way up to the fast critical point. This suggests that the details of the so-called “astrophysical load”, where the electromagnetic energy is transferred to particles, may have no effect on the efficiency of the Blandford-Znajek mechanism. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0402/0402430v2.pdf"}
{"id": "astro-ph0403407", "abstract": "  We show how the viscous evolution of Keplerian accretion discs can be understood in terms of simple kinetic theory. Although standard physics texts give a simple derivation of momentum transfer in a linear shear flow using kinetic theory, many authors, as detailed by Hayashi     Matsuda 2001, have had difficulties applying the same considerations to a circular shear flow. We show here how this may be done, and note that the essential ingredients are to take proper account of, first, isotropy locally in the frame of the fluid and, second, the geometry of the mean flow. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0403/0403407v1.pdf"}
{"id": "astro-ph0406073", "abstract": "  We present a numerical method for studying the normal modes of accretion flows around black holes. In this first paper, we focus on two-dimensional, viscous, hydrodynamic disks, for which the linear modes have been calculated analytically in previous investigations. We use pseudo-spectral methods and low storage Runge-Kutta methods to solve the continuity equation, the Navier-Stokes equation, and the energy equation. We devise a number of test problems to verify the implementation. These tests demonstrate the ability of spectral methods to handle accurately advection problems and to reproduce correctly the stability criteria for differentially rotating hydrodynamic flows. They also show that our implementation is able to handle sound wave correctly with non-reflective boundary conditions, to recover the standard solution for a viscous spreading ring, and produce correctly the Shakura-Sunyaev steady disk solution. Finally, we have applied our algorithm to the problem of a non-axisymmetric viscous spreading ring and verify that such configuration is unstable to non-antisymmetric perturbations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0406/0406073v2.pdf"}
{"id": "astro-ph0407104", "abstract": "  We analyze the possible existence of a pulsational instability excited by the ϵ-mechanism during the last few centuries of evolution of a Chandrasekhar mass white dwarf prior to its explosion as a Type Ia supernova. Our analysis is motivated by the temperature sensitivity of the nuclear energy generation rate (∼ T^23) in a white dwarf whose structural adiabatic index is near 4/3. Based upon a linear stability analysis, we find that the fundamental mode and higher order radial modes are indeed unstable and that the fundamental mode has the shortest growth time scale. However, the growth time scale for such instability never becomes shorter than the evolutionary timescale. Therefore, even though the star is pulsationally unstable, we do not expect these radial modes to have time to grow and to affect the structure and explosion properties of Type Ia supernovae. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0407/0407104v1.pdf"}
{"id": "astro-ph0407193", "abstract": "  Deep color magnitude diagrams extending to the main sequence provide the most direct measure of the detailed star formation history in a stellar population. With large investments of observing time, HST can obtain such data for populations out to 1 Mpc, but its field of view is extremely small in comparison to the size of Local Group galaxies. This limitation severely constrains our understanding of galaxy formation. For example, the largest galaxy in the Local Group, Andromeda, offers an ideal laboratory for studying the formation of large spiral galaxies, but the galaxy shows substructure on a variety of scales, presumably due to its violent merger history. Within its remaining lifetime, HST can only sample a few sight-lines through this complex galaxy. In contrast, a wide field imager could provide a map of Andromeda's halo, outer disk, and tidal streams, revealing the spatially-dependent star formation history in each structure. The same data would enable many secondary studies, such as the age variation in Andromeda's globular cluster system, gigantic samples of variable stars, and microlensing tracers of the galaxy's dark matter distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0407/0407193v1.pdf"}
{"id": "astro-ph0408002", "abstract": "  We report late-time observations of the radio afterglow of GRB 030329. The light curves show a clear achromatic flattening at 50 days after the explosion. We interpret this flattening as resulting from the blast wave becoming trans-relativistic. Modeling of this transition enables us to make estimates of the energy content of the burst, regardless of the initial jet structure or the distribution of initial Lorentz factors of the ejecta. We find, in accordance with other events, that GRB 030329 is well-described by an explosion with total energy of a few times 10^51 erg expanding into a circumburst medium with a density of order unity. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0408/0408002v1.pdf"}
{"id": "astro-ph0408225", "abstract": "  Recent findings indicate that the Monogem Ring supernova remnant and the associated pulsar PSR B0656+14 may be the 'Single Source' responsible for the formation of the sharp knee in the cosmic ray energy spectrum at ∼3PeV. We estimate the contribution of the pulsar B0656+14 to the cosmic rays in the PeV region and conclude that the pulsar cannot contribute more than 15", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0408/0408225v1.pdf"}
{"id": "astro-ph0409606", "abstract": "  In this second paper in our series, we continue to test primordial scenarios of globular cluster formation which predict that globular clusters formed in the early universe in the potential of dark matter minihalos. In this paper we use high-resolution N-body simulations to model tidal stripping experienced by primordial dark-matter dominated globular clusters in the static gravitational potential of the host dwarf galaxy. We test both cuspy Navarro-Frenk-White (NFW) and flat-core Burkert models of dark matter halos. Our primordial globular cluster with an NFW dark matter halo survives severe tidal stripping, and after 10 orbits is still dominated by dark matter in its outskirts. Our cluster with Burkert dark matter halo loses almost all its dark matter to tidal stripping, and starts losing stars at the end of our simulations. The results of this paper reinforce our conclusion in Paper I that current observations of globular clusters are consistent with the primordial picture of globular cluster formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0409/0409606v1.pdf"}
{"id": "astro-ph0409708", "abstract": "  Using high-resolution N-body/SPH simulations with 2× 10^6 particles, we investigate the evolution of stellar and gaseous galactic cores during the hierarchical formation of a spiral galaxy. We find that the galactic core (r < 300 pc) coevolves with the host galaxy. The average mass ratio between the baryonic core and the halo is nearly constant, ∼ 0.04 from z ∼ 10 to z ∼ 2. However, there are several `rapid-growing phases' during the evolution, in which the rate of mass accretion to the central sub-kpc region is ten times higher (∼ 1 M_⊙ yr pc^-1) than the average accretion rate. The rapid growth of the inner core is associated with the major merger events with a time-delay. We also find that the spin-axis of the gas core frequently changes. As a result, the angular momentum vector of the central part of the galaxy is independent of the rotation of the outer part. Our results suggest that if a constant fraction of the baryonic mass in the central several 100 pc of a galaxy is converted into a massive black hole, the black hole mass should correlate with the total mass of the galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0409/0409708v1.pdf"}
{"id": "astro-ph0501255", "abstract": "  RX J0806.3+1527 is suspected to be a double-degenerate white dwarf binary. We present first results of our NLTE analysis of its optical spectrum. The VLT/FORS1 data show a composite spectrum consisting of a blue continuum and superimposed emission lines of the HeII Pickering series and, possibly, the H Balmer series. Our models are based on hot white dwarf atmospheres and include illumination effects onto the secondary star. The physical parameters and chemical abundances derived from the comparison of the observed spectrum with a grid of model atmospheres provide constraints on the true nature of this enigmatic binary and on the models proposed so far. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0501/0501255v1.pdf"}
{"id": "astro-ph0502293", "abstract": "  We have used long-baseline near-IR interferometry to resolve the peculiar eruptive variable V838 Mon and to provide the first direct measurement of its angular size. Assuming a uniform disk model for the emission we derive an apparent angular diameter at the time of observations (November-December 2004) of 1.83 ± 0.06 milli-arcseconds. For a nominal distance of 8±2 kpc, this implies a linear radius of 1570 ± 400 R_⊙. However, the data are somewhat better fit by elliptical disk or binary component models, and we suggest that the emission may be strongly affected by ejecta from the outburst. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0502/0502293v2.pdf"}
{"id": "astro-ph0502356", "abstract": "  The Painleve test is very useful to construct not only the Laurent series solutions of systems of nonlinear ordinary differential equations but also the elliptic and trigonometric ones. The standard methods for constructing the elliptic solutions consist of two independent steps: transformation of a nonlinear polynomial differential equation into a nonlinear algebraic system and a search for solutions of the obtained system. It has been demonstrated by the example of the generalized Henon-Heiles system that the use of the Laurent series solutions of the initial differential equation assists to solve the obtained algebraic system. This procedure has been automatized and generalized on some type of multivalued solutions. To find solutions of the initial differential equation in the form of the Laurent or Puiseux series we use the Painleve test. This test can also assist to solve the inverse problem: to find the form of a polynomial potential, which corresponds to the required type of solutions. We consider the five-dimensional gravitational model with a scalar field to demonstrate this. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0502/0502356v3.pdf"}
{"id": "astro-ph0502505", "abstract": "  We present the first optical observations of a Gamma Ray Burst (GRB) afterglow using the 2-m robotic Liverpool Telescope (LT), which is owned and operated by Liverpool John Moores University and situated on La Palma. We briefly discuss the capabilities of LT and its suitability for rapid follow-up observations of early optical and infrared GRB light curves. In particular, the combination of aperture, site, instrumentation and rapid response (robotic over-ride mode aided by telescope's rapid slew and fully-opening enclosure) makes the LT ideal for investigating the nature of short bursts, optically-dark bursts, and GRB blast-wave physics in general. We briefly describe the LT's key position in the RoboNet-1.0 network of robotic telescopes. We present the LT observations of GRB041006 and use its gamma-ray properties to predict the time of the break in optical light curve, a prediction consistent with the observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0502/0502505v2.pdf"}
{"id": "astro-ph0503073", "abstract": "  We present preliminary results of a simultaneous X-ray/optical campaign of the prototypical LMXB Sco X-1 at 1-10 Hz time resolution. Lightcurves of the high excitation Bowen/HeII emission lines were obtained through narrow interference filters with ULTRACAM, and these were cross-correlated with X-ray lightcurves. We find evidence for correlated variability, in particular when Sco X-1 enters the Flaring Branch. The Bowen/HeII lightcurves lag the X-ray lightcurves with a light travel time which is consistent with reprocessing in the companion star. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0503/0503073v1.pdf"}
{"id": "astro-ph0504294", "abstract": "  One of the fundamental and yet untested predictions of inflationary models is the generation of a very weak cosmic background of gravitational radiation. We investigate the sensitivity required for a space-based gravitational wave laser interferometer with peak sensitivity at ∼ 1 Hz to observe such signal as a function of the model parameters and compare it with indirect limits that can be set with data from present and future cosmic microwave background missions. We concentrate on signals predicted by slow-roll single field inflationary models and instrumental configurations such as those proposed for the LISA follow-on mission: Big Bang Observer. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0504/0504294v2.pdf"}
{"id": "astro-ph0505025", "abstract": "  We present a homogeneous compilation of HI spectral parameters extracted from global 21 cm line spectra for some 9000 galaxies in the local universe (heliocentric velocity -200 < V_Sun < 28,000 km/s) obtained with a variety of large single dish radio telescopes but reanalyzed using a single set of parameter extraction algorithms. Corrections to the observed HI line flux for source extent and pointing offsets and to the HI line widths for instrumental broadening and smoothing are applied according to model estimates to produce a homogenous catalog of derived properties with quantitative error estimates. Where the redshift is available from optical studies, we also provide flux measurements for an additional 156 galaxies classified as marginal HI detections and rms noise limits for 494 galaxies classified as nondetections. Given the diverse nature of the observing programs contributing to it, the characteristics of the combined dataset are heterogeneous, and as such, the compilation is neither integrated HI line flux nor peak flux limited. However, because of the large statistical base and homogenous reprocessing, the spectra and spectral parameters of galaxies in this optically targeted sample can be used to complement data obtained at other wavelengths to characterize the properties of galaxies in the local universe and to explore the large scale structures in which they reside. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0505/0505025v1.pdf"}
{"id": "astro-ph0506601", "abstract": "  The detailed observations of the diffuse ionized gas through the emission lines Hα, [NII], and [SII] in the Perseus Arm of our Galaxy by the Wisconsin Hα Mapper (WHAM)–survey challenge photoionization models. They have to explain the observed rise in the line ratios [NII]/Hα and [SII]/Hα. The models described here consider for the first time the detailed observational geometry toward the Perseus Arm. The models address the vertical variation of the line ratios up to height of 2 kpc above the midplane. The rising trends of the line ratios are matched. The increase in the line ratios is reflected in a rise of the temperature of the gas layer. This is due to the progressive hardening of the radiation going through the gas. However an extra heating above photoionization is needed to explain the absolute values. Two different extra heating rates are investigated which are proportional to n^0 and n^1. The models show that a combination of both are best to explain the data, where the extra heating independent of density is dominant for z > 0.8 kpc. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0506/0506601v1.pdf"}
{"id": "astro-ph0508055", "abstract": "  In this third paper in a series presenting observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS) of the Io plasma torus, we show remarkable, though subtle, spatio-temporal variations in torus properties. The Io torus is found to exhibit significant, near-sinusoidal variations in ion composition as a function of azimuthal position. The azimuthal variation in composition is such that the mixing ratio of S II is strongly correlated with the mixing ratio of S III and the equatorial electron density and strongly anti-correlated with the mixing ratios of both S IV and O II and the equatorial electron temperature. Surprisingly, the azimuthal variation in ion composition is observed to have a period of 10.07 hours–1.5", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0508/0508055v1.pdf"}
{"id": "astro-ph0509838", "abstract": "  The steady-state structure of self-gravitating, magnetized accretion disks is studied using a set of self-similar solutions which are appropriate in the outer regions. The disk is assumed to be isothermal and the magnetic field outside of the disk is treated in a phenomenological way. However, the internal field is determined self-consistently. The behaviour of the solutions are investigated by changing the input parameters of the model, i.e. mass accretion rate, coefficients of viscosity and resistivity, and the magnetic field configuration. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0509/0509838v1.pdf"}
{"id": "astro-ph0509846", "abstract": "  Special features of surface gravity waves in deep fluid flow with constant vertical shear of velocity is studied. It is found that the mean flow velocity shear leads to non-trivial modification of surface gravity wave modes dispersive characteristics. Moreover, the shear induces generation of surface gravity waves by internal vortex mode perturbations. The performed analytical and numerical study provides, that surface gravity waves are effectively generated by the internal perturbations at high shear rates. The generation is different for the waves propagating in the different directions. Generation of surface gravity waves propagating along the main flow considerably exceeds the generation of surface gravity waves in the opposite direction for relatively small shear rates, whereas the later wave is generated more effectively for the high shear rates. From the mathematical point of view the wave generation is caused by non self-adjointness of the linear operators that describe the shear flow. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0509/0509846v1.pdf"}
{"id": "astro-ph0511047", "abstract": "  We introduce a new technique for constructing three-dimensional (3D) models of incompressible Riemann S-type ellipsoids and compressible triaxial configurations that share the same velocity field as that of   Riemann S-type ellipsoids. Our incompressible models are exact steady-state configurations; our compressible models represent approximate steady-state equilibrium configurations. Models built from this method can be used to study a variety of relevant astrophysical and geophysical problems. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0511/0511047v1.pdf"}
{"id": "astro-ph0511561", "abstract": "  The paper presents an integrated view of the population structure and its role in establishing the ionisation state of light elements in dynamic, finite density, laboratory and astrophysical plasmas. There are four main issues, the generalised collisional-radiative picture for metastables in dynamic plasmas with Maxwellian free electrons and its particularising to light elements, the methods of bundling and projection for manipulating the population equations, the systematic production/use of state selective fundamental collision data in the metastable resolved picture to all levels for collisonal-radiative modelling and the delivery of appropriate derived coefficients for experiment analysis. The ions of carbon, oxygen and neon are used in illustration. The practical implementation of the methods described here is part of the ADAS Project. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0511/0511561v1.pdf"}
{"id": "astro-ph0601464", "abstract": "  The 2-10 keV continuum of AGN is generally well represented by a single power law. However, at smaller energies the continuum displays an excess with respect to the extrapolation of this power law, called the ”soft X-ray excess”. Until now this soft X-ray excess was attributed, either to reflection of the hard X-ray source by the accretion disk, or to the presence of an additional comptonizing medium, giving a steep spectrum. An alternative solution proposed by Gierlinski and Done (2004) is that a single power law well represents both the soft and the hard X-ray emission and the impression of the soft X-ray excess is due to absorption of a primary power law by a relativistic wind. We examine the advantages and drawbacks of reflection versus absorption models, and we conclude that the observed spectra can be well modeled, either by absorption (for a strong excess), or by reflection (for a weak excess). However the physical conditions required by the absorption models do not seem very realistic: we would prefer an ”hybrid model”. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0601/0601464v1.pdf"}
{"id": "astro-ph0601667", "abstract": "  We qualitatively study the effects of gravitational microlensing on our view of unresolved extragalactic star formation regions. Using a general gravitational microlensing configuration, we perform a number of simulations that reveal that specific imprints of the star forming region are imprinted, both photometrically and spectroscopically, upon observations. Such observations have the potential to reveal the nature and size of these star forming regions, through the degree of variability observed in a monitoring campaign, and hence resolve the star formation regions in distant galaxies which are too small to be probed via more standard techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0601/0601667v1.pdf"}
{"id": "astro-ph0602218", "abstract": "  We report the discovery of a rich population of low mass stars in the young, massive star forming region N66/NGC346 in the Small Magellanic Cloud, from deep V, I and H alpha images taken with the HST/ACS. These stars have likely formed together with the NGC346 cluster,  3-5 Myr ago. Their magnitude and colors are those of pre-main sequence stars in the mass range 0.6-3 Mo, mostly concentrated in the main cluster, but with secondary subclusters spread over a region across  45 pc. These subclusters appear to be spatially coincident with previously known knots of molecular gas identified in ground based and ISO observations. We show that N66/NGC346 is a complex region, being shaped by its massive stars, and the observations presented here represent a key step towards the understanding of how star formation occurred and has progressed in this low metallicity environment. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0602/0602218v1.pdf"}
{"id": "astro-ph0603804", "abstract": "  We continue our programme of extended single-site observations of pulsting subdwarf B (sdB) stars and present the results of extensive time series photometry to resolve the pulsation spectra for use in asteroseismological analyses. PG 0154+182, HS 1824+5745, and HS 2151+0857 were observed at the MDM Observatory during 2004 and 2005. Our observations are sufficient to resolve the pulsations of all three target stars. We extend the number of known frequencies for PG 0154+182 from one to six, confirm that HS 1824+5745 is a mono-periodic pulsator, and extend the number of known frequencies to five for HS 2151+0857. We perform standard tests to search for multiplet structure, measure amplitude variations as pertains to stochastic excitation, and examine the mode density to constrain the mode degree l. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0603/0603804v1.pdf"}
{"id": "astro-ph0608701", "abstract": "  We reinvestigate the generation and accumulation of magnetic flux in optically thin accretion flows around active gravitating objects. The source of the magnetic field is the azimuthal electric current associated with the Poynting-Robertson drag on the electrons of the accreting plasma. This current generates magnetic field loops which open up because of the differential rotation of the flow. We show through simple numerical simulations that what regulates the generation and accumulation of magnetic flux near the center is the value of the plasma conductivity. Although the conductivity is usually considered to be effectively infinite for the fully ionized plasmas expected near the inner edge of accretion disks, the turbulence of those plasmas may actually render them much less conducting due to the presence of anomalous resistivity. We have discovered that if the resistivity is sufficiently high throughout the turbulent disk while it is suppressed interior to its inner edge, an interesting steady-state process is established: accretion carries and accumulates magnetic flux of one polarity inside the inner edge of the disk, whereas magnetic diffusion releases magnetic flux of the opposite polarity to large distances. In this scenario, magnetic flux of one polarity grows and accumulates at a steady rate in the region inside the inner edge and up to the point of equipartition when it becomes dynamically important. We argue that this inward growth and outward expulsion of oppositely-directed magnetic fields that we propose may account for the  30 min cyclic variability observed in the galactic microquasar GRS1915+105. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0608/0608701v1.pdf"}
{"id": "astro-ph0610443", "abstract": "  We derive the theoretical red edge of the pulsating GW Vir stars by using full evolutionary calculations that involve mass loss and diffusion. We put the emphasis on the fact that the specific mass loss law used in the evolutionary computations determines the red edge's position. By combining this specific property with the observed location of the red edge in the effective temperature-surface gravity domain, we obtain interesting constraints on possible mass loss laws for PG 1159 stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610443v1.pdf"}
{"id": "astro-ph0610498", "abstract": "  We investigate the effect of dark energy on the limits on the shear anisotropy in spatially homogeneous Bianchi cosmological models obtained from measurements of the temperature anisotropies in the cosmic microwave background. We shall primarily assume that the dark energy is modelled by a cosmological constant. In general, we find that there are tighter bounds on the shear than in models with no cosmological constant, although the limits are (Bianchi) model dependent. In addition, there are special spatially homogeneous cosmological models whose rate of expansion is highly anisotropic, but whose cosmic microwave background temperature is measured to be exactly isotropic at one instant of time. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610498v2.pdf"}
{"id": "astro-ph0610899", "abstract": "  We use a new approach to obtain limits on the absorbing columns towards an initial sample of 10 long Gamma-Ray Bursts observed with BeppoSAX and selected on the basis of their good optical and nIR coverage, from simultaneous fits to nIR, optical and X-ray afterglow data, in count space and including the effects of metallicity. In no cases is a MW-like extinction preferred, when testing MW, LMC and SMC extinction laws. The 2175A bump would in principle be detectable in all these afterglows, but is not present in the data. An SMC-like gas-to-dust ratio or lower value can be ruled out for 4 of the hosts analysed here (assuming SMC metallicity and extinction law) whilst the remainder of the sample have too large an error to discriminate. We provide a more accurate estimate of the line-of-sight extinction and improve upon the uncertainties for the majority of the extinction measurements made in previous studies of this sample. We discuss this method to determine extinction values in comparison with the most commonly employed existing methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610899v2.pdf"}
{"id": "astro-ph0701624", "abstract": "  In a recent paper, Liddle and Urena-Lopez suggested that to have a unified model of inflation and dark matter is imperative to have a proper reheating process where part of the inflaton field remains. In this paper I propose a model where this is possible. I found that, incorporating the effect of plasma masses generated by the inflaton products, enable us to stop the process. A numerical estimated model is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0701/0701624v2.pdf"}
{"id": "astro-ph0702749", "abstract": "  The timing and duration of exoplanet transits has a dependency on observer position due to parallax. In the case of an Earth-bound observer with a 2 AU baseline the dependency is typically small and slightly beyond the limits of current timing precision capabilities. However, it can become an important systematic effect in high-precision repeated transit measurements for long period systems due to its relationship to secular perspective acceleration phenomena. In this short paper we evaluate the magnitude and characteristics of transit parallax in the case of exoplanets using simplified geometric examples. We also discuss further implications of the effect, including its possible exploitation to provide immediate confirmation of planetary transits and/or unique constraints on orbital parameters and orientations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0702/0702749v1.pdf"}
{"id": "astro-ph0703732", "abstract": "  Vortices have been postulated at a range of size scales in the universe including at the stellar size-scale. Whilst hydrodynamically simulating the wind from an asymptotic giant branch (AGB) star moving through and sweeping up its surrounding interstellar medium (ISM), we have found vortices on the size scale of 10^-1 pc to 10^1 pc in the wake of the star. These vortices appear to be the result of instabilities at the head of the bow shock formed upstream of the AGB star. The instabilities peel off downstream and form vortices in the tail of AGB material behind the bow shock, mixing with the surrounding ISM. We suggest such structures are visible in the planetary nebula Sh 2-188. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0703/0703732v1.pdf"}
{"id": "astro-ph9509141", "abstract": "  The Solar system beyond Neptune is believed to house a population of small primordial bodies left over from the planet formation process. The region up to heliocentric distance ∼ 50 AU (a.k.a. the Kuiper Belt) may be the source of the observed short period comets. In this region, the phase space structure near orbital resonances with Neptune is of special interest for the long term stability of orbits. There is reason to believe that a significant fraction (perhaps most) of the Kuiper Belt objects reside preferentially in these resonance locations. This paper describes the dynamics of small objects near the major orbital resonances with Neptune. Estimates of the widths of stable resonance zones as well as the properties of resonant orbits are obtained from the circular, planar restricted three-body model. Although this model does not contain the full complexity of the long term orbital dynamics of Kuiper Belt objects subject to the full N-body perturbations of all the planets, it does provide a baseline for the phase space structure and properties of resonant orbits in the trans-Neptunian Solar system. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9509/9509141v1.pdf"}
{"id": "astro-ph9601158", "abstract": "  We present a re-analysis of the cosmic confusion hypothesis, elucidating the degree to which “confusion” can be expected to hold in a class of flat, adiabatic models. This allows us to devise a simple and accurate fitting function for the height of the first peak in the radiation power spectrum in a wide range of inflationary inspired models. The range preferred by current data is given, together with a discussion of the impact of measurements of the peak height on constraining models of structure formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9601/9601158v1.pdf"}
{"id": "astro-ph9605011", "abstract": "  We show that the Keplerian thin disk in quiescent Soft X-ray Transients cannot extend down to the last stable orbit around the central black hole. We analyse the properties of the Narayan, McClintock     Yi (1996) model of quiescent Soft X-ray Transients in which the cold Keplerian disk has its inner edge at a large transition radius and transforms to a hot, advection-dominated flow on the inside. We show that outbursts of transient sources could be triggered in this model either by a pure thermal accretion disk instability or by a disk instability generated by an enhanced mass transfer from the stellar companion. Both mechanisms operate in the outer thin disk and could be at work, either in different systems or in the same system at different epochs, depending on the mass transfer rate and the value of the viscosity parameter α_t of the thin disk. We show that the recurrence time between outbursts in SXTs can be explained with values of α_t similar to these required by the dwarf nova disk instability model instead of the unreasonably low values needed in the model in which the thin disks extends down to the last stable orbit. We extend the Narayan, McClintock     Yi (1996) model to the case when the outer disk is non-stationary. We show that such disk is too cold to account for the observed UV flux. This difficulty is common to all models in which the outer disk is assumed to be optically thick. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9605/9605011v1.pdf"}
{"id": "astro-ph9610258", "abstract": "  With the advent of RXTE, which is capable of broad spectral coverage and fast timing, as well as other instruments which are increasingly being used in multi-wavelength campaigns (via both space-based and ground-based observations), we must demand more of our theoretical models. No current model mimics all facets of a system as complex as an x-ray binary. However, a modern theory should qualitatively reproduce – or at the very least not fundamentally disagree with - all of Cygnus X-1's most basic average properties: energy spectrum (viewed within a broader framework of black hole candidate spectral behavior), power spectrum (PSD), and time delays and coherence between variability in different energy bands. Below we discuss each of these basic properties in turn, and we assess the health of one of the currently popular theories: Comptonization of photons from a cold disk. We find that the data pose substantial challenges for this theory, as well as all other currently discussed models. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9610/9610258v1.pdf"}
{"id": "astro-ph9611061", "abstract": "  The spectral shape of IR emission from Herbig Ae/Be stars has been invoked as evidence for accretion disks around high-mass protostars. Instead, we present here models based on spherical envelopes with r^-1.5 dust density profile that successfully explain the observed spectral shapes. The spectral energy distributions (SEDs) of eight primary candidates for protostellar disks are fitted in detail for all wavelengths available, from visual to far IR. The only envelope property adjusted in individual sources is the overall visual optical depth, and it ranges from 0.3 to 3. In each case, our models properly reproduce the data for both IR excess, visual extinction and reddening. The success of our models shows that accretion disks cannot make a significant contribution to the radiation observed in these pre-main sequence stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9611/9611061v1.pdf"}
{"id": "astro-ph9703200", "abstract": "  Radio observations of SN 1986E have shown a clear detection of emission at 6 cm wavelength about 8 months after optical discovery. Combined with a number of new upper limits and a study of the possible models, it appears that SN 1986E was probably a fairly normal Type IIL supernova, somewhat similar to SN 1980K, with radio emission at roughly expected levels. This detection continues the correlation between radio detection and late time optical emission. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9703/9703200v1.pdf"}
{"id": "astro-ph9705044", "abstract": "  We investigate advection dominated, transsonic accretion flows in the vicinity of a Kerr black hole. We take into account all relativistic effects in the dynamics of the flow and in the propagation of light. We assume the matter to be weakly magnetized and cool via the thermal synchrotron and Bremsstrahlung radiation. We include also the effects of Comptonization. We calculate the spectra of radiation as seen by observers located at different positions relative to the equatorial plane of the disk. The radiation emitted by the accreting matter is anisotropic and observers near the equatorial plane register a higher energy flux. This effect is more pronounced in the case of slowly rotating black holes. We calculate also the shape of a hypothetical gamma line, which may be produced by the thermonuclear reactions in the inner part of the flow. The line is strongly broadened, but the fact that the flow is quasi-spherical removes the two-peak shape of the line seen in the spectra emitted from thin, Keplerian disks. The kinematics of the advection dominated flows is not unique (as opposed to Keplerian disks or spherical free-fall) and it would probably be difficult to find strong limits on source models using the spectral observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9705/9705044v1.pdf"}
{"id": "astro-ph9709059", "abstract": "  Gravitational lensing is now widely and successfully used to study a range of astronomical phenomena, from individual objects, like galaxies and clusters, to the mass distribution on various scales, to the overall geometry of the Universe. Here we describe and assess the use of gravitational lensing as “gold standards” in addressing one of the fundamental problems in astronomy, the determination of the absolute distance scale to extragalactic objects. This is commonly parameterized by the Hubble constant, H_0, the current expansion rate of the Universe. The elegance of the underlying geometrical principle of the gravitational lensing method combined with the recent advances in observations and modelling makes it a very promising technique for measuring H_0. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9709/9709059v1.pdf"}
{"id": "astro-ph9710039", "abstract": "  We use fully self-consistent N-body simulations of barred galaxies to show that dynamical friction from a dense dark matter halo dramatically slows the rotation rate of bars. Our result supports previous theoretical predictions for a bar rotating within a massive halo. On the other hand, low density halos, such as those required for maximum disks, allow the bar to continue to rotate at a high rate. There is somewhat meager observational evidence indicating that bars in real galaxies do rotate rapidly and we use our result to argue that dark matter halos must have a low central density in all high surface brightness disk galaxies, including the Milky Way. Bars in galaxies that have larger fractions of dark matter should rotate slowly, and we suggest that a promising place to look for such candidate objects is among galaxies of intermediate surface brightness. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9710/9710039v2.pdf"}
{"id": "astro-ph9710065", "abstract": "  Beryllium and oxygen abundances have been derived in a sample of F-type field stars for which lithium abundances had been measured previously, with the aim of obtaining observational constraints to discriminate between the different mixing mechanisms proposed. Mixing associated with the transport of angular momentum in the stellar interior and internal gravity waves within the framework of rotating evolutionary models, appear to be promising ways to explain the observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9710/9710065v1.pdf"}
{"id": "astro-ph9802325", "abstract": "  Spiral density wave theories demand that grand design spiral structure be bounded, at most, between the inner and outer Lindblad resonances of the spiral pattern. The corotation resonance lies between the outer and inner Lindblad resonances. The locations of the resonances are at radii whose ratios to each other are rather independent of the shape of the rotation curve. The measured ratio of outer to inner extent of spiral structure for a given spiral galaxy can be compared to the standard ratio of corotation to inner Lindblad resonance radius. In the case that the measured ratio far exceeds the standard ratio, it is likely that the corotation resonance is within the bright optical disk. Studying such galaxies can teach us how the action of resonances sculpts the appearance of spiral disks. This paper reports observations of 140 disk galaxies, leading to resonance ratio tests for 109 qualified spirals. It lists candidates that have a good chance of having the corotation resonance radius within the bright optical disk. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9802/9802325v1.pdf"}
{"id": "astro-ph9806076", "abstract": "  We present an optical imaging study of 20 southern-sky nova remnants which has resulted in the discovery of four previously unknown nova shells – V842 Cen, RR Cha, DY Pup and HS Pup. The study has also revealed previously unobserved features in three other known shells – those of BT Mon, CP Pup and RR Pic. The images of BT Mon, V842 Cen, RR Cha, DY Pup and HS Pup have been processed using several deconvolution algorithms (Richardson-Lucy, maximum entropy and clean) in addition to straightforward point-source subtraction in an attempt to resolve the shells from the central stars. The use of four different methods enables us to make a qualitative judgement of the results. Notably, the shell of RR Pic displays tails extending outwards from clumps in the main ejecta similar to those previously detected in DQ Her. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9806/9806076v1.pdf"}
{"id": "astro-ph9806207", "abstract": "  We report on results of an observation with the Rossi X-Ray Timing Explorer (RXTE) of PSR B1706-44 with a live time of 132 ks, to search for pulsed X-ray emission. PSR B1706-44 is a radio and high-energy gamma-ray pulsar (detected by EGRET), but no pulsed emission has been detected in the X-ray band. Since most of the other known gamma-ray pulsars emit pulsed X-rays, it is expected that PSR B1706-44 would also be an X-ray pulsar. However, while the ROSAT PSPC detected a source at the pulsar position, it did not detect pulsations, giving a pulsed fraction upper limit of 18", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9806/9806207v1.pdf"}
{"id": "astro-ph9808103", "abstract": "  We give a rigorous derivation of a theorem showing that charged particles in an arbitrary electromagnetic field with at least one ignorable spatial coordinate remain forever tied to a given magnetic-field line. Such a situation contrasts the significant motions normal to the magnetic field that are expected in most real three-dimensional systems. It is pointed out that, while the significance of the theorem has not been widely appreciated, it has important consequences for a number of problems and is of particular relevance for the acceleration of cosmic rays by shocks. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9808/9808103v1.pdf"}
{"id": "astro-ph9810071", "abstract": "  We present results of a study of very low mass halo stars. Using a sample of proper motion stars identified from plate material taken as part of the first and second Palomar Sky Surveys, we measure the space density, metallicity distribution, and kinematics of the Population II M subdwarfs. Our overall luminosity function is in good agreement with previous analyses of the space density of nearby very-low-mass halo subdwarfs, and confirms the discrepancy between local analyses and the space densities inferred from deep HST starcounts. We show for the first time that both the metallicity distribution and kinematics of late-type halo subdwarfs are consistent with those of their higher mass metal-poor counterparts. Dividing our sample by abundance, we find no evidence that the mass function of field halo stars is dependent upon metallicity. We provide data for three nearby subdwarfs that may merit additional observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9810/9810071v1.pdf"}
{"id": "astro-ph9810135", "abstract": "  We present a deep BVrI multicolor catalog of galaxies in a 5.62 sq.arcmin field 80 arcsec south of the high redshift (z=4.7) quasar BR 1202-0725, derived from observations with the direct CCD camera SUSI at the ESO NTT. The formal 5σ magnitude limits (in 2 x FWHM apertures) are 26.9, 26.5, 25.9 and 25.3 in B, V, r and I respectively.   Counts, colors for the star and galaxy samples are discussed and a comparison with a deep HST image in the I band is presented. The percentage of merged or blended galaxies in the SUSI data to this magnitude limit is estimated to be not higher than 1", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9810/9810135v1.pdf"}
{"id": "astro-ph9810488", "abstract": "  Microlensing surveys search for the transient brightening of a background star that is the signature of gravitational lensing by a foreground compact object. This technique is an elegant way to search for astrophysical candidates that might comprise the dark matter halo of the Milky Way. While the current projects have successfully detected the phenomenon of microlensing and have reported many important results, the relatively large event rate reported towards the LMC remains a puzzle. The first step in resolving this mystery is determining the location of the excess lensing population. This will require a microlensing survey with an order of magnitude increase in sensitivity over current projects. I summarize the present status of microlensing surveys, and present (and advocate!) a next-generation project that should be capable of unambiguously determining whether the dark halo of the Galaxy is indeed made up of MACHOs, or whether the observed events are due to previously unappreciated ordinary stellar populations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9810/9810488v1.pdf"}
{"id": "astro-ph9901128", "abstract": "  I briefly summarize the main tenets of unified schemes of BL Lacs and low-luminosity radio galaxies, discussing in particular the evolution of this field after the Como 1988 meeting. I also examine some of the open problems and complications of the simplest scheme. Finally, the question of the existence of two classes of BL Lacs and our related change of perspective in the past few years are also addressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9901/9901128v1.pdf"}
{"id": "astro-ph9902242", "abstract": "  The Cosmic Microwave Background (CMB) provides a precious window on fundamental physics at very high energy scales, possibly including quantum gravity, GUTs and supersymmetry. The CMB has already enabled defect-based rivals to inflation to be discarded, and will be able to falsify many inflationary models. In combination with other cosmological observations, including those of high-redshift supernovae and large-scale structure, the CMB is on the way to providing a detailed budget for the density of the Universe, to be compared with particle-physics calculations for neutrinos and cold dark matter. Thus CMB measurements complement experiments with the LHC and long-baseline neutrino beams. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9902/9902242v1.pdf"}
{"id": "astro-ph9903049", "abstract": "  We present, for the first time, the structure of the axisymmetric force-free magnetosphere of an aligned rotating magnetic dipole, in the case in which there exists a sufficiently large charge density (whose origin we do not question) to satisfy the ideal MHD condition, E· B=0, everywhere. The unique distribution of electric current along the open magnetic field lines which is required for the solution to be continuous and smooth is obtained numerically. With the geometry of the field lines thus determined we compute the dynamics of the associated MHD wind. The main result is that the relativistic outflow contained in the magnetosphere is not accelerated to the extremely relativistic energies required for the flow to generate gamma rays. We expect that our solution will be useful as the starting point for detailed studies of pulsar magnetospheres under more general conditions, namely when either the force-free and/or the ideal MHD condition E· B=0 are not valid in the entire magnetosphere. Based on our solution, we consider that the most likely positions of such an occurrence are the polar cap, the crossings of the zero space charge surface by open field lines, and the return current boundary, but not the light cylinder. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9903/9903049v1.pdf"}
{"id": "astro-ph9905121", "abstract": "  We have observed the black hole candidate X-ray binary GX 339-4 at radio wavelengths before, during and after the 1998 high/soft X-ray state transition. We find that the radio emission from the system is strongly correlated with the hard X-ray emission and is reduced by a factor > 25 during the high/soft state compared to the more usual low/hard state. At the points of state transition we note brief periods of unusually optically-thin radio emission which may correspond to discrete ejection events. We propose that in the low/hard state black hole X-ray binaries produce a quasi-continuous outflow, in the high/soft state this outflow is suppressed, and that state transitions often result in one or more discrete ejection events. Future models for low/hard states, such as ADAF/ADIOS solutions, need to take into account strong outflow of relativistic electrons from the system. We propose that the inferred Comptonising corona and the base of the jet-like outflow are the same thing, based upon the strong correlation between radio and hard X-ray emission in GX 339-4 and other X-ray binaries, and the similarity in inferred location and composition of these two components. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9905/9905121v1.pdf"}
{"id": "astro-ph9905253", "abstract": "  Clusters of galaxies are revealing themselves as powerful sources of non thermal radiation in a wide range of wavelengths. In order to account for these multifrequency observations equipartition of cosmic rays (CRs) with the thermal gas in clusters of galaxies is often invoked. This condition might suggest a dynamical role played by cosmic rays in the virialization of these large scale structures and is now testable through gamma ray observations. We show here, in the specific case of the Coma and Virgo clusters, for which upper limits on the gamma ray emission exist, that equipartition implies gamma ray fluxes that are close or even in excess of the EGRET limit, depending on the adopted model of CR injection. We use this bound to limit the validity of the equipartition condition. We also show that, contrary to what claimed in previous calculations, the equipartition assumption implies gamma ray fluxes in the TeV range which can be detectable even by currently operating gamma ray observatories if the injection cosmic ray spectrum is flatter than E^-2.4. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9905/9905253v1.pdf"}
{"id": "astro-ph9906364", "abstract": "  Recent ASCA observations of G347.3-0.5, an SNR discovered in the ROSAT All-Sky Survey, reveal nonthermal emission from a region along the northwestern shell (Koyama et al. 1997). Here we report on new pointed ASCA observations of G347.3-.5 which confirm this result for all the bright shell regions and also reveal similar emission, although with slightly different spectral properties, from the remainder of the SNR. Curiously, no thermal X-ray emission is detected anywhere in the remnant. We derive limits on the amount of thermal emitting material present in G347.3-0.5 and present new radio continuum, CO and infrared results which indicate that the remnant is distant and of moderate age. We show that our observations are broadly consistent with a scenario that has most of the supernova remnant shock wave still within the stellar wind bubble of its progenitor star, while part of it appears to be interacting with denser material. A point source at the center of the remnant has spectral properties similar to those expected for a neutron star and may represent the compact relic of the supernova progenitor. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9906/9906364v1.pdf"}
{"id": "astro-ph9909141", "abstract": "  Recent theoretical and observational progress has substantially improved the definition of the lower main sequence and established a new basis for a comparison of main sequence stars and the secondaries in CVs. The evolutionary sequences of Kolb     Baraffe [1999] imply that the secondaries in many CVs are expanded compared with main sequence stars of the same mass as a consequence of unusually high mass transfer rates and/or pre-CV nuclear evolution. We show that the location of the secondaries of all well-studied CVs in the spectral type period diagram implies that they are consistent with having near-solar metallicities. We show, furthermore, that the surface brightness of K/M stars depends on gravity and metallicity and present new Barnes-Evans relations valid for dwarfs of near-solar metallicity and the secondaries in CVs of the galactic disk population. Distances derived by the surface brightness method agree with recent measurements of the trigonometric parallaxes of a few selected systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9909/9909141v1.pdf"}
{"id": "astro-ph9909355", "abstract": "  We present a 2 - 10 keV ASCA observation of the field around the soft gamma repeater SGR1627-41. A quiescent X-ray source was detected in this observation whose position was consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this SGR. In 2 - 10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power law, blackbody, or bremsstrahlung function, with unabsorbed flux  5 x 10^-12 erg cm^-2 s^-1. We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both noted in the earlier BeppoSAXobservations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9909/9909355v1.pdf"}
{"id": "astro-ph9910527", "abstract": "  The energy density of a scalar field ϕ with potential V(ϕ) ∝ϕ^-α, α > 0, behaves like a time-variable cosmological constant that could contribute significantly to the present energy density. Predictions of this spatially-flat model are compared to recent Type Ia supernovae apparent magnitude versus redshift data. A large region of model parameter space is consistent with current observations. (These constraints are based on the exact scalar field model equations of motion, not on the widely used time-independent equation of state fluid approximation equations of motion.) We examine the consequences of also incorporating constraints from recent measurements of the Hubble parameter and the age of the universe in the constant and time-variable cosmological constant models. We also study the effect of using a non-informative prior for the density parameter. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9910/9910527v1.pdf"}
{"id": "astro-ph9911482", "abstract": "  A high-frequency survey of the Galactic plane for radio pulsars is in progress, using the multibeam receiver on the 64-m Parkes radiotelescope. We describe the survey motivations, the observing plan and the inital results. The survey is discovering many pulsars, more than 500 so far. Eight of the new pulsars are binary, one with a massive companion. At least eight are young, with characteristic ages of less than 100 kyr. Two of these (Kaspi et al, this Conference) have surface dipole magnetic field strengths greater than any other known radio pulsar. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9911/9911482v1.pdf"}
{"id": "astro-ph9912285", "abstract": "  Following a summary of the basic principles of pulsar timing, we present a review of recent results from timing observations of relativistic binary pulsars. In particular, we summarize the status of timing observations of the much celebrated original binary pulsar PSR B1913+16, draw attention to the recent confirmation of strong evidence for geodetic precession in this system, review the recent measurement of multiple post-Keplerian binary parameters for PSR B1534+12, and describe the Parkes Multibeam survey, a major survey of the Galactic Plane which promises to discover new relativistic binary pulsar systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9912/9912285v1.pdf"}
{"id": "astro-ph9912481", "abstract": "  Recent observations with the Hubble Space Telescope (HST) have revealed that a large fraction of late-type (Sc and later) spiral galaxies harbor a bright, compact stellar cluster in their dynamical centers. Statistics of the mass, age, and star formation history of these clusters as a function of their host galaxy's Hubble type can be used to constrain models of secular galaxy evolution. Since late-type spirals by definition do not possess a prominent bulge, their nuclear clusters are more easily separated from the underlying disk population. Their spectroscopic properties can thus be studied from ground-based observations. Here, I will discuss plans for, and first results of, a program to study a sample of known nuclear clusters in late-type spirals. For one galaxy (IC 342), we have used high-resolution near infrared spectroscopy to determine the cluster mass directly via its stellar velocity dispersion. The analysis conclusively shows a very low mass-to-light ratio for the nuclear cluster in IC 342, indicative of a young cluster age (about 50 Myrs). From probability arguments, this result favors the scenario that such bursts are a recurrent phenomenon in late-type spiral nuclei. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9912/9912481v1.pdf"}
{"id": "chao-dyn9809011", "abstract": "  The theory of scarring of eigenfunctions of classically chaotic systems by short periodic orbits is extended in several ways. The influence of short-time linear recurrences on correlations and fluctuations at long times is emphasized. We include the contribution to scarring of nonlinear recurrences associated with homoclinic orbits, and treat the different scenarios of random and nonrandom long-time recurrences. The importance of the local classical structure around the periodic orbit is emphasized, and it is shown for an optimal choice of test basis in phase space, scars must persist in the semiclassical limit. The crucial role of symmetry is also discussed, which together with the nonlinear recurrences gives a much improved account of the actual strength of scars for given classical orbits and in individual wavefunctions. Quantitative measures of scarring are provided and comparisons are made with numerical data. ", "pdf_url": "gs://arxiv-dataset/arxiv/chao-dyn/pdf/9809/9809011v1.pdf"}
{"id": "cond-mat0006281", "abstract": "  The properties of scattering phases in quantum dots are analyzed with the help of lattice models. We first derive the expressions relating the different scattering phases and the dot Green functions. We analyze in detail the Friedel sum rule and discuss the deviation of the phase of the transmission amplitude from the Friedel phase at the zeroes of the transmission. The occurrence of such zeroes is related to the parity of the isolated dot levels. A statistical analysis of the isolated dot wave-functions reveals the absence of significant correlations in the parity for large disorder and the appearance, for weak disorder, of certain dot states which are strongly coupled to the leads. It is shown that large differences in the coupling to the leads give rise to an anomalous charging of the dot levels. A mechanism for the phase lapse observed experimentally based on this property is discussed and illustrated with model calculations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0006/0006281v1.pdf"}
{"id": "cond-mat0008091", "abstract": "  The experimental time scale dependence of thermodynamic relations in out-of-equilibrium systems with aging phenomena is investigated theoretically by using only aging properties of the two-time correlation functions and the generalized fluctuation-dissipation theorem (FDT). We show that there are two experimental time regimes characterized by different thermal properties. In the first regime where the waiting time is much longer than the measurement time, the principle of minimum work holds even though a system is out of equilibrium. In the second regime where both the measurement time and the waiting time are long, the thermal properties are completely different from properties in equilibrium. For the single-correlation-scale systems such as p-spin spherical spin-glasses, contrary to a fundamental assumption of thermodynamics, the work done in an infinitely slow operation depends on the path of change of the external field even when the waiting time is infinite. On the other hand, for the multi-correlation-scale systems such as Sherrington-Kirkpatrick model, the work done in an infinitely slow operation is independent of the path. Our results imply that in order to describe thermodynamic properties of systems with aging it is essential to consider the experimental time scales and history of a system as a state variable is necessary. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0008/0008091v2.pdf"}
{"id": "cond-mat0101098", "abstract": "  The composition-independent virial coefficients of a d-dimensional binary mixture of (additive) hard hyperspheres following from a recent proposal for the equation of state of the mixture [Santos, A., Yuste, S. B., and López de Haro, M., 1999, Molec. Phys., 96, 1] are examined. Good agreement between theoretical estimates and available exact or numerical results is found for d=2, 3, 4 and 5, except for mixtures whose components are very disparate in size. A slight modification that remedies this deficiency is introduced and the resummation of the associated virial series is carried out, leading to a new proposal for the equation of state. The case of binary hard-sphere mixtures (d=3) is analyzed in some detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0101/0101098v2.pdf"}
{"id": "cond-mat0107192", "abstract": "  We have presented a theoretical study of electrorotation assay based on the spectral representation theory. We consider unshelled and shelled spheroidal particles as an extension to spherical ones. From the theoretical analysis, we find that the coating can change the characteristic frequency at which the maximum rotational angular velocity occurs. The shift in the characteristic frequency is attributed to a change in the dielectric properties of the bead-coating complex with respect to those of the uncoated particles. By adjusting the dielectric properties and the thickness of the coating, it is possible to obtain good agreement between our theoretical predictions and the assay data. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0107/0107192v3.pdf"}
{"id": "cond-mat0109424", "abstract": "  A new extension of the attractive Hubbard model is constructed to study the critical behavior near a finite temperature superconducting phase transition in two dimensions using the recently developed meron-cluster algorithm. Unlike previous calculations in the attractive Hubbard model which were limited to small lattices, the new algorithm is used to study the critical behavior on lattices as large as 128× 128. These precise results for the first time show that a fermionic system can undergo a finite temperature phase transition whose critical behavior is well described by the predictions of Kosterlitz and Thouless almost three decades ago. In particular it is confirmed that the spatial winding number susceptibility obeys the well known predictions of finite size scaling for T<T_c and up to logarithmic corrections the pair susceptibility scales as L^2-η at large volumes with 0≤η≤ 0.25 for 0≤ T≤ T_c. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0109/0109424v1.pdf"}
{"id": "cond-mat0204549", "abstract": "  The spectral density for vector vibrations in the f.c.c. lattice with force-constant disorder is analysed within the coherent potential approximation. The phase diagram showing the weak- and strong-scattering regimes is presented and compared with that for electrons. The weak-scattering regime for external long-wavelength vibrational plane waves is shown to be due to sum-rule correlations in the dynamical matrix. A secondary peak below the Brillouin peak for sufficiently large wavevectors is found for the lattice models. The results obtained are supported by precise numerical solutions. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0204/0204549v1.pdf"}
{"id": "cond-mat0205598", "abstract": "  We study the emergency of mutual cooperation in evolutionary prisoner's dilemma games when the players are located on a square lattice. The players can choose one of the three strategies: cooperation (C), defection (D) or \"tit for tat\" (T), and their total payoffs come from games with the nearest neighbors. During the random sequential updates the players adopt one of their neighboring strategies if the chosen neighbor has higher payoff. We compare the effect of two types of external constraints added to the Darwinian evolutionary processes. In both cases the strategy of a randomly chosen player is replaced with probability P by another strategy. In the first case, the strategy is replaced by a randomly chosen one among the two others, while in the second case the new strategy is always C. Using generalized mean-field approximations and Monte Carlo simulations the strategy concentrations are evaluated in the stationary state for different strength of external constraints characterized by the probability P. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0205/0205598v1.pdf"}
{"id": "cond-mat0206311", "abstract": "  We theoretically study the interplay between electrical and mechanical properties of suspended, doubly clamped carbon nanotubes in which charging effects dominate. In this geometry, the capacitance between the nanotube and the gate(s) depends on the distance between them. This dependence modifies the usual Coulomb models and we show that it needs to be incorporated to capture the physics of the problem correctly. We find that the tube position changes in discrete steps every time an electron tunnels onto it. Edges of Coulomb diamonds acquire a (small) curvature. We also show that bistability in the tube position occurs and that tunneling of an electron onto the tube drastically modifies the quantized eigenmodes of the tube. Experimental verification of these predictions is possible in suspended tubes of sub-micron length. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0206/0206311v2.pdf"}
{"id": "cond-mat0210097", "abstract": "  We critically discuss the concept of “synchronized flow” from a historical, empirical, and theoretical perspective. Problems related to the measurement of vehicle data are highlighted, and questionable interpretations are identified. Moreover, we propose a quantitative and consistent theory of the empirical findings based on a phase diagram of congested traffic states, which is universal for all conventional traffic models having the same instability diagram and a fundamental diagram. New empirical and simulation data supporting this approach are presented as well. We also give a short overview of the various phenomena observed in panicking pedestrian crowds relevant from the point of evacuation of buildings, ships, and stadia. Some of these can be applied to the optimization of production processes, e.g. the “slower-is-faster effect”. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0210/0210097v1.pdf"}
{"id": "cond-mat0301342", "abstract": "  A coarsened model for a binary system with limited miscibility of components is proposed; the system is described in terms of structural states in small parts of the material. The material is assumed to have two alternative types of crystalline local arrangements associated with two components of the alloy. Fluctuating characteristics of a cluster are the type and the space orientation of its crystalline arrangement. There are two different phase transitions in the model system, an orientation order-disorder transition representing melting, and a phase transition between phases differing in concentration of components. Depending on the parameters characterizing the interaction in the system, this last transition may take place both in the crystalline and in the amorphous (molten) phase. A special approximation is used to study the thermodynamics of the system. The calculated phase diagram describes, at least qualitatively, the most important features of a binary system. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0301/0301342v1.pdf"}
{"id": "cond-mat0304121", "abstract": "  We consider the time-dependent electron transport through a quantum dot coupled to two leads in the presence of the additional over-dot (bridge) tunneling channel. By using the evolution operator method together with the wide-band limit approximation we derived the analytical formulaes for the quantum dot charge and current flowing in the system. The influence of the external microwave field on the time-average quantum dot charge, the current and the derivatives of the average current with respect to the gate and source-drain voltages has been investigated for a wide range of parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0304/0304121v1.pdf"}
{"id": "cond-mat0304259", "abstract": "  One common feature of a vehicle, an ant and a kinesin motor is that they all convert chemical energy, derived from fuel or food, into mechanical energy required for their forward movement; such objects have been modelled in recent years as self-driven “particles”. Cytoskeletal filaments, e.g., microtubules, form a “rail” network for intra-cellular transport of vesicular cargo by molecular motors like, for example, kinesins. Similarly, ants move along trails while vehicles move along lanes. Therefore, the traffic of vehicles and organisms as well as that of molecular motors can be modelled as systems of interacting self-driven particles; these are of current interest in non-equilibrium statistical mechanics. In this paper we point out the common features of these model systems and emphasize the crucial differences in their physical properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0304/0304259v1.pdf"}
{"id": "cond-mat0304301", "abstract": "  We consider a stochastic SIS infection model for a population partitioned into m households assuming random mixing. We solve the model in the limit m →∞ by using the self-consistent field method of statistical physics. We derive a number of explicit results, and give numerical illustrations. We then do numerical simulations of the model for finite m and without random mixing. We find in many of these cases that the self-consistent field method is a very good approximation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0304/0304301v1.pdf"}
{"id": "cond-mat0304647", "abstract": "  We report on the growth of domains of standing waves in electroconvection in a nematic liquid crystal. An ac voltage is applied to the system, forming an initial state that consists of travelling striped patterns with two different wavenumbers, zig and zag rolls. The standing waves are generated by suddenly applying a periodic modulation of the amplitude of the applied voltage that is approximately resonant with the travelling frequency of the pattern. By varying the modulation frequency, we are able to vary the steady-state, average wavenumber. We characterize the growth by measuring the structure factor for the pattern, the amplitude of the pattern, and the domain-wall length. An interesting feature of the growth is that the evolution of the domain-wall length is strongly affected by changing the selected wavenumber; whereas, the evolution of the structure factor is less sensitive to such changes. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0304/0304647v1.pdf"}
{"id": "cond-mat0305592", "abstract": "  We present a two-dimensional system which exhibits features of self-organized criticality. The avalanches which occur on the surface of a pile of rice are found to exhibit finite size scaling in their probability distribution. The critical exponents are τ = 1.21(2) for the avalanche size distribution and D = 1.99(2) for the cut-off size. Furthermore the geometry of the avalanches is studied leading to a fractal dimension of the active sites of d_B = 1.58(2). Using a set of scaling relations, we can calculate the roughness exponent α = D - d_B = 0.41(3) and the dynamic exponent z = D(2 - τ) = 1.56(8). This result is compared with that obtained from a power spectrum analysis of the surface roughness, which yields α = 0.42(3) and z = 1.5(1) in excellent agreement with those obtained from the scaling relations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0305/0305592v1.pdf"}
{"id": "cond-mat0307282", "abstract": "  We theoretically study in detail the hydrodynamic coupling of two equal-sized colloidal spheres at low Reynolds numbers assuming the particles to be harmonically trapped with respect to both their positions and orientations. By taking into account the rotational motion, we obtain a rich spectrum of collective eigen modes whose properties we determine on the basis of pure symmetry arguments. Extending recent investigations on translational correlations [J.-C. Meiners and S. R. Quake, Phys. Rev. Lett. 82, 2211 (1999)], we derive the complete set of auto- and cross-correlation functions emphasizing the coupling of rotation to translation which we illustrate in a few examples. An important feature of our system is the self-coupling of translation and rotation of one particle mediated by the neighboring particle that is clearly visible in the appropriate auto-correlation function. This coupling is a higher-order effect and therefore not included in the widely used Rotne-Prager approximation for the hydrodynamic mobilities. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0307/0307282v2.pdf"}
{"id": "cond-mat0308039", "abstract": "  We study theoretically the interaction between soft magnetic and superconducting films. It is shown that the vortex induces a magnetization distribution in the magnetic film, thus modifying the magnetic field as well as the interactions with e.g. Bloch walls. In particular, the field from the vortex may change sign close to the core as a result of the vortex-induced magnetization, thus resulting in a crossover from attraction to repulsion between vortices and Bloch walls. Moreover, we show that by tuning the anisotropy field of the magnetic film, one may enhance the interaction between Bloch walls and vortices. Finally, we discuss how the structure of a Bloch wall in presence of the thin film superconductor can be revealed by magneto-optic imaging using an additional magneto-optic indicator. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0308/0308039v1.pdf"}
{"id": "cond-mat0309122", "abstract": "  An analytic solution of the Hartree-Fock problem for a 2DEG at filling 1/3 and half an electron per unit cell is presented. The Coulomb interaction dynamically breaks the first Landau level in three narrow sub-bands, one of which is fully occupied and the other empty, as in the composite fermion model. The localized orbitals associated to the Bloch like single electron wavefunctions are nearly static, resembling the angular momentum eigenstates within a Landau level for non-interacting fermions. Strong correlations are expected owing to the large charge density overlap between neighboring plaquettes. A numerical evaluation brings the cohesive energy close to that of the best present day models. It is also found that correlations are long range, requiring over 50 particles spread over a finite sample to approach convergence. Since presently allowed exact calculations are far from this number, the question of how relevant the considered wave-function is for the description of the ground state of the 2DEG system remains open. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0309/0309122v1.pdf"}
{"id": "cond-mat0309377", "abstract": "  Two-leg spin ladders have a rich phase diagram if rung, diagonal and plaquette couplings are allowed for. Among the possible phases there are two Haldane-type spin liquid phases without local order parameter, which differ, however, in the topology of the short range valence bonds. We show that these phases can be distinguished numerically by two different string order parameters. We also point out that long range string- and dimer orders can coexist. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0309/0309377v1.pdf"}
{"id": "cond-mat0310206", "abstract": "  One of the remarkable properties of the II-VI diluted magnetic semiconductor (ZnMn)Se is the giant spin splitting of the valence band states under application of the magnetic field (giant Zeeman splitting). This splitting reveals strong exchange interaction between Mn moments and semiconductor states. On the other hand, no magnetic phase transition has been observed for systems with small Mn content up to very low temperatures. The latter property shows weakness of the exchange interaction between Mn moments. In this paper, the local density approximation (LDA) and the LDA+U techniques are employed to study exchange interactions in (ZnMn)Se. Supercell and frozen-magnon approaches applied earlier to III-V diluted magnetic semiconductors are used. It is found that both LDA and LDA+U describe successfully the combination of the strong Zeeman splitting and weak interatomic exchange. However, the physical pictures provided by two techniques differ strongly. A detailed analysis shows that the LDA+U method provides the description of the system which is much closer to the experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0310/0310206v1.pdf"}
{"id": "cond-mat0310437", "abstract": "  A Shadow Wave Function (SWF) is employed along with Variational Monte Carlo techniques to describe the ground state properties of solid molecular para-hydrogen. The study has been extended to densities below the equilibrium value, to obtain a parameterization of the SWF useful for the description of inhomogeneous phases. We also present an estimate of the vacancy formation energy as a function of the density, and discuss the importance of relaxation effects near the vacant site. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0310/0310437v1.pdf"}
{"id": "cond-mat0310550", "abstract": "  In the hydrodynamic approximation we obtain analytic solutions to the Gross-Pitaevskii equation with positive scattering length which describe expansions of the Bose-Einstein condensates in quasi-one and quasi-two dimensional geometries. The expansion laws are expressed in terms of the initial sizes of the condensate and the trap frequencies before release, that is in terms of experimentally measurable parameters only. Three-dimensional effects are estimated with the use of variational approach. The analytical formulae show good agreement with available experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0310/0310550v1.pdf"}
{"id": "cond-mat0401331", "abstract": "  We study the collective modes of a confined gaseous cloud of bosons and fermions with mutual attractive interactions at zero temperature. The cloud consists of a Bose-Einstein condensate and a spin-polarized Fermi gas inside a spherical harmonic trap and the coupling between the two species is varied by increasing either the magnitude of the interspecies s-wave scattering length or the number of bosons. The mode frequencies are obtained in the collisional regime by solving the equations of generalized hydrodynamics and are compared with the spectra calculated in the collisionless regime within a random-phase approximation. We find that, as the mixture is driven towards the collapse instability, the frequencies of the modes of fermionic origin show a blue shift which can become very significant for large numbers of bosons. Instead the modes of bosonic origin show a softening, which becomes most pronounced in the very proximity of collapse. Explicit illustrations of these trends are given for the monopolar spectra, but similar trends are found for the dipolar and quadrupolar spectra except for the surface (n=0) modes which are essentially unaffected by the interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0401/0401331v1.pdf"}
{"id": "cond-mat0403605", "abstract": "  We discuss the magnetic phases of the Hubbard model for the honeycomb lattice both in two and three spatial dimensions. A ground state phase diagram is obtained depending on the interaction strength   U and electronic density n. We find a first order phase transition between ferromagnetic regions where the spin is maximally polarized (Nagaoka ferromagnetism) and regions with smaller magnetization (weak ferromagnetism). When taking into account the possibility of spiral states, we find that the lowest critical U is obtained for an ordering momentum different from zero. The evolution of the ordering momentum with doping is discussed. The magnetic excitations (spin waves) in the antiferromagnetic insulating phase are calculated from the random-phase-approximation for the spin susceptibility. We also compute the spin fluctuation correction to the mean field magnetization by virtual emission/absorpion of spin waves. In the large U limit, the renormalized magnetization agrees qualitatively with the Holstein-Primakoff theory of the Heisenberg antiferromagnet, although the latter approach produces a larger renormalization. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0403/0403605v2.pdf"}
{"id": "cond-mat0405490", "abstract": "  In the present paper, we have briefly reviewed Sznajd's sociophysics model and its variants, and also we have proposed a simple Sznajd like sociophysics model based on Ising spin system in order to explain the time evaluation of resistance probability of a closed community against to occupation. Using a numerical method, we have shown that time evaluation of resistance probability of community has a non-exponential character which decays as stretched exponential independent the number of soldiers in one dimensional model. Furthermore, it has been astonishingly found that our simple sociophysics model is belong to the same universality class with random walk process on the trapping space. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0405/0405490v2.pdf"}
{"id": "cond-mat0408703", "abstract": "  The electronic structure and the single-particle spectral density of a stripe array formed by ladder-like domain walls (DWs) and by antiferromagnetic (AF) domains of width 2 lattice spacings are computed and compared with ARPES spectra from some doped cuprates belonging to the 214 family of compounds. We assume that bond order is formed on legs in DWs and that the phase of the sublattice magnetization changes by Pi across each DW. The intensity map plotted in the coordination frame momentum-energy reproduces quite well the ARPES spectra obtained at the doping level of 15", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0408/0408703v3.pdf"}
{"id": "cond-mat0411329", "abstract": "  We present a detailed analysis of the effective force between two smooth spherical colloids floating at a fluid interface due to deformations of the interface. The results hold in general and are applicable independently of the source of the deformation provided the capillary deformations are small so that a superposition approximation for the deformations is valid. We conclude that an effective long–ranged attraction is possible if the net force on the system does not vanish. Otherwise, the interaction is short–ranged and cannot be computed reliably based on the superposition approximation. As an application, we consider the case of like–charged, smooth nanoparticles and electrostatically induced capillary deformation. The resulting long–ranged capillary attraction can be easily tuned by a relatively small external electrostatic field, but it cannot explain recent experimental observations of attraction if these experimental systems were indeed isolated. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0411/0411329v1.pdf"}
{"id": "cond-mat0411536", "abstract": "  High frequency [1-500 MHz] measurements of the Magneto-Impedance (MI) of glass-covered Co_69.4Fe_3.7B_15.9Si_11 microwires are carried out with various metal-to-wire diameter ratios. A twin-peak, anhysteretic behaviour is observed as a function of magnetic field. A maximum in Δ Z/Z appears at different values of the frequency f, 125, 140 and 85 MHz with the corresponding diameter ratio p = 0.80, 0.55 and 0.32. We describe the measurement technique and interpret our results with a thermodynamic model that leads to a clearer view of the effects of p on the maximum value of MI and the anisotropy field. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0411/0411536v1.pdf"}
{"id": "cond-mat0412236", "abstract": "  We study by means of density-functional calculations the role of lateral surface reconstructions in determining the electrical properties of <100> silicon nanowires. The different lateral reconstructions are explored by relaxing all the nanowires with crystalline bulk silicon structure and all possible ideal facets that correspond to an average diameter of 1.5 nm. We show that the reconstruction induces the formation of ubiquitous surface states that turn the wires into semi-metallic or metallic. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0412/0412236v1.pdf"}
{"id": "cond-mat0502416", "abstract": "  Complementary Neutron Spin Echo and X-ray experiments and Molecular Dynamics simulations have been performed on difluorotetrachloroethane (CFCl2-CFCl2) glassy crystal. Static, single-molecule reorientational dynamics and collective dynamics properties are investigated. The orientational disorder is characterized at different temperatures and a change in nature of rotational dynamics is observed. We show that dynamics can be described by some scaling predictions of the Mode Coupling Theory (MCT) and a critical temperature T_c is determined. Our results also confirm the strong analogy between molecular liquids and plastic crystals for which α-relaxation times and non-ergodicity parameters are controlled by the non trivial static correlations as predicted by MCT. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0502/0502416v1.pdf"}
{"id": "cond-mat0504578", "abstract": "  We analyze the spectral and transport properties of ballistic quasi one-dimensional systems in the presence of spin-orbit coupling and in-plane agnetic fields. Our results demonstrate that Rashba precession and intersubband coupling must be treated on equal footing for wavevectors near the magnetic field induced gaps. We find that intersubband coupling limits the occurrence of negative effective masses at the gap edges and modifies the linear conductance curves in the strong coupling limit. The effect of the magnetic field on the spin textured orientation of the wire magnetization is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0504/0504578v2.pdf"}
{"id": "cond-mat0506257", "abstract": "  Experimental evidence suggests that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state may be realized in the unconventional, heavy-fermion superconductor CeCoIn_5. We present a self-consistent calculation of the field versus temperature phase diagram and order parameter structures for the FFLO states of quasi-two-dimensional d-wave superconductors. We calculate the spatially nonuniform order parameter, free energy density, and local density of states for magnetic fields parallel to the superconducting planes. We predict that the lower critical magnetic field transition between the spatially uniform and nonuniform FFLO state is second order. We discuss the signatures of the nonuniform FFLO state which should be observable in scanning tunneling microscopy measurements of the local density of states. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0506/0506257v1.pdf"}
{"id": "cond-mat0506422", "abstract": "  By evaporating a drop of lipid dispersion we generate the myelin morphology often seen in dissolving surfactant powders. We explain these puzzling nonequilibrium structures using a geometric argument: The bilayer repeat spacing increases and thus the repulsion between bilayers decreases when a multilamellar disk is converted into a myelin without gain or loss of material and with number of bilayers unchanged. Sufficient reduction in bilayer repulsion can compensate for the cost in curvature energy, leading to a net stability of the myelin structure. A numerical estimate predicts the degree of dehydration required to favor myelin structures over flat lamellae. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0506/0506422v1.pdf"}
{"id": "cond-mat0508620", "abstract": "  We investigate the ground state phase diagram of the S=1/2 two-leg XXZ spin ladder system with an isotropic interchain coupling. In this model, there is the Berezinskii-Kosterlitz-Thouless transition which occurs at the XY-Haldane and the XY-rung singlet phase boundaries. It was difficult to determine the transition line using traditional methods. We overcome this difficulty using the level spectroscopy method combined with the twisted boundary condition method, and we check the consistency. We find out that the phase boundary between XY phase and Haldane phase lies on the Δ=0 line. And we show that there exist two different XY phases, which we can distinguish investigating a XX correlation function. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0508/0508620v1.pdf"}
{"id": "cond-mat0509625", "abstract": "  Making use of a droplet-epitaxial technique, we realize nanometer-sized quantum ring complexes, consisting of a well-defined inner ring and an outer ring. Electronic structure inherent in the unique quantum system is analyzed using a micro-photoluminescence technique. One advantage of our growth method is that it presents the possibility of varying the ring geometry. Two samples are prepared and studied: a single-wall ring and a concentric double-ring. For both samples, highly efficient photoluminescence emitted from a single quantum structure is detected. The spectra show discrete resonance lines, which reflect the quantized nature of the ring-type electronic states. In the concentric double–ring, the carrier confinement in the inner ring and that in the outer ring are identified distinctly as split lines. The observed spectra are interpreted on the basis of single electron effective mass calculations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0509/0509625v1.pdf"}
{"id": "cond-mat0509754", "abstract": "  A definition of metastable states applicable to arbitrary finite state Markov processes satisfying detailed balance is discussed. In particular, we identify a crucial condition that distinguishes genuine metastable states from other types of slowly decaying modes and which leads to properties similar to those postulated in the restricted ensemble approach <cit.>. The intuitive physical meaning of this condition is simply that the total equilibrium probability of finding the system in the metastable state is negligible. As a concrete application of our formalism we present preliminary results on a 2D kinetic Ising model. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0509/0509754v1.pdf"}
{"id": "cond-mat0510320", "abstract": "  Models of structure formation in the universe postulate that matter distributions observed today in galaxy catalogs arise, through a complex non-linear dynamics, by gravitational evolution from a very uniform initial state. Dark matter plays the central role of providing the primordial density seeds which will govern the dynamics of structure formation. We critically examine the role of cosmological dark matter by considering three different and related issues: Basic statistical properties of theoretical initial density fields, several elements of the gravitational many-body dynamics and key correlation features of the observed galaxy distributions are discussed, stressing some useful analogies with known systems in modern statistical physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0510/0510320v1.pdf"}
{"id": "cond-mat0605008", "abstract": "  We provide a systematic quantitative description of the structure of edge states and magnetosubband evolution in hard wall quantum wires in the integer quantum Hall regime. Our calculations are based on the self-consistent Green's function technique where the electron- and spin interactions are included within the density functional theory in the local spin density approximation. We analyze the evolution of the magnetosubband structure as magnetic field varies and show that it exhibits different features as compared to the case of a smooth confinement. In particularly, in the hard-wall wire a deep and narrow triangular potential well (of the width of magnetic length l_B) is formed in the vicinity of the wire boundary. The wave functions are strongly localized in this well which leads to the increase of the electron density near the edges. Because of the presence of this well, the subbands start to depopulate from the central region of the wire and remain pinned in the well region until they are eventually pushed up by increasing magnetic field. We also demonstrate that the spin polarization of electron density as a function of magnetic field shows a pronounced double-loop pattern that can be related to the successive depopulation of the magnetosubbands. In contrast to the case of a smooth confinement, in hard-wall wires the compressible strips do not form in the vicinity of wire boundaries and spatial spin separation between spin-up and spin-down states near edges is absent. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0605/0605008v1.pdf"}
{"id": "cond-mat0605264", "abstract": "  We study the zero-bias magnetoresistance MR of an interacting quantum dot connected to two ferromagnetic leads and capacitively coupled to a gate voltage source Vg. We investigate the effects of the spin-activity of the contacts between the dot and the leads by introducing an effective exchange field in an Anderson model. This spin-activity makes easier negative MR effects, and can even lead to a giant MR effect with a sign tunable with Vg. Assuming a twofold orbital degeneracy, our approach allows to interpret in an interacting picture the MR(Vg) measured by S. Sahoo et al. [Nature Phys. 2, 99 (2005)] in single wall carbon nanotubes with ferromagnetic contacts. If this experiment is repeated on a larger Vg-range, we expect that the MR(Vg) oscillations are not regular like in the presently available data, due to Coulomb interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0605/0605264v2.pdf"}
{"id": "cond-mat0605310", "abstract": "  Using Monte Carlo simulations within the empirical potential approach, we examine the effect produced by the surface environment on the atomic level stresses in tetrahedral amorphous carbon. Both the distribution of stresses and the distributions of sp^2 and sp^3 atoms as a function of depth from the surface are highly inhomogeneous. They show the same close relationship between local stress and bonding hybridization found previously in the bulk of the material. Compressive local stress favors the formation of sp^3 sites, while tensile stress favors the formation of sp^2 sites. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0605/0605310v1.pdf"}
{"id": "cond-mat0607467", "abstract": "  Magnetic phase transition under hydrostatic pressure in TlCu_0.988Mg_0.012Cl_3 was investigated by magnetization measurements. The parent compound TlCuCl_3 is a coupled spin dimer system, which undergoes a pressure-induced quantum phase transition from a gapped ground state to an antiferromagnetic state at P_ c = 0.42 kbar due to the shrinkage of the gap. At ambient pressure, the present doped system exhibits impurity-induced magnetic ordering at T_ N=2.5 K. With increasing pressure, T_ N increases. This is because the effective exchange interaction J_ eff between unpaired spins is enhanced by the shrinkage of the gap. With a further increase in pressure, the present system undergoes a phase transition to a uniform antiferromagnetic phase due to the closing of the triplet gap in the intact dimers. The crossover from the impurity-induced ordered phase to the uniform antiferromagnetic phase occurs at P ≃ 1.3 kbar. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0607/0607467v1.pdf"}
{"id": "cond-mat0608132", "abstract": "  Recently, different experiments on the transport through atomic-sized contacts made of ferromagnetic materials have produced contradictory results. In particular, several groups have reported the observation of half-integer conductance quantization, which requires having full spin polarization and perfectly conducting channels. Motivated by these surprising results, we have studied theoretically the conductance of ideal atomic contact geometries of the ferromagnetic 3d materials Fe, Co, and Ni using a realistic tight-binding model. Our analysis shows that in the absence of magnetic domains, the d bands of these transition metals play a key role in the electrical conduction. In the contact regime this fact has the following important consequences for the three materials: (i) there are partially open conduction channels and therefore conductance quantization is not expected, (ii) the conductance of the last plateau is typically above G_0=2e^2/h, (iii) both spin species contribute to the transport and thus there is in general no full current polarization, and (iv) both the value of the conductance and the current polarization are very sensitive to the contact geometry and to disorder. In the tunneling regime we find that a strong current polarization can be achieved. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0608/0608132v1.pdf"}
{"id": "cond-mat0609717", "abstract": "  In this paper we present a determinant quantum monte carlo study of the two dimensional Hubbard model with random site disorder. We show that, as in the case of bond disorder, the system undergoes a transition from an Anderson insulating phase to a metallic phase as the onsite repulsion U is increased beyond a critical value U_c. However, there appears to be no sharp signal of this metal-insulator transition in the screened site energies. We observe that, while the system remains metallic for interaction values upto twice U_c, the conductivity is maximal in the metallic phase just beyond U_c, and decreases for larger correlation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0609/0609717v1.pdf"}
{"id": "cond-mat0610336", "abstract": "  A new lattice model of interacting electrons is presented. It can be viewed as a classical Hubbard model in which the energy associated to electron itinerance is proportional to the total number of possible electron jumps. Symmetry properties of the Hubbard model are preserved. In the half-filled band with strong interaction the model becomes the Ising model. The main features of the magnetic behavior of the model in the one-dimensional and mean-field cases are studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0610/0610336v1.pdf"}
{"id": "cond-mat0701202", "abstract": "  We study numerically the dynamics of a one-electron wave packet in a two-dimensional random lattice with long-range correlated diagonal disorder in the presence of a uniform electric field. The time-dependent Schrödinger equation is used for this purpose. We find that the wave packet displays Bloch-like oscillations associated with the appearance of a phase of delocalized states in the strong correlation regime. The amplitude of oscillations directly reflects the bandwidth of the phase and allows to measure it. The oscillations reveal two main frequencies whose values are determined by the structure of the underlying potential in the vicinity of the wave packet maximum. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0701/0701202v1.pdf"}
{"id": "cond-mat9503029", "abstract": "  We consider a two-layer Heisenberg antiferromagnet which can be either in the Néel-ordered or in the disordered phase at T=0, depending on the ratio of the intra- and interlayer exchange constants. We reduce the problem to an interacting Bose-gas and study the sublattice magnetization and the transverse susceptibility in the ordered phase, and the spectrum of quasiparticle excitations in both phases. We compare the results with the spin-wave theory and argue that the longitudinal spin fluctuations, which are not included in the spin-wave description, are small at vanishing coupling between the layers, but increase as the system approaches the transition point. We also compute the uniform susceptibility at the critical point to order O(T^2), and show that the corrections to scaling are numerically small, and the linear behavior of χ_u extends to high temperatures. This is consistent with the results of the recent Monte-Carlo simulations by Sandvik and Scalapino. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9503/9503029v1.pdf"}
{"id": "cond-mat9508089", "abstract": "  We consider a model of Raman scattering for a two–dimensional S=1/2 Heisenberg Anti-Ferromagnet which includes a dynamical spin–phonon interaction. We observe a broadening of the line shape due to increased coupling with excited high–energy spin states. Our results are close to a model of random static exchange interactions, first introduced in this context by Haas et al. [J. Appl. Phys. 75, 6340, (1994)], which, when extended to large numbers of spins, explains experiments in the parent insulating compounds of high-T_c superconductors. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9508/9508089v1.pdf"}
{"id": "cond-mat9512123", "abstract": "  We report results from Monte Carlo simulations of a thin film superconductor in a spherical geometry within the lowest Landau level approximation. We observe the absence of a phase transition to a low temperature vortex solid phase with these boundary conditions; the system remains in the vortex liquid phase for all accessible temperatures. The correlation lengths are measured for phase coherence and density modulation. Both lengths display identical temperature dependences, with an asymptotic scaling form consistent with a continuous zero temperature transition. This contrasts with the first order freezing transition which is seen in the alternative quasi-periodic boundary conditions. The high temperature perturbation theory and the ground states of the spherical system suggest that the thermodynamic limit of the spherical geometry is the same as that on the flat plane. We discuss the advantages and drawbacks of simulations with different geometries, and compare with current experimental conclusions. The effect of having a large scale inhomogeneity in the applied field is also considered. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9512/9512123v2.pdf"}
{"id": "cond-mat9606096", "abstract": "  We have calculated the electronic band structure of the (100) surface of the III–V zinc blende semiconductor compounds, using the standard tight binding method and the surface Green's function matching method. We have found that the creation of the surface gives place to new states in the electronic structure: surface resonances and two dimensional bulk states. The two dimensional bulk states are of the same character of those reported recently in CdTe(100) [Phys. Rev. 50, 1980 (1994)]. We analyze the states in the valence band region and compare with photoemission spectroscopy data. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9606/9606096v1.pdf"}
{"id": "cond-mat9701112", "abstract": "  The Glauber dynamics of various models (REM-like trap models, Brownian motion, BM model, Ising chain and SK model) is analyzed in relation with the existence of ageing. From a finite size Glauber matrix, we calculate a time τ_w(N) after which the system has relaxed to the equilibrium state. The case of metastability is also discussed. If the only non zero overlaps between pure states are only self-overlaps (REM-like trap models, BM model), the existence or absence of ageing depends only on the behavior of the density of eigenvalues for small eigenvalues. We have carried out a detailed numerical and analytical analysis of the density of eigenvalues of the REM-like trap models. In this case, we show that the behavior of the density of eigenvalues for typical trap realizations is related to the spectral dimension of the equivalent random walk model. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9701/9701112v1.pdf"}
{"id": "cond-mat9702198", "abstract": "  We extend our previous first-principles theory for perovskite ferroelectric phase transitions to treat also antiferrodistortive phase transitions. Our approach involves construction of a model Hamiltonian from a Taylor expansion, first-principles calculations to determine expansion parameters, and Monte Carlo simulations to study the resulting system. We apply this approach to three cubic perovskite compounds, SrTiO3, CaTiO3, and NaNbO3, that are known to undergo antiferrodistortive phase transitions. We calculate their transition sequences and transition temperatures at the experimental lattice constants. For SrTiO3, we find our results agree well with experiment. For more complicated compounds like CaTiO3 and NaNbO3, which can have many different structures with very similar energy, the agreement is somewhat less. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9702/9702198v1.pdf"}
{"id": "cond-mat9704208", "abstract": "  Systematic simulations are carried out based on the model of fluidized beds proposed by the present authors [K.Ichiki and H.Hayakawa, Phys. Rev. E vol.52, 658 (1995)]. From our simulation, we confirm that fluidization is a continuous transition. We also confirm the existence of two types of fluidized phases, the channeling phase and the bubbling phase. We find the close relations between the averaged behaviors in fluidized beds and quasi equilibrium states in dense liquids. In fluidized beds, (i) the flow rate plays the role of the effective temperature, and (ii) the existence of a kind of the fluctuation-dissipation relation is suggested. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9704/9704208v1.pdf"}
{"id": "cond-mat9706106", "abstract": "  Some years ago, Luck proposed a relevance criterion for the effect of aperiodic disorder on the critical behaviour of ferromagnetic Ising systems. In this article, we show how Luck's criterion can be derived within an exact renormalisation scheme for Ising quantum chains with coupling constants modulated according to substitution rules. Luck's conjectures for this case are confirmed and refined. Among other outcomes, we give an exact formula for the correlation length critical exponent for arbitrary two-letter substitution sequences with marginal fluctuations of the coupling constants. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9706/9706106v3.pdf"}
{"id": "cond-mat9706131", "abstract": "  The structure of the (√(31)×√(31))R±9^∘ reconstructed phase on sapphire (0001) surface is investigated by means of a simulation based on the energy minimization. The interaction between Al adatoms is described with the semi-empirical many-body Sutton-Chen potential, corrected for the charge transfer between the metallic overlayer and the substrate. The interactions between the Al adatoms and sapphire substrate are described with a simple three-dimensional potential field which has the hexagonal periodicity of sapphire surface. Our energy analysis gave evidence that the structure which is observed at room temperature is in fact a frozen high-temperature structure. In accordance with the X-ray scattering, a hexagonal domain pattern separated by domain walls has been found. The Al adatoms, distributed in two monolayers, are ordered and isomorphic to metallic Al(111) in the domains and disordered in the domain walls. The main reason for the rotational reconstruction is the lattice misfit between the metallic Al and sapphire. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9706/9706131v1.pdf"}
{"id": "cond-mat9709136", "abstract": "  We analyze the dynamical scaling behavior in a two-dimensional spin model with competing interactions after a quench to a striped phase. We measure the growth exponents studying the scaling of the interfaces and the scaling of the shrinking time of a ball of one phase plunged into the sea of another phase. Our results confirm the predictions found in previous papers. The correlation functions measured in the direction parallel and transversal to the stripes are different as suggested by the existence of different interface energies between the ground states of the model. Our simulations show anisotropic features for the correlations both in the case of single-spin-flip and spin-exchange dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9709/9709136v1.pdf"}
{"id": "cond-mat9901172", "abstract": "  We give an overview of the current theory of collective modes in trapped atomic gases at finite temperatures, when the dynamics of the condensate and non-condensate must both be considered. A simple introduction is given to the quantum field formulation of the dynamics of an interacting Bose-condensed system, based on equations of motion for the condensate wavefunction and single-particle Green's functions for the non-condensate atoms. We discuss the nature of excitations in the mean-field collisionless region, including the Beliaev second-order approximation for the self-energies. We also sketch the derivation of coupled two-fluid hydrodynamic equations using a simple kinetic equation which includes collisions between condensate and non-condensate atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9901/9901172v3.pdf"}
{"id": "cond-mat9903324", "abstract": "  We investigate the possibility that freely rotating cylinders with an aspect ratio L/D=0.9 exhibit a cubatic phase similar to the one found for a system of cut-spheres. We present theoretical arguments why a cubatic phase might occur in this particular system. Monte Carlo simulations do not confirm the existence of a cubatic phase for cylinders. However, they do reveal an unexpected phase behavior between the isotropic and crystalline phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9903/9903324v1.pdf"}
{"id": "cond-mat9907373", "abstract": "  A large number ( 10,000) of uniform stainless steel balls comprising less than one layer coverage on a vertically shaken plate provides a rich system for the study of excited granular media. Viewed from above, the horizontal motion in the layer shows interesting collective behavior as a result of inelastic particle-particle collisions. Clusters appear as localized fluctuations from purely random density distributions, as demonstrated by increased particle correlations. The clusters grow as the medium is \"cooled\" by reducing the rate of energy input. Further reduction of the energy input leads to the nucleation of a collapse: a close-packed crystal of particles at rest. High speed photography allows for measurement of particle velocities between collisions. The velocity distributions deviate strongly from a Maxwell distribution at low accelerations, and show approximately exponential tails, possibly due to an observed cross-correlation between density and velocity fluctuations. When the layer is confined with a lid, the velocity distributions at higher accelerations are non-Maxwellian and independent of the granular temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9907/9907373v2.pdf"}
{"id": "cond-mat9908079", "abstract": "  A non-Markovian stochastic predator-prey model is introduced in which the prey are immobile plants and predators are diffusing herbivors. The model is studied by both mean-field approximation (MFA)and computer simulations. The MFA results a series of bifurcations in the phase space of mean predator and prey densities, leading to a chaotic phase. Because of emerging correlations between the two species distributions, the interaction rate alters and if it is set the value which is obtained from the simulation, then the chaotic phase disappears. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9908/9908079v1.pdf"}
{"id": "cond-mat9912386", "abstract": "  Analytical investigations are made on BML two-dimensional traffic flow model with alternative movement and exclude-volume effect. Several exact results are obtained, including the upper critical density above which there are only jamming configurations asymptotically, and the lower critical density below which there are only moving configurations asymptotically. The jamming transition observed in the ensemble average velocity takes place at another critical density p_c(N), which is dependent on the lattice size N and is in the intermediate region between the lower and upper critical densities. It is suggested that p_c(N) is proportional to a power of N, in good agreement with the numerical simulation. The order parameter of this jamming transition is identified. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9912/9912386v1.pdf"}
{"id": "cs0701084", "abstract": "  We discuss the performance of Low-Density-Parity-Check (LDPC) codes decoded by means of Linear Programming (LP) at moderate and large Signal-to-Noise-Ratios (SNR). Utilizing a combination of the previously introduced pseudo-codeword-search method and a new \"dendro\" trick, which allows us to reduce the complexity of the LP decoding, we analyze the dependence of the Frame-Error-Rate (FER) on the SNR. Under Maximum-A-Posteriori (MAP) decoding the dendro-code, having only checks with connectivity degree three, performs identically to its original code with high-connectivity checks. For a number of popular LDPC codes performing over the Additive-White-Gaussian-Noise (AWGN) channel we found that either an error-floor sets at a relatively low SNR, or otherwise a transient asymptote, characterized by a faster decay of FER with the SNR increase, precedes the error-floor asymptote. We explain these regimes in terms of the pseudo-codeword spectra of the codes. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0701/0701084v2.pdf"}
{"id": "cs9907030", "abstract": "  We describe simple linear time algorithms for coloring the squares of balanced and unbalanced quadtrees so that no two adjacent squares are given the same color. If squares sharing sides are defined as adjacent, we color balanced quadtrees with three colors, and unbalanced quadtrees with four colors; these results are both tight, as some quadtrees require this many colors. If squares sharing corners are defined as adjacent, we color balanced or unbalanced quadtrees with six colors; for some quadtrees, at least five colors are required. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/9907/9907030v1.pdf"}
{"id": "gr-qc0005030", "abstract": "  Several different methods have recently been proposed for calculating the motion of a point particle coupled to a linearized gravitational field on a curved background. These proposals are motivated by the hope that the point particle system will accurately model certain astrophysical systems which are promising candidates for observation by the new generation of gravitational wave detectors. Because of its mathematical simplicity, the analogous system consisting of a point particle coupled to a scalar field provides a useful context in which to investigate these proposed methods. In this paper, we generalize the axiomatic approach of Quinn and Wald in order to produce a general expression for the self force on a point particle coupled to a scalar field following an arbitrary trajectory on a curved background. Our equation includes the leading order effects of the particle's own fields, commonly referred to as “self force” or “radiation reaction” effects. We then explore the equations of motion which follow from this expression in the absence of non-scalar forces. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0005/0005030v1.pdf"}
{"id": "gr-qc0110026", "abstract": "  In this paper explore the relation between covariant and canonical approaches to quantum gravity and BF theory. We will focus on the dynamical triangulation and spin-foam models, which have in common that they can be defined in terms of sums over space-time triangulations. Our aim is to show how we can recover these covariant models from a canonical framework by providing two regularisations of the projector onto the kernel of the Hamiltonian constraint. This link is important for the understanding of the dynamics of quantum gravity. In particular, we will see how in the simplest dynamical triangulations model we can recover the Hamiltonian constraint via our definition of the projector. Our discussion of spin-foam models will show how the elementary spin-network moves in loop quantum gravity, which were originally assumed to describe the Hamiltonian constraint action, are in fact related to the time-evolution generated by the constraint. We also show that the Immirzi parameter is important for the understanding of a continuum limit of the theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0110/0110026v1.pdf"}
{"id": "gr-qc0110053", "abstract": "  Gravitational wave astronomy will require the coordinated analysis of data from the global network of gravitational wave observatories. Questions of how to optimally configure the global network arise in this context. We have elsewhere proposed a formalism which is employed here to compare different configurations of the network, using both the coincident network analysis method and the coherent network analysis method. We have constructed a network model to compute a figure-of-merit based on the detection rate for a population of standard-candle binary inspirals. We find that this measure of network quality is very sensitive to the geographic location of component detectors under a coincident network analysis, but comparatively insensitive under a coherent network analysis. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0110/0110053v2.pdf"}
{"id": "gr-qc0202063", "abstract": "  This chapter is concerned with the question: how do gravitational waves (GWs) interact with their detectors? It is intended to be a theory review of the fundamental concepts involved in interferometric and acoustic (Weber bar) GW antennas. In particular, the type of signal the GW deposits in the detector in each case will be assessed, as well as its intensity and deconvolution. Brief reference will also be made to detector sensitivity characterisation, including very summary data on current state of the art GW detectors. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0202/0202063v1.pdf"}
{"id": "gr-qc0205026", "abstract": "  In this paper we review Penrose's Weyl curvature conjecture which states that the concept of gravitational entropy and the Weyl tensor is somehow linked, at least in a cosmological setting. We give a description of a certain entity constructed from the Weyl tensor, from the very early history of our universe until the present day. Inflation is an important mechanism in our early universe for homogenisation and isotropisation, and thus it must cause large effects upon the evolution of the gravitational entropy. Therefore the effects from inflationary fluids and a cosmological constant are studied in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0205/0205026v1.pdf"}
{"id": "gr-qc0206082", "abstract": "  We investigate the limitations of length measurements by accelerated observers in Minkowski spacetime brought about via the hypothesis of locality, namely, the assumption that an accelerated observer at each instant is equivalent to an otherwise identical momentarily comoving inertial observer. We find that consistency can be achieved only in a rather limited neighborhood around the observer with linear dimensions that are negligibly small compared to the characteristic acceleration length of the observer. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0206/0206082v1.pdf"}
{"id": "gr-qc0311002", "abstract": "  Spherically symmetric thin-shell wormholes in the presence of a cosmological constant are constructed applying the cut-and-paste technique implemented by Visser. Using the Darmois-Israel formalism the surface stresses, which are concentrated at the wormhole throat, are determined. This construction allows one to apply a dynamical analysis to the throat, considering linearized radial perturbations around static solutions. For a large positive cosmological constant, i.e., for the Schwarzschild-de Sitter solution, the region of stability is significantly increased, relatively to the null cosmological constant case, analyzed by Poisson and Visser. With a negative cosmological constant, i.e., the Schwarzschild-anti de Sitter solution, the region of stability is decreased. In particular, considering static solutions with a generic cosmological constant, the weak and dominant energy conditions are violated, while for a_0 ≤ 3M the null and strong energy conditions are satisfied. The surface pressure of the static solution is strictly positive for the Schwarzschild and Schwarzschild-anti de Sitter spacetimes, but takes negative values, assuming a surface tension in the Schwarzschild-de Sitter solution, for high values of the cosmological constant and the wormhole throat radius. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0311/0311002v1.pdf"}
{"id": "gr-qc0508058", "abstract": "  Fewster and Mistry have given an explicit, non-optimal quantum weak energy inequality that constrains the smeared energy density of Dirac fields in Minkowski spacetime. Here, their argument is adapted to the case of flat, two-dimensional spacetime. The non-optimal bound thereby obtained has the same order of magnitude, in the limit of zero mass, as the optimal bound of Vollick. In contrast with Vollick's bound, the bound presented here holds for all (non-negative) values of the field mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0508/0508058v2.pdf"}
{"id": "gr-qc9409008", "abstract": "  The naive calculation of black hole evaporation makes the thermal emission depend on the arbitrary high frequency behaviour of the theory where the theory is certainly wrong. Using the sonic analog to black holes– dumb holes– I show numerically that a change in the dispersion relation at high frequencies does not seem to alter the evaporation process, lending weight to the reality of the black hole evaporation process. I also suggest a reason for the insensitivity of the process to high frequency regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9409/9409008v2.pdf"}
{"id": "gr-qc9904009", "abstract": "  We present first results of the non-linear evolution of rotating relativistic stars obtained with an axisymmetric relativistic hydrodynamics code in a fixed spacetime. As initial data we use stationary axisymmetric and perturbed configurations. We find that, in order to prevent (numerical) angular momentum loss at the surface layers of the star a high-resolution grid (or a numerical scheme that retains high order at local extrema) is needed. For non-rotating stars, we compute frequencies of radial and non-radial small-amplitude oscillations, which are in excellent agreement with linear normal mode frequencies computed in the Cowling approximation. As a first application of our code, quasi-radial modes of rapidly rotating relativistic stars are computed. By generalizing our numerical code to 3-D, we plan to study the evolution and non-linear dynamics of toroidal oscillations (r-modes) of rapidly rotating neutron stars, which are a promising source of gravitational waves. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9904/9904009v1.pdf"}
{"id": "hep-ex9507013", "abstract": "  The silicon detectors used in the H1-PLUG calorimeter have shown increasing aging effects during the '94 run period of the electron proton storage ring HERA. These effects were particularly manifest as degradation of the signal to noise level and the calibration stability. The reasons for this behaviour have been found to be correlated with radiation damage to the silicon oxide passivation edges of the detectors in strong and fluctuating increases of the leakage currents and in severe changes of the flat band voltages. Depletion voltages however are found to be stable and therefore bulk damage of the silicon can be excluded. A comparison with measurements made by thermoluminescence dosimeters as well as related laboratory experiments suggest that the aging is due to very low energetic electrons and photons. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/9507/9507013v2.pdf"}
{"id": "hep-lat0010066", "abstract": "  The separation of a heavy quark and antiquark pair leads to the formation of a tube of flux, or \"string\", which should break in the presence of light quark-antiquark pairs. This expected zero-temperature phenomenon has proven elusive in simulations of lattice QCD. In an extension of work reported last year we present clear evidence for string breaking in QCD with two flavors of dynamical staggered sea quarks and apply our results to a simple three-state mixing model for string breaking. We find that mixing is weak and falls to zero at level crossing. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0010/0010066v2.pdf"}
{"id": "hep-lat0405029", "abstract": "  We report on a study of QCD thermodynamics with three flavors of quarks, using a Symanzik improved gauge action and the Asqtad O(a^2) improved staggered quark action. Simulations were carried out with lattice spacings 1/4T, 1/6T and 1/8T both for three degenerate quarks with masses less than or equal to the strange quark mass, m_s, and for degenerate up and down quarks with masses in the range 0.1 m_s ≤m_u,d ≤0.6 m_s, and the strange quark mass fixed near its physical value. We present results for standard thermodynamics quantities, such as the Polyakov loop, the chiral order parameter and its susceptibility. For the quark masses studied to date we find a rapid crossover rather than a bona fide phase transition. We have carried out the first calculations of quark number susceptibilities with three flavors of sea quarks. These quantities are of physical interest because they are related to event-by-event fluctuations in heavy ion collision experiments. Comparison of susceptibilities at different lattice spacings show that our results are close to the continuum values. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0405/0405029v2.pdf"}
{"id": "hep-lat0410002", "abstract": "  We test the finite density algorithm in the canonical ensemble which combines the HMC update with the accept/reject step according to the ratio of the fermion number projected determinant to the unprojected one as a way of avoiding the determinant fluctuation problem. We report our preliminary results on the Polyakov loop in different baryon number sectors which exhibit deconfinement transitions on small lattices. The largest density we obtain around T_c is an order of magnitude larger than that of nuclear matter. From the conserved vector current, we calculate the quark number and verify that the mixing of different baryon sectors is small. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0410/0410002v1.pdf"}
{"id": "hep-ph0001214", "abstract": "  The perspectives of two new nonstandard methods of transversal quark polarization measurement are considered: the jet handedness and the so-called \"Collins effect\" due to spin dependent T-odd fragmentation function responsible for the left-right asymmetry in fragmenting of transversally polarized quarks. Recent experimental indications in favor of these effects are observed: 1.The correlation of the T-odd one-particle fragmentation functions found by DELPHI in Z→ 2-jet decay. Integrated over the fraction of longitudinal and transversal momenta, this correlation is of 1.6", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0001/0001214v1.pdf"}
{"id": "hep-ph0005326", "abstract": "  The recent data for Bose-Einstein Correlations (BEC) of three-charged particles obtained by NA44 Collaboration have been analysed using theoretical formula with Coulomb wave functions. It has been recently proposed by Alt et al. It turns out that there are discrepancies between these data and the respective theoretical values. To resolve this problem we seek a possibly modified theoretical formulation of this problem by introducing the degree of coherence for the exchange effect due to the BEC between two-identical bosons. As a result we obtain a modified formulation for the BEC of three-charged particles showing good agreement with the data. Moreover, we investigate physical connection between our modified formulation and the core-halo model proposed by Csorgo et al. Our study indicates that the interaction region estimated by the BEC of three-charged particles in the S + Pb collisions at 200 GeV/c per nucleon is equal to about 1.5 fm 1.8 fm. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0005/0005326v3.pdf"}
{"id": "hep-ph0110291", "abstract": "  Parton distributions of pseudoscalar pi,K and eta mesons obtained within the NJL model using the Pauli-Villars regularization method are analyzed in terms of LO and NLO evolution, and the valence sea quark and gluon parton distributions for the pion are obtained at Q^2 = 4 GeV^2 and compared to existing parametrizations at that scale. Surprisingly, the NLO order effects turn out to be small compared to the LO ones. The valence distributions are in good agreement with experimental analyses, but the gluon and sea distributions come out to be softer in the high-x region and harder in the low-x region than the experimental analyses suggest. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0110/0110291v1.pdf"}
{"id": "hep-ph0204160", "abstract": "  Assuming the solar neutrino deficit is resolved by the resonant interaction of the neutrino magnetic moment with the solar magnetic field –in the framework of Resonant Spin Flavour Precession (RSFP) scenario– the solar magnetic field profile function has been derived from the scenario in the light of solar neutrino data. An approximate qualitative analysis has been done for vanishing vacuum mixing and it has been found that the profile derived is quite stable in nature. As because on changing the neutrino parameters (μ_ν, Δm^2) and the solar neutrino data the profile is just scaled along the axes. In principle, the nature of the profile is strongly dependent on the solar matter density distribution function. The current approach is quite different from the usual one- in which the best field profile is discovered by performing χ^2_min. calculations using solar neutrino data. Furthermore, the profile derived in the present work –when tested by χ^2_min. calculations– was found to be the best suited one, for the solar interior. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0204/0204160v2.pdf"}
{"id": "hep-ph0207019", "abstract": "  We present results on dijet and W+dijet production at hadron colliders obtained by supplementing the leading log BFKL resummation with energy and momentum conservation. For pure dijet production, the inclusion of the BFKL radiation in the energy conservation leads to a decrease in the parton flux sufficient to counter-act the expected exponential increase in the cross section obtained for the partonic cross section. Other BFKL signatures such as the dijet azimuthal angle decorrelation do still survive. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0207/0207019v1.pdf"}
{"id": "hep-ph0210030", "abstract": "  We present the full next-to-leading order (NLO) corrected inclusive cross section for massive lepton pair production in longitudinally polarized proton-proton collisions. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for Q<50  GeV. Like in unpolarized proton-proton scattering the dominant subprocess is given by the q(q̅)g-channel so that massive lepton pair production provides us with an excellent method to measure the spin density of the gluon. Using our calculations we give predictions for the longitudinal spin asymmetry measurements at the RHIC. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0210/0210030v1.pdf"}
{"id": "hep-ph0210217", "abstract": "  We discuss the inclusive production of J/psi mesons in deep-inelastic scattering (DIS) via the electromagnetic, weak neutral, and charged currents within the factorization formalism of nonrelativistic quantum chromodynamics. Theoretical predictions are confronted with experimental data of e p and nu N DIS taken by the H1 Collaboration at DESY HERA and the CHORUS Collaboration at CERN, respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0210/0210217v1.pdf"}
{"id": "hep-ph0308043", "abstract": "  We reconstruct the Standard Model (SM) quark masses and the Cabibbo-Kobayashi-Maskawa (CKM) matrix from a five-dimensional model, with the fifth dimension compactified on an S^1/Z_2 orbifold. Fermions are localized only at the orbifold fixed points and the induced quark mass matrices are almost democratic. Two specific versions of our model with 15 and 24 parameters are presented, and for both versions we can reproduce the quark mass spectrum and CKM matrix correctly to the level they are observed in current experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0308/0308043v3.pdf"}
{"id": "hep-ph0402044", "abstract": "  Dynamical calculations are performed for all isomultiplets of the flavour antidecuplet to which the newly discovered pentaquark Θ^+ belongs. The framework is a constituent quark model where the short-range interaction has a flavour-spin structure. In this model the lowest pentaquarks have positive parity. Each antidecuplet member is described by a variational solution with the Pauli principle properly taken into account. By fitting the mass of Θ^+ of minimal content uudds̅, the mass of Ξ^–, of minimal content ddss u̅, is predicted at approximately 1960 MeV. The influence of the octet-antidecuplet mixing on the masses of the Y = 1 and 0 pentaquarks is considered within the same model and the role of the kinetic energy plus the hyperfine interaction in this mixing is pointed out. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0402/0402044v2.pdf"}
{"id": "hep-ph0403169", "abstract": "  I discuss why photon production from the Quark Gluon Plasma (QGP) presents an interesting problem, both experimentally and theoretically. I show how the photon emission rate can be computed under the simplifying assumption that the QGP fully thermalizes. The theoretical issues are very similar to those for jet energy loss; so it should be possible to treat them in a common formalism and relate the predictions of one phenomenon to those of the other. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0403/0403169v1.pdf"}
{"id": "hep-ph0408051", "abstract": "  We reinvestigate the infrared behavior of the pressure in the g ϕ^3 scalar theory in six dimensions. This problem was first studied by Almeida and Frenkel and more recently by Carrington et al., that certified their results under certain approximations. We employ an alternative technique, instead of the approximation methods necessary to truncate the Schwinger-Dyson equations, often considered to calculate the pressure nonperturbatively. A daisy-type sum, implemented through the modified self-consistent resummation (MSCR), is enough to take care of the infrared divergences ensuring the finiteness of the pressure. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0408/0408051v3.pdf"}
{"id": "hep-ph0409297", "abstract": "  I discuss the systematic modifications to the perturbative QCD factorization approach in high energy l+A, p+A and A+A reactions. These include transverse momentum diffusion manifest in the Cronin effect and a small increase in the dijet acoplanarity; nuclear size enhanced power corrections that lead to shadowing in deeply inelastic scattering and suppression of single and double inclusive hadron production at forward rapidity at RHIC but disappear as a function of the transverse momentum; inelastic attenuation of the jet cross sections or jet quenching that persists to much higher pT. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0409/0409297v1.pdf"}
{"id": "hep-ph0412056", "abstract": "  Using the QCD dipole picture of the hard BFKL Pomeron, we perform a 3 parameter fit analysis of the recent inclusive structure function experimental measurements at small-x and intermediate Q^2. As a byproduct, the longitudinal structure function and the gluon distribution are predicted without further adjustments. The data description is quite reasonable, being timely a further study using resummed NLO BFKL kernels along the lines of recent theoretical developments. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0412/0412056v1.pdf"}
{"id": "hep-ph0412290", "abstract": "  We investigate the evolution of the networks of the cosmic strings in angled brane inflation. We show how they can be distinguished from the conventional ones. The cosmic strings in angled inflation are the daughter D_p-2 branes that are extended between the mother D_p branes. In the effective action, the strings should have a moduli, since the endpoints of the D_p-2 branes can move freely on the D_p branes. Then naturally the position of the D_p-2 branes, which corresponds to the moduli of the (1+1)-dimensional effective action, can vary along the cosmic strings. The variation of the moduli results in the peculiar (1+1)-dimensional kink configurations. The kinks are the monopoles on the strings. Therefore, the cosmic strings in angled inflation become necklaces. The loops of the necklaces can shrink to produce stable winding states, which look like coils. We show why the cosmological implications of the brane necklaces are important. We point out that the cosmic strings in generic models of brane inflation should become necklaces, depending on the structure of the compactified space and the effective potential of the model. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0412/0412290v4.pdf"}
{"id": "hep-ph0505165", "abstract": "  It is of great interest whether the recent KamLAND bound on the flux of electron antineutrinos from the Sun constrains the electromagnetic properties of the neutrino. We examine the efficiency of the electron antineutrino production in the solar magnetic fields, assuming the neutrinos are Majorana particles with a relatively large transition moment. We consider fields both in the radiative and convective zones of the Sun, with physically plausible strengths, and take into account the recently established values of the oscillation parameters. Our analysis shows that the production rate in question is presently unobservable. In the radiative zone, it is suppressed by the large measured value of the flavor mixing angle which eliminates the resonant level crossing. A corresponding general resonance condition, valid for large as well as small values of the mixing angle, is derived. Likewise, in the convective zone, the strength of the small-scale magnetic field is likely insufficient. Thus, no useful bound on the neutrino transition moment can be derived from the published KamLAND bound. KamLAND may be, however, on the edge of probing an “optimistic” scenario, making further improvements of its sensitivity desirable. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0505/0505165v2.pdf"}
{"id": "hep-ph0512084", "abstract": "  Coherent analyses of experimental results from LHC and ILC will allow us to draw a comprehensive and precise picture of the supersymmetric particle sector. Based on this platform the fundamental supersymmetric theory can be reconstructed at the high scale which is potentially close to the Planck scale. This procedure will be reviewed for three characteristic examples: minimal supergravity as the paradigm; a left-right symmetric extension incorporating intermediate mass scales; and a specific realization of string effective theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0512/0512084v2.pdf"}
{"id": "hep-ph0612153", "abstract": "  In these lectures, we present and discuss the most recent results on inclusive diffraction from the HERA and Tevatron colliders and give the prospects for the future at the LHC. Of special interest is the exclusive production of Higgs boson and heavy objects (W, top, stop pairs) which will require a better understanding of diffractive events and the link between ep and hadronic colliders, as well as precise measurements and analyses of inclusive diffraction at the LHC in particular to constrain further the gluon density in the pomeron. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0612/0612153v1.pdf"}
{"id": "hep-ph0702158", "abstract": "  We study the decorrelation in azimuthal angle of Mueller-Navelet jets at hadron colliders within the BFKL formalism. We introduce NLO terms in the evolution kernel and present a collinearly-improved version of it for all conformal spins. We show how this further resummation has good convergence properties and is closer to the Tevatron data than a simple LO treatment. However, we are still far from a good fit. We offer estimates of these decorrelations for larger rapidity differences which should favor the onset of BFKL effects and encourage experimental studies of this observable at the LHC. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0702/0702158v1.pdf"}
{"id": "hep-ph9605302", "abstract": "  This paper studies two related questions in high energy onium-onium scattering: the probability of producing an unusually large number of particles in a collision, where it is found that the cross section for producing a central multiplicity proportional to k should decrease exponentially in √(k). Secondly, the nature of gluon (dipole) evolution when dipole densities become so high that saturation effects due to dipole-dipole interactions become important: measures of saturation are developed to help understand when saturation becomes important, and further information is obtained by exploiting changes of frame, which interchange unitarity and saturation corrections. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9605/9605302v1.pdf"}
{"id": "hep-ph9606225", "abstract": "  I present a systematic study of all possible four leptons final states from γγ collisions. It is given a detailed account of fermion masses effects which are sizable since several collinear and t channel enancements occur. The effects of angular cuts on the final charged leptons are also discussed. To perform the computation I have used the recently developed ALPHA algorithm (and the resulting code) for the automatic computation of scattering amplitudes. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9606/9606225v1.pdf"}
{"id": "hep-ph9606328", "abstract": "  We study the properties of soliton solutions in an analog of the Skyrme model in 2+1 dimensions whose Lagrangian contains the Skyrme term and the mass term, but no usual kinetic term. The model admits a symmetry under area preserving diffeomorphisms. We solve the dynamical equations of motion analytically for the case of spinning isolated baryon type solitons. We take fully into account the induced deformation of the spinning Skyrmions and the consequent modification of its moment of inertia to give an analytical example of related numerical behaviour found by Piette et al.. We solve the equations of motion also for the case of an infinite, open string, and a closed annular string. In each case, the solitons are of finite extent, so called \"compactons\", being exactly the vacuum outside a compact region. We end with indications on the scattering of baby-Skyrmions, as well as some considerations as the properties of solitons on a curved space. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9606/9606328v3.pdf"}
{"id": "hep-ph9701416", "abstract": "  We simulate the formation of cosmic strings at the zeros of a complex Gaussian field with a power spectrum P(k) ∝ k^n, specifically addressing the issue of the fraction of length in infinite strings. We make two improvements over previous simulations: we include a non-zero random background field in our box to simulate the effect of long-wavelength modes, and we examine the effects of smoothing the field on small scales. The inclusion of the background field significantly reduces the fraction of length in infinite strings for n < -2. Our results are consistent with the possibility that infinite strings disappear at some n = n_c in the range -3 ≤ n_c < -2.2, although we cannot rule out n_c = -3, in which case infinite strings would disappear only at the point where the mean string density goes to zero. We present an analytic argument which suggests the latter case. Smoothing on small scales eliminates closed loops on the order of the lattice cell size and leads to a “lattice-free\" estimate of the infinite string fraction. As expected, this fraction depends on the type of window function used for smoothing. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9701/9701416v1.pdf"}
{"id": "hep-ph9702376", "abstract": "  A new perturbative scheme is proposed for the evaluation of the free energy density of field theories at finite temperature. The screened loop expansion takes into account exactly the phenomenon of screening in thermal propagators. The approach is tested in the N-component scalar field theory at 2-loop level and also at 3-loop in the large N limit. The perturbative series generated by the screened loop expansion shows much better numerical convergence than previous expansions generated in powers of the quartic coupling. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9702/9702376v1.pdf"}
{"id": "hep-ph9711250", "abstract": "  We study various conceivable photoproduction reactions in a polarized ep collider mode of HERA with respect to their sensitivity to the proton's polarized gluon distribution. A special emphasis is put on the `resolved' part of the cross sections which in principle opens the possibility to determine for the first time also the completely unknown parton content of longitudinally polarized photons. In the very promising case of dijet production we also investigate the impact of parton showering, hadronization and jet finding on the parton level results. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9711/9711250v1.pdf"}
{"id": "hep-ph9801266", "abstract": "  In order to describe properties of an equilibrated quark-gluon plasma, QCD at finite temperature (and density) has to be considered. Besides lattice calculations, which can be applied only to static quantities at zero density, perturbative QCD has been used. At finite temperature, however, serious problems such as infrared divergent and gauge dependent results have been encountered. These difficulties can be (partially) avoided if one starts from effective Green functions constructed by resumming a certain class of diagrams (hard thermal loops). Within the last few years this improved perturbation theory (Braaten-Pisarski method) turned out to be a powerful tool for computing interesting quantities of the quark-gluon plasma phase. In the present talk a basic introduction to the Braaten-Pisarski method is provided and its applications and limits are reviewed. In particular, damping rates, the energy loss of energetic partons, thermalization times, the viscosity of the quark-gluon plasma, and the production of photons and dileptons are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9801/9801266v1.pdf"}
{"id": "hep-ph9903441", "abstract": "  A next-to-leading order analysis of inelastic electroproduction of charm is performed using an interpolating scheme which maps smoothly onto massless QCD evolution at large Q^2 and photon-gluon fusion at small Q^2. In contrast with earlier analyses, this scheme allows the inclusion of quark and target mass effects and heavy quark thresholds, as well as possible non-perturbative, or intrinsic, charm contributions. We find no conclusive evidence in favor of an intrinsic charm component in the nucleon, although several data points which disagree with perturbative QCD expectations will need to be checked by future experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9903/9903441v1.pdf"}
{"id": "hep-ph9910338", "abstract": "  At future linear e^+e^- collider experiments in the TeV range, Sudakov double logarithms originating from massive boson exchange can lead to significant corrections to the cross sections of the observable processes. These effects are important for the high precision objectives of the Next Linear Collider. We use the infrared evolution equation, based on a gauge invariant dispersive method, to obtain double logarithmic asymptotics of scattering amplitudes and discuss how it can be applied, in the case of broken gauge symmetry, to the Standard Model of electroweak processes. We discuss the double logarithmic effects to both non-radiative processes and to processes accompanied by soft gauge boson emission. In all cases the Sudakov double logarithms are found to exponentiate. We also discuss double logarithmic effects of a non-Sudakov type which appear in Regge-like processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9910/9910338v1.pdf"}
{"id": "hep-ph9912540", "abstract": "  Under the assumption that the density variation of the electrons can be approximated by an exponential function, the solar Mikheyev-Smirnov-Wolfenstein effect is treated for three generations of neutrinos. The generalized hypergeometric functions that result from the exact solution of this problem are studied in detail, and a method for their numerical evaluation is presented. This analysis plays a central role in the determination of neutrino masses, not only the differences of their squares, under the assumption of universal quark-lepton mixing. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9912/9912540v1.pdf"}
{"id": "hep-th0102101", "abstract": "  We show that the noncommutativity of space-time destroys the renormalizability of the 1/N expansion of the O(N) Gross-Neveu model. A similar statement holds for the noncommutative nonlinear sigma model. However, we show that, up to the subleading order in 1/N expansion, the noncommutative supersymmetric O(N) nonlinear sigma model becomes renormalizable in D=3. We also show that dynamical mass generation is restored and there is no catastrophic UV/IR mixing. Unlike the commutative case, we find that the Lagrange multiplier fields, which enforce the supersymmetric constraints, are also renormalized. For D=2 the divergence of the four point function of the basic scalar field, which in D=3 is absent, cannot be eliminated by means of a counterterm having the structure of a Moyal product. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0102/0102101v2.pdf"}
{"id": "hep-th0211076", "abstract": "  We study the quantum mechanical consistency of noncommutative gauge theories by perturbatively analyzing the Wilsonian quantum effective action in the matrix formulation. In the process of integrating out UV states, we find new divergences having dual UV-IR interpretations and no analogues in ordinary quantum field theories. The appearance of these new UV-IR divergences has profound consequences for the renormalizability of the theory. In particular, renormalizability fails in any nonsupersymmetric noncommutative gauge theory. In fact, we argue that renormalizability generally fails in any noncommutative theory that allows quantum corrections beyond one-loop. Thus, it seems that noncommutative quantum theories are extremely sensitive to the UV, and only the softest UV behavior can be tolerated. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0211/0211076v1.pdf"}
{"id": "hep-th0503162", "abstract": "  Supersymmetric quantum Hall liquids are constructed on a noncommutative superplane.   We explore a supersymmetric formalism of the Landau problem. In the lowest Landau level, there appear spin-less bosonic states and spin-1/2 down fermionic states, which exhibit a super-chiral property. It is shown the Laughlin wavefunction and topological excitations have their superpartners. Similarities between supersymmetric quantum Hall systems and bilayer quantum Hall systems are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0503/0503162v3.pdf"}
{"id": "hep-th0610034", "abstract": "  We examine the mechanism for generating a mass for a U(1) vector field introduced by Stueckelberg. First, it is shown that renormalization of the vector mass is identical to the renormalization of the vector field on account of gauge invariance. We then consider how the vector mass affects the effective potential in scalar quantum electrodynamics at one-loop order. The possibility of extending this mechanism to couple, in a gauge invariant way, a charged vector field to the photon is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0610/0610034v2.pdf"}
{"id": "hep-th0610286", "abstract": "  We study the behaviour of five-dimensional fermions localized on branes, which we describe by domain walls, when two parallel branes collide in a five-dimensional Minkowski background spacetime. We find that most fermions are localized on both branes as a whole even after collision. However, how much fermions are localized on which brane depends sensitively on the incident velocity and the coupling constants unless the fermions exist on both branes. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0610/0610286v2.pdf"}
{"id": "hep-th9707037", "abstract": "  Following recent work by Lambiase and Nesterenko we study in detail the interquark potential for a Nambu-Goto string with point masses attached to its ends. We obtain exact solutions to the gap equations for the Lagrange multipliers and metric components and determine the potential without simplifying assumptions. We also discuss Lüscher term and argue that it remains universal. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9707/9707037v2.pdf"}
{"id": "math-ph0602053", "abstract": "  We study the swimming of non-relativistic deformable bodies in (empty) static curved spaces. We focus on the case where the ambient geometry allows for rigid body motions. In this case the swimming equations turn out to be geometric. For a small swimmer, the swimming distance in one stroke is determined by the Riemann curvature times certain moments of the swimmer. ", "pdf_url": "gs://arxiv-dataset/arxiv/math-ph/pdf/0602/0602053v1.pdf"}
{"id": "math0007155", "abstract": "  In this paper we present the mathematical description and analysis of a fractional-order regulated system in the state space. A little historical background of our results in the analysis and synthesis of the fractional-order dynamical regulated systems is given. The methods and results of simulations of the fractional-order system described by a state space equation equivalent to three-member fractional-order differential equation with a fractional-order PD^δ regulator are then presented. The possibility of investigating the stability of such systems is also considered. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0007/0007155v1.pdf"}
{"id": "math0110029", "abstract": "  This paper explores the potential of a newly developed conjugate filter oscillation reduction (CFOR) scheme for shock-capturing under the influence of natural high-frequency oscillations. The conjugate low-pass and high-pass filters are constructed based on the principle of the discrete singular convolution. Two Euler systems, the advection of an isentropy vortex flow and the interaction of shock-entropy wave are considered to demonstrate the utility of the CFOR scheme. Computational accuracy and order of approximation are examined and compared with the literature. Some of the best numerical results are obtained for the shock-entropy wave interaction. Numerical experiments indicate that the proposed scheme is stable, conservative and reliable for the numerical simulation of hyperbolic conservation laws. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0110/0110029v1.pdf"}
{"id": "math0506054", "abstract": "  To understand an aperiodic tiling (or a quasicrystal modeled on an aperiodic tiling), we construct a space of similar tilings, on which the group of translations acts naturally. This space is then an (abstract) dynamical system. Dynamical properties of the space (such as mixing, or the spectrum of the translation operator) are closely related to bulk properties of the individual tilings (such as the diffraction pattern). The topology of the space of tilings, particularly the Cech cohomology, gives information on how the original tiling can be deformed. Tiling spaces can be constructed as inverse limits of branched manifolds. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0506/0506054v2.pdf"}
{"id": "math0511557", "abstract": "  Motivated by Khovanov homology and relations between the Jones polynomial and graph polynomials, we construct a homology theory for embedded graphs from which the chromatic polynomial can be recovered as the Euler characteristic. For plane graphs, we show that our chromatic homology can be recovered from the Khovanov homology of an associated link. We apply this connection with Khovanov homology to show that the torsion-free part of our chromatic homology is independent of the choice of planar embedding of a graph.   We extend our construction and categorify the Bollobas-Riordan polynomial (a generalisation of the Tutte polynomial to embedded graphs). We prove that both our chromatic homology and the Khovanov homology of an associated link can be recovered from this categorification. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0511/0511557v3.pdf"}
{"id": "nlin0209022", "abstract": "  Evolution of perturbed embedded solitons in the general Hamiltonian fifth-order Korteweg–de Vries (KdV) equation is studied. When an embedded soliton is perturbed, it sheds a one-directional continuous-wave radiation. It is shown that the radiation amplitude is not minimal in general. A dynamical equation for velocity of the perturbed embedded soliton is derived. This equation shows that a neutrally stable embedded soliton is in fact semi-stable. When the perturbation increases the momentum of the embedded soliton, the perturbed state approaches asymptotically the embedded soliton, while when the perturbation reduces the momentum of the embedded soliton, the perturbed state decays into radiation. Classes of initial conditions to induce soliton decay or persistence are also determined. Our analytical results are confirmed by direct numerical simulations of the fifth-order KdV equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0209/0209022v1.pdf"}
{"id": "nlin0303067", "abstract": "  New extra series of conserved densities for the polytropic gas model and nonlinear elasticity equation are obtained without any references to the recursion operator or to the Lax operator formalism. Our method based on the utilization of the symmetry operators and allows us to obtain the densities of arbitrary homogenuity dimensions. The nonpolynomial densities with logarithmics behaviour are presented as an example. The special attention is paid for the singular case (γ=1) for which we found new non homogenious solutions expressed in terms of the elementary functions. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0303/0303067v1.pdf"}
{"id": "nlin0309032", "abstract": "  It is well known that pulse-like solutions of the cubic complex Ginzburg-Landau equation are unstable but can be stabilised by the addition of quintic terms. In this paper we explore an alternative mechanism where the role of the stabilising agent is played by the parametric driver. Our analysis is based on the numerical continuation of solutions in one of the parameters of the Ginzburg-Landau equation (the diffusion coefficient c), starting from the nonlinear Schrödinger limit (for which c=0). The continuation generates, recursively, a sequence of coexisting stable solutions with increasing number of humps. The sequence \"converges\" to a long pulse which can be interpreted as a bound state of two fronts with opposite polarities. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0309/0309032v1.pdf"}
{"id": "nlin0506009", "abstract": "  A method to approximate transmission probabilities for a nonseparable multidimensional barrier is applied to a waveguide model. The method uses complex barrier-crossing orbits to represent reaction probabilities in phase space and is uniform in the sense that it applies at and above a threshold energy at which classical reaction switches on. Above this threshold the geometry of the classically reacting region of phase space is clearly reflected in the quantum representation. Two versions of the approximation are applied. A harmonic version which uses dynamics linearised around an instanton orbit is valid only near threshold but is easy to use. A more accurate and more widely applicable version using nonlinear dynamics is also described. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0506/0506009v1.pdf"}
{"id": "nlin0603047", "abstract": "  We derive a class of discrete nonlinear Schrödinger (DNLS) equations for general polynomial nonlinearity whose stationary solutions can be found from a reduced two-point algebraic problem. It is demonstrated that the derived class of discretizations contains subclasses conserving classical norm or a modified norm and classical momentum. These equations are interesting from the physical standpoint since they support stationary discrete solitons free of the Peierls-Nabarro potential. As a consequence, even in highly-discrete regimes, solitons are not trapped by the lattice and they can be accelerated by even weak external fields. Focusing on the cubic nonlinearity we then consider a small perturbation around stationary soliton solutions and, solving corresponding eigenvalue problem, we (i) demonstrate that solitons are stable; (ii) show that they have two additional zero-frequency modes responsible for their effective translational invariance; (iii) derive semi-analytical solutions for discrete solitons moving at slow speed. To highlight the unusual properties of solitons in the new discrete models we compare them with that of the classical DNLS equation giving several numerical examples. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0603/0603047v2.pdf"}
{"id": "nlin0603074", "abstract": "  We propose a generalization of the discrete Klein-Gordon models free of the Peierls-Nabarro barrier derived in Nonlinearity 12, 1373 (1999) and Phys. Rev. E 72, 035602(R) (2005), such that they support not only kinks but a one-parameter set of exact static solutions. These solutions can be obtained iteratively from a two-point nonlinear map whose role is played by the discretized first integral of the static Klein-Gordon field, as suggested in J. Phys. A 38, 7617 (2005). We then discuss some discrete ϕ^4 models free of the Peierls-Nabarro barrier and identify for them the full space of available static solutions, including those derived recently in Phys. Rev. E 72 036605 (2005) but not limited to them. These findings are also relevant to standing wave solutions of discrete nonlinear Schrödinger models. We also study stability of the obtained solutions. As an interesting aside, we derive the list of solutions to the continuum ϕ^4 equation that fill the entire two-dimensional space of parameters obtained as the continuum limit of the corresponding space of the discrete models. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0603/0603074v2.pdf"}
{"id": "nlin0612040", "abstract": "  In an attempt to characterize the distribution of forms and shapes of nodal domains in wave functions, we define a geometric parameter - the ratio ρ between the area of a domain and its perimeter, measured in units of the wavelength 1/√(E). We show that the distribution function P(ρ) can distinguish between domains in which the classical dynamics is regular or chaotic. For separable surfaces, we compute the limiting distribution, and show that it is supported by an interval, which is independent of the properties of the surface. In systems which are chaotic, or in random-waves, the area-to-perimeter distribution has substantially different features which we study numerically. We compare the features of the distribution for chaotic wave functions with the predictions of the percolation model to find agreement, but only for nodal domains which are big with respect to the wavelength scale. This work is also closely related to, and provides a new point of view on isoperimetric inequalities. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0612/0612040v2.pdf"}
{"id": "nucl-th0103073", "abstract": "  Aspects of the formation and equilibration of a quark-gluon plasma are explored using a quantum kinetic equation, which involves a non-Markovian, Abelian source term for quark and antiquark production and, for the collision term, a relaxation time approximation that defines a time-dependent quasi-equilibrium temperature and collective velocity. The strong Abelian field is determined via the simultaneous solution of Maxwell's equation. A particular feature of this approach is the appearance of plasma oscillations in all thermodynamic observables. Their presence can lead to a sharp increase in the time-integrated dilepton yield. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0103/0103073v1.pdf"}
{"id": "nucl-th0109008", "abstract": "  The deformation of a nucleon embedded in various finite nuclei is considered by taking into account the distortion of the chiral profile functions under the action of an external field representing the nuclear density. The baryon charge distribution of the nucleon inside light, medium-heavy and heavy nuclei is discussed. The mass of the nucleon decreases as it is placed deeper inside the nucleus and reaches its minimum at the center of the nucleus. We discuss the quantization of non-spherical solitons and its consequences for the mass splitting of the delta states. We show that bound nucleons acquire an intrinsic quadrupole moment due to the deformation effects. These effects are maximal for densities of nuclei about ρ(R)∼0.3...0.35 ρ(0). We also point out that scale changes of the electromagnetic radii can not simply be described by an overall swelling factor. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0109/0109008v2.pdf"}
{"id": "nucl-th0204035", "abstract": "  One-loop corrections to ω photoproduction near threshold have been investigated by using the approximation that all relevant transition amplitudes are calculated from the tree diagrams of effective Lagrangians. With the parameters constrained by the data of γ N →π N, γ N →ρ N, and π N →ω N reactions, it is found that the one-loop effects due to the intermediate π N and ρ N states can significantly change the differential cross sections and spin observables. The results from this exploratory investigation suggest strongly that the coupled-channel effects should be taken into account in extracting reliable resonance parameters from the data of vector meson photoproduction in the resonance region. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0204/0204035v3.pdf"}
{"id": "nucl-th0302030", "abstract": "  We reexamine the Glauber model and calculate the total reaction cross section as a function of energy in the low and intermediate energy range, where many of the corrections in the model, are effective.   The most significant effect in this energy range is by the modification of the trajectory due to the Coulomb field. The modification in the trajectory due to nuclear field is also taken into account in a self consistent way.   The energy ranges in which particular corrections are effective, are quantified and it is found that when the center of mass energy of the system becomes 30 times the Coulomb barrier, none of the trajectory modification to the Glauber model is really required.   The reaction cross sections for light and heavy systems, right from near coulomb barrier to intermediate energies have been calculated. The exact nuclear densities and free nucleon-nucleon (NN) cross sections have been used in the calculations. The center of mass correction which is important for light systems, has also been taken into account.   There is an excellent agreement between the calculations with the modified Glauber model and the experimental data. This suggests that the heavy ion reactions in this energy range can be explained by the Glauber model in terms of free NN cross sections without incorporating any medium modification. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0302/0302030v1.pdf"}
{"id": "nucl-th0307043", "abstract": "  We give a brief overview of our current theoretical understanding of ultra-relativistic heavy ion collision and the properties of super-hot nuclear matter. We focus on several issues that have been discussed in connection with experimental results from the CERN SPS and from the Relativistic Heavy Ion Collider RHIC. We give an extrapolation of our current knowledge to LHC energies and ask which physics questions can be addressed at the LHC. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0307/0307043v1.pdf"}
{"id": "nucl-th0409062", "abstract": "  We present several coupled-cluster calculations of ground and excited states of 4He and 16O employing methods from quantum chemistry. A comparison of coupled cluster results with the results of exact diagonalization of the hamiltonian in the same model space and other truncated shell-model calculations shows that the quantum chemistry inspired coupled cluster approximations provide an excellent description of ground and excited states of nuclei, with much less computational effort than traditional large-scale shell-model approaches. Unless truncations are made, for nuclei like 16O, full-fledged shell-model calculations with four or more major shells are not possible. However, these and even larger systems can be studied with the coupled cluster methods due to the polynomial rather than factorial scaling inherent in standard shell-model studies. This makes the coupled cluster approaches, developed in quantum chemistry, viable methods for describing weakly bound systems of interest for future nuclear facilities. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0409/0409062v1.pdf"}
{"id": "nucl-th0412091", "abstract": "  In developing theories of nuclear binding energy such as density-functional theory, the effort required to make a fit can be daunting due to the large number of parameters that may be in the theory and the large number of nuclei in the mass table. For theories based on the Skyrme interaction, the effort can be reduced considerably by using the singular value decomposition to reduce the size of the parameter space. We find that the sensitive parameters define a space of dimension four or so, and within this space a linear refit is adequate for a number of Skyrme parameters sets from the literature. We do not find marked differences in the quality of the fit between the SLy4, the Bky4 and SkP parameter sets. The r.m.s. residual error in even-even nuclei is about 1.5 MeV, half the value of the liquid drop model. We also discuss an alternative norm for evaluating mass fits, the Chebyshev norm. It focuses attention on the cases with the largest discrepancies between theory and experiment. We show how it works with the liquid drop model and make some applications to models based on Skyrme energy functionals. The Chebyshev norm seems to be more sensitive to new experimental data than the root-mean-square norm. The method also has the advantage that candidate improvements to the theories can be assessed with computations on smaller sets of nuclei. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0412/0412091v2.pdf"}
{"id": "nucl-th9501013", "abstract": "  We propose a model that provides a unified description of nuclear equation of state and fragmentations. The equation of state is evaluated in Bragg-Williams as well as in Bethe-Peierls approximations and compared with that in the mean field theory with Skyrme interactions. The model shows a liquid-gas type phase transition. The nuclear fragment distributions are studied for different densities at finite temperatures. Power law behavior for fragments is observed at critical point. The study of fragment distribution and the second moment S_2 shows that the thermal critical point coincides with the percolation point at the critical density. High temperature behavior of the model shows characteristics of chemical equilibrium. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9501/9501013v1.pdf"}
{"id": "nucl-th9710021", "abstract": "  We propose a self-consistant approach to the treatment of nuclear matter as a crystal of solitons in the Wigner-Seitz approximation. Specifically, we use a Bloch-like boundary condition on the quarks at the edge of a spherical cell which allows the dispersion relation for a given radius to be calculated self-consistently along with the meson fields; in previous work some ansatz for the dispersion relation has always been an input. Results in all models are very sensitive to the form of the dispersion relation, so our approach represents a significant advance. We apply the method to both the Friedberg Lee model and the chiral quark-meson model of Birse and Banerjee. Only the latter shows short range repulsion; in the former the transition to a quark plasma occurs at unrealistically low densities. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9710/9710021v1.pdf"}
{"id": "nucl-th9910008", "abstract": "  We examine the time-reversal-violating nuclear “Schiff moment” that induces electric dipole moments in atoms. After presenting a self-contained derivation of the form of the Schiff operator, we show that the distribution of Schiff strength, an important ingredient in the ground-state Schiff moment, is very different from the electric-dipole-strength distribution, with the Schiff moment receiving no strength from the giant dipole resonance in the Goldhaber-Teller model. We then present shell-model calculations in light nuclei that confirm the negligible role of the dipole resonance and show the Schiff strength to be strongly correlated with low-lying octupole strength. Next, we turn to heavy nuclei, examining recent arguments for the strong enhancement of Schiff moments in octupole-deformed nuclei over that of 199Hg, for example. We concur that there is a significant enhancement while pointing to effects neglected in previous work (both in the octupole-deformed nuclides and 199Hg) that may reduce it somewhat, and emphasizing the need for microscopic calculations to resolve the issue. Finally, we show that static octupole deformation is not essential for the development of collective Schiff moments; nuclei with strong octupole vibrations have them as well, and some could be exploited by experiment. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9910/9910008v1.pdf"}
{"id": "nucl-th9910024", "abstract": "  The inclusive electromagnetic responses in the quasi-elastic region are calculated with a model which considers the terms of the cluster expansion containinga single correlation line. The validity of this model is studied by comparing, in nuclear matter, its results with those of a complete calculation. Results in finite nuclei for both one-and two-nucleon emission are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9910/9910024v1.pdf"}
{"id": "patt-sol9703003", "abstract": "  If a magnetic field normal to the surface of a magnetic fluid is increased beyond a critical value a spontaneous deformation of the surface arises (normal field instability). The instability is subcritical and leads to peaks of a characteristic shape. We investigate the neighborhood of this instability experimentally under the influence of a temporal modulation of the magnetic field. We use a small vessel, where only one peak arises. The modulation can either be stabilizing or destabilizing, depending on the frequency and amplitude. We observe a cascade of odd-numbered response-periods up to period 11, and also a domain of even-numbered periods. We propose a minimal model involving a cutoff-condition which captures the essence of the experimental observations.   PACS: 47.20.-k, 47.20.Ky, 75.50.Mm   Keywords: magnetic fluid; nonlinear oscillator; subharmonic response; surface instability; ", "pdf_url": "gs://arxiv-dataset/arxiv/patt-sol/pdf/9703/9703003v1.pdf"}
{"id": "physics0008245", "abstract": "  The approach to the ergodic limit in Monte Carlo simulations is studied using both analytic and numerical methods. With the help of a stochastic model, a metric is defined that enables the examination of a simulation in both the ergodic and non-ergodic regimes. In the non-ergodic regime, the model implies how the simulation is expected to approach ergodic behavior analytically, and the analytically inferred decay law of the metric allows the monitoring of the onset of ergodic behavior. The metric is related to previously defined measures developed for molecular dynamics simulations, and the metric enables the comparison of the relative efficiencies of different Monte Carlo schemes. Applications to Lennard-Jones 13-particle clusters are shown to match the model for Metropolis, J-walking and parallel tempering based approaches. The relative efficiencies of these three Monte Carlo approaches are compared, and the decay law is shown to be useful in determining needed high temperature parameters in parallel tempering and J-walking studies of atomic clusters. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0008/0008245v1.pdf"}
{"id": "physics0106069", "abstract": "  A model is proposed to explain temporal patterns of activity in a class of periodically exploding Strombolian-type volcanos. These patterns include major events (explosions) which follow each other every 10-30 minutes and subsequent tremor with a typical period of 1 second. This two-periodic activity is thought to be caused by two distinct mechanisms of accumulation of the elastic energy in the moving magma column: compressibility of the magma in the lower conduit and viscoelastic response of the almost solid magma plug on the top. A release of the elastic energy happens when a stick-slip dynamic phase transition in a boundary layer along the walls of the conduit occurs; this phase transition is driven by the shear stress accumulated in the boundary layer. The first-order character and intrinsic hysteresis of this phase transition explains the long periods of inactivity in the explosion cycle. Temporal characteristics of the model are found to be qualitatively similar to the acoustic and seismic signals recorded at Karymsky volcano in Kamchatka. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0106/0106069v1.pdf"}
{"id": "physics0204025", "abstract": "  A method to calculate the bound states of three-atoms without resorting to an explicit partial wave decomposition is presented. The differential form of the Faddeev equations in the total angular momentum representation is used for this purpose. The method utilizes Cartesian coordinates combined with the tensor-trick preconditioning for large linear systems and Arnoldi's algorithm for eigenanalysis. As an example, we consider the He_3 system in which the interatomic force has a very strong repulsive core that makes the three-body calculations with standard methods tedious and cumbersome requiring the inclusion of a large number of partial waves. The results obtained compare favorably with other results in the field. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0204/0204025v2.pdf"}
{"id": "physics0205062", "abstract": "  We propose a concept for production of high power coherent attosecond pulses in X-ray range. An approach is based on generation of 8th harmonic of radiation in a multistage HGHG FEL (high gain high harmonic free electron laser) configuration starting from shot noise. Single-spike phenomena occurs when electron bunch is passed through the sequence of four relatively short undulators. The first stage is a conventional \"long\" wavelength (0.8 nm) SASE FEL which operates in the high-gain linear regime. The 0.1 nm wavelength range is reached by successive multiplication (0.8 nm → 0.4 nm → 0.2 nm → 0.1 nm) in a stage sequence. Our study shows that the statistical properties of the high-harmonic radiation from the SASE FEL, operating in linear regime, can be used for selection of radiation pulses with a single spike in time domain. The duration of the spikes is in attosecond range. Selection of single-spike high-harmonic pulses is achieved by using a special trigger in data acquisition system. The potential of X-ray SASE FEL at TESLA at DESY for generating attosecond pulses is demonstrated. Since the design of XFEL laboratory at TESLA is based on the use of long SASE undulators with tunable gap, no special place nor additional FEL undulators are required for attophysics experiments. The use of a 10 GW-level attosecond X-ray pulses at X-ray SASE FEL facility will enable us to track processes inside atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0205/0205062v1.pdf"}
{"id": "physics0311099", "abstract": "  The empirical valence bond (EVB) method [J. Chem. Phys. 52, 1262 (1970)] has always embodied charge transfer processes. The mechanism of that behavior is examined here and recast for use as a new empirical potential energy surface for large-scale simulations. A two-state model is explored. The main features of the model are: (1) Explicit decomposition of the total system electron density is invoked; (2) The charge is defined through the density decomposition into constituent contributions; (3) The charge transfer behavior is controlled through the resonance energy matrix elements which cannot be ignored; and (4) A reference-state approach, similar in spirit to the EVB method, is used to define the resonance state energy contributions in terms of \"knowable\" quantities. With equal validity, the new potential energy can be expressed as a nonthermal ensemble average with a nonlinear but analytical charge dependence in the occupation number. Dissociation to neutral species for a gas-phase process is preserved. A variant of constrained search density functional theory is advocated as the preferred way to define an energy for a given charge. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0311/0311099v1.pdf"}
{"id": "physics0502108", "abstract": "  For classical Hamiltonian systems, the adiabatic condition may fail at some critical points. However, the breakdown of the adiabatic condition does not always make the adiabatic evolution be destroyed. In this paper, we suggest a supplemental condition of the adiabatic evolution for the fixed points of classical Hamiltonian systems when the adiabatic condition breaks down at the critical points. As an example, we investigate the adiabatic evolution of the fixed points of a classical Hamiltonian system which has a number of applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0502/0502108v1.pdf"}
{"id": "physics0512164", "abstract": "  The classical Gibbs-Donnan equilibrium describes excess osmotic pressure associated with confined colloidal charges embedded in an electrolyte solution. In this work, we extend this approach to describe the influence of multivalent ion binding on the equilibrium force acting on a charged rod translocating between two compartments, thereby mimicking ionic effects on force balance during in vitro DNA ejection from bacteriophage. The subtle interplay between Gibbs-Donnan equilibrium and adsorption equilibrium leads to a non-monotonic variation of the ejection force as multivalent salt concentration is increased, in qualitative agreement with experimental observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0512/0512164v1.pdf"}
{"id": "physics0512176", "abstract": "  When recent experimental positronium (Ps) formation cross sections in noble gases have been compared with the most up-to date theoretical studies, the agreement is qualitative, but not quantitative. In this paper we re-examine this process and show that at low energies Ps formation must be treated nonperturbatively. We also look at Ps formation with inner shell electrons. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0512/0512176v1.pdf"}
{"id": "physics0602015", "abstract": "  In this comment we discuss the problem of reconciling the linear efficiency of price returns with the long-memory of supply and demand. We present new evidence that shows that efficiency is maintained by a liquidity imbalance that co-moves with the imbalance of buyer vs. seller initiated transactions. For example, during a period where there is an excess of buyer initiated transactions, there is also more liquidity for buy orders than sell orders, so that buy orders generate smaller and less frequent price responses than sell orders. At the moment a buy order is placed the transaction sign imbalance tends to dominate, generating a price impact. However, the liquidity imbalance rapidly increases with time, so that after a small number of time steps it cancels all the inefficiency caused by the transaction sign imbalance, bounding the price impact. While the view presented by Bouchaud et al. of a fixed and temporary bare price impact is self-consistent and formally correct, we argue that viewing this in terms of a variable but permanent price impact provides a simpler and more natural view. This is in the spirit of the original conjecture of Lillo and Farmer, but generalized to allow for finite time lags in the build up of the liquidity imbalance after a transaction. We discuss the possible strategic motivations that give rise to the liquidity imbalance and offer an alternative hypothesis. We also present some results that call into question the statistical significance of large swings in expected price impact at long times. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0602/0602015v1.pdf"}
{"id": "physics0609100", "abstract": "  The definition of preferences assigned to individuals is a concept that concerns many disciplines, from economics, with the search of an acceptable outcome for an ensemble of individuals, to decision making an analysis of vote systems. We are concerned in the phenomena of good selection and economic fairness. In Arrow's theorem this situation is expressed as the impossibility of aggregate preferences among individuals falling down into some unfairness state. This situation was also analyzed in a previous model in a network of individuals with a random allocation. Both analysis are based on static preferences.   In a real society the individuals are confronted to information exchange which can modify the way that they think. Also, the preference formation of each individual is influenced by this exchange. This consideration reveals why the actual theory is not able to make an accurate analysis of the influence of the individual, or cluster of individuals, in the fairness state. The aim of this investigation is to consider the coupling of two systems, one for the formation of preferences and a second where an allocation of goods is done in an evolutionary environment. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0609/0609100v1.pdf"}
{"id": "physics0612242", "abstract": "  We developed a method to calculate positions and widths of three-body resonances. The method combines the hyperspherical adiabatic approach, slow variable discretization method (Tolstikhin et al., J. Phys. B: At. Mol. Opt. Phys. 29, L389 (1996)), and a complex absorbing potential. The method can be used to obtain resonances having short-range or long-range wave functions. In particular, we applied the method to obtain very shallow three-body Efimov resonances for a model system (Nielsen et al., Phys. Rev. A 66, 012705 (2002)). ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0612/0612242v3.pdf"}
{"id": "physics0701150", "abstract": "  We present a generalization of the often-used Crank-Nicolson (CN) method of obtaining numerical solutions of the time-dependent Schrödinger equation. The generalization yields numerical solutions accurate to order (Δ x)^2r-1 in space and (Δ t)^2M in time for any positive integers r and M, while CN employ r=M=1. We note dramatic improvement in the attainable precision (circa 10 or greater orders of magnitude) along with several orders of magnitude reduction of computational time. The improved method is shown to lead to feasible studies of coherent-state oscillations with additional short-range interactions, wavepacket scattering, and long-time studies of decaying systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0701/0701150v1.pdf"}
{"id": "physics0702126", "abstract": "  We study the dynamics of an infinite regular lattice of classical charged oscillators. Each individual oscillator is described as a point particle subject to a harmonic restoring potential, to the retarded electromagnetic field generated by all the other particles, and to the radiation reaction expressed according to the Lorentz–Dirac equation. Exact normal mode solutions, describing the propagation of plane electromagnetic waves through the lattice, are obtained for the complete linearized system of infinitely many oscillators. At variance with all the available results, our method is valid for any values of the frequency, or of the ratio between wavelength and lattice parameter. A remarkable feature is that the proper inclusion of radiation reaction in the dynamics of the individual oscillators does not give rise to any extinction coefficient for the global normal modes of the lattice. The dispersion relations resulting from our solution are numerically studied for the case of a simple cubic lattice. New predictions are obtained in this way about the behavior of the crystal at frequencies near the proper oscillation frequency of the dipoles. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0702/0702126v2.pdf"}
{"id": "physics9807011", "abstract": "  We present quantum Maxwell-Bloch equations (QMBE) for spatially inhomogeneous semiconductor laser devices. The QMBE are derived from fully quantum mechanical operator dynamics describing the interaction of the light field with the quantum states of the electrons and the holes near the band gap. By taking into account field-field correlations and field-dipole correlations, the QMBE include quantum noise effects which cause spontaneous emission and amplified spontaneous emission. In particular, the source of spontaneous emission is obtained by factorizing the dipole-dipole correlations into a product of electron and hole densities. The QMBE are formulated for general devices, for edge emitting lasers and for vertical cavity surface emitting lasers, providing a starting point for the detailed analysis of spatial coherence in the near field and far field patterns of such laser diodes. Analytical expressions are given for the spectra of gain and spontaneous emission described by the QMBE. These results are applied to the case of a broad area laser, for which the frequency and carrier density dependent spontaneous emission factor beta and the evolution of the far field pattern near threshold are derived. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/9807/9807011v2.pdf"}
{"id": "physics9809002", "abstract": "  The theories of recoil-induced resonances (RIR) [J. Guo, P. R. Berman, B. Dubetsky and G. Grynberg, Phys. Rev. A 46, 1426 (1992)] and the collective atomic recoil laser (CARL) [ R. Bonifacio and L. De Salvo, Nucl. Instrum. Methods A 341, 360 (1994)] are compared. Both theories can be used to derive expressions for the gain experienced by a probe field interacting with an ensemble of two-level atoms that are simultaneously driven by a pump field. It is shown that the RIR and CARL formalisms are equivalent. Differences between the RIR and CARL arise because the theories are typically applied for different ranges of the parameters appearing in the theory. The RIR limit considered in this paper is qP_0/Mω_q≫ 1, while the CARL limit is qP_0/Mω_q≲ 1, where ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/9809/9809002v2.pdf"}
{"id": "quant-ph0104094", "abstract": "  Angular momentum is important concept in physics, and its phase space properties are important in various applications. In this work phase space analysis of the angular momentum is made from its classical definition, and by imposing uncertainty principle its quantum properties are obtained. It is shown that kinetic energy operator is derived, but it has different interpretation of its parts than in the standard treatment. Rigid rotor is discussed and it is shown what is its phase space representation. True rigid rotor is defined and also its phase space properties are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0104/0104094v1.pdf"}
{"id": "quant-ph0302147", "abstract": "  We examine the quantum states produced through parametric amplification with internal quantum noise. The internal diffusion arises by coupling both modes of light to a reservoir for the duration of the interaction time. The Wigner function for the diffused two-mode squeezed state is calculated. The nonlocality, separability, and purity of these quantum states of light are discussed. In addition, we conclude by studying the nonlocality of two other continuous variable states: the Werner state and the phase-diffused state for two light modes. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0302/0302147v1.pdf"}
{"id": "quant-ph0304032", "abstract": "  In this paper, we consider the generalized measurement where one particular quantum signal is unambiguously extracted from a set of non-commutative quantum signals and the other signals are filtered out. Simple expressions for the maximum detection probability and its POVM are derived. We applyl such unambiguous quantum state filtering to evaluation of the sensing of decoherence channels. The bounds of the precision limit for a given quantum state of probes and possible device implementations are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0304/0304032v1.pdf"}
{"id": "quant-ph0404079", "abstract": "  Superselection rules severly constrain the operations which can be implemented on a distributed quantum system. While the restriction to local operations and classical communication gives rise to entanglement as a nonlocal resource, particle number conservation additionally confines the possible operations and should give rise to a new resource. In [Phys. Rev. Lett. 92, 087904 (2004), quant-ph/0310124] we showed that this resource can be quantified by a single additional number, the superselection induced variance (SiV) without changing the concept of entanglement. In this paper, we give the results on pure states in greater detail; additionally, we provide a discussion of mixed state nonlocality with superselection rules where we consider both formation and distillation. Finally, we demonstrate that SiV is indeed a resource, i.e., that it captures how well a state can be used to overcome the restrictions imposed by the superselection rule. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0404/0404079v1.pdf"}
{"id": "quant-ph0405175", "abstract": "  We show that it is possible to transfer two-bit information via encoding a single qubit in a conventional nuclear magnetic resonance (NMR) experiment with two very weakly polarized nuclear spins. Nevertheless, the experiment can not be regarded as a demonstration of superdense coding by means of NMR because it is based on the large number of molecules being involved in the ensemble state rather than the entanglement of the NMR states. Following the discussions, an entanglement witness, particularly applicable for NMR, is introduced based on separate and simultaneous measurement of the individual nuclear spin magnetizations. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0405/0405175v4.pdf"}
{"id": "quant-ph0406092", "abstract": "  We show that existing Runge-Kutta methods for ordinary differential equations (odes) can be modified to solve stochastic differential equations (sdes) with strong solutions provided that appropriate changes are made to the way stepsizes are selected. The order of the resulting sde scheme is half the order of the ode scheme. Specifically, we show that an explicit 9th order Runge-Kutta method (with an embedded 8th order method) for odes yields an order 4.5 method for sdes which can be implemented with variable stepsizes. This method is tested by solving systems of sdes originating from stochastic wave equations arising from master equations and the many-body Schroedinger equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0406/0406092v1.pdf"}
{"id": "quant-ph0410143", "abstract": "  We have developed a concrete quantum simulation scheme and experimentally simulated a pairing model on an NMR quantum computer. The design of our experiment includes choosing an appropriate initial state in order to make our scheme scalable in near future, and the accomplishment of our experiment makes use of twice Fourier transforms so that our method is applicable to other physical models. Our results show that the experimental simulation can give the spectrum of the simulated Hamiltonian. Consequently, the potential power of a quantum computer on the simulation of complex physical systems is verified. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0410/0410143v2.pdf"}
{"id": "quant-ph0411191", "abstract": "  Quantum state sharing is a protocol where perfect reconstruction of quantum states is achieved with incomplete or partial information in a multi-partite quantum networks. Quantum state sharing allows for secure communication in a quantum network where partial information is lost or acquired by malicious parties. This protocol utilizes entanglement for the secret state distribution, and a class of \"quantum disentangling\" protocols for the state reconstruction. We demonstrate a quantum state sharing protocol in which a tripartite entangled state is used to encode and distribute a secret state to three players. Any two of these players can collaborate to reconstruct the secret state, whilst individual players obtain no information. We investigate a number of quantum disentangling processes and experimentally demonstrate quantum state reconstruction using two of these protocols. We experimentally measure a fidelity, averaged over all reconstruction permutations, of F = 0.73. A result achievable only by using quantum resources. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0411/0411191v2.pdf"}
{"id": "0704.1045", "abstract": "  During the last three decades, evidence has mounted that star and planet formation is not an isolated process, but is influenced by current and previous generations of stars. Although cool stars form in a range of environments, from isolated globules to rich embedded clusters, the influences of other stars on cool star and planet formation may be most significant in embedded clusters, where hundreds to thousands of cool stars form in close proximity to OB stars. At the cool stars 14 meeting, a splinter session was convened to discuss the role of environment in the formation of cool stars and planetary systems; with an emphasis on the “hot” environment found in rich clusters. We review here the basic results, ideas and questions presented at the session. We have organized this contribution into five basic questions: what is the typical environment of cool star formation, what role do hot star play in cool star formation, what role does environment play in planet formation, what is the role of hot star winds and supernovae, and what was the formation environment of the Sun? The intention is to review progress made in addressing each question, and to underscore areas of agreement and contention. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1045v1.pdf"}
{"id": "0704.1497", "abstract": "  Kinetically constrained spin models are known to exhibit dynamical behavior mimicking that of glass forming systems. They are often understood as coarse-grained models of glass formers, in terms of some \"mobility\" field. The identity of this \"mobility\" field has remained elusive due to the lack of coarse-graining procedures to obtain these models from a more microscopic point of view. Here we exhibit a scheme to map the dynamics of a two-dimensional soft disc glass former onto a kinetically constrained spin model, providing an attempt at bridging these two approaches. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1497v3.pdf"}
{"id": "0704.1521", "abstract": "  Cosmological shock waves result from supersonic flow motions induced by hierarchical clustering of nonlinear structures in the universe. These shocks govern the nature of cosmic plasma through thermalization of gas and acceleration of nonthermal, cosmic-ray (CR) particles. We study the statistics and energetics of shocks formed in cosmological simulations of a concordance ΛCDM universe, with a special emphasis on the effects of non-gravitational processes such as radiative cooling, photoionization/heating, and galactic superwind feedbacks. Adopting an improved model for gas thermalization and CR acceleration efficiencies based on nonlinear diffusive shock acceleration calculations, we then estimate the gas thermal energy and the CR energy dissipated at shocks through the history of the universe. Since shocks can serve as sites for generation of vorticity, we also examine the vorticity that should have been generated mostly at curved shocks in cosmological simulations. We find that the dynamics and energetics of shocks are governed primarily by the gravity of matter, so other non-gravitational processes do not affect significantly the global energy dissipation and vorticity generation at cosmological shocks. Our results reinforce scenarios in which the intracluster medium and warm-hot intergalactic medium contain energetically significant populations of nonthermal particles and turbulent flow motions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1521v1.pdf"}
{"id": "0704.1572", "abstract": "  The approximate atomic self-interaction corrections (ASIC) method to density functional theory is put to the test by calculating the exchange interaction for a number of prototypical materials, critical to local exchange and correlation functionals. ASIC total energy calculations are mapped onto an Heisenberg pair-wise interaction and the exchange constants J are compared to those obtained with other methods. In general the ASIC scheme drastically improves the bandstructure, which for almost all the cases investigated resemble closely available photo-emission data. In contrast the results for the exchange parameters are less satisfactory. Although ASIC performs reasonably well for systems where the magnetism originates from half-filled bands, it suffers from similar problems than those of LDA for other situations. In particular the exchange constants are still overestimated. This reflects a subtle interplay between exchange and correlation energy, not captured by the ASIC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1572v1.pdf"}
{"id": "0704.2649", "abstract": "  If predictions for species extinctions hold, then the `tree of life' today may be quite different to that in (say) 100 years. We describe a technique to quantify how much each species is likely to contribute to future biodiversity, as measured by its expected contribution to phylogenetic diversity. Our approach considers all possible scenarios for the set of species that will be extant at some future time, and weights them according to their likelihood under an independent (but not identical) distribution on species extinctions. Although the number of extinction scenarios can typically be very large, we show that there is a simple algorithm that will quickly compute this index. The method is implemented and applied to the prosimian primates as a test case, and the associated species ranking is compared to a related measure (the `Shapley index'). We describe indices for rooted and unrooted trees, and a modification that also includes the focal taxon's probability of extinction, making it directly comparable to some new conservation metrics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.2649v1.pdf"}
{"id": "0704.3692", "abstract": "  We perform a time-dependent study of the driven dynamics of overdamped particles which are placed in a one-dimensional, piecewise linear random potential. This set-up of spatially quenched disorder then exerts a dichotomous varying random force on the particles. We derive the path integral representation of the resulting probability density function for the position of the particles and transform this quantity of interest into the form of a Fourier integral. In doing so, the evolution of the probability density can be investigated analytically for finite times. It is demonstrated that the probability density contains both a δ-singular contribution and a regular part. While the former part plays a dominant role at short times, the latter rules the behavior at large evolution times. The slow approach of the probability density to a limiting Gaussian form as time tends to infinity is elucidated in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.3692v2.pdf"}
{"id": "0704.3741", "abstract": "  We present time-resolved photoluminescence measurements on two series of oligo-p-phenylenevinylene materials that self-assemble into supramolecular nanostructures with thermotropic reversibility in dodecane. One set of derivatives form chiral, helical stacks while the second set form less organised, frustrated stacks. Here we study the effects of supramolecular organisation on the resonance energy transfer rates. We measure these rates in nanoassemblies formed with mixed blends of oligomers and compare them with the rates predicted by Foerster theory. Our results and analysis show that control of supramolecular order in the nanometre lengthscale has a dominant effect on the efficiency and dimentionality of resonance energy transfer. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.3741v2.pdf"}
{"id": "0705.0352", "abstract": "  We present a scaling law that predicts the values of the stresses obtained in numerical simulations of saturated MRI-driven turbulence in non-stratified shearing boxes. It relates the turbulent stresses to the strength of the vertical magnetic field, the sound speed, the vertical size of the box, and the numerical resolution and predicts accurately the results of 35 numerical simulations performed for a wide variety of physical conditions. We use our result to show that the saturated stresses in simulations with zero net magnetic flux depend linearly on the numerical resolution and would become negligible if the resolution were set equal to the natural dissipation scale in astrophysical disks. We conclude that, in order for MRI-driven turbulent angular momentum transport to be able to account for the large value of the effective alpha viscosity inferred observationally, the disk must be threaded by a significant vertical magnetic field and the turbulent magnetic energy must be in near equipartition with the thermal energy. This result has important implications for the spectra of accretion disks and their stability. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.0352v2.pdf"}
{"id": "0705.2141", "abstract": "  We show that hard-scattering factorization is violated in the production of high-p_T hadrons in hadron-hadron collisions, in the case that the hadrons are back-to-back, so that k_T factorization is to be used. The explicit counterexample that we construct is for the single-spin asymmetry with one beam transversely polarized. The Sivers function needed here has particular sensitivity to the Wilson lines in the parton densities. We use a greatly simplified model theory to make the breakdown of factorization easy to check explicitly. But the counterexample implies that standard arguments for factorization fail not just for the single-spin asymmetry but for the unpolarized cross section for back-to-back hadron production in QCD in hadron-hadron collisions. This is unlike corresponding cases in e^+e^- annihilation, Drell-Yan, and deeply inelastic scattering. Moreover, the result endangers factorization for more general hadroproduction processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.2141v2.pdf"}
{"id": "0705.2333", "abstract": "  Recent results from the HESS gamma ray telescope have shown the presence of both a diffuse, extended, flux of gamma rays above  0.4 TeV and discrete sources in and near the Galactic Centre. Here, we put forward a possible explanation in terms of the diffusion of cosmic ray protons from a succession of supernova remnants (SNR) in the SgrA* region of the Galaxy plus a contribution from SNR in the rest of the Galactic Centre Region, to be called the Galactic Centre Ridge (GCR). Protons are favoured over electrons because the mG magnetic fields in the Region will attenuate energetic electrons severely. Prominent features are the need for 'anomalous diffusion' of the protons in the whole region and the adoption of low efficiency for SNR acceleration in the high density regions. The latter is related by us to the well-known low 'cosmic ray gradient' in the Galaxy. A corroborating feature is the close correlation of inferred cosmic ray intensity with the smoothed intensity of 5 GHZ radio radiation. We attribute this to the presence of the SNR in the GCR. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.2333v1.pdf"}
{"id": "0705.2448", "abstract": "  Superluminal motion is a common feature of radio jets in powerful gamma-ray emitting active galactic nuclei. Conventionally, the variable emission is assumed to originate near the central supermassive black-hole where the jet is launched on parsec scales or smaller. Here, we report the discovery of superluminal radio features within a distinct flaring X-ray emitting region in the jet of the nearby radio galaxy M87 with the Very Long Baseline Array. This shows that these two phenomenological hallmarks – superluminal motion and high-energy variability – are associated, and we place this activity much further (>=120 pc) from the “central engine” in M87 than previously thought in relativistic jet sources. We argue that the recent excess very high-energy TeV emission from M87 reported by the H.E.S.S. experiment originates from this variable superluminal structure, thus providing crucial insight into the production region of gamma-ray emission in more distant blazars. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.2448v2.pdf"}
{"id": "0705.2596", "abstract": "  Synthetic bio-molecular spiders with \"legs\" made of single-stranded segments of DNA can move on a surface which is also covered by single-stranded segments of DNA complementary to the leg DNA. In experimental realizations, when a leg detaches from a segment of the surface for the first time it alters that segment, and legs subsequently bound to these altered segments more weakly. Inspired by these experiments we investigate spiders moving along a one-dimensional substrate, whose legs leave newly visited sites at a slower rate than revisited sites. For a random walk (one-leg spider) the slowdown does not effect the long time behavior. For a bipedal spider, however, the slowdown generates an effective bias towards unvisited sites, and the spider behaves similarly to the excited walk. Surprisingly, the slowing down of the spider at new sites increases the diffusion coefficient and accelerates the growth of the number of visited sites. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.2596v1.pdf"}
{"id": "0705.3379", "abstract": "  The performance of telescope systems working at microwave or visible/IR wavelengths is typically described in terms of different parameters according to the wavelength range. Most commercial ray tracing packages have been specifically designed for use with visible/IR systems and thus, though very flexible and sophisticated, do not provide the appropriate parameters to fully describe microwave antennas, and thus to compare with specifications. In this work we demonstrate that the Strehl ratio is equal to the phase efficiency when the apodization factor is taken into account. The phase efficiency is the most critical contribution to the aperture efficiency of an antenna, and the most difficult parameter to optimize during the telescope design. The equivalence between the Strehl ratio and the phase efficiency gives the designer/user of the telescope the opportunity to use the faster commercial ray-tracing software to optimize the design. We also discuss the results of several tests performed to check the validity of this relationship that we carried out using a ray-tracing software, ZEMAX and a full Physical Optics software, GRASP9.3, applied to three different telescope designs that span a factor of ≃ 10 in terms of D/lambda. The maximum measured discrepancy between phase efficiency and Strehl ratio varies between≃0.4 and 1.9 up to an offset angle of >40 beams, depending on the optical configuration, but it is always less than 0.5 where the Strehl ratio is >0.95. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.3379v1.pdf"}
{"id": "0706.0350", "abstract": "  We describe an expansion of the solution of the wave equation in the De Sitter - Schwarzschild metric in terms of resonances. The main term in the expansion is due to a zero resonance. The error term decays polynomially if we permit a logarithmic derivative loss in the angular directions and exponentially if we permit an small derivative loss in the angular directions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.0350v1.pdf"}
{"id": "0706.0757", "abstract": "  We analyze a recently proposed method to create fractional quantum Hall (FQH) states of atoms confined in optical lattices [A. Sørensen et al., Phys. Rev. Lett. 94 086803 (2005)]. Extending the previous work, we investigate conditions under which the FQH effect can be achieved for bosons on a lattice with an effective magnetic field and finite onsite interaction. Furthermore, we characterize the ground state in such systems by calculating Chern numbers which can provide direct signatures of topological order and explore regimes where the characterization in terms of wavefunction overlap fails. We also discuss various issues which are relevant for the practical realization of such FQH states with ultracold atoms in an optical lattice, including the presence of the long-range dipole interaction which can improve the energy gap and stabilize the ground state. We also investigate a new detection technique based on Bragg spectroscopy to probe these system in an experimental realization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.0757v1.pdf"}
{"id": "0706.1281", "abstract": "  We compute the Coleman Weinberg effective potential for the Higgs field in RS Gauge-Higgs unification scenarios based on a bulk SO(5) x U(1)_X gauge symmetry, with gauge and fermion fields propagating in the bulk and a custodial symmetry protecting the generation of large corrections to the T parameter and the coupling of the Z to the bottom quark. We demonstrate that electroweak symmetry breaking may be realized, with proper generation of the top and bottom quark masses for the same region of bulk mass parameters that lead to good agreement with precision electroweak data in the presence of a light Higgs. We compute the Higgs mass and demonstrate that for the range of parameters for which the Higgs boson has Standard Model-like properties, the Higgs mass is naturally in a range that varies between values close to the LEP experimental limit and about 160 GeV. This mass range may be probed at the Tevatron and at the LHC. We analyze the KK spectrum and briefly discuss the phenomenology of the light resonances arising in our model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.1281v2.pdf"}
{"id": "0706.1488", "abstract": "  In a quantizing magnetic field, the two-dimensional electron (2DEG) gas has a rich phase diagram with broken translational symmetry phases such as Wigner, bubble, and stripe crystals. In this paper, we derive a method to get the dynamical matrix of these crystals from a calculation of the density response function performed in the Generalized Random Phase Approximation (GRPA). We discuss the validity of our method by comparing the dynamical matrix calculated from the GRPA with that obtained from standard elasticity theory with the elastic coefficients obtained from a calculation of the deformation energy of the crystal. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.1488v2.pdf"}
{"id": "0706.2446", "abstract": "  We briefly recall the physical background of the transport of angular momentum and the mixing of chemicals inside stellar radiation zones and its importance for stellar evolution. Then, we describe its present modeling, its successes and its weaknesses. Next, we introduce the new theoretical developments that allow us to treat in a self-consistent way the effect of the Coriolis force on the low-frequencies internal waves and its consequences for the transport processes. This research is aimed at improving the modeling of stellar interiors in the perspective of future astero and helioseismology missions such as COROT and GOLF-NG. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.2446v1.pdf"}
{"id": "0706.2916", "abstract": "  The possibility of an alternative way to formulate the Hawking radiation in a static Schwarzschild spacetime has been explored. To calculate the Hawking radiation, there can be two possible choices of the spacetime wedge pairs in the Krucal-Szekeres coordinates. One is the wedge pair consists of exterior spacetime of a black hole and the exterior spacetime of a white hole, and the other is that of exterior and interior spacetimes of one black hole. The radiation from the former is the Hawking's original one. Though the the latter has been often regarded as the same phenomena as the former, the result here suggests it is not; its radiation has a temperature twice as high as the Hawking temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.2916v2.pdf"}
{"id": "0706.3088", "abstract": "  Ferromagnetism in the t-t' Hubbard model is investigated on a square lattice. Correlation effects in the form of self-energy and vertex corrections are systematically incorporated within a spin-rotationally-symmetric scheme which explicitly preserves the Goldstone mode and is therefore in accord with the Mermin-Wagner theorem. Interplay of band dispersion and correlation effects on ferromagnetic-state stability are highlighted with respect to both long- and short-wavelength fluctuations, which are shown to have substantially different behaviour. Our approach provides a novel understanding of the enhancement of ferromagnetism near van Hove filling for t' 0.5 in terms of strongly suppressed saddle-point contribution to the destabilizing exchange part of spin stiffness. Finite-temperature electron spin dynamics is investigated directly in terms of spectral-weight transfer across the Fermi energy due to electron-magnon coupling. Relevant in the context of recent magnetization measurements on ultrathin films, the role of strong thermal spin fluctuations in low dimensions is highlighted, in the anisotropy-stabilized ordered state, by determining the thermal decay of magnetization and T_c within a renormalized spin-fluctuation theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.3088v1.pdf"}
{"id": "0706.3592", "abstract": "  A model of dense plasmas relying on the superconfiguration approximation is presented. In each superconfiguration the nucleus is totally screened by the electrons in a Wigner-Seitz sphere (ion-sphere model). Superconfigurations of the same charge are grouped into ions. It is shown that boundary values of the wavefunctions play a crucial role in the form of the Virial theorem from which the pressure formula is derived. Finally, a condition is presented and discussed, which makes the ion-sphere model variational when bound electrons are treated quantum-mechanically and free electrons quasi-classically. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.3592v1.pdf"}
{"id": "0707.2154", "abstract": "  We present results from Chandra and XMM-Newton spectroscopic observations of the nuclei of z<0.5 radio galaxies and quasars from the 3CRR catalog, and examine in detail the dichotomy in the properties of low- and high-excitation radio galaxies. The X-ray spectra of low-excitation sources (those with weak or absent optical emission lines) are dominated by unabsorbed emission from a parsec-scale jet, with no contribution from accretion-related emission. These sources show no evidence for an obscuring torus, and are likely to accrete in a radiatively inefficient manner. High-excitation sources (those with prominent optical emission lines), on the other hand, show a significant contribution from a radiatively efficient accretion disk, which is heavily absorbed in the X-ray when they are oriented close to edge-on with respect to the observer. However, the low-excitation/high-excitation division does not correspond to the FRI/FRII division: thus the Fanaroff-Riley dichotomy remains a consequence of the interaction between the jet and the hot-gas environment through which it propagates. Finally, we suggest that accretion of the hot phase of the IGM is sufficient to power all low-excitation radio sources, while high-excitation sources require an additional contribution from cold gas that in turn forms the cold disk and torus. This model explains a number of properties of the radio-loud active galaxy population, and has important implications for AGN feedback mechanisms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.2154v2.pdf"}
{"id": "0707.2232", "abstract": "  Collisions of antiprotons with He-, Ne-, Ni-like, bare, and neutral uranium are studied theoretically for scattering angles close to 180^∘ and antiproton energies with the interval 100 eV – 10 keV. We investigate the Coulomb glory effect which is caused by a screening of the Coulomb potential of the nucleus and results in a prominent maximum of the differential cross section in the backward direction at some energies of the incident particle. We found that for larger numbers of electrons in the ion the effect becomes more pronounced and shifts to higher energies of the antiproton. On the other hand, a maximum of the differential cross section in the backward direction can also be found in the scattering of antiprotons on a bare uranium nucleus. The latter case can be regarded as a manifestation of the screening property of the vacuum-polarization potential in non-relativistic collisions of heavy particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.2232v1.pdf"}
{"id": "0707.2523", "abstract": "  The photoproduction of quarkonium in coherent hadron-hadron (pp/pA/AA) interactions for LHC energies is an important tool to investigate the QCD dynamics at high energies. In this paper we estimate the integrated cross section and rapidity distribution for J/Psi and Upsilon production using the Color Glass Condensate (CGC) formalism. We predict large rates, implying that the experimental identification could be feasible at the LHC.", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.2523v1.pdf"}
{"id": "0707.3902", "abstract": "  We discuss fragmentation mechanisms and isospin transport occurring in central collisions between neutron rich systems at Fermi energies. In particular, isospin effects are analyzed looking at the correlations between fragment isotopic content and kinematical properties. Simulations are based on an approximate solution of the Boltzmann-Langevin (BL) equation. An attempt to solve the complete BL equation, by introducing full fluctuations in phase space is also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.3902v1.pdf"}
{"id": "0707.4016", "abstract": "  The loop expansion is applied to a chiral effective hadronic lagrangian; with the techniques of Infrared Regularization, it is possible to separate out the short-range contributions and to write them as local products of fields that are already present in our lagrangian. (The appropriate field variables must be re-defined at each order in loops.) The corresponding parameters implicitly include short-range effects to all orders in the interaction, so these effects need not be calculated explicitly. The remaining (long-range) contributions that must be calculated are nonlocal and resemble those in conventional nuclear-structure calculations. Nonlinear isoscalar scalar (σ) and vector (ω) meson interactions are included, which incorporate many-nucleon forces and nucleon substructure. Calculations are carried out at the two-loop level to illustrate these techniques at finite nuclear densities and to verify that the coupling parameters remain natural when fitted to the empirical properties of equilibrium nuclear matter. Contributions from the ω N tensor coupling are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.4016v3.pdf"}
{"id": "0708.0706", "abstract": "  We study a dynamic mechanism to passively suppress the thermal noise of a micromechanical resonator through an intrinsic self-feedback that is genuinely non-Markovian. We use two coupled resonators, one as the target resonator and the other as an ancillary resonator, to illustrate the mechanism and its noise reduction effect. The intrinsic feedback is realized through the dynamics of coupling between the two resonators: the motions of the target resonator and the ancillary resonator mutually influence each other in a cyclic fashion. Specifically, the states that the target resonator has attained earlier will affect the state it attains later due to the presence of the ancillary resonator. We show that the feedback mechanism will bring forth the effect of noise suppression in the spectrum of displacement, but not in the spectrum of momentum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.0706v2.pdf"}
{"id": "0708.0833", "abstract": "  We investigate the ISM environment of GRB 060505. Using optical emission-line diagnostic ratios, we compare the ISM properties of the GRB 060505 host region with the hosts of unambiguous long- and short-duration GRBs. We show that the metallicity, ionization state, and star formation rate of the GRB 060505 environment are more consistent with short-duration GRBs than with long-duration GRBs. We compare the metallicity and star formation rates of the GRB 060505 region with four other star-forming regions within the GRB 060505 host galaxy. We find no significant change in metallicity or star formation rate between the GRB 060505 region and the other four host regions. Our results are consistent with a compact-object-merger progenitor for GRB 060505. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.0833v1.pdf"}
{"id": "0708.1288", "abstract": "  Linear chains of quantum scatterers are studied in the process of lengthening, which is treated and analysed as a discrete dynamical system defined over the manifold of scattering matrices. Elementary properties of such dynamics relate the transport through the chain to the spectral properties of individual scatterers. For a single-scattering channel case some new light is shed on known transport properties of disordered and noisy chains, whereas translationally invariant case can be studied analytically in terms of a simple deterministic dynamical map. The many-channel case was studied numerically by examining the statistical properties of scatterers that correspond to a certain type of transport of the chain i.e. ballistic or (partially) localised. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.1288v1.pdf"}
{"id": "0708.1335", "abstract": "  In this paper we present the design, calibration method, and initial results of the Dual-Beam Imaging Polarimeter (DBIP). This new instrument is designed to measure the optical polarization properties of point sources, in particular Main Belt asteroids. This instrument interfaces between the Tek 2048x2048 camera and the University of Hawaii's 88-inch telescope, and is available for facility use. Using DBIP we are able to measure linear polarization with a 1-sigma Poisson signal noise of 0.03", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.1335v1.pdf"}
{"id": "0708.1350", "abstract": "  It has recently been shown that the marginalization paradox (MP) can be resolved by interpreting improper inferences as probability limits. The key to the resolution is that probability limits need not satisfy the formal Bayes' law, which is used in the MP to deduce an inconsistency. In this paper, I explore the differences between probability limits and the more familiar pointwise limits, which do imply the formal Bayes' law, and show how these differences underlie some key differences in the interpretation of the MP. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.1350v1.pdf"}
{"id": "0708.1670", "abstract": "  We shall first discuss motivation for higher dimension even for classical description of gravitational dynamics and then construct a black hole out of an anti-deSitter (AdS) spacetime by prescribing a coupling between Gauss-Bonnet parameter, constant curvature of extra dimensional space and Λ. This is a creation of pure curvature which establishes the fundamental reciprocity between matter and gravity/curvature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.1670v1.pdf"}
{"id": "0708.2348", "abstract": "  Current explanation of the overabundance of dark matter subhalos in the Local Group (LG) indicates that there maybe a limit on mass of a halo, which can host a galaxy. This idea can be tested using voids in the distribution of galaxies: at some level small voids should not contain any (even dwarf) galaxies. We use observational samples complete to M_B=-12 with distances less than 8 Mpc to construct the void function (VF): the distribution of sizes of voids empty of any galaxies. There are   30 voids with sizes ranging from 1 to 5 Mpc. We also study the distribution of dark matter halos in very high resolution simulations of the LCDM model. The theoretical VF matches the observations remarkably well only if we use halos with circular velocities larger than 45 +/- 10 km/s. This agrees with the Local Group predictions. Small voids look quite similar to heir giant cousins: the density has a minimum at the center of a void and it increases as we get closer to the border. Thus, both the Local Group data and the nearby voids indicate that isolated halos below 45 +/- 10 km/s must not host galaxies and that small (few Mpc) voids are truly dark. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.2348v1.pdf"}
{"id": "0708.2585", "abstract": "  We study the intrinsic properties of attractors in the Boolean dynamics in complex network with scale-free topology, comparing with those of the so-called random Kauffman networks. We have numerically investigated the frozen and relevant nodes for each attractor, and the robustness of the attractors to the perturbation that flips the state of a single node of attractors in the relatively small network (N=30 ∼ 200). It is shown that the rate of frozen nodes in the complex networks with scale-free topology is larger than that in the random Kauffman model. Furthermore, we have found that in the complex scale-free networks with fluctuations of in-degree number the attractors are more sensitive to the state flip of a highly connected node than to the state flip of a less connected node. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.2585v1.pdf"}
{"id": "0708.4395", "abstract": "  We study theoretically the feasibility of using transverse electronic transport within a nanopore for rapid DNA sequencing. Specifically, we examine the effects of the environment and detection probes on the distinguishability of the DNA bases. We find that the intrinsic measurement bandwidth of the electrodes helps the detection of single bases by averaging over the current distributions of each base. We also find that although the overall magnitude of the current may change dramatically with different detection conditions, the intrinsic distinguishability of the bases is not significantly affected by pore size and transverse field strength. The latter is the result of very effective stabilization of the DNA by the transverse field induced by the probes, so long as that field is much larger than the field that drives DNA through the pore. In addition, the ions and water together effectively screen the charge on the nucleotides, so that the electron states participating in the transport properties of the latter ones resemble those of the uncharged species. Finally, water in the environment has negligible direct influence on the transverse electrical current. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.4395v1.pdf"}
{"id": "0708.4407", "abstract": "  The differential encoding/decoding setup introduced by Kiran et al, Oggier-Hassibi and Jing-Jafarkhani for wireless relay networks that use codebooks consisting of unitary matrices is extended to allow codebooks consisting of scaled unitary matrices. For such codebooks to be usable in the Jing-Hassibi protocol for cooperative diversity, the conditions involving the relay matrices and the codebook that need to be satisfied are identified. Using the algebraic framework of extended Clifford algebras, a new class of Distributed Differential Space-Time Codes satisfying these conditions for power of two number of relays and also achieving full cooperative diversity with a low complexity sub-optimal receiver is proposed. Simulation results indicate that the proposed codes outperform both the cyclic codes as well as the circulant codes. Furthermore, these codes can also be applied as Differential Space-Time codes for non-coherent communication in classical point to point multiple antenna systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.4407v2.pdf"}
{"id": "0709.0133", "abstract": "  Lead sulfide is an important semiconductor that has found technological applications for over a century. Raman spectroscopy, a standard tool for the investigation and characterization of semiconductors, has limited application to this material because of the forbidden nature of its first order scattering and its opacity to visible lasers. Nevertheless, useful vibrational spectra from two-phonon processes are obtained with red lasers, probably because of a resonance in the concomitant electronic transitions. Here we report temperature dependent spectra, covering the 10-300 K range, for two samples with different sulfur isotopic compositions. The results are analyzed by comparison with ab initio calculations of the lattice dynamics of PbS and the corresponding densities of one and two-phonon states. Emphasis is placed on the analysis of the two phonon band centered at  430 cm-1. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.0133v1.pdf"}
{"id": "0709.0809", "abstract": "  The propagation of a weak probe field in a laser-driven four-level atomic system is investigated. We choose mercury as our model system, where the probe transition is in the ultraviolet region. A high-resolution peak appears in the optical spectra due to the presence of interacting dark resonances. We show that this narrow peak leads to superluminal light propagation with strong absorption, and thus by itself is only of limited interest. But if in addition a weak incoherent pump field is applied to the probe transition, then the peak structure can be changed such that both sub- and superluminal light propagation or a negative group velocity can be achieved without absorption, controlled by the incoherent pumping strength. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.0809v1.pdf"}
{"id": "0709.1149", "abstract": "  Ontological models are attempts to quantitatively describe the results of a probabilistic theory, such as Quantum Mechanics, in a framework exhibiting an explicit realism-based underpinning. Unlike either the well known quasi-probability representations, or the \"r-p\" vector formalism, these models are contextual and by definition only involve positive probability distributions (and indicator functions). In this article we study how the ontological model formalism can be used to describe arbitrary statistics of a system subjected to a finite set of preparations and measurements. We present three models which can describe any such empirical data and then discuss how to turn an indeterministic model into a deterministic one. This raises the issue of how such models manifest contextuality, and we provide an explicit example to demonstrate this. In the second half of the paper we consider the issue of finding ontological models with as few ontic states as possible. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.1149v2.pdf"}
{"id": "0709.2200", "abstract": "  In this study, we have investigated factors of determination which can affect the connected structure of a stock network. The representative index for topological properties of a stock network is the number of links with other stocks. We used the multi-factor model, extensively acknowledged in financial literature. In the multi-factor model, common factors act as independent variables while returns of individual stocks act as dependent variables. We calculated the coefficient of determination, which represents the measurement value of the degree in which dependent variables are explained by independent variables. Therefore, we investigated the relationship between the number of links in the stock network and the coefficient of determination in the multi-factor model. We used individual stocks traded on the market indices of Korea, Japan, Canada, Italy and the UK. The results are as follows. We found that the mean coefficient of determination of stocks with a large number of links have higher values than those with a small number of links with other stocks. These results suggest that common factors are significantly deterministic factors to be taken into account when making a stock network. Furthermore, stocks with a large number of links to other stocks can be more affected by common factors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.2200v1.pdf"}
{"id": "0709.2770", "abstract": "  The renormalization of the chiral np interaction in the 1S0 channel to N3LO in Weinberg counting for the long distance potential with one single momentum and energy independent counterterm is carried out. This renormalization scheme yields finite and unique results and is free of short distance off-shell ambiguities. We observe good convergence in the entire elastic range below pion production threshold and find that there are some small physical effects missing in the purely pionic chiral NN potential with or without inclusion of explicit Delta degrees of freedom. We also study the renormalizability of the standard Weinberg counting at NLO and N2LO when a momentum dependent polynomial counterterm is included. Our numerical results suggest that the inclusion of this counterterm does not yield a convergent amplitude (at NLO and N2LO). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.2770v2.pdf"}
{"id": "0709.2903", "abstract": "  The question of the origin of hadron masses is one major issue in the understanding of the strong interaction. The challenge is addressed by searching for indications of in-medium modifications of hadron properties and studying hadrons in nuclei. The quest driving in-medium studies is to understand the origin of hadron masses in the context of spontaneous chiral symmetry breaking.   The experimental status of the modification of hadron properties in the nuclear medium is discussed including experiments using hadron, heavy-ion, and photon beams. Particular emphasis is put on the production of light mesons from nuclei.   A number of experimental programs is underway to provide a detailed comparison of properties of free hadrons and hadrons embedded in nuclei. The existing experimental efforts are discussed and possibilities are introduced for the new WASA-at-COSY facility, initially focussed on investigations of symmetries and symmetry breaking, to contribute to the field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.2903v1.pdf"}
{"id": "0709.3463", "abstract": "  We propose to use a quantum ratchet to transport quantum information in a chain of atoms trapped in an optical superlattice. The quantum ratchet is created by a continuous modulation of the optical superlattice which is periodic in time and in space. Though there is zero average force acting on the atoms, we show that indeed the ratchet effect permits atoms on even and odd sites to move along opposite directions. By loading the optical lattice with two-level bosonic atoms, this scheme permits to perfectly transport a qubit or entangled state imprinted in one or more atoms to any desired position in the lattice. From the quantum computation point of view, the transport is achieved by a smooth concatenation of perfect swap gates. We analyze setups with noninteracting and interacting particles and in the latter case we use the tools of optimal control to design optimal modulations. We also discuss the feasibility of this method in current experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.3463v2.pdf"}
{"id": "0709.3539", "abstract": "  We report on a study of the time sequence for the appearance of high-velocity jets and equatorial tori in the transition of stars from the asymptotic giant branch to the planetary nebulae phase. Jets and tori are prominent features of this evolution, but their origins are uncertain. Using the kinematics of molecular tori and molecular or optical jets, we determine the ejection histories for a sample of well-observed cases. We find that jets and tori develop nearly simultaneously. We also find evidence that jets appear slightly later than tori, with a typical jet-lag of a few hundred years. The reconstructed time-lines of this sequence provide good evidence that jets and tori are physically related, and they set new constraints on jet formation scenarios. Some scenarios are ruled out or rendered implausible, and others are challenged at a quantitative level. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.3539v1.pdf"}
{"id": "0710.0693", "abstract": "  We propose a model-independent scaling method to study the physical properties of high-temperature superconductors in the normal state. We have analyze the experimental data of the c-axis resistivity, the in-plane resistivity, the Hall coefficient, the magnetic susceptibility, the spin-lattice relaxation rate, and the thermoelectric power using this method. It is shown that all these physical quantities exhibit good scaling behaviors, controlled purely by the pseudogap energy scale in the normal state. The doping dependence of the pseudogap obtained from this scaling analysis agrees with the experimental results of angle-resolved photoemission and other measurements. It sheds light on the understanding of the basic electronic structure of high-Tc oxides. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.0693v3.pdf"}
{"id": "0710.2742", "abstract": "  The super-inflationary phase is predicted by the Loop Quantum Cosmology. In this paper we study the creation of gravitational waves during this phase. We consider the inverse volume corrections to the equation for the tensor modes and calculate the spectrum of the produced gravitons. The amplitude of the obtained spectrum as well as maximal energy of gravitons strongly depend on the evolution of the Universe after the super-inflation. We show that a further standard inflationary phase is necessary to lower the amount of gravitons below the present bound. In case of the lack of the standard inflationary phase, the present intensity of gravitons would be extremely large. These considerations give us another motivation to introduce the standard phase of inflation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.2742v1.pdf"}
{"id": "0710.4010", "abstract": "  A stochastic theory for the toppling activity in sandpile models is developed, based on a simple mean-field assumption about the toppling process. The theory describes the process as an anti-persistent Gaussian walk, where the diffusion coefficient is proportional to the activity. It is formulated as a generalization of the Itô stochastic differential equation with an anti-persistent fractional Gaussian noise source. An essential element of the theory is re-scaling to obtain a proper thermodynamic limit, and it captures all temporal features of the toppling process obtained by numerical simulation of the Bak-Tang-Wiesenfeld sandpile in this limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.4010v2.pdf"}
{"id": "0710.4283", "abstract": "  Unified generalized Chaplygin gas models assuming an interaction between dark energy and dark matter fluids have been previously proposed. Following these ideas, we consider a particular relation between dark densities, which allows the possibility of a time varying equation of state for dark energy that crosses the phantom divide at a recent epoch. Moreover, these densities decay during all the evolution of the Universe, avoiding a Big Rip. We find also a scaling solution, i.e. these densities are asymptotically proportional in the future, which contributes to the solution of the coincidence problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.4283v3.pdf"}
{"id": "0711.0308", "abstract": "  Hard spheres interacting through a square-well potential were simulated using two different methods: Brownian Cluster Dynamics (BCD) and Event Driven Brownian Dynamics (EDBD). The structure of the equilibrium states obtained by both methods were compared and found to be almost the identical. Self diffusion coefficients (D) were determined as a function of the interaction strength. The same values were found using BCD or EDBD. Contrary the EDBD, BCD allows one to study the effect of bond rigidity and hydrodynamic interaction within the clusters. When the bonds are flexible the effect of attraction on D is relatively weak compared to systems with rigid bonds. D increases first with increasing attraction strength, and then decreases for stronger interaction. Introducing intra-cluster hydrodynamic interaction weakly increases D for a given interaction strength. Introducing bond rigidity causes a strong decrease of D which no longer shows a maximum as function of the attraction strength. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.0308v1.pdf"}
{"id": "0711.0392", "abstract": "  We determine the quark distributions and structure functions for both unpolarized and polarized DIS of leptons on nucleons and nuclei. The scalar and vector mean fields in the nucleus modify the motion of the quarks inside the nucleons. By taking into account this medium modification, we are able to reproduce the experimental data on the unpolarized EMC effect, and to make predictions for the polarized EMC effect. We discuss examples of nuclei where the polarized EMC effect could be measured. We finally present an extension of our model to describe fragmentation functions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.0392v1.pdf"}
{"id": "0711.2580", "abstract": "  Highly relativistic jets are a key element of current gamma-ray burst models, where the jet kinetic energy is converted to radiation energy at optically thin shocks. High-energy neutrinos are also expected, from interactions of protons accelerated in the same shocks. Here we revisit the early evolution of a relativistic jet, while the jet is still inside the star, and investigate its neutrino emission. In particular we study propagation of mildly relativistic and ultrarelativistic jets through a type Ib progenitor, and follow reverse shocks as the jets cross the star. We show that protons can be accelerated to 10^4-10^5 GeV at reverse shocks, and efficiently produce mesons. The mesons experience significant cooling, suppressing subsequent neutrino emission. We show, however, that the neutrino yield from the reverse shock is still reasonably large, especially for low-luminosity and long-duration jets, where meson cooling is less severe. We discuss implications of our results in the context of neutrinos from choked jets, which are completely shock heated and do not break out of the star. From a choked jet with isotropic equivalent energy of 10^53 erg at 10 Mpc, we expect  20 neutrino events at IceCube. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.2580v2.pdf"}
{"id": "0711.3018", "abstract": "  We argue that, within a broad class of extensions of the Standard Model, there is a tight corellation between the dynamics of the electroweak phase transition and the cubic self-coupling of the Higgs boson: Models which exhibit a strong first-order EWPT predict a large deviation of the Higgs self-coupling from the Standard Model prediction, as long as no accidental cancellations occur. Order-one deviations are typical. This shift would be observable at the Large Hadron Collider if the proposed luminosity or energy upgrades are realized, as well as at a future electron-positron collider such as the proposed International Linear Collider. These measurements would provide a laboratory test of the dynamics of the electroweak phase transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.3018v3.pdf"}
{"id": "0711.4664", "abstract": "  Biological soft tissues exhibit elastic properties which can be dramatically different from rubber-type materials (elastomers). To gain a better understanding of the role of constitutive relationships in determining material responses under loads we compare three different types of instabilities (two in compression, one in extension) in hyperelasticity for various forms of strain energy functions typically used for elastomers and for soft tissues. Surprisingly, we find that the strain-hardening property of soft tissues does not always stabilize the material. In particular we show that the stability analyses for a compressed half-space and for a compressed spherical thick shell can lead to opposite conclusions: a soft tissue material is more stable than an elastomer in the former case and less stable in the latter case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.4664v1.pdf"}
{"id": "0711.4712", "abstract": "  The optical implementation of the recently proposed unambiguous identification of coherent states is presented. Our system works as a programmable discriminator between two, in general non-orthogonal weak coherent states. The principle of operation lies in the interference of three light beams - two program states and one unknown coherent state which can be equal to whichever of the two program states. The experiment is based on fiber optics. Its results confirm theoretical predictions and the experimental setup can be straightforwardly extended for higher numbers of program states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.4712v2.pdf"}
{"id": "0712.1628", "abstract": "  Many schemes to realize quantum state transfer in spin chains are not robust to random fluctuations in the spin-spin coupling strength. In efforts to achieve robust quantum state transfer, an adiabatic quantum population transfer scheme is proposed in this study. The proposed scheme makes use of a slowly moving external parabolic potential and is qualitatively explained in terms of the adiabatic following of a quantum state with a moving separatrix structure in the classical phase space of a pendulum analogy. Detailed aspects of our adiabatic population transfer scheme, including its robustness, is studied computationally. Applications of our adiabatic scheme in quantum information transfer are also discussed, with emphasis placed on the usage of a dual spin chain to encode quantum phases. The results should also be useful for the control of electron tunneling in an array of quantum dots. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.1628v1.pdf"}
{"id": "0801.0113", "abstract": "  We present the first experimental evidence for the existence of strongly localized photonic modes due to random two dimensional fluctuations in the dielectric constant. In one direction, the modes are trapped by ordered Bragg reflecting mirrors of a planar, one wavelength long, microcavity. In the cavity plane, they are localized by disorder, which is due to randomness in the position, composition and sizes of quantum dots located in the anti-node of the cavity. We extend the theory of disorder induced strong localization of electron states to optical modes and obtain quantitative agreement with the main experimental observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.0113v4.pdf"}
{"id": "0801.0606", "abstract": "  A model for epidemics on an adaptive network is considered. Nodes follow an SIRS (susceptible-infective-recovered-susceptible) pattern. Connections are rewired to break links from non-infected nodes to infected nodes and are reformed to connect to other non-infected nodes, as the nodes that are not infected try to avoid the infection. Monte Carlo simulation and numerical solution of a mean field model are employed. The introduction of rewiring affects both the network structure and the epidemic dynamics. Degree distributions are altered, and the average distance from a node to the nearest infective increases. The rewiring leads to regions of bistability where either an endemic or a disease-free steady state can exist. Fluctuations around the endemic state and the lifetime of the endemic state are considered. The fluctuations are found to exhibit power law behavior. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.0606v1.pdf"}
{"id": "0801.0934", "abstract": "  It has been revealed by mean-field theories and computer simulations that the nature of the collapse transition of a polymer is influenced by its bending stiffness ϵ_ b. In two dimensions, a recent analytical work demonstrated that the collapse transition of a partially directed lattice polymer is always first-order as long as ϵ_ b is positive   [H. Zhou et al., Phys. Rev. Lett. 97, 158302 (2006)]. Here we employ Monte Carlo simulation to investigate systematically the effect of bending stiffness on the static properties of a 2D lattice polymer. The system's phase-diagram at zero force is obtained. Depending on ϵ_ b and the temperature T, the polymer can be in one of three phases: crystal, disordered globule, or swollen coil. The crystal-globule transition is discontinuous, the globule-coil transition is continuous. At moderate or high values of ϵ_ b the intermediate globular phase disappears and the polymer has only a discontinuous crystal-coil transition. When an external force is applied, the force-induced collapse transition will either be continuous or discontinuous, depending on whether the polymer is originally in the globular or the crystal phase at zero force. The simulation results also demonstrate an interesting scaling behavior of the polymer at the force-induced globule-coil transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.0934v1.pdf"}
{"id": "0801.2406", "abstract": "  We investigate the collective aspects of Rydberg excitation in ultracold mesoscopic systems. Strong interactions between Rydberg atoms influence the excitation process and impose correlations between excited atoms. The manifestations of the collective behavior of Rydberg excitation are the many-body Rabi oscillations, spatial correlations between atoms as well as the fluctuations of the number of excited atoms. We study these phenomena in detail by numerically solving the many-body Schrëdinger equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.2406v1.pdf"}
{"id": "0801.3386", "abstract": "  The mass structure of hadron multiplets is understood to imply the inexactness of SU(3) symmetry. Here we show that these symmetry broken mass splittings amongst baryon and meson multiplet members are close integral multiples of the mass difference between a neutral pion and a muon, the first excitation within the elementary particle mass spectrum. This is found to be equally true for the mass intervals amongst the particles belonging to the multiplets having different spin and parity characteristics. The results reinforce our earlier contention that the mass difference between a neutral pion and a muon is of fundamental importance to the elementary particle mass distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.3386v3.pdf"}
{"id": "0801.3688", "abstract": "  We study the ground state properties of a one-dimensional Bose gas with N-body attractive contact interactions. By using the explicit form of the bright soliton solution of a generalized nonlinear Schroedinger equation, we compute the chemical potential and the ground state energy. For N=3, a localized soliton wave-function exists only for a critical value of the interaction strength: in this case the ground state has an infinite degeneracy that can be parameterized by the chemical potential. The stabilization of the bright soliton solution by an external harmonic trap is also discussed, and a comparison with the effect of N-body attractive contact interactions in higher dimensions is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.3688v1.pdf"}
{"id": "0802.0356", "abstract": "  We predict various detectable mechanical responses to the presence of local DNA defects which are defined as short DNA segments exhibiting mechanical properties obviously different from the 50 nm persistence length based semiflexible polymer model. The defects discussed are kinks and flexible hinges either permanently fixed on DNA or thermally excited. Their effects on extension shift, the effective persistence length, the end-to-end distance distribution, and the cyclization probability are computed using a transfer-matrix method. Our predictions will be useful in future experimental designs to study DNA nicks or mismatch base pairs, mechanics of specific DNA sequences, and specific DNA-protein interaction using magnetic tweezer, fluorescence resonance energy transfer or plasmon resonance technique, and the traditional biochemistry cyclization probability measurements. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.0356v2.pdf"}
{"id": "0802.0568", "abstract": "  We study the baryon vertex (BV) in the presence of medium using DBI action and the force balance condition between BV and the probe branes. We note that a stable BV configuration exists only in some of the confining backgrounds. For the system of finite density, the issue is whether there is a canonical definition for the baryon mass in the medium. In this work, we define it as the energy of the deformed BV satisfying the force balance condition (FBC) with the probe brane. With FBC, lengths of the strings attached to the BV tend to be zero while the compact branes are enlongated to mimic the string. We attribute the deformation energy of the probe brane to the baryon-baryon interaction. We show that for a system with heavy quarks the baryon mass drops monotonically as a function of density while it has minimum in case of light quark system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.0568v3.pdf"}
{"id": "0802.1610", "abstract": "  We study the nonlinear dynamics of collective excitation in a N-site XXZ quantum spin chain, which is manipulated by an oblique magnetic field. We show that, when the tilted field is applied along the magic angle θ_0 =±arccos√(1/3), the anisotropic Heisenberg spin chain becomes isotropic and thus an free propagating spin wave is stimulated. And in the regime of the tilted angle larger and smaller then the magic angle, two types of nonlinear excitations appear, which are bright soliton and dark soliton. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.1610v4.pdf"}
{"id": "0802.4322", "abstract": "  The rapid TeV γ-ray variability detected in the well-known nearby radio galaxy M87 implies an extremely compact emission region (5-10 Schwarzschild radii) near the horizon of the supermassive black hole in the galactic center. TeV photons are affected by dilution due to interaction with the radiation field of the advection-dominated accretion flow (ADAF) around the black hole, and can thus be used to probe the innermost regions around the black hole. We calculate the optical depth of the ADAF radiation field to the TeV photons and find it strongly depends on the spin of the black hole. We find that transparent radii of 10 TeV photons are of 5R_ S and 13R_ S for the maximally rotating and non-rotating black holes, respectively. With the observations, the calculated transparent radii strongly suggest the black hole is spinning fast in the galaxy. TeV photons could be used as a powerful diagnostic for estimating black hole spins in galaxies in the future. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.4322v1.pdf"}
{"id": "0803.1640", "abstract": "  Upcoming Weak Lensing (WL) surveys can be used to constrain Dark Energy (DE) properties, namely if tomographic techniques are used to improve their sensitivity. In this work, we use a Fisher matrix technique to compare the power of CMB anisotropy and polarization data with tomographic WL data, in constraining DE parameters. Adding WL data to available CMB data improves the detection of all cosmological parameters, but the impact is really strong when DE–DM coupling is considered, as WL tomography can then succeed to reduce the errors on some parameters by factors >10. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.1640v2.pdf"}
{"id": "0803.1707", "abstract": "  We have carried out a Schrodinger functional (SF) calculation for the SU(3) lattice gauge theory with two flavors of Wilson fermions in the sextet representation of the gauge group. We find that the discrete beta function, which governs the change in the running coupling under a discrete change of spatial scale, changes sign when the SF renormalized coupling is in the neighborhood of g^2=2.0. The simplest explanation is that the theory has an infrared-attractive fixed point, but more complicated possibilities are allowed by the data. While we compare rescalings by factors of 2 and 4/3, we work at a single lattice spacing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.1707v2.pdf"}
{"id": "0803.2732", "abstract": "  The collective behavior of molecular motor proteins have been investigated in the literature using models to describe the long-time dynamics of a unidimensional continuum motor distribution. Here, we consider the phenomena related to the transport of particles (vesicles, organelles, virus, etc) in the realm of these continuum motor systems. We argue that cargo movement may result from its ability to perturb the existing motor distribution and to surf at the resulting shock waves separating regions of different motor densities within the transient regime. In this case, the observed bidirectionality of cargo movement is naturally associated with reversals of shocks directions. Comparison of the quantitative results predicted by this model with available data for cargo velocity allows us to suggest that geometrical characteristics of the transported particle shall determine the extension and intensity of the perturbation it produces and thus, its dynamics. Possible implications of these ideas to virus movement at the cell body are discussed in connection with their distinguished morphological characteristics. Key words: collective effects of molecular motors; cargo transport; non-linear partial differential equations; shock waves. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0803/0803.2732v1.pdf"}
{"id": "0804.2565", "abstract": "  The excitation of the electronic system induced by the adsorption of a hydrogen atom on the (111) surfaces of copper and silver is investigated using the time-dependent, mean-field Newns-Anderson model. Parameters for the model are obtained by fitting to density functional theory calculations, allowing the charge and energy transfer between adsorbate and surface to be calculated, together with the spectrum of electronic excitations. These results are used to make direct comparisons with experimental measurements of chemicurrents, yielding good agreement for both the magnitude of the current and the ratio of the currents for H and D adsorption. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.2565v1.pdf"}
{"id": "0804.3472", "abstract": "  We consider sputtering of dust grains, believed to be formed in cooling supernovae ejecta, under the influence of reverse shocks. In the regime of self-similar evolution of reverse shocks, we can follow the evolution of ejecta density and temperature analytically as a function of time in different parts of the ejecta, and calculate the sputtering rate of graphite and silicate grains embedded in the ejecta as they encounter the reverse shock. Through analytic (1D) calculations, we find that a fraction of dust mass (1–20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.3472v1.pdf"}
{"id": "0804.3526", "abstract": "  We outline a scenario which traces a direct path from freely-floating nebula particles to the first 10-100km-sized bodies in the terrestrial planet region, producing planetesimals which have properties matching those of primitive meteorite parent bodies. We call this \"primary accretion\". The scenario draws on elements of previous work, and introduces a new critical threshold for planetesimal formation. We presume the nebula to be weakly turbulent, which leads to dense concentrations of aerodynamically size-sorted particles having properties like those observed in chondrites. The fractional volume of the nebula occupied by these dense zones or clumps obeys a probability distribution as a function of their density, and the densest concentrations have particle mass density 100 times that of the gas. However, even these densest clumps are prevented by gas pressure from undergoing gravitational instability in the traditional sense (on a dynamical timescale). While in this state of arrested development, they are susceptible to disruption by the ram pressure of the differentially orbiting nebula gas. However, self-gravity can preserve sufficiently large and dense clumps from ram pressure disruption, allowing their entrained particles to sediment gently but inexorably towards their centers, producing 10-100 km \"sandpile\" planetesimals. Localized radial pressure fluctuations in the nebula, and interactions between differentially moving dense clumps, will also play a role that must be allowed for in future studies. The scenario is readily extended from meteorite parent bodies to primary accretion throughout the solar system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.3526v1.pdf"}
{"id": "0804.3547", "abstract": "  Molecular dynamics simulations of 3C-SiC have been performed as a function of pressure and temperature. These simulations treat both electrons and atomic nuclei by quantum mechanical methods. While the electronic structure of the solid is described by an efficient tight-binding Hamiltonian, the nuclei dynamics is treated by the path integral formulation of statistical mechanics. To assess the relevance of nuclear quantum effects, the results of quantum simulations are compared to others where either the Si nuclei, the C nuclei or both atomic nuclei are treated as classical particles. We find that the experimental thermal expansion of 3C-SiC is realistically reproduced by our simulations. The calculated bulk modulus of 3C-SiC and its pressure derivative at room temperature show also good agreement with the available experimental data. The effect of the electron-phonon interaction on the direct electronic gap of 3C-SiC has been calculated as a function of temperature and related to results obtained for bulk diamond and Si. Comparison to available experimental data shows satisfactory agreement, although we observe that the employed tight-binding model tends to overestimate the magnitude of the electron-phonon interaction. The effect of treating the atomic nuclei as classical particles on the direct gap of 3C-SiC has been assessed. We find that non-linear quantum effects related to the atomic masses are particularly relevant at temperatures below 250 K. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0804/0804.3547v1.pdf"}
{"id": "0805.0637", "abstract": "  We have studied the radial distribution of the early (E/S0) and late (S/Irr) types of satellites around bright host galaxies. We made a volume-limited sample of 4,986 satellites brighter than M_r = -18.0 associated with 2,254 hosts brighter than M_r =-19.0 from the SDSS DR5 sample. The morphology of satellites is determined by an automated morphology classifier, but the host galaxies are visually classified. We found segregation of satellite morphology as a function of the projected distance from the host galaxy. The amplitude and shape of the early-type satellite fraction profile are found to depend on the host luminosity. This is the morphology-radius/density relation at the galactic scale. There is a strong tendency for morphology conformity between the host galaxy and its satellites. The early-type fraction of satellites hosted by early-type galaxies is systematically larger than that of late-type hosts, and is a strong function of the distance from the host galaxies. Fainter satellites are more vulnerable to the morphology transformation effects of hosts. Dependence of satellite morphology on the large-scale background density was detected. The fraction of early-type satellites increases in high density regions for both early and late-type hosts. It is argued that the conformity in morphology of galactic satellite system is mainly originated by the hydrodynamical and radiative effects of hosts on satellites. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.0637v2.pdf"}
{"id": "0805.1093", "abstract": "  Recently, it has been demonstrated that the chemical composition of jets in heavy ion collisions is significantly altered compared to jets in the vacuum. This signal can be used to probe the medium formed in nuclear collisions. In this study we investigate the possibility that fast light quarks and gluons can convert to heavy quarks when passing through a quark gluon plasma. We study the rate of light to heavy jet conversions in a consistent Fokker-Planck framework and investigate their impact on the production of high-p_T charm and bottom quarks at RHIC and LHC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.1093v1.pdf"}
{"id": "0805.1447", "abstract": "  The relationships between braid ordering and the geometry of its closure is studied. We prove that if an essential closed surface F in the complements of closed braid has relatively small genus with respect to the Dehornoy floor of the braid, F is circular-foliated in a sense of Birman-Menasco's Braid foliation theory. As an application of the result, we prove that if Dehornoy floor of braids are larger than three, Nielsen-Thurston classification of braids and the geometry of their closure's complements are in one-to-one correspondence. Using this result, we construct infinitely many hyperbolic knots explicitly from pseudo-Anosov element of mapping class groups. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.1447v2.pdf"}
{"id": "0805.2384", "abstract": "  CLIO (Cryogenic Laser Interferometer Observatory) is a Japanese gravitational wave detector project. One of the main purposes of CLIO is to demonstrate thermal-noise suppression by cooling mirrors for a future Japanese project, LCGT (Large-scale Cryogenic Gravitational Telescope). The CLIO site is in Kamioka mine, as is LCGT. The progress of CLIO between 2005 and 2007 (room- and cryogenic-temperature experiments) is introduced in this article. In a room-temperature experiment, we made efforts to improve the sensitivity. The current best sensitivity at 300 K is about 6 × 10^-21 /√( Hz) around 400 Hz. Below 20 Hz, the strain (not displacement) sensitivity is comparable to that of LIGO, although the baselines of CLIO are 40-times shorter (CLIO: 100m, LIGO: 4km). This is because seismic noise is extremely small in Kamioka mine. We operated the interferometer at room temperature for gravitational wave observations. We obtained 86 hours of data. In the cryogenic experiment, it was confirmed that the mirrors were sufficiently cooled (14 K). However, we found that the radiation shield ducts transferred 300K radiation into the cryostat more effectively than we had expected. We observed that noise caused by pure aluminum wires to suspend a mirror was suppressed by cooling the mirror. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.2384v1.pdf"}
{"id": "0805.2741", "abstract": "  Energy transfer within photosynthetic systems can display quantum effects such as delocalized excitonic transport. Recently, direct evidence of long-lived coherence has been experimentally demonstrated for the dynamics of the Fenna-Matthews-Olson (FMO) protein complex [Engel et al., Nature 446, 782 (2007)]. However, the relevance of quantum dynamical processes to the exciton transfer efficiency is to a large extent unknown. Here, we develop a theoretical framework for studying the role of quantum interference effects in energy transfer dynamics of molecular arrays interacting with a thermal bath within the Lindblad formalism. To this end, we generalize continuous-time quantum walks to non-unitary and temperature-dependent dynamics in Liouville space derived from a microscopic Hamiltonian. Different physical effects of coherence and decoherence processes are explored via a universal measure for the energy transfer efficiency and its susceptibility. In particular, we demonstrate that for the FMO complex an effective interplay between free Hamiltonian and thermal fluctuations in the environment leads to a substantial increase in energy transfer efficiency from about 70", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.2741v2.pdf"}
{"id": "0805.3297", "abstract": "  We present high resolution (R = 90,000) mid-infrared spectra of M dwarfs. The mid infrared region of the spectra of cool low mass stars contain pure rotational water vapour transitions that may provide us with a new methodology in the determination of the effective temperatures for low mass stars. We identify and assign water transitions in these spectra and determine how sensitive each pure rotational water transition is to small (25 K) changes in effective temperature. We find that, of the 36 confirmed and assigned pure rotational water transitions, at least 10 should be sensitive enough to be used as temperature indicators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.3297v1.pdf"}
{"id": "0806.2177", "abstract": "  We study the absorption probability and Hawking radiation of the scalar field in the rotating Gödel black hole in minimal five-dimensional gauged supergravity. We find that Gödel parameter j imprints in the greybody factor and Hawking radiation. It plays a different role from the angular momentum of the black hole in the Hawking radiation and super-radiance. These information can help us know more about rotating Gödel black holes in minimal five-dimensional gauged supergravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.2177v2.pdf"}
{"id": "0806.2422", "abstract": "  We study an inflationary scenario with a vector impurity. We show that the universe undergoes anisotropic inflationary expansion due to a preferred direction determined by the vector. Using the slow-roll approximation, we find a formula to determine anisotropy of the inflationary universe. We discuss possible observable predictions of this scenario. In particular, it is stressed that primordial gravitational waves can be induced from curvature perturbations. Hence, even in low scale inflation, a sizable amount of primordial gravitational waves may be produced during inflation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.2422v3.pdf"}
{"id": "0806.2694", "abstract": "  The scale invariance of natural images suggests an analogy to the statistical mechanics of physical systems at a critical point. Here we examine the distribution of pixels in small image patches and show how to construct the corresponding thermodynamics. We find evidence for criticality in a diverging specific heat, which corresponds to large fluctuations in how \"surprising\" we find individual images, and in the quantitative form of the entropy vs. energy. The energy landscape derived from our thermodynamic framework identifies special image configurations that have intrinsic error correcting properties, and neurons which could detect these features have a strong resemblance to the cells found in primary visual cortex. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.2694v1.pdf"}
{"id": "0806.2837", "abstract": "  Motivated by recent DNA-pulling experiments, we revisit the Poland-Scheraga model of melting a double-stranded polymer. We include distinct bending rigidities for both the double-stranded segments, and the single-stranded segments forming a bubble. There is also bending stiffness at the branch points between the two segment types. The transfer matrix technique for single persistent chains is generalized to describe the branching bubbles. Properties of spherical harmonics are then exploited in truncating and numerically solving the resulting transfer matrix. This allows efficient computation of phase diagrams and force-extension curves (isotherms). While the main focus is on exposition of the transfer matrix technique, we provide general arguments for a reentrant melting transition in stiff double strands. Our theoretical approach can also be extended to study polymers with bubbles of any number of strands, with potential applications to molecules such as collagen. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.2837v1.pdf"}
{"id": "0806.2933", "abstract": "  This paper describes sufficient conditions to ensure the correct ergodicity of the Adaptive Metropolis (AM) algorithm of Haario, Saksman and Tamminen [Bernoulli 7 (2001) 223–242] for target distributions with a noncompact support. The conditions ensuring a strong law of large numbers require that the tails of the target density decay super-exponentially and have regular contours. The result is based on the ergodicity of an auxiliary process that is sequentially constrained to feasible adaptation sets, independent estimates of the growth rate of the AM chain and the corresponding geometric drift constants. The ergodicity result of the constrained process is obtained through a modification of the approach due to Andrieu and Moulines [Ann. Appl. Probab. 16 (2006) 1462–1505]. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.2933v5.pdf"}
{"id": "0807.0132", "abstract": "  We study the gravitational corrections to the Maxwell, Dirac and Klein-Gorden theories in the large extra dimension model in which the gravitons propagate in the (4+n)-dimensional bulk, while the gauge and matter fields are confined to the four-dimensional world. The corrections to the two-point Green's functions of the gauge and matter fields from the exchanges of virtual Kaluza-Klein gravitons are calculated in the gauge independent background field method. In the framework of effective field theory, we show that the modified one-loop renormalizable Lagrangian due to quantum gravitational effects contains a TeV scale Lee-Wick partner of every gauge and matter field as extra degrees of freedom in the theory. Thus the large extra dimension model of gravity provides a natural mechanism to the emergence of these exotic particles which were recently used to construct an extension of the Standard Model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.0132v2.pdf"}
{"id": "0807.0864", "abstract": "  We consider prescriptions that are free from the direct charge-screening effects by quark loops and enable us to clarify the confining nature of a vacuum. We test two candidates for an order parameter, a Polyakov loop (P) evaluated in zero-triality backgrounds and fermionic determinants (𝒟_1,2) with non-zero triality. Especially, 𝒟_1,2 has very small fluctuations in comparison with a Polyakov loop in zero-triality sector, and seems to well reflect the characteristic of a vacuum. Such prescriptions could be still usable for the clarification of the confinement property of a vacuum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.0864v2.pdf"}
{"id": "0807.1421", "abstract": "  A novel approach to solve the Faddeev equation for three-body scattering at arbitrary energies is proposed. This approach disentangles the complicated singularity structure of the free three-nucleon propagator leading to the moving and logarithmic singularities in standard treatments. The Faddeev equation is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial wave decomposition. In its simplest form the Faddeev equation for identical bosons, which we are using, is an integral equation in five variables, magnitudes of relative momenta and angles. The singularities of the free propagator and the deuteron propagator are now both simple poles in two different momentum variables, and thus can both be integrated with standard techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.1421v1.pdf"}
{"id": "0807.1888", "abstract": "  We introduce a minimal Agent Based Model with two classes of agents, fundamentalists (stabilizing) and chartists (destabilizing) and we focus on the essential features which can generate the stylized facts. This leads to a detailed understanding of the origin of fat tails and volatility clustering and we propose a mechanism for the self-organization of the market dynamics in the quasi-critical state. The stylized facts are shown to correspond to finite size effects which, however, can be active at different time scales. This implies that universality cannot be expected in describing these properties in terms of effective critical exponents. The introduction of a threshold in the agents' action (small price fluctuations lead to no-action) triggers the self-organization towards the quasi-critical state. Non-stationarity in the number of active agents and in their action plays a fundamental role. The model can be easily generalized to more realistic variants in a systematic way. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.1888v1.pdf"}
{"id": "0807.2239", "abstract": "  Over the last 15 years, around a hundred very young stars have been observed in the central parsec of our Galaxy. While the presence of young stars forming one or two stellar disks at approx. 0.1 pc from the supermassive black hole (SMBH) can be understood through star formation in accretion disks, the origin of the S stars observed a factor of 10 closer to the SMBH has remained a major puzzle. Here we show the S stars to be a natural consequence of dynamical interaction of two stellar disks at larger radii. Due to precession and Kozai interaction, individual stars achieve extremely high eccentricities at random orientation. Stellar binaries on such eccentric orbits are disrupted due to close passages near the SMBH, leaving behind a single S star on a much tighter orbit. The remaining star may be ejected from the vicinity of the SMBH, thus simultaneously providing an explanation for the observed hypervelocity stars in the Milky Way halo. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.2239v2.pdf"}
{"id": "0807.3829", "abstract": "  We derive the Fundamental Plane (FP) relation for a sample of 1430 early-type galaxies in the optical (r band) and the near-infrared (K band), by combining SDSS and UKIDSS data. With such a large, homogeneous dataset, we are able to assess the dependence of the FP on the waveband. Our analysis indicates that the FP of luminous early-type galaxies is essentially waveband independent, with its coefficients increasing at most by 8", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.3829v1.pdf"}
{"id": "0807.4533", "abstract": "  We present theoretical modelling for the very rapid TeV variability of PKS 2155–304 observed recently by the H.E.S.S. experiment. To explain the light-curve, where at least five flaring events were well observed, we assume five independent components of a jet that are characterized by slightly different physical parameters. An additional, significantly larger component is used to explain the emission of the source at long time scales. This component dominates the emission in the X-ray range, whereas the other components are dominant in the TeV range. The model used for our simulation describes precisely the evolution of the particle energy spectrum inside each component and takes into account light travel time effects. We show that a relatively simple synchrotron self-Compton scenario may explain this very rapid variability. Moreover, we find that absorption of the TeV emission inside the components due to the pair creation process is negligible. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.4533v1.pdf"}
{"id": "0808.1127", "abstract": "  We calculate correlation functions of the energy-momentum tensor in the vicinity of the deconfinement phase transition of (3+1)-dimensional SU(2) gauge theory and discuss their critical behavior in the vicinity of the second order deconfinement transition. We show that correlation functions of the trace of the energy momentum tensor diverge uniformly at the critical point in proportion to the specific heat singularity. Correlation functions of the pressure, on the other hand, stay finite at the critical point. We discuss the consequences of these findings for the analysis of transport coefficients, in particular the bulk viscosity, in the vicinity of a second order phase transition point. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.1127v1.pdf"}
{"id": "0808.1218", "abstract": "  In previous studies, we have examined a resonant excitation of disk oscillations in deformed disks. In these studies, however, mathematical treatment around the resonant points was not rigorous. In this paper the inadequate point is corrected, with no essential changes in the final results. For this excitation process to work, disks must be general relativistic. That is, the non-monotonic radial distribution of epicyclic frequency in relativistic disks is essential for the presence of the resonance and for trapping of oscillations. In this paper, the growth rate of resonant oscillations is expressed in a form more suitable for numerical calculations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.1218v1.pdf"}
{"id": "0808.2809", "abstract": "  Systems of particles in a confining potential exhibit a spatially dependent density which fundamentally alters the nature of phase transitions that occur. A specific instance of this situation, which is being extensively explored currently, concerns the properties of ultra-cold, optically trapped atoms. Of interest is how the superfluid-insulator transition is modified by the inhomogeneity, and, indeed, the extent to which a sharp transition survives at all. This paper explores a classical analog of these systems, the Blume-Capel model with a spatially varying single ion anisotropy and/or temperature gradient. We present results both for the nature of the critical properties and for the validity of the \"local density approximation\" which is often used to model the inhomogeneous case. We compare situations when the underlying uniform transition is first and second order. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.2809v1.pdf"}
{"id": "0808.3368", "abstract": "  We numerically evaluate the Casimir interaction energy for configurations involving two perfectly conducting eccentric cylinders and a cylinder in front of a plane. We consider in detail several special cases. For quasi-concentric cylinders, we analyze the convergence of a perturbative evaluation based on sparse matrices. For concentric cylinders, we obtain analytically the corrections to the proximity force approximation up to second order, and we present an improved numerical procedure to evaluate the interaction energy at very small distances. Finally, we consider the configuration of a cylinder in front of a plane. We first show numerically that, in the appropriate limit, the Casimir energy for this configuration can be obtained from that of two eccentric cylinders. Then we compute the interaction energy at small distances, and compare the numerical results with the analytic predictions for the first order corrections to the proximity force approximation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.3368v2.pdf"}
{"id": "0809.1434", "abstract": "  We have used the Parkes Multibeam system and the Sloan Digital Sky Survey (SDSS) to assemble a sample of 195 galaxies selected originally from their HI signature to avoid biases against unevolved or low surface brightness objects. For each source 9 intrinsic properties are measured homogeneously, as well as inclination and an optical spectrum. The sample, which should be almost entirely free of either misidentification or confusion, includes a wide diversity of galaxies ranging from inchoate, low surface brightness dwarfs to giant spirals. Despite this diversity there are 5 clear correlations among their properties. They include a common dynamical mass-to-light ratio within their optical radii, a correlation between surface-brightness and Luminosity and a common HI surface-density. Such correlation should provide strong constrains on models of galaxy formation and evolution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.1434v1.pdf"}
{"id": "0809.1578", "abstract": "  In many epidemiological models a nonlinear transmission function is used in the form of power law relationship. It is constantly argued that such form reflects population heterogeneities including differences in the mixing pattern, susceptibility, and spatial patchiness, although the function itself is considered phenomenological. Comparison with large-scale simulations show that models with this transmission function accurately approximate data from highly heterogeneous sources. In this note we provide a mechanistic derivation of the power law transmission function, starting with a simple heterogeneous susceptibles–infectives (SI) model, which is based on a standard mass action assumption. We also consider the simplest SI model with separable mixing and compare our results with known results from the literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.1578v1.pdf"}
{"id": "0809.2844", "abstract": "  Spherical truncations of Coulomb interactions in standard models for water permit efficient molecular simulations and can give remarkably accurate results for the structure of the uniform liquid. However truncations are known to produce significant errors in nonuniform systems, particularly for electrostatic properties. Local molecular field (LMF) theory corrects such truncations by use of an effective or restructured electrostatic potential that accounts for effects of the remaining long-ranged interactions through a density-weighted mean field average and satisfies a modified Poisson's equation defined with a Gaussian-smoothed charge density. We apply LMF theory to three simple molecular systems that exhibit different aspects of the failure of a naive application of spherical truncations – water confined between hydrophobic walls, water confined between atomically-corrugated hydrophilic walls, and water confined between hydrophobic walls with an applied electric field. Spherical truncations of 1/r fail spectacularly for the final system in particular, and LMF theory corrects the failings for all three. Further, LMF theory provides a more intuitive way to understand the balance between local hydrogen bonding and longer-ranged electrostatics in molecular simulations involving water. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.2844v1.pdf"}
{"id": "0809.3096", "abstract": "  We demonstrate that the angular distribution of photoelectrons from a strongly polarizable target exposed to a laser field can deviate noticeably from the prediction of conventional theory. Even within the dipole-photon approximation the profile of distribution is modified due to the action of the field of alternating dipole moment induced at the residue by the laser field. This effect, being quite sensitive to the dynamic polarizability of the residue and to its geometry, depends also on the intensity and frequency of the laser field. Numerical results, presented for sodium cluster anions, demonstrate that dramatic changes to the profile occur for the photon energies in vicinities of the plasmon resonances, where the effect is enhanced due to the increase in the residue polarizability. Strong modifications of the characteristics of a single-photon ionization process can be achieved by applying laser fields of comparatively low intensities I_0 ∼10^10-10^11 W/cm^2. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.3096v1.pdf"}
{"id": "0809.3491", "abstract": "  We study the correspondence between field theoretic and holographic dark energy density of the universe with the modified Chaplygin gas (MCG) respectively both in a flat and non-flat FRW universe. We present an equivalent representation of the MCG with a homogeneous minimally coupled scalar field by constructing the corresponding potential. A new scalar field potential is obtained here which is physically realistic and important for cosmological model building. In addition we also present holographic dark energy model described by the MCG. The dynamics of the corresponding holographic dark energy field is determined by reconstructing the potential in a non-flat universe. The stability of the holographic dark energy in this case in a non-flat universe is also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.3491v1.pdf"}
{"id": "0809.4005", "abstract": "  We study energy dissipation and heating by supersonic MHD turbulence in molecular clouds using Athena, a new higher-order Godunov code. We analyze the dependence of the saturation amplitude, energy dissipation characteristics, power spectra, sonic scaling, and indicators of intermittency in the turbulence on factors such as the magnetic field strength, driving scale, energy injection rate, and numerical resolution. While convergence in the energies is reached at moderate resolutions, we find that the power spectra require much higher resolutions that are difficult to obtain. In a 1024^3 hydro run, we find a power law relationship between the velocity dispersion and the spatial scale on which it is measured, while for an MHD run at the same resolution we find no such power law. The time-variability and temperature intermittency in the turbulence both show a dependence on the driving scale, indicating that numerically driving turbulence by an arbitrary mechanism may not allow a realistic representation of these properties. We also note similar features in the power spectrum of the compressive component of velocity for supersonic MHD turbulence as in the velocity spectrum of an initially-spherical MHD blast wave, implying that the power law form does not rule out shocks, rather than a turbulent cascade, playing a significant role in the regulation of energy transfer between spatial scales. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.4005v1.pdf"}
{"id": "0809.4080", "abstract": "  The binding of a transcription factor (TF) to a DNA operator site can initiate or repress the expression of a gene. Computational prediction of sites recognized by a TF has traditionally relied upon knowledge of several cognate sites, rather than an ab initio approach. Here, we examine the possibility of using structure-based energy calculations that require no knowledge of bound sites but rather start with the structure of a protein-DNA complex. We study the PurR E. coli TF, and explore to which extent atomistic models of protein-DNA complexes can be used to distinguish between cognate and non-cognate DNA sites. Particular emphasis is placed on systematic evaluation of this approach by comparing its performance with bioinformatic methods, by testing it against random decoys and sites of homologous TFs. We also examine a set of experimental mutations in both DNA and the protein. Using our explicit estimates of energy, we show that the specificity for PurR is dominated by direct protein-DNA interactions, and weakly influenced by bending of DNA. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.4080v1.pdf"}
{"id": "0810.0128", "abstract": "  We explore the device potential of tunable-gap bilayer graphene FET exploiting the possibility of opening a bandgap in bilayer graphene by applying a vertical electric field via independent gate operation. We evaluate device behavior using atomistic simulations based on the self-consistent solution of the Poisson and Schroedinger equations within the NEGF formalism. We show that the concept works, but bandgap opening is not strong enough to suppress band-to-band tunneling in order to obtain a sufficiently large Ion/Ioff ratio for CMOS device operation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.0128v1.pdf"}
{"id": "0810.0815", "abstract": "  The functional method to derive the fractional Fokker-Planck equation for probability distribution from the Langevin equation with Levy stable noise is proposed. For the Cauchy stable noise we obtain the exact stationary probability density function of Levy flights in different smooth potential profiles. We find confinement of the particle in the superdiffusion motion with a bimodal stationary distribution for all the anharmonic symmetric monostable potentials investigated. The stationary probability density functions show power-law tails, which ensure finiteness of the variance. By reviewing recent results on these statistical characteristics, the peculiarities of Levy flights in comparison with ordinary Brownian motion are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.0815v1.pdf"}
{"id": "0810.2029", "abstract": "  The young sigma Orionis cluster in the Orion Belt is an incomparable site for studying the formation and evolution of high-mass, solar-like, and low-mass stars, brown dwarfs, and substellar objects below the deuterium burning mass limit. The first version of the Mayrit catalogue was a thorough data compilation of cluster members and candidates, which is regularly used by many authors of different disciplines. I show two new applications of the catalogue and advance preliminar results on very wide binarity and the initial mass function from 18 to 0.035 Msol in sigma Orionis. The making-up of a new version of the Mayrit catalogue with additional useful data is in progress. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.2029v1.pdf"}
{"id": "0810.3088", "abstract": "  We construct quantum field theory in an analogue curved spacetime in Bose-Einstein condensates based on the Bogoliubov-de Gennes equations, by exactly relating quantum particles in curved spacetime with Bogoliubov quasiparticle excitations in Bose-Einstein condensates. Here, we derive a simple formula relating the two, which can be used to calculate the particle creation spectrum by solving the time-dependent Bogoliubov-de Gennes equations. Using our formulation, we numerically investigate particle creation in an analogue expanding Universe which can be expressed as Bogoliubov quasiparticles in an expanding Bose-Einstein condensate. We obtain its spectrum, which follows the thermal Maxwell-Boltzmann distribution, the temperature of which is experimentally attainable. Our derivation of the analogy is useful for general Bose-Einstein condensates and not limited to homogeneous ones, and our simulation is the first example of particle creations by solving the Bogoliubov-de Gennes equation in an inhomogeneous condensate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.3088v2.pdf"}
{"id": "0810.3393", "abstract": "  The primary challenge of GOLF-NG (Global Oscillations at Low Frequency New Generation) is the detection of the low-frequency solar gravity and acoustic modes, as well as the possibility to measure the high-frequency chromospheric modes. On June 8th 2008, the first sunlight observations with the multichannel resonant GOLF-NG prototype spectrometer were obtained at the Observatorio del Teide (Tenerife). The instrument performs integrated (Sun-as-a-star), Doppler velocity measurements, simultaneously at eight different heights in the D1 sodium line profile, corresponding to photospheric and chromospheric layers of the solar atmosphere. In order to study its performances, to validate the conceived strategy, and to estimate the necessary improvements, this prototype has been running on a daily basis over the whole summer of 2008 at the Observatorio del Teide. We present here the results of the first GOLF-NG observations, clearly showing the characteristics of the 5-minute oscillatory signal at different heights in the solar atmosphere. We compare these signals with simultaneous observations from GOLF/SOHO and from the Mark-I instrument – a node of the BiSON network, operating at the same site. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.3393v1.pdf"}
{"id": "0810.3948", "abstract": "  LHC searches for new physics focus on combinations of hard physics objects. In this work we propose a qualitatively different soft signal for new physics at the LHC - the \"anomalous underlying event\". Every hard LHC event will be accompanied by a soft underlying event due to QCD and pile-up effects. Though it is often used for QCD and monte carlo studies, here we propose the incorporation of an underlying event analysis in some searches for new physics. An excess of anomalous underlying events may be a smoking-gun signal for particular new physics scenarios such as \"quirks\" or \"hidden valleys\" in which large amounts of energy may be emitted by a large multiplicity of soft particles. We discuss possible search strategies for such soft diffuse signals in the tracking system and calorimetry of the LHC experiments. We present a detailed study of the calorimetric signal in a concrete example, a simple quirk model motivated by folded supersymmetry. In these models the production and radiative decay of highly excited quirk bound states leads to an \"antenna pattern\" of soft unclustered energy. Using a dedicated simulation of a toy detector and a \"CMB-like\" multipole analysis we compare the signal to the expected backgrounds. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.3948v1.pdf"}
{"id": "0810.4194", "abstract": "  It is found that CP symmetry may be explicitly broken in the Higgs sector of a supersymmetric E_6 model with two extra neutral gauge bosons at the one-loop level. The phenomenology of the model, the Higgs sector in particular, is studied for a reasonable parameter space of the model, in the presence of explicit CP violation at the one-loop level. At least one of the neutral Higgs bosons of the model might be produced via the WW fusion process at the Large Hadron Collider. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.4194v2.pdf"}
{"id": "0811.0217", "abstract": "  Spiral wave, whose rotation center can be regarded as a point defect, widely exists in various two dimensional excitable systems. In this paper, by making use of Duan's topological current theory, we obtain the charge density of spiral waves and the topological inner structure of its topological charge. The evolution of spiral wave is also studied from the topological properties of a two-dimensional vector field. The spiral waves are found generating or annihilating at the limit points and encountering, splitting, or merging at the bifurcation points of the two-dimensional vector field. Some applications of our theory are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.0217v1.pdf"}
{"id": "0811.0222", "abstract": "  We analyze in the context of geometrothermodynamics a Legendre invariant metric structure in the equilibrium space of an ideal gas. We introduce the concept of thermodynamic geodesic as a succession of points, each corresponding to a state of equilibrium, so that the resulting curve represents a quasi-static process. A rigorous geometric structure is derived in which the thermodynamic geodesics at a given point split the equilibrium space into two disconnected regions separated by adiabatic geodesics. This resembles the causal structure of special relativity, which we use to introduce the concept of adiabatic cone for thermodynamic systems. This result might be interpreted as an alternative indication of the inter-relationship between relativistic physics and classical thermodynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.0222v2.pdf"}
{"id": "0811.0685", "abstract": "  We develop a general microscopic theory of dc Josephson effect in hybrid SNS structures with ballistic electrodes and spin-active NS interfaces. We establish a direct relation between the spectrum of Andreev levels and the Josephson current which contains complete information about non-trivial interplay between Andreev reflection and spin-dependent interface scattering. The system exhibits a rich structure of properties sensitive to spin-dependent barrier transmissions, spin-mixing angles, relative magnetization orientation of interfaces and the kinematic phase of scattered electrons. We analyze the current-phase relations and identify the conditions for the presence of a pi-junction state in the systems under consideration. We also analyze resonant enhancement of the supercurrent in gate-voltage-driven nanojunctions. As compared to the non-magnetic case, this effect can be strongly modified by spin-dependent scattering at NS interfaces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.0685v2.pdf"}
{"id": "0811.0746", "abstract": "  Very soon the LHC will provide beams for heavy ion collisions at 5.52 TeV/nucleon. This center-of-mass energy results in a large cross-section for producing high-E_T (> 50 GeV) jets that are distinct from the soft, underlying event. This brings with it the possibility of performing full jet reconstruction to directly study jet energy loss in the medium produced in heavy ion collisions. In this note, we present the current state of jet reconstruction performance studies in heavy ion events using the ATLAS detector. We also discuss the possibilities of energy loss measurements available with full jet reconstruction: single jet R_AA and di-jet and γ-jet correlations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.0746v1.pdf"}
{"id": "0811.1555", "abstract": "  Astrophysical and cosmological observations do not require the dark matter particles to be absolutely stable. If they are indeed unstable, their decay into positrons might occur at a sufficiently large rate to allow the indirect detection of dark matter through an anomalous contribution to the cosmic positron flux. In this paper we discuss the implications of the excess in the positron fraction recently reported by the PAMELA collaboration for the scenario of decaying dark matter. To this end, we have performed a model-independent analysis of possible signatures by studying various decay channels in the case of both a fermionic and a scalar dark matter particle. We find that the steep rise in the positron fraction measured by PAMELA at energies larger than 10 GeV can naturally be accommodated in several realizations of the decaying dark matter scenario. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.1555v1.pdf"}
{"id": "0811.1772", "abstract": "  Magnetic layers are narrow regions where the field direction changes sharply. They often occur in the association with neutral points of the magnetic field. We show that an organised field can produce these structures near a rotating black hole, and we identify them as potential sites of magnetic reconnection. To that end we study the field lines affected by the frame-dragging effect, twisting the magnetic structure and changing the position of neutral points. We consider oblique fields in vacuum. We also include the possibility of translational motion of the black hole which may be relevant when the black hole is ejected from the system. The model settings apply to the innermost regions around black holes with the ergosphere dominated by a super-equipartition magnetic field and loaded with a negligible gas content. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.1772v1.pdf"}
{"id": "0811.1834", "abstract": "  Drilling holes in a bulk high-Tc superconductor enhances the oxygen annealing and the heat exchange with the cooling liquid. However, drilling holes also reduces the amount of magnetic flux that can be trapped in the sample. In this paper, we use the Bean model to study the magnetization and the current line distribution in drilled samples, as a function of the hole positions. A single hole perturbs the critical current flow over an extended region that is bounded by a discontinuity line, where the direction of the current density changes abruptly. We demonstrate that the trapped magnetic flux is maximized if the center of each hole is positioned on one of the discontinuity lines produced by the neighbouring holes. For a cylindrical sample, we construct a polar triangular hole pattern that exploits this principle; in such a lattice, the trapped field is  20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.1834v1.pdf"}
{"id": "0811.2220", "abstract": "  We present spatially resolved 3 um spectra of Elias 1 obtained with an adaptive optics system. The central part of the disk is almost devoid of PAH emission at 3.3 um; it shows up only at 30 AU and beyond. The PAH emission extends up to 100 AU, at least to the outer boundary of our observation. The diamond emission, in contrast, is more centrally concentrated, with the column density peaked around 30 AU from the star. There are only three Herbig Ae/Be stars known to date that show diamond emission at 3.53 um. Two of them have low-mass companions likely responsible for the large X-ray flares observed toward the Herbig Ae/Be stars. We speculate on the origin of diamonds in circumstellar disks in terms of the graphitic material being transformed into diamond under the irradiation of highly energetic particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.2220v1.pdf"}
{"id": "0811.2275", "abstract": "  We propose a hole decomposition scheme to exactly solve a class of spin-1 quantum Ising models with transverse or longitudinal single-ion anisotropy. In this scheme, the spin-1 model is mapped onto a family of the S=1/2 transverse Ising models, characterized by the total number of holes. A recursion formula is derived for the partition function based on the reduced S=1/2 Ising model. This simplifies greatly the summation over all the hole configurations. It allows the thermodynamic quantities to be rigorously determined in the thermodynamic limit. The ground state phase diagram is determined for both the uniform and dimerized spin chains. The corresponding thermodynamic properties are calculated and discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.2275v2.pdf"}
{"id": "0812.0007", "abstract": "  We use high resolution cosmological hydrodynamical simulations to demonstrate that cold flow gas accretion, particularly along filaments, modifies the standard picture of gas accretion and cooling onto galaxy disks. In the standard picture, all gas is initially heated to the virial temperature of the galaxy as it enters the virial radius. Low mass galaxies are instead dominated by accretion of gas that stays well below the virial temperature, and even when a hot halo is able to develop in more massive galaxies there exist dense filaments that penetrate inside of the virial radius and deliver cold gas to the central galaxy. For galaxies up to  L*, this cold accretion gas is responsible for the star formation in the disk at all times to the present. Even for galaxies at higher masses, cold flows dominate the growth of the disk at early times. Within this modified picture, galaxies are able to accrete a large mass of cold gas, with lower initial gas temperatures leading to shorter cooling times to reach the disk. Although star formation in the disk is mitigated by supernovae feedback, the short cooling times allow for the growth of stellar disks at higher redshifts than predicted by the standard model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.0007v1.pdf"}
{"id": "0812.2786", "abstract": "  We study isospin effects in semi-peripheral collisions above the Fermi energy by considering the symmetric ^58Ni + ^58Ni and the asymmetric reactions ^58Ni + ^197Au over the incident energy range 52-74 A MeV. A microscopic transport model with two different parameterizations of the symmetry energy term is used to investigate the isotopic content of pre-equilibrium emission and the N/Z diffusion process. Simulations are also compared to experimental data obtained with the INDRA array and bring information on the degree of isospin equilibration observed in Ni + Au collisions. A better overall agreement between data and simulations is obtained when using a symmetry term which linearly increases with nuclear density. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.2786v1.pdf"}
{"id": "0812.2913", "abstract": "  Photo-heating associated with reionisation and kinetic feedback from core-collapse supernovae have previously been shown to suppress the high-redshift cosmic star formation rate. Here we investigate the interplay between photo-heating and supernova feedback using a set of cosmological, smoothed particle hydrodynamics simulations. We show that photo-heating and supernova feedback mutually amplify each other's ability to suppress the star formation rate. Our results demonstrate the importance of the simultaneous, non-independent inclusion of these two processes in models of galaxy formation to estimate the strength of the total negative feedback they exert. They may therefore be of particular relevance to semi-analytic models in which the effects of photo-heating and supernova feedback are implicitly assumed to act independently of each other. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.2913v2.pdf"}
{"id": "0812.3096", "abstract": "  One dimensional systems sometimes show pathologically slow decay of currents. This robustness can be traced to the fact that an integrable model is nearby in parameter space. In integrable models some part of the current can be conserved, explaining this slow decay. Unfortunately, although this conservation law is formally anticipated, in practice it has been difficult to find in concrete cases, such as the Heisenberg model. We investigate this issue both analytically and numerically and find that the appropriate conservation law can be a non-analytic combination of the known local conservation laws and hence is invisible to elementary assumptions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3096v1.pdf"}
{"id": "0812.3763", "abstract": "  Time-dependent speckle pattern of paraelectric barium titanate observed in a soft x-ray laser pump-probe measurement is theoretically investigated as a correlated optical response to the pump and probe pulses. The scattering probability is calculated based on a model with coupled soft x-ray photon and ferroelectric phonon mode. It is found that the speckle variation is related with the relaxation dynamics of ferroelectric clusters created by the pump pulse. Additionally, critical slowing down of cluster relaxation arises on decreasing temperature towards the paraelectric-ferroelectric transition temperature. Relation between critical slowing down, local dipole fluctuation and crystal structure are revealed by quantum Monte Carlo simulation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3763v2.pdf"}
{"id": "0812.3837", "abstract": "  We consider theories where the Standard Model (SM) neutrinos acquire masses through the seesaw mechanism at the weak scale. We show that in such a scenario, the requirement that any pre-existing baryon asymmetry, regardless of its origin, not be washed out leads to correlations between the pattern of SM neutrino masses and the spectrum of new particles at the weak scale, leading to definite predictions for the LHC. For type I seesaw models with a TeV scale Z' coupled to SM neutrinos, we find that for a normal neutrino mass hierarchy, at least one of the right-handed neutrinos must be `electrophobic', decaying with a strong preference into final states with muons and tauons rather than electrons. For inverted or quasi-degenerate mass patterns, on the other hand, we find upper bounds on the mass of at least one right-handed neutrino. In particular, for an inverted mass hierarchy, this bound is 1 TeV, while the corresponding upper limit in the quasi-degenerate case is 300 GeV. Similar results hold in type III seesaw models, albeit with somewhat more stringent bounds. For the Type II seesaw case with a weak scale SU(2) triplet Higgs, we again find that an interesting range of Higgs triplet masses is disallowed by these considerations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3837v2.pdf"}
{"id": "0812.5040", "abstract": "  Typical quantum communication schemes are such that to achieve perfect decoding the receiver must share a reference frame with the sender. Indeed, if the receiver only possesses a bounded-size quantum token of the sender's reference frame, then the decoding is imperfect, and we can describe this effect as a noisy quantum channel. We seek here to characterize the performance of such schemes, or equivalently, to determine the effective decoherence induced by having a bounded-size reference frame. We assume that the token is prepared in a special state that has particularly nice group-theoretic properties and that is near-optimal for transmitting information about the sender's frame. We present a decoding operation, which can be proven to be near-optimal in this case, and we demonstrate that there are two distinct ways of implementing it (corresponding to two distinct Kraus decompositions). In one, the receiver measures the orientation of the reference frame token and reorients the system appropriately. In the other, the receiver extracts the encoded information from the virtual subsystems that describe the relational degrees of freedom of the system and token. Finally, we provide explicit characterizations of these decoding schemes when the system is a single qubit and for three standard kinds of reference frame: a phase reference, a Cartesian frame (representing an orthogonal triad of spatial directions), and a reference direction (representing a single spatial direction). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.5040v2.pdf"}
{"id": "0901.0118", "abstract": "  This paper considers an amplify-and-forward relay network with fading states. Amplify-and-forward scheme (along with its variations) is the core mechanism for enabling cooperative communication in wireless networks, and hence understanding the network stability region under amplify-and-forward scheme is very important. However, in a relay network employing amplify-and-forward, the interaction between nodes is described in terms of real-valued “packets” (signals) instead of discrete packets (bits). This restrains the relay nodes from re-encoding the packets at desired rates. Hence, the stability analysis for relay networks employing amplify-and-forward scheme is by no means a straightforward extension of that in packet-based networks. In this paper, the stability region of a four-node relay network is characterized, and a simple throughput optimal algorithm with joint scheduling and rate allocation is proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.0118v2.pdf"}
{"id": "0901.0892", "abstract": "  We study Einstein static universes in the context of generic f(R) models. It is shown that Einstein static solutions exist for a wide variety of modified gravity models sourced by a barotropic perfect fluid with equation of state w=p/rho, but these solutions are always unstable to either homogeneous or inhomogeneous perturbations. Our general results are in agreement with specific models investigated in that past. We also discuss how our techniques can be applied to other scenarios in f(R) gravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.0892v3.pdf"}
{"id": "0901.3573", "abstract": "  We calculate the non-linear conductance of a quantum point contact using the non-equilibrium Greens function technique within the Hartree approximation of spinless electrons. We quantitative reproduce the 0.25-anomaly in the differential conductance (i.e. the lowest plateau at 0.25-0.3*2e^2/h) as well as an upward bending of higher conductance half-integer plateaus seen in the experiments, and relate these features to the non-linear screening and pinning effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.3573v1.pdf"}
{"id": "0901.3674", "abstract": "  We demonstrate how to directly study non-Abelian statistics for a wide class of exactly solvable many-body quantum systems. By employing exact eigenstates to simulate the adiabatic transport of a model's quasiparticles, the resulting Berry phase provides a direct demonstration of their non-Abelian statistics. We apply this technique to Kitaev's honeycomb lattice model and explicitly demonstrate the existence of non-Abelian Ising anyons confirming the previous conjectures. Finally, we present the manipulations needed to transport and detect the statistics of these quasiparticles in the laboratory. Various physically realistic system sizes are considered and exact predictions for such experiments are provided. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.3674v3.pdf"}
{"id": "0901.3885", "abstract": "  In this paper we study the influence of hard supersymmetry breaking terms in a N=1, d=4 supersymmetric model, in S^1× R^3 spacetime topology. It is found that for some interaction terms and for certain values of the couplings, supersymmetry is unbroken for small lengths of the compact radius, and breaks dynamically as the radius increases. Also for another class of interaction terms, when the radius is large supersymmetry is unbroken and breaks dynamically as the radius decreases. It is pointed out that the two phenomena have similarities with the theory of metastable vacua at finite temperature and with the inverse symmetry breaking of continuous symmetries at finite temperature (where the role of the temperature is played by the compact dimension's radius). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.3885v1.pdf"}
{"id": "0901.4549", "abstract": "  Molecular clouds are expected to emit non-thermal radiation due to cosmic ray interactions in the dense magnetized gas. Such emission is amplified if a cloud is located close to an accelerator of cosmic rays and if energetic particles can leave the accelerator site and diffusively reach the cloud. We consider here the situation in which a molecular cloud is located in the proximity of a supernova remnant which is efficiently accelerating cosmic rays and gradually releasing them in the interstellar medium. We calculate the multiwavelength spectrum from radio to gamma rays which is emerging from the cloud as the result of cosmic ray interactions. The total energy output is dominated by the gamma ray emission, which can exceed the emission in other bands by an order of magnitude or more. This suggests that some of the unidentified TeV sources detected so far, with no obvious or very weak counterparts in other wavelengths, might be in fact associated with clouds illuminated by cosmic rays coming from a nearby source. Moreover, under certain conditions, the gamma ray spectrum exhibit a concave shape, being steep at low energies and hard at high energies. This fact might have important implications for the studies of the spectral compatibility of GeV and TeV gamma ray sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.4549v1.pdf"}
{"id": "0901.4600", "abstract": "  This article reviews recent developments in quantum fluid dynamics and quantum turbulence (QT) for superfluid helium and atomic Bose-Einstein condensates. Quantum turbulence was discovered in superfluid ^4He in the 1950s, but the field moved in a new direction starting around the mid 1990s. Quantum turbulence is comprised of quantized vortices that are definite topological defects arising from the order parameter appearing in Bose-Einstein condensation. Hence QT is expected to yield a simpler model of turbulence than does conventional turbulence. A general introduction to this issue and a brief review of the basic concepts are followed by a description of vortex lattice formation in a rotating atomic Bose-Einstein condensate, typical of quantum fluid dynamics. Then we discuss recent developments in QT of superfluid helium such as the energy spectra and dissipative mechanisms at low temperatures, QT created by vibrating structures, and the visualization of QT. As an application of these ideas, we end with a discussion of QT in atomic Bose-Einstein condensates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.4600v1.pdf"}
{"id": "0902.0712", "abstract": "  The out-of-equilibrium mean-field dynamics of a model for wave-particle interaction is investigated. Such a model can be regarded as a general formulation for all those applications where the complex interplay between particles and fields is known to be central, e.g., electrostatic instabilities in plasma physics, particle acceleration and free-electron lasers (FELs). The latter case is here assumed as a paradigmatic example. A transition separating different macroscopic regimes is numerically identified and interpreted by making use of the so-called violent relaxation theory. In the context of free-electron lasers, such a theory is showed to be effective in predicting the saturated regime for energies below the transition. The transition is explained as a dynamical switch between two metastable regimes, and is related to the properties of a stationary point of an entropic functional. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.0712v2.pdf"}
{"id": "0902.0990", "abstract": "  Spatial interaction between two or more classes or species has important implications in various fields and causes multivariate patterns such as segregation or association. Segregation occurs when members of a class or species are more likely to be found near members of the same class or conspecifics; while association occurs when members of a class or species are more likely to be found near members of another class or species. The null patterns considered are random labeling (RL) and complete spatial randomness (CSR) of points from two or more classes, which is called CSR independence, henceforth. The clustering tests based on nearest neighbor contingency tables (NNCTs) that are in use in literature are two-sided tests. In this article, we consider the directional (i.e., one-sided) versions of the cell-specific NNCT-tests and introduce new directional NNCT-tests for the two-class case. We analyze the distributional properties; compare the empirical significant levels and empirical power estimates of the tests using extensive Monte Carlo simulations. We demonstrate that the new directional tests have comparable performance with the currently available NNCT-tests in terms of empirical size and power. We use four example data sets for illustrative purposes and provide guidelines for using these NNCT-tests. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.0990v1.pdf"}
{"id": "0902.1655", "abstract": "  The beam-beam interaction is one of the dominant sources of emittance growth and luminosity lifetime deterioration. A current carrying wire has been proposed to compensate long-range beam-beam effects in the LHC and strong localized long-range beam-beam effects are experimentally investigated in the RHIC collider. Tune shift, beam transfer function, and beam loss rate are measured in dedicated experiments. In this paper, we report on simulations to study the effect of beam-wire interactions based on diffusive apertures, beam loss rates, and beam transfer function using a parallelized weak-strong beam simulation code (bbsimc). The simulation results are compared with measurements performed in RHIC during 2007 and 2008. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.1655v2.pdf"}
{"id": "0902.4351", "abstract": "  The quasidistributions corresponding to the diagonal representation of quantum states are discussed within the framework of operator-symbol construction. The tomographic-probability distribution describing the quantum state in the probability representation of quantum mechanics is reviewed. The connection of the diagonal and probability representations is discussed. The superposition rule is considered in terms of the density-operator symbols. The separability and entanglement properties of multipartite quantum systems are formulated as the properties of the density-operator symbols of the system states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.4351v1.pdf"}
{"id": "0903.0466", "abstract": "  Collective X-ray Thomson scattering has become a versatile tool for the diagnostics of dense plasmas. Assuming homogeneous density and temperature throughout the target sample, these parameters can be determined directly from the plasmon dispersion and the ratio of plasmon amplitudes via detailed balance. In inhomogeneous media, the scattering signal is an average of the density and temperature dependent scattering cross-section weighted with the density and temperature profiles. We analyse Thomson scattering spectra in the XUV range from near solid density hydrogen targets generated by free electron laser radiation.The influence of plasma inhomogeneities on the scattering spectrum is investigated by comparing density and temperature averaged scattering signals to calculations assuming homogeneous targets. We found discrepancies larger than 10", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.0466v1.pdf"}
{"id": "0903.1507", "abstract": "  The goal of a small and dedicated satellite called the \"Continuous Spectro-Photometry of Black Holes\" or CSPOB is to provide the essential tool for the theoretical understanding of the hydrodynamic and magneto-hydrodynamic flows around black holes. In its life time of about three to four years, only a half a dozen black holes will be observed continuously with a pair of CSPOBs. Changes in the spectral and temporal variability properties of the high-energy emission would be caught as they happen. Several important questions are expected to be answered and many puzzles would be sorted out with this mission. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.1507v1.pdf"}
{"id": "0903.1695", "abstract": "  We construct families of pairs of Heegaard splittings that must be stabilized several times to become equivalent. The first such pair differs only by their orientation. These are genus n splittings of a closed 3-manifold that must be stabilized at least n-2 times to become equivalent. The second is a pair of genus n splittings of a manifold with toroidal boundary that must be stabilized at least n-4 times to become equivalent. The last example is a pair of genus n splittings of a closed 3-manifold that must be stabilized at least 1/2n -3 times to become equivalent, regardless of their orientations. All of these examples are splittings of manifolds that are obtained from simpler manifolds by gluing along incompressible surfaces via \"sufficiently complicated\" maps. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.1695v1.pdf"}
{"id": "0903.2159", "abstract": "  The contribution of white dwarfs of the different Galactic populations to the stellar content of our Galaxy is only poorly known. Some authors claim a vast population of halo white dwarfs, which would be in accordance with some investigations of the early phases of Galaxy formation claiming a top-heavy initial-mass-function. Here, I present a model of the population of white dwarfs in the Milky Way based on observations of the local white dwarf sample and a standard model of Galactic structure. This model will be used to estimate the space densities of thin disc, thick disc and halo white dwarfs and their contribution to the baryonic mass budget of the Milky Way. One result of this investigation is that white dwarfs of the halo population contribute a large fraction of the Galactic white dwarf number count, but they are not responsible for the lion's share of stellar mass in the Milky Way. Another important result is the substantial contribution of the - often neglected - population of thick disc white dwarfs. Misclassification of thick disc white dwarfs is responsible for overestimates of the halo population in previous investigations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.2159v1.pdf"}
{"id": "0903.2365", "abstract": "  It has been observed that exact solutions for electromagnetic (EM) excitations of the Kerr-Schild (KS) geometry form outgoing beams which have very strong back reaction to metric and break the black hole horizon. As a result, interaction of a black hole with nearby electromagnetic field and electromagnetic vacuum has to cover the horizon by a set of fluctuating microholes. We integrate and analyze the Debney-Kerr-Schild equations for electromagnetic excitations of a black-hole and obtain that the exact solutions for outgoing radiation contain two related but radically different components which shed light on a possible semi-classical mechanism of black-hole evaporation: a) first component consists of the singular beam pulses which perforate horizon, breaking its impenetrability, and b) another component is regular and responsible for the loss of mass similar to the known Vaidya `shining star' radiation. We show also that the mysterious twosheeted twistor structure of the Kerr-Schild geometry corresponds to a holographic structure of quantum black hole spacetimes predicted by Stephens, t' Hooft and Whiting. The resulting Kerr-Schild geometry of fluctuating twistor-beams takes an intermediate position between the classical and quantum gravity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.2365v3.pdf"}
{"id": "0903.2787", "abstract": "  We perform a computational study of a variant of the “train” model for earthquakes [PRA 46, 6288 (1992)], where we assume a static friction that is a stochastic function of position rather than being velocity dependent. The model consists of an array of blocks coupled by springs, with the forces between neighbouring blocks balanced by static friction. We calculate the probability, P(s), of the occurrence of avalanches with a size s or greater, finding that our results are consistent with the phenomenology and also with previous models which exhibit a power law over a wide range. We show that the train model may be mapped onto a stochastic sandpile model and study a variant of the latter for non-spherical grains. We show that, in this case, the model has critical behaviour only for grains with large aspect ratio, as was already shown in experiments with real ricepiles. We also demonstrate a way to introduce randomness in a physically motivated manner into the model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.2787v1.pdf"}
{"id": "0903.2973", "abstract": "  The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode through the study of ν_μ→ν_τ oscillations. The apparatus consists of an emulsion/lead target complemented by electronic detectors and it is placed in the high energy long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out in 2007 and 2008 with the detector fully operational with its related facilities for the emulsion handling and analysis. After a brief description of the beam and of the experimental setup we report on the collection, reconstruction and analysis procedures of first samples of neutrino interaction events. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.2973v1.pdf"}
{"id": "0903.3287", "abstract": "  We present a simple framework to compute hyperbolic Voronoi diagrams of finite point sets as affine diagrams. We prove that bisectors in Klein's non-conformal disk model are hyperplanes that can be interpreted as power bisectors of Euclidean balls. Therefore our method simply consists in computing an equivalent clipped power diagram followed by a mapping transformation depending on the selected representation of the hyperbolic space (e.g., Poincaré conformal disk or upper-plane representations). We discuss on extensions of this approach to weighted and k-order diagrams, and describe their dual triangulations. Finally, we consider two useful primitives on the hyperbolic Voronoi diagrams for designing tailored user interfaces of an image catalog browsing application in the hyperbolic disk: (1) finding nearest neighbors, and (2) computing smallest enclosing balls. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.3287v1.pdf"}
{"id": "0903.3484", "abstract": "  In this review given at the Hot and Cool: Bridging Gaps in Massive Star Evolution conference, I present the state of the art in red supergiant star atmosphere modelling. The last generation of hydrostatic 1D LTE MARCS models publicly released in 2008 have allowed great achievements in the past years, like the calibration of effective temperature scales. I rapidly describe this release, and then I discuss in some length the impact of the opacity sampling approximation on the thermal structure of models and on their emergent spectra. I also insist on limitations inherent to these models. Estimates of collisional and radiative time scales for electronic transitions in e.g. TiO suggest that non-LTE effects are important, and should be further investigated. Classical 1D models are not capable either to provide the large and non-gaussian velocity fields we know exist in red supergiants atmospheres. I therefore also present current efforts in 3D radiative hydrodynamical simulation of RSGs. I show that line profiles and shifts are predicted by these simulations, without the need for fudge micro- and macroturbulence velocities. This is a great progress, although line depths and widths are slightly too shallow. This is probably caused by the simplified grey radiative transfer used in these heavy simulations. Future non-grey 3D simulations should provide a better fit to observations in terms of line strengths and widths. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.3484v1.pdf"}
{"id": "0903.4931", "abstract": "  We report theoretical and experimental studies of ambipolar spin diffusion in a semiconductor. A circularly polarized laser pulse is used to excite spin-polarized carriers in a GaAs multiple quantum well sample at 80 K. Diffusion of electron and spin densities is simultaneously measured using a spatially and temporally resolved pump-probe technique. Two regimes of diffusion for spin-polarized electrons are observed. Initially, the rate of spin diffusion is similar to that of density diffusion and is controlled by the ambipolar diffusion coefficient. At later times, the spin diffusion slows down considerably relative to the density diffusion and appears to be controlled by a non-constant (decreasing) spin diffusion coefficient. We suggest that the long-time behavior of the spin density can be understood in terms of an inhomogeneous spin relaxation rate, which grows with decreasing density. The behavior of the spin relaxation rate is consistent with a model of D'yakonov-Perel' relaxation limited by the Coulomb scattering between carriers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0903/0903.4931v1.pdf"}
{"id": "0904.1213", "abstract": "  We investigate the existence and the properties of fully separable (fully factorized) ground states in quantum spin systems. Exploiting techniques of quantum information and entanglement theory we extend a recently introduced method and construct a general, self-contained theory of ground state factorization in frustration free quantum spin models defined on lattices in any spatial dimension and for interactions of arbitrary range. We show that, quite generally, non exactly solvable translationally invariant models in presence of an external uniform magnetic field can admit exact, fully factorized ground state solutions. Unentangled ground states occur at finite values of the Hamiltonian parameters satisfying well defined balancing conditions between the applied field and the interaction strengths. These conditions are analytically determined together with the type of magnetic orderings compatible with factorization and the corresponding values of the fundamental observables such as energy and magnetization. The method is applied to a series of examples of increasing complexity, including translationally-invariant models with short, long, and infinite ranges of interaction, as well as systems with spatial anisotropies, in low and higher dimensions. We also illustrate how the general method, besides yielding a large series of novel exact results for complex models in any dimension, recovers, as particular cases, the results previously achieved on simple models in low dimensions exploiting direct methods based on factorized mean-field ansatz. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.1213v2.pdf"}
{"id": "0904.3235", "abstract": "  In this work we investigate an influence of decoherence effects on quantum states generated as a result of the cross-Kerr nonlinear interaction between two modes. For Markovian losses (both photon loss and dephasing), a region of parameters when losses still do not lead to destruction of non-classicality is identified. We emphasize the difference in impact of losses in the process of state generation as opposed to those occurring in propagation channel. We show moreover, that correlated losses in modern realizations of schemes of large cross-Kerr nonlinearity might lead to enhancement of non-classicality. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.3235v1.pdf"}
{"id": "0904.3376", "abstract": "  The stability and chaotic behaviors of Bose-Einstein condensates with two- and three-atom interactions in optical lattices are discussed with analytical and numerical methods. It is found that the steady-state relative population appears tuning-fork bifurcation when the system parameters are changed to certain critical values. In particular, the existence of three-body interaction not only transforms the bifurcation point of the system but also affects greatly on the macroscopic quantum self-trapping behaviors of the system associated with the critically stable steady-state solution. In addition, we also investigated the influence of the initial conditions, three-body interaction and the energy bias on the macroscopic quantum self-trapping. Finally, by applying the periodic modulation on the energy bias, we find that the relative population oscillation exhibits a process from order to chaos, via a series of period-doubling bifurcations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.3376v2.pdf"}
{"id": "0905.0333", "abstract": "  We analyze the recently released Fermi-LAT data on the sum of electrons and positrons. Compared to a conventional, pre-Fermi, background model, a surprising excess in the several hundred GeV range is found and here we analyze it in terms of dark matter models. We also compare with newly published results from PAMELA and HESS, and find models giving very good fits to these data sets as well. If this dark matter interpretation is correct, we also predict the possibility of a sharp break in the diffuse gamma ray spectrum coming from final state radiation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.0333v1.pdf"}
{"id": "0905.0586", "abstract": "  Open source bioinformatics tools running under MS Windows are rare to find, and those running under Windows HPC cluster are almost non-existing. This is despite the fact that the Windows is the most popular operating system used among life scientists. Therefore, we introduce in this initiative WinBioinfTools, a toolkit containing a number of bioinformatics tools running under Windows High Performance Computing Server 2008. It is an open source code package, where users and developers can share and add to. We currently start with three programs from the area of sequence analysis: 1) CoCoNUT for pairwise genome comparison, 2) parallel BLAST for biological database search, and 3) parallel global pairwise sequence alignment. In this report, we focus on technical aspects concerning how some components of these tools were ported from Linux/Unix environment to run under Windows. We also show the advantages of using the Windows HPC Cluster 2008. We demonstrate by experiments the performance gain achieved when using a computer cluster against a single machine. Furthermore, we show the results of comparing the performance of WinBioinfTools on the Windows and Linux Cluster. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.0586v1.pdf"}
{"id": "0905.0947", "abstract": "  The JILA Multidimensional Optical Nonlinear SpecTRometer (JILA-MONSTR) is a robust, ultra-stable platform consisting nested and folded Michelson interferometers that can be actively phase stabilized. This platform generates a square of identical laser pulses that can be adjusted to have arbitrary time delay between them, while maintaining phase stability. The JILA-MONSTR provides output pulses for nonlinear excitation of materials and phase-stabilized reference pulses for heterodyne detection of the induced signal. This arrangement is ideal for performing coherent optical experiments, such as multidimensional Fourier-transform spectroscopy, which records the phase of the nonlinear signal as a function of the time delay between several of the excitation pulses. The resulting multidimensional spectrum is obtained from a Fourier transform. This spectrum can resolve, separate and isolate coherent contributions to the light-matter interactions associated with electronic excitation at optical frequencies. To show the versatility of the JILA-MONSTR, several demonstrations of two-dimensional Fourier-transform spectroscopy are presented, including an example of a phase-cycling scheme that reduces noise. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.0947v2.pdf"}
{"id": "0905.1895", "abstract": "  It is a challenge to synthesize graphene nanoribbons (GNRs) with narrow widths and smooth edges in large scale. Our first principles study on the hydrogenation of GNRs shows that the hydrogenation starts from the edges of GNRs and proceeds gradually toward the middle of the GNRs so as to maximize the number of carbon-carbon π-π bonds. Furthermore, the partially hydrogenated wide GNRs have similar electronic and magnetic properties as those of narrow GNRs. Therefore, it is not necessary to directly produce narrow GNRs for realistic applications because partial hydrogenation could make wide GNRs \"narrower\". ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.1895v1.pdf"}
{"id": "0905.2043", "abstract": "  We empirically investigated the effects of market factors on the information flow created from N(N-1)/2 linkage relationships among stocks. We also examined the possibility of employing the minimal spanning tree (MST) method, which is capable of reducing the number of links to N-1. We determined that market factors carry important information value regarding information flow among stocks. Moreover, the information flow among stocks evidenced time-varying properties according to the changes in market status. In particular, we noted that the information flow increased dramatically during periods of market crises. Finally, we confirmed, via the MST method, that the information flow among stocks could be assessed effectively with the reduced linkage relationships among all links between stocks from the perspective of the overall market. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.2043v1.pdf"}
{"id": "0905.2825", "abstract": "  In optimizing the topology of wireless networks built of a dynamic set of spatially embedded agents, there are many trade-offs to be dealt with. The network should preferably be as small (in the sense that the average, or maximal, pathlength is short) as possible, it should be robust to failures, not consume too much power, and so on. In this paper, we investigate simple models of how agents can choose their neighbors in such an environment. In our model of attachment, we can tune from one situation where agents prefer to attach to others in closest proximity, to a situation where distance is ignored (and thus attachments can be made to agents further away). We evaluate this scenario with several performance measures and find that the optimal topologies, for most of the quantities, is obtained for strategies resulting in a mix of most local and a few random connections. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.2825v1.pdf"}
{"id": "0905.2896", "abstract": "  We present a new framework for radiation hydrodynamics simulations. Gas dynamics is modelled by the Smoothed Particle Hydrodynamics (SPH) method, whereas radiation transfer is simulated via a time-dependent Monte-Carlo approach that traces photon packets. As a first step in the development of the method, in this paper we consider the momentum transfer between radiation field and gas, which is important for systems where radiation pressure is high. There is no fundamental limitations on the number of radiation sources, geometry or the optical depth of the problems that can be studied with the method. However, as expected for any Monte-Carlo transfer scheme, stochastic noise presents a serious limitation. We present a number of tests that show that the errors of the method can be estimated accurately by considering Poisson noise fluctuations in the number of photon packets that SPH particles interact with per dynamical time. It is found that for a reasonable accuracy the momentum carried by photon packets must be much smaller than a typical momentum of SPH particles. We discuss numerical limitations of the code, and future steps that can be taken to improve performance and applicability of the method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.2896v1.pdf"}
{"id": "0905.3196", "abstract": "  Real data are constrained to finite sampling rates, which calls for a suitable mathematical description of the corrections to the finite-time estimations of the dynamic equations. Often in the literature, lower order discrete time approximations of the modeling diffusion processes are considered. On the other hand, there is a lack of simple estimating procedures based on higher order approximations. For standard diffusion models, that include additive and multiplicative noise components, we obtain the exact corrections to the empirical finite-time drift and diffusion coefficients, based on Itô-Taylor expansions. These results allow to reconstruct the real hidden coefficients from the empirical estimates. We also derive higher-order finite-time expressions for the third and fourth conditional moments, that furnish extra theoretical checks for that class of diffusive models. The theoretical predictions are compared with the numerical outcomes of some representative artificial time-series. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.3196v1.pdf"}
{"id": "0905.3851", "abstract": "  We compare weak and strong coupling theory of counterion-mediated electrostatic interactions between two asymmetrically charged plates with extensive Monte-Carlo simulations. Analytical results in both weak and strong coupling limits compare excellently with simulations in their respective regimes of validity. The system shows a surprisingly rich structure in terms of interactions between the surfaces as well as fundamental qualitative differences in behavior in the weak and the strong coupling limits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.3851v1.pdf"}
{"id": "0906.0185", "abstract": "  Superconducting persistent-current qubits are quantum-coherent artificial atoms with multiple, tunable energy levels. In the presence of large-amplitude harmonic excitation, the qubit state can be driven through one or more of the constituent energy-level avoided crossings. The resulting Landau-Zener-Stueckelberg (LZS) transitions mediate a rich array of quantum-coherent phenomena. We review here three experimental works based on LZS transitions: Mach-Zehnder-type interferometry between repeated LZS transitions, microwave-induced cooling, and amplitude spectroscopy. These experiments exhibit a remarkable agreement with theory, and are extensible to other solid-state and atomic qubit modalities. We anticipate they will find application to qubit state-preparation and control methods for quantum information science and technology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.0185v1.pdf"}
{"id": "0906.0337", "abstract": "  A large class of fractional quantum Hall (FQH) states can be classified according to their pattern of zeros, which describes the way ideal ground state wave functions go to zero as various clusters of electrons are brought together. In this paper we generalize this approach to classify multilayer FQH states. Such a classification leads to the construction of a class of non-Abelian multilayer FQH states that are closely related to ĝ_k parafermion conformal field theories, where ĝ_k is an affine simple Lie algebra. We discuss the possibility of some of the simplest of these non-Abelian states occuring in experiments on bilayer FQH systems at ν = 2/3, 4/5, 4/7, etc. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.0337v1.pdf"}
{"id": "0906.1101", "abstract": "  The canonical answer to the question posed is \"Yes.\" – tacitly assuming that quantum theory and the concept of spacetime are to be unified by `quantizing' a theory of gravitation. Yet, instead, one may ponder: Could quantum mechanics arise as a coarse-grained reflection of the atomistic nature of spacetime? – We speculate that this may indeed be the case. We recall the similarity between evolution of classical and quantum mechanical ensembles, according to Liouville and von Neumann equation, respectively. The classical and quantum mechanical equations are indistinguishable for objects which are free or subject to spatially constant but possibly time dependent, or harmonic forces, if represented appropriately. This result suggests a way to incorporate anharmonic interactions, including fluctuations which are tentatively related to the underlying discreteness of spacetime. Being linear and local at the quantum mechanical level, the model offers a decoherence and natural localization mechanism. However, the relation to primordial deterministic degrees of freedom is nonlocal. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.1101v1.pdf"}
{"id": "0906.1571", "abstract": "  A series of experiments measuring high-energy cosmic rays have recently reported strong indications for the existence of an excess of high-energy electrons and positrons. If interpreted in terms of the decay of dark matter particles, the PAMELA measurements of the positron fraction and the Fermi LAT measurements of the total electron-plus-positron flux restrict the possible decaying dark matter scenarios to a few cases. Analyzing different decay channels in a model-independent manner, and adopting a conventional diffusive reacceleration model for the background fluxes of electrons and positrons, we identify some promising scenarios of dark matter decay and calculate the predictions for the diffuse extragalactic gamma-ray flux, including the contributions from inverse Compton scattering with the interstellar radiation field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.1571v3.pdf"}
{"id": "0906.2574", "abstract": "  We use molecular dynamics to study the nucleation of cracks in a two dimensional material without pre-existing cracks. We study models with zero and non-zero shear modulus. In both situations the time required for crack formation obeys an Arrhenius law, from which the energy barrier and pre-factor are extracted for different system sizes. For large systems, the characteristic time of rupture is found to decrease with system size, in agreement with classical Weibull theory. In the case of zero shear modulus, the energy opposing rupture is identified with the breakage of a single atomic layer. In the case of non-zero shear modulus, thermally activated fracture can only be studied within a reasonable time at very high strains. In this case the energy barrier involves the stretching of bonds within several layers, accounting for a much higher barrier compared to the zero shear modulus case. This barrier is understood within adiabatic simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.2574v1.pdf"}
{"id": "0906.3094", "abstract": "  We investigate a set of discrete-time quantum search algorithms on the n-dimensional hypercube following a proposal by Shenvi, Kempe and Whaley. We show that there exists a whole class of quantum search algorithms in the symmetry reduced space which perform a search of a marked vertex in time of order √(N) where N = 2^n, the number of vertices. In analogy to Grover's algorithm, the spatial search is effectively facilitated through a rotation in a two-level sub-space of the full Hilbert space. In the hypercube, these two-level systems are introduced through avoided crossings. We give estimates on the quantum states forming the 2-level sub-spaces at the avoided crossings and derive improved estimates on the search times. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.3094v1.pdf"}
{"id": "0906.4365", "abstract": "  We report the detection of eclipses in GJ 3236, a bright (I = 11.6) very low mass binary system with an orbital period of 0.77 days. Analysis of light- and radial velocity curves of the system yielded component masses of 0.38 +/- 0.02 and 0.28 +/- 0.02 Msol. The central values for the stellar radii are larger than the theoretical models predict for these masses, in agreement with the results for existing eclipsing binaries, although the present 5", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.4365v1.pdf"}
{"id": "0907.0996", "abstract": "  On January 2, the MAGIC-I Telescope observed GRB090102 (z=1.55) under particularly good observation conditions. Using the recently upgraded MAGIC-1 sum trigger system, upper limits down to below 50 GeV have been obtained. This is the first time that the new trigger system was fully exploited for a Gamma-ray Burst (GRB) observation and shows the capabilities of the MAGIC observatory for future follow-up observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.0996v1.pdf"}
{"id": "0907.3137", "abstract": "  The metrization of the space of neural responses is an ongoing research program seeking to find natural ways to describe, in geometrical terms, the sets of possible activities in the brain. One component of this program are the spike metrics, notions of distance between two spike trains recorded from a neuron. Alignment spike metrics work by identifying \"equivalent\" spikes in one train and the other. We present an alignment spike metric having ℒ_p underlying geometrical structure; the ℒ_2 version is Euclidean and is suitable for further embedding in Euclidean spaces by Multidimensional Scaling methods or related procedures. We show how to implement a fast algorithm for the computation of this metric based on bipartite graph matching theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.3137v2.pdf"}
{"id": "0907.3538", "abstract": "  We evaluate exactly the non-Markovian effect on the decoherence dynamics of a qubit interacting with a dissipative vacuum reservoir and find that the coherence of the qubit can be partially trapped in the steady state when the memory effect of the reservoir is considered. Our analysis shows that it is the formation of a bound state between the qubit and its reservoir that results in this residual coherence in the steady state under the non-Markovian dynamics. A physical condition for the decoherence suppression is given explicitly. Our results suggest a potential way to decoherence control by modifying the system-reservoir interaction and the spectrum of the reservoir to the non-Markovian regime in the scenario of reservoir engineering. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.3538v2.pdf"}
{"id": "0907.3929", "abstract": "  Gate control of phosphorus donor based charge qubits in Si is investigated using a tight-binding approach. Excited molecular states of P2+ are found to impose limits on the allowed donor separations and operating gate voltages. The effects of surface (S) and barrier (B) gates are analyzed in various voltage regimes with respect to the quantum confined states of the whole device. Effects such as interface ionization, saturation of the tunnel coupling, sensitivity to donor and gate placement are also studied. It is found that realistic gate control is smooth for any donor separation, although at certain donor orientations the S and B gates may get switched in functionality. This paper outlines and analyzes the various issues that are of importance in practical control of such donor molecular systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.3929v1.pdf"}
{"id": "0907.4552", "abstract": "  In the framework of supersymmetric Grand Unified Theories, the minimal Higgs sector is often extended by introducing multi-dimensional Higgs representations in order to obtain realistic models. However these constructions should remain anomaly-free, which constraints significantly their structure. We review the necessary conditions for the cancellation of anomalies in general and discuss in detail the different possibilities for SUSY SU(5) models. Alternative anomaly free combinations of Higgs representations, beyond the usual vector-like choice, are identified, and it is shown that their corresponding beta functions are not equivalent. Although the unification of gauge couplings is not affected, the introduction of multi-dimensional representations leads to different scenarios for the perturbative validity of the theory up to the Planck scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.4552v1.pdf"}
{"id": "0907.4634", "abstract": "  A hole spin is a potential solid-state q-bit, that may be more robust against nuclear spin induced dephasing than an electron spin. Here we propose and demonstrate the sequential preparation, control and detection of a single hole spin trapped on a self-assembled InGaAs/GaAs quantum dot. The dot is embedded in a photodiode structure under an applied electric-field. Fast, triggered, initialization of a hole spin is achieved by creating a spin-polarized electron-hole pair with a picosecond laser pulse, and in an applied electric-field, waiting for the electron to tunnel leaving a spin-polarized hole. Detection of the hole spin with picosecond time resolution is achieved a second picosecond laser pulse to probe the positive trion transition, where a trion is created conditional on the hole spin to be detected as a change in photocurrent. Finally, using this setup we observe a Rabi rotation of the hole-trion transition that is conditional on the hole spin, which for a pulse-area of 2π can be used to impart a phase-shift of π between the hole spin states, a non-general manipulation of the hole spin. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.4634v1.pdf"}
{"id": "0908.0335", "abstract": "  The structure and evolution of grain boundaries underlies the nature of polycrystalline materials. Here we describe an experimental apparatus and light reflection technique for measuring disorder at grain boundaries in optically clear material, in thermodynamic equilibrium. The approach is demonstrated on ice bicrystals. Crystallographic orientation is measured for each ice sample. The type and concentration of impurity in the liquid can be controlled and the temperature can be continuously recorded and controlled over a range near the melting point. The general methodology is appropriate for a wide variety of materials. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.0335v2.pdf"}
{"id": "0908.0436", "abstract": "  The Stellar Observations Network Group (SONG) has obtained full funding for the design, construction and implementation of a prototype telescope and instrumentation package for the first network node. We describe the layout of such a node and its instrumentation and expected performance for radial-velocity measurements. The instrumentation consists of a 1m telescope, equipped with two cameras for photometry of microlensing events with the lucky-imaging technique and a high-resolution spectrograph equipped with an iodine cell for obtaining high-precision radial velocities of solar-like stars, in order to do asteroseismology. The telescope will be located in a dome of   4.5 m diameter, with two lucky-imaging cameras at one of the Nasmyth foci and the spectrograph and instrument control computers at a Coudé focus, located in an adjacent container. Currently the prototype telescope and instrumentation are undergoing detailed design. Installation at the first site (Tenerife) is expected during mid-late 2010, followed by extensive testing during 2011. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.0436v1.pdf"}
{"id": "0908.1534", "abstract": "  Atomic diffusion may lead to heavy element accumulation inside stars in certain specific layers. Iron accumulation in the Z-bump opacity region has been invoked by several authors to quantitatively account for abundance anomalies observed in some stars, or to account for stellar oscillations through the induced κ-mechanism. These authors however never took into account the fact that such an accumulation creates an inverse μ-gradient, unstable for thermohaline convection. Here, we present results for A-F stars, where abundance variations are computed with and without this process. We show that iron accumulation is still present when thermohaline convection is taken into account, but much reduced compared to when this physical process is neglected. The consequences of thermohaline convection for A-type stars as well as for other types of stars are presented ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.1534v1.pdf"}
{"id": "0908.1826", "abstract": "  Greedy algorithm are in widespread use for sparse recovery because of its efficiency. But some evident flaws exists in most popular greedy algorithms, such as CoSaMP, which includes unreasonable demands on prior knowledge of target signal and excessive sensitivity to random noise. A new greedy algorithm called AMOP is proposed in this paper to overcome these obstacles. Unlike CoSaMP, AMOP can extract necessary information of target signal from sample data adaptively and operate normally with little prior knowledge. The recovery error of AMOP is well controlled when random noise is presented and fades away along with increase of SNR. Moreover, AMOP has good robustness on detailed setting of target signal and less dependence on structure of measurement matrix. The validity of AMOP is verified by theoretical derivation. Extensive simulation experiment is performed to illustrate the advantages of AMOP over CoSaMP in many respects. AMOP is a good candidate of practical greedy algorithm in various applications of Compressed Sensing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.1826v2.pdf"}
{"id": "0908.2099", "abstract": "  Spin effects in a normal two-dimensional (2D) electron gas in lateral contact with a 2D region with spin-orbit interaction are studied. The peculiarity of this system is the presence of spin-dependent scattering of electrons from the interface. This results in an equilibrium edge spin current and nontrivial spin responses to a particle current. We investigate the spatial distribution of the spin currents and spin density under non-equilibrium conditions caused by a ballistic electron current flowing normal or parallel to the interface. The parallel electron current is found to generate the spin density near the interface and to change the edge spin current. The perpendicular electron current changes the edge spin current proportionally to the electron current and produces a bulk spin current penetrating deep into the normal region. This spin current has two components, one of which is directed normal to the interface and polarized parallel to it, and the second is parallel to the interface and is polarized in the plane perpendicular to the contact line. Both spin currents have a high degree of polarization (∼ 40-60", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.2099v1.pdf"}
{"id": "0908.2331", "abstract": "  The surface current method known in the theory of electromagnetic waves diffraction is generalized to be applied for the problems of diffraction radiation generated by a charged particle moving nearby an ideally-conducting screen in vacuum. An expression for induced surface current density leading to the exact results in the theory of transition radiation is derived, and by using this expression several exact solutions of diffraction radiation problems are found. Limits of applicability for the earlier known models based on the surface current conception are indicated. Properties of radiation from a semi-plane and from a slit in cylinder are investigated at the various distances to observer. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.2331v1.pdf"}
{"id": "0908.2639", "abstract": "  Observations of the HI 21cm transition line promises to be an important probe into the cosmic dark ages and epoch of reionization. One of the challenges for the detection of this signal is the accuracy of the foreground source removal. This paper investigates the extragalactic point source contamination and how accurately the bright sources (≳ 1  Jy) should be removed in order to reach the desired RMS noise and be able to detect the 21cm transition line. Here, we consider position and flux errors in the global sky-model for these bright sources as well as the frequency independent residual calibration errors. The synthesized beam is the only frequency dependent term included here. This work determines the level of accuracy for the calibration and source removal schemes and puts forward constraints for the design of the cosmic reionization data reduction scheme for the upcoming low frequency arrays like MWA,PAPER, etc. We show that in order to detect the reionization signal the bright sources need to be removed from the data-sets with a positional accuracy of ∼ 0.1 arc-second. Our results also demonstrate that the efficient foreground source removal strategies can only tolerate a frequency independent antenna based mean residual calibration error of ≲ 0.2", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.2639v1.pdf"}
{"id": "0908.2690", "abstract": "  We study the virial mass discrepancy in the context of a DPG brane-world scenario and show that such a framework can offer viable explanations to account for the mass discrepancy problem. This is done by defining a geometrical mass 𝒩 that we prove to be proportional to the virial mass. Estimating 𝒩 using observational data, we show that it behaves linearly with r and has a value of the order of M_200, pointing to a possible resolution of the virial mass discrepancy. We also obtain the radial velocity dispersion of galaxy clusters and show that it is compatible with the radial velocity dispersion profile of such clusters. This velocity dispersion profile can be used to differentiate various models predicting the virial mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.2690v1.pdf"}
{"id": "0908.2828", "abstract": "  Recently, a number of authors have proposed decoding schemes for Reed-Solomon (RS) codes based on multiple trials of a simple RS decoding algorithm. In this paper, we present a rate-distortion (R-D) approach to analyze these multiple-decoding algorithms for RS codes. This approach is first used to understand the asymptotic performance-versus-complexity trade-off of multiple error-and-erasure decoding of RS codes. By defining an appropriate distortion measure between an error pattern and an erasure pattern, the condition for a single error-and-erasure decoding to succeed reduces to a form where the distortion is compared to a fixed threshold. Finding the best set of erasure patterns for multiple decoding trials then turns out to be a covering problem which can be solved asymptotically by rate-distortion theory. Next, this approach is extended to analyze multiple algebraic soft-decision (ASD) decoding of RS codes. Both analytical and numerical computations of the R-D functions for the corresponding distortion measures are discussed. Simulation results show that proposed algorithms using this approach perform better than other algorithms with the same complexity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.2828v1.pdf"}
{"id": "0908.3833", "abstract": "  Electrical transport properties as a function of magnetic field and time have been investigated in polycrystalline, Nd_0.84Sr_0.16CoO_3. A strong exchange bias (EB) effect is observed associated with the fairly large intragranular magnetoresistance (MR). The EB effect observed in the MR curve is compared with the EB effect manifested in magnetic hysteresis loop. Training effect, described as the decrease of EB effect when the sample is successively field-cycled at a particular temperature, has been observed in the shift of the MR curve. Training effect could be analysed by the successful models. The EB effect, MR and a considerable time dependence in MR are attributed to the intrinsic nanostructure giving rise to the varieties of magnetic interfaces in the grain interior. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.3833v1.pdf"}
{"id": "0909.2053", "abstract": "  How does the tidal debris of minor galaxy mergers contribute to structures in spiral galaxies or in the intergalactic medium? While major mergers are known to create structures such as tidal dwarf galaxies and star clusters within their tidal debris, less is known about minor mergers (mass ratios between a dwarf galaxy and disk galaxy of less than one-third) and their tidal debris. This work surveys 6 nearby minor mergers using optical broad-band and H-alpha narrow-band imaging to characterize star formation in their tidal debris. Young star clusters with ages less than the dynamical age of the tidal tails are found in all 6 mergers, indicating that the star clusters formed in situ. Even if minor mergers contribute less tidal debris per interaction than major mergers, they are more common and possibly contribute structure to all types of galaxies and to the intergalactic medium throughout the history of the universe. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.2053v1.pdf"}
{"id": "0909.2132", "abstract": "  We investigate a mechanism of the appearance of kinetic friction in granular materials. We consider a small number of intervening inelastic particles between two rough surfaces as one of the simplest dynamical models to study granular friction. The resistance force applied to the upper surface is numerically calculated. We find that the resistance force F(t) is scaled as F'(vt) for a small pulling velocity v. The time average F_0=<F(t)> in the limit v->0 is not zero owing to the mutual collisions between the intervening particles. The nonzero F_0 implies the appearance of kinetic friction in this simple dynamical system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.2132v1.pdf"}
{"id": "0909.2514", "abstract": "  Franson's paradigm for nonlocal dispersion cancellation [J. D. Franson, Phys. Rev. A 45, 3126 (1992)] is studied using two kinds of jointly Gaussian-state signal and reference beams with phase-sensitive cross correlations. The first joint signal-reference state is nonclassical, with a phase-sensitive cross correlation that is at the ultimate quantum-mechanical limit. It models the outputs obtained from continuous-wave spontaneous parametric downconversion. The second joint signal-reference state is classical—it has a proper P representation—with a phase-sensitive cross correlation that is at the limit set by classical physics. Using these states we show that a version of Franson's nonlocal dispersion cancellation configuration has essentially identical quantum and classical explanations except rm for the contrast obtained, which is much higher in the quantum case than it is in the classical case. This work bears on Franson's recent paper [J. D. Franson, arXiv:0907:5196 [quant-ph]], which asserts that there is no classical explanation for all the features seen in quantum nonlocal dispersion cancellation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.2514v1.pdf"}
{"id": "0909.2584", "abstract": "  The time-dependent Dirac equation is solved using the three-dimensional Finite Difference-Time Domain (FDTD) method. The dynamics of the electron wave packet in a vector potential is studied in the arrangements associated with the Aharonov-Bohm effect. The solution of the Dirac equation showed a change in the velocity of the electron wave packet even in a region where no forces acted on the electron. The solution of the Dirac equation agreed with the prediction of classical dynamics under the assumption that the dynamics was defined by the conservation of generalized or canonical momentum. It was also shown that in the case when the magnetic field was not zero, the conservation of generalized or canonical momentum was equivalent to the action of the Lorentz force. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.2584v1.pdf"}
{"id": "0909.2910", "abstract": "  We search for isolated galaxies using a volume-limited sample of galaxies with 0.02< z < 0.04742 from SDSS DR7 supplemented by bright galaxies. We devise a diagnostic tool to select isolated galaxies in different environments using the projected separation (r_p) normalized by the virial radius of the nearest neighbor (r_vir,nei) and the local background density. We find that the isolation condition of r_p>r_vir,nei and ρ<ρ̅ well segregates the CIG galaxies. We confirm the morphology conformity between the host and their satellites, which suggests importance of hydrodynamic interaction among galaxies within their virial radii in galaxy evolution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.2910v2.pdf"}
{"id": "0909.3177", "abstract": "  We report the redshift of a distant, highly obscured submm galaxy (SMG), based entirely on the detection of its CO line emission. We have used the newly commissioned Eight-MIxer Receiver (EMIR) at the IRAM 30m telescope, with its 8 GHz of instantaneous dual-polarization bandwidth, to search the 3-mm atmospheric window for CO emission from SMMJ14009+0252, a bright SMG detected in the SCUBA Lens Survey. A detection of the CO(3–2) line in the 3-mm window was confirmed via observations of CO(5–4) in the 2-mm window. Both lines constrain the redshift of SMMJ14009+0252 to z=2.9344, with high precision (dz=2 10^-4). Such observations will become routine in determining redshifts in the era of the Atacama Large Millimeter/submillimeter Array (ALMA). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.3177v1.pdf"}
{"id": "0909.3627", "abstract": "  Starting with a model Hamiltonian, we study using the uniform expansion method conformational behavior of polyelectrolytes in the presence and absence of salt. The uniform expansion method yields all the important local length scales in the polyelectrolyte: the electrostatic blob size at large fraction of charges, the thermal blob size at low fraction of charges and the sizes of pearls (beads) and necklaces (strings) at intermediate fraction of charges. In the presence of salt, the electrostatic blob size depends on the ionic strength and increases with the increase in the salt concentration. We determine the salt concentration at which the pearl necklace intermediates dissolve and the nature of the transition changes from discontinuous to continuous. This critical salt concentration corresponds to the length scale where the Debye screening length is of the order of the necklace length. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.3627v1.pdf"}
{"id": "0909.3749", "abstract": "  We investigate the physics of coherent quantum phase slips in two distinct circuits containing small Josephson junctions: (i) a single junction embedded in an inductive environment and (ii) a long chain of junctions. Starting from the standard Josephson Hamiltonian, the single junction circuit can be analyzed using quasi-classical methods; we formulate the conditions under which the resulting quasi-charge dynamics is exactly dual to the usual phase dynamics associated with Josephson tunneling. For the chain we use the fact that its collective behavior can be characterized by one variable: the number m of quantum phase slips present on it. We conclude that the dynamics of the conjugate quasi-charge is again exactly dual to the standard phase dynamics of a single Josephson junction. In both cases we elucidate the role of the inductance, essential to obtain exact duality. These conclusions have profound consequences for the behavior of single junctions and chains under microwave irradiation. Since both systems are governed by a model exactly dual to the standard resistively and capacitively shunted junction model, we expect the appearance of current-Shapiro steps. We numerically calculate the corresponding current-voltage characteristics in a wide range of parameters. Our results are of interest in view of a metrological current standard. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.3749v1.pdf"}
{"id": "0909.3906", "abstract": "  We present the results on the photometric and spectroscopic monitoring of a luminous Ap star HD103498. The time-series photometric observations were carried out on 17 nights using three-channel fast photometer attached to the 1.04-m optical telescope at ARIES, Nainital. The photometric data of five nights of year 2007 show clear signature of 15-min periodicity. However, the follow-up observations during 2007–2009 could not repeated any such periodicity. To confirm the photometric light variations, the time-series spectroscopic observations were carried out with the 2.56-m Nordic Optical Telescope (NOT) at La Palma on February 2, 2009. Any radial velocity variations were absent in this data set which is in full agreement with the photometric observations taken near the same night. Model atmosphere and abundance analysis of HD103498 show that the star is evolved from the Main Sequence and its atmospheric abundances are similar to two other evolved Ap stars HD133792 and HD204411: large overabundances of Si, Cr, and Fe and moderate overabundances of the rare-earth elements. These chemical properties and a higher effective temperature distinguish HD103498 from any known roAp star. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.3906v1.pdf"}
{"id": "0909.4610", "abstract": "  We investigate the evolution of the bound state of negatively charged massive particles (CHAMPs) with light elements and discuss its cosmological consequences and the constraint. By numerically solving the Boltzmann equation, we study the time evolutions of such bound states. Since most of negative CHAMPs are captured by He4, its bound state is positively charged and couples with the electromagnetic plasma. When charged particles constitute a dominant non-relativistic component, density fluctuations of matter cannot grow due to the acoustic damping. This results in the suppression of matter power spectrum from which a severe constraint can be obtained. By arguing constraints from other aspects of cosmology, we show that the constraint from large scale structure gives most stringent one in some representative cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.4610v2.pdf"}
{"id": "0909.5217", "abstract": "  A new kind of tripartite coherent-entangled state (CES) |β,γ, x⟩_μντ is proposed, which exhibits the properties of both coherence and entanglement. We investigate its completeness and orthogonality, and find it can make up a representation of tripartite CES. A protocol for generating the tripartite CES is proposed using asymmetric beam splitter. Applications of the tripartite CES in quantum optics are also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0909/0909.5217v1.pdf"}
{"id": "0910.0152", "abstract": "  Parametric down-conversion (PDC) offers the possibility to control the fabrication of non-Gaussian states such as Fock states. However, in conventional PDC sources energy and momentum conservation introduce strict frequency and photon number correlations, which impact the fidelity of the prepared state. In our work we optimize the preparation of single-photon Fock states from the emission of waveguided PDC via spectral filtering. We study the effect of correlations via photon number resolving detection and quantum interference. Our measurements show how the reduction of mixedness due to filtering can be evaluated. Interfering the prepared photon with a coherent state we establish an experimentally measured fidelity of the produced target state of 78", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.0152v2.pdf"}
{"id": "0910.0395", "abstract": "  We introduce Weinberg's idea of asymptotic safety and pave the way towards an asymptotically safe chiral Yukawa system with a U(N_L)_L ⊗ U(1)_R symmetry in a leading-order derivative expansion using nonperturbative functional RG equations. As a toy model sharing important features with the standard model we explicitely discuss N_L=10 for which we find a non-Gaussian fixed point and compute its critical exponents. We observe a reduced hierarchy problem as well as predictions for the toy Higgs and the toy top mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.0395v1.pdf"}
{"id": "0910.1045", "abstract": "  Relativistic models developed for the exclusive and inclusive quasielastic (QE) electron scattering have been extended to charged-current (CC) and neutral-current (NC) neutrino-nucleus scattering. Different descriptions of final-state interactions (FSI) are compared. For the inclusive electron scattering the relativistic Green's function approach is compared with calculations based on the use of relativistic purely real mean field potentials in the final state. Both approaches lead to a redistribution of the strength but conserving the total flux. Results for the differential cross section at different energies are presented. Scaling properties are also analyzed and discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.1045v1.pdf"}
{"id": "0910.1957", "abstract": "  We explore the advantages offered by twin light beams produced in parametric down-conversion for precision measurement. The symmetry of these bipartite quantum states, even under losses, suggests that monitoring correlations between the divergent beams permits a high-precision inference of any symmetry-breaking effect, e.g. fiber birefringence. We show that the quantity of entanglement is not the key feature for such an instrument. In a lossless setting, scaling of precision at the ultimate `Heisenberg' limit is possible with photon counting alone. Even as photon losses approach 100", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.1957v2.pdf"}
{"id": "0910.2482", "abstract": "  A modification of the internal structure of jets is expected due to the production of a dense QCD medium, the Quark Gluon Plasma, in heavy-ion collisions. We discuss some aspects of jet reconstruction in p+p and A+A collisions and emphasize the dramatically increased contribution of the underlying event in nucleus-nucleus collisions as compared with the vacuum case. We conclude with its consequences on the full jet spectrum and fragmentation function extraction at LHC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.2482v1.pdf"}
{"id": "0910.2580", "abstract": "  This article describes the fluid dynamics video, \"A Numerical Simulation of a Plunging Breaking Wave\", which was submitted to the gallery of fluid motion at the 2009 APS/DFD conference. The simulation was of a deep-water plunging breaking wave. It was a two-phase calculation which used a Volume of Fluid (VOF) method to simulate the interface between the two immiscible fluids. Surface tension and viscous effects were not considered. The initial wave was generated by applying a spatio-temporal pressure forcing on the free surface. The video shows the 50", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.2580v1.pdf"}
{"id": "0910.2807", "abstract": "  The effects of polymer additives on Rayleigh–Taylor (RT) instability of immiscible fluids is investigated using the Oldroyd-B viscoelastic model. Analytic results obtained exploiting the phase-field approach show that in polymer solution the growth rate of the instability speeds up with elasticity (but remains slower than in the pure solvent case). Numerical simulations of the viscoelastic binary fluid model confirm this picture. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.2807v1.pdf"}
{"id": "0910.4710", "abstract": "  Recent studies attracted the attention on the inherent structure landscape (ISL) approach as a reduced description of proteins allowing to map their full thermodynamic properties. However, the analysis has been so far limited to a single topology of a two-state folding protein, and the simplifying assumptions of the method have not been examined. In this work, we construct the thermodynamics of four two-state folding proteins of different sizes and secondary structure by MD simulations using the ISL method, and critically examine possible limitations of the method. Our results show that the ISL approach correctly describes the thermodynamics function, such as the specific heat, on a qualitative level. Using both analytical and numerical methods, we show that some quantitative limitations cannot be overcome with enhanced sampling or the inclusion of harmonic corrections. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.4710v2.pdf"}
{"id": "0910.5336", "abstract": "  The X-3.4 class flare of 13 December 2006 was observed with a high cadence of 2 minutes at 0.2 arc-sec resolution by HINODE/SOT FG instrument. The flare ribbons could be seen in G-band images also. A careful analysis of these observations after proper registration of images show flare related changes in penumbral filaments of the associated sunspot, for the first time. The observations of sunspot deformation, decay of penumbral area and changes in magnetic flux during large flares have been reported earlier in the literature. In this Letter, we report lateral motion of the penumbral filaments in a sheared region of the delta-sunspot during the X-class flare. Such shifts have not been seen earlier. The lateral motion occurs in two phases, (i) motion before the flare ribbons move across the penumbral filaments and (ii) motion afterwards. The former motion is directed away from expanding flare ribbons and lasts for about four minutes. The latter motion is directed in the opposite direction and lasts for more than forty minutes. Further, we locate a patch in adjacent opposite polarity spot moving in opposite direction to the penumbral filaments. Together these patches represent conjugate foot-points on either side of the polarity inversion line (PIL), moving towards each other. This converging motion could be interpreted as shrinkage of field lines. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.5336v1.pdf"}
{"id": "0911.0204", "abstract": "  We investigated with XMCD-PEEM magnetic imaging the magnetization reversal processes of Néel caps inside Bloch walls in self-assembled, micron-sized Fe(110) dots with flux-closure magnetic state. In most cases the magnetic-dependent processes are symmetric in field, as expected. However, some dots show pronounced asymmetric behaviors. Micromagnetic simulations suggest that the geometrical features (and their asymmetry) of the dots strongly affect the switching mechanism of the Néel caps. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.0204v1.pdf"}
{"id": "0911.0779", "abstract": "  Stellar clusters are born in cold and dusty molecular clouds and the youngest clusters are embedded to various degrees in dusty dark molecular material. Such embedded clusters can be considered protocluster systems. The most deeply buried examples are so heavily obscured by dust that they are only visible at infrared wavelengths. These embedded protoclusters constitute the nearest laboratories for direct astronomical investigation of the physical processes of cluster formation and early evolution. I review the present state of empirical knowledge concerning embedded cluster systems and discuss the implications for understanding their formation and subsequent evolution to produce bound stellar clusters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.0779v1.pdf"}
{"id": "0911.1011", "abstract": "  We present a new type of the Hamiltonian replica-exchange method, in which not temperatures but the van der Waals radius parameter is exchanged. By decreasing the van der Waals radii that control spatial sizes of atoms, this Hamiltonian replica-exchange method overcomes the steric restrictions and energy barriers. Furthermore, the simulation based on this method escapes from the local-minimum free-energy states and realizes effective sampling in the conformational space. We applied this method to an alanine dipeptide in aqueous solution and showed the effectiveness of the method by comparing the results with those obtained from the conventional canonical method. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.1011v1.pdf"}
{"id": "0911.1014", "abstract": "  We present our optical observations of Swift GRB 070518 afterglow obtained at the 0.8-m Tsinghua University-National Astronomical Observatory of China telescope (TNT) at Xinglong Observatory. Our follow-up observations were performed from 512 sec after the burst trigger. With the upper limit of redshift ∼0.7, GRB 070518 is found to be an optically dim burst. The spectra indices β_ox of optical to X-ray are slightly larger than 0.5, which implies the burst might be a dark burst. The extinction A_V of the host galaxy is 3.2 mag inferred from the X-ray hydrogen column density with Galactic extinction law, and 0.3 mag with SMC extinction law. Also, it is similar to three other low-redshift optically dim bursts, which belong to XRR or XRF, and mid-term duration(T_90<10, except for GRB 070419A, T_90=116s). Moreover, its R band afterglow flux is well fitted by a single power-law with an index of 0.87. The optical afterglow and the X-ray afterglow in the normal segment might have the same mechanism, as they are consistent with the prediction of the classical external shock model. Besides, GRB 070518 agrees with Amati relation under reasonable assumptions. The Ghirlanda relation is also tested with the burst. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.1014v1.pdf"}
{"id": "0911.1757", "abstract": "  It has proven a significant challenge to experiment and phenomenology to extract precise values of the nucleon sigma terms. This difficulty opens the window for lattice QCD simulations to lead the field in resolving this aspect of nucleon structure. Here we report on recent advances in the extraction of nucleon sigma terms in lattice QCD. In particular, the strangeness component is now being resolved to a precision that far surpasses best phenomenological estimates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.1757v1.pdf"}
{"id": "0911.2786", "abstract": "  This talk briefly explains how the breaking of a Lorentz-invariant description of nature at tiny space-time intervals might affect the non-Gaussian character of the primordial fluctuations left by inflation. For example, a model that contains irrelevant operators that only preserve the spatial symmetries along constant-time surfaces can generate a larger non-Gaussian component in the pattern of primordial fluctuations than is ordinarily predicted by inflation. This property can be useful for constraining models that allow some Lorentz violation at short distances, beyond the constraints possible from the power spectrum alone. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.2786v1.pdf"}
{"id": "0911.3733", "abstract": "  We perform first-principles calculations of electronic structure and optical properties for UO2 and PuO2 based on the density functional theory using the generalized gradient approximation (GGA)+U scheme. The main features in orbital-resolved partial density of states for occupied f and p orbitals, unoccupied d orbitals, and related gaps are well reproduced compared to experimental observations. Based on the satisfactory ground-state electronic structure calculations, the dynamical dielectric function and related optical spectra, i.e., the reflectivity, adsorption coefficient, energy-loss, and refractive index spectrum, are obtained. These results are consistent well with the attainable experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.3733v1.pdf"}
{"id": "0911.4189", "abstract": "  Extended high-energy(>100MeV) gamma-ray emission that lasts much longer than the prompt sub-MeV emission has been detected from quite a few gamma-ray bursts (GRBs) by Fermi Large Area Telescope (LAT) recently. A plausible scenario is that this emission is the afterglow synchrotron emission produced by electrons accelerated in the forward shocks. In this scenario, the electrons that produce synchrotron high-energy emission also undergo inverse-Compton (IC) loss and the IC scattering with the synchrotron photons should be in the Klein-Nishina regime. Here we study effects of the Klein-Nishina scattering on the high-energy synchrotron afterglow emission. We find that, at early times the Klein-Nishina suppression effect on those electrons that produce the high-energy emission is usually strong and therefore their inverse-Compton loss is small with a Compton parameter Y < a few for a wide range of parameter space. This leads to a relatively bright synchrotron afterglow at high energies that can be detected by Fermi LAT. As the Klein-Nishina suppression effect weakens with time, the inverse-Compton loss increases and could dominate over the synchrotron loss in some parameter space. This will lead to a faster temporal decay of the high-energy synchrotron emission than what is predicted by the standard synchrotron model, which may explain the observed rapid decay of the early high-energy gamma-ray emission in GRB090510 and GRB090902B. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0911/0911.4189v1.pdf"}
{"id": "0912.0646", "abstract": "  We explain how to implement, in the context of projected entangled-pair states (PEPS), the general procedure of fermionization of a tensor network introduced in [P. Corboz, G. Vidal, Phys. Rev. B 80, 165129 (2009)]. The resulting fermionic PEPS, similar to previous proposals, can be used to study the ground state of interacting fermions on a two-dimensional lattice. As in the bosonic case, the cost of simulations depends on the amount of entanglement in the ground state and not directly on the strength of interactions. The present formulation of fermionic PEPS leads to a straightforward numerical implementation that allowed us to recycle much of the code for bosonic PEPS. We demonstrate that fermionic PEPS are a useful variational ansatz for interacting fermion systems by computing approximations to the ground state of several models on an infinite lattice. For a model of interacting spinless fermions, ground state energies lower than Hartree-Fock results are obtained, shifting the boundary between the metal and charge-density wave phases. For the t-J model, energies comparable with those of a specialized Gutzwiller-projected ansatz are also obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.0646v2.pdf"}
{"id": "0912.2106", "abstract": "  We present the combination of dynamical accretion model based on 3D GRMHD simulations and general relativistic (GR) polarized radiative transfer. We write down the formalism of and perform the GR ray-tracing of cyclo-synchrotron radiation through the model of accretion flow in Sagittarius A*. GR polarimetric imaging is presented as well as the results for spectrum for a probable set of spins and orientations. Precise fitting formulae for Faraday rotation and Faraday conversion coefficients are employed for thermal plasma. The axisymmetic flow pattern and the magnetic field geometry correspond to averaged 3D GRMHD simulations near the black hole, whereas the analytic model was used far from the black hole. The density scaling is found by fitting the sub-mm flux. Spin a=0.7 and inclination angle θ=0.6 produce the best fit to sub-mm flux and linear polarization fraction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.2106v1.pdf"}
{"id": "0912.2265", "abstract": "  We present a computation of elastic energy loss of hard partons traversing the bulk hydrodynamical medium created in ultrarelativistic heavy-ion collisions. The model is based on perturbative Quantum Chromodynamics (pQCD) cross sections for 2→ 2 processes in which a hard incoming parton is assumed to interact with a thermal parton from the medium. We model the interactions of this type in a Monte-Carlo framework to account properly for exact energy-momentum conservation, non-eikonal parton propagation, parton conversion reactions and the possibility to create additional hard recoiling partons from the medium. For the thermodynamical properties of the medium we use a hydrodynamical evolution model. We do not aim at a full description of high transverse momentum (P_T) observables at this point. Rather, we view the model as a starting point in obtaining a baseline of what to expect under the assumptions that the medium is describable by thermal quasifree partons and that their pQCD interactions with the high-energy partons are independent. Deviations from this baseline then call for more sophisticated medium description, as well as inclusion of higher-order processes and coherence effects in the pQCD scatterings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.2265v2.pdf"}
{"id": "0912.2782", "abstract": "  We have investigated Au atomic contacts in H_2 and D_2 environment by conductance measurement and dI/dV spectroscopy. A single H_2 or D_2 molecule was found to bridge Au electrodes. In the case of the Au/H_2/Au junction, symmetric peaks were observed in dI/dV spectra, while they were not observed for the Au/D_2/Au junction. The shape of the peaks in dI/dV spectra originated from the structural change of the single molecule junction induced by the phonon excitation. The structural change could occur only for the Au/H_2/Au junction. The difference in the two single molecule junctions could be explained by larger zero point energy of Au-H_2 vibration mode than that in the Au/H_2/Au junction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.2782v1.pdf"}
{"id": "0912.4154", "abstract": "  The coherent transport properties of armchair graphene nanoconstrictions(GNC) are studied using tight-binding approach and Green's function method. We find a non-bonding state at zero Fermi energy which results in a zero conductance valley, when a single vacancy locates at y=3n± 1 of a perfect metallic armchair graphene nanoribbon(aGNR). However, the non-bonding state doesn't exist when a vacancy locates at y=3n, and the conductance behavior of lowest conducting channel will not be affected by the vacancy. For the square-shaped armchair GNC consisting of three metallic aGNR segments, resonant tunneling behavior is observed in the single channel energy region. We find that the presence of localized edge state locating at the zigzag boundary can affect the resonant tunneling severely. A simplified one dimensional model is put forward at last, which explains the resonant tunneling behavior of armchair GNC very well. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.4154v1.pdf"}
{"id": "0912.4228", "abstract": "  We investigate the correlation between the point disclination energies and the surface curvature modulation of nematic liquid crystal membranes with a Gaussian bump geometry. Due to the correlation, disclinations feel an attractive force that confines them to an annulus region, resulting in a halo distribution around the top of the bump. The halo formation is a direct consequence of the nonzero Gaussian curvature of the bump that affects preferable configurations of liquid crystal molecules around the disclination core. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.4228v3.pdf"}
{"id": "0912.4348", "abstract": "  We propose a version of chaotic inflation, in which a fundamental scale M, well below the Planck scale M_P, fixes the initial value of the effective potential. If this scale happens to be the scale of grand unified theories, there are just enough e-foldings of inflation. An initial epoch of fast-roll breaks scale-invariance at the largest observable scales. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.4348v1.pdf"}
{"id": "1001.0066", "abstract": "  We investigate a matter dominated navigation cosmological model. The influence of a possible drift (wind) in the navigation cosmological model makes the spacetime geometry change from Riemannian to Finslerian. The evolution of the Finslerian Universe is governed by the same gravitational field equation with the familiar Friedmann-Robertson-Walker one. However, the change of space geometry from Riemannian to Finslerian supplies us a new relation between the luminosity distant and redshift. It is shown that the Hubble diagram based on this new relation could account for the observations on distant Type Ia supernovae. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.0066v2.pdf"}
{"id": "1001.0952", "abstract": "  It is shown how to implement quantum feedback and probabilistic error correction in an open quantum system consisting of a single atom, with ground- and excited-state Zeeman structure, in a driven two-mode optical cavity. The ground state superposition is manipulated and controlled through conditional measurements and external fields, which shield the coherence and correct quantum errors. Modeling of an experimentally realistic situation demonstrates the robustness of the proposal for realization in the laboratory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.0952v1.pdf"}
{"id": "1001.4027", "abstract": "  It has been recently pointed out that local volume fluctuations in granular packings follow remarkably well a shifted and rescaled Gamma distribution named the kGamma distribution [T. Aste, T. Di Matteo, Phys. Rev. E 77 (2008) 021309]. In this paper we confirm, extend and discuss this finding by supporting it with additional experimental and simulation data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.4027v1.pdf"}
{"id": "1001.4736", "abstract": "  Broadband noise represents a severe limitation towards the implementation of a solid-state quantum information processor. Considering common spectral forms, we propose a classification of noise sources based on the effects produced instead of on their microscopic origin. We illustrate a multi-stage approach to broadband noise which systematically includes only the relevant information on the environment, out of the huge parametrization needed for a microscopic description. We apply this technique to a solid-state two-qubit gate in a fixed coupling implementation scheme. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.4736v1.pdf"}
{"id": "1001.5066", "abstract": "  We construct non-stationary exact solutions to five dimensional Einstein-Maxwell-Chern-Simons theory with positive cosmological constant. The solutions are based on four-dimensional Atiyah-Hitchin space. In asymptotic regions, the solutions approach to Gibbons-Perry-Sorkin monopole solutions. On the other hand, near the four-dimensional bolt of Atiyah-Hitchin space, our solutions show a bolt structure in five dimensions. The c-function for the solutions shows monotonic increase in time, in agreement with the general expected behaviour of c-function in asymptotically dS spacetimes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.5066v1.pdf"}
{"id": "1001.5356", "abstract": "  We perform an ab-initio calculation for the binding energy of ^6Li using the CD-Bonn 2000 NN potential renormalized with the Lee-Suzuki method. The many-body approach to the problem is the Hybrid Multideterminant method. The results indicate a binding energy of about 31 MeV, within a few hundreds KeV uncertainty. The center of mass diagnostics are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.5356v2.pdf"}
{"id": "1002.0638", "abstract": "  Photons can carry spin angular momentum (SAM) and orbital angular momentum (OAM), which can be used to realize a qubit system and a high-dimension system respectively. This spin-orbital system is very suitable for implementing one-dimensional discrete-time quantum random walks. We propose a simple scheme of quantum walks on the spin-orbital angular momentum space of photons, where photons walk on the infinity OAM space controlled by their SAM. By employing the recent invention of an optical device, the so-called 'q-plate', our scheme is more simple and efficient than others because there is no Mach-Zehnder interferometer in the scheme. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.0638v1.pdf"}
{"id": "1002.1260", "abstract": "  We discuss evidence that quasars, and more generally radio jets, may have played an active role in the formation stage of galaxies by inducing star formation, i.e. through positive feedback. This mechanism first proposed in the 70's has been considered as anecdotic until now, contrary to the opposite effect that is generally put forward, the quenching of star formation in massive galaxies to explain the galaxy bimodality, downsizing and the universal black hole mass over bulge stellar mass ratio. This suggestion is based on the recent discovery of an ultra-luminous infrared galaxies, i.e. an extreme starburst, which appears to be triggered by a radio jet from the QSO HE0450-2958 at z=0.2863, together with the finding in several systems of an offset between molecular gas and quasars, which may be explained by the positive feedback effect of radio jets on their local environment. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.1260v1.pdf"}
{"id": "1002.3493", "abstract": "  Typical protocols for peer-to-peer file sharing over the Internet divide files to be shared into pieces. New peers strive to obtain a complete collection of pieces from other peers and from a seed. In this paper we investigate a problem that can occur if the seeding rate is not large enough. The problem is that, even if the statistics of the system are symmetric in the pieces, there can be symmetry breaking, with one piece becoming very rare. If peers depart after obtaining a complete collection, they can tend to leave before helping other peers receive the rare piece. Assuming that peers arrive with no pieces, there is a single seed, random peer contacts are made, random useful pieces are downloaded, and peers depart upon receiving the complete file, the system is stable if the seeding rate (in pieces per time unit) is greater than the arrival rate, and is unstable if the seeding rate is less than the arrival rate. The result persists for any piece selection policy that selects from among useful pieces, such as rarest first, and it persists with the use of network coding. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.3493v2.pdf"}
{"id": "1002.3724", "abstract": "  As an emerging field, MS-based proteomics still requires software tools for efficiently storing and accessing experimental data. In this work, we focus on the management of LC-MS data, which are typically made available in standard XML-based portable formats. The structures that are currently employed to manage these data can be highly inefficient, especially when dealing with high-throughput profile data. LC-MS datasets are usually accessed through 2D range queries. Optimizing this type of operation could dramatically reduce the complexity of data analysis. We propose a novel data structure for LC-MS datasets, called mzRTree, which embodies a scalable index based on the R-tree data structure. mzRTree can be efficiently created from the XML-based data formats and it is suitable for handling very large datasets. We experimentally show that, on all range queries, mzRTree outperforms other known structures used for LC-MS data, even on those queries these structures are optimized for. Besides, mzRTree is also more space efficient. As a result, mzRTree reduces data analysis computational costs for very large profile datasets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.3724v2.pdf"}
{"id": "1002.3745", "abstract": "  We performed density functional studies of electronic properties and mechanisms of hydrogen transport in Rb3H(SeO4)2 crystal which represents technologically promising class M3H(XO4)2 of proton conductors (M=Rb,Cs, NH4; X=S,Se). The electronic structure calculations show a decisive role of lattice dynamics in the process of proton migration. In the obtained revised mechanism of proton transport, the strong displacements of the vertex oxygens play a key role in the establishing the continuous hydrogen transport and in the achieving low activation energies of proton conduction which is in contrast to the standard two-stage Grotthuss mechanism of proton transport. Consequently, any realistic model description of proton transport should inevitably involve the interactions with the sublattice of the XO4 groups. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.3745v5.pdf"}
{"id": "1003.0837", "abstract": "  We propose a similarity-based method, using the similarity between nodes, to address the problem of classification in partially labeled networks. The basic assumption is that two nodes are more likely to be categorized into the same class if they are more similar. In this paper, we introduce ten similarity indices, including five local ones and five global ones. Empirical results on the co-purchase network of political books show that the similarity-based method can give high accurate classification even when the labeled nodes are sparse which is one of the difficulties in classification. Furthermore, we find that when the target network has many labeled nodes, the local indices can perform as good as those global indices do, while when the data is sparce the global indices perform better. Besides, the similarity-based method can to some extent overcome the unconsistency problem which is another difficulty in classification. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.0837v1.pdf"}
{"id": "1003.2564", "abstract": "  GALEX near ultraviolet (NUV) and far-ultraviolet (FUV) light curves of three extremely low accretion rate polars show distinct modulations in their UV light curves. While these three systems have a range of magnetic fields from 13 to 70 MG, and of late type secondaries (including a likely brown dwarf in SDSSJ121209.31+013627.7), the accretion rates are similar, and the UV observations imply some mechanism is operating to create enhanced emission zones on the white dwarf. The UV variations match in phase to the two magnetic poles viewed in the optical in WX LMi and to the single poles evident in the optical in SDSSJ1212109.31+013627.7 and SDSSJ103100.55+202832.2. Simple spot models of the UV light curves show that if hot spots are responsible for the UV variations, the temperatures are on the order of 10,000-14,000K. For the single pole systems, the size of the FUV spot must be smaller than the NUV and in all cases, the geometry is likely more complicated than a simple circular spot. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.2564v1.pdf"}
{"id": "1003.2576", "abstract": "  Co-doped ZnO is the prototypical dilute magnetic oxide showing many of the characteristics of ferromagnetism. The microscopic origin of the long range order however remains elusive, since the conventional mechanisms for the magnetic interaction, such as super-exchange and double exchange, fail either at the fundamental or at a quantitative level. Intriguingly, there is a growing evidence that defects both in point-like or extended form play a fundamental role in driving the magnetic order. Here we explore one of such possibilities by performing ab initio density functional theory calculations for the magnetic interaction of Co ions at or near a ZnO {101̅0} surface. We find that extended surface states can hybridize with the e-levels of Co and efficiently mediate the magnetic order, although such a mechanism is effective only for ions placed in the first few atomic planes near the surface. We also find that the magnetic anisotropy changes at the surface from an hard-axis easy-plane to an easy axis, with an associated increase of its magnitude. We then conclude that clusters with high densities of surfacial Co ions may display blocking temperatures much higher than in the bulk. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.2576v1.pdf"}
{"id": "1003.3252", "abstract": "  The population of compact massive galaxies observed at z > 1 are hypothesised, both observationally and in simulations, to be merger remnants of gas-rich disc galaxies. To probe such a scenario we analyse a sample of 12 gas-rich and active star forming sub-mm galaxies (SMGs) at 1.8 < z < 3. We present a structural and size measurement analysis for all of these objects using very deep ACS and NICMOS imaging in the GOODS-North field. Our analysis reveals a heterogeneous mix of morphologies and sizes. We find that four galaxies (33", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.3252v1.pdf"}
{"id": "1003.3272", "abstract": "  This paper discusses the potential of graphics processing units (GPUs) in high-dimensional optimization problems. A single GPU card with hundreds of arithmetic cores can be inserted in a personal computer and dramatically accelerates many statistical algorithms. To exploit these devices fully, optimization algorithms should reduce to multiple parallel tasks, each accessing a limited amount of data. These criteria favor EM and MM algorithms that separate parameters and data. To a lesser extent block relaxation and coordinate descent and ascent also qualify. We demonstrate the utility of GPUs in nonnegative matrix factorization, PET image reconstruction, and multidimensional scaling. Speedups of 100 fold can easily be attained. Over the next decade, GPUs will fundamentally alter the landscape of computational statistics. It is time for more statisticians to get on-board. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.3272v1.pdf"}
{"id": "1004.2082", "abstract": "  Quantum discord (QD) reveals the nonclassical nature of correlations in bipartite quantum states, going beyond the entanglement-separability paradigm. In this article we discuss the suitability of QD in what concern its possible asymmetry with relation to the bipartition we choose to compute it. We obtain an analytical formula for a symmetrized version of QD (SQD) in Bell-diagonal states. We observe that if correlation is regarded as a shared property, then the SQD could be a convenient quantifier for asymmetric states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.2082v4.pdf"}
{"id": "1004.2458", "abstract": "  We present results of direct imaging observations for HAT-P-7 taken with the Subaru HiCIAO and the Calar Alto AstraLux. Since the close-in transiting planet HAT-P-7b was reported to have a highly tilted orbit, massive bodies such as giant planets, brown dwarfs, or a binary star are expected to exist in the outer region of this system. We show that there are indeed two candidates for distant faint stellar companions around HAT-P-7. We discuss possible roles played by such companions on the orbital evolution of HAT-P-7b. We conclude that as there is a third body in the system as reported by Winn et al. (2009, ApJL, 763, L99), the Kozai migration is less likely while planet-planet scattering is possible. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.2458v1.pdf"}
{"id": "1004.2610", "abstract": "  The influence of the spin-orbit interactions on the energy spectrum of two-electron laterally coupled quantum dots is investigated. The effective Hamiltonian for a spin qubit pair proposed in F. Baruffa et al., Phys. Rev. Lett. 104, 126401 (2010) is confronted with exact numerical results in single and double quantum dots in zero and finite magnetic field. The anisotropic exchange Hamiltonian is found quantitatively reliable in double dots in general. There are two findings of particular practical importance: i) The model stays valid even for maximal possible interdot coupling (a single dot), due to the absence of a coupling to the nearest excited level, a fact following from the dot symmetry. ii) In a weak coupling regime, the Heitler-London approximation gives quantitatively correct anisotropic exchange parameters even in a finite magnetic field, although this method is known to fail for the isotropic exchange. The small discrepancy between the analytical model (which employes the linear Dresselhaus and Bychkov-Rashba spin-orbit terms) and the numerical data for GaAs quantum dots is found to be mostly due to the cubic Dresselhaus term. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.2610v2.pdf"}
{"id": "1004.3437", "abstract": "  We present results of an analytic and numerical calculation that studies the relationship between the time of initial foot contact and the ground reaction force of human gait and explores the dynamic principle of center of mass. Assuming the ground reaction force of both feet to be the same in the same phase of a stride cycle, we establish the relationships between the time of initial foot contact and the ground reaction force, acceleration, velocity, displacement and average kinetic energy of center of mass. We employ the dispersion to analyze the effect of the time of the initial foot contact that imposes upon these physical quantities. Our study reveals that when the time of one foot's initial contact falls right in the middle of the other foot's stride cycle, these physical quantities reach extrema. An action function has been identified as the dispersion of the physical quantities and optimized analysis used to prove the least-action principle in gait. In addition to being very significant to the research domains such as clinical diagnosis, biped robot's gait control, the exploration of this principle can simplify our understanding of the basic properties of gait. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.3437v1.pdf"}
{"id": "1004.4777", "abstract": "  We compare classes of finite relational structures via monadic second-order transductions. More precisely, we study the preorder where we set C ⊆K if, and only if, there exists a transduction τ such that C⊆τ(K). If we only consider classes of incidence structures we can completely describe the resulting hierarchy. It is linear of order type ω+3. Each level can be characterised in terms of a suitable variant of tree-width. Canonical representatives of the various levels are: the class of all trees of height n, for each n ∈N, of all paths, of all trees, and of all grids. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.4777v4.pdf"}
{"id": "1004.5272", "abstract": "  We give examples of rank one compact surfaces on which there exist recurrent geodesics that cannot be shadowed by periodic geodesics. We build rank one compact surfaces such that ergodic measures on the unit tangent bundle of the surface are not dense in the set of probability measures invariant by the geodesic flow. Finally, we give examples of complete rank one surfaces for which the non wandering set of the geodesic flow is connected, the periodic orbits are dense in that set, yet the geodesic flow is not transitive in restriction to its non wandering set. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.5272v1.pdf"}
{"id": "1005.2443", "abstract": "  In this paper, a transmission strategy of fountain codes over cooperative relay networks is proposed. When more than one relay nodes are available, we apply network coding to fountain-coded packets. By doing this, partial information is made available to the destination node about the upcoming message block. It is therefore able to reduce the required number of transmissions over erasure channels, hence increasing the effective throughput. Its application to wireless channels with Rayleigh fading and AWGN noise is also analysed, whereby the role of analogue network coding and optimal weight selection is demonstrated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.2443v1.pdf"}
{"id": "1005.3080", "abstract": "  Spin-polarized symmetric nuclear matter is studied within the Dirac-Brueckner-Hartree-Fock approach. We pay particular attention to the difference between the one-body potentials of upward and downward polarized nucleons. This is formally analogous to the \"Lane potential\" for isospin-asymmetric nuclear matter. We point out the necessity for additional information on this fundamentally important quantity and suggest ways to constrain it. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.3080v1.pdf"}
{"id": "1005.3399", "abstract": "  We present a QCD-based model where rescattering between final state partons in deep inelastic scattering leads to events with large rapidity gaps and a leading proton. In the framework of this model the amplitude for multiple gluon exchanges is calculated in the eikonal approximation to all orders in perturbation theory. Both large and small invariant mass M_X limits are considered. The model successfully describes the precise HERA data on the diffractive deep inelastic cross section in the whole available kinematical range and gives new insight into the density of gluons at very small momentum fractions in the proton. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.3399v2.pdf"}
{"id": "1005.4359", "abstract": "  Many-electron systems confined to a quasi-1D geometry by a cylindrical distribution of positive charge have been investigated by density functional computations in the unrestricted local spin density approximation. Our investigations have been focused on the low density regime, in which electrons are localised. The results reveal a wide variety of different charge and spin configurations, including linear and zig-zag chains, single and double-strand helices, and twisted chains of dimers. The spin-spin coupling turns from weakly anti-ferromagnetic at relatively high density, to weakly ferromagnetic at the lowest densities considered in our computations. The stability of linear chains of localised charge has been investigated by analysing the radial dependence of the self-consistent potential and by computing the dispersion relation of low-energy harmonic excitations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.4359v1.pdf"}
{"id": "1005.4446", "abstract": "  In this paper we present a novel genetic algorithm (GA) solution to a simple yet challenging commercial puzzle game known as the Zen Puzzle Garden (ZPG). We describe the game in detail, before presenting a suitable encoding scheme and fitness function for candidate solutions. We then compare the performance of the genetic algorithm with that of the A* algorithm. Our results show that the GA is competitive with informed search in terms of solution quality, and significantly out-performs it in terms of computational resource requirements. We conclude with a brief discussion of the implications of our findings for game solving and other \"real world\" problems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.4446v1.pdf"}
{"id": "1005.5112", "abstract": "  Based on results of density functional theory (DFT) calculations with the local spin density approximation (LSDA) and the generalized gradient approximation (GGA), we propose a new magnetic material, CsCl-type FeSe. The calculations reveal the existence of ferromagnetic (FM) and antiferromagnetic (AFM) states over a wide range of lattice constants. At 3.12 Å in the GGA, the equilibrium state is found to be AFM with a local Fe magnetic moment of ± 2.69 μ_B. A metastable FM state with Fe and Se local magnetic moments of 2.00 μ_B and -0.032 μ_B, respectively, lies 171.7 meV above the AFM state. Its equilibrium lattice constant is ∼ 2 % smaller than that of the AFM state, implying that when the system undergoes a phase transition from the AFM state to the FM one, the transition is accompanied by volume contraction. Such an AFM-FM transition is attributed to spin-density z-reflection symmetry; the symmetry driven AFM-FM transition is not altered by spin-orbit coupling. The relative stability of different magnetic phases is discussed in terms of the local density of states. We find that CsCl-type FeSe is mechanically stable, but the magnetic states are expected to be brittle. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.5112v2.pdf"}
{"id": "1005.5213", "abstract": "  Using the different versions of phenomenological proximity potential as well as other parametrizations within the proximity concept, we perform a detailed comparative study of fusion barriers for asymmetric colliding nuclei with asymmetry parameter as high as 0.23. In all, 12 different proximity potentials are robust against the experimental data of 60 reactions. Our detailed study reveals that the surface energy coefficient as well as radius of the colliding nuclei depend significantly on the asymmetry parameter. All models are able to explain the fusion barrier heights within ±10", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.5213v2.pdf"}
{"id": "1005.5717", "abstract": "  On microstructured hydrophobic surfaces, geometrical patterns may lead to the appearance of a superhydrophobic state, where gas bubbles at the surface can have a strong impact on the fluid flow along such surfaces. In particular, they can strongly influence a detected slip at the surface. We present two-phase lattice Boltzmann simulations of a flow over structured surfaces with attached gas bubbles and demonstrate how the detected slip depends on the pattern geometry, the bulk pressure, or the shear rate. Since a large slip leads to reduced friction, our results allow to assist in the optimization of microchannel flows for large throughput. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.5717v1.pdf"}
{"id": "1006.1123", "abstract": "  The 2009 run provided the first proton-proton collisions from the Large Hadron Collider (LHC) at center of mass energies of 900 GeV and 2.36 TeV. The Compact Muon Solenoid (CMS) experiment has recorded a large sample of minimum bias events from these collisions. We present results from the all silicon tracking detectors from this run. The performance of the tracker and track reconstruction algorithms are considered including signal-to-noise, efficiencies and comparisons to simulation for track parameter and resonance reconstruction performance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.1123v1.pdf"}
{"id": "1006.1732", "abstract": "  The effects of boundary impurities on the entanglement entropy in an antiferromagnetic Heisenberg opened spin-1/2 chain are investigated. The method of density-matrix renormalization-group is used to obtain the bipartite entanglement. The entropy increases when the length of the subsystem increases. It will approach to a constant when system length is very large. With the same impurity interaction, qutrit impurities of spin-1 can increase the entanglement entropy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.1732v1.pdf"}
{"id": "1006.1826", "abstract": "  Surface reconstructions on the polar ZnO(0001) surface are investigated using empirical potential models. Several possible reconstructions based around triangular motifs are investigated. The quenching of the dipole moment in the material dominates the energetics of the surface patterns so that no one particular size of surface triangular island or pit is strongly favoured. We employ Monte Carlo simulations to explore which patterns emerge from a high temperature quench and during deposition of additional ZnO monolayers. The simulations show that a range of triangular islands and pits evolve in competition with one another. The surface patterns we discover are qualitatively similar to those observed experimentally. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.1826v1.pdf"}
{"id": "1006.2076", "abstract": "  We investigate the dynamics of a single phonon (oscillator) mode linearly coupled to an electronic few-level system in contact with external particle reservoirs (leads). A stationary electronic current through the system generates non-trivial dynamical behaviour of the oscillator. Using Feynman-Vernon influence functional theory, we derive a Langevin equation for the oscillator trajectory that is non-perturbative in the system-leads coupling and from which we extract effective oscillator potentials and friction coefficients. For the two simplest cases of a single and two coupled electronic levels, we discuss various regimes of the oscillator dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.2076v1.pdf"}
{"id": "1006.2279", "abstract": "  The breaking stress (the maximum of the stress-strain curve) of neutron star crust is important for neutron star physics including pulsar glitches, emission of gravitational waves from static mountains, and flares from star quakes. We perform many molecular dynamic simulations of the breaking stress at different coupling parameters (inverse temperatures) and strain rates. We describe our results with the Zhurkov model of strength. We apply this model to estimate the breaking stress for timescales  1 s - 1 year, which are most important for applications, but much longer than can be directly simulated. At these timescales the breaking stress depends strongly on the temperature. For coupling parameter <200, matter breaks at very small stress, if it is applied for a few years. This viscoelastic creep can limit the lifetime of mountains on neutron stars. We also suggest an alternative model of timescale-independent breaking stress, which can be used to estimate an upper limit on the breaking stress. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.2279v1.pdf"}
{"id": "1006.4595", "abstract": "  How do individuals accumulate wealth as they interact economically? We outline the consequences of a simple microscopic model in which repeated pairwise exchanges of assets between individuals build the wealth distribution of a population. This distribution is determined for generic exchange rules — transactions that involve a fixed amount or a fixed fraction of individual wealth, as well as random or greedy exchanges. In greedy multiplicative exchange, a continuously evolving power law wealth distribution arises, a feature that qualitatively mimics empirical observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.4595v2.pdf"}
{"id": "1006.5194", "abstract": "  A relativistic version of cold emission of electrons in presence of strong magnetic field, relevant for strongly magnetized neutron stars is obtained. It is found that in this scenario, a scalar type potential barrier does not allow quantum tunneling through the surface. Whereas, in presence of a vector type surface barrier, the probability of electron emission is much larger compared to the original Fowler-Nordheim cold emission of electrons. It is found that the relativistic version in presence of strong magnetic field does not follow exponential decay. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.5194v2.pdf"}
{"id": "1006.5338", "abstract": "  Stationary and isotropic iteration stable random tessellations are considered, which can be constructed by a random process of cell division. The collection of maximal polytopes at a fixed time t within a convex window W⊂ R^d is regarded and formulas for mean values, variances, as well as a characterization of certain covariance measures are proved. The focus is on the case d≥ 3, which is different from the planar one, treated separately in <cit.>. Moreover, a multivariate limit theorem for the vector of suitably rescaled intrinsic volumes is established, leading in each component – in sharp contrast to the situation in the plane – to a non-Gaussian limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.5338v2.pdf"}
{"id": "1006.5654", "abstract": "  The young open cluster Collinder 419 surrounds the massive O star, HD 193322, that is itself a remarkable multiple star system containing at least four components. Here we present a discussion of the cluster distance based upon new spectral classifications of the brighter members, UBV photometry, and an analysis of astrometric and photometric data from the UCAC3 and 2MASS catalogs. We determine an average cluster reddening of E(B-V)=0.37 +- 0.05 mag and a cluster distance of 741 +- 36 pc. The cluster probably contains some very young stars that may include a reddened M3 III star, IRAS 20161+4035. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.5654v2.pdf"}
{"id": "1007.0976", "abstract": "  Of concern in this paper is an investigation of heat and mass transfer over a stretching sheet under the influence of an applied uniform magnetic field and the effects of Hall current are taken into account. The non-linear boundary layer equations together with the boundary conditions are reduced to a system of non-linear ordinary differential equations by using the similarity transformation. The system of non-linear ordinary differential equations are solved by developing a suitable numerical techniques such as finite difference scheme and Newton's method of linearization. The numerical results concerned with the velocity, temperature and concentration profiles as well as the skin-friction coefficient, local Nusselt number Nu and the local sherhood number Sh for various values of the nondimensional parameters presented graphically. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.0976v1.pdf"}
{"id": "1007.1179", "abstract": "  We describe a compression method for floating-point astronomical images that gives compression ratios of 6 – 10 while still preserving the scientifically important information in the image. The pixel values are first preprocessed by quantizing them into scaled integer intensity levels, which removes some of the uncompressible noise in the image. The integers are then losslessly compressed using the fast and efficient Rice algorithm and stored in a portable FITS format file. Quantizing an image more coarsely gives greater image compression, but it also increases the noise and degrades the precision of the photometric and astrometric measurements in the quantized image. Dithering the pixel values during the quantization process can greatly improve the precision of measurements in the images. This is especially important if the analysis algorithm relies on the mode or the median which would be similarly quantized if the pixel values are not dithered. We perform a series of experiments on both synthetic and real astronomical CCD images to quantitatively demonstrate that the magnitudes and positions of stars in the quantized images can be measured with the predicted amount of precision. In order to encourage wider use of these image compression methods, we have made available a pair of general-purpose image compression programs, called fpack and funpack, which can be used to compress any FITS format image. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.1179v1.pdf"}
{"id": "1007.2465", "abstract": "  Based on a semiclassical expansion for quantum chromodynamics in the instanton liquid background, the correlation function of the 0^++ scalar glueball current is given, and the properties of the 0^++ scalar glueball are studied in the framework of Gaussian sum rules. Besides the pure classical and quantum contributions, the contributions arising from the interactions between the classical instanton fields and quantum gluons are come into play. Instead of the usual zero-width approximation for the resonance, the Breit-Wigner form for the spectral function of the finite-width resonance is adopted. The family of the Gaussian sum rules for the scalar glueball in quantum chromodynamics with and without light quarks is studied. A consistency between the subtracted and unsubtracted sum rules is very well justified, and the values of the decay width and the coupling to the corresponding current for the 0^++ resonance, in which the scalar glueball fraction is dominant, are obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2465v2.pdf"}
{"id": "1007.2882", "abstract": "  The results from data taken during the last several years at the Relativistic Heavy-Ion Collider (RHIC) will be reviewed in the paper. Several selected topics that further our understanding of constituent quark scaling, jet quenching and color screening effect of heavy quarkonia in the hot dense medium will be presented. Detector upgrades will further probe the properties of Quark Gluon Plasma. Future measurements with upgraded detectors will be presented. The discovery perspectives from future measurements will also be discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2882v1.pdf"}
{"id": "1007.3391", "abstract": "  We consider a quantum memory scheme based on the conversion of a signal pulse into a long-lived spin coherence via stimulated off-resonant Raman process. For a storing medium consisting of alkali atoms, we have calculated the Autler-Townes resonance structure created by a strong control field. By taking into account the upper hyperfine states of the D1 optical transition, we show important deviations from the predictions of the usual three-level Lambda-scheme approximation and we demonstrate an enhancement of the process for particular detunings of the control. We estimate the memory efficiency one can obtain using this configuration. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.3391v1.pdf"}
{"id": "1007.3454", "abstract": "  The latest progress in calculating electroweak gauge boson production in association with QCD jets at hadron colliders is summarized. Particular emphasis is given to the recently completed QCD one-loop calculations of W+3jets and Wb final states. Furthermore recent developments in improving Monte Carlo event generators by means of combining tree-level matrix elements with parton showers is reviewed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.3454v1.pdf"}
{"id": "1007.4754", "abstract": "  We consider an idealized situation where the Quark-Gluon Plasma (QGP) is described by a perfect, 3+1 dimensional fluid dynamic model starting from an initial state and expanding until a final state where freeze-out and/or hadronization takes place. We study the entropy production with attention to effects of (i) numerical viscosity, (ii) late stages of flow where the Bag Constant and the partonic pressure are becoming similar, (iii) and the consequences of final freeze-out and constituent quark matter formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.4754v1.pdf"}
{"id": "1007.4788", "abstract": "  We present the Australia Telescope Compact Array (ATCA) observations of the SiO masers in the Galactic center in transitions of v=1, J=2–1 at 86 GHz and v=1, J=1–0 at 43 GHz. Two 86-GHz SiO masers were detected within the central parsec, and they are associated with IRS 10EE and IRS 15NE, respectively. We detected eighteen 43-GHz SiO masers within a projected separation of <2 pc from Sagittarius A* (Sgr A*), among which seven masers are newly discovered from our observations. This raises the total number of 43-GHz SiO masers within the central 4 parsecs of the GC region to 22. Simultaneous observations at 86 and 43 GHz showed that the intensity of 43-GHz SiO maser is  3 times higher than that of 86-GHz maser in IRS 10EE (an OH/IR star), while the integrated flux of the SiO maser emission at 43 GHz is comparable with that at 86 GHz in IRS 15NE (an ordinary Mira variable). These results are consistent with previous observations of massive late-type stars in the Galaxy in which the 86-GHz SiO maser is in general weaker than the 43-GHz SiO maser in OH/IR stars, while the two transitions are comparably strong in Mira stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.4788v1.pdf"}
{"id": "1007.5214", "abstract": "  I briefly review recent observations of regions forming low mass stars. The discussion is cast in the form of seven questions that have been partially answered, or at least illuminated, by new data. These are the following: where do stars form in molecular clouds; what determines the IMF; how long do the steps of the process take; how efficient is star formation; do any theories explain the data; how are the star and disk built over time; and what chemical changes accompany star and planet formation. I close with a summary and list of open questions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.5214v1.pdf"}
{"id": "1008.0222", "abstract": "  We review the motivation for hidden Higgs scenarios and discuss the light CP odd Higgs scenario in the NMSSM as an example. We summarize experimental constraints including recent limits from BaBar and Aleph. The main part of the talk is the discussion of dominant decay modes of the standard model like Higgs boson, and related decay modes of the charged Higgs and heavy CP even Higgs bosons, in these scenarios with the focus on signatures and prospects for the LHC. Examples include the direct production of a light CP odd Higgs boson, and a light charged Higgs boson in top quark decays. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.0222v1.pdf"}
{"id": "1008.0504", "abstract": "  In this paper, the electronic band structures and its transport properties in the gapped graphene superlattices, with one-dimensional (1D) periodic potentials of square barriers, are systematically investigated. It is found that a zero averaged wave-number (zero-k ) gap is formed inside the gapped graphene-based superlattices, and the condition for obtaining such a zero-k gap is analytically presented. The properties of this zero-k gap including its transmission, conductance and Fano factor are studied in detail. Finally it is revealed that the properties of the electronic transmission, conductance and Fano factor near the zero-k gap are very insensitive to the structural disorder for the finite graphene-based periodic-barrier systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.0504v1.pdf"}
{"id": "1008.0938", "abstract": "  Zipf's law seems to be ubiquitous in human languages and appears to be a universal property of complex communicating systems. Following the early proposal made by Zipf concerning the presence of a tension between the efforts of speaker and hearer in a communication system, we introduce evolution by means of a variational approach to the problem based on Kullback's Minimum Discrimination of Information Principle. Therefore, using a formalism fully embedded in the framework of information theory, we demonstrate that Zipf's law is the only expected outcome of an evolving, communicative system under a rigorous definition of the communicative tension described by Zipf. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.0938v3.pdf"}
{"id": "1008.1118", "abstract": "  We present a hybrid model of the unitary-evolution-based quantum computation model and the measurement-based quantum computation model. In the hybrid model part of a quantum circuit is simulated by unitary evolution and the rest by measurements on star graph states, thereby combining the advantages of the two standard quantum computation models. In the hybrid model, a complicated unitary gate under simulation is decomposed in terms of a sequence of single-qubit operations, the controlled-Z gates, and multi-qubit rotations around the z-axis. Every single-qubit- and the controlled-Z gate are realized by a respective unitary evolution, and every multi-qubit rotation is executed by a single measurement on a required star graph state. The classical information processing in our model only needs an information flow vector and propagation matrices. We provide the implementation of multi-control gates in the hybrid model. They are very useful for implementing Grover's search algorithm, which is studied as an illustrating example. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.1118v2.pdf"}
{"id": "1008.1646", "abstract": "  In this article, we investigate the next-to-leading order contribution of the higher-twist Feynman diagrams to the large-p_T inclusive pion production cross section in proton-proton collisions and present the general formulae for the higher-twist differential cross sections in the case of the running coupling and frozen coupling approaches. We compared the resummed next-to-leading order higher-twist cross sections with the ones obtained in the framework of the frozen coupling approach and leading-twist cross section. The structure of infrared renormalon singularities of the higher twist subprocess cross section and it's resummed expression (the Borel sum) are found. It is shown that the resummed result depends on the choice of the meson wave functions used in the calculations. We discuss the phenomenological consequences of possible higher-twist contributions to the meson production in proton-proton collisions in next-to-leading order at RHIC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.1646v2.pdf"}
{"id": "1008.1801", "abstract": "  High energy electrons and positrons from annihilating dark matter can imprint unique angular anisotropies on the diffuse gamma-ray flux by inverse Compton scattering off the interstellar radiation field. We develop a numerical tool to compute gamma-ray emission from such electrons and positrons produced in the smooth host halo and in substructure halos with masses down to 10^(-6)M_sun. We show that the angular power spectrum from inverse Compton scattering is exponentially suppressed below an angular scale determined by the diffusion length of electrons and positrons. We also find that the total flux and the shape of the angular power spectrum depends sensitively on the spatial distribution of subhalos in the Milky Way. Finally, the contribution from the smooth host halo component to the gamma-ray mean intensity is negligibly small compared to subhalos. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.1801v3.pdf"}
{"id": "1008.2142", "abstract": "  We compute the shift in the frequency of the spin resonance in a solid that rotates in the field of a circularly polarized electromagnetic wave. Electron spin resonance, nuclear magnetic resonance, and ferromagnetic resonance are considered. We show that contrary to the case of the rotating LC circuit, the shift in the frequency of the spin resonance has strong dependence on the symmetry of the receiver. The shift due to rotation occurs only when rotational symmetry is broken by the anisotropy of the gyromagnetic tensor, by the shape of the body, or by magnetocrystalline anisotropy. General expressions for the resonance frequency and power absorption are derived and implications for experiment are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.2142v1.pdf"}
{"id": "1008.2277", "abstract": "  This paper deals with chain graphs under the classic Lauritzen-Wermuth-Frydenberg interpretation. We prove that the regular Gaussian distributions that factorize with respect to a chain graph G with d parameters have positive Lebesgue measure with respect to ℝ^d, whereas those that factorize with respect to G but are not faithful to it have zero Lebesgue measure with respect to ℝ^d. This means that, in the measure-theoretic sense described, almost all the regular Gaussian distributions that factorize with respect to G are faithful to it. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.2277v1.pdf"}
{"id": "1008.3009", "abstract": "  Nonlinear oscillators can mutually synchronize when they are driven by common external impulses. Two important scenarios are (i) synchronization resulting from phase locking of each oscillator to regular periodic impulses and (ii) noise-induced synchronization caused by Poisson random impulses, but their difference has not been fully quantified. Here we analyze a pair of uncoupled oscillators subject to common random impulses with gamma-distributed intervals, which can be smoothly interpolated between regular periodic and random Poisson impulses. Their dynamics are charac- terized by phase distributions, frequency detuning, Lyapunov exponents, and information-theoretic measures, which clearly reveal the differences between the two synchronization scenarios. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.3009v1.pdf"}
{"id": "1008.3646", "abstract": "  We give a method to construct cospectral graphs for the normalized Laplacian by a local modification in some graphs with special structure. Namely, under some simple assumptions, we can replace a small bipartite graph with a cospectral mate without changing the spectrum of the entire graph. We also consider a related result for swapping out biregular bipartite graphs for the matrix A+tD.   We produce (exponentially) large families of non-bipartite, non-regular graphs which are mutually cospectral, and also give an example of a graph which is cospectral with its complement but is not self-complementary. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.3646v2.pdf"}
{"id": "1008.5340", "abstract": "  In this paper, we introduce a distributed dynamic routing algorithm for secondary users (SUs) to minimize their interference with the primary users (PUs) in multi-hop cognitive radio (CR) networks. We use the medial axis with a relaxation factor as a reference path which is contingent on the states of the PUs. Along the axis, we construct a hierarchical structure for multiple sources to reach cognitive pilot channel (CPC) base stations. We use a temporal and spatial dynamic non-cooperative game to model the interactions among SUs as well as their influences from PUs in the multi-hop structure of the network. A multi-stage fictitious play learning is used for distributed routing in multi-hop CR networks. We obtain a set of mixed (behavioral) Nash equilibrium strategies of the dynamic game in closed form by backward induction. The proposed algorithm minimizes the overall interference and the average packet delay along the routing path from SU nodes to CPC base stations in an optimal and distributed manner ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1008/1008.5340v1.pdf"}
{"id": "1009.0069", "abstract": "  The Hopfield network is reconstructed as an inverse Ising problem by passing messages. The applied susceptibility propagation algorithm is shown to improve significantly on other mean-field-type methods and extends well into the low temperature region. However, this iterative algorithm is limited by the nature of the supplied data. Its performance deteriorates as the data becomes highly magnetized, and this method finally fails in the presence of the frozen type data where at least two of its magnetizations are equal to one in absolute value. On the other hand, a threshold behavior is observed for the susceptibility propagation algorithm and the transition from good reconstruction to poor one becomes sharper as the network size increases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.0069v2.pdf"}
{"id": "1009.0558", "abstract": "  This paper proposes a robust control method based on sliding mode design for two-level quantum systems with bounded uncertainties. An eigenstate of the two-level quantum system is identified as a sliding mode. The objective is to design a control law to steer the system's state into the sliding mode domain and then maintain it in that domain when bounded uncertainties exist in the system Hamiltonian. We propose a controller design method using the Lyapunov methodology and periodic projective measurements. In particular, we give conditions for designing such a control law, which can guarantee the desired robustness in the presence of the uncertainties. The sliding mode control method has potential applications to quantum information processing with uncertainties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.0558v2.pdf"}
{"id": "1009.2159", "abstract": "  We study the quantum-jump-based feedback control on the entanglement shared between two qubits with one of them subject to decoherence, while the other qubit is under the control. This situation is very relevant to a quantum system consisting of nuclear and electron spins in solid states. The possibility to prolong the coherence time of the dissipative qubit is also explored. Numerical simulations show that the quantum-jump-based feedback control can improve the entanglement between the qubits and prolong the coherence time for the qubit subject directly to decoherence. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.2159v1.pdf"}
{"id": "1009.3362", "abstract": "  We introduce from an experimental point of view the main concepts of fluctuation theorems for work, heat and entropy production in out of equilibrium systems. We will discuss the important difference between the applications of these concepts to stochastic systems and to a second class of systems (chaotic systems) where the fluctuations are induced either by chaotic flows or by fluctuating driving forces. We will mainly analyze the stochastic systems using the measurements performed in two experiments : a) a harmonic oscillator driven out of equilibrium by an external force b) a colloidal particle trapped in a time dependent double well potential. We will rapidly describe some consequences of fluctuation theorems and some useful applications to the analysis of experimental data. As an example the case of a molecular motor will be analyzed in some details. Finally we will discuss the problems related to the applications of fluctuation theorems to chaotic systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.3362v2.pdf"}
{"id": "1009.4846", "abstract": "  Anomalous diffusion has been widely observed by single particle tracking microscopy in complex systems such as biological cells. The resulting time series are usually evaluated in terms of time averages. Often anomalous diffusion is connected with non-ergodic behaviour. In such cases the time averages remain random variables and hence irreproducible. Here we present a detailed analysis of the time averaged mean squared displacement for systems governed by anomalous diffusion, considering both unconfined and restricted (corralled) motion. We discuss the behaviour of the time averaged mean squared displacement for two prominent stochastic processes, namely, continuous time random walks and fractional Brownian motion. We also study the distribution of the time averaged mean squared displacement around its ensemble mean, and show that this distribution preserves typical process characteristic even for short time series. Recently, velocity correlation functions were suggested to distinguish between these processes. We here present analytucal expressions for the velocity correlation functions. Knowledge of the results presented here are expected to be relevant for the correct interpretation of single particle trajectory data in complex systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.4846v2.pdf"}
{"id": "1009.5052", "abstract": "  We investigate rectification of a low-frequency ac bias in Y-junctions of one-channel Luttinger liquid wires with repulsive electron interaction. Rectification emerges due to three scatterers in the wires. We find that it is possible to achieve a higher rectification current in a Y-junction than in a single wire with an asymmetric scatterer at the same interaction strength and voltage bias. The rectification effect is the strongest in the absence of the time-reversal symmetry. In that case, the maximal rectification current can be comparable with the total current ∼ e^2V/h even for low voltages, weak scatterers and modest interaction strength. In a certain range of low voltages, the rectification current can grow as the voltage decreases. This leads to a bump in the I-V curve. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.5052v3.pdf"}
{"id": "1009.5235", "abstract": "  We present a new sample of Compact Steep Spectrum (CSS) sources with radio luminosity below 10^26 W/Hz at 1.4 GHz called the low luminosity compact (LLC) objects. The sources have been selected from FIRST survey and observed with MERLIN at L-band and C-band. The main criterion used for selection was luminosity of the objects and approximately one third of the CSS sources from the new sample have a value of radio luminosity comparable to FRIs. About 80", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.5235v1.pdf"}
{"id": "1009.5972", "abstract": "  We propose a focus of attention mechanism to speed up the Perceptron algorithm. Focus of attention speeds up the Perceptron algorithm by lowering the number of features evaluated throughout training and prediction. Whereas the traditional Perceptron evaluates all the features of each example, the Attentive Perceptron evaluates less features for easy to classify examples, thereby achieving significant speedups and small losses in prediction accuracy. Focus of attention allows the Attentive Perceptron to stop the evaluation of features at any interim point and filter the example. This creates an attentive filter which concentrates computation at examples that are hard to classify, and quickly filters examples that are easy to classify. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.5972v1.pdf"}
{"id": "1010.0916", "abstract": "  The earliest results of CMS exhibit central pseudo rapidity densities larger than the predictions of the different models. Introducing on this basis new guidelines with larger multiplicities of secondaries in the models implemented in the simulations, we examine the consequences in γ ray families (spikes in rapidity distribution, coplanar emission) and very large EAS (penetration power in the atmosphere) ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.0916v1.pdf"}
{"id": "1010.1657", "abstract": "  In this work, the effects of quantum interference and spontaneously generated coherence (SGC) are theoretically analyzed in a four level system of a ^87Rb atom. For the effects of SGC, we find that a new kind of EIT channel can be induced due to destructive interference, and the nonlinear Kerr absorption can be coherently narrowed or eliminated under different strengths of the coupling and switching fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.1657v2.pdf"}
{"id": "1010.3531", "abstract": "  The capacity to resist attacks from the environment is crucial to the survival of all organisms. We quantitatively analyze the susceptibility of protein interaction networks of numerous organisms to random and malicious attacks. We find for all organisms studied that random rewiring improves protein network robustness, so that actual networks are more fragile than rewired surrogates. This unexpected fragility contrasts with the behavior of networks such as the Internet, whose robustness decreases with random rewiring. We trace this surprising effect to the modular structure of protein networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.3531v1.pdf"}
{"id": "1010.3708", "abstract": "  We calculate the differential Drell-Yan production cross section in proton-nucleus collisions by including both next-to-leading order perturbative effects and effects of the nuclear medium. We demonstrate that dilepton production in fixed target experiments is an excellent tool to study initial-state parton energy loss in large nuclei and to accurately determine the stopping power of cold nuclear matter. We provide theoretical predictions for the attenuation of the Drell-Yan cross section at large values of Feynman x_F and show that for low proton beam energies experimental measurements at Fermilab's E906 can clearly distinguish between nuclear shadowing and energy loss effects. If confirmed by data, our results may help determine the quark radiation length in cold nuclear matter X_0 ∼ 10^-13 m. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.3708v2.pdf"}
{"id": "1010.4399", "abstract": "  This paper describes the techniques and physical parameters used to produce stable centimetric water drops in microgravity, and to study single cavitation bubbles inside such drops (Parabolic Flight Campaigns, European Space Agency ESA). While the main scientific results have been presented in a previous paper, we shall herein provide the necessary technical background, with potential applications to other experiments. First, we present an original method to produce and capture large stable drops in microgravity. This technique succeeded in generating quasi-spherical water drops with volumes up to 8 ml, despite the residual g-jitter. We find that the equilibrium of the drops is essentially dictated by the ratio between the drop volume and the contact surface used to capture the drop, and formulate a simple stability criterion. In a second part, we present a setup for creating and studying single cavitation bubbles inside those drops. In addition, we analyze the influence of the bubble size and position on the drop behaviour after collapse, i.e. jets and surface perturbations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.4399v1.pdf"}
{"id": "1010.5056", "abstract": "  Recently the H.E.S.S. collaboration announced the detection of an unidentified gamma-ray source with an off-set from the galactic plane of 3.5 degrees: HESS J1507-622. If the distance of the object is larger than about one kpc it would be physically located outside the galactic disk. The density profile of the ISM perpendicular to the galactic plane, which acts as target material for hadronic gamma-ray production, drops quite fast with increasing distance. This fact places distance dependent constraints on the energetics and properties of off-plane gamma-ray sources like HESS J1507-622 if a hadronic origin of the gamma-ray emission is assumed. For the case of this source it is found that there seems to be no simple way to link this object to the remnant of a stellar explosions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.5056v1.pdf"}
{"id": "1010.5334", "abstract": "  We review a reduction formula by Petersson that reduces the calculation of a one-loop amplitude with N external lines in n<N space-time dimensions to the case n=N and give it a geometric interpretation. In the case n=N the calculation of the euclidean amplitude is shown to be equivalent to the calculation of the volume of a tetrahedron spanned by the momenta in (n-1)-dimensional hyperbolic space. The underlying geometry is intimately linked to the geometry of the reduction formula. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.5334v1.pdf"}
{"id": "1010.5856", "abstract": "  We investigate the liquid-gas phase transition of hot protoneutron stars shortly after their birth following supernova explosion and the composition and structure of hyperon-rich (proto)neutron stars within a relativistic mean-field model where the nuclear symmetry energy has been constrained from the measured neutron skin thickness of finite nuclei. Light clusters are abundantly formed with increasing temperature well inside the neutrino-sphere for an uniform supernova matter. Liquid-gas phase transition is found to suppress the cluster yield within the coexistence phase as well as decrease considerably the neutron-proton asymmetry over a wide density range. We find symmetry energy has a modest effect on the boundaries and the critical temperature for the liquid-gas phase transition, and the composition depends more sensitively on the number of trapped neutrinos and temperature of the protoneutron star. The influence of hyperons in the dense interior of stars makes the overall equation of state soft. However, neutrino trapping distinctly delays the appearance of hyperons due to abundance of electrons. We also find that a softer symmetry energy further makes the onset of hyperon less favorable. The resulting structures of the (proto)neutron stars with hyperons and with liquid-gas phase transition are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1010/1010.5856v1.pdf"}
{"id": "1011.2033", "abstract": "  The effect of dephasing on electron transport through a benzene molecule is carefully examined using a phenomenological model introduced by Büttiker. Within a tight-binding framework all the calculations are performed based on the Green's function formalism. We investigate the influence of dephasing on transmission probability and current-voltage characteristics for three different configurations (ortho, meta and para) of the molecular system depending on the locations of two contacting leads. The presence of dephasing provides a significant change in the spectral properties of the molecule and exhibits several interesting patterns that have so far remain unexplored. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2033v2.pdf"}
{"id": "1011.2959", "abstract": "  The robustness of multipartite entanglement of systems undergoing decoherence is of central importance to the area of quantum information. Its characterization depends however on the measure used to quantify entanglement and on how one partitions the system. Here we show that the unambiguous assessment of the robustness of multipartite entanglement is obtained by considering the loss of functionality in terms of two communication tasks, namely the splitting of information between many parties and the teleportation of states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2959v1.pdf"}
{"id": "1011.3952", "abstract": "  We have studied the dynamics of chloride and potassium ions in the interior of the OmpF porin under the influence of an external electric field. From the results of extensive all-atom molecular dynamics simulations of the system we computed several first passage time (FPT) quantities to characterize the dynamics of the ions in the interior of the channel. Such FPT quantities obtained from MD simulations demonstrate that it is not possible to describe the dynamics of chloride and potassium ions inside the whole channel with a single constant diffusion coefficient. However, we showed that a valid, statistically rigorous, description in terms of a constant diffusion coefficient D and an effective deterministic force Feff can be obtained after appropriate subdivison of the channel in different regions suggested by the X-ray structure. These results have important implications for popular simplified descriptions of channels based on the 1D Poisson-Nernst-Planck (PNP) equations. Also, the effect of entropic barriers on the diffusion of the ions is identified and briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.3952v1.pdf"}
{"id": "1011.4500", "abstract": "  We consider a model of DBI inflation where two stacks of mobile branes are moving ultra relativistically in a warped throat. The stack closer to the tip of the throat is annihilated with the background anti-branes while inflation proceeds by the second stack. The effects of branes annihilation and particles creation during DBI inflation on the curvature perturbations power spectrum and the scalar spectral index are studied. We show that for super-horizon scales, modes which are outside the sound horizon at the time of branes collision, the spectral index has a shift to blue spectrum compared to the standard DBI inflation. For small scales the power spectrum approaches to its background DBI inflation value with the decaying superimposed oscillatory modulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.4500v3.pdf"}
{"id": "1012.1947", "abstract": "  This paper introduces a general theoretical framework to analyze noise limited networks. More precisely, we consider two homogenous Poisson point processes of base stations and users. General model of radio signal propagation and effect of fading are also considered. The main difference of our model with respect to other existing models is that a user connects to his best servers but not necessarily the closest one. We provide general formula for the outage probability. We study functionals related to the SNR as well as the sum of these functionals over all users per cell. For the latter, the expectation and bounds on the variance are obtained. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.1947v1.pdf"}
{"id": "1012.2413", "abstract": "  We prove an inequality between horizon area and angular momentum for a class of axially symmetric black holes. This class includes initial conditions with an isometry which leaves fixed a two-surface. These initial conditions have been extensively used in the numerical evolution of rotating black holes. They can describe highly distorted black holes, not necessarily near equilibrium. We also prove the inequality on extreme throat initial data, extending previous results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.2413v2.pdf"}
{"id": "1012.3578", "abstract": "  For active galactic nuclei (AGNs) we study the role of the mechanism of quasi-linear diffusion (QLD) in producing the high energy emission in the MeV-GeV domains strongly connected with the submillimeter/infrared radiation. Considering the kinetic equation governing the stationary regime of the QLD we investigate the feedback of the diffusion on electrons. We show that this process leads to the distribution of particles by the pitch angles, implying that the synchrotron mechanism is no longer prevented by energy losses. Examining a reasonable interval of physical parameters, we show that it is possible to produce MeV-GeV gamma-rays, strongly correlated with submillimeter/infrared bands. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.3578v1.pdf"}
{"id": "1012.3799", "abstract": "  The quasi-periodic doubling cascade is shown to occur in the transition from regular to weakly turbulent behaviour in simulations of incompressible Navier-Stokes flow on a three-periodic domain. Special symmetries are imposed on the flow field in order to reduce the computational effort. Thus we can apply tools from dynamical systems theory such as continuation of periodic orbits and computation of Lyapunov exponents. We propose a model ODE for the quasi-period doubling cascade which, in a limit of a perturbation parameter to zero, avoids resonance related problems. The cascade we observe in the simulations is then compared to the perturbed case, in which resonances complicate the bifurcation scenario. In particular, we compare the frequency spectrum and the Lyapunov exponents. The perturbed model ODE is shown to be in good agreement with the simulations of weak turbulence. The scaling of the observed cascade is shown to resemble the unperturbed case, which is directly related to the well known doubling cascade of periodic orbits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.3799v1.pdf"}
{"id": "1012.5136", "abstract": "  We present a novel method to evaluate the Alfven speed and the magnetic field strength along the streamer plasma sheet in the outer corona. The method is based on recent observations of streamer waves, which are regarded as the fast kink body mode carried by the plasma sheet structure and generated upon the impact of a fast CME (coronal mass ejection) on a nearby streamer. The mode propagates outwards with a phase speed consisting of two components. One is the phase speed of the mode in the plasma rest frame, the other is the speed of the solar wind streaming along the plasma sheet. The former can be well represented by the Alfven speed outside the plasma sheet, according to a linear wave dispersion analysis with a simplified slab model of magnetized plasmas. The radial profiles of the Alfven speed can be deduced with constraints put on the speed of the solar wind, which is done by making use of the measurements of streamer blobs flowing passively in the wind. The radial profiles of the strength of the coronal magnetic field can be depicted once the electron density distribution is specified, this is done by inverting the observed polarized brightness data. Comparing the diagnostic results corresponding to the first wave trough and the following crest, we find that both the Alfven speed and magnetic field strength at a fixed distance decline with time. This is suggestive of the recovering process of the CME-disturbed corona. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.5136v1.pdf"}
{"id": "1012.5279", "abstract": "  We report state-of-the-art quantum Monte Carlo calculations of the singlet n →π^* (CO) vertical excitation energy in the acrolein molecule, extending the recent study of Bouabça et al. [J. Chem. Phys. 130, 114107 (2009)]. We investigate the effect of using a Slater basis set instead of a Gaussian basis set, and of using state-average versus state-specific complete-active-space (CAS) wave functions, with or without reoptimization of the coefficients of the configuration state functions (CSFs) and of the orbitals in variational Monte Carlo (VMC). It is found that, with the Slater basis set used here, both state-average and state-specific CAS(6,5) wave functions give an accurate excitation energy in diffusion Monte Carlo (DMC), with or without reoptimization of the CSF and orbital coefficients in the presence of the Jastrow factor. In contrast, the CAS(2,2) wave functions require reoptimization of the CSF and orbital coefficients to give a good DMC excitation energy. Our best estimates of the vertical excitation energy are between 3.86 and 3.89 eV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.5279v1.pdf"}
{"id": "1012.5691", "abstract": "  Plasma with a temperature close to the chromospheric one is ejected in solar eruptions. Such plasma can occult some part of emission of compact sources in active regions as well as quiet solar areas. Absorption phenomena can be observed in the microwave range as the so-called 'negative bursts' and also in the He II 304 A line. The paper considers three eruptive events associated with rather powerful flares. Parameters of absorbing material of an eruption are estimated from multi-frequency records of a 'negative burst' in one event. 'Destruction' of an eruptive filament and its dispersion like a cloud over a huge area observed as a giant depression of the 304 A line emission has been revealed in a few events. One such event out of three ones known to us is considered in this paper. Another event is a possibility. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1012/1012.5691v2.pdf"}
{"id": "1101.0102", "abstract": "  We study the electronic structure of a spherical jellium in the presence of a central Gaussian impurity. We test how well the resulting inhomogeneity effects beyond spherical jellium are reproduced by several approximations of density functional theory (DFT). Four rungs of Perdew's ladder of DFT functionals, namely local density approximation (LDA), generalized gradient approximation (GGA), meta-GGA and orbital-dependent hybrid functionals are compared against our quantum Monte Carlo (QMC) benchmarks. We identify several distinct transitions in the ground state of the system as the electronic occupation changes between delocalized and localized states. We examine the parameter space of realistic densities (1 ≤ r_s≤ 5) and moderate depths of the Gaussian impurity (Z<7). The selected 18 electron system (with closed-shell ground state) presents 1d → 2s transitions while the 30 electron system (with open-shell ground state) exhibits 1f → 2p transitions. For the former system, the accuracy for the transitions is clearly improving with increasing sophistication of functionals with meta-GGA and hybrid functionals having only small deviations from QMC. However, for the latter system, we find much larger differences for the underlying transitions between our pool of DFT functionals and QMC. We attribute this failure to treatment of the exact exchange within these functionals. Additionally, we amplify the inhomogeneity effects by creating the system with spherical shell which leads to even larger errors in DFT approximations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.0102v2.pdf"}
{"id": "1101.0696", "abstract": "  We study the Efimov effect in a harmonic oscillator in the hyperspherical formulation, and show how a reduced model allows for a description that is a generalization of the Efimov effect in free space and leads to results that are easily interpreted. Efimov physics may be observed by varying the value of the scattering length, since in the regime where the trimers have a mixed harmonic oscillator and Efimov character, the inelastic properties of these states are still manageable. The model also allows for the study of non-universal Efimov trimers by including the effective range scattering parameter. While we find that in a certain regime the effective range parameter can take over the role of the three-body parameter, interestingly, we obtain a numerical relationship between these two parameters different from what was found in other models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.0696v1.pdf"}
{"id": "1101.1096", "abstract": "  Dust production among post-main-sequence stars is investigated in the Galactic globular cluster 47 Tucanae (NGC 104) based on infrared photometry and spectroscopy. We identify metallic iron grains as the probable dominant opacity source in these winds. Typical evolutionary timescales of AGB stars suggest the mass-loss rates we report are too high. We suggest that this is because the iron grains are small or elongated and/or that iron condenses more efficiently than at solar metallicity. Comparison to other works suggests metallic iron is observed to be more prevalent towards lower metallicities. The reasons for this are explored, but remain unclear. Meanwhile, the luminosity at which dusty mass loss begins is largely invariant with metallicity, but its presence correlates strongly with long-period variability. This suggests that the winds of low-mass stars have a significant driver that is not radiation pressure, but may be acoustic driving by pulsations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.1096v1.pdf"}
{"id": "1101.1227", "abstract": "  We show that the recently observed elemental abundance pattern of the carbon-rich metal-poor Damped Lyman α (DLA) system is in excellent agreement with the nucleosynthesis yields of faint core-collapse supernovae of primordial stars. The observed abundance pattern is not consistent with the nucleosynthesis yields of pair-instability supernovae. The DLA abundance pattern is very similar to that of carbon-rich extremely metal-poor (EMP) stars, and the contributions from low-mass stars and/or binary effects should be very small in DLAs. This suggests that chemical enrichment by the first stars in the first galaxies is driven by core-collapse supernovae from ∼ 20-50 M_⊙ stars, and also supports the supernova scenario as the enrichment source of EMP stars in the Milky Way Galaxy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.1227v2.pdf"}
{"id": "1101.1740", "abstract": "  We present a numerical method to compute the optimal maintenance time for a complex dynamic system applied to an example of maintenance of a metallic structure subject to corrosion. An arbitrarily early intervention may be uselessly costly, but a late one may lead to a partial/complete failure of the system, which has to be avoided. One must therefore find a balance between these too simple maintenance policies. To achieve this aim, we model the system by a stochastic hybrid process. The maintenance problem thus corresponds to an optimal stopping problem. We propose a numerical method to solve the optimal stopping problem and optimize the maintenance time for this kind of processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.1740v2.pdf"}
{"id": "1101.1830", "abstract": "  We try to interpret the recently updated measurement of the cosmic ray electron (CRE) spectrum observed by Fermi-LAT, together with PAMELA data on positron fraction, in a single-component scenario adopting different propagation setups; we find that the model is not adequate to reproduce the two datasets, so the evidence of an extra primary component of electrons and positrons is strengthened. Instead, a double component scenario computed in a Kraichnan-like diffusion setup (which is suggested by B/C and p̅ data) gives a satisfactory fit of all exisiting measurements. We confirm that nearby pulsars are good source candidates for the required e^± extra-component and we show that the predicted CRE anisotropy in our scenario is compatible with Fermi-LAT recently published constraints. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.1830v1.pdf"}
{"id": "1101.2371", "abstract": "  We present a comprehensive computational study on the properties of face-centered cubic and hexagonal chalcogenide Ge2Sb2Te5. We calculate the electronic structure using density functional theory (DFT); the obtained density of states (DOS) compares favorably with experiments, also looking suitable for transport analysis. Optical constants including refraction index and absorption coefficient capture major experimental features, aside from an energy shift owed to an underestimate of the band gap that is typical of DFT calculations. We also compute the phonon DOS for the hexagonal phase, obtaining a speed of sound and thermal conductivity in good agreement with the experimental lattice contribution. The calculated heat capacity reaches   1.4 x 106 J/(m3 K) at high temperature, in agreement with experimental data, and provides insight into the low-temperature range (< 150 K), where data are unavailable. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.2371v2.pdf"}
{"id": "1101.2760", "abstract": "  In this letter we investigate the role of regular (curvature singularity-free) black holes in the framework of UV self-complete quantum gravity. The existence of a minimal length, shielding the trans-Planckian regime to any physical probe, is self-consistently included into the black hole probe itself. In this way we obtain to slightly shift the barrier below the Planck Length, with the UV self-complete scenario self-consistently confirmed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.2760v2.pdf"}
{"id": "1101.3739", "abstract": "  In the propagation of optical pulses through dispersive media, the frequency degree of freedom acts as an effective decohering environment on the polarization state of the pulse. Here we discuss the application of open-loop dynamical-decoupling techniques for suppressing such a polarization decoherence in one-way communication channels. We describe in detail the experimental proof of principle of the \"bang-bang\" protection technique recently applied to flying qubits in [Damodarakurup et al., Phys. Rev. Lett. 103, 040502]. Bang-bang operations are implemented through appropriately oriented waveplates and dynamical decoupling is shown to be potentially useful to contrast a generic decoherence acting on polarization qubits propagating in dispersive media like, e.g., optical fibers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.3739v2.pdf"}
{"id": "1101.4984", "abstract": "  We outline a model for a cognitive epigenetic system based on elements of the Shannon theory of information and the statistical physics of the generalized Onsager relations. Particular attention is paid to the concept of the rate distortion function and from another direction as motivated by the thermodynamics of computing, the fundamental homology with the free energy density of a physical system. A unifying aspect of the dynamic framework involves the concept of a groupoid and of a groupoid atlas. From a stochastic differential equation we postulate a multidimensional Ito process for an epigenetic system from which a stochastic flow may permeate through components of this atlas. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.4984v1.pdf"}
{"id": "1101.5118", "abstract": "  We develop a systematic framework for exclusive rare B decays of the type B -> K(*)l+l- at large dilepton invariant mass q^2. It is based on an operator product expansion (OPE) for the required matrix elements of the nonleptonic weak Hamiltonian in this kinematic regime. Our treatment differs from previous work by a simplified operator basis, the explicit calculation of matrix elements of subleading operators, and by a quantitative estimate of duality violation. The latter point is discussed in detail, including the connection with the existence of an OPE and an illustration within a simple toy model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.5118v1.pdf"}
{"id": "1101.5674", "abstract": "  The low-mass condensations (LMCs) have been observed within the molecular cloud cores. In this research, we investigate the effect of isobaric thermal instability (TI) applied for forming these LMCs. For this purpose, at first we investigate the occurrence of TI in the molecular clouds. Then, for studying the significance of linear isobaric TI, we use a contracting axisymmetric cylindrical core with axial magnetic field. Consideration to cooling and heating mechanisms in the molecular clouds shows that including the heating due to ambipolar diffusion can lead to the occurrence of TI in a time-scale smaller than dynamical time-scale. Application of linear perturbation analysis shows that isobaric TI can take place in outer region of the molecular cloud cores. Furthermore, the results showthat perturbations with wavelengths greater than few astronomical units are protected from destabilization property of thermal conduction, so they can grow to form LMCs. Thus, the results show that the mechanism of TI can be used to explain the formation of LMCs as the progenitors of collapsing proto-stellar entities, brown dwarfs, or proto-planets. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.5674v1.pdf"}
{"id": "1102.0611", "abstract": "  Astrometric observations of the radio source occultations by solar system bodies may be of large interest for testing gravity theories, dynamical astronomy, and planetary physics. In this paper, we present an updated list of the occultations of astrometric radio sources by planets expected in the nearest years. Such events, like the solar eclipses, generally speaking, can be only observed in a limited region. The map of the shadow path is provided for the events occurred in regions with several VLBI stations and hence the most interesting for radio astronomy experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.0611v1.pdf"}
{"id": "1102.1028", "abstract": "  Current-induced dynamics in spin valves including composite free layer with antiferromagnetic interlayer exchange coupling is studied theoretically within the diffusive transport regime. We show that current-induced dynamics of a synthetic antiferromagnet is significantly different from dynamics of a synthetic ferrimagnet. From macrospin simulations we obtain conditions for switching the composite free layer, as well as for appearance of various self-sustained dynamical modes. Numerical simulations are compared with simple analytical models of critical current based on linearized Landau-Lifshitz-Gilbert equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.1028v2.pdf"}
{"id": "1102.1666", "abstract": "  The time it takes a quantum system to complete a tunneling event (which in the case of cross-barrier tunneling can be viewed as the time spent in a classically forbidden area) is related to the time required for a state to evolve to an orthogonal state, and an observation, i.e., a quantum mechanical projection on a particular basis, is required to distinguish one state from another. We have performed time-resolved measurements of Landau-Zener tunneling of Bose-Einstein condensates in accelerated optical lattices, clearly resolving the steplike time dependence of the band populations. The use of different protocols enabled us to access the tunneling probability, in two different bases, namely, the adiabatic basis and the diabatic basis. The adiabatic basis corresponds to the eigenstates of the lattice, and the diabatic one to the freeparticle momentum eigenstates. Our findings pave the way towards more quantitative studies of the tunneling time for LZ transitions, which are of current interest in the context of optimal quantum control and the quantum speed limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.1666v1.pdf"}
{"id": "1102.2501", "abstract": "  We consider Einstein-Maxwell-Dilaton (EMD) Lagrangian supplemented by double Liouville potentials to enrich our system and investigate the resulting dynamics. The general solution provides us alternative structures induced on the 3-dimensional domain wall (DW) moving in the 4-dimensional bulk. In particular, the local maximum in the potential suggests a maximum bounce (or onset for a contraction phase) of the 3-dimensional Friedmann-Robertson-Walker (FRW) universe on the DW. Depending on the choice of parameters we plot various cases of physical interest. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.2501v2.pdf"}
{"id": "1102.3994", "abstract": "  We consider the coherent exciton transport, modeled by continuous-time quantum walks, on Erdös-Rény graphs in the presence of a random distribution of traps. The role of trap concentration and of the substrate dilution is deepened showing that, at long times and for intermediate degree of dilution, the survival probability typically decays exponentially with a (average) decay rate which depends non monotonically on the graph connectivity; when the degree of dilution is either very low or very high, stationary states, not affected by traps, get more likely giving rise to a survival probability decaying to a finite value. Both these features constitute a qualitative difference with respect to the behavior found for classical walks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.3994v1.pdf"}
{"id": "1102.5607", "abstract": "  We perform a theoretical investigation on the thermal conductivity of single-walled boron nitride nanotubes (SWBNT) using the kinetic theory. By fitting to the phonon spectrum of boron nitride sheet, we develop an efficient and stable Tersoff-derived interatomic potential which is suitable for the study of heat transport in sp2 structures. We work out the selection rules for the three-phonon process with the help of the helical quantum numbers (κ, n) attributed to the symmetry group (line group) of the SWBNT. Our calculation shows that the thermal conductivity κ_ ph diverges with length as κ_ ph∝ L^β with exponentially decaying β(T)∝ e^-T/T_c, which results from the competition between boundary scattering and three-phonon scattering for flexure modes. We find that the two flexure modes of the SWBNT make dominant contribution to the thermal conductivity, because their zero frequency locates at κ=±α where α is the rotational angle of the screw symmetry in SWBNT. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1102/1102.5607v2.pdf"}
{"id": "1103.0977", "abstract": "  We derive the sum rule for the spectral function of the stress-energy tensor in the bulk (uniform dilatation) channel in a general class of strongly coupled field theories. This class includes theories holographically dual to a theory of gravity coupled to a single scalar field, representing the operator of the scale anomaly. In the limit when the operator becomes marginal, the sum rule coincides with that in QCD. Using the holographic model, we verify explicitly the cancellation between large and small frequency contributions to the spectral integral required to satisfy the sum rule in such QCD-like theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.0977v1.pdf"}
{"id": "1103.1366", "abstract": "  The search for new interactions of neutrinos beyond those of the Standard Model may help to elucidate the mechanism responsible for neutrino masses. Here we combine existing accelerator neutrino data with restrictions coming from a recent atmospheric neutrino data analysis in order to lift parameter degeneracies and improve limits on new interactions of muon neutrinos with quarks. In particular we re-consider the results of the NuTeV experiment in view of a new evaluation of its systematic uncertainties. We find that, although constraints for muon neutrinos are better than those applicable to tau or electron neutrinos, they lie at the few × 10^-2 level, not as strong as previously believed. We briefly discuss prospects for further improvement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.1366v1.pdf"}
{"id": "1103.1512", "abstract": "  Ultrafast laser-induced demagnetization of Gd(0001) has been investigated by magneto-induced optical second harmonic generation and the magneto-optical Kerr effect which facilitate a comparison of surface and bulk dynamics. We observe pronounced differences in the transient changes of the surface and bulk sensitive magneto-optical signals which we attribute to transfer of optically excited, spin-polarized carriers between surface and bulk states of the Gd(0001) film. A fluence dependent analysis of the bulk magnetization dynamics results in a weak variation of the demagnetization time constant, which starts at about 700 fs and increases by 10", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.1512v1.pdf"}
{"id": "1103.3093", "abstract": "  This paper studies interference alignment (IA) based multi-cell cooperative resource allocation for the downlink OFDMA with universal frequency reuse. Unlike the traditional scheme that treats subcarriers as separate dimensions for resource allocation, the IA technique is utilized to enable frequency-domain precoding over parallel subcarriers. In this paper, the joint optimization of frequency-domain precoding via IA, subcarrier user selection and power allocation is investigated for a cooperative three-cell OFDMA system to maximize the downlink throughput. Numerical results for a simplified symmetric channel setup reveal that the IA-based scheme achieves notable throughput gains over the traditional scheme only when the inter-cell interference link has a comparable strength as the direct link, and the receiver SNR is sufficiently large. Motivated by this observation, a practical hybrid scheme is proposed for cellular systems with heterogenous channel conditions, where the total spectrum is divided into two subbands, over which the IAbased scheme and the traditional scheme are applied for resource allocation to users located in the cell-intersection region and cellnon- intersection region, respectively. It is shown that this hybrid resource allocation scheme flexibly exploits the downlink IA gains for OFDMA-based cellular systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.3093v1.pdf"}
{"id": "1103.3368", "abstract": "  We consider the Chalker-Coddington network model for the Integer Quantum Hall Effect, and examine the possibility of solving it exactly. In the supersymmetric path integral framework, we introduce a truncation procedure, leading to a series of well-defined two-dimensional loop models, with two loop flavours. In the phase diagram of the first-order truncated model, we identify four integrable branches related to the dilute Birman-Wenzl-Murakami braid-monoid algebra, and parameterised by the loop fugacity n. In the continuum limit, two of these branches (1,2) are described by a pair of decoupled copies of a Coulomb-Gas theory, whereas the other two branches (3,4) couple the two loop flavours, and relate to an SU(2)_r × SU(2)_r / SU(2)_2r Wess-Zumino-Witten (WZW) coset model for the particular values n= -2cos[π/(r+2)] where r is a positive integer. The truncated Chalker-Coddington model is the n=0 point of branch 4. By numerical diagonalisation, we find that its universality class is neither an analytic continuation of the WZW coset, nor the universality class of the original Chalker-Coddington model. It constitutes rather an integrable, critical approximation to the latter. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.3368v1.pdf"}
{"id": "1103.3952", "abstract": "  We construct mixing processes over an infinite alphabet and ergodic processes over a finite alphabet for which Shannon mutual information between adjacent blocks of length n grows as n^β, where β∈(0,1). The processes are a modification of nonergodic Santa Fe processes, which were introduced in the context of natural language modeling. The rates of mutual information for the latter processes are alike and also established in this paper. As an auxiliary result, it is shown that infinite direct products of mixing processes are also mixing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.3952v2.pdf"}
{"id": "1103.4494", "abstract": "  In this paper, we model dwarf galaxies as a two-component system of gravitationally coupled stars and atomic hydrogen gas in the external force field of a pseudo-isothermal dark matter halo, and numerically obtain the radial distribution of H i vertical scale heights. This is done for a group of four dwarf galaxies (DDO 154, Ho II, IC 2574 and NGC 2366) for which most necessary input parameters are available from observations. The formulation of the equations takes into account the rising rotation curves generally observed in dwarf galaxies. The inclusion of self-gravity of the gas into the model at par with that of the stars results in scale heights that are smaller than what was obtained by previous authors. This is important as the gas scale height is often used for deriving other physical quantities. The inclusion of gas self-gravity is particularly relevant in the case of dwarf galaxies where the gas cannot be considered a minor perturbation to the mass distribution of the stars. We find that three out of four galaxies studied show a flaring of their H i disks with increasing radius, by a factor of a few within several disk scale lengths. The fourth galaxy has a thick H i disk throughout. This arises as a result of the gas velocity dispersion remaining constant or decreasing only slightly while the disk mass distribution declines exponentially as a function of radius. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.4494v1.pdf"}
{"id": "1103.4756", "abstract": "  The paper addresses the realization and identification problem or a subclass of piecewise-affine hybrid systems. The paper provides necessary and sufficient conditions for existence of a realization, a characterization of minimality, and an identification algorithm for this subclass of hybrid systems. The considered system class and the identification problem are motivated by applications in systems biology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1103/1103.4756v1.pdf"}
{"id": "1104.3459", "abstract": "  We propose a numerical method for resummation of perturbative series, which is based on the stochastic perturbative solution of Schwinger-Dyson equations. The method stochastically estimates the coefficients of perturbative series, and incorporates Borel resummation in a natural way. Similarly to the \"worm\" algorithm, the method samples open Feynman diagrams, but with an arbitrary number of external legs. As a test of our numerical algorithm, we study the scale dependence of the renormalized coupling constant in a theory of one-component scalar field with quartic interaction. We confirm the triviality of this theory in four and five space-time dimensions, and the instability of the trivial fixed point in three dimensions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.3459v2.pdf"}
{"id": "1104.3751", "abstract": "  Corrugation instabilities occurring for solutions of the Riemann problem in relativistic hydrodynamics in which the fluid moves with a non-zero velocity tangent to the initial discontinuity are studied numerically. We perform simulations both for ultrarelativistic and perfect gas equations of state. We focus on a set of problems with moderately relativistic velocities but exhausting all possible wave patterns of solutions. Perturbations are applied to the shape of the initial discontinuity. Instabilities that develop are only restricted to a region around a contact discontinuity. Both shock and rarefaction waves appear to be stable. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.3751v1.pdf"}
{"id": "1104.4707", "abstract": "  We study the ground state properties of the Kitaev-Heisenberg model in a magnetic field and explore the evolution of spin correlations in the presence of non-magnetic vacancies. By means of exact diagonalizations, the phase diagram without vacancies is determined as a function of the magnetic field and the ratio between Kitaev and Heisenberg interactions. We show that in the (antiferromagnetic) stripe ordered phase the static susceptibility and its anisotropy can be described by a spin canting mechanism. This accounts as well for the transition to the polarized phase when including quantum fluctuations perturbatively. Effects of spin vacancies depend sensitively on the type of the ground state. In the liquid phase, the magnetization pattern around a single vacancy in a small field is determined, and its spatial anisotropy is related to that of non-zero further neighbor correlations induced by the field and/or Heisenberg interactions. In the stripe phase, the joint effect of a vacancy and a small field breaks the six-fold symmetry of the model and stabilizes a particular stripe pattern. Similar symmetry-breaking effects occur even at zero field due to effective interactions between vacancies. This selection mechanism and intrinsic randomness of vacancy positions may lead to spin-glass behavior. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.4707v3.pdf"}
{"id": "1104.5093", "abstract": "  Geomagnetism is characterized by intermittent polarity reversals and rapid fluctuations. We have recently proposed a coupled macro-spin model to describe these dynamics based on the idea that the whole dynamo mechanism is described by the coherent interactions of many small dynamo elements. In this paper, we further develop this idea and construct a minimal model for magnetic variations. This simple model naturally yields many of the observed features of geomagnetism: its time evolution, the power spectrum, the frequency distribution of stable polarity periods, etc. This model has coexistent two phases; i.e. the cluster phase which determines the global dipole magnetic moment and the expanded phase which gives random perpetual perturbations that yield intermittent polarity flip of the dipole moment. This model can also describe the synchronization of the spin oscillation. This corresponds to the case of sun and the model well describes the quasi-regular cycles of the solar magnetism. Furthermore, by analyzing the relevant terms of MHD equation based on our model, we have obtained a scaling relation for the magnetism for planets, satellites, sun, and stars. Comparing it with various observations, we can estimate the scale of the macro-spins. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1104/1104.5093v1.pdf"}
{"id": "1105.0056", "abstract": "  We investigate the effects of quenched disorder, in the form of site and bond dilution, on the physics of the S=1/2 antiferromagnetic Heisenberg model on even-leg ladders. Site dilution is found to prune rung singlets and thus create localized moments which interact via a random, unfrustrated network of effective couplings, realizing a random-exchange Heisenberg model (REHM) in one spatial dimension. This system exhibits a power-law diverging correlation length as the temperature decreases. Contrary to previous claims, we observe that the scaling exponent is non-universal, i.e., doping dependent. This finding can be explained by the discrete nature of the values taken by the effective exchange couplings in the doped ladder. Bond dilution on even-leg ladders leads to a more complex evolution with doping of correlations, which are weakly enhanced in 2-leg ladders, and are even suppressed for low dilution in the case of 4-leg and 6-leg ladders. We clarify the different aspects of correlation enhancement and suppression due to bond dilution by isolating the contributions of rung-bond dilution and leg-bond dilution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.0056v2.pdf"}
{"id": "1105.0105", "abstract": "  Many mechanical systems are large and complex, despite being composed of simple subsystems. In order to understand such large systems it is natural to tear the system into these subsystems. Conversely we must understand how to invert this tearing. In other words, we must understand interconnection. Such an understanding has already successfully understood in the context of Hamiltonian systems on vector spaces via the port-Hamiltonian systems program. In port-Hamiltonian systems theory, interconnection is achieved through the identification of shared variables, whereupon the notion of composition of Dirac structures allows one to interconnect two systems. In this paper we seek to extend the port-Hamiltonian systems program to Lagrangian systems on manifolds and extend the notion of composition of Dirac structures appropriately. In particular, we will interconnect Lagrange-Dirac systems by modifying the respective Dirac structures of the involved subsystems. We define the interconnection of Dirac structures via an interaction Dirac structure and a tensor product of Dirac structures. We will show how the dynamics of the interconnected system is formulated as a function of the subsystems, and we will elucidate the associated variational principles. We will then illustrate how this theory extends the theory of port-Hamiltonian systems and the notion of composition of Dirac structures to manifolds with couplings which do not require the identification of shared variables. Lastly, we will close with some examples: a mass-spring mechanical systems, an electric circuit, and a nonholonomic mechanical system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.0105v2.pdf"}
{"id": "1105.0411", "abstract": "  The non-stationary evolution of observable quantities in complex systems can frequently be described as a juxtaposition of quasi-stationary spells. Given that standard theoretical and data analysis approaches usually rely on the assumption of stationarity, it is important to detect in real time series intervals holding that property. With that aim, we introduce a segmentation algorithm based on a fully non-parametric approach. We illustrate its applicability through the analysis of real time series presenting diverse degrees of non-stationarity, thus showing that this segmentation procedure generalizes and allows to uncover features unresolved by previous proposals based on the discrepancy of low order statistical moments only. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.0411v2.pdf"}
{"id": "1105.0928", "abstract": "  It has been known for some time that the Milky Way is a barred disk galaxy. More recently several studies inferred from starcount observations that the Galaxy must contain a separate, new, flat long bar component, twisted relative to the barred bulge. Here we use a simulation with a boxy bulge and bar to suggest that these observations can be reproduced with a single structure. In this simulation a stellar bar evolved from the disk, and the boxy bulge originated from it through secular evolution and the buckling instability. We calculate starcount distributions for this model at different longitudes and latitudes, in a similar way as observers have done for resolved starcounts. Good agreement between the simulation and the observations can be achieved for a suitable snapshot, even though the simulation has a single boxy bulge and bar structure. In this model, part of the long bar signature is due to a volume effect in the starcounts, and another part is due to chosing a snapshot in which the planar part of the boxy bulge and bar has developed leading ends through interaction with the adjacent spiral arm heads. We also provide predictions from this model for the line-of-sight velocity distributions at the longitudes with the long bar signature, for comparison with upcoming surveys. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.0928v1.pdf"}
{"id": "1105.1588", "abstract": "  We discuss the relation between the polarization of inclusively produced (anti)-hyperons and the incident baryon states in the framework of the constituent quark-diquark cascade model. We assume that there is an intrinsic diquark-antidiquark state in the incident baryon, in which the intrinsic diquark immediately fragments into a non-leading baryon and the antidiquark behaves as a valence constituent. It is also assumed that the valence (anti)diquark in the incident nucleon tends to combine selectively with a spin-down sea quark and, on the othe hand, the spin-up valence quark in the projectile is chosen by a sea (anti)diquadk in preference to the spin-down valence quark. It is found that the incident spin-1/2 baryon is mainly composed of a spin-0 valence diquark and a valence quark, and contains an intrinsic diquark-antidiquark state with a probability of about 7", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.1588v2.pdf"}
{"id": "1105.1681", "abstract": "  We consider non-stationary spherically symmetric n-dimensional charged black holes with varying mass m(v) and/or electric charge q(v), described by generic charged Vaidya metrics with cosmological constant Λ in double null coordinates, and perform a comprehensive numerical analysis of the fundamental quasinormal modes (QNM) for minimally coupled scalar fields. We show that the \"instantaneous\" quasinormal frequencies exhibit the same sort of non-stationary behavior reported previously for the four-dimensional uncharged case with Λ=0. Such property seems to be very robust, independent of the spacetime dimension and of the metric parameters, provided they be consistent with the existence of an event horizon. The study of time dependent Reissner-Nordström black holes allows us to go a step further and quantify the deviation of the stationary regime for QNM with respect to charge variations as well. We also look for signatures in the quasinormal frequencies from the creation of a Reissner-Nordström naked spacetime singularity. Even though one should expect the breakdown of our approach in the presence of naked singularities, we show that it is possible, in principle, to obtain some information about the naked singularity from the QNM frequencies, in agreement with the previous results of Ishibashi and Hosoya showing that it would be indeed possible to have regular scattering from naked singularities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.1681v2.pdf"}
{"id": "1105.2256", "abstract": "  We investigate the quantum entanglement dynamics of undriven anharmonic (nonlinear) oscillators with quartic potentials. We first consider the indirect interaction between two such nonlinear oscillators mediated by a third, linear oscillator and show that it leads to a time-varying entanglement of the oscillators, the entanglement being strongly influenced by the nonlinear oscillator dynamics. In the presence of dissipation, the role of nonlinearity is strongly manifested in the steady state dynamics of the indirectly coupled anharmonic oscillators. We further illustrate the effect of nonlinearities by studying the coupling between an electromagnetic field in a cavity with one movable mirror which is modeled as a nonlinear oscillator. For this case we present a full analytical treatment, which is valid in a regime where both the nonlinearity and the coupling due to radiation pressure is weak. We show that, without the need of any conditional measurements on the cavity field, the state of the movable mirror is non-classical as a result of the combined effect of the intrinsic nonlinearity and the radiation pressure coupling. This interaction is also shown to be responsible for squeezing the movable mirror's position quadrature beyond the minimum uncertainty state even when the mirror is initially prepared in its ground state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.2256v2.pdf"}
{"id": "1105.3329", "abstract": "  We consider various 2D lattice equations and their integrability, from the point of view of 3D consistency, Lax pairs and Bäcklund transformations. We show that these concepts, which are associated with integrability, are not strictly equivalent. In the course of our analysis, we introduce a number of black and white lattice models, as well as variants of the functional Yang-Baxter equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.3329v1.pdf"}
{"id": "1105.3945", "abstract": "  These notes summarise a talk surveying the combinatorial or Hamiltonian quantisation of three dimensional gravity in the Chern-Simons formulation, with an emphasis on the role of quantum groups and on the way the various physical constants (c,G,Λ,ħ) enter as deformation parameters. The classical situation is summarised, where solutions can be characterised in terms of model spacetimes (which depend on c and Λ), together with global identifications via elements of the corresponding isometry groups. The quantum theory may be viewed as a deformation of this picture, with quantum groups replacing the local isometry groups, and non-commutative spacetimes replacing the classical model spacetimes. This point of view is explained, and open issues are sketched. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.3945v1.pdf"}
{"id": "1105.5047", "abstract": "  We show by direct calculation that the replica and cavity methods are exactly equivalent for the spectrum of Erdos-Renyi random graph. We introduce a variational formulation based on the cavity method and use it to find approximate solutions for the density of eigenvalues. We also use this variational method for calculating spectra of sparse covariance matrices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.5047v1.pdf"}
{"id": "1105.5162", "abstract": "  We compare the first results on searches for supersymmetry with the Large Hadron Collider (LHC) to the current and near-term performance of experiments sensitive to neutralino dark matter. We limit our study to the particular slices of parameter space of the constrained minimal supersymmetric extension to the Standard Model where CMS and ATLAS exclusion limits have been presented so far. We show where, on that parameter space, the lightest neutralino possesses a thermal relic abundance matching the value inferred by cosmological observations. We then calculate rates for, and estimate the performance of, experiments sensitive to direct and indirect signals from neutralino dark matter. We argue that this is a unique point in time, where the quest for supersymmetry – at least in one of its practical and simple incarnations – is undergoing a close scrutiny from the LHC and from dark matter searches that is both synergistic and complementary. Should the time of discovery finally unravel, the current performances of the collider program and of direct and indirect dark matter searches are at a conjuncture offering unique opportunities for a breakthrough on the nature of physics beyond the Standard Model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.5162v2.pdf"}
{"id": "1105.6158", "abstract": "  We develop a general theory of a boson decomposition for both local and non-local interactions in lattice fermion models which allows us to describe fermionic degrees of freedom and collective charge and spin excitations on equal footing. An efficient perturbation theory in the interaction of the fermionic and the bosonic degrees of freedom is constructed in so-called dual variables in the path-integral formalism. This theory takes into account all local correlations of fermions and collective bosonic modes and interpolates between itinerant and localized regimes of electrons in solids. The zero-order approximation of this theory corresponds to extended dynamical mean-field theory (EDMFT), a regular way to calculate nonlocal corrections to EDMFT is provided. It is shown that dual ladder summation gives a conserving approximation beyond EDMFT. The method is especially suitable for consideration of collective magnetic and charge excitations and allows to calculate their renormalization with respect to \"bare\" RPA-like characteristics. General expression for the plasmonic dispersion in correlated media is obtained. As an illustration it is shown that effective superexchange interactions in the half-filled Hubbard model can be derived within the dual-ladder approximation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.6158v2.pdf"}
{"id": "1106.3154", "abstract": "  Early-type galaxies are characterized by many scaling relations. One of them, the so-called fundamental plane is a relatively tight correlation between three variables, and has resisted a clear physical understanding despite many years of intensive research. Here, we show that the correlation between the three variables of the fundamental plane can be the artifact of the effect of another parameter influencing all, so that the fundamental plane may be understood as a confounding correlation. Indeed, the complexity of the physics of galaxies and of their evolution suggests that the main confounding parameter must be related to the level of diversification reached by the galaxies. Consequently, many scaling relations for galaxies are probably evolutionary correlations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.3154v1.pdf"}
{"id": "1106.4309", "abstract": "  We study an M-theory solution for the holographic flow of AdS4 times Sasaki-Einstein 7-manifolds with skew-whiffing, perturbed by a mass operator. The infrared solution contains the 5 dimensional Schrodinger geometry after considering the gravity dual of the standard non-relativistic limit of relativistic field theories. The mass deformation of the field theory is discussed in detail for the case with 7 manifold being a round sphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.4309v2.pdf"}
{"id": "1107.0301", "abstract": "  We discuss general thermodynamic properties of molecular structure formation processes like protein folding by means of simplified, coarse-grained models. The conformational transitions accompanying these processes exhibit similarities to thermodynamic phase transitions, but also significant differences as the systems that we investigate here are very small. The usefulness of a microcanonical statistical analysis of these transitions in comparison with a canonical interpretation is emphasized. The results are obtained by employing sophisticated generalized-ensemble Markov-chain Monte Carlo methodologies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.0301v1.pdf"}
{"id": "1107.2667", "abstract": "  We derive the steady state solution of the Fokker-Planck equation that describes the dynamics of the nondegenerate optical parametric oscillator in the truncated Wigner representation of the density operator. We assume that the pump mode is strongly damped, which permits its adiabatic elimination. When the elimination is correctly executed, the resulting stochastic equations contain multiplicative noise terms, and do not admit a potential solution. However, we develop an heuristic scheme leading to a satisfactory steady-state solution. This provides a clear view of the intracavity two-mode entangled state valid in all operating regimes of the OPO. A nongaussian distribution is obtained for the above threshold solution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.2667v1.pdf"}
{"id": "1107.4865", "abstract": "  Given a causal model of some domain and a particular story that has taken place in this domain, the problem of actual causation is deciding which of the possible causes for some effect actually caused it. One of the most influential approaches to this problem has been developed by Halpern and Pearl in the context of structural models. In this paper, I argue that this is actually not the best setting for studying this problem. As an alternative, I offer the probabilistic logic programming language of CP-logic. Unlike structural models, CP-logic incorporates the deviant/default distinction that is generally considered an important aspect of actual causation, and it has an explicitly dynamic semantics, which helps to formalize the stories that serve as input to an actual causation problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.4865v1.pdf"}
{"id": "1107.5668", "abstract": "  The first molecules detected at infrared wavelengths in the ejecta of a Type II supernova, namely SN1987A, consisted of CO and SiO. Since then, confirmation of the formation of these two species in several other supernovae a few hundred days after explosion has been obtained. However, supernova environments appear to hamper the synthesis of large, complex species due to the lack of microscopically-mixed hydrogen deep in supernova cores. Because these environments also form carbon and silicate dust, it is of importance to understand the role played by molecules in the depletion of elements and how chemical species get incorporated into dust grains. In the present paper, we review our current knowledge of the molecular component of supernova ejecta, and present new trends and results on the synthesis of molecules in these harsh, explosive events. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1107/1107.5668v1.pdf"}
{"id": "1108.4009", "abstract": "  This paper presents the analysis of axisymmetric helical magnetorotational instability (HMRI) in the inviscid limit, which is relevant for astrophysical conditions. The inductionless approximation defined by zero magnetic Prandtl number is adopted to distinguish the HMRI from the standard MRI in the cylindrical Taylor-Couette flow subject to a helical magnetic field. Using a Chebyshev collocation method convective and absolute instability thresholds are computed in terms of the Elsasser number for a fixed ratio of inner and outer radii λ=2 and various ratios of rotation rates and helicities of the magnetic field. It is found that the extension of self-sustained HMRI modes beyond the Rayleigh limit does not reach the astrophysically relevant Keplerian rotation profile not only in the narrow- but also in the finite-gap approximation. The Keppler limit can be attained only by the convective HMRI mode provided that the boundaries are perfectly conducting. However, this mode requires not only a permanent external excitation to be observable but also has a long axial wave length, which is not compatible with limited thickness of astrophysical accretion disks. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.4009v3.pdf"}
{"id": "1108.5041", "abstract": "  We study the pathologies in AdS black branes in Lovelock theory. More precisely, we examine the conditions that AdS black branes have the naked singularity, the ghost instability and the dynamical instability. From the point of view of the AdS/CFT correspondence, the pathologies in AdS black branes indicate the pathologies in the corresponding CFT. Hence, we need to be careful when we apply AdS/CFT in Lovelock theory to various phenomena such as the shear viscosity to entropy ratio in strongly coupled quantum filed theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.5041v1.pdf"}
{"id": "1109.0664", "abstract": "  Most of the thermodynamic analysis of ovens are focused on efficiency, but they need to behaves under real-life conditions, then the effectiveness of the ovens plays a crucial role in their design. In this paper we present a thermodynamical model able to describe the temperature evolution in ovens, furnaces or kilns to harden, burn or dry different products and which provides a methodology to design these heating devices. We use the required temperature evolution for each product and process as main ingredient in the methodology and procedure to design ovens and we place in the right role the efficiency criteria. We use global energy balance equation for the oven under transient situation as the thermodynamic starting point for developing the model. Our approach is able to consider different configurations for these heating devices, or recirculating or open situations, etc. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.0664v1.pdf"}
{"id": "1109.0857", "abstract": "  The ground state properties of a paramagnetic Mott insulator are investigated in the presence of an external electrical field using the inhomogeneous Gutzwiller approximation for a single band Hubbard model in a slab geometry. The metal insulator transition is shifted towards higher Hubbard repulsions by applying an electric field perpendicular to the slab. The spatial distribution of site dependent quasiparticle weight shows that the quasiparticle weight is maximum in few layers beneath the surface. Moreover only at higher Hubbard repulsion, larger than the bulk critical U, the electric field will be totally screened only for centeral cites. Our results show that by presence of an electric field perpendicular to a thin film made of a strongly correlated material, states near the surface will remain metallic while the bulk becomes insulating after some critical U. In contrast, in the absence of the electric field the surface becomes insulating before the bulk. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.0857v1.pdf"}
{"id": "1109.2296", "abstract": "  We consider a bandit problem over a graph where the rewards are not directly observed. Instead, the decision maker can compare two nodes and receive (stochastic) information pertaining to the difference in their value. The graph structure describes the set of possible comparisons. Consequently, comparing between two nodes that are relatively far requires estimating the difference between every pair of nodes on the path between them. We analyze this problem from the perspective of sample complexity: How many queries are needed to find an approximately optimal node with probability more than 1-δ in the PAC setup? We show that the topology of the graph plays a crucial in defining the sample complexity: graphs with a low diameter have a much better sample complexity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.2296v1.pdf"}
{"id": "1109.2662", "abstract": "  The limit theorems of discrete- and continuous-time quantum walks on the line have been intensively studied. We show a relation among limit distributions of quantum walks, Heun differential equations and Gauss differential equations. Indeed, we derive the second-order Fucksian differential equations which limit density functions of quantum walks satisfy. Moreover, using both differential equations, we discuss a relationship between discrete- and continuous-time quantum walks. Taking suitable limit, we can transform a Heun equation obtained from the limit density function of the discrete-time quantum walk to a Gauss equation given by that of the continuous-time quantum walk. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.2662v3.pdf"}
{"id": "1109.5529", "abstract": "  We study Ising chains with arbitrary multispin finite-range couplings, providing an explicit solution of the associated inverse Ising problem, i.e. the problem of inferring the values of the coupling constants from the correlation functions. As an application, we reconstruct the couplings of chain Ising Hamiltonians having exponential or power-law two-spin plus three- or four-spin couplings. The generalization of the method to ladders and to Ising systems where a mean-field interaction is added to general finite-range couplings is as well as discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.5529v2.pdf"}
{"id": "1109.6575", "abstract": "  A relativistically invariant quantum theory first advanced by Bakamjian and Thomas has proven very useful in modeling few-body systems. For three particles or more, this approach is known formally to fail the constraint of cluster separability, whereby symmetries and conservation laws that hold for a system of particles also hold for isolated subsystems. Cluster separability can be restored by means of a recursive construction using unitary transformations, but implementation is difficult in practice, and the quantitative extent to which the Bakamjian-Thomas approach violates cluster separability has never been tested. This paper provides such a test by means of a model of a scalar probe in a three-particle system for which (1) it is simple enough that there is a straightforward solution that satisfies Poincaré invariance and cluster separability, and (2) one can also apply the Bakamjian-Thomas approach. The difference between these calculations provides a measure of the size of the corrections from the Sokolov construction that are needed to restore cluster properties. Our estimates suggest that, in models based on nucleon degrees of freedom, the corrections that restore cluster properties are too small to effect calculations of observables. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.6575v3.pdf"}
{"id": "1109.6584", "abstract": "  We present results from an 87-ks Suzaku observation of the canonical low-excitation radio galaxy (LERG) NGC 6251. We have previously suggested that LERGs violate conventional AGN unification schemes: they may lack an obscuring torus and are likely to accrete in a radiatively inefficient manner, with almost all of the energy released by the accretion process being channeled into powerful jets. We model the 0.5-20 keV Suzaku spectrum with a single power law of photon index Γ=1.82^+0.04_-0.05, together with two collisionally ionized plasma models whose parameters are consistent with the known galaxy- and group-scale thermal emission. Our observations confirm that there are no signatures of obscured, accretion-related X-ray emission in NGC 6251, and we show that the luminosity of any such component must be substantially sub-Eddington in nature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.6584v1.pdf"}
{"id": "1110.1312", "abstract": "  It has long been thought that the pulsed X-ray properties of rotation-powered pulsars are stable on long time scales. However, long-term, systematic studies of individual sources have been lacking. Furthermore, dramatic X-ray variability has now been observed from two pulsars having inferred sub-critical dipole magnetic fields. Here we present an analysis of the long-term pulsed X-ray properties of the young, energetic pulsar PSR B1509-58 using data from the Rossi X-ray Timing Explorer. We measured the 2-50 keV pulsed flux for 14.7 yr of X-ray observations and found that it is consistent with being constant on all relevant time scales, and place a 3 sigma upper limit on day-to-week variability of <28", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.1312v1.pdf"}
{"id": "1110.1370", "abstract": "  Magnetic impurities affect the spectrum of excitations of a superconductor and thus influence its impedance. We concentrate on the dissipative part of the surface impedance. We investigate its dependence on frequency, the density and strength of magnetic impurities, and the density and temperature of quasiparticles. Even a small concentration of weak magnetic impurities significantly modifies the excitation spectrum in the vicinity of the BCS gap. Therefore, we give special attention to the absorption threshold behavior at zero temperature and to the low-frequency absorption by quasiparticles. The discrete energy states introduced at low density of magnetic impurities may serve as traps for nonequilibrium quasiparticles, reducing the absorption in some range of low radiation frequencies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.1370v2.pdf"}
{"id": "1110.1380", "abstract": "  Redshift surveys are a powerful tool of modern cosmology. We discuss two aspects of their power to map the distribution of mass and light in the universe: (1) measuring the mass distribution extending into the infall regions of rich clusters and (2) applying deep redshift surveys to the selection of clusters of galaxies and to the identification of very large structures (Great Walls). We preview the HectoMAP project, a redshift survey with median redshift z = 0.34 covering 50 square degrees to r= 21. We emphasize the importance and power of spectroscopy for exploring and understanding the nature and evolution of structure in the universe. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.1380v1.pdf"}
{"id": "1110.2588", "abstract": "  We consider the phenomenology of CP violation in a color-octet extended scalar sector for tt̅ production and decay at the LHC. In particular we study the effect of the two neutral color-octet scalars S_I and S_R that occur in the model. There are two new sources of CP violation: a phase in the couplings of S_I,R to top-quarks; and two phases in the quartic couplings of the scalar potential. In resonant production of a single S_I,R followed by its decay into tt̅ pairs through the parton level process gg to S_I,R to tt̅, we find large raw CP asymmetries which can reach 12", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.2588v1.pdf"}
{"id": "1110.3374", "abstract": "  Using direct numerical simulations, the fragmentation of falling liquid droplets in a quiescent media is studied. Three simulations with different Eotvos numbers were performed. An adaptive volume of fluid(VOF) method based on octree meshing is used, providing a notable reduction of computational cost. The current video includes 4 main parts describing the fragmentation of the falling droplet. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.3374v1.pdf"}
{"id": "1110.3443", "abstract": "  We present fluid dynamics videos of the flight of some of the smallest insects including the jewel wasp, Ampulex compressa, and thrips, Thysanoptera spp. The fruit fly, Drosophila melanogaster, is large in comparison to these insects. While the fruit fly flies at Re ≈ 120, the jewel wasp flies at Re ≈ 60, and thrips flies at Re ≈ 10. Differences in the general structures of the wakes generated by each species are observed. The differences in the wakes correspond to changes in the ratio of lift forces (vertical component) to drag forces (horizontal component) generated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.3443v1.pdf"}
{"id": "1110.3842", "abstract": "  In the collapsar model for common gamma-ray bursts, the formation of a centrifugally supported disk occurs during the first ∼10 seconds following the collapse of the iron core in a massive star. This only occurs in a small fraction of massive stellar deaths, however, and requires unusual conditions. A much more frequent occurrence could be the death of a star that makes a black hole and a weak or absent outgoing shock, but in a progenitor that only has enough angular momentum in its outermost layers to make a disk. We consider several cases where this is likely to occur - blue supergiants with low mass loss rates, tidally-interacting binaries involving either helium stars or giant stars, and the collapse to a black hole of very massive pair-instability supernovae. These events have in common the accretion of a solar mass or so of material through a disk over a period much longer than the duration of a common gamma-ray burst. A broad range of powers is possible, 10^47 to 10^50erg s^-1, and this brightness could be enhanced by beaming. Such events were probably more frequent in the early universe where mass loss rates were lower. Indeed this could be one of the most common forms of gamma-ray transients in the universe and could be used to study first generation stars. Several events could be active in the sky at any one time. A recent example of this sort of event may have been the SWIFT transient Sw-1644+57. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.3842v1.pdf"}
{"id": "1110.5312", "abstract": "  Calculations carried out to model the evolution of Star 32 under different assumptions about the stellar wind mass-loss rate provide robust limits on the present mass of the star. The obtained range is 31 to 35.5 Msun, which is in very good agreement with the orbital solution of Orosz et al., namely 28.3 to 35.3 Msun. The initial mass of Star 32 had to be in the range 35 to 40 Msun and the present age of the system is 3.7 to 4.0 Myr. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.5312v1.pdf"}
{"id": "1110.6084", "abstract": "  We consider a multi-armed bandit problem in a setting where each arm produces a noisy reward realization which depends on an observable random covariate. As opposed to the traditional static multi-armed bandit problem, this setting allows for dynamically changing rewards that better describe applications where side information is available. We adopt a nonparametric model where the expected rewards are smooth functions of the covariate and where the hardness of the problem is captured by a margin parameter. To maximize the expected cumulative reward, we introduce a policy called Adaptively Binned Successive Elimination (abse) that adaptively decomposes the global problem into suitably \"localized\" static bandit problems. This policy constructs an adaptive partition using a variant of the Successive Elimination (se) policy. Our results include sharper regret bounds for the se policy in a static bandit problem and minimax optimal regret bounds for the abse policy in the dynamic problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.6084v3.pdf"}
{"id": "1110.6277", "abstract": "  We present a systematic analysis of the X-ray spectra of NGC 1313 X-1 and NGC 1313 X-2, using three years of XMM-Newton observations. We fitted the continuum with a Comptonization model plus a multicolor blackbody disc, that describes the effects of an accretion disc plus a corona. We checked the consistency of this spectral model on the basis of the variability patterns of its spectral parameters. We found that the two sources show different spectral states. We tentatively interpret the observed behaviour of NGC 1313 X-1 and X-2 within the framework of near Eddington and/or super-Eddington accretion. We also attempted to determine the chemical abundances in the local environment of NGC 1313 X-1 and X-2 from the EPIC and RGS spectra. The results appear to indicate subsolar metallicity for both sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.6277v2.pdf"}
{"id": "1110.6747", "abstract": "  Nanodiamond exhibits unpaired electrons in magnetization, EPR, NMR and Auger relaxation. Wave functions and eigenenergies of a bound electron in a nanodiamond crystal have been calculated. It has been proved by using quantum mechanical analysis that unpaired electrons are self-condition of a nanodiamond as a limited crystal according to Tamm theory of surface states. The surface electron floating over a nanodiamond gives paramagnetic response and stabilizes the nanoparticle at small range of size. Possibly the spin of the floating electron can be used for floating point calculation in future quantum computers on the base of nanodiamond qubits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.6747v2.pdf"}
{"id": "1111.1925", "abstract": "  We use the self-consistent model technique developed by Martín-Manjón et al. (2008) that combines the chemical evolution with stellar population synthesis and photo-ionization codes, to study the star formation scenarios capable of reproducing the observed properties of star-forming galaxies.   The comparison of our model results with a database of HII galaxies shows that the observed spectra and colors of the present burst and the older underlying population are reproduced by models in a bursting scenario with star formation efficiency involving close to 20 per cent of the total mass of gas, and inter-burst times longer than 100 Myr, and more probably around 1 Gyr. Other modes like gasping and continuous star formation are not favored. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.1925v1.pdf"}
{"id": "1111.2088", "abstract": "  We present the analysis of two Suzaku observations of GX 301-2 at two orbital phases after the periastron passage. Variations in the column density of the line-of-sight absorber are observed, consistent with accretion from a clumpy wind. In addition to a CRSF, multiple fluorescence emission lines were detected in both observations. The variations in the pulse profiles and the CRSF throughout the pulse phase have a signature of a magnetic dipole field. Using a simple dipole model we calculated the expected magnetic field values for different pulse phases and were able to extract a set of geometrical angles, loosely constraining the dipole geometry in the neutron star. From the variation of the CRSF width and energy, we found a geometrical solution for the dipole, making the inclination consistent with previously published values. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.2088v1.pdf"}
{"id": "1111.3954", "abstract": "  We investigate how large lepton asymmetries affect the evolution of the early universe at times before big bang nucleosynthesis and in particular how they influence the relic density of WIMP dark matter. In comparison to the standard calculation of the relic WIMP abundance we find a decrease, depending on the lepton flavour asymmetry. We find an effect of up to 20 per cent for lepton flavour asymmetries l_f=  O(0.1). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.3954v2.pdf"}
{"id": "1111.4208", "abstract": "  We study non-thermal emissions from cool cores in galaxy clusters. We adopted a recent model, in which cosmic-rays (CRs) prevail in the cores and stably heat them through CR streaming. The non-thermal emissions come from the interaction between CR protons and intracluster medium (ICM). Comparison between the theoretical predictions and radio observations shows that the overall CR spectra must be steep, and most of the CRs in the cores are low-energy CRs. Assuming that the CRs are injected through AGN activities, we study the nature of the shocks that are responsible for the CR acceleration. The steep CR spectra are likely to reflect the fact that the shocks travel in hot ICM with fairly small Much numbers. We also study the dependence on the CR streaming velocity. The results indicate that synchrotron emissions from secondary electrons should be observed as radio mini-halos in the cores. In particular, low-frequency observations (e.g. LOFAR) are promising. On the other hand, the steepness of the spectra makes it difficult to detect non-thermal X-ray and gamma-ray emissions from the cores. The low-energy CRs may be heating optical filaments observed in the cores. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.4208v1.pdf"}
{"id": "1111.6390", "abstract": "  A scheme is proposed, that allows one for performing homodyne detection of the matter-wave field of ultracold bosonic atoms. It is based on a pump-probe lasers setup, that both illuminates a Bose-Einstein condensate, acting as reference system, and a second ultracold gas, composed by the same atoms but in a quantum phase to determine. Photon scattering outcouples atoms from both systems, which then propagate freely. Under appropriate conditions, when the same photon can either be scattered by the Bose-Einstein condensate or by the other quantum gas, both flux of outcoupled atoms and scattered photons exhibit oscillations, whose amplitude is proportional to the condensate fraction of the quantum gas. This setup allows one, for instance, to perform thermometry of a condensate or to monitor the Mott-insulator/superfluid phase transition in optical lattices, and can be extended in order to measure the first-order correlation function of a quantum gas. The dynamics here discussed make use of the entanglement between atoms and photons, which is established by the scattering process, in order to access detailed information on the quantum state of matter. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.6390v1.pdf"}
{"id": "1112.0547", "abstract": "  Geometric integration theory can be employed when numerically solving ODEs or PDEs with constraints. In this paper, we present several one-step algorithms of various orders for ODEs on a collection of spheres. To demonstrate the versatility of these algorithms, we present representative calculations for reduced free rigid body motion (a conservative ODE) and a discretization of micromagnetics (a dissipative PDE). We emphasize the role of isotropy in geometric integration and link numerical integration schemes to modern differential geometry through the use of partial connection forms; this theoretical framework generalizes moving frames and connections on principal bundles to manifolds with nonfree actions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.0547v1.pdf"}
{"id": "1112.0972", "abstract": "  The modulation of an optical lattice potential that breaks time-reversal symmetry enables the realization of complex tunneling amplitudes in the corresponding tight-binding model. For a superfluid Fermi gas in a triangular lattice potential with complex tunnelings the pairing function acquires a complex phase, so the frustrated magnetism of fermions can be realized.Bose-Fermi mixture of bosonic molecules and unbound fermions in the lattice shows also an interesting behavior. Due to boson-fermion coupling, the fermions become slaved by the bosons and the corresponding pairing function takes the complex phase determined by bosons. In the presence of bosons the Fermi system can reveal both gap and gapless superfluidity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.0972v4.pdf"}
{"id": "1112.1109", "abstract": "  Model lattices consisting of balls connected by central-force springs provide much of our understanding of mechanical response and phonon structure of real materials. Their stability depends critically on their coordination number z. d-dimensional lattices with z=2d are at the threshold of mechanical stability and are isostatic. Lattices with z<2d exhibit zero-frequency \"floppy\" modes that provide avenues for lattice collapse. The physics of systems as diverse as architectural structures, network glasses, randomly packed spheres, and biopolymer networks is strongly influenced by a nearby isostatic lattice. We explore elasticity and phonons of a special class of two-dimensional isostatic lattices constructed by distorting the kagome lattice. We show that the phonon structure of these lattices, characterized by vanishing bulk moduli and thus negative Poisson ratios and auxetic elasticity, depends sensitively on boundary conditions and on the nature of the kagome distortions. We construct lattices that under free boundary conditions exhibit surface floppy modes only or a combination of both surface and bulk floppy modes; and we show that bulk floppy modes present under free boundary conditions are also present under periodic boundary conditions but that surface modes are not. In the the long-wavelength limit, the elastic theory of all these lattices is a conformally invariant field theory with holographic properties, and the surface waves are Rayleigh waves. We discuss our results in relation to recent work on jammed systems. Our results highlight the importance of network architecture in determining floppy-mode structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.1109v1.pdf"}
{"id": "1112.1160", "abstract": "  The Laplace operator in infinite quantum waveguides (e.g., a bent strip or a twisted tube) often has a point-like eigenvalue below the essential spectrum that corresponds to a trapped eigenmode of finite L2 norm. We revisit this statement for resonators with long but finite branches that we call \"finite waveguides\". Although now there is no essential spectrum and all eigenfunctions have finite L2 norm, the trapping can be understood as an exponential decay of the eigenfunction inside the branches. We describe a general variational formalism for detecting trapped modes in such resonators. For finite waveguides with general cylindrical branches, we obtain a sufficient condition which determines the minimal length of branches for getting a trapped eigenmode. Varying the branch lengths may switch certain eigenmodes from non-trapped to trapped states. These concepts are illustrated for several typical waveguides (L-shape, bent strip, crossing of two stripes, etc.). We conclude that the well-established theory of trapping in infinite waveguides may be incomplete and require further development for being applied to microscopic quantum devices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.1160v1.pdf"}
{"id": "1112.1763", "abstract": "  In the forthcoming ISDA Standard Credit Support Annex (SCSA), the trades denominated in non-G5 currencies as well as those include multiple currencies are expected to be allocated to the USD silo, where the contracts are collateralized by USD cash, or a different currency with an appropriate interest rate overlay to achieve the same economic effects. In this paper, we have presented a simple generic valuation framework for the clean price under the USD silo with the the detailed procedures for the initial term structure construction. We have also shown that Cross Currency Swap (CCS) basis spread can be expressed as a difference between two swap rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.1763v1.pdf"}
{"id": "1112.2072", "abstract": "  Modified-Electroconvulsive Therapy (m-ECT) is administered for the treatment of various psychiatric disorders. The Seizure Generalization Hypothesis holds that propagation of the induced seizure throughout the whole brain is essential for the effective ECT intervention. However, we encounter many clinical cases where, due to high thresholds, seizure is not induced by the maximum dose of electrical charge. Some studies have indicated that the ultrabrief pulse method, in which pulse width is less than 0.5millisecond (ms), is more effective at inducing seizure than conventional brief pulse (0.5ms-2.0ms). Contrary to the studies, we experienced a case of schizophrenia in which m-ECT with 1.0 and 1.5 ms width pulse (referred to as 'long' brief pulse as 0.5ms width pulse is the default in Japan) succeeded in inducing seizure, whereas ultrabrief pulse failed to induce seizure. This case is described in detail. Moreover, we discuss the underlying mechanism of this phenomenon. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.2072v1.pdf"}
{"id": "1112.4838", "abstract": "  In minimal anomaly-mediated supersymmetry breaking models, tachyonic sleptons are avoided by introducing a common scalar mass similar to the one introduced in minimal supergravity. This may lead to non-minimal flavour-violating interactions, e.g., in the squark sector. In this paper, we analyze the viable anomaly-mediated supersymmetry breaking parameter space in the light of the latest limits on low-energy observables and LHC searches, complete our analytical calculations of flavour-violating supersymmetric particle production at hadron colliders with those related to gluino production, and study the phenomenological consequences of non-minimal flavour violation in anomaly-mediated supersymmetry breaking scenarios at the LHC. Related cosmological aspects are also briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.4838v2.pdf"}
{"id": "1112.5414", "abstract": "  We study transport in two-terminal metal/quantum spin-Hall insulator (QSHI)/metal junctions. We show that the conductance signals originating from the bulk and the edge contributions are not additive. While for a long junction the transport is determined by the edge states contribution, for a short junction, the conductance signal is built from both bulk and edge states in the ratio which depends on the width of the sample. Further, in the topological insulator regime the conductance for short junctions shows a non-monotonic behavior as a function of the sample length. Surprisingly this non-monotonic behavior of conductance can be traced to the formation of an effectively propagating solution which is robust against scalar disorder. Our predictions should be experimentally verifiable in HgTe QWs and Bi_2Se_3 thin films. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.5414v1.pdf"}
{"id": "1112.6135", "abstract": "  The cross-Kerr nonlinearity (XKNL) effect can induce efficient photon interactions in principle with which photonic multiqubit gates can be performed using far fewer physical resources than linear optical schemes. Unfortunately, it is extremely challenging to generate giant cross-Kerr nonlinearities. In recent years, much effort has been made to perform multiqubit gates via weak XKNLs. However, the required nonlinearity strengths are still difficult to achieve in the experiment. We here propose an XKNL-based scheme for realizing a two-photon polarization-parity gate, a universal two-qubit gate, in which the required strength of the nonlinearity could be orders of magnitude weaker than those required for previous schemes. The scheme utilizes a ring cavity fed by a coherent state as a quantum information bus which interacts with a path mode of the two polarized photons (qubits). The XKNL effect makes the bus pick up a phase shift dependent on the photon number of the path mode. Even when the potential phase shifts are very small they can be effectively measured using photon-number resolving detectors, which accounts for the fact that our scheme can work in the regime of tiny XKNL. The measurement outcome reveals the parity (even parity or odd parity) of the two polarization qubits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.6135v2.pdf"}
{"id": "1201.1983", "abstract": "  Model quantum Hall states including Laughlin, Moore-Read and Read-Rezayi states are generalized into appropriate anisotropic form. The generalized states are exact zero-energy eigenstates of corresponding anisotropic two- or multi-body Hamiltonians, and explicitly illustrate the existence of geometric degrees of in the fractional quantum Hall effect. These generalized model quantum Hall states can provide a good description of the quantum Hall system with anisotropic interactions. Some numeric results of these anisotropic quantum Hall states are also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.1983v1.pdf"}
{"id": "1201.3434", "abstract": "  We present a realization of two-qubit controlled-phase gate, based on the linear and nonlinear properties of the probe and signal optical pulses in an asymmetric GaAs/AlGaAs double quantum wells. It is shown that, in the presence of cross-phase modulation, a giant cross-Kerr nonlinearity and mutually matched group velocities of the probe and signal optical pulses can be achieved while realizing the suppression of linear and self-Kerr optical absorption synchronously. These characteristics serve to exhibit an all-optical two-qubit controlled-phase gate within efficiently controllable photon-photon entanglement by semiconductor mediation. In addition, by using just polarizing beam splitters and half-wave plates, we propose a practical experimental scheme to discriminate the maximally entangled polarization state of two-qubit through distinguishing two out of the four Bell states. This proposal potentially enables the realization of solid states mediated all-optical quantum computation and information processing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.3434v2.pdf"}
{"id": "1201.4757", "abstract": "  High spin states in ^112In were investigated using ^100Mo(^16O, p3n) reaction at 80 MeV. The excited level have been observed up to 5.6 MeV excitation energy and spin ∼ 20ħ with the level scheme showing three dipole bands. The polarization and lifetime measurements were carried out for the dipole bands. Tilted axis cranking model calculations were performed for different quasi-particle configurations of this doubly odd nucleus. Comparison of the calculations of the model with the B(M1) transition strengths of the positive and negative parity bands firmly established their configurations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.4757v1.pdf"}
{"id": "1201.5044", "abstract": "  Quantum Hall (QH) and quantum spin Hall (QSH) phases have very different edge states and, when going from one phase to the other, the direction of one edge state must be reversed. We study this phenomena in graphene in presence of a strong perpendicular magnetic field on top of a spin-orbit (SO) induced QSH phase. We show that, below the SO gap, the QSH phase is virtually unaffected by the presence of the magnetic field. Above the SO gap, the QH phase is restored. An electrostatic gate placed on top of the system allows to create a QSH-QH junction which is characterized by the existence of a spin-polarized chiral state, propagating along the topological interface. We find that such a setup naturally provides an extremely sensitive spin-polarized current switch. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.5044v2.pdf"}
{"id": "1201.5442", "abstract": "  We use 3D radiative MHD simulations to investigate the formation and dynamics of small-scale (less than 0.5 Mm in diameter) vortex tubes spontaneously generated by turbulent convection in quiet-Sun regions with initially weak mean magnetic fields. The results show that the vortex tubes penetrate into the chromosphere and substantially affect the structure and dynamics of the solar atmosphere. The vortex tubes are mostly concentrated in intergranular lanes and are characterized by strong (near sonic) downflows and swirling motions that capture and twist magnetic field lines, forming magnetic flux tubes that expand with height and which attain magnetic field strengths ranging from 200 G in the chromosphere to more than 1 kG in the photosphere. We investigate in detail the physical properties of these vortex tubes, including thermodynamic properties, flow dynamics, and kinetic and current helicities, and conclude that magnetized vortex tubes provide an important path for energy and momentum transfer from the convection zone into the chromosphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.5442v1.pdf"}
{"id": "1201.5800", "abstract": "  In this paper we theoretically study electromagnetic reflection, transmission, and scattering properties of periodic and random arrays of particles which exhibit both electric-mode and magnetic-mode resonances. We compare the properties of regular and random grids and explain recently observed dramatic differences in resonance broadening in the electric and magnetic modes of random arrays. We show that randomness in the particle positioning influences equally on the scattering loss from both electric and magnetic dipoles, however, the observed resonance broadening can be very different depending on the absorption level in different modes as well as on the average electrical distance between the particles. The theory is illustrated by an example of a planar metasurface composed of cut-wire pairs. We show that in this particular case at the magnetic resonance the array response is almost not affected by positioning randomness due to lower frequency and higher absorption losses in that mode. The developed model allows predictions of behavior of random grids based on the knowledge of polarizabilities of single inclusions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.5800v1.pdf"}
{"id": "1202.0547", "abstract": "  It has often been suggested that an alternative to the standard CO/21-cm method for estimating the mass of the interstellar medium (ISM) in a galaxy might be to estimate the mass of the ISM from the continuum dust emission. In this paper, we investigate the potential of this technique using Herschel observations of ten galaxies in the Herschel Reference Survey and in the Herschel Virgo Cluster Survey. We show that the emission detected by Herschel is mostly from dust that has a temperature and emissivity index similar to that of dust in the local ISM in our galaxy, with the temperature generally increasing towards the centre of each galaxy. We calibrate the dust method using the CO and 21-cm observations to provide an independent estimate of the mass of hydrogen in each galaxy, solving the problem of the uncertain `X factor' for the molecular gas by minimizing the dispersion in the ratio of the masses estimated using the two methods. With the calibration for the dust method and the estimate of the X-factor produced in this way, the dispersion in the ratio of the two gas masses is 30", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.0547v1.pdf"}
{"id": "1202.2433", "abstract": "  We report an ab initio calculation of the shielding of the nuclear magnetic moment by the bound electron in hydrogen-like ions. This investigation takes into account several effects that have not been calculated before (electron self-energy, vacuum polarization, nuclear magnetization distribution), thus bringing the theory to the point where further progress is impeded by the uncertainty due to nuclear-structure effects. The QED corrections are calculated to all orders in the nuclear binding strength parameter and, independently, to the leading order in the expansion in this parameter. The results obtained lay the ground for the high-precision determination of nuclear magnetic dipole moments from measurements of the g-factor of hydrogen-like ions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.2433v1.pdf"}
{"id": "1202.2447", "abstract": "  Regarding the intraday sequence of high frequency returns of the S   P index as daily realizations of a given stochastic process, we first demonstrate that the scaling properties of the aggregated return distribution can be employed to define a martingale stochastic model which consistently replicates conditioned expectations of the S   P 500 high frequency data in the morning of each trading day. Then, a more general formulation of the above scaling properties allows to extend the model to the afternoon trading session. We finally outline an application in which conditioned forecasting is used to implement a trend-following trading strategy capable of exploiting linear correlations present in the S   P dataset and absent in the model. Trading signals are model-based and not derived from chartist criteria. In-sample and out-of-sample tests indicate that the model-based trading strategy performs better than a benchmark one established on an asymmetric GARCH process, and show the existence of small arbitrage opportunities. We remark that in the absence of linear correlations the trading profit would vanish and discuss why the trading strategy is potentially interesting to hedge volatility risk for S   P index-based products. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.2447v2.pdf"}
{"id": "1202.4428", "abstract": "  A family of novel models of liquid on a 2D lattice (2D lattice liquid models) have been proposed as primitive models of soft-material membrane. As a first step, we have formulated them as single-component, single-layered, classical particle systems on a two-dimensional surface with no explicit viscosity. Among the family of the models, we have shown and constructed two stochastic models, a vicious walk model and a flow model, on an isotropic regular lattice and on the rectangular honeycomb lattice of various sizes. In both cases, the dynamics is governed by the nature of the frustration of the particle movements. By simulations, we have found the approximate functional form of the frustration probability, and peculiar anomalous diffusions in their time-averaged mean square displacements in the flow model. The relations to other existing statistical models and possible extensions of the models are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.4428v2.pdf"}
{"id": "1202.4779", "abstract": "  The accurate description of the optical spectra of insulators and semiconductors remains an important challenge for time-dependent density-functional theory (TDDFT). Evidence has been given in the literature that TDDFT can produce bound as well as continuum excitons for specific systems, but there are still many unresolved basic questions concerning the role of dynamical exchange and correlation (xc). In particular, the role of the long spatial range and the frequency dependence of the xc kernel f_ xc for excitonic binding are still not very well explored. We present a minimal model for excitons in TDDFT, consisting of two bands from a one-dimensional Kronig-Penney model and simple approximate xc kernels, which allows us to address these questions in a transparent manner. Depending on the system, it is found that adiabatic xc kernels can produce a single bound exciton, and sometimes two bound excitons, where the long spatial range of f_ xc is not a necessary condition. It is shown how the Wannier model, featuring an effective electron-hole interaction, emerges from TDDFT. The collective, many-body nature of excitons is explicitly demonstrated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.4779v1.pdf"}
{"id": "1202.6196", "abstract": "  Several major milestones and discoveries were attained during the lifetime of the Tevatron proton-antiproton collider at Fermilab, from 1987 to 2011. One of the most important was the discovery of the top quark in 1995, followed by an intense program to study that particle in greater detail. In this article, I give an overview of the history of the top quark, its current status as well as the still to be completed legacy measurements at the Tevatron. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.6196v1.pdf"}
{"id": "1202.6375", "abstract": "  The semiclassical SU(3) Skyrme model is traditionally considered as describing a rigid quantum rotator with the profile function being fixed by the classical solution of the corresponding SU(2) Skyrme model. In contrast, we go beyond the classical profile function by quantizing the SU(3) Skyrme model canonically. The quantization of the model is performed in terms of the collective coordinate formalism and leads to the establishment of purely quantum corrections of the model. These new corrections are of fundamental importance. They are crucial in obtaining stable quantum solitons of the quantum SU(3) Skyrme model, thus making the model self-consistent and not dependent on the classical solution of the SU(2) case. We show that such a treatment of the model leads to a family of stable quantum solitons that describe the baryon octet and decuplet and reproduce their masses in a qualitative agreement with the empirical values. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.6375v2.pdf"}
{"id": "1203.0781", "abstract": "  This manuscript proposes a posterior mean (PM) super-resolution (SR) method with a compound Gaussian Markov random field (MRF) prior. SR is a technique to estimate a spatially high-resolution image from observed multiple low-resolution images. A compound Gaussian MRF model provides a preferable prior for natural images that preserves edges. PM is the optimal estimator for the objective function of peak signal-to-noise ratio (PSNR). This estimator is numerically determined by using variational Bayes (VB). We then solve the conjugate prior problem on VB and the exponential-order calculation cost problem of a compound Gaussian MRF prior with simple Taylor approximations. In experiments, the proposed method roughly overcomes existing methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.0781v3.pdf"}
{"id": "1203.1179", "abstract": "  We propose an efficient strategy to suppress epidemic explosion in heterogeneous metapopulation networks, wherein each node represents a subpopulation with any number of individuals and is assigned a curing rate that is proportional to k^α with k the node degree and α an adjustable parameter. We have performed stochastic simulations of the dynamical reaction-diffusion processes associated with the susceptible-infected-susceptible model in scale-free networks. We found that the epidemic threshold reaches a maximum when the exponent α is tuned to be α_opt≃ 1.3. This nontrivial phenomenon is robust to the change of the network size and the average degree. In addition, we have carried out a mean field analysis to further validate our scheme, which also demonstrates that epidemic explosion follows different routes for α larger or less than α_opt. Our work suggests that in order to effectively suppress epidemic spreading on heterogeneous complex networks, subpopulations with higher degrees should be allocated more resources than just being linearly dependent on the degree k. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.1179v3.pdf"}
{"id": "1203.5980", "abstract": "  We outline a rigorous method which can be used to solve the many-body Schroedinger equation for a Coulomb interacting electronic system in an external classical magnetic field as well as a quantized electromagnetic field. Effects of the geometry of the electronic system as well as the polarization of the quantized electromagnetic field are explicitly taken into account. We accomplish this by performing repeated truncations of many-body spaces in order to keep the size of the many particle basis on a manageable level. The electron-electron and electron-photon interactions are treated in a nonperturbative manner using \"exact numerical diagonalization\". Our results demonstrate that including the diamagnetic term in the photon-electron interaction Hamiltonian drastically improves numerical convergence. Additionally, convergence with respect to the number of photon states in the joint photon-electron Fock space basis is fast. However, the convergence with respect to the number of electronic states is slow and is the main bottleneck in calculations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.5980v1.pdf"}
{"id": "1203.6093", "abstract": "  The community structure of complex networks reveals both their organization and hidden relationships among their constituents. Most community detection methods currently available are not deterministic, and their results typically depend on the specific random seeds, initial conditions and tie-break rules adopted for their execution. Consensus clustering is used in data analysis to generate stable results out of a set of partitions delivered by stochastic methods. Here we show that consensus clustering can be combined with any existing method in a self-consistent way, enhancing considerably both the stability and the accuracy of the resulting partitions. This framework is also particularly suitable to monitor the evolution of community structure in temporal networks. An application of consensus clustering to a large citation network of physics papers demonstrates its capability to keep track of the birth, death and diversification of topics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.6093v1.pdf"}
{"id": "1203.6128", "abstract": "  An efficient optimal-control theory based on the Krotov method is introduced for a non-Markovian open quantum system with a time-nonlocal master equation in which the control parameter and the bath correlation function are correlated. This optimal-control method is developed via a quantum dissipation formulation that transforms the time-nonlocal master equation to a set of coupled linear time-local equations of motion in an extended auxiliary Liouville space. As an illustration, the optimal-control method is applied to find the control sequences for high-fidelity Z gates and identity gates of a qubit embedded in a non-Markovian bath. Z gates and identity gates with errors less than 10^-5 for a wide range of bath decoherence parameters can be achieved for the non-Markovian open qubit system with control over only the σz term. The control-dissipation correlation and the memory effect of the bath are crucial in achieving the high-fidelity gates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.6128v1.pdf"}
{"id": "1204.1551", "abstract": "  Catastrophes of all kinds can be roughly defined as short duration-large amplitude events following and followed by long periods of \"ripening\". Major earthquakes surely belong to the class of 'catastrophic' events. Because of the space-time scales involved, an experimental approach is often difficult, not to say impossible, however desirable it could be. Described in this article is a \"laboratory\" setup that yields data of a type that is amenable to theoretical methods of prediction. Observations are made of a critical slowing down in the noisy signal of a solder wire creeping under constant stress. This effect is shown to be a fair signal of the forthcoming catastrophe in both of two dynamical models. The first is an \"abstract\" model in which a time dependent quantity drifts slowly but makes quick jumps from time to time. The second is a realistic physical model for the collective motion of dislocations (the Ananthakrishna set of equations for creep). Hope thus exists that similar changes in the response to noise could forewarn catastrophes in other situations, where such precursor effects should manifest early enough. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.1551v1.pdf"}
{"id": "1204.2169", "abstract": "  We study spatiotemporal correlations and temporal diversities of handset-based service usages by analyzing a dataset that includes detailed information about locations and service usages of 124 users over 16 months. By constructing the spatiotemporal trajectories of the users we detect several meaningful places or contexts for each one of them and show how the context affects the service usage patterns. We find that temporal patterns of service usages are bound to the typical weekly cycles of humans, yet they show maximal activities at different times. We first discuss their temporal correlations and then investigate the time-ordering behavior of communication services like calls being followed by the non-communication services like applications. We also find that the behavioral overlap network based on the clustering of temporal patterns is comparable to the communication network of users. Our approach provides a useful framework for handset-based data analysis and helps us to understand the complexities of information and communications technology enabled human behavior. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.2169v3.pdf"}
{"id": "1204.2282", "abstract": "  The location and asymptotic behaviour for large n of the zeros of exceptional Jacobi and Laguerre polynomials are discussed. The zeros of exceptional polynomials fall into two classes: the regular zeros, which lie in the interval of orthogonality and the exceptional zeros, which lie outside that interval. We show that the regular zeros have two interlacing properties: one is the natural interlacing between consecutive polynomials as a consequence of their Sturm-Liouville character, while the other one shows interlacing between the zeros of exceptional and classical polynomials. A generalization of the classical Heine-Mehler formula is provided for the exceptional polynomials, which allows to derive the asymptotic behaviour of their regular zeros. We also describe the location and the asymptotic behaviour of the exceptional zeros, which converge for large n to fixed values. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.2282v1.pdf"}
{"id": "1204.2496", "abstract": "  With more and more extrasolar planets discovered in and around binary star systems, questions concerning the determination of the classical Habitable Zone arise. Do the radiative and gravitational perturbations of the second star influence the extent of the Habitable Zone significantly, or is it sufficient to consider the host-star only? In this article we investigate the implications of stellar companions with different spectral types on the insolation a terrestrial planet receives orbiting a Sun-like primary. We present time independent analytical estimates and compare these to insolation statistics gained via high precision numerical orbit calculations. Results suggest a strong dependence of permanent habitability on the binary's eccentricity, as well as a possible extension of Habitable Zones towards the secondary in close binary systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.2496v1.pdf"}
{"id": "1204.3291", "abstract": "  Phase coherence and vortex order in the fully frustrated XY model on a two-dimensional honeycomb lattice are studied by extensive Monte Carlo simulations using the parallel tempering method and finite-size scaling. No evidence is found for an equilibrium order-disorder or a spin/vortex-glass transition, suggested in previous simulation works. Instead, the scaling analysis of correlations of phase and vortex variables in the full equilibrated system is consistent with a phase transition where the critical temperature vanishes and the correlation lengths diverge as a power-law with decreasing temperatures and corresponding critical exponents ν_ph and ν_v. This behavior and the near agreement of the critical exponents suggest a zero-temperature transition scenario where phase and vortex variables remain coupled on large length scales. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.3291v1.pdf"}
{"id": "1205.0436", "abstract": "  We investigate a double quantum dot coupled to a transmission line resonator. By driving a current through the double dot, a population inversion between the dot levels can be created, and a lasing state of the radiation field is generated within a sharp resonance window. The transport current correlates with the lasing state. The sharp resonance condition allows for resolving small differences in the dot properties. Dissipative processes in the quantum dots and their effect on the lasing and transport behavior are investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.0436v2.pdf"}
{"id": "1205.2454", "abstract": "  During development, epithelial tissues undergo extensive morphogenesis based on coordinated changes of cell shape and position over time. Continuum mechanics describes tissue mechanical state and shape changes in terms of strain and stress. It accounts for individual cell properties using only a few spatially averaged material parameters. To determine the mechanical state and parameters in the Drosophila pupa dorsal thorax epithelium, we sever in vivo the adherens junctions around a disk-shaped domain comprising typically hundred cells. This enables a direct measurement of the strain along different orientations at once. The amplitude and anisotropy of the strain increase during development. We also measure the stress to viscosity ratio and similarly find an increase in amplitude and anisotropy. The relaxation time is of order of ten seconds. We propose a space-time, continuous model of the relaxation. Good agreement with experimental data validates the description of the epithelial domain as a continuous, linear, visco-elastic material. We discuss the relevant time and length scales. Another material parameter, the ratio of external friction to internal viscosity, is estimated by fitting the initial velocity profile. Together, our results contribute to quantify forces and displacements, and their time evolution during morphogenesis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.2454v1.pdf"}
{"id": "1206.0037", "abstract": "  What should be the quasinormal modes associated with a spacetime that contains a naked singularity instead of a black hole? In the present work we address this problem by studying the scattering of scalar fields on a curved background described by a Reissner-Nordström spacetime with |q| > m. We show that there is a qualitative difference between cases with 1 < q^2/m^2 ≲ 9/8 and cases with q^2/m^2 ≳ 9/8. We discuss the necessary conditions for the well-posedness of the problem, and present results for the low damped modes in the low l and large l limit. We also consider the asymptotically highly damped quasinormal modes. We present strong evidence that such modes are absent in the case of a naked Reissner-Nordström singularity, corroborating recent conjectures relating them to classical and quantum properties of horizons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.0037v3.pdf"}
{"id": "1206.1948", "abstract": "  Fundamental limits of the cognitive interference channel (CIC) with two pairs of transmitter-receiver has been under exploration for several years. In this paper, we study the discrete memoryless cognitive interference channel (DM-CIC) in which the cognitive transmitter non-causally knows the message of the primary transmitter. The capacity of this channel is not known in general; it is only known in some special cases. Inspired by the concept of less noisy broadcast channel (BC), in this work we introduce the notion of less noisy cognitive interference channel. Unlike BC, due to the inherent asymmetry of the cognitive channel, two different less noisy channels are distinguishable; these are named the primary-less-noisy and cognitive-less-noisy channels. We derive capacity region for the latter case, by introducing inner and outer bounds on the capacity of the DM-CIC and showing that these bounds coincide for the cognitive-less-noisy channel. Having established the capacity region, we prove that superposition coding is the optimal encoding technique. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.1948v2.pdf"}
{"id": "1206.1972", "abstract": "  A calculational study of the trihalomethanes chloroform (CHCl_3) and bromoform (CHBr_3) adsorbed on graphene is presented. The study uses the van der Waals density functional method vdW-DF to obtain adsorption energies and adsorption structures for these molecules of environmental concern. In this study chloroform is found to adsorb with the H atom pointing away from graphene, with adsorption energy 357 meV (34.4 kJ/mol). For bromoform the calculated adsorption energy is 404 meV (39.0 kJ/mol). The corrugation of graphene as seen by chloroform is small, the difference in adsorption energy along the graphene plane is less than 6 meV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.1972v1.pdf"}
{"id": "1206.2502", "abstract": "  The observation of the polarization emerging from a rotating star at different phases opens up the possibility to map the magnetic field in the stellar surface thanks to the well-known Zeeman Doppler Imaging. When the magnetic field is sufficiently weak, the circular and linear polarization profiles locally in each point of the star are proportional to the first and second derivatives of the unperturbed intensity profile, respectively. We show that the weak-field approximation (for weak lines in the case of linear polarization) can be generalized to the case of a rotating star including the Doppler effect and taking into account the integration on the stellar surface. The Stokes profiles are written as a linear combination of wavelength-dependent terms expressed as series expansions in terms of Hermite polynomials. These terms contain the surface integrated magnetic field and velocity components. The direct numerical evaluation of these quantities is limited to rotation velocities not larger than 8 times the Doppler width of the local absorption profiles. Additionally, we demonstrate that, in a rotating star, the circular polarization flux depends on the derivative of the intensity flux with respect to the wavelength and also on the profile itself. Likewise, the linear polarization depends on the profile and on its first and second derivative with respect to the wavelength. We particularize the general expressions to a rotating dipole. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.2502v1.pdf"}
{"id": "1206.3584", "abstract": "  We use STEREO imagery to study the morphology of a shock driven by a fast coronal mass ejection (CME) launched from the Sun on 2011 March 7. The source region of the CME is located just to the east of a coronal hole. The CME ejecta is deflected away from the hole, in contrast with the shock, which readily expands into the fast outflow from the coronal hole. The result is a CME with ejecta not well centered within the shock surrounding it. The shock shape inferred from the imaging is compared with in situ data at 1 AU, where the shock is observed near Earth by the Wind spacecraft, and at STEREO-A. Shock normals computed from the in situ data are consistent with the shock morphology inferred from imaging. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.3584v1.pdf"}
{"id": "1206.3836", "abstract": "  The probability-generating function of the number of electron-positron pairs produced in a uniform electric field is constructed. The mean and variance of the numbers of pairs are calculated, and analytical expressions for the probability of low numbers of electron-positron pairs are given. A recursive formula is derived for evaluating the probability of any number of pairs. In electric fields of supercritical strength |eE| > πm^2/ ln2, where e is the electron charge, E is the electric field, and m is the electron mass, a branch-point singularity of the probability-generating function penetrates the unit circle |z| = 1, which leads to the asymptotic divergence of the cumulative probability. This divergence indicates a failure of the continuum limit approximation. In the continuum limit and for any field strength, the positive definiteness of the probability is violated in the tail of the distribution. Analyticity, convergence, and positive definiteness are restored upon the summation over discrete levels of electrons in the normalization volume. Numerical examples illustrating the field strength dependence of the asymptotic behavior of the probability distribution are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.3836v3.pdf"}
{"id": "1206.4806", "abstract": "  The understanding of nonlinear PT-symmetric quantum systems, arising for example in the theory of Bose-Einstein condensates in PT-symmetric potentials, is widely based on numerical investigations, and little is known about generic features induced by the interplay of PT-symmetry and nonlinearity. To gain deeper insights it is important to have analytically solvable toy-models at hand. In the present paper the stationary states of a simple toy-model of a PT-symmetric system are investigated. The model can be interpreted as a simple description of a Bose-Einstein condensate in a PT-symmetric double well trap in a two-mode approximation. The eigenvalues and eigenstates of the system can be explicitly calculated in a straight forward manner; the resulting structures resemble those that have recently been found numerically for a more realistic PT-symmetric double delta potential. In addition, a continuation of the system is introduced that allows an interpretation in terms of a simple linear matrix model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.4806v1.pdf"}
{"id": "1206.5168", "abstract": "  A model for low-energy meson-baryon interaction in the strange sector is presented. The interaction is described in terms of separable potentials with multiple partial waves considered. A general solution of Lippmann-Schwinger equation for the scattering of spin zero and spin one-half particles is derived.   Next, the general framework is applied to the K̅N sector in a simple model with only the S- and P-waves taken into account. The separable potential is designed to match the chiral perturbation theory at lowest nontrivial order. It is shown that although a simple model with three free parameters works well for the S-wave, it fails to reproduce the P-wave features of kaon-nucleon physics. Most importantly, the P-wave interaction is too weak to express a resonant behavior that could be identified as Σ(1385) resonance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.5168v2.pdf"}
{"id": "1206.5406", "abstract": "  This work originates from a heart's images tracking which is to generate an apparent continuous motion, observable through intensity variation from one starting image to an ending one both supposed segmented. Given two images ρ_0 and ρ_1, we calculate an evolution process ρ(t,·) which transports ρ_0 to ρ_1 by using the optical flow. In this paper we propose an algorithm based on a fixed point formulation and a space-time least squares formulation of the transport equation for computing a transport problem. Existence results are given for a transport problem with a minimum divergence for a dual norm or a weighted H^1_0-semi norm, for the velocity. The proposed transport is compare with the transport introduced by Dacorogna-Moser. The strategy is implemented in a 2D case and numerical results are presented with a first order Lagrange finite element, showing the efficiency of the proposed strategy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.5406v1.pdf"}
{"id": "1206.6371", "abstract": "  The nonlinear theory of collective plasmon-polariton propagation along the infinite chain of metallic nanoparticles is developed within RPA quasiclassical approach to surface plasmons in large nano-spheres (10-50 nm for radius) of Au or Ag. The wave type self-modes in the chain are determined and analyzed with respect to nano-sphere size and chain-separation parameters. At some regions for parameters the undamped modes occur. They were found on the rim of stability within the linear theory. The nonlinear corrections stabilize, however, diverging modes of the linear approach and considerably enlarge the region of undamped propagation. Nonlinearity is associated with relativistic corrections to the Lorentz friction. According to the nonlinear behavior, the region of parameters when undamped stable modes occur, covers the instability region of the linear theory. The remarkable property of fixed amplitude of the undamped collective propagating wave independently of initial conditions (even if they are extremely small) has been identified and described. The group velocity of this wave propagation is calculated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.6371v2.pdf"}
{"id": "1206.6716", "abstract": "  We introduce an adiabatic long-range quantum communication proposal based on a quantum dot array. By adiabatically varying the external gate voltage applied on the system, the quantum information encoded in the electron can be transported from one end dot to another. We numerically solve the Schrödinger equation for a system with a given number of quantum dots. It is shown that this scheme is a simple and efficient protocol to coherently manipulate the population transfer under suitable gate pulses. The dependence of the energy gap and the transfer time on system parameters is analyzed and shown numerically. We also investigate the adiabatic passage in a more realistic system in the presence of inevitable fabrication imperfections. This method provides guidance for future realizations of adiabatic quantum state transfer in experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.6716v1.pdf"}
{"id": "1207.0700", "abstract": "  We analyze the results of the German Team Handball Bundesliga for ten seasons in a model-free statistical time series approach. We will show that the home advantage is nearly negligible compared to the total sum of goals. Specific interest has been spent on the time evolution of the team fitness expressed in terms of the goal difference. In contrast to soccer, our results indicate a decay of the team fitness values over a season while the long time correlation behavior over years is nearly comparable. We are able to explain the dominance of a few teams by the large value for the total number of goals in a match. A method for the prediction of match winners is presented in good accuracy with the real results. We analyze the properties of promoted teams and indicate drastic level changes between the Bundesliga and the second league. Our findings reflect in good agreement recent discussions on modern successful attack strategies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.0700v1.pdf"}
{"id": "1207.2851", "abstract": "  Gate instability/hysteresis in modulation-doped p-type AlGaAs/GaAs heterostructures impedes the development of nanoscale hole devices, which are of interest for topics from quantum computing to novel spin physics. We present an extended study conducted using custom-grown, matched modulation-doped n-type and p-type heterostructures, with/without insulated gates, aimed at understanding the origin of the hysteresis. We show the hysteresis is not due to the inherent `leakiness' of gates on p-type heterostructures, as commonly believed. Instead, hysteresis arises from a combination of GaAs surface-state trapping and charge migration in the doping layer. Our results provide insights into the physics of Si acceptors in AlGaAs/GaAs heterostructures, including widely-debated acceptor complexes such as Si-X. We propose methods for mitigating the gate hysteresis, including poisoning the modulation-doping layer with deep-trapping centers (e.g., by co-doping with transition metal species), and replacing the Schottky gates with degenerately-doped semiconductor gates to screen the conducting channel from GaAs surface-states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.2851v2.pdf"}
{"id": "1207.5446", "abstract": "  Cryptographic standards serve two important goals: making different implementations interoperable and avoiding various known pitfalls in commonly used schemes. This chapter discusses Public-Key Cryptography Standards (PKCS) which have significant impact on the use of public key cryptography in practice. PKCS standards are a set of standards, called PKCS #1 through #15. These standards cover RSA encryption, RSA signature, password-based encryption, cryptographic message syntax, private-key information syntax, selected object classes and attribute types, certification request syntax, cryptographic token interface, personal information exchange syntax, and cryptographic token information syntax. The PKCS standards are published by RSA Laboratories. Though RSA Laboratories solicits public opinions and advice for PKCS standards, RSA Laboratories retain sole decision-making authority on all aspects of PKCS standards. PKCS has been the basis for many other standards such as S/MIME. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.5446v1.pdf"}
{"id": "1207.6358", "abstract": "  We investigate the influence of the geometry of the solar filament magnetic structure on the large-amplitude longitudinal oscillations. A representative filament flux tube is modeled as composed of a cool thread centered in a dipped part with hot coronal regions on either side. We have found the normal modes of the system, and establish that the observed longitudinal oscillations are well described with the fundamental mode. For small and intermediate curvature radii and moderate to large density contrast between the prominence and the corona, the main restoring force is the solar gravity. In this full wave description of the oscillation a simple expression for the oscillation frequencies is derived in which the pressure-driven term introduces a small correction. We have also found that the normal modes are almost independent of the geometry of the hot regions of the tube. We conclude that observed large-amplitude longitudinal oscillations are driven by the projected gravity along the flux tubes, and are strongly influenced by the curvature of the dips of the magnetic field in which the threads reside. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.6358v1.pdf"}
{"id": "1208.1556", "abstract": "  The quantum renormalization group method is applied to study the quantum criticality and entanglement entropy of the ground state of the Ising chain in the presence of antisymmetric anisotropic couplings and alternating exchange interactions. The quantum phase transitions can be characterized by the discontinuity in the second derivative of the energy of renormalized ground state. The phase diagram is obtained by the critical boundary line. The first derivative of entanglement entropy also diverges at the same critical points after enough iterations of the renormalization of coupling constants. The antisymmetric anisotropy and alternating interaction can enhance the renormalized entanglement via the creation of quantum fluctuations. The scaling behavior of the derivative of the entropy around the critical points manifest the logarithm dependence on the size of the spin system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.1556v1.pdf"}
{"id": "1208.2548", "abstract": "  We present analytical solutions of the geodesic equations of test particles and light in the five dimensional singly spinning black ring spacetime for special cases, since it does not appear possible to separate the Hamilton-Jacobi-equation for singly spinning black rings in general. Based on the study of the polynomials in the equations of motion we characterize the motion of test particles and light and discuss the associated orbits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.2548v3.pdf"}
{"id": "1208.6400", "abstract": "  Non-equilibrium radiation diffusion is an important mechanism of energy transport in Inertial Confinement Fusion, astrophysical plasmas, furnaces and heat exchangers. In this paper, an analytical solution to the non-equilibrium Marshak diffusion problem in a planar slab and spherical shell of finite thickness is presented. Using Laplace transform method, the radiation and material energy densities are obtained as a function of space and time. The variation in integrated energy densities and leakage currents are also studied. In order to linearize the radiation transport and material energy equation, the heat capacity is assumed to be proportional to the cube of the material temperature. The steady state energy densities show linear variation along the depth of the planar slab, whereas non-linear dependence is observed for the spherical shell. The analytical energy densities show good agreement with those obtained from finite difference method using small mesh width and time step. The benchmark results obtained in this work can be used to validate and verify non equilibrium radiation diffusion computer codes in both planar and spherical geometry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1208/1208.6400v2.pdf"}
{"id": "1209.1201", "abstract": "  This Symposium was focused on the hunt for the progenitors of Supernovae of Type Ia. Is there a main channel for the production of SNeIa? If so, are these elusive progenitors Single Degenerate or Double Degenerate systems? Although most participants seemed to favour the Single Degenerate channel, there was no general agreement on the type of binary system at play. An observational puzzle that was highlighted was the apparent paucity of Super-Soft Sources in our Galaxy and also in external galaxies. The Single Degenerate channel (and as it was pointed out, quite possibly also the Double Degenerate channel) requires the binary system to pass through a phase of steady nuclear burning. However, the observed number of Super-Soft sources falls short by a factor of up to 100 in explaining the estimated birth rates of SNeIa. Thus, are these Super-Soft sources somehow hidden away and radiating at different wavelengths or are we missing some important pieces of this puzzle that may lead to the elimination of a certain class of progenitor? Another unanswered question concerns the dependence of SNeIa luminosities on the age of their host galaxy. Several hypotheses were put forward, but none was singled out as the most likely explanation.   It is fair to say that at the end of the Symposium the definitive answer to the vexed progenitor question remained is well and truly wide open. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.1201v1.pdf"}
{"id": "1209.5916", "abstract": "  We employ three-dimensional state of the art magnetohydrodynamic models of the early solar wind and heliosphere and a two-dimensional model for cosmic ray transport to investigate the cosmic ray spectrum and flux near the Archean Earth. We assess how sensitive the cosmic ray spectrum is to changes in the sunspot placement and magnetic field strength, the large scale dipole magnetic field strength, the wind ram pressure, and the Sun's rotation period. Overall, our results confirm earlier work that suggested the Archean Earth would have experienced a greatly reduced cosmic ray flux than is the case today. The cosmic ray reduction for the early Sun is mainly due to the shorter solar rotation period and tighter winding of the Parker spiral, and to the different surface distribution of the more active solar magnetic field. These effects lead to a global reduction of the cosmic ray flux at 1AU by up to two orders of magnitude or more. Variations in the sunspot magnetic field have more effect on the flux than variations in the dipole field component. The wind ram pressure affects the cosmic ray flux through its influence on the size of the heliosphere via the pressure balance with the ambient interstellar medium. Variations in the interstellar medium pressure experienced by the solar system in orbit through Galaxy could lead to order of magnitude changes in the cosmic ray flux at Earth on timescales of a few million years. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.5916v1.pdf"}
{"id": "1209.5986", "abstract": "  We consider signal reconstruction from the norms of subspace components generalizing standard phase retrieval problems. In the deterministic setting, a closed reconstruction formula is derived when the subspaces satisfy certain cubature conditions, that require at least a quadratic number of subspaces. Moreover, we address reconstruction under the erasure of a subset of the norms; using the concepts of p-fusion frames and list decoding, we propose an algorithm that outputs a finite list of candidate signals, one of which is the correct one. In the random setting, we show that a set of subspaces chosen at random and of cardinality scaling linearly in the ambient dimension allows for exact reconstruction with high probability by solving the feasibility problem of a semidefinite program. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.5986v3.pdf"}
{"id": "1210.1967", "abstract": "  We study the particle number production and its time variation using non-equilibrium quantum field theory. We study the model proposed by Hotta et.al. <cit.> for particle number production with a heavy neutral scalar and a light complex scalar. The interaction Lagrangian contains CP violating phase and particle number violating interaction among the scalars. The particle number violating mass term is also introduced, which splits a complex scalar into two real scalars with small non-degenerate mass. Therefore, the term generates particle and anti-particle mixing. We study the long time behavior of the particle number production rate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.1967v2.pdf"}
{"id": "1210.4555", "abstract": "  We investigate an open XXZ spin 1/2 chain driven out of equilibrium by coupling with boundary reservoirs targeting different spin orientations in XY plane. Symmetries of the model are revealed which appear to be different for spin chains of odd and even sizes. As a result, spin current is found to alternate with chain length, ruling out the possibility of ballistic transport. Heat transport is switched off completely by virtue of another global symmetry. Further, we investigate the model numerically and analytically. At strong coupling, we find exact nonequilibrium steady state using a perturbation theory. The state is determined by solving secular conditions which guarantee self-consistency of the perturbative expansion. We find nontrivial dependence of the magnetization current on the spin chain anisotropy Δ in the critical region |Δ|<1, and a phenomenon of tripling of the twisting angle along the chain for narrow lacunes of Δ. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.4555v2.pdf"}
{"id": "1210.7783", "abstract": "  We develop a numerical method for pricing multidimensional vanilla options in the Black-Scholes framework. In low dimensions, we improve an adaptive integration algorithm proposed by two of the authors by introducing a new splitting strategy based on a geometrical criterion. In higher dimensions, this new algorithm is used as a control variate after a dimension reduction based on principal component analysis. Numerical tests are performed on the pricing of basket, put on minimum and digital options in dimensions up to ten. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.7783v1.pdf"}
{"id": "1211.0110", "abstract": "  The line and continuum spectra of the merger galaxy Arp 220 are analysed with the aim of investigating the ionizing and heating sources. We refer to radio, optical, infrared and X-ray spectra. The results show that in agreement with other merger galaxies, the optical lines are emitted from gas photoionised by the AGN and heated by the shocks in the extended NLR. The infrared lines are better explained by the emission from gas close to the starburst. The starburst dominates the infrared emission. [OI] and [CI] lines in the far-infrared are formed in the internal region of extended clouds and are therefore absorbed, while [CII] lines are emitted from the external edges of outflowing clouds. The O/H relative abundances are about solar and N/H are higher than solar by a factor of 1.5, throughout the starburst region, while in the AGN extended NLR the O/H ratio is half solar. A relatively high dust-to-gas ratio is indicated by modelling the dust reprocessed radiation peak consistently with bremsstrahlung emitted from the clouds. The observed radio emission is thermal bremsstrahlung, while synchrotron radiation created by the Fermi mechanism at the shock front is absorbed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.0110v1.pdf"}
{"id": "1211.1053", "abstract": "  We present a theoretical description of excitons and positively and negatively charged trions in \"giant\" CdSe/CdS core-shell nanocrystals (NCs). The developed theory provides the parameters describing the fine structure of excitons in CdSe/CdS core/thick shell NCs as a function of the CdSe/CdS conduction band offset and the CdSe core radius. We have also developed a general theory describing the fine structure of positively charged trions created in semiconductor NCs with a degenerate valence band. The calculations take into account the complex structure of the CdSe valence band and inter-particle Coulomb and exchange interaction. Presented in this paper are the CdSe core size and CdSe/CdS conduction band offset dependences (i) of the positively charged trion fine structure, (ii) of the binding energy of the negatively charged trion, and (iii) of the radiative decay time for excitons and trions. The results of theoretical calculations are in qualitative agreement with available experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.1053v1.pdf"}
{"id": "1211.1255", "abstract": "  The human brain processes information showing learning and prediction abilities but the underlying neuronal mechanisms still remain unknown. Recently, many studies prove that neuronal networks are able of both generalizations and associations of sensory inputs. In this paper, following a set of neurophysiological evidences, we propose a learning framework with a strong biological plausibility that mimics prominent functions of cortical circuitries. We developed the Inductive Conceptual Network (ICN), that is a hierarchical bio-inspired network, able to learn invariant patterns by Variable-order Markov Models implemented in its nodes. The outputs of the top-most node of ICN hierarchy, representing the highest input generalization, allow for automatic classification of inputs. We found that the ICN clusterized MNIST images with an error of 5.73", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.1255v1.pdf"}
{"id": "1211.2775", "abstract": "  In this paper, we have investigated theoretically the influence of atomic collisions on the behaviour of a one-dimensional Bose-Einstein condensate inside a driven optical cavity. We develop the discrete-mode approximation for the condensate taking into account the interband transitions due to the s-wave scattering interaction. We show that in the Bogoliubov approximation the atom-atom interaction shifts the energies of the excited modes and also plays the role of an optical parametric amplifier for the Bogoliubov side mode which can affect its normal-mode splitting behaviour. On the other hand due to the atomic collisions the resonance frequency of the cavity is shifted which leads to the decrease of the number of cavity photons and the depletion of the Bogoliubov mode. Besides, it reduces the effective atom-photon coupling parameter which consequently leads to the decrease of the entanglement between the Bogoliubov mode and the optical field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.2775v1.pdf"}
{"id": "1211.4834", "abstract": "  The two papers referred to in the title, claiming the detection of a large-scale massive hot gaseous halo around the Galaxy, have generated a lot of confusion and unwarranted excitement (including public news coverage). However, the papers are seriously flawed in many aspects, including problematic analysis and assumptions, as well as mis-reading and mis-interpreting earlier studies, which are inconsistent with the claim. Here we show examples of such flaws. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.4834v1.pdf"}
{"id": "1211.5484", "abstract": "  Identifying the importance of nodes of complex networks is of interest to the research of Social Networks, Biological Networks etc.. Current researchers have proposed several measures or algorithms, such as betweenness, PageRank and HITS etc., to identify the node importance. However, these measures are based on different aspects of properties of nodes, and often conflict with the others. A reasonable, fair standard is needed for evaluating and comparing these algorithms. This paper develops a framework as the standard for ranking the importance of nodes. Four intuitive rules are suggested to measure the node importance, and the equivalence classes approach is employed to resolve the conflicts and aggregate the results of the rules. To quantitatively compare the algorithms, the performance indicators are also proposed based on a similarity measure. Three widely used real-world networks are used as the test-beds. The experimental results illustrate the feasibility of this framework and show that both algorithms, PageRank and HITS, perform well with bias when dealing with the tested networks. Furthermore, this paper uses the proposed approach to analyze the structure of the Internet, and draws out the kernel of the Internet with dense links. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.5484v1.pdf"}
{"id": "1212.0348", "abstract": "  We study the conformational properties of heteropolymers containing two types of monomers A and B, modeled as self-avoiding random walks on a regular lattice. Such a model can describe in particular the sequences of hydrophobic and hydrophilic residues in proteins (K.F. Lau and K.A. Dill, Macromolecules 22, 3986 (1989)) and polyampholytes with oppositely charged groups (Y. Kantor and M. Kardar, Europhys. Lett.28, 169 (1994)). Treating the sequences of the two types of monomers as quenched random variables, we provide a systematic analysis of possible generalizations of this model. To this end we apply the pruned-enriched Rosenbluth chain-growth algorithm (PERM), which allows us to obtain the phase diagrams of extended and compact states coexistence as function of both the temperature and fraction of A and B monomers along the heteropolymer chain. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.0348v2.pdf"}
{"id": "1212.0478", "abstract": "  We investigate the relationship between the structure of a discrete graphical model and the support of the inverse of a generalized covariance matrix. We show that for certain graph structures, the support of the inverse covariance matrix of indicator variables on the vertices of a graph reflects the conditional independence structure of the graph. Our work extends results that have previously been established only in the context of multivariate Gaussian graphical models, thereby addressing an open question about the significance of the inverse covariance matrix of a non-Gaussian distribution. The proof exploits a combination of ideas from the geometry of exponential families, junction tree theory and convex analysis. These population-level results have various consequences for graph selection methods, both known and novel, including a novel method for structure estimation for missing or corrupted observations. We provide nonasymptotic guarantees for such methods and illustrate the sharpness of these predictions via simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.0478v2.pdf"}
{"id": "1212.1995", "abstract": "  We present a time-dependent spectral model of the nebula 3C58 and compare it with available data. The model is for a leptonic nebula, in which particles are subject to synchrotron, inverse Compton, self-synchrotron Compton, adiabatic, and bremsstrahlung processes. We find that 3C58 is compatible with being a particle dominated nebula, with a magnetic field of 35μG. A broken power law injection fits well the multi-frequency data, with a break energy at about 40 GeV. We find that 3C58 is not expected to appear in VERITAS or MAGIC II, unless the local IR background is a factor of ∼20 off Galactic models averages. For cases in which the CMB dominates the inverse Compton contribution, we find that 3C58 will not be visible either for the Cherenkov Telescope Array. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.1995v1.pdf"}
{"id": "1212.2054", "abstract": "  We propose a disk encryption method, called secure disk mixed system (SDMS) in this paper, for data protection of disk storages such as USB flash memory, USB hard disk and CD/DVD. It is aimed to solve temporal and spatial limitation problems of existing disk encryption methods and to control security performance flexibly according to the security requirement of system. SDMS stores data by encrypting with different encryption key per sector and updates sector encryption keys each time data is written. Security performance of SDMS is analyzed at the end of the paper. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.2054v1.pdf"}
{"id": "1212.2084", "abstract": "  In the present paper we study generation of the synchrotron emission by means of the feedback of Cherenkov drift waves on the particle distribution via the diffusion process. It is shown that despite the efficient synchrotron losses the excited Cherenkov drift instability leads to the quasi-linear diffusion (QLD), effect of which is balanced by dissipation factors and as a result the pitch angles are prevented from damping, maintaining the corresponding synchrotron emission. The model is analyzed for a wide range of physical parameters and it is shown that the mechanism of QLD guarantees the generation of electromagnetic radiation from soft X-rays up to soft γ-rays, strongly correlated with Cherenkov drift emission ranging from IR up to UV energy domains. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.2084v1.pdf"}
{"id": "1212.2269", "abstract": "  Stochastic resonance (SR) is a well known phenomenon in dynamical systems. It consists of the amplification and optimization of the response of a system assisted by stochastic noise. Here we carry out the first experimental study of SR in single DNA hairpins which exhibit cooperatively folding/unfolding transitions under the action of an applied oscillating mechanical force with optical tweezers. By varying the frequency of the force oscillation, we investigated the folding/unfolding kinetics of DNA hairpins in a periodically driven bistable free-energy potential. We measured several SR quantifiers under varied conditions of the experimental setup such as trap stiffness and length of the molecular handles used for single-molecule manipulation. We find that the signal-to-noise ratio (SNR) of the spectral density of measured fluctuations in molecular extension of the DNA hairpins is a good quantifier of the SR. The frequency dependence of the SNR exhibits a peak at a frequency value given by the resonance matching condition. Finally, we carried out experiments in short hairpins that show how SR might be useful to enhance the detection of conformational molecular transitions of low SNR. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.2269v1.pdf"}
{"id": "1212.4501", "abstract": "  An implementation of quantum absorption chillers with three qubits has been recently proposed, that is ideally able to reach the Carnot performance regime. Here we study the working efficiency of such self-contained refrigerators, adopting a consistent treatment of dissipation effects. We demonstrate that the coefficient of performance at maximum cooling power is upper bounded by 3/4 of the Carnot performance. The result is independent of the details of the system and the equilibrium temperatures of the external baths. We provide design prescriptions that saturate the bound in the limit of a large difference between the operating temperatures. Our study suggests that delocalized dissipation, which must be taken into account for a proper modelling of the machine-baths interaction, is a fundamental source of irreversibility which prevents the refrigerator from approaching the Carnot performance arbitrarily closely in practice. The potential role of quantum correlations in the operation of these machines is also investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.4501v3.pdf"}
{"id": "1212.4666", "abstract": "  We discuss the statistical properties of the volume of the nodal set of wave function for two paradigmatic model systems which we consider in arbitrary dimension s≥ 2: the cuboid as a paradigm for a regular shape with separable wave functions, planar random waves as an established model for chaotic wave functions in irregular shapes. We give explicit results for the mean and variance of the nodal volume in arbitrary dimension, and for their limiting distribution. For the mean nodal volume we calculate the effect of the boundary of the cuboid where Dirichlet boundary conditions reduce the nodal volume compared to the bulk. Boundary effects for chaotic wave functions are calculated using random waves which satisfy a Dirichlet boundary condition on a hyperplane. We put forward several conjectures what properties of cuboids generalise to general regular shapes with separable wave functions and what properties of random waves can be expected for general irregular shapes. These universal features clearly distinct between the two cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.4666v1.pdf"}
{"id": "1212.5800", "abstract": "  We analyze the two-loop level R-parity violating supersymmetric contribution to the electric and chromoelectric dipole moments of the fermion with neutrino and gaugino in the intermediate state. It is found that this contribution can be sufficiently enhanced with large tan β and that it can have comparable size with the currently known R-parity violating Barr-Zee type process in the TeV scale supersymmetry breaking. We also give new limits on the R-parity violating couplings from the experimental data of the electric dipole moments of the neutron and the electron. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.5800v1.pdf"}
{"id": "1212.5867", "abstract": "  Continuous-Time Quantum Monte Carlo (CT-QMC) method combined with Dynamical Mean Field Theory (DMFT) is used to calculate both Periodic Anderson Model (PAM) and Kondo Lattice Model (KLM). Different parameter sets of both models are connected by the Schrieffer-Wolff transformation. For degeneracy N=2, a special particle-hole symmetric case of PAM at half filling which always fixes one electron per impurity site is compared with the results of the KLM. We find a good mapping between PAM and KLM in the limit of large on-site Hubbard interaction U for different properties like self-energy, quasiparticle residue and susceptibility. This allows us to extract quasiparticle mass renormalizations for the f electrons directly from KLM. The method is further applied to higher degenerate case and to realsitic heavy fermion system CeRhIn5 in which the estimate of the Sommerfeld coefficient is proven to be close to the experimental value. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1212/1212.5867v1.pdf"}
{"id": "1301.3772", "abstract": "  We present an overview of recent developments in numerical relativity studies of higher dimensional spacetimes with a focus on time evolutions of black-hole systems. After a brief review of the numerical techniques employed for these studies, we summarize results grouped into the following three areas: (i) Numerical studies of fundamental properties of black holes, (ii) Applications of black-hole collisions to the modeling of Trans-Planckian scattering, (iii) Numerical studies of asymptotically anti-de Sitter spacetimes in the context of the gauge-gravity duality. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.3772v2.pdf"}
{"id": "1301.4464", "abstract": "  The compressive yield stress of particle gels shows a highly nonlinear dependence on the packing fraction. We have studied continuous compression processes, and discussed the packing fraction dependence with the particle scale rearrangements. The 2D simulation of uniaxial compression was applied to fractal networks, and the required compressive stresses were evaluated for a wide range of packing fractions that approached close packing. The compression acts to reduce the size of the characteristic structural entities (i.e. the correlation length of the structure). We observed three stages of compression: (I) elastic-dominant regime; (II) single-mode plastic regime, where the network strengths are determined by the typical length scale and the rolling mode; and (III) multi-mode plastic regime, where sliding mode and connection breaks are important. We also investigated the way of losing the fractal correlation under compression. It turns out that both fractal dimension D_f and correlation length ξ start to change from the early stage of compression, which is different from the usual assumption in theoretical models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.4464v3.pdf"}
{"id": "1301.5146", "abstract": "  We have studied the high-frequency properties of the non-equilibrium electron gas in GaN samples subjected to electric and magnetic fields. Spectra of the complex tensor of the dynamical mobility have been calculated for THz frequency range. For the compensated GaN and low temperatures, in the intervals of electric fields of the few kV/cm and magnetic fields of the few T the existence of the cyclotron and optical phonon transit-time resonances has been identified. We have shown that interplay of two resonances gives rise to specific spectra of THz transmission and absorption (or gain). We suggest that experimental investigation of these effects will facilitate elaboration of field controlled devices for THz optoelectronics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.5146v1.pdf"}
{"id": "1301.5848", "abstract": "  Replicating or caching popular content in memories distributed across the network is a technique to reduce peak network loads. Conventionally, the main performance gain of this caching was thought to result from making part of the requested data available closer to end users. Instead, we recently showed that a much more significant gain can be achieved by using caches to create coded-multicasting opportunities, even for users with different demands, through coding across data streams. These coded-multicasting opportunities are enabled by careful content overlap at the various caches in the network, created by a central coordinating server.   In many scenarios, such a central coordinating server may not be available, raising the question if this multicasting gain can still be achieved in a more decentralized setting. In this paper, we propose an efficient caching scheme, in which the content placement is performed in a decentralized manner. In other words, no coordination is required for the content placement. Despite this lack of coordination, the proposed scheme is nevertheless able to create coded-multicasting opportunities and achieves a rate close to the optimal centralized scheme. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.5848v3.pdf"}
{"id": "1301.6168", "abstract": "  We present the analysis of 1,207 RR Lyrae found in photometry taken by the Catalina Survey's Mount Lemmon telescope. By combining accurate distances for these stars with measurements for  14,000 type-AB RR Lyrae from the Catalina Schmid telescope, we reveal an extended association that reaches Galactocentric distances beyond 100 kpc and overlaps the Sagittarius streams system. This result confirms earlier evidence for the existence of an outer halo tidal stream resulting from a disrupted stellar system. By comparing the RR Lyrae source density with that expected based on halo models, we find the detection has  8 sigma significance. We investigate the distances, radial velocities, metallicities, and period-amplitude distribution of the RR Lyrae. We find that both radial velocities and distances are inconsistent with current models of the Sagittarius stream. We also find tentative evidence for a division in source metallicities for the most distant sources. Following prior analyses, we compare the locations and distances of the RR Lyrae with photometrically selected candidate horizontal branch stars and find supporting evidence that this structure spans at least 60 deg of the sky. We investigate the prospects of an association between the stream and unusual globular cluster NGC 2419. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.6168v1.pdf"}
{"id": "1301.6175", "abstract": "  Quantum electrodynamics in three dimensions in the bispinor formulation is considered. It is shown that the Dyson-Schwinger equations for fermion and boson propagators may be self-consistently solved in the infrared domain if on uses the Salam's vertex function. The parameters defining the behavior of the propagators are found numerically for different values of coupling constant and gauge parameter. For weak coupling the approximated analytical solutions are obtained. The renormalized gauge boson propagator (transverse part) is shown in the infrared domain to be practically gauge independent. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.6175v1.pdf"}
{"id": "1301.6634", "abstract": "  Azimuthal age/color gradients across spiral arms are a signature of long-lived spirals. From a sample of 19 normal (or weakly barred) spirals where we have previously found azimuthal age/color gradient candidates, 13 objects were further selected if a two-armed grand-design pattern survived in a surface density stellar mass map. Mass maps were obtained from optical and near-infrared imaging, by comparing with a Monte Carlo library of stellar population synthesis models that allowed us to obtain the mass-to-light ratio in the J band, (M/L)_J, as a function of (g-i) versus (i-J) color. The selected spirals were analyzed with Fourier methods in search for other signatures of long-lived modes related to the gradients, such as the gradient divergence toward corotation, and the behavior of the phase angle of the two-armed spiral in different wavebands, as expected from theory. The results show additional signatures of long-lived spirals in at least 50", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.6634v2.pdf"}
{"id": "1301.6838", "abstract": "  An essential feature of genuine quantum correlation is the simultaneous existence of correlation in complementary bases. We reveal this feature of quantum correlation by defining measures based on invariance under a basis change. For a bipartite quantum state, the classical correlation is the maximal correlation present in a certain optimum basis, while the quantum correlation is characterized as a series of residual correlations in the mutually unbiased bases. Compared with other approaches to quantify quantum correlation, our approach gives information-theoretical measures that directly reflect the essential feature of quantum correlation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.6838v3.pdf"}
{"id": "1301.6882", "abstract": "  We study a general Majorana junction, where N helical nanowires are connected to a common s-wave superconductor proximity-inducing Majorana bound states in the wires. The normal part of each wire (j=1,...,N) acts as connected lead, where electrons can tunnel into the respective Majorana state γ_A,j. The Majorana states at the other end, γ_B,j, are coupled to each other by an arbitrary tunnel matrix. We examine the conditions for even-odd parity effects in the tunnel conductance for various junction topologies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.6882v2.pdf"}
{"id": "1301.6912", "abstract": "  We study the temperature dependent dynamical processes of a Si10H16 cluster and obtain a blue shift of the Si-Si vibrational modes with transverse acoustic character and a red shift of the other vibrational modes with increasing temperature. We link this behavior to the bond length expansion and the varying sign of the Grueneisen parameter. We further present a computational approach able to extract the vibron-vibron coupling strength in clusters or molecules. Our approach is based on ab initio Born-Oppenheimer molecular dynamics and a projection formalism able to deliver the individual vibron occupation numbers. From the Fourier transform of the vibron energy autocorrelation function we obtain the coupling strength of each vibron to the most strongly coupled vibronic states. We find vibron-vibron coupling strength up to 2.5 THz with a moderate increase of about 5 ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.6912v3.pdf"}
{"id": "1301.7340", "abstract": "  In atomic force microscopy (AFM) tip-surface interactions are usually considered as functions of the tip position only, so-called force curves. However, tip-surface interactions often depend on the tip velocity and the past tip trajectory. Here, we introduce a compact and general description of these interactions appropriate to dynamic AFM where the measurement of force is restricted to a narrow frequency band. We represent the tip-surface interaction in terms of a force disk in the phase space of position and velocity. Determination of the amplitude dependence of tip-surface forces at a fixed static probe height allows for a comprehensive treatment of conservative and dissipative interactions. We illuminate the fundamental limitations of force reconstruction with narrow band dynamic AFM and we show how the amplitude dependence of the Fourier component of the force at the tip oscillation frequency, gives qualitative insight into the detailed nature of the tip-surface interaction. With minimal assumptions this amplitude dependence force spectroscopy allows for a quantitative reconstruction of the effective conservative tip-surface force as well as a position-dependent damping factor. We demonstrate this reconstruction on simulated intermodulation AFM data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.7340v1.pdf"}
{"id": "1302.0362", "abstract": "  A formalism is developed which describes the extent to which stochastic oscillations in biochemical models are synchronised. It is based on the calculation of the complex coherence function within the linear noise approximation. The method is illustrated on a simple example and then applied to study the synchronisation of chemical concentrations in social amoeba. The degree to which variation of rate constants in different cells and the volume of the cells affects synchronisation of the oscillations is explored, and the phase lag calculated. In all cases the analytical results are shown to be in good agreement with those obtained through numerical simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.0362v1.pdf"}
{"id": "1302.1354", "abstract": "  The specific behavior of spinor field in curve space-time with the exception of FRW model almost always gives rise to non-trivial non-diagonal components of the energy-momentum tensor. This non-triviality of non-diagonal components of the energy-momentum tensor imposes some severe restrictions either on the spinor field or on the metric functions. In this paper within the scope of an anisotropic Bianchi type-I Universe we study the role of spinor field in the evolution of the Universe. It is found that there exist two possibilities. In one scenario the initially anisotropic Universe evolves into an isotropic one asymptotically, but in this case the spinor field itself undergoes some severe restrictions. In the second scenario the isotropization takes places almost at the beginning of the process. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.1354v2.pdf"}
{"id": "1302.2012", "abstract": "  We have studied the behavior of the electronic energy spin-splitting of InGaAs-InAlAs based double quantum wells (narrow gap structures) under in-plane magnetic and transverse electric fields. We have developed an improved 8x8 version of the Transfer Matrix Approach that consider contributions from abrupt interfaces and external fields when tunneling through central barrier exists. We have included the Landé g-factor dependence on the external applied field. Also, we have calculated electron density of states and photoluminescence excitation. Variations of the electron spin-splitting energy lead to marked peculiarities in the density of states. Because the density of states is directly related to photoluminescence excitation, these peculiarities are observable by this technique. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.2012v3.pdf"}
{"id": "1302.2160", "abstract": "  The quantum critical Antiferromagnetic (AFM) fluctuation spectra measured by inelastic neutron scattering recently in two heavy fermion superconductors are used together with their other measured properties to calculate their D-wave superconducting transition temperatures T_ c. To this end, the linearized Eliashberg equations for D-wave superconductivity induced by AFM fluctuations are solved in models of fermions with various levels of nesting. The results for the ratio of T_ c to the characteristic spin-fluctuation energy are well parametrized by a dimensionless coupling constant and the AFM correlation length. Comparing the results with experiments suggests that one may reasonably conclude that superconductivity in these compounds is indeed caused by AFM fluctuations. This conclusion is strengthened by a calculation with the same parameters of the measured coefficient of the normal state quantum-critical resistivity ∝ T^3/2 characteristic of gaussian AFM quantum-critical fluctuations. The calculations give details of the superconducting coupling as a function of the correlation length and the integrated fluctuation spectra useful in other compounds. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.2160v2.pdf"}
{"id": "1302.2778", "abstract": "  We develop the synchronization theory of microwave induced zero-resistance states (ZRS) for two-dimensional electron gas in a magnetic field. In this theory the dissipative effects lead to synchronization of cyclotron phase with driving microwave phase at certain resonant ratios between microwave and cyclotron frequencies. This synchronization produces stabilization of electron transport along edge channels and at the same time it gives suppression of dissipative scattering on local impurities and dissipative conductivity in the bulk, thus creating the ZRS phases at that frequency ratios. The electron dynamics along edge and around circular disk impurity is well described by the Chirikov standard map. The theoretical analysis is based on extensive numerical simulations of classical electron transport in a strongly nonlinear regime. We also discuss the value of activation energy obtained in our model and the experimental signatures that could establish the synchronization origin of ZRS. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.2778v1.pdf"}
{"id": "1302.3166", "abstract": "  Multiple-antenna \"based\" transmitter (TX) cooperation has been established as a promising tool towards avoiding, aligning, or shaping the interference resulting from aggressive spectral reuse. The price paid in the form of feedback and exchanging channel state information (CSI) between cooperating devices in most existing methods is often underestimated however. In reality, feedback and information overhead threatens the practicality and scalability of TX cooperation approaches in dense networks. Hereby we addresses a \"Who needs to know what?\" problem, when it comes to CSI at cooperating transmitters. A comprehensive answer to this question remains beyond our reach and the scope of this paper. Nevertheless, recent results in this area suggest that CSI overhead can be contained for even large networks provided the allocation of feedback to TXs is made non-uniform and to properly depend on the network's topology. This paper provides a few hints toward solving the problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.3166v1.pdf"}
{"id": "1302.3969", "abstract": "  Since the complexity of the practical environment, many distributed networked systems can not be illustrated with the integer-order dynamics and only be described as the fractional-order dynamics. Suppose multi-agent systems will show the individual diversity with difference agents, where the heterogeneous (integer-order and fractional-order) dynamics are used to illustrate the agent systems and compose integer-fractional compounded-order systems. Applying Laplace transform and frequency domain theory of the fractional-order operator, consensus of delayed multi-agent systems with directed weighted topologies is studied. Since integer-order model is the special case of fractional-order model, the results in this paper can be extend to the systems with integer-order models. Finally, numerical examples are used to verify our results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.3969v1.pdf"}
{"id": "1302.5949", "abstract": "  Calculations of the number of equivalence classes of Sudoku boards has to this point been done only with the aid of a computer, in part because of the unnecessarily large symmetry group used to form the classes. In particular, the relationship between relabeling symmetries and positional symmetries such as row/column swaps is complicated. In this paper we focus first on the smaller Shidoku case and show first by computation and then by using connectivity properties of simple graphs that the usual symmetry group can in fact be reduced to various minimal subgroups that induce the same action. This is the first step in finding a similar reduction in the larger Sudoku case and for other variants of Sudoku. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.5949v1.pdf"}
{"id": "1303.1285", "abstract": "  We study the reconstruction of bandlimited fields from samples taken at unknown but statistically distributed sampling locations. The setup is motivated by distributed sampling where precise knowledge of sensor locations can be difficult.   Periodic one-dimensional bandlimited fields are considered for sampling. Perfect samples of the field at independent and identically distributed locations are obtained. The statistical realization of sampling locations is not known. First, it is shown that a bandlimited field cannot be uniquely determined with samples taken at statistically distributed but unknown locations, even if the number of samples is infinite. Next, it is assumed that the order of sample locations is known. In this case, using insights from order-statistics, an estimate for the field with useful asymptotic properties is designed. Distortion (mean-squared error) and central-limit are established for this estimate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.1285v1.pdf"}
{"id": "1303.3012", "abstract": "  In order to test gravitation in the Solar System, it is necessary to improve the orbit restitution of interplanetary spacecrafts. The addition of an accelerometer on board is a major step toward this goal because this instrument measures the non-gravitational acceleration of the spacecraft. It must be able to perform measurements at low frequencies with no bias to provide an additional observable of interest.   Since electrostatic accelerometers suffer a bias, a technological upgrade has been proposed by Onera. It consists in adding to an electrostatic accelerometer a rotating platform which allows modulating the signal of interest and retrieving it without bias after post-processing. Using this principle, a measurement method and a post-processing method have been developed. The objective of this article is to validate these methods experimentally. To do so, a horizontally controlled pendulum was used to apply a known signal to an accelerometer mounted on a rotating platform. The processing of the experimental data demonstrates the ability to make acceleration measurements with no bias. In addition, the experimental precision on the unbiased acceleration obtained after post-processing corresponds to the precision predicted theoretically. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.3012v1.pdf"}
{"id": "1303.3892", "abstract": "  We study a black hole solution for the generalized Einstein Hilbert action with scale dependent couplings G(r) and Lambda(r). The form of the couplings is not imposed, but rather deduced from the existence of a non trivial symmetrical solution. A classical-like choice of the integration constants is found. Finally, the induced flow of the couplings is derived and compared to the flow that is obtained in the context of the exact renormalization group approach. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.3892v1.pdf"}
{"id": "1303.4230", "abstract": "  The Aharonov–Bohm effect is considered as a scattering event with nonrelativistic charged particles of the wavelength which is less than the transverse size of an impenetrable magnetic vortex. The quasiclassical WKB method is shown to be efficient in solving this scattering problem. We find that the scattering cross section consists of two terms, one describing the classical phenomenon of elastic reflection and another one describing the quantum phenomenon of diffraction; the Aharonov–Bohm effect is manifested as a fringe shift in the diffraction pattern. Both the classical and the quantum phenomena are independent of the choice of a boundary condition at the vortex edge, providing that probability is conserved. We show that a propagation of charged particles can be controlled by altering the flux of a magnetic vortex placed on their way. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.4230v2.pdf"}
{"id": "1303.4253", "abstract": "  Catalyzed symmetry breaking arises from a parametric enhancement of critical fluctuations independently of the coupling strength. Symmetry-breaking fermionic long-range fluctuations exhibit such an enhancement on negatively curved spaces, as is known from mean-field studies. We study gravitational catalysis from the viewpoint of the functional renormalization group using the 3d Gross-Neveu model as a specific example. We observe gravitational catalysis towards a phase of broken discrete chiral symmetry both on a maximally symmetric (AdS) and on a purely spatially curved manifold for constant negative curvature (Lobachevsky plane). The resulting picture for gravitational catalysis obtained from the renormalization flow is closely related to that of magnetic catalysis. As an application, we estimate the curvature required for subcritical systems of finite length to acquire a gravitionally catalyzed gap. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.4253v1.pdf"}
{"id": "1303.6075", "abstract": "  We study initial cuts of models of weak two-sorted Bounded Arithmetics with respect to the strength of their theories and show that these theories are stronger than the original one. More explicitly we will see that polylogarithmic cuts of models of 𝐕^0 are models of 𝐕𝐍𝐂^1 by formalizing a proof of Nepomnjascij's Theorem in such cuts. This is a strengthening of a result by Paris and Wilkie. We can then exploit our result in Proof Complexity to observe that Frege proof systems can be sub exponentially simulated by bounded depth Frege proof systems. This result has recently been obtained by Filmus, Pitassi and Santhanam in a direct proof. As an interesting observation we also obtain an average case separation of Resolution from AC0-Frege by applying a recent result with Tzameret. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.6075v2.pdf"}
{"id": "1303.6401", "abstract": "  Investigating long series of spectral and photometric observations, we found that the orbital elements of epsilon Aur are subject to much larger uncertainties than usually believed. The H alpha emission is found to move basically with the F primary but its exact location should still be investigated. We also find strong additional absorption and large reddening of the object near the third contact during the eclipse. Episodic atmospheric mass transfer from the F primary towards its companion is tentatively suggested. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.6401v1.pdf"}
{"id": "1303.6518", "abstract": "  Sink Mobility is becoming popular due to excellent load balancing between nodes and ultimately resulting in prolonged network lifetime and throughput. A major challenge is to provide reliable and energy-efficient operations are to be taken into consideration for differentmobility patterns of sink. Aim of this paper is lifetime maximization of Delay TolerantWireless Sensor Networks (WSNs) through the manipulation of Mobile Sink (MS) on different trajectories. We propose Square Routing Protocol with MS (SRP-MS) based on existing SEP (Stable Election Protocol) by making it Cluster Less (CL) and introducing sink mobility. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.6518v1.pdf"}
{"id": "1303.6537", "abstract": "  The states of an open quantum system are coupled via the environment of scattering wavefunctions. The complex coupling coefficients ω between system and environment arise from the principal value integral and the residuum. At high level density where the resonance states overlap, the dynamics of the system is determined by exceptional points. At these points, the eigenvalues of two states are equal and the corresponding eigenfunctions are linearly dependent. It is shown in the present paper that Im(ω) and Re(ω) influence the system properties differently in the surrounding of exceptional points. Controlling the system by a parameter, the eigenvalues avoid crossing in energy near an exceptional point under the influence of Re(ω) in a similar manner as it is well known from discrete states. Im(ω) however leads to width bifurcation and finally (when the system is coupled to one channel, i.e. to a common continuum of scattering wavefunctions), to a splitting of the system into two parts with different characteristic time scales. Physically, the system is stabilized by this splitting since the lifetimes of most (N-1) states are longer than before while that of only one state is shorter. In the cross section the short-lived state appears as a background term in high-resolution experiments. The wavefunctions of the long-lived states are mixed in those of the original ones in a comparably large parameter range. Numerical results for the eigenvalues and eigenfunctions are shown for N=2,  4 and 10 states coupled mostly to 1 channel. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.6537v1.pdf"}
{"id": "1303.6594", "abstract": "  We investigate the dynamics of a plasmonic oscillation over a metal nanoparticle when it is strongly coupled to a quantum emitter (e.g. quantum dot, molecule). We simulate the density matrix evolution for a simple model; coupled classical–quantum oscillators system. We show that lifetime of the plasmonic oscillations can be increased several orders of magnitude, upto the decay time of the quantum emitter. This effect shows itself as the narrowing of the plasmon emission band in the spaser (surface plasmon amplification by stimulated emission of radiation) experiment [Nature, 2009, 460, 1110], where a gold nanoparticle interacts with the surrounding molecules. Enhancement of the plasmonic excitation lifetime enables stimulated emission to overcome the spontaneous one. The enhancement occurs due to the emergence of a phenomenon analogous to electromagnetically induced transparency (EIT). The effect can find applications in many areas of nanoscale physics, such as in quantum information with plasmons and in increasing solar cell efficiency. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1303/1303.6594v3.pdf"}
{"id": "1304.2911", "abstract": "  We report the successful fabrication of lateral organic spin valves with a channel length in the sub 100 nm regime. The fabication process is based on in-situ shadow evaporation under UHV conditions and therefore yields clean and oxygen-free interfaces between the ferromagnetic metallic electrodes and the organic semiconductor. The spin valve devices consist of Nickel and Cobalt-iron electrodes and the high mobility n-type organic semiconductor N,N'-bis(heptafluorobutyl)-3,4:9,10-perylene diimide. Our studies comprise fundamental investigations of the process' and materials' suitability for the fabrication of lateral spin valve devices as well as magnetotransport measurements at room temperature. The best devices exhibit a magnetoresistance of up to 50", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.2911v2.pdf"}
{"id": "1304.3214", "abstract": "  Based on micromagnetic theory we have derived analytical expressions for the magnetic small-angle neutron scattering (SANS) cross section of a two-phase particle-matrix-type ferromagnet. The approach—valid close to magnetic saturation—provides access to several features of the spin structure such as perturbing magnetic anisotropy and magnetostatic fields. Depending on the applied magnetic field and on the magnitude H_p of the magnetic anisotropy field relative to the magnitude Δ M of the jump in the longitudinal magnetization at the particle-matrix interface, we observe a variety of angular anisotropies in the magnetic SANS cross section. In particular, the model explains the \"clover-leaf\"-shaped angular anisotropy which was previously observed for several nanostructured magnetic materials, and it provides access to the magnetic interaction parameters such as the average exchange-stiffness constant. It is also shown that the ratio H_p / Δ M decisively determines the asymptotic power-law exponent and the range of spin-misalignment correlations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.3214v1.pdf"}
{"id": "1304.7223", "abstract": "  We assume some standard choices for the branch cuts of a group of functions and consider the problem of then calculating the branch cuts of expressions involving those functions. Typical examples include the addition formulae for inverse trigonometric functions. Understanding these cuts is essential for working with the single-valued counterparts, the common approach to encoding multi-valued functions in computer algebra systems. While the defining choices are usually simple (typically portions of either the real or imaginary axes) the cuts induced by the expression may be surprisingly complicated. We have made explicit and implemented techniques for calculating the cuts in the computer algebra programme Maple. We discuss the issues raised, classifying the different cuts produced. The techniques have been gathered in the BranchCuts package, along with tools for visualising the cuts. The package is included in Maple 17 as part of the FunctionAdvisor tool. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.7223v3.pdf"}
{"id": "1305.1386", "abstract": "  Hamiltonian systems, when coupled via time–delayed interactions, do not remain conservative. In the uncoupled system, the motion can typically be periodic, quasiperiodic or chaotic. This changes drastically when delay coupling is introduced since now attractors can be created in the phase space. In particular for sufficiently strong coupling there can be amplitude death (AD), namely the stabilization of point attractors and the cessation of oscillatory motion. The approach to the state of AD or oscillation death is also accompanied by a phase–flip in the transient dynamics. A discussion and analysis of the phenomenology is made through an application to the specific cases of harmonic as well as anharmoniccoupled oscillators, in particular the Hénon-Heiles system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.1386v1.pdf"}
{"id": "1305.3360", "abstract": "  The systematic study of the correlation between the experimental giant dipole resonance (GDR) width and the average deformation <β> of the nucleus at finite excitation is presented for the mass region A   59 to 208. We show that the width of the GDR (Γ) and the quadrupole deformation of the nucleus do not follow a linear relation, as predicted earlier, due to the GDR induced quadrupole moment and the correlation also depends on the mass of the nuclei. The different empirical values of <β> extracted from the experimental GDR width match exceptionally well with the thermal shape fluctuation model. As a result, this universal correlation between <β> and Γprovides a direct experimental probe to determine the nuclear deformation at finite temperature and angular momentum in the entire mass region. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.3360v1.pdf"}
{"id": "1305.4533", "abstract": "  The magnetization of neutron star matter in magnetic fields is studied by employing the FSUGold interaction. It is found that the magnetic susceptibilities of the charged particles (proton, electron and muon) can be larger than that of neutron. The effects of the anomalous magnetic moments (AMM) of each component on the magnetic susceptibility are examined in detail. It is found that the proton and electron AMM affect their respective magnetic susceptibility evidently in strong magnetic fields. In addition, they are the protons instead of the electrons that contribute most significantly to the magnetization of the neutron star matter in a relative weak magnetic field, and the induced magnetic field due to the magnetization can be appear to be very large. Finally, the effect of the density-dependent symmetry energy on the magnetization is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.4533v1.pdf"}
{"id": "1305.5118", "abstract": "  The interaction radius of a resonance is an important physical quantity to describe the structure of a resonance. But, for a long time, physicists do not find a reliable way to measure the magnitude of the interaction radius of a resonance. In this paper, a method is proposed to measure the interaction radius in physics analysis.   It is found that the centrifugal barrier effects have great influence to physical results obtained in the PWA fit, and the interaction radius of some resonances can be well measured in the fit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.5118v1.pdf"}
{"id": "1305.5687", "abstract": "  We consider a system of two coupled particles evolving in a periodic and spatially symmetric potential under the influence of external driving and damping. The particles are driven individually in such a way that in the uncoupled regime, one particle evolves on a chaotic attractor, while the other evolves on regular periodic attractors. Notably only the latter supports coherent particle transport. The influence of the coupling between the particles is explored, and in particular how it relates to the emergence of a directed current. We show that increasing the (weak) coupling strength subdues the current in a process, which in phase-space, is related to a merging crisis of attractors forming one large chaotic attractor in phase-space. Further, we demonstrate that complete current suppression coincides with a chaos-hyperchaos transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.5687v1.pdf"}
{"id": "1305.5871", "abstract": "  We present a theoretical study of the collective optical effects which can occur in groups of three and four quantum dots. We define conditions for stable subradiant (dark) states, rapidly decaying superradiant states,and spontaneous trapping of excitation. Each quantum dot is treated like a two-level system. The quantum dots are though realistic, meaning that they may have different transition energies and dipole moments. The dots interact via a short-range coupling which allows excitation transfer across the dots, but conserves the total population. We calculate the time evolution of single- and biexciton states using the Linblad equation. In the steady state the individual populations of each dot may have permanent oscillations with frequencies given by the energy separation between the subradiant eigenstates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.5871v2.pdf"}
{"id": "1305.6445", "abstract": "  The effects of gluon radiation by charm quarks on the transport coefficients e.g. drag, longitudinal and transverse diffusion and shear viscosity have been studied within the ambit of perturbative quantum chromodynamics (pQCD) and kinetic theory. We found that while the soft gluon radiation has substantial effects on the transport coefficients of the charm quarks in the quark gluon plasma its effects on the equilibrium distribution function is insignificant. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.6445v1.pdf"}
{"id": "1306.0512", "abstract": "  We present a catalog of precise eclipse times and analysis of third body signals among 1279 close binaries in the latest Kepler Eclipsing Binary Catalog. For these short period binaries, Kepler's 30 minute exposure time causes significant smearing of light curves. In addition, common astrophysical phenomena such as chromospheric activity, as well as imperfections in the light curve detrending process, can create systematic artifacts that may produce fictitious signals in the eclipse timings. We present a method to measure precise eclipse times in the presence of distorted light curves, such as in contact and near-contact binaries which exhibit continuously changing light levels in and out of eclipse. 236 systems for which we find a timing variation signal compatible with the presence of a third body are identified. These are modeled for the light time travel effect and the basic properties of the third body are derived. This study complements Orosz et al. (2013; in prep), which focuses on eclipse timing variations of longer period binaries with flat out-of-eclipse regions. Together, these two papers provide comprehensive eclipse timings for all binaries in the Kepler Eclipsing Binary Catalog, as an ongoing resource freely accessible online to the community. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.0512v2.pdf"}
{"id": "1306.0675", "abstract": "  Scattering of a quantum particle from an oscillating barrier or well does not generally conserve the particle energy owing to energy exchange with the photon field, and an incoming particle-free state is scattered into a set of outgoing (transmitted and reflected) free states according to Floquet scattering theory. Here we introduce two families of oscillating non-Hermitian potential wells in which Floquet scattering is fully suppressed for any energy of the incident particle. The scattering-free oscillating potentials are synthesized by application of the Darboux transformation to the time-dependent Schrödinger equation. For one of the two families of scattering-free potentials, the oscillating potential turns out to be fully invisible. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.0675v1.pdf"}
{"id": "1306.5640", "abstract": "  The effects of randomly pinning particles in a model glass-forming fluid are studied, with a focus on the dynamically heterogeneous relaxation in the presence of pinning. We show how four-point dynamical correlations can be analysed in real space, allowing direct extraction of a length scale that characterises dynamical heterogeneity. In the presence of pinning, the relaxation time of the glassy system increases by up to two decades, but there is almost no increase in either the four-point correlation length or the strength of the four-point correlations. We discuss the implications of these results for theories of the glass transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.5640v1.pdf"}
{"id": "1306.6874", "abstract": "  We consider the problem of reconstruction of dielectrics from blind backscattered experimental data. Experimental data were collected by a device, which was built at University of North Carolina at Charlotte. This device sends electrical pulses into the medium and collects the time resolved backscattered data on a part of a plane. The spatially distributed dielectric constant ε_r(𝐱),𝐱∈ℝ^3 is the unknown coefficient of a wave-like PDE. This coefficient is reconstructed from those data in blind cases. To do this, a globally convergent numerical method is used. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.6874v1.pdf"}
{"id": "1307.0062", "abstract": "  Current-induced spin-transfer torques (STTs) have been studied in Fe, Co and Ni domain walls (DWs) by the method based on the first-principles noncollinear calculations of scattering wave functions expanded in the tight-binding linearized muffin-tin orbital (TB-LMTO) basis. The results show that the out-of-plane component of nonadiabatic STT in Fe DW has localized form, which is in contrast to the typical nonlocal oscillating nonadiabatic torques obtained in Co and Ni DWs. Meanwhile, the degree of nonadiabaticity in STT is also much greater for Fe DW. Further, our results demonstrate that compared to the well-known first-order nonadiabatic STT, the torque in the third-order spatial derivative of local spin can better describe the distribution of localized nonadiabatic STT in Fe DW. The dynamics of local spin driven by this third-order torques in Fe DW have been investigated by the Landau-Lifshitz-Gilbert (LLG) equation. The calculated results show that with the same amplitude of STTs the DW velocity induced by this third-order term is about half of the wall speed for the case of the first-order nonadiabatic STT. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.0062v1.pdf"}
{"id": "1307.1848", "abstract": "  We show how to lift a generic non-scale invariant action in Einstein frame into a locally conformally-invariant (or Weyl-invariant) theory and present a new general form for Lagrangians consistent with Weyl symmetry. Advantages of such a conformally invariant formulation of particle physics and gravity include the possibility of constructing geodesically complete cosmologies. We present a conformal-invariant version of the standard model coupled to gravity, and show how Weyl symmetry may be used to obtain unprecedented analytic control over its cosmological solutions. Within this new framework, generic FRW cosmologies are geodesically complete through a series of big crunch - big bang transitions. We discuss a new scenario of cosmic evolution driven by the Higgs field in a “minimal”", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.1848v3.pdf"}
{"id": "1307.5315", "abstract": "  A common strategy to measure the Abelian geometric phase for a qubit is to let it evolve along an 'orange slice' shaped path connecting two antipodal points on the Bloch sphere by two different semi- great circles. Since the dynamical phases vanish for such paths, this allows for direct measurement of the geometric phase. Here, we generalize the orange slice setting to the non-Abelian case. The proposed method to measure the non-Abelian geometric phase can be implemented in a cyclic chain of four qubits with controllable interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.5315v5.pdf"}
{"id": "1307.8380", "abstract": "  We present follow-up observations at 5, 8 and 30 GHz of the K-band Northern Wide Survey (KNoWS) 20 GHz Bright Sample, performed with the 32-m Medicina Radio Telescope and the 32-m Torun Radio Telescope. The KNoWS sources were selected in the Northern Polar Cap (Delta > 72 deg) and have a flux density limit S(20GHz) = 115 mJy. We include NVSS 1.4 GHz measurements to derive the source radio spectra between 1.4 and 30 GHz. Based on optical identifications, 68 per cent of the sources are QSOs, and 27 per cent are radio galaxies. A redshift measurement is available for 58 per cent of the sources. The radio spectral properties of the different source populations are found to be in agreement with those of other high-frequency selected samples. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.8380v1.pdf"}
{"id": "1308.1203", "abstract": "  We show that a conformal-invariant dark sector, interacting conformally with the Standard Model (SM) fields through the Higgs portal, provides a viable framework where cold dark matter (CDM) and invisible Higgs decays can be addressed concurrently. Conformal symmetry naturally subsumes the Z_2 symmetry needed for stability of the CDM. It also guarantees that the weaker the couplings of the dark sector fields to the SM Higgs field, the smaller the masses they acquire through elektroweak breaking. The model comfortably satisfies the bounds from Large Hadron Collider (LHC) and Planck Space Telescope (Planck 2013). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.1203v2.pdf"}
{"id": "1308.1435", "abstract": "  The CMS collaboration at the LHC has reported a remarkable and unexpected phenomenon in very high-multiplicity high energy proton-proton collisions: a positive correlation between two particles produced at similar azimuthal angles, spanning a large range in rapidity. We suggest that this \"ridge\"-like correlation may be a reflection of the rare events generated by the collision of aligned flux tubes connecting the valence quarks in the wave functions of the colliding protons. The \"spray\" of particles resulting from the approximate line source produced in such inelastic collisions then gives rise to events with a strong correlation between particles produced over a large range of both positive and negative rapidity. We suggest an additional variable that is sensitive to such a line source which is related to a commonly used measure, ellipticity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.1435v2.pdf"}
{"id": "1308.1517", "abstract": "  We consider theoretically THz lasing in a system consisting of a quantum well placed inside an optical microcavity and a THz cavity in the regime of two-photon excitation of 2p dark exciton states. The stability of the system with varying parameters of the microcavity under coherent pumping is studied. We show that the nonlinearity provided by two photon absorption can give rise to bistability and hysteresis in the THz output. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.1517v1.pdf"}
{"id": "1308.2223", "abstract": "  Cold debris disks trace the limits of planet formation or migration in the outer regions of planetary systems, and thus have the potential to answer many of the outstanding questions in wide-orbit planet formation and evolution. We characterized the infrared excess spectral energy distributions of 174 cold debris disks around 546 main-sequence stars observed by both Spitzer IRS and MIPS. We found a trend between the temperature of the inner edges of cold debris disks and the stellar type of the stars they orbit. This argues against the importance of strictly temperature-dependent processes (e.g. non-water ice lines) in setting the dimensions of cold debris disks. Also, we found no evidence that delayed stirring causes the trend. The trend may result from outward planet migration that traces the extent of the primordial protoplanetary disk, or it may result from planet formation that halts at an orbital radius limited by the efficiency of core accretion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.2223v1.pdf"}
{"id": "1308.2677", "abstract": "  The sandpile group Pic^0(G) of a finite graph G is a discrete analogue of the Jacobian of a Riemann surface which was rediscovered several times in the contexts of arithmetic geometry, self-organized criticality, random walks, and algorithms. Given a ribbon graph G, Holroyd et al. used the \"rotor-routing\" model to define a free and transitive action of Pic^0(G) on the set of spanning trees of G. However, their construction depends a priori on a choice of basepoint vertex. Ellenberg asked whether this action does in fact depend on the choice of basepoint. We answer this question by proving that the action of Pic^0(G) is independent of the basepoint if and only if G is a planar ribbon graph. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.2677v2.pdf"}
{"id": "1308.3851", "abstract": "  In this paper, we construct two component dark matter model and revisit fine-tuning, unitarity and vacuum stability problem in this framework. Through Higgs-portal interactions, the additional scalar and vector singlet field can interact with the SM particles. The parameter space of the model are severely constraint by observed relic density and direct detection experiments. We found that, unlike the SM, the fine-tuning problem is relaxed due to the modified Veltman condition. The vacuum stability problem is addressed, the additional contributions from two DM singlets to the β function make the Higgs quartic coupling λ(μ) be positive up to Planck scale in some parameter space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.3851v2.pdf"}
{"id": "1308.4140", "abstract": "  With the advent of high-resolution high-sensitivity observations, spiral patterns have been revealed around several asymptotic giant branch (AGB) stars. Such patterns can provide possible evidence for the existence of central binary stars embedded in outflowing circumstellar envelopes. Here, we suggest the viability of explaining the previously observed incomplete ring-like patterns with the spiral-shell structure due to the motion of (unknown) binary components viewed at an inclination with respect to the orbital plane. We describe a method of extracting such spiral-shells from an incomplete ring-like pattern to place constraints on the characteristics of the central binary stars. The use of gas kinematics is essential in facilitating a detailed modeling for the three-dimensional structure of the circumstellar pattern. We show that a hydrodynamic radiative transfer model can reproduce the structure of the HC3N molecular line emission of the extreme carbon star, CIT 6. This method can be applied to other sources in the AGB phase and to the outer ring-like patterns of pre-planetary nebulae for probing the existence of embedded binary stars, which are highly anticipated with future observations using the Atacama Large Millimeter/submillimeter Array. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.4140v1.pdf"}
{"id": "1308.4950", "abstract": "  We solve the local and global structural identifiability problems for viscoelastic mechanical models represented by networks of springs and dashpots. We propose a very simple characterization of both local and global structural identifiability based on identifiability tables, with the purpose of providing a guideline for constructing arbitrarily complex, identifiable spring-dashpot networks. We illustrate how to use our results in a number of examples and point to some applications in cardiovascular modeling. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.4950v2.pdf"}
{"id": "1309.0216", "abstract": "  In the present work, the analytical description of an intermolecular vibrational energy transfer, analyzed by two dimensional infrared spectroscopy, is established. The energy transfer process takes place between the dark combination states of low frequency modes pertaining to different molecules. The appearance of the cross peaks results from coherent transfer between these combination states and an optically active state of the acceptor molecule. Such a process has recently been observed experimentally between the nitrile groups of acetonitrile-d3 and benzonitrile molecules. This molecular system will be used as a model for the simulations of their two-dimensional infrared spectra. The dependence of the cross-peak growth, which is a signature of the intermolecular energy transfer, will be discussed in detail as a function of the molecular dynamical constants. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.0216v2.pdf"}
{"id": "1309.0800", "abstract": "  Recently, it has been presented some algorithms and physical models which give prospects for construction of quantum computers capable to solve systems of linear equations. The common feature which is shared in these works is the use of qubits which allow to solve systems with 2^n variables. In this work we propose a quantum circuit based on qutrits architecture which directly allows for solving systems of equations with three variables. Proposed circuit can be easily generalized to those with 3^n variables. We also present some numerical experiments to verify the correctness of proposed solution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.0800v1.pdf"}
{"id": "1309.3058", "abstract": "  We present a general method to detect nonclassical radiation fields with systems of on-off detectors. We especially study higher order correlations for the identification of nonclassical radiation. This allows us to directly characterize quantum correlations by the statistics measured with systems of on-off detectors. Additionally, we generalize our method to multiple detector systems for measurements of correlations between light fields. We also consider multi-mode radiation fields and isolate nonclassicality in terms of the space time correlations. Finally, we present results for the quantum statistics using on-off detectors operating in nonlinear detection modes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.3058v2.pdf"}
{"id": "1309.5011", "abstract": "  The technical merits of weak value amplification techniques are analyzed. We consider models of several different types of technical noise in an optical context and show that weak value amplification techniques (which only use a small fraction of the photons) compare favorably with standard techniques (which uses all of them). Using the Fisher information metric, we demonstrate that weak value techniques can put all of the Fisher information about the detected parameter into a small portion of the events and show how this fact alone gives technical advantages. We go on to consider a time correlated noise model, and find that a Fisher information analysis indicates that while the standard method can have much larger information about the detected parameter than the postselected technique. However, the estimator needed to gather the information is technically difficult to implement, showing that the inefficient (but practical) signal-to-noise estimation of the parameter is usually superior. We also describe other technical advantages unique to imaginary weak value amplification techniques, focusing on beam deflection measurements. In this case, we discuss combined noise types (such as detector transverse jitter, angular beam jitter before the interferometer and turbulence) for which the interferometric weak value technique gives higher Fisher information over conventional methods. We go on to calculate the Fisher information of the recently proposed photon recycling scheme for beam deflection measurements, and show it further boosts the Fisher information by the inverse postselection probability relative to the standard measurement case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.5011v1.pdf"}
{"id": "1309.5014", "abstract": "  Transmitting messages in the most efficient way as possible has always been one of politicians main concerns during electoral processes. Due to the rapidly growing number of users, online social networks have become ideal platforms for politicians to interact with their potential voters. Exploiting the available potential of these tools to maximize their influence over voters is one of politicians actual challenges. To step in this direction, we have analyzed the user activity in the online social network Twitter, during the 2011 Spanish Presidential electoral process, and found that such activity is correlated with the election results. We introduce a new measure to study political support in Twitter, which we call the Relative Support. We have also characterized user behavior by analyzing the structural and dynamical patterns of the complex networks emergent from the mention and retweet networks. Our results suggest that the collective attention is driven by a very small fraction of users. Furthermore we have analyzed the interactions taking place among politicians, observing a lack of debate. Finally we develop a network growth model to reproduce the interactions taking place among politicians. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.5014v1.pdf"}
{"id": "1309.5765", "abstract": "  In the CERN NA63 collaboration we have addressed the question of the potential inadequacy of the commonly used Migdal formulation of the Landau-Pomeranchuk-Migdal (LPM) effect by measuring the photon emission by 20 and 178 GeV electrons in the range 100 MeV - 4 GeV, in targets of LowDensityPolyEthylene (LDPE), C, Al, Ti, Fe, Cu, Mo and, as a reference target, Ta. For each target and energy, a comparison between simulated values based on the LPM suppression of incoherent bremsstrahlung is shown, taking multi-photon effects into account. For these targets and energies, we find that Migdal's theoretical formulation is adequate to a precision of better than about 5", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.5765v1.pdf"}
{"id": "1309.5872", "abstract": "  Over the next decade, cosmological measurements of the large-scale structure of the Universe will be sensitive to the combined effects of dynamical dark energy and massive neutrinos. The matter power spectrum is a key repository of this information. We extend higher-order perturbative methods for computing the power spectrum to investigate these effects over quasi-linear scales. Through comparison with N-body simulations we establish the regime of validity of a Time-Renormalization Group (Time-RG) perturbative treatment that includes dynamical dark energy and massive neutrinos. We also quantify the accuracy of Standard (SPT), Renormalized (RPT) and Lagrangian Resummation (LPT) perturbation theories without massive neutrinos. We find that an approximation that neglects neutrino clustering as a source for nonlinear matter clustering predicts the Baryon Acoustic Oscillation (BAO) peak position to 0.25", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.5872v2.pdf"}
{"id": "1309.6067", "abstract": "  We present a semiempirical pseudopotential method based on screened atomic pseudopotentials and derived from ab initio calculations. This approach is motivated by the demand for pseudopotentials able to address nanostructures, where ab initio methods are both too costly and insufficiently accurate at the level of the local-density approximation, while mesoscopic effective-mass approaches are inapplicable due to the small size of the structures along, at least, one dimension. In this work we improve the traditional pseudopotential method by a two-step process: First, we invert a set of self-consistently determined screened ab initio potentials in wurtzite GaN for a range of unit cell volumes, thus determining spherically-symmetric and structurally averaged atomic potentials. Second, we adjust the potentials to reproduce observed excitation energies. We find that the adjustment represents a reasonably small perturbation over the potential, so that the ensuing potential still reproduces the original wave functions, while the excitation energies are significantly improved. We furthermore deal with the passivation of the dangling bonds of free surfaces which is relevant for the study of nanowires and colloidal nanoparticles. We present a methodology to derive passivant pseudopotentials from ab initio calculations. We apply our pseudopotential approach to the exploration of the confinement effects on the electronic structure of GaN nanowires. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.6067v1.pdf"}
{"id": "1309.6405", "abstract": "  We discuss characterization of experimental quantum gates by the error matrix, which is similar to the standard process matrix χ in the Pauli basis, except the desired unitary operation is factored out, by formally placing it either before or after the error process. The error matrix has only one large element, which is equal to the process fidelity, while other elements are small and indicate imperfections. The imaginary parts of the elements along the left column and/or top row directly indicate the unitary imperfection and can be used to find the needed correction. We discuss a relatively simple way to calculate the error matrix for a composition of quantum gates. Similarly, it is rather straightforward to find the first-order contribution to the error matrix due to the Lindblad-form decoherence. We also discuss a way to identify and subtract the tomography procedure errors due to imperfect state preparation and measurement. In appendices we consider several simple examples of the process tomography and also discuss an intuitive physical interpretation of the Lindblad-form decoherence. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.6405v2.pdf"}
{"id": "1309.6540", "abstract": "  Correctly interpreting observations of sources such as type Ia supernovae (SNe Ia) require knowledge of the power spectrum of matter on AU scales - which is very hard to model accurately. Because under-dense regions account for much of the volume of the universe, light from a typical source probes a mean density significantly below the cosmic mean. The relative sparsity of sources implies that there could be a significant bias when inferring distances of SNe Ia, and consequently a bias in cosmological parameter estimation. While the weak lensing approximation should in principle give the correct prediction for this, linear perturbation theory predicts an effectively infinite variance in the convergence for ultra-narrow beams. We attempt to quantify the effect typically under-dense lines of sight might have in parameter estimation by considering three alternative methods for estimating distances, in addition to the usual weak lensing approximation. We find in each case this not only increases the errors in the inferred density parameters, but also introduces a bias in the posterior value. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.6540v2.pdf"}
{"id": "1310.0533", "abstract": "  Mira variables, RR Lyrae variables, and type II Cepheids all represent evolved states of low-mass stars, and long term observations have revealed that changes in pulsation period occur for each of these classes of variable. Most Mira variables show small or no period changes, but a few show large period changes that can plausibly be associated with thermal pulses on the asymptotic red giant branch. Individual RR Lyrae stars show period changes that do not accord with the predictions of stellar evolution theory. This may be especially true for RR Lyrae stars that exhibit the Blazhko effect. However, the average period changes of all of the RR Lyrae variables within a globular cluster prove a better but still imperfect match for the predictions of evolutionary theory. The observed period changes of short period type II Cepheids (BL Her stars) as well as those of long period type II Cepheids (W Vir stars) are in broad agreement with the rates of period changes expected from their evolutionary motions through the instability strip. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.0533v1.pdf"}
{"id": "1310.0735", "abstract": "  We study the relaxation dynamics of a nonequilibrium Luttinger liquid after a sudden interaction switch-on (\"quench\"), focussing on a double-step initial momentum distribution function. In the framework of the non-equilibrium bosonization, the results are obtained in terms of singular Fredholm determinants that are evaluated numerically and whose asymptotics are found analytically. While the quasi-particle weights decay exponentially with time after the quench, this is not a relaxation into a thermal state, in view of the integrability of the model. The steady-state distribution emerging at infinite times retains two edges which support Luttinger-liquid-like power-law singularities smeared by dephasing. The obtained critical exponents and the dephasing length are found to depend on the initial nonequilibrium state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.0735v1.pdf"}
{"id": "1310.1768", "abstract": "  We demonstrate that a phase-independent quantum amplifier of a polarization qubit is a complementary amplifier of the heralded qubit amplifier [N. Gisin, S. Pironio and N. Sangouard, Phys. Rev. Lett. 105, 070501 (2010)]. It employs the multi-functional cloner in 1 to 2 copying regime, capable of providing approximate copies of qubits given by various probability distributions, and is optimized for distributions with axial symmetry. Direct applications of the proposed solution are possible in quantum technologies, doubling the range where quantum information is coherently broadcast. It also outperforms natural nonlinear amplifiers that use stimulated emission in bulk nonlinear materials. We consider the amplifier to be an important tool for amplifying quantum information sent via quantum channels with phase-independent damping. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.1768v5.pdf"}
{"id": "1310.3173", "abstract": "  Massive Open Online Courses are an exciting new avenue for instruction and research, yet they are full of unknowns. In the Spring of 2013, MITx released its first introductory physics MOOC through the edX platform, generating a total enrollment of 43,000 students from around the world. We describe the population of participants in terms of their age, gender, level of education, and country of origin, highlighting both the diversity of 8.02x enrollees as well as gender gap and retention. Using three midterm exams and the final as waypoints, we highlight performance by different demographic subpopulations and their retention rates. Our work is generally aimed at making a bridge between available MOOC data and topics associated with the Physics Education Research community. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.3173v1.pdf"}
{"id": "1310.3372", "abstract": "  The energy spectra of quasi-one dimensional quasiperiodic ladder networks are analyzed within a tight binding description. In particular, we show that if a selected set of sites in each strand of a ladder is tunnel-coupled to quantum dots attached from a side, absolutely continuous subbands can be generated in the spectrum if one tunes the dot potential and the dot-strand coupling appropriately. Typical cases with two and three strand Fibonacci ladders in the off diagonal model are discussed in details. We also discuss the possibility of re-entrant insulator-metal transition for a general n-strand ladder network when n becomes large. The observations remain valid even in the case of a disordered ladder network with the same constituents. The results are analytically exact. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.3372v2.pdf"}
{"id": "1310.4272", "abstract": "  We show that a layered superconductor, described by a two-component order parameter, has a gapped state above the ground state, topologically protected from decay, containing flow and counter flow in the absence of an applied magnetic field. This state is made of skyrmions, breaks time reversal symmetry and produces a weak local magnetic field below the present threshold of detection by μSR and NMR/NQR. We estimate the density of carriers that condense into the pseudogap. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.4272v1.pdf"}
{"id": "1310.6915", "abstract": "  A novel theory of F(R) gravity with the Lagrangian density L=[R-(b/β)arctan(β R)]/(2κ^2) is analyzed. Constant curvature solutions of the model are found, and the potential of the scalar field and the mass of a scalar degree of freedom in Einstein's frame are derived. The cosmological parameters of the model are calculated, which are in agreement with the PLANCK data. Critical points for the de Sitter phase and the matter dominated epoch of autonomous equations are obtained and studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.6915v3.pdf"}
{"id": "1310.7437", "abstract": "  We show that the running of the Higgs-gaugino-higgsino couplings present in Partial Split Supersymmetry can severely affect the neutrino masses generated through Bilinear R-parity Violation. We find a working scenario where the predicted neutrino observables satisfy the experimental constraints when the running is neglected. After including the running, we show that already with a split supersymmetric scale of 10000 GeV the atmospheric mass leaves the allowed experimental window, and that the solar mass leaves it even earlier, with a split supersymmetric scale of 1000 GeV. This shows that the correct prediction of neutrino observables in these models necessitates the inclusion of the running of these couplings. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.7437v1.pdf"}
{"id": "1310.7447", "abstract": "  A new method for removing impulse noise from speech in the wavelet transform domain is proposed. The method utilizes the multiresolution property of the wavelet transform, which provides finer time resolution at the higher frequencies than the short-time Fourier transform (STFT), to effectively identify and remove impulse noise. It uses two features of speech to discriminate speech from impulse noise: one is the slow time-varying nature of speech and the other is the Lipschitz regularity of the speech components. On the basis of these features, an algorithm has been developed to identify and suppress wavelet coefficients that correspond to impulse noise. Experiment results show that the new method is able to significantly reduce impulse noise without degrading the quality of the speech signal or introducing any audible artifacts. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.7447v1.pdf"}
{"id": "1310.8627", "abstract": "  We show that the first order (non co-orbital) corotation torques are significantly modified by entropy gradients in a non-barotropic protoplanetary disk. Such non-barotropic torques can dramatically alter the balance that, for barotropic cases, results in the net eccentricity damping for giant gap-clearing planets embedded in the disk. We demonstrate that stellar illumination can heat the gap enough for the planet's orbital eccentricity to instead be excited. We also discuss the \"Eccentricity Valley\" noted in the known exoplanet population, where low-metallicity stars have a deficit of eccentric planets between ∼ 0.1 and ∼ 1 AU compared to metal-rich systems (Dawson     Murray-Clay 2013). We show that this feature in the planet distribution may be due to the self-shadowing of the disk by a rim located at the dust sublimation radius ∼ 0.1 AU, which is known to exist for several T Tauri systems. In the shadowed region between ∼ 0.1 and ∼ 1 AU lack of gap insolation allows disk interactions to damp eccentricity. Outside such shadowed regions stellar illumination can heat the planetary gaps and drive eccentricity growth for giant planets. We suggest that the self-shadowing does not arise at higher metallicity due to the increased optical depth of the gas interior to the dust sublimation radius. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.8627v2.pdf"}
{"id": "1311.0006", "abstract": "  How cosmic rays sample the multi-phase interstellar medium (ISM) in starburst galaxies has important implications for many science goals, including evaluating the cosmic ray calorimeter model for these systems, predicting their neutrino fluxes, and modeling their winds. Here, we use Monte Carlo simulations to study cosmic ray sampling of a simple, two-phase ISM under conditions similar to those of the prototypical starburst galaxy M82. The assumption that cosmic rays sample the mean density of the ISM in the starburst region is assessed over a multi-dimensional parameter space where we vary the number of molecular clouds, the galactic wind speed, the extent to which the magnetic field is tangled, and the cosmic ray injection mechanism. We evaluate the ratio of the emissivity from pion production in molecular clouds to the emissivity that would be observed if the cosmic rays sampled the mean density, and seek areas of parameter space where this ratio differs significantly from unity. The assumption that cosmic rays sample the mean density holds over much of parameter space; however, this assumption begins to break down for high cloud density, injection close to the clouds, and a very tangled magnetic field. We conclude by evaluating the extent to which our simulated starburst region behaves as a proton calorimeter and constructing the time-dependent spectrum of a burst of cosmic rays. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.0006v1.pdf"}
{"id": "1311.0129", "abstract": "  The origin of equilibrium gravitational configurations is sought in terms of the stability of their trajectories, as described by the curvature of their Lagrangian configuration manifold of particle positions — a context in which subtle spurious effects originating from the singularity in the two body potential become particularly clear. We focus on the case of spherical systems, which support only regular orbits in the collisionless limit, despite the persistence of local exponential instability of N-body trajectories in the anomalous case of discrete point particle representation even as N →∞. When the singularity in the potential is removed, this apparent contradiction disappears. In the absence of fluctuations, equilibrium configurations generally correspond to positive scalar curvature, and thus support stable trajectories. A null scalar curvature is associated with an effective, averaged, equation of state describing dynamically relaxed equilibria with marginally stable trajectories. The associated configurations are quite similar to those of observed elliptical galaxies and simulated cosmological halos, and are necessarily different from the systems dominated by isothermal cores, expected from entropy maximization in the context of the standard theory of violent relaxation. It is suggested that this is the case because a system starting far from equilibrium does not reach a 'most probable state' via violent relaxation, but that this process comes to an end as the system finds and (settles in) a configuration where it can most efficiently wash out perturbations. We explicitly test this interpretation by means of direct simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.0129v1.pdf"}
{"id": "1311.1492", "abstract": "  Epitaxially grown quantum dots (QDs) are promising sources of non-classical states of light such as single photons and entangled photons. However, in order for them to be used as a resource for long-distance quantum communication, distributed quantum computation, or linear optics quantum computing, these photons must be coupled efficiently to long-lived quantum memories as part of a quantum repeater network. Here, we theoretically examine the prospects for efficient storage and retrieval of a QD-generated single photon with a 1 ns lifetime in a multi-level atomic system. We calculate using an experimentally demonstrated optical depth of 150 that the storage (total) efficiency can exceed 46", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.1492v1.pdf"}
{"id": "1311.3197", "abstract": "  Systems with a bulk first-order transition can display diverging correlation lengths close to a surface. This surface induced disordering yields a special type of surface criticality. Using extensive numerical simulations we study surface quantities in the two-dimensional Potts model with a large number of states q which undergoes a discontinuous bulk transition. The surface critical exponents are thereby found to depend on the value of q, which is in contrast to prior claims that these exponents should be universal and independent of q. It follows that surface induced disordering at first-order transitions is characterized by exponents that depend on the details of the model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.3197v1.pdf"}
{"id": "1311.4054", "abstract": "  We calculate the force of a quasicircularly polarized guided light field of a nanofiber on a dielectric spherical particle. We show that the orbital parts of the axial and azimuthal components of the Poynting vector are always positive while the spin parts can be either positive or negative. We find that, for appropriate values of the size parameter of the particle, the azimuthal component of the force is directed oppositely to the circulation direction of the energy flow around the nanofiber. The occurrence of such a negative azimuthal force indicates that the particle undergoes a negative torque. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.4054v1.pdf"}
{"id": "1311.4431", "abstract": "  Molecular communication emerges as a promising communication paradigm for nanotechnology. However, solid mathematical foundations for information-theoretic analysis of molecular communication have not yet been built. In particular, no one has ever proven that the channel coding theorem applies for molecular communication, and no relationship between information rate capacity (maximum mutual information) and code rate capacity (supremum achievable code rate) has been established. In this paper, we focus on a major subclass of molecular communication - the diffusion-based molecular communication. We provide solid mathematical foundations for information theory in diffusion-based molecular communication by creating a general diffusion-based molecular channel model in measure-theoretic form and prove its channel coding theorems. Various equivalence relationships between statistical and operational definitions of channel capacity are also established, including the most classic information rate capacity and code rate capacity. As byproducts, we have shown that the diffusion-based molecular channel is with \"asymptotically decreasing input memory and anticipation\" and \"d-continuous\". Other properties of diffusion-based molecular channel such as stationarity or ergodicity are also proven. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.4431v1.pdf"}
{"id": "1311.5557", "abstract": "  Background: The reconstruction of the phylogenetic tree topology of four taxa is, still nowadays, one of the main challenges in phylogenetics. Its difficulties lie in considering not too restrictive evolutionary models, and correctly dealing with the long-branch attraction problem. The correct reconstruction of 4-taxon trees is crucial for making quartet-based methods work and being able to recover large phylogenies.   Results: In this paper we consider an expectation-maximization method for maximizing the likelihood of (time nonhomogeneous) evolutionary Markov models on trees. We study its success on reconstructing 4-taxon topologies and its performance as input method in quartet-based phylogenetic reconstruction methods such as QFIT and QuartetSuite. Our results show that the method proposed here outperforms neighbor-joining and the usual (time-homogeneous continuous-time) maximum likelihood methods on 4-leaved trees with among-lineage instantaneous rate heterogeneity, and perform similarly to usual continuous-time maximum-likelihood when data satisfies the assumptions of both methods.   Conclusions: The method presented in this paper is well suited for reconstructing the topology of any number of taxa via quartet-based methods and is highly accurate, specially regarding largely divergent trees and time nonhomogeneous data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.5557v2.pdf"}
{"id": "1311.5636", "abstract": "  Feature selection plays a pivotal role in learning, particularly in areas were parsimonious features can provide insight into the underlying process, such as biology. Recent approaches for non-linear feature selection employing greedy optimisation of Centred Kernel Target Alignment(KTA), while exhibiting strong results in terms of generalisation accuracy and sparsity, can become computationally prohibitive for high-dimensional datasets. We propose randSel, a randomised feature selection algorithm, with attractive scaling properties. Our theoretical analysis of randSel provides strong probabilistic guarantees for the correct identification of relevant features. Experimental results on real and artificial data, show that the method successfully identifies effective features, performing better than a number of competitive approaches. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.5636v1.pdf"}
{"id": "1311.6457", "abstract": "  Stationary, D-dimensional test branes, interacting with N-dimensional Myers-Perry bulk black holes, are investigated in arbitrary brane and bulk dimensions. The branes are asymptotically flat and axisymmetric around the rotation axis of the black hole with a single angular momentum. They are also spherically symmetric in all other dimensions allowing a total of O(1)xO(D-2) group of symmetry. It is shown that even though this setup is the most natural extension of the spherical symmetric problem to the simplest rotating case in higher dimensions, the obtained solutions are not compatible with the spherical solutions in the sense that the latter ones are not recovered in the non-rotating limit. The brane configurations are qualitatively different from the spherical problem, except in the special case of a 3-dimensional brane. Furthermore, a quasi-static phase transition between the topologically different solutions cannot be studied here, due to the lack of a general, stationary, equatorial solution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.6457v1.pdf"}
{"id": "1312.0373", "abstract": "  Based on Grad-Shafranov-like equations, a gyrotropic plasma where the pressures in the static regime are only functions of the amplitude of the local magnetic field is shown to be amenable to a variational principle with a free energy density given by the parallel tension. This approach is used to demonstrate that small- amplitude static holes constructed slightly below the mirror instability threshold identify with lump solitons of KPII equation and turn out to be unstable. It is also shown that regularizing effects such as finite Larmor radius corrections cannot be ignored in the description of large-amplitude mirror structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.0373v1.pdf"}
{"id": "1312.2241", "abstract": "  Agent-Based Modeling and Simulation (ABMS) is a simple and yet powerful method for simulation of interactions among individual agents. Using ABMS, different phenomena can be modeled and simulated without spending additional time on unnecessary complexities. Although ABMS is well-matured in many different fields such as economic, social, and natural phenomena, it has not received much attention in the context of mobile ad-hoc networks (MANETs). In this paper, we present ABMQ, a powerful Agent-Based platform suitable for modeling and simulation of self-organization in wireless networks, and particularly MANETs. By utilizing the unique potentials of Qt Application Framework, ABMQ provides the ability to easily model and simulate self-organizing algorithms, and then reuse the codes and models developed during simulation process for building real third-party applications for several desktop and mobile platforms, which substantially decreases the development time and cost, and prevents probable bugs that can happen as a result of rewriting codes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.2241v1.pdf"}
{"id": "1312.2621", "abstract": "  We theoretically investigate the quantum statistical properties of light transmitted through an atomic medium with strong optical non-linearity induced by Rydberg-Rydberg van der Waals interactions. In our setup, atoms are located in a cavity and non-resonantly driven on a two-photon transition from their ground state to a Rydberg level via an intermediate state by the combination of the weak signal field and a strong control beam. To characterize the transmitted light we compute the second-order correlation function g^(2)(τ). The simulations we obtained on the specific case of rubidium atoms suggest that the bunched or antibunched nature of the outgoing beam can be chosen at will by appropriately tuning the physical parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.2621v1.pdf"}
{"id": "1312.3323", "abstract": "  The hundreds of exoplanets that have been discovered in the past two decades offer a new perspective on planetary structure. Instead of being the archetypal examples of planets, those of our Solar System are merely possible outcomes of planetary system formation and evolution, and conceivably not even terribly common outcomes (although this remains an open question). Here, we review the diverse range of interior structures that are known to, and speculated to, exist in exoplanetary systems – from mostly degenerate objects that are more than 10 times as massive as Jupiter, to intermediate-mass Neptune-like objects with large cores and moderate hydrogen/helium envelopes, to rocky objects with roughly the mass of the Earth. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.3323v1.pdf"}
{"id": "1312.4739", "abstract": "  Donors in silicon are now demonstrated as one of the leading candidates for implementing qubits and quantum information processing. Single qubit operations, measurements and long coherence times are firmly established, but progress on controlling two qubit interactions has been slower. One reason for this is that the inter donor exchange coupling has been predicted to oscillate with separation, making it hard to estimate in device designs. We present a multivalley effective mass theory of a donor pair in silicon, including both a central cell potential and the effective mass anisotropy intrinsic in the Si conduction band. We are able to accurately describe the single donor properties of valley-orbit coupling and the spatial extent of donor wave functions, highlighting the importance of fitting measured values of hyperfine coupling and the orbital energy of the 1s levels. Ours is a simple framework that can be applied flexibly to a range of experimental scenarios, but it is nonetheless able to provide fast and reliable predictions. We use it to estimate the exchange coupling between two donor electrons and we find a smoothing of its expected oscillations, and predict a monotonic dependence on separation if two donors are spaced precisely along the [100] direction. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.4739v2.pdf"}
{"id": "1312.6100", "abstract": "  The equilibrium properties of block copolymer micelles confined in polymer thin films are investigated using self-consistent field theory. The theory is based on a model system consisting of AB diblock copolymers and A homopolymers. Two different methods, based on the radius of gyration tensor and the spherical harmonics expansion, are used to characterize the micellar shape. The results reveal that the morphology of micelles in thin films depends on the thickness of the thin films and the selectivity of the confining surfaces. For spherical (cylindrical) micelles, the spherical (cylindrical) symmetry is broken by the presence of the one-dimensional confinement, whereas the top-down symmetry is broken by the selectivity of the confining surfaces. Morphological transitions from spherical or cylindrical micelles to cylinders or lamella are predicted when the film thickness approaches the micellar size. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.6100v1.pdf"}
{"id": "1401.1071", "abstract": "  The thermodynamic properties of the electron gas in multilayer graphene depend strongly on the number of layers and the type of stacking. Here we analyse how those properties change when we vary the number of layers for rhombohedral stacked multilayer graphene and compare our results with those from a conventional two dimensional electron gas. We show that the highly degenerate zero energy Landau level which is partly filled with electrons and partly with holes has a strong influence on the value of the different thermodynamic quantities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.1071v1.pdf"}
{"id": "1401.1378", "abstract": "  During the last 30 years, and more specifically during the last 10 years, many experiments have been carried out worldwide using different techniques to study the shell evolution of nuclei far from stability. What seemed not conceivable some decades ago became rather common: all known magic numbers that are present in the valley of stability disappear far from stability and are replaced by new ones at the drip line. By gathering selected experimental results, beautifully consistent pictures emerge, that very likely take root in the properties of the nuclear forces.The present manuscript describes some of these discoveries and proposes an intuitive understanding of these shell evolutions derived from observations. Extrapolations to yet unstudied regions, as where the explosive r-process nucleosynthesis occurs, are proposed. Some remaining challenges and puzzling questions are also addressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.1378v1.pdf"}
{"id": "1401.2609", "abstract": "  We introduce a two-dimensional, distribution-valued field which we call the quadratic field associated to the one-dimensional Ornstein-Uhlenbeck process. We show that the stationary quadratic fluctuations of the simple exclusion process, when rescaled in the diffusive scaling, converge to this quadratic field. We show that this quadratic field evaluated at the diagonal corresponds to the Wick-renormalized square of the Ornstein-Uhlenbeck process, and we use this new representation in order to prove some small and large-time properties of it. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.2609v1.pdf"}
{"id": "1401.3586", "abstract": "  This article presents direct numerical simulations of the growth of turbulent spots in the transitional regime of plane Couette flow. A quantitative description of the growth process and of the detail of the quadrupolar flow around the spot is given. Focus is put on formation of spanwise vorticity in the velocity streaks that resembles a secondary shear instability. The main features of the instability (coherence lengths, advection velocity) are studied in the context of the turbulent spot, below and above the threshold Reynolds number of appearance of the oblique turbulent bands of plane Couette flow. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.3586v1.pdf"}
{"id": "1401.4284", "abstract": "  The nature of electronic eigenstates and quantum transport in a comb-shaped Fibonacci nanostructure model is investigated within a tight-binding framework. Periodic linear chains are side-attached to a Fibonacci chain, giving it the shape of an aperiodic comb. The effect of the side-attachments on the usual Cantor set energy spectrum of a Fibonacci chain is analyzed using the Greens function technique. A special correlation between the coupling of the side-attached chain with the Fibonacci chain and the inter-atomic coupling of the Fibonacci chain results in a dramatic triggering of the fragmented Cantor set energy spectrum into multiple sets of continuous sub-bands of extended eigenstates. The result is valid even for a disordered comb and turns out to be a rare exception of the conventional Anderson localization problem. The electronic transport thus can be made selectively ballistic within desired energy regimes. The number and the width of such continuous sub-bands can be easily controlled by tuning the number of atomic sites in the side-coupled periodic linear chains. This gives us a scope of proposing such aperiodic nanostructures as potential candidates for prospective energy selective nanoscale filtering devices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.4284v1.pdf"}
{"id": "1401.5129", "abstract": "  Description of nonclassicality of states has hitherto been through violation of Bell inequality and non-separability, with the latter being a stronger constraint. In this paper, we show that this can be further sharpened, by introducing the concept of classical simulation. A state admits classical simulation if it can be mimicked fully by a separable state of higher dimension. A nonclassical state, which we call exceptional, does not admit classical simulation. Focusing on two qubit states, we show that exceptionality is more stringent than violation of Bell inequality, and involves an intricate interplay of coherence and entanglement. The new criterion is shown to provide a natural description of entangled states which respect Bell inequality, and also a way of enumerating the classical resources that are required to simulate a quantum state. Possible implications to quantum dynamics and quantum information are briefly touched upon. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5129v1.pdf"}
{"id": "1401.5911", "abstract": "  We characterise the eigenfunctions of an equilateral triangle billiard in terms of its nodal domains. The number of nodal domains has a quadratic form in terms of the quantum numbers, with a non-trivial number-theoretic factor. The patterns of the eigenfunctions follow a group-theoretic connection in a way that makes them predictable as one goes from one state to another. Extensive numerical investigations bring out the distribution functions of the mode number and signed areas. The statistics of the boundary intersections is also treated analytically. Finally, the distribution functions of the nodal loop count and the nodal counting function are shown to contain information about the classical periodic orbits using the semiclassical trace formula. We believe that the results belong generically to non-separable systems, thus extending the previous works which are concentrated on separable and chaotic systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5911v2.pdf"}
{"id": "1401.6668", "abstract": "  We present a generalization of Hilfer derivatives in which Riemann–Liouville integrals are replaced by more general Prabhakar integrals. We analyze and discuss its properties. Further, we show some applications of these generalized Hilfer-Prabhakar derivatives in classical equations of mathematical physics, like the heat and the free electron laser equations, and in difference-differential equations governing the dynamics of generalized renewal stochastic processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.6668v2.pdf"}
{"id": "1402.0445", "abstract": "  After the discovery of the 125 GeV scalar boson with gauge properties similar to the Standard Model Higgs, the search for beyond the SM interactions will focus on studying the discovered particles' coupling properties more precisely and shedding light on the relation of fermion masses with the electroweak vacuum. The large mass of the top quark and the SM-predicted order one top Yukawa coupling is a natural candidate for BSM physics, though experimentally challenging to constrain. In this paper, we argue that investigating angular correlations in pp→ tHj production provides an excellent handle to constrain the top Yukawa coupling y_t via direct measurements, even when we focus on rare exclusive final states. We perform a hadron-level analysis and show that we may expect to constrain y_t≳ 0.5  y_t^SM at 95", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.0445v2.pdf"}
{"id": "1402.0513", "abstract": "  We investigated the impacts of magnetorotational instability (MRI) on the dynamics of weakly magnetized, rapidly rotating core-collapse by conducting high resolution MHD simulations in axisymmetry with simplified neutrino transfer. We found that an initially sub-magnetar class magnetic field is drastically amplified by MRI and substantially affects the dynamics thereafter. Although the magnetic pressure is not strong enough to eject matter, the amplified magnetic field efficiently transfers angular momentum from higher to lower latitudes, which causes the expansion of the heating region at low latitudes due to the extra centrifugal force. This then enhance the efficiency of neutrino heating and eventually leads to neutrino-driven explosion. This is a new scenario of core-collapse supernovae that has never been demonstrated by numerical simulations so far. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.0513v2.pdf"}
{"id": "1402.0534", "abstract": "  We study conditions under which carbon clusters of different sizes form and stabilize. We describe an approach to equilibrium by simulating tenuous carbon gas dynamics to long times. First, we use reactive molecular dynamics simulations to describe the nucleation of long chains, large clusters, and complex cage structures in carbon and hydrogen rich interstellar gas phases. We study how temperature, particle density, presence of hydrogen, and carbon inflow affect the nucleation of molecular moieties with different characteristics, in accordance with astrophysical conditions. We extend the simulations to densities which are orders of magnitude lower than current laboratory densities, to temperatures relevant to circumstellar environments of planetary nebulae, and to longtime (microsecond) formation timescales. We correlate cluster size distributions from dynamical simulations with thermodynamic equilibrium intuitions, where at low temperatures and gas densities, entropy plays a significant role. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.0534v1.pdf"}
{"id": "1402.1487", "abstract": "  A class of states of the electromagnetic field involving superpositions of all the excited states above a specified low energy eigenstate of the electromagnetic field is introduced. These states and the photon-added coherent states are shown to be the limiting cases of a generalized photon-added coherent states. This new class of states is nonclassical, non-Gaussian and has equal uncertainties in the field quadratures. For suitable choices of parameters, these uncertainties are very close to those of the coherent states. Nevertheless, these states exhibit sub-Poissonian photon number distribution, which is a nonclassical feature. Under suitable approximations, these states become the generalized Bernoulli states of the field. Nonclassicality of these states is quantified using their entanglement potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1402/1402.1487v1.pdf"}
{"id": "1403.1192", "abstract": "  Detection of radiation signals is at the heart of precision metrology and sensing. In this article we show how the fluctuations in photon counting signals can be exploited to optimally extract information about the physical parameters that govern the dynamics of the emitter. For a simple two-level emitter subject to photon counting, we show that the Fisher information and the Cramér- Rao sensitivity bound based on the full detection record can be evaluated from the waiting time distribution in the fluorescence signal which can, in turn, be calculated for both perfect and imperfect detectors by a quantum trajectory analysis. We provide an optimal estimator achieving that bound. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.1192v2.pdf"}
{"id": "1403.3617", "abstract": "  We have obtained extensive high-quality spectroscopic observations of the OGLE-LMC-CEP-1718 eclipsing binary system in the Large Magellanic Cloud which Soszynski et al. (2008) had identified as a candidate system for containing two classical Cepheids in orbit. Our spectroscopic data clearly demonstrate binary motion of the Cepheids in a 413-day eccentric orbit, rendering this eclipsing binary system the first ever known to consist of two classical Cepheid variables. After disentangling the four different radial velocity variations in the system we present the orbital solution and the individual pulsational radial velocity curves of the Cepheids. We show that both Cepheids are extremely likely to be first overtone pulsators and determine their respective dynamical masses, which turn out to be equal to within 1.5 ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.3617v1.pdf"}
{"id": "1403.3919", "abstract": "  Relic gravitational waves (RGWs) leave well-understood imprints on the anisotropies in the temperature and polarization of cosmic microwave background (CMB) radiation. In the TT and TE information channels, which have been well observed by WMAP and Planck missions, RGWs compete with density perturbations mainly at low multipoles. It is dangerous to include high-multipole CMB data in the search for gravitational waves, as the spectral indices may not be constants. In this paper, we repeat our previous work [W.Zhao     L.P.Grishchuk, Phys.Rev.D 82, 123008 (2010)] by utilizing the Planck TT and WMAP TE data in the low-multipole range ℓ≤100. We find that our previous result is confirmed with higher confidence. The constraint on the tensor-to-scalar ratio from Planck TT and WMAP TE data is r∈ [0.06, 0.60] (68", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.3919v2.pdf"}
{"id": "1403.4344", "abstract": "  Since observation on a quantum system may cause the system state collapse, it is usually hard to find a way to monitor a quantum process, which is a quantum system that continuously evolves. We propose a protocol that can debug a quantum process by monitoring, but not disturb the evolution of the system. This protocol consists of an error detector and a debugging strategy. The detector is a projection operator that is orthogonal to the anticipated system state at a sequence of time points, and the strategy is used to specify these time points. As an example, we show how to debug the computational process of quantum search using this protocol. By applying the Skolem–Mahler–Lech theorem in algebraic number theory, we find an algorithm to construct all of the debugging protocols for quantum processes of time independent Hamiltonians. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.4344v1.pdf"}
{"id": "1403.4609", "abstract": "  We present an analysis of the star formation history (SFH) of a field near the half light radius in the Local Group dwarf irregular galaxy IC 1613 based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. Our observations reach the oldest main sequence turn-off, allowing a time resolution at the oldest ages of  1 Gyr. Our analysis shows that the SFH of the observed field in IC 1613 is consistent with being constant over the entire lifetime of the galaxy. These observations rule out an early dominant episode of star formation in IC 1613. We compare the SFH of IC 1613 with expectations from cosmological models. Since most of the mass is in place at early times for low mass halos, a naive expectation is that most of the star formation should have taken place at early times. Models in which star formation follows mass accretion result in too many stars formed early and gas mass fractions which are too low today (the \"over-cooling problem\"). The depth of the present photometry of IC 1613 shows that, at a resolution of  1 Gyr, the star formation rate is consistent with being constant, at even the earliest times, which is difficult to achieve in models where star formation follows mass assembly. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.4609v1.pdf"}
{"id": "1403.5183", "abstract": "  Theoretical studies of quarkonia can elucidate some of the important properties of the quark–gluon plasma, the state of matter realised when the temperature exceeds 150 MeV, currently probed by heavy-ion collisions experiments at BNL and the LHC. We report on our results of lattice studies of bottomonia for temperatures in the range 100 MeV < T < 450 MeV, introducing and discussing the methodologies we have applied. Of particular interest is the analysis of the spectral functions, where Bayesian methods borrowed and adapted from nuclear and condensed matter physics have proven very successful. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.5183v1.pdf"}
{"id": "1403.5669", "abstract": "  The Rastall's theory is a modification of General Relativity touching one of the cornestone of gravity theory: the conservation laws. In Rastall's theory, the energy-momentum tensor is not conserved anymore, depending now on the gradient of the Ricci curvature. In this sense, this theory can be seen as a classical implementation of quantum effects in a curved background space-time. We exploit this structure in order to reproduce some results of an effective theory of quantum loop cosmology. Later, we propose a model for the dark sector of the universe. In this case, the corresponding ΛCDM model appears as the only model consistent with observational data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.5669v1.pdf"}
{"id": "1403.5817", "abstract": "  We study the tilt of the primordial gravitational waves spectrum. A hint of blue tilt is shown from analyzing the BICEP2 and POLARBEAR data. Motivated by this, we explore the possibilities of blue tensor spectra from the very early universe cosmology models, including null energy condition violating inflation, inflation with general initial conditions, and string gas cosmology, etc. For the simplest G-inflation, blue tensor spectrum also implies blue scalar spectrum. In general, the inflation models with blue tensor spectra indicate large non-Gaussianities. On the other hand, string gas cosmology predicts blue tensor spectrum with highly Gaussian fluctuations. If further experiments do confirm the blue tensor spectrum, non-Gaussianity becomes a distinguishing test between inflation and alternatives. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.5817v3.pdf"}
{"id": "1403.6613", "abstract": "  Extreme UltraViolet images of the corona contain information over a large range of spatial scales, and different structures such as active regions, quiet Sun and filament channels contain information at very different brightness regimes. Processing of these images is important to reveal information, often hidden within the data, without introducing artifacts or bias. It is also important that any process be computationally efficient, particularly given the fine spatial and temporal resolution of Atmospheric Imaging Assembly on the Solar Dynamics Observatory (AIA/SDO) , and consideration of future higher-resolution observations. A very efficient process is described here which is based on localized normalizing of the data at many different spatial scales. The method reveals information at the finest scales, whilst maintaining enough of the larger-scale information to provide context. It also intrinsically flattens noisy regions and can reveal structure in off-limb regions out to the edge of the field of view. The method is also successfully applied to a white light coronagraph observation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.6613v1.pdf"}
{"id": "1403.7398", "abstract": "  Two critical points have been revealed in the normal-state phase diagram of the electron-doped cuprate superconductor Nd_2-xCe_xCuO_4 by exploring the Fermi surface properties of high quality single crystals by high-field magnetotransport. First, the quantitative analysis of the Shubnikov-de Haas effect shows that the weak superlattice potential responsible for the Fermi surface reconstruction in the overdoped regime extrapolates to zero at the doping level x_c = 0.175 corresponding to the onset of superconductivity. Second, the high-field Hall coefficient exhibits a sharp drop right below optimal doping x_opt = 0.145 where the superconducting transition temperature is maximum. This drop is most likely caused by the onset of long-range antiferromagnetic ordering. Thus, the superconducting dome appears to be pinned by two critical points to the normal state phase diagram. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.7398v2.pdf"}
{"id": "1403.7513", "abstract": "  We investigated experimentally the ray-wave correspondence in organic microlasers of various triangular shapes. Triangular billiards are of interest since they are the simplest cases of polygonal billiards and the existence and properties of periodic orbits in triangles are not yet fully understood. The microlasers with symmetric shapes that were investigated exhibited states localized on simple periodic orbits, and their lasing characteristics like spectra and far-field distributions could be well explained by the properties of the periodic orbits. Furthermore, asymmetric triangles that do not feature simple periodic orbits were studied. Their lasing properties were found to be more complicated and could not be explained by periodic orbits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.7513v3.pdf"}
{"id": "1404.0193", "abstract": "  Using the previously developed model to describe laminar/turbulent states of a viscous fluid flow, which treats the flow as a collection of coherent structures of various size (Chekmarev, Chaos, 2013, 013144), the statistical temperature of the flow state is determined as a function of the Reynolds number. It is shown that at small Reynolds numbers, associated with laminar states, the temperature is positive, while at large Reynolds numbers, associated with turbulent states, it is negative. At intermediate Reynolds numbers, the temperature changes from positive to negative as the size of the coherent structures increases, similar to what was predicted by Onsager for a system of parallel point-vortices in an inviscid fluid. It is also shown that in the range of intermediate Reynolds numbers the temperature exhibits a power-law divergence characteristic of second-order phase transitions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.0193v1.pdf"}
{"id": "1404.1672", "abstract": "  The CALICE collaboration is developing a granular electromagnetic calorimeter using small scintillator strips for a future linear collider experiment. On developing of   10^7 channel-ECAL in particle flow approach, CALICE is developing a technological prototype with 144 of 5 x 45 x (1 - 2) mm^3 strips on each 180 x 180 mm^2 base board unit in tandem with developing the design of scintillator strip and pixelated photon detector and their coupling after established the physics prototype which has required performance. A method of event reconstruction in such ECAL is also developed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.1672v1.pdf"}
{"id": "1404.1805", "abstract": "  A key feature of non-equilibrium thermodynamics is the Markovian, deterministic relaxation of coarse observables such as, for example, the temperature difference between two macroscopic objects which evolves independently of almost all details of the initial state. We demonstrate that the unitary dynamics for moderately sized spin-1/2 systems may yield the same type of relaxation dynamics for a given magnetization difference. This observation might contribute to the understanding of the emergence of thermodynamics within closed quantum systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.1805v1.pdf"}
{"id": "1404.3259", "abstract": "  We explore the nature of the small-scale solar dynamo by tracking magnetic features. We investigate two previously-explored categories of the small-scale solar dynamo: shallow and deep. Recent modeling work on the shallow dynamo has produced a number of scenarios for how a strong network concentration can influence the formation and polarity of nearby small-scale magnetic features. These scenarios have measurable signatures, which we test for here using magnetograms from the Narrowband Filter Imager (NFI) on Hinode. We find no statistical tendency for newly-formed magnetic features to cluster around or away from network concentrations, nor do we find any statistical relationship between their polarities. We conclude that there is no shallow or \"surface\" dynamo on the spatial scales observable by Hinode/NFI. In light of these results, we offer a scenario in which the sub-surface field in a deep solar dynamo is stretched and distorted via turbulence, allowing the field to emerge at random locations on the photosphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.3259v1.pdf"}
{"id": "1404.5787", "abstract": "  The recently discovered multiband superconductors have created a new class of novel superconductors. In these materials multiple superconducting gaps arise due to the formation of Cooper pairs on different sheets of the Fermi surfaces. An important feature of these superconductors is the interband couplings, which not only change the individual gap properties, but also create new collective modes. Here we investigate the effect of the interband couplings in the Ginzburg-Landau theory. We produce a general τ^(2n+1)/2 expansion (τ = 1-T/T_c) and show that this expansion has unexpected behaviour for n≥ 2. This point emphasises the weaker validity of the GL theory for lower temperatures and gives credence to the existence of hidden criticality near the critical temperature of the uncoupled subdominant band. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.5787v1.pdf"}
{"id": "1404.7160", "abstract": "  Reflection of a microscopic particle from a mesoscopic/macroscopic `mirror' generates two-body correlated interference from the incident and reflected particle substates and their associated mirror substates. The microscopic momentum exchanged generates two mirror substates which interfere to produce fringes which do not vanish as the mirror mass increases. The small displacement between these mirror states can yield negligible environmental decoherence times. Mirror coherence lengths impose constraints on the extent of this interference, which are mitigated using interference of the two-body states associated with the particle reflecting from both of the two surfaces of a slab of matter in a manner analogous to the classical interference of a pulse of light reflecting from a `thin film'. This two-body correlated interference is modeled as a particle traversing a finite well with both the particle and well treated quantum mechanically. Such a treatment predicts the expected `thin-film' interference but only as a special case of a more general result. It is also shown that measurements on only the reflected particle (yielding a marginal probability density function) can act as a probe to reveal the quantum state of the macroscopic reflector. For equal masses, coherence of the particle substate is transferred to the mirror substate, a quantum manifestation of a familiar classical result. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.7160v3.pdf"}
{"id": "1404.7277", "abstract": "  We show that a discrete tight-binding model representing either a random or a quasiperiodic array of bonds, can have the entire energy spectrum or a substantial part of it absolutely continuous, populated by extended eigenfunctions only, when atomic sites are coupled to the lattice locally, or non-locally from one side. The event can be fine-tuned by controlling only the host-adatom coupling in one case, while in two other cases cited here an additional external magnetic field is necessary. The delocalization of electronic states for the group of systems presented here is sensitive to a subtle correlation between the numerical values of the Hamiltonian parameters - a fact that is not common in the conventional cases of Anderson localization. Our results are analytically exact, and supported by numerical evaluation of the density of states and electronic transmission coefficient. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.7277v2.pdf"}
{"id": "1404.7444", "abstract": "  Recent observations of sunspot's umbra suggested that it may be finely structured at a sub-arcsecond scale representing a mix of hot and cool plasma elements. In this study we report the first detailed observations of the umbral spikes, which are cool jet-like structures seen in the chromosphere of an umbra. The spikes are cone-shaped features with a typical height of 0.5-1.0 Mm and a width of about 0.1 Mm. Their life time ranges from 2 to 3 min and they tend to re-appear at the same location. The spikes are not associated with photospheric umbral dots and they rather tend to occur above darkest parts of the umbra, where magnetic fields are strongest. The spikes exhibit up and down oscillatory motions and their spectral evolution suggests that they might be driven by upward propagating shocks generated by photospheric oscillations. It is worth noting that triggering of the running penumbral waves seems to occur during the interval when the spikes reach their maximum height. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.7444v1.pdf"}
{"id": "1405.1767", "abstract": "  We examine the hypothesis that magnetic fields are inflating the radii of fully convective main sequence stars in detached eclipsing binaries (DEBs). The magnetic Dartmouth stellar evolution code is used to analyze two systems in particular: Kepler-16 and CM Draconis. Magneto-convection is treated assuming stabilization of convection and also by assuming reductions in convective efficiency due to a turbulent dynamo. We find that magnetic stellar models are unable to reproduce the properties of inflated fully convective main sequence stars, unless strong interior magnetic fields in excess of 10 MG are present. Validation of the magnetic field hypothesis given the current generation of magnetic stellar evolution models therefore depends critically on whether the generation and maintenance of strong interior magnetic fields is physically possible. An examination of this requirement is provided. Additionally, an analysis of previous studies invoking the influence of star spots is presented to assess the suggestion that star spots are inflating stars and biasing light curve analyses toward larger radii. From our analysis, we find that there is not yet sufficient evidence to definitively support the hypothesis that magnetic fields are responsible for the observed inflation among fully convective main sequence stars in DEBs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.1767v1.pdf"}
{"id": "1405.2789", "abstract": "  An intriguing interpretation of the time-evolution of dynamical systems is to view it as a computation that transforms an initial state to a final one. This paradigm has been explored in discrete systems such as cellular automata models, where the relation between dynamics and computation has been examined in detail. Here, motivated by microfluidic experiments on arrays of chemical oscillators, we show that computation can be achieved in continuous-state, continuous-time systems by using complex spatiotemporal patterns generated through a reaction-diffusion mechanism in coupled relaxation oscillators. We present two paradigms that illustrate this computational capability, namely, using perturbations to (i) generate propagating configurations in a system of initially exactly synchronized oscillators, and (ii) transform one time-invariant pattern to another. In particular, we have demonstrated a possible implementation of NAND logic. This raises the possibility of universal computation in such systems as all logic gates can be constructed from NAND gates. Our work suggests that more complex schemes can potentially implement arbitrarily complicated computation using reaction-diffusion processes, bridging pattern formation with universal computability. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.2789v1.pdf"}
{"id": "1405.3070", "abstract": "  The full counting statistics of charge transport is the probability distribution p_n(t_m) that n electrons have flown through the system in measuring time t_m. The cumulant generating function (CGF) of this distribution F(χ,t_m) has been well studied in the long time limit t_m→∞, however there are relatively few results on the finite measuring time corrections to this. In this work, we study the leading finite time corrections to the CGF of interacting Fermi systems with a single transmission channel at zero temperature but driven out of equilibrium by a bias voltage. We conjecture that the leading finite time corrections are logarithmic in t_m with a coefficient universally related to the long time limit. We provide detailed numerical evidence for this with reference to the self-dual interacting resonant level model. This model further contains a phase transition associated with the fractionalisation of charge at a critical bias voltage. This transition manifests itself technically as branch points in the CGF. We provide numerical results of the dependence of the CGF on measuring time for model parameters in the vicinity of this transition, and thus identify features in the time evolution associated with the phase transition itself. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.3070v1.pdf"}
{"id": "1406.0355", "abstract": "  We investigate the nonclassical properties of output fields propagated through a contradirectional asymmetric nonlinear optical coupler consisting of a linear waveguide and a nonlinear (quadratic) waveguide operated by second harmonic generation. In contrast to the earlier results, all the initial fields are considered weak and a completely quantum mechanical model is used here to describe the system. Perturbative solutions of Heisenberg's equations of motion for various field modes are obtained using Sen-Mandal technique. Obtained solutions are subsequently used to show the existence of single-mode and intermodal squeezing, single-mode and intermodal antibunching, two-mode and multi-mode entanglement in the output of contradirectional asymmetric nonlinear optical coupler. Further, existence of higher order nonclassicality is also established by showing the existence of higher order antibunching, higher order squeezing and higher order entanglement. Variation of observed nonclassical characters with different coupling constants and phase mismatch is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.0355v1.pdf"}
{"id": "1406.0702", "abstract": "  We propose the use of topographic modulation of surfaces to select and localize particles in nematic colloids. By considering convex and concave deformations of one of the confining surfaces we show that the colloid-flat surface repulsion may be enhanced or switched into an attraction. In particular, we find that when the colloidal particles have the same anchoring conditions as the patterned surfaces, they are strongly attracted to concave dimples, while if they exhibit different anchoring conditions they are pinned at the top of convex protrusions. Although dominated by elastic interactions the first mechanism is reminiscent of the depletion induced attraction or of the key-lock mechanism, while the second is specific to liquid crystal colloids. These long-ranged, highly tunable, surface-colloid interactions contribute for the development of template-assisted assembly of large colloidal crystals, with well defined symmetries, required for applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.0702v1.pdf"}
{"id": "1406.4991", "abstract": "  The Euler-Lagrange equation of the phase-field crystal (PFC) model has been solved under appropriate boundary conditions to obtain the equilibrium free energy of the body centered cubic crystal-liquid interface for 18 orientations at various reduced temperatures in the range ϵ∈[0,0.5]. While the maximum free energy corresponds to the { 100} orientation for all ϵ values, the minimum is realized by the { 111} direction for small ϵ (<0.13), and by the { 211} orientation for higher ϵ. The predicted dependence on the reduced temperature is consistent with the respective mean field critical exponent. The results are fitted with an eight-term Kubic harmonic series, and are used to create stereographic plots displaying the anisotropy of the interface free energy. We have also derived the corresponding Wulff shapes that vary with increasing ϵ from sphere to a polyhedral form that differs from the rhombo-dodecahedron obtained previously by growing a bcc seed until reaching equilibrium with the remaining liquid. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.4991v1.pdf"}
{"id": "1406.5416", "abstract": "  The Coulomb repulsion between ions in a linear Paul trap give rise to anharmonic terms in the potential energy when expanded about the equilibrium positions. We examine the effect of these anharmonic terms on the accuracy of a quantum simulator made from trapped ions. To be concrete, we consider a linear chain of Yb^171+ ions stabilized close to the zigzag transition. We find that for typical experimental temperatures, frequencies change by no more than a factor of 0.01% due to the anharmonic couplings. Furthermore, shifts in the effective spin-spin interactions (driven by a spin-dependent optical dipole force) also tend to be small for detunings to the blue of the transverse center-of-mass frequency. However, detuning the spin interactions near other frequencies can lead to nonnegligible anharmonic contributions to the effective spin-spin interactions. We also examine an odd behavior exhibited by the harmonic spin-spin interactions for a range of intermediate detunings, where nearest neighbor spins with a larger spatial separation on the ion chain interact more strongly than nearest neighbors with a smaller spatial separation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.5416v1.pdf"}
{"id": "1406.5974", "abstract": "  Current approaches for building quantum computing devices focus on two-level quantum systems which nicely mimic the concept of a classical bit, albeit enhanced with additional quantum properties. However, rather than artificially limiting the number of states to two, the use of d-level quantum systems (qudits) could provide advantages for quantum information processing. Among other merits, it has recently been shown that multi-level quantum systems can offer increased stability to external disturbances - a key problem in current technologies. In this study we demonstrate that topological quantum memories built from qudits, also known as abelian quantum double models, exhibit a substantially increased resilience to noise. That is, even when taking into account the multitude of errors possible for multi-level quantum systems, topological quantum error correction codes employing qudits can sustain a larger error rate than their two-level counterparts. In particular, we find strong numerical evidence that the thresholds of these error-correction codes are given by the hashing bound. Considering the significantly increased error thresholds attained, this might well outweigh the added complexity of engineering and controlling higher dimensional quantum systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.5974v1.pdf"}
{"id": "1406.6252", "abstract": "  We consider quantum plasmas of electrons and motionless ions. We describe separate evolution of spin-up and spin-down electrons. We present corresponding set of quantum hydrodynamic equations. We assume that plasmas are placed in an uniform external magnetic field. We account different occupation of spin-up and spin-down quantum states in equilibrium degenerate plasmas. This effect is included via equations of state for pressure of each species of electrons. We study oblique propagation of longitudinal waves. We show that instead of two well-known waves (the Langmuir wave and the Trivelpiece–Gould wave), plasmas reveal four wave solutions. New solutions exist due to both the separate consideration of spin-up and spin-down electrons and different occupation of spin-up and spin-down quantum states in equilibrium state of degenerate plasmas. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.6252v1.pdf"}
{"id": "1407.1811", "abstract": "  For a system strongly coupled to a heat bath, the quantum coherence of the system and the heat bath plays an important role in the system dynamics. This is particularly true in the case of non-Markovian noise. We rigorously investigate the influence of system-bath coherence by deriving the reduced hierarchal equations of motion (HEOM), not only in real time, but also in imaginary time, which represents an inverse temperature. It is shown that the HEOM in real time obtained when we include the system-bath coherence of the initial thermal equilibrium state possess the same form as those obtained from a factorized initial state. We find that the difference in behavior of systems treated in these two manners results from the difference in initial conditions of the HEOM elements, which are defined in path integral form. We also derive HEOM along the imaginary time path to obtain the thermal equilibrium state of a system strongly coupled to a non-Markovian bath. Then, we show that the steady state hierarchy elements calculated from the real-time HEOM can be expressed in terms of the hierarchy elements calculated from the imaginary-time HEOM. Moreover, we find that the imaginary-time HEOM allow us to evaluate a number of thermodynamic variables, including the free energy, entropy, internal energy, heat capacity, and susceptibility. The expectation values of the system energy and system-bath interaction energy in the thermal equilibrium state are also evaluated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.1811v2.pdf"}
{"id": "1407.2391", "abstract": "  Heterogeneous networks have a key role in the design of future mobile communication networks, since the employment of small cells around a macrocell enhances the network's efficiency and decreases complexity and power demand. Moreover, research on Blind Interference Alignment (BIA) has shown that optimal Degrees of Freedom (DoF) can be achieved in certain network architectures, with no requirement of Channel State Information (CSI) at the transmitters. Our contribution is a generalised model of BIA in a heterogeneous network with one macrocell with K users and K femtocells each with one user, by using Kronecker (Tensor) Product representation. We introduce a solution on how to vary beamforming vectors under power constraints to maximize the sum rate of the network and how optimal DoF can be achieved over K+1 time slots. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.2391v1.pdf"}
{"id": "1407.4253", "abstract": "  Frictional interfaces are abundant in natural and manmade systems and their dynamics still pose challenges of fundamental and technological importance. A recent extensive compilation of multiple-source experimental data has revealed that velocity-strengthening friction, where the steady-state frictional resistance increases with sliding velocity over some range, is a generic feature of such interfaces. Moreover, velocity-strengthening friction has very recently been linked to slow laboratory earthquakes and stick-slip motion. Here we elucidate the importance of velocity-strengthening friction by theoretically studying three variants of a realistic rate-and-state friction model. All variants feature identical logarithmic velocity-weakening friction at small sliding velocities, but differ in their higher velocity behaviors. By quantifying energy partition (e.g. radiation and dissipation), the selection of interfacial rupture fronts and rupture arrest, we show that the presence or absence of velocity-strengthening friction can significantly affect the global interfacial resistance and the total energy released during frictional instabilities (\"event magnitude\"). Furthermore, we show that different forms of velocity-strengthening friction (e.g. logarithmic vs. linear) may result in events of similar magnitude, yet with dramatically different dissipation and radiation rates. This happens because the events are mediated by interfacial rupture fronts with vastly different propagation velocities, where stronger velocity-strengthening friction promotes slower rupture. These theoretical results may have significant implications on our understanding of frictional dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.4253v1.pdf"}
{"id": "1407.4673", "abstract": "  The role of angular momentum in a 2+1-dimensional rotating thin-shell wormhole (TSW) is considered. Particular emphasis is made on stability when the shells (rings) are counterrotating. We find that counter-rotating halves make the TSW supported by the equation of state of a linear gas more stable. Under a small velocity dependent perturbation, however, it becomes unstable. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.4673v2.pdf"}
{"id": "1407.4966", "abstract": "  Relativistic jets associated with long/soft gamma-ray bursts are formed and initially propagate in the interior of the progenitor star. Because of the subsequent loss of their external pressure support after they cross the stellar surface, these flows can be modeled as moving around a corner. A strong steady-state rarefaction wave is formed, and the sideways expansion is accompanied by a rarefaction acceleration. We investigate the efficiency and the general characteristics of this mechanism by integrating the steady-state, special relativistic, magnetohydrodynamic equations, using a special set of partial exact solutions in planar geometry (r self-similar with respect to the \"corner\"). We also derive analytical approximate scalings in the ultrarelativistic cold/magnetized, and hydrodynamic limits. The mechanism is more effective in magnetized than in purely hydrodynamic flows. It substantially increases the Lorentz factor without much affecting the opening of the jet; the resulting values of their product can be much grater than unity, allowing for possible breaks in the afterglow light curves. These findings are similar to the ones from numerical simulations of axisymmetric jets by Komissarov et al and Tchekhovskoy et al, although in our approach we describe the rarefaction as a steady-state simple wave and self-consistently calculate the opening of the jet that corresponds to zero external pressure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.4966v1.pdf"}
{"id": "1407.5355", "abstract": "  In this paper, we address the problem of secure wireless information and power transfer in a large-scale multiple-input multiple-output (LS-MIMO) amplify-and-forward (AF) relaying system. The advantage of LS-MIMO relay is exploited to enhance wireless security, transmission rate and energy efficiency. In particular, the challenging issues incurred by short interception distance and long transfer distance are well addressed simultaneously. Under very practical assumptions, i.e., no eavesdropper's channel state information (CSI) and imperfect legitimate channel CSI, this paper investigates the impact of imperfect CSI, and obtains an explicit expression of the secrecy outage capacity in terms of transmit power and channel condition. Then, we propose an optimal power splitting scheme at the relay to maximize the secrecy outage capacity. Finally, our theoretical claims are validated by simulation results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.5355v1.pdf"}
{"id": "1407.7063", "abstract": "  In quantum reading, a quantum state of light (transmitter) is applied to read classical information. In the presence of noise or for sufficiently weak signals, quantum reading can outperform classical reading by enhanced state distinguishability. Here we show that the enhanced quantum efficiency depends on the presence in the transmitter of a particular type of quantum correlations, the discord of response. Different encodings and transmitters give rise to different levels of efficiency. Considering noisy quantum probes we show that squeezed thermal transmitters with non-symmetrically distributed noise among the field modes yield a higher quantum efficiency compared to coherent thermal quantum states. The noise-enhanced quantum advantage is a consequence of the discord of response being a non-decreasing function of increasing thermal noise under constant squeezing, a behavior that leads to an increased state distinguishability. We finally show that, for non-symmetric squeezed thermal states, the probability of error, as measured by the quantum Chernoff bound, vanishes asymptotically with increasing local thermal noise at finite global squeezing. Therefore, at fixed finite squeezing, noisy but strongly discordant quantum states with large noise imbalance between the field modes can outperform noisy classical resources as well as pure entangled transmitters with the same finite level of squeezing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.7063v2.pdf"}
{"id": "1408.0290", "abstract": "  We present an abundance analysis of eight potential member stars of the old Galactic bulge globular cluster NGC6522. The same stars have previously been studied by Chiappini et al. (2011), who found very high abundances of the slow neutron capture elements compared with other clusters and field stars of similar metallicity, which they interpreted as reflecting nucleosynthesis in rapidly rotating, massive Population III stars. In contrast to their analysis, we do not find any unusual enhancements of the neutron capture elements Sr, Y, Ba and Eu and conclude that previous claims result mainly from not properly accounting for blending lines. Instead we find NGC6522 to be an unremarkable globular cluster with comparable abundance trends to other Galactic globular clusters at the same metallicity ([Fe/H] = -1.15 +/- 0.16). The stars are also chemically similar to halo and bulge field stars at the same metallicity, spanning a small range in [Y/Ba] and with normal α-element abundances. We thus find no observational evidence for any chemical signatures of rapidly rotating Population III stars in NGC 6522. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.0290v1.pdf"}
{"id": "1408.0473", "abstract": "  The derivation of general performance benchmarks is important in the design of highly optimized heat engines and refrigerators. To obtain them, one may model phenomenologically the leading sources of irreversibility ending up with results which are model-independent, but limited in scope. Alternatively, one can take a simple physical system realizing a thermodynamic cycle and assess its optimal operation from a complete microscopic description. We follow this approach in order to derive the coefficient of performance at maximum cooling rate for any endoreversible quantum refrigerator. At striking variance with the universality of the optimal efficiency of heat engines, we find that the cooling performance at maximum power is crucially determined by the details of the specific system-bath interaction mechanism. A closed analytical benchmark is found for endoreversible refrigerators weakly coupled to unstructured bosonic heat baths: an ubiquitous case study in quantum thermodynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.0473v3.pdf"}
{"id": "1408.0761", "abstract": "  Thermal fits have consistently reproduced the experimental particles yields of heavy ion collisions, however, the proton to pion ratio from ALICE Pb+Pb √(s_NN)=2.76 TeV is over-predicted by thermal models- known at the p/π puzzle. Here we test the relevance of the extended mass spectrum, i.e., include Hagedorn states (resonances that follow an exponential mass spectrum and have very short life times) on the p/π puzzle. We find that the extended mass spectrum is able to reproduce particle ratios at both RHIC and the LHC as well as being able to match the lower p/π ratio at the LHC through dynamical chemical equilibration. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.0761v1.pdf"}
{"id": "1408.1402", "abstract": "  Differential spectroscopy during exoplanet transits permits to reconstruct spectra of small stellar surface portions that successively become hidden behind the planet. The center-to-limb behavior of stellar line shapes, asymmetries and wavelength shifts will enable detailed tests of 3-dimensional hydrodynamic models of stellar atmospheres, such that are required for any precise determination of abundances or seismic properties. Such models can now be computed for widely different stars but have been feasible to test in detail only for the Sun with its resolved surface structure. Although very high quality spectra are required, already current data permit reconstructions of line profiles in the brightest transit host stars such as HD209458 (G0 V). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.1402v1.pdf"}
{"id": "1408.2390", "abstract": "  Using direct numerical simulations of Rayleigh-Bénard convection (RBC), we perform a comparative study of the spectra and fluxes of energy and entropy, and the scaling of large-scale quantities for large and infinite Prandtl numbers in two (2D) and three (3D) dimensions. We observe close similarities between the 2D and 3D RBC, in particular the kinetic energy spectrum E_u(k) ∼ k^-13/3, and the entropy spectrum exhibits a dual branch with a dominant k^-2 spectrum. We showed that the dominant Fourier modes in the 2D and 3D flows are very close. Consequently, the 3D RBC is quasi two-dimensional, which is the reason for the similarities between the 2D and 3D RBC for large- and infinite Prandtl numbers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.2390v1.pdf"}
{"id": "1408.3530", "abstract": "  The swimming velocity and rate of dissipation of a linear chain consisting of two or three little spheres and a big sphere is studied on the basis of low Reynolds number hydrodynamics. The big sphere is treated as a passive cargo, driven by the tail of little spheres via hydrodynamic and direct elastic interaction. The fundamental solution of Stokes' equations in the presence of a sphere with no-slip boundary condition, as derived by Oseen, is used to model the hydrodynamic interactions between the big sphere and the little spheres. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.3530v3.pdf"}
{"id": "1408.5162", "abstract": "  We report multi-wavelength observations of the unidentified Fermi object 2FGL J1653.6-0159. With the help of high-resolution X-ray observation, we have identified an X-ray and optical counterpart of 2FGL J1653.6-0159. The source exhibits a periodic modulation of 75 min in optical and possibly also in X-ray. We suggest that 2FGL J1653.6-0159 is a compact binary system with an orbital period of 75 min. Combining the gamma-ray and X-ray properties, 2FGL J1653.6-0159 is potentially a black widow/redback type gamma-ray millisecond pulsar (MSP). The optical and X-ray lightcurve profiles show that the companion is mildly heated by the high-energy emission and the X-rays are from intrabinary shock. Although no radio pulsation has been detected yet, we estimated that the spin period of the MSP is  2ms based on a theoretical model. If pulsation can be confirmed in the future, 2FGL J1653.6-0159 will become the first ultracompact rotation-powered MSP. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.5162v2.pdf"}
{"id": "1408.5305", "abstract": "  We adopt the Ramsey's method of separated oscillatory fields to study coherences of the mechanical system in an optomechanical resonator. The high resolution Ramsey fringes are observed in the emission optical field, when two pulses separated in time are applied. We develop a theory to describe the transient optomechanical behavior underlying the Ramsey fringes. We also perform the experimental demonstration using a silica microresonator. The method is versatile and can be adopted to different types of mechanical resonators, electromechanical resonators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.5305v1.pdf"}
{"id": "1409.0624", "abstract": "  A system is considered, which is subject to external and possibly fatal shocks, with dependence between the fatality of a shock and the system age. Apart from these shocks, the system suffers from competing soft and sudden failures, where soft failures refer to the reaching of a given thresh-old for the degradation level, and sudden failures to accidental failures, characterized by a failure rate. A non-fatal shock increases both degradation level and failure rate of a random amount, with possible dependence between the two increments. The system reliability is calculated by four different methods. Conditions under which the system lifetime is New Better than Used are proposed. The in uence of various parameters of the shocks environment on the system lifetime is studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.0624v1.pdf"}
{"id": "1409.1294", "abstract": "  We study the nonequilibrium spectral function of the single-impurity Anderson model connecting with multi-terminal leads. The full dependence on frequency and bias voltage of the nonequilibrium self-energy and spectral function is obtained analytically up to the second-order perturbation regarding the interaction strength U. High and low bias voltage properties are analyzed for a generic multi-terminal dot, showing a crossover from the Kondo resonance to the Coulomb peaks with increasing bias voltage. For a dot where the particle-hole symmetry is not present, we construct a current-preserving evaluation of the nonequilibrium spectral function for arbitrary bias voltage. It is shown that finite bias voltage does not split the Kondo resonance in this order, and no specific structure due to multiple leads emerges. Overall bias dependence is quite similar to finite temperature effect for a dot with or without the particle-hole symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.1294v1.pdf"}
{"id": "1409.2670", "abstract": "  We consider different properties of small open quantum systems coupled to an environment and described by a non-Hermitian Hamilton operator. Of special interest is the non-analytical behavior of the eigenvalues in the vicinity of singular points, the so-called exceptional points (EPs), at which the eigenvalues of two states coalesce and the corresponding eigenfunctions are linearly dependent from one another. The phases of the eigenfunctions are not rigid in approaching an EP and providing therewith the possibility to put information from the environment into the system. All characteristic properties of non-Hermitian quantum systems hold true not only for natural open quantum systems that suffer loss due to their embedding into the continuum of scattering wavefunctions. They appear also in systems coupled to different layers some of which provide gain to the system. Thereby gain and loss, respectively, may be fixed inside every layer, i.e. characteristic of it. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.2670v2.pdf"}
{"id": "1409.6070", "abstract": "  Convolutional neural networks (CNNs) perform well on problems such as handwriting recognition and image classification. However, the performance of the networks is often limited by budget and time constraints, particularly when trying to train deep networks.   Motivated by the problem of online handwriting recognition, we developed a CNN for processing spatially-sparse inputs; a character drawn with a one-pixel wide pen on a high resolution grid looks like a sparse matrix. Taking advantage of the sparsity allowed us more efficiently to train and test large, deep CNNs. On the CASIA-OLHWDB1.1 dataset containing 3755 character classes we get a test error of 3.82", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.6070v1.pdf"}
{"id": "1409.6359", "abstract": "  In this paper a method is proposed which uses data mining techniques based on rough sets theory to select neighborhood and determine update rule for cellular automata (CA). According to the proposed approach, neighborhood is detected by reducts calculations and a rule-learning algorithm is applied to induce a set of decision rules that define the evolution of CA. Experiments were performed with use of synthetic as well as real-world data sets. The results show that the introduced method allows identification of both deterministic and probabilistic CA-based models of real-world phenomena. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.6359v1.pdf"}
{"id": "1409.7774", "abstract": "  In early HIV infection, the virus population escapes from multiple CD8+ cell responses. The later an escape mutation emerges, the slower it outgrows its competition, i. e. the escape rate is lower. This pattern could indicate that the strength of the CD8+ cell responses is waning, or that later viral escape mutants carry a larger fitness cost. In this paper, we investigate whether the pattern of decreasing escape rate could also be caused by genetic interference among different escape strains. To this end, we developed a mathematical multi-epitope model of HIV dynamics, which incorporates stochastic effects, recombination and mutation. We used cumulative linkage disequilibrium measures to quantify the amount of interference. We found that nearly synchronous, similarly strong immune responses in two-locus systems enhance the generation of genetic interference. This effect, combined with densely spaced sampling times at the beginning of infection, leads to decreasing successive escape rate estimates, even when there were no selection differences among alleles. These predictions are supported by experimental data from one HIV-infected patient. Thus, interference could explain why later escapes are slower. Considering escape mutations in isolation, neglecting their genetic linkage, conceals the underlying haplotype dynamics and can affect the estimation of the selective pressure exerted by CD8+ cells. In systems in which multiple escape mutations appear, the occurrence of interference dynamics should be assessed by measuring the linkage between different escape mutations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.7774v1.pdf"}
{"id": "1409.8128", "abstract": "  We show that the electron thermal conductivity may strongly affect the heliosheath plasma flow and the global pattern of the solar wind (SW) interaction with the local interstellar medium (LISM). In particular, it leads to strong reduction of the inner heliosheath thickness that makes possible to explain (qualitatively) why Voyager 1 (V1) has crossed the heliopause at unexpectedly small heliocentric distance of 122 AU. To estimate the effect of thermal conductivity we consider a limiting case when thermal conduction is very effective. To do that we assume the plasma flow in the entire heliosphere is nearly isothermal.   Due to this effect, the heliospheric distance of the termination shock has increased by about 15 AU in V1 direction compared to the adiabatic case with gamma = 5/3. The heliospheric distance of the heliopause has decreased by about 27 AU. As a result, the thickness of the inner heliosheath in the model has decreased by about 42 AU and become equal to 32 AU. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1409/1409.8128v1.pdf"}
{"id": "1410.2635", "abstract": "  Wolf-Rayet (WR) HII galaxies are local metal-poor star-forming galaxies, observed when the most massive stars are evolving from O stars to WR stars, making them template systems to study distant starbursts. We have been performing a program to investigate the interplay between massive stars and gas in WR HII galaxies using IFS. Here, we highlight some results from the first 3D spectroscopic study of Mrk 178, the closest metal-poor WR HII galaxy, focusing on the origin of the nebular HeII emission and the aperture effects on the detection of WR features. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.2635v1.pdf"}
{"id": "1410.5236", "abstract": "  The supermassive black hole at the Galactic center, Sagittarius A*, has experienced periods of higher activity in the past. The reflection of these past outbursts is observed in the molecular material surrounding the black hole but reconstructing its precise lightcurve is difficult since the distribution of the clouds along the line of sight is poorly constrained. Using Chandra high-resolution data collected from 1999 to 2011 we studied both the 6.4 keV and the 4-8 keV emission of the region located between Sgr A* and the Radio Arc, characterizing its variations down to 15\" angular scale and 1-year time scale. The emission from the molecular clouds in the region varies significantly, showing either a 2-year peaked emission or 10-year linear variations. This is the first time that such fast variations are measured. Based on the cloud parameters, we conclude that these two behaviors are likely due to two distinct past outbursts of Sgr A* during which its luminosity rose to at least 10^39 erg/s. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.5236v1.pdf"}
{"id": "1410.5356", "abstract": "  In this work, we investigate the statistical computation of the Boltzmann entropy of statistical samples. For this purpose, we use both histogram and kernel function to estimate the probability density function of statistical samples. We find that, due to coarse-graining, the entropy is a monotonic increasing function of the bin width for histogram or bandwidth for kernel estimation, which seems to be difficult to select an optimal bin width/bandwidth for computing the entropy. Fortunately, we notice that there exists a minimum of the first derivative of entropy for both histogram and kernel estimation, and this minimum point of the first derivative asymptotically points to the optimal bin width or bandwidth. We have verified these findings by large amounts of numerical experiments. Hence, we suggest that the minimum of the first derivative of entropy be used as a selector for the optimal bin width or bandwidth of density estimation. Moreover, the optimal bandwidth selected by the minimum of the first derivative of entropy is purely data-based, independent of the unknown underlying probability density distribution, which is obviously superior to the existing estimators. Our results are not restricted to one-dimensional, but can also be extended to multivariate cases. It should be emphasized, however, that we do not provide a robust mathematical proof of these findings, and we leave these issues with those who are interested in them. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.5356v1.pdf"}
{"id": "1410.6833", "abstract": "  The structure and strain of ultrathin CoO films grown on a Pt(001) substrate and on a ferromagnetic PtFe pseudomorphic layer on Pt(001) have been determined with insitu and real time surface x-ray diffraction. The films grow epitaxially on both surfaces with an in-plane hexagonal pattern that yields a pseudo-cubic CoO(111) surface. A refined x-ray diffraction analysis reveals a slight monoclinic distortion at RT induced by the anisotropic stress at the interface. The tetragonal contribution to the distortion results in a ratio c/a > 1, opposite to that found in the low temperature bulk CoO phase. This distortion leads to a stable Co2+ spin configuration within the plane of the film. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.6833v1.pdf"}
{"id": "1410.8560", "abstract": "  The merger of a binary of neutron stars provides natural explanations for many of the features of short gamma-ray bursts (SGRBs), such as the generation of a hot torus orbiting a rapidly rotating black hole, which can then build a magnetic jet and provide the energy reservoir to launch a relativistic outflow. Yet, this scenario has problems explaining the recently discovered long-term and sustained X-ray emission associated with the afterglows of a subclass of SGRBs. We propose a new model that explains how an X-ray afterglow can be sustained by the product of the merger and how the X-ray emission is produced before the corresponding emission in the gamma-band, although it is observed to follow it. Overall, our paradigm combines in a novel manner a number of well-established features of the emission in SGRBs and results from simulations. Because it involves the propagation of an ultra-relativistic outflow and its interaction with a confining medium, the paradigm also highlights a unifying phenomenology between short and long GRBs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.8560v2.pdf"}
{"id": "1410.8678", "abstract": "  This is mainly a survey article on the recent development of the theory of graph-like Legendrian unfoldings and its applications. The notion of big Legendrian submanifolds was introduced by Zakalyukin for describing the wave front propagations. Graph-like Legendrian unfoldings belong to a special class of big Legendrian submanifolds. Although this is a survey article, some new original results and the corrected proofs of some results are given. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1410/1410.8678v1.pdf"}
{"id": "1411.0318", "abstract": "  Standard analytical chemical evolution modelling of galaxies has been assuming the stellar initial mass function (IMF) to be invariant and fully sampled allowing fractions of massive stars to contribute even in dwarf galaxies with very low star formation rates (SFRs). Recent observations show the integrated galactic initial mass function (IGIMF) of stars, i.e. the galaxy-wide IMF, to become systematically top-heavy with increasing SFR. This has been predicted by the IGIMF theory, which is here used to develop the analytical theory of the chemical evolution of galaxies. This theory is non-linear and requires the iterative solution of implicit integral equations due to the dependence of the IGIMF on the metallicity and on the SFR. It is shown that the mass-metallicity relation of galaxies emerges naturally, although at low masses the theoretical predictions overestimate the observations by 0.3–0.4 dex. A good agreement with the observation can be obtained only if gas flows are taken into account. In particular, we are able to reproduce the mass–metallicity relation observed by Lee et al. (2006) with modest amounts of infall and with an outflow rate which decreases as a function of the galactic mass. The outflow rates required to fit the data are considerably smaller than required in models with invariant IMFs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.0318v1.pdf"}
{"id": "1411.1859", "abstract": "  We propose a method to study the nature of exotic hadrons by determining the wave function renormalization constant Z from lattice simulations. It is shown that, instead of studying the volume-dependence of the spectrum, one may investigate the dependence of the spectrum on the twisting angle, imposing twisted boundary conditions on the fermion fields on the lattice. In certain cases, e.g., the case of the DK bound state which is addressed in detail, it is demonstrated that the partial twisting is equivalent to the full twisting up to exponentially small corrections. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.1859v1.pdf"}
{"id": "1411.2334", "abstract": "  The heating mechanism of a corona above an accretion disk in active galactic nuclei (AGNs) is still unknown. One possible mechanism is magnetic reconnection heating requiring energy equipartition between magnetic energy and gas energy in the disk. Here, we investigate the expected observed properties in radio band from such a magnetized corona. A magnetized corona can generate synchrotron radiation since a huge amount of electrons exists. Although most of radiation would be absorbed by synchrotron self-absorption, high-frequency end of synchrotron emission can escape from a corona and appears at the sub-mm range. If only thermal electrons exist in a corona, the expected flux from nearby Seyferts is below the Atacama Large Millimeter/ submillimeter Array (ALMA) sensitivity. However, if non-thermal electrons coexist in a corona, ALMA can measure the non-thermal tail of the synchrotron radiation from a corona. Such non-thermal population is naturally expected to exist if the corona is heated by magnetic reconnections. Future ALMA observations will directly probe the coronal magnetic field strength and the existence of non-thermal electrons in coronae of AGNs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.2334v1.pdf"}
{"id": "1411.4729", "abstract": "  We investigate the possibility that electrically neutral porous spheres electrophorese in electrolyte solutions with asymmetric affinity of ions to spheres on the basis of electrohydrodynamics and the Poisson-Boltzmann and Debye-Bueche-Brinkman theories. Assuming a weak electric field and ignoring the double-layer polarization, we obtain analytical expressions for electrostatic potential, electrophoretic mobility, and flow field. In the equilibrium state, the Galvani potential forms across the interface of the spheres. Under a weak electric field, the spheres show finite mobility with the same sign as the Galvani potential. When the radius of the spheres is significantly larger than the Debye and hydrodynamic screening length, the mobility monotonically increases with increasing salinity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.4729v1.pdf"}
{"id": "1411.5174", "abstract": "  The phase diagram of two-color QCD with a chiral chemical potential is studied on the lattice. The focus is on the confinement/deconfinement phase transition and the breaking/restoration of chiral symmetry. The simulations are carried out with dynamical staggered fermions without rooting. The dependence of the Polyakov loop, the chiral condensate and the corresponding susceptibilities on the chiral chemical potential and the temperature are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.5174v1.pdf"}
{"id": "1411.5792", "abstract": "  This paper presents a detailed analysis of two-armed spiral structure in a sample of galax- ies from the Spitzer Infrared Nearby Galaxies Survey (SINGS), with particular focus on the relationships between the properties of the spiral pattern in the stellar disc and the global struc- ture and environment of the parent galaxies. Following Paper I we have used a combination of Spitzer Space Telescope mid-infrared imaging and visible multi-colour imaging to isolate the spiral pattern in the underlying stellar discs, and we examine the systematic behaviours of the observed amplitudes and shapes (pitch angles) of these spirals. In general, spiral morphology is found to correlate only weakly at best with morphological parameters such as stellar mass, gas fraction, disc/bulge ratio, and vflat. In contrast to weak correlations with galaxy structure a strong link is found between the strength of the spiral arms and tidal forcing from nearby companion galaxies. This appears to support the longstanding suggestion that either a tidal interaction or strong bar is a necessary condition for driving grand-design spiral structure. The pitch angles of the stellar arms are only loosely correlated with the pitch angles of the corresponding arms traced in gas and young stars. We find that the strength of the shock in the gas and the contrast in the star formation rate are strongly correlated with the stellar spiral amplitude. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1411/1411.5792v1.pdf"}
{"id": "1412.0675", "abstract": "  Habitable zone dust levels are a key unknown that must be understood to ensure the success of future space missions to image Earth analogues around nearby stars. Current detection limits are several orders of magnitude above the level of the Solar System's Zodiacal cloud, so characterisation of the brightness distribution of exo-zodi down to much fainter levels is needed. To this end, the large Binocular Telescope Interferometer (LBTI) will detect thermal emission from habitable zone exo-zodi a few times brighter than Solar System levels. Here we present a modelling framework for interpreting LBTI observations, which yields dust levels from detections and upper limits that are then converted into predictions and upper limits for the scattered light surface brightness. We apply this model to the HOSTS survey sample of nearby stars; assuming a null depth uncertainty of 10^-4 the LBTI will be sensitive to dust a few times above the Solar System level around Sun-like stars, and to even lower dust levels for more massive stars. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.0675v1.pdf"}
{"id": "1412.2775", "abstract": "  Superconductors are a striking example of a quantum phenomenon in which electrons move coherently over macroscopic distances without scattering. The high-temperature superconducting oxides(cuprates) are the most studied class of superconductors, composed of two-dimensional CuO2 planes separated by other layers which control the electron concentration in the planes. A key unresolved issue in cuprates is the relationship between superconductivity and magnetism. In this paper, we report a sharp phase boundary of static three-dimensional magnetic order in the electron-doped superconductor La2-xCexCuO4-d where small changes in doping or depth from the surface switch the material from superconducting to magnetic. Using low-energy spin polarized muons, we find static magnetism disappears close to where superconductivity begins and well below the doping where dramatic changes in the transport properties are reported. These results indicate a higher degree of symmetry between the electron and hole-doped cuprates than previously thought. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.2775v1.pdf"}
{"id": "1412.3028", "abstract": "  Direct searches for low mass dark matter particles via scattering off target nuclei require detection of recoiling atoms with energies of  1 keV or less. The amount of electronic excitation produced by such atoms is quenched relative to a recoiling electron of the same energy. The Lindhard model of this quenching, as originally formulated, remains widely used after more than 50 years. The present work shows that for very small energies, a simplifying approximation of that model must be removed. Implications for the sensitivity of direct detection experiments are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.3028v1.pdf"}
{"id": "1412.3813", "abstract": "  We present an X-ray absorption model for the interstellar medium, to be referred to as ISMabs, that takes into account both neutral and ionized species of cosmically abundant elements, and includes the most accurate atomic data available. Using high-resolution spectra from eight X-ray binaries obtained with the Chandra High Energy Transmission Grating Spectrometer, we proceed to benchmark the atomic data in the model particularly in the neon K-edge region. Compared with previous photoabsorption models, which solely rely on neutral species, the inclusion of ions leads to improved spectral fits. Fit parameters comprise the column densities of abundant contributors that allow direct estimates of the ionization states. ISMabs is provided in the appropriate format to be implemented in widely used X-ray spectral fitting packages such as XSPEC, ISIS and SHERPA. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.3813v1.pdf"}
{"id": "1412.6703", "abstract": "  One of the most important aims of the fields of robotics, artificial intelligence and artificial life is the design and construction of systems and machines as versatile and as reliable as living organisms at performing high level human-like tasks. But how are we to evaluate artificial systems if we are not certain how to measure these capacities in living systems, let alone how to define life or intelligence? Here I survey a concrete metric towards measuring abstract properties of natural and artificial systems, such as the ability to react to the environment and to control one's own behaviour. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6703v2.pdf"}
{"id": "1412.6729", "abstract": "  We consider a relativistic radiating spherical star in conformally flat spacetimes. In particular we study the junction condition relating the radial pressure to the heat flux at the boundary of the star which is a nonlinear partial differential equation. The Lie symmetry generators that leave the equation invariant are identified and we generate an optimal system. Each element of the optimal system is used to reduce the partial differential equation to an ordinary differential equation which is further analysed. We identify new categories of exact solutions to the boundary conditions. Two classes of solutions are of interest. The first class depends on a self similar variable. The second class is separable in the spacetime variables. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6729v1.pdf"}
{"id": "1412.6819", "abstract": "  We study thermodynamic of strange quark matter (SQM) using the analytic expressions of free and internal energies. We investigate two regimes of the high density and low density separately. As a vital program, in the case of a massless gluon and massless quarks at finite temperature, we also present a geometry of thermodynamics for the gluon and Bosons using a Legendre invariance metric, it is so called as geometrothermodynamic (GTD) to better understanding of the phase transition. The GTD metric and its second order scalar invariant have been obtained, and we clarify the phase transition by study the singularities of the scalar curvature of this Riemannian metric. This method is ensemble dependence and to complete the phase transition. Meanwhile, we also investigate enthalpy and entropy and internal energy representations. Our work exposes new pictures of the nature of phase transitions in SQM. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6819v1.pdf"}
{"id": "1412.8501", "abstract": "  We establish a network formation game for the Internet's Autonomous System (AS) interconnection topology. The game includes different types of players, accounting for the heterogeneity of ASs in the Internet. We incorporate reliability considerations in the player's utility function, and analyze static properties of the game as well as its dynamic evolution. We provide dynamic analysis of its topological quantities, and explain the prevalence of some \"network motifs\" in the Internet graph. We assess our predictions with real-world data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.8501v1.pdf"}
{"id": "1501.02182", "abstract": "  We investigate the power of weak measurements in the framework of quantum state discrimination. First, we define and analyze the notion of weak consecutive measurements. Our main result is a convergence theorem whereby we demonstrate when and how a set of consecutive weak measurements converges to a strong measurement. Second, we show that for a small set of consecutive weak measurements, long before their convergence, one can separate close states without causing their collapse. We thus demonstrate a tradeoff between the success probability and the bias of the original vector towards collapse. Next we use post-selection within the Two-State-Vector Formalism and present the non-linear expansion of the expectation value of the measurement device's pointer to distinguish between two predetermined close vectors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.02182v1.pdf"}
{"id": "1501.04509", "abstract": "  Retrieval and content management are assumed to be mutually exclusive. In this paper we suggest that they need not be so. In the usual information retrieval scenario, some information about queries leading to a website (due to `hits' or `visits') is available to the server administrator of the concerned website. This information can used to better present the content on the website. Further, we suggest that some more information can be shared by the retrieval system with the content provider. This will enable the content provider (any website) to have a more dynamic presentation of the content that is in tune with the query trends, without violating the privacy of the querying user. The result will be a better synchronization between retrieval systems and content providers, with the purpose of improving the user's web search experience. This will also give the content provider a say in this process, given that the content provider is the one who knows much more about the content than the retrieval system. It also means that the content presentation may change in response to a query. In the end, the user will be able to find the relevant content more easily and quickly. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.04509v1.pdf"}
{"id": "1501.05004", "abstract": "  In this article we consider two spin-1/2 chains described, respectively, by the thermodynamic limit of the XY model with the usual two site interaction, and an extension of this model (without taking the thermodynamics limit), called XYT, were a three site interaction term is presented. To investigate the critical behaviour of such systems we employ tools from quantum information theory. Specifically, we show that the local quantum uncertainty, a quantity introduced in order to quantify the minimum quantum share of the variance of a local measurement, can be used to indicate quantum phase transitions presented by these models at zero temperature. Due to the connection of this quantity with the quantum Fisher information, the results presented here may be relevant for quantum metrology and quantum thermodynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.05004v1.pdf"}
{"id": "1501.06102", "abstract": "  This paper outlines research and development of a new Hadoop-based architecture for distributed processing and analysis of electron microscopy of brains. We show development of a new C++ library for implementation of 3D image analysis techniques, and deployment in a distributed map/reduce framework. We demonstrate our new framework on a subset of the Kasthuri11 dataset from the Open Connectome Project. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.06102v1.pdf"}
{"id": "1501.06544", "abstract": "  We calculate an s-wave amplitude matrix for all the possible 2–to–2 body scalar boson elastic scatterings in models with three scalar doublets, including contributions from the longitudinal component of weak gauge bosons via the Equivalence Theorem Approximation. Specifically, we concentrate on the two cases with two[one] active plus one[two] inert doublet fields, referred to as I(1+2)HDM[I(2+1)HDM], under CP conservation. We obtain three analytically irreducible sub-matrices with the 3× 3 form and eighteen eigenvalues for the amplitude matrix as an independent set, where the same formula can be applied to both models. By requiring a perturbative unitarity condition, we can constrain the magnitude of quartic coupling constants in the Higgs potential. This constraint, in particular in the I(1+2)HDM, can be translated into a bound on masses of extra active scalar bosons. Furthermore, when Standard Model-like Higgs boson couplings with weak gauge bosons are deviated from the Standard Model predictions, the unitarity condition provides an upper limit on the masses. We find that stronger upper bounds on the masses of the active CP-even and CP-odd Higgs bosons are obtained under the constraints from the unitarity and vacuum stability conditions, as well as the electroweak S, T and U parameters, as compared to those in 2-Higgs Doublet Models with a softly-broken Z_2 symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.06544v2.pdf"}
{"id": "1502.00223", "abstract": "  In this paper we present the discussion on the salient points of the computational analysis that are at the basis of the paper Rotation Curves of Galaxies by Fourth Order Gravity <cit.>. In fact in this paper any galactic component (bulge, disk and Dark matter component) required an onerous numerical computation since the Gauss theorem is not applicable in the Fourth Order Gravity. The computational and data analysis have been made with the software Mathematica^. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.00223v1.pdf"}
{"id": "1502.01055", "abstract": "  Here we focus on the description of the mechanisms behind the process of information aggregation and decision making, a basic step to understand emergent phenomena in society, such as trends, information spreading or the wisdom of crowds. In many situations, agents choose between discrete options. We analyze experimental data on binary opinion choices in humans. The data consists of two separate experiments in which humans answer questions with a binary response, where one is correct and the other is incorrect. The questions are answered without and with information on the answers of some previous participants. We find that a Bayesian approach captures the probability of choosing one of the answers. The influence of peers is uncorrelated with the difficulty of the question. The data is inconsistent with Weber's law, which states that the probability of choosing an option depends on the proportion of previous answers choosing that option and not on the total number of those answers. Last, the present Bayesian model fits reasonably well to the data as compared to some other previously proposed functions although the latter sometime perform slightly better than the Bayesian model. The asset of the present model is the simplicity and mechanistic explanation of the behavior. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.01055v1.pdf"}
{"id": "1502.02724", "abstract": "  This paper concerns stochastic perturbations of piecewise-smooth ODE systems relevant for vibro-impacting dynamics, where impact events constitute the primary source of randomness. Such systems are characterised by the existence of switching manifolds that divide the phase space into regions where the system is smooth. The initiation of impacts is captured by a grazing bifurcation, at which a periodic orbit describing motion without impacts develops a tangential intersection with a switching manifold. Oscillatory dynamics near regular grazing bifurcations are described by piecewise-smooth maps involving a square-root singularity, known as Nordmark maps. We consider three scenarios where coloured noise only affects impacting dynamics, and derive three two-dimensional stochastic Nordmark maps with the noise appearing in different nonlinear or multiplicative ways, depending on the source of the noise. Consequently the stochastic dynamics differs between the three noise sources, and is fundamentally different to that of a Nordmark map with additive noise. This critical dependence on the nature of the noise is illustrated with a prototypical one-degree-of-freedom impact oscillator. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.02724v1.pdf"}
{"id": "1502.04067", "abstract": "  Bursting neurons fire rapid sequences of action potential spikes followed by a quiescent period. The basic dynamical mechanism of bursting is the slow currents that modulate a fast spiking activity caused by rapid ionic currents. Minimal models of bursting neurons must include both effects. We considered one of these models and its relation with a generalized Kuramoto model, thanks to the definition of a geometrical phase for bursting and a corresponding frequency. We considered neuronal networks with different connection topologies and investigated the transition from a non-synchronized to a partially phase-synchronized state as the coupling strength is varied. The numerically determined critical coupling strength value for this transition to occur is compared with theoretical results valid for the generalized Kuramoto model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.04067v1.pdf"}
{"id": "1502.04612", "abstract": "  We present simultaneous multi-color optical photometry using ULTRACAM of the transiting exoplanet KIC 12557548 b (also known as KIC 1255 b). This reveals, for the first time, the color dependence of the transit depth. Our g and z transits are similar in shape to the average Kepler short-cadence profile, and constitute the highest-quality extant coverage of individual transits. Our Night 1 transit depths are 0.85 +/- 0.04", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.04612v1.pdf"}
{"id": "1502.04719", "abstract": "  We compute the decoupling constant ζ_m relating light quark masses of effective n_l-flavour QCD to (n_l+1)-flavour QCD to four-loop order. Immediate applications are the evaluation of the MS charm quark mass with five active flavours and the bottom quark mass at the scale of the top quark or even at GUT scales. With the help of a low-energy theorem ζ_m can be used to obtain the effective coupling of a Higgs boson to light quarks with five-loop accuracy. We briefly discuss the influence on Γ(H→ bb̅). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.04719v2.pdf"}
{"id": "1502.06991", "abstract": "  If the photospheres of solar-type stars represent the composition of circumstellar disks from which any planets formed, spectroscopic determinations of stellar elemental abundances offer information on the composition of those planets, including smaller, rocky planets. In particular, the C/O ratio is proposed to be a key determinant of the composition of solids that condense from disk gas and are incorporated into planets. Also, planets may leave chemical signatures on the photospheres of their host stars by sequestering heavy elements, or by being accreted by the stars. The presence, absence, and composition of planets could be revealed by small differences in the relative abundances between stars. I critically examine these scenarios and show that (i) a model of Galactic chemical evolution predicts that the C/O ratio is expected to be close to the solar value and vary little between dwarf stars in the solar neighborhood; (ii) spectroscopic surveys of M dwarf stars limit the occurrence of stars with C/O ≳ 1 to <10^-3; and (iii) planetesimal chemistry will be controlled by the composition of oxygen-rich dust inherited from the molecular cloud and processed in a dust-rich environment, not a gas with the stellar composition. A second generation of more reduced planetesimals could be produced by re-equilibration of some material with dust-depleted gas. Finally, I discuss how minor differences in relative abundances between stars that correlate with condensation temperature can be explained by dust-gas segregation, perhaps in circumstellar disks, rather than planet formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.06991v1.pdf"}
{"id": "1502.07056", "abstract": "  We consider linear and nonlinear modes pinned to a grating-free (gapless) layer placed between two symmetric or asymmetric semi-infinite Bragg gratings (BGs), with a possible phase shift between them, in a medium with the uniform Kerr nonlinearity. The asymmetry is defined by a difference between bandgap widths in the two BGs. In the linear system, exact defect modes (DMs) are found. Composite gap solitons pinned to the central layer are found too, in analytical and numerical forms, in the nonlinear model. In the asymmetric system, existence boundaries for the DMs and gap solitons, due to the competition between attraction to the gapless layer and repulsion from the reflectivity step, are obtained analytically. Stability boundaries for solitons in the asymmetric system are identified by means of direct simulations. Collisions of moving BG solitons with the gapless layer are studied too. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.07056v1.pdf"}
{"id": "1502.07553", "abstract": "  The opening of a gap in single-layer graphene is often ascribed to the breaking of the equivalence between the two carbon sublattices. We show by angle-resolved photoemission spectroscopy that Ir- and Na-modified graphene grown on the Ir(111) surface presents a very large unconventional gap that can be described in terms of a phenomenological \"massless\" Dirac model. We discuss the consequences and differences of this model in comparison of the standard massive gap model, and we investigate the conditions under which such anomalous gap can arise from a spontaneous symmetry breaking. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.07553v1.pdf"}
{"id": "1503.01573", "abstract": "  The magnitude of the spin polarization at the Fermi level of ferromagnetic materials at room temperature is a key property for spintronics. Investigating the Heusler compound Co_2MnSi a value of 93% for the spin polarization has been observed at room temperature, where the high spin polarization is related to a stable surface resonance in the majority band extending deep into the bulk. In particular, we identified in our spectroscopical analysis that this surface resonance is embedded in the bulk continuum with a strong coupling to the majority bulk states. The resonance behaves very bulk-like, as it extends over the first six atomic layers of the corresponding (001)-surface. Our study includes experimental investigations, where the bulk electronic structure as well as surface-related features have been investigated using spin-resolved photoelectron spectroscopy (SR-UPS) and for a larger probing depth spin-integrated high energy x-ray photoemission spectroscopy (HAXPES). The results are interpreted in comparison with first-principles band structure and photoemission calculations which consider all relativistic, surface and high-energy effects properly. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.01573v1.pdf"}
{"id": "1503.04394", "abstract": "  Weyl semimetals are three-dimensional topological states of matter, in a sense that they host paired monopoles and antimonopoles of Berry curvature in momentum space, leading to the chiral anomaly. The chiral anomaly has long been believed to give a positive magnetoconductivity or negative magnetoresistivity in strong and parallel fields. However, several recent experiments on both Weyl and Dirac topological semimetals show a negative magnetoconductivity in high fields. Here, we study the magnetoconductivity of Weyl and Dirac semimetals in the presence of short-range scattering potentials. In a strong magnetic field applied along the direction that connects two Weyl nodes, we find that the conductivity along the field direction is determined by the Fermi velocity, instead of by the Landau degeneracy. We identify three scenarios in which the high-field magnetoconductivity is negative. Our findings show that the high-field positive magnetoconductivity may not be a compelling signature of the chiral anomaly and will be helpful for interpreting the inconsistency in the recent experiments and earlier theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.04394v3.pdf"}
{"id": "1503.06330", "abstract": "  We propose a parallel adaptive constraint-tightening approach to solve a linear model predictive control problem for discrete-time systems, based on inexact numerical optimization algorithms and operator splitting methods. The underlying algorithm first splits the original problem in as many independent subproblems as the length of the prediction horizon. Then, our algorithm computes a solution for these subproblems in parallel by exploiting auxiliary tightened subproblems in order to certify the control law in terms of suboptimality and recursive feasibility, along with closed-loop stability of the controlled system. Compared to prior approaches based on constraint tightening, our algorithm computes the tightening parameter for each subproblem to handle the propagation of errors introduced by the parallelization of the original problem. Our simulations show the computational benefits of the parallelization with positive impacts on performance and numerical conditioning when compared with a recent nonparallel adaptive tightening scheme. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.06330v1.pdf"}
{"id": "1503.06399", "abstract": "  We study the concurrence of entanglement between two quantum dots in contact to Majorana bound states on a floating superconducting island. The distance between the Majorana states, the charging energy of the island, and the average island charge are shown to be decisive parameters for the efficiency of entanglement generation. We find that long-range entanglement with basically distance-independent concurrence is possible over wide parameter regions, where the proposed setup realizes a \"Majorana entanglement bridge\". We also study the time-dependent concurrence obtained after one of the tunnel couplings is suddenly switched on, which reveals the timescales for generating entanglement. Accurate analytical expressions for the concurrence are derived both for the static and the time-dependent case. Our results indicate that entanglement formation in interacting Majorana devices can be fully understood in terms of an interplay of elastic cotunneling (also referred to as \"teleportation\") and crossed Andreev reflection processes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.06399v2.pdf"}
{"id": "1503.07193", "abstract": "  This paper studies an optimal control problem for continuous-time stochastic systems subject to reachability objectives specified in a subclass of metric interval temporal logic specifications, a temporal logic with real-time constraints. We propose a probabilistic method for synthesizing an optimal control policy that maximizes the probability of satisfying a specification based on a discrete approximation of the underlying stochastic system. First, we show that the original problem can be formulated as a stochastic optimal control problem in a state space augmented with finite memory and states of some clock variables. Second, we present a numerical method for computing an optimal policy with which the given specification is satisfied with the maximal probability in point-based semantics in the discrete approximation of the underlying system. We show that the policy obtained in the discrete approximation converges to the optimal one for satisfying the specification in the continuous or dense-time semantics as the discretization becomes finer in both state and time. Finally, we illustrate our approach with a robotic motion planning example. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.07193v2.pdf"}
{"id": "1503.08022", "abstract": "  We discuss four-jet production at the LHC. We calculate cross section for both single-parton scattering (SPS) using the ALPGEN code as well as for double-parton scattering (DPS) in leading-order collinear approach. Our results are compared with experimental data obtained recently by the CMS collaboration. We show that the ALPGEN code relatively well describes distributions in transverse momenta and rapidity of each of the four jets ordered by their transverse momenta (leading, subleading etc.). The SPS mechanism does not explain the distributions at large rapidity for the leading jet. The DPS mechanism considerably improves the agreement with the experimental data in this corner of the phase space. In order to enhance the relative DPS contribution we propose to impose different cuts. The relative DPS contribution increases when decreasing the lower cut on the jet transverse momenta as well as when a low lower cut on the rapidity distance between the most remote jets is imposed. We predict very flat distribution in azimuthal angle between the most remote jets with low lower cuts on jets transverse momentum. We identify phase-space corners where the DPS content is enhanced relatively to the SPS one. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.08022v1.pdf"}
{"id": "1503.08125", "abstract": "  We define and study in detail utraslow scaled Brownian motion (USBM) characterised by a time dependent diffusion coefficient of the form D(t)≃ 1/t. For unconfined motion the mean squared displacement (MSD) of USBM exhibits an ultraslow, logarithmic growth as function of time, in contrast to the conventional scaled Brownian motion. In an harmonic potential the MSD of USBM does not saturate but asymptotically decays inverse-proportionally to time, reflecting the highly non-stationary character of the process. We show that the process is weakly non-ergodic in the sense that the time averaged MSD does not converge to the regular MSD even at long times, and for unconfined motion combines a linear lag time dependence with a logarithmic term. The weakly non-ergodic behaviour is quantified in terms of the ergodicity breaking parameter. The USBM process is also shown to be ageing: observables of the system depend on the time gap between initiation of the test particle and start of the measurement of its motion. Our analytical results are shown to agree excellently with extensive computer simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.08125v1.pdf"}
{"id": "1503.08567", "abstract": "  We present the Spitzer Archival Far-InfraRed Extragalactic Survey (SAFIRES). This program produces refined mosaics and source lists for all far-infrared extragalactic data taken during the more than six years of the cryogenic operation of the Spitzer Space Telescope. The SAFIRES products consist of far-infrared data in two wavelength bands (70 um and 160 um) across approximately 180 square degrees of sky, with source lists containing far-infrared fluxes for almost 40,000 extragalactic point sources. Thus, SAFIRES provides a large, robust archival far-infrared data set suitable for many scientific goals. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.08567v1.pdf"}
{"id": "1503.08782", "abstract": "  The problem of estimating the delays and amplitudes of a positive stream of pulses appears in many applications, such as single-molecule microscopy. This paper suggests estimating the delays and amplitudes using a convex program, which is robust in the presence of noise (or model mismatch). Particularly, the recovery error is proportional to the noise level. We further show that the error grows exponentially with the density of the delays and also depends on the localization properties of the pulse. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.08782v3.pdf"}
{"id": "1503.08812", "abstract": "  We propose a class of models which generate three-dimensional random volumes, where each configuration consists of triangles glued together along multiple hinges. The models have matrices as the dynamical variables and are characterized by semisimple associative algebras A. Although most of the diagrams represent configurations which are not manifolds, we show that the set of possible diagrams can be drastically reduced such that only (and all of the) three-dimensional manifolds with tetrahedral decompositions appear, by introducing a color structure and taking an appropriate large N limit. We examine the analytic properties when A is a matrix ring or a group ring, and show that the models with matrix ring have a novel strong-weak duality which interchanges the roles of triangles and hinges. We also give a brief comment on the relationship of our models with the colored tensor models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.08812v2.pdf"}
{"id": "1504.01598", "abstract": "  Successful realization of polarized Drell-Yan physics program is one of the main goals of the second stage of the COMPASS experiment. Drell-Yan measurements with high energy (190 GeV/c) pion beam and transversely polarized NH3 target have been initiated by a pilot-run in the October 2014 and will be followed by 140 days of data taking in 2015. In the past twelve years COMPASS experiment performed series of SIDIS measurements with high energy muon beam and transversely polarized deuteron and proton targets. Results obtained for Sivers effect and other target transverse spin dependent and unpolarized azimuthal asymmetries in SIDIS serve as an important input for general understanding of spin-structure of the nucleon and are being used in numerous theoretical and phenomenological studies being carried out in the field of transvers-spin physics. Measurement of the Sivers and all other azimuthal effects in polarized Drell-Yan at COMPASS will reveal another side of the spin-puzzle providing a link between SIDIS and Drell-Yan branches. This will be a unique possibility to test universality and key-features of transverse momentum dependent distribution functions (TMD PDFs) using essentially same experimental setup and exploring same kinematic domain. In this review man physics aspects of future COMPASS polarized Drell-Yan measurement of azimuthal transverse spin asymmetries will be presented, giving a particular emphasis on the link with very recent COMPASS results obtained for SIDIS transverse spin asymmetries from four \"Drell-Yan\" Q^2-ranges. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.01598v2.pdf"}
{"id": "1504.03676", "abstract": "  We continue our investigation of 2+1 flavor QCD thermodynamics using dynamical Wilson fermions in the fixed scale approach. Two additional pion masses, approximately 440 MeV and 285 MeV, are added to our previous work at 545 MeV. The simulations were performed at 3 or 4 lattice spacings at each pion mass. The renormalized chiral condensate, strange quark number susceptibility and Polyakov loop is obtained as a function of the temperature and we observe a decrease in the light chiral pseudo-critical temperature as the pion mass is lowered while the pseudo-critical temperature associated with the strange quark number susceptibility or the Polyakov loop is only mildly sensitive to the pion mass. These findings are in agreement with previous continuum results obtained in the staggered formulation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.03676v2.pdf"}
{"id": "1504.04626", "abstract": "  Many core-collapse supernova progenitors are presumed to be in binary systems. If a star explodes in a binary system, the early supernova light curve can be brightened by the collision of the supernova ejecta with the companion star. The early brightening can be observed when the observer is in the direction of the hole created by the collision. Based on a population synthesis model, we estimate the fractions of core-collapse supernovae in which the light-curve brightening by the collision can be observed. We find that 0.19", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.04626v2.pdf"}
{"id": "1504.05157", "abstract": "  We investigate the quark-gluon three-point correlation function within a one-loop computation performed in the Curci-Ferrari massive extension of the Faddeev-Popov gauge-fixed action. The mass term is used as a minimal way for taking into account the influence of the Gribov ambiguity. Our results, with renormalization-group improvement, are compared with lattice data. We show that the comparison is in general very satisfactory for the functions which are compatible with chiral symmetry, except for one. We argue that this may be due to large systematic errors when extracting this function from lattice simulations. The quantities which break chiral symmetry are more sensitive to the details of the renormalization scheme. We however manage to reproduce some of them with good precision. The chosen parameters allow to simultaneously fit the quark mass function coming from the quark propagator with a reasonably agreement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.05157v3.pdf"}
{"id": "1504.07160", "abstract": "  We present new integral field spectroscopy of the gravitationally lensed broad absorption line (BAL) quasar H1413+117, covering the ultraviolet to visible rest-frame spectral range. We observe strong microlensing signatures in lensed image D, and we use this microlensing to simultaneously constrain both the broad emission and broad absorption line gas. By modeling the lens system over the range of probable lensing galaxy redshifts and using on a new argument based on the wavelength-independence of the broad line lensing magnifications, we determine that there is no significant broad line emission from smaller than  20 light days. We also perform spectral decomposition to derive the intrinsic broad emission line (BEL) and continuum spectrum, subject to BAL absorption. We also reconstruct the intrinsic BAL absorption profile, whose features allow us to constrain outflow kinematics in the context of a disk-wind model. We find a very sharp, blueshifted onset of absorption of 1,500 km/s in both C IV and N V that may correspond to an inner edge of a disk-wind's radial outflow. The lower ionization Si IV and Al III have higher-velocity absorption onsets, consistent with a decreasing ionization parameter with radius in an accelerating outflow. There is evidence of strong absorption in the BEL component which indicates a high covering factor for absorption over two orders of magnitude in outflow radius. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.07160v1.pdf"}
{"id": "1505.00155", "abstract": "  Culinary systems, the practice of preparing a refined combination of ingredients that is palatable as well as socially acceptable, are examples of complex dynamical systems. They evolve over time and are affected by a large number of factors. Modeling the dynamic nature of evolution of regional cuisines may provide us a quantitative basis and exhibit underlying processes that have driven them into the present day status. This is especially important given that the potential culinary space is practically infinite because of possible number of ingredient combinations as recipes. Such studies also provide a means to compare and contrast cuisines and to unearth their therapeutic value. Herein we provide rigorous analysis of modeling eight diverse Indian regional cuisines, while also highlighting their uniqueness, and a comparison among those models at the level of flavor compounds which opens up molecular level studies associating them especially with non-communicable diseases such as diabetes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.00155v1.pdf"}
{"id": "1505.01965", "abstract": "  We consider a Friedmann-Robertson-Walker spacetime filled with both viscous radiation and nonviscous dust. The former has a bulk viscosity which is proportional to an arbitrary power of the energy density, i.e. ζ∝ρ_v^ν, and viscous pressure satisfying a nonlinear evolution equation. The analysis is carried out in the context of dynamical systems and the properties of solutions corresponding to the fixed points are discussed. For some ranges of the relevant parameter ν we find that the trajectories in the phase space evolve from a FRW singularity towards an asymptotic de Sitter attractor, confirming and extending previous analysis in the literature. For other values of the parameter, instead, the behaviour differs from previous works. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.01965v1.pdf"}
{"id": "1505.02199", "abstract": "  We describe the first DNA-based storage architecture that enables random access to data blocks and rewriting of information stored at arbitrary locations within the blocks. The newly developed architecture overcomes drawbacks of existing read-only methods that require decoding the whole file in order to read one data fragment. Our system is based on new constrained coding techniques and accompanying DNA editing methods that ensure data reliability, specificity and sensitivity of access, and at the same time provide exceptionally high data storage capacity. As a proof of concept, we encoded parts of the Wikipedia pages of six universities in the USA, and selected and edited parts of the text written in DNA corresponding to three of these schools. The results suggest that DNA is a versatile media suitable for both ultrahigh density archival and rewritable storage applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.02199v1.pdf"}
{"id": "1505.04525", "abstract": "  We revise the Levy's construction of Brownian motion as a simple though still rigorous approach to operate with various Gaussian processes. A Brownian path is explicitly constructed as a linear combination of wavelet-based \"geometrical features\" at multiple length scales with random weights. Such a wavelet representation gives a closed formula mapping of the unit interval onto the functional space of Brownian paths. This formula elucidates many classical results about Brownian motion (e.g., non-differentiability of its path), providing intuitive feeling for non-mathematicians. The illustrative character of the wavelet representation, along with the simple structure of the underlying probability space, is different from the usual presentation of most classical textbooks. Similar concepts are discussed for fractional Brownian motion, Ornstein-Uhlenbeck process, Gaussian free field, and fractional Gaussian fields. Wavelet representations and dyadic decompositions form the basis of many highly efficient numerical methods to simulate Gaussian processes and fields, including Brownian motion and other diffusive processes in confining domains. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.04525v1.pdf"}
{"id": "1505.05049", "abstract": "  The structural transformation of multiferroic EuTiO_3 has been intensively investigated by synchrotron x-ray diffraction at pressures up to 50.3 GPa and temperatures from 50 to 500 K. An antiferrodistortive phase transition from cubic Pm-3m to tetragonal I4/mcm space group has been observed, identical to the one that has been previously explored at ambient pressure and low temperatures. Several compression/decompression cycles at different temperatures have been carried out to accurately map the transition, and as a result a P-T phase diagram for EuTiO_3 has been constructed. The observed phase transition exhibits many similarities with isostructural SrTiO_3, although the absence of magnetoelectric interactions in the latter accounts for the different phase boundaries between the two materials. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.05049v1.pdf"}
{"id": "1505.05759", "abstract": "  Following the 12 GeV upgrade, a dedicated experiment is planned with the Hall B CLAS12 detector at Jefferson Lab, with the aim to study electroproduction of nucleon resonances at high photon virtualities up to Q^2 = 12 GeV^2. In this work we present a QCD-based approach to the theoretical interpretation of these upcoming results in the framework of light-cone sum rules that combine perturbative calculations with dispersion relations and duality. The form factors are thus expressed in terms of N^∗(1535) light-front wave functions at small transverse separations, called distribution amplitudes. The distribution amplitudes can therefore be determined from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations. The results of the corresponding next-to-leading order calculation are presented and compared with the existing data. We find that the form factors are dominated by the twist-four distribution amplitudes that are related to the P-wave three-quark wave functions of the N^∗(1535), i.e. to contributions of orbital angular momentum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.05759v2.pdf"}
{"id": "1505.06334", "abstract": "  We consider renormalisable models extended in the scalar sector by a generic scalar field in addition to the standard model Higgs boson field, and work out the effective theory for the latter in the decoupling limit. We match the full theory onto the effective theory at tree and one-loop levels, and concentrate on dimension-6 operators of the Higgs and electroweak gauge fields induced from such matching. The Wilson coefficients of these dimension-6 operators from tree-level matching are further improved by renormalisation group running. For specific SU(2)_L representations of the scalar field, some \"accidental\" couplings with the Higgs field are allowed and can lead to dimension-6 operators at tree and/or one-loop level. Otherwise, two types of interaction terms are identified to have only one-loop contributions, for the Wilson coefficients of which we have obtained a general formula. Using the obtained results, we analyse constraints from electroweak oblique parameters and the Higgs data on several phenomenological models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.06334v2.pdf"}
{"id": "1505.06450", "abstract": "  Growth dynamic of real networks because of emerging complexities is an open and interesting question. Indeed it is not realistic to ignore history impact on the current events. The mystery behind that complexity could be in the role of history in some how. To regard this point, the average effect of history has been included by a kernel function in differential equation of Barabasi Albert (BA) model . This approach leads to a fractional order BA differential equation as a generalization of BA model. As opposed to unlimited growth for degree of nodes, our results show that over time the memory impact will cause a decay for degrees. This gives a higher chance to younger members for turning to a hub. In fact in a real network, there are two competitive processes. On one hand, based on preferential attachment mechanism nodes with higher degree are more likely to absorb links. On the other hand, node history through aging process prevents new connections. Our findings from simulating a network grown by considering these effects also from studying a real network of collaboration between Hollywood movie actors conforms the results and significant effects of history and time on dynamic. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.06450v1.pdf"}
{"id": "1505.07079", "abstract": "  Information Visualization techniques are built on a context with many factors related to both vision and cognition, making it difficult to draw a clear picture of how data visually turns into comprehension. In the intent of promoting a better picture, here, we survey concepts on vision, cognition, and Information Visualization organized in a theorization named Visual Expression Process. Our theorization organizes the basis of visualization techniques with a reduced level of complexity; still, it is complete enough to foster discussions related to design and analytical tasks. Our work introduces the following contributions: (1) a Theoretical compilation of vision, cognition, and Information Visualization; (2) Discussions supported by vast literature; and (3) Reflections on visual-cognitive aspects concerning use and design. We expect our contributions will provide further clarification about how users and designers think about InfoVis, leveraging the potential of systems and techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.07079v2.pdf"}
{"id": "1505.07378", "abstract": "  A simulation of neutrons traversing a shield beneath the COMET scintillator strip cosmic-veto counter is accomplished using the Geant4 toolkit. A Geant4 application is written with an appropriate detector construction and a possible spectrum of neutron's energy. The response of scintillator strips to neutrons is studied in detail. A design of the shield is optimized to ensure the time loss concerned with fake veto signals caused by neutrons from muon captures is tolerable. Materials of shield layers are chosen, and optimum thicknesses of the layers are computed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.07378v1.pdf"}
{"id": "1505.07417", "abstract": "  During LHC Run 1, the LHCb experiment recorded around 10^11 collision events. This paper describes Event Index - an event search system. Its primary function is to quickly select subsets of events from a combination of conditions, such as the estimated decay channel or number of hits in a subdetector. Event Index is essentially Apache Lucene optimized for read-only indexes distributed over independent shards on independent nodes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.07417v2.pdf"}
{"id": "1506.00513", "abstract": "  In analogy to III-V compounds, which have significantly broadened the scope of group IV semiconductors, we propose IV-VI compounds as isoelectronic counterparts to layered group V semiconductors. Using ab initio density functional theory, we study yet unrealized structural phases of silicon mono-sulfide (SiS). We find the black-phosphorus-like α-SiS to be almost equally stable as the blue-phosphorus-like β-SiS. Both α-SiS and β-SiS monolayers display a significant, indirect band gap that depends sensitively on the in-layer strain. Unlike 2D semiconductors of group V elements with the corresponding nonplanar structure, different SiS allotropes show a strong polarization either within or normal to the layers. We find that SiS may form both lateral and vertical heterostructures with phosphorene at a very small energy penalty, offering an unprecedented tunability in structural and electronic properties of SiS-P compounds. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.00513v1.pdf"}
{"id": "1506.00888", "abstract": "  We derive a local-time path-integral representation for a generic one-dimensional time-independent system. In particular, we show how to rephrase the matrix elements of the Bloch density matrix as a path integral over x-dependent local-time profiles. The latter quantify the time that the sample paths x(t) in the Feynman path integral spend in the vicinity of an arbitrary point x. Generalization of the local-time representation that includes arbitrary functionals of the local time is also provided. We argue that the results obtained represent a powerful alternative to the traditional Feynman-Kac formula, particularly in the high and low temperature regimes. To illustrate this point, we apply our local-time representation to analyze the asymptotic behavior of the Bloch density matrix at low temperatures. Further salient issues, such as connections with the Sturm-Liouville theory and the Rayleigh-Ritz variational principle are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.00888v1.pdf"}
{"id": "1506.00988", "abstract": "  We present new traversable wormhole and non-singular black hole solutions in pure, scale-free R^2 gravity. These exotic solutions require no null energy condition violating or \"exotic\" matter and are supported only by the vacuum of the theory. It is well known that f(R) theories of gravity may be recast as dual theories in the Einstein frame. The solutions we present are found when the conformal transformation required to move to the dual frame is singular. For quadratic R^2 gravity, the required conformal factor is identically zero for spacetimes with R=0. Solutions in this case are argued to arise in the strong coupling limit of General Relativity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.00988v2.pdf"}
{"id": "1506.01283", "abstract": "  Well-ordered ultrathin films of NiO have been prepared on an Ag(001) substrate using molecular beam epitaxy. With the help of angle-resolved two-photon photoemission (2PPE) a series of image potential states (IPS) for film thicknesses of 2–4 monolayers (ML) has been identified. By time-resolved 2PPE, the lifetimes of the first three IPS and their dependence on the oxide film thickness have been determined. While the lifetimes of the (n=1) IPS are all in the range of 27–42 fs, the values for the (n=2) IPS decrease from 85 fs for 2 ML to 33 fs for 4 ML. These differences are discussed in terms of a coupling to the layer-dependent electronic structure of the NiO ultrathin films. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.01283v1.pdf"}
{"id": "1506.01364", "abstract": "  It is shown that three-dimensional systems of coupled quantum wires support fractional topological phases composed of closed loops and open planes of two-dimensional fractional quantum Hall subsystems. These phases have topologically protected edge states, and are separated by exotic quantum phase transitions corresponding to a rearrangement of fractional quantum Hall edge modes. Some support for the existence of an extended exotic critical phase separating the bulk gapped fractional topological phases is given. Without electron-electron interactions, similar but unfractionalized bulk gapped phases based on coupled integer quantum Hall states exist. They are separated by an extended critical Weyl semimetal phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.01364v4.pdf"}
{"id": "1506.01815", "abstract": "  We present here a method for the extraction of the differential phase of an atom gradiometer that exploits the correlation of the vibration signal measured by an auxiliary classical sensor, such as a seismometer or an accelerometer. We show that sensitivities close to the quantum projection noise limit can be reached, even when the vibration noise induces phase fluctuations larger than 2π. This method doesn't require the correlation between the atomic and classical signals to be perfect and allows for an exact determination of the differential phase, with no bias. It can also be applied to other configurations of differential interferometers, such as for instance gyrometers, conjugate interferometers for the measurement of the fine structure constant, or differential accelerometers for tests of the equivalence principle or detection of gravitational waves. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.01815v1.pdf"}
{"id": "1506.02291", "abstract": "  We give two determinantal representations for a bivariate polynomial. They may be used to compute the zeros of a system of two of these polynomials via the eigenvalues of a two-parameter eigenvalue problem. The first determinantal representation is suitable for polynomials with scalar or matrix coefficients, and consists of matrices with asymptotic order n^2/4, where n is the degree of the polynomial. The second representation is useful for scalar polynomials and has asymptotic order n^2/6. The resulting method to compute the roots of a system of two bivariate polynomials is competitive with some existing methods for polynomials up to degree 10, as well as for polynomials with a small number of terms. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.02291v1.pdf"}
{"id": "1506.05222", "abstract": "  In this paper, a new mathematical framework to the analysis of millimeter wave cellular networks is introduced. Its peculiarity lies in considering realistic path-loss and blockage models, which are derived from experimental data recently reported in the literature. The path-loss model accounts for different distributions for line-of-sight and non-line-of-sight propagation conditions and the blockage model includes an outage state that provides a better representation of the outage possibilities of millimeter wave communications. By modeling the locations of the base stations as points of a Poisson point process and by relying upon a noise-limited approximation for typical millimeter wave network deployments, exact integral expressions for computing the coverage probability and the average rate are obtained. With the aid of Monte Carlo simulations, the noise-limited approximation is shown to be sufficiently accurate for typical network densities. Furthermore, it is shown that sufficiently dense millimeter wave cellular networks are capable of outperforming micro wave cellular networks, both in terms of coverage probability and average rate. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.05222v1.pdf"}
{"id": "1506.05650", "abstract": "  The quenching of oscillations in interacting systems leads to several unwanted situations, which necessitate a suitable remedy to overcome the quenching. In this connection, this work addresses a mechanism that can resurrect oscillations in a typical situation. Through both numerical and analytical studies, we show the candidate which is capable of resurrecting oscillations is nothing but the feedback, the one which is profoundly used in dynamical control and in bio-therapies. Even in the case of a rather general system, we demonstrate analytically the applicability of the technique over one of the oscillation quenched states called amplitude death state. We also discuss some of the features of this mechanism such as adaptability of the technique with the feedback of only a few of the oscillators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.05650v2.pdf"}
{"id": "1506.05995", "abstract": "  We calculate the joint distribution P(S,Q) of the scattering matrix S and time-delay matrix Q=-iħ S^† dS/dE of a chaotic quantum dot coupled by point contacts to metal electrodes. While S and Q are statistically independent for ballistic coupling, they become correlated for tunnel coupling. We relate the ensemble averages of Q and S and thereby obtain the average density of states at the Fermi level. We apply this to a calculation of the effect of a tunnel barrier on the Majorana resonance in a topological superconductor. We find that the presence of a Majorana bound state is hidden in the density of states and in the thermal conductance if even a single scattering channel has unit tunnel probability. The electrical conductance remains sensitive to the appearance of a Majorana bound state, and we calculate the variation of the average conductance through a topological phase transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.05995v1.pdf"}
{"id": "1506.07479", "abstract": "  Embedding of the 5-dimensional (5D) space of the Bohr Hamiltonian with a deformation-dependent mass (DDM) into a 6-dimensional (6D) space shows that the free parameter in the dependence of the mass on the deformation is connected to the curvature of the 5D space, with the special case of constant mass corresponding to a flat 5D space. Comparison of the DDM Bohr Hamiltonian to the 5D classical limit of Hamiltonians of the 6D interacting boson model (IBM), shows that the DDM parameter is proportional to the strength of the pairing interaction in the U(5) (vibrational) symmetry limit, while it is proportional to the quadrupole-quadrupole interaction in the SU(3) (rotational) symmetry limit, and to the difference of the pairing interactions among s, d bosons and d bosons alone in the O(6) (gamma-soft) limit. The presence of these interactions leads to a curved 5D space in the classical limit of IBM, in contrast to the flat 5D space of the original Bohr Hamiltonian, which is made curved by the introduction of the deformation-dependent mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.07479v1.pdf"}
{"id": "1506.08641", "abstract": "  Power grid outages cause huge economical and societal costs. Disruptions in the power distribution grid are responsible for a significant fraction of electric power unavailability to customers. The impact of extreme weather conditions, continuously increasing demand, and the over-ageing of assets in the grid, deteriorates the safety of electric power delivery in the near future. It is this dependence on electric power that necessitates further research in the power distribution grid security assessment. Thus measures to analyze the robustness characteristics and to identify vulnerabilities as they exist in the grid are of utmost importance. This research investigates exactly those concepts- the vulnerability and robustness of power distribution grids from a topological point of view, and proposes a metric to quantify them with respect to assets in a distribution grid. Real-world data is used to demonstrate the applicability of the proposed metric as a tool to assess the criticality of assets in a distribution grid. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.08641v1.pdf"}
{"id": "1507.01361", "abstract": "  We study cascaded harmonic generation of hybrid surface plasmons in integrated planar waveguides composed of a graphene layer and a doped-semiconductor slab. We derive a comprehensive model of cascaded third harmonic generation through phase-matched nonlinear interaction of fundamental, second harmonic and third harmonic plasmonic modes supported by the structure. We show that hybrid graphene-semiconductor waveguides can simultaneously phase-match these three interacting harmonics, increasing the total third-harmonic output by a factor of 5 compared to the non-cascaded regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.01361v1.pdf"}
{"id": "1507.01764", "abstract": "  The ongoing 11-year cycle of solar activity is considerably less vigorous than the three cycles before. It was preceded by a very deep activity minimum with a low polar magnetic flux, the source of the toroidal field responsible for solar magnetic activity in the subsequent cycle. Simulation of the evolution of the solar surface field shows that the weak polar fields and thus the weakness of the present cycle 24 are mainly caused by a number of bigger bipolar regions emerging at low latitudes with a `wrong' (i.e., opposite to the majority for this cycle) orientation of their magnetic polarities in the North-South direction, which impaired the growth of the polar field. These regions had a particularly strong effect since they emerged within ±10^∘ latitude from the solar equator. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.01764v1.pdf"}
{"id": "1507.02735", "abstract": "  We study a stochastically-driven standard map. The addition of a noise term destroys the invariant manifolds that organize the phase space which allows for more widespread transport than in the noiseless case. Using appropriately defined hitting times to quantify the dynamics, we identify two qualitatively different classes of transport: linear and nonlinear. Linear transport is primarily driven by the stochasticity in the system, while nonlinear transport results from a combination of the nonlinear dynamics and stochasticity and provides a significant speed-up in transport. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.02735v1.pdf"}
{"id": "1507.05211", "abstract": "  Phylogenetic trees are a central tool in understanding evolution. They are typically inferred from sequence data, and capture evolutionary relationships through time. It is essential to be able to compare trees from different data sources (e.g. several genes from the same organisms) and different inference methods. We propose a new metric for robust, quantitative comparison of rooted, labeled trees. It enables clear visualizations of tree space, gives meaningful comparisons between trees, and can detect distinct islands of tree topologies in posterior distributions of trees. This makes it possible to select well-supported summary trees. We demonstrate our approach on Dengue fever phylogenies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.05211v3.pdf"}
{"id": "1507.07096", "abstract": "  The object recognition is a complex problem in the image processing. Mathematical morphology is Shape oriented operations, that simplify image data, preserving their essential shape characteristics and eliminating irrelevancies. This paper briefly describes morphological operators using hypergraph and its applications for thinning algorithms. The morphological operators using hypergraph method is used to preventing errors and irregularities in skeleton, and is an important step recognizing line objects. The morphological operators using hypergraph such as dilation, erosion, opening, closing is a novel approach in image processing and it act as a filter remove the noise and errors in the images. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.07096v1.pdf"}
{"id": "1507.07773", "abstract": "  We study relaxation times, also called mixing times, of quantum many-body systems described by a Lindblad master equation. We in particular study the scaling of the spectral gap with the system length, the so-called dynamical exponent, identifying a number of transitions in the scaling. For systems with bulk dissipation we generically observe different scaling for small and for strong dissipation strength, with a critical transition strength going to zero in the thermodynamic limit. We also study a related phase transition in the largest decay mode. For systems with only boundary dissipation we show a generic bound that the gap can not be larger than 1/L. In integrable systems with boundary dissipation one typically observes scaling 1/L^3, while in chaotic ones one can have faster relaxation with the gap scaling as 1/L and thus saturating the generic bound. We also observe transition from exponential to algebraic gap in systems with localized modes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.07773v2.pdf"}
{"id": "1507.08786", "abstract": "  We have studied the filaments extracted from the column density maps of the nearby Lupus 1, 3, and 4 molecular clouds, derived from photometric maps observed with the Herschel satellite. Filaments in the Lupus clouds have quite low column densities, with a median value of ∼1.5×10^21 cm^-2 and most have masses per unit length lower than the maximum critical value for radial gravitational collapse. Indeed, no evidence of filament contraction has been seen in the gas kinematics. We find that some filaments, that on average are thermally subcritical, contain dense cores that may eventually form stars. This is an indication that in the low column density regime, the critical condition for the formation of stars may be reached only locally and this condition is not a global property of the filament. Finally, in Lupus we find multiple observational evidences of the key role that the magnetic field plays in forming filaments, and determining their confinement and dynamical evolution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.08786v1.pdf"}
{"id": "1508.00262", "abstract": "  Quantum coherence is the outcome of the superposition principle. Recently, it has been theorized as a quantum resource, and is the premise of quantum correlations in multipartite systems. It is therefore interesting to study the coherence content and its distribution in a multipartite quantum system. In this work, we show analytically as well as numerically the reciprocity between coherence and mixedness of a quantum state. We find that this trade-off is a general feature in the sense that it is true for large spectra of measures of coherence and of mixedness. We also study the distribution of coherence in multipartite systems by looking at monogamy-type relation–which we refer to as additivity relation–between coherences of different parts of the system. We show that for the Dicke states, while the normalized measures of coherence violate the additivity relation, the unnormalized ones satisfy the same. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.00262v3.pdf"}
{"id": "1508.00958", "abstract": "  We investigate vortex shedding from a moving penetrable obstacle in a highly oblate Bose-Einstein condensate. The penetrable obstacle is formed by a repulsive Gaussian laser beam that has the potential barrier height lower than the chemical potential of the condensate. The moving obstacle periodically generates vortex dipoles and the vortex shedding frequency f_v linearly increases with the obstacle velocity v as f_v=a(v-v_c), where v_c is a critical velocity. Based on periodic shedding behavior, we demonstrate deterministic generation of a single vortex dipole by applying a short linear sweep of a laser beam. This method will allow further controlled vortex experiments such as dipole-dipole collisions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.00958v1.pdf"}
{"id": "1508.01120", "abstract": "  The effective potential Φ of a classical ion in a weakly correlated quantum plasma in thermodynamic equilibrium at finite temperature is well described by the RPA screened Coulomb potential. Additionally, collision effects can be included via a relaxation time ansatz (Mermin dielectric function). These potentials are used to study the quality of various statically screened potentials that were recently proposed by Shukla and Eliasson (SE) [Phys. Rev. Lett. 108, 165007 (2012)], Akbari–Moghanjoughi (AM) [Phys. Plasmas 22, 022103 (2015)] and Stanton and Murillo (SM) [Phys. Rev. E 91, 033104 (2015)] starting from quantum hydrodynamic theory (QHD). Our analysis reveals that the SE potential is qualitatively different from the full potential, whereas the SM potential (at any temperature) and the AM potential (at zero temperature) are significantly more accurate. This confirms the correctness of the recently derived [Michta et al., Contrib. Plasma Phys. 55, (2015)] pre-factor 1/9 in front of the Bohm term of QHD for fermions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.01120v1.pdf"}
{"id": "1508.01135", "abstract": "  We study x-ray absorption spectra of azobenzene-functionalized self-assembled monolayers (SAMs), investigating excitations from the nitrogen K edge. Azobenzene with H-termination and functionalized with CF3 groups is considered. The Bethe-Salpeter equation is employed to compute the spectra, including excitonic effects, and to determine the character of the near-edge resonances. Our results indicate that core-edge excitations are intense and strongly bound: Their binding energies range from about 6 to 4 eV, going from isolated molecules to densely-packed SAMs. Electron-hole correlation rules these excitations, while the exchange interaction plays a negligible role. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.01135v2.pdf"}
{"id": "1508.02150", "abstract": "  We calculate the finite vacuum energy density of the scalar and electromagnetic fields inside a Casimir apparatus made up of two conducting parallel plates in a general weak gravitational field. The metric of the weak gravitational field has a small deviation from flat spacetime inside the apparatus and we find it by expanding the metric in terms of small parameters of the weak background. We show that the found metric can be transformed via a gauge transformation to the Fermi metric. We solve the Klein-Gordon equation exactly and find mode frequencies in Fermi spacetime. Using the fact that the electromagnetic field can be represented by two scalar fields in the Fermi spacetime, we find general formulas for the energy density and mode frequencies of the electromagnetic field. Some well-known weak backgrounds are examined and consistency of the results with the literature is shown. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.02150v2.pdf"}
{"id": "1508.02376", "abstract": "  Slender bodies capable of spontaneous motion in the absence of external actuation in an otherwise quiescent fluid are common in biological, physical and technological contexts. The interplay between the spontaneous fluid flow, Brownian motion, and the elasticity of the body presents a challenging fluid-structure interaction problem. Here, we model this problem by approximating the slender body as an elastic filament that can impose non-equilibrium velocities or stresses at the fluid-structure interface. We derive equations of motion for such an active filament by enforcing momentum conservation in the fluid-structure interaction and assuming slow viscous flow in the fluid. The fluid-structure interaction is obtained, to any desired degree of accuracy, through the solution of an integral equation. A simplified form of the equations of motion, that allows for efficient numerical solutions, is obtained by applying the Kirkwood-Riseman superposition approximation to the integral equation. We use this form of the equation of motion to study dynamical steady states in free and hinged minimally active filaments. Our model provides the foundation to study collective phenomena in momentum-conserving, Brownian, active filament suspensions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.02376v2.pdf"}
{"id": "1508.03357", "abstract": "  We analyse RXTE/PCA X-ray spectra of the binary X-ray pulsar Her X-1/HZ Her during short high state and one binary orbit in the preceding low state, just before short high turn-on. The spectrum is well described by two continuum components (absorbed and unabsorbed). The resulting spectral parameters are modulated with orbital phase. During low state a significant component of the flux, and its spectrum, is consistent with X-ray reflection off the face of the companion star HZ Her. This component has a significantly harder X-ray spectrum than the rest of the flux from the Her X-1 system. A second component in low state is consistent with emission from the accretion disk corona. During short high a third strong component is present with a softer spectrum, which is associated with the neutron star and accretion disk. Due to this direct emission from the neutron star and accretion disk, the reflected emission is less clear, however parameters and fluxes modulations during short high state indicate its presence. In low state, the hard X-ray flux (h ν > 10 keV) peaks at orbital phase ϕ_orb≃ 0.55, which is expected from a simple model of atmospheric reflection from the companion star. The offset indicates an asymmetry in the X-ray illumination of the companion, which could be due to shadowing of the the inner face of HZ Her by the accretion disk and/or stream. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.03357v1.pdf"}
{"id": "1508.04243", "abstract": "  We find some new exact cosmological solutions for the covariant scalar-tensor-vector gravity theory, the so-called MOdified Gravity (MOG). The exact solution of the vacuum field equations has been derived. Also, for non vacuum cases we have found some exact solutions with the aid of the Noether symmetry approach. More specifically, the symmetry vector and also the Noether conserved quantity associated to the point-like Lagrangian of the theory have been found. Also we find the exact form of the generic vector field potential of this theory by considering the behavior of the relevant point-like Lagrangian under the infinitesimal generator of the Noether symmetry. Finally, we discuss the cosmological implications of the solutions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.04243v1.pdf"}
{"id": "1508.04516", "abstract": "  Elastic models of the glass transition relate the relaxation dynamics and the elastic properties of structural glasses. They are based on the assumption that the relaxation dynamics occurs through activated events in the energy landscape whose energy scale is set by the elasticity of the material. Here we investigate whether such elastic models describe the relaxation dynamics of systems of particles interacting via a purely repulsive harmonic potential, focusing on a volume fraction and temperature range that is characterized by entropy–driven water–like density anomalies. We do find clear correlations between relaxation time and diffusivity on the one hand, and plateau shear modulus and Debye–Waller factor on the other, thus supporting the validity of elastic models of the glass transition. However, we also show that the plateau shear modulus is not related to the features of the underlying energy landscape of the system, at variance with recent results for power–law potentials. This challenges the common potential energy landscape interpretation of elastic models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.04516v1.pdf"}
{"id": "1508.05917", "abstract": "  We discuss the local density approximation approach to calculating the ground state energy of a one-dimensional Fermi gas containing a single impurity, and compare the results with exact numerical values that we have for up to 11 particles for general interaction strengths and up to 30 particles in the strongly interacting case. We also calculate the contact coefficient in the strongly interacting regime. The different theoretical predictions are compared to recent experimental results with few-atom systems. Firstly, we find that the local density approximation suffers from great ambiguity in the few-atom regime, yet it works surprisingly well for some models. Secondly, we find that the strong interaction theories quickly break down when the number of particles increase or the interaction strength decreases. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.05917v4.pdf"}
{"id": "1508.06987", "abstract": "  The self-consistent tilted axis cranking covariant density functional theory based on the point- coupling interaction PC-PK1 is applied to investigate the possible existence of antimagnetic ro- tation in the nucleus Fe-58. The observed data for Band 3 and Band 4 are reproduced well with two assigned configurations. It is found that both bands correspond to a rotation of antimagnetic character, but, due to the presence of considerable deformation, the interplay between antimag- netic rotation and collective motion plays an essential role. In particular for Band 4, collective rotation is dominant in the competition with antimagnetic rotation. Moreover, it is shown that the behavior of the ratios between the dynamic moments of inertia and the B(E2) values reflects the interplay between antimagnetic and collective rotation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.06987v1.pdf"}
{"id": "1508.07772", "abstract": "  We explore a long Josephson contact transporting Cooper pairs between 1D charge-neutral chiral Majorana modes in the leads via charged Dirac chiral modes in the normal region. We investigate the regimes of (i) transparent contacts and (ii) tunnel junctions implemented in 3D topological insulator/superconductor/magnet hybrid structures. The setup acts as a SQUID controlled by the magnetic flux enclosed by the chiral loop of the normal region. This chirality leads to the fractional h/e-periodic pattern of critical current. The current-phase relation can have sawtooth-like shape with spikes at unusual even phases of 2π n. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.07772v3.pdf"}
{"id": "1509.00848", "abstract": "  Tunneling of electrons through rotor-stator anthracene aldehyde molecular interfaces is studied with a combined ab initio and model approach. Molecular electronic structure calculated from first principles is utilized to model different shapes of tunneling barriers. Together with a rectangular barrier, we also consider a sinusoidal shape that captures the effects of the molecular internal structure more realistically. Quasiclassical approach with the Simmons' formula for current density is implemented. Special attention is paid on conformational dependence of the tunneling current. Our results confirm that the presence of the side aldehyde group enhances the interesting electronic properties of the pure anthracene molecule, making it a bistable system with geometry dependent transport properties. We also investigate the transition voltage and we show that confirmation dependent field emission could be observed in these molecular interfaces at realistically low voltages. The present study accompanies our previous work where we investigated the coherent transport via strongly coupled delocalized orbital by application of Non-equilibrium Green's Function Formalism. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.00848v2.pdf"}
{"id": "1509.01565", "abstract": "  We present a catalog of near-infrared (NIR) spectra and associated measurements for 886 nearby M dwarfs. The spectra were obtained with the NASA-Infrared Telescope Facility SpeX Spectrograph during a two-year observing campaign; they have high signal-to-noise ratios (SNR >100-150), span 0.8-2.4 μm and have R∼2000. Our catalog of measured values contains useful T_eff and composition-sensitive features, empirical stellar parameter measurements, and kinematic, photometric, and astrometric properties compiled from the literature. We focus on measures of M dwarf abundances ([Fe/H] and [M/H]), capitalizing on the precision of recently published empirical NIR spectroscopic calibrations. We explore systematic differences between different abundance calibrations, and to other similar M dwarf catalogs. We confirm that the M dwarf abundances we measure show the expected inverse dependence with kinematic, activity, and color-based age indicators. Finally, we provide updated [Fe/H] and [M/H] for 16 M dwarf planet hosts. This catalog represents the largest published compilation of NIR spectra and associated parameters for M dwarfs. It provides a rich and uniform resource for the nearby M dwarfs, and will be especially valuable for measuring Habitable Zone locations and comparative abundances of the M dwarf planet hosts that will be uncovered by upcoming exoplanet surveys. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.01565v1.pdf"}
{"id": "1509.03205", "abstract": "  This paper addresses the problem of binaural localization of a single speech source in noisy and reverberant environments. For a given binaural microphone setup, the binaural response corresponding to the direct-path propagation of a single source is a function of the source direction. In practice, this response is contaminated by noise and reverberations. The direct-path relative transfer function (DP-RTF) is defined as the ratio between the direct-path acoustic transfer function of the two channels. We propose a method to estimate the DP-RTF from the noisy and reverberant microphone signals in the short-time Fourier transform domain. First, the convolutive transfer function approximation is adopted to accurately represent the impulse response of the sensors in the STFT domain. Second, the DP-RTF is estimated by using the auto- and cross-power spectral densities at each frequency and over multiple frames. In the presence of stationary noise, an inter-frame spectral subtraction algorithm is proposed, which enables to achieve the estimation of noise-free auto- and cross-power spectral densities. Finally, the estimated DP-RTFs are concatenated across frequencies and used as a feature vector for the localization of speech source. Experiments with both simulated and real data show that the proposed localization method performs well, even under severe adverse acoustic conditions, and outperforms state-of-the-art localization methods under most of the acoustic conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.03205v3.pdf"}
{"id": "1509.03707", "abstract": "  In this article we present a concrete proposal for spin squeezing the ultracold ground state polar paramagnetic molecule OH, a system currently under fine control in the laboratory. In contrast to existing work, we consider a single, non-interacting molecule with angular momentum greater than 1/2. Starting from an experimentally relevant effective Hamiltonian, we identify a parameter regime where different combinations of static electric and magnetic fields can be used to realize the single-axis twisting Hamiltonian of Kitagawa and Ueda [M. Kitagawa and M. Ueda, Phys. Rev. A 47, 5138 (1993)], the uniform field Hamiltonian proposed by Law et al. [C. K. Law, H. T Ng and P. T. Leung, Phys. Rev. A 63, 055601 (2001)], and a model of field propagation in a Kerr medium considered by Agarwal and Puri [G. S. Agarwal and R. R. Puri, Phys. Rev. A 39, 2969 (1989)]. To support our conclusions, we provide analytical expressions as well as numerical calculations, including optimization of field strengths and accounting for the effects of field misalignment. Our results have consequences for applications such as precision spectroscopy, techniques such as magnetometry, and stereochemical effects such as the orientation-to-alignment transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.03707v2.pdf"}
{"id": "1509.07600", "abstract": "  This paper considers the minimax regret 1-median problem in dynamic path networks. In our model, we are given a dynamic path network consisting of an undirected path with positive edge lengths, uniform positive edge capacity, and nonnegative vertex supplies. Here, each vertex supply is unknown but only an interval of supply is known. A particular assignment of supply to each vertex is called a scenario. Given a scenario s and a sink location x in a dynamic path network, let us consider the evacuation time to x of a unit supply given on a vertex by s. The cost of x under s is defined as the sum of evacuation times to x for all supplies given by s, and the median under s is defined as a sink location which minimizes this cost. The regret for x under s is defined as the cost of x under s minus the cost of the median under s. Then, the problem is to find a sink location such that the maximum regret for all possible scenarios is minimized. We propose an O(n^3) time algorithm for the minimax regret 1-median problem in dynamic path networks with uniform capacity, where n is the number of vertices in the network. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.07600v1.pdf"}
{"id": "1509.08690", "abstract": "  We prove that every bounded rational space curve of degree d and circularity c can be drawn by a linkage with 9/2 d - 6c + 1 revolute joints. Our proof is based on two ingredients. The first one is the factorization theory of motion polynomials. The second one is the construction of a motion polynomial of minimum degree with given orbit. Our proof also gives the explicity construction of the linkage. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.08690v4.pdf"}
{"id": "1510.04302", "abstract": "  We report the observation and the theoretical explanation of the parametric down-conversion nonlinear susceptibility at the K-absorption edge of diamond and at the L_23-absorption edge of a silicon crystal. Using arguments similar to those invoked to successfully predict resonant inelastic x-ray spectra, we derive an expression for the renormalization term of the non-linear susceptibility at the x-ray edges, which can be evaluated by using first-principles calculations of the atomic scattering factor f_1. Our model is shown to reproduce the observed enhancement of the parametric down-conversion at the diamond K and the Si L_23 edges rather than the suppression previously claimed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.04302v1.pdf"}
{"id": "1510.05354", "abstract": "  In this article, we investigate the status of the homomorphism preservation property amongst restricted classes of finite relational structures and algebraic structures. We show that there are many homomorphism-closed classes of finite lattices that are definable by a first-order sentence but not by existential positive sentences, demonstrating the failure of the homomorphism preservation property for lattices at the finite level. In contrast to the negative results for algebras, we establish a finite-level relativised homomorphism preservation theorem in the relational case. More specifically, we give a complete finite-level characterisation of first-order definable finitely generated anti-varieties relative to classes of relational structures definable by sentences of some general forms. When relativisation is dropped, this gives a fresh proof of Atserias's characterisation of first-order definable constraint satisfaction problems over a fixed template, a well known special case of Rossman's Finite Homomorphism Preservation Theorem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.05354v1.pdf"}
{"id": "1510.07501", "abstract": "  The strong CP problem of QCD is at heart a problem of naturalness: why is the FF̃ term highly suppressed in the QCD Lagrangian when it seems necessary to explain why there are three and not four light pions? The most elegant solution posits a spontaneously broken Peccei-Quinn (PQ) symmetry which requires the existence of the axion field a. The axion field settles to the minimum of its potential thus removing the offensive term but giving rise to the physical axion whose coherent oscillations can make up the cold dark matter. Only now are experiments such as ADMX beginning to explore QCD axion parameter space. Since a bonafide scalar particle– the Higgs boson– has been discovered, one might expect its mass to reside at the axion scale f_a  10^11 GeV. The Higgs mass is elegantly stabilized by supersymmetry: in this case the axion is accompanied by its axino and saxion superpartners. Requiring naturalness also in the electroweak sector implies higgsino-like WIMPs so then we expect mixed axion-WIMP dark matter. Ultimately we would expect detection of both an axion and a WIMP while signals for light higgsinos may show up at LHC and must show up at ILC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.07501v1.pdf"}
{"id": "1511.01548", "abstract": "  Nitrogen vacancy (NV) centers can couple to confined phonons in diamond mechanical resonators via the effect of lattice strain on their energy levels. Access to the strong spin-phonon coupling regime with this system requires resonators with nanoscale dimensions in order to overcome the weak strain response of the NV ground state spin sublevels. In this work, we study NVs in diamond cantilevers with lateral dimensions of a few hundred nm. Coupling of the NV ground state spin to the mechanical mode is detected in electron spin resonance (ESR), and its temporal dynamics are measured via spin echo. Our small mechanical mode volume leads to a 10-100X enhancement in spin-phonon coupling strength over previous NV-strain coupling demonstrations. This is an important step towards strong spin-phonon coupling, which can enable phonon-mediated quantum information processing and quantum metrology. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.01548v1.pdf"}
{"id": "1511.03822", "abstract": "  We present experimental evidence that a minute amount of polymer additives can significantly enhance heat transport in the bulk region of turbulent thermal convection. The effects of polymer additives are found to be the suppression of turbulent background fluctuations that give rise to incoherent heat fluxes that make no net contribution to heat transport, and at the same time to increase the coherency of temperature and velocity fields. The suppression of small-scale turbulent fluctuations leads to more coherent thermal plumes that result in the heat transport enhancement. The fact that polymer additives can increase the coherency of thermal plumes is supported by the measurements of a number of local quantities, such as the extracted plume amplitude and width, the velocity autocorrelation functions and the velocity-temperature cross-correlation coefficient. The results from local measurements also suggest the existence of a threshold value for the polymer concentration, only above which can significant modification of the plume coherent properties and enhancement of the local heat flux be observed. Estimation of the plume emission rate suggests that the second effect of polymer additives is to stabilize the thermal boundary layers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.03822v1.pdf"}
{"id": "1511.03856", "abstract": "  Very often it is an implied paradigm of molecular magnetism that magnetic molecules in a crystal interact so weakly that measurements of dc magnetic observables reflect ensemble properties of single molecules. But the number of cases where the assumption of virtually non-interacting molecules does not hold grows steadily. A deviation from the non-interacting case can especially clearly be seen in clusters with antiferromagnetic couplings, where steps of the low-temperature magnetization curve are smeared out with increasing intermolecular interaction. In this investigation we demonstrate with examples in one-, two, and three space dimensions how intermolecular interactions influence typical magnetic observables such as magnetization, susceptibility and specific heat. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.03856v1.pdf"}
{"id": "1511.05548", "abstract": "  Genome sizes have evolved to vary widely, from 250 bases in viroids to 670 billion bases in amoeba. This remarkable variation in genome size is the outcome of complex interactions between various evolutionary factors such as point mutation rate, population size, insertions and deletions, and genome editing mechanisms that may be specific to certain taxonomic lineages. While comparative genomics analyses have uncovered some of the relationships between these diverse evolutionary factors, we still do not understand what drives genome size evolution. Specifically, it is not clear how primordial mutational processes of base substitutions, insertions, and deletions influence genome size evolution in asexual organisms. Here, we use digital evolution to investigate genome size evolution by tracking genome edits and their fitness effects in real time. In agreement with empirical data, we find that mutation rate is inversely correlated with genome size in asexual populations. We show that at low point mutation rate, insertions are significantly more beneficial than deletions, driving genome expansion and acquisition of phenotypic complexity. Conversely, high mutational load experienced at high mutation rates inhibits genome growth, forcing the genomes to compress genetic information. Our analyses suggest that the inverse relationship between mutation rate and genome size is a result of the tradeoff between evolving phenotypic innovation and limiting the mutational load. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.05548v1.pdf"}
{"id": "1511.06317", "abstract": "  We present a novel Monte-Carlo implementation of dynamic colour screening via multiple exchanges of semi-soft gluons as a basic QCD mechanism to understand diffractive electron-proton scattering at the HERA collider. Based on the kinematics of individual events in the standard QCD description of deep inelastic scattering at the parton level, which at low x is dominantly gluon-initiated, the probability is evaluated for additional exchanges of softer gluons resulting in an overall colour singlet exchange leading to a forward proton and a rapidity gap as the characteristic observables for diffractive scattering. The probability depends on the impact parameter of the soft exchanges and varies with the transverse size of the hard scattering subsystem and is therefore influenced by different QCD effects. We account for matrix elements and parton shower evolution either via conventional DGLAP log Q^2-evolution with collinear factorisation or CCFM small-x evolution with k_⊥-factorisation and discuss the sensitivity to the gluon density distribution in the proton and the importance of large log x-contributions. The overall result is that, with only two model parameters which have theoretically motivated values, a satisfactory description of the observed diffractive cross-section at HERA is obtained in a wide kinematical range. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.06317v3.pdf"}
{"id": "1511.08225", "abstract": "  Based on the particle-in-cell (PIC) plasma simulation method, the speed-limited PIC (SLPIC) method delivers faster kinetic plasma simulation in cases where the particle distributions evolve slowly compared with the maximum stable PIC timestep. SLPIC thus offers more feasible, fully kinetic simulation in regimes that historically have required fluid approaches, such as magnetohydrodynamic (MHD), two-fluid, or Boltzmann electron treatments. In particular, SLPIC allows an explicit time advance with steps much larger than the inverse plasma frequency, avoiding the instability explicit PIC faces with large timesteps. SLPIC avoids this instability by slowing down fast particles (e.g., electrons) in a way that is rigorously underpinned by an approximate Vlasov equation; unlike MHD, two-fluid, and Boltzmann electron approaches, SLPIC does not fundamentally neglect any first-principles plasma physics, although the choices of grid cell size, timestep, and number of macroparticles per cell naturally limit the physical phenomena that can be accurately represented. SLPIC can be implemented with minor modifications of a standard PIC code and does not require an implicit time advance. It enables large timesteps in first-principles kinetic plasma simulation of appropriately slow phenomena, and it can handle many of the same complications as PIC, such as boundary conditions and collisions. In an argon plasma sheath test problem, a SLPIC simulation achieved a speed-up of a factor of 160 over the corresponding PIC simulation, without loss of accuracy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1511/1511.08225v3.pdf"}
{"id": "1512.00887", "abstract": "  We derive approximate equations of motion for excited state dynamics of a multilevel open quantum system weakly interacting with light to describe fluorescence detected single molecule spectra. Based on the Frenkel exciton theory, we construct a model for the chlorophyll part of the LHCII complex of higher plants and its interaction with previously proposed excitation quencher in the form of the lutein molecule Lut 1. The resulting description is valid over a broad range of timescales relevant for single molecule spectroscopy, i.e. from ps to minutes. Validity of these equations is demonstrated by comparing simulations of ensemble and single-molecule spectra of monomeric LHCII with experiments. Using a conformational change of the LHCII protein as a switching mechanism, the intensity and spectral time traces of individual LHCII complexes are simulated, and the experimental statistical distributions are reproduced. Based on our model, it is shown that with reasonable assumptions about its interaction with chlorophylls, Lut 1 can act as an efficient fluorescence quencher in LHCII. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.00887v1.pdf"}
{"id": "1512.08424", "abstract": "  We study the applicability of a set of texture descriptors introduced in recent work by the author to texture-based segmentation of images. The texture descriptors under investigation result from applying graph indices from quantitative graph theory to graphs encoding the local structure of images. The underlying graphs arise from the computation of morphological amoebas as structuring elements for adaptive morphology, either as weighted or unweighted Dijkstra search trees or as edge-weighted pixel graphs within structuring elements. In the present paper we focus on texture descriptors in which the graph indices are entropy-based, and use them in a geodesic active contour framework for image segmentation. Experiments on several synthetic and one real-world image are shown to demonstrate texture segmentation by this approach. Forthermore, we undertake an attempt to analyse selected entropy-based texture descriptors with regard to what information about texture they actually encode. Whereas this analysis uses some heuristic assumptions, it indicates that the graph-based texture descriptors are related to fractal dimension measures that have been proven useful in texture analysis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.08424v1.pdf"}
{"id": "1512.08894", "abstract": "  The Bose-Einstein condensation of bound pairs made of equally and oppositely charged fermions in a magnetic field is investigated using a relativistic model. The Gaussian fluctuations have been taken into account in order to study the spectrum of bound pairs in the strong coupling region. We found, in weak coupling reagion, the condensation temperature increases with an increasing magnetic field displaying the magnetic catalysis effect. In strong coupling region, the inverse magnetic catalysis appears when the magnetic field is low and is replaced by the usual magnetic catalysis effect when magnetic field is sufficiently high, in contrast to the nonrelativistic case where the inverse magnetic catalysis prevails in strong coupling region regardless of the strength of the magnetic field. The resulting response to the magnetic field is the consequence of the competition between the dimensional reduction by Landau orbitals in pairing dynamics and the anisotropy of the kinetic spectrum of the bound pairs. We thus conclude that dimensional reduction dominates in weak domain and strong coupling one except the small magnetic field region, where the enhanced fluctuations dominates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.08894v2.pdf"}
{"id": "1601.00016", "abstract": "  This review covers four current questions in the behavior of the atomic and molecular interstellar medium. These include whether the atomic gas originates primarily in cold streams or hot flows onto galaxies; what the filling factor of cold gas actually is in galactic regions observationally determined to be completely molecular; whether molecular hydrogen determines or merely traces star formation; and whether gravity or turbulence drives the dynamical motions observed in interstellar clouds, with implications on their star formation properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.00016v1.pdf"}
{"id": "1601.00066", "abstract": "  The quasi-satellite (QS) phenomenon makes two celestial bodies to fly near each other (Mikkola et al. 2006) and that effect can be used also to make artificial satellites move in tandem. We consider formation flight of two or three satellites in low eccentricity near Earth orbits. With the help of weak ion thrusters it is possible to accomplish tandem flight. With ion thrusters it is also possible to mimic many kinds of mutual force laws between the satellites. We found that both a constant repulsive force or an attractive force that decreases with the distance are able to preserve the formation in which the eccentricities cause the actual relative motion and the weak thrusters keep the mean longitude difference small. Initial values are important for the formation flight but very exact adjustment of orbital elements is not important. Simplicity is one of our goals in this study and this result is achieved at least in the way that, when constant force thrusters are used, the satellites only need to detect the directions of the other ones to fly in tandem. A repulsive acceleration of the order of 10^-6 times the Earth attraction, is enough to effectively eliminate the disruptive effects of all the perturbations at least for a timescale of years. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.00066v1.pdf"}
{"id": "1601.00555", "abstract": "  Since the first detection of intracluster planetary nebulae in 1996, imaging and spectroscopic surveys identified such stars to trace the radial extent and the kinematics of diffuse light in clusters. This topic of research is tightly linked with the studies of galaxy formation and evolution in dense environment, as the spatial distribution and kinematics of planetary nebulae in the outermost regions of galaxies and in the cluster cores is relevant for setting constraints on cosmological simulations. In this sense, extragalactic planetary nebulae play a very important role in the near-field cosmology, in order to measure the integrated mass as function of radius and the orbital distribution of stars in structures placed in the densest regions of the nearby universe. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.00555v1.pdf"}
{"id": "1601.02721", "abstract": "  Currently, there are 24 black hole (BH) X-ray binary systems that have been dynamically confirmed in the Galaxy. Most of them are low-mass X-ray binaries (LMXBs) comprised of a stellar-mass BH and a low-mass donor star. Although the formation of these systems has been extensively investigated, some crucial issues remain unresolved. The most noticeable one is that, the low-mass companion has difficulties in ejecting the tightly bound envelope of the massive primary during the spiral-in process. While initially intermediate-mass binaries are more likely to survive the common envelope (CE) evolution, the resultant BH LMXBs mismatch the observations. In this paper, we use both stellar evolution and binary population synthesis to study the evolutionary history of BH LMXBs. We test various assumptions and prescriptions for the supernova mechanisms that produce BHs, the binding energy parameter, the CE efficiency, and the initial mass distributions of the companion stars. We obtain the birthrate and the distributions of the donor mass, effective temperature and orbital period for the BH LMXBs in each case. By comparing the calculated results with the observations, we put useful constraints on the aforementioned parameters. In particular, we show that it is possible to form BH LMXBs with the standard CE scenario if most BHs are born through failed supernovae. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.02721v1.pdf"}
{"id": "1601.02940", "abstract": "  Common-path digital in-line holography is considered as a valuable 3D diagnostic techniques for a wide range of applications. This configuration is cost effective and relatively immune to variation in the experimental environment. Nevertheless, due to its common-path geometry, the signal to noise-ratio of the acquired hologram is weak as most of the detector (i.e. CCD/CMOS sensor) dynamics is occupied by the reference field signal, whose energy is orders of magnitude higher than the field scattered by the imaged object. As it is intrinsically impossible to modify the ratio of energy of reference to the object field, we propose a co-design approach (Optics/Data Processing) to tackle this issue. The reference to object field ratio is adjusted by adding a 4-f device to a conventional in-line holographic setup, making it possible to reduce the weight of the reference field while keeping the object field almost constant. Theoretical analysis of the Cràmer-Rao lower bounds of the corresponding imaging model illustrate the advantages of this approach. These lower bounds can be asymptotically reached using a parametric inverse problems reconstruction. This implementation results in a 60 ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.02940v1.pdf"}
{"id": "1601.03303", "abstract": "  Fundamental forces of Nature are described by field theories, also known as gauge theories, based on a local gauge invariance. The simplest of them is quantum electrodynamics (QED), which is an example of an Abelian gauge theory. Such theories describe the dynamics of massless photons and their coupling to matter. However, in two spatial dimension (2D) they are known to exhibit gapped phases at low temperature. In the realm of quantum spin systems, it remains a subject of considerable debate if their low energy physics can be described by emergent gauge degrees of freedom. Here we present a class of simple two-dimensional models that admit a low energy description in terms of an Abelian gauge theory. We find rich phase diagrams for these models comprising exotic deconfined phases and gapless phases - a rare example for 2D Abelian gauge theories. The counter-intuitive presence of gapless phases in 2D results from the emergence of additional symmetry in the models. Moreover, we propose schemes to realize our model with current experiments using ultracold bosonic atoms in optical lattices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.03303v2.pdf"}
{"id": "1601.03357", "abstract": "  A method to construct integrable deformations of Hamiltonian systems of ODEs endowed with Lie-Poisson symmetries is proposed by considering Poisson-Lie groups as deformations of Lie-Poisson (co)algebras. Moreover, the underlying Lie-Poisson symmetry of the initial system of ODEs is used to construct integrable coupled systems, whose integrable deformations can be obtained through the construction of the appropriate Poisson-Lie groups that deform the initial symmetry. The approach is applied in order to construct integrable deformations of both uncoupled and coupled versions of certain integrable types of Rössler and Lorenz systems. It is worth stressing that such deformations are of non-polynomial type since they are obtained through an exponentiation process that gives rise to the Poisson-Lie group from its infinitesimal Lie bialgebra structure. The full deformation procedure is essentially algorithmic and can be computerized to a large extent. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.03357v2.pdf"}
{"id": "1601.03879", "abstract": "  It is well known that amorphous solids display a phonon spectrum where the Debye ∼ω^2 law at low frequency melds into an anomalous excess-mode peak (the boson peak) before entering a quasi-localized regime at higher frequencies dominated by scattering. The microscopic origin of the boson peak has remained elusive despite various attempts to put it in a clear connection with structural disorder at the atomic/molecular level. Using numerical calculations on model systems, we show that the microscopic origin of the boson peak is directly controlled by the local breaking of center-inversion symmetry. In particular, we find that both the boson peak and the nonaffine softening of the material display a strong positive correlation with a new order parameter describing the local inversion symmetry of the lattice. The standard bond-orientational order parameter, instead, is shown to be a poor correlator and cannot explain the boson peak in randomly-cut crystals with perfect bond-orientational order. Our results bring a unifying understanding of the boson peak anomaly for model glasses and defective crystals in terms of a universal local symmetry-breaking principle of the lattice. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.03879v3.pdf"}
{"id": "1601.04047", "abstract": "  This is a survey of the electrostatic potentials produced by charged straight-line segments, in various numbers of spatial dimensions, with comparisons between uniformly charged segments and those having non-uniform linear charge distributions that give rise to ellipsoidal equipotentials surrounding the segments. A uniform linear distribution of charge is compatible with ellipsoidal equipotentials only for three dimensions. In higher dimensions, the linear charge density giving rise to ellipsoidal equipotentials is counter-intuitive — the charge distribution has a maximum at the center of the segment and vanishes at the ends of the segment. Only in two dimensions is the continuous charge distribution intuitive — for that one case of ellipsoidal equipotentials, the charge is peaked at the ends of the segment and minimized at the center. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.04047v1.pdf"}
{"id": "1601.04375", "abstract": "  We investigate the large-time scaling regimes arising from a variety of metastable structures in a chain of Ising spins with both first- and second-neighbor couplings while subject to a Kawasaki dynamics. Depending on the ratio and sign of these former, different dynamic exponents are suggested by finite-size scaling analyses of relaxation times. At low but nonzero-temperatures these are calculated via exact diagonalizations of the evolution operator in finite chains under several activation barriers. In the absence of metastability the dynamics is always diffusive. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.04375v2.pdf"}
{"id": "1601.04581", "abstract": "  The CDEX-1 experiment conducted a search of low-mass (< 10 GeV/c2) Weakly Interacting Massive Particles (WIMPs) dark matter at the China Jinping Underground Laboratory using a p-type point-contact germanium detector with a fiducial mass of 915 g at a physics analysis threshold of 475 eVee. We report the hardware set-up, detector characterization, data acquisition and analysis procedures of this experiment. No excess of unidentified events are observed after subtraction of known background. Using 335.6 kg-days of data, exclusion constraints on the WIMP-nucleon spin-independent and spin-dependent couplings are derived. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.04581v1.pdf"}
{"id": "1601.06121", "abstract": "  In this manuscript we introduced the generalized fractional Riemann-Liouville and Caputo like derivative for functions defined on fractal sets. The Gamma, Mittag-Leffler and Beta functions were defined on the fractal sets. The non-local Laplace transformation is given and applied for solving linear and non-linear fractal equations. The advantage of using these new nonlocal derivatives on fractals subset of real-line lies in the fact that they are used for better modelling of processes with memory effect. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.06121v1.pdf"}
{"id": "1601.06699", "abstract": "  Trapping ions in Paul traps requires high radio-frequency voltages, which are generated using resonators. When operating traps in a cryogenic environment, an in-vacuum resonator showing low loss is crucial to limit the thermal load to the cryostat. In this study, we present a guide for the design and production of compact, shielded cryogenic resonators. We produced and characterized three different types of resonators and furthermore demonstrate efficient impedance matching of these resonators at cryogenic temperatures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.06699v1.pdf"}
{"id": "1602.00625", "abstract": "  Ultrafast laser measurements probe the non-equilibrium dynamics of excited electrons in metals with increasing temporal resolution. Electronic structure calculations can provide a detailed microscopic understanding of hot electron dynamics, but a parameter-free description of pump-probe measurements has not yet been possible, despite intensive research, because of the phenomenological treatment of electron-phonon interactions. We present ab initio predictions of the electron-temperature dependent heat capacities and electron-phonon coupling coefficients of plasmonic metals. We find substantial differences from free-electron and semi-empirical estimates, especially in noble metals above transient electron temperatures of 2000 K, because of the previously-neglected strong dependence of electron-phonon matrix elements on electron energy. We also present first-principles calculations of the electron-temperature dependent dielectric response of hot electrons in plasmonic metals, including direct interband and phonon-assisted intraband transitions, facilitating complete theoretical predictions of the time-resolved optical probe signatures in ultrafast laser experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.00625v2.pdf"}
{"id": "1602.00681", "abstract": "  Spatial awareness in mammals is based on an internalized representation of the environment, encoded by large networks of spiking neurons. While such representations can last for a long time, the underlying neuronal network is transient: neuronal cells die every day, synaptic connections appear and disappear, the networks constantly change their architecture due to various forms of synaptic and structural plasticity. How can a network with a dynamic architecture encode a stable map of space? We address this question using a physiological model of a \"flickering\" neuronal network and demonstrate that it can maintain a robust topological representation of space. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.00681v1.pdf"}
{"id": "1602.00753", "abstract": "  Human vision greatly benefits from the information about sizes of objects. The role of size in several visual reasoning tasks has been thoroughly explored in human perception and cognition. However, the impact of the information about sizes of objects is yet to be determined in AI. We postulate that this is mainly attributed to the lack of a comprehensive repository of size information. In this paper, we introduce a method to automatically infer object sizes, leveraging visual and textual information from web. By maximizing the joint likelihood of textual and visual observations, our method learns reliable relative size estimates, with no explicit human supervision. We introduce the relative size dataset and show that our method outperforms competitive textual and visual baselines in reasoning about size comparisons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.00753v1.pdf"}
{"id": "1602.01870", "abstract": "  We study polar coding for stochastic processes with memory. For example, a process may be defined by the joint distribution of the input and output of a channel. The memory may be present in the channel, the input, or both. We show that ψ-mixing processes polarize under the standard Arıkan transform, under a mild condition. We further show that the rate of polarization of the low-entropy synthetic channels is roughly O(2^-√(N)), where N is the blocklength. That is, essentially the same rate as in the memoryless case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.01870v3.pdf"}
{"id": "1602.02286", "abstract": "  The error propagation and statistical-noise reduction method of Reid and Trainor for two-point correlation applications in high-energy collisions is extended to include particle-pair references constructed by mixing two particles from all event-pair combinations within event subsets of arbitrary size. The Reid-Trainor method is also applied to other particle-pair mixing algorithms commonly used in correlation analysis of particle production from high-energy nuclear collisions. The statistical-noise reduction, inherent in the Reid-Trainor event-mixing procedure, is shown to occur for these other event-mixing algorithms as well. Monte Carlo simulation results are presented which verify the predicted degree of noise reduction. In each case the final errors are determined by the bin-wise particle-pair number, rather than by the bin-wise single-particle count. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.02286v2.pdf"}
{"id": "1602.03491", "abstract": "  We analyze in detail an open cavity array using mean-field description, where each cavity field is coupled to a number of three-level atoms. Such system is highly tunable and can be described by a Jaynes-Cummings like Hamiltonian with additional non-linear terms. In the single cavity case we provide simple analytic solutions and show, that the system features a bistable region. The extra non-linear term gives rise to a rich dynamical behaviour including occurrence of limit cycles through Hopf bifurcations. In the limit of large non-linearity, the system exhibits an Ising like phase transition as the coupling between light and matter is varied. We then discuss how these results extend to the two-dimensional case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.03491v1.pdf"}
{"id": "1602.05988", "abstract": "  The grand canonical formalism is employed to study the thermodynamic structure of a model displaying a quantum phase transition when studied with respect to the canonical formalism. A numerical survey shows that the grand partition function diverges following a power law when the interaction parameter approaches a limiting constant. The power-law exponent takes a distinctive value when such limiting constant coincides with the critical point of the subjacent quantum phase transition. An approximated expression for the grand partition function is derived analytically implementing a mean field scheme and a number of thermodynamic observables are obtained. The system observables show signatures that can be used to track the critical point of the underlying transition. This result provides a simple fact that can be exploited to verify the existence of a quantum phase transition avoiding the zero temperature regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.05988v1.pdf"}
{"id": "1602.07284", "abstract": "  The spectrum of nucleon excitations is dominated by broad and overlapping resonances. Polarization observables in photoproduction reactions are key in the study of these excitations. They give indispensable constraints to partial-wave analyses and help clarify the spectrum. A series of polarized photoproduction experiments have been performed at the Thomas Jefferson National Accelerator Facility with the CEBAF Large Acceptance Spectrometer (CLAS). These measurements include data with linearly and circularly polarized tagged-photon beams, longitudinally and transversely polarized proton and deuterium targets, and recoil polarizations through the observation of the weak decay of hyperons. An overview of these studies and recent results will be given. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.07284v1.pdf"}
{"id": "1602.07851", "abstract": "  In this paper we study the effective thermal behaviour of 3D representative volume elements (RVEs) of two-phased composite materials constituted by a matrix with cylindrical and spherical inclusions distributed randomly, with periodic boundaries. Variations around the shape of inclusions have been taken into account, by corrugating shapes, excavating and/or by removing pieces of inclusions. The effective behaviour is computed with the help of homogenization process based on an accelerated FFT-scheme giving the thermal conductivity tensor. Several morphological parameters are also taken into account for instance the number and the volume fraction of each type of inclusions,... in order to analyse the behaviour of the composite for a large number of geometries. We compare the results obtained for RVEs with and without variations, and then with the mechanical results of such composite studied in our previous paper. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.07851v1.pdf"}
{"id": "1602.07984", "abstract": "  We use first-principles theory to predict that the application of uniaxial compressive strain leads to a transition from an antiferromagnetic insulator to a ferromagnetic half-metal phase in LaMnO_3. We identify the Q2 Jahn-Teller mode as the primary mechanism that drives the transition, indicating that this mode can be used to tune the lattice, charge, and spin coupling. Applying ≃ 6 GPa of uniaxial pressure along the [010] direction activates the transition to a half-metallic pseudo-cubic state. The half-metallicity opens the possibility of producing colossal magnetoresistance in the stoichiometric LaMnO_3 compound at significantly lower pressure compared to recently observed investigations using hydrostatic pressure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.07984v1.pdf"}
{"id": "1602.08065", "abstract": "  The EDGES High-Band experiment aims to detect the sky-average brightness temperature of the 21-cm signal from the Epoch of Reionization (EoR) in the redshift range 14.8 ≳ z ≳ 6.5. To probe this redshifted signal, EDGES High-Band conducts single-antenna measurements in the frequency range 90-190 MHz from the Murchison Radio-astronomy Observatory in Western Australia. In this paper, we describe the current strategy for calibration of the EDGES High-Band receiver and report calibration results for the instrument used in the 2015-2016 observational campaign. We propagate uncertainties in the receiver calibration measurements to the antenna temperature using a Monte Carlo approach. We define a performance objective of 1 mK residual RMS after modeling foreground subtraction from a fiducial temperature spectrum using a five-term polynomial. Most of the calibration uncertainties yield residuals of 1 mK or less at 95% confidence. However, current uncertainties in the antenna and receiver reflection coefficients can lead to residuals of up to 20 mK even in low-foreground sky regions. These dominant residuals could be reduced by 1) improving the accuracy in reflection measurements, especially their phase 2) improving the impedance match at the antenna-receiver interface, and 3) decreasing the changes with frequency of the antenna reflection phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.08065v3.pdf"}
{"id": "1602.08770", "abstract": "  In this study, we obtain the size distribution of voids as a 3-parameter redshift independent log-normal void probability function (VPF) directly from the Cosmic Void Catalog (CVC). Although many statistical models of void distributions are based on the counts in randomly placed cells, the log-normal VPF that we here obtain is independent of the shape of the voids due to the parameter-free void finder of the CVC. We use three void populations drawn from the CVC generated by the Halo Occupation Distribution (HOD) Mocks which are tuned to three mock SDSS samples to investigate the void distribution statistically and the effects of the environments on the size distribution. As a result, it is shown that void size distributions obtained from the HOD Mock samples are satisfied by the 3-parameter log-normal distribution. In addition, we find that there may be a relation between hierarchical formation, skewness and kurtosis of the log-normal distribution for each catalog. We also show that the shape of the 3-parameter distribution from the samples is strikingly similar to the galaxy log-normal mass distribution obtained from numerical studies. This similarity of void size and galaxy mass distributions may possibly indicate evidence of nonlinear mechanisms affecting both voids and galaxies, such as large scale accretion and tidal effects. Considering in this study all voids are generated by galaxy mocks and show hierarchical structures in different levels, it may be possible that the same nonlinear mechanisms of mass distribution affect the void size distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.08770v1.pdf"}
{"id": "1602.08959", "abstract": "  Some anisotropy in both mechanical and thermodynamical properties of bismuth is expected. A combination of density functional theory total energy calculations and density functional perturbation theory in the local density approximation is used to compute the elastic constants at 0 K using a finite strain approach and the thermal expansion tensor in the quasiharmonic approximation. The overall agreement with experiment is good. Furthermore, the anisotropy in the thermal expansion is found to arise from the anisotropy in both the directional compressibilities and the directional Grüneisen functions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.08959v1.pdf"}
{"id": "1603.00489", "abstract": "  Object localization is an important computer vision problem with a variety of applications. The lack of large scale object-level annotations and the relative abundance of image-level labels makes a compelling case for weak supervision in the object localization task. Deep Convolutional Neural Networks are a class of state-of-the-art methods for the related problem of object recognition. In this paper, we describe a novel object localization algorithm which uses classification networks trained on only image labels. This weakly supervised method leverages local spatial and semantic patterns captured in the convolutional layers of classification networks. We propose an efficient beam search based approach to detect and localize multiple objects in images. The proposed method significantly outperforms the state-of-the-art in standard object localization data-sets with a 8 point increase in mAP scores. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.00489v2.pdf"}
{"id": "1603.00941", "abstract": "  Magnetic reconnection is a rapid energy release process that is believed to be responsible for flares on the Sun and stars. Nevertheless, such flare-related reconnection is mostly detected to occur in the corona, while there have been few studies concerning the reconnection in the chromosphere or photosphere. Here we present both spectroscopic and imaging observations of magnetic reconnection in the chromosphere leading to a microflare. During the flare peak time, chromospheric line profiles show significant blueshifted/redshifted components on the two sides of the flaring site, corresponding to upflows and downflows with velocities of ±(70–80) km s^-1, comparable with the local Alfvén speed as expected by the reconnection in the chromosphere. The three-dimensional nonlinear force-free field configuration further discloses twisted field lines (a flux rope) at a low altitude, cospatial with the dark threads in He I 10830 Å images. The instability of the flux rope may initiate the flare-related reconnection. These observations provide clear evidence of magnetic reconnection in the chromosphere and show the similar mechanisms of a microflare to those of major flares. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.00941v1.pdf"}
{"id": "1603.01742", "abstract": "  A steepening feature in the outer density profiles of dark matter halos indicating the splashback radius has drawn much attention recently. Possible observational detections have even been made for galaxy clusters. Theoretically, Adhikari et al. have estimated the location of the splashback radius by computing the secondary infall trajectory of a dark matter shell through a growing dark matter halo with an NFW profile. However, since they imposed a shape of the halo profile rather than computing it consistently from the trajectories of the dark matter shells, they could not provide the full shape of the dark matter profile around the splashback radius. We improve on this by extending the self-similar spherical collapse model of Fillmore & Goldreich to a ΛCDM universe. This allows us to compute the dark matter halo profile and the trajectories simultaneously from the mass accretion history. Our results on the splashback location agree qualitatively with Adhikari et al. but with small quantitative differences at large mass accretion rates. We present new fitting formulae for the splashback radius R_ sp in various forms, including the ratios of R_ sp / R_ 200c and R_ sp / R_ 200m. Numerical simulations have made the puzzling discovery that the splashback radius scales well with R_ 200m but not with R_ 200c. We trace the origin of this to be the correlated increase of Ω_ m and the average halo mass accretion rate with an increasing redshift. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.01742v2.pdf"}
{"id": "1603.02946", "abstract": "  The ability to categorize problems is a measure of expertise in a domain. In order to help students learn effectively, instructors and teaching assistants (TAs) should have pedagogical content knowledge. They must be aware of the prior knowledge of students they are teaching, consider the difficulty of the problems from students' perspective and design instruction that builds on what students already know. Here, we discuss the response of graduate students enrolled in a TA training course to categorization tasks in which they were asked to group problems based upon similarity of solution first from their own perspective, and later from the perspective of introductory physics students. Many graduate students performed an expert-like categorization of introductory physics problems. However, when asked to categorize the same problems from the perspective of introductory students, many graduate students expressed dismay, claiming that the task was impossible, pointless and had no relevance to their TA duties. We will discuss how categorization can be a useful tool for scaffolding and improving pedagogical content knowledge of teaching assistants and instructors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.02946v1.pdf"}
{"id": "1603.03096", "abstract": "  We find a sufficient condition to imprint the single-mode bosonic phase-space nonclassicality onto a bipartite state as modal entanglement and vice versa using an arbitrary beam splitter. Surprisingly, the entanglement produced or detected in this way depends only on the nonclassicality of the marginal input or output states, regardless of their purity and separability. In this way, our result provides a sufficient condition for generating entangled states of arbitrary high temperature and arbitrary large number of particles. We also study the evolution of the entanglement within a lossy Mach-Zehnder interferometer and show that unless both modes are totally lost, the entanglement does not diminish. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.03096v2.pdf"}
{"id": "1603.04452", "abstract": "  We study if the parabolic forward-in-time maximal operator is bounded on parabolic BMO. It turns out that for non-negative functions the answer is positive, but the behaviour of sign changing functions is more delicate. The class parabolic BMO and the forward-in-time maximal operator originate from the regularity theory of nonlinear parabolic partial differential equations. In addition to that context, we also study the question in dimension one. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.04452v1.pdf"}
{"id": "1603.04477", "abstract": "  We discuss the transition paths in a coupled bistable system consisting of interacting multiple identical bistable motifs. We propose a simple model of coupled bistable gene circuits as an example, and show that its transition paths are bifurcating. We then derive a criterion to predict the bifurcation of transition paths in a generalized coupled bistable system. We confirm the validity of the theory for the example system by numerical simulation. We also demonstrate in the example system that, if the steady states of individual gene circuits are not changed by the coupling, the bifurcation pattern is not dependent on the number of gene circuits. We further show that the transition rate exponentially decreases with the number of gene circuits when the transition path does not bifurcate, while a bifurcation facilitates the transition by lowering the quasi-potential energy barrier. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.04477v2.pdf"}
{"id": "1603.04798", "abstract": "  In this paper we propose a new method called ND-Tree-based update (or shortly ND-Tree) for the dynamic non-dominance problem, i.e. the problem of online update of a Pareto archive composed of mutually non-dominated points. It uses a new ND-Tree data structure in which each node represents a subset of points contained in a hyperrectangle defined by its local approximate ideal and nadir points. By building subsets containing points located close in the objective space and using basic properties of the local ideal and nadir points we can efficiently avoid searching many branches in the tree. ND-Tree may be used in multiobjective evolutionary algorithms and other multiobjective metaheuristics to update an archive of potentially non-dominated points. We prove that the proposed algorithm has sub-linear time complexity under mild assumptions. We experimentally compare ND-Tree to the simple list, Quad-tree, and M-Front methods using artificial and realistic benchmarks with up to 10 objectives and show that with this new method substantial reduction of the number of point comparisons and computational time can be obtained. Furthermore, we apply the method to the non-dominated sorting problem showing that it is highly competitive to some recently proposed algorithms dedicated to this problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.04798v2.pdf"}
{"id": "1603.04886", "abstract": "  Pulsar wind nebulae (PWNe) are suggested to be acceleration sites of cosmic rays in the Galaxy. While the magnetic field plays an important role in the acceleration process, previous observations of magnetic field configurations of PWNe are rare, particularly for evolved systems. We present a radio polarization study of the \"Snail\" PWN inside the supernova remnant G327.1-1.1 using the Australia Telescope Compact Array. This PWN is believed to have been recently crushed by the supernova (SN) reverse shock. The radio morphology is composed of a main circular body with a finger-like protrusion. We detected a strong linear polarization signal from the emission, which reflects a highly ordered magnetic field in the PWN and is in contrast to the turbulent environment with a tangled magnetic field generally expected from hydrodynamical simulations. This could suggest that the characteristic turbulence scale is larger than the radio beam size. We built a toy model to explore this possibility, and found that a simulated PWN with a turbulence scale of about one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50–75", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.04886v1.pdf"}
{"id": "1603.07848", "abstract": "  Many astronomical objects are surrounded by dusty environments. In such dusty objects, multiple scattering processes of photons by circumstellar (CS) dust grains can effectively alter extinction properties. In this paper, we systematically investigate effects of multiple scattering on extinction laws for steady-emission sources surrounded by the dusty CS medium, using a radiation transfer simulation based on the Monte Carlo technique. In particular, we focus on whether and how the extinction properties are affected by properties of CS dust grains, adopting various dust grain models. We confirm that behaviors of the (effective) extinction laws are highly dependent on the properties of CS grains. Especially, the total-to-selective extinction ratio R_V, which characterizes the extinction law, can be either increased or decreased, compared to the case without multiple scattering. We find that the criterion for this behavior is given by a ratio of albedos in the B and V bands. We also find that either small silicate grains or polycyclic aromatic hydrocarbons (PAHs) are necessary for realizing a low value of R_V as often measured toward Type Ia supernovae, if the multiple scattering by CS dust is responsible for their non-standard extinction laws. Using the derived relations between the properties of dust grains and the resulting effective extinction laws, we propose that the extinction laws toward dusty objects could be used to constrain the properties of dust grains in CS environments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.07848v1.pdf"}
{"id": "1603.08457", "abstract": "  We investigate the origin of the scaling corrections in ballistic deposition models in high dimensions using the method proposed by Alves et al. [Phys Rev. E 90, 052405 (20014)] in d=2+1 dimensions, where the intrinsic width associated with the fluctuations of the height increments during the deposition processes is explicitly taken into account. In the present work, we show that this concept holds for d=3+1 and 4+1 dimensions. We have found that growth and roughness exponents and dimensionless cumulant ratios are in agreement with other models, presenting small finite-time corrections to the scaling, that in principle belong to the Kardar-Parisi-Zhang (KPZ) universality class in both d=3+1 and 4+1. Our results constitute a new evidence that the upper critical dimension of the KPZ class, if it exists, is larger than 4. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.08457v2.pdf"}
{"id": "1603.08641", "abstract": "  We propose a practical approach to manipulate the counter-rotating (CR) interactions in the quantum Rabi model by introducing a sinusoidal modulation to the transition frequency of the quantum two-level system in this model. By choosing appropriate modulation frequency and amplitude, enhancement and suppression of the CR interactions can be achieved in the Jaynes-Cummings regime (including both weak- and strong-coupling cases) as well as the ultrastrong-coupling regime. In particular, we calculate the output photon emission of the cavity vacuum state under enhanced CR terms. Our results show that continuous and steady photon emission from the cavity vacuum can be observed in the Jaynes-Cummings regime as a consequence of this enhancement. Our approach can be realized in superconducting quantum circuits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.08641v1.pdf"}
{"id": "1603.08761", "abstract": "  The formation and evolution of galactic spiral arms is not yet clearly understood despite many analytic and numerical work. Recently, a new idea has been proposed that local density enhancements (waklets) arising in the galactic disk connect with each other and make global spiral arms. However, the understanding of this mechanism is not yet sufficient. We analyze the interaction of wakelets by using N-body simulations including perturbing point masses, which are heavier than individual N-body particles and act as the seeds for wakelets. Our simulation facilitates more straightforward interpretation of numerical results than previous work by putting a certain number of perturbers in a well-motivated configuration. We detected a clear sign of non-linear interaction between wakelets, which make global spiral arms by connecting two adjacent wakelets. We found that the wave number of the strongest non-linear interaction depends on galactic disk mass and shear rate. This dependence is consistent with the prediction of swing amplification mechanism and other previous results. Our results provide unification of previous results which seemed not consistent with each other. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.08761v1.pdf"}
{"id": "1603.09644", "abstract": "  We analyse the proposal of sliding phases (SP) in layers hosting global U(1) symmetric variables with finite inter-layer Josephson coupling. Based on the Kosterlitz-Thouless renormalization group (RG) approach, such phases were predicted to exist in various layered (or 1D quantum coupled) systems. The key in the RG argument is treating the coupling as though the variables are non-compact. Large scale Monte Carlo simulations of a layered model, where the SP is supposed to exist, finds no indication of such a phase. Instead, 3D behavior is observed. This result is consistent with the asymptotically exact analytical solution. A generic argument against SP in translationally invariant systems with short range interactions is provided. We have also suggested an alternative model for the SP – adding long-range interactions to the inter-layer Josephson term. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.09644v1.pdf"}
{"id": "1604.00122", "abstract": "  We study a bilayer Kane-Mele-Hubbard model with lattice distortion and inter-layer spin exchange interaction under cylinder geometry. Our analysis based on real-space dynamical mean field theory with continuous-time quantum Monte Carlo demonstrates the emergence of a topological edge Mott insulating (TEMI) state which hosts gapless edge modes only in collective spin excitations. This is confirmed by the numerical calculations at finite temperatures for the spin-Hall conductivity and the single-particle excitation spectrum; the spin Hall conductivity is almost quantized, σ^xy_spin∼2(e/2π), predicting gapless edge modes carrying the spin current, while the helical edge modes in the single-particle spectrum are gapped out with respecting symmetry. It is clarified how the TEMI state evolves from the ordinary spin Hall insulating state with increasing the Hubbard interaction at a given temperature and then undergoes a phase transition to a trivial Mott insulating state. With a bosonization approach at zero temperature, we further address which collective modes host gapless edge modes in the TEMI state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.00122v1.pdf"}
{"id": "1604.03377", "abstract": "  We propose a simple renormalizable grand unified theory based on the SU(5) gauge symmetry where the neutrino masses are generated at the quantum level through the Zee mechanism. In this model the same Higgs needed to correct the mass relation between charged leptons and down-type quarks plays a crucial role to generate neutrino masses. We show that in this model one can satisfy the constrains coming from the unification of gauge couplings and the mechanism for neutrino masses is discussed in detail. The predictions for proton decay are discussed in order to understand the testability at current and future experiments such as Hyper-Kamiokande. This simple theory predicts a light colored octet which could give rise to exotic signatures at the LHC. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.03377v2.pdf"}
{"id": "1604.04073", "abstract": "  The objective of the present study is to mitigate, or even completely eliminate, the limit cycle oscillations in mechanical systems using a passive nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA). An unconventional aspect of the NLTVA is that the mathematical form of its restoring force is not imposed a priori, as it is the case for most existing nonlinear absorbers. The NLTVA parameters are determined analytically using stability and bifurcation analyses, and the resulting design is validated using numerical continuation. The proposed developments are illustrated using a Van der Pol-Duffing primary system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.04073v1.pdf"}
{"id": "1604.04543", "abstract": "  We present new results from a continuing 5 GHz search for flaring radio emission from a sample of L and T brown dwarfs, conducted with the 305-m Arecibo radio telescope. In addition to the previously reported flaring from the T6.5-dwarf 2MASS J10475385+212423, we have detected and confirmed circularly polarized flares from another T6-dwarf, WISEPC J112254.73+255021.5. Although the flares are sporadic, they appear to occur at a stable period of 0.288 hours. Given the current constraints, periods equal to its second and third subharmonic cannot be ruled out. The stability of this period over the 8-month timespan of observations indicates that, if real, it likely reflects the star's rapid rotation. If confirmed, any of the three inferred periodicities would be much shorter than the shortest, 1.41-hour rotation period of a brown dwarf measured so far. This finding would place a new observational constraint on the angular momentum evolution and rotational stability of substellar objects. The detection of radio emission from the sixth  1000 K dwarf further demonstrates that the coolest brown dwarfs and, possibly, young giant planets, can be efficiently investigated using radio observations at centimeter wavelengths as a tool. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.04543v1.pdf"}
{"id": "1604.05196", "abstract": "  We prove that every Legendrian knot in the tight contact structure of the 3-sphere is determined by the contactomorphism type of its exterior. Moreover, by giving counterexamples we show this to be not true for Legendrian links in the tight 3-sphere. On the way a new user-friendly formula for computing the Thurston-Bennequin invariant of a Legendrian knot in a surgery diagram is given. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.05196v2.pdf"}
{"id": "1604.06581", "abstract": "  Infrastructure as a service (IaaS) systems offer on demand virtual infrastructures so reliably and flexibly that users expect a high service level. Therefore, even with regards to internal IaaS behaviour, production clouds only adopt novel ideas that are proven not to hinder established service levels. To analyse their expected behaviour, new ideas are often evaluated with simulators in production IaaS system-like scenarios. For instance, new research could enable collaboration amongst several layers of schedulers or could consider new optimisation objectives such as energy consumption. Unfortunately, current cloud simulators are hard to employ and they often have performance issues when several layers of schedulers interact in them. To target these issues, a new IaaS simulation framework (called DISSECT-CF) was designed. The new simulator's foundation has the following goals: easy extensibility, support energy evaluation of IaaSs and to enable fast evaluation of many scheduling and IaaS internal behaviour related scenarios. In response to the requirements of such scenarios, the new simulator introduces concepts such as: a unified model for resource sharing and a new energy metering framework with hierarchical and indirect metering options. Then, the comparison of several simulated situations to real-life IaaS behaviour is used to validate the simulator's functionality. Finally, a performance comparison is presented between DISSECT-CF and some currently available simulators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.06581v1.pdf"}
{"id": "1604.08827", "abstract": "  The nature of the icy material accreted by comets during their formation in the outer regions of the protosolar nebula is a major open question in planetary science. Some scenarios of comet formation predict that these bodies agglomerated from crystalline ices condensed in the protosolar nebula. Concurrently, alternative scenarios suggest that comets accreted amorphous ice originating from the interstellar cloud or from the very distant regions of the protosolar nebula. On the basis of existing laboratory and modeling data, we find that the N_2/CO and Ar/CO ratios measured in the coma of the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA instrument aboard the European Space Agency's Rosetta spacecraft match those predicted for gases trapped in clathrates. If these measurements are representative of the bulk N_2/CO and Ar/CO ratios in 67P/Churyumov-Gerasimenko, it implies that the ices accreted by the comet formed in the nebula and do not originate from the interstellar medium, supporting the idea that the building blocks of outer solar system bodies have been formed from clathrates and possibly from pure crystalline ices. Moreover, because 67P/Churyumov-Gerasimenko is impoverished in Ar and N_2, the volatile enrichments observed in Jupiter's atmosphere cannot be explained solely via the accretion of building blocks with similar compositions and require an additional delivery source. A potential source may be the accretion of gas from the nebula that has been progressively enriched in heavy elements due to photoevaporation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.08827v1.pdf"}
{"id": "1604.08863", "abstract": "  In this paper we introduce a numerical method for solving nonlinear Volterra integro-differential equations. In the first step, we apply implicit trapezium rule to discretize the integral in given equation. Further, the Daftardar-Gejji and Jafari technique (DJM) is used to find the unknown term on the right side. We derive existence-uniqueness theorem for such equations by using Lipschitz condition. We further present the error, convergence, stability and bifurcation analysis of the proposed method. We solve various types of equations using this method and compare the error with other numerical methods. It is observed that our method is more efficient than other numerical methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.08863v1.pdf"}
{"id": "1605.00042", "abstract": "  We address the problem of estimating a sparse low-rank matrix from its noisy observation. We propose an objective function consisting of a data-fidelity term and two parameterized non-convex penalty functions. Further, we show how to set the parameters of the non-convex penalty functions, in order to ensure that the objective function is strictly convex. The proposed objective function better estimates sparse low-rank matrices than a convex method which utilizes the sum of the nuclear norm and the ℓ_1 norm. We derive an algorithm (as an instance of ADMM) to solve the proposed problem, and guarantee its convergence provided the scalar augmented Lagrangian parameter is set appropriately. We demonstrate the proposed method for denoising an audio signal and an adjacency matrix representing protein interactions in the `Escherichia coli' bacteria. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.00042v2.pdf"}
{"id": "1605.02045", "abstract": "  Semi-labeled trees are phylogenies whose internal nodes may be labeled by higher-order taxa. Thus, a leaf labeled Mus musculus could nest within a subtree whose root node is labeled Rodentia, which itself could nest within a subtree whose root is labeled Mammalia. Suppose we are given collection 𝒫 of semi-labeled trees over various subsets of a set of taxa. The ancestral compatibility problem asks whether there is a semi-labeled tree 𝒯 that respects the clusterings and the ancestor/descendant relationships implied by the trees in 𝒫. We give a Õ(M_𝒫) algorithm for the ancestral compatibility problem, where M_𝒫 is the total number of nodes and edges in the trees in 𝒫. Unlike the best previous algorithm, the running time of our method does not depend on the degrees of the nodes in the input trees. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.02045v1.pdf"}
{"id": "1605.02474", "abstract": "  We give efficient algorithms for the fundamental problems of Broadcast and Local Broadcast in dynamic wireless networks. We propose a general model of communication which captures and includes both fading models (like SINR) and graph-based models (such as quasi unit disc graphs, bounded-independence graphs, and protocol model). The only requirement is that the nodes can be embedded in a bounded growth quasi-metric, which is the weakest condition known to ensure distributed operability. Both the nodes and the links of the network are dynamic: nodes can come and go, while the signal strength on links can go up or down.   The results improve some of the known bounds even in the static setting, including an optimal algorithm for local broadcasting in the SINR model, which is additionally uniform (independent of network size). An essential component is a procedure for balancing contention, which has potentially wide applicability. The results illustrate the importance of carrier sensing, a stock feature of wireless nodes today, which we encapsulate in primitives to better explore its uses and usefulness. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.02474v1.pdf"}
{"id": "1605.03777", "abstract": "  Beyond the use of genuine monolithic integrated optical platforms, we report here a hybrid strategy enabling on-chip generation of configurable heralded two-photon states. More specifically, we combine two different fabrication techniques, i.e., non-linear waveguides on lithium niobate for efficient photon-pair generation and femtosecond-laser-direct-written waveguides on glass for photon manipulation. Through real-time device manipulation capabilities, a variety of path-coded heralded two-photon states can be produced, ranging from product to entangled states. Those states are engineered with high levels of purity, assessed by fidelities of 99.5±8% and 95.0±8%, respectively, obtained via quantum interferometric measurements. Our strategy therefore stands as a milestone for further exploiting entanglement-based protocols, relying on engineered quantum states, and enabled by scalable and compatible photonic circuits. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.03777v2.pdf"}
{"id": "1605.04755", "abstract": "  It is known that Schrödinger equation fails in describing the dynamics of highly energetic particles. We propose to quantify this lack of Lorentz covariance by evaluating the probability for a particle to be measured outside the set of light cones which are compatible to its initial wave function. We consider a simple case of a particle released from a box, which, in turn, is inside a larger container. It is shown that besides the increasing error at relativistic energies, there may be a complete breakdown, with Schrödinger dynamics implying in deterministic, superluminal signaling for Lorentz factors above 129. In addition, we give an exact asymptotic expression for the violation in local causality by employing the stationary exponent method, from which the Compton wave length of the particle naturally arises as the relevant scale for the stationary points. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.04755v1.pdf"}
{"id": "1605.06327", "abstract": "  In this paper, we consider combinatorial game rulesets based on data structures normally covered in an undergraduate Computer Science Data Structures course: arrays, stacks, queues, priority queues, sets, linked lists, and binary trees. We describe many rulesets as well as computational and mathematical properties about them. Two of the rulesets, Tower Nim and Myopic Col, are new. We show polynomial-time solutions to Tower Nim and to Myopic Col on paths. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.06327v1.pdf"}
{"id": "1605.06455", "abstract": "  We derive a Hamiltonian version of the PT-symmetric discrete nonlinear Schrödinger equation that describes synchronized dynamics of coupled pendula driven by a periodic movement of their common strings. In the limit of weak coupling between the pendula, we classify the existence and spectral stability of breathers (time-periodic solutions localized in the lattice) supported near one pair of coupled pendula. Orbital stability or instability of breathers is proved in a subset of the existence region. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.06455v1.pdf"}
{"id": "1605.07820", "abstract": "  Spinodal decomposition process in the system of immiscible PbTe/CdTe compounds is analyzed as an example of a self-organizing structure. The immiscibility of the constituents leads to the observed morphological transformations like anisotropy driven formation of quantum dots and nanowires, and to the phase separation at the highest temperatures. Proposed model accomplishes bulk and surface diffusion together with the anisotropic mobility of material components. We analyze its properties by kinetic Monte Carlo simulations and show that it is able to reproduce all of the structures observed experimentally in the process of PbTe/CdTe growth. We show that studied mechanisms of dynamic processes play different role in the creation of zero–, one–, two– and finally three-dimensional structures. The shape of grown structures is different for relatively thick multilayers when bulk diffusion cooperates with the anisotropic mobility, in annealed structure when isotropic bulk diffusion only decides about the process and finally for thin multilayers when surface diffusion is the most decisive factor. We compare our results with experimentally grown systems and show that proposed model explains the diversity of observed structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.07820v1.pdf"}
{"id": "1605.09336", "abstract": "  Many creative ideas are being proposed for image sensor designs, and these may be useful in applications ranging from consumer photography to computer vision. To understand and evaluate each new design, we must create a corresponding image processing pipeline that transforms the sensor data into a form that is appropriate for the application. The need to design and optimize these pipelines is time-consuming and costly. We explain a method that combines machine learning and image systems simulation that automates the pipeline design. The approach is based on a new way of thinking of the image processing pipeline as a large collection of local linear filters. We illustrate how the method has been used to design pipelines for novel sensor architectures in consumer photography applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.09336v1.pdf"}
{"id": "1606.00541", "abstract": "  In this paper, we investigate GPU based parallel triangular solvers systematically. The parallel triangular solvers are fundamental to incomplete LU factorization family preconditioners and algebraic multigrid solvers. We develop a new matrix format suitable for GPU devices. Parallel lower triangular solvers and upper triangular solvers are developed for this new data structure. With these solvers, ILU preconditioners and domain decomposition preconditioners are developed. Numerical results show that we can speed triangular solvers around seven times faster. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.00541v1.pdf"}
{"id": "1606.01983", "abstract": "  We discuss the host galaxy metallicity distribution of all long gamma-ray bursts (GRBs) whose redshifts are known to be < 0.4, including newly obtained spectroscopic datasets of the host galaxies of GRB 060614, 090417B, and 130427A. We compare the metallicity distribution of the low-redshift sample to the model predictions, and constrain the relation between metallicity and GRB occurrence. We take account of spatial variation of metallicities among star forming regions within a galaxy. We found that the models, in which only low-metallicity stars produce GRBs with a sharp cutoff of GRB production efficiency around 12+log(O/H) ∼ 8.3, can well reproduce the observed distribution, while the models with no metallicity dependence are not consistent with the observations. We also discuss possible sampling biases we may suffer by collecting long GRBs whose redshifts are known, presenting the photometric observations of the host galaxy of GRB 111225A at z = 0.297 whose redshift has been undetermined until ∼ 2.3 years after the burst. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.01983v2.pdf"}
{"id": "1606.03183", "abstract": "  We two had year-long research leaves in Japan, working together fulltime with several Japanese plus Tony De Groot back in Livermore and Harald Posch in Vienna. We summarize a few of the high spots from that very productive year ( 1989-1990 ), followed by an additional fifteen years' work in Livermore, with extensive travel. Next came our retirement in Nevada in 2005, which has turned out to be a long-term working vacation. Carol narrates this part of our history together. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.03183v2.pdf"}
{"id": "1606.04147", "abstract": "  A large Time Projection Chamber (TPC) is the main device for tracking and charged-particle identification in the ALICE experiment at the CERN LHC. After the second long shutdown in 2019-2020, the LHC will deliver Pb beams colliding at an interaction rate up to 50 kHz, which is about a factor of 100 above the present read-out rate of the TPC. To fully exploit the LHC potential the TPC will be upgraded based on the Gas Electron Multiplier (GEM) technology.   A prototype of an ALICE TPC Outer Read-Out Chamber (OROC) was equipped with twelve large-size GEM foils as amplification stage to demonstrate the feasibility of replacing the current Multi Wire Proportional Chambers with the new technology. With a total area of ∼0.76 m^2 it is the largest GEM-based detector built to date. The GEM OROC was installed within a test field cage and commissioned with radioactive sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.04147v1.pdf"}
{"id": "1606.08561", "abstract": "  We develop a classification algorithm for estimating posterior distributions from positive-unlabeled data, that is robust to noise in the positive labels and effective for high-dimensional data. In recent years, several algorithms have been proposed to learn from positive-unlabeled data; however, many of these contributions remain theoretical, performing poorly on real high-dimensional data that is typically contaminated with noise. We build on this previous work to develop two practical classification algorithms that explicitly model the noise in the positive labels and utilize univariate transforms built on discriminative classifiers. We prove that these univariate transforms preserve the class prior, enabling estimation in the univariate space and avoiding kernel density estimation for high-dimensional data. The theoretical development and both parametric and nonparametric algorithms proposed here constitutes an important step towards wide-spread use of robust classification algorithms for positive-unlabeled data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.08561v2.pdf"}
{"id": "1607.03666", "abstract": "  The effective interaction between two planar walls immersed in a fluid is investigated by use of Density Functional Theory in the super-critical region of the phase diagram. A hard core Yukawa model of fluid is studied with special attention to the critical region. To achieve this goal a new formulation of the Weighted Density Approximation coupled with the Hierarchical Reference Theory, able to deal with critical long wavelength fluctuations, is put forward and compared with other approaches. The effective interaction between the walls is seen to change character on lowering the temperature: The strong oscillations induced by layering of the molecules, typical of the depletion mechanism in hard core systems, are gradually smoothed and, close to the critical point, a long range attractive tail emerges leading to a scaling form which agrees with the expectations based on the critical Casimir effect. Strong corrections to scaling are seen to affect the results up to very small reduced temperatures. By use of Derjaguin approximation, this investigation has natural implications for the aggregation of colloidal particles in critical solvents. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.03666v1.pdf"}
{"id": "1607.05754", "abstract": "  The next generation Advanced ACTPol (AdvACT) experiment is currently underway and will consist of four Transition Edge Sensor (TES) bolometer arrays, with three operating together, totaling  5800 detectors on the sky. Building on experience gained with the ACTPol detector arrays, AdvACT will utilize various new technologies, including 150mm detector wafers equipped with multichroic pixels, allowing for a more densely packed focal plane. Each set of detectors includes a feedhorn array of stacked silicon wafers which form a spline profile leading to each pixel. This is then followed by a waveguide interface plate, detector wafer, back short cavity plate, and backshort cap. Each array is housed in a custom designed structure manufactured from high purity copper and then gold plated. In addition to the detector array assembly, the array package also encloses cryogenic readout electronics. We present the full mechanical design of the AdvACT high frequency (HF) detector array package along with a detailed look at the detector array stack assemblies. This experiment will also make use of extensive hardware and software previously developed for ACT, which will be modified to incorporate the new AdvACT instruments. Therefore, we discuss the integration of all AdvACT arrays with pre-existing ACTPol infrastructure. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.05754v1.pdf"}
{"id": "1607.05856", "abstract": "  The pole structure of the Λ(1405) is examined by fitting the couplings of an underlying Hamiltonian effective field theory to cross sections of K^- p scattering in the infinite-volume limit. Finite-volume spectra are then obtained from the theory, and compared to lattice QCD results for the mass of the Λ(1405). Momentum-dependent, non-separable potentials motivated by the well-known Weinberg-Tomozawa terms are used, with SU(3) flavour symmetry broken in the couplings and masses. In addition, we examine the effect on the behaviour of the spectra from the inclusion of a bare triquark-like isospin-zero basis state. It is found that the cross sections are consistent with the experimental data with two complex poles for the Λ(1405), regardless of whether a bare baryon basis state is introduced or not. However, it is apparent that the bare baryon is important for describing the results of lattice QCD at high pion masses. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.05856v2.pdf"}
{"id": "1607.08857", "abstract": "  A formalism is presented for treating strongly-correlated graphene quantum Hall states in terms of an SO(8) fermion dynamical symmetry that includes pairing as well as particle–hole generators. The graphene SO(8) algebra is isomorphic to an SO(8) algebra that has found broad application in nuclear physics, albeit with physically very different generators, and exhibits a strong formal similarity to SU(4) symmetries that have been proposed to describe high-temperature superconductors. The well-known SU(4) symmetry of quantum Hall ferromagnetism for single-layer graphene is recovered as one subgroup of SO(8), but the dynamical symmetry structure associated with the full set of SO(8) subgroup chains extends quantum Hall ferromagnetism and allows analytical many-body solutions for a rich set of collective states exhibiting spontaneously-broken symmetry that may be important for the low-energy physics of graphene in strong magnetic fields. The SO(8) symmetry permits a natural definition of generalized coherent states that correspond to symmetry-constrained Hartree–Fock–Bogoliubov solutions, or equivalently a microscopically-derived Ginzburg–Landau formalism, exhibiting the interplay between competing spontaneously broken symmetries in determining the ground state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.08857v1.pdf"}
{"id": "1608.00527", "abstract": "  We report on the recovery of the six old novae EL Aql, V606 Aql, V908 Oph, V1149 Sgr, V1583 Sgr and V3964 Sgr, using photometric and spectroscopic data. Analysing several properties, we find that EL Aql is a good candidate for an intermediate polar. Furthermore, the system inclination of EL Aql, V606 Aql, V1583 Sgr and V3964 Sgr appears to be sufficiently high to suggest them as good targets for time series observations. We also eliminate some previously suggested candidates for the post-novae V1301 Aql and V1151 Sgr. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.00527v1.pdf"}
{"id": "1608.01495", "abstract": "  A large number of optimization algorithms have been developed by researchers to solve a variety of complex problems in operations management area. We present a novel optimization algorithm belonging to the class of swarm intelligence optimization methods. The algorithm mimics the decision making process of human groups and exploits the dynamics of this process as an optimization tool for combinatorial problems. In order to achieve this aim, a continuous-time Markov process is proposed to describe the behavior of a population of socially interacting agents, modelling how humans in a group modify their opinions driven by self-interest and consensus seeking. As in the case of a collection of spins, the dynamics of such a system is characterized by a phase transition from low to high values of the overall consenus (magnetization). We recognize this phase transition as being associated with the emergence of a collective superior intelligence of the population. While this state being active, a cooling schedule is applied to make agents closer and closer to the optimal solution, while performing their random walk on the fitness landscape. A comparison with simulated annealing as well as with a multi-agent version of the simulated annealing is presented in terms of efficacy in finding good solution on a NK - Kauffman landscape. In all cases our method outperforms the others, particularly in presence of limited knowledge of the agent. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.01495v1.pdf"}
{"id": "1608.02079", "abstract": "  Recently, Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) detected gravitational wave (GW) transients from mergers of binary black holes (BHs). The system may also produce a wide-angle, relativistic outflow if the claimed short GRB detected by GBM is in real association with GW 150914. It was suggested that mergers of double neutron stars (or neutron star-black hole binaries), another promising source of GW transients, also produce fast, wide-angle outflows. In this paper, we calculate the high-energy gamma-ray emission arising from the blast waves driven by these wide-angle outflows. We find that TeV emission arising from the inverse-Compton process in the relativistic outflow resulted from mergers of binary BHs similar to those in GW 150914 could be detectable by ground-based IACT telescopes such as Cherenkov Telescope Array (CTA) if the sources occur in  a dense medium with density n > 0.3 cm^-3. For neutron star-neutron star (NS-NS) and NS-BH mergers, TeV emission from the wide-angle, mildly-relativistic outflow could be detected as well if they occur in a dense medium with n > 10-100 cm^-3. Thus TeV afterglow emission would be a useful probe of the environment of the GW transients, which could shed light on the evolution channels of the progenitors of GW transients. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.02079v1.pdf"}
{"id": "1608.02593", "abstract": "  I propose an archtitecture for the realization of dissipative quantum many-body spin models. The dissipative processes are mediated by interactions with auxiliary particles and lead to a widely tunable class of correlated quantum jump operators. These findings enable the investigation of purely dissipative spin models, where coherent dynamics is entirely absent. I provide a detailed review of a recently introduced variational method to analyze such dissipative quantum many-body systems, and I discuss a specific example in terms of a purely dissipative Heisenberg model, for which I find an additional disordered phase that is not present in the corresponding ground state phase diagram. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.02593v1.pdf"}
{"id": "1608.03884", "abstract": "  A trace gas sensor, based on quartz-enhanced photoacoustic spectroscopy (QEPAS), consisting of two acoustically coupled micro-resonators (mR) with an off-axis 20 kHz quartz tuning fork (QTF) is demonstrated. The complete acoustically coupled mR system is optimized based on finite element simulations and experimentally verified. The QEPAS sensor is pumped resonantly by a nanosecond pulsed single-mode mid-infrared optical parametric oscillator (MIR OPO). The sensor is used for spectroscopic measurements on methane in the 3.1 um to 3.5 um wavelength region with a resolution bandwidth of 1 cm^-1 and a detection limit of 0.8 ppm. An Allan deviation analysis shows that the detection limit at optimum integration time for the QEPAS sensor is 32 ppbv@190s and that the background noise is solely due to the thermal noise of the QTF. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.03884v1.pdf"}
{"id": "1608.07065", "abstract": "  The question of universality class of pair contact process with diffusion (PCPD) is revisited with an alternative approach. We study persistence in Generalized Pair-Contact Process with diffusion (GPCPD) introduced by Noh and Park, (Phys. Rev. E 69,016122(2004)). This model allows us to interpolate between directed percolation (DP) and PCPD universality classes. We find that transition to nonzero persistence is at same parameter value as transition to zero number density. We obtain finite size scaling and off-critical scaling collapse for persistence and find critical exponents by fitting phenomenological scaling laws to persistence. While the dynamic scaling exponent z varies continuously in GPCPD, the correlation-time exponent ν_∥ matches with directed percolation universality class. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.07065v1.pdf"}
{"id": "1608.07768", "abstract": "  We study observables sensitive to tensor structure of interactions of a hypothetical heavy spin-0 particle. It is assumed that the interactions of this particle are primary with photons; interactions with vector bosons gg, WW, ZZ, and quarks tt̅ are suppressed. The above assumptions favor the production of this hypothetical particle through the vector boson fusion mechanism structurally dominated by γγ and γ Z interactions. This particle will be produced in association with two light quarks. It is shown that the difference in azimuthal angle between the tagging jets provides an observable sensitive to the CP properties of this hypothetical particle. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.07768v1.pdf"}
{"id": "1609.00064", "abstract": "  Recent studies have shown that outflows in at least some broad absorption line (BAL) quasars are extended well beyond the putative dusty torus. Such outflows should be detectable in obscured quasars. We present four WISE selected infrared red quasars with very strong and peculiar ultraviolet Fe ii emission lines: strong UV Fe II UV arising from transitions to ground/low excitation levels, and very weak Fe II at wavelengths longer than 2800 Å. The spectra of these quasars display strong resonant emission lines, such as C IV, Al III and Mg II but sometimes, a lack of non-resonant lines such as C III], S III and He II. We interpret the Fe II lines as resonantly scattered light from the extended outflows that are viewed nearly edge-on, so that the accretion disk and broad line region are obscured by the dusty torus, while the extended outflows are not. We show that dust free gas exposed to strong radiation longward of 912 Å produces Fe II emission very similar to that observed. The gas is too cool to collisionally excite Fe II lines, accounting for the lack of optical emission. The spectral energy distribution from the UV to the mid-infrared can be modeled as emission from a clumpy dusty torus, with UV emission being reflected/scattered light either by the dusty torus or the outflow. Within this scenario, we estimate a minimum covering factor of the outflows from a few to 20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.00064v1.pdf"}
{"id": "1609.00470", "abstract": "  We calculate orbital spin-dependent magnetization in a two-dimensional electron gas with spin-orbit interaction of Rashba type. Such an orbital magnetization is admitted by the time-reversal symmetry of the system, and gives rise to spin currents when the system is not in thermal equilibrium. The theoretical approach is based on the linear response theory and the Matsubara Green's function formalism. To account for the spin-resolved orbital magnetization a spin-dependent vector potential has been introduced. The spin currents which appear in thermal nonequilibrium due to the spin-resolved orbital magnetization play an important role in the spin Nernst effect, and have to be included in order to correctly describe the low-temperature spin Nernst conductivity. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.00470v1.pdf"}
{"id": "1609.01381", "abstract": "  We propose and evaluate the graphene layer (GL) infrared photodetectors (GLIPs) based on the van der Waals (vdW) heterostructures with the radiation absorbing GLs. The operation of the GLIPs is associated with the electron photoexcitation from the GL valence band to the continuum states above the inter-GL barriers (either via tunneling or direct transitions to the continuum states). Using the developed device model, we calculate the photodetector characteristics as functions of the GL-vdW heterostructure parameters. We show that due to a relatively large efficiency of the electron photoexcitation and low capture efficiency of the electrons propagating over the barriers in the inter-GL layers, GLIPs should exhibit the elevated photoelectric gain and detector responsivity as well as relatively high detectivity. The possibility of high-speed operation, high conductivity, transparency of the GLIP contact layers, and the sensitivity to normally incident IR radiation provides additional potential advantages in comparison with other IR photodetectors. In particular, the proposed GLIPs can compete with unitravelling-carrier photodetectors. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.01381v1.pdf"}
{"id": "1609.01458", "abstract": "  In this paper, we discuss a supervisory control problem of modular discrete-event systems that allows for a distributed computation of supervisors. We provide a characterization and an algorithm to compute the supervisors. If the specification does not satisfy the properties, we make use of a relaxation of coordination control to compute a sublanguage of the specification for which the supervisors can be computed in a distributed way. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.01458v1.pdf"}
{"id": "1609.01540", "abstract": "  We consider localized qubits evolving around a black hole following a quantum adiabatic dynamics. We develop a geometric structure (based on fibre bundles) permitting to describe the quantum states of a qubit and the spacetime geometry in a single framework. The quantum decoherence induced by the black hole on the qubit is analysed in this framework (the role of the dynamical and geometric phases in this decoherence is treated), especially for the quantum teleportation protocol when one qubit falls to the event horizon. A simple formula to compute the fidelity of the teleportation is derived. The case of a Schwarzschild black hole is analysed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.01540v2.pdf"}
{"id": "1609.01551", "abstract": "  Magnetic frustration, which is well-defined in insulating systems with localized magnetic moments, yields exotic ground states like spin ices, spin glasses, or spin liquids. In metals magnetic frustration is less well defined because of the incipient delocalization of magnetic moments by the interaction with conduction electrons, viz., the Kondo effect. Hence, the Kondo effect and magnetic frustration are antithetic phenomena. Here we present experimental data of electrical resistivity, magnetization, specific heat and neutron diffraction on CePdAl, which is one of the rare examples of a geometrically frustrated Kondo lattice, demonstrating that the combination of Kondo effect and magnetic frustration leads to an unusual ground state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.01551v1.pdf"}
{"id": "1609.01639", "abstract": "  We analyze in detail a previous proposal by Dvali and Gómez that black holes could be treated as consisting of a Bose-Einstein condensate of gravitons. In order to do so we extend the Einstein-Hilbert action with a chemical potential-like term, thus placing ourselves in a grand-canonical ensemble. The form and characteristics of this chemical potential-like piece are discussed in some detail. We argue that the resulting equations of motion derived from the action could be interpreted as the Gross-Pitaevskii equation describing a graviton Bose-Einstein condensate trapped by the black hole gravitational field. After this, we proceed to expand the ensuring equations of motion up to second order around the classical Schwarzschild metric so that some non-linear terms in the metric fluctuation are kept. Next we search for solutions and, modulo some very plausible assumptions, we find out that the condensate vanishes outside the horizon but is non-zero in its interior. Inspired by a linearized approximation around the horizon we are able to find an exact solution for the mean-field wave function describing the graviton Bose-Einstein condensate in the black hole interior. After this, we can rederive some of the relations involving the number of gravitons N and the black hole characteristics along the lines suggested by Dvali and Gómez. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.01639v3.pdf"}
{"id": "1609.02921", "abstract": "  Most types of supernovae (SNe) have yet to be connected with their progenitor stellar systems. Here, we reanalyze the 10-year SN sample collected during 1998-2008 by the Lick Observatory Supernova Search (LOSS) in order to constrain the progenitors of SNe Ia and stripped-envelope SNe (SE SNe, i.e., SNe IIb, Ib, Ic, and broad-lined Ic). We matched the LOSS galaxy sample with spectroscopy from the Sloan Digital Sky Survey and measured SN rates as a function of galaxy stellar mass, specific star formation rate, and oxygen abundance (metallicity). We find significant correlations between the SN rates and all three galaxy properties. The SN Ia correlations are consistent with other measurements, as well as with our previous explanation of these measurements in the form of a combination of the SN Ia delay-time distribution and the correlation between galaxy mass and age. The ratio between the SE SN and SN II rates declines significantly in low-mass galaxies. This rules out single stars as SE SN progenitors, and is consistent with predictions from binary-system progenitor models. Using well-known galaxy scaling relations, any correlation between the rates and one of the galaxy properties examined here can be expressed as a correlation with the other two. These redundant correlations preclude us from establishing causality - that is, from ascertaining which of the galaxy properties (or their combination) is the physical driver for the difference between the SE SN and SN II rates. We outline several methods that have the potential to overcome this problem in future works. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.02921v2.pdf"}
{"id": "1609.03116", "abstract": "  We use the subgraph replacement method to investigate new properties of the tilings of regions on the square lattice with diagonals drawn in. In particular, we show that the centrally symmetric tilings of a generalization of the Aztec diamond are always enumerated by a simple product formula. This result generalizes the previous work of Ciucu (1997) and Yang (1992) about symmetric tilings of the Aztec diamond. We also use our method to prove a closed-form product formula for the number of centrally symmetric tilings of a quasi-hexagon. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.03116v4.pdf"}
{"id": "1609.03595", "abstract": "  Galaxy mergers are important events that can determine the fate of a galaxy by changing its morphology, star-formation activity and mass growth. Merger systems have commonly been identified from their disturbed morphologies, and we now can employ Integral Field Spectroscopy to detect and analyze the impact of mergers on stellar kinematics as well. We visually classified galaxy morphology using deep images (μ_ r = 28  mag   arcsec^-2) taken by the Blanco 4-m telescope at the Cerro Tololo Inter-American Observatory. In this paper we investigate 63 bright (M_ r<-19.3) spectroscopically-selected galaxies in Abell 119; of which 53 are early type and 20 galaxies show a disturbed morphology by visual inspection. A misalignment between the major axes in the photometric image and the kinematic map is conspicuous in morphologically-disturbed galaxies. Our sample is dominated by early-type galaxies, yet it shows a surprisingly tight Tully-Fisher relation except for the morphologically-disturbed galaxies which show large deviations. Three out of the eight slow rotators in our sample are morphology disturbed. The visually-selected morphologically-disturbed galaxies are generally more asymmetric, visually as well as kinematically. Our findings suggest that galaxy interactions, including mergers and perhaps fly-bys, play an important role in determining the orientation and magnitude of galaxy's angular momentum. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.03595v1.pdf"}
{"id": "1609.05026", "abstract": "  An extreme dissipation event in the bulk of a closed three-dimensional turbulent convection cell is found to be correlated with a strong reduction of the large-scale circulation flow in the system that happens at the same time as a plume emission event from the bottom plate. The reduction in the large-scale circulation opens the possibility for a nearly frontal collision of down- and upwelling plumes and the generation of a high-amplitude thermal dissipation layer in the bulk. This collision is locally connected to a subsequent high-amplitude energy dissipation event in the form of a strong shear layer. Our analysis illustrates the impact of transitions in the large-scale structures on extreme events at the smallest scales of the turbulence, a direct link that is observed in a flow with boundary layers. We also show that detection of extreme dissipation events which determine the far-tail statistics of the dissipation fields in the bulk requires long-time integrations of the equations of motion over at least hundred convective time units. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.05026v1.pdf"}
{"id": "1609.05063", "abstract": "  Tourism industry has grown tremendously in the previous several decades. Despite its global impact, there still remain a number of open questions related to better understanding of tourists and their habits. In this work we analyze the largest data set of travel receipts considered thus far, and focus on exploring and modeling booking behavior of online customers. We extract useful, actionable insights into the booking behavior, and tackle the task of predicting the booking time. The presented results can be directly used to improve booking experience of customers and optimize targeting campaigns of travel operators. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.05063v1.pdf"}
{"id": "1609.05137", "abstract": "  The switching model is a Markov chain approach to sample graphs with fixed degree sequence uniformly at random. The recently invented Curveball algorithm for bipartite graphs applies several switches simultaneously (`trades'). Here, we introduce Curveball algorithms for simple (un)directed graphs which use single or simultaneous trades. We show experimentally that these algorithms converge magnitudes faster than the corresponding switching models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.05137v3.pdf"}
{"id": "1609.07589", "abstract": "  We introduce a new achievability scheme, termed opportunistic network decoupling (OND), operating in virtual full-duplex mode. In the scheme, a novel relay scheduling strategy is utilized in the K× N× K channel with interfering relays, consisting of K source–destination pairs and N half-duplex relays in-between them. A subset of relays using alternate relaying is opportunistically selected in terms of producing the minimum total interference level, thereby resulting in network decoupling. As our main result, it is shown that under a certain relay scaling condition, the OND protocol achieves K degrees of freedom even in the presence of interfering links among relays. Numerical evaluation is also shown to validate the performance of the proposed OND. Our protocol basically operates in a fully distributed fashion along with local channel state information, thereby resulting in a relatively easy implementation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.07589v1.pdf"}
{"id": "1609.07687", "abstract": "  The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.07687v1.pdf"}
{"id": "1609.08613", "abstract": "  We probe the higher-order clustering of the galaxies in the final data release (DR12) of the Sloan Digital Sky Survey Baryon Oscillation Spectroscopic Survey (BOSS) using the method of germ-grain Minkowski Functionals (MFs). Our sample consists of 410,615 BOSS galaxies from the northern Galactic cap in the redshift range 0.450–0.595. We show the MFs to be sensitive to contributions up to the six-point correlation function for this data set. We ensure with a custom angular mask that the results are more independent of boundary effects than in previous analyses of this type. We extract the higher-order part of the MFs and quantify the difference to the case without higher-order correlations. The resulting χ^2 value of over 10,000 for a modest number of degrees of freedom, O(200), indicates a 100-sigma deviation and demonstrates that we have a highly significant signal of the non-Gaussian contributions to the galaxy distribution. This statistical power can be useful in testing models with differing higher-order correlations. Comparing the galaxy data to the QPM and MultiDark-Patchy mocks, we find that the latter better describes the observed structure. From an order-by-order decomposition we expect that, for example, already a reduction of the amplitude of the MD-Patchy mock power spectrum by 5", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.08613v1.pdf"}
{"id": "1609.09300", "abstract": "  We report a simultaneous ground and space-based photometric study of the Beta Cephei star Nu Eridani. Half a year of observations have been obtained by four of the five satellites constituting BRITE-Constellation, supplemented with ground-based photoelectric photometry. We show that carefully combining the two data sets virtually eliminates the aliasing problem that often hampers time-series analyses. We detect 40 periodic signals intrinsic to the star in the light curves. Despite a lower detection limit we do not recover all the pressure and mixed modes previously reported in the literature, but we newly detect six additional gravity modes. This behaviour is a consequence of temporal changes in the pulsation amplitudes that we also detected for some of the p modes. We point out that the dependence of theoretically predicted pulsation amplitude on wavelength is steeper in visual passbands than those observationally measured, to the extent that the three dominant pulsation modes of Nu Eridani would be incorrectly identified using data in optical filters only. We discuss possible reasons for this discrepancy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.09300v1.pdf"}
{"id": "1609.09775", "abstract": "  A cavity quantum electrodynamical scenario is proposed for implementing a Schrödinger microscope capable of amplifying differences between non orthogonal atomic quantum states. The scheme involves an ensemble of identically prepared two-level atoms interacting pairwise with a single mode of the radiation field as described by the Tavis-Cummings model. By repeated measurements of the cavity field and of one atom within each pair a measurement-induced nonlinear quantum transformation of the relevant atomic states can be realized. The intricate dynamical properties of this nonlinear quantum transformation, which exhibits measurement-induced chaos, allows approximate orthogonalization of atomic states by purification after a few iterations of the protocol, and thus the application of the scheme for quantum state discrimination. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.09775v2.pdf"}
{"id": "1610.03437", "abstract": "  In this article, we present a denoising algorithm to improve the interpretation and quality of scanning tunneling microscopy (STM) images. Given the high level of self-similarity of STM images, we propose a denoising algorithm by reformulating the true estimation problem as a sparse regression, often termed sparse coding. We introduce modifications to the algorithm to cope with the existence of artifacts, mainly dropouts, which appear in a structured way as consecutive line segments on the scanning direction. The resulting algorithm treats the artifacts as missing data, and the estimated values outperform those algorithms that substitute the outliers by a local filtering. We provide code implementations for both Matlab and Gwyddion. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.03437v1.pdf"}
{"id": "1610.04002", "abstract": "  Social media platforms are now a key source of information for a large segment of the public. As such, these platforms have a great potential as a means to provide real-time information to emergency management agencies. Moreover, during an emergency, these agencies are very interested in social media as a means to find public-driven response efforts, as well as to track how their handling of that emergency is being perceived. However, there is currently a lack advanced tools designed for monitoring social media during emergencies. The Emergency Analysis Identification and Management System (EAIMS) is a prototype service that aims to fill this technology gap by providing richer analytic and exploration tools than current solutions. In particular, EAIMS provides real-time detection of emergency events, related information finding, information access and credibility analysis tools for use over social media during emergencies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.04002v1.pdf"}
{"id": "1610.06257", "abstract": "  We develop a potentially practical proposal for robust quantum state transfer (QST) between two superconducting qubits coupled by a coplanar waveguide (CPW) resonator. We show that the partial measurement could drastically enhance the fidelity even when the dissipation of qubits and CPW is considered. Unlike many other schemes for QST, our proposal does not require the couplings between the qubits and the CPW resonator to be strong. In fact, our method works much more efficiently in the weak coupling regime. The underlying mechanism is attributed to the probabilistic nature of partial measurement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.06257v1.pdf"}
{"id": "1610.06367", "abstract": "  In the search for CP violation at the T2K and future Hyper-Kamiokande experiments, it is crucial to reduce the present systematic uncertainties. The current T2K near detector, ND280, reduces the uncertainties coming from the neutrino beam and cross-section models from 11.9% to 5.4% in the ν_e appearance channel. These residual uncertainties mostly come from intrinsic limitations of ND280 due to its difference in target material and angular acceptance with the far detector.\n In order to show evidence (subsequently observation) of the CP violation in the T2K phase-II and Hyper-Kamiokande experiments, this paper proposes an upgrade of the ND280 detector. It uses a 3D grid scintillator structure surrounded by Time Projecting Chambers in order to reconstruct particles with ∼ 4π acceptance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.06367v1.pdf"}
{"id": "1610.09310", "abstract": "  We consider a discrete-time random walk on the nodes of an unbounded hexagonal lattice. We determine the probability generating functions, the transition probabilities and the relevant moments. The convergence of the stochastic process to a 2-dimensional Brownian motion is also discussed. Furthermore, we obtain some results on its asymptotic behavior making use of large deviation theory. Finally, we investigate the first-passage-time problem of the random walk through a vertical straight-line. Under suitable symmetry assumptions we are able to determine the first-passage-time probabilities in a closed form, which deserve interest in applied fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.09310v2.pdf"}
{"id": "1611.01161", "abstract": "  Lyman-Alpha (Lyα) is the strongest emission line in the Universe and is frequently used to detect and study the most distant galaxies. Because Lya is a resonant line, photons typically scatter prior to escaping; this scattering process complicates the interpretation of Lyα spectra, but also encodes a wealth of information about the structure and kinematics of neutral gas in the galaxy. Modeling the Lyα line therefore allows us to study tiny-scale features of the gas, even in the most distant galaxies. Curiously, observed Lyα spectra can be modeled successfully with very simple, homogeneous geometries (such as an expanding, spherical shell), whereas more realistic, multiphase geometries often fail to reproduce the observed spectra. This seems paradoxical since the gas in galaxies is known to be multiphase. In this Letter, we show that spectra emerging from extremely clumpy geometries with many clouds along the line of sight converge to the predictions from simplified, homogeneous models. We suggest that this resolves the apparent discrepancy, and may provide a way to study the gas structure in galaxies on scales far smaller than can be probed in either cosmological simulations or direct (i.e., spatially-resolved) observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.01161v1.pdf"}
{"id": "1611.03006", "abstract": "  An increasing number of individuals are turning to Direct-To-Consumer (DTC) genetic testing to learn about their predisposition to diseases, traits, and/or ancestry. DTC companies like 23andme and Ancestry.com have started to offer popular and affordable ancestry and genealogy tests, with services allowing users to find unknown relatives and long-distant cousins. Naturally, access and possible dissemination of genetic data prompts serious privacy concerns, thus motivating the need to design efficient primitives supporting private genetic tests. In this paper, we present an effective protocol for privacy-preserving genetic relatedness test (PPGRT), enabling a cloud server to run relatedness tests on input an encrypted genetic database and a test facility's encrypted genetic sample. We reduce the test to a data matching problem and perform it, privately, using searchable encryption. Finally, a performance evaluation of hamming distance based PP-GRT attests to the practicality of our proposals. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.03006v2.pdf"}
{"id": "1611.03441", "abstract": "  The predictive properties of a retina are studied by measuring the mutual information (MI) between its stimulation and the corresponding firing rates while it is being probed by a train of short pulses with stochastic intervals. Features of the measured MI at various time shifts between the stimulation and the response are used to characterize the predictive properties of the retina. By varying the statistical properties of the pulse train, our experiments show that a retina has the ability to predict future events of the stimulation if the information rate of the stimulation is low enough. Also, this predictive property of the retina occurs at a time scale similar to the well established anticipative phenomenon of omitted stimulus response in a retina. Furthermore, a retina can make use of its predictive ability to distinguish between time series created by an Ornstein–Uhlenbeck and a hidden Markovian process. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.03441v1.pdf"}
{"id": "1611.05579", "abstract": "  Traffic Jam has been a daily problem for people in Jakarta which is one of the busiest city in Indonesia up until now. Even though the official government has tried to reduce the impact of traffic issues by developing a new public transportation which takes up a lot of resources and time, it failed to diminish the problem. The actual concern to this problem actually lies in how people move between places in Jakarta where they always using their own vehicle like cars, and motorcycles that fill most of the street in Jakarta. Among much other public transportations that roams the street of Jakarta, Buses is believed to be an efficient transportation that can move many people at once. However, the location of the bus stop is now have moved to the middle of the main road, and it is too far for the nearby residence to access to it. This paper proposes an optimal location of optimal bus stops in West Jakarta that is experimentally proven to have a maximal distance of 350 m. The optimal location is estimated by means of mean shift clustering method while the optimal routes are calculated using Ant Colony algorithm. The bus stops locations rate of error is 0.07", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.05579v1.pdf"}
{"id": "1611.09040", "abstract": "  The position of a Martian lander is affected by different aspects of Mars' rotational motions: the nutations, the precession, the length-of-day variations and the polar motion. These various motions have a different signature in a Doppler observable between the Earth and a lander on Mars' surface. Knowing the correlations between these signatures and the moments when these signatures are not null during one day or on a longer timescale is important to identify strategies that maximize the geophysical return of observations with a geodesy experiment, in particular for the ones on-board the future NASA InSight or ESA-Roscosmos ExoMars2020 missions.   We provide first-order formulations of the signature of the rotation parameters in the Doppler and range observables. These expressions are functions of the diurnal rotation of Mars, the lander position, the planet radius and the rotation parameter. Additionally, the nutation signature in the Doppler observable is proportional to the Earth declination with respect to Mars.   For a lander on Mars close to the equator, the motions with the largest signature in the Doppler observable are due to the length-of-day variations, the precession rate and the rigid nutations. The polar motion and the liquid core signatures have a much smaller amplitude. For a lander closer to the pole, the polar motion signature is enhanced while the other signatures decrease.   We also numerically evaluate the amplitudes of the rotation parameters signature in the Doppler observable for landers on other planets or moons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.09040v2.pdf"}
{"id": "1612.02116", "abstract": "  Signal processing in biological systems is delicately executed by specialised networks, which are modular assemblies of network motifs. The motifs are independently functional circuits found in enormous numbers in any living cell. A very common network motif is the feed-forward loop (FFL), which regulates a downstream node by an upstream one in a direct and an indirect way within the network. If the direct and indirect regulations go antagonistic, the motif is known as an incoherent FFL (ICFFL). The current study is aimed at exploring the reason for the variation in the evolutionary selection of the four types of ICFFLs. As comparative measures, I compute sensitivity amplification, adaptation precision and efficiency from the temporal dynamics and mutual information between the input-output nodes of the motifs at steady state. The ICFFL II performs very efficiently in adaptation but poor in information processing. On the other hand, ICFFL I and III are better in information transmission compared to adaptation efficiency. Which is the fittest among them under the pressure of natural selection? To sort out this puzzle, I take help from the multi-objective Pareto efficiency. The results, found in the Pareto task space, are in good agreement with the reported abundance level of all the types in eukaryotes as well as prokaryotes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.02116v1.pdf"}
{"id": "1612.02600", "abstract": "  The dynamics of tripartite entanglement of fermionic system in noninertial frames through linear contraction criterion when one or two observers are accelerated is investigated. In one observer accelerated case the entanglement measurement is not invariant with respect to the partial realignment of different subsystems and for two observers accelerated case it is invariant. It is shown that the acceleration of the frame does not generate entanglement in any bipartite subsystems. Unlike the bipartite states, the genuine tripartite entanglement does not completely vanish in both one observer accelerated and two observers accelerated cases even in the limit of infinite acceleration. The degradation of tripartite entanglement is fast when two observers are accelerated than when one observer is accelerated. It is shown that tripartite entanglement is a better resource for quantum information processing than the bipartite entanglement in noninertial frames . ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.02600v1.pdf"}
{"id": "1612.02823", "abstract": "  The finding that massive galaxies grow with cosmic time fired the starting gun for the search of objects which could have survived up to the present day without suffering substantial changes (neither in their structures, neither in their stellar populations).   Nevertheless, and despite the community efforts, up to now only one firm candidate to be considered one of these relics is known: NGC 1277. Curiously, this galaxy is located at the centre of one of the most rich near galaxy clusters: Perseus. Is its location a matter of chance? Should relic hunters focus their search on galaxy clusters?   In order to reply this question, we have performed a simultaneous and analogous analysis using simulations (Millennium I-WMAP7) and observations (New York University Value-Added Galaxy Catalogue). Our results in both frameworks agree: it is more probable to find relics in high density environments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.02823v2.pdf"}
{"id": "1612.03392", "abstract": "  In this paper, we theoretically propose an optomechanical scheme to explore the possibility of simulating the propagation of the collective excitations of the photon fluid in a curved spacetime. For this purpose, we introduce two theoretical models for two-dimensional photon gas in a planar optomechanical microcavity and a two-dimensional array of coupled optomechanical systems. In the reversed dissipation regime (RDR) of cavity optomechanics where the mechanical oscillator reaches equilibrium with its thermal reservoir much faster than the cavity modes, the mechanical degrees of freedom can adiabatically be eliminated. The adiabatic elimination of the mechanical mode provides an effective nonlinear Kerr-type photon-photon interaction. Using the nonlinear Schrödinger equation (NLSE), we show that the phase fluctuations in the two-dimensional photon fluid obey the Klein-Gordon equation for a massless scalar field propagating in a curved spacetime. The results reveal that the photon fluid as well as the corresponding metric can be controlled by manipulating the system parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.03392v3.pdf"}
{"id": "1612.04044", "abstract": "  Continuing work initiated in an earlier publication [Ishihara, Suzuki, Ono, Kitamura, Asada, Phys. Rev. D 94, 084015 (2016) ], we discuss a method of calculating the bending angle of light in a static, spherically symmetric and asymptotically flat spacetime, especially by taking account of the finite distance from a lens object to a light source and a receiver. For this purpose, we use the Gauss-Bonnet theorem to define the bending angle of light, such that the definition can be valid also in the strong deflection limit. Finally, this method is applied to Schwarzschild spacetime in order to discuss also possible observational implications. The proposed corrections for Sgr A^∗ for instance are able to amount to ∼ 10^-5 arcseconds for some parameter range, which may be within the capability of near-future astronomy, while also the correction for the Sun in the weak field limit is ∼ 10^-5 arcseconds. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.04044v2.pdf"}
{"id": "1612.05116", "abstract": "  Jewel is a fully dynamical event generator for jet evolution in a dense QCD medium, which has been validated for multiple jet and jet-like observables. Jet constituents (partons) undergo collisions with thermal partons from the medium, leading to both elastic and radiative energy loss. The recoiling medium scattering centers carry away energy and momentum from the jet. Keeping track of these recoils is essential for the description of intra-jet observables. Since the thermal component of the recoils is part of the soft background activity, comparison with data on jet observables requires the implementation of a background subtraction procedure. We will show two independent procedures through which background subtraction can be performed and discuss the impact of the medium recoil on jet shape observables and jet-background correlations. Keeping track of the medium recoil significantly improves the Jewel description of jet shape measurements. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.05116v1.pdf"}
{"id": "1612.06196", "abstract": "  Active colloids and externally actuated semi-flexible filaments provide basic building blocks for designing autonomously motile micro-machines. Here, we show that a passive semi-flexible filament can be actuated and transported by attaching an active colloid to its terminus. We study the dynamics of this assembly when it is free, tethered, or clamped using overdamped equations of motion that explicitly account for active fluid flow and the forces it mediates. Linear states are destabilized by buckling instabilities to produce stable states of non-zero curvature and writhe. We demarcate boundaries of these states in the two-dimensional parameter space representing dimensionless measures of polar and apolar activity. Our proposed assembly can be used as a novel component in the design of micro-machines at low Reynolds number and to study elastic instabilities driven by \"follower\" forces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.06196v1.pdf"}
{"id": "1612.06317", "abstract": "  Hopf algebroids are generalization of Hopf algebras over non-commutative base rings. It consists of a left- and a right-bialgebroid structure related by a map called the antipode. However, if the base ring of a Hopf algebroid is commutative one does not necessarily have a Hopf algebra. Meanwhile, a Hopf category is the categorification of a Hopf algebra. It consists of a category enriched over a braided monoidal category such that every hom-set carries a coalgebra structure together with an antipode functor. In this article, we will introduce the notion of a topological Hopf category- a small category whose set of objects carries a topology and whose categorical structure maps are sufficiently continuous. The main result of this paper is to describe the relation between finitely-generated projective Hopf algebroids over commutative unital C^*-algebras and topological coupled Hopf categories of finite-type whose space of objects is compact and Hausdorff. We will accomplish this by using methods of algebraic geometry and spectral theory. Lastly, we will show that not only the two objects are tightly related, but so are their respective Galois theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.06317v1.pdf"}
{"id": "1612.07023", "abstract": "  We express modular and weak values of observables of three- and higher-level quantum systems in their polar form. The Majorana representation of N-level systems in terms of symmetric states of N-1 qubits provides us with a description on the Bloch sphere. With this geometric approach, we find that modular and weak values of observables of N-level quantum systems can be factored in N-1 contributions. Their modulus is determined by the product of N-1 ratios involving projection probabilities between qubits, while their argument is deduced from a sum of N-1 solid angles on the Bloch sphere. These theoretical results allow us to study the geometric origin of the quantum phase discontinuity around singularities of weak values in three-level systems. We also analyze the three-box paradox [1] from the point of view of a bipartite quantum system. In the Majorana representation of this paradox, an observer comes to opposite conclusions about the entanglement state of the particles that were successfully pre- and postselected. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.07023v2.pdf"}
{"id": "1612.07100", "abstract": "  The possible effect of solar variability, accordingly cosmic rays variation on atmospheric physics and chemistry is highly debated over the last years. According to several recent models the induced by cosmic rays atmospheric ionization plays a key role in several different processes. At recent, an apparent effect on minor constituents and aerosols over polar regions during major solar proton events was observed. The ion production rate during ground level enhancements is a superposition of the contribution of cosmic rays with galactic and solar origin. The solar cycle 23 provided several strong ground level enhancements. The period of end October - beginning of November 2003 was characterized by a strong cosmic ray variability, namely a sequence of three GLEs was observed. In addition, there were several Forbush decreases, which led to a suppression of galactic cosmic ray flux. As a consequence the cosmic ray induced ion production in the atmosphere and the corresponding ionization effect were subject of dynamical changes. Here we compute the complex ion production due to cosmic rays during the Halloween sequence of ground level enhancements on October-November 2003 and we estimate the ionization effect. The spectral and angular characteristics of the solar protons are explicitly considered throughout the events as well their time evolution. The ionization effect during the period is computed at several altitudes above the sea level in a region with R_c ≤ 1 GV and R_c ≤ 2 GV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.07100v1.pdf"}
{"id": "1612.07425", "abstract": "  We investigate methods to vaccinate contact networks – i.e. removing nodes in such a way that disease spreading is hindered as much as possible – with respect to their cost-efficiency. Any real implementation of such protocols would come with costs related both to the vaccination itself, and gathering of information about the network. Disregarding this, we argue, would lead to erroneous evaluation of vaccination protocols. We use the susceptible-infected-recovered model – the generic model for diseases making patients immune upon recovery – as our disease-spreading scenario, and analyze outbreaks on both empirical and model networks. For different relative costs, different protocols dominate. For high vaccination costs and low costs of gathering information, the so-called acquaintance vaccination is the most cost efficient. For other parameter values, protocols designed for query-efficient identification of the network's largest degrees are most efficient. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.07425v2.pdf"}
{"id": "1612.07431", "abstract": "  We propose a dual cavity Fabry-Perot interferometer as a wavelength calibrator and a stability tracking device for astronomical spectrograph. The FPI consists of two adjoining cavities engraved on a low expansion monoblock spacer. A low-finesse astro-cavity is intended for generating a uniform grid of reference lines to calibrate the spectrograph and a high-finesse lock-cavity is meant for tracking the stability of the reference lines using optical frequency standards. The differential length changes in two cavities due to temperature and vibration perturbations are quantitatively analyzed using finite element method. An optimized mounting geometry with fractional length changes Δ L/L ≈ 1.5× 10^-12 is suggested. We also identify conditions necessary to suppress relative length variations between two cavities well below 10^-10 m, thus facilitating accurate dimension tracking and generation of stable reference spectra for Doppler measurement at 10 cms^-1 level. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.07431v2.pdf"}
{"id": "1612.08084", "abstract": "  Gene expression levels carry information about signals that have functional significance for the organism. Using the gap gene network in the fruit fly embryo as an example, we show how this information can be decoded, building a dictionary that translates expression levels into a map of implied positions. The optimal decoder makes use of graded variations in absolute expression level, resulting in positional estimates that are precise to  1", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.08084v1.pdf"}
{"id": "1612.08562", "abstract": "  A precision measurement of the proton flux in primary cosmic rays with rigidity from 1 GV to 1.8 TV is presented based on 300 million events. The results show that the proton flux is smooth and exhibits no sharp structures with rigidity. The detailed variation with rigidity of the flux spectral index is presented. The spectral index is progressively hardening at high rigidities. Solar effects are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.08562v1.pdf"}
{"id": "1701.01347", "abstract": "  The aim of this work is to study the imprints that different models for black hole (BH) and neutron star (NS) formation have on the Galactic distribution of X-ray binaries (XRBs) which contain these objects. We find that the root mean square of the height above the Galactic plane of BH- and NS-XRBs is a powerful proxy to discriminate among different formation scenarios, and that binary evolution following the BH/NS formation does not significantly affect the Galactic distributions of the binaries. We find that a population model in which at least some BHs receive a (relatively) high natal kick fits the observed BH-XRBs best. For the NS case, we find that a high NK distribution, consistent with the one derived from the measurement of pulsar proper motion, is the most preferable. We also analyse the simple method we previously used to estimate the minimal peculiar velocity of an individual BH-XRB at birth. We find that this method may be less reliable in the bulge of the Galaxy for certain models of the Galactic potential, but that our estimate is excellent for most of the BH-XRBs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.01347v1.pdf"}
{"id": "1701.01491", "abstract": "  We investigate the use of maximum distance separable (MDS) codes to cache popular content to reduce the download delay of wireless content delivery. In particular, we consider a cellular system where devices roam in an out of a cell according to a Poisson random process. Popular content is cached in a limited number of the mobile devices using an MDS code and can be downloaded from the mobile devices using device-to-device communication. We derive an analytical expression for the delay incurred in downloading content from the wireless network and show that distributed caching using MDS codes can dramatically reduce the download delay with respect to the scenario where content is always downloaded from the base station and to the case of uncoded distributed caching. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.01491v1.pdf"}
{"id": "1701.01697", "abstract": "  Pseudocapacitors are energy-storage devices characterized by fast and reversible redox reactions that enable them to store large amounts of electrical energy at high rates. We simulate the response of pseudocapacitive electrodes under realistic conditions to identify the microscopic factors that determine their performance, focusing on ruthenia (RuO2) as a prototypical electrode material. Electronic-structure methods are used together with a self-consistent continuum solvation (SCCS) model to build a complete dataset of free energies as the surface of the charged electrode is gradually covered with protons under applied voltage. The resulting dataset is exploited to compute hydrogen-adsorption isotherms and charge-voltage responses by means of grand-canonical sampling, finding close agreement with experimental voltammetry. These simulations reveal that small changes on the order of 5 μF/cm2 in the intrinsic double-layer capacitance of the electrode-electrolyte interface can induce variations of up to 40 μF/cm2 in the overall pseudocapacitance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.01697v2.pdf"}
{"id": "1701.02472", "abstract": "  The Cell Formation Problem has been studied as an optimization problem in manufacturing for more than 90 years. It consists of grouping machines and parts into manufacturing cells in order to maximize loading of cells and minimize movement of parts from one cell to another. Many heuristic algorithms have been proposed which are doing well even for large-sized instances. However, only a few authors have aimed to develop exact methods and most of these methods have some major restrictions such as a fixed number of production cells for example. In this paper we suggest a new mixed-integer linear programming model for solving the cell formation problem with a variable number of manufacturing cells. The popular grouping efficacy measure is used as an objective function. To deal with its fractional nature we apply the Dinkelbach approach. Our computational experiments are performed on two testsets: the first consists of 35 well-known instances from the literature and the second contains 32 instances less popular. We solve these instances using CPLEX software. Optimal solutions have been found for 63 of the 67 considered problem instances and several new solutions unknown before have been obtained. The computational times are greatly decreased comparing to the state-of-art approaches. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.02472v2.pdf"}
{"id": "1701.03201", "abstract": "  The synchronized magnetization dynamics in ferromagnets on a nonmagnetic heavy metal caused by the spin Hall effect is investigated theoretically. The direct and inverse spin Hall effects near the ferromagnetic/nonmagnetic interface generate longitudinal and transverse electric currents. The phenomenon is known as the spin Hall magnetoresistance effect, whose magnitude depends on the magnetization direction in the ferromagnet due to the spin transfer effect. When another ferromagnet is placed onto the same nonmagnet, these currents are again converted to the spin current by the spin Hall effect and excite the spin torque to this additional ferromagnet, resulting in the excitation of the coupled motions of the magnetizations. The in-phase or antiphase synchronization of the magnetization oscillations, depending on the value of the Gilbert damping constant and the field-like torque strength, is found in the transverse geometry by solving the Landau-Lifshitz-Gilbert equation numerically. On the other hand, in addition to these synchronizations, the synchronization having a phase difference of a quarter of a period is also found in the longitudinal geometry. The analytical theory clarifying the relation among the current, frequency, and phase difference is also developed, where it is shown that the phase differences observed in the numerical simulations correspond to that giving the fixed points of the energy supplied by the coupling torque. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.03201v2.pdf"}
{"id": "1701.05433", "abstract": "  Using Brownian dynamics (BD) simulations we investigate a dense system of charged colloids exposed to shear flow in a confined (slit-pore) geometry. The equilibrium system at zero flow consists of three, well-pronounced layers with square-like crystalline in-plane structure. We demonstrate that, for sufficiently large shear rates, the middle layer separates into two sublayers where the particles organize into moving lanes with opposite velocities. The formation of this micro-laned state results in a destruction of the applied shear profile. It has a strong impact not only on the structure of the system, but also on its rheology as measured by the stress tensor. At higher shear rates we observe a disordered state and finally a recrystallization reminiscent of the behavior of bilayer films. We expect the shear-induced laning to be a generic feature of thin films with three or more layers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.05433v1.pdf"}
{"id": "1701.06958", "abstract": "  We targeted the massive star forming region W33A using the Atacama Large Sub/Millimeter Array (ALMA) in band 6 (230 GHz) and 7 (345 GHz) to search for a sub-1000au disc around the central O-type massive young stellar object (MYSO) W33A MM1-Main. Our data achieves a resolution of  0.2\" ( 500au) and resolves the central core, MM1, into multiple components and reveals complex and filamentary structures. There is strong molecular line emission covering the entire MM1 region. The kinematic signatures are inconsistent with only Keplerian rotation although we propose that the shift in the emission line centroids within  1000au of MM1-Main could hint at an underlying compact disc with Keplerian rotation. We cannot however rule out the possibility of an unresolved binary or multiple system. A putative smaller disc could be fed by the large scale spiral `feeding filament' we detect in both gas and dust emission. We also discuss the nature of the now-resolved continuum sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.06958v1.pdf"}
{"id": "1701.08097", "abstract": "  Dissipation using a finite environment coupled to a single harmonic oscillator have been studied quite extensively. We extend the study by looking at the dynamics of the dissipation when we introduce a second bath of N identical quartic systems different from the 1st bath. We look at the energy flow into the environment as a function of the chaotic parameters of the bath and also try to develop a linear response theory to describe the system. The energy flow is always more to the more chaotic system irrespective of the initial energy of the baths. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.08097v1.pdf"}
{"id": "1701.08807", "abstract": "  Data immersion has advantages in astrophysical visualization. Complex multi-dimensional data and phase spaces can be explored in a seamless and interactive viewing environment. Putting the user in the data is a first step toward immersive data analysis. We present a technique for creating 360 degree spherical panoramas with astrophysical data. The three-dimensional software package Blender and the Google Spatial Media module are used together to immerse users in data exploration. Several examples employing these methods exhibit how the technique works using different types of astronomical data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.08807v1.pdf"}
{"id": "1701.09077", "abstract": "  We investigate the impact of the local spin texture on the differential conductance by scanning tunneling microscopy. In the focus is the previously found non-collinear magnetoresistance, which originates from spin mixing effects upon electron hopping between adjacent sites with canted magnetic moments. In the present work it is studied with lateral resolution both for the zero magnetic field spin spiral state as well as for individual magnetic skyrmions at different magnetic field values. We analyze in detail the response of the differential conductance and find different dependencies of peak energy and peak intensity on the local properties of the non-collinear spin texture. We find that in the center of a skyrmion the peak energy and intensity scale roughly linear with the angle between nearest neighbor moments. Elsewhere in the skyrmion, where the non-collinearity is not isotropic and the magnetization quantization axis varies, the behavior of the peak energy is more complex. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.09077v1.pdf"}
{"id": "1702.02819", "abstract": "  We report on the observation of magnetic quantum ratchet effect in (Cd,Mn)Te- and CdTe-based quantum well structures with an asymmetric lateral dual grating gate superlattice subjected to an external magnetic field applied normal to the quantum well plane. A dc electric current excited by cw terahertz laser radiation shows 1/B-oscillations with an amplitude much larger as compared to the photocurrent at zero magnetic field. We show that the photocurrent is caused by the combined action of a spatially periodic in-plane potential and the spatially modulated radiation due to the near field effects of light diffraction. Magnitude and direction of the photocurrent are determined by the degree of the lateral asymmetry controlled by the variation of voltages applied to the individual gates. The observed magneto-oscillations with enhanced photocurrent amplitude result from Landau quantization and, for (Cd,Mn)Te at low temperatures, from the exchange enhanced Zeeman splitting in diluted magnetic heterostructures. Theoretical analysis, considering the magnetic quantum ratchet effect in the framework of semiclassical approach, describes quite well the experimental results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.02819v1.pdf"}
{"id": "1702.04127", "abstract": "  Atmospheric channels are a promising candidate to establish secure quantum communication on a global scale. However, due to their turbulent nature, it is crucial to understand the impact of the atmosphere on the quantum properties of light and examine it experimentally. In this paper, we introduce a method to probe atmospheric free-space links with quantum light on a laboratory scale. In contrast to previous works, our method models arbitrary intensity losses caused by turbulence to emulate general atmospheric conditions. This allows us to characterize turbulent quantum channels in a well-controlled manner. To implement this technique, we perform a series of measurements with different constant attenuations and simulate the fluctuating losses by combining the obtained data. We directly test the proposed method with an on-chip source of nonclassical light and a time-bin-multiplexed detection system. With the obtained data, we characterize the nonclassicality of the generated states for different atmospheric noise models and analyze a post-selection protocol. This general technique in atmospheric quantum optics allows for studying turbulent quantum channels and predicting their properties for future applications. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.04127v2.pdf"}
{"id": "1702.06023", "abstract": "  The intermediate state dependence of photoelectron circular dichroism (PECD) in resonance-enhanced multi-photon ionization of fenchone in the gas phase is experimentally studied. By scanning the excitation wavelength from 359 to 431 nm we simultaneously excite up to three electronically distinct resonances. In the PECD experiment performed with a broadband femtosecond laser their respective contributions to the photoelectron spectrum can be resolved. High-resolution spectroscopy allows us to identify two of the resonances as belonging to the B- and C-bands, which involve excitation to states with 3s and 3p Rydberg character, respectively. We observe a sign change in the PECD signal depending on which electronic state is used as an intermediate. Additionally, scanning the laser wavelength reveals a decrease of PECD magnitude with increasing photoelectron energy for the 3s state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.06023v1.pdf"}
{"id": "1703.01147", "abstract": "  We calculate the universal spectrum of trimer and tetramer states in heteronuclear mixtures of ultracold atoms with different masses in the vicinity of the heavy-light dimer threshold. To extract the energies, we solve the three- and four-body problem for simple two- and three-body potentials tuned to the universal region using the Gaussian expansion method. We focus on the case of one light particle of mass m and two or three heavy bosons of mass M with resonant heavy-light interactions. We find that trimer and tetramer cross into the heavy-light dimer threshold at almost the same point and that as the mass ratio M/m decreases, the distance between the thresholds for trimer and tetramer states becomes smaller. We also comment on the possibility of observing exotic three-body states consisting of a dimer and two atoms in this region and compare with previous work. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.01147v2.pdf"}
{"id": "1703.05993", "abstract": "  In high energy experiments such as active beam dump searches for rare decays and missing energy events, the beam purity is a crucial parameter. In this paper we present a technique to reject heavy charged particle contamination in the 100 GeV electron beam of the H4 beam line at CERN SPS. The method is based on the detection with BGO scintillators of the synchrotron radiation emitted by the electrons passing through a bending dipole magnet. A 100 GeV π^- beam is used to test the method in the NA64 experiment resulting in a suppression factor of 10^-5 while the efficiency for electron detection is ∼95", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.05993v1.pdf"}
{"id": "1703.06508", "abstract": "  Stick-slip, manifest as intermittent tangential motion between two solids, is a well-known friction instability that occurs in a number of natural and engineering systems. In the context of adhesive polymer interfaces, this phenomenon has often been solely associated with Schallamach waves, which are termed slow waves due to their low propagation speeds. We study the dynamics of a model polymer interface using coupled force measurements and high speed in situ imaging, to explore the occurrence of stick-slip linked to other slow wave phenomena. Two new waves—slip pulse and separation pulse—both distinct from Schallamach waves, are described. The slip pulse is a sharp stress front that propagates in the same direction as the Schallamach wave, while the separation pulse involves local interface detachment and travels in the opposite direction. Transitions between these stick-slip modes are easily effected by changing the sliding velocity or normal load. The properties of these three waves, and their relation to stick-slip is elucidated. We also demonstrate the important role of adhesion in effecting wave propagation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.06508v1.pdf"}
{"id": "1703.09893", "abstract": "  Using axisymmetric simulations coupling special relativistic MHD, an approximate post-Newtonian gravitational potential and two-moment neutrino transport, we show different paths for the formation of either protomagnetars or stellar mass black holes. The fraction of prototypical stellar cores which should result in collapsars depends on a combination of several factors, among which the structure of the progenitor star and the profile of specific angular momentum are probably the foremost. Along with the implosion of the stellar core, we also obtain supernova-like explosions driven by neutrino heating and hydrodynamic instabilities or by magneto-rotational effects in cores of high-mass stars. In the latter case, highly collimated, mildly relativistic outflows are generated. We find that after a rather long post-collapse phase (lasting >  1 sec) black holes may form in cases both of successful and failed supernovalike explosions. A basic trend is that cores with a specific angular momentum smaller than that obtained by standard, one-dimensional stellar evolution calculations form black holes (and eventually collapsars). Complementary, protomagnetars result from stellar cores with the standard distribution of specific angular momentum obtained from prototypical stellar evolution calculations including magnetic torques and moderate to large mass loss rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.09893v2.pdf"}
{"id": "1703.10028", "abstract": "  We numerically show that time delayed coherent feedback controls the statistical output characteristics of driven quantum emitters. Quantum feedback allows to enhance or suppress a wide range of classical and nonclassical features of the emitted quantum light. As exemplary quantum system, we use a pumped cavity containing two emitters. By applying phase-selective feedback, we demonstrate that photon antibunching and bunching can be increased in orders of magnitude due to intrinsically and externally controllabe quantum interferences. Our modelling is based on a fully non-Markovian quantum simulation of a structured photon continuum. We show that an approximative method in the Schrödinger picture allows a very good estimate for quantum feedback induced features for low pump rates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1703/1703.10028v1.pdf"}
{"id": "adap-org9611006", "abstract": "  Altruistic behaviour is disadvantageous for the individual while is advantageous for its group. If the target of the selection is the individual, one would expect the selection process to lead to populations formed by wholly homogeneous groups, made up of either altruistic or egoistic individuals, where the winning choice depends on the balance beetwen group advantage and individual disadvantage. We show in a simple model that populations formed by inhomogeneous groups can be stabilized in some circumstances. We argue that this condition is realized when there is a relative advantage conferred by the presence of a few altruists to all the members of the group. ", "pdf_url": "gs://arxiv-dataset/arxiv/adap-org/pdf/9611/9611006v1.pdf"}
{"id": "adap-org9812004", "abstract": "  Clustering and correlation effects are frequently observed in chaotic systems in situations where, because of the positivity of the Lyapunov exponents, no dimension reduction is to be expected. In this paper, using a globally coupled network of Bernoulli units, one finds a general mechanism by which strong correlations and slow structures are obtained at the synchronization edge. A structure index is defined, which diverges at the transition points. Some conclusions are drawn concerning the construction of an ergodic theory of self-organization. ", "pdf_url": "gs://arxiv-dataset/arxiv/adap-org/pdf/9812/9812004v1.pdf"}
{"id": "adap-org9912004", "abstract": "  We examine the dynamics of an age-structured population model in which the life expectancy of an offspring may be mutated with respect to that of the parent. While the total population of the system always reaches a steady state, the fitness and age characteristics exhibit counter-intuitive behavior as a function of the mutational bias. By analytical and numerical study of the underlying rate equations, we show that if deleterious mutations are favored, the average fitness of the population reaches a steady state, while the average population age is a decreasing function of the overall fitness. When advantageous mutations are favored, the average population fitness grows linearly with time t, while the average age is independent of fitness. For no mutational bias, the average fitness grows as t^2/3. ", "pdf_url": "gs://arxiv-dataset/arxiv/adap-org/pdf/9912/9912004v1.pdf"}
{"id": "astro-ph0001393", "abstract": "  While most of the microwave background fluctuations on angular scales greater than a few arcminutes were generated at z > 800, the low redshift universe does distort the microwave background. Since the Sloan Digital Sky Survey (SDSS) traces the structures in the low-redshift universe, we can gain additional insights into the physics of the low-redshift universe by cross-correlating microwave background maps with template maps produced from the SDSS. We present a formalism for cross-correlating data from the Microwave Anisotropy Probe (MAP) with the Sloan Survey for the thermal Sunyaev-Zel'dovich (SZ) effect, the Integrated Sachs-Wolfe (ISW) effect, and weak lensing. This formalism is used to compute the signal-to-noise for cross-correlating these effects with various classes of tracer objects from the SDSS. It is found that the anticipated samples of SDSS quasars and galaxies with photometrically-determined redshifts would be good tracers for cross-correlating with the CMB. We find that the SZ-galaxy cross-correlation would give good constraints on pressure fluctuations in supercluster-scale gas. Cross-correlating weakly-lensed quasars with maps of the convergence of the CMB is found to give strong constraints on Omega_0 as well as the equation of state w. We find that the ISW cross-correlation gives poor signal-to-noise using these techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0001/0001393v3.pdf"}
{"id": "astro-ph0002408", "abstract": "  In this work we analyze the beryllium-iron chemical diagram from the point of view of non-LTE effects. Be abundances were re-calculated by considering non-LTE corrections in ionization equilibrium (logg) and Fe abundances ([Fe/H]). These corrections seem do not affect the linear relation between Be-Fe for metal-poor stars already found in the literature for LTE derived abundances. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0002/0002408v1.pdf"}
{"id": "astro-ph0003279", "abstract": "  Effects of young stellar clusters on their gas and dust environment are probed using mid-infrared (MIR) wavelengths. The strong MIR [NeIII]/[NeII] ratios (5 to 10) reveal the presence of current massive stars less than 5 Myr. Using MIR line ratios along with optical and NIR data from the literature, composite SEDs are constructed for NGC 1569, NGC 1140 and IIZw40. The stellar SEDs are then used as input to a dust model to study the impact of the hard, penetrating radiation field on the dust components, particularly in low metallicity environments, where the destructive effects of the massive stellar clusters on the environments occur on global scales. For example, the smallest dust particles are destroyed over larger regions in the dwarf galaxies than in normal metallicity starbursts. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0003/0003279v1.pdf"}
{"id": "astro-ph0003425", "abstract": "  The presence of a substantial number of hot stars in the extremely metal-rich open cluster NGC6791 has been a mystery. If these hot stars are in their core helium burning phase, they are significantly bluer (hotter) than predicted by canonical stellar evolution theory. No obvious explanation is available yet. We consider the effects of mass loss during the evolution of horizontal branch (HB) stars as their possible origin. We find that the addition of mass loss causes HB stars to evolve to be hotter and fainter. Mass loss has a more pronounced effect for less massive stars and thus naturally widens the temperature (and color) distribution on the HB. If mass loss rates are higher for more metal-rich stars, this phenomenon would be even more pronounced in the metal-rich populations, such as NGC6791. We find that mass loss on the HB may be a viable method of forming subdwarf B (sdB) stars both in the field and in clusters, especially when the metallicity is high. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0003/0003425v1.pdf"}
{"id": "astro-ph0004252", "abstract": "  The 3rd EGRET Catalog of High-energy Gamma-ray Sources contains 170 unidentified sources, and there is great interest in the nature of these sources. One means of determining source class is the study of flux variability on time scales of days; pulsars are believed to be stable on these time scales while blazars are known to be highly variable. In addition, previous work has demonstrated that 3EG J0241-6103 and 3EG J1837-0606 are candidates for a new gamma-ray source class. These sources near the Galactic plane display transient behavior but cannot be associated with any known blazars. Although many instances of flaring AGN have been reported, the EGRET database has not been systematically searched for occurrences of short-timescale (∼1 day) variability. These considerations have led us to conduct a systematic search for short-term variability in EGRET data, covering all viewing periods through proposal cycle 4. Six 3EG catalog sources are reported here to display variability on short time scales; four of them are unidentified. In addition, three non-catalog variable sources are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0004/0004252v1.pdf"}
{"id": "astro-ph0005423", "abstract": "  We study the effect of cooling flows in galaxy clusters on the Sunyaev-Zel'dovich (SZ) distortion and the possible cosmological implications. The SZ effect, alongwith X-ray observations of clusters, is used to determine the Hubble constant, H_∘. Blank sky surveys of SZ effect are being planned to constrain the geometry of the universe through cluster counts. It is also known that a significant fraction of clusters has cooling flows in them, which changes the pressure profile of intracluster gas. Since the SZ decrement depends essentially on the pressure profile, it is important to study possible changes in the determination of cosmological parameters in the presence of a cooling flow. We build several representative models of cooling flows and compare the results with the corresponding case of gas in hydrostatic equilibrium. We find that cooling flows can lead to an overestimation of the Hubble constant. Specifically, we find that for realistic models of cooling flow with mass deposition (varying ṁ with radius), there is of the order ∼ 10", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0005/0005423v1.pdf"}
{"id": "astro-ph0006282", "abstract": "  January 2000 completes the first season of intensive, wide-field observations of microlensing and stellar variability in M31 by MEGA (Microlensing Exploration of the Galaxy and Andromeda) at the Isaac Newton 2.5m Telescope, the KPNO 4m, and the 1.3m and 2.5m telescopes of MDM Observatory. In preliminary analysis, we detect  50000 variable objects, including some consistent with microlensing events. We present the level of sensitivity to be reached in our planned three-year program to test for the presence of a significant halo microlensing population in M31, as well as its spatial distribution and mass-function. We also discuss our application of image subtraction to these wide fields and HST WFPC2 Snapshot followup observations to confirm candidates identified from previous years' surveys.   We present intermediate results from our smaller-field survey, on the MDM 1.3m and Vatican Advanced Technology 1.8m Telescope, from 1994-1998, wherein we have discovered 8 additional probable microlensing events, over about one-half the time base of the project, in addition to confirming three of our original 6 microlensing candidates from 1995. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0006/0006282v2.pdf"}
{"id": "astro-ph0007325", "abstract": "  Using RXTE/PCA data, we have studied the time lag (TL) properties of a sample of four accreting neutron stars (NSs), namely 1E1724-3045, GS1826-238, 4U1705-44 and 4U1728-34. The aim of the study is to identify the spectral and timing state(s) in which TLs are detected. Along this work, we have discovered TLs between the 7-40 keV hard and 2-7 keV soft photons from 4U1728-34 with amplitudes similar to those seen in 4U1705-44 (i.e. 2 ms at 5 Hz). We show that the TLs are only seen in the low states of those sources, but that within the so-called “island” spectral state, some sources display TLs whereas some do not. On the other hand, we have found that TLs are detected when the associated Power Density Spectrum (PDS) shows excess power at high frequencies (above 1 Hz). ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0007/0007325v1.pdf"}
{"id": "astro-ph0007367", "abstract": "  The HEGRA system of imaging atmospheric Cherenkov telescopes provides for specially selected classes of events an angular resolution of better than 3'. By comparing the measured angular distribution of TeV gamma rays from the Crab Nebula with the distribution expected on the basis of Monte Carlo simulations, and with measurements of gamma rays from the point source Mrk 501, we conclude that the rms size of the VHE gamma-ray emission region in the Crab Nebula is less than 1.5'. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0007/0007367v1.pdf"}
{"id": "astro-ph0008424", "abstract": "  Correlations discovered between millisecond timing properties and spectral properties in neutron star x-ray binaries are described and then interpreted in relation to accretion flows in the systems. Use of joint timing and spectral observations to test for the existence of the marginally stable orbit, a key prediction of strong field general relativity, is described and observations of the neutron star x-ray binary 4U1820-303 which suggest that the signature of the marginally stable orbit has been detected are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0008/0008424v1.pdf"}
{"id": "astro-ph0011068", "abstract": "  This work provides an in-depth mathematical description of the response functions that are used for spatial and spectral analysis of X-ray data. The use of such functions is well-known to anyone familiar with the analysis of X-ray data where they may be identified with the quantities contained in the Ancillary Response File (ARF), the Redistribution Matrix File (RMF), and the Exposure Map. Starting from first-principles, explicit mathematical expressions for these functions, for both imaging and dispersive modes, are arrived at in terms of the underlying instrumental characteristics of the telescope including the effects of pointing motion. The response functions are presented in the context of integral equations relating the expected detector count rate to the source spectrum incident upon the telescope. Their application to the analysis of several source distributions is considered. These include multiple, possibly overlapping, and spectrally distinct point sources, as well as extended sources. Assumptions and limitations behind the usage of these functions, as well as their practical computation are addressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011068v1.pdf"}
{"id": "astro-ph0011435", "abstract": "  At early times the Universe was filled up with an extremely dense and hot gas. Due to the expansion it cooled below the binding energies of atoms which led to the formation of the first nuclei. In the physical environment of the post-recombination period of hydrogen, molecules such as H_2, HD and LiH can be formed. The proto-object formation, resulting from the growth of linear density fluctuations in the early Universe, can have an important impact on the chemical state of the Universe. Hence it can be enriched with metals, and thus lead to the formation of the first pre-biotic molecules. In this contribution, I will present some scheme for the formation of primordial molecules and discuss the consequence of the formation of first stars on the existence of possible primordial pre-biotic. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011435v1.pdf"}
{"id": "astro-ph0012133", "abstract": "  First attempts are made to derive astrophysical implications of the collision of clumped stellar winds from order of magnitude estimates and preliminary numerical simulations. Compared to colliding smooth winds, we find that the most significant differences occur in widely separated systems like WR 140. Clumped winds de-stabilize the wind-wind interaction zone of such systems. Highly compressed, cold knots of WR-wind material can form. Hydrogen rich material is likely to be mixed into these knots by the excited turbulence. Such knots, therefore, are good candidates to form dust. We briefly discuss to what degree our results can be applied to other systems and look at different possibilities for the origin and nature of the inhomogeneities in hot star winds. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0012/0012133v1.pdf"}
{"id": "astro-ph0012232", "abstract": "  We present the projected metallicity profiles for a sample of 17 rich galaxy clusters observed by BeppoSAX. We find that the 8 non-cooling flow clusters have flat metallicity profiles. On the contrary, a strong enhancement in the abundance is found in the central regions of the cooling flow clusters. All the non-cooling flow clusters present evidence of recent merger activity suggesting that the merger events redistributes efficiently the metal content of the intracluster medium. For the cooling flow clusters with better statistics and available optical data (A85, A496, A2029 and Perseus) we have tested whether the observed abundance excess is due to metals ejected from the galaxies located in the cluster core. We find that at a resolution > 100 kpc the observed projected abundance excess profiles are consistent with originating from a deprojected metal excess distribution tracing the optical light distribution. In the one case (i.e. Perseus) with higher resolution (  50 kpc), we find that the observed metal abundance excess distribution is broader than the predicted one. Such a difference can be reconciled if we assume that the metals have drifted away from their parent ejecting galaxies by a few tens of kpc, or, alternatively, if we assume that the cluster light profile has become significantly more centrally peaked because of the formation process of the central dominant cluster galaxy since the last major merger occurred. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0012/0012232v1.pdf"}
{"id": "astro-ph0101006", "abstract": "  Gamma-ray bursts are believed to originate from internal shocks which arise in an irregular relativistic wind. The process has been thought to be inefficient, converting only a few percent of the kinetic energy into gamma-rays. We define ultra efficient internal shocks as those in which the fraction of emitted energy is larger than the fraction of energy given to the radiating electrons at each collision.   We show that such a scenario is possible and even plausible. In our model, colliding shells which do not emit all their internal energy are reflected from each other and it causes subsequent collisions, allowing more energy to be emitted. As an example, we obtain about 60", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0101/0101006v1.pdf"}
{"id": "astro-ph0101233", "abstract": "  I review some of the basic observational details of jets from X-ray binaries, or `microquasars'. It is shown that in both (Z and Atoll) NS and BHC systems radio emission, and therefore jet formation, is correlated with the presence of hard (30-500 keV) X-ray emission. At gamma-ray (> 500 keV) energies, the relation is not so clear. Possible physical connections between the presence of a jet, with a population of relativistic electrons, and the emission of hard X-rays, are briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0101/0101233v1.pdf"}
{"id": "astro-ph0101505", "abstract": "  I report on a sample of new type I X-ray bursters, firstly detected with the Wide Field Cameras on board BeppoSAX and then studied with the Narrow Field Instruments on a broad spectral range (0.1-200 keV). Properties of the transient/persistent emission are summarized and the broad band X-ray spectra discussed in detail for a few sources. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0101/0101505v1.pdf"}
{"id": "astro-ph0103464", "abstract": "  The presence of two globular cluster subpopulations in early-type galaxies is now the norm rather than the exception. Here we present two more examples for which the host galaxy appears to have undergone a recent merger. Using multi-colour Keck imaging of NGC 1052 and NGC 7332 we find evidence for a bimodal globular cluster colour distribution in both galaxies, with roughly equal numbers of blue and red globular clusters. The blue ones have similar colours to those in the Milky Way halo and are thus probably very old and metal-poor. If the red GC subpopulations are at least solar metallicity, then stellar population models indicate young ages. We discuss the origin of globular clusters within the framework of formation models. We conclude that recent merger events in these two galaxies have had little effect on their overall GC systems. We also derive globular cluster density profiles, global specific frequencies and in the case of NGC 1052, radial colour gradients and azimuthal distribution. In general these globular cluster properties are normal for early-type galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0103/0103464v1.pdf"}
{"id": "astro-ph0104092", "abstract": "  We report the discovery of a gravitationally lensed quasar resulting from our survey for lenses in the southern sky. Radio images of PMN J1632-0033 with the VLA and ATCA exhibit two compact, flat-spectrum components with separation 1.47\" and flux density ratio 13.2. Images with the HST reveal the optical counterparts to the radio components and also the lens galaxy. An optical spectrum of the bright component, obtained with the first Magellan telescope, reveals quasar emission lines at redshift 3.42. Deeper radio images with MERLIN and the VLBA reveal a faint third radio component located near the center of the lens galaxy, which is either a third image of the background quasar or faint emission from the lens galaxy. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0104/0104092v2.pdf"}
{"id": "astro-ph0107091", "abstract": "  This review aims to give a summary of our understanding of galaxy evolution as infered from studies of nearby galaxies; how observations made with the Hubble Space Telescope have contributed significantly to our detailed understanding of the older stellar populations in Local Group dwarf galaxies. Recent results from VLT are also promising interesting future prospects for the study of resolved stellar populations in nearby dwarf galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0107/0107091v1.pdf"}
{"id": "astro-ph0107141", "abstract": "  We present results of a high-resolution imaging survey of barred S0–Sa galaxies which demonstrate that the central regions of these galaxies are surprisingly complex. We see many inner bars — small, secondary bars (typically less than a kiloparsec in radius) located inside of, and probably rotating faster than, the large primary bars. These are present in about one quarter to one third of all our sample. In contrast to some theoretical expectations, they do not seem to enhance AGN activity significantly. A third of barred S0's appear to host kiloparsec-scale disks within their bars; but the frequency of such inner disks is much lower in our S0/a and Sa galaxies. In addition, we find one example of a triple barred galaxy, and two cases of purely stellar nuclear rings — probably the fossil remnants of past circumnuclear starbursts.   We comment briefly on results from an ongoing analysis of known double-barred systems, extending to Hubble types as late as Sbc, and discuss their characteristic sizes and orientations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0107/0107141v1.pdf"}
{"id": "astro-ph0107392", "abstract": "  We present results from stacking analyses, using the 1 Ms Chandra Deep Field North data, that constrain the X-ray emission of Lyman break galaxies at z = 2-4. Stacking the counts from 24 individually undetected Lyman break galaxies located within the Hubble Deep Field North, we have obtained average detections of these objects in the resulting 0.5-8.0 keV and 0.5-2.0 keV images; these images have effective exposure times of 22.4 Ms (260 days). Monte Carlo testing empirically shows the detections to be highly significant. The average rest-frame 2-8 keV luminosity of a Lyman break galaxy is derived to be 3.2 x 10^41 erg s^-1, comparable to that of the most X-ray luminous starbursts in the local Universe. The observed ratio of X-ray to B-band luminosity is somewhat, but not greatly, higher than that seen from local starbursts. The X-ray emission probably arises from a combination of high-mass X-ray binaries, \"super-Eddington\" X-ray sources, and low-luminosity active galactic nuclei. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0107/0107392v1.pdf"}
{"id": "astro-ph0107529", "abstract": "  We present measurements of the effective temperatures and surface gravities for a sample of hot DA white dwarfs, using the Lyman line data available from the HUT, ORFEUS and FUSE far-UV space missions. Comparing the results with those from the standard Balmer line technique, we find that there is a general good overall agreement between the two methods. However, significant differences are found for a number of stars, but not always of a consistent nature in that sometimes the Balmer temperature exceeds that derived from the Lyman lines and in other instances is lower. We conclude that, with the latest model atmosphere calculations, these discrepancies probably do not arise from an inadequate theoretical treatment of the Lyman lines but rather from systematic effects in the observation and data reduction processes, which dominate the statistical errors in these spectra. If these systematic data reduction effects can be adequately controlled, the Lyman line temperature and gravity measurements are consistent with those obtained from the Balmer lines when allowance is made for reasonable observational uncertainties. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0107/0107529v1.pdf"}
{"id": "astro-ph0109206", "abstract": "  Based on a linear and non-linear study of radial pulsations in the envelopes of classical novae (Schenker 1999), I discuss the results both from the point of view of pulsation theory as well as their consequences for current nova models.   Starting from initially static envelope structures at various stages during the decline of a nova outburst, strong `running wave' instabilities have been found that rapidly grow into shocks. Improved analytical concepts give a new direction to the interpretation of such highly non-adiabatic radial pulsations.   For direct observational confirmation a search for short period variability in the UV and soft X-ray is suggested during the very late decline phase. Speculative consequences for mass loss scenarios in novae due to these instabilities will need some more work in the future. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0109/0109206v1.pdf"}
{"id": "astro-ph0109240", "abstract": "  Starting in 1999, the Rossi X-ray Timing Explorer (RXTE) has monitored the central bulge region of the Galaxy with the Proportional Counter Array (PCA), resolving about 50 binary X-ray sources, including 18 sources discovered by RXTE and BeppoSAX. The accretion rates that RXTE observed from these sources ranged from highs approaching Eddington limits to lows that may correspond to mass exchange for a binary period near the minimum of 80 minutes. Several neutron star binaries with low peak luminosity have outburst or cycle time-scales which are shorter than those of brighter and better known counterparts. We compare the characteristics of the binaries with low rates of mass exchange to predictions of their evolution. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0109/0109240v1.pdf"}
{"id": "astro-ph0109331", "abstract": "  We use new and published medium resolution 0.6–2.5 μm spectra of L and T dwarfs to develop a unified classification system for both of these new spectral classes. Two indices of the system at 1.2 μm and 1.5 μm are based on nearby absorption bands of water vapor and two are associated with methane bands near 1.6 μm and 2.2 μm. The 1.5 μm index is monotonic through the L and T sequences, and forms the backbone of the system; the indices for the other bands provide extensive, but only partial, coverage. We correlate the 1.5 μm index with continuum indices shortward of 1 μm devised by others for classifying L dwarfs, in order to obtain a tight link between optical and infrared classifications. Our proposed system defines ten spectral subclasses for L (L0–L9) and nine for T (T0–T8). The boundary between L and T is defined to be the onset of absorption by methane in the H band. Methane absorption in the K band near 2.2 μm is found to begin approximately at L8. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0109/0109331v1.pdf"}
{"id": "astro-ph0110551", "abstract": "  The balloon-borne submillimeter instrument PRONAOS has observed one square degree areas towards the Orion and M17 molecular clouds. The 2' - 3.5' resolution maps obtained in four wide wavelength bands between 200 microns and 600 microns, exhibit the dust distribution in these regions. We analyze the temperature and spectral index of the dust, and we show the anticorrelation between these two parameters. We derive estimations of the ISM column densities and masses in these regions. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0110/0110551v1.pdf"}
{"id": "astro-ph0111380", "abstract": "  We study the structure of shocks in clumpy media, using a multifluid formalism. As expected, shocks broaden as they weaken: for sufficiently weak shocks, no viscous subshock appears in the structure. This has significant implications for the survival of dense clouds in regions overrun by shocks in a wide range of astrophysical circumstances, from planetary nebulae to the nuclei of starburst galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0111/0111380v1.pdf"}
{"id": "astro-ph0112136", "abstract": "  We compute spectra from accretion disks around rapidly rotating neutron stars. The full effect of general relativity is considered for the structure calculation of the stars. We take into account the Doppler shift, gravitational redshift and light-bending effects in order to compute the observed spectra. To facilitate direct comparison with observations, a simple empirical function is presented which describes the numerically computed spectra well. This function can in principle be used to distinguish between the Newtonian spectra and the relativistic spectra. We also discuss the possibility of constraining neutron star's equation of state using our spectral models. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0112/0112136v1.pdf"}
{"id": "astro-ph0202094", "abstract": "  We consider approaches to cosmological parameter estimation in the inflationary cosmology, focussing on the required accuracy of the initial power spectra. Parametrizing the spectra, for example by power-laws, is well suited to testing the inflationary paradigm but will only correctly estimate cosmological parameters if the parametrization is sufficiently accurate, and we investigate conditions under which this is achieved both for present data and for upcoming satellite data. If inflation is favoured, reliable estimation of its physical parameters requires an alternative approach adopting its detailed predictions. For slow-roll inflation, we investigate the accuracy of the predicted spectra at first and second order in the slow-roll expansion (presenting the complete second-order corrections for the tensors for the first time). We find that within the presently-allowed parameter space, there are regions where it will be necessary to include second-order corrections to reach the accuracy requirements of MAP and Planck satellite data. We end by proposing a data analysis pipeline appropriate for testing inflation and for cosmological parameter estimation from high-precision data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0202/0202094v2.pdf"}
{"id": "astro-ph0203517", "abstract": "  Pulsars provide unique probes of the large-scale interstellar magnetic field in the Galactic disk. Up to now, the limited Galactic distribution of the known pulsar population has restricted these investigations to within a few kiloparsec of the Sun. The Parkes multibeam pulsar survey has discovered many more-distant pulsars which enables us for the first time to explore the magnetic field in most of the nearby half of the Galactic disk. Here we report the detection of counterclockwise magnetic fields in the Norma spiral arm using pulsar rotation measures. The fields are coherent in direction over a linear scale of ∼ 5 kpc along the arm and have a strength of -4.4±0.9 μG. The magnetic field between the Carina-Sagittarius and Crux-Scutum arms is confirmed to be coherent from l∼45 to l∼305 over a length of ∼ 10 kpc. These results strengthen arguments for a bisymmetric spiral model for the field configuration in the Galactic disk. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0203/0203517v2.pdf"}
{"id": "astro-ph0204391", "abstract": "  We present a two-dimensional version of the classical one-dimensional Kolmogorov-Smirnov (K-S) test, extending an earlier idea due to Peacock (1983) and an implementation proposed by Fasano     Franceschini (1987). The two-dimensional K-S test is used to optimise the goodness of fit in an iterative source-detection scheme for astronomical images. The method is applied to a ROSAT/HRI x-ray image of the post core-collapse globular cluster NGC 6397 to determine the most probable source distribution in the cluster core. Comparisons to other widely-used source detection methods, and to a Chandra image of the same field, show that our iteration scheme is superior in measuring statistics-limited sources in severely crowded fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0204/0204391v1.pdf"}
{"id": "astro-ph0204409", "abstract": "  We report the discovery of millisecond oscillations in the X-ray emission from the X-ray transient SAX J1750.8-2900. Millisecond quasiperiodic oscillations (kHz QPOs) were present in the persistent emission with frequencies ranging from 543 Hz to 1017 Hz. Oscillations at a frequency of 600.75 Hz were present in the brightest X-ray burst observed. We derive an upper limit on the source distance of 6.3 +/- 0.7 kpc from this X-ray burst. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0204/0204409v1.pdf"}
{"id": "astro-ph0206068", "abstract": "  The angular correlation function of the background shear-foreground galaxy distribution probes the three dimensional cross power spectrum between mass and galaxies. The same cross power spectrum is also probed when foreground galaxy distribution is cross-correlated with a distribution of background sources disjoint in redshift space. The kernels that project three dimensional clustering to the two dimensional angular space is different for these two probes. When combined, they allow a study of the galaxy-mass cross power spectrum from linear to non-linear scales. By inverting the background shear-foreground galaxy correlation function measured by the Sloan Digital Sky Survey, we present a first estimate of the cross power spectrum between mass and galaxies at low redshifts. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0206/0206068v1.pdf"}
{"id": "astro-ph0206080", "abstract": "  The RS CVn-type binary σ Geminorum was observed during a large, long-duration flare simultaneously with XMM-Newton and the VLA. The light curves show a characteristic time dependence that is compatible with the Neupert effect observed in solar flares: The time derivative of the X-ray light curve resembles the radio light curve. This observation can be interpreted in terms of a standard flare scenario in which accelerated coronal electrons reach the chromosphere where they heat the cool plasma and induce chromospheric evaporation. Such a scenario can only hold if the amount of energy in the fast electrons is sufficient to explain the X-ray radiative losses. We present a plausibility analysis that supports the chromospheric evaporation model. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0206/0206080v1.pdf"}
{"id": "astro-ph0208250", "abstract": "  The detection of a massive jet-ejection event from SS433 with RXTE is reported. SS433 in its high state has been monitored with RXTE from 2001/11/09 (MJD = 52222) to 2001/11/25 (MJD = 52238), following a radio flare on 2001/11/02 (MJD = 52215). An irregular temporal variation with time scales of 100-1000 s appears in the light curve, and the amplitude increases day by day. This is the first detection of such a fast variation from the source. In addition to the fast variations, the daily light curve scatters with a time scale of  day from 2001/11/17 (MJD = 52230). Following the scatter, another radio flare has been detected on 2001/11/22 (MJD = 52235), which has been obviously formed during the X-ray scatter. This is a preliminary report on a massive jet-ejection event witnessed in X-ray band for the first time. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0208/0208250v1.pdf"}
{"id": "astro-ph0210118", "abstract": "  The Deep Lens Survey (DLS) is a deep BVRz' imaging survey of seven 2x2 degree fields, with all data to be made public. The primary scientific driver is weak gravitational lensing, but the survey is also designed to enable a wide array of other astrophysical investigations. A unique feature of this survey is the search for transient phenomena. We subtract multiple exposures of a field, detect differences, classify, and release transients on the Web within about an hour of observation. Here we summarize the scientific goals of the DLS, field and filter selection, observing techniques and current status, data reduction, data products and release, and transient detections. Finally, we discuss some lessons which might apply to future large surveys such as LSST. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0210/0210118v2.pdf"}
{"id": "astro-ph0210376", "abstract": "  We present near-infrared high resolution observations of the young binary system Z Canis Majoris using the adaptive optics system at the Keck-II telescope. Both components are unresolved at 1.25 and 1.65 microns, although high dynamic range images reveal a previously unknown jet-like feature in the circumstellar environment. We argue that this feature probably arises from light scattered off the walls of a jet-blown cavity, and proper motion studies of this feature can probe the dynamics of the bipolar outflow. Potentially, the morphology of the dust-laden cavity walls offers a new probe of the momentum profile and collimation of bipolar winds from young stellar objects. We also derive high precision binary parameters, which when combined with historical data have allowed the first detection of orbital motion. Lastly, our observations confirm the high degree of flux variability in the system; the North-West binary component is dominant at H-band, in contrast to all previous observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0210/0210376v1.pdf"}
{"id": "astro-ph0210644", "abstract": "  We report the possible discovery of multiple gravitationally-lensed images of QSOs with angular separations on arcminute scales. The QSOs were selected from the completed 2dF QSO survey as having redshifts and optical colours which are statistically consistent. In this paper we present higher-quality optical spectra of the candidates and discuss the likelihood of their genuinely being systems lensed by massive clusters of galaxies. From a comparison of the spectra it appears that up to six pairs of QSOs may be lensed multiple images, although the true number may be less than that and further observations should be undertaken to amass more evidence and to detect the lensing clusters. Two of the candidates may be associated with low redshift clusters of galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0210/0210644v2.pdf"}
{"id": "astro-ph0211183", "abstract": "  High resolution studies of circular polarization allow us see where it arises in a jet, study its local fractional level and spectrum, and compare these results to local measures of linear polarization and Faraday rotation. Here we not only review past results from Very Long Baseline Array (VLBA) circular polarization studies, but we also present preliminary new results on two quasars. In the core of PKS 0607-157, we find strong circular polarization at 8 GHz and much weaker levels at 15 GHz. Combined with the linear polarization data, we favor a simple model where the circular is produced by Faraday conversion driven by a small amount of Faraday rotation. In the core of 3C345, we find strong circular polarization at 15 GHz in a component with distinct linear polarization. This core component is optically thick at 8 GHz, where we detect no circular polarization. With opposite trends in frequency for PKS 0607-157 and 3C345, it seems clear that local conditions in a jet can have a strong effect on circular polarization and need to be taken into account when studying inhomogeneous objects with multi-frequency observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0211/0211183v2.pdf"}
{"id": "astro-ph0211241", "abstract": "  We present the results of optical photometry of the recurrent nova CI Aql in later phase of the outburst which occurred in 2000. Our observation revealed that the object reached the quiescent level between 2001 December and 2002 April and therefore that CI Aql is a unique recurrent nova characterized by an extremely long (1.4–1.7 yr) plateau phase. The light curve obtained in the outburst suggests that the object is the first example of an intermediate between classical novae and recurrent novae. In comparison with estimation given in published theoretical calculations, the long duration of the plateau phase supports a higher hydrogen content of the white-dwarf envelope, while such an abundance of hydrogen requires a later cessation of the wind which is in disagreement with the sudden fading observed in late November of 2000. The light curve obtained in later phase of the outburst indicates that the object was fainter and the gradual decline was steeper than predicted. These discrepancies between the observation and theoretical prediction require drastic modification of the present model of CI Aql. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0211/0211241v1.pdf"}
{"id": "astro-ph0301547", "abstract": "  Strong cluster eccentricity evolution for z ≤ 0.13 has appeared in a variety of observational data sets. We examine the evolution of eccentricity in simulated galaxy clusters using a variety of simulation methodologies, amplitude normalizations, and background cosmologies. We do not find find such evolution for z < 0.1 in any of our simulation ensembles. We suggest a systematic error in the form of a redshift-dependent selection effect in cluster catalogs or missing physics in cluster simulations important enough to modify the cluster morphology. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0301/0301547v3.pdf"}
{"id": "astro-ph0302536", "abstract": "  Weak gravitational lensing by intervening large-scale structure induces a distinct signature in the cosmic microwave background (CMB) that can be used to reconstruct the weak-lensing displacement map. Estimators for individual   Fourier modes of this map can be combined to produce an estimator for the lensing-potenial power spectrum. The naive estimator for this quantity will be biased upwards by the uncertainty associated with reconstructing individual modes; we present an iterative scheme for removing this bias. The variance and covariance of the lensing-potenial power spectrum estimator are calculated and evaluated numerically in a   ΛCDM universe for Planck and future polarization-sensitive CMB experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0302/0302536v1.pdf"}
{"id": "astro-ph0303104", "abstract": "  XAssist is a NASA AISR-funded project for the automation of X-ray astrophysics, with emphasis on galaxies. It is nearing completion of its initially funded effort, and is working well for Chandra and ROSAT HRI data. Initial support for XMM-Newton data is present as well. It is capable of data reprocessing, source detection, and preliminary spatial, temporal and spectral analysis for each source with sufficient counts. The bulk of the system is written in Python, which in turn drives underlying software (CIAO for Chandra data, etc.). Future work will include a GUI (mainly for beginners and status monitoring) and the exposure of at least some functionality as web services. The latter will help XAssist to eventually become part of the VO, making advanced queries possible, such as determining the X-ray fluxes of counterparts to HST or SDSS sources (including the use of unpublished X-ray data), and add the ability of “on-the-fly” X-ray processing. Pipelines are running on ROSAT, Chandra and now XMM-Newton observations of galaxies to demonstrate XAssist's capabilities, and the results are available online (in real time) at http://www.xassist.org . XAssist itself as well as various associated projects are available for download. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0303/0303104v1.pdf"}
{"id": "astro-ph0303133", "abstract": "  We present results from four Rossi X-ray Timing Explorer (RXTE) observations of the bright low mass X-ray binary LMC X-2. During these observations, which span a year and include over 160 hrs of data, the source exhibits clear evolution through three branches on its hardness-intensity and color-color diagrams, consistent with the flaring, normal, and horizontal branches (FB, NB, HB) of a Z-source, and remarkably similar to Z-tracks derived for GX 17+2, Sco X-1 and GX 349+2. LMC X-2 was observed in the FB, NB, and HB for roughly 30", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0303/0303133v1.pdf"}
{"id": "astro-ph0303142", "abstract": "  We present the first measurement of the stellar kinematics in the polar ring of NGC 4650A. There is well defined rotation, with the stars and gas rotating in the same direction, and with similar amplitude. The gaseous and stellar kinematics suggest an approximately flat rotation curve, providing further support for the hypothesis that the polar material resides in a disk rather than in a ring. The kinematics of the emission line gas at and near the center of the S0 suggests that the polar disk lacks a central hole. We have not detected evidence for two, equal mass, counterrotating stellar polar streams, as is predicted in the resonance levitation model proposed by Tremaine     Yu. A merger seems the most likely explanation for the structure and kinematics of NGC 4650A. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0303/0303142v1.pdf"}
{"id": "astro-ph0303446", "abstract": "  We present a new method to compute wavelength- and phase-dependent limb darkening corrections for classical Cepheids. These corrections are derived from hydrodynamic simulations and radiative transfer modeling with a full set of atomic and molecular opacities. Comparison with hydrostatic models having the same stellar parameters show a larger limb darkening for most phases in our models, and temporal variations related to the hydrodynamics of the stellar pulsation. We assess the implications of our results with respect to the geometric Baade-Wesselink method, which uses interferometric measurements of Cepheid angular diameters to determine their distances and radii. The relevance of the hydrodynamic effects predicted by our model on the limb darkening of pulsating Cepheids is finally discussed in terms of the predicted capabilities of the VLTI. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0303/0303446v1.pdf"}
{"id": "astro-ph0303521", "abstract": "  The key algorithms and features of the Gasoline code for parallel hydrodynamics with self-gravity are described. Gasoline is an extension of the efficient Pkdgrav parallel N-body code using smoothed particle hydrodynamics. Accuracy measurements, performance analysis and tests of the code are presented. Recent successful Gasoline applications are summarized. These cover a diverse set of areas in astrophysics including galaxy clusters, galaxy formation and gas-giant planets. Future directions for gasdynamical simulations in astrophysics and code development strategies for tackling cutting edge problems are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0303/0303521v1.pdf"}
{"id": "astro-ph0304424", "abstract": "  Ap/Bp stars are magnetic chemically peculiar early A and late B type stars of the main sequence. They exhibit peculiar surface abundance anomalies that are thought to be the result of gravitational settling and radiative levitation. The physics of diffusion in these stars are reviewed briefly and some model predictions are discussed. While models reproduce some observations reasonably well, more work is needed before the behavior of diffusing elements in a complex magnetic field is fully understood. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0304/0304424v1.pdf"}
{"id": "astro-ph0305380", "abstract": "  When using Fe as a surrogate for “metallicity”, the metallicity is best represented by the dominant species of Fe. Accordingly, we have derived a new globular cluster metallicity scale based on the equivalent widths of FeII lines measured from high resolution spectra of giant stars. The scale is primarily based on the results of analyses by the Lick-Texas group of 149 stars in 11 clusters, supplemented by other high resolution studies in five additional clusters. We also derive ab initio the true distance moduli for M3, M5, M13, M15, and M92 as a means of setting stellar surface gravities. We find that [Fe/H]II is correlated linearly with W', the reduced strength of the near-infrared CaII triplet defined by Rutledge et al (1997), although the correlation coefficients depend on the stellar atmosphere model employed. In addition to the 66 globular cluster metallicity estimates presented in a recent PASP review, we present here an additional 39 globular cluster metallicity estimates based on transformations from Q39, the photometric index defined by Zinn (1980). ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0305/0305380v1.pdf"}
{"id": "astro-ph0305485", "abstract": "  We discuss two experiments - the Very Small Array (VSA) and the Arcminute MicroKelvin Imager (AMI) - and their prospects for observing the CMB at high angular multipoles. Whilst the VSA is primarily designed to observe primary anisotropies in the CMB, AMI is designed to image secondary anisotropies via the Sunyaev-Zel'dovich effect. The combined l-range of these two instruments is between l = 150 and  10000. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0305/0305485v1.pdf"}
{"id": "astro-ph0308101", "abstract": "  We have obtained adaptive optics, high spatial resolution (0.15 arcsecond) K-band spectra and images of the region around the two active nuclei in NGC 6240 which show the presence of circumnuclear shocks. The data are consistent with the thermal excitation mechanism being the dominant one in the nuclear region. UV fluorescence and associative detachment may also contribute to the fraction of the energy emitted through molecular hydrogen transitions. The near-IR continuum emission appears closely associated with the two active nuclei. The morphological similarities between the near-IR images and the Chandra X-ray images indicate the same mechanisms may be responsible for the emission in near-IR and X-ray band. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0308/0308101v1.pdf"}
{"id": "astro-ph0308242", "abstract": "  In their study of the evolution of galaxies within clusters, Butcher and Oemler discovered evidence for a strong evolution in star-formation rate with redshift. Later studies confirmed this conclusion and uncovered several aspects of the effect: photometric, spectroscopic, and morphological. This article reviews a broad sample of these works and discusses selection effects, biases, and driving mechanisms that might be responsible for the changes in star-formation rate. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0308/0308242v2.pdf"}
{"id": "astro-ph0308446", "abstract": "  We use statistical inference theory to explore the constraints from future galaxy weak lensing (cosmic shear) surveys combined with the current CMB constraints on cosmological parameters, focusing particularly on the running of the spectral index of the primordial scalar power spectrum, α_s. Recent papers have drawn attention to the possibility of measuring α_s by combining the CMB with galaxy clustering and/or the Lyman-α forest. Weak lensing combined with the CMB provides an alternative probe of the primordial power spectrum. We run a series of simulations with variable runnings and compare them to semi-analytic non-linear mappings to test their validity for our calculations. We find that a “Reference” cosmic shear survey with f_sky=0.01 and 6.6× 10^8 galaxies per steradian can reduce the uncertainty on n_s and α_s by roughly a factor of 2 relative to the CMB alone. We investigate the effect of shear calibration biases on lensing by including the calibration factor as a parameter, and show that for our Reference Survey, the precision of cosmological parameter determination is only slightly degraded even if the amplitude calibration is uncertain by as much as 5", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0308/0308446v2.pdf"}
{"id": "astro-ph0309617", "abstract": "  The recent findings of Romanowsky et al., of an “unexpectedly” small mass discrepancy within 5 effective radii in several elliptical galaxies, are not surprising in the context of MOND. As we show here, they are, in fact, in full concordance with its predictions. One is dealing with high-surface-density galaxies with mean accelerations rather larger than the acceleration constant of MOND. These findings continue, and are now the extreme examples of, the trend predicted by MOND: the mass discrepancy sets in at larger and larger scaled radii in galaxies with larger and larger mean surface densities; or, equivalently, mean accelerations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0309/0309617v2.pdf"}
{"id": "astro-ph0309803", "abstract": "  A prediction of standard Big Bang cosmology is that the observed UHECR (ultra-high-energy cosmic rays) spectrum will exhibit a cutoff at the GKZ limit, resulting from interaction with the photons that constitute the cosmic microwave background. We show that for the Quasi-Static Universe (QSU) model, in which photon energy is an invariant in the cosmological reference frame, the photon number density in the universe today is a factor of 10^9 less than in the standard model. As a consequence, the mean free path of UHECRs will exceed the horizon distance of the universe, rendering it essentially transparent to UHECRs. The QSU model therefore predicts that no cutoff will be observed in the UHECR spectrum. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0309/0309803v1.pdf"}
{"id": "astro-ph0310046", "abstract": "  We present observations of 86 post-Asymptotic Giant Branch (post-AGB) stars of OH maser transitions, taken with the Parkes Telescope between September 2002 and August 2003. Post-AGB stars are the precursors of planetary nebulae, which have a wide range of morphologies that are not well explained. By studying the circumstellar envelopes of post-AGB stars through the masers produced in them, we hope to shed light on the origin of planetary nebula morphologies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0310/0310046v1.pdf"}
{"id": "astro-ph0310311", "abstract": "  An isolated massive star can blow a bubble, while a group of massive stars can blow superbubbles. In this paper, we examine three intriguing questions regarding bubbles and superbubbles: (1) why don't we see interstellar bubbles around every O star? (2) how hot are the bubble interiors? and (3) what is going on at the hot/cold gas interface in a bubble? ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0310/0310311v1.pdf"}
{"id": "astro-ph0310431", "abstract": "  The idea that GRBs originate from uniform jets has been used to explain numerous observations of breaks in the GRB afterglow lightcurves. We explore the possibility that GRBs instead originate from a structured jet that may be quasi-universal, where the variation in the observed properties of GRBs is due to the variation in the observer viewing angle. We test how various models reproduce the jet data of Bloom, Frail,     Kulkarni (2003), which show a negative correlation between the isotropic energy output and the inferred jet opening angle (in a uniform jet configuration). We find, consistent with previous studies, that a power-law structure for the jet energy as a function of angle gives a good description. However, a Gaussian jet structure can also reproduce the data well, particularly if the parameters of the Gaussian are allowed some scatter. We place limits on the scatter of the parameters in both the Gaussian and power-law models needed to reproduce the data, and discuss how future observations will better distinguish between these models for the GRB jet structure. In particular, the Gaussian model predicts a turnover at small opening angles and in some cases a sharp cutoff at large angles, the former of which may already have been observed. We also discuss the predictions each model makes for the observed luminosity function of GRBs and compare these predictions with the existing data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0310/0310431v1.pdf"}
{"id": "astro-ph0310557", "abstract": "  Clusters of galaxies are massive enough to be considered representative samples of the Universe, and to retain all of the heavy elements synthesized in their constituent stars. Since most of these metals reside in hot plasma, X-ray spectroscopy of clusters provides a unique and fundamental tool for studying chemical evolution. I review the current observational status of X-ray measurements of the chemical composition of the intracluster medium, and its interpretation in the context of the nature and history of star and galaxy formation processes in the Universe. I provide brief historical and cosmological contexts, an overview of results from the mature ASCA observatory database, and new results from the Chandra and XMM-Newton X-ray observatories. I conclude with a summary of important points and promising future directions in this rapidly growing field. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0310/0310557v1.pdf"}
{"id": "astro-ph0401119", "abstract": "  We present the results of radio searches for pulsars within unidentified EGRET source error boxes. Using the Parkes multibeam system, we have surveyed 56 sources at Galactic latitudes |b| > 5 deg which do not appear to be associated with blazars. This population has been suggested to be distributed like the local star forming region known as the Gould Belt, the Galactic Halo, and/or the millisecond pulsars. We have discovered several new pulsars in this survey, including three new binary systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0401/0401119v1.pdf"}
{"id": "astro-ph0402213", "abstract": "  Fast variability studies of accreting black holes in the Galaxy offer us a unique opportunity to measure the spins of black holes and test the strong-field behavior of general relativity. In this review, I summarize the arguments often used in attempts of measuring the spins of black holes, concentrating on their theoretical foundations. I also argue that X-ray studies of accreting black holes will be able to provide in the future strong constraints on deviations from general relativity in the strong-field regime. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0402/0402213v1.pdf"}
{"id": "astro-ph0402309", "abstract": "  We investigate the influence of blending on the Cepheid distance scale using two Local Group galaxies, M31 and M33. Blending leads to systematically low distances to galaxies observed with the HST, and therefore to systematically high estimates of H_0. High-resolution HST images are compared to our ground-based data, obtained as part of the DIRECT project, for a sample of 22 Cepheids in M31 and 102 Cepheids in M33. For a sample of 22 Cepheids in M31, the average (median) flux contribution from luminous companions not resolved on the ground-based images in the V-band, S_V, is about 19", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0402/0402309v1.pdf"}
{"id": "astro-ph0402374", "abstract": "  The source of the very bright Gamma-Ray Burst GRB 030329 is close enough to us for there to be a hope to measure or significantly constrain its putative superluminal motion. Such a phenomenon is expected in the “Cannonball” (CB) model of GRBs. Recent precise data on the optical and radio afterglow of this GRB –which demonstrated its very complex structure– allow us to pin down the CB-model's prediction for the afterglow-source position as a function of time. It has been stated that (the unpublished part of) the new radio data “unequivocably disprove” the CB model. We show how greatly exaggerated that obituary announcement was, and how precise a refined analysis of the data would have to be, to be still of interest. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0402/0402374v1.pdf"}
{"id": "astro-ph0403614", "abstract": "  Scalar-tensor theories of gravity provide a consistent framework to accommodate an ultra-light quintessence scalar field. While the equivalence principle is respected by construction, deviations from General Relativity and standard cosmology may show up at nucleosynthesis, CMB, and solar system tests of gravity. After imposing all the bounds coming from these observations, we consider the expansion rate of the universe at WIMP decoupling, showing that it can lead to an enhancement of the dark matter relic density up to few orders of magnitude with respect to the standard case. This effect can have an impact on supersymmetric candidates for dark matter. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0403/0403614v2.pdf"}
{"id": "astro-ph0404070", "abstract": "  Two FORTRAN programs are presented which plot the Hertzsprung-Russell diagram and the temporal evolution of such stellar quantities as: central and photospheric isotopic abundances, central densities and temperatures, luminosities,effective temperatures and photospheric radii for a wide range of stellar masses. The programs, which are modifications and extensions of some modules of the TYCHO 6.0 stellar evolution package, are accompanied by various control input files as well as by a library of data. The data library is actually one of the output files generated by TYCHO 7.0 (a modified version of TYCHO 6.0), while the plots themselves are generated by the PGPLOT Graphics Subroutine Library which is also publicly available and well cited. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0404/0404070v1.pdf"}
{"id": "astro-ph0407392", "abstract": "  We derive here the mean temperature profile for a sample of hot, medium distant clusters recently observed with XMM-Newton, whose profiles are available from the literature, and compare it with the mean temperature profile found from BeppoSAX data. The XMM-Newton and BeppoSAX profiles are in good agreement between 0.05 and 0.25 r_180. From 0.25 to about 0.5 r_180 both profiles decline, however the BeppoSAX profile does so much more rapidly than the XMM-Newton profile. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0407/0407392v1.pdf"}
{"id": "astro-ph0408535", "abstract": "  We report detection of the low-mass secondary in the spectroscopic binary Haro 1-14c in the Ophiuchus star forming region. The secondary/primary mass ratio is 0.310± 0.014. With an estimated photometric primary mass of 1.2 M_⊙, the secondary mass is ∼ 0.4 M_⊙ and the projected semi-major axis is ∼ 1.5 AU. The system is well-suited for astrometric mapping of its orbit with the current generation of ground-based IR interferometers. This could yield precision values of the system's component masses and distance. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0408/0408535v1.pdf"}
{"id": "astro-ph0409555", "abstract": "  Model-predicted and observed properties of the brightness distribution on M-type Mira disks are discussed. Fundamental issues of limb-darkening and diameter definition, of assigning observational data to diameter-type quantities and of interpreting such quantities in terms of model diameters are outlined. The influence of model properties upon interpretation of measured data is clarified. The dependence of the centre-to-limb variation (CLV) of intensity on wavelength, on stellar parameters and on variablity phase and cycle may be used for analyzing the geometrical and physical structure of the Mira atmosphere, for determining fundamental stellar parameters, and for investigating the quality of models. Desirable future observations include simultaneous observations in different spectral features at different phases and cycles, observation of the position of the shock front and observation of the time- and wavelength-dependence of deviations from spherical symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0409/0409555v1.pdf"}
{"id": "astro-ph0410068", "abstract": "  Changing the form of the star cluster mass function (CMF) can effectively change the upper end of the stellar initial mass function. The yields of from supernovae are very sensitive to the mass of the progenitor star. We show that by changing the parameters of the CMF, it is possible to change the yields of oxygen and magnesium by a factor of ∼ 1.5 and of metals in general by a factor of ∼ 1.8. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0410/0410068v1.pdf"}
{"id": "astro-ph0410363", "abstract": "  The interstellar thick disks of galaxies contain not only gas, but significant quantities of dust. Most of our knowledge of extraplanar dust in disk galaxies comes from direct broadband optical imaging of these systems, wherein the dust is identified due to the irregular extinction it produces against the thick disk and bulge stars. This observational technique is sensitive to only the most dense material, and we argue much of the material identified in this way traces a cold phase of the interstellar thick disks in galaxies. The presence of a cold, dense phase likely implies the interstellar pressures in the thick disks of spiral galaxies can be quite high. This dense phase of the interstellar medium may also fueling thick disk star formation, and H-alpha observations are now revealing H II regions around newly-formed OB stars associations in several galaxies. We argue that the large quantities of dust and the morphologies of the structures traced by the dust imply that much of the extraplanar material in disk galaxies must have been expelled from the underlying thin disk. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0410/0410363v1.pdf"}
{"id": "astro-ph0411381", "abstract": "  A search for aligned events has been done throughout the muon groups events measured by Baksan Underground Scintillation Telescope (BUST) during a period of 7.7 years. Only groups of multiplicity >3 for muon threshold energy equal to 0.85 TeV were selected for the analysis. A distribution of the events on alignment parameter λ has been obtained and compared with the results of Monte-Carlo simulation made for this experiment. The upper limit for aligned muon event flux as low as 5.3·10^-15 cm^-2 sec^-1 sr^-1 is given. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0411/0411381v1.pdf"}
{"id": "astro-ph0411484", "abstract": "  There are some discrepancies in the results on energy spectrum from Yakutsk, AGASA, and HiRes experiments. In this work differential energy spectrum of primary cosmic rays based on the Yakutsk EAS Array data is presented. For the largest events values of S_600 and axes coordinates have been obtained using revised lateral distribution function. Simulation of converter's response at large distances showed no considerable underestimation of particle density. Complex shape of spectrum in region of > 10^17 eV is confirmed. After adjustment of parameters and additional exposition at the Yakutsk array there are three events with energy > 10^20 eV. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0411/0411484v1.pdf"}
{"id": "astro-ph0412549", "abstract": "  We present the results from the first quasi-simultaneous multi-frequency (2.3, 5.0, 8.4 and 15 GHz) Very Long Baseline Interferometry (VLBI) observations of a compact steep spectrum (CSS) superluminal source 3C138. For the first time, the spectral distribution of the components within its central 10 milli-arcsecond (mas) region was obtained. This enables us to identify the component at the western end as the location of the nuclear activity on the assumption that the central engine is associated with one of the detected components. The possibility that none of these visible components is the true core is also discussed. The new measurements further clarify the superluminal motions of its inner jet components. The multi-frequency data reveal a convex spectrum in one jet component, inferring the existence of free-free absorption by the ambient dense plasma. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0412/0412549v1.pdf"}
{"id": "astro-ph0501050", "abstract": "  I discuss the dynamical interaction of galactic disks with the surrounding dark matter halos. In particular it is demonstrated that if the self-gravitating shearing sheet, a model of a patch of a galactic disk, is embedded in a live dark halo, this has a strong effect on the dynamics of density waves in the sheet. I describe how the density waves and the halo interact via halo particles either on orbits in resonance with the wave or on non-resonant orbits. Contrary to expectation the presence of the halo leads to a very considerable enhancement of the amplitudes of the density waves in the shearing sheet. This effect appears to be the equivalent of the recently reported enhanced growth of bars in numerically simulated stellar disks embedded in live dark halos. Finally I discuss the counterparts of the perturbations of the disk in the dark halo. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0501/0501050v1.pdf"}
{"id": "astro-ph0501116", "abstract": "  X-ray ionized reflection occurs when a surface is irradiated with X-rays so intense that its ionization state is determined by the ionization parameter xi propto F/n, where F is the incident flux and n the gas density. It occurs in accretion, onto compact objects including black holes in both active galaxies and stellar-mass binaries, and possibly in gamma-ray bursts. Computation of model reflection spectra is often time-consuming. Here we present the results from a comprehensive grid of models computed with our code, which has now been extended to include what we consider to be all energetically-important ionization states and transitions. This grid is being made available as an ionized-reflection model, REFLION, for XSPEC. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0501/0501116v1.pdf"}
{"id": "astro-ph0501132", "abstract": "  We use simulated maps to investigate the ability of high resolution, low noise surveys of the CMB to create catalogues of Clusters of galaxies by detecting the characteristic signature imprinted by the Sunyaev Zeldovich effect. We compute the completeness of the catalogues in our simulations for several survey strategies, and evaluate the relative merit of some Fourier and wavelet based filtering techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0501/0501132v1.pdf"}
{"id": "astro-ph0501438", "abstract": "  The CELESTE atmospheric Cherenkov detector ran until June 2004. It has observed the blazars Mrk 421, 1ES 1426+428 and Mrk 501. We significantly improved our understanding of the atmosphere using a LIDAR, and of the optical throughput of the detector using stellar photometry. The new data analysis provides better background rejection. We present our light curve for Mrk 421 for the 2002-2004 season and a comparison with X-ray data and the 2004 observation of 1ES 1426+428. The new analysis will allow a more sensitive search for a signal from Mrk 501. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0501/0501438v3.pdf"}
{"id": "astro-ph0501652", "abstract": "  In this paper, we study the possibility of building two-field models of dark energy with equation of state across -1. Specifically we will consider two classes of models: one consists of two scalar fields (Quintessence+Phantom) and another includes one scalar (Phantom) and one spinor field (Neutrino). Our studies indicate to some extent that two-field models give rise to a simple realization of the dynamical dark energy model with the equation of state across w = -1. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0501/0501652v1.pdf"}
{"id": "astro-ph0502039", "abstract": "  Results on steady TeV γ-ray point source search using data taken from the Tibet HD (Feb. 1997 – Sep. 1999) and Tibet III (Nov. 1999 – Oct. 2001) arrays are presented. From 0^∘ to 60^∘ in declination, significant excesses from the well-known steady source Crab Nebula and the high state of the flare type source Markarian 421 are observed. Because the levels of significance from other positions are not sufficiently high, 90", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0502/0502039v2.pdf"}
{"id": "astro-ph0502116", "abstract": "  Rotochemical heating originates in a departure from beta equilibrium due to spin-down compression in a rotating neutron star. The main consequence is that the star eventually arrives at a quasi-equilibrium state, in which the thermal photon luminosity depends only on the current value of the spin-down power, which is directly measurable. Only in millisecond pulsars the spin-down power remains high long enough for this state to be reached with a substantial luminosity. We report an extensive study of the effect of this heating mechanism on the thermal evolution of millisecond pulsars, developing a general formalism in the slow-rotation approximation of general relativity that takes the spatial structure of the star fully into account, and using a sample of realistic equations of state to solve the non-superfluid case numerically. We show that nearly all observed millisecond pulsars are very likely to be in the quasi-equilibrium state. Our predicted quasi-equilibrium temperatures for PSR J0437-4715 are only 20", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0502/0502116v1.pdf"}
{"id": "astro-ph0503598", "abstract": "  We present an empirical method for converting single-point near-infrared J, H, and K measurements of fundamental-mode Cepheids to mean magnitudes, using complete light curves in V or I bands. The algorithm is based on the template light curves in the near-infrared bandpasses. The mean uncertainty of the method is estimated to about 0.03 mag, which is smaller than the uncertainties obtained in other approaches to the problem in the literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0503/0503598v2.pdf"}
{"id": "astro-ph0506753", "abstract": "  A recent study has claimed that the rotation curve shapes and mass densities of Low Surface Brightness (LSB) galaxies are largely consistent with ΛCDM predictions, in contrast to a large body of observational work. I demonstrate that the method used to derive this conclusion is incapable of distinguishing the characteristic steep CDM mass-density distribution from the core-dominated mass-density distributions found observationally: even core-dominated pseudo-isothermal haloes would be inferred to be consistent with CDM. This method can therefore make no definitive statements on the (dis)agreement between the data and CDM simulations. After introducing an additional criterion that does take the slope of the mass-distribution into account I find that only about a quarter of the LSB galaxies investigated are possibly consistent with CDM. However, for most of these the fit parameters are so weakly constrained that this is not a strong conclusion. Only 3 out of 52 galaxies have tightly constrained solutions consistent with ΛCDM. Two of these galaxies are likely dominated by stars, leaving only one possible dark matter dominated, CDM-consistent candidate, forming a mere 2 per cent of the total sample. These conclusions are based on comparison of data and simulations at identical radii and fits to the entire rotation curves. LSB galaxies that are consistent with CDM simulations, if they exist, seem to be rare indeed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0506/0506753v1.pdf"}
{"id": "astro-ph0507551", "abstract": "  We have determined the total numbers and specific frequencies of blue, metal-poor globular clusters (GCs) in eight spiral and early-type galaxies. These data, along with five measurements from the literature, show a trend of increasing blue GC specific frequency with increasing mass of the host galaxy. The increase is not accounted for in a simple galaxy formation model in which ellipticals and their GC systems are formed by the merger of typical spiral galaxies. The data appear broadly consistent with hierarchical formation scenarios in which metal-poor GCs are formed over a finite period in the early Universe during the initial stages of galaxy assembly. In this picture, the observed trend is related to biasing, in the sense that the more massive galaxies of today began assembling earlier and therefore formed relatively more GCs during this early epoch of metal-poor GC formation. We discuss how comparisons of the observed specific frequency of metal-poor GCs with model calculations can constrain the formation redshift of these objects. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0507/0507551v1.pdf"}
{"id": "astro-ph0508635", "abstract": "  Many past attempts to kill MOND have only strengthened the theory. Better data on galaxy velocity curves clearly favor MOND (without fine-tuning) over cold dark matter. The usual critism on the incompleteness of classical MOND has spurred a Modified Relativity (MR) by Bekenstein. After outlining cosmology and lensing in MOND, we review MOND on small scales. We point out some potential problems of MOND in two-body relaxation and tidal truncation. We argue that the tidal field in any MOND-like gravity theory predicts that the Roche lobe sizes of a binary system are simply proportional to the binary baryonic mass ratio to the power 1/3. An immediate application of this result is that the tidal field and tidal truncation radii of million-star globular clusters and million-star dwarf galaxies (e.g., the Milky Way satellites NGC2419 and Carina) would be very similar because of the one-to-one relation between gravity and baryon distribution. This prediction appears, however, inconsistent with the fact that all globulars are truncated to much smaller sizes than all dwarf galaxies. Whether tide is uniquely determined by baryons can also be used to falsify any MOND-like gravity theory, whether classical or relativistic. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0508/0508635v1.pdf"}
{"id": "astro-ph0509213", "abstract": "  We present the results of a search for time correlations in high energy cosmic ray data (primary E > 10^14 eV) collected by the California HIgh school Cosmic ray ObServatory (CHICOS) array. Data from 69 detector sites spread over an area of 400 km^2 were studied for evidence of isolated events separated by more than 1 km with coincidence times ranging from 1 microseconds up to 1 second. We report upper limits for the coincidence probability as a function of coincidence time. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0509/0509213v1.pdf"}
{"id": "astro-ph0510539", "abstract": "  The cooling of baryons in the centers of dark matter halos leads to a more concentrated dark matter distribution. This effect has traditionally been calculated using the model of adiabatic contraction, which assumes spherical symmetry, while in hierarchical formation scenarios halos grow via multiple violent mergers. We test the adiabatic contraction model in high-resolution cosmological simulations and find that the dissipation of gas indeed increases the density of dark matter and steepens its radial profile compared to the case without cooling. Although the standard model systematically overpredicts the increase of dark matter density, a simple modification of the assumed invariant from M(r)r to M(<r>)r, where <r> is the orbit-averaged particle position, reproduces the simulated profiles within 10", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0510/0510539v1.pdf"}
{"id": "astro-ph0510624", "abstract": "  We present new deep near-infrared images of dark clouds in the Perseus molecular complex. These images show beautiful extended emission which we model as scattered ambient starlight and name “cloudshine”. The brightness and color variation of cloudshine complicates the production of extinction maps, the best tracer of column density in clouds. However, since the profile of reflected light is essentially a function of mass distribution, cloudshine provides a new way to study the structure of dark clouds. Previous work has used optical scattered light to study the density profile of tenuous clouds; extending this technique into the infrared provides a high-resolution view into the interiors of very dense clouds, bypassing the complexities of using thermal dust emission, which is biased by grain temperature, or molecular tracers, which have complicated depletion patterns. As new wide-field infrared cameras are used to study star-forming regions at greater depth, cloudshine will be widely observed and should be seen as a new high-resolution tool, rather than an inconvenience. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0510/0510624v2.pdf"}
{"id": "astro-ph0510685", "abstract": "  Motivated by theoretical predictions that first stars were predominantly very massive, we investigate the physics of the transition from an early epoch dominated by massive Pop III stars to a later epoch dominated by familiar low-mass Pop II/I stars by means of a numerically-generated catalogue of dark matter halos coupled with a self-consistent treatment of chemical and radiative feedback. Depending on the strength of the chemical feedback, Pop III stars can contribute a substantial fraction (several percent) of the cosmic star formation activity even at moderate redshifts, z = 5. We find that the three z = 10 sources tentatively detected in NICMOS UDFs should be powered by Pop III stars, if these are massive; however, this scenario fails to reproduce the derived WMAP electron scattering optical depth. Instead, both the UDFs and WMAP constraints can be fulfilled if stars at any time form with a more standard, slightly top-heavy, Larson IMF in the range 1 Msun < M < 100 Msun. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0510/0510685v1.pdf"}
{"id": "astro-ph0511288", "abstract": "  We present an analysis of the 2-150 keV spectrum of the transient X-ray pulsar V0332+53 taken with the Rossi X-Ray Timing Explorer (RXTE) in 2004 December. We report on the detection of three cyclotron resonance features at 27, 51, and 74 keV in the phase-averaged data, corresponding to a polar magnetic field of 2.7 x 10^12 G. After 4U0115+63, this makes V0332+53 the second accreting neutron star in which more than two cyclotron lines have been detected; this has now also been confirmed by INTEGRAL. Pulse-phase spectroscopy reveals remarkably little variability of the cyclotron line through the 4.4 s X-ray pulse. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0511/0511288v1.pdf"}
{"id": "astro-ph0512257", "abstract": "  In an investigative 16 hour L band observation using the MERLIN radio interferometric array, we have resolved both the pulsar PSR B1951+32 and structure within the flat spectral radio continuum region, believed to be the synchrotron nebula associated with the interaction of the pulsar and its `host' supernova remnant CTB 80. The extended structure we see, significant at ∼ 4.5 σ, is of dimensions 2.5\" × 0.75\", and suggests a sharp bow shaped arc of shocked emission, which is correlated with similar structure observed in lower resolution radio maps and X-ray images. Using this MERLIN data as a new astrometric reference for other multiwavelength data we can place the pulsar at one edge of the HST reported optical synchrotron knot, ruling out previous suggested optical counterparts, and allowing an elementary analysis of the optical synchrotron emission which appears to trail the pulsar. The latter is possibly a consequence of pulsar wind replenishment, and we suggest that the knot is a result of magnetohydrodynamic (MHD) instabilities. These being so, it suggests a dynamical nature to the optical knot, which will require high resolution optical observations to confirm. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0512/0512257v1.pdf"}
{"id": "astro-ph0601306", "abstract": "  An efficient algorithm for adaptive kernel smoothing (AKS) of two-dimensional imaging data has been developed and implemented using the Interactive Data Language (IDL). The functional form of the kernel can be varied (top-hat, Gaussian etc.) to allow different weighting of the event counts registered within the smoothing region. For each individual pixel the algorithm increases the smoothing scale until the signal-to-noise ratio (s.n.r.) within the kernel reaches a preset value. Thus, noise is suppressed very efficiently, while at the same time real structure, i.e. signal that is locally significant at the selected s.n.r. level, is preserved on all scales. In particular, extended features in noise-dominated regions are visually enhanced. The ASMOOTH algorithm differs from other AKS routines in that it allows a quantitative assessment of the goodness of the local signal estimation by producing adaptively smoothed images in which all pixel values share the same signal-to-noise ratio above the background.   We apply ASMOOTH to both real observational data (an X-ray image of clusters of galaxies obtained with the Chandra X-ray Observatory) and to a simulated data set. We find the ASMOOTHed images to be fair representations of the input data in the sense that the residuals are consistent with pure noise, i.e. they possess Poissonian variance and a near-Gaussian distribution around a mean of zero, and are spatially uncorrelated. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0601/0601306v1.pdf"}
{"id": "astro-ph0601687", "abstract": "  Rate of period change Ṗ for a Cepheid is shown to be a parameter that is capable of indicating the instability strip crossing mode for individual objects, and, in conjunction with light amplitude, likely location within the instability strip. Observed rates of period change in over 200 Milky Way Cepheids are demonstrated to be in general agreement with predictions from stellar evolutionary models, although the sample also displays features that are inconsistent with some published models and indicative of the importance of additional factors not fully incorporated in models to date. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0601/0601687v2.pdf"}
{"id": "astro-ph0602004", "abstract": "  Despite a rich diversity in observational properties, gamma-ray bursts (GRBs) can be divided into two broad categories based on their duration and spectral hardness – the long-soft and the short-hard GRBs. The discovery of afterglows from long GRBs in 1997, and their localization to arcsecond accuracy, was a watershed event. The ensuing decade of intense study led to the realization that long-soft GRBs are located in star forming galaxies, produce about 10^51 erg in collimated relativistic ejecta, are accompanied by supernovae, and result from the death of massive stars. While theoretical arguments suggest that short GRBs have a different physical origin, the lack of detectable afterglows prevented definitive conclusions. The situation changed dramatically starting in May 2005 with the discovery of the first afterglows from short GRBs localized by Swift and HETE-2. Here I summarize the discovery of these afterglows and the underlying host galaxies, and draw initial conclusions about the nature of the progenitors and the properties of the bursts. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0602/0602004v1.pdf"}
{"id": "astro-ph0602101", "abstract": "  The cosmic stellar birth rate can be measured by standard astronomical techniques. It can also be probed via the cosmic stellar death rate, though until recently, this was much less precise. However, recent results based on measured supernova rates, and importantly, also on the attendant diffuse fluxes of neutrinos and gamma rays, have become competitive, and a concordant history of stellar birth and death is emerging. The neutrino flux from all past core-collapse supernovae, while faint, is realistically within reach of detection in Super-Kamiokande, and a useful limit has already been set. I will discuss predictions for this flux, the prospects for neutrino detection, the implications for understanding core-collapse supernovae, and a new limit on the contribution of type-Ia supernovae to the diffuse gamma-ray background. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0602/0602101v1.pdf"}
{"id": "astro-ph0602107", "abstract": "  We obtained high resolution, high S/N spectroscopy for the very metal-poor star HD122563 with the Subaru Telescope High Dispersion Spectrograph. Previous studies have shown that this object has excesses of light neutron-capture elements, while its abundances of heavy ones are very low. In our spectrum covering 3070 - 4780 A of this object, 19 neutron-capture elements have been detected, including seven for the first time in this star (Nb, Mo, Ru, Pd, Ag, Pr, and Sm). Upper limits are given for five other elements including Th. The abundance pattern shows a gradually decreasing trend, as a function of atomic number, from Sr to Yb, which is quite different from those in stars with excesses of r-process elements. This abundance pattern of neutron-capture elements provides new strong constraints on the models of nucleosynthesis responsible for the very metal-poor stars with excesses of light neutron-capture elements but without enhancement of heavy ones. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0602/0602107v1.pdf"}
{"id": "astro-ph0602312", "abstract": "  We present the second in a series of results in which we have searched for undiscovered neutron stars in supernova remnants (SNRs). This paper deals with the largest six SNRs in our sample, too large for Chandra or XMM-Newton to cover in a single pointing. These SNRs are nearby, with typical distances of <1 kpc. We therefore used the ROSAT Bright Source Catalog and past observations in the literature to identify X-ray point sources in and near the SNRs. Out of 54 sources, we were immediately able to identify optical/IR counterparts to 41 from existing data. We obtained Chandra snap-shot images of the remaining 13 sources. Of these, 10 were point sources with readily identified counterparts, two were extended, and one was not detected in the Chandra observation but is likely a flare star. One of the extended sources may be a pulsar wind nebula, but if so it is probably not associated with the nearby SNR. We are then left with no identified neutron stars in these six SNRs down to luminosity limits of 1̃e32 ergs/s. These limits are generally less than the luminosities of typical neutron stars of the same ages, but are compatible with some lower-luminosity sources such as the neutron stars in the SNRs CTA 1 and IC 443. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0602/0602312v1.pdf"}
{"id": "astro-ph0602364", "abstract": "  The ultraluminous X-ray sources (ULXs) were isolated in external galaxies for the last 5 years. Their X-ray luminosities exceed 100-10000 times those of brightest Milky Way black hole binaries and they are extremely variable. There are two models for the ULXs, the best black hole candidates. 1. They are supercritical accretion disks around a stellar mass black hole like that in SS433, observed close to the disk axes. 2. They are Intermediate Mass Black Holes (of 100-10000 solar masses). Critical observations which may throw light upon the ULXs nature come from observations of nebulae around the ULXs. We present results of 3D-spectroscopy of nebulae around several ULXs located in galaxies at 3-6 Mpc distances. We found that the nebulae to be powered by their central black holes. The nebulae are shocked and dynamically perturbed probably by jets. The nebulae are compared with SS433 nebula (W50). ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0602/0602364v1.pdf"}
{"id": "astro-ph0603130", "abstract": "  The Galactic Bulge region is a rich host of variable high-energy point sources. These sources include bright and relatively faint X-ray transients, X-ray bursters, persistent neutron star and black-hole candidate binaries, X-ray pulsars, etc.. We have a program to monitor the Galactic Bulge region regularly and frequently with the gamma-ray observatory INTEGRAL. As a service to the scientific community the high-energy light curves of all the active sources as well as images of the region are made available through the WWW. We show the first results of this exciting new program. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0603/0603130v1.pdf"}
{"id": "astro-ph0606435", "abstract": "  We analyze the processes relevant for star formation in a model with dark matter in the form of sterile neutrinos. Sterile neutrino decays produce an X-ray background radiation that has a two-fold effect on the collapsing clouds of hydrogen. First, the X-rays ionize the gas and cause an increase in the fraction of molecular hydrogen, which makes it easier for the gas to cool and to form stars. Second, the same X-rays deposit a certain amount of heat, which could, in principle, thwart the cooling of gas. We find that, in all the cases we have examined, the overall effect of sterile dark matter is to facilitate the cooling of gas. Hence, we conclude that dark matter in the form of sterile neutrinos can help the early collapse of gas clouds and the subsequent star formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0606/0606435v3.pdf"}
{"id": "astro-ph0607010", "abstract": "  This is the first paper in a series where we study the influence of turbulent diffusion and advective transport on the chemical evolution of protoplanetary disks, using a 2D flared disk model and a 2D mixing gas-grain chemical code with surface reactions. A first interesting result concerns the abundance of gas-phase CO in the outer regions of protoplanetary disks. In this Letter we argue that the gas-phase CO concentration in the disk regions, where the temperature is lower than ∼25 K, can be significantly enhanced due to the combined effect of vertical and radial mixing. This finding has a potential implication for the current observational data on the DM Tau disk chemistry. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0607/0607010v1.pdf"}
{"id": "astro-ph0608408", "abstract": "  The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak gravitational lensing data. Multi-color, high-resolution HST ACS images allow detection of many more arc candidates than were previously known, especially around the subcluster. Using the known redshift of one of the multiply imaged systems, we determine the remaining source redshifts using the predictive power of the strong lens model. Combining this information with shape measurements of \"weakly\" lensed sources, we derive a high-resolution, absolutely-calibrated mass map, using no assumptions regarding the physical properties of the underlying cluster potential. This map provides the best available quantification of the total mass of the central part of the cluster. We also confirm the result from Clowe et al. (2004,2006a). ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0608/0608408v1.pdf"}
{"id": "astro-ph0608501", "abstract": "  Tissot indicatrices have provided visual measures of local area and isotropy distortions. Here we show how large scale distortions of flexion (bending) and skewness (lopsidedness) can be measured. Area and isotropy distortions depend on the map projection metric, flexion and skewness, which manifest themselves on continental scales, depend on the first derivatives of the metric. We introduce new indicatrices that show not only area and isotropy distortions but flexion and skewness as well. We present a table showing error measures for area, isotropy, flexion, skewness, distances, and boundary cuts allowing us to compare different world map projections. We find that the Winkel-Tripel projection (already adopted for world maps by the National Geographic), has low distortion on most measures and excellent quality overall. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0608/0608501v2.pdf"}
{"id": "astro-ph0609433", "abstract": "  We present spectra of 59 nearby stars candidates, M dwarfs and white dwarfs, previously identified using high proper motion catalogues and the DENIS database. We review the existing spectral classification schemes and spectroscopic parallax calibrations in the near-infrared J-band and derive spectral types and distances of the nearby candidates. 42 stars have spectroscopic distances smaller than 25 pc, three of them being white dwarfs. Two targets lie within 10 pc, one M8 star at 10.0 pc (APMPM J0103-3738), and one M4 star at 8.3 pc (LP 225-57). One star, LHS 73, is found to be among the few subdwarfs lying within 20 pc. Furthermore, together with LHS 72, it probably belongs to the closest pair of subdwarfs we know. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0609/0609433v1.pdf"}
{"id": "astro-ph0609812", "abstract": "  We consider the dynamical evolution of a disk of stars orbiting a central black hole. In particular, we focus on the effect of the stellar mass function on the evolution of the disk, using both analytic arguments and numerical simulations. We apply our model to the ring of massive stars at  0.1pc from the Galactic Center, assuming that the stars formed in a cold, circular disk, and find that our model requires the presence of a significant population of massive (>100Msun) stars in order to explain the the observed eccentricities of 0.2-0.3. Moreover, in order to limit the damping of the heavier stars' eccentricities, we also require fewer low-mass stars than expected from a Salpeter mass function, giving strong evidence for a significantly “top-heavy” mass function in the rings of stars seen near to the Galactic Center. We also note that the maximum possible eccentricities attainable from circular initial conditions at ages of <10Myr are around 0.4-0.5, and suggest that any rings of stars found with higher eccentricities were probably not formed from circular disks. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0609/0609812v1.pdf"}
{"id": "astro-ph0610131", "abstract": "  Variability amplitudes larger than 1 magnitude over time-scales of a few tens of minutes have recently been reported in the optical light-curves of several blazars. In order to independently verify the real occurrence of such extremely violent events, we undertook an observational study of a selected sample of three blazars: PKS 0048-097, PKS 0754+100, and PKS 1510-089. Possible systematic error sources during data acquisition and reduction were carefully evaluated. We indeed found flux variability at intra-night time-scales in all three sources, although no extremely violent behaviour, as reported by other authors, was detected. We show that an incorrect choice of the stars used for differential photometry will, under fairly normal conditions, lead to spurious variability with large amplitudes on short time-scales. Wrong results of this kind can be avoided with the use of simple error-control techniques. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610131v1.pdf"}
{"id": "astro-ph0610731", "abstract": "  The nature of the cosmic dark matter is unknown. The most compelling hypothesis is that dark matter consists of weakly interacting massive particles (WIMPs) in the 100 GeV mass range. Such particles would annihilate in the galactic halo, producing high-energy gamma rays which might be detectable in gamma ray telescopes such as the GLAST satellite. We investigate the ability of GLAST to distinguish between WIMP annihilation sources and astrophysical sources. Focusing on the galactic satellite halos predicted by the cold dark matter model, we find that the WIMP gamma-ray spectrum is nearly unique; separation of the brightest WIMP sources from known source classes can be done in a convincing way by including spectral and spatial information. Candidate WIMP sources can be further studied with Imaging Atmospheric Cerenkov Telescopes. Finally, Large Hadron Collider data might have a crucial impact on the study of galactic dark matter. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0610/0610731v2.pdf"}
{"id": "astro-ph0611347", "abstract": "  Straight-forward models of X-ray reflection in the inner region of accretion discs predict that primary X-ray flux and the flux reflected off the surface of the disc should vary together, albeit a short light travel time delay. Most of the observations, however, show that the X-ray flux can vary while the reflected features remain constant. Here we propose a simple explanation to this. In all likelihood, the emission of a moderately optically thick magnetic flare atop an accretion disc is anisotropic. A constant energy release rate in a flare will appear to produce a variable X-ray flux as the flare rotates with the accretion disc anchoring the magnetic tube. The reflector, on the other hand, receives a constant X-ray flux from the flare. Since the reflected emission is azimuthally symmetric, the observer will see a roughly constant reflected flux (neglecting relativistic effects). The model does not produce quasi-periodic oscillations (QPO) if magnetic flux tubes are sheared out faster than they complete one orbit. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0611/0611347v1.pdf"}
{"id": "astro-ph0611422", "abstract": "  Techniques to extract information from spectra of unresolved multi-component systems are revised, with emphasis on recent developments and practical aspects. We review the cross-correlation techniques developed to deal with such spectra, discuss the determination of the broadening function and compare techniques to reconstruct component spectra. The recent results obtained by separating or disentangling the component spectra is summarized. An evaluation is made of possible indeterminacies and random and systematic errors in the component spectra. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0611/0611422v1.pdf"}
{"id": "astro-ph0611656", "abstract": "  We have analysed publicly available MACHO observations of 6833 variable stars in the Large Magellanic Cloud, classified as eclipsing binaries. After finding that a significant fraction of the sample was misclassified, we redetermined periods and variability class for all stars, producing a clean sample of 3031 eclipsing binaries. We have investigated their distribution in the period-color-luminosity space, which was used, for example, to assign a foreground probability to every object and establish new period-luminosity relations to selected types of eclipsing stars. We found that the orbital period distribution of LMC binaries is very similar to those of the SMC and the Milky Way. We have also determined the rate of period change for every star using the O-C method, discovering about 40 eclipsing binaries with apsidal motion, 45 systems with cyclic period changes and about 80 stars with parabolic O-C diagrams. In a few objects we discovered gradual amplitude variation, which can be explained by changes in the orbital inclination caused by a perturbing third body in the system. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0611/0611656v1.pdf"}
{"id": "astro-ph0612257", "abstract": "  I present a technique to remove the residual OH airglow emission from near infrared spectra. Historically, the need to subtract out the strong and variable OH airglow emission lines from 1-2.5um spectra has imposed severe restrictions on observational strategy. For integral field spectroscopy, where the field of view is limited, the standard technique is to observe blank sky frames at regular intervals. However, even this does not usually provide sufficient compensation if individual exposure times are longer than 2-3minutes due to (1) changes in the absolute flux of the OH lines, (2) variations in flux among the individual OH lines, and (3) effects of instrumental flexure which can lead to `P-Cygni' type residuals. The data processing method presented here takes all of these effects into account and serendipitously also improves background subtraction between the OH lines. It allows one, in principle, to use sky frames taken hours or days previously so that observations can be performed in a quasi-stare mode. As a result, the observing efficiency (i.e. fraction of time spent on a source) at the telescope can be dramatically increased. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0612/0612257v1.pdf"}
{"id": "astro-ph0612452", "abstract": "  There is now strong observational evidence that the expansion of the universe is accelerating. The standard explanation invokes an unknown \"dark energy\" component. But such scenarios are faced with serious theoretical problems, which has led to increased interest in models where instead General Relativity is modified in a way that leads to the observed accelerated expansion. The question then arises whether the two scenarios can be distinguished. Here we show that this may not be so easy, demonstrating explicitely that a generalised dark energy model can match the growth rate of the DGP model and reproduce the 3+1 dimensional metric perturbations. Cosmological observations are then unable to distinguish the two cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0612/0612452v1.pdf"}
{"id": "astro-ph0612455", "abstract": "  We have observed a sample of 13 large, powerful Fanaroff-Riley type II radio galaxies with the Very Large Array in multiple configurations and at multiple frequencies. We have combined our measurements of spectral indices, rotation measures and structural parameters such as arm-length ratios, axial ratios and misalignment angles, with similar data from the literature and revisited some well-known radio galaxy correlations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0612/0612455v1.pdf"}
{"id": "astro-ph0701129", "abstract": "  The aim of our observations is to investigate the intranight variability properties and the spectral variability of BL Lacertae. 799 optical multi-band observations were intensively made with the Beijing-Arizona-Taiwan-Connecticut (BATC) 60/90cm Schmidt telescope during the outburst composed of two subsequent flares in 2005. The second flare, whose rising phase lasted at least 44 days, was observed with amplitudes of more than 1.1 mag in three BATC optical bands. In general, on intranight timescale the amplitude of variability and the variation rate are larger at the shorter wavelength, and the variation rate is comparable in the rising and decaying phases within each band. A possible time lag between the light curves in bands e and m, around 11.6 minutes, was obtained. Based on the analysis of the colour index variation with the source brightness, the variability of BL Lacertae can be interpreted as having two components: a \"strongly-chromatic\" intranight component and a \"mildly-chromatic\" internight component, which may be the results of both intrinsic physical mechanism and geometric effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0701/0701129v1.pdf"}
{"id": "astro-ph0701770", "abstract": "  Observations at radio wavelengths address key problems in astrophysics, astrobiology, and lunar structure including the first light in the Universe (the Epoch of Reionization), the presence of magnetic fields around extrasolar planets, particle acceleration mechanisms, and the structure of the lunar ionosphere. Moreover, achieving the performance needed to address these scientific questions demands observations at wavelengths longer than those that penetrate the Earth's ionosphere, observations in extremely \"radio quiet\" locations such as the Moon's far side, or both. We describe a series of lunar-based radio wavelength interferometers of increasing capability. The Radio Observatory for Lunar Sortie Science (ROLSS) is an array designed to be deployed during the first lunar sorties (or even before via robotic rovers) and addressing particle acceleration and the lunar ionosphere. Future arrays would be larger, more capable, and deployed as experience is gained in working on the lunar surface. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0701/0701770v1.pdf"}
{"id": "astro-ph0702200", "abstract": "  X-ray variability of the microquasar XTE J1550-564 is studied with time domain techniques for the data from the RXTE/PCA observation in September 8, 1998. The 2–60 keV averaged shot is obtained from superposing shots with one millisecond time bin through aligning their peaks. The spectral behavior during the averaged shot exhibits prominent differences from that observed in Cyg X-1. The hardness ratio of (13–60 keV)/(2–13 keV) or (16–60 keV)/(13–16 keV) during a shot is lower or higher than that of steady emission respectively. The correlation coefficient between intensity and hardness ratio of (13–60 keV)/(2–13 keV) or (16–60 keV)/(13–16 keV) is negative or positive respectively. These results may indicate that physical processes in the low state of XTE J1550-564 are different from those in Cyg X-1. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0702/0702200v1.pdf"}
{"id": "astro-ph9401002", "abstract": "  The thermal nucleation of quark matter bubbles inside neutron stars is examined for various temperatures which the star may realistically encounter during its lifetime. It is found that for a bag constant less than a critical value, a very large part of the star will be converted into the quark phase within a fraction of a second. Depending on the equation of state for neutron star matter and strange quark matter, all or some of the outer parts of the star may subsequently be converted by a slower burning or a detonation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9401/9401002v1.pdf"}
{"id": "astro-ph9411057", "abstract": "  Standard models for the chemical evolution of the Galaxy are reviewed with particular emphasis on the history of the abundance gradients in the disk. The effects on the disk structure and metallicity of gas accretion are discussed, showing that a significant fraction of the current disk mass has been accreted in the last Gyrs and that the chemical abundances of the infalling gas can be non primordial but should not exceed 0.3 Z(sun). The distributions with time and with galactocentric distance of chemical elements are discussed, comparing the observational data with the corresponding theoretical predictions by standard models, which reproduce very well the ISM abundances at various epochs, but not equally well all the features derived from observations of old stellar objects. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9411/9411057v1.pdf"}
{"id": "astro-ph9604064", "abstract": "  Current measurements of the Hubble constant H_0 on scale less than ∼100 Mpc appear to be controversial, while the observations made at high redshift seem to provide a relatively low value. On the other hand, the Hubble expansion is driven by the matter content of the universe. The dynamical analysis on scale of a few ∼10 Mpc indicates that the matter density Ω_0 is only ∼0.2–0.3, which is significantly smaller than Ω_0=1 predicted in the standard inflation model. This might support the tendency of a decreasing Hubble constant towards distance. In this paper, we discuss the influence of a possible variant Hubble constant on two fundamental relations in astronomy: the magnitude-redshift (m–z) and the number-magnitude relations. Using a distant type Ia supernova at z=0.458, we show that the deceleration parameter q_0 or Ω_0 cannot be determined from the m–z relation at moderate/high redshift unless the variation of the Hubble constant is a priori measured. It is further demonstrated that the number density of distant sources would be underestimated when their local calibration is employed, which may partially account for the number excess of the faint blue galaxies observed at moderate/high redshift. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9604/9604064v1.pdf"}
{"id": "astro-ph9606085", "abstract": "  We have used optical echelle spectra along with ROSAT and ASCA X-ray spectra to test the hypothesis that the southern portion of the N44 X-ray bright region is the result of a blowout structure. Three pieces of evidence now support this conclusion. First, the filamentary optical morphology corresponding with the location of the X-ray bright South Bar suggests the blowout description (Chu et al 1993). Second, optical echelle spectra show evidence of high velocity ( 90 km/sec) gas in the region of the blowout. Third, X-ray spectral fits show a lower temperature for the South Bar than the main superbubble region of Shell 1. Such a blowout can affect the evolution of the superbubble and explain some of the discrepancy discussed by Oey     Massey (1995) between the observed shell diameter and the diameter predicted on the basis of the stellar content and Weaver et al.'s (1977) pressure-driven bubble model. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9606/9606085v1.pdf"}
{"id": "astro-ph9610108", "abstract": "  The long-term variability of a sample of 149 optically selected QSOs in the field of the Selected Area 94 has been studied in the R-band. The relations between variability and luminosity and between variability and redshift have been investigated by means of “robust” statistical estimators, allowing to disentangle the effects of the measurement errors. The results are compared with the corresponding properties of the variability in the B-band for the same sample. An anti-correlation between the R-band variability and the intrinsic luminosity is found, analogously to what is observed in the B-band. The amplitude of the R-band variability turns out to be smaller (of a factor 1.13 ± 0.05) than the B-band variability. The implications in terms of the black-hole, starburst and microlensing models are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9610/9610108v1.pdf"}
{"id": "astro-ph9701181", "abstract": "  The production of 26Al by explosions of classical novae has been computed by means of a hydrodynamic code that follows both the accretion and the explosion stages. A special emphasis has been put on the analysis of the influence of the initial abundances of the accreted envelope, as well as on the nuclear reaction rates involved. With the most recent values of chemical composition and reaction rates available, 26Al production is lowered with respect to previous computations. According to our results, the final contribution of novae to the galactic 26Al is at most 0.4 M_sun, which is a small part of the estimated 26Al in the Galaxy derived from COMPTEL observations of the 1809 keV emission. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9701/9701181v1.pdf"}
{"id": "astro-ph9702119", "abstract": "  We present optical photometry of the eclipsing supersoft source, CAL87. These observations comprise long term data accumulated as a by-product of the MACHO Project, and high speed white light photometry of a single eclipse. We (i) derive an improved ephemeris of To = HJD 2450111.5144(3) + 0.44267714(6)E for the time of minimum light, (ii) find the eclipse structure to be stable over a period of 4 years, and (iii) investigate the colour variation as a function of orbital phase. The resolution afforded by the high speed nature of the white light observations enables us to see new structure in the light curve morphology. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9702/9702119v1.pdf"}
{"id": "astro-ph9704131", "abstract": "  X-ray spectroscopy of Seyfert 1 galaxies often reveal absorption edges resulting from photoionized gas along the line-of-sight to the central engine, the so-called warm absorber. I discuss how recent ASCA observations of warm absorber variability in MCG-6-30-15 can lead us to reject a one-zone model and, instead, have suggested a multi-zone warm absorber. The evidence for dust within the warm absorbers of MCG-6-30-15 and IRAS 13349+2438 is also addressed. These dusty warm absorbers reveal themselves by significantly reddening the optical flux without heavily absorbing the soft X-ray photons. Thermal emission from this warm/hot dust may be responsible for the infra-red bump commonly seen in the broad band spectrum of many Seyfert galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9704/9704131v1.pdf"}
{"id": "astro-ph9704168", "abstract": "  More than 100 microlensing events have been detected during the last  4 years, most of them towards the Galactic Bulge. Since the line of sight towards the Bulge passes through the disk and the Bulge itself, the known stars towards the Bulge play a dominant role as gravitational lenses. If these stars have planets around them, then the signature of the planets can be seen as sharp, extra peaks on the microlensing light curves. Frequent, continuous monitoring of the on-going microlensing events thus provides a powerful new method to search for planets around lensing stars.   Here I first review the background on stars acting as gravitational lenses. I then review the theoretical work on possible observational features due to planets, and the probability of detecting the planets through microlensing. I then discuss the status/strategy/results of the observational programs currently active in this field. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9704/9704168v1.pdf"}
{"id": "astro-ph9705015", "abstract": "  Five fields located close to the center of the globular cluster NGC 104=47 Tuc were surveyed in a search for variable stars. We present V-band light curves for 42 variables. This sample includes 13 RR Lyr stars – 12 of them belong to the Small Magellanic Cloud (SMC) and 1 is a background object from the galactic halo. Twelve eclipsing binaries were identified – 9 contact systems and 3 detached/semi-detached systems. Seven eclipsing binaries are located in the blue straggler region on the cluster color-magnitude diagram (CMD) and four binaries can be considered main-sequence systems. One binary is probably a member of the SMC. Eight contact binaries are likely members of the cluster and one is most probably a foreground star. We show that for the surveyed region of 47 Tuc, the relative frequency of contact binaries is very low as compared with other recently surveyed globular clusters. The sample of identified variables also includes 15 red variables with periods ranging from about 2 days to several weeks. A large fraction of these 15 variables probably belong to the SMC but a few stars are likely to be red giants in 47 Tuc. VI photometry for about 50 000 stars from the cluster fields was obtained as a by product of our survey. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9705/9705015v1.pdf"}
{"id": "astro-ph9706200", "abstract": "  The structure of static atmospheres around unmagnetized neutron stars undergoing steady, spherical accretion is discussed. We focus on the “hot” configurations presented by Turolla et al. (1994) and calculate the radiation spectrum using a characteristics method. In particular, it is found that e^+–e^- pair production may affect significantly the external atmospheric layers, where positron and proton number densities become of the same order. The consequent increase of the scattering opacity lowers the Eddington limit and this, in turn, may drive a dynamical instability if the accretion luminosity is large enough, ultimately producing a rapid expulsion of the envelope. If “hot” states are indeed accessible, this mechanism could give rise to transient phenomena in hard X–rays of potential great astrophysical interest. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9706/9706200v1.pdf"}
{"id": "astro-ph9707052", "abstract": "  We present a broad band X-ray observation of the Cas A supernova remnant, obtained with the 4 narrow field instruments on board the BeppoSAX satellite. The X-ray spectrum thus obtained spans more than two decades in energy, from  0.5 to  80 keV. The complete spectrum is fit with a two-component non-equilibrium ionization (NEI) model plus a power-law component which dominates at the higher energies. The influence of the hard X-ray tail on the parameters derived for the thermal emission is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9707/9707052v1.pdf"}
{"id": "astro-ph9707202", "abstract": "  We analyze a composite broad-band optical/UV/Xgamma-ray spectrum of the Seyfert 1 galaxy NGC 5548. The spectrum consists of an average of simultaneous optical/IUE/Ginga observations accompanied by ROSAT and GRO/OSSE data from non-simultaneous observations. We show that the broad-band continuum is inconsistent with simple disk models extending to the soft X-rays. Instead, the soft-excess is well described by optically thick, low temperature, thermal Comptonization which may dominate the entire big blue bump. This might explain the observed tight UV/soft X-ray variability correlation and absence of a Lyman edge in this object. However, the plasma parameters inferred by the spectrum need stratification in optical depth and/or temperature to prevent physical inconsistency. The optical/UV/soft X-ray component contributes about half of the total source flux. The spectral variations of the soft-excess are consistent with that of the UV and argue that the components are closely related. The overall pattern of spectral variability suggests variations of the source geometry, and shows the optical/UV/soft X-ray component to be harder when brighter, while the hard X-ray component is softer when brighter. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9707/9707202v1.pdf"}
{"id": "astro-ph9707307", "abstract": "  We report the detection of OH satellite line masers at 1720 MHz and 1612 MHz from the nuclear region of the starburst galaxy M82. The observations were aimed at detecting 1720 MHz maser emission from the known radio emitting SNR in the nuclear region. At 1720 MHz we detect six features above the 5-sigma limit set by noise, four in emission and two in absorption. Three of the emission features appear closely associated with known discrete continuum radio sources, and one of the absorption features is precisely coincident with the discrete continuum source 44.01+59.6. The latter source also exhibits strong 1612 MHz emission at the same velocity. No other 1612 MHz features were detected. All of the 1720 MHz emission features are consistent with masers pumped by collisions with molecular hydrogen at densities between 10^3 cm^-3 and 10^5 cm^-3, and T_k between 50 K and 250 K. The absorption and emission associated with the two satellite lines in 44.01+59.6, together with other evidence, points to the possibility that this source is the AGN in M82. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9707/9707307v2.pdf"}
{"id": "astro-ph9707321", "abstract": "  We review the recent multifrequency studies of galactic black hole binaries, aiming at revealing the underlying emission processes and physical properties in these systems. The optical and infrared observations are important for determining their system parameters, such as the companion star type, orbital period and separation, inclination angle and the black hole mass. The radio observations are useful for studying high energy electron acceleration process, jet formation and transport. X-ray observations can be used to probe the inner accretion disk region in order to understand the fundamental physics of the accretion disk in the strongest gravitational field and the properties of the black hole. Future higher sensitivity and better resolution instrumentation will be needed to answer the many fundamental questions that have arisen. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9707/9707321v2.pdf"}
{"id": "astro-ph9707353", "abstract": "  We present a model for the inverted radio spectra of active active galactic nuclei as well as the central regions of normal galaxies. The model is based on the unified scenario for active galaxies, stating that the central engines of active galaxies consists of a supermassive black hole surrounded by an accretion disk and a radio jet. The nuclei of normal (i. e. less active) galaxies are supposed to be scaled-down versions of the same phenomenon. We show that the radio emission of a jet component, becoming optically thin to the radio emission of a monoenergetic pair plasma at decreasing frequencies as it moves outward and expands, is well suited to explain the observational results. We present a model calculation for the special case of the nucleus of M 81. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9707/9707353v1.pdf"}
{"id": "astro-ph9710062", "abstract": "  An alternative to the standard cold dark matter model has been recently proposed in which a significant fraction of the energy density of the universe is due to a dynamical scalar field (Q) whose effective equation-of-state differs from that of matter, radiation or cosmological constant (Λ). In this paper, we determine how the Q-component modifies the primordial inflation gravitational wave (tensor metric) contribution to the cosmic microwave background anisotropy and, thereby, one of the key tests of inflation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9710/9710062v1.pdf"}
{"id": "astro-ph9711302", "abstract": "  We investigate two chemical abundance calibrations for the narrow-line-region (NLR) of active galaxies in terms of three easily observable optical emission-line ratios, namely, [OIII]λλ4959,5007/Hβ, [NII]λλ6548,84/Hα and [OII]λ3727/[OIII]λλ4959,5007. The calibrations are obtained from a grid of models on the assumption that the main process responsible for the production of these lines is photoionization by a “typical” active galactic nucleus continuum. The chemical elements vary their abundance together with oxygen, except nitrogen, which is assumed to be a product of secondary nucleosynthesis. The calibrations are calculated for the range 8.4 ≤ 12+log(O/H) ≤ 9.4, and tested using NLR data for a sample of Seyfert's and LINER's having HII regions in the vicinity of the nucleus. The gaseous abundances of these HII regions have been determined in previous works, and the NLR abundances are obtained on the assumption that they can be extrapolated from those of the HII regions. The calibrations work very well for the Seyfert's, giving abundance values which agree with those obtained from the HII regions, and can thus be used for quick estimates of the chemical abundances of the NLR's. For the LINER's, the calibrations give lower values than those derived from the corresponding HII regions, suggesting that the assumptions of the models do not apply for them, and that there are different physical processes at work in the NLR of the LINER's. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9711/9711302v1.pdf"}
{"id": "astro-ph9712240", "abstract": "  We develop a simple, time-dependent Comptonization model to probe the origins of spectral variability in accreting neutron star systems. In the model, soft “seed photons” are injected into a corona of hot electrons, where they are Compton upscattered before escaping as hard X-rays. The model describes how the hard X-ray spectrum varies when the properties of either the soft photon source or the Comptonizing medium undergo small oscillations. Observations of the resulting spectral modulations can determine whether the variability is due to (i) oscillations in the injection of seed photons, (ii) oscillations in the coronal electron density, or (iii) oscillations in the coronal energy dissipation rate. Identifying the origin of spectral variability should help clarify how the corona operates and its relation to the accretion disk. It will also help in finding the mechanisms underlying the various quasi-periodic oscillations (QPO) observed in the X-ray outputs of many accreting neutron star and black hole systems. As a sample application of our model, we analyze a kilohertz QPO observed in the atoll source 4U 1608-52. We find that the QPO is driven predominantly by an oscillation in the electron density of the Comptonizing gas. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9712/9712240v1.pdf"}
{"id": "astro-ph9712274", "abstract": "  The combination of the broad band coverage and moderate spectral resolution of the LECS and MECS instruments on-board BeppoSAX allow the spectra of AGN to be studied in unprecedented detail down to 0.1 keV. We describe the calibration and the performance of the LECS and report on observations of low-energy absorption features in the spectra of both a low (MCG-6-30-15) and a high luminosity (3C 273) AGN. These features provide important diagnostics on the location and nature of the material surrounding the AGN. A comparison of LECS and ASCA/SIS low energy performance is also presented in the case of 3C 273. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9712/9712274v1.pdf"}
{"id": "astro-ph9802313", "abstract": "  The study of the very young open cluster NGC 6231 clearly shows the presence of a mass segregation for the most massive stars. These observations, combined with those concerning other young objects and very recent numerical simulations, strongly support the hypothesis of an initial origin for the mass segregation of the most massive stars. These results led to the conclusion that massive stars form near the center of clusters. They are strong constraints for scenarii of star and stellar cluster formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9802/9802313v1.pdf"}
{"id": "astro-ph9803007", "abstract": "  Since their discovery in 1973, Gamma-Ray Bursts (GRBs) have remained for many years one of the most elusive mysteries in High Energy-Astrophysics. The main problem regarding the nature of GRBs has usually been the lack of knowledge of their distance scale. About 300 GRBs are detected annually by BATSE in the full sky, but only a few of them can be localized accurately to less than half a degree. For many years, follow-up observations by other satellites and ground-based telescopes were conducted, but no counterparts at other wavelengths were found. The breakthrough took place in 1997, thanks to the observation by BeppoSAX and RossiXTE of the fading X-ray emission that follows the more energetic gamma-ray photons once the GRB event has ended. This emission (the afterglow) extends at longer wavelengths, and the good accuracy in the position determination by BeppoSAX has led to the discovery of the first optical counterparts -for GRB 970228, GRB 970508, and GRB 971214-, greatly improving our understanding of these puzzling sources. Now it is widely accepted that most bursts originate at cosmological distances but the final solution of the GRB problem is still far away. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9803/9803007v3.pdf"}
{"id": "astro-ph9804237", "abstract": "  We summarize the status of a “targeted” redshift survey aimed at establishing the properties of galaxies and their large scale distribution in the redshift range 2.5 < z < 3.5. At the time of this writing, we have obtained spectra of more than 400 galaxies in this redshift range, all identified using the “Lyman break” color-selection technique. We present some of the first results on the general clustering properties of the Lyman break galaxies. The galaxies are very strongly clustered, with co-moving correlation length similar to present-day galaxies, and they are evidently strongly biased relative to the mass distribution at these early epochs, which is consistent with hierarchical galaxy formation models if Lyman break galaxies trace the most massive halos at z   3. Prospects for large surveys for galaxies beyond z   4 are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9804/9804237v1.pdf"}
{"id": "astro-ph9805189", "abstract": "  Preliminary results from a study of the isotopic compositions of the elements Hg and Pt in a number of HgMn stars are presented. This work represents an improvement over previous studies thanks to the very high spectral resolution available (R = 118 000) and to the new information on wavelengths and atomic structure of Hg II and Pt II. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9805/9805189v1.pdf"}
{"id": "astro-ph9806007", "abstract": "  We consider a recently-proposed alternative explanation of the CV period gap in terms of a revised mass-radius relation for the lower main sequence. We show that no such thermal-equilibrium relation is likely to produce a true gap. Using population synthesis techniques we calculate a model population that obeys the claimed equilibrium mass-radius relation. A theoretical period histogram obtained from this population shows two prominent period spikes rather than a gap. We consider also recent arguments suggesting that the period gap itself may not be real. We argue that, far from demonstrating a weakness of the interrupted-braking picture, the fact that most CV subtypes prefer one side of the gap or the other is actually an expected consequence of it. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9806/9806007v1.pdf"}
{"id": "astro-ph9806042", "abstract": "  We show that the crust-core interface in neutron stars acts as a potential barrier to the peripheral neutron vortices approaching the interface in the model in which these are coupled to the proton vortex clusters. This elementary barrier because of the interaction of vortex magnetic flux with the Meissner currents set up by the crustal magnetic field at the interface. The dominant part of the force is derived from to the cluster-interface interaction. As a result of the stopping of the continuous neutron vortex current through the interface, angular momentum is stored in the superfluid layers in the vicinity of the crust-core interface during the interglitch period. Discontinuous annihilation of proton vortices on the boundary restores the neutron vortex current and spins up the observable crust on short time-scales, leading to a glitch in the spin characteristics of a pulsar. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9806/9806042v2.pdf"}
{"id": "astro-ph9809120", "abstract": "  The Submillimetre Common-User Bolometer Array (SCUBA) is a new continuum camera operating on the James Clerk Maxwell Telescope (JCMT) on Mauna Kea, Hawaii. It consists of two arrays of bolometric detectors; a 91 pixel 350/450 micron array and a 37 pixel 750/850 micron array. Both arrays can be used simultaneously and have a field-of-view of approximately 2.4 arcminutes in diameter on the sky.   Ideally, performance should be limited solely by the photon noise from the sky background at all wavelengths of operation. However, observations at submillimetre wavelengths are hampered by “sky-noise” which is caused by spatial and temporal fluctuations in the emissivity of the atmosphere above the telescope. These variations occur in atmospheric cells that are larger than the array diameter, and so it is expected that the resultant noise will be correlated across the array and, possibly, at different wavelengths.   In this paper we describe our initial investigations into the presence of sky-noise for all the SCUBA observing modes, and explain our current technique for removing it from the data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9809/9809120v1.pdf"}
{"id": "astro-ph9809398", "abstract": "  We present the results and parameterization of the 0.5-2 keV Luminosity Function of AGNs from various ROSAT Surveys, ranging from the ROSAT bright Survey from the ROSAT All-Sky Survey (RASS) to the Ultra-Deep survey on the Lockman hole. A Luminosity-dependent density evolution model, where the density evolution rate drops at low luminosities, gives an excellent parametric description of the overall XLF covering wide ranges of redshift and luminosity.   The number density evolution of high-luminosity AGNs in our sample shows a similar behavior to optical and radio surveys, except that we do not find evidence for the rapid decrease of the number density at z>2.7. The discrepancy is marginally significant and including more deep survey results would make better determination of the behavior. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9809/9809398v1.pdf"}
{"id": "astro-ph9810263", "abstract": "  Blazars are characterized by large amplitude and fast variability, indicating that the electron distribution is rapidly changing, often on time scales shorter than the light crossing time. The emitting region is sufficiently compact to let radiative losses dominate the cooling of high energy electrons. We study the time dependent behaviour of the electron distribution after episodic electron injection phases, and calculate the observed synchrotron and self Compton radiation spectra. Since photons produced in different part of the source have different travel times, the observed spectrum is produced by the electron distribution at different stages of evolution. Even a homogeneous source then resembles an inhomogeneous one. Time delays between the light curves of fluxes at different frequencies are possible, as illustrated for the specific case of the BL Lac object Mkn 421. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9810/9810263v1.pdf"}
{"id": "astro-ph9811125", "abstract": "  The first results from the HI Parkes All-Sky Survey (HIPASS) provide a spectacular view of the global HI distribution in the vicinity of the Magellanic Clouds and the southern Milky Way. A 2400 square degree mosaic around the South Celestial Pole (SCP) reveals the existence of a narrow, continuous counter-stream which 'leads' the direction of motion of the Clouds, i.e. opposite in direction to the Stream. This strongly supports the gravitational model for the Stream in which the leading and trailing streams are tidally torn from the body of the Magellanic Clouds. The data also reveal additional tidal features in the Bridge region which appear to emanate from the LMC, and a distinct spiral structure within the LMC itself. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9811/9811125v1.pdf"}
{"id": "astro-ph9811134", "abstract": "  Mass accretion is the key factor for evolution of galaxies. It can occur through secular evolution, when gas in the outer parts is driven inwards by dynamical instabilities, such as spirals or bars. This secular evolution proceeds very slowly when spontaneous, and can be accelerated when triggered by companions. Accretion can also occur directly through merging of small companions, or more violent interaction and coalescence. We discuss the relative importance of both processes, their time-scale and frequency along a Hubble time. Signatures of both processes can be found in the Milky Way. It is however likely that our Galaxy had already gathered the bulk of its mass about 8-10 Gyr ago, as is expected in hierarchical galaxy formation scenarios. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9811/9811134v1.pdf"}
{"id": "astro-ph9811289", "abstract": "  Observations of normal galactic star-forming regions suggest there is widespread near-uniformity in the initial stellar mass function (IMF) in spite of diverse physical conditions. Fluctuations may come largely from statistical effects and observational selection. There are also tantalizing, but uncertain reports that the IMF shifts systematically in peculiar regions, giving a low mass bias in quiescent gas, and a high mass bias in active starbursts. Theoretical proposals for the origin of the IMF are reviewed. The theories generally focus on a combination of four physical effects: wind-limited accretion of stellar mass, coalescence of protostellar gas clumps, mass limitations at the thermal Jeans mass, and power-law cloud structure. Hybrid theories combining the best of each may be preferred. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9811/9811289v1.pdf"}
{"id": "astro-ph9901065", "abstract": "  The broad Iron line in MCG-6-30-15 is fitted to the Comptonization model where line broadening occurs due to Compton down-scattering in a highly ionized optically thick cloud. These results are compared to the disk line model where the broadening is due to Gravitational/Doppler effects in the vicinity of a black hole. We find that both models fit the data well and it is not possible to differentiate between them by fitting only the ASCA data. The best fit temperature and optical depth of the cloud are found to be kT = 0.54 keV and τ = 4.0 from the Comptonization model. This model further suggests that while the temperature can be assumed to be constant, the optical depth varies during the observation period. We emphasis an earlier conclusion that simultaneous broad band data (3 - 50 keV) can rule out (or confirm) the Comptonization model. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9901/9901065v1.pdf"}
{"id": "astro-ph9901294", "abstract": "  Based on consistent evolutionary and pulsation calculations, we analyse the effect of metallicity and of different convection treatments in the stellar models on period - magnitude, - color and - radius relationships. In order to perform an accurate comparison with observations, we have computed grids of atmosphere models and synthetic spectra for different metallicities, covering the range of effective temperatures and gravities relevant for Cepheids. The models are compared to recent observations of galactic and Magellanic Clouds Cepheids. Unprecedented level of agreement is found between models and observations. We show that within the range of metallicity for the Galaxy and the Magellanic Clouds, a change of slope in the period - luminosity (PL) relationship is predicted at low periods, due to the reduction of the blue loop during core He burning. The minimum mass undergoing a blue loop and consequently the critical period at which this change of slope occurs depend on the metallicity Z and on the convection treatment in the stellar models. However, besides this change of slope, we do not find any significant effect of metallicity on period - magnitude relationships from V to K bands, and on period - color relationships in IR colors. We only find a detectable effect of Z on (B-V) colors. These results are not affected by uncertainties inherent to current stellar models, mainly due to convection treatment. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9901/9901294v1.pdf"}
{"id": "astro-ph9902138", "abstract": "  We propose a new hypothesis for the origin of the major part of non-solar hadronic cosmic rays (CRs) at all energies: highly relativistic, narrowly collimated jets from the birth or collapse of neutron stars (NSs) in our Galaxy accelerate ambient disk and halo matter to CR energies and disperse it in hot spots which they form when they stop in the Galactic halo. Such events are seen as cosmological gamma-ray bursts (GRBs) in other galaxies when their beamed radiation happens to point towards Earth. This source of CRs is located in the Galactic halo. It therefore explains the absence of the Greisen-Zatsepin-Kuz'min cutoff in the spectrum of the ultra-high energy CRs. The position in energy of the “ankle” in the CR energy spectrum is shown to arise in a natural way. Moreover, an origin of lower energy CRs in the Galactic halo naturally accounts for the high degree of isotropy of CRs around 100 TeV from airshower observations, and the small galactocentric gradient of low-energy CRs derived from gamma-ray observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9902/9902138v2.pdf"}
{"id": "astro-ph9902155", "abstract": "  Tremendous progress has been made recently in modelling the morphology and kinematics of centers of galaxies. Increasingly realistic models are built for central bar, bulge, nucleus and black hole of galaxies, including our own. The newly revived Schwarzschild method has played a central role in these theoretical modellings. Here I will highlight some recent work at Leiden on extending the Schwarzschild method in a few directions. After a brief discussion of (i) an analytical approach to include stochastic orbits (Zhao 1996), and (ii) the “pendulum effect” of loop and boxlet orbits (Zhao, Carollo, de Zeeuw 1999), I will concentrate on the very promising (iii) spectral dynamics method, with which not only can one obtain semi-analytically the actions of individual orbits as previously known, but also many other physical quantities, such as the density in configuration space and the line-of-sight velocity distribution of a superposition of orbits (Copin, Zhao     de Zeeuw 1999). The latter method also represents a drastic reduction of storage space for the orbit library and an increase in accuracy over the grid-based Schwarzschild method. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9902/9902155v1.pdf"}
{"id": "astro-ph9903126", "abstract": "  We have investigated the bimodal distribution of the duration of BATSE gamma-ray bursts (GRBs) by analyzing light curves of 64 ms time resolution. We define the average pulse width of GRBs from the auto-correlation function of GRB profiles. The distribution of the average pulse width of GRBs is bimodal, suggesting that GRBs are composed of long-pulse GRBs and short-pulse GRBs. The average pulse width of long-pulse GRBs appears correlated with the peak flux, consistent with the time dilation effect anticipated from the cosmological origin of GRBs. However, the correlation between the average pulse width and the peak flux for the short-pulse GRBs doesn't show such a tendency, which needs further study with higher time resolution data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9903/9903126v1.pdf"}
{"id": "astro-ph9903347", "abstract": "  A deep underwater Cherenkov telescope has been operating since 1993 in stages of growing size at 1.1 km depth in Lake Baikal. The key component of the telescope is the Optical Module (OM) which houses the highly sensitive phototube QUASAR-370. We describe design and parameters of the QUASAR-370, the layout of the optical module, the front-end electronics and the calibration procedures, and present selected results from the five-year operation underwater. Also, future developments with respect to a telescope consisting from several thousand OMs are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9903/9903347v1.pdf"}
{"id": "astro-ph9904069", "abstract": "  Deep J and Ks band images covering a 5×5 arcmin area centered on the NTT Deep Field have been obtained during the Science Verification of SOFI at the NTT. These images were made available via the Web in early June. The preliminary results we have obtained by the analysis of these data are the following: 1) the counts continue to rise with no evidence of a turnover or of a flattening down to the limits of the survey (Ks=22.5 and J=24); 2) we find a slope dlog(N)/dm∼0.37 in agreement with most of the faintest surveys but much steeper than the Hawaii survey; 3) fainter than Ks∼19 and J∼20, the median J-K color of galaxies shows a break in its reddening trend turning toward bluer colors; 4) faint bluer galaxies also display a larger compactness index, and a smaller apparent size. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9904/9904069v1.pdf"}
{"id": "astro-ph9904208", "abstract": "  We extend our spiral galaxy models that successfully describe nearby template spectra as well as the redshift evolution of CFRS and HDF spirals to include - in a chemically consistent way - the redshift evolution of a series of individual elements. Comparison with observed DLA abundances shows that DLAs might well be the progenitors of present-day spiral types Sa through Sd. Our models bridge the gap between high redshift DLA and nearby spiral HII region abundances. The slow redshift evolution of DLA abundances is a natural consequence of the long SF timescales for disks, the scatter at any redshift reflects the range of SF timescales from early to late spiral types. We claim that while at high redshift all spiral progenitor types seem to give rise to DLA absorption, towards low redshifts, the early type spirals seem to drop out of DLA samples due to low gas and/or high metal and dust content. Model implications for the spectrophotometric properties of the DLA galaxy population are discussed in the context of campaigns for the optical identifications of DLA galaxies both at low and high redshift. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9904/9904208v1.pdf"}
{"id": "astro-ph9905173", "abstract": "  We present high-resolution mid-infrared observations of the nearby late-type young binary system Hen 3-600. The binary, at a distance of ∼ 50 pc, could be a member of the TW Hydrae Association, the nearest known group of young stars, with an age of a few million years. Our images make it possible for the first time to determine which star in the pair, separated by 1.4”, harbors the mid-infrared excess detected by IRAS. In the near-infrared, where the radiation is primarily photospheric, Hen 3-600A (M3) and Hen 3-600B (M3.5) have a flux ratio of 1.6. At 4.8μm, 10.8μm, and 18.2μm, the primary becomes increasingly dominant over the secondary, suggesting that most of the circumstellar dust in the system resides around Hen 3-600A. Comparison of the spectral energy distribution (SED) of Hen 3-600A to the median SED of classical T Tauri stars suggests that its disk may be truncated by the secondary and provides tentative evidence for a central disk hole. The distribution of dust in the Hen 3-600 system may provide important clues to the formation and evolution of protoplanetary disks in close binaries. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9905/9905173v1.pdf"}
{"id": "astro-ph9906045", "abstract": "  The X-ray binary Cygnus X-2 (Cyg X-2) has recently been shown to contain a secondary that is much more luminous and hotter than is appropriate for a low-mass subgiant. We present detailed binary-evolution calculations which demonstrate that the present evolutionary state of Cyg X-2 can be understood if the secondary had an initial mass of around 3.5 M_sun and started to transfer mass near the end of its main-sequence phase (or, somewhat less likely, just after leaving the main sequence). Most of the mass of the secondary must have been ejected from the system during an earlier rapid mass-transfer phase. In the present phase, the secondary has a mass of around 0.5 M_sun with a non-degenerate helium core. It is burning hydrogen in a shell, and mass transfer is driven by the advancement of the burning shell. Cyg X-2 therefore is related to a previously little studied class of intermediate-mass X-ray binaries (IMXBs). We suggest that perhaps a significant fraction of X-ray binaries presently classified as low-mass X-ray binaries may be descendants of IMXBs and discuss some of the implications. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9906/9906045v1.pdf"}
{"id": "astro-ph9907313", "abstract": "  The optical expansion parallax of NGC 6543 has been detected and measured using two epochs of HST images separated by a time baseline of only three years. We have utilized three separate methods of deriving the angular expansion of bright fiducials, the results of which are in excellent agreement. We combine our angular expansion estimates with spectroscopically obtained expansion velocities to derive a distance to NGC 6543 of 1001±269 pc. The deduced kinematic age of the inner bright core of the nebula is 1039±259 years; however, the kinematic age of the polar caps that surround the core is larger - perhaps the result of deceleration or earlier mass ejection. The morphology and expansion patterns of NGC 6543 provide insight into a complex history of axisymmetric, interacting stellar mass ejections. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9907/9907313v1.pdf"}
{"id": "astro-ph9907413", "abstract": "  For amorphous carbon several laboratory extinction data are available, which show quite a wide range of differences due to the structural complexity of this material. We have calculated self-consistent dynamic models of circumstellar dust-shells around carbon-rich asymptotic giant branch stars, based on a number of these data sets. The structure and the wind properties of the dynamical models are directly influenced by the different types of amorphous carbon. In our test models the mass loss is not severely dependent on the difference in the optical properties of the dust, but the influence on the degree of condensation and the final outflow velocity is considerable. Furthermore, the spectral energy distributions and colours resulting from the different data show a much wider spread than the variations within the models due to the variability of the star. Silicon carbide was also considered in the radiative transfer calculations to test its influence on the spectral energy distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9907/9907413v1.pdf"}
{"id": "astro-ph9908094", "abstract": "  We report on a 30 ks observation of the high-mass X-ray binary pulsar OAO1657-415 performed by BeppoSAX on September 1998. The wide band spectrum is well fit by both a cutoff power law, or a power law modified by a high energy cutoff, plus a fluorescence Iron line at 6.5 keV. The two models are statistically equivalent. The inclusion of a cyclotron resonance feature at  36 keV – corresponding to a magnetic field strength 3.2 (1+z) x 10^12 G, where z is the gravitational redshift – improves significantly the X^2 for the cutoff model but only marginally for the power law plus high energy cutoff model. The statistical significance of our data is not adequate to discriminate between the two models, and even the \"Normalized Crab Ratio\" technique, successfully used to pinpoint cyclotron features in the spectra of other X-ray pulsars, is not conclusive in answering the question whether the feature is real or it is an artifact due to an improper modeling of the continuum used to fit the data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9908/9908094v1.pdf"}
{"id": "astro-ph9909156", "abstract": "  We study the effect of non-radial motions on the mass function, the velocity dispersion function (hereafter VDF) and on the shape of clusters of galaxies using the model introduced in Del Popolo     Gambera (1998a,b; 1999). The mass function of clusters, obtained using the quoted model, is compared with the statistical data by Bahcall     Cen (1992a,b) and Girardi et al. (1998), while the VDF is compared with the Center for Astrophysics (hereafter CfA) data by Zabludoff et al. (1993) for local clusters and those of Mazure et al. (1996) and Fadda et al. (1996). In both cases the model predictions are in good agreement with the observational data showing once more how non-radial motions can reduce many of the discrepancies between Cold Dark Matter (hereafter CDM) model predictions and observational data. Finally we study the effect of non-radial motions on the intrinsic shape of clusters of galaxies showing that non-radial motions produce clusters less elongated with respect to CDM model in agreement with de Theije et al. (1995, 1997) results. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9909/9909156v1.pdf"}
{"id": "astro-ph9911184", "abstract": "  By combining OSSE, SMM and TGRS observations of the galactic center region, Purcell et al. (1997) and Cheng et al. (1997) produced the first maps of galactic positron annihilation. That data-set has been augmented with additional data, both recent and archival, and re-analyzed to improve the spectral fitting. The improved spectral fitting has enabled the first maps of positronium continuum emission and the most extensive maps of 511 keV line emission. Bulge and disk combinations have been compared with the 511 keV line data, demonstrating that extended bulges are favored over a GC point source for every disk model tested. This result is independent of whether OSSE-only, OSSE/SMM, or OSSE/SMM/TGRS data-sets are used. The estimated bulge to disk ratio (and to a lesser extent the total flux) is shown to be dependent upon the assumption of bulge shape. A positive latitude enhancement is shown to have an effect upon the B/D ratio, but this effect is secondary to the choice of bulge shape. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9911/9911184v1.pdf"}
{"id": "astro-ph9912091", "abstract": "  Recent numerical simulations have lead to a paradigm shift in our understanding of the intergalactic medium, and the loss of a physical justification for Voigt profile fitting of the Lyman-alpha forest. Many individual lines seen in simulated spectra have significant departures from the Voigt profile, yet could be well fitted by a blend of two or more such lines. We discuss the expected effect on the line profiles due to ongoing gravitational structure formation and Hubble expansion. We develop a method to detect departures from Voigt profiles of the absorption lines in a statistical way and apply this method to simulated Lyman-alpha forest spectra, confirming that the profiles seen do statistically differ from Voigt profiles. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9912/9912091v1.pdf"}
{"id": "chao-dyn9303017", "abstract": "  The problem of noise-induced escape from a metastable state arises in physics, chemistry, biology, systems engineering, and other areas. The problem is well understood when the underlying dynamics of the system obey detailed balance. When this assumption fails many of the results of classical transition-rate theory no longer apply, and no general method exists for computing the weak-noise asymptotics of fundamental quantities such as the mean escape time. In this paper we present a general technique for analysing the weak-noise limit of a wide range of stochastically perturbed continuous-time nonlinear dynamical systems. We simplify the original problem, which involves solving a partial differential equation, into one in which only ordinary differential equations need be solved. This allows us to resolve some old issues for the case when detailed balance holds. When it does not hold, we show how the formula for the mean escape time asymptotics depends on the dynamics of the system along the most probable escape path. We also present new results on short-time behavior and discuss the possibility of focusing along the escape path. ", "pdf_url": "gs://arxiv-dataset/arxiv/chao-dyn/pdf/9303/9303017v2.pdf"}
{"id": "chao-dyn9704008", "abstract": "  We consider a model proposed earlier by us for describing a form of plastic instability found in creep experiments . The model consists of three types of dislocations and some transformations between them. The model is known to reproduce a number of experimentally observed features. The mechanism for the phenomenon has been shown to be Hopf bifurcation with respect to physically relevant drive parameters. Here, we present a mathematical analysis of adiabatically eliminating the fast mode and obtaining a Ginzburg-Landau equation for the slow modes associated with the steps on creep curve. The transition to the instability region is found to be one of subcritical bifurcation over most of the interval of one of the parameters while supercritical bifurcation is found in a narrow mid-range of the parameter. This result is consistent with experiments. The dependence of the amplitude and the period of strain jumps on stress and temperature derived from the Ginzburg-Landau equation are also consistent with experiments. On the basis of detailed numerical solution via power series expansion, we show that high order nonlinearities control a large portion of the subcritical domain. ", "pdf_url": "gs://arxiv-dataset/arxiv/chao-dyn/pdf/9704/9704008v1.pdf"}
{"id": "chao-dyn9906039", "abstract": "  Divergence in antigen response of the immune network is discussed, based on shape-space modelling. The present model extends the shape-space model by introducing the evolution of specificity of idiotypes. When the amount of external antigen increases, stability of the immune network changes and the network responds to the antigen. It is shown that specific and non-specific responses emerge as a function of antigen levels. A specific response is observed with a fixed point attractor, and a non-specific response is observed with a long-lived chaotic transient state of the lymphocyte population dynamics. The network topology also changes between these two states. The relevance of such a long-lived transient state is discussed with respect to immune function. ", "pdf_url": "gs://arxiv-dataset/arxiv/chao-dyn/pdf/9906/9906039v1.pdf"}
{"id": "chao-dyn9909009", "abstract": "  We compute the Lyapunov exponents and the Kolmogorov-Sinai (KS) entropy for a self-bound N-body system that is realized as a convex billiard. This system exhibits truly high-dimensional chaos, and 2N-4 Lyapunov exponents are found to be positive. The KS entropy increases linearly with the numbers of particles. We examine the chaos generating defocusing mechanism and investigate how high-dimensional chaos develops in this system with no dispersing elements. ", "pdf_url": "gs://arxiv-dataset/arxiv/chao-dyn/pdf/9909/9909009v1.pdf"}
{"id": "cond-mat0002378", "abstract": "  We study one- and two-dimensional models which undergo a transition between active and absorbing phases. The transition point in these models is of novel type: jump of the order parameter coincides with its power-law singularity. Some arguments supported by Monte Carlo simulations prompted us to predict the exact location of the transition point. Both models possess gauge-like symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0002/0002378v3.pdf"}
{"id": "cond-mat0003027", "abstract": "  Molecular dynamics simulations of SPC/E water confined in a Silica pore are presented. The simulations have been performed at different hydration levels and temperatures to study the single-particle dynamics. Due to the confinement and to the presence of a hydrophilic surface, the dynamic behaviour of the liquid appears to be strongly dependent on the hydration level. On lowering temperature and/or hydration level the intermediate scattering function displays a double-step relaxation behaviour whose long time tail is strongly non-exponential. At higher hydrations two quite distinct subsets of water molecules are detectable. Those belonging to the first two layers close to the substrate suffer a severe slowing down already at ambient temperature. While the behaviour of the remaining ones is more resemblant to that of supercooled bulk SPC/E water. At lower hydrations and/or temperatures the onset of a slow dynamics due to the cage effect and a scenario typical of supercooled liquids approaching the kinetic glass transition is observed. Moreover, for low hydrations and/or temperatures, the intermediate scattering function clearly displays an overshoot, which can be assigned to the so called “Boson Peak”. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0003/0003027v1.pdf"}
{"id": "cond-mat0005407", "abstract": "  The transmission poles of N number of identical Dirac delta potentials placed periodically in one-dimension are examined in the complex-energy plane. The numerical results show that the imaginary part of the poles scales with 1/N. An approximate form of the poles is derived which supports the scaling behaviour of the poles found numerically. It is shown that the imaginary part of the poles are proportional to their real part for the poles close to the ends of the bands. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0005/0005407v1.pdf"}
{"id": "cond-mat0009172", "abstract": "  We report experimental results on the behavior of an ensemble of inelastically colliding particles, excited by a vibrated piston in a vertical cylinder. When the particle number is increased, we observe a transition from a regime where the particles have erratic motions (granular \"gas\") to a collective behavior where all the particles bounce like a nearly solid body. In the gaslike regime, we measure the pressure at constant volume, and the bed expansion at constant external pressure, as a function of the number N of particles. We also measure the density of particles as a function of the altitude, and find that the \"atmosphere\" is exponential far enough from the piston. From these three independent measurements, we determine a \"state equation\" between pressure, volume, particle number and the vibration amplitude and frequency. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0009/0009172v1.pdf"}
{"id": "cond-mat0101137", "abstract": "  We have performed first-principles calculations of Si/SiO_2 superlattices in order to examine their electronic states, confinement and optical transitions, using linearized-augmented-plane-wave techniques and density-functional theory. Two atomic models having fairly simple interface structure are considered; they differ in the way dangling bonds at interfaces are satisfied. We compare our first-principles band structures with those from tight-binding calculations. The real and imaginary parts of the dielectric function are calculated at the Fermi-Golden-rule level and used to estimate the absorption coefficients. Confinement is confirmed by the dispersionless character of the electronic band structures in the growth direction. Optical enhancement is shown to exist by comparing the direct and indirect transitions in the band structures with the related transitions in bulk-Si. The role played by the interface on the optical properties is assessed by comparing the absorption coefficients from the two models. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0101/0101137v1.pdf"}
{"id": "cond-mat0101362", "abstract": "  We consider a two-particle system in which a particle is held fixed, and the other one rotates around the axis perpendicular to the line joining the particles centers. The rotating particle leads to a displacement of its polarization charge on the surface. Our results show that the rotational motion of the particles generally reduces the force between the particles. The dependence of interparticle force on the angular velocity of rotation will be discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0101/0101362v1.pdf"}
{"id": "cond-mat0102438", "abstract": "  An electronic phase separation model provides a natural explanation for a large variety of experimental results in the cuprates, including evidence for both stripes and larger domains, and a termination of the phase separation in the slightly overdoped regime, when the average hole density equals that on the charged stripes. Several models are presented for charged stripes, showing how density waves, superconductivity, and strong correlations compete with quantum size effects (QSEs) in narrow stripes. The energy bands associated with the charged stripes develop in the middle of the Mott gap, and the splitting of these bands can be understood by considering the QSE on a single ladder. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0102/0102438v2.pdf"}
{"id": "cond-mat0103136", "abstract": "  With Monte Carlo simulations, we investigate short-time critical dynamics of the three-dimensional anti-ferromagnetic Ising model with a globally conserved magnetization m_s (not the order parameter). From the power law behavior of the staggered magnetization (the order parameter), its second moment and the auto-correlation, we determine all static and dynamic critical exponents as well as the critical temperature. The universality class of m_s=0 is the same as that without a conserved quantity, but the universality class of non-zero m_s is different. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0103/0103136v1.pdf"}
{"id": "cond-mat0103138", "abstract": "  The electrical resistivity, thermoelectric power and electronic thermal conductivity of simple (isotropic) metals are studied in a uniform way. Starting from results of a variational solution of the Boltzmann equation, a generalized Matthiessen rule is used in order to superpose the inelastic (or not) electron-phonon and elastic electron-impurity scattering cross sections (\"matrix elements\"). The temperature dependence relative to these processes is given through simple functions and physical parameters over the usually investigated range of temperature for each transport coefficient. The coherence of such results is emphasized. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0103/0103138v1.pdf"}
{"id": "cond-mat0104515", "abstract": "  In the paper a possibility of metallic ferromagnetic state realization in a generalized Hubbard model with more complete accounting of electron-electron interactions, in particular, the correlated hopping and exchange interaction integrals is investigated. Recently obtained by means of mean-field approximation single electron energy spectrum is used for the description of finite temperature properties of the system. In the paper the expression for the critical temperature of ferromagnet-paramagnet transition is found, the behaviour of temperature dependencies of magnetization and paramagnetic susceptibility is analyzed. Taking into account the correlated hopping allows to explain some peculiarity of ferromagnetic behaviour of transition metals, their alloys and compounds. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0104/0104515v1.pdf"}
{"id": "cond-mat0105045", "abstract": "  We present the first microscopic images of the prewetting transition of a liquid film on a solid surface. Pictures of the local coverage map of a helium film on a cesium metal surface are taken while the temperature is raised through the transition. The film edge is found to advance at constant temperature by successive avalanches in a creep motion with a macroscopic correlation length. The creep velocity varies strongly in a narrow temperature range. The retreat motion is obtained only at much lower temperature, conforming to the strong hysteresis observed for prewetting transition on a disordered surface. Prewetting transition on such disordered surfaces appears to give rise to dynamical phenomena similar to what is observed for domain wall motions in 2D magnets. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0105/0105045v1.pdf"}
{"id": "cond-mat0105178", "abstract": "  We study the phase diagram of the spin-orbital model in both the weak and strong limits of the quartic spin-orbital exchange interaction. This allows us to study quantum phase transitions in the model and to approach from both sides the most interesting intermediate-coupling regime and in particular the SU(4)-symmetric point of the Hamiltonian. It was suggested earlier by Li et al [Phys.Rev.Lett. vol. 81, 3527 (1999)] that at this point the ground state of the system is a plaquette spin-orbital liquid. We argue that the state is more complex. There is plaquette order, but it is anisotropic: bonds in one direction are stronger than those in the perpendicular direction. This order is somewhat similar to that found recently in the frustrated J_1-J_2 Heisenberg spin model. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0105/0105178v1.pdf"}
{"id": "cond-mat0106099", "abstract": "  Hartree-Fock theory predicted stripe or bubble phase in the third and higher Landau levels for two-dimensional electrons, and experimental evidences has been accumulated. In this paper theoretical confirmation of the stripe phase and bubble phase in higher Landau level is given by means of the density matrix renormalization group (DMRG) method, which can give essentially exact ground state for electron systems with up to 18 electrons. From the study of the pair correlation function, the stripe phase, bubble phase, and the Wigner crystal phase are identified, and phase diagram is obtained. The reentrant integer quantum Hall state is identified as the bubble state. The phase diagram of the fourth Landau level shows more diversity than the third level. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0106/0106099v1.pdf"}
{"id": "cond-mat0107126", "abstract": "  Persistent currents and Drude weights are investigated for the tight-binding approximation to one-dimensional rings threaded by a magnetic flux and with potential given by some almost-periodic substitution sequences with different degrees of randomness, and for various potential strengths. The Drude weight D distinguishes correctly conductors and insulators, in accordance with the results shown by the currents. In the case of insulators the decay of D(N) for large ring lengths N provides an estimate for the localization length of the system. It is shown that the more random the sequence does not imply the smaller conducting properties. This discrepancy between the hierarchy of disorder of the sequences and the capacity of conduction of the system is explained by the gaps in the energy spectra. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0107/0107126v1.pdf"}
{"id": "cond-mat0107141", "abstract": "  The retrieval behavior and thermodynamic properties of symmetrically diluted Q-Ising neural networks are derived and studied in replica-symmetric mean-field theory generalizing earlier works on either the fully connected or the symmetrical extremely diluted network. Capacity-gain parameter phase diagrams are obtained for the Q=3, Q=4 and Q=∞ state networks with uniformly distributed patterns of low activity in order to search for the effects of a gradual dilution of the synapses. It is shown that enlarged regions of continuous changeover into a region of optimal performance are obtained for finite stochastic noise and small but finite connectivity. The de Almeida-Thouless lines of stability are obtained for arbitrary connectivity, and the resulting phase diagrams are used to draw conclusions on the behavior of symmetrically diluted networks with other pattern distributions of either high or low activity. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0107/0107141v2.pdf"}
{"id": "cond-mat0108017", "abstract": "  Distributions derived from non-extensive Tsallis statistics are closely connected with dynamics described by a nonlinear Fokker-Planck equation. The combination shows promise in describing stochastic processes with power-law distributions and superdiffusive dynamics. We investigate intra-day price changes in the S   P500 stock index within this framework by direct analysis and by simulation. We find that the power-law tails of the distributions, and the index's anomalously diffusing dynamics, are very accurately described by this approach. Our results show good agreement between market data, Fokker-Planck dynamics, and simulation. Thus the combination of the Tsallis non-extensive entropy and the nonlinear Fokker-Planck equation unites in a very natural way the power-law tails of the distributions and their superdiffusive dynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0108/0108017v1.pdf"}
{"id": "cond-mat0110392", "abstract": "  Quantitatively-unexplained stationary waves or ridges often encircle icicles. Such waves form when roughly 0.1 mm-thick layers of water flow down the icicle. These waves typically have a wavelength of 1cm approximately independent of external temperature, icicle thickness, and the volumetric rate of water flow. In this paper we show that these waves can not be obtained by naive Mullins-Sekerka instability, but are caused by a quite new surface instability related to the thermal diffusion and hydrodynamic effect of thin water flow. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0110/0110392v6.pdf"}
{"id": "cond-mat0112506", "abstract": "  Ion current fluctuations occurring within open and closed states of large conductance locust potassium channel (BK channel) were investigated for the existence of correlation. Both time series, extracted from the ion current signal, were studied by the autocorrelation function (AFA) and the detrended fluctuation analysis (DFA) methods. The persistent character of the short- and middle-range correlations of time series is shown by the slow decay of the autocorrelation function. The DFA exponent α is significantly larger than 0.5. The existence of strongly-persistent long-range correlations was detected only for closed-states fluctuations, with α=0.98±0.02. The long-range correlation of the BK channel action is therefore determined by the character of closed states. The main outcome of this study is that the memory effect is present not only between successive conducting states of the channel but also independently within the open and closed states themselves. As the ion current fluctuations give information about the dynamics of the channel protein, our results point to the correlated character of the protein movement regardless whether the channel is in its open or closed state. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0112/0112506v1.pdf"}
{"id": "cond-mat0201113", "abstract": "  Phase transformations such as freezing typically start with heterogeneous nucleation. Heterogeneous nucleation near a wetting transition, of a crystalline phase is studied. The wetting transition occurs at or near a vapour-liquid transition which occurs in a metastable fluid. The fluid is metastable with respect to crystallisation, and it is the crystallisation of this fluid phase that we are interested in. At a wetting transition a thick layer of a liquid phase forms at a surface in contact with the vapour phase. The crystalline nucleus is then immersed in this liquid layer, which reduces the free energy barrier to nucleation and so dramatically increases the nucleation rate. The variation in the rate of heterogeneous nucleation close to wetting transitions is calculated for systems in which the longest-range forces are dispersion forces. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0201/0201113v1.pdf"}
{"id": "cond-mat0201559", "abstract": "  Surnames and nonrecombining alleles are inherited from a single parent in a highly similar way. A simple birth-death model with mutations can accurately describe this process. Exponentially growing and constant populations are investigated, and we study how different compositions of the founder populations can be observed in present-day diversity distributions. We analyse different quantities in the statistically stationary state, both through analytic and numerical methods. Our results compare favourably to field data for family sizes in several countries. We discuss the relationship between the distribution of surnames and the genetic diversity of a population. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0201/0201559v1.pdf"}
{"id": "cond-mat0202137", "abstract": "  A method is presented for the optimization of one-body and inhomogeneous two-body terms in correlated electronic wave functions of Jastrow-Slater type. The most general form of inhomogeneous correlation term which is compatible with crystal symmetry is used and the energy is minimized with respect to all parameters using a rapidly convergent iterative approach, based on Monte Carlo sampling of the energy and fitting energy fluctuations. The energy minimization is performed exactly within statistical sampling error for the energy derivatives and the resulting one- and two-body terms of the wave function are found to be well-determined. The largest calculations performed require the optimization of over 3000 parameters. The inhomogeneous two-electron correlation terms are calculated for diamond and rhombohedral graphite. The optimal terms in diamond are found to be approximately homogeneous and isotropic over all ranges of electron separation, but exhibit some inhomogeneity at short- and intermediate-range, whereas those in graphite are found to be homogeneous at short-range, but inhomogeneous and anisotropic at intermediate- and long-range electron separation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0202/0202137v1.pdf"}
{"id": "cond-mat0202281", "abstract": "  We have investigated the Faraday rotation of in-plane magnetized bismuth - substituted ferrite garnet films grown by liquid phase epitaxy on (100) oriented gadolinium gallium garnet substrates. The Faraday spectra were measured for photon energies between 1.7 - 2.6 eV. To interprete the spectra, we use a model based on two electric dipole transitions, one tetrahedral and one octahedral. Furthermore, the Faraday rotation sensitivity was measured at 2.3 eV, and found to be in good agreement with the theoretical predicitions. In particular, we find that the sensitivity increases linearly with the bismuth content and nonlinearly with the gallium content. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0202/0202281v1.pdf"}
{"id": "cond-mat0203574", "abstract": "  An open quantum system consists of leads connected to a device of interest. Within the nonequilibrium Green's function technique, we examine the replacement of leads by self-energies in continuum calculations. Our starting point is a formulation of the problem for continuum systems by T.E. Feuchtwang. In this approach there is considerable flexibility in the choice of unperturbed Green's functions. We examine the consequences of this freedom on the treatment of leads. For any choice the leads can be replaced by coupling self-energies which are simple functions of energy. We find that the retarded self-energy depends on the details of the choice of unperturbed Green's function, and can take any value. However, the nonequilibrum self-energy or scattering function can be taken to be independent of this choice. Expressed in terms of these self-energies, nonequilibrium transport calculations take a particularly simple form. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0203/0203574v1.pdf"}
{"id": "cond-mat0204334", "abstract": "  We present a description of the behavior of a superfluid gas of fermions in the presence of a Feshbach resonance over the complete range of magnetic field detunings. Starting from a resonance Hamiltonian, we exploit a functional method to describe the continuous behavior from Bardeen-Cooper-Schrieffer to Bose-Einstein condensation type superfluidity. Our results show an ability for a resonance system to exhibit a high critical temperature comparable to the Fermi temperature. The results are derived in a manner that is shown to be consistent with the underlying microscopic scattering physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0204/0204334v2.pdf"}
{"id": "cond-mat0204394", "abstract": "  It has been observed experimentally that under certain conditions pulsed laser deposition (PLD) produces smoother surfaces than ordinary molecular beam epitaxy (MBE). So far the mechanism leading to the improved quality of surfaces in PLD is not yet fully understood. In the present work we investigate the physical properties of a simple model for PLD in which the transient mobility of adatoms and diffusion along edges is neglected. Analyzing the crossover from MBE to PLD, the scaling properties of the time-dependent nucleation density as well as the influence of Ehrlich-Schwoebel barriers we find that there is indeed a range of parameters where the surface quality in PLD is better than in MBE. However, since the improvement is weak and occurs only in a small range of parameters we conclude that deposition in pulses alone cannot explain the experimentally observed smoothness of PLD-grown surfaces. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0204/0204394v1.pdf"}
{"id": "cond-mat0205625", "abstract": "  We employ the method of the theory of open quantum systems to analyze spin relaxation and decoherence in semiconductors in the presence of a magnetic field. We derive a set of Bloch equations for electron spin with a fully microscopic determination of longitudinal and transverse relaxation times. Electron scattering from optical and acoustic phonons and random impurities is taken into account. We obtain explicit expressions for the spin relaxation times in terms of material constants and coupling strengths, exhibiting formal agreement with earlier treatments in the zero magnetic field limit with microscopic specification of their phenomenological parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0205/0205625v1.pdf"}
{"id": "cond-mat0206247", "abstract": "  We propose a variational wave function for the ground state of the magnetic heavy fermion (HF) systems, in which both the Kondo and the RKKY interactions are variationally incorporated and the local f-orbital state exists as a linear combination of a full local moment state and a fully compensated state (mixed moment state). We describe the mechanism for the mixed moment ground state based on the large-N treatment of the Kondo lattice Hamiltonian added with RKKY interaction. With the mixed moment ground state we can explain several puzzling experiments in magnetic HF compounds such as a small value of local moment, coexistence of the antiferromagnetic (AFM) and the paramagnetic (PM) phases, local quantum criticality, etc. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0206/0206247v2.pdf"}
{"id": "cond-mat0207189", "abstract": "  Strongly interacting systems are characterized by heavily dressed entities with internal degrees of freedom, which, on a local level, can be described in terms of coherent quantum states. We examine the modification of these local coherent quantum states when such entities condense into a macroscopic coherent quantum state, such as superfluidity. As an example, we consider a system of electrons coupled to local lattice deformations. Significant changes in the phonon clouds surrounding the charge carriers occur when the system develops into a spatially phase-locked state. The question of localized self-trapped charge carriers (bipolarons) in the normal state becoming delocalized upon entering the superconducting phase is discussed in terms of squeezing of the local coherent phonon states. Suggestions for experimental verifications of these features associated with the lattice dynamics are made. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0207/0207189v1.pdf"}
{"id": "cond-mat0207272", "abstract": "  Electron scattering on both neutral (X) and charged (X^-) excitons in quantum wells is studied theoretically. A microscopic model is presented, taking into account both elastic and dissociating scattering. The model is based on calculating the exciton-electron direct and exchange interaction matrix elements, from which we derive the exciton scattering rates. We find that for an electron density of 10^9  cm^-2 in a GaAs QW at T=5K, the X^- linewidth due to electron scattering is roughly twice as large as that of the neutral exciton. This reflects both the X^- larger interaction matrix elements compared with those of X, and their different dependence on the transferred momentum. Calculated reflection spectra can then be obtained by considering the three electronic excitations of the system, namely, the heavy-hole and light-hole 1S neutral excitons, and the heavy-hole 1S charged exciton, with the appropriate oscillator strengths. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0207/0207272v2.pdf"}
{"id": "cond-mat0208322", "abstract": "  Depletion interactions between colloidal particles dispersed in a fluid medium are effective interactions induced by the presence of other types of colloid. They are not instantaneous but build up in time. We show by means Brownian dynamics simulations that the fluctuations in the depletion force between two guest particles in a host dispersion of differently sized colloids do not decay exponentially with time, but show a power-law dependence. A simple scaling theory accurately describes the dependence of the magnitude of these fluctuations on time, on the inter-particle distance and on the size ratio of guest and host particles. The consequences in particular for the dynamics of colloidal mixtures are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0208/0208322v1.pdf"}
{"id": "cond-mat0209034", "abstract": "  For ultracold and Bose-condensed atoms contained in periodic optical potential wells the quantized nature of their motion is clearly visible. The motion of the atomic wavepacket can also be accurately controlled. For those systems the long-range character of the atomic interaction and of the external potential play a key role in the quantum mechanical evolution. The basic facets of the experimental and theoretical research for atoms within optical lattice structures will be reviewed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0209/0209034v1.pdf"}
{"id": "cond-mat0209408", "abstract": "  A bit-string model for the evolution of a population of haploid organisms, subject to competition, reproduction with mutation and selection is studied, using mean field theory and Monte Carlo simulations. We show that, depending on environmental flexibility and genetic variability, the model exhibits a phase transtion between extinction and survival. The mean-field theory describes the infinite-size limit, while simulations are used to study quasi-stationary properties. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0209/0209408v1.pdf"}
{"id": "cond-mat0212440", "abstract": "  The dynamics of polymer translocation through a pore has been the subject of recent theoretical and experimental works. We have considered theoretical estimates and performed computer simulations to understand the mechanism of DNA uptake into the cell nucleus, a phenomenon experimentally investigated by attaching a small bead to the free end of the double helix and pulling this bead with the help of an optical trap. The experiments show that the uptake is monotonous and slows down when the remaining DNA segment becomes very short. Numerical and analytical studies of the entropic repulsion between the DNA filament and the membrane wall suggest a new interpretation of the experimental observations. Our results indicate that the repulsion monotonically decreases as the uptake progresses. Thus, the DNA is pulled in (i) either by a small force of unknown origin, and then the slowing down can be interpreted only statistically; (ii) or by a strong but slow ratchet mechanism, which would naturally explain the observed monotonicity, but then the slowing down requires additional explanations. Only further experiments can unambiguously distinguish between these two mechanisms. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0212/0212440v1.pdf"}
{"id": "cond-mat0303597", "abstract": "  A quantum Monte Carlo algorithm for the transverse Ising model with arbitrary short- or long-range interactions is presented. The algorithm is based on sampling the diagonal matrix elements of the power series expansion of the density matrix (stochastic series expansion), and avoids the interaction summations necessary in conventional methods. In the case of long-range interactions, the scaling of the computation time with the system size N is therefore reduced from N^2 to Nln(N). The method is tested on a one-dimensional ferromagnet in a transverse field, with interactions decaying as 1/r^2. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0303/0303597v2.pdf"}
{"id": "cond-mat0306188", "abstract": "  We report adjustable magnetic `bouncing' and focusing of a dilute ^87Rb Bose gas. Both the condensate production and manipulation are realised using a particularly straight-forward apparatus. The bouncing region is comprised of approximately concentric ellipsoidal magnetic equipotentials with a centre that can be adjusted vertically. We extend, and discuss the limitations of, simple Thomas-Fermi and Monte-Carlo theoretical models for the bouncing, which at present find close agreement with the condensate's evolution. Very strong focusing has been inferred and the observation of atomic matter-wave diffraction should be possible. Prospects look bright for applications in matter-wave atom-optics, due to the very smooth nature of the mirror. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0306/0306188v1.pdf"}
{"id": "cond-mat0306219", "abstract": "  Electronic and atomic structures of the clean, and As and Te covered Si(211) surface are studied using pseudopotential density functional method. The clean surface is found to have (2 X 1) and rebonded (1 X 1) reconstructions as stable surface structures, but no π-bonded chain reconstruction. Binding energies of As and Te adatoms at a number of symmetry sites on the ideal and (2 X 1) reconstructed surfaces have been calculated because of their importance in the epitaxial growth of CdTe and other materials on the Si(211) surface. The special symmetry sites on these surfaces having the highest binding energies for isolated As and Te adatoms are identified. But more significantly, several sites are found to be nearly degenerate in binding energy values. This has important consequences for epitaxial growth processes. Optimal structures calculated for 0.5 ML of As and Te coverage reveal that the As adatoms dimerize on the surface while the Te adatoms do not. However, both As and Te covered surfaces are found to be metallic in nature. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0306/0306219v1.pdf"}
{"id": "cond-mat0306276", "abstract": "  We present measurements of the magnetoresistance of long and narrow quasi one-dimensional gold wires containing magnetic iron impurities. The electron phase coherence time extracted from the weak antilocalisation shows a pronounced plateau in a temperature region of 300 mK - 800 mK, associated with the phase breaking due to the Kondo effect. Below the Kondo temperature, the phase coherence time increases, as expected in the framework of Kondo physics. At much lower temperatures, the phase coherence time saturates again, in contradiction with standard Fermi liquid theory. In the same temperature regime, the resistivity curve displays a characteristic maximum at zero magnetic field, associated with the formation of a spin glass state. We argue that the interactions between the magnetic moments are responsible for the low temperature saturation of the phase coherence time. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0306/0306276v1.pdf"}
{"id": "cond-mat0306292", "abstract": "  We study a random magnetic resonance force microscopy (MRFM) signal caused by the thermal vibrations of high frequency cantilever modes in the oscillating cantilever-driven adiabatic reversals (OSCAR) technique. We show that the regular MRFM signal with a characteristic decay time, τ_m, is followed by a non-dissipative random signal with a characteristic time τ_r. We present the estimates for the values of τ_m and τ_r. We argue that this random MRFM signal can be used for spin detection. It has a “signature” of a sharp peak in its Fourier spectrum. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0306/0306292v1.pdf"}
{"id": "cond-mat0306469", "abstract": "  We show that the various crossovers between dynamical regimes observed in experiments and simulations of supercooled liquids can be explained in simple terms from the existence and statistical properties of dynamical heterogeneities. We confirm that dynamic heterogeneity is responsible for the slowing down of glass formers at temperatures well above the dynamic singularity T_c predicted by mode coupling theory. Our results imply that activated processes govern the long-time dynamics even in the temperature regime where they are neglected by mode-coupling theory. We show that alternative interpretations based on topographic properties of the potential energy landscape are complicated and inefficient ways of describing simple physical features which are naturally accounted for within our approach. We show in particular that the reported links between mode coupling and landscape singularities do not exist. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0306/0306469v2.pdf"}
{"id": "cond-mat0307038", "abstract": "  First principles density functional calculations are used to study the early oxidation stages of the Mg(0001) surface for oxygen coverages 1/16 <= Theta <= 3 monolayers. It is found that at very low coverages O is incorporated below the topmost Mg layer in tetrahedral sites. At higher oxygen-load the binding in on-surface sites is increased but at one monolayer coverage the on-surface binding is still about 60 meV weaker than for subsurface sites. The subsurface octahedral sites are found to be unfavorable compared to subsurface tetrahedral sites and to on-surface sites. At higher coverages oxygen adsorbs both under the surface and up. Our calculations predict island formation and clustering of incorporated and adsorbed oxygen in agreement with previous calculations. The calculated configurations are compared with the angle-scanned x-ray photoelectron diffraction experiment to determine the geometrical structure of the oxidized Mg(0001) surface. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0307/0307038v1.pdf"}
{"id": "cond-mat0307702", "abstract": "  Our study presents experimental measurements of the contact and longitudinal voltage drops in Hall bars, as a function of the current amplitude. We are interested in the heating phenomenon which takes place before the breakdown of the quantum Hall effect, i.e. the pre-breakdown regime. Two types of samples has been investigated, at low temperature (4.2 and 1.5K) and high magnetic field (up to 13 T). The Hall bars have several different widths, and our observations clearly demonstrate that the size of the sample influences the heating phenomenon. By measuring the critical currents of both contact and longitudinal voltages, as a function of the filling factor (around i=2), we highlight the presence of a high electric field domain near the source contact, which is observable only in samples whose width is smaller than 400 microns. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0307/0307702v1.pdf"}
{"id": "cond-mat0308032", "abstract": "  We have developed a nonlinear differential effective dipole approximation (NDEDA), in an attempt to investigate the effective linear and third-order nonlinear susceptibility of composite media in which graded spherical inclusions with weak nonlinearity are randomly embedded in a linear host medium. Alternatively, based on a first-principles approach, we derived exactly the linear local field inside the graded particles having power-law dielectric gradation profiles. As a result, we obtain also the effective linear dielectric constant and third-order nonlinear susceptibility. Excellent agreement between the two methods is numerically demonstrated. As an application, we apply the NDEDA to investigate the surface plasma resonant effect on the optical absorption, optical nonlinearity enhancement, and figure of merit of metal-dielectric composites. It is found that the presence of gradation in metal particles yields a broad resonant band in the optical region, and further enhances the figure of merit. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0308/0308032v1.pdf"}
{"id": "cond-mat0308218", "abstract": "  We have analyzed numerically the response and noise-limited charge sensitivity of a radio-frequency single-electron transistor (RF-SET) in a non-superconducting state using the orthodox theory. In particular, we have studied the performance dependence on the quality factor Q of the tank circuit for Q both below and above the value corresponding to the impedance matching between the coaxial cable and SET. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0308/0308218v1.pdf"}
{"id": "cond-mat0311230", "abstract": "  Logistic growth process with nonlocal interactions is considered in one dimension. Spontaneous breakdown of translational invariance is shown to take place at some parameter region, and the bifurcation regime is identified for short and long range interactions. Domain walls between regions of different order parameter are expressed as soliton solutions of the reduced dynamics for nearest neighbor interactions. The analytic results are confirmed by numerical simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0311/0311230v2.pdf"}
{"id": "cond-mat0401075", "abstract": "  We have first successfully transferred the 129Xe polarization of natural isotopic composition to the proton of solid-state 1HCl via Spin Polarization-Induced Nuclear Overhauser Effect (SPINOE), by mixing the hyperpolarized 129Xe gas and the 1HCl gas and then cooling them to their condensated state in a flow system. The solid-state enhanced factor of the NMR signal of 6 for 1H was observed, and the equation of solid-state polarization enhancement via cross relaxation has also been theoretically deduced. Using this equation, the theoretically calculated enhancement is in agreement with the measured value within error. Also, this technique is maybe useful to establish a solid state NMR quantum computer. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0401/0401075v1.pdf"}
{"id": "cond-mat0401493", "abstract": "  The steady states of three families of one-dimensional non-equilibrium models with open boundaries, first proposed in [22], are studied using a matrix product formalism. It is shown that their associated quadratic algebras have two-dimensional representations, provided that the transition rates lie on specific manifolds of parameters . Exact expressions for the correlation functions of each model have also been obtained. We have also studied the steady state properties of one of these models, first introduced in [23], with more details. By introducing a canonical ensemble we calculate the canonical partition function of this model exactly. Using the Yang-Lee theory of phase transitions we spot a second-order phase transition from a power-law to a jammed phase. The density profile of particles in each phase has also been studied. A simple generalization of this model in which both the left and the right boundaries are open has also been introduced. It is shown that double shock structures may evolve in the system under certain conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0401/0401493v1.pdf"}
{"id": "cond-mat0401573", "abstract": "  We introduce a generalized non-uniform mean-field formalism to describe the dissociation of weak rod-like polyelectrolytes (PEs). Our approach allows for two-sublattice symmetry breaking which in titration curves is associated with a plateau for intermediate dissociation degrees. We first test our method in the case of a single weak PE by comparison with exact enumeration studies and show that it gives quantitatively accurate results for the dissociation degree in the full range of pH values, and in specific performs much better than the nearest-neighbor approximation (where exact solutions are possible). We then study charge regulation of the coupled system of a weak polyacid and a weak polybase as a function of their mutual distance, which has some relevance for PE-multilayer formation and for PE complexation. An intricate interplay of the degree of dissociation and the effective interaction between the PEs as a function of their mutual distance is found. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0401/0401573v1.pdf"}
{"id": "cond-mat0402023", "abstract": "  The dynamics of electrons in the presence of a positive ion is considered for conditions of weak electron-electron couping but strong electron-ion coupling. The equilibrium electron density and electric field time correlation functions are evaluated for semi-classical conditions using a classical statistical mechanics with a regularized electron-ion interaction for MD simulation. The theoretical analysis for the equilibrium state is obtained from the corresponding nonlinear Vlasov equation. Time correlation functions for the electrons are determined from the linearized Vlasov equation. The resulting electron dynamics is described in terms of a distribution of single electron-ion trajectories screened by an inhomogeneous electron gas dielectric function. The results are applied to calculation of the autocorrelation function for the electron electric field at the ion for 0≤ Z≤ 40, including conditions of strong electron-ion coupling. The electron stopping power and self-diffusion coefficient are determined from these results, and all properties calculated are compared with those obtained from semi-classical molecular dynamics simulation. The agreement with semi-classical MD simulation is found to be reasonable. The theoretical description provides an instructive interpretation for the strong electron-ion results. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0402/0402023v1.pdf"}
{"id": "cond-mat0402073", "abstract": "  The probability distribution of the mesoscopic local density of states (LDOS) for a single-channel disordered quantum wire with chiral symmetry is computed in two different geometries. An approximate ansatz is proposed to describe the crossover of the probability distributions for the conductance and LDOS between the chiral and standard symmetry classes of a single-channel disordered quantum wire. The accuracy of this ansatz is discussed by comparison with a large-deviation ansatz introduced by Schomerus and Titov in Phys. Rev. B 67, 100201(R) (2003). ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0402/0402073v2.pdf"}
{"id": "cond-mat0403162", "abstract": "  We study heat conduction in a one-dimensional chain of particles with longitudinal as well as transverse motions. The particles are connected by two-dimensional harmonic springs together with bending angle interactions. The problem is analyzed by mode-coupling theory and compared with molecular dynamics. We find very good, quantitative agreement for the damping of modes between a full mode-coupling theory and molecular dynamics result, and a simplified mode-coupling theory gives qualitative description of the damping. The theories predict generically that thermal conductance diverges as N^1/3 as the size N increases for systems terminated with heat baths at the ends. The N^2/5 dependence is also observed in molecular dynamics which we attribute to crossover effect. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0403/0403162v1.pdf"}
{"id": "cond-mat0404394", "abstract": "  We consider a system where localized bound electron pairs form an array of \"Andreev\"-like scattering centers and are coupled to a fermionic subsystem of uncorrelated electrons. By means of a path-integral approach, which describes the bound electron pairs within a coherent pseudospin representation, we derive and analyze the effective action for the collective phase modes which arise from the coupling between the two subsystems once the fermionic degrees of freedom are integrated out. This effective action has features of a quantum phase model in the presence of a Berry phase term and exhibits a coupling to a field which describes at the same time the fluctuations of density of the bound pairs and those of the amplitude of the fermion pairs. Due to the competition between the local and the hopping induced non-local phase dynamics it is possible, by tuning the exchange coupling or the density of the bound pairs, to trigger a transition from a phase ordered superconducting to a phase disordered insulating state. We discuss the different mechanisms which control this occurrence and the eventual destruction of phase coherence both in the weak and strong coupling limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0404/0404394v1.pdf"}
{"id": "cond-mat0404445", "abstract": "  The strongly damping-dependent nonlinear dynamical response of classical superparamagnets is investigated by means of an analytical approach. Using rigorous balance equations for the spin occupation numbers a simple approximate expression is derived for the nonlinear susceptibility. The results are in good agreement with those obtained from the exact (continued-fraction) solution of the Fokker-Planck equation. The formula obtained could be of assistance in the modelling of the experimental data and the determination of the damping coefficient in superparamagnets. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0404/0404445v1.pdf"}
{"id": "cond-mat0404640", "abstract": "  We study the discrete Gierer-Meinhardt model of reaction-diffusion on three different types of networks: regular, random and scale-free. The model dynamics lead to the formation of stationary Turing patterns in the steady state in certain parameter regions. Some general features of the patterns are studied through numerical simulation. The results for the random and scale-free networks show a marked difference from those in the case of the regular network. The difference may be ascribed to the small world character of the first two types of networks. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0404/0404640v1.pdf"}
{"id": "cond-mat0406070", "abstract": "  We draw attention to a clear dichotomy between small-world networks exhibiting exponential neighborhood growth, and fractal-like networks where neighborhoods grow according to a power law. This distinction is observed in a number of real-world networks, and is related to the degree correlations and geographical constraints. We conclude by pointing out that the status of human social networks in this dichotomy is far from clear. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0406/0406070v1.pdf"}
{"id": "cond-mat0407631", "abstract": "  A new description of the binary fluid problem via the lattice Boltzmann method is presented which highlights the use of the moments in constructing two equilibrium distribution functions. This offers a number of benefits, including better isotropy, and a more natural route to the inclusion of multiple relaxation times for the binary fluid problem. In addition, the implementation of solid colloidal particles suspended in the binary mixture is addressed, which extends the solid-fluid boundary conditions for mass and momentum to include a single conserved compositional order parameter. A number of simple benchmark problems involving a single particle at or near a fluid-fluid interface are undertaken and show good agreement with available theoretical or numerical results. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0407/0407631v2.pdf"}
{"id": "cond-mat0408234", "abstract": "  We study mobility and interaction of gap solitons in a Bose-Einstein condensate (BEC) confined by an optical lattice potential. Such localized wavepackets can exist only in the gaps of the matter-wave band-gap spectrum and their interaction properties are shown to serve as a measure of discreteness imposed onto a BEC by the lattice potential. We show that inelastic collisions of two weakly localized near-the-band-edge gap solitons provide simple and effective means for generating strongly localized in-gap solitons through soliton fusion. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0408/0408234v1.pdf"}
{"id": "cond-mat0408372", "abstract": "  The parallel computational complexity or depth of growing network models is investigated. The networks considered are generated by preferential attachment rules where the probability of attaching a new node to an existing node is given by a power, α of the connectivity of the existing node. Algorithms for generating growing networks very quickly in parallel are described and studied. The sublinear and superlinear cases require distinct algorithms. As a result, there is a discontinuous transition in the parallel complexity of sampling these networks corresponding to the discontinuous structural transition at α=1, where the networks become scale free. For α>1 networks can be generated in constant time while for 0 ≤α < 1 logarithmic parallel time is required. The results show that these networks have little depth and embody very little history dependence despite being defined by sequential growth rules. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0408/0408372v2.pdf"}
{"id": "cond-mat0410422", "abstract": "  We report on a nanoscale patterning method on Si substrates using self-assembled metal islands and low-energy ion-beam irradiation. The Si nanostructures produced on the Si substrate have a one-to-one correspondence with the self-assembled metal (Ag, Au, Pt) nanoislands initially grown on the substrate. The surface morphology and the structure of the irradiated surface were studied by high-resolution transmission electron microscopy (HRTEM). TEM images of ion-beam irradiated samples show the formation of sawtooth-like structures on Si. Removing metal islands and the ion-beam induced amorphous Si by etching, we obtain a crystalline nanostructure of Si. The smallest structures emit red light when exposed to a UV light. The size of the nanostructures on Si is governed by the size of the self-assembled metal nanoparticles grown on the substrate for this replica nanopatterning. The method can easily be extended for tuning the size of the Si nanostructures by the proper choice of the metal nanoparticles and the ion energy in ion-irradiation. It is suggested that off-normal irradiation can also be used for tuning the size of the nanostructures. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0410/0410422v2.pdf"}
{"id": "cond-mat0410694", "abstract": "  After briefly describing the present status of the spin glass theory, we present a conjecture on the exact location of the multicritical point in the phase diagram of finite-dimensional spin glasses. The theory enables us to understand in a unified way many numerical results for two-, three- and four-dimensional models including the +-J Ising model, random Potts model, random lattice gauge theory, and random Zq model. It is also suggested from the same theoretical framework that models with symmetric distribution of randomness in exchange interaction have no finite-temperature transition on the square lattice. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0410/0410694v1.pdf"}
{"id": "cond-mat0411330", "abstract": "  We study the non-equilibrium behavior of the three-dimensional Gaussian random-field Ising model at T=0 in the presence of a uniform external field using a 2-spin-flip dynamics. The deterministic, history-dependent evolution of the system is compared with the one obtained with the standard 1-spin-flip dynamics used in previous studies of the model. The change in the dynamics yields a significant suppression of coercivity, but the distribution of avalanches (in number and size) stays remarkably similar, except for the largest ones that are responsible for the jump in the saturation magnetization curve at low disorder in the thermodynamic limit. By performing a finite-size scaling study, we find strong evidence that the change in the dynamics does not modify the universality class of the disorder-induced phase transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0411/0411330v1.pdf"}
{"id": "cond-mat0412010", "abstract": "  The cross over from low to high carrier densities in a many-polaron system is studied in the framework of the one-dimensional spinless Holstein model, using unbiased numerical methods. Combining a novel quantum Monte Carlo approach and exact diagonalization, accurate results for the single-particle spectrum and the electronic kinetic energy on fairly large systems are obtained. A detailed investigation of the quality of the Monte Carlo data is presented. In the physically most important adiabatic intermediate electron-phonon coupling regime, for which no analytical results are available, we observe a dissociation of polarons with increasing band filling, leading to normal metallic behavior, while for parameters favoring small polarons, no such density-driven changes occur. The present work points towards the inadequacy of single-polaron theories for a number of polaronic materials such as the manganites. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0412/0412010v2.pdf"}
{"id": "cond-mat0501634", "abstract": "  We have studied the electron transport through a quantum dot coupled to three leads in the presence of external microwave fields supplied to different parts of the considered mesoscopic system. Additionally, we introduced a possible nonresonant tunneling channels between leads. The quantum dot charge and currents were determined in terms of the appropriate evolution operator matrix elements and under the wide band limit the analytical formulas for time-averaged currents and differential conductance were obtained. We have also examined the response of the considered system on the rectangular-pulse modulation imposed on different quantum dot-leads barriers as well as the time-dependence of currents flowing in response to suddenly removed (or included) connection of a quantum dot with one of the leads. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0501/0501634v1.pdf"}
{"id": "cond-mat0502386", "abstract": "  We discuss the mechanism of anomalous Hall effect related to the contribution of electron states below the Fermi surface (induced by the Berry phase in momentum space). Our main calculations are made within a model of two-dimensional electron gas with spin-orbit interaction of the Rashba type, taking into account the scattering from impurities. We demonstrate that such an \"intrinsic\" mechanism can dominate but there is a competition with the impurity-scattering mechanism, related to the contribution of states in the vicinity of Fermi surface. We also show that the contribution to the Hall conductivity from electron states close to the Fermi surface has the intrinsic properties as well. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0502/0502386v2.pdf"}
{"id": "cond-mat0503448", "abstract": "  We present a detailed description of the generalized geometric cluster algorithm for the efficient simulation of continuum fluids. The connection with well-known cluster algorithms for lattice spin models is discussed, and an explicit full cluster decomposition is derived for a particle configuration in a fluid. We investigate a number of basic properties of the geometric cluster algorithm, including the dependence of the cluster-size distribution on density and temperature. Practical aspects of its implementation and possible extensions are discussed. The capabilities and efficiency of our approach are illustrated by means of two example studies. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0503/0503448v1.pdf"}
{"id": "cond-mat0504244", "abstract": "  There have been recent reports of charge ordering around x=0.5 in the bilayer manganites. At x=0.5, there appears to be a coexistence region of layered A-type antiferromagnetc and charge order. There are also reports of orbital order in this region without any Jahn-Teller effect. Based on physical grounds, this region is investigated from a model that incorporates the two e_g orbitals at each Mn site and a near-neighbour Coulomb repulsion. It is shown that there indeed is both charge and orbital order close to the half-doped region coincident with a layered magnetic structure. Although the orbital order is known to drive the magnetic order, the layered magnetic structure is also favoured in this system by the lack of coherent transport across the planes and the reduced dimensionality of the lattice. The anisotropic hopping across the e_g orbitals and the underlying layered structure largely determine the orbital arrangements in this region, while the charge order is primarily due to the long range interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0504/0504244v1.pdf"}
{"id": "cond-mat0505440", "abstract": "  We study target-searching processes on a percolation, on which a hunter tracks a target by smelling odors it emits. The odor intensity is supposed to be inversely proportional to the distance it propagates. The Monte Carlo simulation is performed on a 2-dimensional bond-percolation above the threshold. Having no idea of the location of the target, the hunter determines its moves only by random attempts in each direction. For lager percolation connectivity p≳ 0.90, it reveals a scaling law for the searching time versus the distance to the position of the target. The scaling exponent is dependent on the sensitivity of the hunter. For smaller p, the scaling law is broken and the probability of finding out the target significantly reduces. The hunter seems trapped in the cluster of the percolation and can hardly reach the goal. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0505/0505440v1.pdf"}
{"id": "cond-mat0506376", "abstract": "  Quantum interference between one- and two-photon absorption pathways allows coherent control of interband transitions in unbiased bulk semiconductors; carrier population, carrier spin polarization, photocurrent injection, and spin current injection may all be controlled. We extend the theory of these processes to include the electron-hole interaction. Our focus is on photon energies that excite carriers above the band edge, but close enough to it so that transition amplitudes based on low order expansions in 𝐤 are applicable; both allowed-allowed and allowed-forbidden two-photon transition amplitudes are included. Analytic solutions are obtained using the effective mass theory of Wannier excitons; degenerate bands are accounted for, but envelope-hole coupling is neglected. We find a Coulomb enhancement of two-color coherent control process, and relate it to the Coulomb enhancements of one- and two-photon absorption. In addition, we find a frequency dependent phase shift in the dependence of photocurrent and spin current on the optical phases. The phase shift decreases monotonically from π /2 at the band edge to 0 over an energy range governed by the exciton binding energy. It is the difference between the partial wave phase shifts of the electron-hole envelope function reached by one- and two-photon pathways. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0506/0506376v1.pdf"}
{"id": "cond-mat0508267", "abstract": "  We present a detailed numerical study of the elementary condensation events (avalanches) associated to the adsorption of ^4He in silica aerogels. We use a coarse-grained lattice-gas description and determine the nonequilibrium behavior of the adsorbed gas within a local mean-field analysis, neglecting thermal fluctuations and activated processes. We investigate the statistical properties of the avalanches, such as their number, size and shape along the adsorption isotherms as a function of gel porosity, temperature, and chemical potential. Our calculations predict the existence of a line of critical points in the temperature-porosity diagram where the avalanche size distribution displays a power-law behavior and the adsorption isotherms have a universal scaling form. The estimated critical exponents seem compatible with those of the field-driven Random Field Ising Model at zero temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0508/0508267v2.pdf"}
{"id": "cond-mat0508598", "abstract": "  Statistical mechanics is applied to lossy compression using multilayer perceptrons for unbiased Boolean messages. We utilize a tree-like committee machine (committee tree) and tree-like parity machine (parity tree) whose transfer functions are monotonic. For compression using committee tree, a lower bound of achievable distortion becomes small as the number of hidden units K increases. However, it cannot reach the Shannon bound even where K -> infty. For a compression using a parity tree with K >= 2 hidden units, the rate distortion function, which is known as the theoretical limit for compression, is derived where the code length becomes infinity. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0508/0508598v2.pdf"}
{"id": "cond-mat0510022", "abstract": "  We present the formulation for finding the distribution of eigenstrains, i.e. the sources of residual stress, from a set of measurements of residual elastic strain (e.g. by diffraction), or residual stress, or stress redistribution, or distortion. The variational formulation employed seeks to achieve the best agreement between the model prediction and some measured parameters in the sense of a minimum of a functional given by a sum over the entire set of measurements. The advantage of this approach lies in its flexibility: different sets of measurements and information about different components of the stress-strain state can be incorporated. We demonstrate the power of the technique by analysing experimental data for welds in thin sheet of a nickel superalloy aerospace material. Very good agreement can be achieved between the prediction and the measurement results without the necessity of using iterative solution. In practice complete characterisation of residual stress states is often very difficult, due to limitations of facility access, measurement time or specimen dimensions. Implications of the new technique for experimental analysis are all the more significant, since it allows the reconstruction of the entire stress state from incomplete sets of data. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0510/0510022v1.pdf"}
{"id": "cond-mat0510730", "abstract": "  We present the results of Monte Carlo simulations of the magnetic properties of a model for a single nanoparticle consisting in a ferromagnetic core surrounded by an antiferromagnetic shell. The simulations of hysteresis loops after cooling in a magnetic field display exchange bias effects. In order to understand the origin of the loop shifts, we have studied the thermal dependence of the shell and interface magnetizations under field cooling. These results, together with inspection of the snapshots of the configurations attained at low temperature, show the existence of a net magnetization at the interface which is responsible for the bias of the hysteresis loops. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0510/0510730v1.pdf"}
{"id": "cond-mat0511460", "abstract": "  The competition between d-wave superconductivity (SC) and antiferromagnetism (AF) in the high-Tc cuprates is investigated by studying the hole- and electron-doped two-dimensional Hubbard model with a recently proposed variational quantum-cluster theory. The approach is shown to provide a thermodynamically consistent determination of the particle number, provided that an overall shift of the on-site energies is treated as a variational parameter. The consequences for the single-particle excitation spectra and for the phase diagram are explored. By comparing the single-particle spectra with quantum Monte-Carlo (QMC) and experimental data, we verify that the low-energy excitations in a strongly-correlated electronic system are described appropriately. The cluster calculations also reproduce the overall ground-state phase diagram of the high-temperature superconductors. In particular, they include salient features such as the enhanced robustness of the antiferromagnetic state as a function of electron doping and the tendency towards phase separation into a mixed antiferromagnetic-superconducting phase at low-doping and a pure superconducting phase at high (both hole and electron) doping. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0511/0511460v3.pdf"}
{"id": "cond-mat0511746", "abstract": "  We investigate theoretically the low-temperature physics of a two-component ultracold mixture of bosons and fermions in disordered optical lattices. We focus on the strongly correlated regime. We show that, under specific conditions, composite fermions, made of one fermion plus one bosonic hole, form. The composite picture is used to derive an effective Hamiltonian whose parameters can be controlled via the boson-boson and the boson-fermion interactions, the tunneling terms and the inhomogeneities. We finally investigate the quantum phase diagram of the composite fermions and we show that it corresponds to the formation of Fermi glasses, spin glasses, and quantum percolation regimes. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0511/0511746v3.pdf"}
{"id": "cond-mat0512627", "abstract": "  We consider various incommensurate (IC) order parameters for electrons on a square lattice which reduce to d_x^2-y^2-density wave (DDW) order when the ordering wavevector Q→ (π,π). We describe the associated charge and current distributions and their experimental signatures. Such orders can arise at the mean-field level in extended Hubbard models. We compare the phase diagrams of these models with experiments in the underdoped cuprates, where (1) DDW order is a possible explanation of the pseudogap, and (2) there are experimental indications of incommensurability. We find various types of IC DDW and discuss their possible relevance to the physics of the cuprates. Our main finding is that IC DDW order is generally accompanied by superconducting order, but the magnitude of the IC wavevector can be small. A comparison with the analogous AF-ICSDW transition is given. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0512/0512627v4.pdf"}
{"id": "cond-mat0603280", "abstract": "  We present a detailed study of the magnetic structure and spin waves in the Fe jarosite compound KFe_3(SO_4)_2(OH)_6 for the most general Hamiltonian involving one- and two-spin interactions which are allowed by symmetry. We compare the calculated spin-wave spectrum with the recent neutron scattering data of Matan et al. for various model Hamiltonians which include, in addition to isotropic Heisenberg exchange interactions between nearest (J_1) and next-nearest (J_2) neighbors, single ion anisotropy and Dzyaloshinskii-Moriya (DM) interactions. We concluded that DM interactions are the dominant anisotropic interaction, which not only fits all the splittings in the spin-wave spectrum but also reproduces the small canting of the spins out of the Kagomé plane. A brief discussion of how representation theory restricts the allowed magnetic structure is also given. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0603/0603280v1.pdf"}
{"id": "cond-mat0603495", "abstract": "  A pioneering experiment [E. Schuster, E. Buks, M. Heiblum, D. Mahalu, V. Umansky, and Hadas Shtrikman, Nature 385, 417 (1997)] reported the measurement of the transmission phase of an electron traversing a quantum dot and found the intriguing feature of a sudden phase drop in the conductance valleys. Based on the Friedel sum rule for a spinless effective one-dimensional system, it has been previously argued [H.-W. Lee, Phys. Rev. Lett. 82, 2358 (1999)] that the sudden phase drop should be accompanied by the vanishing of the transmission amplitude, or transmission zero. Here we address roles of strong electron-electron interactions on the electron transport through a two-level quantum dot where one level couples with the leads much more strongly than the other level does [P. G. Silvestrov and Y. Imry, Phys. Rev. Lett. 85, 2565 (2000)]. We perform a perturbative conductance calculation with an explicit account of large charging energy and verify that the resulting conductance exhibits transmission zero, in agreement with the analysis based on the Friedel sum rule. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0603/0603495v2.pdf"}
{"id": "cond-mat0604068", "abstract": "  In a recent article [M. Merolle et al., Proc. Natl. Acad. Sci. USA 102, 10837 (2005)] it was argued that dynamic heterogeneity in d-dimensional glass formers is a manifestation of an order-disorder phenomenon in the d+1 dimensions of spacetime. By considering a dynamical analogue of the free energy, evidence was found for phase coexistence between active and inactive regions of spacetime, and it was suggested that this phenomenon underlies the glass transition. Here we develop these ideas further by investigating in detail the one-dimensional Fredrickson-Andersen (FA) model in which the active and inactive phases originate in the reducibility of the dynamics. We illustrate the phase coexistence by considering the distributions of mesoscopic spacetime observables. We show how the analogy with phase coexistence can be strengthened by breaking microscopic reversibility in the FA model, leading to a non-equilibrium theory in the directed percolation universality class. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0604/0604068v2.pdf"}
{"id": "cond-mat0605066", "abstract": "  A novel Genetic Algorithm is described that is suitable for determining the global minimum energy configurations of crystal structures and which can also be used as a polymorph search technique. This algorithm requires no prior assumptions about unit cell size, shape or symmetry, nor about the ionic configuration within the unit cell. This therefore enables true ab initio crystal structure and polymorph prediction. Our new algorithm uses a real-space representation of the population members, and makes use of a novel periodic cut for the crossover operation. Results on large Lennard-Jones systems with FCC- and HCP-commensurate cells show robust convergence to the bulk structure from a random initial assignment and an ability to successfully discriminate between competing low enthalpy configurations. Results from an ab initio carbon polymorph search show the spontaneous emergence of both Lonsdaleite and graphite like structures. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0605/0605066v1.pdf"}
{"id": "cond-mat0605528", "abstract": "  We investigate the dynamics of Bloch electrons using a density operator method and connect this approach with previous theories based on wave packets. We study non-interacting systems with negligible disorder and strong spin-orbit interactions, which have been at the forefront of recent research on spin-related phenomena. We demonstrate that the requirement of gauge invariance results in a shift in the position at which the Wigner function of Bloch electrons is evaluated. The present formalism also yields the correction to the carrier velocity arising from the Berry phase. The gauge-dependent shift in carrier position and the Berry phase correction to the carrier velocity naturally appear in the charge and current density distributions. In the context of spin transport we show that the spin velocity may be defined in such a way as to enable spin dynamics to be treated on the same footing as charge dynamics. Aside from the gauge-dependent position shift we find additional, gauge-covariant multipole terms in the density distributions of spin, spin current and spin torque. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0605/0605528v1.pdf"}
{"id": "cond-mat0607690", "abstract": "  Properties of polyelectrolytes in tetravalent salt solutions are intensively investigated by a coarse-grained model. The concentration of salt and the size of tetravalent counterions are found playing a decisive role on chain properties. If the size of tetravalent counterions is compatible with the one of monomers, the chains show extended structures at low and at high salt concentrations, whereas at intermediate salt concentrations, they acquire compact and prolate structures. The swelling exponent of a chain against salt concentration behaves in an analogous way as the morphological quantities. Under certain condition, the electrostatics gives a negative contribution to the persistence length, in companion with a salt-induced mechanical instability of polyelectrolytes. Nearly at the same moment, it appears like-charge attraction between chains. The equal size of the tetravalent ions and the monomers is the optimal condition to attain the strongest attraction between chains and the most compact chain structure. Moreover, the ions form a multi-layer organization around a chain and, thus, the integrated charge distribution reveals an oscillatory behavior. The results suggest that charge inversion has no direct connection with redissolution of polyelectrolytes at high salt concentrations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0607/0607690v1.pdf"}
{"id": "cond-mat0608512", "abstract": "  We study the spin-spin coupling between two single-electron quantum dots due to the Coulomb and spin-orbit interactions, in the absence of tunneling between the dots. We find an anisotropic XY spin-spin interaction that is proportional to the Zeeman splitting produced by the external magnetic field. This interaction is studied both in the limit of weak and strong Coulomb repulsion with respect to the level spacing of the dot. The interaction is found to be a non-monotonic function of inter-dot distance a_0 and external magnetic field, and, moreover, vanishes for some special values of a_0 and/or magnetic field orientation. This mechanism thus provides a new way to generate and tune spin interaction between quantum dots. We propose a scheme to measure this spin-spin interaction based on the spin-relaxation-measurement technique. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0608/0608512v1.pdf"}
{"id": "cond-mat0610296", "abstract": "  We calculate the zero temperature conductance and characteristic correlation functions of a molecule with a center of mass (CM) motion which modulates couplings to the leads. In the first model studied, the CM vibrational mode is simultaneously coupled to the electron density on the molecule. The conductance is suppressed in regimes corresponding to non-integer occupancy of the molecule. In the second model, where the CM mode is not directly coupled to the electron density, the suppression of conductance is related to the dynamic breaking of the inversion symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0610/0610296v1.pdf"}
{"id": "cond-mat0610711", "abstract": "  The model of diamagnetic phase transition in beryllium which takes into account the quasi 2-dimensional shape of the Fermi surface of beryllium is proposed. It explains correctly the recent experimental data on observation of non-homogeneous phase in beryllium at the conditions of strong dHvA effect when the strong correlation of electron gas results in instability of homogeneous phase and formation of Condon domain structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0610/0610711v1.pdf"}
{"id": "cond-mat0612172", "abstract": "  We generalized the recently introduced new impurity solver based on the diagrammatic expansion around the atomic limit and Quantum Monte Carlo summation of the diagrams. We present generalization to the cluster of impurities, which is at the heart of the cluster Dynamical Mean-Field methods, and to realistic multiplet structure of a correlated atom, which will allow a high precision study of actinide and lanthanide based compounds with the combination of the Dynamical Mean-Field theory and band structure methods. The approach is applied to both, the two dimensional Hubbard and t-J model within Cellular Dynamical Mean Field method. The efficient implementation of the new algorithm, which we describe in detail, allows us to study coherence of the system at low temperature from the underdoped to overdoped regime. We show that the point of maximal superconducting transition temperature coincides with the point of maximum scattering rate although this optimal doped point appears at different electron densities in the two models. The power of the method is further demonstrated on the example of the Kondo volume collapse transition in Cerium. The valence histogram of the DMFT solution is presented showing the importance of the multiplet splitting of the atomic states. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0612/0612172v1.pdf"}
{"id": "cond-mat0612653", "abstract": "  We develop a perturbative approach that allows one to study the surface scattering in quasi-1D waveguides with rough boundaries. Our approach is based on the construction of an effective “bulk” potential of a very complicated structure. The detailed analysis of this potential reveals that apart from the well known terms considered in the previous studies, one should keep specific terms that depend on the square of the derivative of the boundaries. As was found, in spite of an apparent smallness of these square-gradient scattering (SGS) terms, there is a physically important region of parameters, in which they can not be neglected. Our approach also demonstrates that the contribution of the SGS-mechanism of scattering strongly depends on the type of the rough boundaries (uncorrelated, symmetric or antisymmetric) ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0612/0612653v1.pdf"}
{"id": "cond-mat0701095", "abstract": "  Magnetic flux in mesoscopic rings under the quantum Smoluchowski regime is investigated. Quantum corrections to the dissipative current are shown to form multistable steady states and can result in statistical enhancement of the magnetic flux. The relevance of quantum correction effects is supported v ia the entropic criterion. A possible application for a qutrit architecture of quantum information is proposed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0701/0701095v2.pdf"}
{"id": "cond-mat0701164", "abstract": "  We present a detailed treatment of the nonequilibrium Green's function method for thermal transport due to atomic vibrations in nanostructures. Some of the key equations, such as self-energy and conductance with nonlinear effect, are derived. A self-consistent mean-field theory is proposed. Computational procedures are discussed. The method is applied to a number of systems including one-dimensional chains, a benzene ring junction, and carbon nanotubes. Mean-field calculations of the Fermi-Pasta-Ulam model are compared with classical molecular dynamics simulations. We find that nonlinearity suppresses thermal transport even at moderately high temperatures. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0701/0701164v1.pdf"}
{"id": "cond-mat0701390", "abstract": "  We study propagation of short laser pulses in a Bose-Einstein condensate taking into account dispersive effects under the conditions for electromagnetically induced transparency. We calculate dispersion coefficients using typical experimental parameters of slow-light schemes in condensates. By numerically propagating the laser pulse, and referring to theoretical estimations, we determine the conditions for which dispersion starts to introduce distortions on the pulse shape. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0701/0701390v1.pdf"}
{"id": "cond-mat9510056", "abstract": "  We study diffusion on a substrate with permanent traps distributed with critical positional correlation, modeled by their placement on the perimeters of a critical percolation cluster. We perform a numerical analysis of the vibrational density of states and the largest eigenvalue of the equivalent scalar elasticity problem using the method of Arnoldi and Saad. We show that the critical trap correlation increases the exponent appearing in the stretched exponential behavior of the low frequency density of states by approximately a factor of two as compared to the case of no correlations. A finite size scaling hypothesis of the largest eigenvalue is proposed and its relation to the density of states is given. The numerical analysis of this scaling postulate leads to the estimation of the stretch exponent in good agreement with the density of states result. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9510/9510056v1.pdf"}
{"id": "cond-mat9610087", "abstract": "  A general method for obtaining the oscillation periods of the interlayer exchange coupling is presented. It is shown that it is possible for the coupling to oscillate with additional periods beyond the ones predicted by the RKKY theory. The relation between the oscillation periods and the spacer Fermi surface is clarified, showing that non-RKKY periods do not bear a direct correspondence with the Fermi surface. The interesting case of a FCC(110) structure is investigated, unmistakably proving the existence and relevance of non-RKKY oscillations. The general conditions for the occurrence of non-RKKY oscillations are also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9610/9610087v1.pdf"}
{"id": "cond-mat9701006", "abstract": "  The equilibrium conditions impose nontrivial geometrical constraints on the configurations that a two-dimensional foam can attain. In the first place, the three centers of the films that converge to a vertex have to be on a line, i.e. all vertices are aligned. Moreover an equilibrated foam must admit a reciprocal figure. This means that it must be possible to find a set of points P_i on the plane, one per bubble, such that the segments (P_i P_j) are normal to the corresponding foam films. It is furthermore shown that these constraints are equivalent to the requirement that the foam be a Sectional Multiplicative Voronoi Partition (SMVP). A SMVP is a cut with a two-dimensional plane, of a three-dimensional Multiplicative Voronoi Partition. Thus given an arbitrary equilibrated foam, we can always find point-like sources (one per bubble) in three dimensions that reproduce this foam as a generalized Voronoi partition. These sources are the only degrees of freedom that we need in oder to fully describe the foam. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9701/9701006v1.pdf"}
{"id": "cond-mat9702042", "abstract": "  The question of whether the pseudogap in high T_c cuprates is related to super conducting precursor effects or to the existence of extrinsic bosonic massive excitations is investigated on the basis of the Boson-Fermion model. The characteristic three peak structure of the electronic spectral function and the temperature dependent Fermi vector derived here are signatures for a two component scenario which can be tested by ARPES and BIS experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9702/9702042v3.pdf"}
{"id": "cond-mat9704176", "abstract": "  We investigate quantum phase transitions in two-dimensional superconducting arrays with general capacitance matrices and discrete charge states. We use the perturbation theory together with the simulated annealing method to obtain the zero-temperature phase diagrams, which display various lobe-like structures of insulating solid phases, and examine the possibility of supersolid phase. At nonzero temperatures, an effective classical Hamiltonian is obtained through the use of the variational method in the path-integral formalism, and the corresponding phase diagram is found approximately. The insulating lobes of the solid phases are shown to exist at sufficiently low temperatures, and results of Monte Carlo simulations are also presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9704/9704176v1.pdf"}
{"id": "cond-mat9802295", "abstract": "  We study the random link traveling salesman problem, where lengths l_ij between city i and city j are taken to be independent, identically distributed random variables. We discuss a theoretical approach, the cavity method, that has been proposed for finding the optimal tour length over this random ensemble, given the assumption of replica symmetry. Using finite size scaling and a renormalized model, we test the cavity predictions against the results of simulations, and find excellent agreement over a range of distributions. We thus provide numerical evidence that the replica symmetric solution to this problem is the correct one. Finally, we note a surprising result concerning the distribution of kth-nearest neighbor links in optimal tours, and invite a theoretical understanding of this phenomenon. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9802/9802295v3.pdf"}
{"id": "cond-mat9804031", "abstract": "  We report on a first-principles study of the structure of O/Rh(001) at half a monolayer of oxygen coverage, performed using density-functional theory. We find that oxygen atoms sit at the center of the black squares of a chess-board, c(2× 2), pattern. This structure is unstable against a rhomboid distortion of the black squares, which shortens the distance between an O atom and two of the four neighboring Rh atoms, while lengthening the distance with respect to the other two. We actually find that the surface energy is further lowered by allowing the O atom to get off the short diagonal of the rhombus so formed. We predict that the latter distortion is associated with an order-disorder transition, occurring below room temperature. The above rhomboid distortion of the square lattice may be seen as a rotation of the empty, white, squares. Our findings are at variance with recent claims based on STM images, according to which it is instead the black squares which would rotate. We argue that these images are indeed compatible with our predicted reconstruction pattern. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9804/9804031v1.pdf"}
{"id": "cond-mat9804188", "abstract": "  We study the influence of disorder and randomly distributed impurities on the properties of correlated antiferromagnets. To this end the Hubbard model with (i) random potentials, (ii) random hopping elements, and (iii) randomly distributed values of interaction is treated using quantum Monte Carlo and dynamical mean-field theory. In cases (i) and (iii) weak disorder can lead to an enhancement of antiferromagnetic (AF) order: in case (i) by a disorder-induced delocalization, in case (iii) by binding of free carriers at the impurities. For strong disorder or large impurity concentration antiferromagnetism is eventually destroyed. Random hopping leaves the local moment stable but AF order is suppressed by local singlet formation. Random potentials induce impurity states within the charge gap until it eventually closes. Impurities with weak interaction values shift the Hubbard gap to a density off half-filling. In both cases an antiferromagnetic phase without charge gap is observed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9804/9804188v2.pdf"}
{"id": "cond-mat9805015", "abstract": "  We develop a finite temperature perturbation theory (beyond the mean field) for a Bose-condensed gas and calculate temperature-dependent damping rates and energy shifts for Bogolyubov excitations of any energy. The theory is generalized for the case of excitations in a spatially inhomogeneous (trapped) Bose-condensed gas, where we emphasize the principal importance of inhomogeneouty of the condensate density profile and develop the method of calculating the self-energy functions. The use of the theory is demonstrated by calculating the damping rates and energy shifts of low-energy quasiclassical excitations, i.e. the quasiclassical excitations with energies much smaller than the mean field interaction between particles. In this case the boundary region of the condensate plays a crucial role, and the result for the damping rates and energy shifts is completely different from that in spatially homogeneous gases. We also analyze the frequency shifts and damping of sound waves in cylindrical Bose condensates and discuss the role of damping in the recent MIT experiment on the sound propagation. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9805/9805015v2.pdf"}
{"id": "cond-mat9806163", "abstract": "  We study the steady state of diffusion-limited coalescence, A+A<–>A, in the presence of a trap and with a background drift. In one dimension this model can be analyzed exactly through the method of inter-particle distribution functions (IPDF). Because of the irreversible trap the steady state of the system is a non-equilibrium state. An interesting phase transition, controlled by the drift away from the trap, takes place: from a non-trivial steady state, when the drift is weak, to a trivial steady state (the vacuum), as the drift increases beyond some critical point. Surprisingly, regardless of the drift strength, the computed IPDF resembles that of an homogeneous equilibrium system, without the trap. We suggest that this is due to \"shielding\": the particle nearest to the trap shields the remaining particles from the effects of the trap. Finally, we compare the exact solution to that of a reaction-diffusion equation, and we determine the optimal values of the appropriate rate coefficients. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9806/9806163v1.pdf"}
{"id": "cond-mat9806204", "abstract": "  A recently proposed ab initio Hartree-Fock approach aimed at directly obtaining the Wannier functions of a crystalline insulator is applied to polymers. The systems considered are the LiH chain and trans-polyacetylene. In addition to being the first application of our approach to one-dimensional systems, this work also demonstrates its applicability to covalent systems. Both minimal as well as extended basis sets were employed in the present study and excellent agreement was obtained with the Bloch orbital based approaches. Cohesive energies, optimized lattice parameters and the band structure are presented. Localization characteristics of the Wannier functions are also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9806/9806204v1.pdf"}
{"id": "cond-mat9810295", "abstract": "  Many things will have to go right for quantum computation to become a reality in the lab. For any of the presently-proposed approaches involving spin states in solids, an essential requirement is that these spins should be measured at the single-Bohr-magneton level. Fortunately, quantum computing provides a suggestion for a new approach to this seemingly almost impossible task: convert the magnetization into a charge, and measure the charge. I show how this might be done by exploiting the spin filter effect provided by ferromagnetic tunnel barriers, used in conjunction with one-electron quantum dots. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9810/9810295v1.pdf"}
{"id": "cond-mat9901066", "abstract": "  We investigate the combined influence of a magnetic field and a harmonic interparticle interaction on the thermodynamic properties of a finite number of spin polarized fermions in a confiment potential. This study is an extension using our path integral approach of symmetrized density matrices for identical particles. The thermodynamical properties are calculated for a three dimensional model of N harmonically interacting spin polarized fermions in a parabolic potential well in the presence of a magnetic field. The free energy and the internal energy are obtained for a limited number of particles. Deviations from the thermodynamical limit become negligible for about 100 or more particles, but even for a smaller number of fermions present in the well, scaling relations similar to those of the continuum approximation to the density of states are already satisfied. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9901/9901066v1.pdf"}
{"id": "cond-mat9901336", "abstract": "  We propose a model to describe the quasistatic shearing of dry granular materials, which notably captures the differences in velocity profiles recently observed in 2 and 3-D Couette flow experiments. In our scheme, the steady-state flow is due to the intermittent motion of particle clusters moving together with the wall. The motion of a cluster is associated with the transient formation of a fracture inside the sheared pack. The model is based on the existence of a persistence length for the fractures, which imposes a self-similar structure on the clusters. Through a probabilistic approach, we can evaluate the rate of appearance of a cluster of a given size and obtain a prediction for the average velocity profiles. We also predict the existence of large stress fluctuations at the moving wall, which characteristics are in good agreement with experimental data. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9901/9901336v2.pdf"}
{"id": "cond-mat9902064", "abstract": "  We show that the intermediate scattering function S_n(q,t) for neutron scattering (ns) can be expanded naturely with respect to a set of molecular correlation functions that give a complete description of the translational and orientational two-point correlations in the liquid. The general properties of this expansion are discussed with special focus on the q-dependence and hints for a (partial) determination of the molecular correlation functions from neutron scattering results are given. The resulting representation of the static structure factor S_n(q) is studied in detail for a model system using data from a molecular dynamics simulation of a supercooled liquid of rigid diatomic molecules. The comparison between the exact result for S_n(q) and different approximations that result from a truncation of the series representation demonstrates its good convergence for the given model system. On the other hand it shows explicitly that the coupling between translational (TDOF) and orientational degrees of freedom (ODOF) of each molecule and rotational motion of different molecules can not be neglected in the supercooled regime.Further we report the existence of a prepeak in the ns-static structure factor of the examined fragile glassformer, demonstrating that prepeaks can occur even in the most simple molecular liquids. Besides examining the dependence of the prepeak on the scattering length and the temperature we use the expansion of S_n(q) into molecular correlation functions to point out intermediate range orientational order as its principle origin. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9902/9902064v1.pdf"}
{"id": "cond-mat9902071", "abstract": "  We investigate the effective properties (conductivity, diffusivity and elastic moduli) of model random composite media derived from Gaussian random fields and overlapping hollow spheres. The morphologies generated in the models exhibit low percolation thresholds and give a realistic representation of the complex microstructure observed in many classes of composites. The statistical correlation functions of the models are derived and used to evaluate rigorous bounds on each property. Simulation of the effective conductivity is used to demonstrate the applicability of the bounds. The key morphological features which effect composite properties are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9902/9902071v1.pdf"}
{"id": "cond-mat9903174", "abstract": "  The crossover from thermal hopping to quantum tunneling is studied. We show that the decay rate Γ with dissipation can accurately be determined near the crossover temperature. Besides considering the Wentzel-Kramers-Brillouin (WKB) exponent, we also calculate contribution of the fluctuation modes around the saddle point and give an extended account of a previous study of crossover region. We deal with two dangerous fluctuation modes whose contribution can't be calculated by the steepest descent method and show that higher order couplings between the two dangerous modes need to be taken into considerations. At last the crossover from thermal hopping to quantum tunneling in the molecular magnet Mn_12Ac is studied. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9903/9903174v1.pdf"}
{"id": "cond-mat9905002", "abstract": "  Recent experiments on the S=1/2 antiferromagnetic chain compound, Cu benzoate, discovered an unexpected gap scaling as approximately the 2/3 power of an applied magnetic field. A theory of this gap, based on an effective staggered field, orthogonal to the applied uniform field, resulting from a staggered gyromagnetic tensor and a Dzyaloshinskii-Moriya interaction, leading to a sine-Gordon quantum field theory, has been developed. Here we discuss many aspects of this subject in considerable detail, including a review of the S=1/2 chain in a uniform field, a spin-wave theory analysis of the uniform plus staggered field problem, exact amplitudes for the scaling of gap, staggered susceptibility and staggered magnetization with field or temperature, intensities of soliton and breather peaks in the structure function and field and temperature dependence of the total susceptibility. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9905/9905002v1.pdf"}
{"id": "cond-mat9906422", "abstract": "  I-V characteristics of the high T_c superconductor Bi_2Sr_2Ca_1C_2O_8 shows a strong hysteresis, producing many branches. The origin of hysteresis jumps is studied by use of the model of multi-layered Josephson junctions proposed by one of the authors (T. K.). The charging effect at superconducting layers produces a coupling between the next nearest neighbor phase-differences, which determines the structure of hysteresis branches. It will be shown that a solution of phase motions is understood as a combination of rotating and oscillating phase-differences, and that, at points of hysteresis jumps, there occurs a change in the number of rotating phase-differences. Effects of dissipation are analyzed. The dissipation in insulating layers works to damp the phase motion itself, while the dissipation in superconducting layers works to damp relative motions of phase-differences. Their effects to hysteresis jumps are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9906/9906422v1.pdf"}
{"id": "cond-mat9906436", "abstract": "  We study spatio-temporal pattern formation in a ring of N oscillators with inhibitory unidirectional pulselike interactions. The attractors of the dynamics are limit cycles where each oscillator fires once and only once. Since some of these limit cycles lead to the same pattern, we introduce the concept of pattern degeneracy to take it into account. Moreover, we give a qualitative estimation of the volume of the basin of attraction of each pattern by means of some probabilistic arguments and pattern degeneracy, and show how are they modified as we change the value of the coupling strength. In the limit of small coupling, our estimative formula gives a perfect agreement with numerical simulations. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9906/9906436v1.pdf"}
{"id": "cond-mat9908199", "abstract": "  The diatomic linear chain of masses coupled by harmonic springs is a textboook model for vibrational normal modes (phonons) in crystals. In addition to propagating acoustic and optic branches, this model is known to support a “gap mode” localized at the surface, provided the atom at the surface has light rather than heavy mass. An elementary argument is given which explains this mode and provides values for the frequency and localization length. By reinterpreting this mode in different ways, we obtain the frequency and localization lengths for three other interesting modes: (1) the surface vibrational mode of a light mass impurity at the surface of a monatomic chain; (2) the localized vibrational mode of a stacking fault in a diatomic chain; and (3) the localized vibrational mode of a light mass impurity in a monatomic chain. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9908/9908199v1.pdf"}
{"id": "cond-mat9912108", "abstract": "  We generalize the earlier theory by Fredrickson [J. Rheol. v.38, 1045 (1994)] to study the orientational behaviour of the hexagonal phase of diblock copolymer melt subjected to steady shear flow. We use symmetry arguments to show that the orientational ordering in the hexagonal phase is a much weaker effect than in the lamellae. We predict the parallel orientation to be stable at low and the perpendicular orientation at high shear rates. Our analysis reproduces the experimental results by Tepe et al. [Macromolecules v.28, 3008 (1995)] and explains the difficulties in experimental observation of the different orientations in the hexagonal phase. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9912/9912108v1.pdf"}
{"id": "cs0306063", "abstract": "  Registration and management of users in a large scale Grid computing environment presents new challenges that are not well addressed by existing protocols. Within a single Virtual Organization (VO), thousands of users will potentially need access to hundreds of computing sites, and the traditional model where users register for local accounts at each site will present significant scaling problems. However, computing sites must maintain control over access to the site and site policies generally require individual local accounts for every user. We present here a model that allows users to register once with a VO and yet still provides all of the computing sites the information they require with the required level of trust. We have developed tools to allow sites to automate the management of local accounts and the mappings between Grid identities and local accounts. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0306/0306063v1.pdf"}
{"id": "cs0407044", "abstract": "  In this paper, we propose an effective search procedure that interleaves two steps: subproblem generation and subproblem solution. We mainly focus on the first part. It consists of a variable domain value ranking based on reduced costs. Exploiting the ranking, we generate, in a Limited Discrepancy Search tree, the most promising subproblems first. An interesting result is that reduced costs provide a very precise ranking that allows to almost always find the optimal solution in the first generated subproblem, even if its dimension is significantly smaller than that of the original problem. Concerning the proof of optimality, we exploit a way to increase the lower bound for subproblems at higher discrepancies. We show experimental results on the TSP and its time constrained variant to show the effectiveness of the proposed approach, but the technique could be generalized for other problems. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0407/0407044v1.pdf"}
{"id": "cs0505022", "abstract": "  The performance of collaborative beamforming is analyzed using the theory of random arrays. The statistical average and distribution of the beampattern of randomly generated phased arrays is derived in the framework of wireless ad hoc sensor networks. Each sensor node is assumed to have a single isotropic antenna and nodes in the cluster collaboratively transmit the signal such that the signal in the target direction is coherently added in the far- eld region. It is shown that with N sensor nodes uniformly distributed over a disk, the directivity can approach N, provided that the nodes are located sparsely enough. The distribution of the maximum sidelobe peak is also studied. With the application to ad hoc networks in mind, two scenarios, closed-loop and open-loop, are considered. Associated with these scenarios, the effects of phase jitter and location estimation errors on the average beampattern are also analyzed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0505/0505022v1.pdf"}
{"id": "cs0506079", "abstract": "  We give new proofs of soundness (all representable functions on base types lies in certain complexity classes) for Elementary Affine Logic, LFPL (a language for polytime computation close to realistic functional programming introduced by one of us), Light Affine Logic and Soft Affine Logic. The proofs are based on a common semantical framework which is merely instantiated in four different ways. The framework consists of an innovative modification of realizability which allows us to use resource-bounded computations as realisers as opposed to including all Turing computable functions as is usually the case in realizability constructions. For example, all realisers in the model for LFPL are polynomially bounded computations whence soundness holds by construction of the model. The work then lies in being able to interpret all the required constructs in the model. While being the first entirely semantical proof of polytime soundness for light logi cs, our proof also provides a notable simplification of the original already semantical proof of polytime soundness for LFPL. A new result made possible by the semantic framework is the addition of polymorphism and a modality to LFPL thus allowing for an internal definition of inductive datatypes. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0506/0506079v3.pdf"}
{"id": "cs0601023", "abstract": "  An algorithm for exact maximum likelihood(ML) decoding on tail-biting trellises is presented, which exhibits very good average case behavior. An approximate variant is proposed, whose simulated performance is observed to be virtually indistinguishable from the exact one at all values of signal to noise ratio, and which effectively performs computations equivalent to at most two rounds on the tail-biting trellis. The approximate algorithm is analyzed, and the conditions under which its output is different from the ML output are deduced. The results of simulations on an AWGN channel for the exact and approximate algorithms on the 16 state tail-biting trellis for the (24,12) Extended Golay Code, and tail-biting trellises for two rate 1/2 convolutional codes with memories of 4 and 6 respectively, are reported. An advantage of our algorithms is that they do not suffer from the effects of limit cycles or the presence of pseudocodewords. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0601/0601023v2.pdf"}
{"id": "cs0604075", "abstract": "  We investigate a prototypical agent-based model, the Naming Game, on random geometric networks. The Naming Game is a minimal model, employing local communications that captures the emergence of shared communication schemes (languages) in a population of autonomous semiotic agents. Implementing the Naming Games on random geometric graphs, local communications being local broadcasts, serves as a model for agreement dynamics in large-scale, autonomously operating wireless sensor networks. Further, it captures essential features of the scaling properties of the agreement process for spatially-embedded autonomous agents. We also present results for the case when a small density of long-range communication links are added on top of the random geometric graph, resulting in a \"small-world\"-like network and yielding a significantly reduced time to reach global agreement. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0604/0604075v3.pdf"}
{"id": "cs0612073", "abstract": "  We address the maximum attainable rate of fingerprinting codes under the marking assumption, studying lower and upper bounds on the value of the rate for various sizes of the attacker coalition. Lower bounds are obtained by considering typical coalitions, which represents a new idea in the area of fingerprinting and enables us to improve the previously known lower bounds for coalitions of size two and three. For upper bounds, the fingerprinting problem is modelled as a communications problem. It is shown that the maximum code rate is bounded above by the capacity of a certain class of channels, which are similar to the multiple-access channel. Converse coding theorems proved in the paper provide new upper bounds on fingerprinting capacity.   It is proved that capacity for fingerprinting against coalitions of size two and three over the binary alphabet satisfies 0.25 ≤ C_2,2≤ 0.322 and 0.083 ≤ C_3,2≤ 0.199 respectively. For coalitions of an arbitrary fixed size t, we derive an upper bound (tln2)^-1 on fingerprinting capacity in the binary case. Finally, for general alphabets, we establish upper bounds on the fingerprinting capacity involving only single-letter mutual information quantities. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0612/0612073v3.pdf"}
{"id": "cs9811009", "abstract": "  This paper presents a partial solution to a component of the problem of lexical choice: choosing the synonym most typical, or expected, in context. We apply a new statistical approach to representing the context of a word through lexical co-occurrence networks. The implementation was trained and evaluated on a large corpus, and results show that the inclusion of second-order co-occurrence relations improves the performance of our implemented lexical choice program. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/9811/9811009v1.pdf"}
{"id": "cs9905011", "abstract": "  The mortality related to cervical cancer can be substantially reduced through early detection and treatment. However, current detection techniques, such as Pap smear and colposcopy, fail to achieve a concurrently high sensitivity and specificity.   In vivo fluorescence spectroscopy is a technique which quickly, non-invasively and quantitatively probes the biochemical and morphological changes that occur in pre-cancerous tissue.   A multivariate statistical algorithm was used to extract clinically useful information from tissue spectra acquired from 361 cervical sites from 95 patients at 337, 380 and 460 nm excitation wavelengths. The multivariate statistical analysis was also employed to reduce the number of fluorescence excitation-emission wavelength pairs required to discriminate healthy tissue samples from pre-cancerous tissue samples. The use of connectionist methods such as multi layered perceptrons, radial basis function networks, and ensembles of such networks was investigated. RBF ensemble algorithms based on fluorescence spectra potentially provide automated, and near real-time implementation of pre-cancer detection in the hands of non-experts. The results are more reliable, direct and accurate than those achieved by either human experts or multivariate statistical algorithms. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/9905/9905011v1.pdf"}
{"id": "gr-qc0003029", "abstract": "  I describe a new algorithm for solving nonlinear wave equations. In this approach, evolution takes place on characteristic hypersurfaces. The algorithm is directly applicable to electromagnetic, Yang-Mills and gravitational fields and other systems described by second differential order hyperbolic equations. The basic ideas should also be applicable to hydrodynamics. It is an especially accurate and efficient way for simulating waves in regions where the characteristics are well behaved. A prime application of the algorithm is to Cauchy-characteristic matching, in which this new approach is matched to a standard Cauchy evolution to obtain a global solution. In a model problem of a nonlinear wave, this proves to be more accurate and efficient than any other present method of assigning Cauchy outer boundary conditions. The approach was developed to compute the gravitational wave signal produced by collisions of two black holes. An application to colliding black holes is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0003/0003029v1.pdf"}
{"id": "gr-qc0101030", "abstract": "  The tiny general relativistic Lense-Thirring effect can be measured by means of a suitable combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. This observable is affected, among other factors, by the Earth' s solid and ocean tides. They induce long-period orbital perturbations that, over observational periods of few years, may alias the detection of the gravitomagnetic secular trend of interest. In this paper we calculate explicitly the most relevant tidal perturbations acting upon LAGEOSs and assess their influence on the detection of the Lense-Thirring effect. The present day level of knowledge of the solid and ocean tides allow us to conclude that their influence on it ranges from almost 4", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0101/0101030v1.pdf"}
{"id": "gr-qc0105100", "abstract": "  Gravitational wave detectors will need optimal signal-processing algorithms to extract weak signals from the detector noise. Most algorithms designed to date are based on the unrealistic assumption that the detector noise may be modeled as a stationary Gaussian process. However most experiments exhibit a non-Gaussian “tail” in the probability distribution. This “excess” of large signals can be a troublesome source of false alarms. This article derives an optimal (in the Neyman-Pearson sense, for weak signals) signal processing strategy when the detector noise is non-Gaussian and exhibits tail terms. This strategy is robust, meaning that it is close to optimal for Gaussian noise but far less sensitive than conventional methods to the excess large events that form the tail of the distribution. The method is analyzed for two different signal analysis problems: (i) a known waveform (e.g., a binary inspiral chirp) and (ii) a stochastic background, which requires a multi-detector signal processing algorithm. The methods should be easy to implement: they amount to truncation or clipping of sample values which lie in the outlier part of the probability distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0105/0105100v2.pdf"}
{"id": "gr-qc0109016", "abstract": "  The hoop conjecture is well confirmed in momentarily static spaces, but it has not been investigated systematically for the system with relativistic motion. To confirm the hoop conjecture for non-time-symmetric initial data, we consider the initial data of two colliding black holes with momentum and search an apparent horizon that encloses two black holes. In testing the hoop conjecture, we use two definitions of gravitational mass : one is the ADM mass and the other is the quasi-local mass defined by Hawking. Although both definitions of gravitational mass give fairly consistent picture of the hoop conjecture, the hoop conjecture with the Hawking mass can judge the existence of an apparent horizon for wider range of parameters of the initial data compared to the ADM mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0109/0109016v1.pdf"}
{"id": "gr-qc0305036", "abstract": "  We study the definition of perturbations in the presence of a submanifold, like e.g. a brane. In the standard theory of cosmological perturbations, one compares quantities at the same coordinate points in the non-perturbed and the perturbed manifolds, identified via a (non-unique) mapping between the two manifolds. In the presence of a physical submanifold one needs to modify this definition in order to evaluate perturbations of quantities at the submanifold location. As an application, we compute the perturbed metric and the extrinsic curvature tensors at the brane position in a general gauge. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0305/0305036v1.pdf"}
{"id": "gr-qc0406116", "abstract": "  The energy method can be used to identify well-posed initial boundary value problems for quasi-linear, symmetric hyperbolic partial differential equations with maximally dissipative boundary conditions. A similar analysis of the discrete system can be used to construct stable finite difference equations for these problems at the linear level. In this paper we apply these techniques to some test problems commonly used in numerical relativity and observe that while we obtain convergent schemes, fast growing modes, or “artificial instabilities,” contaminate the solution. We find that these growing modes can partially arise from the lack of a Leibnitz rule for discrete derivatives and discuss ways to limit this spurious growth. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0406/0406116v1.pdf"}
{"id": "gr-qc0510106", "abstract": "  Charged stars have the potential of becoming charged black holes or even naked singularities. It is presented a set of numerical solutions of the Tolman-Oppenheimer-Volkov equations that represents spherical charged compact stars in hydrostatic equilibrium. The stellar models obtained are evolved forward in time integrating the Einstein-Maxwell field equations. It is assumed an equation of state of a neutron gas at zero temperature. The charge distribution is taken as been proportional to the rest mass density distribution. The set of solutions present an unstable branch, even with charge to mass ratios arbitrarily close to the extremum case. It is performed a direct check of the stability of the solutions under strong perturbations, and for different values of the charge to mass ratio. The stars that are in the stable branch oscillates and do not collapse, while models in the unstable branch collapse directly to form black holes. Stars with a charge greater or equal than the extreme value explode. When a charged star is suddenly discharged, it don't necessarily collapse to form a black hole. A non-linear effect that gives rise to the formation of an external shell of matter (see Ghezzi and Letelier 2005), is negligible in the present simulations. The results are in agreement with the third law of black hole thermodynamics and with the cosmic censorship conjecture. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0510/0510106v1.pdf"}
{"id": "gr-qc0601102", "abstract": "  The evolution of the methods used to find solutions of Einstein's field equations during the last 100 years is described. Early papers used assumptions on the coordinate forms of the metrics. Since the 1950s more invariant methods have been deployed in most new papers. The uses to which the solutions found have been put are discussed, and it is shown that they have played an important role in the development of many aspects, both mathematical and physical, of general relativity. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0601/0601102v2.pdf"}
{"id": "gr-qc0607055", "abstract": "  Field theories whose full action is Lorentz invariant (or diffeomorphism invariant) can exhibit superluminal behaviors through the breaking of local Lorentz invariance. Quantum induced superluminal velocities are well-known examples of this effect. The issue of the causal behavior of such propagations is somewhat controversial in the literature and we intend to clarify it. We provide a careful analysis of the meaning of causality in classical relativistic field theories, and we stress the role played by the Cauchy problem and the notions of chronology and time arrow. We show that superluminal behavior threaten causality only if a prior chronology on spacetime is chosen. In the case where superluminal propagations occur, however, there is at least two non conformally related metrics on spacetime and thus two available notions of chronology. These two chronologies are on equal footing and it would thus be misleading to choose ab initio one of them to define causality. Rather, we provide a formulation of causality in which no prior chronology is assumed. We argue this is the only way to deal with the issue of causality in the case where some degrees of freedom propagate faster than others. We actually show that superluminal propagations do not threaten causality. As an illustration of these conceptual issues, we consider two field theories, namely k-essences scalar fields and bimetric theories of gravity, and we derive the conditions imposed by causality. We discuss various applications such as the dark energy problem, MOND-like theories of gravity and varying speed of light theories. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0607/0607055v2.pdf"}
{"id": "gr-qc0611052", "abstract": "  We consider full perturbations to a covariantly defined Schwarzschild spacetime. By constructing complex quantities, we derive two decoupled, covariant and gauge-invariant, wave-like equations for spin-weighted scalars. These arise naturally from the Bianchi identities and comprise a covariant representation of the Bardeen-Press equations for scalars with spin-weight ±2. Furthermore, the covariant and gauge-invariant 1+1+2 formalism is employed, and consequently, the physical interpretation of the energy-momentum perturbations is transparent. They are written explicitly in terms of the energy-momentum specified on spacelike three-slices. Ultimately, a Cauchy problem is constructed whereby, an initial three-slice may be perturbed by an energy-momentum source, which induces resultant gravitational fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0611/0611052v1.pdf"}
{"id": "gr-qc0702088", "abstract": "  Physical consequences from gravitation equations based on Poincaré ideas of relativity of space and time in respect of measuring instruments are considered. The most interesting of them are the possibility of the existence of stable supermassive configurations (10^2÷ 10^12 M_⊙) which can exist in galactic centres, and an explanation of the acceleration of the Universe expansion as a manifestation of the gravitational force properties in the theory under consideration. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0702/0702088v3.pdf"}
{"id": "gr-qc0703058", "abstract": "  In the context of a gravity's rainbow, the asymptotic quasinormal modes of the scalar perturbation in the quantum modified Schwarzschild black holes are investigated. By using the monodromy method, we calculated and obtained the asymptotic quasinormal frequencies, which are dominated not only by the mass parameter of the spacetime, but also by the energy functions from the modified dispersion relations. However, the real parts of the asymptotic quasinormal modes is still T_Hln 3, which is consistent with Hod's conjecture. In addition, for the quantum corrected black hole, the area spacing is calculated and the result is independent of the energy functions, in spite of the area itself is energy dependence. And that, by relating the area spectrum to loop quantum gravity, the Barbero-Immirzi parameter is given and it remains the same as from the usual black hole. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0703/0703058v1.pdf"}
{"id": "gr-qc9508017", "abstract": "  This article is intended to provide a pedagogical account of issues related to, and recent work on, gravitational waves from coalescing compact binaries (composed of neutron stars and/or black holes). These waves are the most promising for kilometer-size interferometric detectors such as LIGO and VIRGO. Topics discussed include: interferometric detectors and their noise; coalescing compact binaries and their gravitational waveforms; the technique of matched filtering for signal detection and measurement; waveform calculations in post-Newtonian theory and in the black-hole perturbation approach; and the accuracy of the post-Newtonian expansion. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9508/9508017v1.pdf"}
{"id": "gr-qc9705034", "abstract": "  We ascertain the effectiveness of the second post-Newtonian approximation to the gravitational waves emitted during the adiabatic inspiral of a compact binary system as templates for signal searches with kilometer-scale interferometric detectors. The reference signal is obtained by solving the Teukolsky equation for a small mass moving on a circular orbit around a large nonrotating black hole. Fitting factors computed from this signal and these templates, for various types of binary systems, are all above the 90", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9705/9705034v1.pdf"}
{"id": "gr-qc9712079", "abstract": "  A spherical gravitational wave antenna is distinct from other types of gravitational wave antennas in that only a single detector is necessary to determine the direction and polarization of a gravitational wave. Zhou and Michelson showed that the inverse problem can be solved using the maximum likelihood method if the detector outputs are independent and have normally distributed noise with the same variance. This paper presents an analytic solution using only linear algebra that is found to produce identical results as the maximum likelihood method but with less computational burden. Applications of this solution to gravitational waves in alternative symmetric metric theories of gravity and impulsive excitations also are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9712/9712079v2.pdf"}
{"id": "gr-qc9801060", "abstract": "  We study the nonlinear gravitational collapse of a charged massless scalar-field. We confirm the existence of oscillatory inverse power-law tails along future timelike infinity, future null infinity and along the future outer-horizon. The nonlinear dumping exponents are in excellent agreement with the analytically predicted ones. Our results prove the analytic conjecture according to which a charged hair decays slower than a neutral one and also suggest the occurrence of mass-inflation along the Cauchy horizon of a dynamically formed charged black-hole. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9801/9801060v2.pdf"}
{"id": "hep-ex0012045", "abstract": "  After a quick review of astrophysically relevant limits, I present a summary of MeV scale tau neutrino mass limits derived from accelerator based experiments.   I argue that the current published limits appear to be too consistent, and that we therefore cannot conclude that the tau neutrino mass limit is as low as usually claimed. I provide motivational arguments calling into question the assumed statistical properties of the usual maxumum likelihood estimators, and provide a prescription for deriving a more robust and understandable mass limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0012/0012045v1.pdf"}
{"id": "hep-ex0102028", "abstract": "  The production of fast neutrons (1 MeV - 1 GeV) in high energy muon-nucleus interactions is poorly understood, yet it is fundamental to the understanding of the background in many underground experiments. The aim of the present experiment (CERN NA55) was to measure spallation neutrons produced by 190 GeV/c muons scattering on carbon, copper and lead targets. We have investigated the energy spectrum and angular distribution of spallation neutrons, and we report the result of our measurement of the neutron production differential cross section. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0102/0102028v3.pdf"}
{"id": "hep-ex0209036", "abstract": "  This paper presents the recent results from Super-Kamiokande atmospheric neutrinos and from K2K accelerator neutrinos. Both results show the signal of neutrino oscillation, and provide new and precise information of oscillation parameters. The oscillation parameters are constraint to be between 1.5*10^-3 eV^2 and 3.9*10^-3 eV^2 for Δm^2 and to be greater than 0.92 for sin^2 2θ. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0209/0209036v1.pdf"}
{"id": "hep-ex0405016", "abstract": "  A low-energy γγ collider has been discussed in the context of a testbed for a γγ interaction region at the Next Linear Collider (NLC). We consider the production of heavy mesons at such a testbed using Compton-backscattered photons and demonstrate that their production rivals or exceeds those by BELLE, BABAR or LEP where they are produced indirectly via virtual γγ luminosities. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0405/0405016v1.pdf"}
{"id": "hep-ex0611023", "abstract": "  The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode, through the study of nu_mu to nu_tau oscillations. The apparatus consists of a lead/emulsion-film target complemented by electronic detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. In August 2006 a first run with CNGS neutrinos was successfully conducted. A first sample of neutrino events was collected, statistically consistent with the integrated beam intensity. After a brief description of the beam and of the various sub-detectors, we report on the achievement of this milestone, presenting the first data and some analysis results. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/0611/0611023v1.pdf"}
{"id": "hep-ex9509014", "abstract": "  We report a large enhancement of 1.7 in deuteron polarization up to values of 0.6 due to frequency modulation of the polarizing microwaves in a two liters polarized target using the method of dynamic nuclear polarization. This target was used during a deep inelastic polarized muon-deuteron scattering experiment at CERN. Measurements of the electron paramagnetic resonance absorption spectra show that frequency modulation gives rise to additional microwave absorption in the spectral wings. Although these results are not understood theoretically, they may provide a useful testing ground for the deeper understanding of dynamic nuclear polarization. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ex/pdf/9509/9509014v1.pdf"}
{"id": "hep-lat0010050", "abstract": "  The geometry of 4D simplicial quantum gravity with a U(1) gauge field is studied numerically. The phase diagram shows a continuous transition when gravity is coupled with a U(1) gauge field. At the critical point measurements of the curvature distribution of S^4 space shows an inflated geometry with homogeneous and symmetric nature. Also, by choosing a 4-simplex and fixing the scalar curvature geometry of the space is measured. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0010/0010050v2.pdf"}
{"id": "hep-lat0110125", "abstract": "  Cluster variables have recently revolutionized numerical work in certain models involving fermionic variables. This novel representation of fermionic partition functions is continuing to find new applications. After describing results from a study of a two dimensional Hubbard type model that confirm a superconducting transition in the Kosterlitz-Thouless universality class, we show how a cluster type algorithm can be devised to study the chiral limit of strongly coupled lattice gauge theories with staggered fermions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0110/0110125v1.pdf"}
{"id": "hep-lat0207021", "abstract": "  The critical behaviour of several spin models can be simply described as percolation of some suitably defined clusters, or droplets: the onset of the geometrical transition coincides with the critical point and the percolation exponents are equal to the thermal exponents. It is still unknown whether, given a model, one can define at all the droplets. In the cases where this is possible, the droplet definition depends in general on the specific model at study and can be quite involved. We propose here a simple general definition for the droplets: they are clusters obtained by joining nearest-neighbour spins of the same sign with some bond probability p_B, which is the minimal probability that still allows the existence of a percolating cluster at the critical temperature T_c. By means of lattice Monte Carlo simulations we find that this definition indeed satisfies the conditions required for the droplets, for many classical spin models, discrete and continuous, both in two and in three dimensions. In particular, our prescription allows to describe exactly the confinement-deconfinement transition of SU(N) gauge theories as Polyakov loop percolation. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0207/0207021v1.pdf"}
{"id": "hep-lat0310047", "abstract": "  We present a chronological review of the progress in calculating weak matrix elements using staggered fermions. We review the perturbative calculation of one-loop matching formula including both current-current diagrams and penguin diagrams using improved staggered fermions. We also present preliminary results of weak matrix elements relevant to CP violation calculated using the improved (HYP (II)) staggered fermions. Since the complete set of matching coefficients at the one-loop level became available recently, we have constructed lattice operators with all the g^2 corrections included. The main results include both Δ I = 3/2 and Δ I = 1/2 contributions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0310/0310047v1.pdf"}
{"id": "hep-lat0609010", "abstract": "  Time correlation functions of a hybrid exotic meson operator, with JPC=1-+, generated in quenched lattice QCD are subjected to a (Bayesian) maximum entropy analysis. Five distinct spectral levels are uncovered. Their extrapolation into the physical pion mass region suggests a possible relationship to experimentally known states pi1(1400) and pi1(1600), and also to a state in the 2 GeV region carrying the same quantum numbers. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0609/0609010v1.pdf"}
{"id": "hep-lat9807031", "abstract": "  We propose various improvements of finite step-size updating for full QCD on the lattice that might turn finite step-size updating into a viable alternative to the hybrid Monte Carlo algorithm. These improvements are noise reduction of the noisy estimator of the fermion determinant, unbiased inclusion of the hopping parameter expansion and a multi-level Metropolis scheme. First numerical tests are performed for the 2 dimensional Schwinger model with two flavours of Wilson fermions and for QCD two flavours of Wilson fermions and Schr\"odinger functional boundary conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/9807/9807031v1.pdf"}
{"id": "hep-ph0101231", "abstract": "  I have discussed in my talk several remaining issues in the standard three-flavor mixing scheme of neutrinos, in particilar, the sign of Δ m^2_13 and the leptonic CP violating phase. In this report I focus on two topics: (1) supernova method for determining the former sign, and (2) illuminating how one can detect the signatures for both of them in long-baseline (10 km) neutrino oscillation experiments. I do this by formulating perturbative frameworks appropriate for the two typical options of such experiments, the high energy and the low energy options with beam energies of ∼ 10 GeV and ∼ 100 MeV, respectively. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0101/0101231v1.pdf"}
{"id": "hep-ph0111093", "abstract": "  We study the dipole picture for the description of the deep inelastic scattering, focusing on the structure functions which are driven directly by the gluon distribution. One performs estimates using the effective dipole cross section given by the Glauber-Mueller approach in QCD, which encodes the corrections due to the unitarity effects associated with the saturation phenomenon. We also address issues about frame invariance of the calculations when analysing the observables. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0111/0111093v2.pdf"}
{"id": "hep-ph0206257", "abstract": "  It has recently been suggested that the existence of bare strange stars is incompatible with low scale gravity scenarios. It has been claimed that in such models, high energy neutrinos incident on the surface of a bare strange star would lead to catastrophic black hole growth. We point out that for the flat large extra dimensional case, the parts of parameter space which give rise to such growth are ruled out by other methods. We then go on to show in detail how black holes evolve in the the Randall-Sundrum two brane scenario where the extra dimensions are curved. We find that catastrophic black hole growth does not occur in this situation either. We also present some general expressions for the growth of five dimensional black holes in dense media. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0206/0206257v3.pdf"}
{"id": "hep-ph0207331", "abstract": "  We study the consequences of noise and dissipation for parametric resonance during preheating. The effective equations of motion for the inflaton and the radiation field are obtained and shown to present self-consistent noise and dissipation terms. The equations exhibit the usual parametric resonance phenomenon, allowing for exponential amplification of the radiation modes inside the instability bands. By focusing on the dimension of the border of those bands we explicitly show that they are fractal, indicating the strong dependence of the outcome in the initial conditions. The simultaneous effect of noise and dissipation to the fractality of the borders are then examined. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0207/0207331v1.pdf"}
{"id": "hep-ph0304011", "abstract": "  One of the main aims of present and upcoming high energy heavy ion collision experiments is to study new phases of matter at extreme temperature and density. It is expected that a nontrivial classical pion field configuration can occasionally form during the out-of-equilibrium chiral phase transition. We have recently shown that, contrarily to what has been assumed so far, this configuration is not identical to the so-called disoriented chiral condensate (DCC), proposed in the early 1990's. A detailed analysis reveals that a more realistic picture is that of an “unpolarized” DCC, where the Fourier modes of the field have completely independent orientations in isospin space instead of being aligned with each other as in the original DCC. This has important implications concerning the possible detection of the phenomenon. In particular, the main expected signature of the original DCC, which is used in most experimental searches, is absent in the unpolarized case. We point out that the fact that no evidence of DCC formation has been reported so far in nuclear collisions actually agrees with our present theoretical understanding. New experimental strategies should be designed to look for the unpolarized DCC in existing data from SPS as well as in future searches at RHIC and LHC. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0304/0304011v1.pdf"}
{"id": "hep-ph0305018", "abstract": "  We solve the homogeneous Bethe-Salpeter (HBS) equation for the scalar, pseudoscalar, vector, and axial-vector bound states of quark and anti-quark in large Nf QCD with the improved ladder approximation in the Landau gauge. The quark mass function in the HBS equation is obtained from the Schwinger-Dyson (SD) equation in the same approximation for consistency with the chiral symmetry. Amazingly, due to the fact that the two-loop running coupling of large Nf QCD is explicitly written in terms of an analytic function, large Nf QCD turns out to be the first example in which the SD equation can be solved in the complex plane and hence the HBS equation directly in the time-like region. We find that approaching the chiral phase transition point from the broken phase, the scalar, vector, and axial-vector meson masses vanish to zero with the same scaling behavior, all degenerate with the massless pseudoscalar meson. This may suggest a new type of manifestation of the chiral symmetry restoration in large Nf QCD. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0305/0305018v2.pdf"}
{"id": "hep-ph0306054", "abstract": "  A portion of the HEP community has perceived the need for a minimization package written in C++ and taking advantage of the Object-Oriented nature of that langauge. To be acceptable for HEP, such a package must at least encompass all the capabilities of Minuit. Aside from the slight plus of not relying on outside Fortran compilation, the advantages that a C++ package based on O-O design would confer over the multitude of available C++ Minuit-wrappers include: Easier extensibility to different algorithms and forms opf constraints; and usage modes which would not be available in the global-common-based Minuit design. An example of the latter is a job persuing two ongoing minimization problems simultaneously. We discuss the design and implementation of such a package, which extends Minuit only in minor ways but which greatly diminishes the programming effort (if not the algorithm thought) needed to make more significant extensions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0306/0306054v1.pdf"}
{"id": "hep-ph0308175", "abstract": "  It has been estimated that the entire Earth generates heat corresponding to about 40 TW (equivalent to 10,000 nuclear power plants) which is considered to originate mainly from the radioactive decay of elements like U, Th and K, deposited in the crust and mantle of the Earth. Radioactivity of these elements produce not only heat but also antineutrinos (called geo-antineutrinos) which can be observed by terrestrial detectors. We investigate the possibility of discriminating among Earth composition models predicting different total radiogenic heat generation, by observing such geo-antineutrinos at Kamioka and Gran Sasso, assuming KamLAND and Borexino (type) detectors, respectively, at these places. By simulating the future geo-antineutrino data as well as reactor antineutrino background contributions, we try to establish to which extent we can discriminate among Earth composition models for given exposures (in units of kt· yr) at these two sites on our planet. We use also information on neutrino mixing parameters coming from solar neutrino data as well as KamLAND reactor antineutrino data, in order to estimate the number of geo-antineutrino induced events. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0308/0308175v2.pdf"}
{"id": "hep-ph0310114", "abstract": "  One of the main activities in high-energy and nuclear physics is the search for the so-called quark-gluon plasma, a new state of matter which should have existed a few microseconds after the Big Bang. A quark-gluon plasma consists of free color charges, i.e. quarks and gluons, interacting by the strong (instead of electromagnetic) force. Theoretical considerations predict that the critical temperature for the phase transition from nuclear matter to a quark-gluon plasma is about 150 - 200 MeV. In the laboratory such a temperature can be reached in a so-called relativistic heavy-ion collision in accelerator experiments. Using the color charge instead of the electric charge, the Coulomb coupling parameter of such a system is of the order 10 - 30. Hence the quark-gluon plasma is a strongly coupled, relativistic plasma, in which also quantum effects are important. In the present work the experimental and theoretical status of the quark-gluon plasma physics will be reviewed, emphasizing the similarities and differences with usual plasma physics. Furthermore, the mixed phase consisting of free quarks and gluons together with hadrons (e.g. pions) will be discussed, which can be regarded as a complex plasma due to the finite extent of the hadrons. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0310/0310114v1.pdf"}
{"id": "hep-ph0310146", "abstract": "  We consider the breaking of the global conservation of gauge field charges which are commonly thought to survive the spontaneous breakdown of gauge symmetry brought about by Kalb-Ramond fields. Depending on the dilaton field and also the size of the compactifying space, the global charge breaking may take place due to world sheet instantons. In going to 3+1 dimensions one could have a serious problem in order to produce the hierarchies between the quark and the charged lepton masses using the mass protecting charges with the Green-Schwartz anomaly cancellation. Various unnatural features of this type of models are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0310/0310146v2.pdf"}
{"id": "hep-ph0404042", "abstract": "  Solar neutrino physics enters a stage of precision measurements. In this connection we present a precise analytic description of the neutrino conversion in the context of LMA MSW solution of the solar neutrino problem. Using the adiabatic perturbation theory we derive an analytic formula for the ν_e survival probability which takes into account the non-adiabatic corrections and the regeneration effect inside the Earth. The probability is averaged over the neutrino production region. We find that the non-adiabatic corrections are of the order 10^-9-10^-7. Using the formula for the Earth regeneration effect we discuss features of the zenith angle dependence of the ν_e flux. In particular, we show that effects of small structures at the surface of the Earth can be important. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0404/0404042v3.pdf"}
{"id": "hep-ph0405104", "abstract": "  The classical Einstein gravity description of black hole production in transplanckian collisions in TeV-scale gravity is tested for self-consistency. In addition to the \"curvature must be small\" test, which was shown to be violated in [hep-ph/0401116], it is proposed to estimate quantum fluctuations in the Aichelburg-Sexl shock waves corresponding to the colliding particles. Using linearized quantum gravity, it is found that the occupation numbers of gravitons with characteristic frequency are too small to resolve the classical width of the shocks. This raises further doubts in the classical gravity picture of black hole creation and the geometric cross section estimate based on it. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0405/0405104v1.pdf"}
{"id": "hep-ph0405252", "abstract": "  The numerical solution for the B=2 static soliton of the SU(2) Skyrme model shows a profile function dependence which is not exactly radial. We propose to quantify this with the introduction of an axially symmetric oblate ansatz parametrized by a scale factor d. We then obtain a relatively deformed bound soliton configuration with M_B=2/M_B=1=1.958. This is the first step towards to description of B>1 quantized states such as the deuteron with a non-rigid oblate ansatz where deformations due to centrifugal effects are expected to be more important. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0405/0405252v2.pdf"}
{"id": "hep-ph0406307", "abstract": "  We analytically discuss the resonance conditions among several neutrinos in matter. The discriminant for the characteristic equation of the Hamiltonian is expressed by the coefficients of the equation. The result of the computation for the discriminants tells us that the neutrino energy and the matter density are in inverse proportion to each other at the resonance states in not only 2- but also 3- and 4-neutrino models. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0406/0406307v3.pdf"}
{"id": "hep-ph0411012", "abstract": "  By assuming the existence of the sequential fourth generation to the minimal supersymmetric standard model (MSSM), we study the possibility of a strongly first-order electroweak phase transition. We find that there is a parameter region of the MSSM where the electroweak phase transition is strongly first order. In that parameter region, the mass of the lighter scalar Higgs boson is calculated to be above the experimental lower bound, and the scalar quarks of the third and the fourth generations are heavier than the corresponding quarks. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0411/0411012v2.pdf"}
{"id": "hep-ph0503271", "abstract": "  Precision measurements of anisotropies in the cosmic microwave background and of the clustering of large-scale structure have supposedly confirmed that the primordial density perturbation has a (nearly) scale-invariant spectrum. However this conclusion is based on assumptions about the world model and the nature of the dark matter. Physical models of inflation suggest that the spectrum may not in fact be scale-free, which would imply rather different cosmological parameters on the basis of the same observational data. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0503/0503271v2.pdf"}
{"id": "hep-ph0506235", "abstract": "  We investigate the space of functions in which the BFKL kernel acts. For the amplitudes which describe the scattering of colorless projectiles it is convenient to define, in transverse coordinates, the Moebius space in which the solutions to the BFKL equation vanish as the coordinates of the two reggeized gluons coincide. However, in order to fulfill the bootstrap relation for the BFKL kernel it is necessary to modify the space of functions. We define and investigate a new space of functions and show explicitly that the bootstrap relation is valid for the corresponding spectral form of the kernel. We calculate the generators of the resulting deformed representation of the sl(2,C) algebra. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0506/0506235v1.pdf"}
{"id": "hep-ph0508113", "abstract": "  The left-right supersymmetric model contains a right-handed gaugino, as well as several higgsinos, in addition to the minimal supersymmetric model. Thus several CP-noninvariant phases appear in this sector. We analyze their impact on chargino masses and find that only two combinations are physically relevant. We then study the production of charginos in e+e- annihilation and chargino decays into a sneutrino and a lepton, and investigate the effects of CP-phases. We also study the CP-odd asymmetry in the production and subsequent decay at the linear collider with longitudinally polarized beams and find a large enhancement when the decay channel to the right sneutrino is available. The effects of the phases in the left-right supersymmetric chargino sector are different from the minimal supersymmetric standard model, and signals from this sector would be able to distinguish between different gauge symmetries. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0508/0508113v2.pdf"}
{"id": "hep-ph0508181", "abstract": "  The synergy between the Large Hadron Collider and the International Linear Collider during concurrent running of the two machines has the potential to maximise the physics gain from both facilities. Some examples of detailed case studies of the interplay between the LHC and ILC are given, with a particular emphasis on new results that have been obtained after the first LHC / ILC Study Group report was released. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0508/0508181v1.pdf"}
{"id": "hep-ph0509298", "abstract": "  The evaluation of Yukawa-enhanced two-loop contributions to the MSSM Higgs-boson mass is considered. We prove the common assumption that regularization by dimensional reduction preserves supersymmetry at the required level. Thus generating counterterms by multiplicative renormalization is correct. Technically, we identify a suitable Slavnov-Taylor identity, use a recently developed method to evaluate it at the two-loop level, and show that it is valid in dimensional reduction. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0509/0509298v1.pdf"}
{"id": "hep-ph0510252", "abstract": "  Uncertainties of the MSSM predictions are due to an unknown SUSY breaking mechanism. To reduce these uncertainties, one usually imposes constraints on the MSSM parameter space. Recently, two new constraints became available, both from astrophysics: WMAP precise measurement of the amount of the Dark Matter in the Universe and EGRET data on an excess in diffuse gamma ray flux. Being interpreted as a manifestation of supersymmetry these data lead to severe constraints on parameter space and single out a very restricted area. The key feature of this area is the splitting of light gauginos from heavy squarks and sleptons. We study the phenomenological properties of this scenario, in particular, the cross-sections of superparticle production, their decay patterns and signatures for observation at hadron colliders, Tevatron and LHC. We found that weakly interacting particles in this area are very light so that the cross-sections may reach fractions of a pb with jets and/or leptons as final states accompanied by missing energy taken away by light neutralino with a mass around 100 GeV. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0510/0510252v2.pdf"}
{"id": "hep-ph0511069", "abstract": "  The skewing factor, defined as the ratio of the imaginary parts of the amplitudes Im A(γ^* p →γ^* p)/Im A(γ^* p →γ p) is extracted for the first time from the data using recent Deeply Virtual Compton Scattering (DVCS) and the inclusive inelastic cross section measurements at DESY-HERA. The results values are compared to theoretical predictions for NLO QCD and the colour dipole approach. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0511/0511069v1.pdf"}
{"id": "hep-ph0511214", "abstract": "  Saturation is expected to occur when a high density of partons (mainly gluons)- or equivalently strong fields in Quantum Chromodynamics (QCD) - is realized in the weak coupling regime. A way to reach saturation is through the high-energy evolution of an extended target probed at a fixed hard scale. In this case, the transition to saturation is expected to occur from nonlinear perturbative QCD dynamics. We discuss this approach to saturation, which is mathematically characterized by the appearance of traveling wave patterns in a suitable kinematical representation. A short review on traveling waves in high energy QCD and a first evidence of this phenomenon in deep-inelastic proton scattering are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0511/0511214v1.pdf"}
{"id": "hep-ph0601016", "abstract": "  We review the main proposals of particle physics for the composition of the cold dark matter in the universe. Strong axion contribution to cold dark matter is not favored if the Peccei-Quinn field emerges with non-zero value at the end of inflation and the inflationary scale is superheavy since, under these circumstances, it leads to unacceptably large isocurvature perturbations. The lightest neutralino is the most popular candidate constituent of cold dark matter. Its relic abundance in the constrained minimal supersymmetric standard model can be reduced to acceptable values by pole annihilation of neutralinos or neutralino-stau coannihilation. Axinos can also contribute to cold dark matter provided that the reheat temperature is adequately low. Gravitinos can constitute the cold dark matter only in limited regions of the parameter space. We present a supersymmetric grand unified model leading to violation of Yukawa unification and, thus, allowing an acceptable b-quark mass within the constrained minimal supersymmetric standard model with mu>0. The model possesses a wide range of parameters consistent with the data on the cold dark matter abundance as well as other phenomenological constraints. Also, it leads to a new version of shifted hybrid inflation. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0601/0601016v3.pdf"}
{"id": "hep-ph0604193", "abstract": "  Phenomenological bounds on the neutrino mixing matrix U are used to determine numerically the allowed range of real elements (CP conserving case) for the symmetric neutrino mass matrix Mn (Majorana case). For this purpose an adaptive Monte Carlo generator has been used. Histograms are constructed to show which forms of the neutrino mass matrix Mn are possible and preferred. We confirm results found in the literature which are based on analytical calculations, though a few differences appear. These cases correspond to some textures with two zeros. The results show that actually both normal and inverted mass hierarchies are still possible at 3 sigma confidence level. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0604/0604193v2.pdf"}
{"id": "hep-ph0611247", "abstract": "  The structure of events in high-energy collisions is complex and not predictable from first principles. Event generators allow the problem to be subdivided into more manageable pieces, some of which can be described from first principles, while others need to be based on appropriate models with parameters tuned to data. In these lectures we provide an overview, discuss how matrix elements are used, introduce the machinery for initial- and final-state parton showers, explain how matrix elements and parton showers can be combined for optimal accuracy, introduce the concept of multiple parton–parton interactions, comment briefly on the hadronization issue, and provide an outlook for the future. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0611/0611247v1.pdf"}
{"id": "hep-ph0612306", "abstract": "  The anomaly of a discrete symmetry is defined as the Jacobian of the path-integral measure. Assuming that the anomaly at low energies is cancelled by the Green-Schwarz (GS) mechanism at a fundamental scale, we investigate possible Kac-Moody levels for anomalous discrete family symmetries. As the first example, we consider discrete abelian baryon number and lepton number symmetries in the minimal supersymmetric standard model with the see-saw mechanism, and we find that the ordinary unification of gauge couplings is inconsistent with the GS conditions, indicating the possible existence of further Higgs doublets. We consider various recently proposed supersymmetric models with a non-abelian discrete family symmetry. In a supersymmetric example with Q_6 family symmetry, the GS conditions are such that the gauge coupling unification appears close to the Planck scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0612/0612306v2.pdf"}
{"id": "hep-ph9307259", "abstract": "  We have performed a complete one-loop calculation of γγ→ ZZ in the Standard Model, including both gauge bosons and fermions in the loop. We confirm the large irreducible continuum background from the W-boson loop found by Jikia. We have included the photon-photon luminosity, and find that the continuum background of transverse Z boson pairs prohibits finding a heavy Higgs with mass 350 GeV in this decay mode. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9307/9307259v1.pdf"}
{"id": "hep-ph9403374", "abstract": "  We assume that nucleon antinucleon annihilation is a fast process leading to a classical coherent pion pulse. We develop the quantum description of such pion waves based on the method of coherent states. We study the consequences of such a description for averages of charge types and moments of distributions of pion momenta with iso-spin and four-momentum conservation taken into account. We briefly discuss the applicability of our method to annihilation at rest, where we find agreement with experiment, and suggest other avenues for its use. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9403/9403374v1.pdf"}
{"id": "hep-ph9511416", "abstract": "  It is claimed that radiative corrections maintain the proportionality between the neutrino mass and the neutrino-majoron coupling and never give rise to enhanced decay rates in conventional majoron models. The coupling of a majoron to neutrinos is calculated at one loop level in various models, including the singlet majoron model and the Zee model with a majoron. When the respective corrections to the mass matrix are taken into account the would-be non-diagonal terms in the neutrino-majoron coupling are rotated away. It is pointed out that the coincidence between neutrino mass matrices and neutrino-majoron couplings is not accidental, but is a general consequence of Noether's theorem. Noether's theorem also implies that the majoron coupling to charged fermions is always diagonal in the fermion mass basis, and it vanishes completely in the singlet majoron models. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9511/9511416v1.pdf"}
{"id": "hep-ph9602258", "abstract": "  Open heavy flavour production at e^+e^- colliders in deeply inelastic eγ scattering has an interesting feature: the structure function F_2(x,Q^2) for this process is calculable for x>0.01, and is essentially proportional to the gluon density in the photon for smaller x values. We give estimates for event rates at LEP2 and a Next Linear Collider in x,Q^2 bins, and present differential distributions in the transverse momentum and rapidity of the heavy quark for the case of charm. We include all next-to-leading-order QCD corrections, and find theoretical uncertainties are well under control. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9602/9602258v1.pdf"}
{"id": "hep-ph9605328", "abstract": "  A formalism for studying heavy quarks in terms of model Dyson-Schwinger equations is developed. The formalism is the natural extension of a technique which has proved successful in a number of studies of light hadron physics. The dressed heavy quark propagator, calculated to leading order in the inverse quark mass, is incorporated in a treatment of mesons consisting of a heavy quark and light antiquark via the ladder approximation Bethe-Salpeter equation. In the limit of infinite heavy quark mass the model is found to respect the spectrum degeneracies present in Heavy Quark Effective Theory. An exploratory numerical analysis of a simple form of the model is carried out to assess its viability for studying D and B mesons. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9605/9605328v2.pdf"}
{"id": "hep-ph9612206", "abstract": "  Until the mystery of confinement is understood from the first principles, so called `soft physics' remains an important area of research, providing valuable information on underlying dynamics of strong interactions at long distances. In this short review an attempt is made to summarize recent experimental results on multiparticle production in e+e- annihilation and on diffraction at HERA. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9612/9612206v3.pdf"}
{"id": "hep-ph9703302", "abstract": "  We present a next-to-leading order calculation for the virtual photoproduction of one and two jets in ep collisions. Soft and collinear singularities are extracted using the phase space slicing method. The collinear photon initial state singularity depends logarithmically on the mass of the virtual photon and is absorbed into the virtual photon structure function. An MS factorization scheme is defined similarly to the real photon case. Numerical results are presented for HERA conditions using the Snowmass jet definition for inclusive single jet and dijet cross sections. We study the dependence of these cross sections on the transverse energies and rapidities of the jets. Finally, we compare the ratio of the experimentally defined resolved and direct cross sections with recent ZEUS data as a function of the photon virtuality P^2. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9703/9703302v1.pdf"}
{"id": "hep-ph9710499", "abstract": "  A successful interpretation of the cross sections for elastic and inelastic vector meson production can be made if one assumes the underlying dynamics to be governed by hard partonic subprocesses. Extending these partonic approaches to longitudinally polarized electron-proton collisions, we estimate the expected production asymmetries at the HERA collider. The anticipated statistical errors on these asymmetries mostly turn out to be larger than the asymmetries themselves, such that an experimental observation of these asymmetries at HERA looks not feasible. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9710/9710499v1.pdf"}
{"id": "hep-ph9802308", "abstract": "  We describe the effective heavy meson lagrangian for S- and P-wave heavy-light mesons in terms of a model based on meson-quark interactions, where mesonic transition amplitudes are represented by diagrams with heavy mesons attached to loops containing heavy and light constituent quarks. The model is relativistic and incorporates the heavy quark symmetries. The universal form factors of the heavy meson transition amplitudes are calculated together with their slopes and compared to existing data and limits. As further applications of the model, strong and radiative decays of D* and B* are considered. The agreement with data is surprisingly good and shows that the model offers a viable alternative to effective meson lagrangians which require a larger number of input parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9802/9802308v2.pdf"}
{"id": "hep-ph9804323", "abstract": "  We describe a general approach to quark flavor tagging in polarized hadronic processes, with particular emphasis on semi-inclusive deep inelastic scattering. A formalism is introduced that allows one to relate chosen quark flavor polarizations to an arbitrary combination of final-state hadron spin asymmetries. Within the context of the presented formalism, we quantify the sensitivity of various semi-inclusive hadron asymmetries to the light quark flavors. We show that unpolarized Lambda's may allow one to measure strange quark and antiquark polarizations independently. We also highlight several applications of our formalism, particularly to measurements intended to probe further the spin structure of the nucleon. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9804/9804323v2.pdf"}
{"id": "hep-ph9809494", "abstract": "  Cross sections for proton inelastic collision with different nuclei are described within the Glauber and multiple scattering approximations. A significant difference between approximate `Glauber' formula and exact calculations with a geometrical scaling assumption for very high-energy cross section is shown. Experimental values of proton-proton cross sections obtained using extensive air shower data are based on the relationship of proton-proton and respective proton-air absorption cross sections. According to obtained results values reported by the Akeno and Fly's Eye experimental groups are about 10", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9809/9809494v1.pdf"}
{"id": "hep-ph9811214", "abstract": "  We consider the dependences of the average number of interacting nucleons in high energy heavy ion collisions on the impact parameter in two cases, when the colliding nuclei have equal atomic weights, and when one nucleus is significantly more heavy in comparison with the second one. We argue that in the case of trigger of some rare event (say, J/ψ, or Υ production) the multiplicity of the secondaries can change several times for minimum bias sample, but it should be stable in the case of central events. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9811/9811214v1.pdf"}
{"id": "hep-ph9901350", "abstract": "  The measurements of the fluxes of atmospheric neutrinos give evidence for the disappearance of muon neutrinos. The determination of the dependence of the disappearance probability on the neutrino energy and trajectory allows in principle to establish unambiguosly the existence of neutrino oscillations. Alternative mechanisms for the disappearance of the neutrinos have been proposed, but do not provide a viable description of the data, if one includes both events where the neutrinos interact in the detector and ν-induced upward going muons. The proposed mechanisms differ in the energy dependence of the disappearance probability and the upward going muon data that are produced by high energy neutrinos give a crucial constraint. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9901/9901350v1.pdf"}
{"id": "hep-ph9905461", "abstract": "  We examine the maximal ν_e →ν_s solution to the solar neutrino problem. This solution can be motivated by the exact parity model and other theories. The ν_e survival probability exhibits one of three qualitatively different behaviours depending on the value of Δ m^2, viz. approximately energy independent, just-so or MSW. By the last of these we mean an enhanced night-time event rate due to regeneration in the Earth. We study all of these possibilities in the context of the recent SuperKamiokande data. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9905/9905461v2.pdf"}
{"id": "hep-ph9906220", "abstract": "  We outline major ideas involved in discussion of color coherence phenomena (CCP) at intermediate energies. We point out that the recent advances in calculating cross sections of hard exclusive processes off light nuclei allow to use the lightest nuclei for sensitive tests of CCP. Consistency of the results of the measurements of color transparency in quasielastic A(p,2p) and A(e,e'p) processes is emphasized. Evidence for presence of significant color fluctuations in nucleons and pions emerging from the study of diffractive processes is summarized. A new class of hard processes leading to three particle final state is suggested for electron and hadron projectiles. A number of new experiments are suggested to probe color fluctuations in hadrons. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9906/9906220v1.pdf"}
{"id": "hep-ph9908307", "abstract": "  We calculate the subjet rates for jets produced in hadron collisions. The kt algorithm is used to define the jets and allows the theoretical calculation to sum both the leading and next-to-leading logarithms in the resolution variable, ycut. We also ensure that our calculation matches exactly the leading order in alpha_s result and has sensible behaviour near thresholds. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9908/9908307v1.pdf"}
{"id": "hep-ph9908390", "abstract": "  We show that in some regions of supersymmetric parameter space, CP violating effects that mix the CP-even and CP-odd Higgs bosons can enhance the neutralino annihilation rate, and hence the indirect detection rate of neutralino dark matter, by factors of 10^6. The same CP violating effects can reduce the neutralino scattering rate off nucleons, and hence the direct detection rate of neutralino dark matter, by factors of 10^-7. We study the dependence of these effects on the phase of the trilinear coupling A, and find cases in the region being probed by dark matter searches which are experimentally excluded when CP is conserved but are allowed when CP is violated. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9908/9908390v1.pdf"}
{"id": "hep-ph9910477", "abstract": "  Once superpartners are discovered at colliders, the next challenge will be to determine the parameters of the supersymmetric Lagrangian. We illustrate how the relative phases of the gluino, SU(2), and U(1) gauginos and the Higgsino mass parameter mu can be measured at a hadron collider without ad hoc assumptions about the underlying physics, focusing on Fermilab. We also discuss how the gluino and LSP masses can be measured. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9910/9910477v1.pdf"}
{"id": "hep-ph9912351", "abstract": "  The quark-antiquark potential is constructed by making use of a new analytic running coupling in QCD. This running coupling arises under “analytization” of the renormalization group equation. The rising behavior of the quark-antiquark potential at large distances, which provides the quark confinement, is shown explicitly. At small distances, the standard behavior of this potential originating in the QCD asymptotic freedom is revealed. The higher loop corrections and the scheme dependence of the approach are briefly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/9912/9912351v2.pdf"}
{"id": "hep-th0207123", "abstract": "  We investigate the various time-dependent bubble spacetimes that can be obtained from double analytic continuation of asymptotically locally flat/AdS spacetimes with NUT charge. We find different time-dependent explicit solutions of general relativity from double analytic continuations of Taub-Nut(-AdS) and Kerr-Nut(-AdS) spacetimes. One solution in particular has Milne-like evolution throughout, and another is a NUT-charged generalization of the AdS soliton. These solutions are all four dimensional. In certain situations the NUT charge induces an ergoregion into the bubble spacetime and in other situations it quantitatively modifies the evolution of the bubble, as when rotation is present. In dimensions greater than four, no consistent bubble solutions are found that have only one timelike direction. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0207/0207123v1.pdf"}
{"id": "hep-th0209010", "abstract": "  We discuss the construction of multi-caloron solutions with non-trivial holonomy, both as approximate superpositions and exact self-dual solutions. The charge k SU(n) moduli space can be described by kn constituent monopoles. Exact solutions help us to understand how these constituents can be seen as independent objects, which seems not possible with the approximate superposition. An \"impurity scattering\" calculation provides relatively simple expressions. Like at zero temperature an explicit parametrization requires solving a quadratic ADHM constraint, achieved here for a class of axially symmetric solutions. We will discuss the properties of these exact solutions in detail, but also demonstrate that interesting results can be obtained without explicitly solving for the constraint. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0209/0209010v1.pdf"}
{"id": "hep-th0211244", "abstract": "  We present a general procedure for calculating one-loop “Casimir” energy densities for a scalar field coupled to a fixed potential in renormalized quantum field theory. We implement direct subtraction of counterterms computed precisely in dimensional regularization with a definite renormalization scheme. Our procedure allows us to test quantum field theory energy conditions in the presence of background potentials spherically symmetric in some dimensions and independent of others. We explicitly calculate the energy density for several examples. For a square barrier, we find that the energy is negative and divergent outside the barrier, but there is a compensating divergent positive contribution near the barrier on the inside. We also carry out calculations with exactly solvable ^2 potentials, which arise in the study of solitons and domain walls. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0211/0211244v2.pdf"}
{"id": "hep-th0309086", "abstract": "  We show how to reconstruct a field theory from the spectrum of bound states on a topological defect. We apply our recipe to the case of kinks in 1+1 dimensions with one or two bound states. Our recipe successfully yields the sine-Gordon and λϕ^4 field theories when suitable bound state spectra are assumed. The recipe can also be used to globally reconstruct the inflaton potential of inflationary cosmology if the inflaton produces a topological defect. We discuss how defects can provide “smoking gun” evidence for a class of inflationary models. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0309/0309086v2.pdf"}
{"id": "hep-th0309266", "abstract": "  In the models of brane construction, the isometry of a compactified space might be broken by branes. In four-dimensional effective Lagrangian, the breaking of the isometry is seen as the spontaneous breaking of the corresponding effective symmetry. Then it seems natural to expect that there are various kinds of defects that will be implemented by the spontaneous symmetry breaking. These defects are parametrized by the brane positions. In this paper we consider two kinds of such “brane defects”, which are formed by the local fluctuations of the locations of branes along their transversal directions. The fluctuation of a brane position might leads to winding (or wraping) around a non-contractible circle of the compactified space. These “primary” brane defects are already discussed by several authors. On the other hand, if there are multiple branes in the compactified space and their configuration in a compactified space is determined by the potential that depends only on their relative positions, one might find incidental symmetry in the effective potential, which is spontaneously broken by branes. We examined the latter “incidental” symmetry breakings and stable defect configurations. We paid special attention to the difference between “primary” brane defects. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0309/0309266v2.pdf"}
{"id": "hep-th0402114", "abstract": "  A classical spinning particle based on the Kerr-Newman black hole (BH) solution is considered. For parameters of spinning particles |a|>>m, the BH horizons disappear and BH image is drastically changed. We show that it turns into a skeleton formed by two coupled stringy systems. One of them is the Kerr singular ring which can be considered as a circular D-string with an orientifold world-sheet.   Analyzing the aligned to the Kerr congruence electromagnetic excitations of this string, we obtain the second stringy system which consists of two axial half-infinite chiral D-strings. These axial strings are similar to the Dirac monopole strings but carry the induced chiral traveling pp-waves. Their field structure can be described by the field model suggested by Witten for the cosmic superconducting strings.   We discuss a relation of this stringy system to the Dirac equation and argue that this stringy system can play a role of a classical carrier of the wave function. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0402/0402114v1.pdf"}
{"id": "hep-th0403161", "abstract": "  A graviton of a nonzero mass and decay width propagates five physical polarizations. The question of interactions of these polarizations is crucial for viability of models of massive/metastable gravity. This question is addressed in the context of the DGP model of a metastable graviton. First, I argue that the well-known breakdown of a naive perturbative expansion at a low scale is an artifact of the weak-field expansion itself. Then, I propose a different expansion – the constrained perturbation theory – in which the breakdown does not occur and the theory is perturbatively tractable all the way up to its natural ultraviolet cutoff. In this approach the couplings of the extra polarizations to matter and their selfcouplings appear to be suppressed and should be neglected in measurements at sub-horizon scales. The model reproduces results of General Relativity at observable distances with high accuracy, while predicting deviations from them at the present-day horizon scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0403/0403161v2.pdf"}
{"id": "hep-th0404210", "abstract": "  The full ADHM-Nahm formalism is employed to find exact higher charge caloron solutions with non-trivial holonomy, extended beyond the axially symmetric solutions found earlier. Particularly interesting is the case where the constituent monopoles, that make up these solutions, are not necessarily well-separated. This is worked out in detail for charge 2. We resolve the structure of the extended core, which was previously localized only through the singularity structure of the zero-mode density in the far field limit. We also show that this singularity structure agrees exactly with the abelian charge distribution as seen through the abelian component of the gauge field. As a by-product zero-mode densities for charge 2 magnetic monopoles are found. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0404/0404210v2.pdf"}
{"id": "hep-th0502166", "abstract": "  We analyze the energy extraction by the Penrose process in higher dimensions. Our result shows the efficiency of the process from higher dimensional black holes and black rings can be rather high compared with than that in four dimensional Kerr black hole. In particular, if one rotation parameter vanishes, the maximum efficiency becomes infinitely large because the angular momentum is not bounded from above. We also apply a catastrophe theory to analyze the stability of black rings. It indicates a branch of black rings with higher rotational energy is unstable, which should be a different type of instability from the Gregory-Laflamme's one. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0502/0502166v1.pdf"}
{"id": "hep-th0511186", "abstract": "  We study the generation and evolution of gravitational waves (tensor perturbations) in the context of Randall-Sundrum braneworld cosmology. We assume that the initial and final stages of the background cosmological model are given by de Sitter and Minkowski phases, respectively, and they are connected smoothly by a radiation-dominated phase. This setup allows us to discuss the quantum-mechanical generation of the perturbations and to see the final amplitude of the well-defined zero mode. Using the Wronskian formulation, we numerically compute the power spectrum of gravitational waves, and find that the effect of initial vacuum fluctuations in the Kaluza-Klein modes is subdominant, contributing not more than 10", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0511/0511186v2.pdf"}
{"id": "hep-th0604059", "abstract": "  It is shown that due to radiative corrections a photon having a non vanishing component of its momentum perpendicular to it, bears a non-zero magnetic moment. All modes of propagation of the polarization operator in one loop approximation are discussed and in this field regime the dispersion equation and the corresponding magnetic moment are derived. Near the first thresholds of cyclotron resonance the photon magnetic moment has a peak larger than the electron anomalous magnetic moment. Related to this magnetic moment, the arising of some sort of photon \"dynamical mass\" and a gyromagnetic ratio are discussed. These latter results might be interesting in an astrophysical context. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0604/0604059v1.pdf"}
{"id": "hep-th0604194", "abstract": "  We study scalar field theories on Poincare invariant commutative nonassociative spacetimes. We compute the one-loop self-energy diagrams in the ordinary path integral quantization scheme with Feynman's prescription, and find that the Cutkosky rule is satisfied. This property is in contrast with that of noncommutative field theory, since it is known that noncommutative field theory with space/time noncommutativity violates unitarity in the above standard scheme, and the quantization procedure will necessarily become complicated to obtain a sensible Poincare invariant noncommutative field theory. We point out a peculiar feature of the non-locality in our nonassociative field theories, which may explain the property of the unitarity distinct from noncommutative field theories. Thus commutative nonassociative field theories seem to contain physically interesting field theories on deformed spacetimes. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0604/0604194v2.pdf"}
{"id": "hep-th0701038", "abstract": "  We investigate the stability of asymptotically anti-de Sitter gravity coupled to tachyonic scalar fields with mass at or slightly above the Breitenlohner-Freedman bound. The boundary conditions in these “designer gravity” theories are defined in terms of an arbitrary function W. Previous work had suggested that the energy in designer gravity is bounded below if i) W has a global minimum and ii) the scalar potential admits a superpotential P. More recently, however, certain solutions were found (numerically) to violate the proposed energy bound. We resolve the discrepancy by observing that a given scalar potential can admit two possible branches of the corresponding superpotential, P_±. When there is a P_- branch, we rigorously prove a lower bound on the energy; the P_+ branch alone is not sufficient. Our numerical investigations i) confirm this picture, ii) confirm other critical aspects of the (complicated) proofs, and iii) suggest that the existence of P_- may in fact be necessary (as well as sufficient) for the energy of a designer gravity theory to be bounded below. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0701/0701038v3.pdf"}
{"id": "hep-th0703213", "abstract": "  We study the behavior of quark and diquark condensates in dense quark matter under the influence of a gravitational field adopting as a simple model the static D-dimensional Einstein Universe. Calculations are performed in the framework of the extended Nambu–Jona-Lasinio model at finite temperature and quark density on the basis of the thermodynamic potential and the gap equations. Quark and diquark condensates as functions of the chemical potential and temperature at different values of the curvature have been studied. Phase portraits of the system have been constructed. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0703/0703213v1.pdf"}
{"id": "hep-th9311105", "abstract": "  A system of electrons in the two-dimensional honeycomb lattice with Coulomb interactions is described by a renormalizable quantum field theory similar but not equal to QED_3. Renormalization group techniques are used to investigate the infrared behaviour of the system that flows to a fixed point with non-Fermi liquid characteristics. There are anomalous dimensions in the fermionic observables, no quasiparticle pole, and anomalous screening of the Coulomb interaction. These results are robust as the Fermi level is not changed by the interaction. The system resembles in the infrared the one-dimensional Luttinger liquid. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9311/9311105v1.pdf"}
{"id": "hep-th9608071", "abstract": "  The Casimir energy corresponding to a massive scalar field with Dirichlet boundary conditions on a spherical bag is obtained. The field is considered, separately, inside and outside the bag. The renormalization procedure that is necessary to apply in each situation is studied in detail, in particular the differences occurring with respect to the case when the field occupies the whole space. The final result contains several constants that experience renormalization and can be determined only experimentally. The non-trivial finite parts that appear in the massive case are found exactly, providing a precise determination of the complete, renormalized zero-point energy for the first time. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9608/9608071v1.pdf"}
{"id": "math-ph0502049", "abstract": "  In order to describe excitable reaction-diffusion systems, we derive a two-dimensional model with a Hopf and a semilocal saddle-node homoclinic bifurcation. This model gives the theoretical framework for the analysis of the saddle-node homoclinic bifurcation as observed in chemical experiments, and for the concepts of excitability and excitability threshold. We show that if diffusion drives an extended system across the excitability threshold then, depending on the initial conditions, wave trains, propagating solitary pulses and propagating pulse packets can exist in the same extended system. The extended model shows chemical turbulence for equal diffusion coefficients and presents all the known types of topologically distinct activity waves observed in chemical experiments. In particular, the approach presented here enables to design experiments in order to decide between excitable systems with sharp and finite width thresholds. ", "pdf_url": "gs://arxiv-dataset/arxiv/math-ph/pdf/0502/0502049v1.pdf"}
{"id": "math0006234", "abstract": "  We prove a conjecture of Cohn and Propp, which refines a conjecture of Bosley and Fidkowski about the symmetry of the set of alternating sign matrices (ASMs). We examine data arising from the representation of an ASM as a collection of paths connecting 2n vertices and show it to be invariant under the dihedral group D_2n rearranging those vertices, which is much bigger than the group of symmetries of the square. We also generalize conjectures of Propp and Wilson relating some of this data for different values of n. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0006/0006234v2.pdf"}
{"id": "math0302288", "abstract": "  We interpret magnetic billiards as Finsler ones and describe an analog of the string construction for magnetic billiards. Finsler billiards for which the law \"angle of incidence equals angle of reflection\" are described. We characterize the Finsler metrics in the plane whose geodesics are circles of a fixed radius. This is a magnetic analog of Hilbert's fourth problem asking to describe the Finsler metrics whose geodesics are straight lines. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0302/0302288v1.pdf"}
{"id": "math0502147", "abstract": "  We present a simple combinatorial model for the characters of the irreducible integrable highest weight modules for complex symmetrizable Kac-Moody algebras. This model can be viewed as a discrete counterpart to the Littelmann path model. We describe crystal graphs and give a Littlewood-Richardson rule for decomposing tensor products of irreducible representations. The new model is based on the notion of a lambda-chain, which is a chain of positive roots defined by certain interlacing conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0502/0502147v4.pdf"}
{"id": "math0507031", "abstract": "  Patience Sorting is a combinatorial algorithm that can be viewed as an iterated, non-recursive form of the Schensted Insertion Algorithm. In recent work the authors extended Patience Sorting to a full bijection between the symmetric group and certain pairs of combinatorial objects (called pile configurations) that are most naturally defined in terms of generalized permutation pattern and barred pattern avoidance. This Extended Patience Sorting Algorithm is very similar to the Robinson-Schensted-Knuth (or RSK) Correspondence, which is itself built from repeated application of the Schensted Insertion Algorithm.   In this work we introduce a geometric form for the Extended Patience Sorting Algorithm that is in some sense a natural dual algorithm to G. Viennot's celebrated Geometric RSK Algorithm. Unlike Geometric RSK, though, the lattice paths coming from Patience Sorting are allowed to intersect. We thus also give a characterization for the intersections of these lattice paths in terms of the pile configurations associated with a given permutation under the Extended Patience Sorting Algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0507/0507031v2.pdf"}
{"id": "math0604607", "abstract": "  Here we treat the transmission of disease through a population as a standard Galton-Watson branching process, modified to take the presence of vaccination into account. Vaccination reduces the number of secondary infections produced per infected individual. We show that introducing vaccination in a population therefore reduces the expected time to extinction of the infection. We also prove results relating the distribution of number of secondery infections with and without vaccinations. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0604/0604607v1.pdf"}
{"id": "math0605065", "abstract": "  The paper has 2 main goals: 1. We propose a variant of the CAPM based on coherent risk. 2. In addition to the real-world measure and the risk-neutral measure, we propose the third one: the extreme measure. The introduction of this measure provides a powerful tool for investigating the relation between the first two measures. In particular, this gives us - a new way of measuring reward; - a new approach to the empirical asset pricing. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0605/0605065v1.pdf"}
{"id": "math9807134", "abstract": "  We consider a model of a two-dimensional interface of the SOS type, with finite-range, even, strictly convex, twice continuously differentiable interactions. We prove that, under an arbitrarily weak potential favouring zero-height, the surface has finite mean square heights. We consider the cases of both square well and δ potentials. These results extend previous results for the case of nearest-neighbours Gaussian interactions in <cit.> and <cit.>. We also obtain estimates on the tail of the height distribution implying, for example, existence of exponential moments. In the case of the δ potential, we prove a spectral gap estimate for linear functionals. We finally prove exponential decay of the two-point function (1) for strong δ-pinning and the above interactions, and (2) for arbitrarily weak δ-pinning, but with finite-range Gaussian interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/9807/9807134v1.pdf"}
{"id": "nlin0002016", "abstract": "  We investigate the long-time evolution of weakly perturbed single-site breathers (localized stationary states) in the discrete nonlinear Schroedinger (DNLS) equation. The perturbations we consider correspond to time-periodic solutions of the linearized equations around the breather, and can be either (i) spatially localized, or (ii) spatially extended. For case (i), which corresponds to the excitation of an internal mode of the breather, we find that the nonlinear interaction between the breather and its internal mode always leads to a slow growth of the breather amplitude and frequency. In case (ii), corresponding to interaction between the breather and a standing-wave phonon, the breather will grow provided that the wave vector of the phonon is such that the generation of radiating higher-harmonics at the breather is possible. In other cases, breather decay is observed. This condition yields a limit value for the breather frequency above which no further growth is possible. We also discuss another mechanism for breather growth and destruction which becomes important when the amplitude of the perturbation is non-negligible, and which originates from the oscillatory instabilities of the nonlinear standing-wave phonons. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0002/0002016v1.pdf"}
{"id": "nlin0008036", "abstract": "  A light reflection technique is used to measure quantitatively the surface elevation of Faraday waves. The performed measurements cover a wide parameter range of driving frequencies and sample viscosities. In the capillary wave regime the bifurcation diagrams exhibit a frequency independent scaling proportional to the wavelength. We also provide numerical simulations of the full Navier-Stokes equations, which are in quantitative agreement up to supercritical drive amplitudes of 20", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0008/0008036v1.pdf"}
{"id": "nlin0212017", "abstract": "  The S-matrix theory formulation of closed-orbit theory recently proposed by Granger and Greene is extended to atoms in crossed electric and magnetic fields. We then present a semiclassical quantization of the hydrogen atom in crossed fields, which succeeds in resolving individual lines in the spectrum, but is restricted to the strongest lines of each n-manifold. By means of a detailed semiclassical analysis of the quantum spectrum, we demonstrate that it is the abundance of bifurcations of closed orbits that precludes the resolution of finer details. They necessitate the inclusion of uniform semiclassical approximations into the quantization process. Uniform approximations for the generic types of closed-orbit bifurcation are derived, and a general method for including them in a high-resolution semiclassical quantization is devised. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0212/0212017v1.pdf"}
{"id": "nlin0301039", "abstract": "  We study a model for polaron-like charge transport mechanism along DNA molecules with emphasis on the impact of parametrical and structural disorder. Our model Hamiltonian takes into account the coupling of the charge carrier to two different kind of modes representing fluctuating twist motions of the base pairs and H-bond distortions within the double helix structure of λ-DNA. Localized stationary states are constructed with the help of a nonlinear map approach for a periodic double helix and in the presence of intrinsic static parametrical and/or structural disorder reflecting the impact of ambient solvent coordinates. It is demonstrated that charge transport is mediated by moving polarons respectively breather compounds carrying not only the charge but causing also local temporal deformations of the helix structure through the traveling torsion and bond breather components illustrating the interplay of structure and function in biomolecules. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0301/0301039v1.pdf"}
{"id": "nlin0406045", "abstract": "  We discuss the quasiclassical approximation for the equations of motions of a nonlinear chain of phonons and electrons having phonon mediated hopping. Describing the phonons and electrons as even and odd grassmannian functions and using the continuum limit we show that the equations of motions lead to a Zakharov-like system for bosonic and fermionic fields. Localised and nonlocalised solutions are discussed using the Hirota bilinear formalism. Nonlocalised solutions turn out to appear naturally for any choice of wave parameters. The bosonic localised solution has a fermionic dressing while the fermionic one is an oscillatory localised field. They appear only if some constraints on the dispersion are imposed. In this case the density of fermions is a strongly localised travelling wave. Also it is shown that in the multiple scales approach the emergent equation is linear. Only for the resonant case we get a nonlinear fermionic Yajima-Oikawa system. Physical implications are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0406/0406045v1.pdf"}
{"id": "nlin0601035", "abstract": "  New method for finding exact solutions of nonlinear differential equations is presented. It is based on constructing the polygon corresponding to the equation studied. The algorithms of power geometry are used. The method is applied for finding one – parameter exact solutions of the generalized Korteveg – de Vries – Burgers equation, the generalized Kuramoto - Sivashinsky equation, and the fifth – order nonlinear evolution equation. All these nonlinear equations contain the term u^mu_x. New exact solitary waves are found. ", "pdf_url": "gs://arxiv-dataset/arxiv/nlin/pdf/0601/0601035v1.pdf"}
{"id": "nucl-ex0010010", "abstract": "  We describe a direct method for monitoring the geometrical dimensions of a synchrotron beam at the target position for internal target installations. The method allows for the observation of the proton beam size as well as the position of the beam relative to the target. As a first demonstration of the technique, we present results obtained by means of the COSY-11 detection system installed at the cooler synchrotron COSY. The influence of the stochastic cooling on the COSY proton beam dimensions is also investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0010/0010010v1.pdf"}
{"id": "nucl-ex0110015", "abstract": "  The yields and velocity distributions of heavy residues and fission fragments from the reaction of 20 MeV/nucleon 197Au + 90Zr have been measured using the MSU A1200 fragment separator. A bimodal distribution of residues is observed, with one group, resulting from peripheral collisions, having fragment mass numbers A=160-200, while the other group, resulting from “hard” collisions, has A=120-160. This latter group of residues can be distinguished from fission fragments by their lower velocities. A model combining deep-inelastic transfer and incomplete fusion for the primary interaction stage and a statistical evaporation code for the deexcitation stage has been used to describe the properties of the product distributions. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0110/0110015v1.pdf"}
{"id": "nucl-ex0410009", "abstract": "  Jet quenching in the matter created in high energy nucleus-nucleus collisions provides a tomographic tool to probe the medium properties. Recent experimental results from the Relativistic Heavy-Ion Collider (RHIC) on characterization of jet production via dihadron correlations at high transverse momentum are reviewed. Expectations from the dihadron measurements for the lower energy =62.4 GeV RHIC run are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0410/0410009v1.pdf"}
{"id": "nucl-ex0510069", "abstract": "  We present results on the parity violation effects and global system polarization measurements in Au+Au collisions at sqrt(s_NN) = 62 GeV obtained with the STAR detector at RHIC. The parity violation effects are studied by three particle azimuthal correlations of charged particles. The global polarization of the system is examined by measuring the polarization of strange hyperons with respect to the collision reaction plane. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0510/0510069v2.pdf"}
{"id": "nucl-th0104029", "abstract": "  The mass shift, width broadening, and spectral density for the ρ and ω mesons in a heat bath of nucleons and pions are calculated using a general formula which relates the self-energy to the real and imaginary parts of the forward scattering amplitude. We use experimental data to saturate the scattering amplitude at low energies with resonances and include a background Pomeron term, while at high energies a Regge parameterization is used. The real part obtained directly is compared with the result of a dispersion integral over the imaginary part. The peaks of the spectral densities are little shifted from their vacuum positions, but the widths are considerably increased due to collisional broadening. Where possible we compare with the UrQMD model and find quite good agreement. At normal nuclear matter density and a temperature of 150 MeV the spectral density of the ρ meson has a width of 345 MeV, while that for the ω is in the range 90–150 MeV. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0104/0104029v1.pdf"}
{"id": "nucl-th0108041", "abstract": "  We provide evidence for a high precision model-independent low momentum nucleon-nucleon interaction. Performing a momentum-space renormalization group decimation, we find that the effective interactions constructed from various high precision nucleon-nucleon interaction models, such as the Paris, Bonn, Nijmegen, Argonne, CD Bonn and Idaho potentials, are identical. This model-independent low momentum interaction, called V_low k, reproduces the same phase shifts and deuteron pole as the input potential models, without ambiguous assumptions on the high momentum components, which are not constrained by low energy data and lead to model-dependent results in many-body applications. V_low k is energy-independent and does not necessitate the calculation of the Brueckner G matrix. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0108/0108041v3.pdf"}
{"id": "nucl-th0204006", "abstract": "  We consider a reformulation of QED in which covariant Green functions are used to solve for the electromagnetic field in terms of the fermion fields. It is shown that exact few-fermion eigenstates of the resulting Hamiltonian can be obtained in the canonical equal-time formalism for the case where there are no free photons. These eigenstates lead to two- and three-body Dirac-like equations with electromagnetic interactions. Perturbative and some numerical solutions of the two-body equations are presented for positronium and muonium-like systems, for various strengths of the coupling. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0204/0204006v2.pdf"}
{"id": "nucl-th0209045", "abstract": "  We have developed a new Hartree-Fock-Bogoliubov (HFB) code which has been specifically designed to study ground state properties of nuclei near the neutron and proton drip lines. The unique feature of our code is that it takes into account the strong coupling to high-energy continuum states, up to an equivalent single-particle energy of 60 MeV. We solve the HFB equations for deformed, axially symmetric even-even nuclei in coordinate space on a 2-D lattice with Basis-Spline methods. For the p-h channel, the Skyrme (SLy4) effective N-N interaction is utilized, and for the p-p and h-h channel we use a delta interaction. We present results for binding energies, deformations, normal densities and pairing densities, Fermi levels, and pairing gaps. In particular, we will discuss neutron-rich isotopes of oxygen (O-22) and tin (Sn-150). ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0209/0209045v1.pdf"}
{"id": "nucl-th0210028", "abstract": "  The effect of non-locality in the NN interaction models is examined. It is shown that this feature can explain differences in predictions made from models evidencing a difference with this respect. This is done for both static and dynamical observables, taking into account that a non-local term can be transformed away by performing a unitary transformation. Some results for the deuteron form factors, the A(Q^2) structure function and the T_20(Q^2) tensor polarization are given as an example. A few cases where discrepancies cannot be explained are also considered. They point to differences in the models as for the deuteron asymptotic normalizations, A_S and A_D, which are not affected by the present analysis. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0210/0210028v1.pdf"}
{"id": "nucl-th0301072", "abstract": "  We show that formally for the standard ansatz relativistic point-coupling mean-field (RMF-PC) model a lagrangian density L is not equivalent in Hartree and Hartree-Fock approximations. The equivalency can be achieved only if we use a “complete” ansatz at the cost of introducing new parameters in the model. An approximate treatment of the exchange terms from standard RMF-PC indicates that these effects cannot be easily, if at all, absorbed by a Dirac-Hartree approximation. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0301/0301072v1.pdf"}
{"id": "nucl-th0304057", "abstract": "  Various phenomenological models of particle multiplicity distributions are discussed using a general form of a unified model which is based on the grand canonical partition function and Feynman's path integral approach to statistical processes. These models can be written as special cases of a more general distribution which has three control parameters which are a, x, z. The relation to these parameters to various physical quantities are discussed. A connection of the parameter a with Fisher's critical exponent τ is developed. Using this grand canonical approach, moments, cumulants and combinants are discussed and a physical interpretation of the combinants are given and their behavior connected to the critical exponent τ. Various physical phenomena such as hierarchical structure, void scaling relations, KNO scaling features, clan variables, and branching laws are shown in terms of this general approach. Several of these features which were previously developed in terms of the negative binomial distribution are found to be more general. Both hierarchical structure and void scaling relations depend on the Fisher exponent τ. Applications of our approach to the charged particle multiplicity distribution in jets of L3 and H1 data are given. It is shown that just looking at the mean and fluctuation of data is not enough to distinguish these distributions or the underlying mechanism. The mean, fluctuation and third cummulant of distribution determine three parameters x, z, a. We find that a generalized random work model fits the data better than the widely used negative binomial model. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0304/0304057v1.pdf"}
{"id": "nucl-th0310086", "abstract": "  The influence of hole-hole propagation in addition to the conventional particle-particle propagation, on the energy per nucleon and the momentum distribution is investigated. The results are compared to the Brueckner-Hartree-Fock (BHF) calculations with a continuous choice and conventional choice for the single-particle spectrum. The Bethe-Goldstone equation has been solved using realistic NN interactions. Also, the structure of nucleon self-energy in nuclear matter is evaluated. All the self-energies are calculated self-consistently. Starting from the BHF approximation without the usual angle-average approximation, the effects of hole-hole contributions and a self-consistent treatment within the framework of the Green function approach are investigated. Using the self-consistent self-energy, the hole and particle self-consistent spectral functions including the particle-particle and hole-hole ladder contributions in nuclear matter are calculated using realistic NN interactions. We found that, the difference in binding energy between both results, i.e. BHF and self-consistent Green function, is not large. This explains why is the BHF ignored the 2h1p contribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0310/0310086v1.pdf"}
{"id": "nucl-th0403086", "abstract": "  The nuclear incompressibility K_∞ is deduced from measurements of the Isoscalar Giant Monopole Resonance (ISGMR) in medium-heavy nuclei, and the resulting value turns out to be model dependent. Since the considered nuclei have neutron excess, it has been suggested that the model dependence is due to the different behaviour of the symmetry energy in different models. To clarify this issue, we make a systematic and careful analysis based on new Skyrme forces which span a wide range of values for K_∞, for the value of the symmetry energy at saturation and for its density dependence. By calculating, in a fully self-consistent fashion, the ISGMR centroid energy in ^208Pb we reach, for the first time within the non-relativistic framework, three important conclusions: (i) the monopole energy, and consequently the deduced value of K_∞, depend on a well defined parameter related to the shape of the symmetry energy curve and called K_sym; (ii) Skyrme forces of the type of SLy4 predict K_∞ around 230 MeV, in agreement with the Gogny force (previous estimates using Skyrme interactions having been plagued by lack of full self-consistency); (iii) it is possible to build forces which predict K_∞ around 250 MeV, although part of this increase is due to our poor knowledge of the density dependence and effective mass. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0403/0403086v1.pdf"}
{"id": "nucl-th0506020", "abstract": "  The η-nucleon (ηN) interactions are deduced from the heavy baryon chiral perturbation theory up to the next-to-leading-order terms. Combining the relativistic mean-field theory for nucleon system, we have studied the in-medium properties of η-meson. We find that all the elastic scattering ηN interactions come from the next-to-leading-order terms. The ηN sigma term is found to be about 280±130 MeV. The off-shell terms are also important to the in-medium properties of η-meson. On application of the latest determination of the ηN scattering length, the ratio of η-meson effective mass to its vacuum value is near 0.84±0.015, while the optical potential is about -(83±5) MeV, at the normal nuclear density. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0506/0506020v2.pdf"}
{"id": "nucl-th0506031", "abstract": "  We study the modification of the nucleon nucleon interaction in a nuclear medium in the scalar isoscalar channel, mediated by the exchange of two correlated (σ channel) or uncorrelated pions. For this purpose we use a standard approach for the renormalization of pions in nuclei. The corrections obtained for the NN interaction in the medium in this channel are of the order of 20", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0506/0506031v2.pdf"}
{"id": "nucl-th0512003", "abstract": "  We address the problem of calculating momentum distributions of particles emerging from the three-body decay of a many-body resonance. We show that these distributions are determined by the asymptotics of the coordinate-space complex-energy wave-function of the resonance. We use the hyperspherical adiabatic expansion method where all lengths are proportional to the hyperradius. The structures of the resonances are related to different decay mechanisms. For direct decay all inter-particle distances increase proportional to the hyperradius at intermediate and large distances. Sequential three-body decay proceeds via spatially confined quasi-stationary two-body configurations. Then two particles remain close while the third moves away. The wave function may contain mixtures which produce coherence effects at small distances, but the energy distributions can still be added incoherently. Two-neutron halos are discussed in details and illustrated by the 2^+ resonance in ^6He. The dynamic evolution of the decay process is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0512/0512003v1.pdf"}
{"id": "nucl-th0604068", "abstract": "  We solve the generalized relativistic harmonic oscillator in 1+1 dimensions, i.e., including a linear pseudoscalar potential and quadratic scalar and vector potentials which have equal or opposite signs. We consider positive and negative quadratic potentials and discuss in detail their bound-state solutions for fermions and antifermions. The main features of these bound states are the same as the ones of the generalized three-dimensional relativistic harmonic oscillator bound states. The solutions found for zero pseudoscalar potential are related to the spin and pseudospin symmetry of the Dirac equation in 3+1 dimensions. We show how the charge conjugation and γ^5 chiral transformations relate the several spectra obtained and find that for massless particles the spin and pseudospin symmetry related problems have the same spectrum, but different spinor solutions. Finally, we establish a relation of the solutions found with single-particle states of nuclei described by relativistic mean-field theories with scalar, vector and isoscalar tensor interactions and discuss the conditions in which one may have both nucleon and antinucleon bound states. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0604/0604068v1.pdf"}
{"id": "nucl-th0605047", "abstract": "  We studied the ground and excited states of ^12C based on variational calculations after spin-parity projection in a framework of antisymmetrized molecular dynamics(AMD). The calculations systematically reproduce various experimental data. It was found that the sub-shell closure and SU(3)-limit 3α cluster components are contained in the ground state, while various 3α cluster structures develop in the excited states. We discussed effects of α breaking and show the importance of coexistence of the cluster and shell-model-like aspects. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0605/0605047v1.pdf"}
{"id": "nucl-th9706022", "abstract": "  Dilepton and photon production in heavy-ion collisions at SPS energies are studied in the relativistic transport model that incorporates self-consistently the change of hadron masses in dense matter. It is found that the dilepton spectra in proton-nucleus reactions can be well described by the conventional mechanism of Dalitz decay and direct vector meson decay. However, to provide a quantitative explanation of the observed dilepton spectra in central heavy-ion collisions requires contributions other than these direct decays and also various medium effects. Introducing a decrease of vector meson masses in hot dense medium, we find that these heavy-ion data can be satisfactorily explained. Furthermore, the single photon spectra in our calculations with either free or in-medium meson masses do not exceed the upper bound deduced from the experiments by the WA80 Collaboration. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9706/9706022v1.pdf"}
{"id": "nucl-th9801011", "abstract": "  Parity violating elastic electron-nucleus scattering provides an accurate and model independent measurement of neutron densities, because the Z^0 couples primarily to neutrons. Coulomb distortion corrections to the parity violating asymmetry A_l are calculated exactly using a relativistic optical model. Distortions significantly reduce A_l in a heavy nucleus. However even with distortions, an experiment to measure the neutron radius is feasible. This will aid the interpretation of future atomic parity violation measurements and provide fundamental nuclear structure information. Coulomb distortions and small differences between neutron and proton radii could be important for a standard model test on ^4He, ^12C or ^16O. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9801/9801011v2.pdf"}
{"id": "nucl-th9802019", "abstract": "  The cross sections of the reaction pp → N K Y for K^+ or K^0 mesons and Λ or Σ hyperons are calculated within the boson exchange model including pion and kaon exchange diagrams. We analyze the dependence of the results on the accuracy of the input π N amplitude. By fixing the π NN coupling constant and the cut-off parameter Λ_π at the π NN vertex we calculate the contribution from the kaon exchange diagram and obtain the ratio of the KN Λ and KN Σ coupling constants by a fit to the experimental data. This ratio is in a good agreement with the SU(6) prediction. Our calculated total cross sections for the different reaction channels are fitted by simple expressions and compared with other parameterizations used in the literature. Furthermore, the gross features of the production cross section close to threshold are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9802/9802019v2.pdf"}
{"id": "nucl-th9906016", "abstract": "  The self-energy of the K^- meson in nuclear matter is calculated in a self-consistent microscopic approach, using a K̅N interaction obtained from the lowest-order meson-baryon chiral Lagrangian. The effective K̅N interaction in the medium is derived by solving the coupled-channel Bethe-Salpeter equation including Pauli blocking on the nucleons, mean-field binding potentials for the baryons and the self-energy of the πand K̅ mesons. The incorporation of the self-consistent K̅ self-energy in the description, in addition to the Pauli blocking effects, yields a weaker attractive in-medium K̅N interaction and a Λ(1405) which dissolves faster with increasing matter density, as a result of the K̅ spectral function being spread out over a wide range of energies. These effects are further magnified when the intermediate pions are dressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/9906/9906016v1.pdf"}
{"id": "physics0008108", "abstract": "  An alternative being considered for the Next Linear Collider (NLC) is not to tunnel in a straight line but to bend the Main Linac into an arc so as to follow an equipotential. We begin here an examination of the effects that this would have on vertical dispersion, with its attendant consequences on synchrotron radiation and emittance growth by looking at two scenarios: a gentle continuous bending of the beam to follow an equipotential surface, and an introduction of sharp bends at a few sites in the linac so as to reduce the maximum sagitta produced. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0008/0008108v1.pdf"}
{"id": "physics0106044", "abstract": "  We study the interaction of strong femtosecond laser pulses with the C_60 molecule employing time-dependent density functional theory with the ionic background treated in a jellium approximation. The laser intensities considered are below the threshold of strong fragmentation but too high for perturbative treatments such as linear response. The nonlinear response of the model to excitations by short pulses of frequencies up to 45eV is presented and analyzed with the help of Kohn-Sham orbital resolved dipole spectra. In femtosecond laser pulses of 800nm wavelength ionization is found to occur multiphoton-like rather than via excitation of a “giant” resonance. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0106/0106044v3.pdf"}
{"id": "physics0106060", "abstract": "  The NLC extraction line provides a secondary focal point with a low beta function and 2 cm dispersion which can be used for measurement of the beam energy spectrum. In this study, tracking simulations were performed to transport the 0.5 TeV electron beam from the Interaction Point (IP) to the secondary focus (SF), “measure” the resultant transverse beam profile and reconstruct the disrupted IP energy spread. In the simulation, the obtained energy spectrum reproduced the initial IP spread reasonably well, especially with the vertical dispersion at SF which provides larger ratio of dispersion to the betatron beam size. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0106/0106060v1.pdf"}
{"id": "physics0106090", "abstract": "  The problem of the dynamo effect for a Kraichnan incompressible helicity-free velocity field is considered. Exploiting a quantum formalism first introduced by Kazantsev (A.P. Kazantsev, Sov. Phys. JETP 26, 1031-1034 (1968)), we show that a critical magnetic Reynolds number exists for the presence of dynamo. The value of the Prandtl number influences the spatial distribution of the magnetic field and its growth in time. The magnetic field correlation length is always the largest between the diffusive scale and the viscous scale of the flow. In the same way the field growth is characterized by a time scale that corresponds to the largest between the diffusive and the viscous characteristic time. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0106/0106090v1.pdf"}
{"id": "physics0108034", "abstract": "  This letter reports on a new method of analysing experimentally gained time series with respect to different types of noise involved, namely, we show that it is possible to differentiate between dynamical and measurement noise. This method does not depend on previous knowledge of model equations. For the complicated case of a chaotic dynamics spoiled at the same time by dynamical and measurement noise, we even show how to extract from data the magnitude of both types of noise. As a further result, we present a new criterion to verify the correct embedding for chaotic dynamics with dynamical noise. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0108/0108034v2.pdf"}
{"id": "physics0304054", "abstract": "  Seeing the Earth crust as crisscrossed by faults filled with fluid at close to lithostatic pressures, we develop a model in which its elastic modulii are different in net tension versus compression. In constrast with standard nonlinear effects, this “threshold nonlinearity” is non-perturbative and occurs for infinitesimal perturbations around the lithostatic pressure taken as the reference. For a given earthquake source, such nonlinear elasticity is shown to (i) rotate, widen or narrow the different lobes of stress transfer, (ii) to modify the 1/r^2 2D-decay of elastic stress Green functions into the generalized power law 1/r^γ where γ depends on the azimuth and on the amplitude of the modulii asymmetry. Using reasonable estimates, this implies an enhancement of the range of interaction between earthquakes by a factor up to 5-10 at distances of several tens of rupture length. This may explain certain long-range earthquake triggering and hydrological anomalies in wells and suggest to revisit the standard stress transfer calculations which use linear elasticity. We also show that the standard double-couple of forces representing an earthquake source leads to an opening of the corresponding fault plane, which suggests a mechanism for the non-zero isotropic component of the seismic moment tensor observed for some events. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0304/0304054v2.pdf"}
{"id": "physics0306114", "abstract": "  Almost all groups involved in linear collider detector studies have their own simulation software framework. Using a common persistency scheme would allow to easily share results and compare reconstruction algorithms. We present such a persistency framework, called LCIO (Linear Collider I/O). The framework has to fulfill the requirements of the different groups today and be flexible enough to be adapted to future needs. To that end we define an `abstract object persistency layer' that will be used by the applications. A first implementation, based on a sequential file format (SIO) is completely separated from the interface, thus allowing to support additional formats if necessary. The interface is defined with the AID (Abstract Interface Definition) tool from freehep.org that allows creation of Java and C++ code synchronously. In order to make use of legacy software a Fortran interface is also provided. We present the design and implementation of LCIO. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0306/0306114v1.pdf"}
{"id": "physics0309122", "abstract": "  We show how it is possible to controllably rotate or align microscopic particles of isotropic nonabsorbing material in a TEM00 Gaussian beam trap, with simultaneous measurement of the applied torque using purely optical means. This is a simple and general method of rotation, requiring only that the particle is elongated along one direction. Thus, this method can be used to rotate or align a wide range of naturally occurring particles. The ability to measure the applied torque enables the use of this method as a quantitative tool–the rotational equivalent of optical tweezers based force measurement. As well as being of particular value for the rotation of biological specimens, this method is also suitable for the development of optically-driven micromachines. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0309/0309122v1.pdf"}
{"id": "physics0310126", "abstract": "  We investigate “shell structure” from Babylonian times: periodicities and beats in computer-simulated lunar data corresponding to those observed by Babylonian scribes some 2500 years ago. We discuss the mathematical similarity between the Babylonians' recently reconstructed method of determining one of the periods of the moon with modern Fourier analysis and the interpretation of shell structure in finite fermion systems (nuclei, metal clusters, quantum dots) in terms of classical closed or periodic orbits. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0310/0310126v2.pdf"}
{"id": "physics0311014", "abstract": "  This work confirms that not only surface plasmons but many other kinds of electromagnetic eigenmodes should be considered in explaining the values of the transmittivity through a slab bearing a two-dimensional periodic corrugation. Specifically, the role of Brewster-Zennek modes appearing in metallic films exhibiting regions of weak positive dielectric constant. It is proposed that these modes play a significant role in the light transmission in a thin chromium film perforated with normal cylindrical holes, for appropriate lattice parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0311/0311014v2.pdf"}
{"id": "physics0403120", "abstract": "  Daily temperature anomaly records are analyzed (61 for Australia, 18 for Hungary) by means of detrended fluctuation analysis. Positive long range asymptotic correlations extending up to 5-10 years are detected for each case. Contrary to earlier claims, the correlation exponent is not universal for continental stations. Interestingly, the dominant factor is geographic latitude over Australia: the general tendency is a decrease of correlation exponent with increasing distance from the equator. This tendency is in a complete agreement with the results found by Tsonis et al. (1999) for 500-hPa height anomalies in the northern hemisphere. The variance of fluctuations exhibits an opposite trend, the larger is the distance from the equator, the larger the amplitude of intrinsic fluctuations. The presence of Tropospheric Biennial Oscillation is clearly identified for three stations at the north-eastern edge of the Australian continent. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0403/0403120v1.pdf"}
{"id": "physics0406029", "abstract": "  We report on a coastal experiment to study GPS L1 reflections. The campaign was carried out at the Barcelona Port breaker and dedicated to the development of sea-state retrieval algorithms. An experimental system built for this purpose collected and processed GPS data to automatically generate a times series of the interferometric complex field (ICF). The ICF was analyzed off line and compared to a simple developed model that relates ICF coherence time to the ratio of significant wave height (SWH) and mean wave period (MWP). The analysis using this model showed good consistency between the ICF coherence time and nearby oceanographic buoy data. Based on this result, preliminary conclusions are drawn on the potential of coastal GNSS-R for sea state monitoring using semi-empirical modeling to relate GNSS-R ICF coherence time to SWH. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0406/0406029v1.pdf"}
{"id": "physics0406098", "abstract": "  We present the design and construction of a SQUID-based magnetometer for operation down to temperatures T = 10 mK, while retaining the compatibility with the sample holders typically used in commercial SQUID magnetometers. The system is based on a dc-SQUID coupled to a second-order gradiometer. The sample is placed inside the plastic mixing chamber of a dilution refrigerator and is thermalized directly by the 3He flow. The movement though the pickup coils is obtained by lifting the whole dilution refrigerator insert. A home-developed software provides full automation and an easy user interface. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0406/0406098v1.pdf"}
{"id": "physics0411115", "abstract": "  Using the Morlet continuous wavelet transform on data over the period 1871-1990, it is found that the global wavelet cross spectra between two solar activity indices and seven major Indian monsoon rainfall time series show significant power around the period of the 11 year solar cycle, passing the χ^2 test of significance proposed by Torrence and Compo (1998) at levels exceeding 95", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0411/0411115v1.pdf"}
{"id": "physics0411141", "abstract": "  Using coherence analysis (which is an extensively used method to study the correlations in frequency domain, between two simultaneously measured signals) we estimate the time delay between two signals. This method is suitable for time delay estimation of narrow band coherence signals for which the conventional methods cannot be reliably applied. We show by analysing coupled Rössler attractors with a known delay, that the method yields satisfactory results. Then, we apply this method to human pathologic tremor. The delay between simultaneously measured traces of Electroencephalogram (EEG) and Electromyogram (EMG) data of subjects with essential hand tremor is calculated. We find that there is a delay of 11-27 milli-seconds (ms) between the tremor correlated parts (cortex) of the brain (EEG) and the trembling hand (EMG) which is in agreement with the experimentally observed delay value of 15 ms for the cortico-muscular conduction time. By surrogate analysis we calculate error-bars of the estimated delay. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0411/0411141v1.pdf"}
{"id": "physics0509058", "abstract": "  Mandelbrot introduced the concept of fractals to describe the non-Euclidean shape of many aspects of the natural world. In the time series context he proposed the use of fractional Brownian motion (fBm) to model non-negligible temporal persistence, the \"Joseph Effect\"; and Levy flights to quantify large discontinuities, the \"Noah Effect\". In space physics, both effects are manifested in the intermittency and long-range correlation which are by now well-established features of geomagnetic indices and their solar wind drivers. In order to capture and quantify the Noah and Joseph effects in one compact model we propose the application of the \"bridging\" fractional Levy motion (fLm) to space physics. We perform an initial evaluation of some previous scaling results in this paradigm, and show how fLm can model the previously observed exponents. We suggest some new directions for the future. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0509/0509058v3.pdf"}
{"id": "physics0509142", "abstract": "  This study investigates that a characteristic time scale on an exchange rate market (USD/JPY) is examined for the period of 1998 to 2000. Calculating power spectrum densities for the number of tick quotes per minute and averaging them over the year yield that the mean power spectrum density has a peak at high frequencies. Consequently it means that there exist the characteristic scales which dealers act in the market. A simple agent model to explain this phenomenon is proposed. This phenomena may be a result of stochastic resonance with exogenous periodic information and physiological fluctuations of the agents. This may be attributed to the traders' behavior on the market. The potential application is both quantitative characterization and classification of foreign currency markets. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0509/0509142v1.pdf"}
{"id": "physics0602178", "abstract": "  For real world systems, nonuniform medium is ubiquitous. Therefore, we investigate the diffusion-limited-aggregation process on a two dimensional directed small-world network instead of regular lattice. The network structure is established by rewiring connections on the two dimensional directed lattice. Those rewired edges are controlled by two parameters θ and m, which characterize the spatial length and the density of the long-range connections, respectively. Simulations show that there exists a maximum value of the fractal dimension when θ equals zero. Interestingly, we find that the symmetry of the aggregation pattern is broken when rewired connections are long enough, which may be an explanation for the formation of asymmetrical fractal in nature. Then, we perform multifractal analysis on the patterns further. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0602/0602178v1.pdf"}
{"id": "physics0603069", "abstract": "  The optical theorem is applied to the process of electron-positron pair creation in the superposition of a nuclear Coulomb and a strong laser field. We derive new representations for the total production rate as two-fold integrals, both for circular laser polarization and for the general case of elliptic polarization, which has not been treated before. Our approach allows us to obtain by analytical means the asymptotic behaviour of the pair creation rate for various limits of interest. In particular, we consider pair production by two-photon absorption and show that, close to the energetic threshold of this process, the rate obeys a power law in the laser frequency with different exponents for linear and circular laser polarization. With the help of the upcoming x-ray laser sources our results could be tested experimentally. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0603/0603069v1.pdf"}
{"id": "physics0603222", "abstract": "  This paper presents a statistical analysis of the structure of Peer-to-Peer (P2P) social networks that captures social associations of distributed peers in resource sharing. Peer social networks appear to be mainly composed of pure resource providers that guarantee high resource availability and reliability of P2P systems. The major peers that both provide and request resources are only a small fraction. The connectivity between peers, including undirected, directed (out and in) and weighted connections, is scale-free and the social networks of all peers and major peers are small world networks. The analysis also confirms that peer social networks show in general disassortative correlations, except that active providers are connected between each other and by active requesters. The study presented in this paper gives a better understanding of peer relationships in resource sharing, which may help a better design of future P2P networks and open the path to the study of transport processes on top of real P2P topologies. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0603/0603222v1.pdf"}
{"id": "physics0605115", "abstract": "  Financial markets are highly correlated systems that reveal both the inter-market dependencies and the correlations among their different components. Standard analyzing techniques include correlation coefficients for pairs of signals and correlation matrices for rich multivariate data. In the latter case one constructs a real symmetric matrix with real non-negative eigenvalues describing the correlation structure of the data. However, if one performs a correlation-function-like analysis of multivariate data, when a stress is put on investigation of delayed dependencies among different types of signals, one can calculate an asymmetric correlation matrix with complex eigenspectrum. From the Random Matrix Theory point of view this kind of matrices is closely related to Ginibre Orthogonal Ensemble (GinOE). We present an example of practical application of such matrices in correlation analyses of empirical data. By introducing the time lag, we are able to identify temporal structure of the inter-market correlations. Our results show that the American and German stock markets evolve almost simultaneously without a significant time lag so that it is hard to find imprints of information transfer between these markets. There is only an extremely subtle indication that the German market advances the American one by a few seconds. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0605/0605115v1.pdf"}
{"id": "physics0607185", "abstract": "  In a previous Letter [Phys. Rev. Lett. 96, 123401 (2006)] we have shown by means of three-dimensional particle-in-cell simulations and a simple rigid-sphere model that nonlinear resonance absorption is the dominant collisionless absorption mechanism in the intense, short-pulse laser cluster interaction. In this paper we present a more detailed account of the matter. In particular we show that the absorption efficiency is almost independent of the laser polarization. In the rigid-sphere model, the absorbed energy increases by many orders of magnitude at a certain threshold laser intensity. The particle-in-cell results display maximum fractional absorption around the same intensity. We calculate the threshold intensity and show that it is underestimated by the common over-barrier ionization estimate. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0607/0607185v1.pdf"}
{"id": "physics0701183", "abstract": "  We report on a scheme to improve the pointing stability of the first order beam diffracted by an acousto-optic modulator (AOM). Due to thermal effects inside the crystal, the angular position of the beam can change by as much as 1 mrad when the radio-frequency power in the AOM is reduced to decrease the first order beam intensity. This is done for example to perform forced evaporative cooling in ultracold atom experiments using far-off-resonant optical traps. We solve this problem by driving the AOM with two radio-frequencies f_1 and f_2. The power of f_2 is adjusted relative to the power of f_1 to keep the total power constant. Using this, the beam displacement is decreased by a factor of twenty. The method is simple to implement in existing experimental setups, without any modification of the optics. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0701/0701183v1.pdf"}
{"id": "physics0701216", "abstract": "  We show theoretically that thermomechanical effects in dye-doped nematic liquid crystals when illuminated by laser beams, can become important and lead to molecular reorientation at intensities substantially lower than that needed for optical Fréedericksz transition. We propose a 1D model that assumes homogenous intensity distribution in the plane of the layer and is capable to describe such a thermally induced threshold lowering. We consider a particular geometry, with a linearly polarized light incident perpendicularly on a layer of homeotropically aligned dye-doped nematics. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0701/0701216v1.pdf"}
{"id": "physics0702079", "abstract": "  A small depression is created in a straight optical fiber taper to form a local probe suitable for studying closely spaced, planar microphotonic devices. The tension of the \"dimpled\" taper controls the probe-sample interaction length and the level of noise present during coupling measurements. Practical demonstrations with high-Q silicon microcavities include testing a dense array of undercut microdisks (maximum Q = 3.3x10^6) and a planar microring (Q = 4.8x10^6). ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0702/0702079v1.pdf"}
{"id": "physics9806033", "abstract": "  In the past many papers have appeared which simulated surface growth with different growth models. The results showed that, if models differed only slightly in their `growth' rules, the resulting surfaces may belong to different universality classes, i.e. they are described by different differential equations. In the present paper we describe a mapping of “growth rules” to differential operators and give plausibility arguments for this mapping. We illustrate the validity of our theory by applying it to published results. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/9806/9806033v1.pdf"}
{"id": "physics9811013", "abstract": "  In order to study photomultiplier's short-term gain stability at high counting rate, we constructed an LED pulsed light source and its output monitor system. For the monitor system, we employed a photon counting method using a photomultiplier as a monitor photon detector. It is found that the method offers a simple way to monitor outputs from a pulsed light source and that, together with an LED light source, it provides a handy way to investigate photomultiplier's rate effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/9811/9811013v1.pdf"}
{"id": "physics9909049", "abstract": "  The Monte Carlo simulation of the dynamics of complex molecules produces trajectories with a large number of different configurations to sample configuration space. It is expected that these configurations can be classified into a small number of conformations representing essential changes in the shape of the molecule. We present a method to visualize these conformations by point sets in the plane based on a geometrical distance measure between individual configurations. It turns out that different conformations appear as well-separated point sets. The method is further improved by performing a cluster analysis of the data set. The point-cluster representation is used to control a three-dimensional molecule viewer application to show individual configurations and conformational changes. The extraction of essential coordinates and visualization of molecular shape is discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/9909/9909049v1.pdf"}
{"id": "q-bio0401005", "abstract": "  Neural circuits often face the problem of classifying stimuli into discrete groups and making decisions based on such classifications. Neurons of these circuits can be distinguished according to their correlations with different features of stimulus or response, which allows defining sensory or motor neuronal types. In this study we define the third class of neurons, which is responsible for making decision. We suggest two descriptions for contribution of units to decision making: first, as a spatial derivative of correlations between neural activity and the decision; second, as an impact of variability in a given neuron on the response. These two definitions are shown to be equivalent, when they can be compared. We also suggest an experimental strategy for determining contributions to decision making, which uses electric stimulation with time- varying random current. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0401/0401005v1.pdf"}
{"id": "q-bio0407021", "abstract": "  We analyze a mathematical model of the epizootic of Hantavirus in mice population, including the effect of species which compete with the host. We show that the existence of the second species has an important consequence for the prevalence of the infectious agent in the host. When the two mice species survive in the ecosystem, the competitive pressure of the second species may lead to reduction or complete elimination of the prevalence of infection. The transition between the disappearance of the infection and its presence occurs at a critical value of the competitor's population, resembling a second order phase transition in a statistical system. The results provide a rigorous framework for the study of the impact of biodiversity in the propagation of infectious diseases, and further lends itself to future experimental verification. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0407/0407021v2.pdf"}
{"id": "q-bio0608006", "abstract": "  Adhesion-dependent cells actively sense the mechanical properties of their environment through mechanotransductory processes at focal adhesions, which are integrin-based contacts connecting the extracellular matrix to the cytoskeleton. Here we present first steps towards a quantitative understanding of focal adhesions as mechanosensors. It has been shown experimentally that high levels of force are related to growth of and signaling at focal adhesions. In particular, activation of the small GTPase Rho through focal adhesions leads to the formation of stress fibers. Here we discuss one way in which force might regulate the internal state of focal adhesions, namely by modulating the internal rupture dynamics of focal adhesions. A simple two-spring model shows that the stiffer the environment, the more efficient cellular force is built up at focal adhesions by molecular motors interacting with the actin filaments. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0608/0608006v1.pdf"}
{"id": "q-bio0608042", "abstract": "  We show that the nearest neighbour distribution of distances between basis pairs of some intron-less and intron-containing coding regions are the same when a procedure, called unfolding, is applied. Such a procedure consists in separating the secular variations from the oscillatory terms. The form of the distribution obtained is quite similar to that of a random, i.e. Poissonian, sequence. This is done for the HUMBMYH7CD, DROMYONMA, HUMBMYH7 and DROMHC sequences. The first two correspond to highly coding regions while the last two correspond to non-coding regions. We also show that the distributions before the unfolding procedure depend on the secular part but, after the unfolding procedure we obtain an striking result: all distributions are similar to each other. The result becomes independent of the content of introns or the species we have chosen. This is in contradiction with the results obtained with the detrended fluctuation analysis in which the correlations yield different results for intron-less and intron-containing regions. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0608/0608042v1.pdf"}
{"id": "q-bio0701016", "abstract": "  The authors study the short-time dynamics of helix-forming polypeptide chains using an all-atom representation of the molecules and an implicit solvation model to approximate the interaction with the surrounding solvent. The results confirm earlier observations that the helix-coil transition in proteins can be described by a set of critical exponents. The high statistics of the simulations allows the authors to determine the exponents values with increased precision and support universality of the helix-coil transition in homopolymers and (helical) proteins. ", "pdf_url": "gs://arxiv-dataset/arxiv/q-bio/pdf/0701/0701016v1.pdf"}
{"id": "quant-ph0001065", "abstract": "  We suggest a tunable optical device to synthesize Fock states and their superpositions starting from a coherent source. The scheme involves an avalanche triggering photodetector and a ring cavity coupled to a traveling wave through a cross-Kerr medium. Low quantum efficiency at the photodetector improves the synthesizing quality at the expense of reducing the synthesizing rate. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0001/0001065v1.pdf"}
{"id": "quant-ph0105137", "abstract": "  We develop a systematic theory of quantum fluctuations in the driven parametric oscillator (OPO), including the region near threshold. This allows us to treat the limits imposed by nonlinearities to quantum squeezing and noise reduction, in this non-equilibrium quantum phase-transition. In particular, we compute the squeezing spectrum near threshold, and calculate the optimum value. We find that the optimal noise reduction occurs at different driving fields, depending on the ratio of damping rates. The largest spectral noise reductions are predicted to occur with a very high-Q second-harmonic cavity. Our analytic results agree well with stochastic numerical simulations. We also compare the results obtained in the positive-P representation, as a fully quantum mechanical calculation, with the truncated Wigner phase space equation, also known as semiclassical theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0105/0105137v1.pdf"}
{"id": "quant-ph0109001", "abstract": "  The Larmor precession of a neutral spinning particle in a magnetic field confined to the region of a one dimensional-rectangular barrier is investigated for both a nonrelativistic and a relativistic incoming particle. The spin precession serves as a clock to measure the time spent by a quantum particle traversing a potential barrier. With the help of general spin coherent state it is explicitly shown that the precession time is equal to the dwell time in both the nonrelativistic and relativistic cases. We also present a numerical estimation of the precession time showing an apparent superluminal tunneling. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0109/0109001v1.pdf"}
{"id": "quant-ph0207087", "abstract": "  We study a four-level atomic scheme interacting with four lasers in a closed-loop configuration with a  (diamond) geometry. We investigate the influence of the laser phases on the steady state. We show that, depending on the phases and the decay characteristic, the system can exhibit a variety of behaviors, including population inversion and complete depletion of an atomic state. We explain the phenomena in terms of multi-photon interference. We compare our results with the phase-dependent phenomena in the double-Λ scheme, as studied in [Korsunsky and Kosachiov, Phys. Rev A 60, 4996 (1999)]. This investigation may be useful for developing non-linear optical devices, and for the spectroscopy and laser-cooling of alkali-earth atoms. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0207/0207087v1.pdf"}
{"id": "quant-ph0208141", "abstract": "  The time evolution of anharmonic molecular wave packets is investigated under the influence of the environment consisting of harmonic oscillators. These oscillators represent photon or phonon modes and assumed to be in thermal equilibrium. Our model explicitly incorporates the fact that in the case of a nonequidistant spectrum the rates of the environment induced transitions are different for each transition. The nonunitary time evolution is visualized by the aid of the Wigner function related to the vibrational state of the molecule. The time scale of decoherence is much shorter than that of dissipation, and gives rise to states which are mixtures of localized states along the phase space orbit of the corresponding classical particle. This behavior is to a large extent independent of the coupling strength, the temperature of the environment and also of the initial state. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0208/0208141v1.pdf"}
{"id": "quant-ph0306183", "abstract": "  The Grover quantum search algorithm is generalized to deal with an arbitrary mixed initial state. The probability to measure a marked state as a function of time is calculated, and found to depend strongly on the specific initial state. The form of the function, though, remains as it is in the case of initial pure state. We study the role of the von Neumann entropy of the initial state, and show that the entropy cannot be a measure for the usefulness of the algorithm. We give few examples and show that for some extremely mixed initial states carrying high entropy, the generalized Grover algorithm is considerably faster than any classical algorithm. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0306/0306183v1.pdf"}
{"id": "quant-ph0308068", "abstract": "  Motivated by the ideas of using cold alkaline earth atoms trapped in an optical lattice for realization of optical atomic clocks, we investigate theoretically the perturbative effects of atom-atom interactions on a clock transition frequency. These interactions are mediated by the dipole fields associated with the optically excited atoms. We predict resonance-like features in the frequency shifts when constructive interference among atomic dipoles occur. We theoretically demonstrate that by fine-tuning the coherent dipole-dipole couplings in appropriately designed lattice geometries, the undesirable frequency shifts can be greatly suppressed. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0308/0308068v1.pdf"}
{"id": "quant-ph0309076", "abstract": "  We investigate a circular cavity billiard within which a pair of identical hard disks of smaller but finite size is confined. Each disk shows a free motion except when bouncing elastically with its partner and with the boundary wall. Despite its circular symmetry, this system is nonintegrable and almost chaotic because of the (short-range) interaction between the disks. We quantize the system by incorporating the excluded volume effect for the wavefunction. Eigenvalues and eigenfunctions are obtained by tuning the relative size between the disks and the billiard. We define the volume V of the cavity and the pressure P, i.e., the derivative of each eigenvalue with respect to V. Reflecting the fact that the energy spectra of eigenvalues versus the disk size show a multitude of level repulsions, P-V characteristics shows the anomalous fluctuations accompanied by many van der Waals-like peaks in each of individual excited eigenstates taken as a quasi-equilibrium. For each eigenstate, we calculate the expectation values of the square distance between two disks, and point out their relationship with the pressure fluctuations. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0309/0309076v1.pdf"}
{"id": "quant-ph0403119", "abstract": "  These notes are more or less a faithful representation of my talk at the Workshop on “Quantum Coding and Quantum Computing” held at the University of Virginia. As such it is an introduction for non-physicists to the topics of the quantum theory of light and entangled states of light. In particular, I discuss the photon concept and what is really entangled in an entangled state of light (it is not the photons). Moreover, I discuss an example that highlights the peculiar behavior of entanglement in an infinite-dimensional Hilbert space. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0403/0403119v1.pdf"}
{"id": "quant-ph0503020", "abstract": "  We analyze the quantum entanglement between two interacting atoms trapped in a spherical harmonic potential. At ultra-cold temperature, ground state entanglement is generated by the dominated s-wave interaction. Based on a regularized pseudo-potential Hamiltonian, we examine the quantum entanglement by performing the Schmidt decomposition of low-energy eigenfunctions. We indicate how the atoms are paired and quantify the entanglement as a function of a modified s-wave scattering length inside the trap. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0503/0503020v2.pdf"}
{"id": "quant-ph0504147", "abstract": "  The dynamics of an atomic few-level system can depend on the phase of driving fields coupled to the atom if certain conditions are satisfied. This is of particular interest to control interference effects, which can alter the system properties considerably. In this article, we discuss the mechanisms of such phase control and interference effects in an atomic three-level system in Λ configuration, where the upper state spontaneously decays into the two lower states. The lower states are coupled by a driving field, which we treat as quantized. This allows for an interpretation on the single photon level for both the vacuum and the driving field. By analyzing the system behavior for a driving field initially in non-classical states with only few Fock number states populated, we find that even though the driving field is coupled to the lower states only, it induces a multiplet of upper states. Then interference occurs independently in three-level subsystems in V configuration, each formed by two adjacent upper states and a single dressed lower state. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0504/0504147v1.pdf"}
{"id": "quant-ph0508182", "abstract": "  The state of a particle in space and time is characterized by its mass and spin, which therefore determine the inertial properties of the particle. The coupling of intrinsic spin with rotation is examined and the corresponding inertial effects of intrinsic spin are studied. An experiment to measure directly the spin-rotation coupling via neutron interferometry is analyzed in detail. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0508/0508182v2.pdf"}
{"id": "quant-ph0510213", "abstract": "  We present the design and experimental proof of principle of a low threshold optical parametric oscillator (OPO) that continuously oscillates over a large bandwidth allowed by phase matching. The large oscillation bandwidth is achieved with a selective two-photon loss that suppresses the inherent mode competition, which tends to narrow the bandwidth in conventional OPOs. Our design performs pairwise mode-locking of many frequency pairs, in direct equivalence to passive mode-locking of ultrashort pulsed lasers. The ability to obtain high powers of continuous and broadband down-converted light enables the optimal exploitation of the correlations within the down-converted spectrum, thereby strongly affecting two-photon interactions even at classically high power levels, and opening new venues for applications such as two-photon spectroscopy and microscopy and optical spread spectrum communication. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0510/0510213v2.pdf"}
{"id": "quant-ph0511137", "abstract": "  This paper develops a scattering theory to examine how point impurities affect transport through quantum wires. While some of our new results apply specifically to hard-walled wires, others–for example, an effective optical theorem for two-dimensional waveguides–are more general. We apply the method of images to the hard-walled guide, explicitly showing how scattering from an impurity affects the wire's conductance. We express the effective cross section of a confined scatterer entirely in terms of the empty waveguide's Green's function, suggesting a way in which to use semiclassical methods to understand transport properties of smooth wires. In addition to predicting some new phenomena, our approach provides a simple physical picture for previously observed effects such as conductance dips and confinement-induced resonances. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0511/0511137v3.pdf"}
{"id": "quant-ph0512069", "abstract": "  We consider the problem of evaluating the entanglement of non-Gaussian mixed states generated by photon subtraction from entangled squeezed states. The entanglement measures we use are the negativity and the logarithmic negativity. These measures possess the unusual property of being computable with linear algebra packages even for high-dimensional quantum systems. We numerically evaluate these measures for the non-Gaussian mixed states which are generated by photon subtraction with on/off photon detectors. The results are compared with the behavior of certain operational measures, namely the teleportation fidelity and the mutual information in the dense coding scheme. It is found that all of these results are mutually consistent, in the sense that whenever the enhancement is seen in terms of the operational measures, the negativity and the logarithmic negativity are also enhanced. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0512/0512069v2.pdf"}
{"id": "quant-ph0601069", "abstract": "  We investigate the short-time dynamics of a delta-function potential barrier on an initially confined wave-packet. There are mainly two conclusions: A) At short times the probability density of the first particles that passed through the barrier is unaffected by it. B) When the barrier is absorptive (i.e., its potential is imaginary) it affects the transmitted wave function at shorter times than a real potential barrier. Therefore, it is possible to distinguish between an imaginary and a real potential barrier by measuring its effect at short times only on the transmitting wavefunction. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0601/0601069v1.pdf"}
{"id": "quant-ph0605024", "abstract": "  Entanglement and entanglement-assisted are useful resources to enhance the mutual information of the Pauli channels, when the noise on consecutive uses of the channel has some partial correlations. In this paper, We study quantum communication channels with correlated noise and derive a general expression for the mutual information of quantum channel, for the product, maximally entangled state coding and entanglement-assisted systems with correlated noise in the Pauli quantum channels. Hence, we suggest more efficient coding in the entanglement-assisted systems for the transmission of classical information and derive a general expression for the entanglement-assisted classical capacity. Our results show that in the presence of memory, a higher amount of classical information is transmitted by two or four consecutive uses of entanglement-assisted systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0605/0605024v2.pdf"}
{"id": "quant-ph0606195", "abstract": "  Chains of first-order SUSY transformations for the spin equation are studied in detail. It is shown that the transformation chains are related with a olynomial pseudo-supersymmetry of the system. Simple determinant formulas for the final Hamiltonian of a chain and for solutions of the spin equation are derived. Applications are intended for a two-level atom in an electromagnetic field with a possible time-dependence of the field frequency. For a specific form of this dependence, the time oscillations of the probability to populate the excited level disappear. Under certain conditions this probability becomes a function tending monotonously to a constant value which can exceed 1/2. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0606/0606195v1.pdf"}
{"id": "quant-ph0606207", "abstract": "  In this paper we study the concurrence and the block-block entanglement in the S=1/2 spin ladder with four-spin ring exchange by the exact diagonalization method of finite cluster of spins. The relationship between the global phase diagram and the ground-state entanglement is investigated. It is shown that the block-block entanglement of different block size and geometry manifests richer information of the system. We find that the extremal point of the two-site block-block entanglement on the rung locates a transition point exactly due to SU(4) symmetry at this point. The scaling behavior of the block-block entanglement is discussed. Our results suggest that the block-block entanglement can be used as a convenient marker of quantum phase transition in some complex spin systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0606/0606207v1.pdf"}
{"id": "quant-ph0610238", "abstract": "  Quantum entanglement is a concept commonly used with reference to the existence of certain correlations in quantum systems that have no classical interpretation. It is a useful resource to enhance the mutual information of memory channels or to accelerate some quantum processes as, for example, the factorization in Shor's Algorithm. Moreover, entanglement is a physical observable directly measured by the von Neumann entropy of the system. We have used this concept in order to give a physical meaning to the electron correlation energy in systems of interacting electrons. The electronic correlation is not directly observable, since it is defined as the difference between the exact ground state energy of the many–electrons Schroedinger equation and the Hartree–Fock energy. We have calculated the correlation energy and compared with the entanglement, as functions of the nucleus–nucleus separation using, for the hydrogen molecule, the Configuration Interaction method. Then, in the same spirit, we have analyzed a dimer of ethylene, which represents the simplest organic conjugate system, changing the relative orientation and distance of the molecules, in order to obtain the configuration corresponding to maximum entanglement. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0610/0610238v1.pdf"}
{"id": "quant-ph0702211", "abstract": "  Given a single copy of a mixed state of the form ρ=λρ_1+(1-λ)ρ_2, what is the optimal measurement to estimate the parameter λ, if ρ_1 and ρ_2 are known? We present a general strategy to obtain the optimal measurements employing a Bayesian estimator. The measurements are chosen to minimize the deviation between the estimated- and the true value of λ. We explicitly determine the optimal measurements for a general two-dimensional system and for important higher dimensional cases. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0702/0702211v2.pdf"}
{"id": "quant-ph0703254", "abstract": "  Recently Bender, Brody, Jones and Meister found that in the quantum brachistochrone problem the passage time needed for the evolution of certain initial states into specified final states can be made arbitrarily small, when the time-evolution operator is taken to be non-Hermitian but PT-symmetric. Here we demonstrate that such phenomena can also be obtained for non-Hermitian Hamiltonians for which PT-symmetry is completely broken, i.e. dissipative systems. We observe that the effect of a tunable passage time can be achieved by projecting between orthogonal eigenstates by means of a time-evolution operator associated to a non-Hermitian Hamiltonian. It is not essential that this Hamiltonian is PT-symmetric. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0703/0703254v2.pdf"}
{"id": "quant-ph9903049", "abstract": "  Classical and quantum error correction are presented in the form of Maxwell's demon and their efficiency analyzed from the thermodynamic point of view. We explain how Landauer's principle of information erasure applies to both cases. By then extending this principle to entanglement manipulations we rederive upper bounds on purification procedures thereby linking the ”no local increase of entanglement” principle to the Second Law of thermodynamics. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9903/9903049v2.pdf"}
{"id": "quant-ph9912051", "abstract": "  In order to extend the recently proposed Monte Carlo Hamiltonian to many-body systems, we suggest to concept of a stochastic basis. We apply it to the chain of N_s=9 coupled anharmonic oscillators. We compute the spectrum of excited states in a finite energy window and thermodynamical observables free energy, average energy, entropy and specific heat in a finite temperature window. Comparing the results of the Monte Carlo Hamiltonian with standard Lagrangian lattice calculations, we find good agreement. However, the Monte Carlo Hamiltonian results show less fluctuations under variation of temperature. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/9912/9912051v2.pdf"}
{"id": "0704.1001", "abstract": "  We propose a Hodge field theory construction that captures algebraic properties of the reduction of Zwiebach invariants to Gromov-Witten invariants. It generalizes the Barannikov-Kontsevich construction to the case of higher genera correlators with gravitational descendants.   We prove the main theorem stating that algebraically defined Hodge field theory correlators satisfy all tautological relations. From this perspective the statement that Barannikov-Kontsevich construction provides a solution of the WDVV equation looks as the simplest particular case of our theorem. Also it generalizes the particular cases of other low-genera tautological relations proven in our earlier works; we replace the old technical proofs by a novel conceptual proof. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1001v1.pdf"}
{"id": "0704.1592", "abstract": "  We present observations of a solar quiet region obtained by the ground-based Dutch Open Telescope (DOT), and by instruments on the spacecraft SOHO and TRACE. The observations were obtained during a coordinated observing campaign on October 2005. The aim of this work is to present the rich diversity of fine-scale structures that are found at the network boundaries and their appearance in different instruments and different spectral lines that span the photosphere to the corona. Detailed studies of these structures are crucial to understanding their dynamics in different solar layers, as well as the role such structures play in the mass balance and heating of the solar atmosphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0704/0704.1592v1.pdf"}
{"id": "0705.1944", "abstract": "  We derive the exact solution for the optical conductivity σ(ω) of one hole in the Holstein-t-J model in the framework of dynamical mean-field theory (DMFT). We investigate the magnetic and phonon features associated with polaron formation as a function of the exchange coupling J, of the electron-phonon interaction λ and of the temperature. Our solution directly relates the features of the optical conductivity to the excitations in the single-particle spectral function, revealing two distinct mechanisms of closing and filling of the optical pseudogap that take place upon varying the microscopic parameters. We show that the optical absorption at the polaron crossover is characterized by a coexistence of a magnon peak at low frequency and a broad polaronic band at higher frequency. An analytical expression for σ(ω) valid in the polaronic regime is presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.1944v2.pdf"}
{"id": "0705.1974", "abstract": "  We investigate the effects of risk perception in a simple model of epidemic spreading. We assume that the perception of the risk of being infected depends on the fraction of neighbors that are ill. The effect of this factor is to decrease the infectivity, that therefore becomes a dynamical component of the model. We study the problem in the mean-field approximation and by numerical simulations for regular, random and scale-free networks.   We show that for homogeneous and random networks, there is always a value of perception that stops the epidemics. In the “worst-case” scenario of a scale-free network with diverging input connectivity, a linear perception cannot stop the epidemics; however we show that a non-linear increase of the perception risk may lead to the extinction of the disease. This transition is discontinuous, and is not predicted by the mean-field analysis. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0705/0705.1974v3.pdf"}
{"id": "0706.1905", "abstract": "  Vibrational energy transfer of the amide I mode of N-methylacetamide (NMA) is studied theoretically using the vibrational configuration interaction method. A quartic force field of NMA is constructed at the B3LYP/6-31G+(d) level of theory and its accuarcy is checked by comparing the resulting anharmonic frequencies with available theoretical and experimental values. Quantum dynamics calculations for the amide I mode excitation clarify the dominant energy transfer pathways, which sensitively depend on the anharmonic couplings among vibrational modes. A ratio of the anharmonic coupling to the frequency mismatch is employed to predict and interpret the dominant energy flow pathways. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0706/0706.1905v1.pdf"}
{"id": "0707.0014", "abstract": "  We examine the possibility of distinguishing a supersymmetric gluino from a Kaluza-Klein gluon of universal extra dimensions (UED) at the Large Hadron Collider (LHC). We focus on the case when all kinematically allowed tree-level decays of this particle are 3-body decays into two jets and a massive daughter (typically weak gaugino or Kaluza-Klein weak gauge boson). We show that the shapes of the dijet invariant mass distributions differ significantly in the two models, as long as the mass of the decaying particle mA is substantially larger than the mass of the massive daughter mB. We present a simple analysis estimating the number of events needed to distinguish between the two models under idealized conditions. For example, for mA/mB=10, we find the required number of events to be of order several thousand, which should be available at the LHC within a few years. This conclusion is confirmed by a parton level Monte Carlo study which includes the effects of experimental cuts and the combinatoric background. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0707/0707.0014v1.pdf"}
{"id": "0708.3432", "abstract": "  The influence of Gaussian laser pulses on the transport through molecular wires is investigated within a tight-binding model for spinless electrons including correlation. Motivated by the phenomenon of coherent destruction of tunneling for monochromatic laser fields, situations are studied in which the maximum amplitude of the electric field fulfills the conditions for the destructive quantum effect. It is shown that, as for monochromatic laser pulses, the average current through the wire can be suppressed. For parameters of the model, which do not show a net current without any optical field, a Gaussian laser pulse can establish a temporary current. In addition, the effect of electron correlation on the current is investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.3432v1.pdf"}
{"id": "0708.3758", "abstract": "  We have tested the application to Sloan Digital Sky Survey data of the software package MATCH, which fits color-magnitude diagrams (CMDs) to estimate stellar population parameters and distances. These tests on a set of six globular clusters show that these techniques recover their known properties. New ways of using the CMD-fitting software enable us to deal with an extended distribution of stars along the line-of-sight, to constrain the overall properties of sparsely populated objects, and to detect the presence of stellar overdensities in wide-area surveys. We then also apply MATCH to CMDs for twelve recently discovered Milky Way satellites to derive in a uniform fashion their distances, ages and metallicities. While the majority of them appear consistent with a single stellar population, CVn I, UMa II, and Leo T exhibit (from SDSS data alone) a more complex history with multiple epochs of star formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0708/0708.3758v2.pdf"}
{"id": "0709.2683", "abstract": "  The setup of two different small scale teststands for measurements regarding an electron Cherenkov detector as part of the ILC polarimeters is presented. Component measurements already carried out are analyzed and others, foreseen for the near future, are discussed. The larger one of the two teststands features the old Cherenkov detector of the SLD experiment, which will be used as a reference for a number of crucial measurements. Especially, the requirements for the non-linearity of the read-out chain are studied in greater detail and methods for its precise measurement before and during operation are being developed accordingly. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.2683v1.pdf"}
{"id": "0709.4484", "abstract": "  In this paper, we study time-optimal control problems related to system of two coupled qubits where the time scales involved in performing unitary transformations on each qubit are significantly different. In particular, we address the case where unitary transformations produced by evolutions of the coupling take much longer time as compared to the time required to produce unitary transformations on the first qubit but much shorter time as compared to the time to produce unitary transformations on the second qubit. We present a canonical decomposition of SU(4) in terms of the subgroup SU(2)xSU(2)xU(1), which is natural in understanding the time-optimal control problem of such a coupled qubit system with significantly different time scales. A typical setting involves dynamics of a coupled electron-nuclear spin system in pulsed electron paramagnetic resonance experiments at high fields. Using the proposed canonical decomposition, we give time-optimal control algorithms to synthesize various unitary transformations of interest in coherent spectroscopy and quantum information processing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0709/0709.4484v1.pdf"}
{"id": "0710.5395", "abstract": "  We investigate the ballistic motion of electrons in III-V semiconductor quantum wells with Rashba spin-orbit coupling in a perpendicular magnetic field. Taking into account the full quantum dynamics of the problem, we explore the modifications of classical cyclotron orbits due to spin-orbit interaction. As a result, for electron energies comparable with the cyclotron energy the dynamics are particularly rich and not adequately described by semiclassical approximations. Our study is complementary to previous semiclassical approaches concentrating on the regime of weaker fields. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0710/0710.5395v2.pdf"}
{"id": "0711.1297", "abstract": "  Dark matter caustics are small scale, high density structures believed to exist in galaxies like ours. If the dark matter consists of Weakly Interacting Massive Particles, these caustics may be detected by means of the gamma rays produced by dark matter particle annihilation. We discuss particle annihilation in outer and inner caustics and provide sky maps of the expected gamma ray distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.1297v2.pdf"}
{"id": "0711.1716", "abstract": "  The purpose of the paper is to introduce some conjectures regarding the analytic continuation and the arithmetic properties of quantum invariants of knotted objects. More precisely, we package the perturbative and nonperturbative invariants of knots and 3-manifolds into two power series of type P and NP, convergent in a neighborhood of zero, and we postulate their arithmetic resurgence. By the latter term, we mean analytic continuation as a multivalued analytic function in the complex numbers minus a discrete set of points, with restricted singularities, local and global monodromy. We point out some key features of arithmetic resurgence in connection to various problems of asymptotic expansions of exact and perturbative Chern-Simons theory with compact or complex gauge group. Finally, we discuss theoretical and experimental evidence for our conjecture. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0711/0711.1716v3.pdf"}
{"id": "0712.0555", "abstract": "  We analyzed uvby and Hp light curves of 19 well observed magnetic CP stars selected from the \"On-line database of photometric observations of mCP stars\" of which light curves in all the five colours were similar. We assumed that among these photometrically simply behaving (PSB) stars could be found such ones which have a single photometric spot. The insight into such simple situations would help us to comprehend more complicated cases. Light curves of the 19 PSB mCP stars proved to be generally nearly symmetric but surprisingly diverse. The analysis shows that only in the case of HD 110956B, HD 188041, and perhaps HD 193722 we are able to explain their photometric behaviour by a simple one-spot model. Consequently, occurrence of more than one photometric spot on an mCP star is typical. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.0555v1.pdf"}
{"id": "0712.1747", "abstract": "  In transport calculations for molecular junctions based on density functional theory the choice of exchange and correlation functional may dramatically affect the results. In particular local and semi-local functionals tend to over-delocalize the molecular levels thus artificially increasing their broadening. In addition the same molecular levels are usually misplaced with respect to the Fermi level of the electrodes. These shortfalls are reminiscent of the inability of local functionals to describe Mott-Hubbard insulators, but they can be corrected with a simple and computationally undemanding self-interaction correction scheme. We apply such a scheme, as implemented in our transport code Smeagol, to a variety of phenyl-based molecular junctions attached to gold electrodes. In general the corrections reduce the current, since the resonant Kohn-Sham states of the molecule are shifted away from the contact Fermi level. In contrast, when the junction is already described as insulating by local exchange and correlation potentials, the corrections are minimal and the I-V is only weakly modified. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.1747v1.pdf"}
{"id": "0712.3448", "abstract": "  The structural and electronic properties of gold decorated Si(335) surface are studied by means of density-functional calculations. The resulting structural model indicates that the Au atoms substitute some of the Si atoms in the middle of the terrace in the surface layer. Calculated electronic band structure near the Fermi energy features two metallic bands, one coming from the step edge Si atoms and the other one having its origin in hybridization between the Au and neighboring Si atoms in the middle of the terrace. The obtained electronic bands remain in good agreement with photoemission data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0712/0712.3448v1.pdf"}
{"id": "0801.2312", "abstract": "  A first-principles calculation of the impurity screening in Si and Ge nanocrystals is presented. We show that isocoric screening gives results in agreement with both the linear response and the point-charge approximations. Based on the present ab initio results, and by comparison with previous calculations, we propose a physical real-space interpretation of the several contributions to the screening. Combining the Thomas-Fermi theory and simple electrostatics, we show that it is possible to construct a model screening function that has the merit of being of simple physical interpretation. The main point upon which the model is based is that, up to distances of the order of a bond length from the perturbation, the charge response does not depend on the nanocrystal size. We show in a very clear way that the link between the screening at the nanoscale and in the bulk is given by the surface polarization. A detailed discussion is devoted to the importance of local field effects in the screening. Our first-principles calculations and the Thomas-Fermi theory clearly show that in Si and Ge nanocrystals, local field effects are dominated by surface polarization, which causes a reduction of the screening in going from the bulk down to the nanoscale. Finally, the model screening function is compared with recent state-of-the-art ab initio calculations and tested with impurity activation energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0801/0801.2312v1.pdf"}
{"id": "0802.1683", "abstract": "  The competition between reptation and Rouse Dynamics is incorporated in the Rubinstein-Duke model for polymer motion by extending it with sideways motions, which cross barriers and create or annihilate hernias. Using the Density-Matrix Renormalization-Group Method as solver of the Master Equation, the renewal time and the diffusion coefficient are calculated as function of the length of the chain and the strength of the sideways motion. These new types of moves have a strong and delicate influence on the asymptotic behavior of long polymers. The effects are analyzed as function of the chain length in terms of effective exponents and crossover scaling functions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0802/0802.1683v1.pdf"}
{"id": "0805.0401", "abstract": "  In the framework of Left-Right symmetric model, we investigate an interesting scenario, in which the so-called VEV seesaw problem can be naturally solved with Z_2 symmetry. In such a scenario, we find a pair of stable weakly interacting massive particles (WIMPs), which may be the cold dark matter candidates. However, the WIMP-nucleon cross section is 3-5 orders of magnitude above the present upper bounds from the direct dark matter detection experiments for m ∼ 10^2-10^4 GeV. As a result, the relic number density of two stable particles has to be strongly suppressed to a very small level. Nevertheless, our analysis shows that this scenario can't provide very large annihilation cross sections so as to give the desired relic abundance except for the resonance case. Only for the case if the rotation curves of disk galaxies are explained by the Modified Newtonian Dynamics (MOND), the stable WIMPs could be as the candidates of cold dark matter. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.0401v2.pdf"}
{"id": "0805.1936", "abstract": "  Kepler will monitor a sufficient number of stars that it is likely to detect single transits of planets with periods longer than the mission lifetime. We show that by combining the exquisite Kepler photometry of such transits with precise radial velocity observations taken over a reasonable timescale (  6 months) after the transits, and assuming circular orbits, it is possible to estimate the periods of these transiting planets to better than 20", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0805/0805.1936v3.pdf"}
{"id": "0806.1063", "abstract": "  Tumor growth has long been a target of investigation within the context of mathematical and computer modelling. The objective of this study is to propose and analyze a two-dimensional probabilistic cellular automata model to describe avascular solid tumor growth, taking into account both the competition between cancer cells and normal cells for nutrients and/or space and a time-dependent proliferation of cancer cells. Gompertzian growth, characteristic of some tumors, is described and some of the features of the time-spatial pattern of solid tumors, such as compact morphology with irregular borders, are captured. The parameter space is studied in order to analyze the occurrence of necrosis and the response to therapy. Our findings suggest that transitions exist between necrotic and non-necrotic phases (no-therapy cases), and between the states of cure and non-cure (therapy cases). To analyze cure, the control and order parameters are, respectively, the highest probability of cancer cell proliferation and the probability of the therapeutic effect on cancer cells. With respect to patterns, it is possible to observe the inner necrotic core and the effect of the therapy destroying the tumor from its outer borders inwards. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.1063v1.pdf"}
{"id": "0806.2958", "abstract": "  The propagation of azimuthally symmetric guided waves in multiwalled carbon nanotubes (MWCNTs) was analyzed theoretically in the mid-infrared and the visible regimes. The MWCNTs were modeled as ensembles of concentric, cylindrical, conducting shells. Slightly attenuated guided waves and antenna resonances due to the edge effect exist for not-too-thick MWCNTs in the far- and mid-infrared regimes. Interband transitions hinder the propagation of guided waves and have a deleterious effect on the performance of a finite-length MWCNT as an antenna. Propagation of surface-plasmon waves along an MWCNT with a gold core was also analyzed. In the near-infrared and the visible regimes, the shells behave effectively as lossy dielectrics suppressing surface-plasmon-wave propagation along the gold core. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.2958v1.pdf"}
{"id": "0806.3554", "abstract": "  We study the heavy-heavy-light quark (QQq) potential in SU(3) quenched lattice QCD, and discuss one of the roles of the finite-mass valence quark in the inter-quark potential. Monte Carlo simulations are performed with the standard gauge action on the 16^4 lattice at β =6.0 and the O(a)-improved Wilson fermion action at four hopping parameters. For statistical improvement, the gauge configuration is fixed with the Coulomb gauge. We calculate the potential energy of QQq systems as a function of the inter-heavy-quark distance R in the range of R ≤ 0.8 fm. The QQq potential is well described with a Coulomb plus linear potential, and the effective string tension between the two heavy quarks is significantly smaller than the string tension σ≃ 0.89 GeV/fm. It would generally hold that the effect of the finite-mass valence quark reduces the inter-two-quark confinement force in baryons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0806/0806.3554v2.pdf"}
{"id": "0807.4763", "abstract": "  We present two simple cryogenic RF ion trap systems in which cryogenic temperatures and ultra high vacuum pressures can be reached in as little as 12 hours. The ion traps are operated either in a liquid helium bath cryostat or in a low vibration closed cycle cryostat. The fast turn around time and availability of buffer gas cooling made the systems ideal for testing surface-electrode ion traps. The vibration amplitude of the closed cycled cryostat was found to be below 106 nm. We evaluated the systems by loading surface-electrode ion traps with ^88Sr^+ ions using laser ablation, which is compatible with the cryogenic environment. Using Doppler cooling we observed small ion crystals in which optically resolved ions have a trapped lifetime over 2500 minutes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0807/0807.4763v1.pdf"}
{"id": "0808.0472", "abstract": "  The first phase of stellar evolution in the history of the universe may be Dark Stars, powered by dark matter heating rather than by fusion. Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first stars in the the universe. This talk presents the story of these Dark Stars. We make predictions that the first stars are very massive (∼ 800 M_⊙), cool (6000 K), bright (∼ 10^6 L_⊙), long-lived (∼ 10^6 years), and probable precursors to (otherwise unexplained) supermassive black holes. Later, once the initial DM fuel runs out and fusion sets in, DM annihilation can predominate again if the scattering cross section is strong enough, so that a Dark Star is born again. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.0472v1.pdf"}
{"id": "0808.2298", "abstract": "  Low energy supersymmetric models provide a solution to the hierarchy problem and also have the necessary ingredients to solve two of the most outstanding issues in cosmology: the origin of the baryon asymmetry and the source of dark matter. In the MSSM, weak scale generation of the baryon asymmetry may be achieved in the presence of light stops, with masses lower than about 130 GeV. Moreover, the proper dark matter density may be obtained in the stop-neutralino co-annihilation region, where the stop-neutralino mass difference is smaller than a few tens of GeV. Searches for scalar top quarks (stops) in pair production processes at the Tevatron and at the Large Hadron Collider (LHC) become very challenging in this region of parameters. At the LHC, however, light stops proceeding from the decay of gluino pairs may be identified, provided the gluino mass is smaller than about 900 GeV. In this article we propose an alternative method for stop searches in the co-annihilation region, based on the search for these particles in events with missing energy plus one hard photon or jet. We show that this method is quite efficient and, when complemented with ongoing Tevatron searches, allows to probe stop masses up to about 160 GeV, fully probing the region of parameters consistent with electroweak baryogenesis in the MSSM. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0808/0808.2298v1.pdf"}
{"id": "0809.3223", "abstract": "  We propose that the properties of glass transition can be understood on the basis of elastic waves. Elastic waves originating from atomic jumps in a liquid propagate local expansion due to the anharmonicity of interatomic potential. This creates dynamic compressive stress, which increases the activation barrier for other events in a liquid. The non-trivial point is that the range of propagation of high-frequency elastic waves, d_ el, increases with liquid relaxation time τ. A self-consistent calculation shows that this increase gives the Vogel-Fulcher-Tammann (VFT) law. In the proposed theory, we discuss the origin of two dynamic crossovers in a liquid: 1) the crossover from exponential to non-exponential and from Arrhenius to VFT relaxation at high temperature and 2) the crossover from the VFT to a more Arrhenius-like relaxation at low temperature. The corresponding values of τ at the two crossovers are in quantitative parameter-free agreement with experiments. The origin of the second crossover allows us to reconcile the ongoing controversy surrounding the possible divergence of τ. The crossover to Arrhenius relaxation universally takes place when d_ el reaches system size, thus avoiding divergence and associated theoretical complications such as identifying the nature of the phase transition and the second phase itself. Finally, we discuss the effect of volume on τ and the origin of liquid fragility. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.3223v3.pdf"}
{"id": "0809.3313", "abstract": "  Many important techniques for investigating the properties of extragalactic radio sources, such as spectral-index and rotation-measure mapping, involve the comparison of images at two or more frequencies. In the case of radio interferometric data, this can be done by comparing the CLEAN maps obtained at the different frequencies. However, intrinsic differences in images due to the frequency dependence of the radio emission can be distorted by additional differences that arise due to source variability (if the data to be compared is obtained at different times), image misalignment, and the frequency dependence of the sensitivity to weak emission and the angular resolution provided by the observations (the resolution of an interferometer depends on the lengths of its baselines in units of the observing wavelength). These effects must be corrected for as best as possible before multi-frequency data comparison techniques can be applied. We consider the origins for the afore-mentioned factors, outline the standard techniques used to overcome these difficulties, and describe in detail a technique developed by us, based on the cross-correlation technique widely used in other fields, to correct for misalignments between maps at different frequencies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0809/0809.3313v1.pdf"}
{"id": "0810.2722", "abstract": "  The revision of the photospheric abundances proferred by Asplund et al has rendered opacity theory inconsistent with the seismologically determined opacity through the Sun. This highlights the need for a direct seismological measurement of solar abundances. Here we describe the technique used to measure abundances with seismology, examine our ability to detect differences between solar models using this technique, and discuss its application in the Sun. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0810/0810.2722v1.pdf"}
{"id": "0811.4301", "abstract": "  We study in the BFKL approach the total hadronic cross section for the collision of two virtual photons for energies in the range of LEP2 and of future linear colliders. The BFKL resummation is done at the next-to-leading order in the BFKL Green's function; photon impact factors are taken instead at the leading order, but with the inclusion of the subleading terms required by invariance under changes of the renormalization scale and of the BFKL scale s_0. We compare our results with previous estimations based on a similar kind of approximation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0811/0811.4301v1.pdf"}
{"id": "0812.2125", "abstract": "  Using turbulent MHD simulations (magnetic Reynolds numbers up to 8000) and Hinode observations, we study effects of turbulence on measuring the solar magnetic field outside active regions. Firstly, from synthetic Stokes V profiles for the FeI lines at 630.1 and 630.2 nm, we show that a peaked probability distribution function (PDF) for observationally-derived field estimates is consistent with a monotonic PDF for actual vertical field strengths. Hence, the prevalence of weak fields is greater than would be naively inferred from observations. Secondly, we employ the fractal self-similar geometry of the turbulent solar magnetic field to derive two estimates (numerical and observational) of the true mean vertical unsigned flux density. We also find observational evidence that the scales of magnetic structuring in the photosphere extend at least down to an order of magnitude smaller than 200 km: the self-similar power-law scaling in the signed measure from a Hinode magnetogram ranges (over two decades in length scales and including the granulation scale) down to the 200 km resolution limit. From the self-similar scaling, we determine a lower bound for the true quiet-Sun mean vertical unsigned flux density of  50 G. This is consistent with our numerically-based estimates that 80", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.2125v2.pdf"}
{"id": "0812.2597", "abstract": "  We normalize the combinatorial Laplacian of a graph by the degree sum, look at its eigenvalues as a probability distribution and then study its Shannon entropy. Equivalently, we represent a graph with a quantum mechanical state and study its von Neumann entropy. At the graph-theoretic level, this quantity may be interpreted as a measure of regularity; it tends to be larger in relation to the number of connected components, long paths and nontrivial symmetries. When the set of vertices is asymptotically large, we prove that regular graphs and the complete graph have equal entropy, and specifically it turns out to be maximum. On the other hand, when the number of edges is fixed, graphs with large cliques appear to minimize the entropy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.2597v2.pdf"}
{"id": "0812.3694", "abstract": "  We establish a framework for oracle identification problems in the continuous variable setting, where the stated problem necessarily is the same as in the discrete variable case, and continuous variables are manifested through a continuous representation in an infinite-dimensional Hilbert space. We apply this formalism to the Deutsch-Jozsa problem and show that, due to an uncertainty relation between the continuous representation and its Fourier-transform dual representation, the corresponding Deutsch-Jozsa algorithm is probabilistic hence forbids an exponential speed-up, contrary to a previous claim in the literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0812/0812.3694v1.pdf"}
{"id": "0901.3274", "abstract": "  We present an interesting monogamy equation for (2 ⊗ 2 ⊗ n)-dimensional pure states, by which a quantity is found to characterize the tripartite entanglement with the GHZ type and W typeentanglements as a whole. In particular, we, for the first time, reveals that for any quantum state of a pair of qubits, the difference between the two remarkable entanglement measures, concurrence and negativity, characterizes the W type entanglement of tripartite pure states with the two-qubit state as reduced density. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.3274v1.pdf"}
{"id": "0901.4768", "abstract": "  We analyze the non-local transport properties of a d-wave superconductor coupled to metallic electrodes at nanoscale distances. We show that the non-local conductance exhibits an algebraical decay with distance rather than the exponential behavior which is found in conventional superconductors. Crossed Andreev processes, associated with electronic entanglement, are favored for certain orientations of the symmetry axes of the superconductor with respect to the leads. These properties would allow its experimental detection using present technologies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0901/0901.4768v1.pdf"}
{"id": "0902.1324", "abstract": "  The goal of this paper is to survey the properties of the eigenvalue relaxation for least squares binary problems. This relaxation is a convex program which is obtained as the Lagrangian dual of the original problem with an implicit compact constraint and as such, is a convex problem with polynomial time complexity. Moreover, as a main pratical advantage of this relaxation over the standard Semi-Definite Programming approach, several efficient bundle methods are available for this problem allowing to address problems of very large dimension. The necessary tools from convex analysis are recalled and shown at work for handling the problem of exactness of this relaxation. Two applications are described. The first one is the problem of binary image reconstruction and the second is the problem of multiuser detection in CDMA systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.1324v2.pdf"}
{"id": "0902.4613", "abstract": "  The Pierre Auger Observatory, recently completed, has been operational since 2004. As a hybrid experiment, it allows for a wide range of measurements of UHECR-induced extensive air showers (EAS), including measurements of the EAS particle content on ground which is sensitive to high-energy hadronic interactions. We present the results of several independent measurements of the EAS muon content on ground in Auger data at a primary energy of 10 EeV. We discuss implications on high-energy hadronic interaction models and cosmic ray composition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0902/0902.4613v1.pdf"}
{"id": "0904.0720", "abstract": "  Semi-analytical model for calculating acoustic response to a line-focused laser pulse in an optically absorptive isotropic cylinder is proposed and implemented. It is assumed that the laser input is absorbed over the volume and thus creates a radially distributed thermoelastic source. Closed-form solution is obtained in the Fourier domain. Two inverse Fourier transforms in frequency and circumferential wave number yield the sought waveforms of acoustic response in the time-space domain. Numerical simulation is compared to the calculation based on a surface dipole source. The two signals have essentially different shapes of the wave-arrival peaks when the optical penetration is large enough. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0904/0904.0720v1.pdf"}
{"id": "0905.1085", "abstract": "  With photon-number resolving detectors, we show compression of interference fringes with increasing photon numbers for a Fabry-Perot interferometer. This feature provides a higher precision in determining the position of the interference maxima compared to a classical detection strategy. We also theoretically show supersensitivity if N-photon states are sent into the interferometer and a photon-number resolving measurement is performed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.1085v2.pdf"}
{"id": "0905.2137", "abstract": "  Simulation of chemical activity of corrugated graphene within density functional theory predicts an enhancement of its chemical activity if the ratio of height of the corrugation (ripple) to its radius is larger than 0.07. Further growth of the curvature of the ripples results in appearance of midgap states which leads to an additional strong increase of chemisororption energy. These results open a way for tunable functionalization of graphene, namely, depending of curvature of the ripples one can provide both homogeneous (for small curvatures) and spot-like (for large curvatures) functionalization. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.2137v2.pdf"}
{"id": "0905.3648", "abstract": "  The ATLAS BPTX stations are comprised of electrostatic button pick-up detectors, located 175 m away along the beam pipe on both sides of ATLAS. The pick-ups are installed as a part of the LHC beam instrumentation and used by ATLAS for timing purposes.   The usage of the BPTX signals in ATLAS is twofold: they are used both in the trigger system and for LHC beam monitoring. The BPTX signals are discriminated with a constant-fraction discriminator to provide a Level-1 trigger when a bunch passes through ATLAS. Furthermore, the BPTX detectors are used by a stand-alone monitoring system for the LHC bunches and timing signals. The BPTX monitoring system measures the phase between collisions and clock with a precision better than 100 ps in order to guarantee a stable phase relationship for optimal signal sampling in the subdetector front-end electronics. In addition to monitoring this phase, the properties of the individual bunches are measured and the structure of the beams is determined.   On September 10, 2008, the first LHC beams reached the ATLAS experiment. During this period with beam, the ATLAS BPTX system was used extensively to time in the read-out of the sub-detectors. In this paper, we present the performance of the BPTX system and its measurements of the first LHC beams. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0905/0905.3648v1.pdf"}
{"id": "0906.2190", "abstract": "  We present measurements of the clustering of hot and cold patches in the microwave background sky as measured from the Wilkinson Microwave Anisotropy Probe (WMAP) five-year data. These measurements are compared with theoretical predictions which assume that the cosmological signal obeys Gaussian statistics. We find significant differences from the simplest Gaussian-based prediction. However, the measurements are sensitive to the fact that the noise is spatially inhomogeneous (e.g., because different parts of the sky were observed for different lengths of time). We show how to account for this spatial inhomogeneity when making predictions. Differences from the Gaussian-based expectation remain even after this more careful accounting of the noise. In particular, we note that hot and cold pixels cluster differently within the same temperature thresholds at few-degree scales. While these findings may indicate primordial non-Gaussianity, we discuss other plausible explanations for these discrepancies. In addition, we find some deviations from Gaussianity at sub-degree scales, especially in the W band, whose origin may be associated with extragalactic dust emission. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.2190v1.pdf"}
{"id": "0906.2618", "abstract": "  This letter presents a novel analysis of the action/energy density distribution around a static quark-antiquark pair in SU(3) lattice quantum chromodynamics. Using the Fourier transformation of the link variable, we remove the high-momentum gluon and extract the flux-tube component from the action/energy density. When the high-momentum gluon is removed, the statistical fluctuation is drastically suppressed, and the singularities from the quark self-energy disappear. The obtained flux-tube component is broadly distributed around the line connecting the quark and the antiquark. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.2618v2.pdf"}
{"id": "0906.4075", "abstract": "  In order to assess the performance of liquid xenon detectors for use in positron emission tomography we studied the scintillation light and ionization charge produced by 511 keV photons in a small prototype detector. Scintillation light was detected with large area avalanche photodiodes while ionization electrons were collected on an anode instrumented with low noise electronics after drifting up to 3 cm. Operational conditions were studied as a function of the electric field. Energy resolutions of <10 ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0906/0906.4075v1.pdf"}
{"id": "0907.1096", "abstract": "  Using mean-field theory, we study the equilibrium properties of boson-fermion mixtures confined in a harmonic pancake-shaped trap at zero temperature. When the modulus of the s-wave scattering lengths are comparable to the mixture thickness, two-dimensional scattering events introduce a logarithmic dependence on density in the coupling constants, greatly modifying the density profiles themselves. We show that for the case of a negative boson-fermion three-dimensional s-wave scattering length, the dimensional crossover stabilizes the mixture against collapse and drives it towards spatial demixing. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.1096v1.pdf"}
{"id": "0907.4124", "abstract": "  We review recent theoretical results on generalized parton distributions (GPDs) of nuclei, emphasizing the following three roles of nuclear GPDs: (i) complementarity to free proton GPDs, (ii) the enhancement of traditional nuclear effects such as nuclear binding, EMC effect, nuclear shadowing, and (iii) an access to novel nuclear effects such as medium modifications of bound nucleons. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.4124v2.pdf"}
{"id": "0907.5241", "abstract": "  We formulate the head-to-head matchups between Major League Baseball pitchers and batters from 1954 to 2008 as a bipartite network of mutually-antagonistic interactions. We consider both the full network and single-season networks, which exhibit interesting structural changes over time. We find interesting structure in the network and examine their sensitivity to baseball's rule changes. We then study a biased random walk on the matchup networks as a simple and transparent way to compare the performance of players who competed under different conditions and to include information about which particular players a given player has faced. We find that a player's position in the network does not correlate with his success in the random walker ranking but instead has a substantial effect on its sensitivity to changes in his own aggregate performance. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0907/0907.5241v2.pdf"}
{"id": "0908.1297", "abstract": "  Recent advances in the photon tagging facilities together with the novel, high resolution fast calorimetry made possible to perform photoproduction cross section measurements of pseudoscalar mesons on nuclei with a percent level accuracy. The extraction of the radiative decay widths, needed for testing the symmetry breaking effects in QCD, from these measurements at small angles is done by the Primakoff method. This method requires theoretical treatment of all processes participating in these reactions at the same percent level. The most updated description of general processes, including the nuclear coherent amplitude, is done in our previous paper. In this work, based on the framework of Glauber multiple scattering theory, we obtain analytical expressions for the incoherent cross section of the photoproduction of pseudoscalar mesons off nuclei accounting for the mesons absorption in nuclei and Pauli suppression at forward production angles. As illustrations of the obtained formulas, we calculate the incoherent cross section for photoproduction from a closed shell nucleus, 16^O, and from an unclosed shell nucleus, 12^C. These calculations allow one to compare different approaches and estimate their impact on the incoherent cross section of the processes under consideration. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0908/0908.1297v1.pdf"}
{"id": "0910.3949", "abstract": "  We try to address quantitatively the question whether a new mass is needed to fit current supernovae data. For this purpose, we consider an infra-red modification of gravity that does not contain any new mass scale but systematic subleading corrections proportional to the curvature. The modifications are of the same type as the one recently derived by enforcing the \"Ultra Strong Equivalence Principle\" (USEP) upon a Friedmann-Lemaitre-Robertson-Walker universe in the presence of a scalar field. The distance between two comoving observers is altered by these corrections and the observations at high redshift affected at any time during the cosmic evolution. While the specific values of the parameters predicted by USEP are ruled out, there are regions of parameter space that fit SnIa data very well. This allows an interesting possibility to explain the apparent cosmic acceleration today without introducing either a dark energy component or a new mass scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.3949v2.pdf"}
{"id": "0910.4288", "abstract": "  We propose and numerically simulate a semiconductor device based on coupled quantum wires, suitable for deterministic quantum teleportation of electrons trapped in the minima of surface acoustic waves.We exploit a network of interacting semiconductor quantum wires able to provide the universal set of gates for quantum information processing, with the qubit defined by the localization of a single electron in one of two coupled channels.The numerical approach is based on a time-dependent solution of the three-particle Schrödinger equation. First, a maximally entangled pair of electrons is obtained via Coulomb interaction between carriers in different channels. Then, a complete Bell-state measurement involving one electron from this pair and a third electron is performed. Finally, the teleported state is reconstructed by means of local one-qubit operations. The large estimated fidelity explicitely suggests that an efficient teleportation process could be reached in an experimental setup. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.4288v2.pdf"}
{"id": "0910.4423", "abstract": "  The Floquet spectra of a class of driven SU(2) systems have been shown to display butterfly patterns with multifractal properties. The implication of such critical spectral behavior for the Floquet eigenstate statistics is studied in this work. Following the methodologies for understanding the fractal behavior of energy eigenstates of time-independent systems on the Anderson transition point, we analyze the distribution profile, the mean value, and the variance of the logarithm of the inverse participation ratio of the Floquet eigenstates associated with multifractal Floquet spectra. The results show that the Floquet eigenstates also display fractal behavior, but with features markedly different from those in time-independent Anderson-transition models. This motivated us to propose a new type of random unitary matrix ensemble, called \"power-law random banded unitary matrix\" ensemble, to illuminate the Floquet eigenstate statistics of critical driven systems. The results based on the proposed random matrix model are consistent with those obtained from our dynamical examples with or without time-reversal symmetry. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0910/0910.4423v2.pdf"}
{"id": "0912.2647", "abstract": "  In this work we describe our implementation of a thermodynamic energy equation into the global corona model of the Space Weather Modeling Framework (SWMF), and its development into the new Lower Corona (LC) model. This work includes the integration of the additional energy transport terms of coronal heating, electron heat conduction, and optically thin radiative cooling into the governing magnetohydrodynamic (MHD) energy equation. We examine two different boundary conditions using this model; one set in the upper transition region (the Radiative Energy Balance model), as well as a uniform chromospheric condition where the transition region can be modeled in its entirety. Via observation synthesis from model results and the subsequent comparison to full sun extreme ultraviolet (EUV) and soft X-Ray observations of Carrington Rotation (CR) 1913 centered on Aug 27, 1996, we demonstrate the need for these additional considerations when using global MHD models to describe the unique conditions in the low corona. Through multiple simulations we examine ability of the LC model to asses and discriminate between coronal heating models, and find that a relative simple empirical heating model is adequate in reproducing structures observed in the low corona. We show that the interplay between coronal heating and electron heat conduction provides significant feedback onto the 3D magnetic topology in the low corona as compared to a potential field extrapolation, and that this feedback is largely dependent on the amount of mechanical energy introduced into the corona. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/0912/0912.2647v1.pdf"}
{"id": "1001.1834", "abstract": "  The single stable isotope of beryllium is a pure product of cosmic-ray spallation in the ISM. Assuming that the cosmic-rays are globally transported across the Galaxy, the beryllium production should be a widespread process and its abundance should be roughly homogeneous in the early-Galaxy at a given time. Thus, it could be useful as a tracer of time. In an investigation of the use of Be as a cosmochronometer and of its evolution in the Galaxy, we found evidence that in a log(Be/H) vs. [alpha/Fe] diagram the halo stars separate into two components. One is consistent with predictions of evolutionary models while the other is chemically indistinguishable from the thick-disk stars. This is interpreted as a difference in the star formation history of the two components and suggests that the local halo is not a single uniform population where a clear age-metallicity relation can be defined. We also found evidence that the star formation rate was lower in the outer regions of the thick disk, pointing towards an inside-out formation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.1834v1.pdf"}
{"id": "1001.4138", "abstract": "  We investigate simulated turbulent flow within thermally driven stellar convection zones. Different driving sources are studied, including cooling at the top of the convectively unstable region, as occurs in surface convection zones; and heating at the base by nuclear burning. The transport of enthalpy and kinetic energy, and the distribution of turbulent kinetic energy dissipation are studied. We emphasize the importance of global constraints on shaping the quasi-steady flow characteristics, and present an analysis of turbulent convection which is posed as a boundary value problem that can be easily incorporated into standard stellar evolution codes for deep, efficient convection. Direct comparison is made between the theoretical analysis and the simulated flow and very good agreement is found. Some common assumptions traditionally used to treat quasi-steady turbulent flow in stellar models are briefly discussed. The importance and proper treatment of convective boundaries are indicated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1001/1001.4138v1.pdf"}
{"id": "1002.0350", "abstract": "  We consider the interference of two photons with different colors in the context of a Hong-Ou-Mandel experiment, in which single photons enter each of the input ports of a beam splitter, and exit in the same, albeit undetermined, output port. Such interference is possible if one uses an active (energy-non-conserving) beam splitter. We find scenarios in which one \"red\" and one \"blue\" photon enter the beam splitter, and either two red or two blue photons exit, but never one of each color. We show how the precise form of the active beam-splitter transformation determines in what way the spectral degrees of freedom of the input photons should be related to each other for perfect destructive interference of the different-color components in the output. We discuss two examples of active beam splitters: one is a gedanken experiment involving a moving mirror and the other is a more realistic example involving four-wave mixing in an optical fiber. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.0350v1.pdf"}
{"id": "1002.4721", "abstract": "  We generalize tensor-scalar theories of gravitation by the introduction of an abnormally weighting type of energy. This theory of tensor-scalar anomalous gravity is based on a relaxation of the weak equivalence principle that is now restricted to ordinary visible matter only. As a consequence, the convergence mechanism toward general relativity is modified and produces naturally cosmic acceleration as an inescapable gravitational feedback induced by the mass-variation of some invisible sector. The cosmological implications of this new theoretical framework are studied. This glimpses at an enticing new symmetry between the visible and invisible sectors, namely that the scalar charges of visible and invisible matter are exactly opposite. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1002/1002.4721v1.pdf"}
{"id": "1003.4018", "abstract": "  Models of galaxy formation invoke the major merger of gas-rich progenitor galaxies as the trigger for significant phases of black hole growth and the associated feedback that suppresses star formation to create red spheroidal remnants. However, the observational evidence for the connection between mergers and active galactic nucleus (AGN) phases is not clear. We analyze a sample of low-mass early-type galaxies known to be in the process of migrating from the blue cloud to the red sequence via an AGN phase in the green valley. Using deeper imaging from SDSS Stripe 82, we show that the fraction of objects with major morphological disturbances is high during the early starburst phase, but declines rapidly to the background level seen in quiescent early-type galaxies by the time of substantial AGN radiation several hundred Myr after the starburst. This observation empirically links the AGN activity in low-redshift early-type galaxies to a significant merger event in the recent past. The large time delay between the merger-driven starburst and the peak of AGN activity allows for the merger features to decay to the background and hence may explain the weak link between merger features and AGN activity in the literature. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.4018v1.pdf"}
{"id": "1003.5095", "abstract": "  We studied the question of parity breaking in a supersymmetric left-right model, in which the left-right symmetry is broken with Higgs doublets (carrying B-L=± 1). Unlike the left-right symmetric models with triplet Higgs scalars (carrying B-L=± 2), in this model it is possible to break parity spontaneously by adding a parity odd singlet. We then discussed how neutrino mass of type III seesaw can be invoked in this model by adding extra fermion singlets. We considered simple forms of the mass matrices that are consistent with the unification scheme and demonstrate how they can reproduce the required neutrino mixing matrix. In this model, the baryon asymmetry of the universe is generated via leptogenesis. The required mass scales in the model is then found to be consistent with the gauge coupling unification. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1003/1003.5095v1.pdf"}
{"id": "1004.1933", "abstract": "  Active particles contain internal degrees of freedom with the ability to take in and dissipate energy and, in the process, execute systematic movement. Examples include all living organisms and their motile constituents such as molecular motors. This article reviews recent progress in applying the principles of nonequilibrium statistical mechanics and hydrodynamics to form a systematic theory of the behaviour of collections of active particles – active matter – with only minimal regard to microscopic details. A unified view of the many kinds of active matter is presented, encompassing not only living systems but inanimate analogues. Theory and experiment are discussed side by side. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.1933v1.pdf"}
{"id": "1004.4110", "abstract": "  The diamond norm measures the distance between two quantum channels. From an operational vewpoint, this norm measures how well we can distinguish between two channels by applying them to input states of arbitrarily large dimensions. In this paper, we show that the diamond norm can be conveniently and in a physically transparent way computed by means of a Monte-Carlo algorithm based on the Fano representation of quantum states and quantum operations. The effectiveness of this algorithm is illustrated for several single-qubit quantum channels. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1004/1004.4110v1.pdf"}
{"id": "1005.5519", "abstract": "  We prove a theorem on the magnetic energy minimum in a system of perfect, or ideal, conductors. It is analogous to Thomson's theorem on the equilibrium electric field and charge distribution in a system of conductors. We first prove Thomson's theorem using a variational principle. Our new theorem is then derived by similar methods. We find that magnetic energy is minimized when the current distribution is a surface current density with zero interior magnetic field; perfect conductors are perfectly diamagnetic. The results agree with currents in superconductors being confined near the surface. The theorem implies a generalized force that expels current and magnetic field from the interior of a conductor that loses its resistivity. Examples of solutions that obey the theorem are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1005/1005.5519v1.pdf"}
{"id": "1006.3478", "abstract": "  The fidelity decay in a microwave billiard is considered, where the coupling to an attached antenna is varied. The resulting quantity, coupling fidelity, is experimentally studied for three different terminators of the varied antenna: a hard wall reflection, an open wall reflection, and a 50 Ohm load, corresponding to a totally open channel. The model description in terms of an effective Hamiltonian with a complex coupling constant is given. Quantitative agreement is found with the theory obtained from a modified VWZ approach [Verbaarschot et al, Phys. Rep. 129, 367 (1985)]. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1006/1006.3478v2.pdf"}
{"id": "1007.0801", "abstract": "  We present the first results on the black hole candidate XTE J1752-223 from the Gas Slit Camera (GSC) on-board the Monitor of All-sky X-ray Image (MAXI) on the International Space Station. Including the onset of the outburst reported by the Proportional Counter Array on-board the Rossi X-ray Timing Explorer on 2009 October 23, the MAXI/GSC has been monitoring this source approximately 10 times per day with a high sensitivity in the 2-20 keV band. XTE J1752-223 was initially in the low/hard state during the first 3 months. An anti-correlated behavior between the 2-4 keV and 4-20 keV bands were observed around January 20, 2010, indicating that the source exhibited the spectral transition to the high/soft state. A transient radio jet may have been ejected when the source was in the intermediate state where the spectrum was roughly explained by a power-law with a photon index of 2.5-3.0. The unusually long period in the initial low/hard state implies a slow variation in the mass accretion rate, and the dramatic soft X-ray increase may be explained by a sudden appearance of the accretion disk component with a relatively low innermost temperature (0.4-0.7 keV). Such a low temperature might suggest that the maximum accretion rate was just above the critical gas evaporation rate required for the state transition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.0801v1.pdf"}
{"id": "1007.2048", "abstract": "  The results of an observational campaign on the new δ Scuti pulsator HD 207331 are reported. The star was observed photometrically from August 26 to September 2, 2009 from the Observatorio San Pedro Mártir (0.84-m telescope, Mexico) and the Observatorio del Teide (0.80-m telescope, Spain). An overall run of 53.8 h of useful data was collected from the two sites. Four oscillation frequencies for HD 207331 have been found above a 99% confidence level. These results confirm the multiperiodic pulsation nature of the star suggested in previous observations with sparse data. Spectroscopic observations carried out in 2009 allowed us to derive its spectral type and luminosity class as well as to estimate its rotation rate. A simple comparison with models is performed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1007/1007.2048v1.pdf"}
{"id": "1009.4790", "abstract": "  Solar oscillations are expected to be excited by turbulent flows in the intergranular lanes near the solar surface. Time series recorded by the IMaX instrument aboard the Sunrise observatory reveal solar oscillations at high resolution, which allow studying the properties of oscillations with short wavelengths. We analyze two times series with synchronous recordings of Doppler velocity and continuum intensity images with durations of 32min and 23min, resp., recorded close to the disk center of the Sun to study the propagation and excitation of solar acoustic oscillations. In the Doppler velocity data, both the standing acoustic waves and the short-lived, high-degree running waves are visible. The standing waves are visible as temporary enhancements of the amplitudes of the large-scale velocity field due to the stochastic superposition of the acoustic waves. We focus on the high-degree small-scale waves by suitable filtering in the Fourier domain. Investigating the propagation and excitation of f- and p_1-modes with wave numbers k > 1.41/Mm we find that also exploding granules contribute to the excitation of solar p-modes in addition to the contribution of intergranular lanes. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.4790v1.pdf"}
{"id": "1009.5947", "abstract": "  Recently, Fossati et al. observed that the UV transit of WASP-12b showed an early ingress compared to the optical transit. We suggest that the resulting early ingress is caused by a bow shock ahead of the planetary orbital motion. In this Letter we investigate the conditions that might lead to the formation of such a bow shock. We consider two scenarios: (1) the stellar magnetic field is strong enough to confine the hot coronal plasma out to the planetary orbit and (2) the stellar magnetic field is unable to confine the plasma, which escapes in a wind. In both cases, a shock capable of compressing plasma to the observed densities will form around the planet for plasma temperatures T < (4 - 5) x 10^6 K. In the confined case, the shock always forms directly ahead of the planet, but in the wind case the shock orientation depends on the wind speed and hence on the plasma temperature. For higher wind temperatures, the shock forms closer to the line of centers between the planet and the star. We conclude that shock formation leading to an observable early UV ingress is likely to be a common feature of transiting systems and may prove to be a useful tool in setting limits on planetary magnetic field strengths Bp. In the case of WASP-12b, we derive an upper limit of about Bp=24 G. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1009/1009.5947v1.pdf"}
{"id": "1011.0526", "abstract": "  It is conventionally thought that the state equation of dense matter softens and thus cannot result in high maximum mass if pulsars are quark stars, and that a recently discovered 2M_⊙ pulsar (PSR J1614-2230) may make quark stars to be unlikely. However, this standard point of view would be revisited and updated if quark clustering could occur in cold quark matter because of the strong coupling between quarks at realistic baryon densities of compact stars, and it is addressed that the state equation of clustering quark matter stiffs to support compact stars with maximum mass M_ max>2M_⊙. In this brief note, it is demonstrated that large parameter spaces are allowed for M_ max>2M_⊙ in a Lennard-Jones model of clustered quark matter, and the newly measured highest mass of PSR J1614-2230 would be meaningful to constrain the number of quarks inside single quark-cluster, to be N_q<∼ 10^3. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.0526v2.pdf"}
{"id": "1011.0654", "abstract": "  We study the correspondence between the non-trivial topological properties associated with the individual valleys of gapped bilayer graphene (BLG), as a prototypical multi-valley system, and the gapless modes at its edges and other interfaces. We find that the exact connection between the valley-specific Hall conductivity and the number of gapless edge modes does not hold in general, but is dependent on the boundary conditions, even in the absence of intervalley coupling. This non-universality is attributed to the absence of a well-defined topological invariant within a given valley of BLG; yet, a more general topological invariant may be defined in certain cases, which explains the distinction between the BLG-vacuum and BLG-BLG interfaces. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.0654v1.pdf"}
{"id": "1011.2313", "abstract": "  Information about primary transmitter location is crucial in enabling several key capabilities in cognitive radio networks, including improved spatio-temporal sensing, intelligent location-aware routing, as well as aiding spectrum policy enforcement. Compared to other proposed non-interactive localization algorithms, the weighted centroid localization (WCL) scheme uses only the received signal strength information, which makes it simple to implement and robust to variations in the propagation environment. In this paper we present the first theoretical framework for WCL performance analysis in terms of its localization error distribution parameterized by node density, node placement, shadowing variance, correlation distance and inaccuracy of sensor node positioning. Using this analysis, we quantify the robustness of WCL to various physical conditions and provide design guidelines, such as node placement and spacing, for the practical deployment of WCL. We also propose a power-efficient method for implementing WCL through a distributed cluster-based algorithm, that achieves comparable accuracy with its centralized counterpart. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2313v3.pdf"}
{"id": "1011.2621", "abstract": "  Millisecond x-ray pulsars have weak magnetic dipole moments of ∼ 10^16 T m^3 compared to ordinary X-ray pulsars with dipole moments of 10^20 T m^3. For this reason a surrounding accretion disc can extend closer to the neutron star, and thus reach a higher temperature, at which the opacity is dominated by electron scattering and radiation pressure is strong. We compute the self-similar structure of such a geometrically thin axisymmetric accretion disc with an internal dynamo. Such models produce significantly stronger torques on the neutron star than models without dynamos, and can explain the strong spin variations in some millisecond X-ray pulsars. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.2621v1.pdf"}
{"id": "1011.5604", "abstract": "  In the context of averaging an inhomogeneous cosmological model, we propose a natural measure identical to the Kullback-Leibler relative information entropy, which expresses the distinguishability of the local inhomogeneous density field from its spatial average on arbitrary compact domains. This measure is expected to be an increasing function in time and thus to play a significant role in studying gravitational entropy. To verify this conjecture, we explore the time evolution of the measure using the linear perturbation theory of a spatially flat FLRW model and a spherically symmetric nonlinear solution. We discuss the generality and conditions for the time-increasing nature of the measure, and also the connection to the backreaction effect caused by inhomogeneities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1011/1011.5604v1.pdf"}
{"id": "1101.4543", "abstract": "  Two large northern polar crown prominences that erupted on 2010 April 13 and 2010 August 1 were analysed using images obtained from the Extreme UltraViolet Imager on the twin Solar Terrestrial Relations Observatory spacecraft. Several features along the prominence legs were reconstructed using a stereoscopic reconstruction technique developed by us. The three-dimensional changes exhibited by the prominences can be explained as an interplay between two different motions, namely helical twist in the prominence spine, and overall non-radial equatorward motion of the entire prominence structure. The sense of twist in both the prominences is determined from the changes in latitudes and longitudes of the reconstructed features. The prominences are observed starting from a few hours before the eruption. Increase in height before and during the eruption allowed us to study kinematics of the prominences in the two phases of eruption, the slow rise and the fast eruptive phase. A constant value of acceleration was found for each reconstructed feature in each phase, but it showed significant change from one leg to the other in both the prominences. The magnitude of acceleration during the eruptive phase is found to be commensurate with the net effect of the two motions stated above. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1101/1101.4543v1.pdf"}
{"id": "1105.0771", "abstract": "  This article gives an overview of many of the recent developments in understanding the structure of relativistic scattering amplitudes in gauge theories ranging from QCD to N=4 super-Yang-Mills theory, as well as (super)gravity. I also provide a pedagogical introduction to some of the basic tools used to organize and illuminate the color and kinematic structure of amplitudes. This article is an invited review introducing a special issue of Journal of Physics A devoted to \"Scattering Amplitudes in Gauge Theories\". ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.0771v2.pdf"}
{"id": "1105.3196", "abstract": "  We study the low-energy limit of a quarter-filled one-dimensional Mott insulator. We analytically determine the local density of states in the presence of a strong impurity potential, which is modeled by a boundary. To this end we calculate the Green function using field theoretical methods. The Fourier transform of the local density of states shows signatures of a pinning of the spin-density wave at the impurity as well as several dispersing features at frequencies above the charge gap. These features can be interpreted as propagating spin and charge degrees of freedom. Their relative strength can be attributed to the \"quasi-fermionic\" behavior of charge excitations with equal momenta. Furthermore, we discuss the effect of bound states localized at the impurity. Finally, we give an overview of the local density of states in various one-dimensional systems and discuss implications for scanning tunneling microscopy experiments. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.3196v3.pdf"}
{"id": "1105.3427", "abstract": "  This paper proposes real-time sequential convex programming (RTSCP), a method for solving a sequence of nonlinear optimization problems depending on an online parameter. We provide a contraction estimate for the proposed method and, as a byproduct, a new proof of the local convergence of sequential convex programming. The approach is illustrated by an example where RTSCP is applied to nonlinear model predictive control. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.3427v1.pdf"}
{"id": "1105.3915", "abstract": "  The statistics of records in sequences of independent, identically distributed random variables is a classic subject of study. One of the earliest results concerns the stochastic independence of record events. Recently, records statistics beyond the case of i.i.d. random variables have received much attention, but the question of independence of record events has not been addressed systematically. In this paper, we study this question in detail for the case of independent, non-identically distributed random variables, specifically, for random variables with a linearly moving mean. We find a rich pattern of positive and negative correlations, and show how their asymptotics is determined by the universality classes of extreme value statistics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.3915v3.pdf"}
{"id": "1105.4753", "abstract": "  We study the lightest masses in the fermionic sector of an anomalous U(1)' extension of the minimal supersymmetric standard model inspired by brane constructions. The LSP of this model is an XWIMP (extremely weak interaction particle) which is shown to have a relic density satisfying WMAP data. This computation is carried out numerically after having adapted the DarkSUSY package to our case. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1105/1105.4753v1.pdf"}
{"id": "1106.1395", "abstract": "  We discuss utility based pricing and hedging of jump diffusion processes with emphasis on the practical applicability of the framework. We point out two difficulties that seem to limit this applicability, namely drift dependence and essential risk aversion independence. We suggest to solve these by a re-interpretation of the framework. This leads to the notion of an implied drift. We also present a heuristic derivation of the marginal indifference price and the marginal optimal hedge that might be useful in numerical computations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.1395v2.pdf"}
{"id": "1106.1396", "abstract": "  We extensively study the growing behavior of the energy and the pressure components depending on the space-time rapidity in the framework of the Glasma, which describes the early-time dynamics in the ultra-relativistic heavy-ion collisions. We simulate the Glasma solving the classical equations of motion in the SU(2) Yang-Mills theory and systematically investigate the dependence of the Glasma instability on the model parameters. We have checked that the transverse and longitudinal grid sizes in our simulation are large enough to handle cutoff effects under control. By comparing the numerical results from several initial conditions with different magnitudes of instability seed and also those with different wave-numbers for rapidity fluctuations, we clearly see that unstable modes dominantly grow up in the linear regime and we also confirm non-linear effects in the time evolution. To extract more detailed information on the evolving Glasma, we decompose the energy into the components in terms of rapidity wave-numbers. We observe an energy flow from low wave-number modes into higher wave-number modes due to non-linearity in the equations of motion. We find that the energy spectrum approaches an asymptotic scaling that is consistent with Kolmogorov's power-law form even in the expanding system of the Glasma. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.1396v2.pdf"}
{"id": "1106.3090", "abstract": "  We have performed unpolarized and polarized neutron diffraction experiments on monodisperse 8 nm and 13 nm antiferromagnetic MnO nanoparticles. For the 8 nm sample, the antiferromagnetic transition temperature T_N (114 K) is suppressed compared to the bulk material (119 K) while for the 13 nm sample T_N (120 K) is comparable to the bulk. The neutron diffraction data of the nanoparticles is well described using the bulk MnO magnetic structure but with a substantially reduced average magnetic moment of 4.2±0.3 μ_B/Mn for the 8 nm sample and 3.9±0.2 μ_B/Mn for the 13 nm sample. An analysis of the polarized neutron data on both samples shows that in an individual MnO nanoparticle about 80", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1106/1106.3090v1.pdf"}
{"id": "1108.1978", "abstract": "  We provide two mathematical descriptions of Spekkens's toy qubit theory, an inductively one in terms of a small set of generators, as well as an explicit closed form description. It is a subcategory MSpek of the category of finite sets, relations and the cartesian product. States of maximal knowledge form a subcategory Spek. This establishes the consistency of the toy theory, which has previously only been constructed for at most four systems. Our model also shows that the theory is closed under both parallel and sequential composition of operations (= symmetric monoidal structure), that it obeys map-state duality (= compact closure), and that states and effects are in bijective correspondence (= dagger structure). From the perspective of categorical quantum mechanics, this provides an interesting alternative model which enables us to describe many quantum phenomena in a discrete manner, and to which mathematical concepts such as basis structures, and complementarity thereof, still apply. Hence, the framework of categorical quantum mechanics has delivered on its promise to encompass theories other than quantum theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1108/1108.1978v1.pdf"}
{"id": "1109.0408", "abstract": "  In a system of non-linear chemical reactions called the Brusselator, we show that intrinsic noise can be regulated to drive it to exhibit resonance in the presence of a sub-threshold signal. The phenomena of periodic stochastic resonance and aperiodic stochastic resonance, hitherto studied mostly with extrinsic noise, is demonstrated here to occur with inherent systemic noise using exact stochastic simulation algorithm due to Gillespie. The role of intrinsic noise in a couple of other phenomena is also discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1109/1109.0408v1.pdf"}
{"id": "1110.0125", "abstract": "  In this work, we present a topological characterization of superconductivity in a prototype electron fractionalization model for doped Mott insulators. In this model, spinons and holons are coupled via the mutual Chern-Simons gauge fields. We obtain a low-lying effective description of the collective current fluctuations by integrating out the matter fields, which replaces the conventional Ginzburg-Landau action to describe the generalized rigidity of superconductivity. The superconducting phase coherence is essentially characterized by a topological order parameter related to a Gaussian linking number, and an experiment is proposed to probe this topological property. We further show that a gauge-neutral fermionic mode can naturally emerge in this model, which behaves like a Bogoliubov quasiparticle. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.0125v2.pdf"}
{"id": "1110.0700", "abstract": "  Neutral stellar core at or over nuclear densities is described by a positive charged baryon core and negative charged electron fluid since they possess different masses and interactions. Based on a simplified model of a gravitationally collapsing or pulsating baryon core, we approximately integrate the Einstein-Maxwell equations and the equations for the number and energy-momentum conservation of complete degenerate electron fluid. We show possible electric processes that lead to the production of electron-positron pairs in the boundary of a baryon core and calculate the number and energy of electron-positron pairs. This can be relevant for understanding the energetic sources of supernovae and gamma-ray bursts. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1110/1110.0700v3.pdf"}
{"id": "1111.1966", "abstract": "  The dynamics of three soft interacting particles on a ring is shown to correspond to the motion of one particle inside a soft triangular billiard. The dynamics inside the soft billiard depends only on the masses ratio between particles and softness ratio of the particles interaction. The transition from soft to hard interaction can be appropriately explored using potentials for which the corresponding equations of motion are well defined in the hard wall limit. Numerical examples are shown for the soft Toda-like interaction and the error function. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.1966v1.pdf"}
{"id": "1111.5074", "abstract": "  We present a complete-quantum description of multi-particle Szilard engine which consists of a working substance and a Maxwell's demon. The demon is modeled as a multi-level quantum system with specific quantum control and the working substance consists of identical particles obeying Bose-Einstein or Fermi-Dirac statistics. In this description, a reversible scheme to erase the demon's memory by a lower temperature heat bath is used. We demonstrate that (1) the quantum control of the demon can be optimized for single-particle Szilard engine so that the efficiency of the demon-assisted thermodynamic cycle could reach the Carnot cycle's efficiency; (2) the low-temperature behavior of the working substance is very sensitive to the quantum statistics of the particles and the insertion position of the partition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1111/1111.5074v2.pdf"}
{"id": "1112.0066", "abstract": "  In this work we propose a new orbital architecture for the two proposed circumbinary planets around the polar eclipsing binary HU Aquarii. We base the new two-planet, light-travel time model on the result of a Monte Carlo simulation driving a least-squares Levenberg-Marquardt minimisation algorithm on the observed eclipse egress times. Our best-fitting model with χ_r^2=1.43 resulted in high final eccentricities for the two companions leading to an unstable orbital configuration. From a large ensemble of initial guesses we examined the distribution of final eccentricities and semi-major axes for different χ_r^2 parameter intervals and encountered qualitatively a second population of best-fitting parameters. The main characteristic of this population is described by low-eccentric orbits favouring long-term orbital stability of the system. We present our best-fitting model candidate for the proposed two-planet system and demonstrate orbital stability over one million years using numerical integrations. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.0066v1.pdf"}
{"id": "1112.2159", "abstract": "  We theoretically investigate spin-resolved currents flowing in large-area graphene, with and without defects, doped with single atoms of noble metals (Cu, Ag and Au) and 3d-transition metals (Mn,Fe,Co and Ni). We show that the presence of a local magnetic moment is a necessary but not sufficient condition to have a non zero current polarization. An essential requirement is the presence of spin-split localized levels near the Fermi energy that strongly hybridize with the graphene pi-bands. We also show that a gate potential can be used to tune the energy of these localized levels, leading to an external way to control the degree of spin-polarized current without the application of a magnetic field. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.2159v1.pdf"}
{"id": "1112.2589", "abstract": "  Of the approximately 400 known Galactic classical novae, only ten of them, the recurrent novae, have been seen to erupt more than once. At least eight of these recurrents are known to harbor evolved secondary stars, rather than the main sequence secondaries typical in classical novae. In this paper, we propose a new nova classification system, based solely on the evolutionary state of the secondary, and not (like the current schemes) based on the properties of the outbursts. Using archival optical and near-infrared photometric observations of a sample of thirty eight quiescent Galactic novae we show that the evolutionary state of the secondary star in a quiescent system can predicted and several objects are identified for follow-up observations; CI Aql, V2487 Oph, DI Lac and EU Sct. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1112/1112.2589v1.pdf"}
{"id": "1201.1680", "abstract": "  The radius of neutron stars can in principle be measured via the normalisation of a blackbody fitted to the X-ray spectrum during thermonuclear (type-I) X-ray bursts, although few previous studies have addressed the reliability of such measurements. Here we examine the apparent radius in a homogeneous sample of long, mixed H/He bursts from the low-mass X-ray binaries GS 1826-24 and KS 1731-26. The measured blackbody normalisation (proportional to the emitting area) in these bursts is constant over a period of up to 60s in the burst tail, even though the flux (blackbody temperature) decreased by a factor of 60-75", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1201/1201.1680v1.pdf"}
{"id": "1202.0630", "abstract": "  Slow relaxation and aging of the conductance are experimental features of a range of materials, which are collectively known as electron glasses. We report dynamic Monte Carlo simulations of the standard electron glass lattice model. In a non-equilibrium state, the electrons will often form a Fermi distribution with an effective electron temperature higher than the phonon bath temperature. We study the effective temperature as a function of time in three different situations: relaxation after a quench from an initial random state, during driving by an external electric field and during relaxation after such driving. We observe logarithmic relaxation of the effective temperature after a quench from a random initial state as well as after driving the system for some time t_w with a strong electric field. For not too strong electric field and not too long t_w we observe that data for the effective temperature at different waiting times collapse when plotted as functions of t/t_w – the so-called simple aging. During the driving period we study how the effective temperature is established, separating the contributions from the sites involved in jumps from those that were not involved. It is found that the heating mainly affects the sites involved in jumps, but at strong driving, also the remaining sites are heated. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.0630v1.pdf"}
{"id": "1202.2400", "abstract": "  SN2006oz is a super-luminous supernova with a mysterious bright precursor that has resisted explanation in standard models. However, such a precursor has been predicted in the dual-shock quark nova (dsQN) model of super-luminous supernovae – the precursor is the SN event while the main light curve of the SLSN is powered by the Quark-Nova (QN; explosive transition of the neutron star to a quark star). As the SN is fading, the QN re-energizes the SN ejecta, producing a \"double-humped\" light curve. In this paper, we show the dsQN model successfully reproduces the observed light curve of SN2006oz. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.2400v1.pdf"}
{"id": "1202.4028", "abstract": "  We theoretically evaluate establishing remote entanglement between distinguishable matter qubits through interference and detection of two emitted photons. The fidelity of the entanglement operation is analyzed as a function of the temporal and frequency mode-matching between the photons emitted from each quantum memory. With a general analysis, we define limits on the absolute magnitudes of temporal and frequency mode-mismatches in order to maintain entanglement fidelities greater than 99", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.4028v1.pdf"}
{"id": "1202.5814", "abstract": "  The Dynamical Mean-Field theory (DMFT) approach to the Hubbard model requires a method to solve the problem of a quantum impurity in a bath of non-interacting electrons. Iterated Perturbation Theory (IPT) has proven its effectiveness as a solver in many cases of interest. Based on general principles and on comparisons with an essentially exact Continuous-Time Quantum Monte Carlo (CTQMC) solver, here we show that the standard implementation of IPT fails away from half-filling when the interaction strength is much larger than the bandwidth. We propose a slight modification to the IPT algorithm that replaces one of the equations by the requirement that double occupancy calculated with IPT gives the correct value. We call this method IPT-D. We recover the Fermi liquid ground state away from half-filling. The Fermi liquid parameters, density of states, chemical potential, energy and specific heat on the FCC lattice are calculated with both IPT-D and CTQMC as benchmark examples. We also calculated the resistivity and the optical conductivity within IPT-D. Particle-hole asymmetry persists even at coupling twice the bandwidth. Several algorithms that speed up the calculations are described in appendices. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1202/1202.5814v2.pdf"}
{"id": "1203.1857", "abstract": "  We propose a startling hybrid quantum architecture for simulating a localization-delocalization transition. The concept is based on an array of superconducting flux qubits which are coupled to a diamond crystal containing nitrogen-vacancy (NV) centers. The underlying description is a Jaynes-Cummings-lattice in the strong-coupling regime. However, in contrast to well-studied coupled cavity arrays the interaction between lattice sites is mediated here by the qubit rather than by the oscillator degrees of freedom. Nevertheless, we point out that a transition between a localized and a delocalized phase occurs in this system as well. We demonstrate the possibility of monitoring this transition in a non-equilibrium scenario, including decoherence effects. The proposed scheme allows the monitoring of localization-delocalization transitions in Jaynes-Cummings-lattices by use of currently available experimental technology. Contrary to cavity-coupled lattices, our proposed recourse to stylized qubit networks facilitates (i) to investigate localization-delocalization transitions in arbitrary dimensions and (ii) to tune the inter-site coupling in-situ. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.1857v2.pdf"}
{"id": "1203.4365", "abstract": "  Stochastic simulations of coarse-grained protein models are used to investigate the propensity to form knots in early stages of protein folding. The study is carried out comparatively for two homologous carbamoyltransferases, a natively-knotted N-acetylornithine carbamoyltransferase (AOTCase) and an unknotted ornithine carbamoyltransferase (OTCase). In addition, two different sets of pairwise amino acid interactions are considered: one promoting exclusively native interactions, and the other additionally including non-native quasi-chemical and electrostatic interactions. With the former model neither protein show a propensity to form knots. With the additional non-native interactions, knotting propensity remains negligible for the natively-unknotted OTCase while for AOTCase it is much enhanced. Analysis of the trajectories suggests that the different entanglement of the two transcarbamylases follows from the tendency of the C-terminal to point away from (for OTCase) or approach and eventually thread (for AOTCase) other regions of partly-folded protein. The analysis of the OTCase/AOTCase pair clarifies that natively-knotted proteins can spontaneously knot during early folding stages and that non-native sequence-dependent interactions are important for promoting and disfavoring early knotting events. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1203/1203.4365v1.pdf"}
{"id": "1204.0818", "abstract": "  We present a sensor capable of detecting solution-based nanoparticles using an optical fiber tip functionalized with a photonic crystal cavity. When sensor tips are retracted from a nanoparticle solution after being submerged, we find that a combination of convective fluid forces and optically-induced trapping cause an aggregation of nanoparticles to form directly on cavity surfaces. A simple readout of quantum dot photoluminescence coupled to the optical fiber shows that nanoparticle presence and concentration can be detected through modified cavity properties. Our sensor can detect both gold and iron oxide nanoparticles and can be utilized for molecular sensing applications in biomedicine. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.0818v1.pdf"}
{"id": "1204.2885", "abstract": "  We predict a clean signal at the Large Hadron Collider (√(s))=14 TeV for a scenario where there is a top-like, charge +2/3 vectorlike isosinglet fermion. Such a quark, via mixing with the standard model top, can undergo decays via both flavour-changing Z-boson coupling and flavour-changing Yukawa interactions. We concentrate on the latter channel, and study the situation where, following its pair-production, the heavy quark pair gives rise to two tops and two Higgs boson. We show that the case where each Higgs decays in the bb̅ channel, there can be a rather distinct and background-free signal that can unveil the existence of the vectorlike isosinglet quark of this kind. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1204/1204.2885v1.pdf"}
{"id": "1205.0183", "abstract": "  One of the biggest challenges the current STT-RAM industry faces is maintaining a high thermal stability while trying to switch within a given voltage pulse and energy cost. In this paper, we present a physics based analytical model that uses a modified Simmons' tunneling expression to capture the spin dependent tunneling in a magnetic tunnel junction(MTJ). Coupled with an analytical derivation of the critical switching current based on the Landau-Lifshitz-Gilbert equation, and the write error rate derived from a solution to the Fokker-Planck equation, this model provides us a quick estimate of the energydelay- reliability tradeoffs in perpendicular STTRAMs due to thermal fluctuations. In other words, the model provides a simple way to calculate the energy consumed during a write operation that ensures a certain error rate and delay time, while being numerically far less intensive than a full-fledged stochastic calculation. We calculate the worst case energy consumption during anti-parallel (AP) to parallel (P) and P to AP switchings and quantify how increasing the anisotropy field HK and lowering the saturation magnetization MS, can significantly reduce the energy consumption. A case study on how manufacturing variations of the MTJ cell can affect the energy consumption and delay is also reported. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1205/1205.0183v1.pdf"}
{"id": "1206.4092", "abstract": "  Collective low lying levels of light and medium Xenon isotopes are deduced from the Generalized Bohr Hamiltonian (GBH). The microscopic seven functions entering into the GBH are built from a deformed mean field of the Woods-Saxon type. Theoretical spectra are found to be close to the ones of the experimental data taking into account that the calculations are completely microscopic, that is to say, without any fitting of parameters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.4092v1.pdf"}
{"id": "1206.5394", "abstract": "  We study the nature of motion in a 3D potential composed of perturbed elliptic oscillators. Our technique is to use the results obtained from the 2D potential in order to find the initial conditions generating regular or chaotic orbits in the 3D potential. Both 2D and 3D potentials display exact periodic orbits together with extended chaotic regions. Numerical experiments suggest, that the degree of chaos increases rapidly, as the energy of the test particle increases. About 97", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.5394v1.pdf"}
{"id": "1206.6177", "abstract": "  This paper deals with the structural analysis problem of dynamic lumped process high-index DAE models. We consider two methods for index reduction of such models by differentiation: Pryce's method and the symbolic differential elimination algorithm rifsimp. Discussion and comparison of these methods are given via a class of fundamental process simulation examples. In particular, the efficiency of the Pryce method is illustrated as a function of the number of tanks in process design. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1206/1206.6177v1.pdf"}
{"id": "1207.1152", "abstract": "  We present a theory of organic magnetoresistance (OMR) based on the quenching of the quantum correlation between the carrier's spin and its local environment when the incoherent hopping takes place. We prove that this process contributes a spin-dependent prefactor to the attempt-to-escape frequency in the hopping rate, with its value modulated by the magnetic field. The resulting OMR exhibits a positive Lorentzian saturation component and a negative small-field component, which are independent of model parameters. These behaviors, with their isotope effects, are in good agreement with experimental results. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.1152v2.pdf"}
{"id": "1207.2188", "abstract": "  We investigate the problem of teleporting unknown qudit states via pure quantum channels with nonmaximal Schmidt rank. This process is mapped to the problem of discriminating among nonorthogonal symmetric states which are linearly dependent and equally likely. It is shown that by applying an optimized maximum-confidence (MC) measurement for accomplishing this task, one reaches the maximum possible teleportation fidelity after a conclusive event in the discrimination process, which in turn occurs with the maximum success probability. In this case, such fidelity depends only on the Schmidt rank of the channel and it is larger than the optimal one achieved, deterministically, by the standard teleportation protocol. Furthermore, we show that there are quantum channels for which it is possible to apply a k-stage sequential MC measurement in the discrimination process such that a conclusive event at any stage leads to a teleportation fidelity above the aforementioned optimal one and, consequently, increases the overall success probability of teleportation with a fidelity above this limit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.2188v1.pdf"}
{"id": "1207.7204", "abstract": "  Many critical properties of the Hintermann-Merlini model are known exactly through the mapping to the eight-vertex model. Wu [J. Phys. C 8, 2262 (1975)] calculated the spontaneous magnetizations of the model on two sublattices by relating them to the conjectured spontaneous magnetization and polarization of the eight-vertex model, respectively. The latter conjecture remains unproved. In this paper, we numerically study the critical properties of the model by means of a finite-size scaling analysis based on transfer matrix calculations and Monte Carlo simulations. All analytic predictions for the model are confirmed by our numerical results. The central charge c=1 is found for the critical manifold investigated. In addition, some unpredicted geometry properties of the model are studied. Fractal dimensions of the largest Ising clusters on two sublattices are determined. The fractal dimension of the largest Ising cluster on the sublattice A takes fixed value D_ a=1.888(2), while that for sublattice B varies continuously with the parameters of the model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1207/1207.7204v2.pdf"}
{"id": "1209.1310", "abstract": "  We set up a left ring of fractions over a certain ring of boundary problems for linear ordinary differential equations. The fraction ring acts naturally on a new module of generalized functions. The latter includes an isomorphic copy of the differential algebra underlying the given ring of boundary problems. Our methodology employs noncommutative localization in the theory of integro-differential algebras and operators. The resulting structure allows to build a symbolic calculus in the style of Heaviside and Mikusinski, but with the added benefit of incorporating boundary conditions where the traditional calculi allow only initial conditions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.1310v1.pdf"}
{"id": "1209.5427", "abstract": "  The flux and nuclear composition of ultra-high energy cosmic rays depend on the cosmic distribution of their sources. Data from cosmic ray observatories are yet inconclusive about their exact location or distribution, but provide a measure for the average local density of these emitters. Due to the discreteness of the emitters the flux and nuclear composition is expected to show ensemble fluctuations on top of the statistical variations, i.e. \"cosmic variance\". This effect is strongest for the most energetic cosmic rays due to the limited propagation distance in the cosmic radiation background and is hence a local phenomenon. For the statistical analysis of cosmic ray emission models it is important to quantify the possible level of this variance. In this paper we present a completely analytic method that describes the variation of the flux and nuclear composition with respect to the local source density. We highlight that proposed future space-based observatories with exposures of O(10^6 km^2 sr yr) will attain sensitivity to observe these spectral fluctuations in the cosmic ray energy spectrum at Earth relative to the overall power-law fit. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1209/1209.5427v2.pdf"}
{"id": "1210.1767", "abstract": "  We propose and discuss a new approach to the analysis of the correlation functions which contain light-like Wilson lines or loops, the latter being cusped in addition. The objects of interest are therefore the light-like Wilson null-polygons, the soft factors of the parton distribution and fragmentation functions, high-energy scattering amplitudes in the eikonal approximation, gravitational Wilson lines, etc. Our method is based on a generalization of the universal quantum dynamical principle by J. Schwinger and allows one to take care of extra singularities emerging due to light-like or semi-light-like cusps. We show that such Wilson loops obey a differential equation which connects the area variations and renormalization group behavior of those objects and discuss the possible relation between geometrical structure of the loop space and area evolution of the light-like cusped Wilson loops. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.1767v2.pdf"}
{"id": "1210.8022", "abstract": "  The variance of difference of photocounts (VDPs) is an established measure of quantum correlations for quantum states of light. It enables us to discriminate between the classical correlation of a two-mode coherent state and the quantum correlation of a twin-beam state. We study the effect of loss and saturation of the photon-number-resolving detector on the measurement of the VDPs. An analytic function is derived for this variance, both for the coherent and the twin-beam states. It is found that the VDPs is no longer a reliable entanglement measure in the nonlinear regime of the detector response but it remains useful in some range of values of average photon numbers of the incident light. We also quantify the linear regime of the detector with saturation which will be useful for calibration of the detector quantum efficiency. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1210/1210.8022v3.pdf"}
{"id": "1211.4913", "abstract": "  We develop a mathematical model for sap exudation in a maple tree that is based on a purely physical mechanism for internal pressure generation in trees in the leafless state. There has been a long-standing controversy in the tree physiology literature over precisely what mechanism drives sap exudation, and we aim to cast light on this issue. Our model is based on the work of Milburn and O'Malley [Can. J. Bot., 62(10):2101-2106, 1984] who hypothesized that elevated sap pressures derive from compressed gas that is trapped within certain wood cells and subsequently released when frozen sap thaws in the spring. We also incorporate the extension of Tyree [in Tree Sap, pp. 37-45, eds. M. Terazawa et al., Hokkaido Univ. Press, 1995] who argued that gas bubbles are prevented from dissolving because of osmotic pressure that derives from differences in sap sugar concentrations and the selective permeability of cell walls. We derive a system of differential-algebraic equations based on conservation principles that is used to test the validity of the Milburn-O'Malley hypothesis and also to determine the extent to which osmosis is required. This work represents the first attempt to derive a detailed mathematical model of sap exudation at the micro-scale. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1211/1211.4913v1.pdf"}
{"id": "1301.0344", "abstract": "  Multiview video has recently emerged as a means to improve user experience in novel multimedia services. We propose a new stochastic model to characterize the traffic generated by a Multiview Video Coding (MVC) variable bit rate source. To this aim, we resort to a Poisson Hidden Markov Model (P-HMM), in which the first (hidden) layer represents the evolution of the video activity and the second layer represents the frame sizes of the multiple encoded views. We propose a method for estimating the model parameters in long MVC sequences. We then present extensive numerical simulations assessing the model's ability to produce traffic with realistic characteristics for a general class of MVC sequences. We then extend our framework to network applications where we show that our model is able to accurately describe the sender and receiver buffers behavior in MVC transmission. Finally, we derive a model of user behavior for interactive view selection, which, in conjunction with our traffic model, is able to accurately predict actual network load in interactive multiview services. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1301/1301.0344v1.pdf"}
{"id": "1302.5213", "abstract": "  We construct a reference benchmark set for atomic and molecular random-phase-approximation (RPA) correlation energies in a density functional theory (DFT) framework at the complete basis set limit. This set is used to evaluate the accuracy of some popular extrapolation schemes for RPA all-electron molecular calculations. The results indicate that for absolute energies accurate results, clearly outperforming raw data, are achievable with two-point extrapolation schemes based on quintuple- and sextuple-zeta basis sets. Moreover, we show that results in good agreement with the benchmark can also be also obtained by using a semiempirical extrapolation procedure based on quadruple- and quintuple-zeta basis sets. Finally, we analyze the performance of different extrapolation schemes for atomization energies. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1302/1302.5213v1.pdf"}
{"id": "1304.2641", "abstract": "  Given an undirected graph G, the Minimum Sum Coloring problem (MSCP) is to find a legal assignment of colors (represented by natural numbers) to each vertex of G such that the total sum of the colors assigned to the vertices is minimized. This paper presents a memetic algorithm for MSCP based on a tabu search procedure with two neighborhoods and a multi-parent crossover operator. Experiments on a set of 77 well-known DIMACS and COLOR 2002-2004 benchmark instances show that the proposed algorithm achieves highly competitive results in comparison with five state-of-the-art algorithms. In particular, the proposed algorithm can improve the best known results for 17 instances. We also provide upper bounds for 18 additional instances for the first time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1304/1304.2641v1.pdf"}
{"id": "1305.6373", "abstract": "  We investigate the flavour decomposition of the electromagnetic form factors of the nucleon, based on the chiral quark-soliton model (χQSM) with symmetry-conserving quantisation. We consider the rotational 1/N_c and linear strange-quark mass (m_s) corrections. We discuss the results of the flavour-decomposed electromagnetic form factors in comparison with the recent experimental data. In order to see the effects of the strange quark, we compare the SU(3) results with those of SU(2). We finally discuss the transverse charge densities for both unpolarised and polarised nucleons. The transverse charge density inside a neutron turns out to be negative in the vicinity of the centre within the SU(3) χQSM, which can be explained by the contribution of the strange quark. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1305/1305.6373v3.pdf"}
{"id": "1306.2745", "abstract": "  Population III stars forming in the infant universe at z=30 heralded the end of the cosmic dark ages. They are presumed to be assembled in so-called minihaloes with virial temperatures of a few thousand K where collapse is triggered by molecular hydrogen cooling. A central question concerns their final masses, and whether fragmentation occurs during their formation. While studies employing Lagrangian codes suggest fragmentation via a self-gravitating disk, recent high resolution simulations indicated that disk formation is suppressed. Here we report the first high-resolution large-eddy simulations performed with the Eulerian grid-based code Enzo following the evolution beyond the formation of the first peak, to investigate the accretion of the central massive clump and potential fragmentation. For a total of 3 halos, we see that a disk forms around the first clump. The central clump reaches ∼10 solar masses after 40 years, while subsequent accretion is expected at a rate of 10^-2 solar masses per year. In one of these halos, additional clumps form as a result of fragmentation which proceeds at larger scales. We note that subgrid-scale turbulence yields relevant contributions to the stability of the protostellar disks. We conclude that the first protostar may reach masses up to 40-100 M_⊙, which are only limited by the effect of radiative feedback. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.2745v1.pdf"}
{"id": "1306.5823", "abstract": "  We report here measurements on a dark magneto-optical trap (DMOT) of ^85Rb atoms using an optical nanofibre (ONF) with a waist of ∼ 1 μm. The DMOT is created using a doughnut-shaped repump beam along with a depump beam for efficient transfer of cold atoms from the bright hyperfine ground state (F=3) into the dark hyperfine ground state (F=2). The fluorescence from the cold ^85Rb atoms of the DMOT is detected by coupling it into the fibre-guided modes of the ONF. The measured fractional population of cold atoms in the bright hyperfine ground state (p) is as low as ∼0.04. The dependence of loading rate of DMOT on cooling laser intensity is investigated and also compared with the loading rate of a bright-MOT (BMOT). This work lays the foundation for the use of an ONF for probing of a small number of atoms in an optically-dense cold atomic cloud. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1306/1306.5823v2.pdf"}
{"id": "1307.6244", "abstract": "  The object of this study is one of the most energetic and luminous molecular outflows known in the Galaxy, G331.512-0.103. Observations with ALMA Band 7 (350 GHz; 0.86 mm) reveal a very compact, extremely young bipolar outflow and a more symmetric outflowing shocked shell surrounding a very small region of ionized gas. The velocities of the bipolar outflow are about 70 km s^-1 on either side of the systemic velocity. The expansion velocity of the shocked shell is  24 km s^-1, implying a crossing time of about 2000 yrs. Along the symmetry axis of the outflow, there is a velocity feature, which could be a molecular \"bullet\" of high-velocity dense material. The source is one of the youngest examples of massive molecular outflow found associated with a high-mass star. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1307/1307.6244v2.pdf"}
{"id": "1308.4729", "abstract": "  Many applications in science call for the numerical simulation of systems on manifolds with spherical topology. Through use of integer spin weighted spherical harmonics we present a method which allows for the implementation of arbitrary tensorial evolution equations. Our method combines two numerical techniques that were originally developed with different applications in mind. The first is Huffenberger and Wandelt's spectral decomposition algorithm to perform the mapping from physical to spectral space. The second is the application of Luscombe and Luban's method, to convert numerically divergent linear recursions into stable nonlinear recursions, to the calculation of reduced Wigner d-functions. We give a detailed discussion of the theory and numerical implementation of our algorithm. The properties of our method are investigated by solving the scalar and vectorial advection equation on the sphere, as well as the 2+1 Maxwell equations on a deformed sphere. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1308/1308.4729v2.pdf"}
{"id": "1309.4492", "abstract": "  The possibility of observing supernova (SN) neutrinos through the process of coherent elastic neutrino-nucleus scattering (CENNS) in future ton scale detectors designed primarily for direct detection of dark matter is investigated. In particular, we focus on the possibility of distinguishing the various phases of the SN neutrino emission. The neutrino emission rates from the recent long term Basel/Darmstadt simulations are used to calculate the expected event rates. The recent state-of-the-art SN simulations predict closer fluxes among different neutrino flavors and lower average energies compared to the earlier simulation models. We find that our estimated total event rates are typically a factor of two lower than those predicted using older simulation models. We further find that, with optimistic assumptions on the detector's time resolution (  10 ms) and energy threshold (  0.1 keV), the neutrinos associated with the accretion phase of the SN can in principle be demarcated out with, for example, a 10-ton Xe detector, although distinguishing the neutrinos associated with the neutronization burst phase of the explosion would typically require several tens of ton detectors. We also comment on the possibility of studying the properties of non-electron flavor neutrinos from the CENNS of SN neutrinos. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1309/1309.4492v1.pdf"}
{"id": "1310.3632", "abstract": "  We present compact Q-balls in an (Anti-)de Sitter background in D dimensions, obtained with a V-shaped potential of the scalar field. Beyond critical values of the cosmological constant compact Q-shells arise. By including the gravitational back-reaction, we obtain boson stars and boson shells with (Anti-)de Sitter asymptotics. We analyze the physical properties of these solutions and determine their domain of existence. In four dimensions we address some astrophysical aspects. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1310/1310.3632v1.pdf"}
{"id": "1311.0269", "abstract": "  Power efficiency is becoming an ever more important metric for both high performance and high throughput computing. Over the course of next decade it is expected that flops/watt will be a major driver for the evolution of computer architecture. Servers with large numbers of ARM processors, already ubiquitous in mobile computing, are a promising alternative to traditional x86-64 computing. We present the results of our initial investigations into the use of ARM processors for scientific computing applications. In particular we report the results from our work with a current generation ARMv7 development board to explore ARM-specific issues regarding the software development environment, operating system, performance benchmarks and issues for porting High Energy Physics software. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1311/1311.0269v2.pdf"}
{"id": "1312.2672", "abstract": "  The non-integrable Dicke model and its integrable approximation, the Tavis-Cummings (TC) model, are studied as functions of both the coupling constant and the excitation energy. The present contribution extends the analysis presented in the previous paper by focusing on the statistical properties of the quantum fluctuations in the energy spectrum and their relation with the excited state quantum phase transitions (ESQPT). These properties are compared with the dynamics observed in the semi-classical versions of the models. The presence of chaos for different energies and coupling constants is exhibited, employing Poincaré sections and Peres lattices in the classical and quantum versions, respectively. A clear correspondence between the classical and quantum result is found for systems containing between 𝒩 = 80 to 200 atoms. A measure of the Wigner character of the energy spectrum for different couplings and energy intervals is also presented employing the statistical Anderson-Darling test. It is found that in the Dicke Model, for any coupling, a low energy regime with regular states is always present. The richness of the onset of chaos is discussed both for finite quantum systems and for the semi-classical limit, which is exact when the number of atoms in the system tends to infinite. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.2672v2.pdf"}
{"id": "1312.4432", "abstract": "  Quantum criticality provides an important route to revealing universal non-equilibrium behaviour. A canonical example of a quantum critical point is the Bose-Hubbard model, which we study under the application of an electric field. A Boltzmann transport formalism and ϵ-expansion are used to obtain the non-equilibrium conductivity and current noise. This approach allows us to explicitly identify how a universal non-equilibrium steady state is maintained, by identifying the rate-limiting step in balancing Joule heating and dissipation to a heat bath. It also reveals that the non-equilibrium distribution function is very far from a thermal distribution. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1312/1312.4432v2.pdf"}
{"id": "1401.5332", "abstract": "  A recently introduced active phase field crystal model describes the formation of ordered resting and traveling crystals in systems of self-propelled particles. Increasing the active drive, a resting crystal can be forced to perform collectively ordered migration as a single traveling object. We demonstrate here that these ordered migrating structures are linearly stable. In other words, during migration, the single crystalline texture together with the globally ordered collective motion is preserved even on large length scales. Furthermore, we consider self-propelled particles on a substrate that are surrounded by a thin fluid film. We find that in this case the resulting hydrodynamic interactions can destabilize the order. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5332v1.pdf"}
{"id": "1401.5487", "abstract": "  We discuss the spectrum of Var C in M33 obtained just before the onset of its current brightening and recent spectra during its present \"eruption\" or optically thick wind stage. These spectra illustrate the typical LBV transition in apparent spectral type or temperature that characterizes the classical LBV or S Dor-type variability. LBVs are known to have slow, dense winds during their maximum phase. Interestingly, Var C had a slow wind even during its hot, quiescent stage in comparison with the normal hot supergiants with similar temperatures. Its outflow or wind speeds also show very little change between these two states. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.5487v1.pdf"}
{"id": "1401.6251", "abstract": "  We propose a new approach to comparing simulated observations that enables us to determine the significance of the underlying physical effects. We utilize the methodology of experimental design, a subfield of statistical analysis, to establish a framework for comparing simulated position-position-velocity data cubes to each other. We propose three similarity metrics based on methods described in the literature: principal component analysis, the spectral correlation function, and the Cramer multi-variate two sample similarity statistic. Using these metrics, we intercompare a suite of mock observational data of molecular clouds generated from magnetohydrodynamic simulations with varying physical conditions. Using this framework, we show that all three metrics are sensitive to changing Mach number and temperature in the simulation sets, but cannot detect changes in magnetic field strength and initial velocity spectrum. We highlight the shortcomings of one-factor-at-a-time designs commonly used in astrophysics and propose fractional factorial designs as a means to rigorously examine the effects of changing physical properties while minimizing the investment of computational resources. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1401/1401.6251v1.pdf"}
{"id": "1403.0049", "abstract": "  Quantum squeezing in mechanical systems is not only a key signature of macroscopic quantum effects, but can also be utilized to advance the metrology of weak forces. Here we show that strong mechanical squeezing in the steady state can be generated in an optomechanical system with mechanical nonlinearity and red-detuned monochromatic driving on the cavity mode. The squeezing is achieved as the joint effect of nonlinearity-induced parametric amplification and cavity cooling, and is robust against thermal fluctuations of the mechanical mode. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1403/1403.0049v2.pdf"}
{"id": "1404.0394", "abstract": "  The multiple futile cycle is an important building block in networks of chemical reactions arising in molecular biology. A typical process which it describes is the addition of n phosphate groups to a protein. It can be modelled by a system of ordinary differential equations depending on parameters. The special case n = 2 is called the dual futile cycle. The main result of this paper is a proof that there are parameter values for which the system of ODE describing the dual futile cycle has two distinct stable stationary solutions. The proof is based on bifurcation theory and geometric singular perturbation theory. An important entity built of three coupled multiple futile cycles is the MAPK cascade. It is explained how the ideas used to prove bistability for the dual futile cycle might help to prove the existence of periodic solutions for the MAPK cascade. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.0394v1.pdf"}
{"id": "1404.5216", "abstract": "  Motivated by the findings of logarithmic spreading of entanglement in a many-body localized system, we more closely examine the spreading of entanglement in the fully many-body localized phase, where all many-body eigenstates are localized. Performing full diagonalizations of an XXZ spin model with random longitudinal fields, we identify two factors contributing to the spreading rate: the localization length (ξ), which depends on the disorder strength, and the final value of entanglement per spin (s_∞), which primarily depends on the initial state. We find that the entanglement entropy grows with time as ∼ξ× s_∞log t, providing support for the phenomenology of many-body localized systems recently proposed by Huse and Oganesyan [arXiv:1305.4915v1]. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.5216v2.pdf"}
{"id": "1404.5641", "abstract": "  Quantum manifestations of various properties of metallic thin films by quantum size effect (QSE) have been studied intensively. Here, using first-principles calculations, we show quantum manifestation in dielectric properties of Al(111) ultrathin films. The QSE on the dielectric function is revealed, which arises from size dependent contributions from both intraband and interband electronic transitions. More importantly, the in-plane interband transitions in the films thinner than 15 monolayers are found to be smaller than the bulk counterpart in the energy range from 1.5 eV to 2.5 eV. This indicates less energy loss with plasmonic material of Al in the form of ultrathin film. Our findings may shed light on searching for low-loss plasmonic materials via quantum size effect. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1404/1404.5641v1.pdf"}
{"id": "1405.1839", "abstract": "  The close proximity of short period hot-Jupiters to their parent star means they are subject to extreme tidal forces. This has a profound effect on their structure and, as a result, density measurements that assume that the planet is spherical can be incorrect. We have simulated the tidally distorted surface for 34 known short period hot-Jupiters, assuming surfaces of constant gravitational equipotential for the planet, and the resulting densities have been calculated based only on observed parameters of the exoplanet systems. Comparing these results to the density values assuming the planets are spherical shows that there is an appreciable change in the measured density for planets with very short periods (typically less than two days). For one of the shortest-period systems, WASP-19b, we determine a decrease in bulk density of 12", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1405/1405.1839v1.pdf"}
{"id": "1406.2072", "abstract": "  We study strong coupling between plasmons in monolayer charge-doped graphene and excitons in a narrow gap semiconductor quantum well separated from graphene by a potential barrier. We show that the Coulomb interaction between excitons and plasmons result in mixed states described by a Hamiltonian similar to that for exciton-polaritons and derive the exciton-plasmon coupling constant that depends on system parameters. We calculate numerically the Rabi splitting of exciton- plasmariton dispersion branches for several semiconductor materials and find that it can reach values of up to 50 - 100 meV. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1406/1406.2072v2.pdf"}
{"id": "1407.7562", "abstract": "  The theorems of vector analysis (divergence theorem, etc.) are typically first applied in the undergraduate physics curriculum in the context of the electromagnetic field and the differential forms of Maxwell's equations. However, these tools are analyzed in depth several courses later in the junior-senior level. I discuss here a \"bridge\" problem, using the language of vector calculus in a mechanics setting to understand Archimedes' principle as a consequence of hydrostatic equilibrium and the superposition of the external forces. It is my hope that this treatment will help students better integrate and understand understand these and similar vector analysis results in contexts beyond electromagnetism. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1407/1407.7562v1.pdf"}
{"id": "1408.0112", "abstract": "  Linear gyro-kinetic simulations of the classical tearing mode in three-dimensional toroidal geometry were performed using the global gyro kinetic turbulence code, GKW . The results were benchmarked against a cylindrical ideal MHD and analytical theory calculations. The stability, growth rate and frequency of the mode were investigated by varying the current profile, collisionality and the pressure gradients. Both collision-less and semi-collisional tearing modes were found with a smooth transition between the two. A residual, finite, rotation frequency of the mode even in the absense of a pressure gradient is observed which is attributed to toroidal finite Larmor-radius effects. When a pressure gradient is present at low collisionality, the mode rotates at the expected electron diamagnetic frequency. However the island rotation reverses direction at high collisionality. The growth rate is found to follow a η^1/7 scaling with collisional resistivity in the semi-collisional regime, closely following the semi-collisional scaling found by Fitzpatrick. The stability of the mode closely follows the stability using resistive MHD theory, however a modification due to toroidal coupling and pressure effects is seen. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1408/1408.0112v1.pdf"}
{"id": "1412.6005", "abstract": "  The charge of an ideal parallel capacitor leads to the resolution of the wave equation for the electric field with prescribed initial conditions and boundary constraints. Independently of the capacitor's shape and the applied voltage, none of the corresponding solutions is compatible with the full set of Maxwell's equations. The paradoxical situation persists even by weakening boundary conditions, resulting in the impossibility to describe a trivial phenomenon such as the capacitor's charging process, by means of the standard Maxwellian theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1412/1412.6005v1.pdf"}
{"id": "1501.02579", "abstract": "  Using a Bayesian approach, we consider the problem of recovering sparse signals under additive sparse and dense noise. Typically, sparse noise models outliers, impulse bursts or data loss. To handle sparse noise, existing methods simultaneously estimate the sparse signal of interest and the sparse noise of no interest. For estimating the sparse signal, without the need of estimating the sparse noise, we construct a robust Relevance Vector Machine (RVM). In the RVM, sparse noise and ever present dense noise are treated through a combined noise model. The precision of combined noise is modeled by a diagonal matrix. We show that the new RVM update equations correspond to a non-symmetric sparsity inducing cost function. Further, the combined modeling is found to be computationally more efficient. We also extend the method to block-sparse signals and noise with known and unknown block structures. Through simulations, we show the performance and computation efficiency of the new RVM in several applications: recovery of sparse and block sparse signals, housing price prediction and image denoising. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.02579v1.pdf"}
{"id": "1501.04091", "abstract": "  We study a linear threshold agent-based model (ABM) for the spread of political revolutions on social networks using empirical network data. We propose new techniques for building a hierarchy of simplified ordinary differential equation (ODE) based models that aim to capture essential features of the ABM, including effects of the actual networks, and give insight in the parameter regime transitions of the ABM. We relate the ABM and the hierarchy of models to a population-level compartmental ODE model that we proposed previously for the spread of political revolutions [1], which is shown to be mathematically consistent with the proposed ABM and provides a way to analyze the global behaviour of the ABM. This consistency with the linear threshold ABM also provides further justification a posteriori for the compartmental model of [1]. Extending concepts from epidemiological modelling, we define a basic reproduction number R_0 for the linear threshold ABM and apply it to predict ABM behaviour on empirical networks. In small-scale numerical tests we investigate experimentally the differences in spreading behaviour that occur under the linear threshold ABM model when applied to some empirical online and offline social networks, searching for quantitative evidence that political revolutions may be facilitated by the modern online social networks of social media. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.04091v1.pdf"}
{"id": "1501.05330", "abstract": "  Many techniques for measuring neutron star radii rely on absolute flux measurements in the X-rays. As a result, one of the fundamental uncertainties in these spectroscopic measurements arises from the absolute flux calibrations of the detectors being used. Using the stable X-ray burster, GS 1826-238, and its simultaneous observations by Chandra HETG/ACIS-S and RXTE/PCA as well as by XMM-Newton EPIC-pn and RXTE/PCA, we quantify the degree of uncertainty in the flux calibration by assessing the differences between the measured fluxes during bursts. We find that the RXTE/PCA and the Chandra gratings measurements agree with each other within their formal uncertainties, increasing our confidence in these flux measurements. In contrast, XMM-Newton EPIC-pn measures 14.0±0.3 ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1501/1501.05330v2.pdf"}
{"id": "1502.04937", "abstract": "  Future experiments of nuclear and particle physics are moving towards the high luminosity regime, in order to access suppressed processes like rare B decays or exotic charmonium resonances. In this scenario, high rate capability is a key requirement for electronics instrumentation, together with excellent timing resolution for precise event reconstruction. The development of dedicated FrontEnd Electronics (FEE) for detectors has become increasingly challenging. A current trend in R   D is towards multipurpose FEE which can be easily adapted to a great variety of detectors, without impairing the required high performance. We report on high-precision timing solutions which utilise high-bandwidth preamplifiers and fast discriminators providing Time-over-Threshold information, which can be used for charge measurements or walk corrections thus improving the obtainable timing resolution. The output signal are LVDS and can be directly fed into a multi-hit TDC readout. The performance of the electronics was investigated for single photon signals, typical for imaging Cherenkov detectors. The opposite condition of light signals arising from plastic scintillators, was also studied. High counting rates per channel of several MHz were achieved, and a timing resolution of better than 100 ps could be obtained in a test experiment using the full readout chain. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.04937v1.pdf"}
{"id": "1502.05415", "abstract": "  The Bethe-Salpeter equation in the diquark channel is investigated by employing the Dyson-Schwinger method together with the Munczek-Nemirovsky model. The novelty of our study is a resummation of completely crossed ladder diagrams in the Bethe-Salpeter kernel. These diagrams are enhanced due to their color factors in the diquark channel, but not in the meson channel. In our analysis, diquark bound-state solutions exist in the Bethe-Salpeter equation. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1502/1502.05415v3.pdf"}
{"id": "1503.00128", "abstract": "  We present a variational study of pseudo-spin 1/2 Bose gases in a harmonic trap with weak 3D spin-orbit coupling of ·𝐩 type. This spin-orbit coupling mixes states with different parities, which inspires us to approximate the single particle state with the eigenstates of the total angular momentum, i.e. superposition of harmonic s-wave and p-wave states. As the time reversal symmetry is protected by two-body interaction, we set the variational order parameter as the combination of two mutually time reversal symmetric eigenstates of the total angular momentum. The variational results essentially reproduce the 3D skyrmion-like ground state recently identified by Kawakami et al.. We show that these skyrmion-like ground states emerging in this model are primarily caused by p wave spatial mode involving in the variational order parameter that drives two spin components spatially separated. We find the ground state of this system falls into two phases with different density distribution symmetries depending on the relative magnitude of intraspecies and interspecies interaction: Phase I has parity symmetric and axisymmetric density distributions, while Phase II is featured with special joint symmetries of discrete rotational and time reversal symmetry. With the increasing interaction strength the transition occurs between two phases with distinct density distributions, while the topological 3D skyrmion-like spin texture is symmetry protected. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1503/1503.00128v1.pdf"}
{"id": "1504.00501", "abstract": "  The thermodynamic entropy of an isolated system is given by its von Neumann entropy. Over the last few years, there is an intense activity to understand thermodynamic entropy from the principles of quantum mechanics. More specifically, is there a relation between the (von Neumann) entropy of entanglement between a system and some (separate) environment is related to the thermodynamic entropy? It is difficult to obtain the relation for many body systems, hence, most of the work in the literature has focused on small number systems. In this work, we consider black-holes — that are simple yet macroscopic systems — and show that a direct connection could not be made between the entropy of entanglement and the Hawking temperature. In this work, within the adiabatic approximation, we explicitly show that the Hawking temperature is indeed given by the rate of change of the entropy of entanglement across a black hole's horizon with regard to the system energy. This is yet another numerical evidence to understand the key features of black hole thermodynamics from the viewpoint of quantum information theory. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.00501v2.pdf"}
{"id": "1504.03901", "abstract": "  The properties of the entanglement entropy (EE) of a clean Cayley tree (CT) are studied. The EE shows a completely different behaviour depending on the way the CT is partitioned into two regions and whether we consider the ground-state or highly excited many-particle wave function. The ground-state EE increases logarithmically as function of number of generation if a single branch is pruned off the tree, while it grows exponentially if the region around the root is trimmed. On the other hand, in both cases the highly excited states' EE grows exponentially. Implications of these results to general graphs and disordered systems are shortly discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1504/1504.03901v1.pdf"}
{"id": "1505.01332", "abstract": "  We introduce and analyze a class of growing geometric random graphs that are invariant under rescaling of space and time. Directed connections between nodes are drawn according to influence zones that depend on node position in space and time, mimicking the heterogeneity and increased specialization found in growing networks. Through calculations and numerical simulations we explore the consequences of scale-invariance for geometric random graphs generated this way. Our analysis reveals a dichotomy between scale-free and Poisson distributions of in- and out-degree, the existence of a random number of hub nodes, high clustering, and unusual percolation behaviour. These properties are similar to those of empirically observed web graphs. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.01332v2.pdf"}
{"id": "1505.02015", "abstract": "  We present a theoretical study on the electron transmission through the AB-BA stacking boundary in multilayer graphene. Using the tight-binding model and the transfer matrix method, we calculate the electron transmission probability through the boundary as a function of electron Fermi energy in multilayers from bilayer to five-layer. We find that the transmission is strongly suppressed particularly near the band touching point, suggesting that the electronic conductivity in general multilayer graphenes is significantly interfered by stacking fault. The conductivity suppression by stacking fault is the strongest in the bilayer graphene, while it is gradually relaxed as increasing the number of layers. At a large carrier density, we observe an even-odd effect where the transmission is relatively lower in trilayer and five-layer than in bilayer and four-layer, and this is related to the existence of a monolayer-like linear band in odd layers. For bilayer graphene, we also study the effect of the perpendicular electric field opening an energy gap, and show that the band deformation enhances the electron transmission at a fixed carrier density. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1505/1505.02015v2.pdf"}
{"id": "1506.04611", "abstract": "  We explain how hierarchical organization of biological systems emerges naturally during evolution, through a transition in the units of individuality. We will show how these transitions are the result of competing selective forces operating at different levels of organization, each level having different units of individuality. Such a transition represents a singular point in the evolutionary process, which we will show corresponds to a phase transition in the way information is encoded, with the formation of self-reinforcing information bottlenecks. We present an abstract model for characterizing these transitions that is quite general, applicable to many different versions of such transitions. As a concrete example, we consider the transition to multicellularity. Specifically, we study a stochastic model where isolated communities of interacting individuals (e.g. cells) undergo a transition to higher-order individuality (e.g. multicellularity). This transition is indicated by the marked decrease in the number of cells utilized to generate new communities from pre-existing ones. In this sense, the community begins to reproduce as a whole via a decreasing number of cells. We show that the fitness barrier to this transition is strongly reduced by horizontal gene transfer. These features capture two of the most prominent aspects of the transition to multicellularity: the evolution of a developmental process and reproduction through a unicellular bottleneck. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.04611v1.pdf"}
{"id": "1506.07836", "abstract": "  The Brown-Resnick max-stable process has proven to be well-suited for modeling extremes of complex environmental processes, but in many applications its likelihood function is intractable and inference must be based on a composite likelihood, thereby preventing the use of classical Bayesian techniques. In this paper we exploit a case in which the full likelihood of a Brown-Resnick process can be calculated, using componentwise maxima and their partitions in terms of individual events, and we propose two new approaches to inference. The first estimates the partitions using declustering, while the second uses random partitions in a Markov chain Monte Carlo algorithm. We use these approaches to construct a Bayesian hierarchical model for extreme low temperatures in northern Fennoscandia. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1506/1506.07836v2.pdf"}
{"id": "1507.07519", "abstract": "  Disordered biopolymer gels have striking mechanical properties including strong nonlinearities. In the case of athermal gels (such as collagen-I) the nonlinearity has long been associated with a crossover from a bending dominated to a stretching dominated regime of elasticity. The physics of this crossover is related to the existence of a central-force isostatic point and to the fact that for most gels the bending modulus is small. This crossover induces scaling behavior for the elastic moduli. In particular, for linear elasticity such a scaling law has been demonstrated [Broedersz et al. Nature Physics, 2011 7, 983]. In this work we generalize the scaling to the nonlinear regime with a two-parameter scaling law involving three critical exponents. We test the scaling law numerically for two disordered lattice models, and find a good scaling collapse for the shear modulus in both the linear and nonlinear regimes. We compute all the critical exponents for the two lattice models and discuss the applicability of our results to real systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1507/1507.07519v1.pdf"}
{"id": "1508.02323", "abstract": "  Adding a scalar triplet to the Standard Model is one of the simplest ways of giving mass to neutrinos, providing at the same time a mechanism to stabilize the theory's vacuum. In this paper, we revisit these aspects of the type-II seesaw model pointing out that the bounded-from-below conditions for the scalar potential in use in the literature are not correct. We discuss some scenarios where the correction can be significant and sketch the typical scalar boson profile expected by consistency. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.02323v2.pdf"}
{"id": "1508.06547", "abstract": "  Cosmological dynamics of scalar field with a monomial potential ϕ^n with a general background equation of state is revisited. It is known that if n is smaller than a critical value, the scalar field exhibits a coherent oscillation and if n is larger it obeys a scaling solution without oscillation. We study in detail the case where n is equal to the critical value, and find a peculiar scalar dynamics which is neither oscillating nor scaling solution, and we call it a pseudo scaling solution. We also discuss cosmological implications of a pseudo scaling scalar dynamics, such as the curvature perturbation and the domain wall problem. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.06547v2.pdf"}
{"id": "1508.07778", "abstract": "  Blind quantum computation (BQC) enables a client without enough quantum power to delegate his quantum computation to a quantum server, while keeping the input data, the algorithm and the result unknown to the server. In the studies of practical BQC protocol, an important problem is how to reduce the quantum requirement of the client. Multi-server BQC protocols have been proposed to solve this problem. We review the double-server and triple-server protocols [Li et al., Phys. Rev. A 89, 040302(R) (2014)], and propose a modified double-server BQC protocol with a trusted center. In our protocol, the servers are allowed to communicate mutually, and the client is completely classical. Furthermore, our double-server protocol can be modified into a single-server protocol by simply combining the two servers. Compared with the triple-server protocol, our double-server and single-server protocols are more simple and the client is not required to have the ability to access quantum channel. So our protocols are more practical when quantum computer is applied in the `cloud' model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1508/1508.07778v2.pdf"}
{"id": "1509.02379", "abstract": "  The gaseous proportional counter is a device that can be used to detect ionizing radiation. These devices can be as simple as a cylindrical cathode and a very thin anode wire centered along its axis. By applying a high voltage, a strong electric field is generated close to the anode wire. Ion-pairs, generated by passing ionizing radiation, create avalanches once they drift into the strong electric field region near the anode. The electrical charges created by the avalanche generate an observable signal which is proportional to the energy loss of the incoming radiation. We discuss the construction of such a device. Our detector was built from an ordinary aluminium beverage can and uses a common electric wire strand as the anode. The construction of this detector offers students at universities or technically oriented high schools a detailed understanding of the design and operation of gaseous radiation detectors. The equipment required to complete the project should be available at most institutions. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.02379v1.pdf"}
{"id": "1509.04407", "abstract": "  In this paper, we present a study on persistent and gradual penumbral decay and correlated decline of the photospheric transverse field component during 10-20 hours before a major flare (X1.8) eruption on 2011 September 7. This long-term pre-eruption behavior is corroborated with the well-imaged pre-flare filament rising, the consistent expansion of coronal arcades overlying the filament, as well as the NLFFF modelling results in the literature. We suggest that both the long-term pre-flare penumbral decay and the transverse field decline are the photospheric manifestation of the gradual rise of the coronal filament-flux rope system. We also suggest that a C3 flare and subsequent reconnection process preceding the X1.8 flare play an important role in triggering the later major eruption. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.04407v1.pdf"}
{"id": "1509.08848", "abstract": "  In this work we study the process of energy dissipation triggered by a slow large scale motion of a magnetized conducting fluid. Our consideration is motivated by the problem of heating the solar corona, which is believed to be governed by fast reconnection events set off by the slow motion of magnetic field lines anchored in the photospheric plasma. To elucidate the physics governing the disruption of the imposed laminar motion and the energy transfer to small scales, we propose a simplified model where the large-scale motion of magnetic field lines is prescribed not at the footpoints but rather imposed volumetrically. As a result, the problem can be treated numerically with an efficient, highly-accurate spectral method, allowing us to use a resolution and statistical ensemble exceeding those of the previous work. We find that, even though the large-scale deformations are slow, they eventually lead to reconnection events that drive a turbulent state at smaller scales. The small-scale turbulence displays many of the universal features of field-guided MHD turbulence like a well developed inertial range spectrum. Based on these observations, we construct a phenomenological model that gives the scalings of the amplitude of the fluctuations and the energy dissipation rate as functions of the input parameters. We find a good agreement between the numerical results and the predictions of the model. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.08848v2.pdf"}
{"id": "1509.09138", "abstract": "  This work presents a smart trespasser detection and alert system which aims to increase the amount of security as well as the likelihood of positively identifying or stopping trespassers and intruders as compared to other commonly deployed home security system. Using multiple sensors, this system can gauge the extent of danger exhibited by a person or animal in or around the home premises, and can forward certain critical information regarding the same to home owners as well as other specified persons such as relevant security authorities. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1509/1509.09138v1.pdf"}
{"id": "1510.01371", "abstract": "  The microscopic mechanisms controlling heterogeneous ice nucleation are complex and remain poorly understood. Although good ice nucleators are generally believed to match ice lattice and to bind water, counter examples are often identified. Here we show, by advanced molecular simulations, that the heterogeneous nucleation of ice on graphitic surface is controlled by the coupling of surface crystallinity and surface hydrophilicity. Molecular level analysis reveals that the crystalline graphitic lattice with an appropriate hydrophilicity may indeed template ice basal plane by forming a strained ice layer, thus significantly enhancing its ice nucleation efficiency. Remarkably, the templating effect is found to transit from within the first contact layer of water to the second as the hydrophilicity increases, yielding an oscillating distinction between the crystalline and amorphous graphitic surfaces in their ice nucleation efficiencies. Our study sheds new light on the long-standing question of what constitutes a good ice nucleator. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1510/1510.01371v1.pdf"}
{"id": "1512.03162", "abstract": "  This paper reviews the state of the art in spin-torque and spin Hall effect driven nano-oscillators. After a brief introduction to the underlying physics, the authors discuss different implementations of these oscillators, their functional properties in terms of frequency range, output power, phase noise, and modulation rates, and their inherent propensity for mutual synchronization. Finally, the potential for these oscillators in a wide range of applications, from microwave signal sources and detectors to neuromorphic computation elements, is discussed together with the specific electronic circuitry that has so far been designed to harness this potential. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.03162v1.pdf"}
{"id": "1512.04167", "abstract": "  In this paper, we study shock structures of collisionless shocks in partially ionized plasmas by means of two-dimensional hybrid simulations, where the shock is a perpendicular shock with shock velocity Vsh   40 Va   1333 km/s and the upstream ionization fraction is 0.5. We find that large density fluctuations and large magnetic fields fluctuations are generated both in the upstream and downstream regions. In addition, we find that the velocity distribution of downstream hydrogen atoms has three components. Observed shock structures suggest that diffusive shock acceleration can operate at perpendicular shocks propagating into partially ionized plasmas in real three-dimensional systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1512/1512.04167v1.pdf"}
{"id": "1601.02290", "abstract": "  We study the dynamics of two gray solitons in a Bose-Einstein condensate confined by a toroidal trap with a tight confinement in the radial direction. Gross-Pitaevskii simulations show that solitons can be long living objects passing through many collisional processes. We have observed quite different behaviors depending on the soliton velocity. Very slow solitons, obtained by perturbing the stationary solitonic profile, move with a constant angular velocity until they collide elastically and move in the opposite direction without showing any sign of lowering their energy. In this case the density notches are always well separated and the fronts are sharp and straight. Faster solitons present vortices around the notches, which play a central role during the collisions. We have found that in these processes the solitons lose energy, as the outgoing velocity turns out to be larger than the incoming one. To study the dynamics, we model the gray soliton state with a free parameter that is related to the soliton velocity. We further analyze the energy, soliton velocity and turning points in terms of such a free parameter, finding that the main features are in accordance with the infinite one-dimensional system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.02290v1.pdf"}
{"id": "1601.06582", "abstract": "  We explore the implications of the conservation law(s) and the corresponding \"continuity equation(s)\", resulting from the coupling between the positional and the orientational order in main-chain polymer nematics, by showing that the vectorial and tensorial forms of these equations are in general not equivalent and can not be reduced to one another, but neither are they disjoint alternatives. We analyze the relation between them and elucidate the fundamental role that the chain backfolding plays in the determination of their relative strength and importance. Finally, we show that the correct penalty potential in the effective free energy, implementing these conservation laws, should actually connect both the tensorial and the vectorial constraints. We show that the consequences of the polymer chains connectivity for their consistent mesoscopic description are thus not only highly non-trivial but that its proper implementation is absolutely crucial for a consistent coarse grained description of the main-chain polymer nematics. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1601/1601.06582v2.pdf"}
{"id": "1602.06352", "abstract": "  One finding of cognitive research is that people do not automatically acquire usable knowledge by spending lots of time on task. Because students' knowledge hierarchy is more fragmented, \"knowledge chunks\" are smaller than those of experts. The limited capacity of short term memory makes the cognitive load high during problem solving tasks, leaving few cognitive resources available for metacognition. The abstract nature of the laws of physics and the chain of reasoning required to draw meaningful inferences makes these issues critical. In order to help students, it is crucial to consider the difficulty of a problem from the perspective of students. We are developing and evaluating interactive problem-solving tutorials to help students in the introductory physics courses learn effective problem-solving strategies while solidifying physics concepts. The self-paced tutorials can provide guidance and support for a variety of problem solving techniques, and opportunity for knowledge and skill acquisition. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1602/1602.06352v1.pdf"}
{"id": "1603.00527", "abstract": "  We provide a general and tractable framework under which all multiple yield curve modeling approaches based on affine processes, be it short rate, Libor market, or HJM modeling, can be consolidated. We model a numeraire process and multiplicative spreads between Libor rates and simply compounded OIS rates as functions of an underlying affine process. Besides allowing for ordered spreads and an exact fit to the initially observed term structures, this general framework leads to tractable valuation formulas for caplets and swaptions and embeds all existing multi-curve affine models. The proposed approach also gives rise to new developments, such as a short rate type model driven by a Wishart process, for which we derive a closed-form pricing formula for caplets. The empirical performance of two specifications of our framework is illustrated by calibration to market data. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.00527v2.pdf"}
{"id": "1603.09254", "abstract": "  Quantitatively assessing relationships between latent variables and observed variables is important for understanding and developing generative models and representation learning. In this paper, we propose latent-observed dissimilarity (LOD) to evaluate the dissimilarity between the probabilistic characteristics of latent and observed variables. We also define four essential types of generative models with different independence/conditional independence configurations. Experiments using tractable real-world data show that LOD can effectively capture the differences between models and reflect the capability for higher layer learning. They also show that the conditional independence of latent variables given observed variables contributes to improving the transmission of information and characteristics from lower layers to higher layers. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.09254v1.pdf"}
{"id": "1603.09607", "abstract": "  We discuss quantum interference phenomena in a system consisting from a laser driven three-level ladder-type emitter possessing orthogonal transition dipoles and embedded in a leaking optical resonator. The cavity mean-photon number vanishes due to the destructive nature of the interference phenomena. The effect occurs for some particular parameter regimes which were identified. Furthermore, upper bare-state population inversion occurs as well. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1603/1603.09607v1.pdf"}
{"id": "1604.02595", "abstract": "  At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution dE_FWHM = 3.7eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterised the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.02595v1.pdf"}
{"id": "1604.04712", "abstract": "  Wavefunction extrapolation greatly reduces the number of self-consistent field (SCF) iterations and thus the overall computational cost of Born-Oppenheimer molecular dynamics (BOMD) that is based on the Kohn-Sham density functional theory. Going against the intuition that the higher order of extrapolation possesses a better accuracy, we demonstrate, from both theoretical and numerical perspectives, that the extrapolation accuracy firstly increases and then decreases with respect to the order, and an optimal extrapolation order in terms of minimal number of SCF iterations always exists. We also prove that the optimal order tends to be larger when using larger MD time steps or more strict SCF convergence criteria. By example BOMD simulations of a solid copper system, we show that the optimal extrapolation order covers a broad range when varying the MD time step or the SCF convergence criterion. Therefore, we suggest the necessity for BOMD simulation packages to open the user interface and to provide more choices on the extrapolation order. Another factor that may influence the extrapolation accuracy is the alignment scheme that eliminates the discontinuity in the wavefunctions with respect to the atomic or cell variables. We prove the equivalence between the two existing schemes, thus the implementation of either of them does not lead to essential difference in the extrapolation accuracy. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.04712v2.pdf"}
{"id": "1604.07046", "abstract": "  We consider the dynamics of a reaction-diffusion system on a multigraph. The species share the same set of nodes but can access different links to explore the embedding spatial support. By acting on the topology of the networks we can control the ability of the system to self-organise in macroscopic patterns, emerging as a symmetry breaking instability of an homogeneous fixed point. Two different cases study are considered: on the one side, we produce a global modification of the networks, starting from the limiting setting where species are hosted on the same graph. On the other, we consider the effect of inserting just one additional single link to differentiate the two graphs. In both cases, patterns can be generated or destroyed, as follows the imposed, small, topological perturbation. Approximate analytical formulae allows to grasp the essence of the phenomenon and can potentially inspire innovative control strategies to shape the macroscopic dynamics on multigraph networks ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.07046v1.pdf"}
{"id": "1604.07831", "abstract": "  How the accreted mass settling on the surface of a neutron star affects the topology of the magnetic field and how the secular evolution of the binary system depends on the magnetic field change is still an open issue. We report evidence for a clear drop in the observed magnetic field in the accreting pulsar V0332+53 after undergoing a bright 3-month long X-ray outburst. We determine the field from the position of the fundamental cyclotron line in its X-ray spectrum and relate it to the luminosity. For equal levels of luminosity, in the declining phase we measure a systematically lower value of the cyclotron line energy with respect to the rising phase. This results in a drop of  1.7 x 10^11 G of the observed field between the onset and the end of the outburst. The settling of the accreted plasma onto the polar cap seems to induce a distortion of the magnetic field lines weakening their intensity along the accretion columns. Therefore the dissipation rate of the magnetic field could be much faster than previously estimated, unless the field is able to restore its original configuration on a time-scale comparable with the outbursts recurrence time. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1604/1604.07831v1.pdf"}
{"id": "1605.08826", "abstract": "  We consider the dynamics of a two-level system (qubit) driven by strong and short resonant pulses in the framework of Floquet theory. First we derive analytical expressions for the quasienergies and Floquet states of the driven system. If the pulse amplitude varies very slowly, the system adiabatically follows the instantaneous Floquet states, which acquire dynamical phases that depend on the evolution of the quasienergies over time. The difference between the phases acquired by the two Floquet states corresponds to a qubit state rotation, generalizing the notion of Rabi oscillations to the case of large driving amplitudes. If the pulse amplitude changes very fast, the evolution is non-adiabatic, with transitions taking place between the Floquet states. We quantify and analyze the nonadiabatic transitions during the pulse by employing adiabatic perturbation theory and exact numerical simulations. We find that, for certain combinations of pulse rise and fall times and maximum driving amplitude, a destructive interference effect leads to a remarkably strong suppression of transitions between the Floquet states. This effect provides the basis of a quantum control protocol, which we name Floquet Interference Efficient Suppression of Transitions in the Adiabatic basis (FIESTA), that can be used to design ultra-fast high-fidelity single-qubit quantum gates. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.08826v2.pdf"}
{"id": "1605.08838", "abstract": "  We study dueling bandits with weak utility-based regret when preferences over arms have a total order and carry observable feature vectors. The order is assumed to be determined by these feature vectors, an unknown preference vector, and a known utility function. This structure introduces dependence between preferences for pairs of arms, and allows learning about the preference over one pair of arms from the preference over another pair of arms. We propose an algorithm for this setting called Comparing The Best (CTB), which we show has constant expected cumulative weak utility-based regret. We provide a Bayesian interpretation for CTB, an implementation appropriate for a small number of arms, and an alternate implementation for many arms that can be used when the input parameters satisfy a decomposability condition. We demonstrate through numerical experiments that CTB with appropriate input parameters outperforms all benchmarks considered. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1605/1605.08838v2.pdf"}
{"id": "1606.00140", "abstract": "  We present a multi-wavelength analysis of the host galaxy of short-duration gamma-ray burst (GRB) 150101B. Follow-up optical and X-ray observations suggested that the host galaxy, 2MASX J12320498-1056010, likely harbors a low-luminosity active galactic nuclei (AGN). Our modeling of the spectral energy distribution (SED) has confirmed the nature of the AGN, making it the first reported GRB host that contains an AGN. We have also found the host galaxy is a massive elliptical galaxy with stellar population of ∼ 5.7 Gyr, one of the oldest among the short-duration GRB hosts. Our analysis suggests that the host galaxy can be classified as an X-ray bright, optically normal galaxy (XBONG), and the central AGN is likely dominated by a radiatively inefficient accretion flow (RIAF). Our work explores interesting connection that may exist between GRB and AGN activities of the host galaxy, which can help understand the host environment of the GRB events and the roles of AGN feedback. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1606/1606.00140v1.pdf"}
{"id": "1607.06040", "abstract": "  Electricity transmission networks dissipate a non-negligible fraction of the power they transport due to the heat loss in the transmission lines. In this work we explore how the transport of energy can be more efficient by adding to the network multiple batteries that can coordinate their operations. Such batteries can both charge using the current excess in the network or discharge to meet the network current demand. Either way, the presence of batteries in the network can be leveraged to mitigate the intrinsic uncertainty in the power generation and demand and, hence, transport the energy more efficiently through the network. We consider a resistive DC network with stochastic external current injections or consumptions and show how the expected total heat loss depends on the network structure and on the batteries operations. Furthermore, in the case where the external currents are modeled by Ornstein-Uhlenbeck processes, we derive the dynamical optimal control for the batteries over a finite time interval. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1607/1607.06040v1.pdf"}
{"id": "1608.02684", "abstract": "  We have studied the atomic and magnetic structure of the dilute ferromagnetic semiconductor system (Ba,K)(Zn,Mn)_2As_2 through atomic and magnetic pair distribution function analysis of temperature-dependent x-ray and neutron total scattering data. We detected a change in curvature of the temperature-dependent unit cell volume of the average tetragonal crystallographic structure at a temperature coinciding with the onset of ferromagnetic order. We also observed the existence of a well-defined local orthorhombic structure on a short length scale of ≲ 5 Å, resulting in a rather asymmetrical local environment of the Mn and As ions. Finally, the magnetic PDF revealed ferromagnetic alignment of Mn spins along the crystallographic c-axis, with robust nearest-neighbor ferromagnetic correlations that exist even above the ferromagnetic ordering temperature. We discuss these results in the context of other experiments and theoretical studies on this system. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1608/1608.02684v1.pdf"}
{"id": "1609.04524", "abstract": "  Engineering a sensor system for detecting an extremely tiny signal such as the gravitational-wave force is a very important subject in quantum physics. A major obstacle to this goal is that, in a simple detection setup, the measurement noise is lower bounded by the so-called standard quantum limit (SQL), which is originated from the intrinsic mechanical back-action noise. Hence, the sensor system has to be carefully engineered so that it evades the back-action noise and eventually beats the SQL. In this paper, based on the well-developed geometric control theory for classical disturbance decoupling problem, we provide a general method for designing an auxiliary (coherent feedback or direct interaction) controller for the sensor system to achieve the above-mentioned goal. This general theory is applied to a typical opto-mechanical sensor system. Also, we demonstrate a controller design for a practical situation where several experimental imperfections are present. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.04524v1.pdf"}
{"id": "1609.04577", "abstract": "  The present work discusses motion of neutral and charged particles in Reissner - Nordstrom spacetime. The constant energy paths are derived in a variational principle framework using the Jacobi metric which is parameterized by conserved particle energy. Of particular interest is the case of particle charge and Reissner-Nordstrom black hole charge being of same sign since this leads to a clash of opposing forces - gravitational (attractive) and Coulomb (repulsive). Our paper aims to compliment the recent works of Pugliese, Quevedo and Ruffini [1,2]. The energy dependent Gaussian curvature (induced by Jacobi metric), plays an important role in classifying the trajectories. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.04577v4.pdf"}
{"id": "1609.07095", "abstract": "  Wigner's little groups are subgroups of the Lorentz group dictating the internal space-time symmetries of massive and massless particles. These little groups are like O(3) and E(2) for massive and massless particles respectively. While the geometry of the O(3) symmetry is familiar to us, the geometry of the flat plane cannot explain the E(2)-like symmetry for massless particles. However, the geometry of a circular cylinder can explain the symmetry with the helicity and gauge degrees of freedom. It is shown further that the symmetry of the massless particle can be obtained as a zero-mass limit of O(3)-like symmetry for massive particles. It is shown further that the polarization of massless neutrinos is a consequence of gauge invariance, while the symmetry of massive neutrinos is still like O(3). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1609/1609.07095v1.pdf"}
{"id": "1610.05893", "abstract": "  Aiming at testing the validity of our magnesium atomic model and investigating the effects of non-local thermodynamical equilibrium (NLTE) on the formation of the H-band neutral magnesium lines, we derive the differential Mg abundances from selected transitions for 13 stars either adopting or relaxing the assumption of local thermodynamical equilibrium (LTE). Our analysis is based on high-resolution and high signal-to-noise ratio H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and optical spectra from several instruments. The absolute differences between the Mg abundances derived from the two wavelength bands are always less than 0.1 dex in the NLTE analysis, while they are slightly larger for the LTE case. This suggests that our Mg atomic model is appropriate for investigating the NLTE formation of the H-band Mg lines. The NLTE corrections for the Mg I H-band lines are sensitive to the surface gravity, becoming larger for smaller log g values, and strong lines are more susceptible to departures from LTE. For cool giants, NLTE corrections tend to be negative, and for the strong line at 15765 Å they reach -0.14 dex in our sample, and up to -0.22 dex for other APOGEE stars. Our results suggest that it is important to include NLTE corrections in determining Mg abundances from the H-band Mg I transitions, especially when strong lines are used. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.05893v1.pdf"}
{"id": "1610.09563", "abstract": "  We obtain two-dimensional exact analytic solutions for the structure of the hot accretion flows without wind. We assume that the only non-zero component of the stress tensor is T_rφ. Furthermore we assume that the value of viscosity coefficient α varies with θ. We find radially self-similar solutions and compare them with the numerical and the analytical solutions already studied in the literature. The no-wind solution obtained in this paper may be applied to the nuclei of some cool-core clusters. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1610/1610.09563v1.pdf"}
{"id": "1611.07431", "abstract": "  The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) is an approved project to add tracking and timing information at approximately ±210 m from the interaction point around the CMS detector. It is designed to operate at high luminosity with up to 50 interactions per 25 ns bunch crossing to perform measurements of e.g. the quartic gauge couplings and search for rare exclusive processes. During 2016, CT-PPS took data in normal high-luminosity proton-proton LHC collisions. In the coming years, high radiation doses and large multiple-vertex interactions will represent difficult challenges that resemble those of the high-luminosity LHC program. A coordinated effort of detector upgrades with the goal of reaching the physics goals while mitigating the degradation effects is under way. Upgrades to the tracking and timing detectors are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.07431v1.pdf"}
{"id": "1611.09447", "abstract": "  The Blandford-Znajek process, the steady electromagnetic energy extraction from a rotating black hole, is widely believed to work for driving relativistic jets, although it is still under debate where the electric current is driven. We address this issue analytically by investigating the time-dependent state in the Boyer-Lindquist and Kerr-Schild coordinate systems. This analysis suggests that a non-ideal magnetohydrodynamic region is required in the time-dependent state, while not in the steady state. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1611/1611.09447v1.pdf"}
{"id": "1612.05185", "abstract": "  We study the possibility of radiative electroweak symmetry breaking where loop corrections to the mass parameter of the Higgs boson trigger the symmetry breaking in various extensions of the Standard Model (SM). Although the mechanism fails in the SM, it is shown to be quite successful in several extensions which share a common feature of having an additional scalar around the TeV scale. The positive Higgs mass parameter at a high energy scale is turned negative in the renormalization group flow to lower energy by the cross couplings between the scalars in the Higgs potential. The type-II seesaw model with a TeV scale weak scalar triplet, a two-loop radiative neutrino mass model with new scalars at the TeV scale, the inert doublet model, scalar singlet dark matter model, and a universal seesaw model with an additional U(1) broken at the TeV scale are studied and shown to exhibit successful radiative electroweak symmetry breaking. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.05185v1.pdf"}
{"id": "1612.06396", "abstract": "  Satellite-based quantum terminals are a feasible way to extend the reach of quantum communication protocols such as quantum key distribution (QKD) to the global scale. To that end, prior demonstrations have shown QKD transmissions from airborne platforms to receivers on ground, but none have shown QKD transmissions from ground to a moving aircraft, the latter scenario having simplicity and flexibility advantages for a hypothetical satellite. Here, we demonstrate QKD from a ground transmitter to a receiver prototype mounted on an airplane in flight. We have specifically designed our receiver prototype to consist of many components that are compatible with the environment and resource constraints of a satellite. Coupled with our relocatable ground station system, optical links with distances of 3-10 km were maintained and quantum signals transmitted while traversing angular rates similar to those observed of low-Earth-orbit satellites. For some passes of the aircraft over the ground station, links were established within 10 s of position data transmission, and with link times of a few minutes and received quantum bit error rates typically 3-5", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.06396v2.pdf"}
{"id": "1612.07631", "abstract": "  Silicon photomultipliers (SiPMs) are a good alternative to photomultiplier tubes (PMTs) because their gain and quantum efficiency are comparable to PMTs. However, the largest single-chip SiPM is still less than 1 cm^2. In order to use SiPMs with scintillators that have reasonable sensitivity, it is necessary to use multiple SiPMs. In this work, scintillation detectors are constructed and tested with a custom 2x2 SiPM array. The layout of the SiPMs and the geometry of the scintillator were determined by performing Geant4 simulations. Cubic NaI, CsI, and CLYC with 18 mm sides have been tested. The output of the scintillation detectors are stabilized over the temperature range between –20 and 50 ^∘C by matching the gain of the SiPMs in the array. The energy resolution for these detectors has been measured as a function of temperature. Furthermore, neutron detection for the CLYC detector was studied in the same temperature range. Using pulse-shape discrimination, neutrons can be cleanly identified without contribution from γ-photons. As a result, these detectors are suitable for deploying in spectroscopic personal radiation detectors (SPRD). ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1612/1612.07631v1.pdf"}
{"id": "1701.00024", "abstract": "  We present results of three-dimensional, multi-physics simulations of an AGN jet colliding with an intergalactic cloud. The purpose of these simulations is to assess the degree of \"positive feedback,\" i.e. jet-induced star formation, that results. We have specifically tailored our simulation parameters to facilitate comparison with recent observations of Minkowski's Object (M.O.), a stellar nursery located at the termination point of a radio jet coming from galaxy NGC 541. As shown in our simulations, such a collision triggers shocks which propagate around and through the cloud. These shocks condense the gas and under the right circumstances may trigger cooling instabilities, creating runaway increases in density, to the point that individual clumps can become Jeans unstable. Our simulations provide information about the expected star formation rate, total mass converted to H1, H_2, and stars, and the relative velocity of the stars and gas. Our results confirm the possibility of jet-induced star formation, and agree well with the observations of M.O. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.00024v2.pdf"}
{"id": "1701.02254", "abstract": "  Generalised dichotomic quantum measurements are fully characterised by two real parameters, dubbed as sharpness parameter and biasedness parameter. The trade-off between the degree of joint measurability, sharpness and biasedness of generalised measurements was known in the case of pairs of qubit observables. In the present work we generalise the notion of sharpness and biasedness measure of multi-outcome generalised measurements pertaining to multilevel systems. A trade-off between the amount of quantum mechanical (QM) violation of macrorealism (MR), sharpness and biasedness is established. Specifically we found that the minimum value of sharpness parameter, above which the QM violations of different necessary conditions of MR persist, decreases with increase in biasedness. We also analysed the effect of biasedness parameter on the magnitudes of QM violations of different necessary conditions of MR for multilevel spin systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.02254v3.pdf"}
{"id": "1701.05317", "abstract": "  Topological matter is a popular topic in both condensed matter and cold atom research. In the past decades, a variety of models have been identified with fascinating topological features. Some, but not all, of the models can be found in materials. As a fully controllable system, cold atoms trapped in optical lattices provide an ideal platform to simulate and realize these topological models. Here we present a proposal for synthesizing topological models in cold atoms based on a one-dimensional (1D) spin-dependent optical lattice potential. In our system, features such as staggered tunneling, staggered Zeeman field, nearest-neighbor interaction, beyond-near-neighbor tunneling, etc. can be readily realized. They underlie the emergence of various topological phases. Our proposal can be realized with current technology and hence has potential applications in quantum simulation of topological matter. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.05317v1.pdf"}
{"id": "1701.06539", "abstract": "  In a generalized tournament, players may have an arbitrary number of matches against each other and the outcome of the games is measured on a cardinal scale with a lower and upper bound. An axiomatic approach is applied to the problem of ranking the competitors. Self-consistency requires assigning the same rank for players with equivalent results, while a player showing an obviously better performance than another should be ranked strictly higher. According to order preservation, if two players have the same pairwise ranking in two tournaments where the same players have played the same number of matches, then their pairwise ranking is not allowed to change in the aggregated tournament. We reveal that these two properties cannot be satisfied simultaneously on this universal domain. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.06539v6.pdf"}
{"id": "1701.08888", "abstract": "  Item recommendation task predicts a personalized ranking over a set of items for each individual user. One paradigm is the rating-based methods that concentrate on explicit feedbacks and hence face the difficulties in collecting them. Meanwhile, the ranking-based methods are presented with rated items and then rank the rated above the unrated. This paradigm takes advantage of widely available implicit feedback. It, however, usually ignores a kind of important information: item reviews. Item reviews not only justify the preferences of users, but also help alleviate the cold-start problem that fails the collaborative filtering. In this paper, we propose two novel and simple models to integrate item reviews into Bayesian personalized ranking. In each model, we make use of text features extracted from item reviews using word embeddings. On top of text features we uncover the review dimensions that explain the variation in users' feedback and these review factors represent a prior preference of users. Experiments on six real-world data sets show the benefits of leveraging item reviews on ranking prediction. We also conduct analyses to understand the proposed models. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1701/1701.08888v2.pdf"}
{"id": "1702.01968", "abstract": "  Topology optimization offers great opportunities to design permanent magnetic systems that have specific external field characteristics. Additive manufacturing of polymer bonded magnets with an end-user 3D printer can be used to manufacture permanent magnets with structures that have been difficult or impossible to manufacture previously. This work combines these two powerful methods to design and manufacture permanent magnetic system with specific properties. The topology optimization framework is simple, fast, and accurate. It can be also used for reverse engineering of permanent magnets in order to find the topology from field measurements. Furthermore, a magnetic system that generate a linear external field above the magnet is presented. With a volume constraint the amount of magnetic material can be minimized without losing performance. Simulations and measurements of the printed system show a very good agreement. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.01968v1.pdf"}
{"id": "1702.04273", "abstract": "  We present here a generalization of the thermal discrete dipole approximation (TDDA) that allows us to describe the near-field radiative heat transfer between finite objects of arbitrary shape that exhibit magneto-optical (MO) activity. We also extend the TDDA approach to describe the thermal emission of a finite object with and without MO activity. Our method is also valid for optically anisotropic materials described by an arbitrary permittivity tensor and we provide simple closed formulas for the basic thermal quantities that considerably simplify the implementation of TDDA method. Moreover, we show that employing our TDDA approach one can rigorously demonstrate Kirchhoff's radiation law relating the emissivity and absorptivity of an arbitrary MO object. Our work paves the way for the theoretical study of the active control of emission and radiative heat transfer between MO systems of arbitrary size and shape. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.04273v2.pdf"}
{"id": "1702.04805", "abstract": "  Electron emission from liquid into gaseous xenon is a cornerstone of dark matter search detectors such as ZEPLIN, XENON, LUX and LZ. The probability of emission is a function of the applied electric field E, and electrons which fail to pass from the liquid into the gas have been previously hypothesized to become thermalized and trapped. This article shows, for the first time, quantitative agreement between an electron emission model and existing data. The model predicts that electrons in the liquid must surmount a typical potential barrier phi_b=0.34+-0.01 eV in order to escape into the gas. This value is a factor of about x2 smaller than has previously been calculated or inferred. Knowledge of phi_b allows calculation of the lifetime of thermalized, trapped electrons. The value is O(10) ms, which appears to be compatible with XENON10 observations of electron train backgrounds. As these backgrounds limit the sensitivity of dark sector dark matter searches, possible mitigations are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.04805v1.pdf"}
{"id": "1702.08455", "abstract": "  Inspired by Lifshitz theory for quantum critical phenomena in condensed matter, Horava proposed a theory for quantum gravity with an anisotropic scaling in ultraviolet. In Horava-Lifshitz gravity (HLG), we have studied the impacts of six types of equations of state on the evolution of various cosmological parameters such as Hubble parameters and scale factor. From the comparison of the general relativity gravity with the HLG with detailed and without with non-detailed balance conditions, remarkable differences are found. Also, a noticeable dependence of singular and non-singular Big Bang on the equations of state is observed. We conclude that HLG explains various epochs in the early universe and might be able to reproduce the entire cosmic history with and without singular Big Bang. ", "pdf_url": "gs://arxiv-dataset/arxiv/arxiv/pdf/1702/1702.08455v1.pdf"}
{"id": "astro-ph0001486", "abstract": "  In an effort to shed more light on the formation process of binary stars, we have started a program to study multiplicity among nearby low- and intermediate-mass protostars using the OVRO Millimeter Array. Here, we describe the project and present the first results on the protostellar core in the Bok globule CB230 (L1177). At 10 arcsec resolution, the molecular core is resolved into two components separated by 5000 AU. The morphology and kinematics of the double core suggest that it formed from a single cloud core due to rotational fragmentation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0001/0001486v2.pdf"}
{"id": "astro-ph0005161", "abstract": "  We propose a simple unifying structure for the inner regions of quasars and AGN. This empirically derived model links together the BALs, the narrow UV/X-ray ionized absorbers, the BELR, and the Compton scattering/fluorescing regions into a single structure. The model also suggests an origin for the large-scale bi-conical outflows. Some other potential implications of this structure are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0005/0005161v1.pdf"}
{"id": "astro-ph0005294", "abstract": "  We have constructed a family of simple models for spiral galaxy evolution to allow us to investigate observational trends in star formation history with galaxy parameters. The models are used to generate broad band colours from which ages and metallicities are derived in the same way as the data. We generate a grid of model galaxies and select only those which lie in regions of parameter space covered by the sample. The data are consistent with the proposition that the star formation history of a region within a galaxy depends primarily on the local surface density of the gas but that one or two additional ingredients are required to fully explain the observational data. The observed age gradients appear steeper than those produced by the density dependent star formation law, indicating that the star formation law or infall history must vary with galactocentric radius. Furthermore, the metallicity-magnitude and age-magnitude correlations are not reproduced by a local density dependence alone. These correlations require one or both of the following: (i) a combination of mass dependent infall and metal enriched outflow, or (ii) a mass dependent galaxy formation epoch. Distinguishing these possibilities on the basis of current data is extremely difficult. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0005/0005294v1.pdf"}
{"id": "astro-ph0008339", "abstract": "  The Heidelberg Dark Matter Search Experiment (HDMS) is a new ionization Germanium experiment in a special design. Two concentric Ge crystals are housed by one cryostat system, the outer detector acting as an effective shield against multiple scattered photons for the inner crystal, which is the actual dark matter target. We present first results after successfully running the prototype detector for a period of about 15 months in the Gran Sasso Underground Laboratory. We analyze the results in terms of limits on WIMP-nucleon cross sections and present the status of the full scale experiment, which will be installed in Gran Sasso in the course of this year. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0008/0008339v1.pdf"}
{"id": "astro-ph0008415", "abstract": "  In order to establish an objective framework for studying galaxy morphology, we have developed a quantitative two-parameter description of galactic structure that maps closely on to Hubble's original tuning fork. Any galaxy can be placed in this \"Hubble space\", where the x-coordinate measures position along the early-to-late sequence, while the y-coordinate measures in a quantitative way the degree to which the galaxy is barred. The parameters defining Hubble space are sufficiently robust to allow the formation of Hubble's tuning fork to be mapped out to high redshifts. In the present paper, we describe a preliminary investigation of the distribution of local galaxies in Hubble space, based on the CCD imaging atlas of Frei et al. (1996). We find that barred, weakly-barred, and unbarred galaxies are remarkably well-separated on this diagnostic diagram. The spiral sequence is clearly bimodal and indeed approximates a tuning fork: strongly-barred and unbarred spirals do not simply constitute the extrema of a smooth unimodal distribution of bar strength, but rather populate two parallel sequences. Strongly barred galaxies lie on a remarkably tight sequence, strongly suggesting the presence of an underlying unifying physical process. Rather surprisingly, weakly barred systems do not seem to correspond to objects bridging the parameter space between unbarred and strongly barred galaxies, but instead form an extension of the regular spiral sequence. This relation lends support to models in which the bulges of late-type spirals originate from secular processes driven by bars. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0008/0008415v1.pdf"}
{"id": "astro-ph0011021", "abstract": "  The phases of the Fourier modes appearing in a plane-wave expansion of cosmological density fields play a vital role in determining the morphology of gravitationally-developed clustering. We demonstrate this qualitatively and quantitatively using simulations. In particular, we use cross-correlation and rank-correlation techniques to quantify the agreement between a simulated distribution and phase-only reconstructions. The phase-only reconstructions exhibit a high degree of correlation with the original distributions, showing how meaningful spatial reconstruction of cosmological density fields depends more on phase accuracy than on amplitudes. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011021v2.pdf"}
{"id": "astro-ph0011180", "abstract": "  We investigate the relative sensitivities of several tests for deviations from Gaussianity in the primordial distribution of density perturbations. We consider models for non-Gaussianity that mimic that which comes from inflation as well as that which comes from topological defects. The tests we consider involve the cosmic microwave background (CMB), large-scale structure (LSS), high-redshift galaxies, and the abundances and properties of clusters. We find that the CMB is superior at finding non-Gaussianity in the primordial gravitational potential (as inflation would produce), while observations of high-redshift galaxies are much better suited to find non-Gaussianity that resembles that expected from topological defects. We derive a simple expression that relates the abundance of high-redshift objects in non-Gaussian models to the primordial skewness. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0011/0011180v2.pdf"}
{"id": "astro-ph0103303", "abstract": "  We address the question of the relations between the black hole's mass, the accretion rate, the bolometric luminosity, the optical luminosity and the size of the Broad Line Region (BLR) in Active Galactic Nuclei, using recent observational data obtained from monitoring campaigns. We show that a standard accretion disc cannot account for the observed optical luminosity, unless it radiates at super-Eddington rates. This implies the existence of another, dominant emission mechanism in the optical range, or a non standard disc (non stationary, ADAF and/or strong outflows). Narrow Line Seyfert 1 galaxies (NLS1s) are most extreme in this context: they have larger bolometric to Eddington luminosity ratios than Broad Line Seyfert 1 (BLS1s), and most likely a larger \"non disc\" component in the optical range. From realistic simulations of self-gravitating α-discs, we have systematically localized the gravitationally unstable disc and shown that, given uncertainties on both the model and observations, it coincides quite well with the size of the BLR. We therefore suggest that the gravitationally unstable disc is the source which releases BLR clouds in the medium. However the influence of the ionization parameter is also required to explain the correlation found between the size of the BLR and the luminosity. In this picture the size of the BLR in NLS1s (relative to the black hole size) is larger (and the emission line width smaller) than in BLS1s simply because their Eddington ratio is larger. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0103/0103303v1.pdf"}
{"id": "astro-ph0103479", "abstract": "  We present first results of a survey of the Leo I group at 10 Mpc for M_R < -10 dwarf galaxies. This is part of a larger program to measure the faint end of the galaxy luminosity function in nearby poor groups. Our method is optimized to find Local-Group-like dwarfs down to dwarf spheroidal surface brightnesses, but we also find very large LSB dwarfs in Leo I with no Local Group counterpart. A preliminary measurement of the luminosity function yields a slope consistent with that measured in the Local Group. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0103/0103479v1.pdf"}
{"id": "astro-ph0108426", "abstract": "  The ever-increasing quality and complexity of astronomical data underscores the need for new and powerful data analysis applications. This need has led to the development of Sherpa, a modeling and fitting program in the CIAO software package that enables the analysis of multi-dimensional, multi-wavelength data. In this paper, we present an overview of Sherpa's features, which include: support for a wide variety of input and output data formats, including the new Model Descriptor List (MDL) format; a model language which permits the construction of arbitrarily complex model expressions, including ones representing instrument characteristics; a wide variety of fit statistics and methods of optimization, model comparison, and parameter estimation; multi-dimensional visualization, provided by ChIPS; and new interactive analysis capabilities provided by embedding the S-Lang interpreted scripting language. We conclude by showing example Sherpa analysis sessions. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0108/0108426v1.pdf"}
{"id": "astro-ph0111282", "abstract": "  We report the results of experiments aimed at reducing the major problem with cooling flow models of rich cluster X-ray sources: the fact that most of the cooled gas or its products have not been found. Here we show that much of the X-ray emission usually attributed to cooling flows can, in fact, be modeled by a power-law component which is indicative of a source(s) other than thermal bremsstrahlung from the intracluster medium. We find that adequate simultaneous fits to ROSAT PSPCB and ASCA GIS/SIS spectra of the central regions of ten clusters are obtained for two-component models that include a thermal plasma component that is attributable to hot intracluster gas and a power-law component that is likely generated by compact sources and/or extended non-thermal emission. For five of the clusters that purportedly have massive cooling flows, the best-fit models have power-law components that contribute ∼ 30 ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0111/0111282v1.pdf"}
{"id": "astro-ph0209095", "abstract": "  In this contribution, first results of deep VLT photometry (V,I) in the central region of the Hydra I and Centaurus galaxy clusters are presented. In both galaxy clusters, many star clusters have been identified down to the turnover magnitude of the globular cluster luminosity function at V=26.0 mag. They are distributed not only around the several early-type galaxies, but also in the intra-cluster field, as far as 250 kpc from the cluster centers. Outside the bulges of the central galaxies in Hydra I and Centaurus, the intra-cluster globular cluster system is dominated by blue clusters whose spatial distribution is similar to that of the (newly discovered) dwarf galaxies. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0209/0209095v1.pdf"}
{"id": "astro-ph0307433", "abstract": "  AGILE (Astro-rivelatore Gamma ad Immagini LEggero) is a Small Scientific Mission of the Italian Space Agency (ASI) with a Science Program open to the national and international community. Its main goal is to develop and operate a scientific satellite devoted to Gamma-ray (30 MeV - 50 GeV) and hard X-ray (10 - 40 keV) Astrophysics during the years 2005 - 2007. ASI plans to handle AGILE data through the ASI Science Data Center in collaboration with the AGILE Team. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0307/0307433v1.pdf"}
{"id": "astro-ph0309430", "abstract": "  We present new interpretation of Ton S180 spectrum obtained by Chandra Spectrometer (Low Energy Transmission Grating). Several narrow absorption lines and a few emission disk lines have been successfully fitted to the data. We have not found any significant edges accompanying line emission. We propose the interpretation of narrow lines consistent with the paper recently written by Krolik (2002), where warm absorber is strongly inhomogeneous. Such situation is possible in so called multi-phase medium, where regions with different ionization states, densities and temperatures may coexist in thermal equilibrium under constant pressure. We illustrate this scenario with theoretical spectra of radiation transfered through a stratified cloud with constant pressure (instead of constant density) computed by code titan in plane parallel approximation. Detected spectral features are faint and their presence do not alter the broad band continuum. We model the broad band continuum of Ton S180 assuming an irradiated accretion disk with a dissipative warm skin. The set of parameters appropriate for the data cannot be determined uniquely but models with low values of the black hole mass have too hot and radially extended warm skin to explain the formation of soft X-ray disk lines seen in the data. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0309/0309430v1.pdf"}
{"id": "astro-ph0312226", "abstract": "  We investigate the evolution and number distribution of radio halos in galaxy clusters. Without re-acceleration or regeneration, the relativistic electrons responsible for the diffuse radio emission will lose their energy via inverse-Compton and synchrotron losses in a rather short time, and radio halos will have lifetimes ∼ 0.1 Gyr. Radio halos could last for ∼ Gyr if a significant level of re-acceleration is involved. The lifetimes of radio halos would be comparable with the cosmological time if the radio-emitting electrons are mainly the secondary electrons generated by pion decay following proton-proton collisions between cosmic-ray protons and the thermal intra-cluster medium within the galaxy clusters. Adopting both observational and theoretical constraints for the formation of radio halos, we calculate the formation rates and the comoving number density of radio halos in the hierarchical clustering scheme. Comparing with observations, we find that the lifetimes of radio halos are ∼ Gyr. Our results indicate that a significant level of re-acceleration is necessary for the observed radio halos and the secondary electrons may not be a dominant origin for radio halos. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0312/0312226v2.pdf"}
{"id": "astro-ph0312562", "abstract": "  We present a new method for estimating the corotation radius in tightly wound spiral galaxies, through analysis of the radial variation of the offset between arms traced by the potential (P-arms) and those traced by dust (D-arms). We have verified the predictions of semi-analytical theory through hydrodynamical simulations and have examined the uniqueness of the galactic parameters that can be deduced by this method. We find that if the range of angular offsets measured at different radii in a galaxy is greater than around pi/4, it is possible to locate the radius of corotation to within   25", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0312/0312562v1.pdf"}
{"id": "astro-ph0403518", "abstract": "  We propose a new imaging gamma-ray detector in the MeV region. By measuring the directions and energies of not only a scattered gamma ray but also a recoil electron, the direction of an incident gamma ray would be essentially reconstructed event by event. Furthermore, one of two measured (zenith and azimuth) angles of a recoil electron gives us an additional redundancy which enables us to reject the background events by kinematic constraints. In order to measure the track of a recoil electron, the micro Time Projection Chamber(μ-TPC) has been developed, which can measure the successive positions of the track of charged particles in a few hundred micron meter pitch. The μ-TPC consists of the new type of a gas proportional chamber: micro PIxel gas Chamber (μ-PIC) which is one of wireless gas chambers and expected to be robust and stable. Using this μ-TPC and the Anger camera for the detection of a scattered gamma ray, we have obtained the first gamma-ray image by the full reconstruction of the direction of gamma rays event by event. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0403/0403518v1.pdf"}
{"id": "astro-ph0405073", "abstract": "  A toy model for magnetic extraction of energy from black hole (BH) accretion disk is discussed by considering the restriction of the screw instability to the magnetic field configuration. Three mechanisms of extracting energy magnetically are involved. (1) The Blandford-Znajek (BZ) process is related to the open magnetic field lines connecting the BH with the astrophysical load; (2) the magnetic coupling (MC) process is related to the closed magnetic field lines connecting the BH with its surrounding disk; and (3) a new scenario (henceforth the DL process) for extracting rotational energy from the disk is related to the open field lines connecting the disk with the astrophysical load. The expressions for the electromagnetic powers and torques are derived by using the equivalent circuits corresponding to the above energy mechanisms. It turns out that the DL power is comparable with the BZ and MC powers as the BH spin approaches unity. The radiation from a quasi-steady thin disk is discussed in detail by applying the conservation laws of mass, energy and angular momentum to the regions corresponding to the MC and DL processes. In addition, the poloidal currents and the current densities in BH magnetosphere are calculated by using the equivalent circuits. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0405/0405073v2.pdf"}
{"id": "astro-ph0405199", "abstract": "  We report the discovery of several optical burst-like events from the low-mass X-ray binary MS1603.6+2600 (UW CrB). The events last for a few tens of seconds, exhibit a very fast rise and slow decay, and involve optical brightening of a factor of 2-3. The flares appear distinct from the lower level flickering and instead strongly resemble reprocessed type-I X-ray bursts as seen in a number of other neutron star low-mass X-ray binaries. In conjunction with the previously reported candidate X-ray burst, these confirm that the compact object in UW CrB is a neutron star. We examine the optical burst brightness and recurrence times and discuss how the nature of the system can be constrained. We conclude that the source is most likely an accretion disk corona source at an intermediate distance, rather than a nearby quiescent system or very distant dipper. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0405/0405199v1.pdf"}
{"id": "astro-ph0407206", "abstract": "  We examine the composition of matter as it flows away from gamma ray burst accretion disks, in order to determine what sort of nucleosynthesis may occur. Since there is a large flux of neutrinos leaving the surface of the disk, the electron fraction of the outflowing material will change due to charged current neutrino interactions. We calculate the electron fraction in the wind using detailed neutrino fluxes from every point on the disk and study a range of trajectories and outflow conditions for several different accretion disk models. We find that low electron fractions, conducive to making r-process elements, only appear in outflows from disks with high accretion rates that have a significant region both of trapped neutrinos and antineutrinos. Disks with lower accretion rates that have only a significant region of trapped neutrinos can have outflows with very high electron fractions, whereas the lowest accretion rate disks with little trapping have outflow electrons fractions of closer to one half. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0407/0407206v1.pdf"}
{"id": "astro-ph0411139", "abstract": "  New results of 300 hours of operation of the Tunka array are presented.   An improved parametrization of the Cherenkov light lateral distribution function (LDF), based on CORSIKA Monte Carlo simulations and the experiment QUEST, has been used for the reconstruction of EAS parameters. The corrected energy spectrum in the knee region is obtained. The mean depth of the EAS maximum has been derived both from the analysis of LDF steepness and the FWHM of Cerenkov light pulse. The mean mass composition around the knee is estimated. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0411/0411139v1.pdf"}
{"id": "astro-ph0503597", "abstract": "  Using a combination of Keck spectroscopy and near-infrared imaging, we investigate the K-band and stellar mass Tully-Fisher relation for 101 disk galaxies at 0.2 < z < 1.2, with the goal of placing the first observational constraints on the assembly history of halo and stellar mass. Our main result is a lack of evolution in either the K-band or stellar mass Tully-Fisher relation from z = 0 - 1.2. Furthermore, although our sample is not statistically complete, we consider it suitable for an initial investigation of how the fraction of total mass that has condensed into stars is distributed with both redshift and total halo mass. We calculate stellar masses from optical and near-infrared photometry and total masses from maximum rotational velocities and disk scale lengths, utilizing a range of model relationships derived analytically and from simulations. We find that the stellar/total mass distribution and stellar-mass Tully-Fisher relation for z > 0.7 disks is similar to that at lower redshift, suggesting that baryonic mass is accreted by disks along with dark matter at z < 1, and that disk galaxy formation at z < 1 is hierarchical in nature. We briefly discuss the evolutionary trends expected in conventional structure formation models and the implications of extending such a study to much larger samples. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0503/0503597v1.pdf"}
{"id": "astro-ph0505500", "abstract": "  With Teragauss magnetic fields, surface gravity sufficiently strong to significantly modify light paths, central densities higher than that of a standard nucleus, and rotation periods of only hundredths of a second, young neutron stars are sites of some of the most extreme physical conditions known in the Universe. They generate magnetic winds with particles that are accelerated to energies in excess of a TeV. These winds form synchrotron-emitting bubbles as the particle stream is eventually decelerated to match the general expansion caused by the explosion that formed the neutron stars. The structure of these pulsar wind nebulae allow us to infer properties of the winds and the pulsating neutron stars themselves. The surfaces of the the stars radiate energy from the rapidly cooling interiors where the physical structure is basically unknown because of our imprecise knowledge of the strong interaction at ultrahigh densities. Here I present a summary of recent measurements that allow us to infer the birth properties of neutron stars and to probe the nature of their winds, the physics of their atmospheres, and the structure of their interiors. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0505/0505500v1.pdf"}
{"id": "astro-ph0506618", "abstract": "  Fundamental astronomical questions on the composition of the universe, the abundance of Earth-like planets, and the cause of the brightest explosions in the universe are being attacked by robotic telescopes costing billions of dollars and returning vast pipelines of data. The success of these programs depends on the accuracy of automated real time processing of the astronomical images. In this paper the needs of modern astronomical pipelines are discussed in the light of fuzzy-logic based decision-making. Several specific fuzzy-logic algorithms have been develop for the first time for astronomical purposes, and tested with excellent results on data from the existing Night Sky Live sky survey. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0506/0506618v1.pdf"}
{"id": "astro-ph0506644", "abstract": "  We present Very Large Array observations at 3.5 cm of the nearby young star TW Hya that show the emission is constant in time over weeks, months and years, and spatially resolved with peak brightness temperature  10 K at  0.25 (15 AU) resolution. These features are naturally explained if the emission mechanism at this wavelength is thermal emission from dust particles in the disk surrounding the star. To account quantitatively for the observations, we construct a self-consistent accretion disk model that incorporates a population of centimeter size particles that matches the long wavelength spectrum and spatial distribution. A substantial mass fraction of orbiting particles in the TW Hya disk must have agglomerated to centimeter size. These data provide the first clear indication that dust emission from protoplanetary disks may be observed at centimeter wavelengths, and that changes in the spectral slope of the dust emission may be detected, providing constraints on dust evolution and the planet formation process. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0506/0506644v1.pdf"}
{"id": "astro-ph0507580", "abstract": "  VITRUV is a second generation spectro-imager for the PRIMA enabled Very Large Telescope Interferometer. By combining simultaneously up to 8 telescopes VITRUV makes the VLTI up to 6 times more efficient. This operational gain allows two novel scientific methodologies: 1) massive surveys of sizes; 2) routine interferometric imaging. The science cases presented concentrate on the qualitatively new routine interferometric imaging methodology. The science cases are not exhaustive but complementary to the PRIMA reference mission. The focus is on: a) the close environment of young stars probing for the initial conditions of planet formation and disk evolution; b) the surfaces of stars tackling dynamos, activity, pulsation, mass-loss and evolution; c) revealing the origin of the extraordinary morphologies of Planetary Nebulae and related stars; d) studying the accretion-ejection structures of stellar black-holes (microquasars) in our galaxy; e) unveiling the different interacting components (torus, jets, BLRs) of Active Galactic Nuclei; and f) probing the environment of nearby supermassive black-holes and relativistic effects in the Galactic Center black-hole. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0507/0507580v1.pdf"}
{"id": "astro-ph0510301", "abstract": "  Using a sample of nearly 20,000 massive early-type galaxies selected from the Sloan Digital Sky Survey, we study the color-magnitude relation for the most luminous (L > 2.2 L^*) field galaxies in the redshift range 0.1<z<0.4 in several colors. The intrinsic dispersion in galaxy colors is quite small in all colors studied, but the 40 milli-mag scatter in the bluest colors is a factor of two larger than the 20 milli-mag measured in the reddest bands. While each of three simple models constructed for the star formation history in these systems can satisfy the constraints placed by our measurements, none of them produce color distributions matching those observed. Subdividing by environment, we find the dispersion for galaxies in clusters to be about 11", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0510/0510301v1.pdf"}
{"id": "astro-ph0606013", "abstract": "  Motivated by recent observations of plateaus and minima in the radial abundance distributions of heavy elements in the Milky Way and some other spiral galaxies, we propose a dynamical mechanism for the formation of such features around corotation. Our numerical simulations show that the non-axisymmetric gravitational field of spiral density waves generates cyclone and anticylone gas flows in the vicinity of corotation. The anticyclones flatten the pre-existing negative abundance gradients by exporting many more atoms of heavy elements outside corotation than importing inside it. This process is very efficient and forms plateaus of several kiloparsec in size around corotation after two revolution periods of a galaxy. The strength of anticyclones and, consequently, the sizes of plateaus depend on the pitch angle of spiral arms and are expected to increase along the Hubble sequence. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0606/0606013v1.pdf"}
{"id": "astro-ph0609338", "abstract": "  Lensing tomography with multi-color imaging surveys can probe dark energy and the cosmological power spectrum. However accurate photometric redshifts for tomography out to high redshift require imaging in five or more bands, which is expensive to carry out over thousands of square degrees. Since lensing makes coarse, statistical use of redshift information, we explore the prospects for tomography using limited color information from two or three band imaging. With an appropriate calibration sample, we find that it is feasible to create up to four redshift bins using imaging data in just the g, r and i bands. We construct such redshift sub-samples from mock catalogs by clustering galaxies in color space and discarding regions with poorly-defined redshift distributions. The loss of galaxy number density decreases the accuracy of lensing measurements, but even losing half or more of the galaxies is not a severe loss for large area surveys. We estimate the errors on lensing power spectra and dark energy parameters with color tomography and discuss trade-offs in survey area and filter choice. We discuss the systematic errors that may change our conclusions, especially the information needed to tackle intrinsic alignments. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0609/0609338v3.pdf"}
{"id": "astro-ph0701515", "abstract": "  Using the results of recent optical surveys we conclude that the non-detection of quasars down to faint magnitudes implies a significant flattening of the high redshift (z 6) optical active galactic nuclei (AGN) luminosity function for M_1450>-24.7. We find that all the data are consistent with a faint-end slope for the optical AGN luminosity function of β=-2.2 and β=-2.8, at the 90", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0701/0701515v2.pdf"}
{"id": "astro-ph0702277", "abstract": "  Polarization is the next frontier of CMB analysis, but its signal is dominated over much of the sky by foregrounds which must be carefully removed. To determine the efficacy of this cleaning it is necessary to have sensitive tests for residual foreground contamination in polarization sky maps. The dominant Galactic foregrounds introduce a large-scale anisotropy on to the sky, so it makes sense to use a statistic sensitive to overall directionality for this purpose. Here we adapt the rapidly computable D statistic of Bunn and Scott to polarization data, and demonstrate its utility as a foreground monitor by applying it to the low resolution WMAP 3-yr sky maps. With a thorough simulation of the maps' noise properties, we find no evidence for contamination in the foreground cleaned sky maps. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0702/0702277v2.pdf"}
{"id": "astro-ph0703596", "abstract": "  We show that radiative feedback due to reionization has a pronounced effect on the extent of mechanical feedback due to galactic outflows. The photoionization of the Intergalactic Medium (IGM) suppresses low-mass galaxy formation by photoheating the gas and limiting atomic line cooling. The number of low-mass galaxies is central for the enrichment of the IGM as these objects have the capacity to enrich a significant fraction (by volume) of the Universe. We use a modified version of our galactic outflow model, combined with a simple criterion for suppression, to investigate the potential impact upon the IGM. We find that this suppression strongly reduces the enrichment of the IGM and is sensitive to the reionization history. We also investigate the contribution of halos of different masses with varying degrees of suppression. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/0703/0703596v2.pdf"}
{"id": "astro-ph9608058", "abstract": "  We propose a new formation mechanism (direct-supernova) for low-mass X-ray binaries (LMXBs) that does not involve any prior phase of mass transfer. Survival through the supernova (SN) explosion and shrinkage of the orbit is achieved by a kick velocity of appropriate magnitude and direction imparted to the neutron star at its birth. We present analytical population synthesis calculations of LMXBs forming via both the direct-SN and the helium-star SN mechanisms, and compare the results. We find that the direct-SN channel contributes a non-negligible fraction of the total LMXB population, depending strongly on the r.m.s. magnitude of the kick velocity. More importantly, the direct-SN mechanism provides a natural way for the formation of low-mass binary pulsars in nearly circular orbits with orbital periods in excess of about 100 days, which cannot have been formed via the helium-star SN mechanism. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9608/9608058v1.pdf"}
{"id": "astro-ph9608159", "abstract": "  We present cross sections and reaction rates for merging to occur during encounters of equal-mass spherical galaxies. As an application, we determine the rate of galaxy merging in clusters of galaxies. We present results for two types of Plummer models (a full and a truncated one), two King models and the Hernquist model. Cross sections are determined on the basis of a large number (∼ 500) of simulations of galaxy encounters, using the 10-Gigaflops GRAPE 3A special-purpose computer. We characterize the overall merger rate of galaxies in a galaxy cluster by a single number, derived from our cross sections by an integration over galaxy encounter velocities in the limit of a constant density in velocity space. For small clusters, where the cluster velocity dispersion may not significantly exceed the internal velocity dispersion of the individual galaxies, this constant-density approximation may not be valid. For those cases, we present separate results, based on integrations of our cross sections over Maxwellian velocity distributions. Finally, tidal effects from the cluster potential as well as from neighboring galaxies may prevent a barely bound galaxy pair from spiraling in after their first encounter. We give a quantitative estimate of the resulting reduction in the actual merger rate, due to these tidal interactions. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9608/9608159v2.pdf"}
{"id": "astro-ph9610059", "abstract": "  In this paper we discuss the chemical evolution of elliptical galaxies and its consequences on the evolution of the intracluster medium (ICM). We use chemical evolution models taking into account dark matter halos and compare the results with previous models where dark matter was not considered. In particular, we examine the evolution of the abundances of some relevant heavy elements such as oxygen, magnesium and iron and conclude that models including dark matter halos and an initial mass function (IMF) containing more massive stars than the Salpeter (1955) IMF, better reproduce the observed abundances of Mg and Fe both in the stellar populations and in the ICM (ASCA results). We also discuss the origin of gas in galaxy clusters and conclude that most of it should have a primordial origin. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9610/9610059v1.pdf"}
{"id": "astro-ph9704262", "abstract": "  Recent observations of quasars, Mrk 335 and the HST quasar composite spectrum, have indicated that many of them have remarkably soft ionizing continua (fnu   nu^-2.0, 13.6 eV – 100 eV). We point out that the number of E > 54.4 eV photons is insufficient to create the observed strengths of the He II emission lines. While the numbers of photons which energize C IV 1549 and O VI 1034 are sufficient, even the most efficiently emitting clouds for these two lines must each cover at least 20", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9704/9704262v1.pdf"}
{"id": "astro-ph9801232", "abstract": "  We identify the X-Ray reflected component in the Ginga spectra of Nova Muscae 1991, a Black Hole transient system used as the prototype for the recent model of Esin, McClintock     Narayan (1997) based on advection dominated disk solutions. We see that the reflected spectrum is generally significantly relativistically smeared, and use this, together with the amplitude of reflection, to track the innermost extent of the accretion disk. The optically thick disk switches from being highly ionized to nearly neutral during the transition from high to low state, and the inner radius of the disk moves outwards during the low state decline. Qualitatively, this overall trend is compatible with Esin et al.'s model, but quantitatively, the retreat of the inner disk during the high to low state transition is much slower than predicted. The hard (low state) spectra are not produced solely by an optically thin accretion flow: optically thick material within 20-100 Rg is generally present. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9801/9801232v1.pdf"}
{"id": "astro-ph9804146", "abstract": "  OH(1720 MHz) masers unaccompanied by 1665/7 MHz line masers have recently been proposed as indicators of the interaction of supernova remnants (SNRs) and molecular clouds. We present a model for the masing region in which water produced in a C-type shock wave driven into the molecular cloud is dissociated as a result of the X-ray flux from the SNR. We note that the magnetic field strengths inferred from Zeeman splitting of the 1720 MHz line measure the internal pressure of the supernova remnant.   In addition, we discuss the interaction of Sgr A East, a SNR candidate, with the 50 km/s cloud at the Galactic Centre and present near-infrared observations of H_2 emission towards the regions where OH(1720 MHz) maser emission is concentrated. The magnetic field strength obtained from earlier Zeeman measurements is consistent with rough pressure equilibrium between the postshock gas and the X-ray gas filling Sgr A East detected by ASCA. Further, the intensity of the v=1-0 S(1) line of H_2 is consistent with the shock strength expected to be driven into the molecular gas by this pressure. The relative intensities of the H_2 lines in Sgr A East imply mainly collisional excitation. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9804/9804146v1.pdf"}
{"id": "astro-ph9812013", "abstract": "  Recent work on the mass distribution in spiral galaxies, using mainly HI observations, is reviewed. The principal problem is still to determine to what extent the dark matter is important in the inner parts of a galaxy, or in other words, how dominant is the self-gravitation of the disc. Studies of the shapes of rotation curves show that in detail there is sufficient individuality in spiral galaxies to prohibit the construction of “Universal Rotation Curves”. A detailed account is given of the method of Athanassoula et al. (1987), where swing amplifier criteria are applied to set a range in the mass-to-light ratio of the disc. To restrict this range further, other methods might be useful. For a number of bright spirals the rotation curve drops just outside the optical image, but this feature by itself cannot constrain unambiguously the mass models. The use of velocity dispersions seems a promising way, though the observational problems are hard. Within the uncertainties, discs can be close to “maximum”, even though a range of values cannot be excluded. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9812/9812013v1.pdf"}
{"id": "astro-ph9902221", "abstract": "  We present RXTE observations of two recently identified massive X-ray binaries. RX J0440.9+4431/BSD 24-491 and RX J1037.5-564/LS 1698 are confirmed as accreting Be/X-ray systems following the discovery of X-ray pulsations, with barycentric pulse periods of 202.5±0.5 s and 860±2 s respectively. The X-ray spectral analysis shows that the energy spectra of the pulsars can be represented by a power-law, modified at low energy by an absorption component and at high energy by a cut-off. Very weak Fe lines may be present. Both sources appear to display a low cut-off energy when compared to typical X-ray pulsars, low X-ray variability (factor of < 10), and no dependence of the X-ray spectrum with energy. Given the similarity of these X-ray properties with those of the other persistent BeXRB pulsars, 4U0352+309/X Per and RX J0146.9+6121/LS I +61 235, we suggest that RX J0440.9+4431/BSD 24-491 and RX J1037.5-564/LS 1698 are also members of this subclass. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9902/9902221v1.pdf"}
{"id": "astro-ph9903224", "abstract": "  We have observed YZ Cnc at two day intervals from 6 to 24 April 1998, covering two full outburst cycles. The 0.1-2.4 keV flux is lower during optical outburst than in quiescence, and lowest at the end of the outburst. The decline of the X-ray flux in the quiescent interval appears to be in contrast to prediction of simple models for accretion-disk instabilities. Variability on h̃our time scales is present, but appears not related to the orbital phase. YZ Cnc was less luminous in X-rays during our 1998 observations than in earlier ROSAT observations. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9903/9903224v1.pdf"}
{"id": "astro-ph9904082", "abstract": "  Atmospheric Cerenkov telescopes are used to detect electromagnetic showers from primary gamma rays of energy  300 GeV -  10 TeV and to discriminate these from cascades due to hadrons using the Cerenkov images. The geomagnetic field affects the development of showers and is shown to diffuse and distort the images. When the component of the field normal to the shower axis is sufficiently large (> 0.4 G) the performance of gamma ray telescopes may be affected, although corrections should be possible. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9904/9904082v1.pdf"}
{"id": "astro-ph9905208", "abstract": "  We present 83 new galaxy radial velocities in the field of 18 APM clusters with redshifts between 0.06 and 0.13. The clusters have Abell identifications and the galaxies were selected within 0.75 h^-1Mpc in projection from their centers. We derive new cluster velocity dispersions for 13 clusters using our data and published radial velocities.   We analyze correlations between cluster velocity dispersions and cluster richness counts as defined in Abell and APM catalogs. The correlations show a statistically significant trend although with a large scatter suggesting that richness is a poor estimator of cluster mass irrespectively of cluster selection criteria and richness definition. We find systematically lower velocity dispersions in the sample of Abell clusters that do not fulfill APM cluster selection criteria suggesting artificially higher Abell richness counts due to contamination by projection effects in this subsample. ", "pdf_url": "gs://arxiv-dataset/arxiv/astro-ph/pdf/9905/9905208v1.pdf"}
{"id": "cond-mat0008390", "abstract": "  We propose using short-period superlattices as substrates to control the vibrational relaxation dynamics of adsorbate overlayers. The mass modulation of superlattices creates both band gaps and large spectral enhancements in the phonon density of states. These modifications can dramatically alter the coupling between vibrational modes of the adsorbate overlayer and the substrate lattice, thereby significantly affecting the lifetime of adsorbate modes. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0008/0008390v1.pdf"}
{"id": "cond-mat0009082", "abstract": "  Small-world networks (SWN), obtained by randomly adding to a regular structure additional links (AL), are of current interest. In this article we explore (based on physical models) a new variant of SWN, in which the probability of realizing an AL depends on the chemical distance between the connected sites. We assume a power-law probability distribution and study random walkers on the network, focussing especially on their probability of being at the origin. We connect the results to Lévy Flights, which follow from a mean field variant of our model. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0009/0009082v1.pdf"}
{"id": "cond-mat0204086", "abstract": "  The dynamics of a Bose-Einstein condensate in a double-well potential are analysed in terms of transitions between energy eigenstates. By solving the time-dependent and time-independent Gross-Pitaevskii equation in one dimension, we identify tunnelling resonances associated with level crossings, and determine the critical velocity that characterises the resonance. We test the validity of a non-linear two-state model, and show that for the experimentally interesting case, where the critical velocity is large, the influence of higher-lying states is important. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0204/0204086v1.pdf"}
{"id": "cond-mat0305436", "abstract": "  The reweighted random series techniques provide finite-dimensional approximations to the quantum density matrix of a physical system that have fast asymptotic convergence. We study two special reweighted techniques that are based upon the Levy-Ciesielski and Wiener-Fourier series, respectively. In agreement with the theoretical predictions, we demonstrate by numerical examples that the asymptotic convergence of the two reweighted methods is cubic for smooth enough potentials. For each reweighted technique, we propose some minimalist quadrature techniques for the computation of the path averages. These quadrature techniques are designed to preserve the asymptotic convergence of the original methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0305/0305436v1.pdf"}
{"id": "cond-mat0306319", "abstract": "  The dynamical instabilities and ensuing dynamics of singly- and doubly-quantized vortex states of Bose-Einstein condensates with attractive interactions are investigated using full 3D numerical simulations of the Gross-Pitaevskii equation. With increasing the strength of attractive interactions, a series of dynamical instabilities such as quadrupole, dipole, octupole, and monopole instabilities emerge. The most prominent instability depends on the strength of interactions, the geometry of the trapping potential, and deviations from the axisymmetry due to external perturbations. Singly-quantized vortices split into two clusters and subsequently undergo split-merge cycles in a pancake-shaped trap, whereas the split fragments immediately collapse in a spherical trap. Doubly-quantized vortices are always unstable to disintegration of the vortex core. If we suddenly change the strength of interaction to within a certain range, the vortex splits into three clusters, and one of the clusters collapses after a few split-merge cycles. The vortex split can be observed using a current experimental setup of the MIT group. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0306/0306319v2.pdf"}
{"id": "cond-mat0308287", "abstract": "  The remagnetization dynamics of monolayer dot array superlattice XY 2-D spin model with dipole-dipole interactions is simulated. Within the proposed model of array, the square dots are described by the spatially modulated exchange-couplings. The dipole-dipole interactions are approximated by the hierarchical sums and spin dynamics is considered in regime of the Landau-Lifshitz equation. The simulation of reversal for 40 000 spins exhibits formation of nonuniform intra-dot configurations with nonlinear wave/anti-wave pairs developed at intra-dot and inter-dot scales. Several geometric and parametric dependences are calculated and compared with oversimplified four-spin model of reversal. The role of initial conditions and the occurrence of coherent rotation mode is also investigated. The emphasis is on the classification of intra-dot or inter-dot (interfacial) magnetic configurations done by adaptive neural network with varying number of neurons. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0308/0308287v1.pdf"}
{"id": "cond-mat0309568", "abstract": "  We study a generic reaction-diffusion model for single-species population dynamics that includes reproduction, death, and competition. The population is assumed to be confined in a refuge beyond which conditions are so harsh that they lead to certain extinction. Standard continuum mean field models in one dimension yield a critical refuge length L_c such that a population in a refuge larger than this is assured survival. Herein we extend the model to take into account the discreteness and finiteness of the population, which leads us to a stochastic description. We present a particular critical criterion for likely extinction, namely, that the standard deviation of the population be equal to the mean. According to this criterion, we find that while survival can no longer be guaranteed for any refuge size, for sufficiently weak competition one can make the refuge large enough (certainly larger than L_c) to cause extinction to be unlikely. However, beyond a certain value of the competition rate parameter it is no longer possible to escape a likelihood of extinction even in an infinite refuge. These unavoidable fluctuations therefore have a severe impact on refuge design issues. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0309/0309568v1.pdf"}
{"id": "cond-mat0404103", "abstract": "  We derive explicit formulas for time decay, for the European call and put options at expiry, and use them to calculate analytical approximations to the price of the American put and early exercise boundary near expiry. We show that for many families of non-Gaussian processes used in empirical studies of financial markets, the early exercise boundary for the American put without dividends is separated from the strike price by a non-vanishing margin on the interval [0,T). As the riskless rate vanishes and the drift decreases accordingly so that the stock remains a martingale, the optimal exercise price goes to zero uniformly over the interval [0, T). The implications for parameters' fitting are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0404/0404103v1.pdf"}
{"id": "cond-mat0406648", "abstract": "  A short review is presented of a recently developed computational approach which allows the study of the resistance noise over the full range of bias values, from the linear regime up to electrical breakdown. Resistance noise is described in terms of two competing processes in a random resistor network. The two processes are thermally activated and driven by an electrical bias. In the linear regime, a scaling relation has been found between the relative variance of resistance fluctuations and the average resistance. The value of the critical exponent is significantly higher than that associated with 1/f noise. In the nonlinear regime, occurring when the bias overcomes the threshold value, the relative variance of resistance fluctuations scales with the bias. Two regions can be identified in this regime: a moderate bias region and a pre-breakdown one. In the first region, the scaling exponent has been found independent of the values of the model parameters and of the bias conditions. A strong nonlinearity emerges in the pre-breakdown region which is also characterized by non-Gaussian noise. The results compare well with measurements of electrical breakdown in composites and with electromigration experiments in metallic lines. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0406/0406648v1.pdf"}
{"id": "cond-mat0412269", "abstract": "  We investigate density fluctuations in a coherent ensemble of interacting fermionic atoms. Adapting the concept of full counting statistics, well-known from quantum optics and mesoscopic electron transport, we study second-order as well as higher-order correlators of density fluctuations. Using the mean-field BCS state to describe the whole interval between the BCS limit and the BEC limit, we obtain an exact expression for the cumulant-generating function of the density fluctuations of an atomic cloud. In the two-dimensional case, we obtain a closed analytical expression. Poissonian fluctuations of a molecular condensate on the BEC side are strongly suppressed on the BCS side. The size of the fluctuations in the BCS limit is a direct measure of the pairing potential. We also discuss the BEC-BCS crossover of the third cumulant and the temperature dependence of the second cumulant. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0412/0412269v2.pdf"}
{"id": "cond-mat0502653", "abstract": "  The unusual band structure of carbon nanotubes (CNs) results in their remarkable magnetic properties. The application of magnetic field parallel to the tube axis can change the conducting properties of the CN from metallic to semiconducting and vice versa. Apart from that B induces (via the Bohm-Aharonov effect) orbital magnetic moments μ_orb in the nanotube. These moments are studied both in pure and hole- or electron-doped CNs, isolated or in a circuit. Remarkably, μ_orb in pure CNs depends uniquely on their original conducting properties, length, and temperature, but it does not depend on the nanotube radius or the particular chirality. In doped nanotubes the magnetic moments can be strongly altered and depend on the radius and chirality.Temperature can even change their character from diamagnetic at low T to paramagnetic at high T. A full electron-hole symmetry in doped tubes is also revealed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0502/0502653v1.pdf"}
{"id": "cond-mat0505232", "abstract": "  We study the statistical properties of the sampled scale-free networks, deeply related to the proper identification of various real-world networks. We exploit three methods of sampling and investigate the topological properties such as degree and betweenness centrality distribution, average path length, assortativity, and clustering coefficient of sampled networks compared with those of original networks. It is found that the quantities related to those properties in sampled networks appear to be estimated quite differently for each sampling method. We explain why such a biased estimation of quantities would emerge from the sampling procedure and give appropriate criteria for each sampling method to prevent the quantities from being overestimated or underestimated. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0505/0505232v4.pdf"}
{"id": "cond-mat0507534", "abstract": "  Quite a few low-dimensional magnets are quantum-disordered “spin liquids” with a characteristic gap in the magnetic excitation spectrum. Among these are antiferromagnetic chains of integer quantum spins. Their generic feature are long-lived massive (gapped) excitations (magnons) that are subject to Zeeman splitting in external magnetic fields. The gap in one of the magnon branches decreases with field, driving a soft-mode quantum phase transition. The system then enters a qualitatively new high-field phase. The actual properties at high fields, particularly the spin dynamics, critically depend on the system under consideration. Recent neutron scattering studies of organometallic polymer crystals NDMAP (Haldane spin chains with anisotropy) and NTENP (dimerized S=1 chains) revealed rich and unique physics. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0507/0507534v1.pdf"}
{"id": "cond-mat0509456", "abstract": "  This paper reviews the status of molecular dynamics as a method in describing solid-solid phase transitions, and its relationship to continuum approaches. Simulation work done in NiTi and Zr using first principles and semi-empirical potentials is presented. This shows failures of extending equilibrium thermodynamics to the nanoscale, and the crucial importance of system-specific details to the dynamics of martensite formation. The inconsistency between experimental and theoretical crystal structures in NiTi is described, together with its possible resolution in terms of nanoscale effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0509/0509456v1.pdf"}
{"id": "cond-mat0511152", "abstract": "  The giant vortex states of a multiply connected superconductor, with radius comparable to the penetration depth and the coherence length, are theoretically investigated based on the nonlinear Ginzburg-Landau theory, in which the induced magnetic field by the super-currents is accurately taken into account. The solutions of Ginzburg-Landau equations are found to be actually independent of the angular momentum L in a gauge invariant point of view, provided that the hole is in the center. Different cases with the paramagnetic current, the diamagnetic current, and the coexistence of the above two, have been studied numerically. The interpretation of the L-independent solutions of Ginzburg-Landau equations is given based on the same principle of Aharonov-Bohm effect, and could be observed by Little-Parks like oscillations near the phase boundary. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0511/0511152v1.pdf"}
{"id": "cond-mat0608205", "abstract": "  A method of moment inequalities is used to derive the principle of minimum growth rate in multiplicatively interacting stochastic processes(MISPs). When a value of a power-law exponent at the tail of probability distribution function exists in a range 0 < s ≤ 1, a first-order moment diverges and an equality for a growth rate of systems breaks down. From the estimate of inequalities, we newly find a conditional inequality which determines the growth rate, and then the exponent in 0 < s ≤ 1. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0608/0608205v1.pdf"}
{"id": "cond-mat0608361", "abstract": "  We study the spectrum of vibrational modes in metal nanoparticles with a dielectric core. Vibrational modes are excited by the rapid heating of the particle lattice that takes place after laser excitation, and can be monitored by means of pump-probe spectroscopy as coherent oscillations of transient optical spectra. In nanoshells, the presence of two metal surfaces results in a substantially different energy spectrum of acoustic vibrations than for solid particles. We calculated the energy spectrum as well as the damping of nanoshell vibrational modes. The oscillator strength of fundamental breathing mode is larger than that in solid nanoparticles. At the same time, in very thin nanoshells, the fundamental mode is overdamped due to instantaneous energy transfer to the surrounding medium. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0608/0608361v1.pdf"}
{"id": "cond-mat0609100", "abstract": "  Molecular dynamics computer simulations are used to investigate thedynamics of a binary mixture of charged (Yukawa) particles with a size-ratio of 1:5. We find that the system undergoes a phase transition where the large particles crystallize while the small particles remain in a fluid-like (delocalized) phase. Upon decreasing temperature below the transition, the small particles become increasingly localized on intermediate time scales. This is reflected in the incoherent intermediate scattering functions by the appearance of a plateau with a growing height. At long times, the small particles show a diffusive hopping motion. We find that these transport properties are related to structural correlations and the single-particle potential energy distribution of the small particles. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0609/0609100v1.pdf"}
{"id": "cond-mat0610820", "abstract": "  A procedure to characterize chaotic dynamical systems with concepts of complex networks is pursued, in which a dynamical system is mapped onto a network. The nodes represent the regions of space visited by the system, while edges represent the transitions between these regions. Parameters used to quantify the properties of complex networks, including those related to higher order neighborhoods, are used in the analysis. The methodology is tested for the logistic map, focusing the onset of chaos and chaotic regimes. It is found that the corresponding networks show distinct features, which are associated to the particular type of dynamics that have generated them. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0610/0610820v2.pdf"}
{"id": "cond-mat0701175", "abstract": "  The magneto-conductivity of a single graphene layer where the electrons are described by the Dirac Hamiltonian weakly modulated by a periodic potential is calculated. It is shown that Weiss oscillations periodic in the inverse magnetic field appear, that are more pronounced and less damped with the increment of temperature as compared with the same oscillations in a typical two-dimensional electron system with a standard parabolic energy spectrum. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0701/0701175v1.pdf"}
{"id": "cond-mat0703579", "abstract": "  Self-consistent solutions of microscopic Eilenberger theory are presented for a two-dimensional model of a superconducting channel with a geometric constriction. Magnetic fields, external ones as well as those caused by the supercurrents, are included and the relevant equations are solved numerically without further assumptions. Results concerning the influence of temperature, geometric parameters, of κ=λ_L/ξ_0 and of external magnetic fields on the Andreev bound states in the weak link and on the current-phase relation are presented. We find that the Andreev bound states within the junction obtain peculiar substructure when a finite supercurrent flows. As long as the London penetration depth is comparable to or bigger than the extension of the constriction, the Josephson effect is independent of κ. Furthermore, the weak link is very insensitive to external magnetic fields. Features restricted to a self-consistent calculation are discussed. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/0703/0703579v2.pdf"}
{"id": "cond-mat9605135", "abstract": "  We introduce coarse-grained hydrodynamic equations of motion for diffusion-annihilation system with a power-law long-range interaction. By taking into account fluctuations of the conserved order parameter - charge density - we derive an analytically solvable approximation for the nonconserved order parameter - total particle density. Asymptotic solutions are obtained for the case of random Gaussian initial conditions and for system dimensionality d ≥ 2. Large-t, intermediate-t and small-t asymptotics were calculated and compared with existing scaling theories, exact results and simulation data. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9605/9605135v3.pdf"}
{"id": "cond-mat9706171", "abstract": "  We use the functional integral technique of Edwards and Lenard to solve the statistical mechanics of a one dimensional Coulomb gas with boundary interactions leading to surface charging. The theory examined is a one dimensional model for a soap film. Finite size effects and the phenomenon of charge regulation are studied. We also discuss the pressure of disjunction for such a film. Even in the absence of boundary potentials we find that the presence of a surface affects the physics in finite systems. In general we find that in the presence of a boundary potential the long distance disjoining pressure is positive but may become negative at closer interplane separations. This is in accordance with the attractive forces seen at close separations in colloidal and soap film experiments and with three dimensional calculations beyond mean field. Finally our exact results are compared with the predictions of the corresponding Poisson-Boltzmann theory which is often used in the context of colloidal and thin liquid film systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9706/9706171v2.pdf"}
{"id": "cond-mat9804261", "abstract": "  We compute bulk properties of Heisenberg spin-1/2 ladders using Rayleigh-Schrödinger perturbation theory in the rung and plaquette bases. We formulate a method to extract high-order perturbative coefficients in the bulk limit from solutions for relatively small finite clusters. For example, a perturbative calculation for an isotropic 2× 12 ladder yields an eleventh-order estimate of the ground-state energy per site that is within 0.02", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9804/9804261v1.pdf"}
{"id": "cond-mat9805403", "abstract": "  In thin films of smectic-C liquid crystals, localized regions containing additional smectic layers form circular inclusions that carry a topological charge. Such inclusions nucleate a companion topological defect. These inclusion-defect pairs are modeled as topological dipoles within the context of a one-coupling constant approximation to the 2D Frank free energy. Deviations of the dipole direction from a preferred orientation cause the dipoles to acquire a logarithmic charge. Thermal fluctuations of the dipole direction are calculated and found to be large, scaling as the logarithm of the system size. In addition to dipole-dipole interactions arising from the topological charges, we also find that the thermal fluctuations of the dipole directions are coupled through a preference for global charge neutrality of the logarithmic charges. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9805/9805403v1.pdf"}
{"id": "cond-mat9811404", "abstract": "  We consider the effect of intermolecular interactions on the optimal size-distribution of N hard spheres that occupy a fixed total volume. When we minimize the free-energy of this system, within the Percus-Yevick approximation, we find that no solution exists beyond a quite low threshold (η 0.260). Monte Carlo simulations reveal that beyond this density, the size-distribution becomes bi-modal. Such distributions cannot be reproduced within the Percus-Yevick approximation. We present a theoretical argument that supports the occurrence of a non-monotonic size-distribution and emphasizing the importance of finite size effects. ", "pdf_url": "gs://arxiv-dataset/arxiv/cond-mat/pdf/9811/9811404v1.pdf"}
{"id": "cs0506073", "abstract": "  An iterative algorithm is presented for soft-input-soft-output (SISO) decoding of Reed-Solomon (RS) codes. The proposed iterative algorithm uses the sum product algorithm (SPA) in conjunction with a binary parity check matrix of the RS code. The novelty is in reducing a submatrix of the binary parity check matrix that corresponds to less reliable bits to a sparse nature before the SPA is applied at each iteration. The proposed algorithm can be geometrically interpreted as a two-stage gradient descent with an adaptive potential function. This adaptive procedure is crucial to the convergence behavior of the gradient descent algorithm and, therefore, significantly improves the performance. Simulation results show that the proposed decoding algorithm and its variations provide significant gain over hard decision decoding (HDD) and compare favorably with other popular soft decision decoding methods. ", "pdf_url": "gs://arxiv-dataset/arxiv/cs/pdf/0506/0506073v2.pdf"}
{"id": "gr-qc0604034", "abstract": "  Cauchy-Characteristic Matching (CCM), the combination of a central 3+1 Cauchy code with an exterior characteristic code connected across a time-like interface, is a promising technique for the generation and extraction of gravitational waves. While it provides a tool for the exact specification of boundary conditions for the Cauchy evolution, it also allows to follow gravitational radiation all the way to infinity, where it is unambiguously defined.   We present a new fourth order accurate finite difference CCM scheme for a first order reduction of the wave equation around a Schwarzschild black hole in axisymmetry. The matching at the interface between the Cauchy and the characteristic regions is done by transfering appropriate characteristic/null variables. Numerical experiments indicate that the algorithm is fourth order convergent. As an application we reproduce the expected late-time tail decay for the scalar field. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0604/0604034v2.pdf"}
{"id": "gr-qc0606001", "abstract": "  Recently, it was shown that differential rotation is an unavoidable feature of nonlinear r-modes. We investigate the influence of this differential rotation on the detectability of gravitational waves emitted by a newly born, hot, rapidly-rotating neutron star, as it spins down due to the r-mode instability. We conclude that gravitational radiation may be detected by the advanced laser interferometer detector LIGO if the amount of differential rotation at the time the r-mode instability becomes active is not very high. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/0606/0606001v1.pdf"}
{"id": "gr-qc9603025", "abstract": "  We adopt the point of view that (Riemannian) classical and (loop-based) quantum descriptions of geometry are macro- and micro-descriptions in the usual statistical mechanical sense. This gives rise to the notion of geometrical entropy, which is defined as the logarithm of the number of different quantum states which correspond to one and the same classical geometry configuration (macro-state). We apply this idea to gravitational degrees of freedom induced on an arbitrarily chosen in space 2-dimensional surface. Considering an `ensemble' of particularly simple quantum states, we show that the geometrical entropy S(A) corresponding to a macro-state specified by a total area A of the surface is proportional to the area S(A)=α A, with α being approximately equal to 1/16π l_p^2. The result holds both for case of open and closed surfaces. We discuss briefly physical motivations for our choice of the ensemble of quantum states. ", "pdf_url": "gs://arxiv-dataset/arxiv/gr-qc/pdf/9603/9603025v3.pdf"}
{"id": "hep-lat0003018", "abstract": "  The concept of simulating a variant of QCD with sea quarks which interact with the gluon configuration only via global gluonic quantities like ∫ FF̃ dx and ∫ FF dx is tested for the case of the massive 2-flavour Schwinger model. It is found to amount to an importance sampling method which generates -at essentially the costs of a quenched run- an ensemble in between a full and a quenched one, thus providing a competitive alternative to the quenched approximation. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/0003/0003018v2.pdf"}
{"id": "hep-lat9608123", "abstract": "  We investigate the performance of the hybrid Monte Carlo algorithm in updating non-trivial global topological structures. We find that the hybrid Monte Carlo algorithm has serious problems decorrelating the global topological charge. This represents a warning which must be seriously considered when simulating full QCD, regardless of the number and type of fermions, with this or any similar algorithm. Simulated tempering is examined as a means of accelerating the decorrelation. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-lat/pdf/9608/9608123v1.pdf"}
{"id": "hep-ph0002124", "abstract": "  Considering neutrinos as time-like leptons one may estimate the three-body decay probability of muon neutrinos in long base-line accelerator experiments. In the extreme assumption of time-space symmetry the absolute value of the transcendent mass of a muon neutrino is equal to the rest mass of its bradyon partner which is, however, strongly suppressed in measurements using the weak interaction. This decay, neglecting small oscillations or other effects, leads to a strong dependence of the effect on the base-line distance. As a result, few hundred kilometre long baseline experiments might hardly see muon-like events. Total rates of electron-like events from three-body decay are calculated for K2K, MINOS and ICARUS. Shorter base-line experiments able to see clearly the effect of muon neutrino decay are very promissing component of long base-line projects. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0002/0002124v2.pdf"}
{"id": "hep-ph0210381", "abstract": "  The mass spectra and electromagnetic decay rates of charmonium, bottomonium and B_c mesons are comprehensively investigated in the relativistic quark model. The presence of only heavy quarks allows the expansion in powers of their velocities. All relativistic corrections of order v^2/c^2, including retardation effects and one-loop radiative corrections, are systematically taken into account in the computations of the mass spectra. The obtained wave functions are used for the calculation of radiative magnetic dipole (M1) and electric dipole (E1) transitions. It is found that relativistic effects play a substantial role. Their account and the proper choice of the Lorentz structure of the quark-antiquark interaction in a meson is crucial for bringing theoretical predictions in accord with experimental data. A detailed comparison of the calculated decay rates and branching fractions with available experimental data for radiative decays of charmonium and bottomonium is presented. The possibilities to observe the currently missing spin-singlet S and P states as well as D states in bottomonium are discussed. The results for B_c masses and decays are compared with other quark model predictions. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0210/0210381v2.pdf"}
{"id": "hep-ph0504276", "abstract": "  We investigate predictions of a minimal realistic non-supersymmetric SU(5) grand unified theory. To accomplish unification and generate neutrino mass we introduce one extra Higgs representation–a 15 of SU(5)–to the particle content of the minimal Georgi-Glashow scenario. Generic prediction of this setup is a set of rather light scalar leptoquarks. In the case of the most natural implementation of the type II see-saw mechanism their mass is in the phenomenologically interesting region (O(10^2–10^3) GeV). As such, our scenario has a potential to be tested at the next generation of collider experiments, particularly at the Large Hadron Collider (LHC) at CERN. The presence of the 15 generates additional contributions to proton decay which, for light scalar leptoquarks, can be more important than the usual gauge d=6 ones. We exhaustively study both and show that the scenario is not excluded by current experimental bounds on nucleon lifetimes. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-ph/pdf/0504/0504276v1.pdf"}
{"id": "hep-th0101156", "abstract": "  In the framework of causal perturbation theory we consider a massive scalar field coupled to gravity. In the field theoretic approach to quantum gravity (QG) we start with a massless second rank tensor field. This tensor field is then quantized in a covariant way in Minkowski space. This article deals with the adiabatic limit for graviton radiative corrections in a scattering process of two massive scalar particles. We compute the differential cross-section for bremsstrahlung processes in which one of the outgoing particles emites a graviton of low energy, a so called soft graviton. Since the emited graviton will not be detected we have to integrate over all soft gravitons. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0101/0101156v3.pdf"}
{"id": "hep-th0206115", "abstract": "  We discuss the hierarchy of Yukawa couplings in a supersymmetric three family Standard-like string Model. The model is constructed by compactifying Type IIA string theory on a Z_2 x Z_2 orientifold in which the Standard Model matter fields arise from intersecting D6-branes. When lifted to M theory, the model amounts to compactification of M-theory on a G_2 manifold. While the actual fermion masses depend on the vacuum expectation values of the multiple Higgs fields in the model, we calculate the leading worldsheet instanton contributions to the Yukawa couplings and examine the implications of the Yukawa hierarchy. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0206/0206115v3.pdf"}
{"id": "hep-th0304264", "abstract": "  This paper discusses Skyrmions on the 3-sphere coupled to fermions. The resulting Dirac equation commutes with a generalized angular momentum G. For G = 0 the Dirac equation can be solved explicitly for a constant Skyrme configuration and also for a SO(4) symmetric hedgehog configuration. We discuss how the spectrum changes due to the presence of a non-trivial winding number, and also consider more general Skyrme configurations numerically. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0304/0304264v1.pdf"}
{"id": "hep-th0308116", "abstract": "  We study the evolution of bubble spacetimes in vacuum and electrovac scenarios by numerical means. We find strong evidence against the formation of naked singularities in (i) scenarios with negative masses displaying initially collapsing conditions and (ii) scenarios with negative masses displaying initially expanding conditions, previously reported to give rise to such singularities. Additionally, we show that the presence of strong gauge fields implies that an initially collapsing bubble bounces back and expands. By fine-tuning the strength of the gauge field we find that the solution approaches a static bubble solution. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0308/0308116v1.pdf"}
{"id": "hep-th0510052", "abstract": "  We review different computation methods for the renormalised energy momentum tensor of a quantised scalar field in an Einstein Static Universe. For the extensively studied conformally coupled case we check their equivalence; for different couplings we discuss violation of different energy conditions. In particular, there is a family of masses and couplings which violate the weak and strong energy conditions but do not lead to spacelike propagation. Amongst these cases is that of a minimally coupled massless scalar field with no potential. We also point out a particular coupling for which a massless scalar field has vanishing renormalised energy momentum tensor. We discuss the backreaction problem and in particular the possibility that this Casimir energy could both source a short inflationary epoch and avoid the big bang singularity through a bounce. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0510/0510052v1.pdf"}
{"id": "hep-th0511059", "abstract": "  In this work, we study the three-dimensional non-Abelian noncommutative supersymmetric Chern-Simons model with the U(N) gauge group. Using a superfield formulation, we prove that, for the pure gauge theory, the Green functions are one-loop finite in any gauge, if the gauge superpotential belongs to the fundamental representation of u(N); this result also holds when matter in the fundamental representation is included. However, the cancellation of both ultraviolet and ultraviolet/infrared infrared divergences only happens in a special gauge if the coupling of the matter is in the adjoint representation. We also look into the finite one-loop quantum corrections to the effective action: in the pure gauge sector the Maxwell together with its corresponding gauge fixing action are generated; in the matter sector, the Chern-Simons term is generated, inducing a shift in the classical Chern-Simons coefficient. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0511/0511059v3.pdf"}
{"id": "hep-th0608219", "abstract": "  We study the general chaotic features of dynamics of the phantom field modelled in terms of a single scalar field conformally coupled to gravity. We demonstrate that the dynamics of the FRW model with dark energy in the form of phantom field can be regarded as a scattering process of two types: multiple chaotic and classical non-chaotic. It depends whether the spontaneously symmetry breaking takes place. In the first class of models with the spontaneously symmetry breaking the dynamics is similar to the Yang-Mills theory. We find the evidence of a fractal structure in the phase space of initial conditions. We observe similarities to the phenomenon of a multiple scattering process around the origin. In turn the class of models without the spontaneously symmetry breaking can be described as the classical non-chaotic scattering process and the methods of symbolic dynamic are also used in this case. We show that the phantom cosmology can be treated as a simple model with scattering of trajectories which character depends crucially on a sign of a square of mass. We demonstrate that there is a possibility of chaotic behavior in the flat Universe with a conformally coupled phantom field in the system considered on non-zero energy level. We obtain that the acceleration is a generic feature in the considered model without the spontaneously symmetry breaking. We observe that the effective EOS coefficient oscillates and then approach to w=-1. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/0608/0608219v3.pdf"}
{"id": "hep-th9509147", "abstract": "  A discussion of an extended class of higher-derivative classical theories of gravity is presented. A procedure is given for exhibiting the new propagating degrees of freedom, at the full non-linear level, by transforming the higher-derivative action to a canonical second-order form. For general fourth-order theories, described by actions which are general functions of the scalar curvature, the Ricci tensor and the full Riemann tensor, it is shown that the higher-derivative theories may have multiple stable vacua. The vacua are shown to be, in general, non-trivial, corresponding to deSitter or anti-deSitter solutions of the original theory. It is also shown that around any vacuum the elementary excitations remain the massless graviton, a massive scalar field and a massive ghost-like spin-two field. The analysis is extended to actions which are arbitrary functions of terms of the form ∇^2kR, and it is shown that such theories also have a non-trivial vacuum structure. ", "pdf_url": "gs://arxiv-dataset/arxiv/hep-th/pdf/9509/9509147v3.pdf"}
{"id": "math-ph0610087", "abstract": "  The main objective of this article is to study the dynamics of the stratified rotating Boussinesq equations, which are a basic model in geophysical fluid dynamics. First, for the case where the Prandtl number is greater than one, a complete stability and bifurcation analysis near the first critical Rayleigh number is carried out. Second, for the case where the Prandtl number is smaller than one, the onset of the Hopf bifurcation near the first critical Rayleigh number is established, leading to the existence of nontrivial periodic solutions. The analysis is based on a newly developed bifurcation and stability theory for nonlinear dynamical systems (both finite and infinite dimensional) by two of the authors [16]. ", "pdf_url": "gs://arxiv-dataset/arxiv/math-ph/pdf/0610/0610087v2.pdf"}
{"id": "math0609765", "abstract": "  The reasons of the crisis in the contemporary (Riemannian) geometry are discussed. The conventional method of the generalized geometries construction, based on a use of the topology, leads to a overdetermination of the Riemannian geometry. In other words, at the Riemannian geometry construction one uses the needless information (topology), which disagrees with other original axioms. The crisis manifests in the fact, that the mathematical community cannot see and does not want to see the overdetermination of the Riemannian geometry. The most geometers-topologists deny the alternative method of the generalized geometry construction, which does not uses the topology, because it does not contain theorems. Most geometers see the geometry presentation as a set of definitions and theorems. They cannot imagine the geometry presentation without customary theorems. As a result the most clever topologists, which have acknowledged the negligible role of the topology in the geometry construction and inconsistency of the conventional method of the generalized geometry construction, appear in the difficult situation (conflict with the mathematical community). ", "pdf_url": "gs://arxiv-dataset/arxiv/math/pdf/0609/0609765v1.pdf"}
{"id": "nucl-ex0103002", "abstract": "  A fossil bone from the archaeological site Malu Rosu Giurgiu, in Romania has been analyzed by accelerator mass spectrometry to estimate its age by determining its ^14C content. The radiocarbon age of the bone is in agreement with the date obtained by the method for age determination, based on fluorine content. This is the first radiocarbon dating for the final Neolithic period, for this archaeological settlement in the Romanian region. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0103/0103002v1.pdf"}
{"id": "nucl-ex0512029", "abstract": "  The two innermost layers of the ALICE inner tracking system are instrumented with silicon pixel detectors. Single chip assembly prototypes of the ALICE pixels have been tested in high energy particle beams at the CERN SPS. Detection efficiency and spatial precision have been studied as a function of the threshold and the track incidence angle. The experimental method, data analysis and main results are presented. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-ex/pdf/0512/0512029v1.pdf"}
{"id": "nucl-th0408073", "abstract": "  We are concerned with few-particle correlations in a fermionic system at finite temperature and density. Within the many-body Green functions formalism the description of correlations is provided by the Dyson equation approach that leads to effective few-body equations. They contain the dominant medium effects, which are self energy corrections and the Pauli blocking. Hence the effective two-body interactions between quasiparticles are momentum/energy-dependent and therefore they can be usesed in the medium modified, momentum space, integral AGS equations for three- and four-body systems. To investigate correlations and clusters beyond four-body, we employ, instead, the configuration space two-variable integro-differential equations (IDEA) for A-body bound systems which are based on Hyperspherical Harmonics and the Faddeev decomposition of the wave function in two-body amplitudes. This requires the transformation of the energy dependent two-body interactions to equivalent local, energy independent, ones. To achieve this we use inverse scattering techniques the resulting interactions being, on– and (to all practical purposes) off–shell equivalent to the energy dependent potentials. In this way we obtain binding energy results for the 2–, 3–, 4–, and 16–particle in a medium at a finite temperature and various densities. Several aspects of the problem are discussed and the behavior of the potential surfaces obtained in the extreme adiabatic approximation, below and above the Mott transition, is investigated. ", "pdf_url": "gs://arxiv-dataset/arxiv/nucl-th/pdf/0408/0408073v1.pdf"}
{"id": "physics0410014", "abstract": "  The excited state electronic structure of π conjugated phenylene-acetylene oligomers is calculated using time-dependent density functional theory (TD-DFT) approaches. The theoretical fluorescence spectra are analyzed in terms of Frank-Condon active nuclear normal modes and shown to compare well with experiment. Theoretical and experimental results for the optical absorption and emission spectra of these molecules indicate that the conjugation length can be significantly reduced by conformational rotations about the triple-bonded carbon links. This has serious implications on the electronic functionalities of polyphenylene-acetylene based molecular wires and their possible use as charge/energy conduits in nano-assemblies. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0410/0410014v1.pdf"}
{"id": "physics0502061", "abstract": "  We present experimental measurements of the mean energy in the vicinity of the first and second quantum resonances of the atom optics kicked rotor for a number of different experimental parameters. Our data is rescaled and compared with the one parameter epsilon–classical scaling function developed to describe the quantum resonance peaks. Additionally, experimental data is presented for the “classical” resonance which occurs in the limit as the kicking period goes to zero. This resonance is found to be analogous to the quantum resonances, and a similar one-parameter classical scaling function is derived, and found to match our experimental results. The width of the quantum and classical resonance peaks is compared, and their Sub-Fourier nature examined. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0502/0502061v1.pdf"}
{"id": "physics0510085", "abstract": "  The Time Projection Chamber (TPC) for the International Linear Collider will need to measure about 200 track points with a resolution close to 100 μm. A Micro Pattern Gas Detector (MPGD) readout TPC could achieve the desired resolution with existing techniques using sub-millimeter width pads at the expense of a large increase in the detector cost and complexity. We have recently applied a new MPGD readout concept of charge dispersion to a prototype GEM-TPC and demonstrated the feasibility of achieving good resolution with pads similar in width to the ones used for the proportional wire TPC. The charge dispersion studies were repeated with a Micromegas TPC amplification stage. We present here our first results on the Micromegas-TPC resolution with charge dispersion. The TPC resolution with the Micromegas readout is compared to our earlier GEM results and to the resolution expected from electron statistics and transverse diffusion in a gaseous TPC. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0510/0510085v1.pdf"}
{"id": "physics0609187", "abstract": "  In this paper, we report on new high-precision absolute distance measurements performed with frequency scanned interferometry using a pair of single-mode optical fibers. Absolute distances were determined by counting the interference fringes produced while scanning the frequencies of the two chopped lasers. High-finesse Fabry-Perot interferometers were used to determine frequency changes during scanning. Dual lasers with oppositely scanning directions, combined with a multi-distance-measurement technique previously reported, were used to cancel drift errors and to suppress vibration effects and interference fringe uncertainties. Under realistic conditions, a precision about 0.2 microns was achieved for a distance of 0.41 meters. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0609/0609187v1.pdf"}
{"id": "physics0612174", "abstract": "  Computational tools for normal mode analysis, which are widely used in physics and materials science problems, are designed here in a single package called NMscatt (Normal Modes     scattering) that allows arbitrarily large systems to be handled. The package allows inelastic neutron and X-ray scattering observables to be calculated, allowing comparison with experimental data produced at large scale facilities. Various simplification schemes are presented for analysing displacement vectors, which are otherwise too complicated to understand in very large systems. ", "pdf_url": "gs://arxiv-dataset/arxiv/physics/pdf/0612/0612174v1.pdf"}
{"id": "quant-ph0002002", "abstract": "  A lower bound on the amount of noise that must be added to a GHZ-like entangled state to make it separable (also called the random robustness) is found using the transposition condition. The bound is applicable to arbitrary numbers of subsystems, and dimensions of Hilbert space, and is shown to be exact for qubits. The new bound is compared to previous such bounds on this quantity, and found to be stronger in all cases. It implies that increasing the number of subsystems, rather than increasing their Hilbert space dimension is a more effective way of increasing entanglement. An explicit decomposition into an ensemble of separable states, when the state is not entangled,is given for the case of qubits. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0002/0002002v1.pdf"}
{"id": "quant-ph0009066", "abstract": "  An analogous model system for quantum information processing is discussed, based on classical wave optics. The model system is applied to three examples that involve three qubits: (i) three-particle Greenberger-Horne-Zeilinger entanglement, (ii) quantum teleportation, and (iii) a simple quantum error correction network. It is found that the model system can successfully simulate most features of entanglement, but fails to simulate quantum nonlocality. Investigations of how far the classical simulation can be pushed show that quantum nonlocality is the essential ingredient of a quantum computer, even more so than entanglement. The well known problem of exponential resources required for a classical simulation of a quantum computer, is also linked to the nonlocal nature of entanglement, rather than to the nonfactorizability of the state vector. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0009/0009066v2.pdf"}
{"id": "quant-ph0108065", "abstract": "  We have proposed the construction of optical quantum computer (OQC) on regular domain structure (RDS) crystal. By using RDS crystal, we can perform all the logical operations on one RDS crystal. Moreover, RDS crystals are parctically independent to the heating effects i.e., can perform logic operations constantly without cooling the RDS crystal. Also, we have proposed the quantum parallelsim i.e., parallel coherent laser beams are injected at the input of the RDS crystals. By using the RDS crystal we can perform the reduce the requirements of the linear and nonlinear optical components. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0108/0108065v1.pdf"}
{"id": "quant-ph0209094", "abstract": "  Due to the no-cloning theorem, the unknown quantum state can only be cloned approximately or exactly with some probability. There are two types of cloners: universal and state-dependent cloner. The optimal universal cloner has been found and could be viewed as a special state-dependent quantum cloner which has no information about the states. In this paper, we investigate the state-dependent cloning when the state-set contains more than two states. We get some bounds of the global fidelity for these processes. This method is not dependent on the number of the states contained in the state-set. It is also independent of the numbers of copying. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0209/0209094v1.pdf"}
{"id": "quant-ph0305186", "abstract": "  We study the multiorder coherent Raman scattering of a quantum probe field in a far-off-resonance medium with a prepared coherence. Under the conditions of negligible dispersion and limited bandwidth, we derive a Bessel-function solution for the sideband field operators. We analytically and numerically calculate various quantum statistical characteristics of the sideband fields. We show that the multiorder coherent Raman process can replicate the statistical properties of a single-mode quantum probe field into a broad comb of generated Raman sidebands. We also study the mixing and modulation of photon statistical properties in the case of two-mode input. We show that the prepared Raman coherence and the medium length can be used as control parameters to switch a sideband field from one type of photon statistics to another type, or from a non-squeezed state to a squeezed state and vice versa. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0305/0305186v1.pdf"}
{"id": "quant-ph0505072", "abstract": "  We show how defects in a spin chain described by the XXZ model may be used to generate entangled states, such as Bell and W states, and how to maintain them with high fidelity. In the presence of several excitations, we also discuss how the anisotropy of the system may be combined with defects to effectively assist in the creation of the desired states. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0505/0505072v1.pdf"}
{"id": "quant-ph0703049", "abstract": "  The geometric phase induced in an auxiliary qubit by a many-body system is calculated and discussed. Two kinds of coupling between the auxiliary qubit and the many-body system are considered, which lead to dephasing and dissipation in the qubit, respectively. As an example, we consider the XY spin-chain dephasingly couple to a qubit, the geometric phase induced in the qubit is presented and discussed. The results show that the geometric phase might be used to signal the critical points of the many-body system, and it tends to zero with the parameters of the many-body system going away from the critical points. ", "pdf_url": "gs://arxiv-dataset/arxiv/quant-ph/pdf/0703/0703049v1.pdf"}