Datasets:

liamdugan

/

super-clean-raid-human

like 0

900b4d48-57d7-4d1e-b9c8-3408f6862441

900b4d48-57d7-4d1e-b9c8-3408f6862441

900b4d48-57d7-4d1e-b9c8-3408f6862441

human

none

abstracts

Polymer Quantum Mechanics and its Continuum Limit

A rather non-standard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schroedinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schroedinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free partic

155af688-1516-45dc-acf1-0c2da584f37c

155af688-1516-45dc-acf1-0c2da584f37c

155af688-1516-45dc-acf1-0c2da584f37c

human

none

abstracts

Spectroscopic Observations of the Intermediate Polar EX Hydrae in Quiescence

Results from spectroscopic observations of the Intermediate Polar (IP) EX Hya in quiescence during 1991 and 2001 are presented. Spin-modulated radial velocities consistent with an outer disc origin were detected for the first time in an IP. The spin pulsation was modulated with velocities near ~500-600 km/s. These velocities are consistent with those of material circulating at the outer edge of the accretion disc, suggesting corotation of the accretion curtain with material near the Roche lobe radius. Furthermore, spin Doppler tomograms have revealed evidence of the accretion curtain emission extending from velocities of ~500 km/s to ~1000 km/s. These findings have confirmed the theoretical model predictions of King & Wynn (1999), Belle et al. (2002) and Norton et al. (2004) for EX Hya, which predict large accretion curtains that extend to a distance close to the Roche lobe radius in this system. Evidence for overflow stream of material falling onto the magnetosphere was observed, co

5a2e5e1f-a4b5-418d-8ece-5671b48563e4

5a2e5e1f-a4b5-418d-8ece-5671b48563e4

5a2e5e1f-a4b5-418d-8ece-5671b48563e4

human

none

abstracts

Stochastic Lie group integrators

We present Lie group integrators for nonlinear stochastic differential equations with non-commutative vector fields whose solution evolves on a smooth finite dimensional manifold. Given a Lie group action that generates transport along the manifold, we pull back the stochastic flow on the manifold to the Lie group via the action, and subsequently pull back the flow to the corresponding Lie algebra via the exponential map. We construct an approximation to the stochastic flow in the Lie algebra via closed operations and then push back to the Lie group and then to the manifold, thus ensuring our approximation lies in the manifold. We call such schemes stochastic Munthe-Kaas methods after their deterministic counterparts. We also present stochastic Lie group integration schemes based on Castell--Gaines methods. These involve using an underlying ordinary differential integrator to approximate the flow generated by a truncated stochastic exponential Lie series. They become stochastic Lie g

a383f716-79f7-4c56-89c4-6faf0fa5214b

a383f716-79f7-4c56-89c4-6faf0fa5214b

a383f716-79f7-4c56-89c4-6faf0fa5214b

human

none

abstracts

ALMA as the ideal probe of the solar chromosphere

The very nature of the solar chromosphere, its structuring and dynamics, remains far from being properly understood, in spite of intensive research. Here we point out the potential of chromospheric observations at millimeter wavelengths to resolve this long-standing problem. Computations carried out with a sophisticated dynamic model of the solar chromosphere due to Carlsson and Stein demonstrate that millimeter emission is extremely sensitive to dynamic processes in the chromosphere and the appropriate wavelengths to look for dynamic signatures are in the range 0.8-5.0 mm. The model also suggests that high resolution observations at mm wavelengths, as will be provided by ALMA, will have the unique property of reacting to both the hot and the cool gas, and thus will have the potential of distinguishing between rival models of the solar atmosphere. Thus, initial results obtained from the observations of the quiet Sun at 3.5 mm with the BIMA array (resolution of 12 arcsec) reveal signi

fb6613ca-b272-4f6a-9675-12438ac3cfae

fb6613ca-b272-4f6a-9675-12438ac3cfae

fb6613ca-b272-4f6a-9675-12438ac3cfae

human

none

abstracts

Probing non-standard neutrino interactions with supernova neutrinos

We analyze the possibility of probing non-standard neutrino interactions (NSI, for short) through the detection of neutrinos produced in a future galactic supernova (SN).We consider the effect of NSI on the neutrino propagation through the SN envelope within a three-neutrino framework, paying special attention to the inclusion of NSI-induced resonant conversions, which may take place in the most deleptonised inner layers. We study the possibility of detecting NSI effects in a Megaton water Cherenkov detector, either through modulation effects in the $\bar\nu_e$ spectrum due to (i) the passage of shock waves through the SN envelope, (ii) the time dependence of the electron fraction and (iii) the Earth matter effects; or, finally, through the possible detectability of the neutronization $\nu_e$ burst. We find that the $\bar\nu_e$ spectrum can exhibit dramatic features due to the internal NSI-induced resonant conversion. This occurs for non-universal NSI strengths of a few %, and for ve

d1918e2e-5034-419e-8fd4-9d51887abb1d

d1918e2e-5034-419e-8fd4-9d51887abb1d

d1918e2e-5034-419e-8fd4-9d51887abb1d

human

none

abstracts

A remark on the number of steady states in a multiple futile cycle

The multisite phosphorylation-dephosphorylation cycle is a motif repeatedly used in cell signaling. This motif itself can generate a variety of dynamic behaviors like bistability and ultrasensitivity without direct positive feedbacks. In this paper, we study the number of positive steady states of a general multisite phosphorylation-dephosphorylation cycle, and how the number of positive steady states varies by changing the biological parameters. We show analytically that (1) for some parameter ranges, there are at least n+1 (if n is even) or n (if n is odd) steady states; (2) there never are more than 2n-1 steady states (in particular, this implies that for n=2, including single levels of MAPK cascades, there are at most three steady states); (3) for parameters near the standard Michaelis-Menten quasi-steady state conditions, there are at most n+1 steady states; and (4) for parameters far from the standard Michaelis-Menten quasi-steady state conditions, there is at most one steady s

eae08989-2da4-4116-b438-8570c70ede0f

eae08989-2da4-4116-b438-8570c70ede0f

eae08989-2da4-4116-b438-8570c70ede0f

human

none

abstracts

The discrete dipole approximation for simulation of light scattering by particles much larger than the wavelength

In this manuscript we investigate the capabilities of the Discrete Dipole Approximation (DDA) to simulate scattering from particles that are much larger than the wavelength of the incident light, and describe an optimized publicly available DDA computer program that processes the large number of dipoles required for such simulations. Numerical simulations of light scattering by spheres with size parameters x up to 160 and 40 for refractive index m=1.05 and 2 respectively are presented and compared with exact results of the Mie theory. Errors of both integral and angle-resolved scattering quantities generally increase with m and show no systematic dependence on x. Computational times increase steeply with both x and m, reaching values of more than 2 weeks on a cluster of 64 processors. The main distinctive feature of the computer program is the ability to parallelize a single DDA simulation over a cluster of computers, which allows it to simulate light scattering by very large particl

f6ac770a-910d-4384-ac2a-fd1c45fa6e87

f6ac770a-910d-4384-ac2a-fd1c45fa6e87

f6ac770a-910d-4384-ac2a-fd1c45fa6e87

human

none

abstracts

Scalar radius of the pion and zeros in the form factor

The quadratic pion scalar radius, \la r^2\ra^\pi_s, plays an important role for present precise determinations of \pi\pi scattering. Recently, Yndur\'ain, using an Omn\`es representation of the null isospin(I) non-strange pion scalar form factor, obtains \la r^2\ra^\pi_s=0.75\pm 0.07 fm^2. This value is larger than the one calculated by solving the corresponding Muskhelishvili-Omn\`es equations, \la r^2\ra^\pi_s=0.61\pm 0.04 fm^2. A large discrepancy between both values, given the precision, then results. We reanalyze Yndur\'ain's method and show that by imposing continuity of the resulting pion scalar form factor under tiny changes in the input \pi\pi phase shifts, a zero in the form factor for some S-wave I=0 T-matrices is then required. Once this is accounted for, the resulting value is \la r^2\ra_s^\pi=0.65\pm 0.05 fm^2. The main source of error in our determination is present experimental uncertainties in low energy S-wave I=0 \pi\pi phase shifts. Another important contribution

f1547b8e-916b-49f0-a882-8c9c1246399c

f1547b8e-916b-49f0-a882-8c9c1246399c

f1547b8e-916b-49f0-a882-8c9c1246399c

human

none

abstracts

Quantum Group of Isometries in Classical and Noncommutative Geometry

We formulate a quantum generalization of the notion of the group of Riemannian isometries for a compact Riemannian manifold, by introducing a natural notion of smooth and isometric action by a compact quantum group on a classical or noncommutative manifold described by spectral triples, and then proving the existence of a universal object (called the quantum isometry group) in the category of compact quantum groups acting smoothly and isometrically on a given (possibly noncommutative) manifold satisfying certain regularity assumptions. In fact, we identify the quantum isometry group with the universal object in a bigger category, namely the category of `quantum families of smooth isometries', defined along the line of Woronowicz and Soltan. We also construct a spectral triple on the Hilbert space of forms on a noncommutative manifold which is equivariant with respect to a natural unitary representation of the quantum isometry group. We give explicit description of quantum isometry gr

3a681765-f380-4ba1-8a3a-8f6115e26f7c

3a681765-f380-4ba1-8a3a-8f6115e26f7c

3a681765-f380-4ba1-8a3a-8f6115e26f7c

human

none

abstracts

Nonequilibrium entropy limiters in lattice Boltzmann methods

We construct a system of nonequilibrium entropy limiters for the lattice Boltzmann methods (LBM). These limiters erase spurious oscillations without blurring of shocks, and do not affect smooth solutions. In general, they do the same work for LBM as flux limiters do for finite differences, finite volumes and finite elements methods, but for LBM the main idea behind the construction of nonequilibrium entropy limiter schemes is to transform a field of a scalar quantity - nonequilibrium entropy. There are two families of limiters: (i) based on restriction of nonequilibrium entropy (entropy "trimming") and (ii) based on filtering of nonequilibrium entropy (entropy filtering). The physical properties of LBM provide some additional benefits: the control of entropy production and accurate estimate of introduced artificial dissipation are possible. The constructed limiters are tested on classical numerical examples: 1D athermal shock tubes with an initial density ratio 1:2 and the 2D lid-dri

5a6a5750-9f67-4d02-947b-867ae538899b

5a6a5750-9f67-4d02-947b-867ae538899b

5a6a5750-9f67-4d02-947b-867ae538899b

human

none

abstracts

Evolution of solitary waves and undular bores in shallow-water flows over a gradual slope with bottom friction

This paper considers the propagation of shallow-water solitary and nonlinear periodic waves over a gradual slope with bottom friction in the framework of a variable-coefficient Korteweg-de Vries equation. We use the Whitham averaging method, using a recent development of this theory for perturbed integrable equations. This general approach enables us not only to improve known results on the adiabatic evolution of isolated solitary waves and periodic wave trains in the presence of variable topography and bottom friction, modeled by the Chezy law, but also importantly, to study the effects of these factors on the propagation of undular bores, which are essentially unsteady in the system under consideration. In particular, it is shown that the combined action of variable topography and bottom friction generally imposes certain global restrictions on the undular bore propagation so that the evolution of the leading solitary wave can be substantially different from that of an isolated sol

233c25a7-5423-42cb-a2ab-08f98ae4661d

233c25a7-5423-42cb-a2ab-08f98ae4661d

233c25a7-5423-42cb-a2ab-08f98ae4661d

human

none

abstracts

Intelligent location of simultaneously active acoustic emission sources: Part I

The intelligent acoustic emission locator is described in Part I, while Part II discusses blind source separation, time delay estimation and location of two simultaneously active continuous acoustic emission sources. The location of acoustic emission on complicated aircraft frame structures is a difficult problem of non-destructive testing. This article describes an intelligent acoustic emission source locator. The intelligent locator comprises a sensor antenna and a general regression neural network, which solves the location problem based on learning from examples. Locator performance was tested on different test specimens. Tests have shown that the accuracy of location depends on sound velocity and attenuation in the specimen, the dimensions of the tested area, and the properties of stored data. The location accuracy achieved by the intelligent locator is comparable to that obtained by the conventional triangulation method, while the applicability of the intelligent locator is m

355df5df-b616-43d9-a708-570f4d6305e9

355df5df-b616-43d9-a708-570f4d6305e9

355df5df-b616-43d9-a708-570f4d6305e9

human

none

abstracts

A Global Approach to the Theory of Special Finsler Manifolds

The aim of the present paper is to provide a global presentation of the theory of special Finsler manifolds. We introduce and investigate globally (or intrinsically, free from local coordinates) many of the most important and most commonly used special Finsler manifolds: locally Minkowskian, Berwald, Landesberg, general Landesberg, $P$-reducible, $C$-reducible, semi-$C$-reducible, quasi-$C$-reducible, $P^{*}$-Finsler, $C^{h}$-recurrent, $C^{v}$-recurrent, $C^{0}$-recurrent, $S^{v}$-recurrent, $S^{v}$-recurrent of the second order, $C_{2}$-like, $S_{3}$-like, $S_{4}$-like, $P_{2}$-like, $R_{3}$-like, $P$-symmetric, $h$-isotropic, of scalar curvature, of constant curvature, of $p$-scalar curvature, of $s$-$ps$-curvature. The global definitions of these special Finsler manifolds are introduced. Various relationships between the different types of the considered special Finsler manifolds are found. Many local results, known in the literature, are proved globally and several new results a

0d03f97e-6045-47fc-aeab-1f39c2fa8b43

0d03f97e-6045-47fc-aeab-1f39c2fa8b43

0d03f97e-6045-47fc-aeab-1f39c2fa8b43

human

none

abstracts

Potassium intercalation in graphite: A van der Waals density-functional study

Potassium intercalation in graphite is investigated by first-principles theory. The bonding in the potassium-graphite compound is reasonably well accounted for by traditional semilocal density functional theory (DFT) calculations. However, to investigate the intercalate formation energy from pure potassium atoms and graphite requires use of a description of the graphite interlayer binding and thus a consistent account of the nonlocal dispersive interactions. This is included seamlessly with ordinary DFT by a van der Waals density functional (vdW-DF) approach [Phys. Rev. Lett. 92, 246401 (2004)]. The use of the vdW-DF is found to stabilize the graphite crystal, with crystal parameters in fair agreement with experiments. For graphite and potassium-intercalated graphite structural parameters such as binding separation, layer binding energy, formation energy, and bulk modulus are reported. Also the adsorption and sub-surface potassium absorption energies are reported. The vdW-DF descript

e4f50801-7727-4a65-a35f-fd4aa7f0e69b

e4f50801-7727-4a65-a35f-fd4aa7f0e69b

e4f50801-7727-4a65-a35f-fd4aa7f0e69b

human

none

abstracts

Intelligent Life in Cosmology

I shall present three arguments for the proposition that intelligent life is very rare in the universe. First, I shall summarize the consensus opinion of the founders of the Modern Synthesis (Simpson, Dobzhanski, and Mayr) that the evolution of intelligent life is exceedingly improbable. Second, I shall develop the Fermi Paradox: if they existed they'd be here. Third, I shall show that if intelligent life were too common, it would use up all available resources and die out. But I shall show that the quantum mechanical principle of unitarity (actually a form of teleology!) requires intelligent life to survive to the end of time. Finally, I shall argue that, if the universe is indeed accelerating, then survival to the end of time requires that intelligent life, though rare, to have evolved several times in the visible universe. I shall argue that the acceleration is a consequence of the excess of matter over antimatter in the universe. I shall suggest experiments to test these claims.

f46ab681-2468-4c51-aad1-2fff117fff11

f46ab681-2468-4c51-aad1-2fff117fff11

f46ab681-2468-4c51-aad1-2fff117fff11

human

none

abstracts

The Mass and Radius of the Unseen M-Dwarf Companion in the Single-Lined Eclipsing Binary HAT-TR-205-013

We derive masses and radii for both components in the single-lined eclipsing binary HAT-TR-205-013, which consists of a F7V primary and a late M-dwarf secondary. The system's period is short, $P=2.230736 \pm 0.000010$ days, with an orbit indistinguishable from circular, $e=0.012 \pm 0.021$. We demonstrate generally that the surface gravity of the secondary star in a single-lined binary undergoing total eclipses can be derived from characteristics of the light curve and spectroscopic orbit. This constrains the secondary to a unique line in the mass-radius diagram with $M/R^2$ = constant. For HAT-TR-205-013, we assume the orbit has been tidally circularized, and that the primary's rotation has been synchronized and aligned with the orbital axis. Our observed line broadening, $V_{\rm rot} \sin i_{\rm rot} = 28.9 \pm 1.0$ \kms, gives a primary radius of $R_{\rm A} = 1.28 \pm 0.04$ \rsun. Our light curve analysis leads to the radius of the secondary, $R_{\rm B} = 0.167 \pm 0.006$ \rsun, a

8d3c8295-a47f-485b-9c6f-5553a4a47b3b

8d3c8295-a47f-485b-9c6f-5553a4a47b3b

8d3c8295-a47f-485b-9c6f-5553a4a47b3b

human

none

abstracts

Intersection Bodies and Generalized Cosine Transforms

Intersection bodies represent a remarkable class of geometric objects associated with sections of star bodies and invoking Radon transforms, generalized cosine transforms, and the relevant Fourier analysis. The main focus of this article is interrelation between generalized cosine transforms of different kinds in the context of their application to investigation of a certain family of intersection bodies, which we call $\lam$-intersection bodies. The latter include $k$-intersection bodies (in the sense of A. Koldobsky) and unit balls of finite-dimensional subspaces of $L_p$-spaces. In particular, we show that restrictions onto lower dimensional subspaces of the spherical Radon transforms and the generalized cosine transforms preserve their integral-geometric structure. We apply this result to the study of sections of $\lam$-intersection bodies. New characterizations of this class of bodies are obtained and examples are given. We also review some known facts and give them new proofs

109883f5-9344-4a74-9405-47a05ac21e1f

109883f5-9344-4a74-9405-47a05ac21e1f

109883f5-9344-4a74-9405-47a05ac21e1f

human

none

abstracts

Nilpotent symmetry invariance in the superfield formulation: the (non-)Abelian 1-form gauge theories

We capture the off-shell as well as the on-shell nilpotent Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST symmetry invariance of the Lagrangian densities of the four (3 + 1)-dimensional (4D) (non-)Abelian 1-form gauge theories within the framework of the superfield formalism. In particular, we provide the geometrical interpretations for (i) the above nilpotent symmetry invariance, and (ii) the above Lagrangian densities, in the language of the specific quantities defined in the domain of the above superfield formalism. Some of the subtle points, connected with the 4D (non-)Abelian 1-form gauge theories, are clarified within the framework of the above superfield formalism where the 4D ordinary gauge theories are considered on the (4, 2)-dimensional supermanifold parametrized by the four spacetime coordinates x^\mu (with \mu = 0, 1, 2, 3) and a pair of Grassmannian variables \theta and \bar\theta. One of the key results of our present investigation is a great deal of simplification in

120ac19a-80fe-4e24-9a04-57a93feaed67

120ac19a-80fe-4e24-9a04-57a93feaed67

120ac19a-80fe-4e24-9a04-57a93feaed67

human

none

abstracts

Littlewood-Richardson polynomials

We introduce a family of rings of symmetric functions depending on an infinite sequence of parameters. A distinguished basis of such a ring is comprised by analogues of the Schur functions. The corresponding structure coefficients are polynomials in the parameters which we call the Littlewood-Richardson polynomials. We give a combinatorial rule for their calculation by modifying an earlier result of B. Sagan and the author. The new rule provides a formula for these polynomials which is manifestly positive in the sense of W. Graham. We apply this formula for the calculation of the product of equivariant Schubert classes on Grassmannians which implies a stability property of the structure coefficients. The first manifestly positive formula for such an expansion was given by A. Knutson and T. Tao by using combinatorics of puzzles while the stability property was not apparent from that formula. We also use the Littlewood-Richardson polynomials to describe the multiplication rule in the a

e1f42987-5127-477f-8a21-e1e272a2cf99

e1f42987-5127-477f-8a21-e1e272a2cf99

e1f42987-5127-477f-8a21-e1e272a2cf99

human

none

abstracts

Lagrangian quantum field theory in momentum picture. IV. Commutation relations for free fields

Possible (algebraic) commutation relations in the Lagrangian quantum theory of free (scalar, spinor and vector) fields are considered from mathematical view-point. As sources of these relations are employed the Heisenberg equations/relations for the dynamical variables and a specific condition for uniqueness of the operators of the dynamical variables (with respect to some class of Lagrangians). The paracommutation relations or some their generalizations are pointed as the most general ones that entail the validity of all Heisenberg equations. The simultaneous fulfillment of the Heisenberg equations and the uniqueness requirement turn to be impossible. This problem is solved via a redefinition of the dynamical variables, similar to the normal ordering procedure and containing it as a special case. That implies corresponding changes in the admissible commutation relations. The introduction of the concept of the vacuum makes narrow the class of the possible commutation relations; in pa

4ad1cd03-f601-44d9-8f2d-7528c882ccba

4ad1cd03-f601-44d9-8f2d-7528c882ccba

4ad1cd03-f601-44d9-8f2d-7528c882ccba

human

none

abstracts

Order of Epitaxial Self-Assembled Quantum Dots: Linear Analysis

Epitaxial self-assembled quantum dots (SAQDs) are of interest for nanostructured optoelectronic and electronic devices such as lasers, photodetectors and nanoscale logic. Spatial order and size order of SAQDs are important to the development of usable devices. It is likely that these two types of order are strongly linked; thus, a study of spatial order will also have strong implications for size order. Here a study of spatial order is undertaken using a linear analysis of a commonly used model of SAQD formation based on surface diffusion. Analytic formulas for film-height correlation functions are found that characterize quantum dot spatial order and corresponding correlation lengths that quantify order. Initial atomic-scale random fluctuations result in relatively small correlation lengths (about two dots) when the effect of a wetting potential is negligible; however, the correlation lengths diverge when SAQDs are allowed to form at a near-critical film height. The present work rei

bd4b45ff-98ad-4361-9708-a156890bab63

bd4b45ff-98ad-4361-9708-a156890bab63

bd4b45ff-98ad-4361-9708-a156890bab63

human

none

abstracts

Dynamical Objects for Cohomologically Expanding Maps

The goal of this paper is to construct invariant dynamical objects for a (not necessarily invertible) smooth self map of a compact manifold. We prove a result that takes advantage of differences in rates of expansion in the terms of a sheaf cohomological long exact sequence to create unique lifts of finite dimensional invariant subspaces of one term of the sequence to invariant subspaces of the preceding term. This allows us to take invariant cohomological classes and under the right circumstances construct unique currents of a given type, including unique measures of a given type, that represent those classes and are invariant under pullback. A dynamically interesting self map may have a plethora of invariant measures, so the uniquess of the constructed currents is important. It means that if local growth is not too big compared to the growth rate of the cohomological class then the expanding cohomological class gives sufficient "marching orders" to the system to prohibit the format

bf68e931-83a2-400d-a069-8f7f2dd575b0

bf68e931-83a2-400d-a069-8f7f2dd575b0

bf68e931-83a2-400d-a069-8f7f2dd575b0

human

none

abstracts

Matter-Wave Bright Solitons with a Finite Background in Spinor Bose-Einstein Condensates

We investigate dynamical properties of bright solitons with a finite background in the F=1 spinor Bose-Einstein condensate (BEC), based on an integrable spinor model which is equivalent to the matrix nonlinear Schr\"{o}dinger equation with a self-focusing nonlineality. We apply the inverse scattering method formulated for nonvanishing boundary conditions. The resulting soliton solutions can be regarded as a generalization of those under vanishing boundary conditions. One-soliton solutions are derived in an explicit manner. According to the behaviors at the infinity, they are classified into two kinds, domain-wall (DW) type and phase-shift (PS) type. The DW-type implies the ferromagnetic state with nonzero total spin and the PS-type implies the polar state, where the total spin amounts to zero. We also discuss two-soliton collisions. In particular, the spin-mixing phenomenon is confirmed in a collision involving the DW-type. The results are consistent with those of the previous studie

19daa111-c3a4-41ff-b96b-f822ed034f15

19daa111-c3a4-41ff-b96b-f822ed034f15

19daa111-c3a4-41ff-b96b-f822ed034f15

human

none

abstracts

Why there is something rather than nothing (out of everything)?

The path integral over Euclidean geometries for the recently suggested density matrix of the Universe is shown to describe a microcanonical ensemble in quantum cosmology. This ensemble corresponds to a uniform (weight one) distribution in phase space of true physical variables, but in terms of the observable spacetime geometry it is peaked about complex saddle-points of the {\em Lorentzian} path integral. They are represented by the recently obtained cosmological instantons limited to a bounded range of the cosmological constant. Inflationary cosmologies generated by these instantons at late stages of expansion undergo acceleration whose low-energy scale can be attained within the concept of dynamically evolving extra dimensions. Thus, together with the bounded range of the early cosmological constant, this cosmological ensemble suggests the mechanism of constraining the landscape of string vacua and, simultaneously, a possible solution to the dark energy problem in the form of the q

27fcc305-b6db-40e0-b39c-693cef987709

27fcc305-b6db-40e0-b39c-693cef987709

27fcc305-b6db-40e0-b39c-693cef987709

human

none

abstracts

A Universality in PP-Waves

We discuss a universality property of any covariant field theory in space-time expanded around pp-wave backgrounds. According to this property the space-time lagrangian density evaluated on a restricted set of field configurations, called universal sector, turns out to be same around all the pp-waves, even off-shell, with same transverse space and same profiles for the background scalars. In this paper we restrict our discussion to tensorial fields only. In the context of bosonic string theory we consider on-shell pp-waves and argue that universality requires the existence of a universal sector of world-sheet operators whose correlation functions are insensitive to the pp-wave nature of the metric and the background gauge flux. Such results can also be reproduced using the world-sheet conformal field theory. We also study such pp-waves in non-polynomial closed string field theory (CSFT). In particular, we argue that for an off-shell pp-wave ansatz with flat transverse space and dilat

85eb0061-205f-47a8-b63f-08391f3587b7

85eb0061-205f-47a8-b63f-08391f3587b7

85eb0061-205f-47a8-b63f-08391f3587b7

human

none

abstracts

Some new experimental photonic flame effect features

The results of the spectral, energetical and temporal characteristics of radiation in the presence of the photonic flame effect are presented. Artificial opal posed on Cu plate at the temperature of liquid nitrogen boiling point (77 K) being irradiated by nanosecond ruby laser pulse produces long- term luminiscence with a duration till ten seconds with a finely structured spectrum in the the antistocks part of the spectrum. Analogous visible luminescence manifesting time delay appeared in other samples of the artificial opals posed on the same plate. In the case of the opal infiltrated with different nonlinear liquids the threshold of the luminiscence is reduced and the spatial disribution of the bright emmiting area on the opal surface is being changed. In the case of the putting the frozen nonlinear liquids on the Cu plate long-term blue bright luminiscence took place in the frozen species of the liquids. Temporal characteristics of this luminiscence are nearly the same as in opal

4ff03e33-4563-409a-9eac-0ca5e656d556

4ff03e33-4563-409a-9eac-0ca5e656d556

4ff03e33-4563-409a-9eac-0ca5e656d556

human

none

abstracts

A general approach to statistical modeling of physical laws: nonparametric regression

Statistical modeling of experimental physical laws is based on the probability density function of measured variables. It is expressed by experimental data via a kernel estimator. The kernel is determined objectively by the scattering of data during calibration of experimental setup. A physical law, which relates measured variables, is optimally extracted from experimental data by the conditional average estimator. It is derived directly from the kernel estimator and corresponds to a general nonparametric regression. The proposed method is demonstrated by the modeling of a return map of noisy chaotic data. In this example, the nonparametric regression is used to predict a future value of chaotic time series from the present one. The mean predictor error is used in the definition of predictor quality, while the redundancy is expressed by the mean square distance between data points. Both statistics are used in a new definition of predictor cost function. From the minimum of the predic

8a782ba1-ae93-48dc-bc39-3c245b34c9e5

8a782ba1-ae93-48dc-bc39-3c245b34c9e5

8a782ba1-ae93-48dc-bc39-3c245b34c9e5

human

none

abstracts

Timing and Lensing of the Colliding Bullet Clusters: barely enough time and gravity to accelerate the bullet

We present semi-analytical constraint on the amount of dark matter in the merging bullet galaxy cluster using the classical Local Group timing arguments. We consider particle orbits in potential models which fit the lensing data. {\it Marginally consistent} CDM models in Newtonian gravity are found with a total mass M_{CDM} = 1 x 10^{15}Msun of Cold DM: the bullet subhalo can move with V_{DM}=3000km/s, and the "bullet" X-ray gas can move with V_{gas}=4200km/s. These are nearly the {\it maximum speeds} that are accelerable by the gravity of two truncated CDM halos in a Hubble time even without the ram pressure. Consistency breaks down if one adopts higher end of the error bars for the bullet gas speed (5000-5400km/s), and the bullet gas would not be bound by the sub-cluster halo for the Hubble time. Models with V_{DM}~ 4500km/s ~ V_{gas} would invoke unrealistic large amount M_{CDM}=7x 10^{15}Msun of CDM for a cluster containing only ~ 10^{14}Msun of gas. Our results are generalisable

d2d2b5e3-af80-40e7-b083-ecad1d00d40c

d2d2b5e3-af80-40e7-b083-ecad1d00d40c

d2d2b5e3-af80-40e7-b083-ecad1d00d40c

human

none

abstracts

On Ando's inequalities for convex and concave functions

For positive semidefinite matrices $A$ and $B$, Ando and Zhan proved the inequalities $||| f(A)+f(B) ||| \ge ||| f(A+B) |||$ and $||| g(A)+g(B) ||| \le ||| g(A+B) |||$, for any unitarily invariant norm, and for any non-negative operator monotone $f$ on $[0,\infty)$ with inverse function $g$. These inequalities have very recently been generalised to non-negative concave functions $f$ and non-negative convex functions $g$, by Bourin and Uchiyama, and Kosem, respectively. In this paper we consider the related question whether the inequalities $||| f(A)-f(B) ||| \le ||| f(|A-B|) |||$, and $||| g(A)-g(B) ||| \ge ||| g(|A-B|) |||$, obtained by Ando, for operator monotone $f$ with inverse $g$, also have a similar generalisation to non-negative concave $f$ and convex $g$. We answer exactly this question, in the negative for general matrices, and affirmatively in the special case when $A\ge ||B||$. In the course of this work, we introduce the novel notion of $Y$-dominated majorisation bet

ebacde3d-cc94-4b89-9279-10b7ed14287a

ebacde3d-cc94-4b89-9279-10b7ed14287a

ebacde3d-cc94-4b89-9279-10b7ed14287a

human

none

abstracts

Multiple Parton Scattering in Nuclei: Quark-quark Scattering

Modifications to quark and antiquark fragmentation functions due to quark-quark (antiquark) double scattering in nuclear medium are studied systematically up to order \cal{O}(\alpha_{s}^2)$ in deeply inelastic scattering (DIS) off nuclear targets. At the order $\cal{O}(\alpha_s^2)$, twist-four contributions from quark-quark (antiquark) rescattering also exhibit the Landau-Pomeranchuck-Midgal (LPM) interference feature similar to gluon bremsstrahlung induced by multiple parton scattering. Compared to quark-gluon scattering, the modification, which is dominated by $t$-channel quark-quark (antiquark) scattering, is only smaller by a factor of $C_F/C_A=4/9$ times the ratio of quark and gluon distributions in the medium. Such a modification is not negligible for realistic kinematics and finite medium size. The modifications to quark (antiquark) fragmentation functions from quark-antiquark annihilation processes are shown to be determined by the antiquark (quark) distribution density in th

de3c568d-b7fe-450c-888c-504d1fe35308

de3c568d-b7fe-450c-888c-504d1fe35308

de3c568d-b7fe-450c-888c-504d1fe35308

human

none

abstracts

Langmuir blodgett assembly of densely aligned single walled carbon nanotubes from bulk materials

Single walled carbon nanotubes exhibit advanced electrical and surface properties useful for high performance nanoelectronics. Important to future manufacturing of nanotube circuits is large scale assembly of SWNTs into aligned forms. Despite progress in assembly and oriented synthesis, pristine SWNTs in aligned and close-packed form remain elusive and needed for high current, speed and density devices through collective operations of parallel SWNTs. Here, we develop a Langmuir Blodgett method achieving monolayers of aligned SWNTs with dense packing, central to which is a non covalent polymer functionalization by PmPV imparting high solubility and stability of SWNTs in an organic solvent DCE. Pressure cycling or annealing during LB film compression reduces hysteresis and facilitates high degree alignment and packing of SWNTs characterized by microscopy and polarized Raman spectroscopy. The monolayer SWNTs are readily patterned for device integration by microfabrication, enabling the

299488be-8583-496c-b5f8-41089fd0cb1a

299488be-8583-496c-b5f8-41089fd0cb1a

299488be-8583-496c-b5f8-41089fd0cb1a

human

none

abstracts

Nonlinear Dynamics of the Phonon Stimulated Emission in Microwave Solid-State Resonator of the Nonautonomous Phaser Generator

The microwave phonon stimulated emission (SE) has been experimentally and numerically investigated in a nonautonomous microwave acoustic quantum generator, called also microwave phonon laser or phaser (see previous works arXiv:cond-mat/0303188 ; arXiv:cond-mat/0402640 ; arXiv:nlin.CG/0703050) Phenomena of branching and long-time refractority (absence of the reaction on the external pulses) for deterministic chaotic and regular processes of SE were observed in experiments with various levels of electromagnetic pumping. At the pumping level growth, the clearly depined increasing of the number of coexisting SE states has been observed both in real physical experiments and in computer simulations. This confirms the analytical estimations of the branching density in the phase space. The nature of the refractority of SE pulses is closely connected with the pointed branching and reflects the crises of strange attractors, i.e. their collisions with unstable periodic components of the higher

0c6e03f6-7e9a-4d71-bac4-637cd1e75205

0c6e03f6-7e9a-4d71-bac4-637cd1e75205

0c6e03f6-7e9a-4d71-bac4-637cd1e75205

human

none

abstracts

Magnetic Fingerprints of sub-100 nm Fe Nanodots

Sub-100 nm nanomagnets not only are technologically important, but also exhibit complex magnetization reversal behaviors as their dimensions are comparable to typical magnetic domain wall widths. Here we capture magnetic "fingerprints" of 1 billion Fe nanodots as they undergo a single domain to vortex state transition, using a first-order reversal curve (FORC) method. As the nanodot size increases from 52 nm to 67 nm, the FORC diagrams reveal striking differences, despite only subtle changes in their major hysteresis loops. The 52 nm nanodots exhibit single domain behavior and the coercivity distribution extracted from the FORC distribution agrees well with a calculation based on the measured nanodot size distribution. The 58 and 67 nm nanodots exhibit vortex states, where the nucleation and annihilation of the vortices are manifested as butterfly-like features in the FORC distribution and confirmed by micromagnetic simulations. Furthermore, the FORC method gives quantitative measure

4a2ebec8-d6bf-4753-96fa-fdd9486acf44

4a2ebec8-d6bf-4753-96fa-fdd9486acf44

4a2ebec8-d6bf-4753-96fa-fdd9486acf44

human

none

abstracts

An online repository of Swift/XRT light curves of GRBs

Context. Swift data are revolutionising our understanding of Gamma Ray Bursts. Since bursts fade rapidly, it is desirable to create and disseminate accurate light curves rapidly. Aims. To provide the community with an online repository of X-ray light curves obtained with Swift. The light curves should be of the quality expected of published data, but automatically created and updated so as to be self-consistent and rapidly available. Methods. We have produced a suite of programs which automatically generates Swift/XRT light curves of GRBs. Effects of the damage to the CCD, automatic readout-mode switching and pile-up are appropriately handled, and the data are binned with variable bin durations, as necessary for a fading source. Results. The light curve repository website (http://www.swift.ac.uk/xrt_curves) contains light curves, hardness ratios and deep images for every GRB which Swift's XRT has observed. When new GRBs are detected, light curves are created and updated within mi

fdf546e1-e622-4fb7-bc26-12796f93191b

fdf546e1-e622-4fb7-bc26-12796f93191b

fdf546e1-e622-4fb7-bc26-12796f93191b

human

none

abstracts

Vortices in Bose-Einstein Condensates: Theory

Vortices are pervasive in nature, representing the breakdown of laminar fluid flow and hence playing a key role in turbulence. The fluid rotation associated with a vortex can be parameterized by the circulation $\Gamma=\oint {\rm d}{\bf r}\cdot{\bf v}({\bf r})$ about the vortex, where ${\bf v}({\bf r})$ is the fluid velocity field. While classical vortices can take any value of circulation, superfluids are irrotational, and any rotation or angular momentum is constrained to occur through vortices with quantized circulation. Quantized vortices also play a key role in the dissipation of transport in superfluids. In BECs quantized vortices have been observed in several forms, including single vortices, vortex lattices, and vortex pairs and rings. The recent observation of quantized vortices in a fermionic gas was taken as a clear signature of the underlying condensation and superfluidity of fermion pairs. In addition to BECs, quantized vortices also occur in superfluid Helium, nonlinear

053ac8e0-ccd7-4f6e-b3f8-efebe310b3f8

053ac8e0-ccd7-4f6e-b3f8-efebe310b3f8

053ac8e0-ccd7-4f6e-b3f8-efebe310b3f8

human

none

abstracts

Reexamination of spin decoherence in semiconductor quantum dots from equation-of-motion approach

The longitudinal and transversal spin decoherence times, $T_1$ and $T_2$, in semiconductor quantum dots are investigated from equation-of-motion approach for different magnetic fields, quantum dot sizes, and temperatures. Various mechanisms, such as the hyperfine interaction with the surrounding nuclei, the Dresselhaus spin-orbit coupling together with the electron--bulk-phonon interaction, the $g$-factor fluctuations, the direct spin-phonon coupling due to the phonon-induced strain, and the coaction of the electron--bulk/surface-phonon interaction together with the hyperfine interaction are included. The relative contributions from these spin decoherence mechanisms are compared in detail. In our calculation, the spin-orbit coupling is included in each mechanism and is shown to have marked effect in most cases. The equation-of-motion approach is applied in studying both the spin relaxation time $T_1$ and the spin dephasing time $T_2$, either in Markovian or in non-Markovian limit. Wh

b7e46c1a-954c-45f3-b799-6047d881b031

b7e46c1a-954c-45f3-b799-6047d881b031

b7e46c1a-954c-45f3-b799-6047d881b031

human

none

abstracts

Extraction of physical laws from joint experimental data

The extraction of a physical law y=yo(x) from joint experimental data about x and y is treated. The joint, the marginal and the conditional probability density functions (PDF) are expressed by given data over an estimator whose kernel is the instrument scattering function. As an optimal estimator of yo(x) the conditional average is proposed. The analysis of its properties is based upon a new definition of prediction quality. The joint experimental information and the redundancy of joint measurements are expressed by the relative entropy. With the number of experiments the redundancy on average increases, while the experimental information converges to a certain limit value. The difference between this limit value and the experimental information at a finite number of data represents the discrepancy between the experimentally determined and the true properties of the phenomenon. The sum of the discrepancy measure and the redundancy is utilized as a cost function. By its minimum a reas

c7cced45-d2ce-4a8d-b728-edc7c9ed9d39

c7cced45-d2ce-4a8d-b728-edc7c9ed9d39

c7cced45-d2ce-4a8d-b728-edc7c9ed9d39

human

none

abstracts

A computer program for fast non-LTE analysis of interstellar line spectra

The large quantity and high quality of modern radio and infrared line observations require efficient modeling techniques to infer physical and chemical parameters such as temperature, density, and molecular abundances. We present a computer program to calculate the intensities of atomic and molecular lines produced in a uniform medium, based on statistical equilibrium calculations involving collisional and radiative processes and including radiation from background sources. Optical depth effects are treated with an escape probability method. The program is available on the World Wide Web at http://www.sron.rug.nl/~vdtak/radex/index.shtml . The program makes use of molecular data files maintained in the Leiden Atomic and Molecular Database (LAMDA), which will continue to be improved and expanded. The performance of the program is compared with more approximate and with more sophisticated methods. An Appendix provides diagnostic plots to estimate physical parameters from line intensity

42c464f3-e0f7-42ff-ae10-8b828f1f0bf3

42c464f3-e0f7-42ff-ae10-8b828f1f0bf3

42c464f3-e0f7-42ff-ae10-8b828f1f0bf3

human

none

abstracts

Estimation of experimental data redundancy and related statistics

Redundancy of experimental data is the basic statistic from which the complexity of a natural phenomenon and the proper number of experiments needed for its exploration can be estimated. The redundancy is expressed by the entropy of information pertaining to the probability density function of experimental variables. Since the calculation of entropy is inconvenient due to integration over a range of variables, an approximate expression for redundancy is derived that includes only a sum over the set of experimental data about these variables. The approximation makes feasible an efficient estimation of the redundancy of data along with the related experimental information and information cost function. From the experimental information the complexity of the phenomenon can be simply estimated, while the proper number of experiments needed for its exploration can be determined from the minimum of the cost function. The performance of the approximate estimation of these statistics is demo

915e6628-caff-4c99-8044-baecfbc68e54

915e6628-caff-4c99-8044-baecfbc68e54

915e6628-caff-4c99-8044-baecfbc68e54

human

none

abstracts

Reparametrization Invariance, the controversial extraction of $\alpha$ from $B\to\pi\pi$ and New Physics

The extraction of the weak phase $\alpha$ from $B\to\pi\pi$ decays has been controversial from a statistical point of view, as the frequentist vs. bayesian confrontation shows. We analyse several relevant questions which have not deserved full attention and pervade the extraction of $\alpha$. Reparametrization Invariance proves appropriate to understand those issues. We show that some Standard Model inspired parametrizations can be senseless or inadequate if they go beyond the minimal Gronau and London assumptions: the single weak phase $\alpha$ just in the $\Delta I=3/2$ amplitudes, the isospin relations and experimental data. Beside those analyses, we extract $\alpha$ through the use of several adequate parametrizations, showing that there is no relevant discrepancy between frequentist and bayesian results. The most relevant information, in terms of $\alpha$, is the exclusion of values around $\alpha\sim \pi/4$; this result is valid in the presence of arbitrary New Physics contribu

a64356af-9ee7-4b9c-9e18-3a9b4896f3df

a64356af-9ee7-4b9c-9e18-3a9b4896f3df

a64356af-9ee7-4b9c-9e18-3a9b4896f3df

human

none

abstracts

Switching mechanism of photochromic diarylethene derivatives molecular junctions

The electronic transport properties and switching mechanism of single photochromic diarylethene derivatives sandwiched between two gold surfaces with closed and open configurations are investigated by a fully self-consistent nonequilibrium Green's function method combined with density functional theory. The calculated transmission spectra of two configurations are strikingly distinctive. The open form lacks any significant transmission peak within a wide energy window, while the closed structure has two significant transmission peaks on the both sides of the Fermi level. The electronic transport properties of the molecular junction with closed structure under a small bias voltage are mainly determined by the tail of the transmission peak contributed unusually by the perturbed lowest perturbed unoccupied molecular orbital. The calculated on-off ratio of currents between the closed and open configurations is about two orders of magnitude, which reproduces the essential features of the

fdb29030-ce84-48a8-bd64-c404e6b358ea

fdb29030-ce84-48a8-bd64-c404e6b358ea

fdb29030-ce84-48a8-bd64-c404e6b358ea

human

none

abstracts

Temperature Dependence of the Tensile Properties of Single Walled Carbon Nanotubes: O(N) Tight Binding MD Simulation

This paper examines the effect of temperature on the structural stability and mechanical properties of 20 layered (10,10) single walled carbon nanotubes (SWCNTs) under tensile loading using an O(N) tight binding molecular dynamics (TBMD) simulation method. We observed that (10,10) tube can sustain its structural stability for the strain values of 0.23 in elongation and 0.06 in compression at 300K. Bond breaking strain value decreases with increasing temperature under streching but not under compression. The elastic limit, Young's modulus, tensile strength and Poisson ratio are calculated as 0.10, 0.395 TPa, 83.23 GPa, 0.285, respectively, at 300K. In the temperature range from 300K to 900K; Young's modulus and the tensile strengths are decreasing with increasing temperature while the Poisson ratio is increasing. At higher temperatures, Young's modulus starts to increase while the Poisson ratio and tensile strength decrease. In the temperature range from 1200K to 1800K, the SWCNT is a

6f1a2ee2-1b96-409f-8ae3-3122e6c00ee2

6f1a2ee2-1b96-409f-8ae3-3122e6c00ee2

6f1a2ee2-1b96-409f-8ae3-3122e6c00ee2

human

none

abstracts

Monoid generalizations of the Richard Thompson groups

The groups G_{k,1} of Richard Thompson and Graham Higman can be generalized in a natural way to monoids, that we call M_{k,1}, and to inverse monoids, called Inv_{k,1}; this is done by simply generalizing bijections to partial functions or partial injective functions. The monoids M_{k,1} have connections with circuit complexity (studied in another paper). Here we prove that M_{k,1} and Inv_{k,1} are congruence-simple for all k. Their Green relations J and D are characterized: M_{k,1} and Inv_{k,1} are J-0-simple, and they have k-1 non-zero D-classes. They are submonoids of the multiplicative part of the Cuntz algebra O_k. They are finitely generated, and their word problem over any finite generating set is in P. Their word problem is coNP-complete over certain infinite generating sets. Changes in this version: Section 4 has been thoroughly revised, and errors have been corrected; however, the main results of Section 4 do not change. Sections 1, 2, and 3 are unchanged, except for th

ce01e69e-93f1-4edb-9805-be4719456262

ce01e69e-93f1-4edb-9805-be4719456262

ce01e69e-93f1-4edb-9805-be4719456262

human

none

abstracts

The Reliability on the Direction of the Incident Neutrino for the Fully Contained Events and Partially Contained Events due to QEL in the Super-Kamiokande

In the SK analysis of the neutrino events for [Fully Contained Events] and [Partially Contained Events] on their zenith angle distribution, it is assumed that the zenith angle of the incident neutrino is the same as that of the detected charged lepton. In the present paper, we examine the validity of [the SK assumption on the direction] of the incident neutrinos. Concretely speaking, we analyze muon-like events due to QEL. For the purpose, we develop [Time Sequential Monte Carlo Simulation] to extract the conclusion on the validity of the SK assumption. In our [Time Sequential Simulation], we simulate every physical process concerned as exactly as possible without any approximation. From the comparison between the zenith angle distributon of the emitted muons under [the SK assumption on the direction] and the corresponding one obtained under our [Time Sequential Simulation], it is concluded that the measurement of the direction of the incident neutrino for the neutrino events occur

00afe8c2-3519-4d8e-b343-e377a8767e81

00afe8c2-3519-4d8e-b343-e377a8767e81

00afe8c2-3519-4d8e-b343-e377a8767e81

human

none

abstracts

Intricate Knots in Proteins: Function and Evolution

A number of recently discovered protein structures incorporate a rather unexpected structural feature: a knot in the polypeptide backbone. These knots are extremely rare, but their occurrence is likely connected to protein function in as yet unexplored fashion. Our analysis of the complete Protein Data Bank reveals several new knots which, along with previously discovered ones, can shed light on such connections. In particular, we identify the most complex knot discovered to date in human ubiquitin hydrolase, and suggest that its entangled topology protects it against unfolding and degradation by the proteasome. Knots in proteins are typically preserved across species and sometimes even across kingdoms. However, we also identify a knot which only appears in some transcarbamylases while being absent in homologous proteins of similar structure. The emergence of the knot is accompanied by a shift in the enzymatic function of the protein. We suggest that the simple insertion of a short D

ccecf094-ff51-4c78-81c3-46578263c8f7

ccecf094-ff51-4c78-81c3-46578263c8f7

ccecf094-ff51-4c78-81c3-46578263c8f7

human

none

abstracts

Quantum mechanical approach to decoherence and relaxation generated by fluctuating environment

We consider an electrostatic qubit, interacting with a fluctuating charge of single electron transistor (SET) in the framework of exactly solvable model. The SET plays a role of the fluctuating environment affecting the qubit's parameters in a controllable way. We derive the rate equations describing dynamics of the entire system for both weak and strong qubit-SET coupling. Solving these equation we obtain decoherence and relaxation rates of the qubit, as well as the spectral density of the fluctuating qubit's parameters. We found that in the weak coupling regime the decoherence and relaxation rates are directly related to the spectral density taken at Rabi or at zero frequency, depending on what a particular qubit's parameters is fluctuating. This relation holds also in the presence of weak back-action of the qubit on the fluctuating environment. In the case of strong back-action, such simple relationship no longer holds, even if the qubit-SET coupling is small. It does not hold eit

0bd532ca-dd6e-43a8-9db4-f1a15924b3be

0bd532ca-dd6e-43a8-9db4-f1a15924b3be

0bd532ca-dd6e-43a8-9db4-f1a15924b3be

human

none

abstracts

Analysis of random Boolean networks using the average sensitivity

In this work we consider random Boolean networks that provide a general model for genetic regulatory networks. We extend the analysis of James Lynch who was able to proof Kauffman's conjecture that in the ordered phase of random networks, the number of ineffective and freezing gates is large, where as in the disordered phase their number is small. Lynch proved the conjecture only for networks with connectivity two and non-uniform probabilities for the Boolean functions. We show how to apply the proof to networks with arbitrary connectivity $K$ and to random networks with biased Boolean functions. It turns out that in these cases Lynch's parameter $\lambda$ is equivalent to the expectation of average sensitivity of the Boolean functions used to construct the network. Hence we can apply a known theorem for the expectation of the average sensitivity. In order to prove the results for networks with biased functions, we deduct the expectation of the average sensitivity when only functions

e0bf458e-2d27-4a56-aa46-3c8f73190bcd

e0bf458e-2d27-4a56-aa46-3c8f73190bcd

e0bf458e-2d27-4a56-aa46-3c8f73190bcd

human

none

abstracts

Chandra Observations of Supernova 1987A

We have been monitoring Supernova (SN) 1987A with {\it Chandra X-Ray Observatory} since 1999. We present a review of previous results from our {\it Chandra} observations, and some preliminary results from new {\it Chandra} data obtained in 2006 and 2007. High resolution imaging and spectroscopic studies of SN 1987A with {\it Chandra} reveal that X-ray emission of SN 1987A originates from the hot gas heated by interaction of the blast wave with the ring-like dense circumstellar medium (CSM) that was produced by the massive progenitor's equatorial stellar winds before the SN explosion. The blast wave is now sweeping through dense CSM all around the inner ring, and thus SN 1987A is rapidly brightening in soft X-rays. At the age of 20 yr (as of 2007 January), X-ray luminosity of SN 1987A is $L_{\rm X}$ $\sim$ 2.4 $\times$ 10$^{36}$ ergs s$^{-1}$ in the 0.5$-$10 keV band. X-ray emission is described by two-component plane shock model with electron temperatures of $kT$ $\sim$ 0.3 and 2 keV

d58157b5-89e1-4965-808d-1df408e537e0

d58157b5-89e1-4965-808d-1df408e537e0

d58157b5-89e1-4965-808d-1df408e537e0

human

none

abstracts

Three Particle Correlations from STAR

Two-particle correlations have shown modification to the away-side shape in central Au+Au collisions relative to $pp$, d+Au and peripheral Au+Au collisions. Different scenarios can explain this modification including: large angle gluon radiation, jets deflected by transverse flow, path length dependent energy loss, Cerenkov gluon radiation of fast moving particles, and conical flow generated by hydrodynamic Mach-cone shock-waves. Three-particle correlations have the power to distinguish the scenarios with conical emission, conical flow and Cerenkov radiation, from other scenarios. In addition, the dependence of the observed shapes on the $p_T$ of the associated particles can be used to distinguish conical emission from a sonic boom (Mach-cone) and from QCD-Cerenkov radiation. We present results from STAR on 3-particle azimuthal correlations for a high $p_T$ trigger particle with two softer particles. Results are shown for $pp$, d+Au and high statistics Au+Au collisions at $\sqrt{s_{N

798b451f-518a-49b9-9f47-910fafe66fa0

798b451f-518a-49b9-9f47-910fafe66fa0

798b451f-518a-49b9-9f47-910fafe66fa0

human

none

abstracts

Correlated modulation between the redshifted Fe K alpha line and the continuum emission in NGC 3783

It has been suggested that X-ray observations of rapidly variable Seyfert galaxies may hold the key to probe the gas orbital motions in the innermost regions of accretion discs around black holes and, thus, trace flow patterns under the effect of the hole strong gravitational field. We explore this possibility analizing XMM-Newton observations of the seyfert 1 galaxy NGC 3783. A detiled time-resolved spectral analysis is performed down to the shortest possible time-scales (few ks) using "excess maps" and cross-correlating light curves in different energy bands. In addition to a constant core of the Fe K alpha line, we detected a variable and redshifted Fe K alpha emission feature between 5.3-6.1 keV. The line exhibits a modulation on a time-scale of 27 ks that is similar to and in phase with a modulation of the 0.3-10 keV source continuum. The time-scale of the correlated variability of the redshifted Fe line and continuum agrees with the local dynamical time-scale of the accretion d

0c82de12-1e7c-478f-a613-401c8cfea68a

0c82de12-1e7c-478f-a613-401c8cfea68a

0c82de12-1e7c-478f-a613-401c8cfea68a

human

none

abstracts

Two new basaltic asteroids in the Outer Main Belt?

The identification of basaltic asteroids in the asteroid Main Belt and the description of their surface mineralogy is necessary to understand the diversity in the collection of basaltic meteorites. Basaltic asteroids can be identified from their visible reflectance spectra and are classified as V-type in the usual taxonomies. In this work, we report visible spectroscopic observations of two candidate V-type asteroids, (7472) Kumakiri and (10537) 1991 RY16, located in the outer Main Belt (a > 2.85 UA). These candidate have been previously identified by Roig and Gil-Hutton (2006, Icarus 183, 411) using the Sloan Digital Sky Survey colors. The spectroscopic observations have been obtained at the Calar Alto Observatory, Spain, during observational runs in November and December 2006. The spectra of these two asteroids show the steep slope shortwards of 0.70 microns and the deep absorption feature longwards of 0.75 microns that are characteristic of V-type asteroids. However, the presence

3bb6b5e6-10f9-4d34-ab88-21ac7ff28c53

3bb6b5e6-10f9-4d34-ab88-21ac7ff28c53

3bb6b5e6-10f9-4d34-ab88-21ac7ff28c53

human

none

abstracts

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds VIII. Serpens Observed with MIPS

We present maps of 1.5 square degrees of the Serpens dark cloud at 24, 70, and 160\micron observed with the Spitzer Space Telescope MIPS Camera. More than 2400 compact sources have been extracted at 24um, nearly 100 at 70um, and 4 at 160um. We estimate completeness limits for our 24um survey from Monte Carlo tests with artificial sources inserted into the Spitzer maps. We compare source counts, colors, and magnitudes in the Serpens cloud to two reference data sets, a 0.50 deg^2 set on a low-extinction region near the dark cloud, and a 5.3 deg^2 subset of the SWIRE ELAIS N1 data that was processed through our pipeline. These results show that there is an easily identifiable population of young stellar object candidates in the Serpens Cloud that is not present in either of the reference data sets. We also show a comparison of visual extinction and cool dust emission illustrating a close correlation between the two, and find that the most embedded YSO candidates are located in the areas

abeec449-9e17-4660-9813-9ff77735ab4f

abeec449-9e17-4660-9813-9ff77735ab4f

abeec449-9e17-4660-9813-9ff77735ab4f

human

none

abstracts

Modeling the three-point correlation function

We present new predictions for the galaxy three-point correlation function (3PCF) using high-resolution dissipationless cosmological simulations of a flat LCDM Universe which resolve galaxy-size halos and subhalos. We create realistic mock galaxy catalogs by assigning luminosities and colors to dark matter halos and subhalos, and we measure the reduced 3PCF as a function of luminosity and color in both real and redshift space. As galaxy luminosity and color are varied, we find small differences in the amplitude and shape dependence of the reduced 3PCF, at a level qualitatively consistent with recent measurements from the SDSS and 2dFGRS. We confirm that discrepancies between previous 3PCF measurements can be explained in part by differences in binning choices. We explore the degree to which a simple local bias model can fit the simulated 3PCF. The agreement between the model predictions and galaxy 3PCF measurements lends further credence to the straightforward association of galaxies

18d5cd73-8cb8-4380-b4b3-a0c7890b048a

18d5cd73-8cb8-4380-b4b3-a0c7890b048a

18d5cd73-8cb8-4380-b4b3-a0c7890b048a

human

none

abstracts

Formation and Collisional Evolution of Kuiper Belt Objects

This chapter summarizes analytic theory and numerical calculations for the formation and collisional evolution of KBOs at 20--150 AU. We describe the main predictions of a baseline self-stirring model and show how dynamical perturbations from a stellar flyby or stirring by a giant planet modify the evolution. Although robust comparisons between observations and theory require better KBO statistics and more comprehensive calculations, the data are broadly consistent with KBO formation in a massive disk followed by substantial collisional grinding and dynamical ejection. However, there are important problems reconciling the results of coagulation and dynamical calculations. Contrasting our current understanding of the evolution of KBOs and asteroids suggests that additional observational constraints, such as the identification of more dynamical families of KBOs (like the 2003 EL61 family), would provide additional information on the relative roles of collisional grinding and dynamical

91ffdb6a-58e2-4fe7-9719-7354cf122c14

91ffdb6a-58e2-4fe7-9719-7354cf122c14

91ffdb6a-58e2-4fe7-9719-7354cf122c14

human

none

abstracts

REM near-IR and optical multiband observations of PKS2155-304 in 2005

Spectral variability is the main tool for constraining emission models of BL Lac objects. By means of systematic observations of the BL Lac prototype PKS 2155-304 in the infrared-optical band, we explore variability on the scales of months, days and hours. We made our observations with the robotic 60 cm telescope REM located at La Silla, Chile. VRIJHK filters were used. PKS 2155-304 was observed from May to December 2005. The wavelength interval explored, the total number of photometric points and the short integration time render our photometry substantially superior to previous ones for this source. On the basis of the intensity and colour we distinguish three different states of the source, each of duration of months, which include all those described in the literature. In particular, we report the highest state ever detected in the H band. The source varied by a factor of 4 in this band, much more than in the V band (a factor ~2). The source softened with increasing intensity,

49dccba9-0f4c-40db-8d75-64197114e7c7

49dccba9-0f4c-40db-8d75-64197114e7c7

49dccba9-0f4c-40db-8d75-64197114e7c7

human

none

abstracts

Near-Infrared Spectra of the Black Hole X-Ray Binary, A0620-00

We present broadband NIR spectra of A0620-00 obtained with SpeX on the IRTF. The spectrum is characterized by a blue continuum on which are superimposed broad emission lines of HI and HeII and a host of narrower absorption lines of neutral metals and molecules. Spectral type standard star spectra scaled to the dereddened spectrum of A0620-00 in K exceed the A0620-00 spectrum in J and H for all stars of spectral type K7V or earlier, demonstrating that the donor star, unless later than K7V, cannot be the sole NIR flux source in A0620-00. In addition, the atomic absorption lines in the K3V spectrum are too weak with respect to those of A0620-00 even at 100% donor star contribution, restricting the spectral type of the donor star in A0620-00 to later than K3V. Comparison of the A0620-00 spectrum to scaled K star spectra indicates that the CO absorption features are significantly weaker in A0620-00 than in field dwarf stars. Fits of scaled model spectra of a Roche lobe-filling donor star

1461a7a8-efe4-4e9e-b55b-3dc720e571a8

1461a7a8-efe4-4e9e-b55b-3dc720e571a8

1461a7a8-efe4-4e9e-b55b-3dc720e571a8

human

none

abstracts

Modeling the Spectral Energy Distribution and Variability of 3C 66A during the WEBT campaign of 2003 -- 2004

The BL Lac object 3C 66A was observed in an extensive multiwavelength monitoring campaign from July 2003 till April 2004. The spectral energy distribution (SED) was measured over the entire electromagnetic spectrum, with flux measurements from radio to X-ray frequencies and upper limits in the very high energy (VHE) gamma-ray regime. Here, we use a time-dependent leptonic jet model to reproduce the SED and optical spectral variability observed during our multiwavelength campaign. Our model simulations could successfully reproduce the observed SED and optical light curves and predict an intrinsic cutoff value for the VHE gamma-ray emission at ~ 4 GeV. The effect of the optical depth due to the intergalactic infrared background radiation (IIBR) on the peak of the high-energy component of 3C 66A was found to be negligible. Also, the presence of a broad line region (BLR) in the case of 3C 66A may play an important role in the emission of gamma-ray photons when the emission region is very

e53762cb-25e7-47c1-abda-1b50ed05eeef

e53762cb-25e7-47c1-abda-1b50ed05eeef

e53762cb-25e7-47c1-abda-1b50ed05eeef

human

none

abstracts

The HARPS search for southern extra-solar planets. X. A m sin i = 11 Mearth planet around the nearby spotted M dwarf GJ 674

Context: How planet properties depend on stellar mass is a key diagnostic of planetary formation mechanisms. Aims: This motivates planet searches around stars which are significantly more massive or less massive than the Sun, and in particular our radial velocity search for planets around very-low mass stars. Methods: As part of that program, we obtained measurements of GJ 674, an M2.5 dwarf at d=4.5 pc, which have a dispersion much in excess of their internal errors. An intensive observing campaign demonstrates that the excess dispersion is due to two superimposed coherent signals, with periods of 4.69 and 35 days. Results: These data are well described by a 2-planet Keplerian model where each planet has a ~11 Mearth minimum mass. A careful analysis of the (low level) magnetic activity of GJ 674 however demonstrates that the 35-day period coincides with the stellar rotation period. This signal therefore originates in a spot inhomogeneity modulated by stellar rotation. The 4.69-day s

a4315e0a-d969-41e2-bd13-114b80d39c37

a4315e0a-d969-41e2-bd13-114b80d39c37

a4315e0a-d969-41e2-bd13-114b80d39c37

human

none

abstracts

A Comparison between Anomalous 6-cm H$_2$CO Absorption and CO(1-0) Emission in the L1204/S140

We report observations of the dust cloud L1204 with the Onsala 25-m telescope in the 6 cm (1$_{11}-1_{10}$) transition of \htco. The observed region includes the S140 H${\alpha}$ arc. This spectral line is seen here in absorption against the cosmic microwave background, indicating the presence of widespread warm molecular gas at intermediate densities. Overall, the distributions of H$_2$CO and CO (taken from the literature) are fairly similar, though significant differences exist at small scales. Most notably, while the CO peak is nearly coincident with the S140 H${\alpha}$ arc, the maximum H$_2$CO absorption is clearly separated from it by a full 10$'$ beam ($\sim$ 3 pc). We argue that these differences result from differing abundances and excitation requirements. The CO(1-0) line is more optically thick and more biased towards warm gas than the H$_2$CO 6 cm line. On the other hand, formaldehyde is more easily photodissociated and is, therefore, a poorer tracer of the molecular ga

a97afc6f-2dac-414d-bd39-43b170a8a5ea

a97afc6f-2dac-414d-bd39-43b170a8a5ea

a97afc6f-2dac-414d-bd39-43b170a8a5ea

human

none

abstracts

Common Envelope Evolution Redux

Common envelopes form in dynamical time scale mass exchange, when the envelope of a donor star engulfs a much denser companion, and the core of the donor plus the dense companion star spiral inward through this dissipative envelope. As conceived by Paczynski and Ostriker, this process must be responsible for the creation of short-period binaries with degenerate components, and, indeed, it has proven capable of accounting for short-period binaries containing one white dwarf component. However, attempts to reconstruct the evolutionary histories of close double white dwarfs have proven more problematic, and point to the need for enhanced systemic mass loss, either during the close of the first, slow episode of mass transfer that produced the first white dwarf, or during the detached phase preceding the final, common envelope episode. The survival of long-period interacting binaries with massive white dwarfs, such as the recurrent novae T CrB and RS Oph, also presents interpretative diff

6a164ec9-8fa2-4fc1-9214-2bf11baceb1c

6a164ec9-8fa2-4fc1-9214-2bf11baceb1c

6a164ec9-8fa2-4fc1-9214-2bf11baceb1c

human

none

abstracts

Epitaxial graphene

Graphene multilayers are grown epitaxially on single crystal silicon carbide. This system is composed of several graphene layers of which the first layer is electron doped due to the built-in electric field and the other layers are essentially undoped. Unlike graphite the charge carriers show Dirac particle properties (i.e. an anomalous Berry's phase, weak anti-localization and square root field dependence of the Landau level energies). Epitaxial graphene shows quasi-ballistic transport and long coherence lengths; properties which may persists above cryogenic temperatures. Paradoxically, in contrast to exfoliated graphene, the quantum Hall effect is not observed in high mobility epitaxial graphene. It appears that the effect is suppressed due to absence of localized states in the bulk of the material.Epitaxial graphene can be patterned using standard lithography methods and characterized using a wide array of techniques. These favorable features indicate that interconnected room temp

7018d626-6d5b-47a3-bfff-d84aa4a65eb3

7018d626-6d5b-47a3-bfff-d84aa4a65eb3

7018d626-6d5b-47a3-bfff-d84aa4a65eb3

human

none

abstracts

The core binary fractions of star clusters from realistic simulations

We investigate the evolution of binary fractions in star clusters using N-body models of up to 100000 stars. Primordial binary frequencies in these models range from 5% to 50%. Simulations are performed with the NBODY4 code and include a full mass spectrum of stars, stellar evolution, binary evolution and the tidal field of the Galaxy. We find that the overall binary fraction of a cluster almost always remains close to the primordial value, except at late times when a cluster is near dissolution. A critical exception occurs in the central regions where we observe a marked increase in binary fraction with time -- a simulation starting with 100000 stars and 5% binaries reached a core binary frequency as high as 40% at the end of the core-collapse phase (occurring at 16 Gyr with ~20000 stars remaining). Binaries are destroyed in the core by a variety of processes as a cluster evolves, but the combination of mass-segregation and creation of new binaries in exchange interactions produces

29eb6639-77fd-4e94-be57-e4405a6401e3

29eb6639-77fd-4e94-be57-e4405a6401e3

29eb6639-77fd-4e94-be57-e4405a6401e3

human

none

abstracts

A practical Seedless Infrared-Safe Cone jet algorithm

Current cone jet algorithms, widely used at hadron colliders, take event particles as seeds in an iterative search for stable cones. A longstanding infrared (IR) unsafety issue in such algorithms is often assumed to be solvable by adding extra `midpoint' seeds, but actually is just postponed to one order higher in the coupling. A proper solution is to switch to an exact seedless cone algorithm, one that provably identifies all stable cones. The only existing approach takes N 2^N time to find jets among N particles, making it unusable at hadron level. This can be reduced to N^2 ln(N) time, leading to code (SISCone) whose speed is similar to that of public midpoint implementations. Monte Carlo tests provide a strong cross-check of an analytical proof of the IR safety of the new algorithm, and the absence of any 'R_{sep}' issue implies a good practical correspondence between parton and hadron levels. Relative to a midpoint cone, the use of an IR safe seedless algorithm leads to modest c

e08a78ed-403e-4371-890b-33d0f1c1e6f3

e08a78ed-403e-4371-890b-33d0f1c1e6f3

e08a78ed-403e-4371-890b-33d0f1c1e6f3

human

none

abstracts

Isospin breaking in the yield of heavy meson pairs in e+e- annihilation near threshold

We revisit the problem of interplay between the strong and the Coulomb interaction in the charged-to-neutral yield ratio for $B {\bar B}$ and $D {\bar D}$ pairs near their respective thresholds in $e^+e^-$ annihilation. We consider here a realistic situation with a resonant interaction in the isospin I=0 channel and a nonresonant strong scattering amplitude in the I=1 state. We find that the yield ratio has a smooth behavior depending on the scattering phase in the I=1 channel. The same approach is also applicable to the $K {\bar K}$ production at the $\phi(1020)$ resonance, where the Coulomb effect in the charged-to-neutral yield ratio is generally sensitive to the scattering phases in both the isoscalar and the isovector channels. Furthermore, we apply the same approach to the treatment of the effect of the isotopic mass difference between the charged and neutral mesons and argue that the strong-scattering effects generally result in a modification to the pure kinematical effect of

0171a81d-39ee-4d2d-a197-6701744d59df

0171a81d-39ee-4d2d-a197-6701744d59df

0171a81d-39ee-4d2d-a197-6701744d59df

human

none

abstracts

On the number of topological types occurring in a parametrized family of arrangements

Let ${\mathcal S}(\R)$ be an o-minimal structure over $\R$, $T \subset \R^{k_1+k_2+\ell}$ a closed definable set, and $$ \displaylines{\pi_1: \R^{k_1+k_2+\ell}\to \R^{k_1 + k_2}, \pi_2: \R^{k_1+k_2+\ell}\to \R^{\ell}, \ \pi_3: \R^{k_1 + k_2} \to \R^{k_2}} $$ the projection maps. For any collection ${\mathcal A} = \{A_1,...,A_n\}$ of subsets of $\R^{k_1+k_2}$, and $\z \in \R^{k_2}$, let $\A_\z$ denote the collection of subsets of $\R^{k_1}$, $\{A_{1,\z},..., A_{n,\z}\}$, where $A_{i,\z} = A_i \cap \pi_3^{-1}(\z), 1 \leq i \leq n$. We prove that there exists a constant $C = C(T) > 0,$ such that for any family ${\mathcal A} = \{A_1,...,A_n\}$ of definable sets, where each $A_i = \pi_1(T \cap \pi_2^{-1}(\y_i))$, for some $\y_i \in \R^{\ell}$, the number of distinct stable homotopy types of $\A_\z, \z \in \R^{k_2}$, is bounded by $ \displaystyle{C \cdot n^{(k_1+1)k_2},} $ while the number of distinct homotopy types is bounded by $ \displaystyle{C \cdot n^{(k_1+3)k_2}.} $ This generalize

eb657ebc-6ac8-4a0f-93d4-0fb6ad89a5bb

eb657ebc-6ac8-4a0f-93d4-0fb6ad89a5bb

eb657ebc-6ac8-4a0f-93d4-0fb6ad89a5bb

human

none

abstracts

Generalized Twistor Transform And Dualities, With A New Description of Particles With Spin, Beyond Free and Massless

A generalized twistor transform for spinning particles in 3+1 dimensions is constructed that beautifully unifies many types of spinning systems by mapping them to the same twistor, thus predicting an infinite set of duality relations among spinning systems with different Hamiltonians. Usual 1T-physics is not equipped to explain the duality relationships and unification between these systems. We use 2T-physics in 4+2 dimensions to uncover new properties of twistors, and expect that our approach will prove to be useful for practical applications as well as for a deeper understanding of fundamental physics. Unexpected structures for a new description of spinning particles emerge. A unifying symmetry SU(2,3) that includes conformal symmetry SU(2,2)=SO(4,2) in the massless case, turns out to be a fundamental property underlying the dualities of a large set of spinning systems, including those that occur in high spin theories. This may lead to new forms of string theory backgrounds as well

cfb31d0c-ace4-4c88-883d-c38afe1ba1ba

cfb31d0c-ace4-4c88-883d-c38afe1ba1ba

cfb31d0c-ace4-4c88-883d-c38afe1ba1ba

human

none

abstracts

Parametrized Post-Newtonian Expansion of Chern-Simons Gravity

We investigate the weak-field, post-Newtonian expansion to the solution of the field equations in Chern-Simons gravity with a perfect fluid source. In particular, we study the mapping of this solution to the parameterized post-Newtonian formalism to 1 PN order in the metric. We find that the PPN parameters of Chern-Simons gravity are identical to those of general relativity, with the exception of the inclusion of a new term that is proportional to the Chern-Simons coupling parameter and the curl of the PPN vector potentials. We also find that the new term is naturally enhanced by the non-linearity of spacetime and we provide a physical interpretation for it. By mapping this correction to the gravito-electro-magnetic framework, we study the corrections that this new term introduces to the acceleration of point particles and the frame-dragging effect in gyroscopic precession. We find that the Chern-Simons correction to these classical predictions could be used by current and future exp

7c57238f-a8ed-4ab7-a9d9-ecfc58879df2

7c57238f-a8ed-4ab7-a9d9-ecfc58879df2

7c57238f-a8ed-4ab7-a9d9-ecfc58879df2

human

none

abstracts

Spline Single-Index Prediction Model

For the past two decades, single-index model, a special case of projection pursuit regression, has proven to be an efficient way of coping with the high dimensional problem in nonparametric regression. In this paper, based on weakly dependent sample, we investigate the single-index prediction (SIP) model which is robust against deviation from the single-index model. The single-index is identified by the best approximation to the multivariate prediction function of the response variable, regardless of whether the prediction function is a genuine single-index function. A polynomial spline estimator is proposed for the single-index prediction coefficients, and is shown to be root-n consistent and asymptotically normal. An iterative optimization routine is used which is sufficiently fast for the user to analyze large data of high dimension within seconds. Simulation experiments have provided strong evidence that corroborates with the asymptotic theory. Application of the proposed procedu

e6c3a340-90e6-4c34-9707-d34da98c5aca

e6c3a340-90e6-4c34-9707-d34da98c5aca

e6c3a340-90e6-4c34-9707-d34da98c5aca

human

none

abstracts

Measurement of the Aerosol Phase Function at the Pierre Auger Observatory

Air fluorescence detectors measure the energy of ultra-high energy cosmic rays by collecting fluorescence light emitted from nitrogen molecules along the extensive air shower cascade. To ensure a reliable energy determination, the light signal needs to be corrected for atmospheric effects, which not only attenuate the signal, but also produce a non-negligible background component due to scattered Cherenkov light and multiple-scattered light. The correction requires regular measurements of the aerosol attenuation length and the aerosol phase function, defined as the probability of light scattered in a given direction. At the Pierre Auger Observatory in Malargue, Argentina, the phase function is measured on an hourly basis using two Aerosol Phase Function (APF) light sources. These sources direct a UV light beam across the field of view of the fluorescence detectors; the phase function can be extracted from the image of the shots in the fluorescence detector cameras. This paper describ

ec8fd9c9-221a-471d-8d51-6aab539ca059

ec8fd9c9-221a-471d-8d51-6aab539ca059

ec8fd9c9-221a-471d-8d51-6aab539ca059

human

none

abstracts

Periodic accretion from a circumbinary disk in the young binary UZ Tau E

Close pre-main-sequence binary stars are expected to clear central holes in their protoplanetary disks, but the extent to which material can flow from the circumbinary disk across the gap onto the individual circumstellar disks has been unclear. In binaries with eccentric orbits, periodic perturbation of the outer disk is predicted to induce mass flow across the gap, resulting in accretion that varies with the binary period. This accretion may manifest itself observationally as periodic changes in luminosity. Here we present a search for such periodic accretion in the pre-main-sequence spectroscopic binary UZ Tau E. We present BVRI photometry spanning three years; we find that the brightness of UZ Tau E is clearly periodic, with a best-fit period of 19.16 +/- 0.04 days. This is consistent with the spectroscopic binary period of 19.13 days, refined here from analysis of new and existing radial velocity data. The brightness of UZ Tau E shows significant random variability, but the over

0a1c4696-26f8-487d-81c8-d0c534a233f6

0a1c4696-26f8-487d-81c8-d0c534a233f6

0a1c4696-26f8-487d-81c8-d0c534a233f6

human

none

abstracts

Effect of node deleting on network structure

The ever-increasing knowledge of the structure of various real-world networks has uncovered their complex multi-mechanism-governed evolution processes. Therefore, a better understanding of the structure and evolution of these networked complex systems requires us to describe such processes in a more detailed and realistic manner. In this paper, we introduce a new type of network growth rule which comprises addition and deletion of nodes, and propose an evolving network model to investigate the effect of node deleting on network structure. It is found that, with the introduction of node deleting, network structure is significantly transformed. In particular, degree distribution of the network undergoes a transition from scale-free to exponential forms as the intensity of node deleting increases. At the same time, nontrivial disassortative degree correlation develops spontaneously as a natural result of network evolution in the model. We also demonstrate that node deleting introduced i

112a8ffb-e19f-4b4c-8784-0c427e1c1c53

112a8ffb-e19f-4b4c-8784-0c427e1c1c53

112a8ffb-e19f-4b4c-8784-0c427e1c1c53

human

none

abstracts

VLBI observations of nineteen GHz-Peaked-Spectrum radio sources at 1.6 GHz

Aims and Methods: We present the results of VLBI observations of nineteen GHz-Peaked-Spectrum (GPS) radio sources at 1.6 GHz. Of them, 15 sources are selected from the Parkes Half Jansky (PHJ) sample (Snellen 2002), 4 others are from our previous observation list. We aimed at imaging the structure of GPS sources, searching for Compact Symmetric Objects (CSOs) and studying the absorption for the convex radio spectra of GPS sources. Results: We obtained total intensity 1.6 GHz VLBI images of 17 sources for the first time. Of them, 80% show mini-double-lobe radio structure, indicating that they are CSOs or candidates, and their host AGNs could be edge-on to us. This result suggests that there is a high incidence of mini double-lobe sources (or CSOs) in the PHJ sample. The sources J0323+0534, J1135-0021, J1352+0232, J2058+0540, J2123-0112 and J2325-0344 with measured redshift, showing double-lobe structure with sizes of <1 kpc, are classified as CSOs. Three sources J1057+0012, J1600-00

55a86b14-0078-4eba-9dcf-cdb05234c76c

55a86b14-0078-4eba-9dcf-cdb05234c76c

55a86b14-0078-4eba-9dcf-cdb05234c76c

human

none

abstracts

Effects of Dirac sea on pion propagation in asymmetric nuclear matter

We study pion propagation in asymmetric nuclear matter (ANM). One of the interesting consequences of pion propagation in ANM is the mode splitting for the different charged states of pions. First we describe the pion-nucleon dynamics using the non-chiral model where one starts with pseudoscalar (PS) $\pi$N coupling and the pseudovector (PV) representation is obtained via suitable non-linear field transformations. For both of these cases the effect of the Dirac sea is estimated. Subsequently, we present results using the chiral effective Lagrangian where the short-distance behavior (Dirac vacuum) is included by re-defining the field parameters as done in the modern effective field theory approach developed recently. The results are compared with the previous calculations for the case of symmetric nuclear matter (SNM). Closed form analytical results are presented for the effective pion masses and dispersion relations by making hard nucleon loop (HNL) approximation and suitable density

c9fec9b6-d8c9-4e5b-847d-5b494a5903c3

c9fec9b6-d8c9-4e5b-847d-5b494a5903c3

c9fec9b6-d8c9-4e5b-847d-5b494a5903c3

human

none

abstracts

Fabrication of half metallicity in a ferromagnetic metal

We investigate the growth of half metallic phase in a ferromagnetic material using state-of-the-art full potential linearized augmented plane wave method. To address the issue, we have substituted Ti at the Ru-sites in SrRuO3, where SrRuO3 is a ferromagnetic material. Calculated results establish Ti4+ valence states (similar to SrTiO3), which was predicted experimentally. Thus, Ti substitution dilutes the Ru-O-Ru connectivity, which is manifested in the calculated results in the form of significant band narrowing leading to finite gap between t2g and eg bands. At 75% substitution, a large gap (> 2 eV) appears at the Fermi level, e_F in the up spin density of states, while the down spin states contributes at e_F characterizing the system a half-metallic ferromagnet. The t2g - eg gap can be tailored judiciously by tuning Ti concentrations to minimize thermal effects, which is often the major bottleneck to achieve high spin polarization at elevated temperatures in other materials. This

fba8097c-eb5d-4ee8-8b43-4ac3440cad05

fba8097c-eb5d-4ee8-8b43-4ac3440cad05

fba8097c-eb5d-4ee8-8b43-4ac3440cad05

human

none

abstracts

Emergence of spatiotemporal chaos driven by far-field breakup of spiral waves in the plankton ecological systems

Alexander B. Medvinsky \emph{et al} [A. B. Medvinsky, I. A. Tikhonova, R. R. Aliev, B.-L. Li, Z.-S. Lin, and H. Malchow, Phys. Rev. E \textbf{64}, 021915 (2001)] and Marcus R. Garvie \emph{et al} [M. R. Garvie and C. Trenchea, SIAM J. Control. Optim. \textbf{46}, 775-791 (2007)] shown that the minimal spatially extended reaction-diffusion model of phytoplankton-zooplankton can exhibit both regular, chaotic behavior, and spatiotemporal patterns in a patchy environment. Based on that, the spatial plankton model is furtherly investigated by means of computer simulations and theoretical analysis in the present paper when its parameters would be expected in the case of mixed Turing-Hopf bifurcation region. Our results show that the spiral waves exist in that region and the spatiotemporal chaos emerge, which arise from the far-field breakup of the spiral waves over large ranges of diffusion coefficients of phytoplankton and zooplankton. Moreover, the spatiotemporal chaos arising from the f

4ecc493f-dc52-404c-9c61-f5c8c5c05465

4ecc493f-dc52-404c-9c61-f5c8c5c05465

4ecc493f-dc52-404c-9c61-f5c8c5c05465

human

none

abstracts

On the pseudospectrum of elliptic quadratic differential operators

We study the pseudospectrum of a class of non-selfadjoint differential operators. Our work consists in a detailed study of the microlocal properties, which rule the spectral stability or instability phenomena appearing under small perturbations for elliptic quadratic differential operators. The class of elliptic quadratic differential operators stands for the class of operators defined in the Weyl quantization by complex-valued elliptic quadratic symbols. We establish in this paper a simple necessary and sufficient condition on the Weyl symbol of these operators, which ensures the stability of their spectra. When this condition is violated, we prove that it occurs some strong spectral instabilities for the high energies of these operators, in some regions which can be far away from their spectra. We give a precise geometrical description of them, which explains the results obtained for these operators in some numerical simulations giving the computation of false eigenvalues far from

b8abebe2-3287-49b8-9b5c-6b5a051ab198

b8abebe2-3287-49b8-9b5c-6b5a051ab198

b8abebe2-3287-49b8-9b5c-6b5a051ab198

human

none

abstracts

On generalized entropy measures and pathways

Product probability property, known in the literature as statistical independence, is examined first. Then generalized entropies are introduced, all of which give generalizations to Shannon entropy. It is shown that the nature of the recursivity postulate automatically determines the logarithmic functional form for Shannon entropy. Due to the logarithmic nature, Shannon entropy naturally gives rise to additivity, when applied to situations having product probability property. It is argued that the natural process is non-additivity, important, for example, in statistical mechanics, even in product probability property situations and additivity can hold due to the involvement of a recursivity postulate leading to a logarithmic function. Generalizations, including Mathai's generalized entropy are introduced and some of the properties are examined. Situations are examined where Mathai's entropy leads to pathway models, exponential and power law behavior and related differential equations

6c90aab2-aacd-4f2e-8aec-20aca8f3d76c

6c90aab2-aacd-4f2e-8aec-20aca8f3d76c

6c90aab2-aacd-4f2e-8aec-20aca8f3d76c

human

none

abstracts

Solutions of fractional reaction-diffusion equations in terms of the H-function

This paper deals with the investigation of the solution of an unified fractional reaction-diffusion equation associated with the Caputo derivative as the time-derivative and Riesz-Feller fractional derivative as the space-derivative. The solution is derived by the application of the Laplace and Fourier transforms in closed form in terms of the H-function. The results derived are of general nature and include the results investigated earlier by many authors, notably by Mainardi et al. (2001, 2005) for the fundamental solution of the space-time fractional diffusion equation, and Saxena et al. (2006a, b) for fractional reaction- diffusion equations. The advantage of using Riesz-Feller derivative lies in the fact that the solution of the fractional reaction-diffusion equation containing this derivative includes the fundamental solution for space-time fractional diffusion, which itself is a generalization of neutral fractional diffusion, space-fractional diffusion, and time-fractional dif

79e22e6c-8f6f-43fe-a872-70cc57898d48

79e22e6c-8f6f-43fe-a872-70cc57898d48

79e22e6c-8f6f-43fe-a872-70cc57898d48

human

none

abstracts

The effect of a fifth large-scale space-time dimension on the conservation of energy in a four dimensional Universe

The effect of introducing a fifth large-scale space-time dimension to the equations of orbital dynamics was analysed in an earlier paper by the authors. The results showed good agreement with the observed flat rotation curves of galaxies and the Pioneer Anomaly. This analysis did not require the modification of Newtonian dynamics, but rather only their restatement in a five dimensional framework. The same analysis derived a acceleration parameter ar, which plays an important role in the restated equations of orbital dynamics, and suggested a value for ar. In this companion paper, the principle of conservation of energy is restated within the same five-dimensional framework. The resulting analysis provides an alternative route to estimating the value of ar, without reference to the equations of orbital dynamics, and based solely on key cosmological constants and parameters, including the gravitational constant, G. The same analysis suggests that: (i) the inverse square law of gravity

94f6c9b0-8183-493f-8530-7aaaa335fb48

94f6c9b0-8183-493f-8530-7aaaa335fb48

94f6c9b0-8183-493f-8530-7aaaa335fb48

human

none

abstracts

A Multiphilic Descriptor for Chemical Reactivity and Selectivity

In line with the local philicity concept proposed by Chattaraj et al. (Chattaraj, P. K.; Maiti, B.; Sarkar, U. J. Phys. Chem. A. 2003, 107, 4973) and a dual descriptor derived by Toro-Labbe and coworkers (Morell, C.; Grand, A.; Toro-Labbe, A. J. Phys. Chem. A. 2005, 109, 205), we propose a multiphilic descriptor. It is defined as the difference between nucleophilic (Wk+) and electrophilic (Wk-) condensed philicity functions. This descriptor is capable of simultaneously explaining the nucleophilicity and electrophilicity of the given atomic sites in the molecule. Variation of these quantities along the path of a soft reaction is also analyzed. Predictive ability of this descriptor has been successfully tested on the selected systems and reactions. Corresponding force profiles are also analyzed in some representative cases. Also, to study the intra- and intermolecular reactivities another related descriptor namely, the nucleophilicity excess (DelW-+) for a nucleophile, over the electro

ae3a9df3-d5bc-4bcd-a420-84e46f358f33

ae3a9df3-d5bc-4bcd-a420-84e46f358f33

ae3a9df3-d5bc-4bcd-a420-84e46f358f33

human

none

abstracts

Synergistic Effects of MoDTC and ZDTP on Frictional Behaviour of Tribofilms at the Nanometer Scale

The layered structure and the rheological properties of anti-wear films, generated in a rolling/sliding contact from lubricants containing zinc dialkyldithiophosphate (ZDTP) and/or molybdenum dialkyldithiocarbamate (MoDTC) additives, have been studied by dynamic nanoindentation experiments coupled with a simple modelling of the stiffness measurements. Local nano-friction experiments were conducted with the same device in order to determine the evolution of the friction coefficient as a function of the applied pressure for the different lubricant formulations. For the MoDTC film, the applied pressure in the friction test remains low (<0.5 GPa) and the apparent friction coefficient is high ($\mu$ > 0.4). For the tribofilms containing MoDTC together with ZDTP, which permits the applied pressure to increase up to a few GPa through some accommodation process, a very low friction domain appears (0.01 < $\mu$ < 0.05), located a few nanometers below the surface of the tribofilm. This low fri

4e6dc2b9-0d91-44df-a71e-d2108603d4a1

4e6dc2b9-0d91-44df-a71e-d2108603d4a1

4e6dc2b9-0d91-44df-a71e-d2108603d4a1

human

none

abstracts

Lattice Boltzmann inverse kinetic approach for the incompressible Navier-Stokes equations

In spite of the large number of papers appeared in the past which are devoted to the lattice Boltzmann (LB) methods, basic aspects of the theory still remain unchallenged. An unsolved theoretical issue is related to the construction of a discrete kinetic theory which yields \textit{exactly} the fluid equations, i.e., is non-asymptotic (here denoted as \textit{LB inverse kinetic theory}). The purpose of this paper is theoretical and aims at developing an inverse kinetic approach of this type. In principle infinite solutions exist to this problem but the freedom can be exploited in order to meet important requirements. In particular, the discrete kinetic theory can be defined so that it yields exactly the fluid equation also for arbitrary non-equilibrium (but suitably smooth) kinetic distribution functions and arbitrarily close to the boundary of the fluid domain. Unlike previous entropic LB methods the theorem can be obtained without functional constraints on the class of the initial

a4efcbf1-8dc7-4305-bac4-5f8388540d92

a4efcbf1-8dc7-4305-bac4-5f8388540d92

a4efcbf1-8dc7-4305-bac4-5f8388540d92

human

none

abstracts

Phonon-mediated decay of an atom in a surface-induced potential

We study phonon-mediated transitions between translational levels of an atom in a surface-induced potential. We present a general master equation governing the dynamics of the translational states of the atom. In the framework of the Debye model, we derive compact expressions for the rates for both upward and downward transitions. Numerical calculations for the transition rates are performed for a deep silica-induced potential allowing for a large number of bound levels as well as free states of a cesium atom. The total absorption rate is shown to be determined mainly by the bound-to-bound transitions for deep bound levels and by bound-to-free transitions for shallow bound levels. Moreover, the phonon emission and absorption processes can be orders of magnitude larger for deep bound levels as compared to the shallow bound ones. We also study various types of transitions from free states. We show that, for thermal atomic cesium with temperature in the range from 100 $\mu$K to 400 $\mu

a9fad31f-1bc7-4cd0-8791-a4f9959e9e4a

a9fad31f-1bc7-4cd0-8791-a4f9959e9e4a

a9fad31f-1bc7-4cd0-8791-a4f9959e9e4a

human

none

abstracts

Diffuse X-ray Emission from the Carina Nebula Observed with Suzaku

A number of giant HII regions are associated with soft diffuse X-ray emission. Among these, the Carina nebula possesses the brightest soft diffuse emission. The required plasma temperature and thermal energy can be produced by collisions or termination of fast winds from main-sequence or embedded young O stars, but the extended emission is often observed from regions apart from massive stellar clusters. The origin of the X-ray emission is unknown. The XIS CCD camera onboard Suzaku has the best spectral resolution for extended soft sources so far, and is therefore capable of measuring key emission lines in the soft band. Suzaku observed the core and the eastern side of the Carina nebula (Car-D1) in 2005 Aug and 2006 June, respectively. Spectra of the south part of the core and Car-D1 similarly showed strong L-shell lines of iron ions and K-shell lines of silicon ions, while in the north of the core these lines were much weaker. Fitting the spectra with an absorbed thin-thermal plasm

1cb02c46-ec7a-4fb4-aca3-787ff92d2793

1cb02c46-ec7a-4fb4-aca3-787ff92d2793

1cb02c46-ec7a-4fb4-aca3-787ff92d2793

human

none

abstracts

FIRST-based survey of Compact Steep Spectrum sources, V. Milliarcsecond-scale morphology of CSS objects

Multifrequency VLBA observations of the final group of ten objects in a sample of FIRST-based compact steep spectrum (CSS) sources are presented. The sample was selected to investigate whether objects of this kind could be relics of radio-loud AGNs switched off at very early stages of their evolution or possibly to indicate intermittent activity. Initial observations were made using MERLIN at 5 GHz. The sources have now been observed with the VLBA at 1.7, 5 and 8.4 GHz in a snapshot mode with phase-referencing. The resulting maps are presented along with unpublished 8.4-GHz VLA images of five sources. Some of the sources discussed here show a complex radio morphology and therefore a complicated past that, in some cases, might indicate intermittent activity. One of the sources studied - 1045+352 - is known as a powerful radio and infrared-luminous broad absorption line (BAL) quasar. It is a young CSS object whose asymmetric two-sided morphology on a scale of several hundred parsecs, e

fe287737-49f9-4369-b063-07cfb125001f

fe287737-49f9-4369-b063-07cfb125001f

fe287737-49f9-4369-b063-07cfb125001f

human

none

abstracts

Investigation of relaxation phenomena in high-temperature superconductors HoBa2Cu3O7-d at the action of pulsed magnetic fields

It is used the mechanical method of Abrikosov vortex stimulated dynamics investigation in superconductors. With its help it was studied relaxation phenomena in vortex matter of high-temperature superconductors. It established that pulsed magnetic fields change the course of relaxation processes taking place in vortex matter. The study of the influence of magnetic pulses differing by their durations and amplitudes on vortex system of isotropic high-temperature superconductors system HoBa2Cu3O7-d showed the presence of threshold phenomena. The small duration pulses does not change the course of relaxation processes taking place in vortex matter. When the duration of pulses exceeds some critical value (threshold), then their influence change the course of relaxation process which is revealed by stepwise change of relaxing mechanical moment . These investigations showed that the time for formatting of Abrikosov vortex lattice in HoBa2Cu3O7-d is of the order of 20 microsec. which on the o

c54dd23b-1346-41e8-bb6d-cd0b08257787

c54dd23b-1346-41e8-bb6d-cd0b08257787

c54dd23b-1346-41e8-bb6d-cd0b08257787

human

none

abstracts

Trigonometric parallaxes of high velocity halo white dwarf candidates

The status of 38 halo white dwarf candidates identified by Oppenheimer et al. (2001) has been intensively discussed by various authors. In analyses undertaken to date, trigonometric parallaxes are crucial missing data. Distance measurements are mandatory to kinematically segregate halo object from disk objects and hence enable a more reliable estimate of the local density of halo dark matter residing in such objects. We present trigonometric parallax measurements for 15 candidate halo white dwarfs (WDs) selected from the Oppenheimer et al. (2001) list. We observed the stars using the ESO 1.56-m Danish Telescope and ESO 2.2-m telescope from August 2001 to July 2004. Parallaxes with accuracies of 1--2 mas were determined yielding relative errors on distances of $\sim5$% for 6 objects, $\sim12$% for 3 objects, and $\sim20$% for two more objects. Four stars appear to be too distant (probably farther than 100 pc) to have measurable parallaxes in our observations. Distances, absolute mag

c8998bee-16ed-424f-aa05-884f21aac576

c8998bee-16ed-424f-aa05-884f21aac576

c8998bee-16ed-424f-aa05-884f21aac576

human

none

abstracts

AMR simulations of the low T/|W| bar-mode instability of neutron stars

It has been recently argued through numerical work that rotating stars with a high degree of differential rotation are dynamically unstable against bar-mode deformation, even for values of the ratio of rotational kinetic energy to gravitational potential energy as low as O(0.01). This may have implications for gravitational wave astronomy in high-frequency sources such as core collapse supernovae. In this paper we present high-resolution simulations, performed with an adaptive mesh refinement hydrodynamics code, of such low T/|W| bar-mode instability. The complex morphological features involved in the nonlinear dynamics of the instability are revealed in our simulations, which show that the excitation of Kelvin-Helmholtz-like fluid modes outside the corotation radius of the star leads to the saturation of the bar-mode deformation. While the overall trends reported in an earlier investigation are confirmed by our work, we also find that numerical resolution plays an important role dur

688c8cd2-bc14-409b-86b8-ccebd696d9d7

688c8cd2-bc14-409b-86b8-ccebd696d9d7

688c8cd2-bc14-409b-86b8-ccebd696d9d7

human

none

abstracts

Torsional oscillations of longitudinally inhomogeneous coronal loops

We explore the effect of an inhomogeneous mass density field on frequencies and wave profiles of torsional Alfven oscillations in solar coronal loops. Dispersion relations for torsional oscillations are derived analytically in limits of weak and strong inhomogeneities. These analytical results are verified by numerical solutions, which are valid for a wide range of inhomogeneity strength. It is shown that the inhomogeneous mass density field leads to the reduction of a wave frequency of torsional oscillations, in comparison to that of estimated from mass density at the loop apex. This frequency reduction results from the decrease of an average Alfven speed as far as the inhomogeneous loop is denser at its footpoints. The derived dispersion relations and wave profiles are important for potential observations of torsional oscillations which result in periodic variations of spectral line widths. Torsional oscillations offer an additional powerful tool for a development of coronal seismo

e4b76652-0b33-46fd-a190-6f0be3c35b09

e4b76652-0b33-46fd-a190-6f0be3c35b09

e4b76652-0b33-46fd-a190-6f0be3c35b09

human

none

abstracts

Pseudo-random Puncturing: A Technique to Lower the Error Floor of Turbo Codes

It has been observed that particular rate-1/2 partially systematic parallel concatenated convolutional codes (PCCCs) can achieve a lower error floor than that of their rate-1/3 parent codes. Nevertheless, good puncturing patterns can only be identified by means of an exhaustive search, whilst convergence towards low bit error probabilities can be problematic when the systematic output of a rate-1/2 partially systematic PCCC is heavily punctured. In this paper, we present and study a family of rate-1/2 partially systematic PCCCs, which we call pseudo-randomly punctured codes. We evaluate their bit error rate performance and we show that they always yield a lower error floor than that of their rate-1/3 parent codes. Furthermore, we compare analytic results to simulations and we demonstrate that their performance converges towards the error floor region, owning to the moderate puncturing of their systematic output. Consequently, we propose pseudo-random puncturing as a means of improvin

b22d4223-ce68-42d0-8d34-7f0a0d2ffde0

b22d4223-ce68-42d0-8d34-7f0a0d2ffde0

b22d4223-ce68-42d0-8d34-7f0a0d2ffde0

human

none

abstracts

Metal-insulator transition in the low-dimensional organic conductor (TMTSF)2FSO3 probed by infrared microspectroscopy

We present measurements of the infrared response of the quasi-one-dimensional organic conductor (TMTSF)2$SO3 along (E||a) and perpendicular (E||b') to the stacking axis as a function of temperature. Above the metal-insulator transition related to the anion ordering the optical conductivity spectra show a Drude-like response. Below the transition an energy gap of about 1500 cm-1 (185 meV) opens, leading to the corresponding charge transfer band in the optical conductivity spectra. The analysis of the infrared-active vibrations gives evidence for the long-range crystal structure modulation below the transition temperature and for the short-range order fluctuations of the lattice modulation above the transition temperature. Also we report about a new infrared mode at around 710 cm-1 with a peculiar temperature behavior, which has so far not been observed in any other (TMTSF)2X salt showing a metal-insulator transition. A qualitative model based on the coupling between the TMTSF molecule

cc815d3c-088e-4b56-88c5-5bee6a8f8531

cc815d3c-088e-4b56-88c5-5bee6a8f8531

cc815d3c-088e-4b56-88c5-5bee6a8f8531

human

none

abstracts

Reality of linear and angular momentum expectation values in bound states

In quantum mechanics textbooks the momentum operator is defined in the Cartesian coordinates and rarely the form of the momentum operator in spherical polar coordinates is discussed. Consequently one always generalizes the Cartesian prescription to other coordinates and falls in a trap. In this work we introduce the difficulties one faces when the question of the momentum operator in spherical polar coordinate comes. We have tried to point out most of the elementary quantum mechanical results, related to the momentum operator, which has coordinate dependence. We explicitly calculate the momentum expectation values in various bound states and show that the expectation value really turns out to be zero, a consequence of the fact that the momentum expectation value is real. We comment briefly on the status of the angular variables in quantum mechanics and the problems related in interpreting them as dynamical variables. At the end, we calculate the Heisenberg's equation of motion for th

9316c9a9-dcf5-45bb-a958-71fa85de700d

9316c9a9-dcf5-45bb-a958-71fa85de700d

9316c9a9-dcf5-45bb-a958-71fa85de700d

human

none

abstracts

Rich methane premixed laminar flames doped by light unsaturated hydrocarbons - Part I : allene and propyne

The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of C3H4 was added, corresponding to a ratio C3H4/CH4 of 12% and an equivalence ratio of 1.55. The three flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz microprobe. Quantified species included carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, propane, 1,2-butadiene, 1,3-butadiene, 1-butene, isobutene, 1-butyne, vinylacetylene, and benzene. The temperature was measured using a PtRh

b02fe561-dbe3-44cf-9c44-769b1d8f831f

b02fe561-dbe3-44cf-9c44-769b1d8f831f

b02fe561-dbe3-44cf-9c44-769b1d8f831f

human

none

abstracts

Exponential growth rates in a typed branching diffusion

We study the high temperature phase of a family of typed branching diffusions initially studied in [Ast\'{e}risque 236 (1996) 133--154] and [Lecture Notes in Math. 1729 (2000) 239--256 Springer, Berlin]. The primary aim is to establish some almost-sure limit results for the long-term behavior of this particle system, namely the speed at which the population of particles colonizes both space and type dimensions, as well as the rate at which the population grows within this asymptotic shape. Our approach will include identification of an explicit two-phase mechanism by which particles can build up in sufficient numbers with spatial positions near $-\gamma t$ and type positions near $\kappa \sqrt{t}$ at large times $t$. The proofs involve the application of a variety of martingale techniques--most importantly a ``spine'' construction involving a change of measure with an additive martingale. In addition to the model's intrinsic interest, the methodologies presented contain ideas that wi

90b07d14-8904-4309-9655-0d5d911dad98

90b07d14-8904-4309-9655-0d5d911dad98

90b07d14-8904-4309-9655-0d5d911dad98

human

none

abstracts

Clustering features of $^9$Be, $^{14}$N, $^7$Be, and $^8$B nuclei in relativistic fragmentation

Recent studies of clustering in light nuclei with an initial energy above 1 A GeV in nuclear treack emulsion are overviewed. The results of investigations of the relativistic $^9$Be nuclei fragmentation in emulsion, which entails the production of He fragments, are presented. It is shown that most precise angular measurements provided by this technique play a crucial role in the restoration of the excitation spectrum of the $\alpha$ particle sysytem. In peripheral interactions $^9$Be nuclei are dissociated practically totally through the 0$^+$ and 2$^+$ states of the $^8$Be nucleus. The results of investigations of the dissociation of a $^{14}$N nucleus of momentum 2.86 A GeV/c in emulsion are presented as example of more complicated system. The momentum and correlation characteristics of $\alpha$ particles for the $^{14}$N$\to3\alpha+X$ channel in the laboratory system and the rest systems of 3$\alpha$ particles were considered in detail. Topology of charged fragments produced i

f6e6da2e-0265-4e31-bd67-442eede5d1b8

f6e6da2e-0265-4e31-bd67-442eede5d1b8

f6e6da2e-0265-4e31-bd67-442eede5d1b8

human

none

abstracts

Sterile neutrinos at the CNGS

We study the potential of the CNGS beam in constraining the parameter space of a model with one sterile neutrino separated from three active ones by an $\mathcal{O}(\eVq)$ mass-squared difference, $\Dmq_\Sbl$. We perform our analysis using the OPERA detector as a reference (our analysis can be upgraded including a detailed simulation of the ICARUS detector). We point out that the channel with the largest potential to constrain the sterile neutrino parameter space at the CNGS beam is $\nu_\mu \to \nu_\tau$. The reason for that is twofold: first, the active-sterile mixing angle that governs this oscillation is the less constrained by present experiments; second, this is the signal for which both OPERA and ICARUS have been designed, and thus benefits from an extremely low background. In our analysis we also took into account $\nu_\mu \to \nu_e$ oscillations. We find that the CNGS potential to look for sterile neutrinos is limited with nominal intensity of the beam, but it is significant

218e79f5-ba00-41e2-ab78-bafd01ab2430

218e79f5-ba00-41e2-ab78-bafd01ab2430

218e79f5-ba00-41e2-ab78-bafd01ab2430

human

none

abstracts

Evolution of the Carter constant for inspirals into a black hole: effect of the black hole quadrupole

We analyze the effect of gravitational radiation reaction on generic orbits around a body with an axisymmetric mass quadrupole moment Q to linear order in Q, to the leading post-Newtonian order, and to linear order in the mass ratio. This system admits three constants of the motion in absence of radiation reaction: energy, angular momentum, and a third constant analogous to the Carter constant. We compute instantaneous and time-averaged rates of change of these three constants. For a point particle orbiting a black hole, Ryan has computed the leading order evolution of the orbit's Carter constant, which is linear in the spin. Our result, when combined with an interaction quadratic in the spin (the coupling of the black hole's spin to its own radiation reaction field), gives the next to leading order evolution. The effect of the quadrupole, like that of the linear spin term, is to circularize eccentric orbits and to drive the orbital plane towards antialignment with the symmetry axis.

02ffd37a-1f71-4b4b-8322-e2d4c83c27c1

02ffd37a-1f71-4b4b-8322-e2d4c83c27c1

02ffd37a-1f71-4b4b-8322-e2d4c83c27c1

human

none

abstracts

Simulation of Robustness against Lesions of Cortical Networks

Structure entails function and thus a structural description of the brain will help to understand its function and may provide insights into many properties of brain systems, from their robustness and recovery from damage, to their dynamics and even their evolution. Advances in the analysis of complex networks provide useful new approaches to understanding structural and functional properties of brain networks. Structural properties of networks recently described allow their characterization as small-world, random (exponential) and scale-free. They complement the set of other properties that have been explored in the context of brain connectivity, such as topology, hodology, clustering, and hierarchical organization. Here we apply new network analysis methods to cortical inter-areal connectivity networks for the cat and macaque brains. We compare these corticocortical fibre networks to benchmark rewired, small-world, scale-free and random networks, using two analysis strategies, in w

2162d503-35a3-48cc-ab6e-1ee8c36ecaff

2162d503-35a3-48cc-ab6e-1ee8c36ecaff

2162d503-35a3-48cc-ab6e-1ee8c36ecaff

human

none

abstracts

An invariance principle for semimartingale reflecting Brownian motions in domains with piecewise smooth boundaries

Semimartingale reflecting Brownian motions (SRBMs) living in the closures of domains with piecewise smooth boundaries are of interest in applied probability because of their role as heavy traffic approximations for some stochastic networks. In this paper, assuming certain conditions on the domains and directions of reflection, a perturbation result, or invariance principle, for SRBMs is proved. This provides sufficient conditions for a process that satisfies the definition of an SRBM, except for small random perturbations in the defining conditions, to be close in distribution to an SRBM. A crucial ingredient in the proof of this result is an oscillation inequality for solutions of a perturbed Skorokhod problem. We use the invariance principle to show weak existence of SRBMs under mild conditions. We also use the invariance principle, in conjunction with known uniqueness results for SRBMs, to give some sufficient conditions for validating approximations involving (i) SRBMs in convex

93424dfd-73e9-4cb1-81a2-b8436e4a928a

93424dfd-73e9-4cb1-81a2-b8436e4a928a

93424dfd-73e9-4cb1-81a2-b8436e4a928a

human

none

abstracts

Stopping effects in U+U collisions with a beam energy of 520 MeV/nucleon

A Relativistic Transport Model (ART1.0) is applied to simulate the stopping effects in tip-tip and body-body U+U collisions, at a beam kinetic energy of 520 MeV/nucleon. Our simulation results have demonstrated that both central collisions of the two extreme orientations can achieve full stopping, and also form a bulk of hot, dense nuclear matter with a sufficiently large volume and long duration, due to the largely deformed uranium nuclei. The nucleon sideward flow in the tip-tip collisions is nearly 3 times larger than that in body-body ones at normalized impact parameter $b/b_{max}<0.5$, and that the body-body central collisions have a largest negative nucleon elliptic flow $v_{2}=-12%$ in contrast to zero in tip-tip ones. Thus the extreme circumstance and the novel experimental observables in tip-tip and body-body collisions can provide a good condition and sensitive probe to study the nuclear EoS, respectively. The Cooling Storage Ring (CSR) External Target Facility (ETF) to be