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Title: Calculation of prompt diphoton production cross sections at Tevatron and LHC energiesCategory: hep-phAuthors: C. Bal\'azs, E. L. Berger, P. M. Nadolsky, C.-P. YuanStudy Abstract: A fully differential calculation in perturbative quantum chromodynamics is presented for the production of massive photon pairs at hadron colliders. All next-to-leading order perturbative contributions from quark-antiquark, gluon-(anti)quark, and gluon-gluon subprocesses are included, as well as all-orders resummation of initial-state gluon radiation valid at next-to-next-to-leading logarithmic accuracy. The region of phase space is specified in which the calculation is most reliable. Good agreement is demonstrated with data from the Fermilab Tevatron, and predictions are made for more detailed tests with CDF and DO data. Predictions are shown for distributions of diphoton pairs produced at the energy of the Large Hadron Collider (LHC). Distributions of the diphoton pairs from the decay of a Higgs boson are contrasted with those produced from QCD processes at the LHC, showing that enhanced sensitivity to the signal can be obtained with judicious selection of events. Comments: 37 pages, 15 figures; published version

Title: Sparsity-certifying Graph DecompositionsCategory: math.CO cs.CGAuthors: Ileana Streinu and Louis TheranStudy Abstract: We describe a new algorithm, the $(k,\ell)$-pebble game with colors, and use it obtain a characterization of the family of $(k,\ell)$-sparse graphs and algorithmic solutions to a family of problems concerning tree decompositions of graphs. Special instances of sparse graphs appear in rigidity theory and have received increased attention in recent years. In particular, our colored pebbles generalize and strengthen the previous results of Lee and Streinu and give a new proof of the Tutte-Nash-Williams characterization of arboricity. We also present a new decomposition that certifies sparsity based on the $(k,\ell)$-pebble game with colors. Our work also exposes connections between pebble game algorithms and previous sparse graph algorithms by Gabow, Gabow and Westermann and Hendrickson. Comments: To appear in Graphs and Combinatorics

Title: The evolution of the Earth-Moon system based on the dark matter field fluid modelCategory: physics.gen-phAuthors: Hongjun PanStudy Abstract: The evolution of Earth-Moon system is described by the dark matter field fluid model proposed in the Meeting of Division of Particle and Field 2004, American Physical Society. The current behavior of the Earth-Moon system agrees with this model very well and the general pattern of the evolution of the Moon-Earth system described by this model agrees with geological and fossil evidence. The closest distance of the Moon to Earth was about 259000 km at 4.5 billion years ago, which is far beyond the Roche's limit. The result suggests that the tidal friction may not be the primary cause for the evolution of the Earth-Moon system. The average dark matter field fluid constant derived from Earth-Moon system data is 4.39 x 10^(-22) s^(-1)m^(-1). This model predicts that the Mars's rotation is also slowing with the angular acceleration rate about -4.38 x 10^(-22) rad s^(-2). Comments: 23 pages, 3 figures

Title: A determinant of Stirling cycle numbers counts unlabeled acyclic single-source automataCategory: math.COAuthors: David CallanStudy Abstract: We show that a determinant of Stirling cycle numbers counts unlabeled acyclic single-source automata. The proof involves a bijection from these automata to certain marked lattice paths and a sign-reversing involution to evaluate the determinant. Comments: 11 pages

Title: Bosonic characters of atomic Cooper pairs across resonanceCategory: cond-mat.mes-hallAuthors: Y. H. Pong and C. K. LawStudy Abstract: We study the two-particle wave function of paired atoms in a Fermi gas with tunable interaction strengths controlled by Feshbach resonance. The Cooper pair wave function is examined for its bosonic characters, which is quantified by the correction of Bose enhancement factor associated with the creation and annihilation composite particle operators. An example is given for a three-dimensional uniform gas. Two definitions of Cooper pair wave function are examined. One of which is chosen to reflect the off-diagonal long range order (ODLRO). Another one corresponds to a pair projection of a BCS state. On the side with negative scattering length, we found that paired atoms described by ODLRO are more bosonic than the pair projected definition. It is also found that at $(k_F a)^{-1} \ge 1$, both definitions give similar results, where more than 90% of the atoms occupy the corresponding molecular condensates. Comments: 6 pages, 4 figures, accepted by PRA

Title: Polymer Quantum Mechanics and its Continuum LimitCategory: gr-qcAuthors: Alejandro Corichi, Tatjana Vukasinac and Jose A. ZapataStudy Abstract: 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 particle and a simple cosmological model. Comments: 16 pages, no figures. Typos corrected to match published version

Title: Numerical solution of shock and ramp compression for general material propertiesCategory: cond-mat.mtrl-sciAuthors: Damian C. SwiftStudy Abstract: A general formulation was developed to represent material models for applications in dynamic loading. Numerical methods were devised to calculate response to shock and ramp compression, and ramp decompression, generalizing previous solutions for scalar equations of state. The numerical methods were found to be flexible and robust, and matched analytic results to a high accuracy. The basic ramp and shock solution methods were coupled to solve for composite deformation paths, such as shock-induced impacts, and shock interactions with a planar interface between different materials. These calculations capture much of the physics of typical material dynamics experiments, without requiring spatially-resolving simulations. Example calculations were made of loading histories in metals, illustrating the effects of plastic work on the temperatures induced in quasi-isentropic and shock-release experiments, and the effect of a phase transition. Comments: Minor corrections

Title: Partial cubes: structures, characterizations, and constructionsCategory: math.COAuthors: Sergei OvchinnikovStudy Abstract: Partial cubes are isometric subgraphs of hypercubes. Structures on a graph defined by means of semicubes, and Djokovi\'{c}'s and Winkler's relations play an important role in the theory of partial cubes. These structures are employed in the paper to characterize bipartite graphs and partial cubes of arbitrary dimension. New characterizations are established and new proofs of some known results are given. The operations of Cartesian product and pasting, and expansion and contraction processes are utilized in the paper to construct new partial cubes from old ones. In particular, the isometric and lattice dimensions of finite partial cubes obtained by means of these operations are calculated. Comments: 36 pages, 17 figures

Title: Computing genus 2 Hilbert-Siegel modular forms over $\Q(\sqrt{5})$ via the Jacquet-Langlands correspondenceCategory: math.NT math.AGAuthors: Clifton Cunningham and Lassina DembeleStudy Abstract: In this paper we present an algorithm for computing Hecke eigensystems of Hilbert-Siegel cusp forms over real quadratic fields of narrow class number one. We give some illustrative examples using the quadratic field $\Q(\sqrt{5})$. In those examples, we identify Hilbert-Siegel eigenforms that are possible lifts from Hilbert eigenforms. Comments: 14 pages; title changed; to appear in Experimental Mathematics

Title: Iterated integral and the loop productCategory: math.CA math.ATAuthors: Koichi FujiiStudy Abstract: In this article we discuss a relation between the string topology and differential forms based on the theory of Chen's iterated integrals and the cyclic bar complex. Comments: 18 pages, 1 figure

Title: Fermionic superstring loop amplitudes in the pure spinor formalismCategory: hep-thAuthors: Christian StahnStudy Abstract: The pure spinor formulation of the ten-dimensional superstring leads to manifestly supersymmetric loop amplitudes, expressed as integrals in pure spinor superspace. This paper explores different methods to evaluate these integrals and then uses them to calculate the kinematic factors of the one-loop and two-loop massless four-point amplitudes involving two and four Ramond states. Comments: 22 pages; signs and coefficients adjusted for anticommuting superfields, section 4.3 changed accordingly, reference added

Title: Lifetime of doubly charmed baryonsCategory: hep-phAuthors: Chao-Hsi Chang, Tong Li, Xue-Qian Li and Yu-Ming WangStudy Abstract: In this work, we evaluate the lifetimes of the doubly charmed baryons $\Xi_{cc}^{+}$, $\Xi_{cc}^{++}$ and $\Omega_{cc}^{+}$. We carefully calculate the non-spectator contributions at the quark level where the Cabibbo-suppressed diagrams are also included. The hadronic matrix elements are evaluated in the simple non-relativistic harmonic oscillator model. Our numerical results are generally consistent with that obtained by other authors who used the diquark model. However, all the theoretical predictions on the lifetimes are one order larger than the upper limit set by the recent SELEX measurement. This discrepancy would be clarified by the future experiment, if more accurate experiment still confirms the value of the SELEX collaboration, there must be some unknown mechanism to be explored. Comments: 17 pages, 3 figures and 1 table

Title: Spectroscopic Observations of the Intermediate Polar EX Hydrae in QuiescenceCategory: astro-phAuthors: Nceba Mhlahlo, David H. Buckley, Vikram S. Dhillon, Steven B. Potter, Brian Warner and Patric A. WoudtStudy Abstract: 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, confirming the result of Belle et al. (2005) that disc overflow in EX Hya is present during quiescence as well as outburst. It appears that the hbeta and hgamma spin radial velocities originated from the rotation of the funnel at the outer disc edge, while those of halpha were produced due to the flow of material along the field lines far from the white dwarf (narrow component) and close to the white dwarf (broad-base component), in agreement with the accretion curtain model. Comments: 10 pages, 11 figures (figures 3, 4, 7 and 8 at reduced resolution, originals available on request). Accepted for publication in Monthly Notices of the Royal Astronomical Society

Title: In quest of a generalized Callias index theoremCategory: hep-thAuthors: Andreas GustavssonStudy Abstract: We give a prescription for how to compute the Callias index, using as regulator an exponential function. We find agreement with old results in all odd dimensions. We show that the problem of computing the dimension of the moduli space of self-dual strings can be formulated as an index problem in even-dimensional (loop-)space. We think that the regulator used in this Letter can be applied to this index problem. Comments: 20 pages, v2: an overall sign and typos corrected

Title: Approximation for extinction probability of the contact process based on the Gr\"obner basisCategory: math.PR math.AGAuthors: Norio KonnoStudy Abstract: In this note we give a new method for getting a series of approximations for the extinction probability of the one-dimensional contact process by using the Gr\"obner basis. Comments: 6 pages, Journal-ref added

Title: Measurement of the Hadronic Form Factor in D0 --> K- e+ nue DecaysCategory: hep-exAuthors: The BABAR Collaboration, B. Aubert, et alStudy Abstract: The shape of the hadronic form factor f+(q2) in the decay D0 --> K- e+ nue has been measured in a model independent analysis and compared with theoretical calculations. We use 75 fb(-1) of data recorded by the BABAR detector at the PEPII electron-positron collider. The corresponding decay branching fraction, relative to the decay D0 --> K- pi+, has also been measured to be RD = BR(D0 --> K- e+ nue)/BR(D0 --> K- pi+) = 0.927 +/- 0.007 +/- 0.012. From these results, and using the present world average value for BR(D0 --> K- pi+), the normalization of the form factor at q2=0 is determined to be f+(0)=0.727 +/- 0.007 +/- 0.005 +/- 0.007 where the uncertainties are statistical, systematic, and from external inputs, respectively. Comments: 21 pages, 13 postscript figures, submitted to Phys. Rev. D, contributed to 42nd Rencontres de Moriond: QCD and Hadronic Interactions

Title: Molecular Synchronization Waves in Arrays of Allosterically Regulated EnzymesCategory: nlin.PS physics.chem-ph q-bio.MNAuthors: Vanessa Casagrande, Yuichi Togashi, Alexander S. MikhailovStudy Abstract: Spatiotemporal pattern formation in a product-activated enzymic reaction at high enzyme concentrations is investigated. Stochastic simulations show that catalytic turnover cycles of individual enzymes can become coherent and that complex wave patterns of molecular synchronization can develop. The analysis based on the mean-field approximation indicates that the observed patterns result from the presence of Hopf and wave bifurcations in the considered system. Comments: 5 pages, 4 figures

Title: Stochastic Lie group integratorsCategory: math.NAAuthors: Simon J.A. Malham and Anke WieseStudy Abstract: 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 group integrator schemes if we use Munthe-Kaas methods as the underlying ordinary differential integrator. Further, we show that some Castell--Gaines methods are uniformly more accurate than the corresponding stochastic Taylor schemes. Lastly we demonstrate our methods by simulating the dynamics of a free rigid body such as a satellite and an autonomous underwater vehicle both perturbed by two independent multiplicative stochastic noise processes. Comments: 20 pages, 4 figures

Title: ALMA as the ideal probe of the solar chromosphereCategory: astro-phAuthors: M. A. Loukitcheva, S. K. Solanki and S. WhiteStudy Abstract: 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 significant oscillations with amplitudes of 50-150 K and frequencies of 1.5-8 mHz with a tendency toward short-period oscillations in internetwork and longer periods in network regions. However higher spatial resolution, such as that provided by ALMA, is required for a clean separation between the features within the solar atmosphere and for an adequate comparison with the output of the comprehensive dynamic simulations. Comments: 4 pages, 2 figures, to appear in the proceedings of the conference Science with ALMA: a new era for Astrophysics, Spain, 2006

Title: Formation of quasi-solitons in transverse confined ferromagnetic film mediaCategory: nlin.PSAuthors: A.A. Serga, M. Kostylev, and B. HillebrandsStudy Abstract: The formation of quasi-2D spin-wave waveforms in longitudinally magnetized stripes of ferrimagnetic film was observed by using time- and space-resolved Brillouin light scattering technique. In the linear regime it was found that the confinement decreases the amplitude of dynamic magnetization near the lateral stripe edges. Thus, the so-called effective dipolar pinning of dynamic magnetization takes place at the edges. In the nonlinear regime a new stable spin wave packet propagating along a waveguide structure, for which both transversal instability and interaction with the side walls of the waveguide are important was observed. The experiments and a numerical simulation of the pulse evolution show that the shape of the formed waveforms and their behavior are strongly influenced by the confinement. Comments: First appeared in Prof. B. Hillebrands' research group Annual Report 2005 (http://www.physik.uni-kl.de/w_hilleb/ann05.html); also presented at Intermag'2006 Conference: M. Kostylev, A.A. Serga, and B. Hillebrands, Digests of International Magnetic Conference, May 8-12, 2006, San Diego, USA, FV03 (2006)

Title: Spectroscopic Properties of Polarons in Strongly Correlated Systems by Exact Diagrammatic Monte Carlo MethodCategory: cond-mat.str-el cond-mat.stat-mechAuthors: A. S. Mishchenko (1 and 2) and N. Nagaosa (1 and 3) ((1) CREST, Japan Science and Technology Agency, (2) Russian Research Centre ``Kurchatov Institute'', (3) The University of Tokyo)Study Abstract: We present recent advances in understanding of the ground and excited states of the electron-phonon coupled systems obtained by novel methods of Diagrammatic Monte Carlo and Stochastic Optimization, which enable the approximation-free calculation of Matsubara Green function in imaginary times and perform unbiased analytic continuation to real frequencies. We present exact numeric results on the ground state properties, Lehmann spectral function and optical conductivity of different strongly correlated systems: Frohlich polaron, Rashba-Pekar exciton-polaron, pseudo Jahn-Teller polaron, exciton, and interacting with phonons hole in the t-J model. Comments: 41 pages, 13 figures, in "Polarons in Advanced Materials" ed. A. S. Alexandrov (Canopus/Springer Publishing, Bristol (2007)), pp. 503-544.

Title: Placeholder Substructures II: Meta-Fractals, Made of Box-Kites, Fill Infinite-Dimensional SkiesCategory: math.RAAuthors: Robert P. C. de MarraisStudy Abstract: Zero-divisors (ZDs) derived by Cayley-Dickson Process (CDP) from N-dimensional hypercomplex numbers (N a power of 2, at least 4) can represent singularities and, as N approaches infinite, fractals -- and thereby,scale-free networks. Any integer greater than 8 and not a power of 2 generates a meta-fractal or "Sky" when it is interpreted as the "strut constant" (S) of an ensemble of octahedral vertex figures called "Box-Kites" (the fundamental building blocks of ZDs). Remarkably simple bit-manipulation rules or "recipes" provide tools for transforming one fractal genus into others within the context of Wolfram's Class 4 complexity. Comments: 31 pp. Second of 3-part "theorem/proof" exposition of 78-slide Powerpoint from Wolfram Science's NKS 2006, available at http://wolframscience.com/conference/2006/presentations/materials/demarrais.ppt [v2: small fixes][v3: Added new Appendix B and small number of corrections (pp. 7, 14, 20) RE: 2nd type of box-kite flow pattern.]

Title: Filling-Factor-Dependent Magnetophonon Resonance in GrapheneCategory: cond-mat.mes-hallAuthors: M. O. Goerbig, J.-N. Fuchs, K. Kechedzhi, Vladimir I. Fal'koStudy Abstract: We describe a peculiar fine structure acquired by the in-plane optical phonon at the Gamma-point in graphene when it is brought into resonance with one of the inter-Landau-level transitions in this material. The effect is most pronounced when this lattice mode (associated with the G-band in graphene Raman spectrum) is in resonance with inter-Landau-level transitions 0 -> (+,1) and (-,1) -> 0, at a magnetic field B_0 ~ 30 T. It can be used to measure the strength of the electron-phonon coupling directly, and its filling-factor dependence can be used experimentally to detect circularly polarized lattice modes. Comments: 4 pages, 2 figures; mistakes due to an erroneous electron-phonon coupling constant have been corrected; mode splitting is larger than originally expected

Title: Pfaffians, hafnians and products of real linear functionalsCategory: math.CA math.PRAuthors: P\'eter E. FrenkelStudy Abstract: We prove pfaffian and hafnian versions of Lieb's inequalities on determinants and permanents of positive semi-definite matrices. We use the hafnian inequality to improve the lower bound of R\'ev\'esz and Sarantopoulos on the norm of a product of linear functionals on a real Euclidean space (this subject is sometimes called the `real linear polarization constant' problem). Comments: 10 pages

Title: Tuning correlation effects with electron-phonon interactionsCategory: cond-mat.str-elAuthors: J.P.Hague and N.d'AmbrumenilStudy Abstract: We investigate the effect of tuning the phonon energy on the correlation effects in models of electron-phonon interactions using DMFT. In the regime where itinerant electrons, instantaneous electron-phonon driven correlations and static distortions compete on similar energy scales, we find several interesting results including (1) A crossover from band to Mott behavior in the spectral function, leading to hybrid band/Mott features in the spectral function for phonon frequencies slightly larger than the band width. (2) Since the optical conductivity depends sensitively on the form of the spectral function, we show that such a regime should be observable through the low frequency form of the optical conductivity. (3) The resistivity has a double kondo peak arrangement Comments: Reprint to improve access. 13 pages, 6 figures.

Title: Crystal channeling of LHC forward protons with preserved distribution in phase spaceCategory: hep-phAuthors: V. M. Biryukov (Serpukhov, IHEP)Study Abstract: We show that crystal can trap a broad (x, x', y, y', E) distribution of particles and channel it preserved with a high precision. This sampled-and-hold distribution can be steered by a bent crystal for analysis downstream. In simulations for the 7 TeV Large Hadron Collider, a crystal adapted to the accelerator lattice traps 90% of diffractively scattered protons emerging from the interaction point with a divergence 100 times the critical angle. We set the criterion for crystal adaptation improving efficiency ~100-fold. Proton angles are preserved in crystal transmission with accuracy down to 0.1 microrad. This makes feasible a crystal application for measuring very forward protons at the LHC. Comments: 11 pages, 3 figures

Title: Probing non-standard neutrino interactions with supernova neutrinosCategory: hep-phAuthors: A. Esteban-Pretel, R. Tom\`as and J. W. F. ValleStudy Abstract: 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 very small flavor-changing NSI above a few$\times 10^{-5}$. Comments: 21 pages, 12 figures, 17 postscript files

Title: Convergence of the discrete dipole approximation. I. Theoretical analysisCategory: physics.optics physics.comp-phAuthors: Maxim A. Yurkin, Valeri P. Maltsev, Alfons G. HoekstraStudy Abstract: We performed a rigorous theoretical convergence analysis of the discrete dipole approximation (DDA). We prove that errors in any measured quantity are bounded by a sum of a linear and quadratic term in the size of a dipole d, when the latter is in the range of DDA applicability. Moreover, the linear term is significantly smaller for cubically than for non-cubically shaped scatterers. Therefore, for small d errors for cubically shaped particles are much smaller than for non-cubically shaped. The relative importance of the linear term decreases with increasing size, hence convergence of DDA for large enough scatterers is quadratic in the common range of d. Extensive numerical simulations were carried out for a wide range of d. Finally we discuss a number of new developments in DDA and their consequences for convergence. Comments: 23 pages, 5 figures; added several corrections according to the published erratum except for Eq.(6) (it was correct in the original paper) and with additional correction in Eq.(96) [$\bar{\mathbf{G}}(...)\mathbf{P}_i^s -\bar{\mathbf{G}}^s(...)\mathbf{P}_i^p$ instead of $(\bar{\mathbf{G}}(...) - \bar{\mathbf{G}}^s(...))\mathbf{P}_i^s$]

Title: Origin of adaptive mutants: a quantum measurement?Category: q-bio.PE q-bio.CB quant-phAuthors: Vasily OgryzkoStudy Abstract: This is a supplement to the paper arXiv:q-bio/0701050, containing the text of correspondence sent to Nature in 1990. Comments: 5 pages

Title: Convergence of the discrete dipole approximation. II. An extrapolation technique to increase the accuracyCategory: physics.optics physics.comp-phAuthors: Maxim A. Yurkin, Valeri P. Maltsev, Alfons G. HoekstraStudy Abstract: We propose an extrapolation technique that allows accuracy improvement of the discrete dipole approximation computations. The performance of this technique was studied empirically based on extensive simulations for 5 test cases using many different discretizations. The quality of the extrapolation improves with refining discretization reaching extraordinary performance especially for cubically shaped particles. A two order of magnitude decrease of error was demonstrated. We also propose estimates of the extrapolation error, which were proven to be reliable. Finally we propose a simple method to directly separate shape and discretization errors and illustrated this for one test case. Comments: 17 pages, 8 figures

Title: A remark on the number of steady states in a multiple futile cycleCategory: q-bio.QM q-bio.MNAuthors: Liming Wang and Eduardo D. SontagStudy Abstract: 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 state. Comments: Resubmit with new results on the upper bound of the number of steady states. 20 pages, 2 figures, See http://www.math.rutgers.edu/~sontag/PUBDIR/index.html for online preprints and reprints of related work

Title: The discrete dipole approximation for simulation of light scattering by particles much larger than the wavelengthCategory: physics.optics physics.comp-phAuthors: Maxim A. Yurkin, Valeri P. Maltsev, Alfons G. HoekstraStudy Abstract: 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 particles, like the ones that are considered in this manuscript. Current limitations and possible ways for improvement are discussed. Comments: 13 pages, 10 figures

Title: The discrete dipole approximation: an overview and recent developmentsCategory: physics.optics physics.comp-phAuthors: Maxim A. Yurkin, Alfons G. HoekstraStudy Abstract: We present a review of the discrete dipole approximation (DDA), which is a general method to simulate light scattering by arbitrarily shaped particles. We put the method in historical context and discuss recent developments, taking the viewpoint of a general framework based on the integral equations for the electric field. We review both the theory of the DDA and its numerical aspects, the latter being of critical importance for any practical application of the method. Finally, the position of the DDA among other methods of light scattering simulation is shown and possible future developments are discussed. Comments: 36 pages, 1 figure; added several corrections according to the published erratum except for Eq.(5) (it was correct in the original paper)

Title: Scalar radius of the pion and zeros in the form factorCategory: hep-ph hep-lat nucl-thAuthors: Jose A. Oller and Luis RocaStudy Abstract: 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 to our error is the not yet settled asymptotic behaviour of the phase of the scalar form factor from QCD. Comments: 18 pages, 3 figures. Some rewriting in the presentation of the results and comments to previous works

Title: Multilinear function series in conditionally free probability with amalgamationCategory: math.OA math.FAAuthors: Mihai PopaStudy Abstract: As in the cases of freeness and monotonic independence, the notion of conditional freeness is meaningful when complex-valued states are replaced by positive conditional expectations. In this framework, the paper presents several positivity results, a version of the central limit theorem and an analogue of the conditionally free R-transform constructed by means of multilinear function series. Comments: Final version, published

Title: Quantum Group of Isometries in Classical and Noncommutative GeometryCategory: math.QA math-ph math.MPAuthors: Debashish GoswamiStudy Abstract: 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 groups of commutative and noncommutative tori, and in this context, obtain the quantum double torus defined in \cite{hajac} as the universal quantum group of holomorphic isometries of the noncommutative torus. Comments: improvements: (i) more general approach through quantum families of isometries, following Woronowicz and Soltan's ideas; (ii) construction of equivaraint spectral triples. also some minor changes. Improved and enlarged version of ICTP preprint IC/2007/017

Title: General System theory, Like-Quantum Semantics and Fuzzy SetsCategory: physics.gen-ph quant-phAuthors: Ignazio LicataStudy Abstract: It is outlined the possibility to extend the quantum formalism in relation to the requirements of the general systems theory. It can be done by using a quantum semantics arising from the deep logical structure of quantum theory. It is so possible taking into account the logical openness relationship between observer and system. We are going to show how considering the truth-values of quantum propositions within the context of the fuzzy sets is here more useful for systemics . In conclusion we propose an example of formal quantum coherence. Comments: 12 pages,3 figures

Title: Nonequilibrium entropy limiters in lattice Boltzmann methodsCategory: cond-mat.stat-mech cond-mat.mtrl-sciAuthors: R.A. Brownlee, A.N. Gorban, J. LevesleyStudy Abstract: 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-driven cavity for Reynolds numbers Re between 2000 and 7500 on a coarse 100*100 grid. All limiter constructions are applicable for both entropic and non-entropic quasiequilibria. Comments: 30 pages, 9 figures, 1 table

Title: Astrophysical gyrokinetics: kinetic and fluid turbulent cascades in magnetized weakly collisional plasmasCategory: astro-ph nlin.CD physics.plasm-ph physics.space-phAuthors: A. A. Schekochihin (Oxford), S. C. Cowley (Culham), W. Dorland (Maryland), G. W. Hammett (Princeton), G. G. Howes (Iowa), E. Quataert (Berkeley), T. Tatsuno (Maryland)Study Abstract: We present a theoretical framework for plasma turbulence in astrophysical plasmas (solar wind, interstellar medium, galaxy clusters, accretion disks). The key assumptions are that the turbulence is anisotropic with respect to the mean magnetic field and frequencies are low compared to the ion cyclotron frequency. The energy injected at the outer scale scale has to be converted into heat, which ultimately cannot be done without collisions. A KINETIC CASCADE develops that brings the energy to collisional scales both in space and velocity. Its nature depends on the physics of plasma fluctuations. In each of the physically distinct scale ranges, the kinetic problem is systematically reduced to a more tractable set of equations. In the "inertial range" above the ion gyroscale, the kinetic cascade splits into a cascade of Alfvenic fluctuations, which are governed by the RMHD equations at both the collisional and collisionless scales, and a passive cascade of compressive fluctuations, which obey a linear kinetic equation along the moving field lines associated with the Alfvenic component. In the "dissipation range" between the ion and electron gyroscales, there are again two cascades: the kinetic-Alfven-wave (KAW) cascade governed by two fluid-like Electron RMHD equations and a passive phase-space cascade of ion entropy fluctuations. The latter cascade brings the energy of the inertial-range fluctuations that was damped by collisionless wave-particle interaction at the ion gyroscale to collisional scales in the phase space and leads to ion heating. The KAW energy is similarly damped at the electron gyroscale and converted into electron heat. Kolmogorov-style scaling relations are derived for these cascades. Astrophysical and space-physical applications are discussed in detail. Comments: aastex using emulateapj, 65 pages, 10 figures; replaced to match published version

Title: Evolution of solitary waves and undular bores in shallow-water flows over a gradual slope with bottom frictionCategory: nlin.PS nlin.SIAuthors: G.A. El, R.H.J. Grimshaw, A.M. KamchatnovStudy Abstract: 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 solitary wave with the same initial amplitude. This non-local effect is due to nonlinear wave interactions within the undular bore and can lead to an additional solitary wave amplitude growth, which cannot be predicted in the framework of the traditional adiabatic approach to the propagation of solitary waves in slowly varying media. Comments: accepted for publication in J. Fluid Mech.

Title: A limit relation for entropy and channel capacity per unit costCategory: quant-ph cs.IT math.ITAuthors: I. Csiszar, F. Hiai and D. PetzStudy Abstract: In a quantum mechanical model, Diosi, Feldmann and Kosloff arrived at a conjecture stating that the limit of the entropy of certain mixtures is the relative entropy as system size goes to infinity. The conjecture is proven in this paper for density matrices. The first proof is analytic and uses the quantum law of large numbers. The second one clarifies the relation to channel capacity per unit cost for classical-quantum channels. Both proofs lead to generalization of the conjecture. Comments: LATEX file, 11 pages

Title: Intelligent location of simultaneously active acoustic emission sources: Part ICategory: cs.NE cs.AIAuthors: T. Kosel and I. GrabecStudy Abstract: 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 more general since analysis of sonic ray paths is avoided. This is a promising method for non-destructive testing of aircraft frame structures by the acoustic emission method. Comments: 5 pages, 5 eps figures, uses IEEEtran.cls

Title: Inference on white dwarf binary systems using the first round Mock LISA Data Challenges data setsCategory: gr-qc astro-phAuthors: Alexander Stroeer, John Veitch, Christian Roever, Ed Bloomer, James Clark, Nelson Christensen, Martin Hendry, Chris Messenger, Renate Meyer, Matthew Pitkin, Jennifer Toher, Richard Umstaetter, Alberto Vecchio and Graham WoanStudy Abstract: We report on the analysis of selected single source data sets from the first round of the Mock LISA Data Challenges (MLDC) for white dwarf binaries. We implemented an end-to-end pipeline consisting of a grid-based coherent pre-processing unit for signal detection, and an automatic Markov Chain Monte Carlo post-processing unit for signal evaluation. We demonstrate that signal detection with our coherent approach is secure and accurate, and is increased in accuracy and supplemented with additional information on the signal parameters by our Markov Chain Monte Carlo approach. We also demonstrate that the Markov Chain Monte Carlo routine is additionally able to determine accurately the noise level in the frequency window of interest. Comments: GWDAW-11 proceeding, submitted to CQG, 10 pages, 3 figures, 1 table; revised values in table

Title: An algorithm for the classification of smooth Fano polytopesCategory: math.COAuthors: Mikkel {\O}broStudy Abstract: We present an algorithm that produces the classification list of smooth Fano d-polytopes for any given d. The input of the algorithm is a single number, namely the positive integer d. The algorithm has been used to classify smooth Fano d-polytopes for d<=7. There are 7622 isomorphism classes of smooth Fano 6-polytopes and 72256 isomorphism classes of smooth Fano 7-polytopes. Comments: 17 pages.

Title: Intelligent location of simultaneously active acoustic emission sources: Part IICategory: cs.NE cs.AIAuthors: T. Kosel and I. GrabecStudy Abstract: Part I describes an intelligent acoustic emission locator, while Part II discusses blind source separation, time delay estimation and location of two continuous acoustic emission sources. Acoustic emission (AE) analysis is used for characterization and location of developing defects in materials. AE sources often generate a mixture of various statistically independent signals. A difficult problem of AE analysis is separation and characterization of signal components when the signals from various sources and the mode of mixing are unknown. Recently, blind source separation (BSS) by independent component analysis (ICA) has been used to solve these problems. The purpose of this paper is to demonstrate the applicability of ICA to locate two independent simultaneously active acoustic emission sources on an aluminum band specimen. The method is promising for non-destructive testing of aircraft frame structures by acoustic emission analysis. Comments: 5 pages, 7 eps figures, uses IEEEtran.cls

Title: Visualizing TeleportationCategory: physics.ed-ph quant-phAuthors: Scott M. CohenStudy Abstract: A novel way of picturing the processing of quantum information is described, allowing a direct visualization of teleportation of quantum states and providing a simple and intuitive understanding of this fascinating phenomenon. The discussion is aimed at providing physicists a method of explaining teleportation to non-scientists. The basic ideas of quantum physics are first explained in lay terms, after which these ideas are used with a graphical description, out of which teleportation arises naturally. Comments: This is a "teaching" article aimed at making teleportation understandable to undergraduate physics majors (and possibly others). Version 2 has previous appendix moved to early sections, and more clearly states aim is to present a way physicists can explain teleportation to non-scientists

Title: Quantum Field Theory on Curved Backgrounds. II. Spacetime SymmetriesCategory: hep-thAuthors: Arthur Jaffe (1) and Gordon Ritter (1) ((1) Harvard University)Study Abstract: We study space-time symmetries in scalar quantum field theory (including interacting theories) on static space-times. We first consider Euclidean quantum field theory on a static Riemannian manifold, and show that the isometry group is generated by one-parameter subgroups which have either self-adjoint or unitary quantizations. We analytically continue the self-adjoint semigroups to one-parameter unitary groups, and thus construct a unitary representation of the isometry group of the associated Lorentzian manifold. The method is illustrated for the example of hyperbolic space, whose Lorentzian continuation is Anti-de Sitter space. Comments: 18 pages, 1 figure

Title: A Global Approach to the Theory of Special Finsler ManifoldsCategory: math.DG gr-qcAuthors: Nabil L. Youssef, S. H. Abed and A. SoleimanStudy Abstract: 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 are obtained. As a by-product, interesting identities and properties concerning the torsion tensor fields and the curvature tensor fields are deduced. Although our investigation is entirely global, we provide; for comparison reasons, an appendix presenting a local counterpart of our global approach and the local definitions of the special Finsler spaces considered. Comments: 32 pages, LaTeX file, Abstract and Introduction modified. Journal-ref removed (it was entered by mistake)

Title: Potassium intercalation in graphite: A van der Waals density-functional studyCategory: cond-mat.soft cond-mat.mtrl-sciAuthors: Eleni Ziambaras, Jesper Kleis, Elsebeth Schroder, and Per HyldgaardStudy Abstract: 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 description, compared with the traditional semilocal approach, is found to weakly soften the elastic response. Comments: 10 pages, 5 figures

Title: Phase diagram of Gaussian-core nematicsCategory: cond-mat.soft cond-mat.mtrl-sciAuthors: Santi Prestipino and Franz SaijaStudy Abstract: We study a simple model of a nematic liquid crystal made of parallel ellipsoidal particles interacting via a repulsive Gaussian law. After identifying the relevant solid phases of the system through a careful zero-temperature scrutiny of as many as eleven candidate crystal structures, we determine the melting temperature for various pressure values, also with the help of exact free energy calculations. Among the prominent features of this model are pressure-driven reentrant melting and the stabilization of a columnar phase for intermediate temperatures. Comments: 15 pages, 1 table, 10 figures, submitted on J. Chem. Phys.

Title: High-spin to low-spin and orbital polarization transitions in multiorbital Mott systemsCategory: cond-mat.str-elAuthors: Philipp Werner and Andrew J. MillisStudy Abstract: We study the interplay of crystal field splitting and Hund coupling in a two-orbital model which captures the essential physics of systems with two electrons or holes in the e_g shell. We use single site dynamical mean field theory with a recently developed impurity solver which is able to access strong couplings and low temperatures. The fillings of the orbitals and the location of phase boundaries are computed as a function of Coulomb repulsion, exchange coupling and crystal field splitting. We find that the Hund coupling can drive the system into a novel Mott insulating phase with vanishing orbital susceptibility. Away from half-filling, the crystal field splitting can induce an orbital selective Mott state. Comments: Published version

Title: The Mass and Radius of the Unseen M-Dwarf Companion in the Single-Lined Eclipsing Binary HAT-TR-205-013Category: astro-phAuthors: T. G. Beatty, J. M. Fernandez, D. W. Latham, G. A. Bakos, G. Kovacs, R. W. Noyes, R. P. Stefanik, G. Torres, M. E. Everett, C. W. HergenrotherStudy Abstract: 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, and the semimajor axis of the orbit, $a = 7.54 \pm 0.30 \rsun = 0.0351 \pm 0.0014$ AU. Our single-lined spectroscopic orbit and the semimajor axis then yield the individual masses, $M_{\rm B} = 0.124 \pm 0.010$ \msun and $M_{\rm A} = 1.04 \pm 0.13$ \msun. Our result for HAT-TR-205-013 B lies above the theoretical mass-radius models from the Lyon group, consistent with results from double-lined eclipsing binaries. The method we describe offers the opportunity to study the very low end of the stellar mass-radius relation. Comments: 18 pages, 9 tables and 6 figures; accepted by ApJ. Added a reference and corrected a typo

Title: Coulomb excitation of unstable nuclei at intermediate energiesCategory: nucl-thAuthors: C.A. Bertulani, G. Cardella, M. De Napoli, G. Raciti, and E. RapisardaStudy Abstract: We investigate the Coulomb excitation of low-lying states of unstable nuclei in intermediate energy collisions ($E_{lab}\sim10-500$ MeV/nucleon). It is shown that the cross sections for the $E1$ and $E2$ transitions are larger at lower energies, much less than 10 MeV/nucleon. Retardation effects and Coulomb distortion are found to be both relevant for energies as low as 10 MeV/nucleon and as high as 500 MeV/nucleon. Implications for studies at radioactive beam facilities are discussed. Comments: 12 pages, 2 figures, accepted for publication in Phys. Lett. B

Title: Intersection Bodies and Generalized Cosine TransformsCategory: math.FAAuthors: Boris RubinStudy Abstract: 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. Comments: 38 pages

Title: Nilpotent symmetry invariance in the superfield formulation: the (non-)Abelian 1-form gauge theoriesCategory: hep-thAuthors: R. P. Malik (Bhu)Study Abstract: 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 the geometrical understanding of the nilpotent (anti-)BRST symmetry invariance. Comments: LaTeX file, 19 pages, journal reference

Title: Littlewood-Richardson polynomialsCategory: math.AG math.COAuthors: A. I. MolevStudy Abstract: 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 algebra of the Casimir elements for the general linear Lie algebra in the basis of the quantum immanants constructed by A. Okounkov and G. Olshanski. Comments: 21 pages, reference to independent work of V. Kreiman was added

Title: Lagrangian quantum field theory in momentum picture. IV. Commutation relations for free fieldsCategory: hep-thAuthors: Bozhidar Z. Iliev (Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia, Bulgaria)Study Abstract: 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 particular, the mentioned redefinition of the dynamical variables is reduced to normal ordering. As a last restriction on that class is imposed the requirement for existing of an effective procedure for calculating vacuum mean values. The standard bilinear commutation relations are pointed as the only known ones that satisfy all of the mentioned conditions and do not contradict to the existing data. Comments: 60 LaTeX pages. The packages AMS-LaTeX and amsfonts are required. This paper is a continuation of the e-print E-prints No. hep-th/0402006, No. hep-th/0405008 and No. hep-th/0505007. For related papers, visit the "publication" pages at http://theo.inrne.bas.bg/~bozho/

Title: A Note About the {Ki(z)} FunctionsCategory: math.NT math.CVAuthors: Branko J. MalesevicStudy Abstract: In the article [Petojevic 2006], A. Petojevi\' c verified useful properties of the $K_{i}(z)$ functions which generalize Kurepa's [Kurepa 1971] left factorial function. In this note, we present simplified proofs of two of these results and we answer the open question stated in [Petojevic 2006]. Finally, we discuss the differential transcendency of the $K_{i}(z)$ functions. Comments: Accepted in Rocky Mountain Journal of mathematics

Title: Dynamical Objects for Cohomologically Expanding MapsCategory: math.DSAuthors: John W. RobertsonStudy Abstract: 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 formation of any other such invariant current of the same type (say from some local dynamical subsystem). Because we use subsheaves of the sheaf of currents we give conditions under which a subsheaf will have the same cohomology as the sheaf containing it. Using a smoothing argument this allows us to show that the sheaf cohomology of the currents under consideration can be canonically identified with the deRham cohomology groups. Our main theorem can be applied in both the smooth and holomorphic setting. Comments: 38 pages

Title: Coincidence of the oscillations in the dipole transition and in the persistent current of narrow quantum rings with two electronsCategory: cond-mat.mes-hallAuthors: He Yanzhang and Bao ChengguangStudy Abstract: The fractional Aharonov-Bohm oscillation (FABO) of narrow quantum rings with two electrons has been studied and has been explained in an analytical way, the evolution of the period and amplitudes against the magnetic field can be exactly described. Furthermore, the dipole transition of the ground state was found to have essentially two frequencies, their difference appears as an oscillation matching the oscillation of the persistent current exactly. A number of equalities relating the observables and dynamical parameters have been found. Comments: 5 pages, 4 figures, submitted

Title: Pairwise comparisons of typological profiles (of languages)Category: physics.soc-phAuthors: S. Wichmann and E.W. HolmanStudy Abstract: No abstract given; compares pairs of languages from World Atlas of Language Structures. Comments: Linguistics, 10 pages including figure and tables,

Title: The decomposition method and Maple procedure for finding first integrals of nonlinear PDEs of any order with any number of independent variablesCategory: math-ph math.MPAuthors: Yu.N. KosovtsovStudy Abstract: In present paper we propose seemingly new method for finding solutions of some types of nonlinear PDEs in closed form. The method is based on decomposition of nonlinear operators on sequence of operators of lower orders. It is shown that decomposition process can be done by iterative procedure(s), each step of which is reduced to solution of some auxiliary PDEs system(s) for one dependent variable. Moreover, we find on this way the explicit expression of the first-order PDE(s) for first integral of decomposable initial PDE. Remarkably that this first-order PDE is linear if initial PDE is linear in its highest derivatives. The developed method is implemented in Maple procedure, which can really solve many of different order PDEs with different number of independent variables. Examples of PDEs with calculated their general solutions demonstrate a potential of the method for automatic solving of nonlinear PDEs. Comments: 13 pages; Submitted to the 10th International Workshop in Computer Algebra in Scientific Computing, CASC 2007

Title: A transcendental approach to Koll\'ar's injectivity theoremCategory: math.AGAuthors: Osamu FujinoStudy Abstract: We treat Koll\'ar's injectivity theorem from the analytic (or differential geometric) viewpoint. More precisely, we give a curvature condition which implies Koll\'ar type cohomology injectivity theorems. Our main theorem is formulated for a compact K\"ahler manifold, but the proof uses the space of harmonic forms on a Zariski open set with a suitable complete K\"ahler metric. We need neither covering tricks, desingularizations, nor Leray's spectral sequence. Comments: 22 pages; a minor revision of the preprint circulated in January 2006, v2: minor modifications, v3: final version, to appear in Osaka J. Math

Title: Strong decays of charmed baryonsCategory: hep-ph hep-ex nucl-exAuthors: Chong Chen, Xiao-Lin Chen, Xiang Liu, Wei-Zhen Deng and Shi-Lin ZhuStudy Abstract: There has been important experimental progress in the sector of heavy baryons in the past several years. We study the strong decays of the S-wave, P-wave, D-wave and radially excited charmed baryons using the $^3P_0$ model. After comparing the calculated decay pattern and total width with the available data, we discuss the possible internal structure and quantum numbers of those charmed baryons observed recently. Comments: 13 pages, 9 figures, 9 tables. Some descriptions changed. Published version in PRD

Title: CP violation in beauty decaysCategory: hep-ph hep-exAuthors: Michael GronauStudy Abstract: Precision tests of the Kobayashi-Maskawa model of CP violation are discussed, pointing out possible signatures for other sources of CP violation and for new flavor-changing operators. The current status of the most accurate tests is summarized. Comments: 27 pages, minor corrections, to be published in Int. J. Mod. Phys. A

Title: Universal Forces and the Dark Energy ProblemCategory: physics.gen-phAuthors: Afsar AbbasStudy Abstract: The Dark Energy problem is forcing us to re-examine our models and our understanding of relativity and space-time. Here a novel idea of Fundamental Forces is introduced. This allows us to perceive the General Theory of Relativity and Einstein's Equation from a new pesrpective. In addition to providing us with an improved understanding of space and time, it will be shown how it leads to a resolution of the Dark Energy problem. Comments: 9 pages. no figures

Title: Linear perturbations of matched spacetimes: the gauge problem and background symmetriesCategory: gr-qcAuthors: Marc Mars, Filipe C. Mena, Raul VeraStudy Abstract: We present a critical review about the study of linear perturbations of matched spacetimes including gauge problems. We analyse the freedom introduced in the perturbed matching by the presence of background symmetries and revisit the particular case of spherically symmetry in n-dimensions. This analysis includes settings with boundary layers such as brane world models and shell cosmologies. Comments: 18 pages, plain LaTeX file

Title: Operator algebras associated with unitary commutation relationsCategory: math.OAAuthors: Stephen C. Power (Lancaster University), Baruch Solel (Technion)Study Abstract: We define nonselfadjoint operator algebras with generators $L_{e_1},..., L_{e_n}, L_{f_1},...,L_{f_m}$ subject to the unitary commutation relations of the form \[ L_{e_i}L_{f_j} = \sum_{k,l} u_{i,j,k,l} L_{f_l}L_{e_k}\] where $u= (u_{i,j,k,l})$ is an $nm \times nm$ unitary matrix. These algebras, which generalise the analytic Toeplitz algebras of rank 2 graphs with a single vertex, are classified up to isometric isomorphism in terms of the matrix $u$. Comments: 38 pages

Title: Shaping the Globular Cluster Mass Function by Stellar-Dynamical EvaporationCategory: astro-phAuthors: Dean E. McLaughlin and S. Michael FallStudy Abstract: We show that the globular cluster mass function (GCMF) in the Milky Way depends on cluster half-mass density (rho_h) in the sense that the turnover mass M_TO increases with rho_h while the width of the GCMF decreases. We argue that this is the expected signature of the slow erosion of a mass function that initially rose towards low masses, predominantly through cluster evaporation driven by internal two-body relaxation. We find excellent agreement between the observed GCMF -- including its dependence on internal density rho_h, central concentration c, and Galactocentric distance r_gc -- and a simple model in which the relaxation-driven mass-loss rates of clusters are approximated by -dM/dt = mu_ev ~ rho_h^{1/2}. In particular, we recover the well-known insensitivity of M_TO to r_gc. This feature does not derive from a literal ``universality'' of the GCMF turnover mass, but rather from a significant variation of M_TO with rho_h -- the expected outcome of relaxation-driven cluster disruption -- plus significant scatter in rho_h as a function of r_gc. Our conclusions are the same if the evaporation rates are assumed to depend instead on the mean volume or surface densities of clusters inside their tidal radii, as mu_ev ~ rho_t^{1/2} or mu_ev ~ Sigma_t^{3/4} -- alternative prescriptions that are physically motivated but involve cluster properties (rho_t and Sigma_t) that are not as well defined or as readily observable as rho_h. In all cases, the normalization of mu_ev required to fit the GCMF implies cluster lifetimes that are within the range of standard values (although falling towards the low end of this range). Our analysis does not depend on any assumptions or information about velocity anisotropy in the globular cluster system. Comments: Final version, matching the published paper

Title: Quantum Deformations of Relativistic SymmetriesCategory: math.QA hep-th math-ph math.MP math.RTAuthors: V.N. Tolstoy (INP, Moscow State University)Study Abstract: We discussed quantum deformations of D=4 Lorentz and Poincare algebras. In the case of Poincare algebra it is shown that almost all classical r-matrices of S. Zakrzewski classification correspond to twisted deformations of Abelian and Jordanian types. A part of twists corresponding to the r-matrices of Zakrzewski classification are given in explicit form. Comments: 10 pages. Invited talk at the XXII Max Born Symposium "Quantum, Super and Twistors", September 27-29, 2006, Wroclaw (Poland), in honour of Jerzy Lukierski.

Title: Matter-Wave Bright Solitons with a Finite Background in Spinor Bose-Einstein CondensatesCategory: cond-mat.other cond-mat.stat-mechAuthors: Tetsuo Kurosaki, Miki WadatiStudy Abstract: 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 studies for bright solitons under vanishing boundary conditions and dark solitons. As a result, we establish the robustness and the usefulness of the multiple matter-wave solitons in the spinor BECs. Comments: 18 pages, 4 figures, LaTeX

Title: Why there is something rather than nothing (out of everything)?Category: hep-thAuthors: A.O.BarvinskyStudy Abstract: 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 quasi-equilibrium decay of the microcanonical state of the Universe. Comments: 4 pages, RevTex, several references added and minor changes done

Title: Formation of density singularities in ideal hydrodynamics of freely cooling inelastic gases: a family of exact solutionsCategory: cond-mat.soft nlin.PS physics.flu-dynAuthors: Itzhak Fouxon, Baruch Meerson, Michael Assaf, Eli LivneStudy Abstract: We employ granular hydrodynamics to investigate a paradigmatic problem of clustering of particles in a freely cooling dilute granular gas. We consider large-scale hydrodynamic motions where the viscosity and heat conduction can be neglected, and one arrives at the equations of ideal gas dynamics with an additional term describing bulk energy losses due to inelastic collisions. We employ Lagrangian coordinates and derive a broad family of exact non-stationary analytical solutions that depend only on one spatial coordinate. These solutions exhibit a new type of singularity, where the gas density blows up in a finite time when starting from smooth initial conditions. The density blowups signal formation of close-packed clusters of particles. As the density blow-up time $t_c$ is approached, the maximum density exhibits a power law $\sim (t_c-t)^{-2}$. The velocity gradient blows up as $\sim - (t_c-t)^{-1}$ while the velocity itself remains continuous and develops a cusp (rather than a shock discontinuity) at the singularity. The gas temperature vanishes at the singularity, and the singularity follows the isobaric scenario: the gas pressure remains finite and approximately uniform in space and constant in time close to the singularity. An additional exact solution shows that the density blowup, of the same type, may coexist with an "ordinary" shock, at which the hydrodynamic fields are discontinuous but finite. We confirm stability of the exact solutions with respect to small one-dimensional perturbations by solving the ideal hydrodynamic equations numerically. Furthermore, numerical solutions show that the local features of the density blowup hold universally, independently of details of the initial and boundary conditions. Comments: 19 pages, 7 figures

Title: A Universality in PP-WavesCategory: hep-thAuthors: Partha MukhopadhyayStudy Abstract: 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 dilaton independent of transverse coordinates the field redefinition relating the low energy effective field theory and CSFT with all the massive modes integrated out is at most quadratic in fields. Because of this simplification it is expected that the off-shell pp-waves can be identified on the two sides. Furthermore, given the massless pp-wave field configurations, an iterative method for computing the higher massive modes using the CSFT equations of motion has been discussed. All our bosonic string theory analyses can be generalised to the common Neveu-Schwarz sector of superstrings. Comments: LaTeX file, 43 pages, one reference added, minor changes made

Title: Clustering in a stochastic model of one-dimensional gasCategory: math.PRAuthors: Vladislav V. VysotskyStudy Abstract: We give a quantitative analysis of clustering in a stochastic model of one-dimensional gas. At time zero, the gas consists of $n$ identical particles that are randomly distributed on the real line and have zero initial speeds. Particles begin to move under the forces of mutual attraction. When particles collide, they stick together forming a new particle, called cluster, whose mass and speed are defined by the laws of conservation. We are interested in the asymptotic behavior of $K_n(t)$ as $n\to \infty$, where $K_n(t)$ denotes the number of clusters at time $t$ in the system with $n$ initial particles. Our main result is a functional limit theorem for $K_n(t)$. Its proof is based on the discovered localization property of the aggregation process, which states that the behavior of each particle is essentially defined by the motion of neighbor particles. Comments: Published in at http://dx.doi.org/10.1214/07-AAP481 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Title: Some new experimental photonic flame effect featuresCategory: physics.opticsAuthors: N.V.TcherniegaStudy Abstract: 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 matrixes. Comments: 9 pages, 10 figures, accepted for publication in JRLR

Title: A general approach to statistical modeling of physical laws: nonparametric regressionCategory: physics.data-an physics.gen-phAuthors: I. GrabecStudy Abstract: 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 predictor cost function, a proper number of data in the model is estimated. Comments: 17 pages, 8 eps figures, uses revtex4.cls

Title: Groups with finitely many conjugacy classes and their automorphismsCategory: math.GRAuthors: Ashot MinasyanStudy Abstract: We combine classical methods of combinatorial group theory with the theory of small cancellations over relatively hyperbolic groups to construct finitely generated torsion-free groups that have only finitely many classes of conjugate elements. Moreover, we present several results concerning embeddings into such groups. As another application of these techniques, we prove that every countable group $C$ can be realized as a group of outer automorphisms of a group $N$, where $N$ is a finitely generated group having Kazhdan's property (T) and containing exactly two conjugacy classes. Comments: 30 pages, 2 figures. Version 2: corrected several misprints and added new Lemma 6.4

Title: Energy density for chiral lattice fermions with chemical potentialCategory: hep-lat hep-phAuthors: Christof Gattringer and Ludovit LiptakStudy Abstract: We study a recently proposed formulation of overlap fermions at finite density. In particular we compute the energy density as a function of the chemical potential and the temperature. It is shown that overlap fermions with chemical potential reproduce the correct continuum behavior. Comments: Minor changes in the text. Version to appear in Phys. Rev. D

Title: Aspects of Electron-Phonon Self-Energy Revealed from Angle-Resolved Photoemission SpectroscopyCategory: cond-mat.supr-con cond-mat.str-elAuthors: W.S. Lee, S. Johnston, T.P. Devereaux, and Z.-X. ShenStudy Abstract: Lattice contribution to the electronic self-energy in complex correlated oxides is a fascinating subject that has lately stimulated lively discussions. Expectations of electron-phonon self-energy effects for simpler materials, such as Pd and Al, have resulted in several misconceptions in strongly correlated oxides. Here we analyze a number of arguments claiming that phonons cannot be the origin of certain self-energy effects seen in high-$T_c$ cuprate superconductors via angle resolved photoemission experiments (ARPES), including the temperature dependence, doping dependence of the renormalization effects, the inter-band scattering in the bilayer systems, and impurity substitution. We show that in light of experimental evidences and detailed simulations, these arguments are not well founded. Comments: 8 pages, 4 figures. Accepted by Phys. Rev. B

Title: Timing and Lensing of the Colliding Bullet Clusters: barely enough time and gravity to accelerate the bulletCategory: astro-phAuthors: HongSheng Zhao (SUPA, St Andrews)Study Abstract: 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 beyond General Relativity, e.g., a speed of $4500\kms$ is easily obtained in the relativistic MONDian lensing model of Angus et al. (2007). However, MONDian model with little hot dark matter $M_{HDM} \le 0.6\times 10^{15}\msun$ and CDM model with a small halo mass $\le 1\times 10^{15}\msun$ are barely consistent with lensing and velocity data. Comments: 5-pages, Physical Review D, rapid publication submitted

Title: Geometry of Locally Compact Groups of Polynomial Growth and Shape of Large BallsCategory: math.GR math.DGAuthors: Emmanuel BreuillardStudy Abstract: We get asymptotics for the volume of large balls in an arbitrary locally compact group G with polynomial growth. This is done via a study of the geometry of G and a generalization of P. Pansu's thesis. In particular, we show that any such G is weakly commensurable to some simply connected solvable Lie group S, the Lie shadow of G. We also show that large balls in G have an asymptotic shape, i.e. after a suitable renormalization, they converge to a limiting compact set which can be interpreted geometrically. We then discuss the speed of convergence, treat some examples and give an application to ergodic theory. We also answer a question of Burago about left invariant metrics and recover some results of Stoll on the irrationality of growth series of nilpotent groups. Comments: slightly expanded and polished new version, 57 pages, 2 figures

Title: Much ado about 248Category: nlin.SIAuthors: M.C. Nucci and P.G.L. LeachStudy Abstract: In this note we present three representations of a 248-dimensional Lie algebra, namely the algebra of Lie point symmetries admitted by a system of five trivial ordinary differential equations each of order forty-four, that admitted by a system of seven trivial ordinary differential equations each of order twenty-eight and that admitted by one trivial ordinary differential equation of order two hundred and forty-four. Comments: 5 pages

Title: Conformal Field Theory and Operator AlgebrasCategory: math-ph math.MP math.OAAuthors: Yasuyuki KawahigashiStudy Abstract: We review recent progress in operator algebraic approach to conformal quantum field theory. Our emphasis is on use of representation theory in classification theory. This is based on a series of joint works with R. Longo. Comments: For the Proceedings of ICMP (Rio de Janeiro, 2006).

Title: Sparsely-spread CDMA - a statistical mechanics based analysisCategory: cs.IT math.ITAuthors: Jack Raymond, David SaadStudy Abstract: Sparse Code Division Multiple Access (CDMA), a variation on the standard CDMA method in which the spreading (signature) matrix contains only a relatively small number of non-zero elements, is presented and analysed using methods of statistical physics. The analysis provides results on the performance of maximum likelihood decoding for sparse spreading codes in the large system limit. We present results for both cases of regular and irregular spreading matrices for the binary additive white Gaussian noise channel (BIAWGN) with a comparison to the canonical (dense) random spreading code. Comments: 23 pages, 5 figures, figure 1 amended since published version

Title: On Ando's inequalities for convex and concave functionsCategory: math.FAAuthors: Koenraad M.R. Audenaert and Jaspal Singh AujlaStudy Abstract: 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 between the spectra of two Hermitian matrices, where $Y$ is itself a Hermitian matrix, and prove a certain property of this relation that allows to strengthen the results of Bourin-Uchiyama and Kosem, mentioned above. Comments: 18 pages

Title: Topology Change of Black HolesCategory: gr-qcAuthors: Daisuke Ida and Masaru SiinoStudy Abstract: The topological structure of the event horizon has been investigated in terms of the Morse theory. The elementary process of topological evolution can be understood as a handle attachment. It has been found that there are certain constraints on the nature of black hole topological evolution: (i) There are n kinds of handle attachments in (n+1)-dimensional black hole space-times. (ii) Handles are further classified as either of black or white type, and only black handles appear in real black hole space-times. (iii) The spatial section of an exterior of the black hole region is always connected. As a corollary, it is shown that the formation of a black hole with an S**(n-2) x S**1 horizon from that with an S**(n-1) horizon must be non-axisymmetric in asymptotically flat space-times. Comments: 13 pages, 12 figures