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Sep 23, 2013
09/13

Sep 23, 2013
by
Jim Geelen; Peter Nelson

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For any positive integer $l$ we prove that if $M$ is a simple matroid with no $(l+2)$-point line as a minor and with sufficiently large rank, then $|E(M)|\le \frac{q^{r(M)}-1}{q-1}$, where $q$ is the largest prime power less than or equal to $l$. Equality is attained by projective geometries over GF$(q)$.

Source: http://arxiv.org/abs/1105.4163v1

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36

Sep 23, 2013
09/13

Sep 23, 2013
by
Ruyue Yang; Feilong Cao; Jingyi Xiong

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This paper discusses the approximation by de la Vall\'{e}e Poussin means $V_nf$ on the unit sphere. Especially, the lower bound of approximation is studied. As a main result, the strong converse inequality for the means is established. Namely, it is proved that there are constants $C_1$ and $C_2$ such that \begin{eqnarray*} C_1\omega(f,\frac{1}{\sqrt n})_p \leq \|V_{n}f-f\|_p \leq C_2\omega(f,\frac{1}{\sqrt n})_p \end{eqnarray*} for any $p$-th Lebesgue integrable or continuous function $f$...

Source: http://arxiv.org/abs/1105.4062v1

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Sep 23, 2013
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Sep 23, 2013
by
Ryo Tamura; Naoki Kawashima

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Using a Monte Carlo method, we study the finite-temperature phase transition in the two-dimensional classical Heisenberg model on a triangular lattice with or without easy-plane anisotropy. The model takes account of competing interactions: a ferromagnetic nearest-neighbor interaction $J_1$ and an antiferromagnetic third nearest-neighbor interaction $J_3$. As a result, the ground state is a spiral spin configuration for $-4 < J_1/J_3 < 0$. In this structure, global spin rotation cannot...

Source: http://arxiv.org/abs/1105.2452v2

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Sep 23, 2013
09/13

Sep 23, 2013
by
Richard Kenyon; Yuval Peres; Boris Solomyak

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We compute the Hausdorff dimension of the "multiplicative golden mean shift" defined as the set of all reals in $[0,1]$ whose binary expansion $(x_k)$ satisfies $x_k x_{2k}=0$ for all $k\ge 1$, and show that it is smaller than the Minkowski dimension.

Source: http://arxiv.org/abs/1105.3441v2

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Sep 23, 2013
09/13

Sep 23, 2013
by
Rocio Gonzalez-Diaz; Maria Jose Jimenez; Belen Medrano; Pedro Real

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This paper presents a set of tools to compute topological information of simplicial complexes, tools that are applicable to extract topological information from digital pictures. A simplicial complex is encoded in a (non-unique) algebraic-topological format called AM-model. An AM-model for a given object K is determined by a concrete chain homotopy and it provides, in particular, integer (co)homology generators of K and representative (co)cycles of these generators. An algorithm for computing...

Source: http://arxiv.org/abs/1105.3620v2

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Sep 23, 2013
09/13

Sep 23, 2013
by
Dirk Pauly

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We continue the study of the operator of generalized Maxwell equations and completely discover the behavior of the solutions of the time-harmonic equations as the frequency tends to zero. Thereby, we identify degenerate operators in terms of special 'polynomially growing' solutions of a corresponding static problem, which must be added to the 'usual' Neumann series in order to describe the low frequency asymptotic adequately.

Source: http://arxiv.org/abs/1105.4088v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Tanwi Bandyopadhyay; Ujjal Debnath

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In this work, we have considered the magnetic universe in non-linear electrodynamics. The Einstein's field equations for non-flat FRW model have been considered when the universe is filled with the matter and magnetic field only. We have discussed the validity of the generalized second law of thermodynamics of the magntic universe bounded by Hubble, apparent, particle and event horizons using Gibb's law and the first law of thermodynamics for interacting and non-interacting scenarios. It has...

Source: http://arxiv.org/abs/1105.5301v1

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21

Sep 23, 2013
09/13

Sep 23, 2013
by
Dirk Pauly

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We prove polynomial and exponential decay at infinity of eigen-vectors of partial differential operators related to radiation problems for time-harmonic generalized Maxwell systems in an exterior domain with non-smooth inhomogeneous, anisotropic coefficients converging near infinity with a certain rate towards the identity. As a canonical application we show that the corresponding eigen-values do not accumulate in R \ {0} and that by means of Eidus' limiting absorption principle a Fredholm...

Source: http://arxiv.org/abs/1105.4105v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
A. E. Golomedov; G. E. Astrakharchik; Yu. E. Lozovik

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A mesoscopic system of indirect dipolar bosons trapped by a harmonic potential is considered. The system has a number of physical realizations including dipole excitons, atoms with large dipolar moment, polar molecules, Rydberg atoms in inhomogenious electric field. We carry out a diffusion Monte Carlo simulation to define the quantum properties of a two-dimensional system of trapped dipoles at zero temperature. In dimensionless units the system is described by two control parameters, namely...

Source: http://arxiv.org/abs/1105.4075v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Yuji Kodama; Lauren Williams

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Soliton solutions of the KP equation have been studied since 1970, when Kadomtsev and Petviashvili proposed a two-dimensional nonlinear dispersive wave equation now known as the KP equation. It is well-known that the Wronskian approach to the KP equation provides a method to construct soliton solutions. The regular soliton solutions that one obtains in this way come from points of the totally non-negative part of the Grassmannian. In this paper we explain how the theory of total positivity and...

Source: http://arxiv.org/abs/1105.4170v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
A. V. Gopala Rao; K. S. Mallesh; K. N. Srinivasa Rao

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We revisit the problem of the Lorentz transformation of time-separations between events in the Minkowski spacetime to show that there exist a whole class of "time-stretching formulas" which "look" exactly like the well known time-dilation formula (TDF) in special relativity. We highlight the essential di?fferences between the TDF and the similar looking time-stretching formulas in view of the fact that occasionally a time-stretching formula has been mistaken for the TDF in...

Source: http://arxiv.org/abs/1105.4085v1

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59

Sep 23, 2013
09/13

Sep 23, 2013
by
Dirk Pauly; Sergey Repin

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This paper is concerned with the derivation of computable and guaranteed upper bounds of the difference between the exact and the approximate solution of an exterior domain boundary value problem for a linear elliptic equation. Our analysis is based upon purely functional argumentation and does not attract specific properties of an approximation method. Therefore, the estimates derived in the paper at hand are applicable to any approximate solution that belongs to the corresponding energy...

Source: http://arxiv.org/abs/1105.4101v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Aurel Schneider; Lawrence M. Krauss; Ben Moore

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Cosmological structure formation predicts that our galactic halo contains an enormous hierarchy of substructures and streams, the remnants of the merging hierarchy that began with tiny Earth mass microhalos. If these structures persist until the present time, they could influence dramatically the detection signatures of weakly interacting elementary particle dark matter (WIMP). Using numerical simulations that follow the tidal disruption within the Galactic potential and heating from stellar...

Source: http://arxiv.org/abs/1105.4106v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
S. E. Woosley

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Most gamma-ray bursts are made during the deaths of massive stars. Here the environmental circumstances, stellar evolutionary paths, and explosion physics that might produce the bursts are reviewed. Neither of the two leading models - collapsar and millisecond magnetar - can be excluded, and both may operate in progenitor stars of different masses, metallicities, and rotation rates. Potential diagnostics are discussed and uncertainties highlighted. Both models are capable of producing a wide...

Source: http://arxiv.org/abs/1105.4193v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Taylor L. Hughes; Andrew Randono

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It is generally assumed that the gravitational field is bosonic. Here we show that a simple propagating torsional theory can give rise to localized geometric structures that can consistently be quantized as fermions under exchange. To demonstrate this, we show that the model can be formally mapped onto the Skyrme model of baryons, and we use well-known results from Skyrme theory. This begs the question: {\it Is geometry bosonic or fermionic (or both)?}

Source: http://arxiv.org/abs/1105.4184v1

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23

Sep 23, 2013
09/13

Sep 23, 2013
by
Margherita Disertori; Jacques Magnen; Vincent Rivasseau

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We introduce a new multiscale decomposition of the Fermi propagator based on its parametric representation. We prove that the corresponding sliced propagator obeys the same direct space bounds than the previous decomposition used by the authors. Therefore non perturbative bounds on completely convergent contributions still hold. In addition the new slicing better preserves momenta, hence should become an important new technical tool for the rigorous analysis of condensed matter systems. In...

Source: http://arxiv.org/abs/1105.4138v1

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27

Sep 23, 2013
09/13

Sep 23, 2013
by
Hamid Torabi; Ali Pakdaman; Behrooz Mashayekhy

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In this paper, we show that the image of the topological fundamental group of a given space $X$ is dense in the topological fundamental group of the quotient space $X/A$ under the induced homomorphism of the quotient map, where $A$ is a suitable subspace of $X$ with some conditions on $X$. Also, we give some application to find out some properties for $\pi_1^{top}(X/A,*)$. In particular, we give some condition in which $\pi_1^{top}(X/A,*)$ is an indiscrete topological group.

Source: http://arxiv.org/abs/1105.4009v1

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35

Sep 23, 2013
09/13

Sep 23, 2013
by
Richard F. Bass

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We prove a stability theorem for the elliptic Harnack inequality: if two weighted graphs are equivalent, then the elliptic Harnack inequality holds for harmonic functions with respect to one of the graphs if and only if it holds for harmonic functions with respect to the other graph. As part of the proof, we give a characterization of the elliptic Harnack inequality.

Source: http://arxiv.org/abs/1105.4087v1

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39

Sep 23, 2013
09/13

Sep 23, 2013
by
Denis V. Novitsky

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Fano mechanism is the universal explanation of asymmetric resonance appearing in different systems. We report the evidence of Fano-like resonance in selective reflection from a resonant two-level medium. We draw an analogy with the asymmetric resonance previously obtained for the coupled oscillators. We also take into account the effects of dielectric background and local-field correction and connect our results with optical bistability.

Source: http://arxiv.org/abs/1105.4020v1

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50

Sep 23, 2013
09/13

Sep 23, 2013
by
Mosleh Almarashi; Stefano Moretti

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We study the detectability of the lightest CP-odd Higgs boson of the NMSSM, $a_1$, at the LHC through its production in association with a bottom-quark pair followed by the $a_1\to b\bar b$ decay. It is shown that, for large $\tan\beta$ and very high luminosity of the LHC, there exist regions of the NMSSM parameter space that can be exploited to detect the $a_1$ through this channel. This signature is a characteristic feature of the NMSSM in comparison to the MSSM, as $a_1$ masses involved are...

Source: http://arxiv.org/abs/1105.4191v1

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24

Sep 23, 2013
09/13

Sep 23, 2013
by
Yue MA

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In this article one will develop a new type of energy method based on a foliation of spacetime into hyperboloidal hypersurfaces . As we will see, with this method, some classical results such as global existence and almost global existence of regular solutions to the quasi-linear wave equations and Klein-Gordon equations will be established in a much simpler and much more natural way. Most importantly, the global existence of regular solutions to a general type of coupled quasilinear...

Source: http://arxiv.org/abs/1105.4137v1

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39

Sep 23, 2013
09/13

Sep 23, 2013
by
Wayne M. Schlingman; Yancy L. Shirley; David E. Bolin; Erik Rosolowsky; John Bally; Cara Battersby; Miranda K. Dunham; Timothy P. Ellsworth-Bowers; Neal J. Evans II; Adam Ginsburg; Guy Stringfellow

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We present the results of observations of 1882 sources in the Bolocam Galactic Plane Survey (BGPS) at 1.1 mm with the 10m Heinrich Hertz Telescope simultaneously in HCO+ J=3-2 and N2H+ J=3-2. We detect 77% of these sources in HCO^+ and 51% in N2H+ at greater than 3$\sigma$. We find a strong correlation between the integrated intensity of both dense gas tracers and the 1.1 mm dust emission of BGPS sources. We determine kinematic distances for 529 sources (440 in the first quadrant breaking the...

Source: http://arxiv.org/abs/1105.4181v1

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27

Sep 23, 2013
09/13

Sep 23, 2013
by
Antonella D'Avanzo

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Monopoles are solutions of an SU(2) gauge theory in $\mathbb{R}^{3}$ satisfying a lower bound for energy and certain asymptotic conditions, which translate as topological properties encoded in their charge. Using methods from integrable systems, monopoles can be described in algebraic-geometric terms via their {spectral curve}, i.e. an algebraic curve, given as a polynomial P in two complex variables, satisfying certain constraints. In this thesis we focus on the Ercolani-Sinha formulation,...

Source: http://arxiv.org/abs/1105.4153v1

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29

Sep 23, 2013
09/13

Sep 23, 2013
by
Dirk Pauly

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We develop a solution theory for a generalized electro-magneto static Maxwell system in an exterior domain with anisotropic coefficients converging at infinity with a certain rate towards the identity. Our main goal is to treat right hand side data from some polynomially weighted Sobolev spaces and obtain solutions which are up to a finite sum of special generalized spherical harmonics in another appropriately weighted Sobolev space. As a byproduct we prove a generalized spherical harmonics...

Source: http://arxiv.org/abs/1105.4070v1

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41

Sep 23, 2013
09/13

Sep 23, 2013
by
Giovanni Puddu

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The Thermal Hartree-Fock-Bogoliubov approximation with reprojection to good quantum numbers is analyzed in a canonical ensemble. Simple recipes are given for the evaluation of traces, gradients and expectation values in the canonical ensemble.

Source: http://arxiv.org/abs/1105.4021v1

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66

Sep 23, 2013
09/13

Sep 23, 2013
by
G. Faldt; C. Wilkin

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Evidence has recently been presented for the existence of a dibaryon of mass 2380 MeV/c^2 and width 70 MeV/c^2, which decays strongly into the d pi0 pi0 channel [M. Bashkanov et al., Phys.Rev.Lett. 102 (2009) 052301; P. Adlarson et al., arXiv:1104.0123]. The decay rate of such a hypothesised dibaryon into the {pn}_{I=0} pi0 pi0 channel is estimated in a weakly model-dependent way by using final state interaction theory. It is shown that, if the resonance exists, it should then show up as...

Source: http://arxiv.org/abs/1105.4142v1

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37

Sep 23, 2013
09/13

Sep 23, 2013
by
A. L. Efros; Brian Skinner; B. I. Shklovskii

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The one-particle density of states (1P-DOS) in a system with localized electron states vanishes at the Fermi level due to the Coulomb interaction between electrons. Derivation of the Coulomb gap uses stability criteria of the ground state. The simplest criterion is based on the excitonic interaction of an electron and a hole and leads to a quadratic 1P-DOS in the three-dimensional (3D) case. In 3D, higher stability criteria, including two or more electrons, were predicted to exponentially...

Source: http://arxiv.org/abs/1105.1712v2

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25

Sep 23, 2013
09/13

Sep 23, 2013
by
Lawrence Wiencke; Fernando Arqueros; John Compton; Maria Monasor; David Pilger; Jaime Rosado

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Pulsed UV lasers can provide useful "testbeams" for observatories that use optical detectors, especially fluorescence detectors, to measure high energy cosmic-rays. The light observed by the detector is proportional to the energy of the laser pulse. Since the absolute laser energy can be measured locally, a well-calibrated laser offers a practical way to test the photometric calibration of the cosmic-ray detector including atmospheric corrections. This poster will describe a robotic...

Source: http://arxiv.org/abs/1105.4016v1

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33

Sep 23, 2013
09/13

Sep 23, 2013
by
Dirk Pauly

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We study in detail Hodge-Helmholtz decompositions in non-smooth exterior domains filled with inhomogeneous and anisotropic media. We show decompositions of alternating differential forms belonging to weighted Sobolev spaces into irrotational and solenoidal forms. These decompositions are essential tools, for example, in electro-magnetic theory for exterior domains. In the appendix we translate our results to the classical framework of vector analysis.

Source: http://arxiv.org/abs/1105.4073v1

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69

Sep 23, 2013
09/13

Sep 23, 2013
by
Dirk Pauly; Sergey Repin; Tuomo Rossi

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In this paper, we consider an initial boundary value problem for Maxwell's equations. For this hyperbolic type problem, we derive guaranteed and computable upper bounds for the difference between the exact solution and any pair of vector fields in the space-time cylinder that belongs to the corresponding admissible energy class. For this purpose, we use a method suggested earlier for the wave equation.

Source: http://arxiv.org/abs/1105.4110v1

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73

Sep 23, 2013
09/13

Sep 23, 2013
by
Mihai Turinici

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The comparison type version of the fixed point result in ordered metric spaces established by Nieto and Rodriguez-Lopez [Acta Math. Sinica (English Series), 23 (2007), 2205-2212] is nothing but a particular case of the classical Banach's contraction principle [Fund. Math., 3 (1922), 133-181].

Source: http://arxiv.org/abs/1105.2401v2

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28

Sep 23, 2013
09/13

Sep 23, 2013
by
Pochung Chen; Zhi-Long Xue; I. P. McCulloch; Ming-Chiang Chung; S. -K. Yip

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We study the phase diagram for spin-2 bosons loaded in a one-dimensional optical lattice. By using non-Abelian density matrix renormalization group (DMRG) method we identify three possible phases: ferromagnetic, dimerized, and trimerized phases. We sketch the phase boundaries based on DMRG. We illustrate two methods for identifying the phases. The first method is based on the spin-spin correlation function while in the second method one observes the excitation gap as a dimerization or a...

Source: http://arxiv.org/abs/1105.3773v2

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34

Sep 23, 2013
09/13

Sep 23, 2013
by
V. S. Pantuev

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Experimental data for hadron radial and elliptic flow are used to investigate their influence on the shape of the thermal photon spectrum at RHIC. Leaving alone the actual mechanism of photon production and its time evolution, we concentrate on the spectrum shape. Radial and longitudinal flow of the bulk can change significantly the observed photon energy spectrum via the Doppler Effect. Experimental thermal photon data are described by local frame temperature parameter which depends on the...

Source: http://arxiv.org/abs/1105.4033v1

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30

Sep 23, 2013
09/13

Sep 23, 2013
by
Richard C. Bradley

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In a paper that appeared in 2010, C. Tone proved a multivariate central limit theorem for some strictly stationary random fields of random vectors satisfying certain mixing conditions. The "normalization" of a given "partial sum" (or "block sum") involved matrix multiplication by a "standard -1/2 power" of its covariance matrix (a symmetric, positive definite matrix), and the limiting multivariate normal distribution had the identity matrix as its...

Source: http://arxiv.org/abs/1105.4132v1

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36

Sep 23, 2013
09/13

Sep 23, 2013
by
Guillaume Hupin; Denis Lacroix; Michael Bender

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The restoration of particle number within Energy Density Functional theory is analyzed. It is shown that the standard method based on configuration mixing leads to a functional of both the projected and non-projected densities. As an alternative that might be advantageous for mass models, nuclear dynamics and thermodynamics, we propose to formulate the functional in terms directly of the one-body and two-body density matrices of the state with good particle number. Our approach does not contain...

Source: http://arxiv.org/abs/1105.4084v1

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38

Sep 23, 2013
09/13

Sep 23, 2013
by
Sergey Bravyi; Jeongwan Haah

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We explore feasibility of a quantum self-correcting memory based on 3D spin Hamiltonians with topological quantum order in which thermal diffusion of topological defects is suppressed by macroscopic energy barriers. To this end we characterize the energy landscape of stabilizer code Hamiltonians with local bounded-strength interactions which have a topologically ordered ground state but do not have string-like logical operators. We prove that any sequence of local errors mapping a ground state...

Source: http://arxiv.org/abs/1105.4159v1

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33

Sep 23, 2013
09/13

Sep 23, 2013
by
Miguel Couceiro; Michel Grabisch

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The symmetric maximum, denoted by v, is an extension of the usual max operation so that 0 is the neutral element, and -x is the symmetric (or inverse) of x, i.e., x v(-x)=0. However, such an extension does not preserve the associativity of max. This fact asks for systematic ways of parenthesing (or bracketing) terms of a sequence (with more than two arguments) when using such an extended maximum. We refer to such systematic (predefined) ways of parenthesing as computation rules. As it turns out...

Source: http://arxiv.org/abs/1105.4174v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Sushant Sachdeva; Rishi Saket

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We study the problem of computing the minimum vertex cover on k-uniform k-partite hypergraphs when the k-partition is given. On bipartite graphs (k = 2), the minimum vertex cover can be computed in polynomial time. For general k, the problem was studied by Lov\'asz, who gave a k/2 -approximation based on the standard LP relaxation. Subsequent work by Aharoni, Holzman and Krivelevich showed a tight integrality gap of (k/2 - o(1)) for the LP relaxation. While this problem was known to be NP-hard...

Source: http://arxiv.org/abs/1105.4175v1

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23

Sep 23, 2013
09/13

Sep 23, 2013
by
Jérémy Le Borgne

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We introduce the notion of semi-characteristic polynomial for a semi-linear map of a finite- dimensional vector space over a field of characteristic p. This polynomial has some properties in common with the classical characteristic polynomial of a linear map. We use this notion to study skew polynomials and linearized polynomials over a finite field, giving an algorithm to compute the splitting field of a linearized polynomial over a finite field and the Galois action on this field. We also...

Source: http://arxiv.org/abs/1105.4083v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
M. Szymczak; P. Wolak; A. Bartkiewicz; H. J. van Langevelde

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We report the discovery of periodic flares of 6.7GHz methanol maser in the young massive stellar object G22.357+0.066. The target was monitored in the methanol maser line over 20 months with the Torun 32m telescope. The emission was also mapped at two epochs using the EVN. The 6.7GHz methanol maser shows periodic variations with a period of 179 days. The periodic behavior is stable for the last three densely sampled cycles and has even been stable over ~12 years, as the archival data suggest....

Source: http://arxiv.org/abs/1105.4089v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Dominik A. Riechers; Jacqueline Hodge; Fabian Walter; Christopher L. Carilli; Frank Bertoldi

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We report the detection of spatially resolved CO(1-0) emission in the z~3.4 submillimeter galaxies (SMGs) SMM J09431+4700 and SMM J13120+4242, using the Expanded Very Large Array (EVLA). SMM J09431+4700 is resolved into the two previously reported millimeter sources H6 and H7, separated by ~30kpc in projection. We derive CO(1-0) line luminosities of L'(CO 1-0) = (2.49+/-0.86) and (5.82+/-1.22) x 10^10 K km/s pc^2 for H6 and H7, and L'(CO 1-0) = (23.4+/-4.1) x 10^10 K km/s pc^2 for SMM...

Source: http://arxiv.org/abs/1105.4177v1

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43

Sep 23, 2013
09/13

Sep 23, 2013
by
Francesco Beritelli; Andrea Spadaccini

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Identity verification is an increasingly important process in our daily lives, and biometric recognition is a natural solution to the authentication problem. One of the most important research directions in the field of biometrics is the characterization of novel biometric traits that can be used in conjunction with other traits, to limit their shortcomings or to enhance their performance. The aim of this work is to introduce the reader to the usage of heart sounds for biometric recognition,...

Source: http://arxiv.org/abs/1105.4058v1

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25

Sep 23, 2013
09/13

Sep 23, 2013
by
Peter Nelson

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For each proper minor-closed subclass $\cM$ of the $\GF(q^2)$-representable matroids containing all simple $\GF(q)$-representable matroids, we give, for all large $r$, a tight upper bound on the number of points in a rank-$r$ matroid in $\cM$, and construct a rank-$r$ matroid in $\cM$ for which equality holds. As a consequence, we give a tight upper bound on the number of points in a $\GF(q^2)$-representable, rank-$r$ matroid with no $\PG(k,q^2)$-minor.

Source: http://arxiv.org/abs/1105.4162v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Zhen Liu; Qian-Ming Zhang; Linyuan Lü; Tao Zhou

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Common-neighbor-based method is simple yet effective to predict missing links, which assume that two nodes are more likely to be connected if they have more common neighbors. In such method, each common neighbor of two nodes contributes equally to the connection likelihood. In this Letter, we argue that different common neighbors may play different roles and thus lead to different contributions, and propose a local na\"{\i}ve Bayes model accordingly. Extensive experiments were carried out...

Source: http://arxiv.org/abs/1105.4005v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
David Cole; Walter Dehnen; Mark Wilkinson

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We consider the infall of a massive clump into a dark-matter halo as a simple and extreme model for the effect of baryonic physics (neglected in gravity-only simulations of large-scale structure formation) on the dark-matter. We find that such an infalling clump is extremely efficient in altering the structure of the halo and reducing its central density: a clump of 1% the mass of the halo can remove about twice its own mass from the inner halo and transform a cusp into a core or weaker cusp....

Source: http://arxiv.org/abs/1105.4050v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Stefan Hollands

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We generalize key aspects of arXiv:1010.5367 (and also arXiv:1010.5327) to the case of {\em massless} $\lambda \phi^{2n}$ quantum field theory on deSitter spacetime. As in that paper, our key objective is to derive a suitable "Mellin-Barnes-type" representation of deSitter correlation functions in a deSitter-invariant state, which holds to arbitrary orders in perturbation theory, and which incorporates renormalization. The representation is suitable for the study of large...

Source: http://arxiv.org/abs/1105.1996v2

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Sep 23, 2013
09/13

Sep 23, 2013
by
Azam Hokmabadi; Behrooz Mashayekhy; Fahimeh Mohammadzadeh

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This article is devoted to present an explicit formula for the $c$th nilpotent multiplier of nilpotent products of some cyclic groups $G={\bf {Z}}\stackrel{n_1}{*}{\bf {Z}}\stackrel{n_2}{*}...\stackrel{n_{t-1}}{*}{\bf {Z}}\stackrel{n_{t}}{*} {\bf {Z}}_{m_{t+1}}\stackrel{n_{t+1}}{*}{\bf {Z}}_{m_{t+2}}\stackrel{n_{t+2}}{*}...\stackrel{n_{k}}{*}{\bf{Z}}_{m_{k+1}}$, where $m_{i+1} | m_i$ for all $t+1 \leq i \leq k$ and $c \geq n_1\geq n_2\geq ...\geq n_t\geq ...\geq n_{k}$ such that $...

Source: http://arxiv.org/abs/1105.4012v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Larry McLerran

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I discuss the phase diagram for QCD in the baryon chemical potential and temperature plane. I argue that there is a new phase of matter different from the deconfined Quark Gluon Plasma: Quarkyonic Matter. Quarkyonic Matter is confined and exists at densities parametrically large compared to the QCD scale, when the number of quark colors, $N_c$ is large. I motivate the possibility that Quarkyonic Matter is in an inhomogeneous phase, and is surrounded by lines of phase transitions, making a Happy...

Source: http://arxiv.org/abs/1105.4103v1

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Sep 23, 2013
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Sep 23, 2013
by
David L. Kaplan; Atish Kamble; Marten H. van Kerkwijk; Wynn C. G. Ho

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We present Hubble Space Telescope optical and ultraviolet photometry for five nearby, thermally emitting neutron stars. With these measurements, all seven such objects have confirmed optical and ultraviolet counterparts. Combining our data with archival space-based photometry, we present spectral energy distributions for all sources and measure the "optical excess": the factor by which the measured photometry exceeds that extrapolated from X-ray spectra. We find that the majority have...

Source: http://arxiv.org/abs/1105.4178v1

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Sep 23, 2013
09/13

Sep 23, 2013
by
Jakob Heide Jørgensen; Tobias Lindstrøm Jensen; Per Christian Hansen; Søren Holdt Jensen; Emil Y. Sidky; Xiaochuan Pan

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Total-variation (TV)-based Computed Tomography (CT) image reconstruction has shown experimentally to be capable of producing accurate reconstructions from sparse-view data. In particular TV-based reconstruction is very well suited for images with piecewise nearly constant regions. Computationally, however, TV-based reconstruction is much more demanding, especially for 3D imaging, and the reconstruction from clinical data sets is far from being close to real-time. This is undesirable from a...

Source: http://arxiv.org/abs/1105.4002v1