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Sep 19, 2013
09/13

by
Rasul Ganikhodjaev; Farrukh Mukhamedov; Mansoor Saburov

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In the present paper we introduce a notion of $G-$decompositions of matrices. Main result of the paper is that a symmetric matrix $A_m$ has a $G-$decomposition in the class of stochastic (resp. substochastic) matrices if and only if $A_m$ belongs to the set ${\mathbf{U}}^m$ (resp. ${\mathbf{U}}_m$). To prove the main result, we study extremal points and geometrical structures of the sets ${\mathbf{U}}^m$, ${\mathbf{U}}_m$. Note that such kind of investigations enables to study Birkhoff's...

Source: http://arxiv.org/abs/1010.5564v2

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31

Sep 23, 2013
09/13

by
A. A. Deriglazov; B. F. Rizzuti

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Formalism of extended Lagrangian represent a systematic procedure to look for the local symmetries of a given Lagrangian action. In this work, the formalism is discussed and applied to a field theory. We describe it in detail for a field theory with first-class constraints present in the Hamiltonian formulation. The method is illustrated on examples of electrodynamics, Yang-Mills field and non-linear sigma model.

Source: http://arxiv.org/abs/1105.4171v1

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Sep 23, 2013
09/13

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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26

Sep 23, 2013
09/13

by
A. S. Seyffert; C. Venter; O. C. de Jager; A. K. Harding

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The Fermi Large Area Telescope (LAT) has recently reported the detection of pulsed gamma-rays from 6 young pulsars (J0631+1036, J0659+1414, J0742-2822, J1420-6048, J1509-5850, and J1718-3825), all exhibiting single-peaked pulse profiles (Weltevrede et al., 2010). High-quality radio polarization data are also available for 5 of these pulsars, allowing derivation of constraints on their viewing geometries. We obtain independent constraints on the viewing geometries of these pulsars by using a...

Source: http://arxiv.org/abs/1105.4094v1

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24

Sep 23, 2013
09/13

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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30

Sep 18, 2013
09/13

by
Jorge V. Rocha; Vitor Cardoso

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We analyze the gravitational perturbations induced by particles falling into a three dimensional, asymptotically AdS black hole geometry. More specifically, we solve the linearized perturbation equations obtained from the geodesic motion of a ring-like distribution of test particles in the BTZ background. This setup ensures that the U(1) symmetry of the background is preserved. The non-asymptotic flatness of the background raises difficulties in attributing the significance of energy and...

Source: http://arxiv.org/abs/1102.4352v2

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Sep 23, 2013
09/13

by
Gian F. Giudice; Tilman Plehn; Alessandro Strumia

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Astrophysical bounds severely limit the possibility of observing collider signals of gravity with less than 3 flat extra dimensions. However, small distortions of the compactified space can lift the masses of the lightest graviton excitations, evading astrophysical bounds without affecting collider signals of quantum gravity. Following this procedure we reconsider theories with one large extra dimension. A slight space warping gives a model which is safe in the infrared against astrophysical...

Source: http://arxiv.org/abs/hep-ph/0408320v2

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40

Sep 23, 2013
09/13

by
Alexander Moreno; Alejandro Muramatsu; Salvatore R. Manmana

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We examine the ground-state phase diagram of the t-J model in one dimension by means of the Density Matrix Renormalization Group. This model is characterized by a rich phase diagram as a function of the exchange interaction J and the density n, displaying Luttinger-liquid (LL) behavior both of repulsive and attractive (i.e. superconducting) nature, a spin-gap phase, and phase-separation. The phase boundaries separating the repulsive from the attractive LL phase as J is increased, and also the...

Source: http://arxiv.org/abs/1012.4028v2

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Sep 23, 2013
09/13

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