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Sep 23, 2013
09/13

by
Satchidananda Naik

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A Closed string field theory action is formulated for $\mathcal N$ =8 self-dual supergravity which is off-shell and Lorentz covariant. The bosonic truncation in the quantum field theory limit gives the Plebanski type of action in the super space.

Source: http://arxiv.org/abs/0903.2872v1

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Sep 23, 2013
09/13

by
Frédéric Faure

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We consider a simple model of partially expanding map on the torus. We study the spectrum of the Ruelle transfer operator and show that in the limit of high frequencies in the neutral direction (this is a semiclassical limit), the spectrum develops a spectral gap, for a generic map. This result has already been obtained by M. Tsujii (05). The novelty here is that we use semiclassical analysis which provides a different and quite natural description. We show that the transfer operator is a...

Source: http://arxiv.org/abs/0903.2747v1

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Sep 23, 2013
09/13

by
W. Münzer; A. Neubauer; S. Mühlbauer; C. Franz; T. Adams; F. Jonietz; R. Georgii; P. Böni; B. Pedersen; M. Schmidt; A. Rosch; C. Pfleiderer

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We report a comprehensive small angle neutron scattering study (SANS) of the magnetic phase diagram of the doped semiconductor Fe_{1-x}Co_{x}Si for x=0.2 and 0.25. For magnetic field parallel to the neutron beam we observe a six-fold intensity pattern under field-cooling, which identifies the A-phase of Fe_{1-x}Co_{x}Si as a skyrmion lattice. The regime of the skyrmion lattice is highly hysteretic and extents over a wide temperature range, consistent with the site disorder of the Fe and Co...

Source: http://arxiv.org/abs/0903.2587v1

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Sep 23, 2013
09/13

by
Enrique Munoz; Jeong-Man Park; Michael W. Deem

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To represent the evolution of nucleic acid and protein sequence, we express the parallel and Eigen models for molecular evolution in terms of a functional integral representation with an $h$-letter alphabet, lifting the two-state, purine/pyrimidine assumption often made in quasi-species theory. For arbitrary $h$ and a general mutation scheme, we obtain the solution of this model in terms of a maximum principle. Euler's theorem for homogeneous functions is used to derive this `thermodynamic'...

Source: http://arxiv.org/abs/0903.2004v2

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Sep 23, 2013
09/13

by
Frans Snik; Theodora Karalidi; Christoph U. Keller

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Linear (spectro) polarimetry is usually performed using separate photon flux measurements after spatial or temporal polarization modulation. Such classical polarimeters are limited in sensitivity and accuracy by systematic effects and noise. We describe a spectral modulation principle that is based on encoding the full linear polarization properties of light in its spectrum. Such spectral modulation is obtained with an optical train of an achromatic quarter-wave retarder, an athermal...

Source: http://arxiv.org/abs/0903.2735v1

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Sep 23, 2013
09/13

by
Michel J. P. Gingras

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Geometric frustration usually arises in systems that comprise magnetic moments (spins) which reside on the sites of a lattice made up of elementary triangular or tetrahedral units and which interact via antiferromagnetic nearest-neighbor exchange. Albeit much less common, geometric frustration can also arise in systems with strong non-collinear single-ion easy-axis (Ising-like) anisotropy and ferromagnetically} coupled spins. This is what happens in some pyrochlore oxide materials where...

Source: http://arxiv.org/abs/0903.2772v1

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Sep 21, 2013
09/13

by
Shin-ichi Kato; Keiji Takano

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A symmetric space analogue of Casselman's criterion for square integrability of representations of a p-adic group is established. It is described in terms of exponents of Jacquet modules along parabolic subgroups associated to the symmetric space.

Source: http://arxiv.org/abs/0902.2302v2

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Sep 22, 2013
09/13

by
Armin Lühr; Alejandro Saenz

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The stopping power of antiprotons in atomic and molecular hydrogen as well as helium was calculated in an impact-energy range from 1 keV to 6.4 MeV. In the case of H2 and He the targets were described with a single-active electron model centered on the target. The collision process was treated with the close-coupling formulation of the impact-parameter method. An extensive comparison of the present results with theoretical and experimental literature data was performed in order to evaluate...

Source: http://arxiv.org/abs/0812.5058v2

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Sep 22, 2013
09/13

by
Ernesto Nungesser; Alan D. Rendall

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A proof of strong cosmic censorship is presented for a class of solutions of the Einstein-Maxwell equations, those with polarized Gowdy symmetry. A key element of the argument is the observation that by means of a suitable choice of variables the central equations in this problem can be written in a form where they are identical to the central equations for general (i.e. non-polarized) vacuum Gowdy spacetimes. Using this it is seen that the deep results of Ringstr\"om on strong cosmic...

Source: http://arxiv.org/abs/0901.4000v2

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Sep 23, 2013
09/13

by
M. Y. Anand; B. A. I Kagali; Jayant Murthy

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In this paper we have analyzed IUE high resolution spectra of the central star (BD+602522) of the Bubble nebula. We discuss velocities of the different regions along the line of sight to the bubble. We find that the Bubble Nebula is younger (by a factor of 100) than the exciting star suggesting that either the bubble is expanding into an inhomogenuous interstellar medium or that the mechanics of the stellar wind are not fully understood.

Source: http://arxiv.org/abs/0903.2828v1

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Sep 22, 2013
09/13

by
Ioan Baldea; Horst Koppel

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We present theoretical results demonstrating that photoionization can be a useful tool for investigating single--electron transistors. Suggestions are given on how to conduct experiments using photoionization alone or in combination with transport measurements.

Source: http://arxiv.org/abs/0811.2757v2

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Sep 23, 2013
09/13

by
Y. J. Uemura

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Recent muon and neutron experiments on the new FeAs-based superconductors revealed phase diagrams characterized by first-order evolution from antiferromagnetic to superconducting states, and an inelastic magnetic resonance mode whose energy scales as $\sim 4 k_{B}T_{c}$. These features exhibit striking commonalities with cuprate, backyball, organic, and heavy-fermion superconductors as well as superfluid $^{4}$He.

Source: http://arxiv.org/abs/0903.2758v1

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Sep 22, 2013
09/13

by
A. Y. Abul-Magd; G. Akemann; P. Vivo

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Using Beck and Cohen's superstatistics, we introduce in a systematic way a family of generalised Wishart-Laguerre ensembles of random matrices with Dyson index $\beta$ = 1,2, and 4. The entries of the data matrix are Gaussian random variables whose variances $\eta$ fluctuate from one sample to another according to a certain probability density $f(\eta)$ and a single deformation parameter $\gamma$. Three superstatistical classes for $f(\eta)$ are usually considered: $\chi^2$-, inverse $\chi^2$-...

Source: http://arxiv.org/abs/0811.1992v2

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Sep 23, 2013
09/13

by
Mario I. Molina; Yuri S. Kivshar

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We study two-color surface solitons in two-dimensional photonic lattices with quadratic nonlinear response. We demonstrate that such parametrically coupled optical localized modes can exist in the corners or at the edges of a square photonic lattice, and we analyze the impact of the phase mismatch on their properties, stability, and the threshold power for their generation.

Source: http://arxiv.org/abs/0903.2858v1

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Sep 23, 2013
09/13

by
Hichem Hajaiej

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We prove the existence of radial and radially decreasing ground states of an m-coupled nonlinear Schrodinger equation with a general nonlinearity.

Source: http://arxiv.org/abs/0903.2854v1

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Sep 21, 2013
09/13

by
C. Bogdanos; A. Dimitriadis; K. Tamvakis

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We consider 5D braneworld models of quasi-localized gravity in which 4D gravity is reproduced at intermediate scales while the extra dimension opens up at both the very short and the very long distances, where the geometry is flat. Our main interest is the interplay between the zero mode of these models, whenever a normalizable zero mode exists, and the effects of zero energy graviton resonant modes coming from the contributions of massive KK modes. We first consider a compactified version of...

Source: http://arxiv.org/abs/0706.1015v2