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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 23, 2013
09/13

by
Marco Pavone; Stephen L. Smith; Francesco Bullo; Emilio Frazzoli

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In this paper we study a dynamic vehicle routing problem in which there are multiple vehicles and multiple classes of demands. Demands of each class arrive in the environment randomly over time and require a random amount of on-site service that is characteristic of the class. To service a demand, one of the vehicles must travel to the demand location and remain there for the required on-site service time. The quality of service provided to each class is given by the expected delay between the...

Source: http://arxiv.org/abs/0903.2695v1

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Sep 23, 2013
09/13

by
S. Qian; L. Zhu; S. Zola; W. Liao; L. Liu; L. Li; M. Winiarski; E. Kuligowska; J. Kreiner

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HS 0705+6700 is a short-period (P=2.3 hours), close binary containing a hot sdB-type primary and a fully convective secondary. We have monitored this eclipsing binary for more than 2 years and as a result, 32 times of light minimum were obtained. Based on our new eclipse times together with these compiled from the literature, it is discovered that the O-C curve of HS 0705+6700 shows a cyclic variation with a period of 7.15 years and a semiamplitude of 92.4 s. The periodic change was analyzed...

Source: http://arxiv.org/abs/0903.1357v2

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Jul 22, 2013
07/13

by
Jorge Noronha; Miklos Gyulassy; Giorgio Torrieri

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We show that far zone Mach and diffusion wake ``holograms'' produced by supersonic strings in anti--de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict $N_c\to\infty$ supergravity limit if Cooper-Frye hadronization is assumed. However, a special {\em nonequilibrium} ``neck'' zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's...

Source: http://arxiv.org/abs/0807.1038v2

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Sep 23, 2013
09/13

by
Jose M. Fernandez; Matthew J. Holman; Joshua N. Winn; Guillermo Torres; Avi Shporer; Tsevi Mazeh; Gilbert A. Esquerdo; Mark E. Everett

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We present photometry of six transits of the exoplanet XO-2b. By combining the light-curve analysis with theoretical isochrones to determine the stellar properties, we find the planetary radius to be 0.996 +0.031/-0.018 rjup and the planetary mass to be 0.565 +/- 0.054 mjup. These results are consistent with those reported previously, and are also consistent with theoretical models for gas giant planets. The mid-transit times are accurate to within 1 min and are consistent with a constant...

Source: http://arxiv.org/abs/0903.2687v1

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Sep 23, 2013
09/13

by
Malgorzata Krolikowska; Grzegorz Sitarski; Andrzej M. Soltan

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The aim is to show that in case of low probability of asteroid collision with Earth, the appropriate selection and weighing of the data are crucial for the impact investigation, and to analyze the impact possibilities using extensive numerical simulations. By means of the Monte Carlo special method a large number of ``clone'' orbits have been generated. A full range of orbital elements in the 6-dimensional parameter space, e.g. in the entire confidence region allowed by the observational...

Source: http://arxiv.org/abs/0903.2727v1

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Sep 21, 2013
09/13

by
Avinash Dhar; Partha Nag

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We discuss chiral symmetry breaking in the intersecting brane model of Sakai and Sugimoto at weak coupling for a generic value of separation $L$ between the flavour $D8$ and anti-$D8$-branes. For any finite value of the radius $R$ of the circle around which the colour $D4$-branes wrap, a non-local Nambu$-$Jona-Lasinio (NJL) type short-range interaction couples the flavour branes and anti-branes. We argue that chiral symmetry is broken in this model only above a certain critical value of the...

Source: http://arxiv.org/abs/0901.4942v2

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Sep 21, 2013
09/13

by
L. Herrera

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We show that small deviations from spherical symmetry, described by means of exact solutions to Einstein equations, provide a mechanism to "bleach" the information about the collapsing body as it falls through the aparent horizon, thereby resolving the information loss paradox. The resulting picture and its implication related to the Landauer's principle in the presence of a gravitational field, is discussed.

Source: http://arxiv.org/abs/0709.4674v4

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Sep 23, 2013
09/13

by
Nima Arkani-Hamed; Freddy Cachazo; Clifford Cheung; Jared Kaplan

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The simplicity and hidden symmetries of (Super) Yang-Mills and (Super)Gravity scattering amplitudes suggest the existence of a "weak-weak" dual formulation in which these structures are made manifest at the expense of manifest locality. We suggest that this dual description lives in (2,2) signature and is naturally formulated in twistor space. We recast the BCFW recursion relations in an on-shell form that begs to be transformed into twistor space. Our twistor transformation is...

Source: http://arxiv.org/abs/0903.2110v2

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Sep 23, 2013
09/13

by
Wen-Li Yang; Yao-Zhong Zhang; Samuel Kault

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Based on the particular orderings introduced for the positive roots of finite dimensional basic Lie superalgebras, we construct the explicit differential operator representations of the $osp(2r|2n)$ and $osp(2r+1|2n)$ superalgebras and the explicit free field realizations of the corresponding current superalgebras $osp(2r|2n)_k$ and $osp(2r+1|2n)_k$ at an arbitrary level $k$. The free field representations of the corresponding energy-momentum tensors and screening currents of the first kind are...

Source: http://arxiv.org/abs/0810.3719v2

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Sep 21, 2013
09/13

by
A. Coley; S. Hervik; G. Papadopoulos; N. Pelavas

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Kundt spacetimes are of great importance in general relativity in 4 dimensions and have a number of topical applications in higher dimensions in the context of string theory. The degenerate Kundt spacetimes have many special and unique mathematical properties, including their invariant curvature structure and their holonomy structure. We provide a rigorous geometrical kinematical definition of the general Kundt spacetime in 4 dimensions; essentially a Kundt spacetime is defined as one admitting...

Source: http://arxiv.org/abs/0901.0394v2

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Sep 23, 2013
09/13

by
M. Ortner; A. Micheli; G. Pupillo; P. Zoller

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In this paper we study the realization of lattice models in mixtures of atomic and dipolar molecular quantum gases. We consider a situation where polar molecules form a self-assembled dipolar lattice, in which atoms or molecules of a second species can move and scatter. We describe the system dynamics in a master equation approach in the Brownian motion limit of slow particles and fast phonons, which we find appropriate for our system. In a wide regime of parameters, the reduced dynamics of the...

Source: http://arxiv.org/abs/0903.2710v1

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Sep 23, 2013
09/13

by
M. Ferrero; P. S. Cornaglia; L. De Leo; O. Parcollet; G. Kotliar; A. Georges

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We present an approach to the normal state of cuprate superconductors which is based on a minimal cluster extension of dynamical mean-field theory. Our approach is based on an effective two-impurity model embedded in a self-consistent bath. The two degrees of freedom of this effective model can be associated to the nodal and antinodal regions of momentum space. We find a metal-insulator transition which is selective in momentum space: At low doping quasiparticles are destroyed in the antinodal...

Source: http://arxiv.org/abs/0903.2480v1

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Sep 23, 2013
09/13

by
J. P. May

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E infinity ring spectra were defined in 1972, but the term has since acquired several alternative meanings. The same is true of several related terms. The new formulations are not always known to be equivalent to the old ones and even when they are, the notion of "equivalence" needs discussion: Quillen equivalent categories can be quite seriously inequivalent. Part of the confusion stems from a gap in the modern resurgence of interest in E infinity structures. E infinity ring spaces...

Source: http://arxiv.org/abs/0903.2813v1

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Sep 22, 2013
09/13

by
A. Fruehbis-Krueger

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Two main algorithmic approaches are known for making Hironaka's proof of resolution of singularities in characteristic zero constructive. Their main difference is the use of different notions of transforms during the resolution process and the use of a stratification by the Hilbert-Samuel function in the one using the strict transform. In this article, a (hybrid-type) algorithmic approach is proposed which allows the use of the strict transform without the full impact of the complexity of the...

Source: http://arxiv.org/abs/0812.1776v2

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Sep 18, 2013
09/13

by
Dev P. Sinha

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We present two models for the space of knots which have endpoints at fixed boundary points in a manifold with boundary, one model defined as an inverse limit of spaces of maps between configuration spaces and another which is cosimplicial. These models build on the calculus of isotopy functors and are weakly homotopy equivalent to knot spaces when the ambient dimension is greater than three. The mapping space model, and the evaluation map on which it builds, is suitable for analysis through...

Source: http://arxiv.org/abs/math/0202287v7

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Sep 20, 2013
09/13

by
Yi Ni

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Ozsvath and Szabo proved that knot Floer homology determines the genera of knots in S^3. We will generalize this deep result to links in homology 3-spheres, by adapting their method. Our proof relies on a result of Gabai and some constructions related to foliations. We also interpret a theorem of Kauffman in the world of knot Floer homology, hence we can compute the top filtration term of the knot Floer homology for alternative links.

Source: http://arxiv.org/abs/math/0506208v4

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Sep 18, 2013
09/13

by
V. Guzey; A. W. Thomas; K. Tsushima

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We study incoherent DVCS on $^4$He in the $^4{\rm He}(e,e^{\prime}\gamma p)X$ reaction, which probes medium-modifications of the bound nucleon GPDs and elastic form factors. Assuming that the bound nucleon GPDs are modified in proportion to the corresponding bound nucleon elastic form factors, as predicted in the Quark-Meson Coupling model, we develop an approach to calculate various incoherent nuclear DVCS observables. As an example, we compute the beam-spin DVCS asymmetry, and predict the...

Source: http://arxiv.org/abs/0806.3288v3

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Sep 23, 2013
09/13

by
F. Breitling

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This work reports on the discovery of HESS J1514-591, a VHE gamma-ray source found at the pulsar wind nebula (PWN) MSH 15-52 and its associated pulsar PSR B1509-58. The discovery was made with the High Energy Stereoscopic System (H.E.S.S.), which currently provides the most sensitive measurement in the energy range of about 0.2-100 TeV. This analysis is the first to include all H.E.S.S. data from observations dedicated to MSH 15-52. The corresponding flux above 1 TeV is...

Source: http://arxiv.org/abs/0903.2056v2

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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 18, 2013
09/13

by
Werner Kirsch; Jessica Langner

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The Penrose-Banzhaf index and the Shapley-Shubik index are the best-known and the most used tools to measure political power of voters in simple voting games. Most methods to calculate these power indices are based on counting winning coalitions, in particular those coalitions a voter is decisive for. We present a new combinatorial formula how to calculate both indices solely using the set of minimal winning coalitions.

Source: http://arxiv.org/abs/0806.3906v5

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Sep 23, 2013
09/13

by
F. Feroz; M. P. Hobson; L. Roszkowski; R. Ruiz de Austri; R. Trotta

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We employ two different statistical tests to examine whether, in the framework of the Constrained MSSM, the experimentally determined values of BR(b->s gamma) and the anomalous magnetic moment of the muon, (g-2), are consistent with each other. Our tests are designed to compare the theoretical predictions of the CMSSM in data space with the actual measurements, once all of the CMSSM free parameters have been integrated out and constrained using all other available data. We investigate the...

Source: http://arxiv.org/abs/0903.2487v1

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Sep 23, 2013
09/13

by
Martino Prizzi

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Under fairly general assumptions, we prove that every compact invariant subset $\mathcal I$ of the semiflow generated by the semilinear damped wave equation \epsilon u_{tt}+u_t+\beta(x)u-\sum_{ij}(a_{ij} (x)u_{x_j})_{x_i}&=f(x,u),&& (t,x)\in[0,+\infty[\times\Omega, u&=0,&&(t,x)\in[0,+\infty[\times\partial\Omega in $H^1_0(\Omega)\times L^2(\Omega)$ is in fact bounded in $D(\mathbf A)\times H^1_0(\Omega)$. Here $\Omega$ is an arbitrary, possibly unbounded, domain in...

Source: http://arxiv.org/abs/0903.2782v1

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Sep 22, 2013
09/13

by
Sreekumar T. Balan; Ofer Lahav

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Retrieval of orbital parameters of extrasolar planets poses considerable statistical challenges.Due to sparse sampling, measurement errors, parameters degeneracy and modelling limitations, there are no unique values of basic parameters, such as period and eccentricity. Here, we estimate the orbital parameters from radial velocity data in a Bayesian framework by utilizing Markov Chain Monte Carlo (MCMC) simulations with the Metropolis-Hastings algorithm. We follow a methodology recently proposed...

Source: http://arxiv.org/abs/0805.3532v3

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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 23, 2013
09/13

by
Koichiro Sadakane; Akira Onuki; Koji Nishida; Satoshi Koizumi; Hideki Seto

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Phase transition is observed between one-phase disordered phase and an ordered phase with multi-lamellar (onion) structures in an off-critical mixture of D$_2$O and 3-methylpyridine (3MP) containing a salt at 85mM. The salt consists of hydrophilic cations and hydrophobic anions, which interact asymmetrically with the solvent composition fluctuations inducing mesophases. The structure factor of the composition distribution obtained from small-angle neutron scattering has a peak at an...

Source: http://arxiv.org/abs/0903.2303v2

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Sep 23, 2013
09/13

by
Tomoko Mizuguchi; Takashi Odagaki

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A simple monatomic system in two dimensions with a double-well interaction potential is investigated in a wide range of temperature by molecular dynamics simulation. The system is melted and equilibrated well above the melting temperature, and then it is quenched to a temperature 88% below the melting temperature Tm at several cooling rates to produce an amorphous state. Various thermodynamic quantities are measured as a function of temperature while the system is heated at a constant rate. The...

Source: http://arxiv.org/abs/0903.2728v1

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Sep 23, 2013
09/13

by
Songzi Du

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This paper works out the rate of convergence of two "natural" random walks on the dicyclic group.

Source: http://arxiv.org/abs/0903.2692v1

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Sep 23, 2013
09/13

by
Kavan Modi

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In recent years there has been a significant development of the dynamical map formalism for initially correlated states of a system and its environment. Based on some of these results, we study quantum process tomography for initially correlated states of the system and the environment. This is beyond the usual assumption that the state of the system and the environment are initially uncorrelated. Since quantum process tomography is an experimental procedure, we wind up having to study the role...

Source: http://arxiv.org/abs/0903.2724v1

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Sep 19, 2013
09/13

by
Bas Spitters

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Locatedness is one of the fundamental notions in constructive mathematics. The existence of a positivity predicate on a locale, i.e. the locale being overt, or open, has proved to be fundamental in constructive locale theory. We show that the two notions are intimately connected. Bishop defines a metric space to be compact if it is complete and totally bounded. A subset of a totally bounded set is again totally bounded iff it is located. So a closed subset of a Bishop compact set is Bishop...

Source: http://arxiv.org/abs/math/0703561v2

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Sep 23, 2013
09/13

by
Dragomir Z. Djokovic; Simone Severini; Ferenc Szollosi

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The main question we raise here is the following one: given a real orthogonal n by n matrix X, is it true that there exists a rational orthogonal matrix Y having the same zero-pattern? We conjecture that this is the case and prove it for n

Source: http://arxiv.org/abs/0903.2853v1

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Jul 20, 2013
07/13

by
Adam Sierakowski

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Let (A,G) be a C*-dynamical system with G discrete. In this paper we investigate the ideal structure of the reduced crossed product C*-algebra and in particular we determine sufficient - and in some cases also necessary - conditions for A to separate the ideals in Ax_rG. When A separates the ideals in Ax_rG, then there is a one-to-one correspondence between the ideals in Ax_rG and the invariant ideals in A. We extend the concept of topological freeness and present a generalization of the...

Source: http://arxiv.org/abs/0804.3772v2

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Sep 23, 2013
09/13

by
Finn Ravndal

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It is pointed out that the Casimir energy in a medium can be obtained most directly from the zero-point energy of the electromagnetic field because of its reduced propagation velocity. This brings to the fore again the old problem related to how the principle of relativity is combined with the Maxwell field equations in a continuous medium.

Source: http://arxiv.org/abs/0903.2737v1

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Sep 23, 2013
09/13

by
P. Boumis; J. Meaburn; M. Lloyd; S. Akras

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A deep wide-field image in the light of the Halpha+[N II] emission lines, of the planetary nebula HFG1 which surrounds the precataclysmic binary system V664 Cas, has revealed a tail of emission at least 20' long, at a position angle of 316deg. Evidence is presented which suggests that this is an ~10^5 y old trail of shocked material, left behind V664 Cas as it ejects matter whilst ploughing through its local interstellar media at anywhere between 29 and 59 km/s depending on its distance from...

Source: http://arxiv.org/abs/0903.2852v1

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Sep 23, 2013
09/13

by
Mark Wildon

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This paper presents a solution to the Knights and Spies Problem: In a room there are n people, each labelled with a unique number between 1 and n. A person may either be a knight or a spy. Knights always tell the truth, while spies may either lie or tell the truth, as they see fit. Each person in the room knows the identity of everyone else. Apart from this, all that is known is that strictly more knights than spies are present. Asking only questions of the form: `Person i, what is the identity...

Source: http://arxiv.org/abs/0903.2869v1

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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
D. B. Melrose; M. Z. Rafat; Q. Luo

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We consider the motion of a charge in a large amplitude electrostatic wave with a triangular wave form relevant to an oscillating model of a pulsar magnetosphere. The (one-dimensional) orbit of a particle in such a wave is found exactly in terms of Weierstrass functions. The result is used to discuss linear acceleration emission (at both low and high frequencies) in an oscillating model for pulsars. An explicit expression for the emissivity is derived in an accompanying paper (Melrose & Luo...

Source: http://arxiv.org/abs/0903.2877v1

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Sep 23, 2013
09/13

by
Jong-Geon Bu; Jae Hyung Yee; Hyeong-Chan Kim

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The differential structure on the kappa-Minkowski spacetime from Jordanian twist of Weyl algebra is constructed, and it is shown to be closed in 4-dimensions in contrast to the conventional formulation. Based on this differential structure, we have formulated a scalar field theory in this kappa-Minkowski spacetime.

Source: http://arxiv.org/abs/0903.0040v2

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Sep 22, 2013
09/13

by
Krzysztof G. Hełminiak

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We study the impact of the atmospheric differential chromatic refraction on the measurements and precision of relative astrometry. Specifically, we address the problem of measuring the separations of close pairs of binary stars with adaptive optics in the J and K bands. We investigate the influence of weather conditions, zenithal distance, star's spectral type and observing wavelength on the astrometric precision and determine the accuracy of these parameters that is necessary to detect...

Source: http://arxiv.org/abs/0805.3369v3

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Sep 23, 2013
09/13

by
Victor Beresnevich; Sanju Velani; Robert C. Vaughan

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The inhomogeneous metric theory for the set of simultaneously $\psi$-approximable points lying on a planar curve is developed. Our results naturally incorporate the homogeneous Khintchine-Jarnik type theorems recently established in [Ann. of Math. (2), 166 (2007), pp. 367-426] and [Invent. Math., 166 (2006), pp. 103-124]. The key lies in obtaining essentially the best possible results regarding the distribution of `shifted' rational points near planar curves.

Source: http://arxiv.org/abs/0903.2817v1

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Sep 18, 2013
09/13

by
R. Lipperheide; U. Wille

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Spin-polarized electron transport in diluted magnetic semiconductors (DMS) in the paramagnetic phase is described within the thermoballistic transport model. In this (semiclassical) model, the ballistic and diffusive transport mechanisms are unified in terms of a thermoballistic current in which electrons move ballistically across intervals enclosed between arbitrarily distributed points of local thermal equilibrium. The contribution of each interval to the current is governed by the momentum...

Source: http://arxiv.org/abs/0809.4353v2

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Sep 23, 2013
09/13

by
J. J. Tobin; L. Hartmann; G. Furesz; M. Mateo; S. T. Megeath

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We present a kinematic study of the Orion Nebula Cluster based upon radial velocities measured by multi-fiber echelle spectroscopy at the 6.5 meter MMT and Magellan telescopes. Velocities are reported for 1613 stars, with multi-epoch data for 727 objects as part of our continuing effort to detect and analyze spectroscopic binaries. We confirm and extend the results of Furesz et al. showing that the ONC is not relaxed, consistent with its youth, and that the stars generally follow the...

Source: http://arxiv.org/abs/0903.2775v1

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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
Andrew V. Knyazev; Klaus Neymeyr

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Preconditioned eigenvalue solvers (eigensolvers) are gaining popularity, but their convergence theory remains sparse and complex. We consider the simplest preconditioned eigensolver--the gradient iterative method with a fixed step size--for symmetric generalized eigenvalue problems, where we use the gradient of the Rayleigh quotient as an optimization direction. A sharp convergence rate bound for this method has been obtained in 2001--2003. It still remains the only known such bound for any of...

Source: http://arxiv.org/abs/0801.3099v3

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Sep 23, 2013
09/13

by
Ghaya Baili; Mehdi Alouini; Thierry Malherbe; Daniel Dolfi; Isabelle Sagnes; Fabien Bretenaker

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The transition between the class-B and class-A dynamical behaviors of a semiconductor laser is directly observed by continuously controlling the lifetime of the photons in a cavity of sub-millimetric to centimetric length. It is experimentally and theoretically proved that the transition from a resonant to an overdamped behavior occurs progressively, without any discontinuity. In particular, the intermediate regime is found to exhibit features typical from both the class-A and class-B regimes....

Source: http://arxiv.org/abs/0903.2827v1

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Sep 23, 2013
09/13

by
G. W. Gibbons; H. Lu; C. N. Pope

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It is well known that every compact simple group manifold G admits a bi-invariant Einstein metric, invariant under G_L\times G_R. Less well known is that every compact simple group manifold except SO(3) and SU(2) admits at least one more homogeneous Einstein metric, invariant still under G_L but with some, or all, of the right-acting symmetry broken. (SO(3) and SU(2) are exceptional in admitting only the one, bi-invariant, Einstein metric.) In this paper, we look for Einstein metrics on three...

Source: http://arxiv.org/abs/0903.2493v1

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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 23, 2013
09/13

by
Robert Koenig; Stephanie Wehner

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A fully general strong converse for channel coding states that when the rate of sending classical information exceeds the capacity of a quantum channel, the probability of correctly decoding goes to zero exponentially in the number of channel uses, even when we allow code states which are entangled across several uses of the channel. Such a statement was previously only known for classical channels and the quantum identity channel. By relating the problem to the additivity of minimum output...

Source: http://arxiv.org/abs/0903.2838v1

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Sep 23, 2013
09/13

by
Dennis E. White

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Let $\{h_1,h_2,...\}$ be a set of algebraically independent variables. We ask which vectors are extreme in the cone generated by $h_ih_j-h_{i+1}h_{j-1}$ ($i\geq j>0$) and $h_i$ ($i>0$). We call this cone the cone of log concavity. More generally, we ask which vectors are extreme in the cone generated by Schur functions of partitions with $k$ or fewer parts. We give a conjecture for which vectors are extreme in the cone of log concavity. We prove the characterization in one direction and...

Source: http://arxiv.org/abs/0903.2831v1

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Sep 18, 2013
09/13

by
V. Weith; A. Krekhov; W. Zimmermann

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We present a theoretical analysis of phase separation in the presence of a spatially periodic forcing of wavenumber q traveling with a velocity v. By an analytical and numerical study of a suitably generalized 2d-Cahn-Hilliard model we find as a function of the forcing amplitude and the velocity three different regimes of phase separation. For a sufficiently large forcing amplitude a spatially periodic phase separation of the forcing wavenumber takes place, which is dragged by the forcing with...

Source: http://arxiv.org/abs/0809.0211v2