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Sep 18, 2013
09/13

by
Stephen Parrott

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A recent Letter in Physical Review Letters, "Contextual Values of Observables in Quantum Measurements", by J. Dressel, S. Agarwal, and A. N. Jordan (abbreviated DAJ below), introduces the concept of "contextual values" and claims that they lead to "a natural definition of a general conditioned average that converges uniquely to the quantum weak value in the minimal disturbance limit". However, they do not define "minimal disturbance limit". The present...

Source: http://arxiv.org/abs/1102.4407v6

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Sep 23, 2013
09/13

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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Sep 23, 2013
09/13

by
Jacek Mulak; Maciej Mulak

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Any electron eigenstate |\Psi>of the paramagnetic ion open-shell is characterized by the three independent multipole asphericities A_{k}= for k=2,4 and 6 related to the second moments of the relevant crystal-field splittings by \sigma_{k}^{2}= ]A_{k}^{2}S_{k}^{2}, where S_{k}^{2}= ]\sum_{q}|B_{kq}|^{2}. The A_{k} can serve as a reliable measure of the state |\Psi>capability for the splitting produced by the k-rank component of the crystal-field Hamiltonian and allow one to verify any...

Source: http://arxiv.org/abs/1105.4168v1

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Sep 21, 2013
09/13

by
Jie-Sheng Yu; Zhi-Feng Sun; Xiang Liu; Qiang Zhao

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Inspired by the newly observed three resonances X(1835), X(2120) and X(2370), in this work we systematically study the two-body strong decays and double pion decays of $\eta(1295)/\eta(1475)$, $\eta(1760)/X(1835)$ and $X(2120)/X(2370)$ by categorizing $\eta(1295)/\eta(1475)$, $\eta(1760)/X(1835)$, X(2120) and X(2370) as the radial excitations of $\eta(548)/\eta^\prime(958)$. Our numerical results indicate the followings: (1) The obtained theoretical strong decay widths of three pseudoscalar...

Source: http://arxiv.org/abs/1104.3064v3

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Sep 22, 2013
09/13

by
Simone Bux; Christine Gnahm; Reinhardt A. W. Maier; Claus Zimmermann; Philippe W. Courteille

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We study collective scattering with Bose-Einstein condensates interacting with a high-finesse ring cavity. The condensate scatters the light of a transverse pump beam superradiantly into modes which, in contrast to previous experiments, are not determined by the geometrical shape of the condensate, but specified by a resonant cavity mode. Moreover, since the recoil-shifted frequency of the scattered light depends on the initial momentum of the scattered fraction of the condensate, we show that...

Source: http://arxiv.org/abs/1101.2391v2

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Sep 23, 2013
09/13

by
L. A. Harland-Lang; V. A. Khoze; M. G. Ryskin; W. J. Stirling

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We present a study of the central exclusive production (CEP) of meson pairs, MMbar, at sufficiently high invariant mass that a perturbative QCD formalism is applicable. Within this framework, MMbar production proceeds via the gg --> MMbar hard scattering sub-process, which can be calculated within the hard exclusive formalism. We present explicit calculations for the gg --> MMbar helicity amplitudes for different meson states and, using these, show results for meson pair CEP in the...

Source: http://arxiv.org/abs/1105.4133v1

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Sep 23, 2013
09/13

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

by
Klaus Halterman; Oriol T. Valls; Mohammad Alidoust

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We study proximity effects in clean nanoscale superconductor-normal metal-superconductor (S$\mid$N$\mid$S) graphene heterostructures using a self-consistent numerical solution to the continuum Dirac Bogoliubov-de Gennes (DBdG) equations. We obtain results for the pair amplitude and the local density of states (DOS), as a function of doping and of the geometrical parameters determining the width of the structures. The superconducting correlations are found to penetrate the normal graphene layers...

Source: http://arxiv.org/abs/1105.4140v1

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Sep 23, 2013
09/13

by
Karthikeyan Rajendran; Ioannis G. Kevrekidis

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We present a computer-assisted approach to coarse-graining the evolutionary dynamics of a system of nonidentical oscillators coupled through a (fixed) network structure. The existence of a spectral gap for the coupling network graph Laplacian suggests that the graph dynamics may quickly become low-dimensional. Our first choice of coarse variables consists of the components of the oscillator states -their (complex) phase angles- along the leading eigenvectors of this Laplacian. We then use the...

Source: http://arxiv.org/abs/1105.4144v1

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Sep 23, 2013
09/13

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

by
Wolfgang Wieland

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Starting from a Hamiltonian description of four dimensional general relativity in presence of a cosmological constant we perform the program of canonical quantisation. This is done using complex Ashtekar variables while keeping the Barbero--Immirzi parameter real. Introducing the SL(2,C) Kodama state formally solving all first class constraints we propose a spinfoam vertex amplitude. We construct SL(2,C) boundary spinnetwork functions coloured by finite dimensional representations of the group,...

Source: http://arxiv.org/abs/1105.2330v2

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Sep 23, 2013
09/13

by
Liam Naughton; Goetz Pfeiffer

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The subgroup pattern of a finite groups $G$ is the table of marks of $G$ together with a list of representatives of the conjugacy classes of subgroups of $G$. In this article we present an algorithm for the computation of the subgroup pattern of a cyclic extension of $G$ from the subgroup pattern of $G$. Repeated application of this algorithm yields an algorithm for the computation of the table of marks of a solvable group $G$, along a composition series of $G$.

Source: http://arxiv.org/abs/1105.4064v1

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Sep 23, 2013
09/13

by
Dorje C. Brody; Eva-Maria Graefe

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The dynamical aspects of a spin-1/2 particle in Hermitian coquaternionic quantum theory is investigated. It is shown that the time evolution exhibits three different characteristics, depending on the values of the parameters of the Hamiltonian. When energy eigenvalues are real, the evolution is either isomorphic to that of a complex Hermitian theory on a spherical state space, or else it remains unitary along an open orbit on a hyperbolic state space. When energy eigenvalues form a complex...

Source: http://arxiv.org/abs/1105.4038v1

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Sep 18, 2013
09/13

by
Camille Ducoin; Jérôme Margueron; Constança Providência; Isaac Vidaña

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The possibility to draw links between the isospin properties of nuclei and the structure of compact stars is a stimulating perspective. In order to pursue this objective on a sound basis, the correlations from which such links can be deduced have to be carefully checked against model dependence. Using a variety of nuclear effective models and a microscopic approach, we study the relation between the predictions of a given model and those of a Taylor density development of the corresponding...

Source: http://arxiv.org/abs/1102.1283v2

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Sep 23, 2013
09/13

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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Sep 21, 2013
09/13

by
Martin Grohe; Marc Thurley

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Homomorphisms between relational structures are not only fundamental mathematical objects, but are also of great importance in an applied computational context. Indeed, constraint satisfaction problems (CSPs), a wide class of algorithmic problems that occur in many different areas of computer science such as artificial intelligence or database theory, may be viewed as asking for homomorphisms between two relational structures [FedVar98]. In a logical setting, homomorphisms may be viewed as...

Source: http://arxiv.org/abs/1104.0185v3

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Sep 23, 2013
09/13

by
Victor Grigoriev; Fabio Biancalana

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We consider a nonlinear microcavity separating a waveguide channel into two parts so as the coupling between them is possible only due to the resonant properties of the microcavity. We provide a rigorous derivation of the equations used in the phenomenological coupled mode theory for such systems. This allows us to find the explicit formulas for all fitting parameters such as decay rates, coupling coefficients and characteristic intensities in terms of the mode profiles. The advantages of using...

Source: http://arxiv.org/abs/1105.4071v1

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Sep 21, 2013
09/13

by
Tomasz Świsłocki; Tomasz Sowiński; Mirosław Brewczyk; Mariusz Gajda

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We study a square plaquette of four optical microtraps containing ultracold $^{87}$Rb atoms in F=1 hyperfine state. In a presence of external resonant magnetic field the dipolar interactions couple initial $m_F=1$ component to other Zeeman sublevels. This process is a generalization of the Einstein-de Haas effect to the case when the external potential has only $C_4$ point-symmetry. We observe that vortex structures appear in the initially empty $m_F=0$ state. Topological properties of this...

Source: http://arxiv.org/abs/1008.2324v4

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Sep 19, 2013
09/13

by
Worasom Kundhikanjana; Keji Lai; Michael A. Kelly; Zhi-Xun Shen

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We report the instrumentation and experimental results of a cryogenic scanning microwave impedance microscope. The microwave probe and the scanning stage are located inside the variable temperature insert of a helium cryostat. Microwave signals in the distance modulation mode are used for monitoring the tip-sample distance and adjusting the phase of the two output channels. The ability to spatially resolve the metal-insulator transition in a doped silicon sample is demonstrated. The data agree...

Source: http://arxiv.org/abs/1010.1509v2

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Sep 23, 2013
09/13

by
Rocio Gonzalez-Diaz; Maria Jose Jimenez; Belen Medrano

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Cohomology and cohomology ring of three-dimensional (3D) objects are topological invariants that characterize holes and their relations. Cohomology ring has been traditionally computed on simplicial complexes. Nevertheless, cubical complexes deal directly with the voxels in 3D images, no additional triangulation is necessary, facilitating efficient algorithms for the computation of topological invariants in the image context. In this paper, we present formulas to directly compute the cohomology...

Source: http://arxiv.org/abs/1105.4183v1