29,244 research outputs found

    Anomalous Lorentz and CPT violation from a local Chern-Simons-like term in the effective gauge-field action

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    We consider four-dimensional chiral gauge theories defined over a spacetime manifold with topology R3√óS1\mathbb{R}^3 \times S^1 and periodic boundary conditions over the compact dimension. The effective gauge-field action is calculated for Abelian U(1)U(1) gauge fields Aőľ(x)A_{\mu}(x) which depend on all four spacetime coordinates (including the coordinate x4‚ąąS1x^{4}\in S^1 of the compact dimension) and have vanishing components A4(x)A_{4}(x) (implying trivial holonomies in the 4-direction). Our calculation shows that the effective gauge-field action contains a local Chern-Simons-like term which violates Lorentz and CPT invariance. This result is established perturbatively with a generalized Pauli-Villars regularization and nonperturbatively with a lattice regularization based on Ginsparg-Wilson fermions.Comment: 48 pages, v7: published versio

    Thermal elastohydrodynamic lubrication of line contacts

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    A numerical solution to the problem of thermal elastohydrodynamic lubrication of line contacts was obtained by using a finite difference formulation. The solution procedure consists of simultaneous solution of the thermal Reynolds equation, the elasticity equation, and the energy equation subject to appropriate boundary conditions. Pressure distribution, film shape, and temperature distribution were obtained for fully flooded conjunctions, a paraffinic lubricant, and various dimensionless speed parameters while the dimensionless load and materials parameters were held constant. Reduction in the minimum film thickness due to thermal effects (as a ratio of thermal to isothermal minimum film thickness) is given by a simple formula as a function of the thermal loading parameter Q: H(min)/H(min,I) = 10/10+ Q(0.4). Plots of pressure distribution, film shape, temperature distribution, and flow are shown for some representative cases

    Interstellar Scintillations of Polarization of Compact Sources

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    We demostrate that the measurement of fluctuations of polarization due to the galactic interstellar scintillations may be used to study the structure of the radiation field at compact radio sources. We develop a mathematical formalism and demonstrate it on a simple analytical model in which the scale of the polarization variation through the source is comparable to the source size. The predicted amplitude of modulation of the polarized radiation flux is ~20% x (pi_s) x (m_sc), where (pi_s) is the characteristic degree of polarization of radiation at the source and (m_sc) is the typical modulation index due to scattering, i.e., (m_sc)~1 for diffractive scintillations and (m_sc)<1 for refractive scintillations.Comment: 5 pages, 2 figures, emilateapj.sty. Submitted to ApJ

    On colouring point visibility graphs

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    In this paper we show that it can be decided in polynomial time whether or not the visibility graph of a given point set is 4-colourable, and such a 4-colouring, if it exists, can also be constructed in polynomial time. We show that the problem of deciding whether the visibility graph of a point set is 5-colourable, is NP-complete. We give an example of a point visibility graph that has chromatic number 6 while its clique number is only 4

    Three flavour Quark matter in chiral colour dielectric model

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    We investigate the properties of quark matter at finite density and temperature using the nonlinear chiral extension of Colour Dielectric Model (CCM). Assuming that the square of the meson fields devlop non- zero vacuum expectation value, the thermodynamic potential for interacting three flavour matter has been calculated. It is found that and and remain zero in the medium whereas changes in the medium. As a result, uu and dd quark masses decrease monotonically as the temperature and density of the quark matter is increased.In the present model, the deconfinement density and temperature is found to be lower compared to lattice results. We also study the behaviour of pressure and energy density above critical temperature.Comment: Latex file. 5 figures available on request. To appear in Phys. Rev.

    Observation of the Faraday effect via beam deflection in a longitudinal magnetic field

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    We report the observation of the magnetic field induced circular differential deflection of light at the interface of a Faraday medium. The difference in the angles of refraction or reflection between the two circular polarization components is a function of the magnetic field strength and the Verdet constant. The reported phenomena permit the observation of the Faraday effect not via polarization rotation in transmission, but via changes in the propagation direction in refraction or in reflection. An unpolarized light beam is predicted to split into its two circular polarization components. The light deflection arises within a few wavelengths at the interface and is therefore independent of pathlength

    Spherical agglomeration of superconducting and normal microparticles with and without applied electric field

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    It was reported by R. Tao and coworkers that in the presence of a strong electric field superconducting microparticles assemble into balls of macroscopic dimensions. Such a finding has potentially important implications for the understanding of the fundamental physics of superconductors. However, we report here the results of experimental studies showing that (i) ball formation also occurs in the absence of an applied electric field, (ii) the phenomenon also occurs at temperatures above the superconducting transition temperature, and (iii) it can also occur for non-superconducting materials. Possible origins of the phenomenon are discussed.Comment: Small changes in response to referee's comments. To be published in Phys. Rev.

    Computational aspects of the maximum diversity problems

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    Cataloged from PDF version of article.We address two variations of the maximum diversity problem which arises when m elements are to be selected from an n-element population based on inter-element distances. We study problem complexity and propose randomized greedy heuristics. Performance of the heuristics is tested on a limited basis

    Job selection in heavily loaded shop

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    Cataloged from PDF version of article.Recently, Slotnick and Morton address a job selection problem in a heavily loaded shop, where a tradeoff is sought between the reward obtained when a job is accepted for processing and the lateness penalty incurred when such a job is actually delivered. They provide a branch and bound algorithm and a couple of heuristics for the problem's solution. They do not;however, resolve the issue of problem complexity. In this note. we first establish that the problem is NP-hard. We then go on to provide two pseudo-polynomial time algorithms which also show that the problem is solvable in polynomial time if either the job processing times or the job weights for the lateness penalty are equal. We further provide a fully polynomial time approximation scheme which always generates a solution within a specified percentage of the optimal. Copyright © 1997 Elsevier Science Lt
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