2,068,329 research outputs found

    Exact Solutions of Classical Electrodynamics and the Yang--Mills--Wong Theory in Even-Dimensional Spacetime

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    Exact solutions of classical gauge theories in even-dimensional (D=2n) spacetimes are discussed. Common and specific properties of these solutions are analyzed for the particular dimensions D=2, D=4, and D=6. A consistent formulation of classical gauge field theories with pointlike charged or colored particles is proposed for D=6. The particle Lagrangian must then depend on the acceleration. The self-interaction of a point particle is considered for D=2 and D=6. In D=2, radiation is absent and all processes are reversible. In D=6, the expression for the radiation rate and the equation of motion of a self-interacting particle are derived; from which follows that the Zitterbewegung always leads to radiation. It is shown that non-Abelian solutions are absent for any D not equal to 4; only Coulomb-like solutions, which correspond to the Abelian limit of the D-dimensional Yang--Mills--Wong theory, are admitted.Comment: LaTeX 2.09, 16 page

    1WHSP: an IR-based sample of \sim1,000 VHE γ\gamma-ray blazar candidates

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    Blazars are the dominant type of extragalactic sources at microwave and at γ\gamma-ray energies. In the most energetic part of the electromagnetic spectrum (E>100GeV) a large fraction of high Galactic latitude sources are blazars of the High Synchrotron Peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. HSP blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray) we estimated synchrotron peak frequencies and fluxes of each object. We assembled a sample including 992 sources, which is currently the largest existing list of confirmed and candidates HSP blazars. All objects are expected to radiate up to the highest γ\gamma-ray photon energies. In fact, 299 of these are confirmed emitters of GeV γ\gamma-ray photons (based on Fermi-LAT catalogues), and 36 have already been detected in the TeV band. The majority of sources in the sample are within reach of the upcoming Cherenkov Telescope Array (CTA), and many may be detectable even by the current generation of Cherenkov telescopes during flaring episodes. The sample includes 425 previously known blazars, 151 new identifications, and 416 HSP candidates (mostly faint sources) for which no optical spectra is available yet. The full 1WHSP catalogue is on-line at http://www.asdc.asi.it/1whsp/ providing a direct link to the SED building tool where multifrequency data can be easily visualised

    Electrical conductivity and thermal dilepton rate from quenched lattice QCD

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    We report on a continuum extrapolation of the vector current correlation function for light valence quarks in the deconfined phase of quenched QCD. This is achieved by performing a systematic analysis of the influence of cut-off effects on light quark meson correlators at T1.45TcT\simeq 1.45 T_c using clover improved Wilson fermions. We discuss resulting constraints on the electrical conductivity and the thermal dilepton rate in a quark gluon plasma. In addition new results at 1.2 and 3.0 TcT_c will be presented.Comment: 4 pages, 6 eps figures, to appear in the proceedings of Quark Matter 2011, 23-28 May 2011, Annecy, Franc

    Design diversity: an update from research on reliability modelling

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    Diversity between redundant subsystems is, in various forms, a common design approach for improving system dependability. Its value in the case of software-based systems is still controversial. This paper gives an overview of reliability modelling work we carried out in recent projects on design diversity, presented in the context of previous knowledge and practice. These results provide additional insight for decisions in applying diversity and in assessing diverseredundant systems. A general observation is that, just as diversity is a very general design approach, the models of diversity can help conceptual understanding of a range of different situations. We summarise results in the general modelling of common-mode failure, in inference from observed failure data, and in decision-making for diversity in development.

    Idl Signal Processing Library 1.0

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    We make available a library of documented IDL .pro files as well as a shareable object library that allows IDL to call routines from LAPACK. The routines are for use in the spectral analysis of time series data. The primary focus of these routines are David Thomson's multitaper methods but a whole range of functions will be made available in future revisions of the submission. At present routines are provided to carry out the following operations: calculate prolate spheroidal sequences and eigenvalues, project time-series into frequency bands, calculate spectral estimates with or without moving windows, and calculate the cross-coherence between two time series as a function of frequency as well as the coherence between frequencies for a single time series.Comment: 13 IDL .pro files, 1 .html file, 1 .ps file, 1 license file. Download the source for the IDL files (save as .tar.gz) Read idl_lib.ps for instructions on use. Originally submitted to the neuro-sys archive which was never publicly announced (was 9801001

    Perturbative treatment of the multichannel interacting resonant level model in steady state non-equilibrium

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    We consider the steady state non-equilibrium physics of the multichannel interacting resonant level model in the weak coupling regime. By using the scattering state method we show in agreement with the rate equations that the negative differential conductance at large enough voltages is due to the renormalization of the hopping amplitude thus of the vertex.Comment: 3+ pages, 4 figure