1,558 research outputs found

    Heat Bath Particle Number Spectrum

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    We calculate the number spectrum of particles radiated during a scattering into a heat bath using the thermal largest-time equation and the Dyson-Schwinger equation. We show how one can systematically calculate {d}/{d\omega} to any order using modified real time finite-temperature diagrams. Our approach is demonstrated on a simple model where two scalar particles scatter, within a photon-electron heat bath, into a pair of charged particles and it is shown how to calculate the resulting changes in the number spectra of the photons and electrons.Comment: 29 pages, LaTeX; 14 figure

    Dynamical Symmetry Breaking in Planar QED

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    We investigate (2+1)-dimensional QED coupled with Dirac fermions both at zero and finite temperature. We discuss in details two-components (P-odd) and four-components (P-even) fermion fields. We focus on P-odd and P-even Dirac fermions in presence of an external constant magnetic field. In the spontaneous generation of the magnetic condensate survives even at infinite temperature. We also discuss the spontaneous generation of fermion mass in presence of an external magnetic field.Comment: 34 pages, 8 postscript figures, final version to appear on J. Phys.

    Free Energy of an SU(2) Model of (2+1)-dimensional QCD in the Constant Condensate Background

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    Gluon and quark contributions to the thermodynamic potential (free energy) of a (2+1)-dimensional QCD model at finite temperature in the background of a constant homogeneous chromomagnetic field H combined with A_0 condensate are calculated. The role of the tachyonic mode in the gluon energy spectrum is discussed. A possibility of the free energy global minimum generation at nonzero values of H and A_0 condensates is investigated.Comment: LaTeX 2e, 14 pages, 6 eps figures, some miscalculations were correcte

    THERMAL EFFECTS ON THE CATALYSIS BY A MAGNETIC FIELD

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    We show that the formation of condensates in the presence of a constant magnetic field in 2+1 dimensions is extremely unstable. It disappears as soon as a heat bath is introduced with or without a chemical potential. We point out some new nonanalytic behavior that develops in this system at finite temperature.Comment: 10 pages, plain Te

    Enhancement of bulk second-harmonic generation from silicon nitride films by material composition

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    We present a comprehensive tensorial characterization of second-harmonic generation from silicon nitride films with varying composition. The samples were fabricated using plasma-enhanced chemical vapor deposition, and the material composition was varied by the reactive gas mixture in the process. We found a six-fold enhancement between the lowest and highest second-order susceptibility, with the highest value of approximately 5 pm/V from the most silicon-rich sample. Moreover, the optical losses were found to be sufficiently small (below 6 dB/cm) for applications. The tensorial results show that all samples retain in-plane isotropy independent of silicon content, highlighting the controllability of the fabrication process.Comment: 4 pages, 3 figures, 2 tables; Re-submitted to Optics Letter

    Generalised chiral QED2 : Anomaly and Exotic Statistics

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    We study the influence of the anomaly on the physical quantum picture of the generalized chiral Schwinger model defined on the circle. We show that the anomaly i) results in the background linearly rising electric field and ii) makes the spectrum of the physical Hamiltonian nonrelativistic without a massive boson. The physical matter fields acquire exotic statistics . We construct explicitly the algebra of the Poincare generators and show that it differs from the Poincare one. We exhibit the role of the vacuum Berry phase in the failure of the Poincare algebra to close. We prove that, in spite of the background electric field, such phenomenon as the total screening of external charges characteristic for the standard Schwinger model takes place in the generalized chiral Schwinger model, too.Comment: LATEX file, 36 pp., to appear in Phys.Rev.

    Back grating optimization for light trapping in thin-film quantum dot solar cells

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    The work presents the design of a diffraction back grating for light-trapping in thin-film GaAs-based quantum dot solar cells. Uni-periodic and bi-periodic gratings made of off-theshelf almost transparent dielectric materials routinely used in photolithography are considered. Gratings are wave-optics simulated by rigorous coupled wave analysis. Optimizing the shape and geometrical aspect ratio of the grating, almost quadrupled photocurrent from quantum dots is demonstrated

    Actions to improve documented pain assessment in adult patients with injury to the upper extremities at the Emergency Department A cross-sectional study

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    Background: Pain is one of the most common symptoms in the Emergency Department (ED) and is the cause of more than half of the visits to the ED. Several attempts to improve pain management have been done by using, for example, standards/guidelines and education. To our knowledge no one has investigated if and how different actions over a longitudinal period affect the frequency of pain documentation in the ED. Therefore the aim of this study was to describe the frequency of documented pain assessments in the ED. Method: A cross-sectional study during 2006-2012 was conducted. The care of patients with wrist/arm fractures or soft tissue injuries on upper extremities was evaluated. Result: Despite various actions our result shows that mandatory pain assessment in the patient's computerized medical record was the only successful intervention to improve the frequencies of documentation of pain assessment during care in the ED. During the study period, no documentation of reassessment of pain was found despite the fact that all patients received pain medication. Conclusion: To succeed in increasing the frequency of documented pain assessment, mandatory pain rating is a successful action. However, the re-evaluation of documented pain assessment was nonexisting. (C) 2016 Elsevier Ltd. All rights reserved.Peer reviewe

    On the Point-Splitting Method of the Commutator Anomaly of the Gauss Law Operators

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    We analyze the generalized point-splitting method and Jo's result for the commutator anomaly. We find that certain classes of general regularization kernels satisfying integral conditions provide a unique result, which, however differs from Faddeev's cohomological result.Comment: 16 pages, RevTex, 1 figure + 1 table, uses psbox.te
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