2,845 research outputs found

    Viscous Corrections to Spectra, Elliptic Flow, and HBT Radii

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    I compute the first viscous correction to the thermal distribution function. With this correction, I calculate the effect of viscosity on spectra, elliptic flow, and HBT radii. Indicating the breakdown of hydrodynamics, viscous corrections become of order one for pT∌1.5p_{T}\sim 1.5 GeV. Viscous corrections to HBT radii are particularly large and reduce the outward and longitudinal radii. This reduction is a direct consequence of the reduction in longitudinal pressure.Comment: Proceedings for QM200

    14N and 15N coupling constants of the oxidized primary donor P-860 of bacterial photosynthesis obtained by electron spin echo envelope modulation spectroscopy

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    An electron spin echo modulation frequency analysis of P+-860 is performed in 14N chromatophores of Rhodospirillum rubrum, and in 15N substituted reaction centers from Rhodopseudomonas sphaeroides 2.4.1. For the 14N material two sets of nuclear quadrupole parameters are obtained. From the frequencies found for 15N reaction centers the perpendicular, parallel and isotropic hyperfine previous termcouplingnext term constants of three of the four bacteriochlorophyll nitrogen nuclei are inferred

    Dilepton production from a viscous QGP

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    This work calculates the first correction to the leading order q\={q} dilepton production rates due to shear viscosity in an expanding gas. The modified rates are integrated over the space-time history of a viscous hydrodynamic simulation of RHIC collisions. The net result is a {\em hardening} of q⊄q_\perp spectrum with the magnitude of the correction increasing with invariant mass. We argue that a thermal description is reliable for invariant masses less than Mmax≈(2τ0T02)/(η/s)M_{max}\approx(2\tau_0 T_0^2)/(\eta/s). For reasonable values of the shear viscosity and thermalization time Mmax≈4.5M_{max}\approx 4.5 GeV. Finally, the early emission from a viscous medium is compared to emission from a longitudinally free streaming plasma. Qualitative differences in q⊄q_\perp spectrum are seen which could be used to extract information on the thermalization time, viscosity to entropy ratio and possibly the thermalization mechanism in heavy-ion collisions.Comment: 17 pages, 8 figure

    A Diagrammatic Interpretation of the Boltzmann Equation

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    We study nonlinear response in weakly coupled nonequilibrium ϕ4\phi^4 theory in the context of both classical transport theory and real time quantum field theory, based on a generalized Kubo formula which we derive. A novel connection between these two approaches is established which provides a diagrammatic interpretation of the Boltzmann equation.Comment: 5 pages in RevTex with 4 Postscript figure

    Cantor Spectrum for Schr\"odinger Operators with Potentials arising from Generalized Skew-shifts

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    We consider continuous SL(2,R)SL(2,\mathbb{R})-cocycles over a strictly ergodic homeomorphism which fibers over an almost periodic dynamical system (generalized skew-shifts). We prove that any cocycle which is not uniformly hyperbolic can be approximated by one which is conjugate to an SO(2,R)SO(2,\mathbb{R})-cocycle. Using this, we show that if a cocycle's homotopy class does not display a certain obstruction to uniform hyperbolicity, then it can be C0C^0-perturbed to become uniformly hyperbolic. For cocycles arising from Schr\"odinger operators, the obstruction vanishes and we conclude that uniform hyperbolicity is dense, which implies that for a generic continuous potential, the spectrum of the corresponding Schr\"odinger operator is a Cantor set.Comment: Final version. To appear in Duke Mathematical Journa

    Exponential Divergence and Long Time Relaxation in Chaotic Quantum Dynamics

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    Phase space representations of the dynamics of the quantal and classical cat map are used to explore quantum--classical correspondence in a K-system: as ℏ→0\hbar \to 0, the classical chaotic behavior is shown to emerge smoothly and exactly. The quantum dynamics near the classical limit displays both exponential separation of adjacent distributions and long time relaxation, two characteristic features of classical chaotic motion.Comment: 10 pages, ReVTeX, to appear in Phys. Rev. Lett. 13 figures NOT included. Available either as LARGE (uuencoded gzipped) postscript files or hard-copies from [email protected]

    Ichthyosis, exocrine pancreatic insufficiency, impaired neutrophil chemotaxis, growth retardation, and metaphyseal dysplasia (Shwachman syndrome).

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    The Shwachman syndrome comprises exocrine pancreatic insufficiency, growth retardation, and bone marrow hypoplasia resulting in neutropenia. Clinical, morphological, and ultrastructural studies, as well as hair analysis, were performed in a patient with Shwachman's syndrome and severe ichthyosis. Clinical findings were lamellar ichthyosiform desquamation on the extremities. The hair was scanty and short on the scalp, in the eyelashes, and in the eyebrows. The nails were hyperkeratotic. Morphologic findings were slight, regular acanthosis and severe diffuse hyperkeratosis with variable parakeratosis. The granular layer was thickened. The papillary dermis showed very slight perivascular lymphocyte infiltration. The most prominent ultrastructural finding was the presence of solitary or multiple droplets of varying size in the cytoplasm of the keratinocytes. Hair analysis revealed no abnormalities; the cystine concentration in hair specimens was normal
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