607 research outputs found

    Quasi-particle model of strongly interacting matter

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    The successful quasi-particle model is compared with recent lattice data of the coefficients in the Taylor series expansion of the excess pressure at finite temperature and baryon density. A chain of approximations, starting from QCD to arrive at the model expressions for the entropy density, is presented.Comment: Nov 2004. 4pp. Invited talk given at 8th International Conference on Strangeness in Quark Matter (SQM2004), Cape Town, South Africa, 15-20 Sep 200

    Quasi-particle model for deconfined matter

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    Our quasi-particle model for deconfined matter near T_c is reviewed. The extrapolation of lattice QCD data to a finite baryo-chemical potential is discussed. Determined by the chiral transition temperature T_c, the resulting equation of state of neutral and beta-stable deconfined matter is soft and limits size and mass of pure quark stars.Comment: Contribution to 5th Intern. Conf. "Quark Confinement and the Hadron Spectrum", Gargnano (It), Sep. 10 - 14, 200

    Gluon Emission of Heavy Quarks: Dead Cone Effect

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    The lowest-order induced soft gluon radiation processes of heavy quarks have been analyzed to quantify the dead cone effect. This effect is most likely expected to suppress significantly the energy loss of charm quarks passing an amorphous color-neutral deconfined medium, as has been concluded from recent experiments at RHIC

    Next--to--Leading Order QCD corrections for the B0B0ˉB^0 \bar{B^0}--mixing with an extended Higgs sector

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    We present a calculation of the B0-B0--mixing including Next--to--Leading Order (NLO) QCD corrections within the Two Higgs Doublet Model (2HDM). The QCD corrections at NLO are contained in the factor denoted by eta_2 which modifies the result obtained at the lowest order of perturbation theory. In the Standard Model case, we confirm the results for eta_2 obtained by Buras, Jamin and Weisz. The factor eta_2 is gauge and renormalization prescription invariant and it does not depend on the infrared behaviour of the theory, which constitutes an important test of the calculations. The NLO--calculations within the 2HDM enhance the LO--result up to 18%, which affects the correlation between M_H and V_{td}.Comment: 22 pages (LaTeX), 22 Postscript figures, version to appear in Nucl. Phys. B, corrected some typos and a sign in the program, which results in changes in Eqs. (71), (74) and (75). Due to these changes Eqs. (23) and (34) may be written in a more compact wa

    Renormalization of the Periodic Scalar Field Theory by Polchinski's Renormalization Group Method

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    The renormalization group (RG) flow for the two-dimensional sine-Gordon model is determined by means of Polchinski's RG equation at next-to-leading order in the derivative expansion. In this work we have two different goals, (i) to consider the renormalization scheme-dependence of Polchinski's method by matching Polchinski's equation with the Wegner-Houghton equation and with the real space RG equations for the two-dimensional dilute Coulomb-gas, (ii) to go beyond the local potential approximation in the gradient expansion in order to clarify the supposed role of the field-dependent wave-function renormalization. The well-known Coleman fixed point of the sine-Gordon model is recovered after linearization, whereas the flow exhibits strong dependence on the choice of the renormalization scheme when non-linear terms are kept. The RG flow is compared to those obtained in the Wegner-Houghton approach and in the dilute gas approximation for the two-dimensional Coulomb-gas.Comment: 14 pages, LaTeX, 1 figure; J. Phys. G (in press
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