Issue Eur. Phys. J. C Volume 62, Number 1, July 2009 Hot Quarks 2008 Page(s) 37 - 54 Section Regular Article - Theoretical Physics DOI 10.1140/epjc/s10052-009-0935-0 Published online 11 March 2009

Eur. Phys. J. C 62, 37-54 (2009)
DOI: 10.1140/epjc/s10052-009-0935-0

Transport coefficients and resonances for a meson gas in chiral perturbation theory

D. Fernández-Fraile and A. Gómez Nicola

Departamento de Física Teórica II, Universidad Complutense, 28040, Madrid, Spain

danfer@fis.ucm.es
gomez@fis.ucm.es

Received 30 September 2008 / Revised version 23 January 2009 / Published online 11 March 2009

Abstract

We present recent results on a systematic method to calculate transport coefficients for a meson gas (in particular, we analyze a pion gas) at low temperatures in the context of Chiral Perturbation Theory (ChPT). Our method is based on the study of Feynman diagrams taking into account collisions in the plasma by means of the non-zero particle width. This implies a modification of the standard ChPT power counting scheme. We discuss the importance of unitarity, which allows for an accurate high-energy description of scattering amplitudes, generating dynamically the ρ(770) and f ₀(600) mesons. Our results are compatible with analyses of kinetic theory, both in the non-relativistic very low-T regime and near the transition. We show the behavior with temperature of the electrical and thermal conductivities as well as of the shear and bulk viscosities. We obtain the result that the bulk viscosity is negligible against the shear viscosity, except near the chiral phase transition where the conformal anomaly might induce larger bulk effects. Various asymptotic limits for transport coefficients, large-N _c scaling and some applications to heavy-ion collisions are studied.

PACS
11.10.Wx
12.39.Fe
25.75.-q

Correspondence: danfer@fis.ucm.es


© Società Italiana di Fisica, Springer-Verlag 2009

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