Transport Coefficients in Quasi-particle Models

TL;DR

This paper investigates the non-equilibrium properties of a quasi-particle fluid near the QCD chiral phase transition, focusing on bulk viscosity and specific heat scaling behaviors within kinetic theory.

Contribution

It provides the first calculation of bulk viscosity scaling near the QCD transition in the 3d O(2) universality class, including effects of Goldstone modes.

Findings

Bulk viscosity does not diverge near the transition.

Goldstone modes influence the specific heat divergence.

Scaling behavior of bulk viscosity remains finite at criticality.

Abstract

We study the non-equilibrium properties of a dynamical fluid composed of quasi-particles whose mass is temperature and charge chemical potential dependent, in kinetic theory under the relaxation time approximation. In particular we calculate the scaling behaviour of bulk viscosity `$\zeta$' near the QCD chiral phase transition in the 3d $\it O$(2) universality class. It is found that the bulk viscosity `$\zeta$' does not show a divergent behaviour near the QCD chiral phase transition. This scaling behaviour of `$\zeta$' prevails in the presence of Gold-stone modes that arise due to the explicit breaking of continuous $\it O$(4) symmetry. On contrary these modes have a significant effect on the scaling behaviour of specific heat $C_V$ which diverges at the critical temperature $T_C$.