Bulk viscosity in quasi particle models

TL;DR

This paper derives a general expression for bulk viscosity in quasi-particle models with temperature-dependent masses, analyzing its critical behavior near phase transitions using kinetic theory and universality class concepts.

Contribution

It introduces a new formulation of bulk viscosity for quasi-particles with dynamic masses and examines its critical properties near phase transitions.

Findings

Bulk viscosity expression derived under relaxation time approximation.

Dynamic masses significantly affect fluid compressibility.

Bulk viscosity does not exhibit singular behavior near critical points.

Abstract

We discuss transport properties of dynamical fluid composed of quasi-particles whose masses depend on temperature and charge chemical potentials. Based on the relativistic kinetic theory formulated under the relaxation time approximation, we derive a general expression for the bulk viscosity in the quasi-particle medium. We show that dynamically generated particle masses imply an essential modification of the fluid compressibility. As an application of our results we consider a class of quasi-particle models with the chiral phase transition belonging to O(4) and Z(2) universality class. Based on the Ginzburg-Landau and the scaling theory we study the critical properties of the bulk viscosity zeta near the phase transition. We show that under the relaxation time approximation the zeta is not expected to show singular behavior near the O(4) and Z(2) critical point through static critical exponents.