Bulk viscosity in quasiparticle models

We discuss transport properties of dynamical fluid composed of quasiparticles 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 quasiparticle 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 quasiparticle 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 ζ near the phase transition. We show that extrapolating the results of kinetic theory under the relaxation time approximation near the critical region the ζ does not show singular behavior near the $O(4)$ and $Z(2)$ critical point through static critical exponents.