Transport Coefficients in Quasi-particle Models
  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 $T_C$. 
Waseem Bashir, Saeed Uddin, Jan Shabir Ahmad
hep-ph