Transport coefficients of transient hydrodynamics for the hadron-resonance gas and thermal-mass quasiparticle models

Abstract

We calculate all transport coefficients of second order transient hydrodynamics in two effective kinetic theory models: a hadron-resonance gas and a quasiparticle model with thermal masses tuned to reproduce QCD thermodynamics. We compare the corresponding results with calculations for an ultrarelativistic single-component gas, that are widely employed in hydrodynamic simulations of heavy ion collisions. We find that both of these effective models display a qualitatively different normalized bulk viscosity, when compared to the calculation for the single-component gas. Indeed, $\zeta /[{\tau }_{\Pi }({\epsilon }_0+P_0)]\simeq 16.91(1/3-c_s^2{)}^2$, for the hadron-resonance gas model, and $\zeta /[{\tau }_{\Pi }({\epsilon }_0+P_0)]\simeq 5(1/3-c_s^2)$ for the quasiparticle model. Differences are also observed for many second-order transport coefficients, specially those related to the bulk viscous pressure. The transport coefficients derived are shown to be consistent with fundamental linear stability and causality conditions.

Comments: 21 pages, 5 figures v2 - published version