Estimating transport coefficients in hot and dense quark matter

TL;DR

This paper calculates shear and bulk viscosities and thermal conductivity of hot, dense quark matter using the NJL model, revealing temperature-dependent behaviors near the Mott transition and critical temperature.

Contribution

It introduces a covariant quasiparticle approach within the NJL model to estimate transport coefficients at finite chemical potential, including detailed temperature dependence.

Findings

Shear viscosity to entropy density ratio has a minimum at the Mott transition.

Bulk viscosity to entropy density decreases sharply near the critical temperature.

Thermal conductivity coefficient shows a minimum at the critical temperature.

Abstract

We compute the transport coefficients, namely, the coefficients of shear and bulk viscosity as well as thermal conductivity for hot and dense quark matter. The calculations are performed within the Nambu- Jona Lasinio (NJL) model. The estimation of the transport coefficients is made using a quasiparticle approach of solving the Boltzmann kinetic equation within the relaxation time approximation. The transition rates are calculated in a manifestly covariant manner to estimate the thermal-averaged cross sections for quark-quark and quark-antiquark scattering. The calculations are performed for finite chemical potential also. Within the parameters of the model, the ratio of shear viscosity to entropy density has a minimum at the Mott transition temperature. At vanishing chemical potential, the ratio of bulk viscosity to entropy density, on the other hand, decreases with temperature with a sharp decrease near the critical temperature, and vanishes beyond it. At finite chemical potential, however, it increases slowly with temperature beyond the Mott temperature. The coefficient of thermal conductivity also shows a minimum at the critical temperature.