Transport coefficients of hot and dense matter

TL;DR

This paper calculates the shear viscosity of the quark-gluon plasma at finite temperature and baryon chemical potential using the dynamical quasiparticle model, finding good agreement with lattice QCD and minimal dependence on baryon chemical potential.

Contribution

It introduces a method to compute shear viscosity of QGP at finite $_B$ using DQPM, matching lattice QCD results and analyzing the $/s$ ratio's behavior.

Findings

The shear viscosity to entropy density ratio $/s$ agrees with lattice QCD results.

The ratio $/s$ shows only modest variation with baryon chemical potential.

The quasiparticle limit remains valid at finite temperature and chemical potential.

Abstract

We present calculations for the shear viscosity of the hot and dense quark-gluon plasma (QGP) using the partonic scattering cross sections as a function of temperature $T$ and baryon chemical potential $\mu_B$ from the dynamical quasiparticle model (DQPM) that is matched to reproduce the equation of state of the partonic system above the deconfinement temperature $T_c$ from lattice QCD. To this aim we calculate the collisional widths for the partonic degrees of freedom at finite $T$ and $\mu_B$ in the time-like sector and conclude that the quasiparticle limit holds sufficiently well. Furthermore, the ratio of shear viscosity $\eta$ over entropy density $s$, i.e. $\eta/s$, is evaluated using these collisional widths and are compared to lQCD calculations for $\mu_B$ = 0 as well. We find that the ratio $\eta/s$ is in agreement with the results of calculations within the original DQPM on the basis of the Kubo formalism. Furthermore, there is only a very modest change of $\eta/s$ with the baryon chemical $\mu_B$ as a function of the scaled temperature $T/T_c(\mu_B)$.