Transport coefficients of gluonic fluid

TL;DR

This paper calculates the shear and bulk viscosity coefficients of a gluonic fluid considering both elastic and inelastic processes, with a focus on the corrected Gunion-Bertsch formula, and compares the results to experimental data.

Contribution

It provides updated calculations of gluonic fluid viscosity coefficients incorporating recent corrections to the Gunion-Bertsch formula and analyzes their dependence on the running coupling constant.

Findings

The shear viscosity to entropy density ratio at α_s=0.3 is approximately 0.24.

The results are consistent with elliptic flow measurements at RHIC.

The sensitivity of η/s to the running coupling constant is discussed.

Abstract

The shear ($\eta$) and bulk ($\zeta$) viscous coefficients have been evaluated for a gluonic fluid. The elastic, $gg \rightarrow gg$ and the inelastic, number non-conserving, $gg\rightarrow ggg$ processes have been considered as the dominant perturbative processes in evaluating the viscous co-efficients to entropy density ($s$) ratios. Recently the processes: $gg \rightarrow ggg$ has been revisited and a correction to the widely used Gunion-Bertsch (GB) formula has been obtained. The $\eta$ and $\zeta$ have been evaluated for gluonic fluid with the formula derived recently. The sensitivity of the quantity, $\eta/s$ on the running coupling constant is also discussed. At $\alpha_s=0.3$ we get $\eta/s=0.24$ which is close to the value obtained from the analysis of the elliptic flow at RHIC experiments.