Transport Coefficients in Gluodynamics: From Weak Coupling towards the Deconfinement Transition

TL;DR

This paper investigates how the ratio of bulk to shear viscosity in gluodynamics transitions from quadratic dependence at high temperatures to linear near the deconfinement transition, revealing insights into the strongly coupled regime.

Contribution

It demonstrates the temperature-dependent behavior of the viscosity ratio in gluodynamics, bridging weak and strong coupling regimes using a phenomenological quasiparticle model.

Findings

At high temperatures, the ratio shows quadratic dependence on the conformality measure.

Near the deconfinement transition, the ratio becomes linearly dependent, matching strongly coupled theories.

The qualitative behavior is robust against variations in the equation of state.

Abstract

We study the ratio of bulk to shear viscosity in gluodynamics within a phenomenological quasiparticle model. We show that at large temperatures this ratio exhibits a quadratic dependence on the conformality measure as known from weak coupling perturbative QCD. In the region of the deconfinement transition, however, this dependence becomes linear as known from specific strongly coupled theories. The onset of the strong coupling behavior is located near the maximum of the scaled interaction measure. This qualitative behavior of the viscosity ratio is rather insensitive to details of the equation of state.