Transport coefficients of the quark-gluon plasma in ultrarelativistic limit

TL;DR

This paper derives and evaluates the transport coefficients of the ultrarelativistic quark-gluon plasma using Chapman-Enskog approximation, revealing temperature-dependent behaviors and dominance of leading order contributions.

Contribution

It provides a novel formulation of transport coefficients in terms of relativistic omega integrals and evaluates their behavior in the ultrarelativistic limit with assumptions on cross sections.

Findings

Bulk viscosity is suppressed at high temperatures.

Shear viscosity scales with the cube of temperature.

Heat conductivity scales with the square of temperature.

Abstract

The calculation of the transport coefficients of the strong quark-gluon plasma (sQGP), i.e. sheer viscosity $\eta$, heat conductivity $\gk$ and bulk viscosity $\zeta$, in the first Chapman-Enskog approximation is presented. Their formulation in terms of two-fold integrals depending on the particle interaction, known as relativistic omega integrals, is derived and their evaluation in the ultrarelativistic limit is worked out assuming a cross section independent of the relative and total momentum of two colliding particles. We find a suppression of the bulk viscosity and a pronounced temperature dependence for the sheer viscosity and heat conductivity. However, at high temperatures, they scale with the third and second power of the temperature respectively as expected. Furthermore, we find that all results in this ultrarelativistic expansion are dominated by the leading order contribution.