Relativistic shock waves in viscous gluon matter

TL;DR

This paper investigates how shear viscosity affects the formation of relativistic shock waves in viscous gluon matter, revealing that higher viscosity suppresses shock development within collision timescales.

Contribution

It demonstrates the transition from ideal to viscous shock waves in gluon matter by varying the shear viscosity to entropy density ratio using a microscopic parton cascade.

Findings

Shock waves form in low-viscosity gluon matter.

An $ ext{eta}/s$ ratio above 0.2 inhibits shock development.

Results agree with viscous hydrodynamic calculations.

Abstract

We solve the relativistic Riemann problem in viscous gluon matter employing a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio $\eta/s$ from zero to infinity. We show that an $\eta/s$ ratio larger than 0.2 prevents the development of well-defined shock waves on timescales typical for ultrarelativistic heavy-ion collisions. Comparisons with viscous hydrodynamic calculations confirm our findings.