Relativistic Shock Waves and Mach Cones in Viscous Gluon Matter

TL;DR

This paper explores the formation and propagation of relativistic shock waves and Mach cones in viscous gluon matter using a microscopic parton cascade, comparing results with Israel-Stewart hydrodynamics to understand viscosity effects.

Contribution

It demonstrates the transition from ideal to viscous shock waves by varying shear viscosity and validates Israel-Stewart hydrodynamics in this context.

Findings

Shock wave behavior varies with viscosity ratio

Mach cone structures form at low viscosity

Signal smears out at higher viscosity levels

Abstract

To investigate the formation and the propagation of relativistic shock waves in viscous gluon matter we solve the relativistic Riemann problem using a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying the shear viscosity to entropy density ratio $\eta/s$. Furthermore we compare our results with those obtained by solving the relativistic causal dissipative fluid equations of Israel and Stewart (IS), in order to show the validity of the IS hydrodynamics. Employing the parton cascade we also investigate the formation of Mach shocks induced by a high-energy gluon traversing viscous gluon matter. For $\eta/s = 0.08$ a Mach cone structure is observed, whereas the signal smears out for $\eta/s \geq 0.32$.