Stress Tensor and Bulk Viscosity in Relativistic Nuclear Collisions

TL;DR

This paper investigates how initial stress tensor conditions and bulk viscosity affect the evolution, entropy production, and cooling of the quark-gluon plasma in relativistic heavy-ion collisions using hydrodynamic models.

Contribution

It provides new insights into the role of bulk viscosity and initial stress conditions on the dynamics and entropy production in relativistic nuclear collisions.

Findings

Bulk viscosity slows system equilibration.

Initial stress tensor conditions influence pressure evolution.

Entropy production is not significantly increased by bulk viscosity.

Abstract

We discuss the influence of different initial conditions for the stress tensor and the effect of bulk viscosity on the expansion and cooling of the fireball created in relativistic heavy-ion collisions. In particular, we explore the evolution of longitudinal and transverse components of the pressure and the extent of dissipative entropy production in the one-dimensional, boost-invariant hydrodynamic model. We find that a bulk viscosity consistent with recent estimates from lattice QCD further slows the equilibration of the system, however it does not significantly increase the entropy produced.