Dissipative effects from transport and viscous hydrodynamics

TL;DR

This study compares covariant transport theory and Israel-Stewart hydrodynamics in a RHIC-like setting, finding good agreement in pressure evolution and elliptic flow for small shear viscosity, supporting hydrodynamics applicability.

Contribution

It demonstrates that Israel-Stewart hydrodynamics can accurately describe quark-gluon plasma dynamics when all terms are included, especially at low shear viscosity.

Findings

Good agreement between theories for eta/s ~ 1/(4 pi)

Agreement persists for large cross sections (~50 mb)

Results support hydrodynamics applicability at low shear viscosity

Abstract

We compare 2->2 covariant transport theory and causal Israel-Stewart hydrodynamics in 2+1D longitudinally boost invariant geometry with RHIC-like initial conditions and a conformal e = 3p equation of state. The pressure evolution in the center of the collision zone and the final differential elliptic flow v2(pT) from the two theories agree remarkably well for a small shear viscosity to entropy density ratio eta/s ~ 1/(4 pi), and also for a large cross section sigma ~ 50 mb. A key to this agreement is keeping ALL terms in the Israel-Stewart equations of motion. Our results indicate promising prospects for the applicability of Israel-Stewart dissipative hydrodynamics at RHIC, provided the shear viscosity of hot and dense quark-gluon matter is indeed very small for the relevant temperatures T ~ 200-500 MeV.