Causal relativistic hydrodynamics for viscous fluids

TL;DR

This paper presents results from a relativistic viscous hydrodynamics code showing that even minimal shear viscosity significantly reduces elliptic flow in heavy-ion collisions, with sensitivity to various physical parameters.

Contribution

It introduces VISH2+1, a new computational tool for solving causal viscous hydrodynamics equations in heavy-ion collision simulations, and systematically studies viscosity effects.

Findings

Minimal shear viscosity reduces elliptic flow substantially.

Elliptic flow reduction depends on initial conditions and equation of state.

The study explores the sensitivity of flow reduction to microscopic relaxation times.

Abstract

We report on recent results from VISH2+1, a code that solves the relativistic Israel-Stewart equations for causal viscous hydrodynamics for heavy-ion collisions with longitudinal boost invariance. We find that even ``minimal'' shear viscosity eta/s=hbar/(4pi) leads to a large reduction of elliptic flow compared to ideal fluid dynamics. We explore systematically the sensitivity of this reduction to the equation of state, system size, initial conditions, and the microscopic relaxation time in different formulations of the Israel-Stewart equations.