Viscous hydrodynamics with bulk viscosity -- uncertainties from relaxation time and initial conditions

TL;DR

This paper investigates how uncertainties in initial conditions and relaxation times affect the estimation of bulk viscosity's impact on elliptic flow suppression in viscous hydrodynamics.

Contribution

It analyzes the uncertainties in bulk viscous pressure and relaxation time and their effects on elliptic flow predictions in viscous hydrodynamics.

Findings

Uncertainties in initial bulk viscous pressure significantly affect v_2 suppression.

Relaxation time variations influence the magnitude of bulk viscous effects.

Bulk viscosity must be carefully constrained to accurately interpret elliptic flow data.

Abstract

Bulk viscosity suppresses elliptic flow v_2, as does shear viscosity. It can thus not be neglected when extracting the shear viscosity from elliptic flow data. We here explore uncertainties in the bulk viscous contribution to viscous v_2 suppression that arise from presently uncontrolled uncertainties in the initial value of the bulk viscous pressure and its microscopic relaxation time.