Viscosity and dissipation - early stages

TL;DR

This paper investigates the impact of viscosity and early-time dynamics on the evolution of relativistic heavy-ion collisions, aiming to improve the understanding of the transition from initial expansion to equilibrium.

Contribution

It provides a dynamical prescription for the transition from early 2D to later 3D expansion considering viscosity effects in heavy-ion collisions.

Findings

Early start-up time is crucial for matching observations.

Viscosity influences deviations from local equilibrium.

The study models the transition from 2D to 3D expansion.

Abstract

A very early start up time of the hydrodynamic evolution is needed in order to reproduce observations from relativistic heavy-ion collisions experiments. At such early times the systems is still not locally equilibrated. Another source of deviations from local equilibrium is the viscosity of the fluid. We study these effects at very early times to obtain a dynamical prescription for the transition from an early 2-dimensional expansion to a nearly equilibrated 3-dimensional expansion at latter stages. The role of viscosity at latter stages of the evolution is also illustrated.