A Parametric Study of Relativistic Hydrodynamics Out of Equilibrium

Abstract

Quark Gluon Plasma (QGP) is a hot and dense state of matter created in relativistic heavy ion collisions. However, it is extremely small in size (of the order of 10−14 m) and found to exist for a short period of time (of the order of 10−23 s). This creates complications in recreating and directly observing and characterising its properties. One of the most sought after properties of QGP is its specific shear viscosity (η/s) since it is believed to be around a very small value paving the way for QGP being dubbed the most ”perfect” fluid ever created in the lab. Finding the exact temperature dependence of η/s is one of the main goals in heavy ion physics. Another comparatively less studied but related property of QGP is its specific bulk viscosity (ζ/s). Not much is known about its temperature dependence but it is believed to influence the radial expansion rate of QGP. In this project, I study the influence of different initial conditions in the form of transverse and longitudinal components of pressure and the effect of different parametrisations of η/s and ζ/s on the expansion and cooling of the fireball created in relativistic heavy-ion collisions in a one-dimensional, boost-invariant hydrodynamic model in two different equations of state. It was found that the bulk viscosity slows down the equilibration of the system, however it meagrely contributes to the entropy produced.