The shear viscosity of quark-gluon plasma under anisotropic scatterings

Abstract

Quark-gluon plasma (QGP) is a state of matter that is formed from relativistic heavy-ion collisions and also in the early universe. The quarks and gluons as quasi-free particles resemble an expanding viscous liquid under extremely high temperatures and densities. The shear viscosity, [eta], of the QGP under isotropic scatterings in full equilibrium (meaning thermal and chemical equilibrium) is already known analytically and numerically. Analytically, the viscosity obtained via the Chapman-Enskog (CE) method agrees well with the numerical Green-Kubo values for the viscosity under anisotropic scatterings as well as isotropic scatterings. In this thesis, we use the CE formula, along with other approximation methods, for viscosity to derive [eta] / s and compare the analytical curves with the numerical values for forward-angle scatterings. My contribution is the correction of two typos in the published CE and ModRTA formulae of viscosity and the application of all obtained formulae to three-dimensional expansion cases under full and partial equilibrium. This includes the calculations of shear viscosity, entropy density, and the [eta] / s ratio of the parton system from the AMPT model as a function of time of the parton evolution.