Holographic Collisions in Non-conformal Theories

TL;DR

This paper uses numerical simulations of gravitational shock wave collisions in a holographic model to explore how non-zero bulk viscosity affects the hydrodynamization process in non-conformal gauge theories, with implications for quark-gluon plasma.

Contribution

It demonstrates two novel effects of bulk viscosity on plasma evolution: increased hydrodynamization time and early hydrodynamic behavior before equilibrium conditions are met.

Findings

Hydrodynamization time increases with bulk viscosity.

Plasma can be well described by hydrodynamics before reaching equilibrium.

Implications for understanding quark-gluon plasma in heavy ion collisions.

Abstract

We numerically simulate gravitational shock wave collisions in a holographic model dual to a non-conformal four-dimensional gauge theory. We find two novel effects associated to the non-zero bulk viscosity of the resulting plasma. First, the hydrodynamization time increases. Second, if the bulk viscosity is large enough then the plasma becomes well described by hydrodynamics before the energy density and the average pressure begin to obey the equilibrium equation of state. We discuss implications for the quark-gluon plasma created in heavy ion collision experiments.