Thermalization of a boost-invariant non-Abelian plasma: Holographic approach with boundary sourcing

TL;DR

This paper uses holographic duality to study how a strongly coupled non-Abelian plasma thermalizes after boundary-driven quenches, providing insights into the thermalization times relevant for quark-gluon plasma in heavy ion collisions.

Contribution

It applies a holographic boundary sourcing method to analyze the thermalization process of a boost-invariant plasma, revealing the dependence of thermalization time on initial temperature and quench dynamics.

Findings

Thermalization occurs within about 1 fm/c for initial temperature of 500 MeV.

The late-time dynamics approach hydrodynamic behavior after boundary quenches.

The method links boundary deformations to bulk gravitational evolution, illuminating out-of-equilibrium processes.

Abstract

In a holographic approach, the evolution of a 4D strongly coupled non-Abelian plasma towards equilibrium can be studied investigating a 5D gravitational dual. The process driving the plasma out-of-equilibrium can be described by boundary sourcing, a deformation of the boundary metric; the analysis of the late-time dynamics allows to understand how the hydrodynamic regime settles in. We apply the method to a boost-invariant case, considering the effects of different quenches, solving the Einstein equations in the bulk and studying the time-dependence of observables such as the effective temperature, the energy density and the pressures. The main outcome is that, if the effective temperature of the system when the quench is switched off is $T_{eff}(\tau^*)=500$ MeV, thermalization is reached within a time of ${\cal O}$(1 fm/c), an important information if the case of the QCD plasma produced in relativistic heavy ion collisions is considered.