Holographic Isotropisation in Gauss-Bonnet Gravity

TL;DR

This paper investigates how Gauss-Bonnet gravity corrections influence the isotropisation process of strongly coupled plasmas, revealing that finite coupling effects tend to delay isotropisation by shifting the pressure anisotropy evolution.

Contribution

It introduces a linear approximation method for Gauss-Bonnet corrections to holographic isotropisation, demonstrating the shift in isotropisation time due to finite coupling effects.

Findings

Pressure anisotropy evolution can be approximated by linear corrections in _{GB}

Gauss-Bonnet term causes a shift in isotropisation time

Finite coupling corrections tend to increase isotropisation time

Abstract

We study holographic isotropisation of homogeneous, strongly coupled, non-Abelian plasmas in Gauss-Bonnet gravity with a negative cosmological constant. We focus on small values of the Gauss-Bonnet coupling parameter $\lambda_{GB}$ and linearise the equations of motion around a time-dependent background solution with $\lambda_{GB}=0$. We numerically solve the linearised equations and show that the entire time evolution of the pressure anisotropy can be well approximated by the linear in $\lambda_{GB}$ corrections to the quasinormal mode expansion, even in the cases of high anisotropy. We finally show that, quite generally, the time evolution of the pressure anisotropy with the Gauss-Bonnet term is approximately {\it shifted} with respect to the evolution without it, with the sign of the shift being directly related to the sign of the $\lambda_{GB}$ parameter. This suggests that finite coupling corrections generically {\it increase} the isotropisation time of strongly coupled plasmas.