Universal relaxation in quark-gluon plasma at strong coupling

TL;DR

This paper investigates relaxation rates in strongly coupled quark-gluon plasma using gauge/gravity duality, finding that thermalization times are largely unaffected by different scale invariance breaking mechanisms.

Contribution

It compares hard and soft scale invariance breaking mechanisms in gauge theory plasma and shows their minimal impact on relaxation times at strong coupling.

Findings

Thermalization time is insensitive to scale-breaking mechanisms.

Relaxation rates are similar across different models of scale invariance breaking.

Results are relevant to understanding QCD quark-gluon plasma.

Abstract

We use top-down gauge theory/string theory correspondence to compute relaxation rates in strongly coupled nonconformal gauge theory plasma. We compare models with difference mechanisms of breaking the scale invariance: "hard breaking" (by relevant operators) and "soft breaking" (by marginal operators). We find that the thermalization time of the transverse traceless fluctuations of the stress-energy tensor is rather insensitive to the mechanisms of breaking the scale invariance over a large range of the scale-breaking parameter $\delta=\frac 13-c_s^2$. We comment on the relevance of the results to QCD quark-gluon plasma.