Thermal quenches in N=2* plasmas

TL;DR

This paper uses gauge/gravity duality to analyze thermal quenches in N=2* plasmas, revealing how the system's response varies with quench speed and introducing new renormalization techniques for time-dependent couplings.

Contribution

It presents a detailed study of thermal quenches in N=2* gauge theories, including the effects of quench rate and new renormalization schemes for time-dependent boundary conditions.

Findings

Fast quenches lead to relaxation governed by the lowest quasinormal mode.

Slow quenches exhibit nearly adiabatic response dictated by late-time mass profiles.

Response depends on the ratio of quench time scale to inverse temperature.

Abstract

We exploit gauge/gravity duality to study `thermal quenches' in a plasma of the strongly coupled N=2* gauge theory. Specifically, we consider the response of an initial thermal equilibrium state of the theory under variations of the bosonic or fermionic mass, to leading order in m/T<<1. When the masses are made to vary in time, novel new counterterms must be introduced to renormalize the boundary theory. We consider transitions the conformal super-Yang-Mills theory to the mass deformed gauge theory and also the reverse transitions. By construction, these transitions are controlled by a characteristic time scale \calt and we show how the response of the system depends on the ratio of this time scale to the thermal time scale 1/T. The response shows interesting scaling behaviour both in the limit of fast quenches with T\calt<<1 and slow quenches with T\calt>>1. In the limit that T\calt\to\infty, we observe the expected adiabatic response. For fast quenches, the relaxation to the final equilibrium is controlled by the lowest quasinormal mode of the bulk scalar dual to the quenched operator. For slow quenches, the system relaxes with a (nearly) adiabatic response that is governed entirely by the late time profile of the mass. We describe new renormalization scheme ambiguities in defining gauge invariant observables for the theory with time dependant couplings.