Gauge/gravity duality and thermalization of a boost-invariant perfect fluid

TL;DR

This paper uses gauge/gravity duality to analyze the thermalization process of a boost-invariant perfect fluid, revealing a universal, short thermalization time relevant to heavy-ion collision experiments.

Contribution

It derives the quasi-normal mode equations for a black hole in AdS space dual to an expanding perfect fluid, providing new insights into rapid thermalization in strongly coupled gauge theories.

Findings

Identifies a universal, small thermalization time scale.

Describes a scaling behavior in proper-time consistent with adiabatic approximation.

Connects gravitational quasi-normal modes to fluid thermalization dynamics.

Abstract

We derive the equation for the quasi-normal modes corresponding to the scalar excitation of a black hole moving away in the fifth dimension. This geometry is the AdS/CFT dual of a boost-invariant expanding perfect fluid in N=4 SUSY Yang-Mills theory at large proper-time. On the gauge-theory side, the dominant solution of the equation describes the decay back to equilibrium of a scalar excitation of the perfect fluid. Its characteristic proper-time can be interpreted as a thermalization time of the perfect fluid, which is a universal (and numerically small) constant in units of the unique scale of the problem. This may provide a new insight on the short thermalization-time puzzle encountered in heavy-ion collision phenomenology. A nontrivial scaling behaviour in proper-time is obtained which can be interpreted in terms of a slowly varying adiabatic approximation.