Holographic Collisions across a Phase Transition

TL;DR

This paper uses holography to study relativistic collisions in strongly coupled gauge theories with phase transitions, revealing universal energy deposition behavior near criticality and evaluating hydrodynamic models' effectiveness.

Contribution

It introduces a holographic analysis of collisions across different phase transition types and assesses hydrodynamic descriptions near critical points.

Findings

Energy is deposited into a long-lived energy blob near criticality.

Second-order hydrodynamics accurately describes the energy distribution.

Müller-Israel-Stewart hydrodynamics does not fit well near the transition.

Abstract

We use holography to analyse relativistic collisions in a one-parameter family of strongly coupled gauge theories with thermal phase transitions. For a critical value of the parameter the transition is second order, for subcritical values it is first order, and for super-critical values it is a smooth crossover. We extract the gauge theory stress tensor from collisions of gravitational shock waves on the dual geometries. Regardless of the nature of the transition, for values of the parameter close to the critical value almost all the energy of the projectiles is deposited into a long-lived, quasi-static blob of energy at mid-rapidity. This configuration is well described by the constitutive relations of second-order hydrodynamics that include all second-order gradients that are purely spatial in the local rest frame. In contrast, a M\"uller-Israel-Stewart-type formulation of hydrodynamics fails to provide a good description. We discuss possible implications for searches of the QCD critical point.