Shocks in Quark-Gluon Plasmas

TL;DR

This paper explores relativistic shock waves in quark-gluon plasmas, analyzing their properties across different theoretical frameworks and finding surprisingly small deviations from classical hydrodynamic profiles.

Contribution

It introduces a variational approximation for relativistic shocks in quark-gluon plasmas and compares these with classical hydrodynamic solutions, highlighting minimal deviations.

Findings

Deviations from classical shock profiles are surprisingly small.

A variational approximation to Einstein equations was developed.

Open questions remain for exact solutions in AdS/CFT context.

Abstract

Hydrodynamics is known to describe matter created in high energy heavy ion collisions well. Large deposition of energy by passing jets should create not only the sound waves, already discussed in literature, but also the shocks waves of finite amplitude. This paper is an introduction to relativistic shocks, which go through elementary energy and momentum continuity argument, to weak shocks treated in Navier-Stokes approximation, to out-of-equilibrium setting of AdS/CFT. While we have not yet found numerical solution to corresponding Einstein equations, we have found a variational approximation to the sum of their squares. Our general conclusion is that deviations from LS and NS hydrodynmical shock profiles are surprisingly small, even for strong shocks. We end with a list of open questions which the exact solution should be able to answer.