Fluid dynamics near the QCD critical point

TL;DR

This paper develops a dynamical model to study QCD phase transitions, capturing nonequilibrium effects and fluctuations near the critical point and first-order transition.

Contribution

It introduces a coupled Langevin framework for chiral and deconfinement transitions, including noise and dissipation, to analyze nonequilibrium dynamics.

Findings

Delay in relaxation times near the transition temperature.

Enhanced thermal fluctuations during first-order transition.

Different dynamical signatures for critical point and first-order scenarios.

Abstract

We present a fully dynamical model to study the chiral and deconfinement transition of QCD simultaneously. The quark degrees of freedom constitute a heat bath in local equilibrium for both order parameters, the sigma field and a dynamical Polyakov loop. The nonequilibrium evolution of these fields is described by Langevin equations including dissipation and noise. In several quench scenarios we are able to observe a delay in the relaxation times near the transition temperature for a critical point as well as a first-order phase transition scenario. During the hydrodynamical expansion of a hot quark fluid we find a strong enhancement of thermal fluctuations at the first-order transition compared to a scenario with a critical point.