Critical Opalescence around the QCD Critical Point and Second-order Relativistic Hydrodynamic Equations Compatible with Boltzmann Equation

TL;DR

This paper investigates density fluctuations near the QCD critical point using relativistic hydrodynamics, suggesting observable signals like suppression of Mach cones could indicate the critical point’s presence.

Contribution

It introduces a rigorous derivation of second-order relativistic hydrodynamic equations compatible with Boltzmann dynamics based on the renormalization group method.

Findings

Sound mode attenuation near QCD critical point

Thermal fluctuation prominence at the critical point

Potential suppression of Mach cones as a signal of the QCD critical point

Abstract

The dynamical density fluctuations around QCD critical point (CP) are analyzed using relativistic dissipative fluid dynamics, and we show that the sound mode around the QCD CP is strongly attenuated whereas the thermal fluctuation stands out there. We speculate that if possible suppression or disappearance of a Mach cone, which seems to be created by the partonic jets at RHIC, is observed as the incident energy of the heavyion collisions is decreased, it can be a signal of the existence of the QCD CP. We have presented the Israel-Stewart type fluid dynamic equations that are derived rigorously on the basis of the (dynamical) renormalization group method in the second part of the talk, which we omit here because of a lack of space.