QCD Critical Points and Their Associated Soft Modes

TL;DR

This paper investigates the nature of critical points in QCD matter, revealing multiple critical points influenced by vector interactions and analyzing how density fluctuations behave as soft modes near these points, with implications for observable phenomena.

Contribution

It introduces the concept of multiple QCD critical points with associated soft modes and analyzes the behavior of density fluctuations as potential soft modes using dissipative relativistic fluid dynamics.

Findings

Multiple critical points exist in QCD matter with color superconductivity.

Entropy fluctuations are enhanced near the QCD critical point.

Mechanical density fluctuations are suppressed, affecting Mach cone observability.

Abstract

The mean-field level calculation shows that the QCD matter can have multiple critical points incorporating the color superconductivity under charge neutrality constraint due to the repulsive vector interaction; this actually implies that the QCD matter is very soft for a simultaneous formation of diquark and chiral condensates coupled with the baryonic density. Dynamical density fluctuations are analyzed as possible soft modes around the QCD critical point using dissipative relativistic fluid dynamics. It is found that the entropy fluctuation solely gets enhanced while the sound modes due to mechanical density fluctuations are strongly attenuated around the QCD CP, which may suggest a suppression or even total disappearance of Mach cone at the CP.