Fate of chiral critical point under the strong isospin asymmetry

TL;DR

This paper investigates how strong isospin asymmetry affects the phase structure near the chiral critical point in quark matter, revealing shifts, new critical points, and the potential disappearance of the CP due to pion condensation.

Contribution

It introduces a Ginzburg-Landau framework to analyze the impact of isospin asymmetry on the QCD phase diagram, including universal relations and effects of the U(1)_A anomaly.

Findings

Isospin asymmetry shifts the critical point location.

New tricritical and triple points emerge with finite isospin density.

The critical point can be washed out by pion condensation.

Abstract

We study the influence of the isospin asymmetry on the phase structure of strongly interacting quark matter near the critical point (CP) using a Ginzburg-Landau approach. The effect is found to be drastic, not only bringing about the shift of the location of the CP, but resulting in a rich phase structure in the vicinity of the CP. In particular, new tricritical and triple points emerge as soon as the isospin density becomes finite. Moreover, we find the CP being washed out from the phase diagram due to the stabilization of a homogeneous charged pion condensate when the isospin chemical potential exceeds a critical value. We derive a model-independent universal relation between the critical isospin chemical potential and the chiral condensate at the CP. We also study the effect of the $\mathrm{U}(1)_\mathrm{A}$ anomaly on the phase transition to the pion condensate in the vicinity of chiral crossover.