Ginzburg-Landau phase diagram for dense matter with axial anomaly, strange quark mass, and meson condensation

TL;DR

This paper explores the phase transitions in dense quark matter, highlighting how axial anomaly and meson condensation influence the critical points and continuity between hadronic and quark phases using a Ginzburg-Landau framework.

Contribution

It extends Ginzburg-Landau analysis to include strange quark mass effects and kaon condensation, revealing conditions for critical points and phase continuity in dense matter.

Findings

Axial anomaly can induce a critical point in the hadron-quark transition.

Kaon condensation can disrupt the continuity between hadronic and quark matter.

Mass terms in the potential determine the occurrence of the 2SC phase.

Abstract

We discuss the phase structure of dense matter, in particular the nature of the transition between hadronic and quark matter. Calculations within a Ginzburg-Landau approach show that the axial anomaly can induce a critical point in this transition region. This is possible because in three-flavor quark matter with instanton effects a chiral condensate can be added to the color-flavor locked (CFL) phase without changing the symmetries of the ground state. In (massless) two-flavor quark matter such a critical point is not possible since the corresponding color superconductor (2SC) does not break chiral symmetry. We study the effects of a nonzero but finite strange quark mass which interpolates between these two cases. Since at ultra-high density the first reaction of CFL to a nonzero strange quark mass is to develop a kaon condensate, we extend previous Ginzburg-Landau studies by including such a condensate. We discuss the fate of the critical point systematically and show that the continuity between hadronic and quark matter can be disrupted by the onset of a kaon condensate. Moreover, we identify the mass terms in the Ginzburg-Landau potential which are needed for the 2SC phase to occur in the phase diagram.