On the $\theta$-angle physics of QCD under pressure: The strange and isospin phase diagram

TL;DR

This paper explores how the $ heta$-angle influences the phase diagram of QCD with three light flavors under nonzero isospin and strangeness chemical potentials, revealing new phases and phase transition characteristics.

Contribution

It provides a detailed analysis of the QCD phase diagram considering the $ heta$-angle, including the discovery of a novel parity-preserving superfluid phase at $ heta=\pi$.

Findings

Identification of phase boundaries and transition types in the $ heta$-dependent QCD phase diagram.

Discovery of a parity-preserving superfluid phase at $ heta=\pi$.

Insights into Dashen's phenomenon in superfluid phases with varying light flavor numbers.

Abstract

We unveil the impact of the $\theta$-angle on the QCD phase diagram at nonzero isospin and strangeness chemical potentials for three light flavors and different quark mass ratios. We establish the phase boundaries as well as the nature of the associated phase transitions. The order parameters and the physical spectrum in the different phases are determined. We further elucidate the physics around $\theta=\pi$ where we discover a novel parity-preserving superfluid phase. Finally, we comment on Dashen's phenomenon in the superfluid phases when varying the number of light flavors.