Chiral symmetry breaking with no bilinear condensate revisited

TL;DR

This paper revisits an alternative chiral symmetry breaking phase without a chiral condensate, analyzing its properties at finite density using chiral perturbation theory and uncovering an exotic phase with unique symmetry breaking features.

Contribution

It provides an analytical study of a hypothetical chiral symmetry breaking phase without a chiral condensate at finite density, expanding understanding of QCD phases.

Findings

Identification of an exotic phase breaking vectorial flavor symmetries

Analytical computation of physical observables in the epsilon-regime

Discovery of a phase analogous to the Aoki phase at nonzero theta

Abstract

While chiral symmetry breaking in the QCD vacuum is attributed to nonzero chiral condensate, an alternative symmetry breaking pattern with no chiral condensate is also possible, as pointed out by Stern. This hypothetical phase was excluded in QCD at zero density long time ago, but nothing forbids it at finite baryon density. In this work, we study the $\theta$ dependence of this unorthodox phase on the basis of chiral perturbation theory. Physical observables such as energy density, topological susceptibility, non-local chiral order parameter and meson masses are computed analytically in the epsilon-regime. At nonzero $\theta$ we find an exotic phase that breaks vectorial flavor symmetries in a way analogous to the Aoki phase in lattice QCD.