Spontaneous P-violation in QCD in extreme conditions

TL;DR

This paper explores the potential for spontaneous parity violation in QCD under extreme conditions like high density and temperature, using a generalized sigma-model to analyze the phenomenon's plausibility and stability.

Contribution

It introduces a novel mechanism for spontaneous parity violation in QCD at finite density and temperature, considering interactions with constituent quarks beyond simple pion-nucleon models.

Findings

Parity violation may be common in dense, hot nuclear matter.

Chiral collapse does not occur in parameter regions supporting parity violation.

Spontaneous parity violation is compatible with stable nuclear matter states.

Abstract

We investigate the possibility of parity being spontaneously violated in QCD at finite baryon density and temperature. The analysis is done for an idealized homogeneous and infinite nuclear matter where the influence of density can be examined with the help of constant chemical potential. QCD is approximated by a generalized sigma-model with two isomultiplets of scalars and pseudoscalars. The interaction with the chemical potential is introduced via the coupling to constituent quark fields as nucleons are not considered as point-like degrees of freedom in our approach. This mechanism of parity violation is based on interplay between lightest and heavier degrees of freedom and it cannot be understood in simple models retaining the pion and nucleon sectors solely. We argue that, in the appropriate environment (dense and hot nuclear matter of a few normal densities and moderate temperatures), parity violation may be the rule rather than the exception and its occurrence is well compatible with the existence of stable bound state of normal nuclear matter. We prove that the so called 'chiral collapse' never takes place for the parameter region supporting spontaneous parity violation.