Spontaneous P-violation in QCD in extreme conditions

Abstract

We investigate the possibility of parity being spontaneously violated in QCD at finite baryon density and temperature. QCD is approximated by a generalized σ 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.