Spontaneous parity violation in extreme conditions: an effective lagrangian analysis

TL;DR

This paper explores how high baryon densities can induce spontaneous parity violation in meson sectors of gauge theories like QCD, using an extended sigma-model to reveal novel mechanisms and phase transitions.

Contribution

It introduces a new mechanism for parity breaking based on meson condensate interplay, extending previous sigma-model analyses to include realistic quark masses and phase transition predictions.

Findings

Predicts a second-order phase transition to parity-broken state at high density.

Demonstrates a first-order transition to nuclear matter with parity conservation.

Shows quark masses do not alter the core parity-breaking phenomena.

Abstract

We investigate how large baryon densities (and possibly high temperatures) may induce spontaneous parity violation in the composite meson sector of vector-like gauge theory (presumably QCD or techni-QCD) . The analysis at intermediate energy scales is done by using an extended $\sigma$-model lagrangian that includes two scalar and two pseudoscalar multiplets and fulfills low-energy constraints for vector-like gauge theories. We elaborate on a novel mechanism of parity breaking based on the interplay between lightest and heavier meson condensates, which therefore cannot be realized in the simplest $\sigma$ model. The results are relevant for an idealized homogeneous and infinite nuclear (quark or techniquark) matter where the influence of density can be examined with the help of a constant chemical potential. The model is able to describe satisfactorily the first-order phase transition to stable nuclear matter, and predicts a second-order phase transition to a state where parity is spontaneously broken. We argue that the parity breaking phenomenon is quite generic when a large enough chemical potential is present. Current quark masses are explicitly taken into account in this work and shown not to change the general conclusions.