Strongly broken Peccei-Quinn symmetry in the early Universe

TL;DR

This paper explores supersymmetric QCD axion models with a temporarily enhanced Peccei-Quinn symmetry breaking in the early Universe, addressing isocurvature issues and linking axion dynamics to baryogenesis.

Contribution

It introduces models where the Peccei-Quinn symmetry breaking varies over time, providing new mechanisms for dark radiation and baryon asymmetry generation.

Findings

Predicts large self-interacting dark radiation from hidden gauge interactions.

Shows axion dynamics can generate observed baryon asymmetry.

Proposes scenarios with temporarily enhanced symmetry breaking in the early Universe.

Abstract

We consider QCD axion models where the Peccei-Quinn symmetry is badly broken by a larger amount in the past than in the present, in order to avoid the axion isocurvature problem. Specifically we study supersymmetric axion models where the Peccei-Quinn symmetry is dynamically broken by either hidden gauge interactions or the $SU(3)_c$ strong interactions whose dynamical scales are temporarily enhanced by the dynamics of flat directions. The former scenario predicts a large amount of self-interacting dark radiation as the hidden gauge symmetry is weakly coupled in the present Universe. We also show that the observed amount of baryon asymmetry can be generated by the QCD axion dynamics via spontaneous baryogenesis. We briefly comment on the case in which the PQ symmetry is broken by a non-minimal coupling to gravity.