The axion potential in quark matter

Abstract

We study the QCD axion potential in hot and dense quark matter, within an NJL-like model that includes the coupling of the axion to quarks. Firstly we compute the effect of the chiral QCD crossover on the axion mass and self-coupling. Then, we compute the axion potential and study the domain walls. We find that the energy barrier between two adjacent vacuum states decreases in the chirally restored phase: this results in a lower surface tension of the walls. Finally we comment on the possibility of abundant production of walls in hot and dense quark matter.