QCD axion from chiral gauge theories

Abstract: We present models of axion based on supersymmetric chiral gauge theories. In these models, the PQ symmetry is spontaneously broken by the non-perturbative dynamics of chiral gauge theory. Thanks to supersymmetry, IR dynamics of the models are calculable. We also present an example of a QCD axion model that is compatible with SU(5) grand unification. We find that the PQ breaking scale should be higher than $\sim 10^{13}~{\rm GeV}$ for the successful GUT unification. In addition, the PQ breaking scale should be higher than the GUT scale to avoid a Landau pole of gauge coupling below the Planck scale.