Speaker
Description
We show how the axion quality problem resulting from the violation of global symmetries by quantum gravity can be solved in presence of a gauged $U(1)_F$ flavor symmetry in a class of models. The gauged $U(1)_F$ explains the hierarchical structure of fermion masses and mixings via the Froggatt-Nielsen mechanism. The axion is realized as a byproduct of an accidental $U(1)$ symmetry with a QCD anomaly present in these models, with the gauged $U(1)_F$ safeguarding the axion potential. Three models, which are generalizations of the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) axion model, are presented realizing this idea. The axion acts as a flavon (flavaxion or axiflavon) in these models, which can be tested in flavor-changing decays of mesons. These models provide an understanding of the hierarchical structure of the fermion masses, solve the strong CP problem, and also explain the dark matter relic abundance in axion without inducing a cosmological domain wall problem.
