Speaker
Description
We explore a class of axion models where an accidental U(1) Peccei-Quinn (PQ)
symmetry automatically arises from the interplay of vertical (grand-unified)
and horizontal (flavor) gauge symmetries. Focusing on a specific SO(10) or Pati-Salam realization, we analyze the quality of the PQ symmetry and demonstrate that
the model non-trivially reproduces the Standard Model flavor structure. A high-quality axion, immune to the PQ quality problem, is obtained for ma ≳ 0.01 eV, corresponding to a post-inflationary PQ-breaking scenario. A distinctive feature of this setup is the presence of parametrically light fermions, known as anomalons, introduced to cancel the gauge anomalies of the flavor symmetry. We
investigate their cosmological production in the early universe, highlighting
how measurements of ∆Neff could serve as a low-energy probe of the UV dy-
namics addressing the PQ-quality problem.
