Axion anomalies

A bstract We study fermions derivatively coupled to axion-like or pseudoscalar fields, and show that the axial vector current of is not conserved in limit where fermion massless. This apparent violation classical chiral symmetry due background axion field. compute contributions this anomalous Ward identity field alone, which arise Minkowski space, as well effects an interaction with external gravitational For case massless fermions, these interactions induce terms effective action can be removed by addition local counterterms. demonstrate counterterms are generated transformation path integral measure when transforming theory from a form manifest one only after using equations motion. work perturbatively space include linearized Using heat kernel method, we properties measure, non-linear gravity gauge fields. Finally, verify our relation considering during pseudoscalar-driven inflation computing divergence de Sitter spacetime.