ELECTRODYNAMICS IN THE PRESENCE OF AN AXION

The low energy limit of an axion field coupled to gauge fields is investigated through the behavior of the gauge fields propagator in a local vacuum angle background. The local (singular) part of the effective action for the axion field is calculated at one-loop level. In the case of a time-like, linearly growing axion field, representing a massive axion, we give an asymptotic expansion of the causal propagator and we solve nonlocally for the first coefficient. We show that, for a generic axionic background, short distance propagation of the gauge field is well defined.