Electrodynamics in the presence of an axion

In this paper, 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 casual propagator and we solve nonlocally for the first coefficient. The authors show that, for a generic axionic background, short distance propagation of the gauge field is well defined