UC Davis

We present a calculable toy model of an axion coupled to magnetic monopoles and electric charges, with manifest electric-magnetic duality. Our axion-photon coupling incurs periodic corrections due to monopoles (equivalently UV instantons), which are large for light monopoles. Axion periodicity is manifestly duality invariant since the axion itself transforms under duality. Our model is the original Seiberg-Witten theory, which naturally hosts an -axion and light monopoles. We calculate the axion-photon amplitude in different duality frames and prove its duality invariance.