Isospin-breaking contribution to the model-independent axion-photon-photon coupling in $U(3)$ chiral theory

Rui Gao, Jin Hao, Chun-Gui Duan +3

We pursue the calculation of the model-independent component of the axion-photon-photon coupling in the $U(3)$ chiral perturbation theory up to next-to-leading order, with the emph…