Reply to "Comment on `Axion induced oscillating electric dipole moments' " [1]

Abstract

We respond to a paper of Flambaum, et.al. [Phys. Rev. D95, no. 5, 058701 (2017)], claiming there is no effective induced oscillating electric dipole moment, e.g., for the electron, arising from interaction with an oscillating cosmic axion background via the anomaly. The relevant Feynman amplitude, Fig.(1), as computed by Flambaum et.al., becomes a total divergence, and vanishes. Contrary to this result, we obtained a nonvanishing amplitude, that yields physical electric dipole radiation for an electron (or any magnetic dipole moment) immersed in a cosmic axion field. We argue that the Flambaum et.al. counter-claim is incorrect, and is based upon a misunderstanding of a physics choice vs. gauge choice, and an assumption that electric dipoles be defined only by coupling to static (constant in time) electric fields.