We discuss spectral distortions, time delays, and refraction of light in an axion or axion-plasma background. This involves solving the full set of geodesic equations associated to the system of Hamiltonian optics, allowing us to self-consistently take into account the evolution of the frequency, momentum, and position of photons. We support our arguments with analytic approximations and full numerical solutions. We also describe both nonintegrated and integrated versions of these effects, the latter of which depends on the whole history of the photon trajectory through the axion background. Remarkably, the introduction of a plasma enhances the sensitivity to axion-induced optical phenomena, allowing chiral refraction, integrated time delays, and integrated frequency shifts to occur at first order in the axion-photon coupling. This suggests a general enhancement of many axion-induced dispersive effects when the background refractive index is different from 1.

• Received 20 March 2020
• Accepted 22 May 2020

DOI:https://doi.org/10.1103/PhysRevD.101.123503

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society