Photon propagation in a cold axion background with and without magnetic field
Abstract
A cold relic axion condensate resulting from vacuum misalignment in the early universe oscillates with a frequency m, where m is the axion mass. We determine the properties of photons propagating in a simplified version of such a background where the sinusoidal variation is replaced by a square wave profile. We prove that previous results that indicated that charged particles moving fast in such a background radiate, originally derived assuming that all momenta involved were much larger than m, hold for long wavelengths too. We also analyze in detail how the introduction of a magnetic field changes the properties of photon propagation in such a medium. We briefly comment on possible astrophysical implications of these results.
Cite
@article{arxiv.1106.1662,
title = {Photon propagation in a cold axion background with and without magnetic field},
author = {Domenec Espriu and Albert Renau},
journal= {arXiv preprint arXiv:1106.1662},
year = {2013}
}
Comments
17 pages, 4 figures, revised version includes an extended discussion on physical implications