Espriu, D. (Domènec)Renau Cerrillo, Albert2019-04-082019-04-082012-01-181550-7998https://hdl.handle.net/2445/131788A 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, which 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.10 p.application/pdfeng(c) American Physical Society, 2012Física de partículesExperimentsFotonsParticle physicsExperimentsPhotonsinfo:eu-repo/semantics/article6196882019-04-08info:eu-repo/semantics/openAccess