Medium Effects on Lasing of Superradiant Axions

Superradiant axions around black holes can potentially decay to photons via lasing. This can jeopardize the possibility of directly detecting gravitational signatures from the axion condensate. The extremely long wavelength of the emitted photons on the other hand eliminates any possibility of electromagnetic signatures. Due to the smallness of the axion mass however, medium effects around the black hole can significantly affect the lasing process. I discuss these medium effects and the conditions under which lasing can take place. For black holes of mass greater than 100M , the axion condensate is unlikely to lase unless the medium around is exceptionally dilute whereas axion condensate around black holes of a few solar masses can.