Dynamical evolution of axion condensates under stimulated decays into photons

Understand

Dark matter axion condensates may experience stimulated decays into photon pairs.

• This effect has been often interpreted as a parametric resonance of photons from the axion-photon coupling, leading to an exponential growth of the photon occupation number in a narrow instability band.
• Most of the previous literature does not consider the possible evolution of the axion field due to the photon growth.
• We revisit this effect presenting a mean field solution of the axion-photon kinetic equations, in terms of number of photons and pair correlations.