The Cosmological Evolution of Light Dark Photon Dark Matter

Light dark photons are subject to various plasma effects, such as Debye screening and resonant oscillations, which can lead to a more complex cosmological evolution than is experienced by conventional cold dark matter candidates. Maintaining a consistent history of dark photon dark matter requires ensuring that the super-thermal abundance present in the early Universe (i) does not deviate significantly after the formation of the CMB, and (ii) does not excessively leak into the Standard Model plasma after BBN. In this talk, I will clarify the roles of resonant and non-resonant absorption and address some implications of plasma inhomogeneities on resonant transitions.