No cosmological constraints on dark photon dark matter from resonant conversion:
Impact of nonlinear plasma dynamics
Anson Hook, Junwu Huang, and Mohamad Shalaby
This work overturns all previous constraints on dark photon dark matter by showing that its resonant conversion into ordinary plasma is highly inefficient, saturating at a very low level. As a result, the limits on dark photon dark matter are weakened by a factor of 3,000 to 10 million, rendering it effectively undetectable by current and near-future cosmological observations.
At the last panel in various animations below: wavemode \(k = 2 \pi / \hspace{-0.1cm} \lambda \), and we mark to two important scales: \(k_D = 1/\hspace{-0.1cm}\lambda_D \) and \(\omega_p =1/ \hspace{-0.1cm}\lambda_e \)
where \(\lambda\) is the wavelength corresponding to the wave mode \(k\), \(\lambda_D\) is the Debye length, and \(\lambda_e\) is electron skin depth