No cosmological constraints on dark photon dark matter from resonant conversion:
Impact of nonlinear plasma dynamics
Anson Hook, Junwu Huang, and Mohamad Shalaby
arxiv:2510.13956
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