Seeing in the Dark: Gravitational Waves from Resonant Production of Dark Photon Dark Matter

Ultralight dark photons (DPs) are well-motivated dark matter candidates. A promising yet underexplored mechanism for their relic abundance is parametric resonance in the Abelian-Higgs model that generates the DP mass. We advance previous analytical studies through dedicated 3D lattice simulations that capture important nonlinear effects, including backreaction and relic partitioning between the dark Higgs and DPs. We further predict the associated stochastic gravitational-wave (GW) signal, which can be within reach of a broad range of detectors, opening a new avenue to probe ultralight DP dark matter.