Cosmic plasma was supposed to rule out dark photons. Simulations say otherwise

For years, one of the strongest cosmological arguments against dark photon dark matter rested on a simple idea: if dark photons converted into ordinary light in the early universe, they should have heated cosmic plasma enough to leave measurable traces.That assumption may not hold.A team from Perimeter Institute and the University of Maryland reports that the conversion process can trigger powerful nonlinear effects in plasma. Those effects quickly disrupt the resonance that drives energy transfer, shutting the process down before much heating occurs.The result weakens some of the strongest cosmological limits on dark photon dark matter across about 10 orders of magnitude in mass, from roughly 10⁻¹⁴ to 10⁻⁴ electron volts.A constraint built on linear physicsOne candidate is the dark photon, a hypothetical light boson that can interact weakly with the electromagnetic current through kinetic mixing.