Early-universe plasma may have stopped dark photons from heating cosmos

A new paper published in Physical Review Letters suggests that a hypothetical dark matter particle called the dark photon might not have heated the early universe as previously believed. This finding could significantly impact the search for dark matter. Junwu Huang and Mohamad Shalaby, researchers at the Perimeter Institute, collaborated with Anson Hook at the University of Maryland to explore this possibility.

Simulations conducted by Shalaby revealed that the conversion of dark photons into ordinary light in the plasma of the early universe is not as linear as previously thought. Instead, the process becomes highly nonlinear, rapidly suppressing the conversion and limiting plasma heating. This means that previous cosmological constraints on the mass of dark photons, which ruled out certain parameter spaces, are invalid.

The new analysis indicates that these constraints apply to a vast range of dark photon masses, from about 10⁻¹⁵ eV to 10⁻⁶ eV, spanning roughly a 10-order magnitude gap. This opens up a new area for experimental searches for dark matter. The discovery challenges the long-held assumption that the conversion of dark photons to ordinary light in plasma is a linear process.

The researchers revisited old textbooks on plasma physics to understand this behavior better. The findings suggest that experiments probing these previously excluded parameter spaces could potentially observe dark photons or other elusive particles. The research also highlights the importance of considering nonlinear effects in various astrophysical systems, such as neutron stars and white dwarfs, where similar nonlinear dynamics could play a role.