Completely dark photons from gravitational particle production during the inflationary era

Starting with the de Broglie-Proca Lagrangian for a massive vector field, we calculate the number density of particles resulting from gravitational particle production (GPP) during inflation, with detailed consideration to the evolution of the number density through the reheating. We find plausible scenarios for the production of dark-photon dark matter of mass in a wide range, as low as a micro-electron volt to 10(14) GeV. Gravitational particle production does not depend on any coupling of the dark photon to standard-model particles.

Automated summary

By utilizing the de Broglie-Proca Lagrangian, this study calculated the particle number density generated by gravitational particle production during inflation, taking into account the evolution of the number density during reheating. The research identified potential scenarios for the production of dark-photon dark matter with mass ranging from a micro-electron volt to 10^14 GeV, independent of any coupling between the dark photon and standard-model particles.