Dark matter production via a non-minimal coupling to gravity

Abstract

We study postinflationary scalar dark matter production via its non-minimalcoupling to gravity. During the inflaton oscillation epoch, dark matter is producedresonantly for a sufficiently large non-minimal coupling ξ ≳ 5. We find thatbackreaction on the curvature and rescattering effects typically become important for thevalues of ξ above 30, which invalidate simple estimates of the productionefficiency. At large couplings, the dark matter yield becomes almost independent of ξ, signifying approximate quasi-equilibrium in the inflaton-dark matter system.Although the analysis gets complicated by the presence of apparent negative energy in theJordan frame, this behaviour can be regularized by introducing mild dark matterself-interaction. Using lattice simulations, we delineate parameter space leading to thecorrect dark matter relic abundance.