Dark matter production via a non-minimal coupling to gravity

We study postinflationary scalar dark matter production via its non-minimal cou-pling to gravity. During the inflaton oscillation epoch, dark matter is produced resonantly for a sufficiently large non-minimal coupling xi >= 5. We find that backreaction on the curvature and rescattering effects typically become important for the values of xi above 30, which inval-idate simple estimates of the production efficiency. At large couplings, the dark matter yield becomes almost independent of xi, signifying approximate quasi-equilibrium in the inflaton-dark matter system. Although the analysis gets complicated by the presence of apparent negative energy in the Jordan frame, this behaviour can be regularized by introducing mild dark matter self-interaction. Using lattice simulations, we delineate parameter space leading to the correct dark matter relic abundance.

Automated summary

We study the production of scalar dark matter through its non-minimal coupling to gravity post-inflation. Resonant dark matter production occurs when the non-minimal coupling xi is greater than or equal to 5 during the inflaton oscillation epoch. For xi values above 30, backreaction on the curvature and rescattering effects become important, invalidating simple estimates of production efficiency. At large couplings, the dark matter yield becomes almost independent of xi, indicating approximate quasi-equilibrium in the inflaton-dark matter system. The presence of apparent negative energy in the Jordan frame complicates the analysis, but can be regulated by introducing mild dark matter self-interaction. Using lattice simulations, we determine the parameter space leading to the correct dark matter relic abundance.