Dark matter from gravitational particle production at reheating

Understand

We show that curvature induced particle production at reheating generates adiabatic dark matter if there are non-minimally coupled spectator scalars weakly coupled to visible matter.

• The observed dark matter abundance implies an upper bound on spectator masses $m$ and non-minimal coupling values $\xi$.
• For example, assuming quadratic inflation, instant reheating and a single spectator scalar with only gravitational couplings, the observed dark matter abundance is obtained for $m\sim 0.1$ GeV and $\xi \sim 1$.
• Larger mass and coupling values of the spectator are excluded as they would lead to overproduction of dark matter.