Gravitational Production of Dark Matter during Reheating

Understand

We consider the direct $s$-channel gravitational production of dark matter during the reheating process.

• Independent of the identity of the dark matter candidate or its non-gravitational interactions, the gravitational process is always present and provides a minimal production mechanism.
• During reheating, a thermal bath is quickly generated with a maximum temperature $T_{\rm max}$, and the temperature decreases as the inflaton continues to decay until the energy densities of radiation and inflaton oscillations are equal, at $T_{\rm RH}$.
• During these oscillations, $s$-channel gravitational production of dark matter occurs.