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 nongravitational 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 Tmax, and the temperature decreases as the inflaton continues to decay until the energy densities of radiation and inflaton oscillations are equal, at TRH. During these oscillations, s-channel gravitational production of dark matter occurs. We show that the abundance of dark matter (fermionic or scalar) depends primarily on the combination Tmax4/TRHMP3. We find that a sufficient density of dark matter can be produced over a wide range of dark matter masses: from 1 GeV to 1 ZeV.
Bibliographical noteFunding Information:
This work was made possible by Institut Pascal at Université Paris-Saclay with the support of the P2I research departments and the P2IO Laboratory of Excellence (program “Investissements d’avenir” No. ANR-11-IDEX-0003-01 Paris-Saclay and No. ANR-10-LABX-0038). This project has received support from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 860881-HIDDeN and the CNRS PICS MicroDark. The work of K. A. O. was supported in part by DOE Grant No. DE-SC0011842 at the University of Minnesota.
© 2021 authors. Published by the American Physical Society.