Gravitational dark matter production

Dark matter, a key constituent of the cosmos, continues to elude a complete understanding within both cosmology and particle physics. As such, uncovering its nature remains a central challenge in contemporary theoretical research. A pivotal aspect of this puzzle involves identifying how dark matter came into existence. This paper explores the gravitational generation of dark matter under two separate scenarios: one in which particle production during reheating occurs purely via gravitational effects, and another where reheating results from the decay of the inflaton field. In both cases, we derive a relationship between the dark matter mass and the reheating temperature, allowing us to constrain the permissible mass range for dark matter particles based on current reheating bounds.