# Gravitational particle creation for dark matter and reheating

## TL;DR

This paper explores how gravitational particle creation during inflation can produce dark matter and reheat the universe, proposing a model with two scalar fields that explains current dark matter abundance.

## Contribution

It introduces a model where gravitational particle creation accounts for both reheating and dark matter production, emphasizing the dominance over thermal processes.

## Key findings

- Gravitational creation surpasses thermal freeze-in in reheating.
- A heavy scalar (~10^{13} GeV) decays into radiation, enabling reheating.
- A stable scalar (~10^3 GeV) can constitute dark matter.

## Abstract

The purely gravitational dark matter (PGDM) which interacts with the standard model particles only by gravitational interaction has recently been discussed. Due to its feeble interaction, PGDM may be produced mainly by the gravitational particle creation, which plays an important role in the reheating after kinetically driven inflation and some potential-driven inflation without subsequent inflaton oscillating phase. Therefore, we consider the possibility of the gravitational reheating model which can also explain the present PGDM density at the same time. We consider a model where two massive scalar fields are incorporated into the standard model besides the inflation sector. We show that the gravitational particle creation prevails over the thermal creation --- the freeze-in process --- and it can actually explain the reheating and the present abundance of dark matter if one of the scalar particles is as heavy as the Hubble parameter during inflation $\sim10^{13}$ GeV and finally decays into radiation via sufficiently weak coupling, and the other is a stable PGDM with its mass of the order of $10^3$ GeV.