Reheating in the kination epoch via multi-channel decay of gravitationally created massive scalars

TL;DR

This paper investigates how gravitationally produced massive scalars decay into other particles during the kination epoch, leading to reheating of the universe with temperatures up to 10^{13} GeV, highlighting the dominance of fermionic decay channels at low masses.

Contribution

It provides a detailed quantitative analysis of reheating via multi-channel decay of scalars in the kination epoch using Boltzmann equations and quantum field theory in curved spacetime.

Findings

Reheating temperature ranges from 10^9 to 10^{13} GeV.

Fermionic decay channels dominate at low scalar masses.

Multiple decay channels influence the reheating process.

Abstract

We provide a detailed study of reheating in the kination regime in a scenario where the particle content is produced by gravitational production of massive scalars decaying into massless scalars and fermions which eventually reheat the Universe. A detailed calculation is given by using Boltzmann equations and decay rates obtained using formalism of quantum field theory in curved spacetime. By numerical calculations the reheating temperature is found to be in the $10^{9}$-$10^{13}$ GeV regime. Moreover, the fermionic channel of decay is found to be the dominant channel of decay when the mass $m$ of the decaying particle is small raising the reheating temperature as opposed to a single scalar decay channel.