Lepton number asymmetries and the lower bound on the reheating temperature

TL;DR

This paper demonstrates that the reheating temperature in the early universe can be as low as around 2 MeV if certain conditions involving neutrino asymmetries and decay processes are met, impacting cosmological models.

Contribution

It introduces a scenario where low reheating temperatures are compatible with large neutrino-antineutrino asymmetries and non-hadronic decays, extending previous bounds.

Findings

Reheating temperature can be as low as 2 MeV.

Large neutrino asymmetries are compatible with low reheating temperatures.

Non-hadronic decay channels influence the reheating process.

Abstract

We show that the reheating temperature of a matter-domination era in the early universe can be pushed down to the neutrino decoupling temperature at around $2 \ {\rm MeV}$ if the reheating takes place through non-hadronic decays of the dominant matter and neutrino-antineutrino asymmetries are still large enough, $|L| \gtrsim \mathcal{O}(10^{-2})$ (depending on the neutrino flavor) at the end of reheating.