Bounds on very low reheating scenarios after Planck

Abstract

We consider the case of very low reheating scenarios ($T_{\mathrm{RH}}\sim \mathcal{O}(\mathrm{MeV})$) with a better calculation of the production of the relic neutrino background (with three-flavor oscillations). At 95% confidence level, a lower bound on the reheating temperature $T_{\mathrm{RH}}>4.1$ MeV is obtained from Big Bang Nucleosynthesis, while $T_{\mathrm{RH}}>4.3$ MeV from Planck data for very light ($\sum m_i=0.06$ eV) neutrinos. If neutrino masses are allowed to vary, Planck data yield $T_{\mathrm{RH}}>4.7$ MeV, the most stringent bound on the reheating temperature to date. Neutrino masses as large as 1 eV are possible for very low reheating temperatures.

9 pages, 9 figures