Leptogenesis With Many Neutrinos

Understand

We consider leptogenesis in scenarios with many neutrino singlets.

• We find that the lower bound for the reheating temperature can be significantly relaxed with respect to the hierarchical three neutrino case.
• We further argue that the upper bound for the neutrino mass scale from leptogenesis gets significantly lifted in these scenarios.
• As a specific realization, we then discuss an extra-dimensional model, where the large number of neutrinos is provided by Kaluza-Klein excitations.