Gravity-induced neutrino–antineutrino oscillation: CPT and lepton number non-conservation under gravity

Abstract

We introduce a new effect in the neutrino oscillation phase which shows that the neutrino–antineutrino oscillation is possible under gravity even if the rest masses of the corresponding eigenstates are the same. This is due to CPT violation, and is possible to demonstrate if the neutrino mass eigenstates are expressed as a combination of neutrino and antineutrino eigenstates, as of the neutral kaon system, with the plausible breaking of lepton number conservation. For Majorana neutrinos, this oscillation is expected to significantly affect the inner edge of neutrino-dominated accretion discs around compact objects by influencing the neutrino sphere which controls the accretion dynamics, and then the related type-II supernova evolution and the r-process nucleosynthesis. On the other hand, in the early universe, in the presence of various lepton number violating processes, this oscillation, we argue, might have led to neutrino asymmetry which resulted in baryogenesis from the B–L symmetry by electro-weak sphaleron processes.