Gravitational Leptogenesis

We introduce a dimension five CP violating coupling between the Ricci scalar and fermions. This operator splits the energy level between neutrinos and antineutrinos and can generate a lepton asymmetry in the radiation era if heavy Majorana neutrinos decouple at the GUT scale. This operator can also generate a lepton asymmetry during warm inflation if the light neutrinos have a Majorana mass m(v) greater than or similar to 0.25 eV which is observable in double beta decay experiments