SPACETIME CURVATURE COUPLING OF SPINORS IN EARLY UNIVERSE: NEUTRINO ASYMMETRY AND A POSSIBLE SOURCE OF BARYOGENESIS

Abstract

It is well known that when a fermion propagates in curved spacetime, its spin couples to the curvature of background spacetime. We propose that this interaction for neutrinos propagating in early curved universe could give rise to a new set of dispersion relations and then neutrino asymmetry at equilibrium. We demonstrate this with the Bianchi models which describe the homogeneous but anisotropic and axially symmetric universe. If the lepton number violating processes freeze out at 10-37 s when temperature T~1015 GeV , neutrino asymmetry of the order of 10-10 can be generated. A net baryon asymmetry of the same magnitude can thus be generated from this lepton asymmetry either by a GUT B-L symmetry or by the electroweak sphaleron processes which have B+L symmetry.