Propagation of fermion in curved space-time generates gravitational interaction due to the coupling between spin of the fermion and space-time curvature. This gravitational interaction appears as a CPT violating term in the Lagrangian. It is seen that this space-time interaction can generate neutrino asymmetry in the Universe. If the background metric is spherically asymmetric, say, of a rotating black hole, this interaction is non-zero, thus the net difference to the number density of the neutrino and anti-neutrino is non-zero.
Publication Source (Journal or Book title)
Pramana - Journal of Physics
Mukhopadhyay, B., & Singh, P. (2004). Neutrino-antineutrino asymmetry around rotating black holes. Pramana - Journal of Physics, 62 (3), 775-778. https://doi.org/10.1007/BF02705368