Cosmological fermion-number non-conservation

It is shown that certain cosmological models have built into the structure of space a 'handedness' which favours neutrinos over antineutrinos. In such models neutrino pairs rather than neutrino-antineutrino pairs can be created from the vacuum thus violating the conservation of lepton number. Both a real and an imaginary time description of the processes is given. The former makes use of Bogoliubov transformations, the latter of axial current anomalies and the Atiyah-Patodi-Singer index theorem for manifolds with boundary. (Auth.)