NONSINGULAR, COSMOLOGICAL SOLUTIONS FOR THE COUPLED DIRAC-EINSTEIN EQUATIONS

The coupled Dirac-Einstein equations for an open Robertson-Walker univ erse admit a discrete spectrum of non-singular recollapsing solutions with associated finite lifetimes. This spectrum can be classified by t opological quantum numbers, and the lifetime is roughly proportional t o these numbers. The rather complicated structure of the spectrum is d ue to the dynamics of the relative phase angle with respect to the pos itive and negative energy components of Dirac's spinor field. The spec trum is characterized by a band structure: the phase angle remains in each allowed band for a relatively long time but then suddenly jumps t o another one.