Non-minimally coupled nonlinear spinor field in Bianchi type-I cosmology

Abstract.

Within the scope of the Bianchi type-I cosmological model we have studied the role of the spinor field in the evolution of the Universe. In doing so, we have considered the case with non-minimal coupling. It was found that the non-diagonal components of the energy-momentum tensor of the spinor field, hence the restrictions on the space-time geometry remain the same as in the case of minimal coupling. Since in this case the diagonal components of the energy-momentum tensor differ, the evolution of the corresponding Universe also differs. For example, while a linear spinor field with non-minimal coupling or a nonlinear spinor field with minimal coupling give rise to an open universe, a nonlinear spinor field with non-minimal coupling with the same parameters can generate a close universe that at the beginning expands, and after attaining some maximum value begins to contract and finally ends in a Big Crunch.