  We consider toy cosmological models in which a classical, homogeneous, spinor
field provides a dominant or sub-dominant contribution to the energy-momentum
tensor of a flat Friedmann-Robertson-Walker universe. We find that, if such a
field were to exist, appropriate choices of the spinor self-interaction would
generate a rich variety of behaviors, quite different from their widely studied
scalar field counterparts. We first discuss solutions that incorporate a stage
of cosmic inflation and estimate the primordial spectrum of density
perturbations seeded during such a stage. Inflation driven by a spinor field
turns out to be unappealing as it leads to a blue spectrum of perturbations and
requires considerable fine-tuning of parameters. We next find that, for simple,
quartic spinor self-interactions, non-singular cyclic cosmologies exist with
reasonable parameter choices. These solutions might eventually be incorporated
into a successful past- and future-eternal cosmological model free of
singularities. In an Appendix, we discuss the classical treatment of spinors
and argue that certain quantum systems might be approximated in terms of such
fields.
