Dirac-field model of inflation in Einstein-Cartan theory

We present a cosmological model in which a single Dirac field with a flat potential can give rise to inflation within the framework of the Einstein-Cartan theory. It is shown that our Dirac-field model leads to a nearly scale-invariant spectrum of density fluctuations owing to the spin-interaction which naturally arises from the field equations of the Einstein-Cartan theory.