Fermion fields in Einstein-Cartan theory and the accelerated-decelerated transition in a primordial Universe

In this work the accelerated-decelerated transition in a primordial Universe is investigated by using the dynamics of fermion fields within the context of Einstein-Cartan theory, where apart from the curvature the space-time is also described by a torsion field. The model analyzed here has only a fermion field as the source of the gravitational field. The term associated with the spin of the fermion field plays the role of the inflaton which contributes to an accelerated regime whereas the one related to the fermion mass behaves as a matter field and is the responsible for a decelerated regime. Hence, by taking into account the spin of a massive fermion field it is possible to characterize the transition from the accelerated to the decelerated periods of the primordial Universe.