Stiff Fluid in Accelerated Universes with Torsion

The flat Friedmann universes filled by stiff fluid and a nonminimallycoupled material scalar field with polynomial potentials of thefourth degree are considered in the framework of theEinstein-Cartan theory. Exact general solution is obtained for arbitrary positive values of the coupling constant . A comparative analysis of the cosmological models with and without stiff fluid is carried out. Some effects of stiff fluid areelucidated. It is shown that singular models with a de Sitter asymptotic and with the power-law asymptotic at late times are possible. It is found that is a specific value of the coupling constant. It is demonstrated that the bouncing models without the particle horizon and with an accelerated expansion by a de Sitter law of an evolution at late times are admissible