Bianchi-type I and V cosmologies in Einstein-Cartan theory

Within the framework of the Einstein-Cartan theory a Weyssenhoff-spinning-fluid-filled homogeneous anisotropic Bianchi-type I and V space-time is studied. The effects of a cosmological constant upon the dynamics of the early Universe are also considered. In the presence of torsion the general solution of the gravitational field equations for a cosmological fluid obeying a linear barotropic equation of state can be expressed in an exact parametric form. Several classes of exact analytical solutions for stiff matter and radiation are also obtained. In the large-time limit the Bianchi-type-V Universe ends in an isotropic open non-flat inflationary era but due to the effects of the spin the isotropization period is shortened. For an appropriate choice of the parameters non-singular behavior occurs and the evolution of the cosmological fluid near the bounce is considered in detail.