Early cosmological models in Lyra's geometry

A spatially homogeneous and isotropic Robertson-Walker model with zero-curvature of the universe is studied within the frame-work of Lyra's manifold. The gauge-function phi (mu) in Lyra's manifold is taken to be time-dependent. Exact solutions of Einstein equations are obtained for two different early phases of the universe viz. Inflationary phase and radiation-dominated phase by using 'gamma-law' equation of state p = (gamma - 1) rho. The gamma -index, describing the material content, varies continuously with cosmic time so that in the course of its evolution, the universe goes through a transition from an inflationary phase to a radiation-dominated phase. The physical properties of the models are also discussed.