The subject of this thesis is the description of the Very Early Universe, from the Big Bang to the beginning of the radiation-dominated Friedman-Roberston-Walker era. We examine a pure gravity inflationary model for the Universe which is based on adding ƐR2 term to the usual gravitational Lagrangian ("improved Starobinsky model"). We find the classical inflationary solution essentially independent of initial conditions. The model has only one free parameter, which is bounded from above by observational constraints on scalar and tensorial perturbations and from below by both the need for standard baryogenesis and the need for galaxy formation. This requires 1011GeV < Ɛ-1/2 < 1013GeV.
The model is interpreted as a Chaotic Inflationary model, with initial conditions for classical evolution being generated by the quantum fluctuations in metric and curvature in Very Early Universe. We discuss those fluctuations using a particular solution of the Wheeler-De Witt equation and find that the inflationary phase is a highly typical event.
