Investigations of the Dynamics and Thermodynamics of the Early Universe for a Variety of Chaotic Inflationary Models.

The inflationary scenario which was proposed by A. Guth in 1981 changed the picture of the very early universe (10^{-44} sec <= t <= 10 ^{-32} sec). Despite all its strength in reshaping the picture of the universe, this scenario had shortcomings. The new and chaotic inflationary scenario have tried to improve the original idea of inflation and remedy its defects. In this dissertation we investigate analytically and numerically a number of potentials in the chaotic version of inflation. The aim is to study their dynamics and some thermodynamic properties in detail. The problems to be solved are: the horizon and flatness problems, the reheating problem, and the density fluctuation problem. The potentials studied are single field potentials ~ phiⁿ for n >= 2, in the scalar field phi and the so called "soft" and "double field" potentials involving two scalar fields. The overall lessons are that the higher power (n > 2) single field potentials are not successful in solving all these problems and that the soft and double field potentials are not very different from single field potentials in their effects on inflation.