Inflationary models in string cosmology

Abstract

Inflation is an acclaimed theory for uncovering how the Universe works and how it came to be. For years, physicists have attempted to not only cement a theory where the accelerated expansion of the Universe can help us to explore primordial states of the Universe, but also to incorporate other existing theories into inflation theory to produce even more ambitious models. Such models attempt to tie quantum field theories into those of inflationary cosmology in pursuit of a unified way of describing the phenoma in the Universe from the smallest of scales to the largest scales observable to man. The goal of this thesis is to explore some of these theories and the steps that have been taken (both mathematically and in idea) to achieve inflationary models that take elements from field theories. We begin from Effective Field theories and initial ideas of inflation, to understanding why inflation is important and why it is a theory so many physicists are invested in. We attempt to analyze some problems that arise in rationalizing inflation, the changes made to overcome them as well as the newer theories where further adjustments are made to make inflation as naturally derived as possible. We venture into string theory and the ideas that lead to the construction of complex inflationary models such as the KKLMMT model. We analyze brane-antibrane interactions and the problems that these interactions bring. We explore how KKLMMT tries to account for such issues by stabilizing various contenders in the theory to possibly reach a final concrete model. Finally, we explore racetrack inflation and reheating, how they arise from the ideas presented by such string cosmology models and what implications they bring to our understanding of the Universe.