Primordial Fluctuations in String Cosmology

TL;DR

This thesis explores string theory-based inflationary models, especially brane inflation, analyzing their theoretical features and potential observational signatures in the early universe.

Contribution

It characterizes string-inspired inflationary scenarios, focusing on brane inflation with non-canonical dynamics and brane annihilation reheating, linking string theory with cosmological observations.

Findings

Identification of distinctive features of string-inspired inflation models

Analysis of observational consequences of brane inflation scenarios

Summary of recent model building efforts at the intersection of string theory and cosmology

Abstract

This thesis is dedicated to the study of inflationary scenarios based on string theory. Inflation is a brief period of accelerated expansion in the very early Universe which gives natural explanations for problems of the Standard Big Bang Model (SBBM) of cosmology. The phenomenological success of inflation provides the motivation for numerous efforts to establish its connection with particle physics. As a promising contender for a unified theory at very high energy scales, string theory is an obvious framework to look for the theoretical foundations of inflation; we therefore try to determine the characteristic features of string-inspired inflationary scenarios, along with their observational consequences. In particular, we shall be interested in models of brane inflation, in which the inflaton field has non-canonical dymanics and where the era of reheating is interpreted as the mutual annihilation of (anti-)branes. This document contains an introduction to cosmology and string theory as well as the model building efforts untertaken at their intersection in recent years. The scientific articles published during the thesis are represented by a short summary each and are available separately on the arXiv.