Aspects of D-brane inflation

Abstract

Inflation has been suggested as a solution to cosmological problems but it ultimately needs to be derived from a fundamental theory such as string theory. In this thesis we study the embedding of inflation into string theory using the D-brane inflation scenario as case study. We first review the relevant aspects of string compactifications and D-branes and construct the effective action of the inflationary D3-brane. We then study multifield D-brane inflation including compactification corrections to the inflaton action that arise from UV deformations of a warped
throat geometry emerging from the ISD supergravity solution. One particular issue here is to investigate in detail the cosmological consequences of realistic angular
dependent potentials in the D-brane inflation scenario in a fully UV/IR consistent way. Embedding a warped throat into a compact Calabi-Yau space with all moduli stabilized breaks the no-scale structure and induces angular dependence in the potential of the probe D3-brane. We solve the D3-brane equations of motion from the DBI action in the warped deformed conifold including linearized as well as non-linear perturbations around the ISD supergravity solution. Our numerical solutions show that angular dependence is a next to leading order correction to the dominant radial motion of the brane, however, just as angular motion typically increases the amount of inflation (spinflation), having additional angular dependence from
linearized perturbations also increases the amount of inflation.