An Inflationary Model in String Theory

TL;DR

This paper presents a string theory-based inflation model where the inflaton is a D3-brane position, demonstrating conditions for slow-roll inflation with low inflation scale and discussing observational constraints and potential generalizations.

Contribution

It constructs a string theory inflation model with moduli stabilization, showing how to achieve a broad potential maximum suitable for slow-roll inflation.

Findings

Inflation scale is approximately 10^{10} GeV.

Model satisfies observational constraints with proper flux adjustments.

Potential for eternal inflation discussed.

Abstract

We construct a model of inflation in string theory after carefully taking into account moduli stabilization. The setting is a warped compactification of Type IIB string theory in the presence of D3 and anti-D3-branes. The inflaton is the position of a D3-brane in the internal space. By suitably adjusting fluxes and the location of symmetrically placed anti-D3-branes, we show that at a point of enhanced symmetry, the inflaton potential V can have a broad maximum, satisfying the condition V''/V << 1 in Planck units. On starting close to the top of this potential the slow-roll conditions can be met. Observational constraints impose significant restrictions. As a first pass we show that these can be satisfied and determine the important scales in the compactification to within an order of magnitude. One robust feature is that the scale of inflation is low, H = O(10^{10}) GeV. Removing the observational constraints makes it much easier to construct a slow-roll inflationary model. Generalizations and consequences including the possibility of eternal inflation are also discussed. A more careful study, including explicit constructions of the model in string theory, is left for the future.