Curvatons in Warped Throats

TL;DR

This paper proposes a string theory-based curvaton model where brane position fluctuations in warped throats generate primordial curvature perturbations, allowing for large non-Gaussianity and testing compactification scenarios.

Contribution

It introduces a novel curvaton mechanism from type IIB string theory involving brane position fluctuations in warped throats, expanding inflation model possibilities.

Findings

Wide parameter range allows a consistent curvaton scenario.

Brane oscillations can produce large non-Gaussianity.

Model provides a testable link between string compactification and cosmological observations.

Abstract

We present a curvaton model from type IIB string theory compactified on a warped throat with approximate isometries. Considering an (anti-)D3-brane sitting at the throat tip as a prototype standard model brane, we show that the brane's position in the isometry directions can play the role of curvatons. The basic picture is that the fluctuations of the (anti-)D3-brane in the angular isometry directions during inflation eventually turns into the primordial curvature perturbations, and subsequently the brane's oscillation excites other open string modes on the brane and reheat the universe. We find in the explicit case of the KS throat that a wide range of parameters allows a consistent curvaton scenario. It is also shown that the oscillations of branes at throat tips are capable of producing large non-Gaussianity, either through curvature or isocurvature perturbations. Since such setups naturally arise in warped (multi-)throat compactifications and are constrained by observational data, the model can provide tests for compactification scenarios. This work gives an explicit example of string theory providing light fields for generating curvature perturbations. Such mechanisms free the inflaton from being responsible for the perturbations, thus open up new possibilities for inflation models.