Comparing Infrared Dirac-Born-Infeld Brane Inflation to Observations

TL;DR

This paper evaluates the IR DBI brane inflation model against current cosmological data, constraining key string theory parameters and highlighting potential observational signatures like non-Gaussianity and spectral index running.

Contribution

It provides the first Bayesian comparison of IR DBI inflation with observational data, constraining microscopic string theory parameters and identifying testable predictions.

Findings

Current data cannot distinguish IR DBI from CDM.

Constraints on string theory parameters such as brane moduli mass and string scale.

Predictions of large non-Gaussianity and regional spectral index running.

Abstract

We compare the Infrared Dirac-Born-Infeld (IR DBI) brane inflation model to observations using a Bayesian analysis. The current data cannot distinguish it from the \LambdaCDM model, but is able to give interesting constraints on various microscopic parameters including the mass of the brane moduli potential, the fundamental string scale, the charge or warp factor of throats, and the number of the mobile branes. We quantify some distinctive testable predictions with stringy signatures, such as the large non-Gaussianity, and the large, but regional, running of the spectral index. These results illustrate how we may be able to probe aspects of string theory using cosmological observations.