Inflation in Realistic D-Brane Models

TL;DR

This paper constructs and analyzes string theory models with D-brane/anti-brane inflation in a realistic flux-stabilized setting, exploring inflationary dynamics, observational predictions, and the role of moduli and D-terms.

Contribution

It presents explicit D-brane inflation models within a realistic string compactification framework, including moduli stabilization and standard-model sectors, and studies their inflationary and observational properties.

Findings

Inflation can occur with specific parameter choices and initial conditions.

D-terms from orbifold modes significantly influence inflation dynamics.

Predicted CMB fluctuations are consistent with observations, with potential for observable gravitational waves.

Abstract

We find successful models of D-brane/anti-brane inflation within a string context. We work within the GKP-KKLT class of type IIB string vacua for which many moduli are stabilized through fluxes, as recently modified to include `realistic' orbifold sectors containing standard-model type particles. We allow all moduli to roll when searching for inflationary solutions and find that inflation is not generic inasmuch as special choices must be made for the parameters describing the vacuum. But given these choices inflation can occur for a reasonably wide range of initial conditions for the brane and antibrane. We find that D-terms associated with the orbifold blowing-up modes play an important role in the inflationary dynamics. Since the models contain a standard-model-like sector after inflation, they open up the possibility of addressing reheating issues. We calculate predictions for the CMB temperature fluctuations and find that these can be consistent with observations, but are generically not deep within the scale-invariant regime and so can allow appreciable values for $dn_s/d\ln k$ as well as predicting a potentially observable gravity-wave signal. It is also possible to generate some admixture of isocurvature fluctuations.