Natural inflation with and without modulations in type IIB string theory

TL;DR

This paper constructs a string theory-based model of natural inflation, incorporating modulations from threshold corrections, and predicts various cosmological observables consistent with recent experimental data.

Contribution

It provides a detailed mechanism for natural inflation within type IIB string theory, including modulations and enhanced axion decay constants, advancing string cosmology models.

Findings

Inflaton potential generated by gaugino condensation with one-loop corrections.

Modulations in the potential lead to varied tensor-to-scalar ratios.

Predictions align with observational data from WMAP, Planck, and BICEP2.

Abstract

We propose a mechanism for the natural inflation with and without modulation in the framework of type IIB string theory on toroidal orientifold or orbifold. We explicitly construct the stabilization potential of complex structure, dilaton and K\"ahler moduli, where one of the imaginary component of complex structure moduli becomes light which is identified as the inflaton. The inflaton potential is generated by the gaugino-condensation term which receives the one-loop threshold corrections determined by the field value of complex structure moduli and the axion decay constant of inflaton is enhanced by the inverse of one-loop factor. We also find the threshold corrections can also induce the modulations to the original scalar potential for the natural inflation. Depending on these modulations, we can predict several sizes of tensor-to-scalar ratio as well as the other cosmological observables reported by WMAP, Planck and/or BICEP2 collaborations.