Kahler Moduli Inflation

TL;DR

This paper demonstrates that Kahler moduli in type IIB flux compactifications can naturally drive slow-roll inflation without fine-tuning, predicting specific spectral index values and requiring large stabilized volumes.

Contribution

It introduces a new class of inflationary models based on Kahler moduli that naturally evade the eta problem without fine-tuning, under certain geometric conditions.

Findings

Inflation occurs without fine-tuning of parameters.

Predicted spectral index range is 0.960 - 0.967.

Stable volume of Calabi-Yau must be O(10^5-10^7) in string units.

Abstract

We show that under general conditions there is at least one natural inflationary direction for the Kahler moduli of type IIB flux compactifications. This requires a Calabi-Yau which has h^{2,1}>h^{1,1}>2 and for which the structure of the scalar potential is as in the recently found exponentially large volume compactifications. We also need - although these conditions may be relaxed - at least one Kahler modulus whose only non-vanishing triple-intersection is with itself and which appears by itself in the non-perturbative superpotential. Slow-roll inflation then occurs without a fine tuning of parameters, evading the eta problem of F-term inflation. In order to obtain COBE-normalised density perturbations, the stabilised volume of the Calabi-Yau must be O(10^5-10^7) in string units, and the inflationary scale M_{infl} ~ 10^{13} GeV. We find a robust model independent prediction for the spectral index of 1 - 2/N_e = 0.960 - 0.967, depending on the number of efoldings.