Tuning and Backreaction in F-term Axion Monodromy Inflation

TL;DR

This paper investigates the challenges of tuning and backreaction in F-term axion monodromy inflation within string theory, exploring how complex structure moduli influence the inflaton potential and the feasibility of large-field inflation models.

Contribution

It analyzes the backreaction effects of complex structure moduli and demonstrates that models with fourfolds or mobile D7-branes can achieve necessary tunings for large-field inflation.

Findings

Backreaction of complex structure moduli can be controlled with additional tunings.

Fourfolds and mobile D7-branes provide enough structural freedom for tuning.

Remaining flux vacua are sufficiently numerous for viable inflation models.

Abstract

We continue the development of axion monodromy inflation, focussing in particular on the backreaction of complex structure moduli. In our setting, the shift symmetry comes from a partial large complex structure limit of the underlying type IIB orientifold or F-theory fourfold. The coefficient of the inflaton term in the superpotential has to be tuned small to avoid conflict with Kahler moduli stabilisation. To allow such a tuning, this coefficient necessarily depends on further complex structure moduli. At large values of the inflaton field, these moduli are then in danger of backreacting too strongly. To avoid this, further tunings are necessary. In weakly coupled type IIB theory at the orientifold point, implementing these tunings appears to be difficult if not impossible. However, fourfolds or models with mobile D7-branes provide enough structural freedom. We calculate the resulting inflaton potential and study the feasibility of the overall tuning given the limited freedom of the flux landscape. Our preliminary investigations suggest that, even imposing all tuning conditions, the remaining choice of flux vacua can still be large enough for such models to provide a promising path to large-field inflation in string theory.