D6-branes and axion monodromy inflation

TL;DR

This paper proposes new large field inflation models in type IIA string theory using D6-branes to generate axion potentials, resulting in flattened potentials compatible with current cosmological observations.

Contribution

It introduces novel D6-brane based inflation scenarios with multi-branched axion potentials and analyzes their compatibility with moduli stabilization and observational data.

Findings

Potential interpolates between linear and quadratic inflation.

Tensor-to-scalar ratio ranges from 0.08 to 0.12.

Flattened potential due to Planck corrections.

Abstract

We develop new scenarios of large field inflation in type IIA string compactifications in which the key ingredient is a D6-brane that creates a potential for a B-field axion. The potential has the multi-branched structure typical of F-term axion monodromy models and, near its supersymmetric minima, it is described by a 4d supergravity model of chaotic inflation with a stabiliser field. The same statement applies to the D6-brane Wilson line, which can also be considered as an inflaton candidate. We analyse both cases in the context of type IIA moduli stabilisation, finding an effective potential for the inflaton system and a simple mechanism to lower the inflaton mass with respect to closed string moduli stabilised by fluxes. Finally, we compute the B-field potential for trans-Planckian field values by means of the DBI action. The effect of Planck suppressed corrections is a flattened potential which, in terms of the compactification parameters, interpolates between linear and quadratic inflation. This renders the cosmological parameters of these models compatible with current experimental bounds, with the tensor-to-scalar ratio ranging as 0.08 < r < 0.12