Signatures of Planck corrections in a spiralling axion inflation model

The minimal sub-Planckian axion inflation model accounts for a large scalar-totensor ratio via a spiralling trajectory in the field space of a complex field Φ. Here we consider how the predictions of the model are modified by Planck scale-suppressed corrections. In the absence of Planck corrections the model is equivalent to a φ4/3 chaotic inflation model. Planck corrections become important when the dimensionless coupling ξ of |Φ|2 to the topological charge density of the strongly-coupled gauge sector FF̃ satisfies ξ ∼ 1. For values of |Φ| which allow the Planck corrections to be understood via an expansion in powers of |Φ|2/M2 Pl , we show that their effect is to produce a significant modification of the tensor-to-scalar ratio from its φ4/3 chaotic inflation value without strongly modifying the spectral index. In addition, to leading order in |Φ|2/M2 Pl , the Planck modifications of ns and r satisfy a consistency relation, ∆ns = −∆r/16. Observation of these modifications and their correlation would allow the model to be distinguished from a simple φ4/3 chaotic inflation model and would also provide a signature for the influence of leading-order Planck corrections.