A minimal sub-Planckian axion inflation model with large tensor-to-scalar ratio

We present a minimal axion inflation model which can generate a large tensorto-scalar ratio while remaining sub-Planckian. The modulus of a complex scalar field Φ with a λ|Φ|4 potential couples directly to the gauge field of a strongly-coupled sector via a term of the form (|Φ|/MP l)FF̃ . This generates a minimum of the potential which is aperiodic in the phase. The resulting inflation model is equivalent to a φ4/(m+1) chaotic inflation model. For the natural case of a leading-order portal-like interaction of the form ΦΦFF̃ , the model is equivalent to a φ4/3 chaotic inflation model and predicts a tensor-to-scalar ratio r = 16/3N = 0.097 and a scalar spectral index ns = 1 − 5/3N = 0.970. The value of |Φ| remains sub-Planckian throughout the observable era of inflation, with |Φ| . 0.01MP l for N . 60 when λ ∼ 1.