A Minimal Sub-Planckian Axion Inflation Model with Large Tensor-to-Scalar Ratio

Abstract

We present a minimal axion inflation model which can generate a large tensor-to-scalar ratio while remaining sub-Planckian. The modulus of a complex scalar field $\Phi$ with a $\lambda |\Phi {|}^4$ potential couples directly to the gauge field of a strongly-coupled sector via a term of the form $(|\Phi |/M_{Pl}{)}^{m}F\tilde{F}$. This generates a minimum of the potential which is aperiodic in the phase. The resulting inflation model is equivalent to a ${\varphi }^{4/(m+1)}$ chaotic inflation model. For the natural case of a leading-order portal-like interaction ${\Phi }^{†}\Phi F\tilde{F}$, the model is equivalent to a ${\varphi }^{4/3}$ chaotic inflation model and predicts a tensor-to-scalar ratio $r=16/3N=0.097$ and a scalar spectral index $n_s=1-5/3N=0.970$. The value of $|\Phi |$ remains sub-Planckian throughout the observable era of inflation, with $|\Phi |\lesssim 0.01M_{Pl}$ for $N\lesssim 60$ when $\lambda \sim 1$.

One minor alteration. Version to be published in JCAP

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Cited by in corpus (3)

• Helical Phase Inflation
• Perspective on completing natural inflation
• Signatures of Planck Corrections in a Spiralling Axion Inflation Model