Scalar-tensor extension of Natural Inflation
  We show that embedding Natural Inflation in a more general scalar-tensor
theory, with non-minimal couplings to the Ricci scalar and the kinetic term,
alleviates the current tension of Natural Inflation with observational data.
The coupling functions respect the periodicity of the potential and the
characteristic shift symmetry $\phi \rightarrow \phi + 2\pi f$ of the original
Natural Inflation model, and vanish at the minimum of the potential.
Furthermore, showing that the theory exhibits a rescaling symmetry in the
regime where the coupling to the Ricci scalar is small and the coupling to the
kinetic term is large, we obtain that the agreement with cosmological data can
take place at an arbitrarily low periodicity scale $f$, solving at tree-level
the problem of super-Planckian periodicity scales needed in Natural Inflation.
