Can a periodic gravity coupling save natural inflation?

Natural inflation, driven by a cosine-shaped potential, was largely ruled out because it requires a field range wider than the Planck scale — a theoretically uncomfortable demand. Adding a periodic coupling to a topological gravity term (Nieh-Yan) alone doesn't fix things, but pairing it with a standard non-minimal coupling to spacetime curvature does. The model matches current CMB observations even when the field's periodicity stays below the Planck scale and the coupling constants are modest, order-of-one numbers.