We present a toy model of an axion gauge field inflation scenario that yields viable density and gravitational wave spectra .
The scenario consists of an axionic inflaton in a steep potential that is effectively flattened by a coupling to a collection of non-Abelian gauge fields .
The model predicts a blue-tilted gravitational wave spectrum that is dominated by one circular polarization , resulting in unique observational targets for cosmic microwave background and gravitational wave experiments .
The handedness of the gravitational wave spectrum is incorporated in a model of leptogenesis through the axial-gravitational anomaly ; assuming electroweak sphaeleron processes convert the lepton asymmetry into baryons , we predict an approximate lower bound on the tensor-to-scalar ratio r \sim 3 - 4 \times 10 ^ { -2 } for models that also explain the matter-antimatter asymmetry of the Universe .