Non-Gaussianities and chiral gravitational waves in natural steep inflation

In a previous paper [Phys. Rev. D 81, 043534 (2010)], we proposed a model where natural inflation is realized on a steep potential [V(phi) similar to cos(phi/f) with f << M-P] as a consequence of the interaction of the inflaton with gauge fields through the coupling phi F-mu nu(F) over tilde (mu nu). In the present work we study the non-Gaussianities and the spectrum of tensor modes generated in this scenario. The non-Gaussianities turn out to be compatible with current observations and can be large enough to be detectable by Planck. The nonobservation of tensor modes imposes new constraints on the parameter space of the system that are about one order of magnitude stronger than those found in our previous paper. More importantly, in certain regions of the parameter space, tensor modes might be detected by upcoming cosmic microwave background (CMB) experiments even if inflation occurs at energies as low as the TeV scale. In this case the tensor modes would be chiral, and would lead to distinctive parity-violating correlation functions in the CMB.