Observable Non-gaussianity, and chiral gravitational waves from vector field production during inflation
Abstract: The observed cosmological perturbations are in excellent agreement with those predicted by inflation. A strong experimental effort is undergoing to extract further information on inflation through non-gaussianity (NG) of the scalar perturbations and through gravity waves (GW). The vacuum modes of the inflaton and of the metric are the most natural candidates for providing observable NG and GW; however, neither effect is guaranteed to be at a detectable level. In this talk we explore an alternative possibility for obtaining such signals as a result of vector field production during inflation. Specifically, in the first part of the talk we show that observable NG at CMB scales, and chiral GW at interferometer scales are generated in models of axion inflation, for very natural values of the axion decay constant. In the second part we discuss a different model (first studied by Ratra in the context of magnetogensis), characterized by a dilation-like kinetic coupling between the inflaton and a vector field. This model generates observable NG, peaked like the local template in the squeezed limit, and with a characteristic quadrupolar dependence on the angle between two modes in the correlation. This model, however, also results in broken statistical isotropy of the primordial perturbations, at a level that typically exceeds the observational bounds.