Tachyon Mediated Non-Gaussianity

TL;DR

This paper explores how extra scalar fields interacting via a tachyonic waterfall field during hybrid inflation can produce significant local non-Gaussianity, compatible with WMAP data and featuring cosmic strings.

Contribution

It introduces a novel scenario where tachyonic fields generate non-Gaussianity in inflation models with extra scalars, connecting string-inspired models to observable cosmological signatures.

Findings

Models produce significant local non-Gaussianity with both bispectrum signs.

Compatibility with WMAP data due to cosmic strings and flat power spectrum.

Illustration using intersecting brane inflation models.

Abstract

We describe a general scenario where primordial non-Gaussian curvature perturbations are generated in models with extra scalar fields. The extra scalars communicate to the inflaton sector mainly through the tachyonic (waterfall) field condensing at the end of hybrid inflation. These models can yield significant non-Gaussianity of the local shape, and both signs of the bispectrum can be obtained. These models have cosmic strings and a nearly flat power spectrum, which together have been recently shown to be a good fit to WMAP data. We illustrate with a model of inflation inspired from intersecting brane models.