Hybrid Inflation in Supergravity without Inflaton Superpotential

Abstract

We propose a new realisation of hybrid inflation in supergravity where the inflaton field does not appear in the superpotential but contributes only through the Kahler potential. The scalar potential derived from an R-invariant superpotential has the same form as that of the Linde's original version. The correct magnitude of the density perturbations amplitude is found without any fine-tuning of the coupling parameter in the superpotential for an acceptable value of the fundamental energy scale of the theory. The eta-problem was also resolved in this model.