Effects of the imaginary inflaton component in supergravity new inflation

Abstract

When models of new inflation are implemented in supergravity, the inflaton is a complex and not a real scalar field. As a complex scalar field has two independent components, supergravity models of new inflation are naturally two-field models. In this paper, we use the δN formalism to analyse how the two-field behaviour modifies the usual single-field predictions. We find that the model reduces to the single-field limit if the inflaton mass term is sufficiently small. Otherwise, the imaginary inflaton component reduces the amplitude As and the spectral index ns of the scalar curvature perturbations. However, the perturbations remain nearly Gaussian, and the reduced bispectrum fNL is too small to be observed.