Abstract
$R+R^2$ Supergravity is known to be equivalent to standard Supergravity coupled to two chiral supermultiples with a no-scale K\"ahler potential. Within this framework, that can accomodate vanishing vacuum energy and spontaneous supersymmetry breaking, we consider modifications of the associated superpotential and study the resulting models, which, viewed as generalizations of the Starobinsky model, for a range of the superpotential parameters, describe viable single-field slow-roll inflation. In all models studied in this work the tensor to scalar ratio is found to be small, well below the upper bound established by the very recent PLANCK and BICEP2 data.
Highlights
A phase of de Sitter expansion in the early universe, namely inflation [1], offers an attractive paradigm for the production of primordial curvature perturbations that generate the large scale structure of the Universe [2] as well as the resolution of a number of issues of the standard hot big bang cosmology
The Starobinsky model is among the few possibilities realizing slow-roll inflation that is in perfect agreement with the PLANCK experiment data [6], its predictions were challenged by BICEP2 results [7], claiming the discovery of primordial gravitational
Given the no-scale supergravity framework, we investigate whether viable inflationary models can be constructed by considering deformations and modifications of the basic superpotential yielding the Starobinsky model
Summary
A phase of de Sitter expansion in the early universe, namely inflation [1], offers an attractive paradigm for the production of primordial curvature perturbations that generate the large scale structure of the Universe [2] as well as the resolution of a number of issues of the standard hot big bang cosmology. Modifications of the basic no-scale Kähler potential and various choices for the superpotential have been studied, leading to a number of inflationary alternatives [13] All these models are necessarily multifield models containing, apart from the inflaton, additional scalar fields. In this paper we study generalizations of the Starobinsky model derived in the framework of no-scale supergravity by considering deformations of the basic superpotential. Given the no-scale supergravity framework, we investigate whether viable inflationary models can be constructed by considering deformations and modifications of the basic superpotential yielding the Starobinsky model. After reviewing the relation of the noscale supergravity realization of the Starobinsky model to a scalar field model nonminimally coupled to gravity and the universal attractor, we proceed to consider generalizations that can lead to viable inflationary models. We consider models based on a SUð1; 1Þ=Uð1Þ × Uð1Þ Kähler potential and proceed with a particular superpotential, showing that for a certain parameter range, we obtain models with viable slow-roll inflation
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