Abstract
Models of cosmological inflation resembling the Starobinsky R+R2 modelemerge naturally among the effective potentials derived from no-scaleSU(N,1)/SU(N) × U(1) supergravity when N > 1. We display several examples inthe SU(2,1)/SU(2) × U(1) case, in which the inflaton may be identifiedwith either a modulus field or a matter field. We discuss how the modulus fieldmay be stabilized in models in which a matter field plays the rôle of the inflaton.We also discuss models that generalizethe Starobinsky model but display different relations between the tilt in the spectrumof scalar density perturbations, ns, the tensor-to-scalar ratio, r, and the numberof e-folds, N*. Finally, we discuss how such models can be probed by present andfuture CMB experiments.
Highlights
The first-year results from the Planck satellite [1] on the Cosmic Microwave Background (CMB) are qualitatively consistent with generic expectations within the framework of cosmological inflation - in particular, there are no signs of primordial non-Gaussianity in the CMB fluctuations or of isocurvature perturbations, and the previous evidence for a tilt in the spectrum of scalar perturbations, ns < 1, has been confirmed - many simple inflationary models are challenged by the Planck data - in particular, previous upper limits on the tensor-to-scalar ratio, r, have been strengthened significantly
In this paper we discuss more generally avatars of no-scale supergravity that reproduce the effective potential of the Starobinsky R + R2 model, as well as related models that yield similar predictions for the CMB
We consider some theoretical possibilities for constructing within the no-scale framework models that resemble the original Starobinsky model but make predictions for the CMB observables that can in principle be distinguished experimentally, while lying within the range allowed by present observations
Summary
The first-year results from the Planck satellite [1] on the Cosmic Microwave Background (CMB) are qualitatively consistent with generic expectations within the framework of cosmological inflation - in particular, there are no signs of primordial non-Gaussianity in the CMB fluctuations or of isocurvature perturbations, and the previous evidence for a tilt in the spectrum of scalar perturbations, ns < 1, has been confirmed - many simple inflationary models are challenged by the Planck data - in particular, previous upper limits on the tensor-to-scalar ratio, r, have been strengthened significantly. While inflationary models in simple supergravity can be constructed to avoid the η problem [12, 13], these models rely on a seemingly accidental cancellation in the inflaton mass [14] For this reason, we have long advocated no-scale supergravity [15,16,17,18] as the natural framework for constructing models of inflation [19,20,21]. In this paper we discuss more generally avatars of no-scale supergravity that reproduce the effective potential of the Starobinsky R + R2 model, as well as related models that yield similar predictions for the CMB.
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