Abstract
We explore the possibility that inflation is driven by supersymmetry breaking with the superpartner of the goldstino (sgoldstino) playing the role of the inflaton. Moreover, we impose an R-symmetry that allows one to satisfy easily the slow-roll conditions, avoiding the so-called eta -problem, and leads to two different classes of small-field inflation models; they are characterised by an inflationary plateau around the maximum of the scalar potential, where R-symmetry is either restored or spontaneously broken, with the inflaton rolling down to a minimum describing the present phase of our Universe. To avoid the Goldstone boson and be left with a single (real) scalar field (the inflaton), R-symmetry is gauged with the corresponding gauge boson becoming massive. This framework generalises a model studied recently by the present authors, with the inflaton identified by the string dilaton and R-symmetry together with supersymmetry restored at weak coupling, at infinity of the dilaton potential. The presence of the D-term allows a tuning of the vacuum energy at the minimum. The proposed models agree with cosmological observations and predict a tensor-to-scalar ratio of primordial perturbations and an inflation scale GeV. H_* may be lowered up to electroweak energies only at the expense of fine-tuning the scalar potential.
Highlights
Inflationary models [1,2,3] in supergravity 1 suffer in general from several problems, such as fine-tuning to satisfy theIn this work we show that all three problems above are solved when the inflaton is identified with the scalar component of the goldstino superfield,2 in the presence of a gauged R-symmetry
We explore the possibility that inflation is driven by supersymmetry breaking with the superpartner of the goldstino playing the role of the inflaton
We impose an R-symmetry that allows one to satisfy the slow-roll conditions, avoiding the so-called ηproblem, and leads to two different classes of small-field inflation models; they are characterised by an inflationary plateau around the maximum of the scalar potential, where R-symmetry is either restored or spontaneously broken, with the inflaton rolling down to a minimum describing the present phase of our Universe
Summary
Inflationary models [1,2,3] in supergravity 1 suffer in general from several problems, such as fine-tuning to satisfy the. Since inflation arises in a plateau around the maximum of the scalar potential (hill-top) no large field initial conditions are needed, while the pseudo-scalar companion of the inflaton is absorbed into the R-gauge field that becomes massive, leading the inflaton as a single scalar field present in the spectrum This model provides a minimal realisation of natural small-field inflation in supergravity, compatible with present observations, as we show below. The scalar potential has a minimum with a tuneable vacuum energy and a maximum that can produce inflation when appropriate corrections are included in the Kähler potential In these coordinates R-symmetry is restored at infinity, corresponding to the weak coupling limit. We first work out model-independent predictions valid under the assumption that inflation ends very rapidly after the inflationary plateau of the scalar potential
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