Inflation via gravitino condensation in dynamically broken supergravity

Abstract

Gravitino-condensate-induced inflation via the super-Higgs effect is a UV-motivated scenario for both inflating the early universe and breaking local supersymmetry dynamically, entirely independent of any coupling to external matter. As an added benefit, this also removes the (as of yet unobserved) massless Goldstino associated to global supersymmetry breaking from the particle spectrum. In this review, we detail the pertinent properties and outline previously hidden details of the various steps required in this context in order to make contact with current inflationary phenomenology. The class of models of SUGRA we use to exemplify our approach are minimal four-dimensional N = 1 supergravity and extensions thereof with broken conformal symmetry. Therein, the gravitino condensate itself can play the role of the inflation, however the requirement of slow-roll necessitates unnaturally large values of the wave function renormalization. Nevertheless, there is an alternative scenario that may provide Starobinsky-type inflation, occurring in the broken-SUGRA phase around the nontrivial minima of the gravitino-condensate effective potential. In this scenario higher curvature corrections to the effective action, crucial for the onset of an inflationary phase, arise as a result of integrating out massive quantum gravitino fields in the path integral. The latter scenario is compatible with Planck satellite phenomenology but not with BICEP2 data.

Starobinsky-Like Inflation and Running Vacuum in the Context of Supergravity

“…It is the purpose of this work to go one step further from demonstrating the compatibility of the dynamically-broken SUGRA scenario [7][8][9] with inflation and to discuss the possibility of a dynamical evolution of the inflationary phase ground state to the standard radiation regime within the context of the running vacuum model (RVM) of the cosmic evolution utilizing an effective "re-normalization group (RG) approach"; see [13][14][15] and [20][21][22] for comprehensive expositions. Specifically, we wish to show that the behaviour of the aforementioned SUGRA scenario effectively mimics the RVM.…”

“…We next proceed to summarize the construction of the one-loop effective action of the massless degrees of freedom after massive gravitino integration in this dynamically-broken SUGRA model with spontaneous breaking of global supersymmetry (SUSY) [7,8].…”

“…As we discussed, this phase is characterized by the dynamical emergence of a de Sitter background. As argued in [7,8], the Starobinsky-type inflation appears much more natural (from the point of view of the order of the parameters involved) than a hill-top inflation scenario [10] in which the gravitino condensate itself is the inflaton field. In the latter, very large values of the wave function re-normalization of the condensate field are required to ensure slow-roll inflation if one insists on (phenomenologically realistic) sub-Planckian supersymmetry breaking scales.…”

“…Following this point of view, we continue in this paper with the investigation of Starobinsky-like models as potential candidates for the realistic implementation of inflation compatible with the data. In previous publications one of us (Nick E. Mavromatos) with collaborators [7,8] discussed the dynamical breaking of supergravity (SUGRA) theories via gravitino condensation and demonstrated [9] the compatibility of this scenario with Starobinsky-like [5] inflationary scenarios. As we discussed, this phase is characterized by the dynamical emergence of a de Sitter background.…”

Starobinsky inflation from new-minimal supergravity

“…For a review on inflationary cosmology after the release of the Planck collaboration's results, and for an approach on the initial conditions problem see also [24]. Note that the embedding of the Starobinsky model has been also studied in the old-minimal supergravity [13,[25][26][27][28][29][30], in no-scale supergravity [31][32][33][34], in the linearized non-minimal (20/20) supergravity [35], and also in a generic supergravity setup via gravitino condensates [36,37].…”