Inflation via Gravitino Condensation in Dynamically Broken Supergravity

TL;DR

This paper explores a supergravity-based inflation model driven by gravitino condensation, which naturally breaks supersymmetry and aligns with Planck data but not BICEP2 results, highlighting novel mechanisms for early universe inflation.

Contribution

It introduces a new inflationary scenario in supergravity where gravitino condensates act as inflatons, providing a UV-motivated, matter-independent inflation model with potential for Starobinsky-like inflation.

Findings

Gravitino condensates can drive inflation in supergravity models.

The model aligns with Planck satellite observations.

Higher curvature corrections emerge from integrating out gravitino fields.

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 conformal extensions thereof (with broken conformal symmetry). Therein, the gravitino condensate itself can play the role of the inflaton, however the requirement of slow-roll necessitates unnaturally large values of the wave-function renormalisation. Nevertheless, there is an alternative scenario that may provide Starobinsky-type inflation, occurring in the broken-SUGRA phase around the non-trivial 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.