Cosmology with Nilpotent Superfields

TL;DR

This paper introduces a simplified supergravity inflationary model using nilpotent superfields, which streamlines existing models and connects to string theory constructs like branes and axion monodromy.

Contribution

It proposes replacing the goldstino multiplet with a nilpotent one, simplifying supergravity inflation models and linking them to brane actions and string theory frameworks.

Findings

Eliminates the need for sgoldstino stabilization.

Simplifies a broad class of inflationary models.

Provides a supersymmetric uplifting mechanism in string theory.

Abstract

We discuss N=1 supergravity inflationary models based on two chiral multiplets, the inflaton and the goldstino superfield. Using superconformal methods for these models, we propose to replace the unconstrained chiral goldstino multiplet by the nilpotent one associated with non-linearly realized supersymmetry of the Volkov-Akulov type. In the new cosmological models, the sgoldstino is proportional to a bilinear combination of fermionic goldstinos. It does not acquire any vev, does nor require stabilization, and does not affect the cosmological evolution. We explain a universal relation of these new models to kappa-symmetric super-Dp-brane actions. This modification significantly simplifies a broad class of the presently existing inflationary models based on supergravity and string theory, including the simplest versions of chaotic inflation, the Starobinsky model, a broad class of cosmological attractors, the Higgs inflation, and much more. In particular, this is a step towards a fully supersymmetric version of the string theory axion monodromy inflation. The new construction serves as a simple and manifestly supersymmetric uplifting tool in the KKLT-type string theory landscape.