The goldstone and goldstino of supersymmetric inflation

TL;DR

This paper develops a minimal supersymmetric effective field theory for inflation, incorporating goldstone and goldstino fields, and analyzes their dynamics and implications within supergravity, revealing subluminal propagation and new parameters affecting inflation.

Contribution

It introduces a constrained superfield formalism for supersymmetric inflation EFT, connecting goldstino dynamics with inflationary backgrounds and supergravity effects.

Findings

Goldstino propagates with subluminal velocities.

EFT includes new parameters related to gravitino mass phase.

Matching with fluid background SUSY breaking results.

Abstract

We construct the minimal effective field theory (EFT) of supersymmetric inflation, whose field content is a real scalar, the goldstone for time-translation breaking, and a Weyl fermion, the goldstino for supersymmetry (SUSY) breaking. The inflating background can be viewed as a single SUSY-breaking sector, and the degrees of freedom can be efficiently parameterized using constrained superfields. Our EFT is comprised of a chiral superfield X_NL containing the goldstino and satisfying X_NL^2 = 0, and a real superfield B_NL containing both the goldstino and the goldstone, satisfying X_NL B_NL = B_NL^3 = 0. We match results from our EFT formalism to existing results for SUSY broken by a fluid background, showing that the goldstino propagates with subluminal velocities. The same effect can also be derived from the unitary gauge gravitino action after embedding our EFT in supergravity. If the gravitino mass is comparable to the Hubble scale during inflation, we identify a new parameter in the EFT related to a time-dependent phase of the gravitino mass parameter. We briefly comment on the leading contributions of goldstino loops to inflationary observables.