The complete action for $\mathcal{N}=2$ de Sitter pure supergravity

TL;DR

This paper constructs a complete, non-unitary ${ m N}=2$ pure supergravity action in four-dimensional de Sitter space, clarifying previous ambiguities and discussing potential Euclidean approaches to quantum gravity.

Contribution

It explicitly constructs the unique ${ m N}=2$ de Sitter supergravity Lagrangian, addressing issues of non-unitarity and revisiting Euclidean formulations.

Findings

Explicit construction of the ${ m N}=2$ de Sitter supergravity action.

Clarification of non-unitarity issues in Lorentzian signature.

Discussion of Euclidean approaches to de Sitter quantum gravity.

Abstract

Supergravity theories in de Sitter spacetime are known to be very constrained, and rather unnatural within String/M Theory. We revisit the seminal paper by Pilch, van Nieuwenhuizen and Sohnius, where the possible existence of a real Lagrangian for ${\cal N}=2$ pure supergravity in four-dimensional de Sitter spacetime was pointed out. We clarify several issues related to the non-unitarity of the theory and explicitly construct the unique, complete theory searched for long ago by the aforementioned authors. We argue that the lack of unitarity of the Lorentzian theory may be revisited in the Euclidean approach to de Sitter quantum gravity, where alternative definitions of unitarity can be introduced.