Linearized supergravity with a dynamical preferred frame

TL;DR

This paper develops a supersymmetric extension of the Einstein-aether gravity model, incorporating a dynamical preferred frame and analyzing its linear perturbations within supergravity frameworks, revealing superluminal modes and phenomenological constraints.

Contribution

It constructs the most general linearized supergravity model with a Lorentz-violating aether field embedded in a chiral superfield, including a detailed spectrum analysis.

Findings

The model contains a single additional coupling parameter.

The spectrum includes superluminal helicity states.

Observational constraints are discussed based on low-energy phenomenology.

Abstract

We study supersymmetric extension of the Einstein-aether gravitational model where local Lorentz invariance is broken down to the subgroup of spatial rotations by a vacuum expectation value of a timelike vector field called aether. Embedding aether into a chiral vector superfield, we construct the most general action which describes dynamics of linear perturbations around the Lorentz-violating vacuum and is invariant under the linearized supergravity transformations. The analysis is performed both in the off-shell non-minimal superfield formulation of supergravity and in the "on-shell" approach invoking only physical component fields. The resulting model contains a single free coupling, in addition to the standard supergravity parameters. The spectrum of physical excitations features an enhanced on-shell gravity multiplet comprising four states with helicities 2, 3/2, 3/2 and 1 propagating with superluminal velocity. The remaining excitations propagate with the speed of light. We outline the observational constraints on the model following from its low-energy phenomenology.