The Link between General Relativity and Shape Dynamics

TL;DR

This paper demonstrates the equivalence between General Relativity and Shape Dynamics through a new linking theory construction, simplifying previous approaches and extending results to asymptotically flat spacetimes.

Contribution

It introduces a general construction principle for linking theories and provides a streamlined proof of the equivalence between General Relativity and Shape Dynamics, including asymptotically flat cases.

Findings

Established the equivalence of GR and Shape Dynamics

Extended the equivalence to asymptotically flat boundary conditions

Developed a Lagrangian formulation of Shape Dynamics

Abstract

We show that one can construct two equivalent gauge theories from a linking theory and give a general construction principle for linking theories which we use to construct a linking theory that proves the equivalence of General Relativity and Shape Dynamics, a theory with fixed foliation but spatial conformal invariance. This streamlines the rather complicated construction of this equivalence performed previously. We use this streamlined argument to extend the result to General Relativity with asymptotically flat boundary conditions. The improved understanding of linking theories naturally leads to the Lagrangian formulation of Shape Dynamics, which allows us to partially relate the degrees of freedom.