Self-gravitating fluid solutions of Shape Dynamics

TL;DR

This paper constructs dynamic, non-vacuum solutions in Shape Dynamics, a conformally invariant gravity theory, demonstrating their Hamiltonian consistency and linking them to the McVittie family, thus expanding the solution space for comparison with General Relativity.

Contribution

It introduces a class of time-dependent, inhomogeneous solutions with perfect fluid sources in Shape Dynamics, extending beyond static vacuum cases and enabling more comprehensive testing of the theory.

Findings

Solutions satisfy Shape Dynamics Hamiltonian constraints

Identified solutions as members of the McVittie family

Demonstrated dynamic, inhomogeneous behavior in non-vacuum context

Abstract

Shape Dynamics is a 3D conformally invariant theory of gravity which possesses a large set of solutions in common with General Relativity. When looked closely, these solutions are found to behave in surprising ways, so in order to probe the fitness of Shape Dynamics as a viable alternative to General Relativity one must find and understand increasingly more complex, less symmetrical exact solutions, on which to base perturbative studies and numerical analyses in order to compare them with data. Spherically symmetric exact solutions have been studied, but only in a static vacuum setup. In this work we construct a class of time-dependent exact solutions of Shape Dynamics from first principles, representing a central inhomogeneity in an evolving cosmological environment. By assuming only a perfect fluid source in a spherically symmetric geometry we show that this fully dynamic non-vacuum solution satisfies in all generality the Hamiltonian structure of Shape Dynamics. The simplest choice of solutions is shown to be a member of the McVittie family.