External Field Effect in Gravity

TL;DR

This paper investigates the external field effect in various gravity theories, highlighting how deviations from Newtonian and Einstein gravity could serve as tests for alternative gravitational models.

Contribution

It explores the conditions under which external field effects arise in non-standard gravity scenarios, proposing their use as diagnostic tools for gravitational theories.

Findings

External field effects occur in non-Newtonian and non-Ricci flat geometries.

Such effects can distinguish between different gravitational theories.

Potential for experimental tests of gravity models using external field effects.

Abstract

In both Newtonian gravity and Einstein gravity there is no force on a test particle located inside a spherical cavity cut out of a static, spherically symmetric mass distribution. Inside the cavity exterior matter is decoupled and there is no external field effect that could act on the test particle. However, for potentials other than the Newtonian potential or for geometries other than Ricci flat ones this is no longer the case, and there then is an external field effect. We explore this possibility in various alternate gravity scenarios, and suggest that such (Machian) external field effects can serve as a diagnostic for gravitational theory.