External Field Effect in Gravity

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.

9 pages, 4 figures. Essay written for the Gravity Research Foundation 2021 Awards for Essays on Gravitation

References in corpus (6)

• The Radial Acceleration Relation in Rotationally Supported Galaxies
• Impact of a global quadratic potential on galactic rotation curves
• The Bullet Cluster 1E0657-558 evidence shows Modified Gravity in the absence of Dark Matter
• Testing the Strong Equivalence Principle: Detection of the External Field Effect in Rotationally Supported Galaxies
• Fundamental parameter-free solutions in Modified Gravity
• Modified Gravity (MOG) fits to observed radial acceleration of SPARC galaxies

Cited by in corpus (5)

• Milky Way and M31 rotation curves: $\Lambda$CDM vs. MOND
• Critique of the use of geodesics in astrophysics and cosmology
• Newtonian Fractional-Dimension Gravity and the External Field Effect
• Imprint of galactic rotation curves and metric fluctuations on the recombination era anisotropy
• Quadratic gravity potentials in de Sitter spacetime from Feynman diagrams