Can Galactic Observations Be Explained by a Relativistic Gravity Theory?

TL;DR

This paper explores whether a relativistic gravity theory can explain galactic dynamics without dark matter, deriving a general metric and comparing predictions with observations, ultimately finding such explanations unlikely.

Contribution

The paper derives a general relativistic metric to order (v/c)^2 and assesses its ability to explain galactic phenomena without dark matter.

Findings

Relativistic gravity theories are unlikely to replace dark matter in explaining galactic behavior.

The derived metric aligns with Newtonian and light deflection tests but fails to account for galaxy rotation curves.

Dark matter remains a necessary component for explaining galactic dynamics according to this analysis.

Abstract

We consider the possibility of an alternative gravity theory explaining the dynamics of galactic systems without dark matter. From very general assumptions about the structure of a relativistic gravity theory we derive a general expression for the metric to order $(v/c)^2$. This allows us to compare the predictions of the theory with various experimental data: the Newtonian limit, light deflection and retardation, rotation of galaxies and gravitational lensing. Our general conclusion is that the possibility for any gravity theory to explain the behaviour of galaxies without dark matter is rather improbable.