Distinguishing Dark Matter, Modified Gravity, and Modified Inertia by the Inner and Outer Parts of Galactic Rotation Curves

Kyu-Hyun Chae

Published 2022-07-22Version 1

Mass discrepancy in galaxies invokes dark matter, or alternatively modification of gravity or inertia. These theoretical possibilities may be distinguished by the statistical relation between the centripetal acceleration of particles in orbital motion and the expected Newtonian acceleration for the observed distribution of baryons in galaxies. Here predictions of cold dark matter halos, modified gravity, and modified inertia are compared and tested by a statistical sample of rotation curves of galaxies. Modified gravity under an estimated mean external field correctly predicts the observed statistical relation of accelerations. Cold dark matter halos predict systematically deviating relations and modified inertia is inconsistent with the apparently seen difference between the inner and outer parts. All aspects of rotation curves are most naturally explained by modified gravity.