Recovering modified Newtonian dynamics by changing inertia

TL;DR

This paper derives MOND phenomena from three assumptions, suggesting a slowly varying universal acceleration constant that explains galactic rotation curves and cluster mass discrepancies, offering a modified inertia perspective.

Contribution

It introduces a modified inertia framework for MOND based on three assumptions, deriving galaxy rotation curves and cosmic acceleration without new gravity theories.

Findings

MOND phenomena derived from modified inertia assumptions

Universal acceleration constant a0 is slowly varying

Explains mass discrepancy in galaxy clusters

Abstract

Milgrom's modified Newtonian dynamics (MOND) has done a great job on accounting for the rotation curves of a variety of galaxies by assuming that Newtonian dynamics breaks down for extremely low acceleration typically found in the galactic contexts. This breakdown of Newtonian dynamics may be a result of modified gravity or a manifest of modified inertia. The MOND phenomena are derived here based on three general assumptions: 1) Gravitational mass is conserved; 2) Inverse-square law is applicable at large distance; 3) Inertial mass depends on external gravitational fields. These assumptions not only recover the deep-MOND behaviour, the accelerating expansion of the universe is also a result of these assumptions. Then Lagrangian formulae are developed and it is found that the assumed universal acceleration constant a0 is actually slowly varying by a factor no more than 4. This varying 'constant' is just enough to account for the mass-discrepancy presented in bright clusters.