A Proposed Observational Test Of Deur's Gravity

There is a fairly straightforward way to distinguish between Deur's approach to gravity and alternative explanations of dark matter phenomena.

Look at the strength of the gravitational field of a spiral galaxy, above or below the disk of the galaxy, by a distance, for example, equal to the distance from the center of the galaxy to its rim.

In a Navarro-Frank-White (NFW) dark matter halo model, or in MOND, the strength of the gravitational field above or below the disk of the galaxy at that distance should be the same as it is at the rim, because those are both spherically symmetric solutions.

But, in Deur's approach to gravity, the strength of the gravitational field above or below the disk of the galaxy at that distance should be weaker than it would be with purely Newtonian gravity in the absence of any dark matter, in an amount that ought to be possible to calculate rather precisely (and to make more precise by calibrating it with the strength of the gravitational field at the rim of the spiral galaxy).

It might be somewhat harder to distinguish, for example, an inferred prolate dark matter halo (which observational evidence strongly favors over a NFW shaped inferred dark matter halo) from Deur's approach to gravity. But, even a prolate dark matter halo should still be stronger than purely Newtonian gravity in the absence of any dark matter above or below the disk of the galaxy at that distance.

This seems like something that could be done by looking at "stray" tracers in the form out of plane stars or satellite galaxies or intergalactic medium, above or below the disk of a spiral galaxy, perhaps also considering the escape velocity of such stars or satellite galaxies in that location, or by considering gravitational lensing of photons in those locations.

Ideally, one would look somewhat off-center of the center of the galaxy to avoid confounds from ultrafast outflows from the center of a spiral galaxy.

If the observations confirm Deur's prediction and are contrary to dark matter particle and MOND theories that could be distinguished from this prediction even without all that great precision, that would be very convincing and striking evidence from an ex ante, untested theoretical prediction of Deur's approach.

This might also distinguish GEM GR effects from gravitational self-interaction effects, although I am less confident of that conclusion. GEM GR effects, since they only work in rotationally supported galaxies, also shouldn't be able to explain inferred dark matter phenomena in galaxy clusters, unlike Deur's approach.