The Solar system test for the general modified gravity theories

In the past few decades, various versions of modified gravity theories were proposed to mimic the effect of dark matter. Compared with the conventional Newtonian or relativistic dynamics, these theories contain some extra apparent force terms in the dynamical equations to replace the role of dark matter. Generally speaking, the extra apparent force terms usually scale with radius so that the effect would be significant only on large scale to explain the missing mass in galaxies or galaxy clusters. Nevertheless, the apparent effect may still be observable in small structures like the Solar system. In this paper, we derive analytic general formulae to represent the contribution of the precession angle of the planets in the Solar system due to the general modified gravity theories, in which the extra apparent force terms can be written in a power law of radius r or an exponential function in r. We have tested three popular modified gravity theories, the modified Newtonian dynamics (MOND), the emergent gravity (EG), and the modified gravity. In particular, based on the Solar system data, we have constrained the parameters involved for two popular general interpolating functions used in MOND. Our results can be generally applied to both of the modified inertia and modified gravity versions of MOND. Copyright © 2022 The Author(s).