A modification of the Newtonian dynamics - Implications for galaxies

A form of the Newtonian dynamics which has been modified with respect to inertia and/or gravity is used to describe the motion of bodies in the gravitational fields of galaxies, under the assumption that galaxies contain no hidden mass. Among the consequences of this method which are presently discussed, it is noted that the Keplerian, circular velocity around a finite galaxy becomes independent of r at large radii, yielding asymptotically flat velocity curves. The discrepancy between the dynamically determined Oort density in the solar neighborhood and the density of observed matter, moreover, is found to disappear. It is predicted in view of these results that rotation curves calculated on the basis of the observed mass distribution and the modified dynamics should agree with the observed velocity curves.