The Effect of Interplay between the Newtonian Gravitational Field and the Cosmological Expansion

We study the motion of a celestial body under the simultaneous effect of the Newtonian and Cosmological fields. The resulting effect is not only interesting in itself, but it could also give a contribution to solve the well-known problem of galactic rotation curves without the assumption of the existence of dark matter. We assume that in the outer regions of galaxies, the stars and the hydrogen clouds follow not only the geodesics of the central field, but also the Hubble flow. By a simple application of the classical kinematics of relative motions, we analyze the effects of the composition of these two motions and we find an increase of the rotation speed with respect to the galactic center that could be the cause of the non Newtonian behavior of rotation curves.