Linear Potentials and Galactic Rotation Curves

We present a simple, closed-form expression for the potential of an axisymmetric disk of stars interacting through gravitational potentials of the form V(r) = -β/r + yr/2, the potential associated with fundamental sources in the conformal invariant fourth-order theory of gravity which has recently been advanced by Mannheim and Kazanas as a candidate alternative to the standard second-order Einstein theory. Using the model, we obtain a reasonable fit to some representative galactic rotation curve data without the need for any non-luminous or dark matter. Our study suggests that the observed flatness of rotation curves might only be an intermediate phenomenon rather than an asymptotic one.