CIRCULAR MOTION IN REISSNER–NORDSTRÖM SPACETIME

We study the motion of neutral test particles along circular orbits in the Reissner-Nordström spacetime. We use the method of the effective potential with the constants of motion associated to the underlying Killing symmetries. A comparison between the black hole and naked singularity cases is performed. In particular we find that in the naked singularity case for r < Q²/M no circular orbits can exist, this radius plays a fundamental role in the physics of the naked singularity. For r > Q²/M and there are two stability regions together with a region where all the circular orbits are instable and a zone in which all trajectory are possible but not circular orbits, for one stability region and a region where all circular orbits are instable appear, finally for there are all stable circular orbits for r > Q²/M.