Circular motion of neutral test particles in Reissner-Nordstrom spacetime

We investigate the motion of neutral test particles in the gravitational field of a mass M with charge Q described by the Reissner-Nordstrom (RN) spacetime. We focus on the study of circular stable and unstable orbits around configurations describing either black holes or naked singularities. We show that at the classical radius, defined as Q(2)/M, there exist orbits with zero angular momentum due to the presence of repulsive gravity. The analysis of the stability of circular orbits indicates that black holes are characterized by a continuous region of stability. In the case of naked singularities, the region of stability can split into two nonconnected regions inside which test particles move along stable circular orbits.