Event horizons in static electrovac space-times
The following theorem is established. Among all static, asymptotically flat electrovac fields with closed, simply-connected equipotential surfacesg0 0=const.. the only ones which have regular event horizonsg0 0=0 are the Reissner-Nordström family of spherisymmetric solutions withm≧G1/2|e|/c. In the special case where the gravitational coupling of the electromagnetic energy density is neglected (G=0) all solutions are computed explicitly, thus extending an earlier result ofGinzburg for a magnetic dipole inSchwarzschild's space-time. Possible implications for gravitational collapse are briefly discussed.