NONLINEAR CHARGED BLACK-HOLES

Very strong electromagnetic fields are characterized by the appearance of non-linearities. In order to explore the consequences of such non- linearities we have solved exactly the combined gravitational non-line ar electromagnetic field equations for a static and spherical symmetri c spacetime, where the source of the curvature is a point electric cha rge. We have chosen a non-linear Lagrangian density in such a way that the Maxwell, the Born-Infeld, and the Heisenberg-Euler theories are i ncluded as particular cases. The general solution can represent a char ged black hole with the same characteristics of the Reissner-Nordstrom one (two horizons and timelike singularity), or it can have only one horizon and a spacelike singularity, as in the Schwarzschild solution.