EVENT HORIZONS AND APPARENT HORIZONS IN SPHERICALLY SYMMETRICAL GEOMETRIES

Spherical configurations that are very massive must be surrounded by a pparent horizons. These, in turn, when placed outside a collapsing bod y, have a fixed area and must propagate outward with a velocity equal to the velocity of radially outgoing photons. That proves, within the framework of the 1+3 formalism and without resorting to the Birkhoff t heorem, that apparent horizons coincide with event horizons in an elec trovacuum. The existence of the maximal slicing of electrovacuum is pr oved and an explicit line element is found in the maximal foliation.