  New formulae are obtained for the energy of K.N. b.h.'s that point out a
gravitomagnetic energy effect. The results are valid for slowly or rapidly
rotating black-holes. The expression of the energy density of Kerr-Newman
back-holes in the slow rotation case, is obtained afterwards, and shown to be
essentially positive. Subsequently,we show how to attain a "repulsive"
gravitation (antigravitation) state identified with negative energy
distribution contents in a limited region of space, without violating the
Positive Energy Theorem.

General Relativity and Quantum Cosmology