MASSLESS STRING THEORY BLACK-HOLES AS BLACK DIHOLES AND QUADRUHOLES

Massless black holes can be understood as bound states of a (positive- mass) extreme a = root 3 black hole and a singular object with opposit e (i.e., negative) mass with vanishing Arnowitt-Deser-Misner (total) m ass but nonvanishing gravitational field. Supersymmetric balance of fo rces is crucial for the existence of this kind of bound states and exp lains why the system does not move at the speed of light. We also expl ain how supersymmetry allows for negative mass as long as it is never isolated but in bound states of total non-negative mass.