Defintion and properties of quasi black holes
Objects that are on the verge of being extremal black holes but actually are distinct in many ways are called quasi-black holes. Quasi-black holes are defined here and treated in a unified way through the displaying of their properties. The main ones are (i) their geometry remains perfectly regular everywhere, in spite of the existence of infinite redshifts, (ii) in the limit, outer and inner regions become mutually impenetrable and disjoint, although, in contrast to the usual black BHs, this separation is of a dynamical nature, rather than purely causal. It is also shown that QBHs have to be extremal.
Joint work with Jose P. S. Lemos.