2 KINDS OF EXTREME BLACK-HOLES AND THEIR CLASSIFICATION

According to different topological configurations, we suggest that the re are two kinds of extreme black holes in the nature. We find that th e Euler characteristic plays an essential role to classify these two k inds of extreme black holes. For the first kind of extreme black holes , Euler characteristic is zero, and for the second kind, Euler charact eristic is two or one provided they are four dimensional holes or two dimensional holes respectively. (C) 1998 Published by Elsevier Science B.V. All rights reserved.