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Frederik Denef Columbia Type II string theory compactified on a Calabi-Yau manifold has a rich spectrum of BPS states obtained by wrapping D-branes around nontrivial cycles in the Calabi-Yau. Being a theory with N=2 residual supersymmetry in four dimensions, the spectrum furthermore has a nontrivial dependence on the geometrical moduli of the Calabi-Yau. We tackle the outstanding problem of determining this spectrum for given moduli values by looking at the corresponding four dimensional supergravity solutions. A rather beautiful picture emerges, involving -- apart from the usual N=2 "attractor" black holes and their less usual "empty hole" siblings - composite non-static black holes with mixed electric and magnetic centers. These provide a surprisingly easy way to understand a number of powerful stability criteria for BPS states without having to go through the more established heavy conformal field theory and algebraic geometry techniques. Emphasis in this talk will be on physical ideas rather than on technicalities.
Wednesday, November 22nd 2000, 13:15 |