Quantum global structure of de Sitter space

I study the global structure of de Sitter space in the semi-classical and one-loop approximations to quantum gravity. The creation and evaporation of neutral black holes causes the fragmentation of de Sitter space into disconnected daughter universes ("proliferation") If the black holes are stabilized by a charge, I find that the decay leads to a necklace of de Sitter universes ("beads'') joined by near-extremal black hole throats. For sufficient charge, more and more beads keep forming on the necklace, so that an unbounded number of universes will be produced. In any case, future infinity will not be connected. This may have implications for a holographic description of quantum gravity in de Sitter space. [S0556-2821(99)02118-9].