Smooth supergravity solutions and string states
In this thesis we study smooth supergravity solutions and their relation to string theory in two different contexts; quotient spaces and asymptotically flat solitonic solutions. We classify discrete cyclic quotients of р + l-dimensional anti-de Sitter space. These provide interesting models for string propagation where a non-perturbative description is available. We establish which quotients have well-behaved causal structures, and of those containing closed timelike curves, which have interpretations as black holes. We explain the relation to previous investigations of quotients of asymptotically flat spacetimes and plane waves, and of black holes in AdS. We construct smooth non-supersymmetric soliton solutions with Dl-brane, D5- brane and momentum charges in type IIB supergravity compactified on T(^4) X S(^1). Such solutions have been conjectured to be related to black hole microstates. The solutions are obtained by considering a known family of U(1) X U(1) invariant metrics, and studying the conditions imposed by requiring smoothness. We discuss the relation of our solutions to states in the CFT describing the D1-D5 system, and describe various interesting features of the geometry. We show that the solutions describing charged rotating black holes in rive- dimensional gauged supergravities found recently by Cvetic, Lü and Pope [1, 2] are completely specified by the mass, charges and angular momentum, demonstrating that an apparent non-uniqueness is a coordinate artefact.