Doctor of Philosophy, The Ohio State University, 2007, Physics

This thesis is devoted to a study of the dynamics of two charge and three charge systems in string theory. We analyze properties of two charge systems in various duality frames and carry out perturbative addition of momentum to these systems. This gives us a picture of microscopic origin of entropy of black holes, supporting the Mathur conjecture. We extend the perturbative construction to provide a microstate for the two charge black ring by adding a small amount of momentum as the third charge. We found it to be completely smooth and horizonless in accord with the Mathur conjecture. We further study dynamics of supertubes in both the weak coupling and the strong coupling regimes which suggests a way to distinguish bound states from unbound states in string theory. We apply these results to supertubes in KK monopole background. We construct metrics describing two charge solutions in four dimensions by adding momentum to a system of N coincident KK monopole solution. We find that adding momentum separates the monopoles and resolves the associated ZN singularities. We also consider branes wrapping cycles in spacetimes generated by two and three charge systems and analyze their supersymmetry properties.

Committee: Samir Mathur (Advisor) Subjects: