Publication : t16/153

Abstract:
There exist many smooth solutions in String Theory characterized by a nontrivial topology threaded by uxes and no localized sources. In this thesis we analyze some of the most important bubbled solutions along with the dierent purposes they are studied for. Some smooth, eleven-dimensional solutions can be interpreted as BPS black hole microstates in the context of the Fuzzball proposal. One can promote these to be microstates for near-BPS black holes by placing probe supertubes at a metastable minimum inside these solutions. We show that these minima can lower their energy when the bubbles move in certain directions in the moduli space, which implies that these near-BPS microstates are in fact unstable. The decay of these solutions corresponds to Hawking radiation and we compare the emission rate and frequency to those of the corresponding black hole. By modifying the asymptotic behavior of these microstates one could be able to construct microstates for ve-dimensional BPS black rings with no electric charge. To do so one needs to nd a new supergravity solution in ve-dimensions whose Killing vector switches from timelike to null in some open regions. We construct explicit examples where the norm of the supersymmetric Killing vector is a real not-everywhere analytic function such that all its derivatives vanish at a point where the Killing vector becomes null. In the Lin-Lunin-Maldacena solution we nd a supersymmetry-breaking mechanism similar to that used for near-BPS microstates. We analyze the potential energy of M2 probes polarized into M5 brane shells. When the charges of the probe are parallel to those of the solution we nd stable congurations, while when the charges are opposite we nd metastable states that break supersymmetry and analyze the decay process to supersymmetric congurations. We analyze also the Klebanov-Strassler solution and construct its T-dual in Type IIA. This is done by just reconstructing the solution expanded on a small region of the deformed conifold, after a thorough analysis to choose the most suitable isometry. Our construction is the rst step in a program to test the stability of antibranes in Type IIA backgrounds.

PhD_thesis_Pasini.pdf