Black Holes from Branes: Various string theoretical constructions
In this dissertation we have studied black holes from various perspectives in string theory. One common theme of all the black holes that we have studied, is that they are constructed from branes. In part I we considered supersymmetry breaking Scherk-Schwarz duality twists and their effect on black holes in string theory. Our setup was type IIB string theory compactified on a four-torus and then further compactified on a circle with a duality twist along the circle. In these reductions we have studied several different brane configurations, the D1-D5-P system and dual configurations, that give rise to five-dimensional black holes in the standard untwisted reduction. Scherk-Schwarz reductions can be lifted to string theory so long as the monodromy is an element of the discrete U-duality group. We have worked out the quantization conditions that this requirement imposes on the twist parameters. Moreover, when the duality twist is a T-duality, the theory at the minimum of the potential can be described as an asymmetric orbifold. We have explicitly constructed this orbifold, and we have argued what conditions the survival of certain D-brane configurations puts on the orbifold. In part II we studied M2-branes and D2-branes wrapping Riemann surfaces with non-constant curvature: spindles and topological discs. These give rise to 4d black hole solutions in N=2 STU supergravity, whose near-horizon is a warped product of AdS2 with the Riemann surface. We have shown that the disc and spindle solutions can be obtained from different global completions of the same local solution, and we have analyzed their properties in detail. We have uplifted various truncations of this family of near-horizon solutions to M-theory and to massive type IIA. We found that some of these uplifts yield smooth solutions, while others yield solutions that have singularities associated to smeared branes or monopoles. In part III we have classified the necessary and sufficient conditions for near-horizon geometries of extremal supersymmetric rotating black holes in 11d supergravity, which are associated to rotating M2-branes. These near-horizon geometries contain an AdS2 factor which is fibered by the internal geometry. We have allowed for the most general fibration and flux configuration supporting rotating M2-branes. Due to the generality of our ansatz the black holes covered by our classification can include both electric and magnetic charges as well as angular momentum in 4d. By use of dualities, we have also presented necessary and sufficient conditions for the near-horizon geometry of a class of rotating black string solutions in type IIB. Finally, we have embedded several known 4d black hole solutions from the literature into our classification.