Publication : t10/083

Abstract:
In this thesis I present the work I did during my PhD at the Institute of Theoretical Physical (IPhT), CEA Saclay, under the supervision of Iosif Bena. The framework I have been working in is string theory, and more precisely supergravities in ten and eleven dimensions, as low energy limits of string theory. The first part of the thesis deals with the study of supersymmetric three-charge black holes and black hole microstates: Using supersymmetric D-branes called supertubes, we have performed a probe analysis of supergravity solutions, and showed how this approach exactly captures, in all known cases, the physical properties of the complete supergravity solution. We also found that when the supertube is in a magnetically charged background, it sees its entropy enhanced with respect to its flat space one. The supergravity solutions sourced by supertubes are regular and horizonless, and hence can be seen, in the “fuzzball proposal”, as black hole microstates. This enhanced entropy could therefore contribute for a large part in a microscopic counting of the black hole entropy. In the second part of the thesis, I present a new class of five-dimensional non-supersymmetric solutions, called “floating brane” solutions. The equations giving these new solutions generalize the BPS equations and have the key property to still be partially first order and linear. The BPS equations, and thus all the known supersymmetric solutions, are recovered as a subcase of the floating brane equations. Some of the new solutions have a horizon and are thus black holes – with different horizon topologies – but some are completely regular and horizonless and should correspond to microstates of non extremal black holes.

Ruef.pdf