Publication : t23/078

Abstract:
Almost a century after being theorized, Black Holes have now been observed in nature, first indirectly by LIGO and VIRGO, then directly by the EHT. According to General Relativity, they are the final state of matter after the collapse of very massive objects: all their mass is concentrated in a spacetime singularity, that is shrouded by a horizon from which nothing can escape. Black Holes lie at the frontier between General Relativity and Quantum Mechanics, and are the source of many puzzles and paradoxes whose answers could shed light on several aspects of Quantum Gravity. Chief among them is the information paradox: black holes can evaporate through Hawking radiation, and it seems that all the information about the original constituents of the black hole is permanently lost at the end of this process. The Fuzzball conjecture is an attempt to solve these paradoxes. It proposes to replace the standard black hole picture by an ensemble of fuzzy, horizonless microstates. These solutions, that are built out of the vast number of degrees of freedom of String Theory, look and behave exactly like black holes at a distance, but differ close to the horizon. Because they are horizonless, these geometries are not subject to the same paradoxes as the black hole. As an Effective Field Theory, General Relativity washes out all the intricate details of these microstates, and can only capture an average description: the black hole with a horizon. This thesis aims to build and study such fuzzball microstates within the framework of Supergravity, the low-energy limit of String Theory. The focus is on addressing two main questions associated to the fuzzball conjecture: Can one construct “typical” microstates that mimic what is expected of black holes ? Can one find enough microstate geometries to recover the full entropy of black holes ?

thesis-houppe.pdf