A Worldsheet Description of Black Hole Microstates

The purpose of this thesis is the study of a particular fuzzball microstate in a full worldsheet theory. It is fairly accepted that black holes are thermodynamic objects, which have an entropy. Fuzzball is the name of a particular description of the microstates giving rise to this entropy. This kind of picture was proposed in the framework of the attempts to resolve the information paradox, since fuzzballs emit the Hawking radiation unitarily. This work focuses on one particular fuzzball microstate for the NS5-P two-charge black hole. The fundamental employed tool is the gauged Wess-Zumino-Witten model, an exactly solvable theory describing the dynamics of strings on a curved background. The results obtained reproduce the supergravity predictions, both in the case of one charge, i. e. NS5-branes on a circle, and of two charges, i. e. supertubes of NS5-branes. The physical vertex operators in the Neveu-Schwarz sector have been constructed by solving the constraints arising from the reparametrization and gauge invariance of the theory. This way stringy effects that are not visible in the supergravity approximation, can be explored.