Macroscopic and Microscopic Description of Black Holes in String Theory

Abstract

We study how to describe 5-dimensional and 4-dimensional black holes by D-branes in string theory. In the 5-dimensional case we arrive at the Tangherlini black hole, while we find the extremal Reissner-Nordström black hole in four dimensions. For both black holes we compute the entropy both macroscopically and microscopically and we check that they agree. The results above are known in literature. Here we work out some examples in detail. Moreover, in this thesis we have computed the black hole charges. In the 4-dimensional case we try to set the magnetic charges to zero by using electromagnetic duality in order to obtain a simpler black hole description. We conclude that this is not possible since two new magnetic charges arise. We interpret how this electromagnetic duality transformation in $d=4$ influences the D-branes in $d=10$. We find that the set of D-branes has been changed to another set of D-branes, which describes the same black hole metric.