Article,
Hidden Structures of Black Holes
(Nov 29, 2010)
Abstract
This thesis investigates two main topics concerning black holes in extensions
of general relativity inspired by string theory. First, the structure of the
equations of motion underlying black hole solutions is considered, in theories
of D-dimensional gravity coupled to scalars and vectors. For solutions
preserving supersymmetry, the equations of motion have a dramatic
simplification: they become first-order instead of the second-order equations
one would expect. Recently, it was found that this is a feature some
non-supersymmetric black hole solutions exhibit as well. We investigate if this
holds more generally, by examining what the conditions are to have first-order
equations for the scalar fields of non-supersymmetric black holes, that mimic
the form of their supersymmetric counterparts. This is illustrated in examples.
Second, the structure of black holes themselves is investigated. String theory
has been successful in explaining the Bekenstein-Hawking entropy for (mainly
supersymmetric) black holes from a microscopic perspective. However, it is not
fully established what the interpretation of the corresponding 'microstates'
should be in the gravitational description where the black hole picture is
valid. There have been recent advances to understand the nature of black hole
microstates in the gravity regime, such as the fuzzball proposal. A related
idea says that black hole configurations with multiple centers are related to
microstates of single-centered black holes. We report on work relating both
pictures. As an aside, a relation between violations of causality for certain
spacetimes (presence of closed timelike curves in the geometry) and a breakdown
of unitarity in the dual conformal field theory is given.
