String theory black holes and cosmology

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String theory is currently the leading candidate for a theory of quantum gravity.  It promises to unify the fundamental forces of particle physics - which are governed by the rules of quantum mechanics - with the force of gravity, as described by Einstein's general theory of relativity.  String theory has the potential to shed light on many basic conceptual questions concerning the fundamental physics of space and time. My research program investigates applications of string theory to two of the most exciting and important such questions.The first such question involves black holes, which provide an ideal theoretical laboratory for the study of quantum gravity.  Many important puzzles, such as the meaning of the singularity at the core of a black hole, can only be addressed using the tools and techniques of string theory. In doing so, we are forced to reconsider many of our intuitive notions of space and time as smooth, classical objects.The second set of questions is motivated by recent astronomical observations indicating that the universe began with a big bang singularity followed by a period of rapid expansion.  Neither of these two features - the cosmological singularity and the exponentially expanding phase - have been successfully described in string theory. These problems, which must be solved if string theory is to successfully describe the observable universe, also provide the exciting prospect of contact with experimental data.This proposed research program will lead to insights spanning several different subfields, ranging from mathematical physics to cosmology, quantum gravity and elementary particle physics, which are crucial to the the study of theoretical physics in Canada.