Classical and Quantum Aspects of Black Holes, Horizons and Asymptotic Symmetries

Harvard University, Cambridge MA

Investigators

Abstract

The visible universe has edges, known as event horizons, which surround a black hole or a region of the universe speeding away faster than light. The nature of these edges has vexed physicists, beginning with Einstein, for nearly a century. They are governed by an elegant and beautiful set of quantum laws discovered four decades ago by Bekenstein and Hawking. These laws indicate that black holes are at once the simplest and most complex objects in the physical universe. They are simple because, according to Einstein's general relativity there is in effect nothing inside - space ends at the horizon. They are complex because the Bekenstein-Hawking laws imply that they must carry the maximal allowable information. The coexistence of these dichotomous descriptions of black holes underlies a deep paradox whose resolution is a focal point of modern physics. While the basic paradox remains unsolved, much has been learned using a variety of apporaches. Resolving the paradox is a central problem in modern physics and will likely lead to profound new insights into the nature of our universe, comparable to those following from quantum mechanics and relativity. In this project we propose specific steps to continue these fruitful investigations as well as more generally address universal aspects of the paradox, in its many manifestations surrounding black hole and other horizons. Our investigations will be informed by important lessons learned in the process of studying string theory (a candidate for a fundamental unified theory of nature), but we will concentrate on universal aspects of large-scale observable phenomena which are independent of any assumptions about the as yet-unknown completion of the fundamental laws of nature. Here we pursue a bottom-up approach working from astrophysically observed properties of horizons, the powerful symmetry -general covariance- underlying Einstein's theory of general relativity, and basic physical and mathematical consistency.