Robert M. Wald

My research centers on general relativity--the theory of space, time, and gravitation formulated by Einstein in 1915--with the goal of gaining deeper insights into spacetime structure and gravitation. Black holes and their thermodynamic properties presently offer us the greatest opportunities to gain such insights. A black hole is a region where gravity is so strong that nothing--not even light--can escape; remarkably, though, because of quantum mechanical processes, particles are spontaneously produced outside a black hole in such a manner that it would appear to a distant observer that the black hole is emitting radiation of exactly the same nature as emitted by an ordinary body in thermal equilibrium. As a consequence, black holes have a non-zero physical temperature and can be assigned a well-defined entropy, which presumably corresponds to their quantum degrees of freedom. My research has included a study of the particle creation process and other phenomena involving quantum fields in the presence of gravity, a derivation of general formula for black hole entropy, and an analysis of the "generalized second law" of thermodynamics, which considers the contributions of black holes to the total entropy of the Universe.