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Classical and Quantum Gravity
Rafael Sorkin works primarily in the area of overlap between high energy physics and gravity. His central interest is the problem of unifying general relativity with quantum mechanics (the so-called problem of quantum gravity), which can also be viewed as the problem of completing the twin revolutions initiated early this century in connection with the study of the very small (atoms), the very fast (light), and the very big (astronomy).
He believes that the successful resolution of this problem will require both a reformulation of gravity in terms of a discrete structure underlying continuous spacetime, and a reformulation of quantum mechanics along the lines of a generalized sum-over-histories. He also believes that the phenomena of topology change and black hole thermodynamics provide important clues to the shape of the final synthesis. In this context he has investigated the quantum properties of topological geons (particles constructed directly from the spacetime topology), finding that they can display remarkable statistical properties, and uncovering evidence that topology change is a necessary feature of any consistent quantum gravity theory; and he has sought the source of a black hole's entropy in the degrees of freedom of its horizon, most recently in its shape variables.
Based in part on such work, he has hypothesized that the sought-for "atoms" of spacetime are the elements of a causal set: a microscopic "family tree" whose defining order-relationship corresponds to the macroscopic relation of before and after. At present he, his collaborators and students are seeking (by analytical methods and computer simulations) to understand the mathematical properties of causal sets in order to formulate for them a dynamical law from which Einstein's equations would emerge in a suitable classical limit.
