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Joshua Goldberg (emeritus)
Syracuse University has a strong program in gravitational physics.
The relativity group has members working in both
theoretical and experimental aspects of the field.
The Syracuse group was led from
its founding in 1947 until 1982 by Peter G. Bergmann.
Josh Goldberg's homepage
has primarily been interested in applying the new Ashtekar
formalism to the study of
canonical fields on null surfaces. The idea here is that one expects
the independent degrees of freedom that propagate along null rays to
be easier to identify on a null surface. This work is being carried
out together with colleagues in England. In addition Goldberg is
interested in better understanding the conservation laws for
energy-momentum and angular momentum in general relativity. These
concepts do not have a local meaning and even their global definitions
are confusing at null infinity.
(list of papers according to SLAC-SPIRES)
Rafael Sorkin's homepage
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 last century in connection with the
study of the very small (atoms), the very fast (light), and the very big
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.
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.