  In three spacetime dimensions, general relativity becomes a topological field
theory, whose dynamics can be largely described holographically by a
two-dimensional conformal field theory at the ``boundary'' of spacetime. I
review what is known about this reduction--mainly within the context of pure
(2+1)-dimensional gravity--and discuss its implications for our understanding
of the statistical mechanics and quantum mechanics of black holes.

General Relativity and Quantum Cosmology;High Energy Physics - Theory