Prof. John Barrett Univ. of Nottingham
	Title: State Sum Models for Quantum Gravity
	Date: August 27, 1998

Abstract

Last year, Louis Crane and I proposed a state sum model for a quantum theory of gravity. In this talk I will explain progress made in understanding one of the versions of the model.

The model is based on relativistic spin network evaluations. These give invariants of graphs embedded in three dimensional space. The underlying geometry for this is (for q=1) the geometry of hyperplanes in four-dimensional Euclidean space.

One case of this is the amplitude of the 4-simplex, which gives the `Regge calculus' Einstein action of the 4-simplex in an appropriate asymptotic limit.

Gluing together the 4-simplex amplitudes to produce a state sum model for a 4-manifold (space-time) is not completely understood. The simplest model leads to wavefunctions in an `area representation'.

Audio

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Slides