Semi-Classical Limits of Simplicial Quantum Gravity

Abstract

We consider the simplicial state-sum model of Ponzano and Regge as a path integral for quantum gravity in three dimensions. We examine the Lorentzian geometry of a single 3-simplex and of a simplicial manifold, and interpret an asymptotic formula for $6j$-symbols in terms of this geometry. This extends Ponzano and Regge's similar interpretation for Euclidean geometry. We give a geometric interpretation of the stationary points of this state-sum, by showing that, at these points, the simplicial manifold may be mapped locally into flat Lorentzian or Euclidean space. This lends weight to the interpretation of the state-sum as a path integral, which has solutions corresponding to both Lorentzian and Euclidean gravity in three dimensions.

14 pages in Plain TeX, (figures available on request), DAMTP-R93/26

References in corpus (2)

• 3-dimensional Gravity from the Turaev-Viro Invariant
• Partition Functions and Topology-Changing Amplitudes in the 3D Lattice Gravity of Ponzano and Regge

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