Conditional probabilities in Ponzano-Regge minisuperspace

Roman Petryk and Kristin Schleich
Phys. Rev. D 67, 024019 – Published 21 January 2003
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Abstract

We examine the Hartle-Hawking no-boundary initial state for the Ponzano-Regge formulation of gravity in three dimensions. We consider the behavior of conditional probabilities and expectation values for geometrical quantities in this initial state for a simple minisuperspace model consisting of a two-parameter set of anisotropic geometries on a 2-sphere boundary. We find dependence on the cutoff used in the construction of Ponzano-Regge amplitudes for expectation values of edge lengths. However, these expectation values are cutoff independent when computed in certain, but not all, conditional probability distributions. Conditions that yield cutoff independent expectation values are those that constrain the boundary geometry to a finite range of edge lengths. We argue that such conditions have a correspondence to fixing a range of local time, as classically associated with the area of a surface for spatially closed cosmologies. Thus these results may hint at how classical spacetime emerges from quantum amplitudes.

  • Received 27 September 2001

DOI:https://doi.org/10.1103/PhysRevD.67.024019

©2003 American Physical Society

Authors & Affiliations

Roman Petryk* and Kristin Schleich

  • Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1

  • *Email address: petryk@physics.ubc.ca
  • Email address: schleich@noether.physics.ubc.ca

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Vol. 67, Iss. 2 — 15 January 2003

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