Feynman Propagator for Spin Foam Quantum Gravity

Daniele Oriti
Phys. Rev. Lett. 94, 111301 – Published 22 March 2005

Abstract

We link the notion causality with the orientation of the spin foam 2-complex. We show that all current spin foam models are orientation independent. Using the technology of evolution kernels for quantum fields on Lie groups, we construct a generalized version of spin foam models, introducing an extra proper time variable. We prove that different ranges of integration for this variable lead to different classes of spin foam models: the usual ones, interpreted as the quantum gravity analogue of the Hadamard function of quantum field theory (QFT) or as inner products between quantum gravity states; and a new class of causal models, the quantum gravity analogue of the Feynman propagator in QFT, nontrivial function of the orientation data, and implying a notion of “timeless ordering”.

  • Received 7 November 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.111301

©2005 American Physical Society

Authors & Affiliations

Daniele Oriti

  • Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom

  • *Electronic address: d.oriti@damtp.cam.ac.uk

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Issue

Vol. 94, Iss. 11 — 25 March 2005

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