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arXiv · 0705.2388

The loop-quantum-gravity vertex-amplitude

Jonathan Engle·Roberto Pereira·Carlo Rovelli
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Abstract

Spinfoam theories are hoped to provide the dynamics of non-perturbative loop quantum gravity. But a number of their features remain elusive. The best studied one -the euclidean Barrett-Crane model- does not have the boundary state space needed for this, and there are recent indications that, consequently, it may fail to yield the correct low-energy $n$-point functions. These difficulties can be traced to the SO(4) -> SU(2) gauge fixing and the way certain second class constraints are imposed, arguably incorrectly, strongly. We present an alternative model, that can be derived as a bona fide quantization of a Regge discretization of euclidean general relativity, and where the constraints are imposed weakly. Its state space is a natural subspace of the SO(4) spin-network space and matches the SO(3) hamiltonian spin network space. The model provides a long sought SO(4)-covariant vertex amplitude for loop quantum gravity.

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Jonathan Engle, Roberto Pereira, Carlo Rovelli. 2007-05-16. The loop-quantum-gravity vertex-amplitude. https://doi.org/10.1103/physrevlett.99.161301

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