Thiemann on the relation between canonical and covariant loop quantum gravity

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SUMMARY

The discussion centers on the paper "Linking covariant and canonical LQG: new solutions to the Euclidean Scalar Constraint" by Emanuele Alesci, Thomas Thiemann, and Antonia Zipfel. The authors demonstrate that for a fixed Barbero-Immirzi parameter of γ=1, the one-vertex amplitude in the KKL prescription successfully annihilates the Euclidean Hamiltonian constraint of Loop Quantum Gravity (LQG). This leads to new solutions within the Euclidean framework, highlighting that these new states depend solely on the diagonal matrix elements of the volume, a property that emerges when utilizing the spin-foam projector.

PREREQUISITES
  • Understanding of Loop Quantum Gravity (LQG)
  • Familiarity with spin-foam models
  • Knowledge of the Barbero-Immirzi parameter
  • Basic grasp of Hamiltonian constraints in quantum gravity
NEXT STEPS
  • Explore the implications of the Barbero-Immirzi parameter in LQG
  • Research the KKL prescription in spin-foam models
  • Investigate the role of diagonal matrix elements in quantum gravity theories
  • Study the relationship between covariant and canonical approaches in LQG
USEFUL FOR

The discussion is beneficial for theoretical physicists, researchers in quantum gravity, and students studying Loop Quantum Gravity and spin-foam models.

tom.stoer
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http://arxiv.org/abs/1109.1290
Linking covariant and canonical LQG: new solutions to the Euclidean Scalar Constraint[/B
Authors: Emanuele Alesci, Thomas Thiemann, Antonia Zipfel
(Submitted on 6 Sep 2011)
Abstract: It is often emphasized that spin-foam models could realize a projection on the physical Hilbert space of canonical Loop Quantum Gravity (LQG). As a first test we analyze the one-vertex expansion of a simple Euclidean spin-foam. We find that for fixed Barbero-Immirzi parameter \gamma=1 the one vertex-amplitude in the KKL prescription annihilates the Euclidean Hamiltonian constraint of LQG. Since for \gamma=1 the Lorentzian part of the Hamiltonian constraint does not contribute this gives rise to new solutions of the Euclidean theory. Furthermore, we find that the new states only depend on the diagonal matrix elements of the volume. This seems to be a generic property when applying the spin-foam projector.

I didn't study the whole paper but looked first at the conclusions: you will find that it's still a a long and stony path ...
 

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