Complete LQG propagator: Difficulties with the Barrett-Crane vertex

Journal Article · Thu Nov 15 04:00:00 EST 2007 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.76.104012· OSTI ID:21027838

Alesci, Emanuele ^[1]; Rovelli, Carlo ^[2]

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1. Dipartimento di Fisica, Universita di Roma Tre, I-00146 Rome (Italy)
2. Centre de Physique Theorique de Luminy, Universite de la Mediterranee, F-13288 Marseille (France)

Some components of the graviton two-point function have been recently computed in the context of loop quantum gravity, using the spinfoam Barrett-Crane vertex. We complete the calculation of the remaining components. We find that, under our assumptions, the Barrett-Crane vertex does not yield the correct long-distance limit. We argue that the problem is general and can be traced to the intertwiner independence of the Barrett-Crane vertex, and therefore to the well-known mismatch between the Barrett-Crane formalism and the standard canonical spin networks. In another paper we illustrate the asymptotic behavior of a vertex amplitude that can correct this difficulty.

• OSTI ID: 21027838
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 10 Vol. 76; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
ASYMPTOTIC SOLUTIONS
DISTANCE
GRAVITONS
PROPAGATOR
QUANTUM GRAVITY
SPIN
VERTEX FUNCTIONS