5,569 research outputs found

    Finiteness of a spinfoam model for euclidean quantum general relativity

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    We prove that a certain spinfoam model for euclidean quantum general relativity, recently defined, is finite: all its all Feynman diagrams converge. The model is a variant of the Barrett-Crane model, and is defined in terms of a field theory over SO(4) X SO(4) X SO(4) X SO(4).Comment: 6 pages, 1 figur

    Statistical and entanglement entropy for black holes in quantum geometry

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    We analyze the relationship between entanglement (or geometric) entropy with statistical mechanical entropy of horizon degrees of freedom when described in the framework of isolated horizons in loop quantum gravity. We show that, once the relevant degrees of freedom are identified, the two notions coincide. The key ingredient linking the two notions is the structure of quantum geometry at Planck scale implied by loop quantum gravity, where correlations between the inside and outside of the black hole are mediated by eigenstates of the horizon area operator.Comment: References adde

    Comments on Challenges for Quantum Gravity

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    We examine radiative corrections arising from Lorentz violating dimension five operators presumably associated with Planck scale physics as recently considered by Myers and Pospelov. We find that observational data result in bounds on the dimensionless parameters of the order 10−1510^{-15}. These represent the most stringent bounds on Lorentz violation to date

    Dynamics of loop quantum gravity and spin foam models in three dimensions

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    We present a rigorous regularization of Rovellis's generalized projection operator in canonical 2+1 gravity. This work establishes a clear-cut connection between loop quantum gravity and the spin foam approach in this simplified setting. The point of view adopted here provides a new perspective to tackle the problem of dynamics in the physically relevant 3+1 case.Comment: To appear in the procedings of the Third International Symposium on Quantum Theory and Symmetries (QTS3), September 200

    Observability and Geometry in Three dimensional quantum gravity

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    We consider the coupling between massive and spinning particles and three dimensional gravity. This allows us to construct geometric operators (distances between particles) as Dirac observables. We quantize the system a la loop quantum gravity: we give a description of the kinematical Hilbert space and construct the associated spin-foam model. We construct the physical disctance operator and consider its quantization.Comment: To appear in the procedings of the Third International Symposium on Quantum Theory and Symmetries (QTS3), September 200