5,528 research outputs found
Finiteness of a spinfoam model for euclidean quantum general relativity
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
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
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 . These represent
the most stringent bounds on Lorentz violation to date
Observability and Geometry in Three dimensional quantum gravity
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
Dynamics of loop quantum gravity and spin foam models in three dimensions
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
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