638 research outputs found
Critical Overview of Loops and Foams
This is a review of the present status of loop and spin foam approaches to
quantization of four-dimensional general relativity. It aims at raising various
issues which seem to challenge some of the methods and the results often taken
as granted in these domains. A particular emphasis is given to the issue of
diffeomorphism and local Lorentz symmetries at the quantum level and to the
discussion of new spin foam models. We also describe modifications of these two
approaches which may overcome their problems and speculate on other promising
research directions.Comment: 75 page
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