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An Introduction to Spin Foam Models of Quantum Gravity and BF Theory

John C. Baez
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Abstract

In loop quantum gravity we now have a clear picture of the quantum geometry of space, thanks in part to the theory of spin networks. The concept of `spin foam' is intended to serve as a similar picture for the quantum geometry of spacetime. In general, a spin network is a graph with edges labelled by representations and vertices labelled by intertwining operators. Similarly, a spin foam is a 2-dimensional complex with faces labelled by representations and edges labelled by intertwining operators. In a `spin foam model' we describe states as linear combinations of spin networks and compute transition amplitudes as sums over spin foams. This paper aims to provide a self-contained introduction to spin foam models of quantum gravity and a simpler field theory called BF theory.

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John C. Baez. 1999-05-21. An Introduction to Spin Foam Models of Quantum Gravity and BF Theory. https://arxiv.org/abs/gr-qc/9905087

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