Schild’s Ladder

by Greg Egan

Quantum Graph Theory is fictitious, but the spin networks on which Sarumpaet’s work is based are part of a real theory, known as loop quantum gravity, discovered by Lee Smolin and Carlo Rovelli. There is a considerable literature on this subject; two comprehensive review papers are: “An Introduction to Spin Foam Models of BF Theory and Quantum Gravity” by John C. Baez, in Geometry and Quantum Physics, edited by Helmut Gausterer, Harald Grosse and Ludwig Pittner, Springer, Berlin, 2000. www.arXiv.org/abs/gr-qc/9905087 and “The Future of Spin Networks” by Lee Smolin, in The Geometric Universe, edited by S. A. Huggett et al., Oxford University Press, Oxford, 1998. www.arXiv.org/abs/gr-qc/9702030