### Towards a Spin Foam Model of Quantum Gravity

NOTE: pdf link for transparencies- http://math.ucr.edu/home/baez/loops05/loops05.pdf Probably not everyones cup of tea. A clip from a lecture by John Baez in conjunction with the LOOPS 'O5 series by the Max Planck Institute of Gravitation (Albert Einstein Institute) regarding a proposal for quantum gravity (the clip appears to start at page 14 of the transparencies). Date- 11th Oct 05. Source- http://math.ucr.edu/home/baez/loops05/ LOOPS '05- http://loops05.aei.mpg.de/ 'Spin foam models include several different classes of physical theories: lattice gauge theories, dynamical triangulation models of quantum gravity, "chain mail" quantum field theories, and topological string theories. Is there a spin foam model of quantum gravity in 4 dimensions? To address this question, we review recent work on causal dynamical triangulations and the renormalization group. This suggests that quantum gravity is a well-defined theory with the curious property that spacetime is effectively 4-dimensional at large distance scales, but 2-dimensional at very short distance scales. This is just what one might expect from a spin foam model, since spacetime is fundamentally 2-dimensional in these theories. We discuss properties a spin foam model should have in order to approximate general relativity at large distance scales.'

Length:
09:43