John Baez

Lecture at Loops '05

October 11, 2005

Towards a Spin Foam Model of Quantum Gravity

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.

You can see the transparencies of this talk, and also a video of it:

Here are some of the papers alluded to in this talk, in the order they're mentioned: Here are some general introductions to spin foams:

© 2005 John Baez