John Baez

Lecture at the Workshop on Quantum Gravity in the Americas: Status and Future Directions

October 29, 2004

The Problem of Dynamics in Quantum Gravity

The problem of dynamics  in quantum gravity is still a big challenge. We don't know how to make spacetime into a truly dynamical entity with local degrees of freedom while taking quantum theory into account. Neither string theory, nor loop quantum gravity, nor the spin foam and causal dynamical triangulation approaches have yet found a background-free quantum theory with local degrees of freedom propagating causally. We sketch some avenues for making progress in this direction.

Click on this to see the transparencies:

Here are some of the papers alluded to in this talk: I also mentioned some work that has not yet appeared on the arXiv. The work of Joshua Willis on no-go theorems for spin networks with compact gauge group has not yet appeared, nor has the work of my student Miguel Carrión Álvarez on Wilson loop dynamics in quantum electromagnetism: this is his PhD thesis, which should be finished by the end of this year! The work of Laurent Freidel and Artem Starodubtsev on 4d quantum gravity as a perturbation of a TQFT has also not appeared yet, but it's foreshadowed in the papers by Starodubtsev listed above. Finally, the so-called "LOST theorem" is the work of Lewandowski, Okolow, Sahlmann and Thiemann. This result has not yet appeared in its entirety, so its name is a pun, but aspects of it can be found in the papers by these authors listed above.

I also wrote an issue of This Week's Finds about this conference: week208.

© 2004 John Baez