Is 3D Quantum Gravity Equivalent to a TQFT?

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SUMMARY

The discussion centers on the equivalence of 3D quantum gravity and topological quantum field theory (TQFT). It references the foundational work of loop quantum gravity (LQG) spin foam models based on BF theory, highlighting that while 3D quantum gravity was assumed to be a TQFT, Witten's commentary indicates unresolved issues as of 2007. The existence of quantum pure 3D gravity was still uncertain in 2009, raising questions about the relationship between quantum 3D BF theory and quantum 3D gravity. The Ponzano-Regge model and Turaev-Viro model are mentioned as potential frameworks for understanding this relationship.

PREREQUISITES
  • Understanding of loop quantum gravity (LQG) spin foam models
  • Familiarity with BF theory and its implications in quantum gravity
  • Knowledge of the Ponzano-Regge model and Turaev-Viro model
  • Basic grasp of topological quantum field theory (TQFT)
NEXT STEPS
  • Research the implications of Witten's commentary on 3D quantum gravity and TQFT
  • Explore the Ponzano-Regge model in detail and its applications in quantum gravity
  • Investigate the Turaev-Viro model and its role in regularizing quantum gravity theories
  • Examine recent developments in 3D quantum gravity and its current status in theoretical physics
USEFUL FOR

The discussion is beneficial for theoretical physicists, researchers in quantum gravity, and students exploring the intersections of quantum field theory and gravity.

atyy
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I'd always assumed it was, since LQG spin foam models are based on BF theory. And it is typically said that in 3D it is BF, and in 4D constrained BF. The 4D quantum case is not known to be gravity, but I had thought the 3D case was.

Yet in http://math.ucr.edu/home/baez/week254.html Baez commentary on Witten's http://arxiv.org/abs/0706.3359 says "Even though Witten is now claiming 3d quantum gravity can't be a TQFT ...", which means the question was not resolved as of 2007.

Apprently, even the existence of quantum pure 3D gravity wasn't known in 2009 http://arxiv.org/abs/0906.1313 (see the fourth problem).

So is quantum 3D BF is quantum 3D gravity?

What is the status of this problem now?
 
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I just remembered, isn't it supposed to naively be the Ponzano-Regge model, and properly regularized by the Turaev-Viro model? eg. http://arxiv.org/abs/0803.3319
 

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