Spin Foams & AdS/CFT: Lattice Gauge Theories

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Discussion Overview

The discussion revolves around the relationship between spin foams and lattice gauge theories, particularly in the context of the AdS/CFT correspondence. Participants explore theoretical connections, implications for gravity models, and the potential for further research in this area.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants note that certain lattice gauge theories can be expressed as spin foams, referencing Conrady's statement about their historical context in strong coupling expansions.
  • Others discuss the generalization of 4D spin foam models to finite groups, suggesting that while the immediate interpretation as gravity models may be lost, they could still provide insights into translation symmetries and renormalization techniques.
  • A participant expresses confusion about the lack of significant efforts to connect holographic duality with loopy gravity approaches, suggesting that such connections could be fruitful.
  • Another participant mentions that Barrett acknowledges the existence of spin foam models of lattice gauge theory but does not connect them to AdS/CFT, which raises questions about the nature of induced gravity.
  • There are references to various papers that explore connections between loop quantum gravity and AdS/CFT, with some participants questioning the explicit use of spin foams in these discussions.
  • Participants share multiple references to papers related to BF theory with matter and string theory, indicating ongoing research in related areas.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the connections between spin foams, lattice gauge theories, and AdS/CFT. Multiple competing views and questions remain unresolved, particularly regarding the significance and implications of these theoretical frameworks.

Contextual Notes

Some discussions highlight limitations in the current understanding of the relationship between these theories, including missing connections and unresolved mathematical steps. The scope of the discussion is primarily theoretical and speculative.

Who May Find This Useful

Researchers and students interested in theoretical physics, particularly those focused on quantum gravity, lattice gauge theories, and holographic duality may find this discussion relevant.

atyy
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Apparently some lattice gauge theories can be formulated as spin foams. Conrady even says "The concept of spin foams is both new and old. It is old in the sense that it is just another name for the plaquette diagrams that appear in the strong coupling expansion of lattice gauge theories". Do these lattice gauge theories have any gravity dual in the AdS/CFT sense?

Reisenberger, http://arxiv.org/abs/gr-qc/9412035
Oeckl and Pfeiffer, http://arxiv.org/abs/hep-th/0008095
Conrady, http://arxiv.org/abs/gr-qc/0504059v2
 
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marcus has just listed in his bibliography a paper that is in the spirit of this question https://www.physicsforums.com/showpost.php?p=3222193&postcount=1451 .

http://arxiv.org/abs/1103.6264
Spin foam models with finite groups
Benjamin Bahr, Bianca Dittrich, James P. Ryan

"As we will show in this work the 4D spin foam models, which as gravity models are based on SO(4), SO(3, 1) or SU(2), can be easily generalized to finite groups (or more generally tensor categories [35]). Although the immediate interpretation as gravity models is lost one can nevertheless ask whether translation symmetries are realized and if not how these could be implemented. This question is much easier to answer for finite groups than in the full gravity case. One can therefore see these models as a test bed for the full theory. This also applies for renormalization and coarse graining techniques which need to be developed to access the large scale limit of spin foams. With finite group models it might be in particular possible to access the many–particle (that is many simplices or building blocks in the triangulation) and small spin (corresponding to small geometrical size of the building blocks) regime. This is in contrast to the few particle and large spin (semi–classical) regime [36] which is accessible so far.

In the emergent gravity approaches [37] one attempts to construct models, which do not necessarily start from gravitational or even geometrical variables, but nevertheless show features, typical of gravity."
 
There is this old paper my Simeon Hellerman which is partially related: http://arxiv.org/abs/hep-th/0207226

More generally, I can't figure out why there isn't a large effort trying to make a connection between holographic duality and loopy gravity approaches. Given what we know about holography already it seems to me almost guaranteed to be a gold mine. And yet apart from a few famous papers from some years ago I'm not aware of anything major being done. It's probably what I would work on if I was a loop person.
 
Another loopy paper thinking about gravity without gravity: http://arxiv.org/abs/1101.6078 .

Barrett explicitly says there are spin foam models of lattice gauge theory, but there is no mention of AdS/CFT, which to my mind is a realization of the spirit of induced gravity.

Strominger has a few interesting comments about induced gravity and black hole entropy here: http://arxiv.org/abs/0906.1313 .

The only loop paper I can think of that draws an explicit connection to AdS/CFT is http://arxiv.org/abs/0905.3627 .

I wonder if Krasnov is still thinking about this http://arxiv.org/abs/hep-th/0311162 . He actually preceded the current twistor craze, and is cited by Witten (though Witten's paper took a different approach, and I'm not sure Witten's paper is directly related to current fashion, except in spirit).

Physics Monkey said:
And yet apart from a few famous papers from some years ago I'm not aware of anything major being done.

What are these famous papers from some years ago?
 
Last edited:
atyy said:
...
The only loop paper I can think of that draws an explicit connection to AdS/CFT is http://arxiv.org/abs/0905.3627 ...

This paper cites Freidel Livine Ponzano-Regge work, but I don't find explicit use of spinfoams.
http://arxiv.org/abs/0804.0632 .

I think you know the paper but point to it since I didn't not see it mentioned here. May not be close enough.
 

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