What is group field theory? Introduction please?

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Discussion Overview

The discussion centers around the concept of group field theory (GFT) as a framework for quantum gravity. Participants explore its relationship to other theories such as loop quantum gravity (LQG), spin foam models (SF), and causal dynamical triangulation (CDT). Questions are raised regarding the goals of GFT, its connections to physics, and its relative lack of visibility in the scientific community.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants reference Wikipedia's overview of GFT, noting its connection to LQG, SF, and CDT, and question the accuracy of this description.
  • There is a claim that every spin foam can be considered a GFT, suggesting a fundamental relationship between the two concepts.
  • One participant questions the significance of stating that every spin foam is a GFT, implying a need for deeper exploration of the implications.
  • References to various academic papers are provided, indicating ongoing research and discussions surrounding GFT, including its mathematical formulations and theoretical implications.
  • Some participants discuss the tension between GFTs and SFMs, particularly regarding the treatment of gravity as an emergent phenomenon versus a fundamental one.

Areas of Agreement / Disagreement

Participants express a range of views on the nature and implications of GFT, with no clear consensus reached on its definitions or significance. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

Participants highlight various assumptions and dependencies in the definitions and relationships between GFT, LQG, SF, and CDT. There are indications of unresolved mathematical steps and differing interpretations of the theories involved.

ensabah6
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wikipedia says

http://en.wikipedia.org/wiki/Group_field_theory

Overview

Group field theory is a theory of quantum gravity. It is closely related to background independent quantum gravity approaches such as loop quantum gravity and spin foam and causal dynamic triangulation.

It makes use of spin networks as simplex and uses quantum field theory to create a feynman graph over Simplicial manifold

Is this correct?


What is group field theory? What is its relation to LQG, SF, CDT, string theory? What does it try to do and why has it not received much press? What is the goal of group field theory? How does it intend to make contact with physics?

So as to not waste this discussion, could I edit content in wikipedia page as it has nothing.


Are these valid references?

References

References:

http://relativity.livingreviews.org/Articles/lrr-2008-5/ see Sec 6.8 Dynamics: III. Group field theory

http://arxiv.org/abs/hep-th/0505016

http://arXiv.org/abs/gr-qc/0607032


[gr-qc/0607032] The group field theory approach to quantum gravity by D Oriti - 2006 -

[0710.3276] Group field theory as the microscopic description of ... by D Oriti - 2007

http://fqxi.org/data/documents/Oriti Azores Talk.pdf

http://arxiv.org/abs/1002.3592

Linearized Group Field Theory and Power Counting Theorems

Joseph Ben Geloun, Thomas Krajewski, Jacques Magnen, Vincent Rivasseau (Submitted on 18 Feb 2010)
 
Last edited by a moderator:
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Every spin foam is a GFT.

Spacetime as a Feynman diagram: the connection formulation
Michael P. Reisenberger, Carlo Rovelli
http://arxiv.org/abs/gr-qc/0002095

Group field is to spin foam as Boulatov-Ooguri is to Pozano-Regge:
Barrett-Crane model from a Boulatov-Ooguri field theory over a homogeneous space
R. De Pietri, L. Freidel, K. Krasnov, C. Rovelli
http://arxiv.org/abs/hep-th/9907154
 
atyy said:
Every spin foam is a GFT.

Spacetime as a Feynman diagram: the connection formulation
Michael P. Reisenberger, Carlo Rovelli
http://arxiv.org/abs/gr-qc/0002095

Group field is to spin foam as Boulatov-Ooguri is to Pozano-Regge:
Barrett-Crane model from a Boulatov-Ooguri field theory over a homogeneous space
R. De Pietri, L. Freidel, K. Krasnov, C. Rovelli
http://arxiv.org/abs/hep-th/9907154
how does that enlarge the thought content? every sf is a sf.

what is gft?
 
http://arxiv.org/abs/1001.5147

"The fourth avenue starts from approaches to quantum gravity in which gravity is to emerge from a more fundamental theory based on abstract structures that, to begin with, have nothing to do with space-time geometry. Examples are matrix models for 2-dimensional gravity and their extension to 3-dimensions —the Boulatov model [16]— where the basic object is a field on a group manifold rather than a matrix. The Boulatov model was further generalized to a group field theory (GFT) tailored to 4-dimensional gravity [4, 17, 18]. The perturbative expansion of this GFT turned out be very closely related to the vertex expansions in SFMs."

"There is a also a tension between SFMs and GFTs. Although fields in GFTs live on an abstract manifold constructed from a Lie group, as in familiar field theories the action has a free part and an interaction term. The interaction term has a coupling constant, , as coefficient. One can therefore carry out a Feynman expansion and express the partition function, propagators, etc, as a perturbation series in . If one sets = 1, the resulting series can be identified with the vertex expansion of SFMs. But if one adopts the viewpoint that the GFT is fundamental and regards gravity as an emergent phenomenon, one is led to allow to run under the renormalization group flow." [My emphasis]
 

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