Loops '05

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selfAdjoint

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john baez said:
I spent all day writing "week222", and then I came here to post a link to it... but I found you'd beaten me to it! How'd you manage that?
We old hands here have learned you can never get one up on Marcus!
 

marcus

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selfAdjoint said:
We old hands here have learned you can never get one up on Marcus!
:biggrin: you jest, and what happened yesterday was coincidence, not diligence, on my part. However here is a case of diligence: Peter Woit recently posted a review of Larry Krauss new book

http://www.math.columbia.edu/~woit/wordpress/?p=281

It seems he liked it----and accordingly copied out for us numerous pithy epigrammatic quotes
 

marcus

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Well it looks like we should all read this June 2005 Perimeter-Cambridge collaboration. Or at least read carefully IN it, especially intro&conclusions, and think a lot about it. Because JB is giving us blindingly obvious signs to do this.

http://arxiv.org/gr-qc/0506067 [Broken]
A group field theory for 3d quantum gravity coupled to a scalar field
Laurent Freidel, Daniele Oriti, James Ryan
11 pages
"We present a new group field theory model, generalising the Boulatov model, which incorporates both 3-dimensional gravity and matter coupled to gravity. We show that the Feynman diagram amplitudes of this model are given by Riemannian quantum gravity spin foam amplitudes coupled to a scalar matter field. We briefly discuss the features of this model and its possible generalisations."

I think the equations in this, sandwiched in between the intro and conclusions, have a beautiful "pre-categorical" look. Only it is all in 3D. If similar work could be done in 4D one might say the QG problem was solved. So the suspenseful issue is extending the results to one-higher dimension.

I am not saying anything that requires any intelligence, i think, anybody who reads this June 2005 Freidel et al would come to similar conclusions.

JB mentions he has these students Wise and Morton and he anticipates fun wising and mortoning these Freidel results.

I decided to change my sig to include this Freidel link
 
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marcus

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http://arxiv.org/gr-qc/0506067 [Broken]
A group field theory for 3d quantum gravity coupled to a scalar field
Laurent Freidel, Daniele Oriti, James Ryan
Isnt the idea nice that you can represent matter as a "topological defect"?
You excise a feynman-diagram out of the spinfoam and that corresponds to putting the life-story of a particle into it. the mind dances a jig

BTW Freidel seems to like the letter DALETH from the hebrew alphabet. IIRC he was already using it in last years papers with David Louapre. Here he is using the Daleth to stand for a Feynman-graph (that is embedded in his spinfoam, if I understand right, he can excise). Daleth looks like a Roman Cap L rotated 180 degrees in the plane of the paper. But written with the tail of a cat dipped in ink (instead of my usual ballpoint)
 
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marcus

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related talks given at Loops '05
John Barrett
http://loops05.aei.mpg.de/index_files/abstract_barrett.html


http://loops05.aei.mpg.de/index_files/abstract_noui.html
Karim Noui
Creation and anhiliation of particles in 3D gravity: toward a background independant field theory



http://loops05.aei.mpg.de/index_files/abstract_starodubtsev.html
Artem Starodubtsev
Scattering problem in background independent quantum gravity
Four dimensional topological field theory allows to define matter particles as charges of the gauge group breaking the gauge symmetry at a point. This is analogous to Deser/Jackiw and t'Hooft particles in 3d gravity. The degrees of freedom of General Relativity can also be introduced by symmetry breaking of the same topological field theory. This provides a framework in which gravity and matter can be considered from a unified point of view. In this framework we study scattering of matter particles due to quantum gravity effects.
 

marcus

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...
John Barrett
http://loops05.aei.mpg.de/index_files/abstract_barrett.html
Three-dimensional quantum gravity coupled to matter

http://loops05.aei.mpg.de/index_files/abstract_noui.html
Karim Noui
Creation and anhiliation of particles in 3D gravity: toward a background independant field theory

http://loops05.aei.mpg.de/index_files/abstract_starodubtsev.html
Artem Starodubtsev
Scattering problem in background independent quantum gravity
Four dimensional topological field theory...
We can expect videos of these and other talks to be available at the Loops website. I heard indirectly that the conference organizers plan to have videos up at the site by beginning of next week.

sounds like a lot of work for the staff at AEI. hope it's not too much of a burden. I guess the thing to do is just check at the above links every so often to see if video files have appeared.
 

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