Can Spinfoam Quantum Gravity Naturally Incorporate Feynman Diagrams?

[marcus]

This seems to be the goal expressed most clearly at Loops '05.
it is a slight redirection or change in emphasis in the common program.
Matter should naturally occur in quantum gravity. It's explicit.

two leading talks in this regard were by Rovelli and Freidel

In the latter's talk, Feynman diagrams of matter are natural observables of spinfoam quantum gravity. It helps to select the correct spinfoam model if one requires it to contain feynman diagrams---as either a zero gravity limit or as a zero order term in perturbation (I seemed to remember both ideas in Freidel's talk)

I am going to list some recent papers by Freidel or by people he occasionally co-authors with, and also some papers which are cited as being in preparation. I want to get an idea of the focus of future work.

a recent Freidel paper
http://arxiv.org/abs/hep-th/0512113
Effective 3d Quantum Gravity and Non-Commutative Quantum Field Theory
cites this future work:
[17] A Baratin, L Freidel, Hidden quantum gravity in Feynman diagrams[/color], to appear
here are other references the paper cites:
http://arxiv.org/refs/hep-th/0512113

for atmosphere, the acknowledgments in this Oriti/Livine paper http://arxiv.org/abs/gr-qc/0512002 say:

"We would like to thank, for hospitality and beverages, Caffe’ Nero in Cambridge and Cafe’ 1842 in Waterloo, where part of this work was done. D.O. thanks also the Perimeter Institute for hospitality during the early stages of this project, and the Kalahari Meerkat Project for hospitality in the Kuruman River Reserve, South Africa, during its completion."

the above Oriti/Livine paper cites
[22] A. Baratin, L. Freidel, E.R. Livine, Solving Spin Foam Models: Instantons and Group Field Theory[/color], in preparation;

Oriti--- in http://arxiv.org/abs/gr-qc/0512048 ---
also cites [15] A. Baratin, L. Freidel, E. Livine, in preparation;

Oriti--- http://arxiv.org/abs/gr-qc/0512069

Freidel's program is find matter as a natural facet quantum gravity---in particular to get FEYNMAN DIAGRAMS out of SPINFOAM. His Loops '05 talk had the clearest statement of this, that I have heard so far. does anyone besides me have it? AEI-Golm seems to have taken the Loops '05 talks off line---hope they restore them soon---so you have to have already downloaded them.

"Background Independent Quantum Field Theory" was the keynote sounded by Rovelli's Loops '05 talk. Another one which i hope several of us downloaded during November when it was available.

rovelli took a few minutes at the beginning to say where he thinks the field is going. And apparently it it not going merely for a quantum theory of spacetime and its geometry----it is going for a quantum theory of spacetime and matter. A way of reformulating QFT where you do not need a spacetime to build it on. A QFT without underlying spacetime premises---- from which spacetime emerges, instead.

So Rovelli was the one who enunciated the B.I.Q.F.T. goal, but in his paper the aim was more modest: he just went after the graviton propagator. Like Freidel, he was using spinfoam formalism (which now far outweighs the older canonical LQG alternative) and he wanted to be able to calculate things like scattering amplitudes and to derive conventional Newton's law.

If anyone wants Rovelli and Freidel talks, and doesn't have them, is there any way those that have them can share?

 

[Almsco]

This is a crucial point in the development of quantum gravity.