Watch Loops05 Talks Online - No Need to Wait

[john baez]

A friend of mine offered to videotape talks at http://loops05.aei.mpg.de/" , so I contacted Thomas Thiemann (one of the organizers) - and he said that they're already planning to videotape the conference!

So, eventually you'll be able to see all the talks.

But there's no need to wait if you want to see http://math.ucr.edu/home/baez/loops05/" .

 

[marcus]

...

But there's no need to wait if you want to see http://math.ucr.edu/home/baez/loops05/" .

JB's lecture notes are interesting and provocative. Hope others read them and we can discuss some of the meaty/gristly parts at this thread.

 

[Chronos]

Thanks, JB!

 

[garrett]

Since I live in Maui, there aren't many times I wish I were somewhere else in the world -- but this week is one of them. Someone please post when these videos and other materials are up on the net. Thanks!

 

[marcus]

Since I live in Maui, there aren't many times I wish I were somewhere else in the world -- but this week is one of them. Someone please post when these videos and other materials are up on the net. Thanks!

I feel the same way about the Berkeley hills looking out over the bay-----that is, I wish I were in the Berlin area right now and it is an unfamiliar sensation.

I remember checking your garrett lisi website out one time. great site/life. fundamental research plus the outdoors IIRC.
how long have you been in Maui, my imperfect memory was that you were living in coastal southern california

========================

LIVE BLOGGING BY ROBERT HELLING
http://atdotde.blogspot.com/2005/10/others.html

just saw this a Not Even Wrong

 

[Kea]

Looked at Helling's blog. Smolin's talk sounds like it was very interesting. Do we have any slides for it anywhere? Helling says he said something about twisted ribbons and CPT.

 

[Kea]

OK. After a quick Google session: apparently whatever Smolin said has something to do with Small World Networks (of course it's really all Category Theory!) which appear in, for instance

http://arxiv.org/PS_cache/quant-ph/pdf/0503/0503188.pdf

 

[marcus]

glad you found something, Kea. I don't have any leads (judging from the report) about that part of Smolin's talk

 

[garrett]

I remember checking your garrett lisi website out one time. great site/life. fundamental research plus the outdoors IIRC.
how long have you been in Maui, my imperfect memory was that you were living in coastal southern california
========================
LIVE BLOGGING BY ROBERT HELLING

Hey Marcus,

Your memory is in excellent shape -- it just needs updating. I got my PhD in San Diego about 7 years ago, then moved to Maui to windsurf and do physics on my own. I've been hopping between here, Colorado, and California since -- enjoying life the best I can, while at the same time working on how to get the standard model out of pure geometry.

Helling's blog entries were a good read -- though they're really just a tease.

 

[marcus]

News from the conference

Here's a Loop Gravity progress report that Lee Smolin posted on Not Even Wrong today, phrased as a response to Robert Helling. He listed a halfdozen or so significant advances, which I have made into a list by spacing so I can focus on them better:
------quote------
Lee Smolin Says:
October 12th, 2005 at 6:32 am
Hi, if I can put a comment here I didnt figure out how to put on Robert’s blog:
Thanks for the comments...We are not afraid of emphasizing open problems but we do hope that people notice when they are solved.
Hence, I would have hoped you noticed and reported that major progress was described concerning the problem of showing that classical spacetime honestly emerges from background independent theories.
1. Rovelli derived the graviton propagator and hence Newton’s law[/color].
2. Freidel and Livine showed in detail that 2+1 quantum gravity with matter has a low energy limit which is an effective QFT on a non-commutative geometry with deformed Poincare invariance. Both results were derived from spin foam models.
Hence, one can no longer say that there is no understanding of how classical spacetime and low energy qft emerges from these theories[/color].
There was still more.
3. Perez showed how regularization ambiguities in the Hamiltonian constraint may be resolved.
4. Markopoulou discussed a new approach to the low energy limit based on her new paper with Kribs.
5. Loll announced major results showing that 3+1 spacetime emerges from causal dynamical triangulations and that at short distances the theory scales as a 1+1 dimensional theory.
6. Livine and Terno showed how to derive the log(area) corrections to black hole entropy and estimate the rate of Hawking radiation.
7. Starodubtsev reported on work with Freidel in which quantum gravity is defined by a perturbation expansion around a topological quantum field theory where the expansion parameter is G Lambda. This is a very promising direction as there are indications (no proof yet) that this new pert. theory is renormalizable and the low energy limit reproduces QFT in DeSitter spcetime……
These, and other results were based on detailed calculations and are solid results. I would have hoped that your report would have focused on the presentation of these major result.
In the face of this kinds of impressive progress, I was not embarrassed to emphasize open issues or speculate a bit about future directions. So my talk was certainly not representative. By the way, I would have thought that as a particle physicist you would have recognized that what I presented was just a preon model. It was translated into the language of LQG with the help of recent work by Bilson-Thompson. This is new stuff and much remains to be done. But you can also no longer say that there is no proposal for unification of matter and geometry[/color] in LQG.
Still to come are new results on rigorous formulations of the theory and at least one striking new results on quantum cosmology, of relevence for upcoming observations.
----endquote----
this is comment #5, currently the most recent comment, at Woit's blog:
http://www.math.columbia.edu/~woit/wordpress/?p=279#comments

 

[Spin_Network]

Since Smolin is giving us a map of significant QG advances presented at Loops '05, we may as well look up some of the papers he is referring to.
One of the paper is
http://www.arxiv.org/abs/gr-qc/0510052
Geometry from quantum particles
David W. Kribs, Fotini Markopoulou
17 pages
"We investigate the possibility that a background independent quantum theory of gravity is not a theory of quantum geometry. We provide a way for global spacetime symmetries to emerge from a background independent theory without geometry. In this, we use a quantum information theoretic formulation of quantum gravity and the method of noiseless subsystems in quantum error correction. This is also a method that can extract particles from a quantum geometric theory such as a spin foam model."
Fotini Markopoulou doesn't need introduction. Here is David Kribs homepage
http://www.uoguelph.ca/~dkribs/
His posting on arxiv goes back to 2003, he got his PhD in 2000, from Waterloo.
Currently Assistant Professor at Guelph. An article he co-authored with Richard Laflamme and David Poulin, published in Physical Review Letters, got a nice spread in Science journal here:
http://www.uoguelph.ca/~dkribs/Science0705.pdf
Here's his research interests page:
http://www.uoguelph.ca/~dkribs/researchfront.html

marcus, I posted to the general relativity board early today:https://www.physicsforums.com/showthread.php?t=93690

due to the new guidlines about correct postings, maybe my thread could be removed by a mentor, not for double postings?

I had considered posting to your loop05, but thought the paper and title was
not part of the loop talk, great to have all the relevant papers in one place,(here in the loop05) thanks for keeping tabs.

 

[marcus]

marcus, I posted to the general relativity board early today:https://www.physicsforums.com/showthread.php?t=93690
due to the new guidlines about correct postings, maybe my thread could be removed by a mentor, not for double postings?
I had considered posting to your loop05, but thought the paper and title was
not part of the loop talk, great to have all the relevant papers in one place,(here in the loop05) thanks for keeping tabs.

I thought about it, and I defer to you. I have plenty to think about without this Markopoulou et al paper. And either forum makes sense since there is no sharp division between quantum gravity and general relativity (one is the quantization of the other). So I am editing so as to minimize discussion of the Markopoulou here---whatever there is can go to your thread

 

[Ratzinger]

I'm in Berlin right now and found out that Lee Smolin is giving a public lecture, named "The unfinished revolution: finishing what Einstein started". So how could I resist?

He started with the question "what is at stake?". Answer: all the big questions (what is time, space, physical law? why is the universe hospitable to life?). After going through the three revolutions (Aristotele, Newton, Einstein) and their notions of space, time, etc., he stressed the importance of relationality in present-day world view, both in qm and gr.

(He said Leibniz was right about relationality, but he had no workable physical theory, so scientist followed Newton for 200 years. Mach and then Einstein rediscovered relational thinking.)

So what are the approaches to attack quantum gravity? There are two, according to Smolin.
1. Einsteins way (rethinking the concepts of space and time, and especially overworking qm)

2. everybody elses way (string theory, loops, etc.)

He admitted that he researches everybody elses way, but pointed out the need for radical and rebellious thinking the Einstein way. He also praised Penrose in that context.


He ended with saying that physicist are standing in the lights and shadows of Einsteins. Lights: Einstein's theories, that they work with. Shadows: neglecting for what is at stake and not sharing Einstein vision of a complete understanding of the universe by rejecting qm.

Edit: 1. I think Renata Loll was also sitting in the audience.
2. Smolin was very excited by the coming representation of Winkler and another guy on Friday.

 

[marcus]

I'm in Berlin right now and found out that Lee Smolin is giving a public lecture, named "The unfinished revolution: finishing what Einstein started". So how could I resist?
He started with the question "what is at stake?". Answer: all the big questions (what is time, space, physical law? why is the universe hospitable to life?). After going through the three revolutions (Aristotele, Newton, Einstein) and their notions of space, time, etc., he stressed the importance of relationality in present-day world view, both in qm and gr.
(He said Leibniz was right about relationality, but he had no workable physical theory, so scientist followed Newton for 200 years. Mach and then Einstein rediscovered relational thinking.)
So what are the approaches to attack quantum gravity? There are two, according to Smolin.
1. Einsteins way (rethinking the concepts of space and time, and especially overworking qm)
2. everybody elses way (string theory, loops, etc.)
He admitted that he researches everybody elses way, but pointed out the need for radical and rebellious thinking the Einstein way. He also praised Penrose in that context.
He ended with saying that physicist are standing in the lights and shadows of Einsteins. Lights: Einstein's theories, that they work with. Shadows: neglecting for what is at stake and not sharing Einstein vision of a complete understanding of the universe by rejecting qm.
Edit: 1. I think Renata Loll was also sitting in the audience.
2. Smolin was very excited by the coming representation of Winkler and another guy on Friday.

Ratzinger, what luck! So glad you were on the scene and could report. Thanks!
I see that the public talk was at the Urania Science Center in downtown Berlin. sounds like a great venue!

 

[marcus]

2. Smolin was very excited by the coming representation of Winkler and another guy on Friday.

here's what that could be about:
http://loops05.aei.mpg.de/index_files/abstract_winkler.html
Quantum Black Holes I: Kinematics
Abstract: We discuss a novel approach to a quantization of spherically symmetric black holes. We present the kinematical setup and focus in particular on a genuinely quantum definition of what a quantum black hole is which avoids fixing classical inputs such as boundaries a priori.

http://loops05.aei.mpg.de/index_files/abstract_husain.html
Prof. Viqar Husain
Quantum Black holes II: Dynamics
Abstract: I will describe an approach to studying gravitational collapse in quantum gravity. The model studied is the spherically symmetric gravity-scalar system, which is a 2D field theory. An ADM Hamiltonian formalism is utilised, together with an alternative quantisation scheme with similarities to loop quantum gravity. The calculational scheme allows an initial quantum state of matter and metric excitations to be followed to black hole formation, and beyond.

what paper already posted would correspond most closely to the plannned talks?
http://www.arxiv.org/abs/gr-qc/0503031
Flat slice Hamiltonian formalism for dynamical black holes
V. Husain, O. Winkler
11 pages
Phys.Rev. D71 (2005) 104001
"We give a Hamiltonian analysis of the asymptotically flat spherically symmetric system of gravity coupled to a scalar field. This 1+1 dimensional field theory may be viewed as the 'standard model' for studying black hole physics. Our analysis is adapted to the flat slice Painleve-Gullstrand coordinates. We give a Hamiltonian action principle for this system, which yields an asymptotic mass formula. We then perform a time gauge fixing that gives a Hamiltonian as the integral of a local density. The Hamiltonian takes a relatively simple form compared to earlier work in Schwarzschild gauge, and therefore provides a setting amenable to full quantisation."

 

[Spin_Network]

I'm in Berlin right now and found out that Lee Smolin is giving a public lecture, named "The unfinished revolution: finishing what Einstein started". So how could I resist?
He started with the question "what is at stake?". Answer: all the big questions (what is time, space, physical law? why is the universe hospitable to life?). After going through the three revolutions (Aristotele, Newton, Einstein) and their notions of space, time, etc., he stressed the importance of relationality in present-day world view, both in qm and gr.
(He said Leibniz was right about relationality, but he had no workable physical theory, so scientist followed Newton for 200 years. Mach and then Einstein rediscovered relational thinking.)
So what are the approaches to attack quantum gravity? There are two, according to Smolin.
1. Einsteins way (rethinking the concepts of space and time, and especially overworking qm)
2. everybody elses way (string theory, loops, etc.)
He admitted that he researches everybody elses way, but pointed out the need for radical and rebellious thinking the Einstein way. He also praised Penrose in that context.
He ended with saying that physicist are standing in the lights and shadows of Einsteins. Lights: Einstein's theories, that they work with. Shadows: neglecting for what is at stake and not sharing Einstein vision of a complete understanding of the universe by rejecting qm.
Edit: 1. I think Renata Loll was also sitting in the audience.
2. Smolin was very excited by the coming representation of Winkler and another guy on Friday.

Many thanks for the first hand review!

Marcus has highlighted the paper authors "other guy".

It is very interesting that Smolin mentions with praise Penrose?

It also amazing that "Light + Shade" were mentioned in a specific context?..I have been listening to this:http://www.mikeoldfield.com/flash/light&shade.html

whilst emerged in some recent books and downloaded papers.

The Light and Shade music, is playing in "my" background as I delve into scientific foregrounds!

Thanks again.

 

[Spin_Network]

here's what that could be about:
http://loops05.aei.mpg.de/index_files/abstract_winkler.html
Quantum Black Holes I: Kinematics
Abstract: We discuss a novel approach to a quantization of spherically symmetric black holes. We present the kinematical setup and focus in particular on a genuinely quantum definition of what a quantum black hole is which avoids fixing classical inputs such as boundaries a priori.
http://loops05.aei.mpg.de/index_files/abstract_husain.html
Prof. Viqar Husain
Quantum Black holes II: Dynamics
Abstract: I will describe an approach to studying gravitational collapse in quantum gravity. The model studied is the spherically symmetric gravity-scalar system, which is a 2D field theory. An ADM Hamiltonian formalism is utilised, together with an alternative quantisation scheme with similarities to loop quantum gravity. The calculational scheme allows an initial quantum state of matter and metric excitations to be followed to black hole formation, and beyond.
what paper already posted would correspond most closely to the plannned talks?
http://www.arxiv.org/abs/gr-qc/0503031
Flat slice Hamiltonian formalism for dynamical black holes
V. Husain, O. Winkler
11 pages
Phys.Rev. D71 (2005) 104001
"We give a Hamiltonian analysis of the asymptotically flat spherically symmetric system of gravity coupled to a scalar field. This 1+1 dimensional field theory may be viewed as the 'standard model' for studying black hole physics. Our analysis is adapted to the flat slice Painleve-Gullstrand coordinates. We give a Hamiltonian action principle for this system, which yields an asymptotic mass formula. We then perform a time gauge fixing that gives a Hamiltonian as the integral of a local density. The Hamiltonian takes a relatively simple form compared to earlier work in Schwarzschild gauge, and therefore provides a setting amenable to full quantisation."

Marcus, I believe this may be of relevance:http://www.arxiv.org/abs/gr-qc/0507088
and an early paper which I believe your linked paper followed from:http://www.arxiv.org/abs/gr-qc/0210011
and this:http://www.arxiv.org/abs/gr-qc/0412039

 

[Spin_Network]

Marcus, I believe this may be of relevance:http://www.arxiv.org/abs/gr-qc/0507088
and an early paper which I believe your linked paper followed from:http://www.arxiv.org/abs/gr-qc/0210011
and this:http://www.arxiv.org/abs/gr-qc/0412039

This could be it?..the test of tests!

http://arxiv.org/abs/quant-ph/0503001

 

[marcus]

This could be it?..the test of tests!
http://arxiv.org/abs/quant-ph/0503001

did you ever wonder how someone with a name like "Joy Christian" could ever pass peer review? and the paper is being published in Physical Review Letters!

seriously, thank you for taking care of business on this thread while we are waiting for news from the conference, most likely by the grace of John Baez, may he report soon!

I have been trying to understand Viqar Husain and Oliver Winkler paper
http://www.arxiv.org/abs/gr-qc/0503031
Flat slice Hamiltonian formalism for dynamical black holes
because in that paper they say they have IN PREPARATION one which probably they will deliver tomorrow at the conference.

the one in preparation is not yet available of course, they saved it for the conference. It is called
Quantum Hamiltonian for dynamical black holes

 

[marcus]

I'm in Berlin right now and found out that Lee Smolin is giving a public lecture, named "The unfinished revolution: finishing what Einstein started". So how could I resist?
He started with the question "what is at stake?". Answer: all the big questions (what is time, space, physical law? why is the universe hospitable to life?). ...

Edit: 1. I think Renata Loll was also sitting in the audience.
2. Smolin was very excited by the coming representation of Winkler and another guy on Friday.

Ratzinger, I see that your biography shows you won the Nobel prize in 2009. What was it in? I hope physics and not something dumb like economics.

Why are you always in Acapulco when the night clubs are better in Berlin?

 

[Ratzinger]

For what the noble prize? The world formula, of course (c’mon Marcus!). Even though a further refinement of game theory sounds tempting, too.

As far as the Berlin night life goes, it’s overestimated. Well, you are save here from foam discos and crazy spring breakers, but hip underground clubs with techno hammering and weird dress codes isn’t my idea of a perfect night either.

But honestly Marcus, you are only killing time here by asking me this while waiting till finally Prof. Baez is answering. You know what, I can picture how all the conference members went together to nearby Caputh (maybe even did some sailing) trying to catch some Einstein spirit. Then came back and quantum gravity solved.

 

[marcus]

For what the noble prize? The world formula, of course...

I suppose that you are kept so busy at the Vatican that you simply don't have time to think about your Nobel prize these days.

========a little news=========

Lee Smolin posted again at Peter Woit's blog:

---quote---
October 16th, 2005 at 5:52 am
Dear Robert,

Thanks, perhaps I misread you. I was perhaps over-reacting to your opening: “I sneaked into the Loops 05 conference…” I hope this was not how you really felt. Certainly, all were welcome, no one was checking badges.

But I also don’t understand why, after doing a good job of just reporting, you feel the need to add comments like, “I expect to read some popular texts on LQG where these topics will be mentioned as ‘understood/solved by the canonical approach’?” Perhaps you are used to an atmosphere in which people are not careful to distinguish conjecture, evidence and proof, but this is not us.

As to the other points, why not read the papers? Kribs and Markopoulou is gr-qc/0510052. Regarding singularity avoidance in the full QFT, the papers are by Johannes Brunnemann and Thomas Thiemann, gr-qc/0505032 and 033. Not surprisingly, the situation is quite a bit more complicated in the full theory than it is in the models, but their conclusion is not pessimistic. They do find states on which the inverse volume is not bounded. But they show it is bounded on a large class of coherent states. The last line of their abstract states, “After outlining what would be required, we present the results of a calculation for LQG which could be a first indication that our criteria at least for curvature singularity avoidance are satisfied in LQG.”

If I may add, the atmosphere in the quantum gravity community is pretty open. Most of us know and easily acknowledge that what we are doing is high risk. Most of us are very self-critical and any honest critic will be made to feel very welcome because you cannot be more critical to us than we are to ourselves.

Looking forward to seeing you next time,

Lee
----endquote---

it was comment 21 of this thread:
http://www.math.columbia.edu/~woit/wordpress/?p=279#comments

The issue of removing the cosmological (classical) singularity is important. Thiemann et al made the point that LQG is not the same as LQC (which is simplified by assuming lots of symmetry) and so it requires additional effort to prove that the big bang infinities are removed in the full LQG theory. In fact Bojowald, who established LQC and got the first results, had been making that point all along, but not so emphatically as Thiemann.

Thiemann and Brunnemann results were hopeful, if not conclusive, as I recall. This seems to be the point of Smolin's quote from their abstract.

 

[marcus]

A friend of mine offered to videotape talks at http://loops05.aei.mpg.de/" , so I contacted Thomas Thiemann (one of the organizers) - and he said that they're already planning to videotape the conference!
So, eventually you'll be able to see all the talks.
But there's no need to wait if you want to see http://math.ucr.edu/home/baez/loops05/" .

JB's TWF #222 is out!

http://math.ucr.edu/home/baez/week222.html

Includes a report from the conference. JB thanks for the whole TWF series, much fascinating about many topics, much news, now photographs.
And especially for the current one---a lot of interest in Loops '05 and this is our first report from a participant. Hope your talk went well.

 

[marcus]

Here is a sample. Scroll about 2/3 down page:

----exerpt TWF #222---
Now I want to talk about Loops '05!

Instead of trying to review all the talks - a hopeless task, since there were 86 - I'll just mention the two strands of work I find most exciting.

First, there's new evidence that a quantum theory of pure gravity (meaning gravity without matter) makes sense in 4-dimensional spacetime.

To understand why this is exciting, you have to realize that in some quarters, the conventional wisdom says a quantum theory of pure gravity can't possibly make sense, except as a crude approximation at large distance scales, because this theory is "perturbatively nonrenormalizable".

Very roughly, this means that as we zoom in and look at the theory at shorter and shorter distance scales, it looks less and less like a "free field theory" where gravitons zip about without interacting. Instead, the interactions get stronger and more complicated!

So, in the jargon of the trade, we don't get a "Gaussian ultraviolet fixed point".

Huh?

Well, roughly, an "ultraviolet fixed point" is a quantum field theory that keeps looking the same as you keep viewing it on shorter and shorter distance scales. A "Gaussian" ultraviolet fixed point is one that's also a free quantum field theory: one where particles don't interact.

If quantum gravity approached a Gaussian ultraviolet fixed point as we zoomed in, we could calculate what gravitons do at arbitrarily high energies (at least perturbatively, as power series in Newton's constant - no guarantee that these series converge). Particle physicists would then be happy and say the theory was "perturbatively renormalizable".

But, it's not.

The conventional wisdom concludes that to save quantum gravity, we must include matter of precisely the right sort to make it perturbatively renormalizable. This is the quest that led people first to supergravity and ultimately to superstring theory - see "week195" for more of this story.

But, as far back as 1979, the particle physicist Weinberg raised the possibility that pure quantum gravity is "nonperturbatively renormalizable", or "asymptotically safe". This means that as we zoom in and look at the theory at shorter and shorter distance scales, it approaches some theory other than that of noninteracting gravitons.

In other words, Weinberg was suggesting that pure quantum gravity approaches a non-obvious ultraviolet fixed point - possibly a "non-Gaussian" one.

The big news is that this seems to be true!
----end quote---

JB I will answer your next post's question here, with an EDIT, to save making a separate post.

How'd you manage that?

Just coincidence. I happened to visit your site a little while ago to see if #222 was up, and it was, so I came here and put link. Your presence here is a pleasure. Hope to hear more about the conference eventually.

 

[john baez]

JB's TWF #222 is out!
http://math.ucr.edu/home/baez/week222.html
Includes a report from the conference. JB thanks for the whole TWF series, much fascinating about many topics, much news, now photographs.

Sure, but I'm still in shock - 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?

Hope your talk went well.

I think so! Due to severe jetlag I only got about 5 hours of sleep the night before, so I was somewhat dazed, but I'd prepared the talk so carefully I was able to deliver it without screwing up, and some people said they liked it, so I guess it was okay.

 

[selfAdjoint]

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]

We old hands here have learned you can never get one up on Marcus!

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]

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
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

 

[marcus]

http://arxiv.org/gr-qc/0506067
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)

 

[marcus]

related talks given at Loops '05
John Barrett
http://loops05.aei.mpg.de/index_files/abstract_barrett.htmlhttp://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[/color] 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]

...
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[/color] 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.