Loops Foams Workshop (3-8 March Zakopane)

[marcus]

http://www.fuw.edu.pl/~kostecki/zakopane08/

Last year about this time there was a Zakopane Quantum Gravity School, we got some great pictures reports and comment from Francesca, F-H, Alejandro Satz, and also the main coordinator Richard Kostecki posted some here at PF about it.

Zakopane is a beautiful ski resort. They needed more and larger whiteboards but otherwise it seemed perfect. It was put on for about 70 postdocs and graduate students beginning research in QG, so it covered a broad menu of active research topics.

Now this year the ESF (European Science Foundation) people have organized another QG event there, but this time it is a WORKSHOP which is different from a school. It is for established experts----invitation only.

Here is a brief summary:
* LQG dynamics: Master constraint programme, status of Hamiltonian constraint, volume operator, relational observables, Loop Quantum Cosmology
* Spin foam models: The new models, effective non-commutative field theory, graviton propagator, Group Field Theory, continuum/semiclassical limit
* Relation between LQG and Spin-foam models: Kinematics, dynamics, covariant LQG, Group Field Theory, 2+1 gravity

Here is the organizing committee:
Hanno Sahlmann
Fernando Barbero
John Barrett
Kristina Giesel
Jerzy Lewandowski
Daniele Oriti

The workshop has a clear focus on Loop-Foam QG, so that some important related areas aren't covered----Triangulaions (CDT), Braid Matter (bid to get the standard particles topologically in LQG spin networks), Asymptotic Safety, ties to Noncommutative Geometry, Modified Gravity. The narrow focus is timely because progress now being made in QG dynamics seems to resolve longstanding difficulties in that department.

 

[marcus]

Francesca, who sometimes posts here, is one of the participants. I hope we hear from her about the workshop!
With one or two notable exceptions, the list of 50-some participants includes everybody you would expect, nearly all the prominent people in the Loops-Foams research community (as far as I can see). Fewer than half are scheduled to give talks. A lot of discussion has been scheduled.
It seems like a way to keep everybody "in the loop" that is all the active researchers should be up-to-date, apprised of the current status on each front. My impression is that Loops Foams is a fast-moving field now and this kind of workshop makes sense in that context----you get to hear the current developments in each of half a dozen related areas where progress is being made.
Monday 12:00 Master constraint and AQG (Thiemann)
14:30 Discussion AQG vs. LQG
15:00 Volume spectrum (Brunnemann)
16:00 Dirac Observables (Dittrich)
17:40 Black hole spectrum (Diaz-Polo)

Tuesday 12:00 Isotropic models in LQC (Ashtekar)
14:30 Selfadjointness of Ham. constraint (Pawlowski)
15:10 Hybrid LQC (Mena)
16:10 Effective EOM in LQC (Bojowald)
17:50 (Non-)embedding LQC in LQG (Fleischhack)

Wednesday everybody goes skiing in the morning
14:30 2+1 gravity (+ matter): canonical vs. SF (Noui)
16:20 Graviton propagator (Speziale)
18:00 SF structure for field theory (Baratin)
18:40 TBA (Meissner)

Thursday 12:00 New vertex I (Rovelli)
14:30 New vertex II (Freidel)
16:20 Technical aspects new vertex (Engle)
17:40 Results for graviton propagator (Bianchi)
18:20 New models for 2+1/3+1 (Tlas)

Friday 12:00 Group field Theory (Ryan)
14:30 Covariant LQG and spin foams (Alexandrov)
16:20 Matter coupling in SF (Fairbairn)
17:40 DSR from quantum gravity (Kowalski-Glikman)

Saturday 12:00 Spherical LQC : towards complete space-time (Pullin)
12:40 QFT on quantum background (Kaminski)

 

[marcus]

This is an interesting change. We haven't heard anything about the workshop!

Some people who occasionally post here are attending. Maybe people in the LQG community have reacted against media attention, so they are not talking to outside and we at PF are included in the blackout. I could understand them being tired of science journalism and the bad effect of media hype on science. Perhaps if I were one of them I would be wanting a quiet workshop with only 50 or so other people.

Check out the list of participants here:
http://www.fuw.edu.pl/~kostecki/zakopane08/
Almost without exception everybody who has made a significant research contribution to LQG/Spinfoam during the period since 2005 is there.

 

[f-h]

Give us a break, we're barely back home yet!

But yeah it was a good workshop, where good work was done continuing on the themes that have been discussed over the last 2-3 years with a particular focus on Loops and Foams (aptly). So nothing much more to say really then what you could infer from the webpage anyways. :)

 

[MTd2]

So, did anything interesting happen there? I just see the scheadule and the participants list

 

[f-h]

What is your definition of interesting?

 

[francesca]

I think that the most interesting thing we saw in Zako is the good collaborative enviroment. Maybe in the past the different points of view made the reciprocal understanding more difficult, while naw I see a concrete desire of convergence. Cool.

 

[MTd2]

What is your definition of interesting?

My definition of interesting is providing at least a bit of information to the outsiders about the discussions, even a bit. There is nothing there. No presentations, no new papers, not even a summary of the technical stuff there. So, it's like telling me "You didn't go there, nothing to see, move along, please." So, for me, there is nothing interesting there. Just a boring website.

 

[f-h]

The point was, as Francesca said, to talk about the stuff published in the last year, gain some understanding of each others thoughts, etc. Convergence. There are many ideas in the literature and people need to talk to each other to find the key similarities and diferences. Understand what you're doing and what I'm doing. Gradual refinement of published ideas and concepts that are being developed, graviton propagator, new vertex models, etc. Take a look at the schedule on the webpage.

So I'm afraid there's not much to tell to outsiders, certainly nothing of the scale of last years "Effective Field Theory is here and brought numbers along."

Sorry.

 

[f-h]

Adding, maybe someone else can think of a better way to extract interesting messages to outsiders then I can, this obviously partially reflects my own research interests :)

 

[MTd2]

Adding, maybe someone else can think of a better way to extract interesting messages to outsiders then I can, this obviously partially reflects my own research interests :)

How about telling why some ideas seemed more appealing or less appealing after the workshop? How about telling some new little insights or ideas that occurred to you during the workshop, or other people, while discussing the topics personaly with them?

Afterall, if nothing new happened, or any no one could have a new idea, there would be no reason to arrange a meeting...

 

[marcus]

I think that the most interesting thing we saw in Zako is the good collaborative enviroment. Maybe in the past the different points of view made the reciprocal understanding more difficult, while now I see a concrete desire of convergence. Cool.

Francesca, in line with what you said, the whole field seems in period of convergence and consolidation.
I see the March loop+foam workshop as a huddle leading into the broader July conference
http://www.maths.nottingham.ac.uk/r...ntum_geometry_and_quantum_gravity_conference/

The preliminary list of talks for the July QG conference gives a sample of how things are moving.

One sees not only a convergence of Loop with Foam approaches in the LQG community but also a wider convergence of LQG with Noncommutative Geometry.

This is headlined by the name of the conference, which essentially says "QG meets QG"
Quantum Gravity meets Quantum Geometry (noncommuntative in particular!).
QG² stands for the double thrust or two-fold nature of QG.

I will get a partial list of talks:


Abhay Ashtekar
Quantum cosmology

Ali Chamseddine
Connections between noncommutative geometry, spectral action and quantum gravity

Bernard Kay
The puzzles of decoherence and thermodynamical behaviour

Vincent Rivasseau
Non-commutative renormalisation

Carlo Rovelli
On the relation between loops and foams

Subir Sarkar
Astroparticle probes of quantum gravity

Harold Steinacker
Dynamical quantum spaces, matrix models and gravity

Ali Chamseddine is a coauthor of Alain Connes of several papers on realizing the standard particles with NCG. Relating this to quantum gravity represents an interesting fusion gambit.

I expect most people actually are familiar with who some of these people are, like Chamseddine, Ashtekar, Rovelli. I will give links to publications by some of the others with whom I'm not as familiar. Here are Bernard Kay's papers:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+A+KAY%2C+Bernard+S&FORMAT=www&SEQUENCE=citecount%28d%29

Here is a sample paper by Rivasseau
http://arxiv.org/abs/0705.0705
Non-commutative Renormalization
Vincent Rivasseau
82 pages, Poincare Seminar
(Submitted on 4 May 2007)

"A new version of scale analysis and renormalization theory has been found on the non-commutative Moyal space. It could be useful for physics beyond the standard model or for standard physics in strong external field. The good news is that quantum field theory is better behaved on non-commutative than on ordinary space: indeed it has no Landau ghost. Noncommutativity might therefore be an alternative to supersymmetry. We review this rapidly growing subject."

Here are 60-some papers by Rivasseau to give an idea of his range of interest and publication:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+A+RIVASSEAU&FORMAT=www&SEQUENCE=ds%28d%29

Here is Subir Sarkar's homepage at Oxford
http://www-thphys.physics.ox.ac.uk/users/SubirSarkar/home.html
Here are some of his 80-odd papers:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+EA+SARKAR%2C+SUBIR+and+not+a+Eidelman+and+not+a+Hagiwara&FORMAT=www&SEQUENCE=citecount%28d%29
He has around 10 papers that each got 100+ cites and about half of these got several hundred cites.

Harold Steinacker is at Uni Munich. Here are 60-some papers of his:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+a+steinacker&FORMAT=www&SEQUENCE=citecount%28d%29
This gives and idea of his research interests.

It seems that there are several people here whose research is in quantum field theory on noncommutative spaces.

That is, IIRC, instead of a smooth manifold for the continuum one has a C* algebra with a Dirac operator defined on it. Somebody please correct me if I missed the target here.

 

[f-h]

How about telling why some ideas seemed more appealing or less appealing after the workshop? How about telling some new little insights or ideas that occurred to you during the workshop, or other people, while discussing the topics personaly with them?

Afterall, if nothing new happened, or any no one could have a new idea, there would be no reason to arrange a meeting...

Sure I can do that, to some degree, stuff I discussed with people privately I do not feel at liberty to neccessarily discuss here.

I personally learned about the role of gauge invariance for propagator calculations. I finally understood Eugenio Bianchis view on diffeomorphisms in Regge Theory (which is in his paper, and which I should have understood much earlier if I had bothered to read it better). There was a lot of disagreement over the Tlas-Oriti GFT with several people saying, nothing new was going on, etc. The boundary state of the propagator calculations is much better motivated from within the model now. Freidel seems to have taken an interest into AdS/CFT. I understood the AQG idea better, no manifold before semi-classicality.

I mean, we are maybe right now in a phase of refining existing ideas, and this refining is sometimes intangible, or doesn't look like very much to outsiders I guess. You just can't expect people to constantly generate ideas, we need to explore the ones that are there first. :) Find how they converge and overlap or differ. It took ten years of subtle refinement of our understanding of Barrett Crane until the damn broke and we got new Vertex models.

Just warning against overly high expectations, we're in this for the long haul.

 

[path-integral]

Hi all!
Finally I've got all slides from talks, and here they are:
http://www.fuw.edu.pl/~kostecki/zakopane08

In my opinion, this workshop has provided very good review of the state of art and the state of problems of LQG, LQC and spinfoams. This was also a great time for discussion in the field. I wish to have some time to write down a report like Alejandro wrote last year, but unfortunately I don't have any real time at the moment :( There were several interesting themes discussed at the time of talks, but not present in the content of slides (for example, a discussion about second class constraints in spin foam models).
If I can recommend some things to read first, i would recommend the talks of thomas thiemann, bianca dittrich and abhay ashtekar.

However, despite being in a good time of development, LQG and spinfoams still cope with the unknown way how to solve the constraints, and it seems that there is still no brave idea how to clearly solve these problems.

 

[jal]

WOW!
I'm looking forward to read some discussions (here) and hearing about "some brave ideas"
jal

 

[jal]

Hi f-h!
Were there any consensus and/or agreements reached by some of the participants on combining some of their approaches to try to resolves any of the constraints?
As a result, would they have set an objective of presenting their progress report for the July QG conference?
jal

 

[f-h]

Scientific progress does not beat to the clock of conference schedules :)
The issue of the constraints will be with us for decades to come most likely. Mostly because it is hard.

 

[marcus]

Since Richard kindly posted links to the slides for each talk, I have been reading some of them. I found Carlo Rovelli's talk especially interesting.

* Sergei Alexandrov - Covariant LQG and spin foam quantization
http://cift.fuw.edu.pl/users/kostecki/zakopane08/alexandrov.pdf

* Abhay Ashtekar - An Overview of Loop Quantum Cosmology of FRW Models
http://cift.fuw.edu.pl/users/kostecki/zakopane08/ashtekar.pdf

* Eugenio Bianchi - Gravitons from Spin Foams II: a simplicial perspective
http://cift.fuw.edu.pl/users/kostecki/zakopane08/bianchi.pdf

* Martin Bojowald - Effective equations of motion in loop quantum cosmology
http://cift.fuw.edu.pl/users/kostecki/zakopane08/bojowald.pdf

* Johannes Brunnemann - Volume Quantization in Loop Quantum Gravity
http://cift.fuw.edu.pl/users/kostecki/zakopane08/brunnemann.pdf

* Jacobo Diaz-Polo - Black hole state counting in Loop Quantum Gravity: The Richness of Discreteness
http://cift.fuw.edu.pl/users/kostecki/zakopane08/diaz-polo.pdf

* Bianca Dittrich - Observables
http://cift.fuw.edu.pl/users/kostecki/zakopane08/dittrich.pdf

* Jonathan Engle - Lorentzian LQG vertex for finite Immirzi parameter
http://cift.fuw.edu.pl/users/kostecki/zakopane08/engle.pdf

* Winston Fairbairn - Particles and strings in BF theory and quantum gravity
http://cift.fuw.edu.pl/users/kostecki/zakopane08/fairbain.pdf

* Christian Fleischhack - On the Configuration Spaces of Homogeneous Loop Quantum Cosmology and Loop Quantum Gravity
http://cift.fuw.edu.pl/users/kostecki/zakopane08/fleischhack.pdf

* Laurent Freidel - Spin foam models for 4d gravity
http://cift.fuw.edu.pl/users/kostecki/zakopane08/freidel.pdf

* Jerzy Kowalski-Glikman - Doubly Special Relativity from Quantum Gravity
http://cift.fuw.edu.pl/users/kostecki/zakopane08/kowalski-glikman.pdf

* Jerzy Lewandowski - QFT in Quantum Spacetime
http://cift.fuw.edu.pl/users/kostecki/zakopane08/lewandowski.ps

* Guillermo Mena - Hybrid loop quantum cosmology: The Gowdy T3 model
http://cift.fuw.edu.pl/users/kostecki/zakopane08/mena.pdf

* Karim Noui - Loops and foams in 3 dimensions
http://cift.fuw.edu.pl/users/kostecki/zakopane08/noui.pdf

* Tomasz Pawlowski - Self-adjointness of Hamiltonian constraint in LQC
http://cift.fuw.edu.pl/users/kostecki/zakopane08/pawlowski.pdf

* Jorge Pullin - Spherically symmetric loop quantum gravity: towards the complete space-time
http://cift.fuw.edu.pl/users/kostecki/zakopane08/pullin.pdf

* Carlo Rovelli - Looppy & Foammy: at long last, falling in love
http://cift.fuw.edu.pl/users/kostecki/zakopane08/rovelli.pdf

* James Ryan - Group field theory: modern perspectives
http://cift.fuw.edu.pl/users/kostecki/zakopane08/ryan.pdf

* Simone Speziale - From the graviton to area-angle Regge calculus
http://cift.fuw.edu.pl/users/kostecki/zakopane08/speziale.pdf

* Thomas Thiemann - Quantum Dynamics of LQG: A Structural Overview
http://cift.fuw.edu.pl/users/kostecki/zakopane08/thiemann.pdf

* Tamer Tlas - New GFT Models in 3 and 4 Dimensions
http://cift.fuw.edu.pl/users/kostecki/zakopane08/tlas.pdf



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