Quantum Gravity School - March 2007

[francesca]

"[URL First Quantum Geometry and Quantum Gravity School
March 23 - April 3, 2007
Zakopane, Poland[/URL]​

Invited Lecturers: Jan Ambjorn, Abhay Ashtekar, Alain Connes*, Laurent Freidel, Shahn Majid, Martin Reuter, Hendryk Pfeiffer*, Jean-Marc Schlenker, Thomas Thiemann

*-to be confirmed​

Local organizer: Jerzy Lewandowski, Kirill Krasnov...

The school will be held within the framework of the new ESF research network Quantum Geometry and Quantum Gravity, coordinated by John Barrett
see http://www.maths.nottingham.ac.uk/qg/" for further information about the network.

The aim of the school is to provide an up-to-date introduction to
the main research topics of the network, namely: loop quantum gravity,
spin foam models, dynamical triangulations, matrix models, and the
application of non-commutative geometry and quantum groups to quantum
gravity. There will be funds to cover the expenses of some
participants (especially PhD students or junior researchers) from the
member countries of the network. I wait for more info

 

[arivero]

Hmm Barret is doing good work.

 

[Hymne]

Will it be recorded for us on the internet?
Anybody that knows online lectures on gravity on Internet?
I think I saw a link to three movies one moth ago in a thread named something like "What is the nowadays accepted gravitational theory?" but didnt find it in the shearch function.

 

[francesca]

online lectures

Anybody that knows online lectures on gravity on Internet?

http://www.perimeterinstitute.ca/in...&task=view&id=113&Itemid=167&p=presentations" by Lee Smolin
http://www.perimeterinstitute.ca/Scientific/Seminars/PIRSA/"
http://relativity.phys.lsu.edu/ilqgs/" (slides&audio)
http://loops05.aei.mpg.de/index_files/Programme.html"
and more... would it be enough by now? well, I've only mentioned some quantum gravity lectures, and more precisely some non-perturbative/background independent quantum gravity lectures...
Have I answered to your question?

ps: the tread you mentioned would be https://www.physicsforums.com/showthread.php?t=145164"

There are several GR texts on the web. Waner or t'Hooft for example. See the same Baez site for links: http://www.math.ucr.edu/home/baez/RelWWW/undergrad.html
There are also videos of 3 1-hour lectures by Sean Carroll.
http://www-conf.slac.stanford.edu/ssi/2005/lec_notes/Carroll/

 

[marcus]

Francesca it sounds very exciting!

Arivero is right about John Barrett doing good work, in several ways.
this QGQG research funding network seems exceptionally well-conceived

I see 9 lecturers, and they have 9 or more days. So they can let each lecturer give a series of talks. They have time to listen a lot to each

I will write down what I think are the specialties of each of the 9 lecturers in the school. It should be interesting to see what kind of mix Barrett and the QGQG and the organizers like Krasnov (who is at Nottingham with Barrett, I think) are putting together. I mean the MIX seems unusual to me. For each teacher in the school I will indicate a little where that person is and what kind of recent research---Francesca please correct me if I am wrong about any of them.Jan Ambjorn, (Utrecht) CDT causal dynamical triangulations---co-author of many CDT papers with Renate Loll--computer simulations of simplicial QG

Abhay Ashtekar, (Penn State) LQG and especially lately LQC loop quantum cosmology, replacing cosm. singularity by big bounce--numerical (computer) work going back through the former singularity

Alain Connes*, (Paris) NCG, realizing the standard model geometrically (John Barrett posted the same result simultaneously)

Laurent Freidel, (Perimeter) Spinfoam, unifying Feynman diagrams with spinfoam, quantum groups, DSR deformed special relativity

Shahn Majid, (London) NCG, quantum groups, recently co-authored with Freidel joining spinfoam with NCG

Martin Reuter, (Mainz), QEG assymptotically safe "quantum Einstein gravity", curing the non-renormalizability of quantized conventional GR.

Hendryk Pfeiffer*, (Cambridge) mathematician, Differential Geometry and Topology

Jean-Marc Schlenker, (Toulouse) mathematician, Differential Geometry and Topology

Thomas Thiemann, (Albert Einstein Institute-Golm) master constraint version of LQG, also AQG (algebraic QG).

 

[marcus]

Francesca, in that line-up of 9 teachers, I think it is only two (Laurent Freidel and Shahn Majid) who have been discussing prospects for near-term observational tests

Majid, in http://arxiv.org/abs/hep-th/0604130 , just said flat out that GRB as observed by some mission like GLAST would afford a chance to test NCG.

Do you know of any of the others being interested particular ideas for testing?
Anyone?

The Majid quote is on page 2 of that paper.

Majid: "...for a model of noncommutative 4D spacetime. Note that although (1)
breaks usual Poincaré invariance, Special Relativity still holds as the quantum
group ‘symmetry’. This is also the first noncommutative spacetime
model with a genuine physical prediction[1], namely a variable speed of
light (VSL). The NASA GLAST satellite to be launched in 2007 may among
other things be able to test this prediction through a statistical analysis of
gamma-ray bursts even in the worst case that we might expect for the parameter
lambda approx. 10^−44 s ( the Planck timescale). Note that the model should not
be confused with an earlier kappa-Poincaré group model[8] where..."

 

[Hymne]

Have I answered to your question?

Yes, thank you very much.

 

[ccdantas]

Very, very, very interesting school!

It's unfortunate, I cannot go.

Christine

 

[francesca]

Do you know of any of the others being interested particular ideas for testing? Anyone?

This school seems to me more devoted to formal developments than to their relationship with esperiments: maybe they see it as a subsequent step for the student...
well, to tell the true I don't mind it...for Christine: thank you for the nice introduction to each listed speaker!

 

[ccdantas]

for Christine: thank you for the nice introduction to each listed speaker!

Hi Francesca,

No, that was Marcus' work!

Thanks anyway for providing the link to the school!

Christine

 

[francesca]

Sorry Marcus and thank you! I red too fast
well, in any case thanks to Christine who corrected me...

 

[RandallB]

Does anyone know if meetings like this establish a standard for Langauge used for presentations and discussions?
Do they allow that to be dictated by the presenter of each topic, and for those that need it, how do they manage translations in a live environment?

added - Just wanted to confirm what is only a guess on my part that English may be the spoken language standard. And to advance in science most must at least have English as a second launguage. (Thanks Marcus)

 

[francesca]

Galileo said that Nature book is written in the mathematical language...
sorry, I'm joking, that's to say that I find the spekers set quite homogeneous because they are all math-minded. Well, the school wants to present different approach even if they haven't achieved a common language, otherwise we eventually have the quantum gravity theory
Dear Randall, you put a proper question, different languages for the same thing are a bit disorienting, expecially for a student... what a mess!

I'm wondering about the level of the school... they wrote it's addressed for graduate students, but...

 

[marcus]

Does anyone know if meetings like this establish a standard for Langauge used for presentations and discussions?
Do they allow that to be dictated by the presenter of each topic, and for those that need it, how do they manage translations in a live environment?

I am guessing that Randall is asking about spoken language like English French Portuguese Italian German. Maybe he is talking about mathematics and technical definitions of terminology. But I don't think so.

we are into a era of more mobility like in Renaissance when scholars could travel all over Europe---they all would read and write the same language Latin.

You can see the video of all the presentations given at the Loops '05 conference (the largest Quantum Gravity conference so far). All the talks are in English although there are very few US people and not all that many from the UK. That conference was near Berlin at the Albert Einstein Institute in Golm.
It is the usual international conference language in continental Europe. Also to some extent even for lectures, seminars, colloquium talks. So a student from some other country (Spain, Germany, Brazil, UK, Italy) can go to Utrecht in Holland and give seminar talks and study there without having to know Dutch!

This is good for scholarship.

 

[marcus]

The list of lecturers to be at the school has changed slightly. for example Etera Livine (who wrote a review paper on COVARIANT LQG recently) will be lecturing and Hendryk Pfeiffer will not be. here is the updated list:

Jan Ambjorn
Abhay Ashtekar
Alain Connes*
Laurent Freidel
Etera Livine
Shahn Majid
Martin Reuter
Jean-Marc Schlenker
Thomas Thiemann
Ruth Williams*

* - to be confirmed

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

many people know the research these people do as well or better than I, so they don't need the list annotated, but I will give some guesses about what these people might talk about

Jan Ambjorn---causal dynamical triangulation (CDT: one of several simplicial QG approaches)
Abhay Ashtekar----(loop) quantum cosmology---the deterministic evolution that replaces the bang singularity
Alain Connes*----obtaining the standard model from non-commutative geometry (NCG)
Laurent Freidel----obtaining Feynman diagrams of usual QFT from spinfoam, the emergence of matter from QG.
Etera Livine----covariant loop quantum gravity (CLQG)
Shahn Majid----NCG---possible connection to DSR and GLAST testability.
Martin Reuter----quantum Einstein gravity (QEG)---showing quantized general relativity to be assymptotically safe
Jean-Marc Schlenker---differential geometry and topology (application?)
Thomas Thiemann----algebraic quantum gravity (AQG) and/or the master constraint program
Ruth Williams*----simplicial QG

* - to be confirmed

=============
for more information:
http://www.fuw.edu.pl/~kostecki/school.html

 

[f-h]

Great, isn't it? ;)

 

[francesca]

Yes, it is

Are you going to come? and your colleagues from Marseille?

 

[f-h]

I fully intend to, but I'm actually in Nottingham now, so I don't know who from Marseille is coming...
Will you be there? Are you studying QG?

 

[francesca]

I worry about the level of lectures...
I'm going to start my (master) thesis in QG next year, maybe starting from the Fall, so...
I fully hope to come too, but maybe it's better if I ask before to my advisors...

 

[f-h]

In that case it might be below the expected level:

"Please note, that if you are a Ph.D. student or a junior researcher we will also need a recommendation letter from a senior scientist. It should be send in PostScript or PDF format at e-mail address QGQG1 @ fuw.edu.pl."

Either way I'd definitely try for it, even if you don't learn that much, in my experience challenging yourself is always a good idea.

 

[francesca]

deadline

​

Application and registration for the participation in the school as well as application for the financial support is open from December, 15 2006 till January, 31 2007. [...]
There is no registration fee but we do not guarantee that everybody who submitted application will be registered. If too many applications will be submitted, priority will have Ph.D. students from member countries of the network recommended by network coordinators.

 

[francesca]

detailed programme

It sounds scaring to me...

Laurent Freidel: Spin-Foam Models
1. General introduction to spin foams
2. 3D Gravity and introduction to some group theory
3. The Ponzano-Regge model derivation and its properties
4. The Ponzano-Regge model + matter
5. Effective field theory

Paweł Kasprzak: Locally compact quantum Lorentz groups
1. C*-algebras. (1h)
a. Morphism of C*-algebras;
b. C*-algebras generated by affiliated elements;
c. W*-algebras.
2. Locally compact quantum groups.(1h)
a. Compact quantum groups of Woronowicz;
b. From multiplicative unitary to locally compact quantum groups;
c. Locally compact quantum groups of Kustermans and Vaes.
3. Rieffel Deformation.(3h)
a. Rieffel Deformation of C*-algebras;
b. Rieffel Deformation of locally compact groups;
c. Heisenberg-Lorentz quantum group;
d. The second example of quantum Lorentz group obtained by Rieffel Deformation.
4. Quantum codouble.(2h)
a. Quantum Lorentz group having Gauss decomposition property;
b. Quantum Lorentz group having Iwasawa decomposition property.

Martin Reuter: Asymptotic Safety in Quantum Einstein Gravity
The basic ideas of the Wilsonian renormalization group and its continuum implementation in terms of the effective average action are reviewed and its application to Quantum Einstein Gravity (QEG) is discussed. This approach is used then to explore the nonperturbative renormalizability (asymptotic safety) of QEG and the fractal-like nature of its effective spacetimes.

Jean-Marc Schlenker: Hyperbolic geometry for 3d gravity
- hyperbolic surfaces, complex surfaces, Teichmüller space
- quadratic holomorphic differentials as the cotangent of Teichmüller space
- measured geodesic lamination as another description of the cotangent of Teichmüller
- Thurston's Earthquake theorem
- quasifuchsian 3-dim hyperbolic manifolds, the Ahlfors-Bers theorem
- 3-dim GHMC AdS manifolds
- the Mess proof of the earthquake theorem through GHMC AdS manifolds.

Ruth Williams: Introduction to Regge calculus
1. Basic formalism; simplex practicalities; Bianchi identities; existence of diffeomorphisms; continuum limit.
2. Regge calculus in 2 dimensions. Regge calculus in 3 dimensions; inclusion of matter; 2+1 Regge calculus and 't Hooft's approach. 3+1 Regge calculus; Sorkin evolution; Lund-Regge approach.
3. Regge calculus in 4 dimensions; weak field calculations; simplicial minisuperspace and quantum cosmology; numerical simulations of discrete quantum gravity; matter; the measure.
4. Regge calculus in a large number of dimensions. Area Regge calculus; motivation and problems; constraints; treating areas as basic variables; discontinous metrics.

 

[f-h]

*g*

Sounds like this is going to be fun :D

 

[francesca]

Francesca pointed out today that the program of talks has now been posted for the QGQG school
http://www.fuw.edu.pl/~kostecki/school.html

this is specifically aimed at getting grad students started in one of the several branches of QG² research, so you don't necessarily have to be following all the talks to benefit from the school

it is like a Smorgasbord where you only take what you want and can handle.

Jan Ambjorn - Matrix models in non-critical string theory and quantum gravity
Abhay Ashtekar - Loop Quantum Cosmology
Laurent Freidel - Spin-Foam Models
Etera Livine -
Paweł Kasprzak - Locally compact quantum Lorentz groups
Martin Reuter - Asymptotic Safety in Quantum Einstein Gravity
Jean-Marc Schlenker - Hyperbolic geometry for 3d gravity
Thomas Thiemann - Loop Quantum Gravity
Ruth Williams - Introduction to Regge Calculus

If I were there I probably would just go to these series

Abhay Ashtekar - Loop Quantum Cosmology
Laurent Freidel - Spin-Foam Models
Etera Livine -
Thomas Thiemann - Loop Quantum Gravity

[...]
I think the last talk is being given by Kristina Giesel, a postdoc at Perimeter.
It looks like AA is giving 7 talks, LF is giving 5 talks, TT is giving 7 with an additional talk by Kristina.

I use to be a plier in this kind of occasion, I'm going to attend all the lectures!
I don't know so much about everything, so maybe I can take advantage
just on hearing a bit of all subjects... :shy:
I'm quite aware of the works by peoples who Marcus pointed out,
what about the others, the more mathematical side of the school?
Does someone have any advice?

 

[path-integral]

Hi,
I'm Rick, one of the local organizers :)
There is one more hot news from today - Carlo Rovelli will also participate as lecturer. So, the current list of speakers and lectures is the following:

Jan Ambjorn - Matrix models in non-critical string theory and quantum gravity
Abhay Ashtekar - Loop Quantum Cosmology
Laurent Freidel - Spin-Foam Models
Etera Livine - Spinfoams: The Barrett-Crane model in 4D and group field theory
Paweł Kasprzak - Locally compact quantum Lorentz groups
Martin Reuter - Asymptotic Safety in Quantum Einstein Gravity
Carlo Rovelli - Carlo Rovelli: Where are we in the path toward quantum gravity?
Jean-Marc Schlenker - Hyperbolic geometry for 3d gravity
Thomas Thiemann - Loop Quantum Gravity
Ruth Williams - Introduction to Regge Calculus

Unfortunately, there were more than 100 people asking for support and we had funds from ESF for support only about 35 :(

 

[marcus]

Hi,
I'm Rick, one of the local organizers :)
There is one more hot news from today - Carlo Rovelli will also participate as lecturer...

that is a great addition to the program!
Will any of your talks, C.R. in particular, be available in some form online?
PDF lecture notes could be of considerable benefit to others if not too much trouble for you to post.

 

[path-integral]

I hope we will publish all lectures in one book with nice title like "An introduction to Quantum Geometry & Gravity" or something like that. However, this would require lecturers to do some job with their notes after the school, so there will be quite big lapse (and shift ) of time between school and the book. However, I would try to make some pressure on lecturers to make some draft copies of PDF/PowerPoint/anything avaible as soon as possible after, or ever at the school's time.

It would be great to record all lectures on some camera, but as I now we (= local organizers) don't have any, and also I don't have any good idea what to do with such recordings (where can be placed such amount if gigabytes?)

 

[francesca]

I would try to make some pressure on lecturers to make some draft copies of PDF/PowerPoint/anything avaible as soon as possible after, or ever at the school's time.

It would be great if we can have something wrote to reed during the school.

It would be great to record all lectures on some camera, but as I now we (= local organizers) don't have any, and also I don't have any good idea what to do with such recordings (where can be placed such amount if gigabytes?)

Maybe it would be enough to record audios with a digital support, in my opinion this would be not so heavy. Then if someone have the time, it's possible to assemble audios and slides...
But can you ask the owners of the ESF network internet page for some space?
It's worthwhile, above all to spread the "good news" of QG

 

[path-integral]

I think the idea of audio recording of lectures is good. I will check is there some ability to put it on the ESF server.

In worst case, we always can distribute it by P2P :)

 

[f-h]

Audio plus somebodies lecture notes...
Unfortunately my note taking is horrible to nonexistent...

 

[francesca]

My notes are amazing... when I write in Italian!
while my comprehension of spoken English have to be improved
I hope that slides (if present) would be detailed enough,
maybe for comprehensive notes we have to wait for the school proceedings!

 

[Timbuqtu]

I will be going to Zakopane too! They have done a great job getting this group of lecturers together. Apart from the people addressed by others, I am pleased to see Jean-Marc Schlencker is going to tell something about 2+1 quantum gravity and related math, since I'm working in that area at the moment.

 

[francesca]

Hi Timothy,
plese tell something more about it!
I look at Schlencker's lecture topics, but it doesn't say so much to me...

​

 

[Timbuqtu]

Hi Francesca. I'll try to shortly summarize some (quantum) gravity in 2+1 dimensions:

The phase space of (classical) general relativity in 2+1 dimensions is much smaller than in 3+1 dimensions, because there are no local degrees of freedom (in absence of matter). The reason is that the Riemann tensor is fully determined by the Ricci tensor and the Einstein equations imply that the Ricci tensor vanishes in vacuum when cosmological constant $$\Lambda=0$$. Consequently spacetime is flat everywhere and looks like Minkowski space (or in case $$\Lambda \neq 0$$ it looks like deSitter or Anti-deSitter). All degrees of freedom reside in the ways of glueing patches of Minkowski space together to form your space time. So actually only topologically non-trivial spacetimes contain (physical) degrees of freedom.

Let's assume our spacetime to have the topology of $$[0,1]\times \Sigma$$ where $$\Sigma$$ is a closed two-dimensional surface. Now topologically such a surface is determined by only its genus g (number of tori attached to each other). Now the geometry of your spacetime is fully determined by the holonomies around a set of (2g) non-contractible loops in your spacetime. Now it turns out that this phase space (the set of holonomies) can be identified with the cotangent bundle of Teichmuller space of your surface $$\Sigma$$. Teichmuller space is the space of all inequivalent Riemann (i.e. complex one-dimensional) surfaces (of a specific genus), which is a widely studied topic in mathematics. Also the physical symplectic structure on your phase space can be canonically defined on your cotangent bundle. That's why a lot of math related to Riemann surface/hyperbolic geometry is studied in 2+1 GR.

Because our phase space is finite-dimensional in 2+1 dimensions (contrary to the 3+1 dimensional case) and the symplectic structure is pretty simple, we can (in principle) easily quantize such a system using normal quantum mechanics. This approach is called reduced phase space quantization because all constraints coming from equations of motion have already been applied and all gauge freedom has been removed before quantization. Of course there are several issues to solve, but despite that you can explicitly write down a quantum theory of your system (which in this case describes a spatially compact spacetime without matter or whatever).

I hope this clarifies the subject a little. Here is a good (introductive) review article on 2+1 dimensional quantum gravity if you want to read more: "Quantum Gravity in 2+1 Dimensions: The Case of a Closed Universe", S. Carlip, http://arxiv.org/abs/gr-qc/0409039.

-- Timothy

 

[francesca]

Definitely a clear introduction, thank you!