Introduction To Loop Quantum Gravity

marcus · Dec 13, 2005

Freidel wraps up 3D, starts on 4D

Loll aside, this is my guess as to the most influential quantum gravity paper of 2005:
http://arxiv.org/abs/hep-th/0512113
Effective 3d Quantum Gravity and Non-Commutative Quantum Field Theory
Laurent Freidel, Etera R. Livine
9 pages
"We show that the effective dynamics of matter fields coupled to 3d quantum gravity is described after integration over the gravitational degrees of freedom by a braided non-commutative quantum field theory symmetric under a kappa-deformation of the Poincaré group."

This paper (summarizing rapid development during the past year or so) pretty well takes care of the 3D case. In the conclusions Freidel discusses the extension to 4D, and cites a paper by Freidel and Baratin in preparation, called Hidden quantum gravity in Feymnan graphs.
but this was also the title of the talk which Aristide Baratin gave at October Loops '05. And we can download the slides. This has a link to the video as well, but i cannot get it to work:
http://loops05.aei.mpg.de/index_files/abstract_baratin.html
Here are Baratin slides for his talk "Hidden quantum gravity in Feymnan graphs".

http://loops05.aei.mpg.de/index_files/PDF_Files/baratin.ppt

Who is Aristide Baratin? Perimeter lists him as one of their grad students. I think Baratin finished Lycee in Paris around 1997 (won an essay prize) and went to Ecole Normal in Lyon (where Freidel works part-time). Perhaps he did his Bac at Lyon and after becoming a grad student moved from Lyon to Perimeter in 2005. I think probably he was born around 1980 and is now in mid Twenties. Anyway he is collaborating with Freidel on the paper where Freidel starts seriously to work on 4D.

There was already some preparation in that paper of Freidel with Artem Starodubtsev, which was also about 4D. I will get some quotes where Freidel gives an idea of what his strategy is.

marcus · Dec 14, 2005

this gives an idea of the success in 3D which Freidel intends to duplicate, if it is possible, in 4D.

--quote from Freidel paper hep-th/0512113--

CONCLUSIONS AND OUTLOOK

To sum up, we have shown that the 3d quantum gravity amplitudes, defined through the Ponzano-Regge spinfoam model, are actually the Feynman diagram evaluations of a (braided) non-commutative quantum field theory. This effective field theory describe the dynamics of the matter field after integration of the gravitational degrees of freedom. This applies as well in the Euclidean case as in the true Lorentzian theory. The noncommutative action is invariant under a kappa-deformation of the Poincaré algebra, which acts non-trivially on the many-particle states.

This is an explicit realization of a quantum field theory in the framework of deformed special relativity. Moreover, the theory naturally comes with a momentum cut-off which does not break the Poincaré symmetry but only deforms it.

This alternative to dimensional regularization was originally proposed by Snyder[15]. However, here we have explicitly shown that the gravitational field acts as such a regulator in the Euclidean sector. Moreover, we have checked that the quantum gravity amplitudes for the trivial topology reduces in the nogravity limit kappa -> 0 to the standard QFT amplitudes, as expected in the semi-classical limit of the theory.

We can see two natural extensions. The first one is that the spinfoam amplitudes provide a generalization of the Feynman rules for non-trivial topology. The second one is the generalization to the four-dimensional space-time. Indeed, we propose a new point of view. We have shown how to write the 3d Feynman evaluations as expectation values of certain observables of a topological (abelian) theory. This (abelian) theory was then identified as a particular limit of the quantum gravity theory. This result suggests that the Feynman evaluations of 4d QFT could be reformulated as expectation values of a 4d topological model. This is supported by the fact that 4d gravity becomes topological in the G ->0 limit [16]. This would be interpreted as the zeroth order of the spinfoam model for 4d quantum gravity [17]
---endquote---

REF [16] IS TO FREIDEL STARODUBTSEV
REF [17] IS TO FREIDEL BARATIN (Hidden quantum gravity in Feynman graphs).

marcus · Dec 14, 2005

Freidel's talk at Loops '05

Freidel talk at October conference was essentially this paper that he just posted, but with a differerent title

The paper is
http://arxiv.org/abs/hep-th/0512113
Effective 3d Quantum Gravity and Non-Commutative Quantum Field Theory

the talk was
http://loops05.aei.mpg.de/index_files/abstract_freidel.html
Effective Field theory from quantum gravity
"The Coupling of matter fields to spin foam models of quantum gravity will be discussed. We will show in the case of three dimensional gravity how the integration of quantum gravity degrees of freedom coupled to matter can be explicitely described in terms of an effective field theory. This theory is a new non commutative field theory obeying the principle of doubly special relativity. We will conclude on the extension of this approach to the four dimensional case."

the slides to the talk are not available, but there was a video. But I can't get it to download. too bad. I think AEI-Golm posted the video files only a limited time. I downloaded a number of them and have them on my hard-drive, but I find that I cannot download the same ones now. the link that USED to work, to get the freidel talk video was:
http://loops05.aei.mpg.de/index_files/Video_freidel.wmv

marcus · Jan 2, 2006

updating post #88

marcus said:
...
Last month at selfAdjoint's suggestion I included "heterotic, superstring" in the list of keywords and did a search using the Harvard ADS abstract service engine.
https://www.physicsforums.com/showthread.php?p=789185#post789185

For continuity I tried the same check today. This is now the papers November thru October, year by year, with any of the same keywords in the abstract.
Code:
2001   1220
2002   1083
2003    972
2004    938
... it NOT AS A SIGN THAT ONE THING IS RIGHT AND ANOTHER WRONG but that for whatever reason people are branching out in more directions, and trying non-string ones.
...

this time of year data becomes available and we can update. this is now for JANUARY THRU DECEMBER year by year----the same keywords
(heterotic, superstring, M-theory, brane, AdS/CFT)

Code:

2001   1204
2002   1188
2003   1081
2004   1012
2005    843

http://adsabs.harvard.edu/physics_service.html

these are figures on stuff that has gotten PUBLISHED in the indicated year. there is also the current rate of preprint postings---here is an arxiv link that may sometimes be useful
http://lanl.arxiv.org/find/nucl-ex,...brane+abs:+OR+M-theory+p-brane/0/1/0/2006/0/1

marcus · Jan 2, 2006

Early in 2005, Freidel and Livine posted
http://arxiv.org/abs/hep-th/0502106
Ponzano-Regge model revisited III: Feynman diagrams and Effective field theory
Laurent Freidel, Etera R. Livine
46 pages
"We study the no gravity limit G_{N}-> 0 of the Ponzano-Regge amplitudes with massive particles and show that we recover in this limit Feynman graph amplitudes (with Hadamard propagator) expressed as an abelian spin foam model. We show how the G_{N} expansion of the Ponzano-Regge amplitudes can be resummed. This leads to the conclusion that the dynamics of quantum particles coupled to quantum 3d gravity can be expressed in terms of an effective new non commutative field theory which respects the principles of doubly special relativity. We discuss the construction of Lorentzian spin foam models including Feynman propagators"

In October Freidel's Loops '05 talk was
http://loops05.aei.mpg.de/index_files/abstract_freidel.html
Effective Field theory from quantum gravity
"The Coupling of matter fields to spin foam models of quantum gravity will be discussed. We will show in the case of three dimensional gravity how the integration of quantum gravity degrees of freedom coupled to matter can be explicitely described in terms of an effective field theory. This theory is a new non commutative field theory obeying the principle of doubly special relativity. We will conclude on the extension of this approach to the four dimensional case."

In December 2005 a related paper appeared
http://arxiv.org/abs/hep-th/0512113
Effective 3d Quantum Gravity and Non-Commutative Quantum Field Theory
"We show that the effective dynamics of matter fields coupled to 3d quantum gravity is described after integration over the gravitational degrees of freedom by a braided non-commutative quantum field theory symmetric under a kappa-deformation of the Poincaré group."

Laurent Freidel's most recent paper was with Shahn Majid:
http://arxiv.org/abs/hep-th/0601004
Noncommutative Harmonic Analysis, Sampling Theory and the Duflo Map in 2+1 Quantum Gravity
54 pages, 2 figs
We show that the *-product for U(su_2) arising in [1] in an effective theory for the Ponzano-Regge quantum gravity model is compatible with the noncommutative bicovariant differential calculus previously proposed for 2+1 Euclidean quantum gravity using quantum group methods in [2]. We show that the effective action for this model essentially agrees with the noncommutative scalar field theory coming out of the noncommutative differential geometry. We show that the required Fourier transform essentially agrees with the previous quantum group Fourier transform. In combining these methods we develop practical tools for noncommutative harmonic analysis for the model including radial quantum delta-functions and Gaussians, the Duflo map and elements of `noncommutative sampling theory' applicable to the bounded SU_2,SO_3 momentum groups. This allows us to understand the bandwidth limitation in 2+1 quantum gravity arising from the bounded momentum. We also argue that the the anomalous extra `time' dimension seen in the noncommutative differential geometry should be viewed as the renormalisation group flow visible in the coarse graining in going from SU_2 to SO_3. Our methods also provide a generalised twist operator for the *-product."

[1] refers to the two 2005 Freidel and Livine papers
[2] is a 2003 paper of Majid and Batista

for quotes and more discussion of this series of papers please scroll back three or four posts to post #91 and #92
at the moment I am trying to connect the dots and understand a little better what is happening here. please help if you think you can explain. It looks like Freidel has found a connection at the 3D level between Regge gravity, Feynman diagrams for particles, and DSR (deformed Poincaré). the same laws that govern gravity also govern particles and produce Feynman vertex amplitudes in the flat limit. It looks like Freidel together with Shahn Majid and others are preparing to try to raise this setup to the 4D level. A fifth dimension has appeared and is being interpreted as a renormalization group parameter (instead of a second dimension of time). If you ask me it is real hard to comprehend, but maybe others will have an easier time with it.

marcus · Jan 3, 2006

If I am right in my guess about where QG is going, then this paper should serve as a kind of FILTER---

marcus said:

Early in 2005, Freidel and Livine posted
http://arxiv.org/abs/hep-th/0502106
Ponzano-Regge model revisited III: Feynman diagrams and Effective field theory
Laurent Freidel, Etera R. Livine
46 pages
"We study the no gravity limit G_{N}-> 0 of the Ponzano-Regge amplitudes with massive particles and show that we recover in this limit Feynman graph amplitudes (with Hadamard propagator) expressed as an abelian spin foam model. We show how the G_{N} expansion of the Ponzano-Regge amplitudes can be resummed. This leads to the conclusion that the dynamics of quantum particles coupled to quantum 3d gravity can be expressed in terms of an effective new non commutative field theory which respects the principles of doubly special relativity. We discuss the construction of Lorentzian spin foam models including Feynman propagators"

...

what I mean is that for the immediate future a good way to find interesting QG papers is to LOOK FOR THOSE WHICH HAVE CITED THIS ONE AS A REFERENCE.

if this is an important germinal paper then it makes our job easier, we can just look here
http://www.citebase.org/cgi-bin/citations?id=oai:arXiv.org:hep-th/0502106

and it says that this February 2005 paper has 11 citations (including some ones that are new to me---that I hadn't noticed when I was scanning arxiv) and these citations are
http://arxiv.org/cits/hep-th/0502106
(but this only gives the titles/authors and not the abstracts)
to see the same list with brief summaries:
http://www.citebase.org/cgi-bin/search?type=identifier&rank=Citations+(Paper)&submit=Cited+By&identifier=oai:arXiv.org:hep-th/0502106

Great! I have been trying to observe QG, and using these search tools, for several years and I am only just learning some laborsaving ways to use the tools.

the thing is: this February 2005 Freidel-Livine paper treats QG DYNAMICS AND MATTER ON THE SAME PLATFORM and unites Feynman diagrams (for the matter) with quantum Gen Rel dynamics for the spacetime

and this paper does it for 3D, so probably the future of QG will be doing similar stuff in 4D-----so this paper filters out future interesting QG papers

if a future paper cites this one, then it has a chance of being interesting.
so we have a new window----namely this citebase.org link.

BTW another link similar to the one a couple of posts back
http://lanl.arxiv.org/find/grp_phys...SCFT+abs:+OR+string+braneworld/0/1/0/2006/0/1

Sauron · Feb 8, 2006

Sorry by the slight off-topic.

I am currently reading the complete thread "intuitive content of loop..." that i had followed discontinously until now.

These one seems to be much of the same stuff ¿Why two duplicate threads?

¿Are topics covered here and uncovered in the other?

marcus · Feb 8, 2006

Sauron said:

Sorry by the slight off-topic.

I am currently reading the complete thread "intuitive content of loop..." that i had followed discontinously until now.

These one seems to be much of the same stuff ¿Why two duplicate threads?

¿Are topics covered here and uncovered in the other?

One difference is I try to make the older, larger thread more INCLUSIVE.
I suppose the other thread gets about 10 times more links per month, although I do not know the exact numbers.
I guess that in a month where I add 2 links to this more selective thread, I might add perhaps 20 links to the more inclusive one.

In the other thread, I try to put in any new QG paper that I think someone of us might be interested in. Even if I am not sure about it, I may put it in just so that it is less likely to be lost---and just in case someone else might be interested. So my own personal bias and interest does not influence it so much.

In this thread the links I put in reflect my own personal judgment of what is most essential and what are the most interesting directions in QG research. I am not always consistent. Last year I focused a lot of my attention on Loll Triangulations gravity (CDT). This year, so far, I am focusing mainly on the Freidel Spinfoam gravity (with its connection to matter and to DSR).

I would like to put in this thread only things that I think are of the utmost importance---and if a month or two pass by with nothing new that is OK, it just means that for me nothing especially important came out for a couple of months. But not being omniscient and clairvoyant, how can I tell what is really important? So in the other thread, to be on the safe side, I include stuff that I think has a chance to be of interest.

If you would like to contribute to our bibliography, Sauron, perhaps you would follow the same plan and preserve the "short list/long list" idea.

marcus · Feb 10, 2006

QG introductory course and QG blogs

(non-string) Quantum Gravity is emerging as a field and becoming more articulate. One of the major milestones marking this is Lee Smolin's course of lectures Introduction to Quantum Gravity
Notice that the title is not LOOP quantum gravity, but more general. Lecture #7 that I watched yesterday was BF theory----Lecture #8 touched on Chern-Simons. In response to a question Smolin also spent some of that day's session introducing the inclusion of matter in QG (by Laurent Freidel and others).

Besides this video course in QG, another signpost is Christine Dantas blog
http://christinedantas.blogspot.com
and her QG reading list.
http://christinedantas.blogspot.com/2006/02/basic-curriculum-for-quantum-gravity.html

As a kind of footnote, I will keep an eye out for other QG BLOGS, which in some sense indicate the growing self-awareness of the field.

One of the members of the Nottingham QG group has
http://realityconditions.blogspot.com
http://realityconditions.blogspot.com/2006/02/monday-quantum-gravity-group-meeting.html
Nottingham University has a major QG research group headed by John Barrett ("Barrett-Crane spinfoam model") and Kiril Krasnov (spinfoam and GFT parallels Freidel's)
http://www.maths.nottingham.ac.uk/QG/QG.html
and the blogger belongs to that group.

the "Reality Conditions" blogger Alejandro Katz just flagged Christine's QG reading list
http://realityconditions.blogspot.com/2006/02/study-guide-for-lqg.html

likewise Nigel's LQG blog
http://lqg.blogspot.com/2006/02/dr-dantas-has-lqg-reading-list.html
and also Victor Rivelles blog "SUM OVER HISTORIES", a mostly in Portuguese QG blog that I did not know of until today.
http://rivelles.blogspot.com/2006/02/road-to-loop-quantum-gravity.html

To get to the video of the Smolin Lectures go to
http://streamer.perimeterinstitute.ca:81/mediasite/viewer/FrontEnd/Front.aspx?&shouldResize=False
and scroll down to Introduction to Quantum Gravity around item #22 on the sidebar menu. It is currently one of the most recent additions to Perimeter online resources and so is near the bottom

marcus · Mar 4, 2006

as of now, the best short overview of LQG so far, in my opinion,
is Rovelli's Slides for a talk he gave in January 2006 at Lyon
it would be great if we had the audio that went with the slides
but the slides are fairly self-explanatory especially you have heard other Rovelli talkshttp://www.cpt.univ-mrs.fr/~rovelli/Lyon2006II.pdfthese 59 slides make an excellent summary of the essential ideas, with lots of sketches and diagrams (pointers to the history of how QG developed are given parenthetically by listing names and dates so you could look it up, but the emphasis is on giving intuitive grasp of the subject at present)

there are other resources at Rovelli homepage
http://www.cpt.univ-mrs.fr/~rovelli/rovelli.html
including a link to a downloadable draft of his book "Quantum Gravity" published by Cambridge University Press in 2004.

the SMOLIN LECTURES available as streaming video here
http://streamer.perimeterinstitute.ca:81/mediasite/viewer/FrontEnd/Front.aspx?&shouldResize=False
(scroll down to Introduction to Quantum Gravity on the sidebar menu)
now comprise 12 lectures-----the table of contents is on two pages so you have to flip the page to find lectures 11 and 12.

the Smolin Lectures are more technical and in-depth, so they complement Rovelli's easy conceptual overview. it helps to look at it from both perspectives

marcus · Apr 8, 2006

check back here later

so as not to lose track of the link, we have a forecast poll on the most influential first-quarter 2006 paper
https://www.physicsforums.com/showthread.php?t=116791

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

this is the thread that has updates of the TOC of the book by Daniele Oriti "Towards QG----a new understanding of space and time" or words to that effect.

last time i checked arXiv had preprints for 7 of the chapters, may be more now
https://www.physicsforums.com/showthread.php?t=113282

in particular see post #3 and 4
https://www.physicsforums.com/showthread.php?p=931982#post931982

marcus · Apr 30, 2006

marcus · May 22, 2006

there is always a danger of losing rare threads, after they are done, unless you keep a list

Mike2 started this one
Quantum foam producing both particles and spacetime
https://www.physicsforums.com/showthread.php?t=121527
it has John Baez telling Carlo Rovelli's Gedankenexperiment where a bolt of gravity wave comes and knocks down the Eiffel Tower

and also it has selfAdjoint's reply to a Zen koan posed by Carl Brannan.
Carl said "What is Energy made of?"
and sA said "Cobordisms"
In this case the answer is as bad as the question.

I forget why this one is good. It has some John Baez remarks but I forget what exactly
Non-string QG positions in US (some data)
https://www.physicsforums.com/showthread.php?t=121501
Oh yeah, I remember several interesting things---about FQX and Huck Finn and various such.
(apparently Baez was holed up with a bad cold in an apartment in Waterloo Ontario and had some time so he posted on this thread)

Baez and Perez beef strings and branes
https://www.physicsforums.com/showthread.php?t=120985
in the first week this got 34 replies and 774 views
must have generated some controversy. Kea was active IIRC and a bunch of others.
Kea has apparently been writing a PhD thesis and hasnt been posting much.
I guess everybody realizes without my needing to say it that the topic of
this thread is potentially kind of important. matter arising in a 4D model

Please help me build a list of references
https://www.physicsforums.com/showthread.php?t=120779
I confess to gross negligence here. We should have done a better job of responding to Kakarukeys.
Kakarukeys (Jiang-Fung Wong) is starting a QG group at Singapore U. He started this thread to get
links for his reading list. Francesca helped. What a serious person she is, never goofing off, just being helpful. Maybe she will become a professor of Quantum Gravity at an Italian university some day.

Nominations 2nd quarter M.I.P. prediction poll
https://www.physicsforums.com/showthread.php?t=117269

there are a lot more but you can't be complete or the list would be useless

marcus · Aug 4, 2006

In case anyone is interested, here are links to these arxiv.org searches.

Year 2001:
http://lanl.arXiv.org/find/grp_phys...m+AND+OR+triply+doubly+special/0/1/0/2001/0/1

Year 2002:
http://lanl.arXiv.org/find/grp_phys...m+AND+OR+triply+doubly+special/0/1/0/2002/0/1

Year 2003:
http://lanl.arXiv.org/find/grp_phys...m+AND+OR+triply+doubly+special/0/1/0/2003/0/1

Year 2004:
http://lanl.arXiv.org/find/grp_phys...m+AND+OR+triply+doubly+special/0/1/0/2004/0/1

Year 2005:
http://arXiv.org/find/grp_physics/1...m+AND+OR+triply+doubly+special/0/1/0/2005/0/1

Year 2006:
http://lanl.arXiv.org/find/grp_phys...m+AND+OR+triply+doubly+special/0/1/0/2006/0/1

Past 12 months:
http://lanl.arXiv.org/find/grp_phys...m+AND+OR+triply+doubly+special/0/1/0/past/0/1

arxiv stats link (thanks to arivero):
http://arxiv.org/Stats/hcamonthly.html

Harvard adsabs link (published articles only)
[e.g. kywd heterotic, superstring, M-theory, brane, AdS/CFT, jan-jun 2001]

http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1)

[e.g. kywd heterotic, superstring, M-theory, brane, AdS/CFT, jan-jun 2006]

http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1)

marcus · Aug 5, 2006

Wikipedia articles:
http://en.wikipedia.org/wiki/Background_independence

http://en.wikipedia.org/wiki/Quantum_gravity

http://en.wikipedia.org/wiki/Loop_quantum_gravity

A recent contributor to Wikipedia active since early 2006 is
147.188.42.5
who, among others, seems to have worked hard and made a significant improvement----I see less evidence of hostile obfuscation than in prior versions.

marcus · Aug 30, 2006

Thomas Thiemann's landmark LQG survey

I think he did a good job. AFAICS.
Lubos Motl immediately attacked him with resounding snorts of contempt. hee hee.

Hans Kastrup, a mentor to both Thiemann and Bojowald, had been urging Thomas to write a reply and rebuttal to Herman Nicolai's "Outsider View" paper. So Thiemann called this an "inside" view.

http://arxiv.org/abs/hep-th/0608210
Loop Quantum Gravity: An Inside View
Thomas Thiemann
58 pages
Report-no: AEI-2006-066

"This is a (relatively) non -- technical summary of the status of the quantum dynamics in Loop Quantum Gravity (LQG). We explain in detail the historical evolution of the subject and why the results obtained so far are non -- trivial. The present text can be viewed in part as a response to an article by Nicolai, Peeters and Zamaklar [hep-th/0501114]. We also explain why certain no go conclusions drawn from a mathematically correct calculation in a recent paper by Helling et al [hep-th/0409182] are physically incorrect."

marcus · Sep 10, 2006

this might turn out to be a useful resource for people interested in learning about LQG

http://relativity.phys.lsu.edu/ilqgs/
International Loop Quantum Gravity Seminar

"This is a seminar on research ... Tuesday at 9am (US Central Time). Audio is distributed via telephone. Slides of the talks are posted in advance here. Talks are recorded and the audio posted here. Among the groups that participate live are PennState, Perimeter Institute, Marseille, AEI-Potsdam, Utrecht, UNAM-Mexico, FUW-Poland, LSU. Others may join soon. Unfortunately, the phone bridge we have has a limited number of lines so we cannot open live participation to everyone. If your group wishes to participate, please write to pullin@lsu.edu You are welcome to join the mailing list."

Seminar Schedule Fall 2006
http://relativity.phys.lsu.edu/ilqgs/schedule.html

Tuesday Sept. 19
LQG FAQ Abhay Ashtekar PennState

Tuesday Sept. 26
Spinfoam graviton propagator: introduction Carlo Rovelli CPT Marseille

Tuesday Oct. 3
Spinfoam graviton propagator Simone Speziale PI

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

this is a new thing, as of now they have an archive of audio and PDF slides from 3 or 4 past talks and just a few future talks scheduled

marcus · Sep 11, 2006

marcus · Sep 12, 2006

someone watching non-string QG might want to have this link to Utrecht ITP
http://www1.phys.uu.nl/wwwitf/
and in particular to consult this page
http://www1.phys.uu.nl/wwwitf/People/Postdocs.htm
(some postdocs: Artem Starodubtsev, Frank Saueressig, Joe Henson, Hanno Sahlmann, possibly Daniele Oriti)
==========
this gives a window on the QG group's seminars at Nottingham
http://www.maths.nottingham.ac.uk/QG/seminars.html
Fall term begins 15 September
PF poster "fh" may be starting there this Fall.
(main people: John Barrett, Kirill Krasnov)

marcus · Sep 20, 2006

marcus · Sep 25, 2006

The University of Nottingham Maths department has a new website
http://www.maths.nottingham.ac.uk/wp/2006/09/

the link I gave in post #109 no longer works.
a new link to the programme in Quantum Geometry and Gravity is

http://www.maths.nottingham.ac.uk/qg/

Note that PF poster "fh" who just did his Masters with Rovelli at Marseille has gone to Nottingham for PhD.
Nottingham has John Barrett (Barrett-Crane spinfoam model) and Kirill Krasnov (group field theory, with L. Freidel).
Barrett got an important result in Non-Commutative Geometry the same time Alain Connes did, this summer.

the links may continue to change, please let me know if these cease working. I want to be able to keep track of what seminar talks they have in the
Nottingham "Quantum Geometry and Quantum Gravity" program.
(there appears to be some connection with the European Science Foundation---does the ESF officially have a QGQG programme?)

the Nottingham QGQG page says:
"Loop Quantum Cosmology
Loop Quantum Cosmology gives a description of the big bang at the beginning of the universe.
Quantum Groups
Quantum groups enable the calculation of this Feynman diagram coupled to 3d quantum gravity. It shows the diagram is knotted.
Quantum Gravity
The black hole in galaxy NGC 4261 pulls in surrounding dust. The challenge is to describe a black hole according to the laws of quantum mechanics."

I see, John Barrett is the chairman of the governing committee of the european-wide QGQG program, the committee is listed here:
http://www.maths.nottingham.ac.uk/qg/AboutQG.html

Here is the list of QG seminars but so far it is from LAST term (spring 2006):
http://wwwold.maths.nottingham.ac.uk/QG/seminars.html

marcus · Sep 28, 2006

the Utrecht QG team has been expanded
http://www1.phys.uu.nl/wwwitf/People/Postdocs.htm
Daniele Oriti has joined the research group there

Here are some of the postdocs now at Utrecht
Dr. Joe Henson
Dr. Daniele Oriti
Dr. Irina Pushkina
Dr. Hanno Sahlmann
Dr. Frank Saueressig
Dr. Artem Starodubtsev

marcus · Oct 7, 2006

marcus said:

some links to the Harvard abstract search tool:
these are for the Jan-August period in six successive years
keywords = superstring, M-theory, brane, heterotic, AdS/CFT

2001: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2002: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2003: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2004: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2005: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2006: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

...

update on the numbers given earlier
2001---868
2002---843
2003---817
2004---668
2005---704
2006---649
===============
update on the QG group at Utrecht
http://www.phys.uu.nl/~loll/Web/group/group.html

Renate Loll lists 8 students (Masters and PhD) plus these postdocs in her group:

Daniele Oriti
Irina Pushkina
Hanno Sahlmann
Artem Starodubtsev
Joe Henson

the main directory for the Utrecht ITF has more information

http://www1.phys.uu.nl/wwwitf/People/Postdocs.htm

marcus · Oct 26, 2006

marcus said:

some links to the Harvard abstract search tool:
these are for the Jan-Sept period in six successive years
keywords = superstring, M-theory, brane, heterotic, AdS/CFT

2001: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2002: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2003: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2004: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2005: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2006: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

the last of these is still collecting abstracts since it is not yet the end of the month.

...

tentatively,
947, 948, 875, 740, 787, 735
======================
similar links but for January-October
2001: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2002: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2003: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2004: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2005: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2006: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

notknowing · Nov 4, 2006

Rothiemurchus said:

The challenge for string theorists and LQG theorists is to explain why the vacuum energy exists at 10^120 J/m^3 ( there is no reason to think there is anything wrong with the QM calculation) but does not curve space-time.How can
quantum gravity be proved if gravity is not understood on its own yet?

It is very simple why it doesn't curve space-time. The cosmological constant term should simply not be present in the Einstein Field equations. It is a big mistake.

marcus · Nov 4, 2006

update on the ILQGS

marcus said:

this might turn out to be a useful resource for people interested in learning about LQG

http://relativity.phys.lsu.edu/ilqgs/
International Loop Quantum Gravity Seminar

"This is a seminar on research ... Tuesday at 9am (US Central Time). Audio is distributed via telephone. Slides of the talks are posted in advance here. Talks are recorded and the audio posted here. Among the groups that participate live are PennState, Perimeter Institute, Marseille, AEI-Potsdam, Utrecht, UNAM-Mexico, FUW-Poland, LSU. ...
Seminar Schedule Fall 2006
http://relativity.phys.lsu.edu/ilqgs/schedule.html

Tuesday Sept. 19
LQG FAQ Abhay Ashtekar PennState

Tuesday Sept. 26
Spinfoam graviton propagator: introduction Carlo Rovelli CPT Marseille

Tuesday Oct. 3
Spinfoam graviton propagator Simone Speziale PI

Winston Fairbairn Fermions in 3D spinfoam QG 7 november

Bianca Dittrich Approximate Observables 28 november

more:
http://relativity.phys.lsu.edu/ilqgs/schedulefa06.html
==================

Spring 2007 schedule starts 8 February, nothing lined up yet

marcus · Nov 14, 2006

Table of Contents for Dan Oriti's book

Christine blogged for exactly one year and did very nicely at it. One of the last blogs was an invited contribution from Daniele Oriti. He gives a draft table of contents for his book, supposed to come out early 2007.

[/b]Approaches to Quantum Gravity: Towards a New Understanding of Space Time and Matter[/b]

In the book he puts together writings by some 20 or so authors and has Q&A discussion with them at the end of each section. The table of contents can be thought of as giving an overview or schematic picture of current state of QG. I will copy Oriti's guest contribution here, for ready access, in case any of us want to refer to it.

===Daniele Oriti November 2006 at Christine's Background Independence===

Invited contribution: Daniele Oriti

Hi Christine,

Thanks once more for the invitation to contribute to your blog. And, once more, let me congratulate for its well-deserved success, so: happy blog-birthday and keep up the good work!

So, you suggested I could write about the book I am editing (Approaches to quantum grvity: towards a new understanding of space, time and matter) and that is going to be published by C.U.P.

Ok.The idea is to present an overview of most of the current approaches to quantum gravity, through a collection of introductory papers and reviews each devoted either to one of them or to one particular aspect of one of them. If you are interested, the exact (but provisional, as for the sectioning) table of content is as follows:

- Foreword; Daniele Oriti

-- Ideas and general formalisms

* Unfinished revolution; Carlo Rovelli
* The fundamental nature of space and time; Gerardus 't Hooft
* Choice of variables and initial value problems in classical General
* Relativity: prolegomena to any future Quantum Gravity; John Stachel
* Non-locality in Quantum Gravity; Rafael Sorkin
* Spacetime symmetries in histories canonical gravity; Ntina Savvidou
* Categorical geometry and the mathematical foundations of quantum gravity; Louis Crane
* Holography: a keystone of any quantum gravity theory? Rafael Bousso
* Questions and Answers

-- String/M-Theory

* Gauge/Gravity duality; Gary Horowitz and Joe Polchinski
* String theory, holography and quantum gravity; Tom Banks
* String field theory; Washington Taylor
* Mirror symmetry and quantum gravity; Brian Greene
* Questions and Answers

-- Loop Quantum Gravity

* Loop Quantum Gravity; Thomas Thiemann
* Towards a covariant loop quantum gravity; Etera Livine
* Questions and Answers

-- Spin Foam Models

* The spin foam representation of loop quantum gravity; Alejandro Perez
* 3-dimensional spin foam quantum gravity; Laurent Freidel
* The group field theory approach to Quantum Gravity; Daniele Oriti
* Questions and Answers

-- Discrete Quantum Gravity

* Quantum Gravity, or The Art of Building Spacetime; Renate Loll, J. Jurkiewicz and Jan Ambjorn
* Quantum Regge calculus; Ruth Williams
* Consistent discretizations as a road to quantum gravity; Rodolfo Gambini and Jorge Pullin
* Questions and Answers

-- Causal Sets

* The causal set approach to Quantum Gravity; Joe Henson
* Towards gravity from the quantum; Fotini Markopoulou
* Questions and Answers

-- Other approaches

* Quantum gravity and precision tests; Cliff Burgess
* Asymptotic safety; Roberto Percacci
* Emergent General Relativity; Olaf Dreyer
* Questions and Answers

-- Effective models and Quantum Gravity phenomenology

* Quantum Gravity phenomenology; Giovanni Amelino-Camelia
* Algebraic approach to quantum gravity II: noncommutative spacetime; Shahn Majid
* Effective non-commutative models of quantum flat spacetime; Florian Girelli
* Doubly special relativity; Jurek Kowalski-Glikman
* Lorentz invariance violation and its role in quantum gravity phenomenology; Daniel Sudarsky, John Collins and Alejandro Perez
* Generic predictions of quantum theories of gravity; Lee Smolin
* Questions and Answers

Most of the contributed papers are ready, four of them are still missing (I am not going to tell which ones!), but should be ready soon (hopefully). Some of the papers (around 15 o so out of 30) are available online on the archives. I would say we are almost there...I expect the whole thing to be ready in the beginning of 2007, included all the editing work etc, and to be published soon after. But that depends also on the CUP and I am not sure of their timetable.

Oveall I am quite happy with it. I think it is going to fulfill its scope and motivations, which were (at least for me): a) to show how active and diverse is quantum gravity research at present, and that there is a variety of approaches being pursued, and lots of new work, new ideas (radical, speculative and solidly grounded in physics and mathematics at the same time), new directions and results (some partial but suggestive, some well-established, some surprising); b) to provide a comparative perspective on what's going on in the field; to foster not only this comparative perspective, but also, possibly, future collaboration ad 'cross-fertilisation' among different approaches; c) to allow newcomers and students as well as whoever is interested in the subject to be introduced nicely to it. Ultimately, and most importantly, d) to show that this stuff is fun and exciting to work on and to read about!

You may have noticed the Q&A sections at the end of each part. The idea is that authors can ask questions to each other, put forward comments and criticisms, and get/give answers. The aim is twofold: first, to improve the comparative aspect of the book, in that possible difficulties of the various approaches could be pointed out if not already discussed in the papers, and to present additional ideas and points of view that can be relevant for a given approach, but maybe originated or suggested by another; second, to give an example of how research progresses: out of discussions, criticisms, debate, indeed, questions and answers...This part is being prepared, and I really hope it is going to be rich in content and useful.

I enjoyed reading all the papers, and the Q&A, received so far, so I hope other readers will enjoy them to, and find the whole thing useful. Ultimetely, we don't know yet what quantum gravity is, how long it is going to take still to find out (not much, I hope!), and which, if any, of all these approaches will be found to be the closest to the final theory. It is well possible that none of them, as they are currently understood, matches reality as it will look once we have understood more of it; I wouldn't be too surprised. However, I also believe that we can learn a lot from all of them, and that the final theory will involve aspects (formalisms and techniques, ideas, motivations, results, we don't know yet) of many, if not all, of them. If this is the case, this book may be of help.
====end quote===

marcus · Nov 16, 2006

some links to the Harvard abstract search tool:
these are for the whole year, in six successive years
keywords = superstring, M-theory, brane, heterotic, AdS/CFT

2001: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2002: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2003: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2004: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2005: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2006: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

the last is still accumulating publications
(additional entries may also show up in earlier years if they come to the librarian's attention belatedly)

the present gross annual publication counts are
1207, 1192, 1107, 1048, 1062, 839 (this last only goes halfway thru November so is bound to increase substantially)

marcus · Dec 19, 2006

some more links to the Harvard abstract search tool:
these are for the whole year, in four successive years
keywords = superstring, worldsheet, M-theory, brane, heterotic, AdS/CFT

2003: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2004: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2005: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

2006: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

the last is still accumulating publications since the year is not over---this is as of 20 December

3246, 3153, 3132, 2958

(additional entries may also show up in earlier years if they come to the librarian's attention belatedly)

marcus · Dec 19, 2006

Francesca alerted us to the QGQG school taking place in March and April at a mountain resort in Poland.
=============
QGQG stands for Quantum Geometry and Quantum Gravity
Formulations of Quantum Gravity based on quantum geometry can be understood to be background independent because the geometry of space is indeterminate and is therefore not fixed in advance, as it would be in a background dependent approach. The school will help to define the field of background independent QG. It is the first project undertaken by the European Science Foundation's newly-formed QGQG Research Network, coordinated by John Barrett (Barrett-Crane spin networks, standard particle model derived from NCG) and by Hermann Nicolai of Albert Einstein Institute (AEI-Golm).
for more information:
http://www.fuw.edu.pl/~kostecki/school.html

The list of those invited to lecture at the school:

Jan Ambjorn (Utrecht)
Abhay Ashtekar (Penn State)
Alain Connes* (Paris)
Laurent Freidel (Perimeter)
Etera Livine (Lyon)
Shahn Majid (London)
Martin Reuter (Mainz)
Jean-Marc Schlenker (Toulouse)
Thomas Thiemann (AEI-Golm)
Ruth Williams* (Cambridge)

* - to be confirmed

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

here are some guesses as to 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 asymptotically 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

Introduction To Loop Quantum Gravity

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