Introduction To Loop Quantum Gravity

[marcus]

Four authors have posted major papers since the last time I updated this short list of sources to keep handy. Steven Weinberg, Roberto Percacci, Kirill Krasnov, and Thomas Thiemann.

http://arxiv.org/abs/0911.3165
Asymptotically Safe Inflation
Steven Weinberg
Discussion: https://www.physicsforums.com/showthread.php?t=355757

http://arxiv.org/abs/0910.5167
Gravity from a Particle Physicist's perspective
R. Percacci
http://arxiv.org/abs/0911.0386
Renormalization Group Flow in Scalar-Tensor Theories. I
Gaurav Narain, Roberto Percacci
Discussion: https://www.physicsforums.com/showthread.php?t=349513

http://arxiv.org/abs/0911.3793
Gravity-Yang-Mills-Higgs unification by enlarging the gauge group
Alexander Torres-Gomez, Kirill Krasnov (University of Nottingham)
Discussion: https://www.physicsforums.com/showthread.php?t=356492

http://arxiv.org/abs/0911.3433
Canonical path integral measures for Holst and Plebanski gravity. I. Reduced Phase Space Derivation
Jonathan Engle, Muxin Han, Thomas Thiemann
Discussion: https://www.physicsforums.com/showthread.php?t=356264

 

[marcus]

Time to do some housekeeping on this list of 4D quantum gravity links to keep handy.

The list of upcoming conferences known as "hyperspace" has moved to the AEI site.
http://hyperspace.aei.mpg.de/category/Conferences/

June 2009 PlanckScale conference video and slides:
http://www.ift.uni.wroc.pl/~planckscale/
http://www.ift.uni.wroc.pl/~planckscale/movie/
http://www.ift.uni.wroc.pl/~rdurka/planckscale/index-video.php

RUTA pointed out these workshops at Ashtekar's Penn State IGC:
http://www.gravity.psu.edu/events/workshops.shtml

Past talks of the International LQG Seminar, online:
http://relativity.phys.lsu.edu/ilqgs/

July 2009 Marcel Twelve conference in Paris (886 participants):
http://www.icra.it/MG/mg12/en/
http://www.icra.it/MG/mg12/talks_plenary/Freidel.pdf

Loops 2009 in Beijing (~230 participants):
http://www.mighty-security.com/loop/timetable1.htm

November 2009 Asymptotic safety conference at Perimeter:
http://www.perimeterinstitute.ca/en/Events/Asymptotic_Safety/Asymptotic_Safety_-_30_Years_Later/
AsymSafe videos:
http://pirsa.org/C09025
November 2009 Horava gravity videos:
http://pirsa.org/C09026

June 2010 Americas QG school at Morelia:
http://www.physics.ucsb.edu/~pasi/

July 2010 GR19 conference in Mexico City:
http://www.gr19.com/index.php

Nottingham QG network:
http://www.maths.nottingham.ac.uk/qg/

Topcited Loop papers after 2006
(keywords "spin, foam", "field theory, group", "quantum gravity, loop space", and "quantum cosmology, loop space"):
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+K+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3E+2006&FORMAT=www&SEQUENCE=citecount%28d%29

Classic online sources.
Rovelli's talk at Strings 2008 Video:
http://cdsweb.cern.ch/record/1121957?ln=en
Slides:
http://indico.cern.ch/getFile.py/acc...s&confId=21917
2003 draft of Rovelli's book online:
http://www.cpt.univ-mrs.fr/~rovelli/book.pdf
Rovelli's chapter in Oriti's book:
http://arxiv.org/abs/gr-qc/0604045
Review of LQG as of May 2008:
http://relativity.livingreviews.org/Articles/lrr-2008-5/
Steven Weinberg's 6 July talk, main CERN link:
http://indico.cern.ch/conferenceDisplay.py?confId=57283
Weinberg video (historical overview up to minute 58 followed by
no-frills approach to unification in the last 12 minutes):
http://cdsweb.cern.ch/record/1188567/
Related Weinberg paper Asymptotically Safe Inflation:
http://arxiv.org/abs/0911.3165
Discussion thread https://www.physicsforums.com/showthread.php?t=355757
Roberto Percacci's Gravity from a Particle Physicist's Perspective:
http://arxiv.org/abs/0910.5167
Narain and Percacci Renormalization Group Flow in Scalar-Tensor Theories. I:
http://arxiv.org/abs/0911.0386
Discussion thread https://www.physicsforums.com/showthread.php?t=349513

Photos from the first Loops conference, at Marseille 2004:
http://math.ucr.edu/home/baez/marseille/

Selected longshots.
Vincent Rivasseau at the 2009 Perimeter AsymSafe conference:
http://pirsa.org/09110049/
Ted Jacobson at the 2009 Perimeter HorGrav conference:
http://pirsa.org/09110066/
Krasnov 2006 video lecture:
http://pirsa.org/06110041/
Krasnov 2008 audio+pdf talk at the ILQGS:
http://relativity.phys.lsu.edu/ilqgs/krasnov020508.pdf
http://relativity.phys.lsu.edu/ilqgs/krasnov020508.aif
Krasnov and Gomez Gravity-Yang-Mills-Higgs unification by enlarging the gauge group:
http://arxiv.org/abs/0911.3793

 

[marcus]

It could be that there will be no Loops 2010 conference, no big international QG meeting.
I've heard nothing about one being organized. On the other hand, I have heard of other comparable or related events:

Sabine Hossenfelder is organizing a Stockholm workshop on the experimental search for QG.
http://backreaction.blogspot.com/2009/11/experimental-search-for-quantum-gravity.html
Here's the website:
http://th.physik.uni-frankfurt.de/~hossi/ESQG10/
This will take place 12-16 July.

Then there is this two-week-long PASI QG school, with lecture-series by Abhay Ashtekar, Carlo Rovell, Laurent Freidel, Renate Loll...
PASI stands for "Panamerican Advanced Studies Institute". The school will be supported by the US National Academy of Sciences. In a way that is even better than having a Loops conference (in terms of some obvious practical goals.) Here is the 2010 QG School website:
http://www.physics.ucsb.edu/~pasi/
This will take place 23 June-3 July.

Thanks to 'Sabah for mentioning the Experimental QG Search workshop. The website already shows an impressive list of QG people who will be participating.

Also being held in 2010 is the 19th international General Relativity and Gravitation conference, GR19. This is a major conference held every three years, bringing all gravity related research programs together. One of the parallel sessions will be devoted to Loop.
http://www.gr19.com/index.php
This will take place 5-9 July.

So things will be happening with some resemblance to an annual meeting, but as far as I know no official Loops 2010 has been announced.

Here's the website for Strings 2010, in case anyone is interested.
http://mitchell.physics.tamu.edu/Conference/string2010/
It will take place 15-19 March.

 

[guedes]

I think it's good to point out the upcoming Quantum Gravity school held in Zakopane taking place 28 February - 4 March. This year the main topic is Open problems in Loop Quantum Gravity and it seems to be quite interesting as a way to settle future directions. The programme (and registration - still opened!) here:
http://www.fuw.edu.pl/~jpa/qgqg3/

*Notice*
At the end of the Loops'09 conference it was announced that there won't be any Loops'10 precisely because of GR19. And so, the next one is Loops'11 to be held in Madrid, Spain.

 

[marcus]

What do the upcoming conference programs tell us?

It's often informative to note the focus of the year's workshops, conferences and schools. Can give an idea about the direction things are going. This year there will be two QG schools (when I started watching in 2003 there were no annual Loop conferences and no QG schools at all.) This year there will also be a workshop on search for observable effects--QG phenomena.

The programs for the year's meetings are mosty not posted yet, but here are links to the websites that we can watch for information as it appears.

QGQG3, The third European QG school, 28 February - 4 March
http://www.fuw.edu.pl/~jpa/qgqg3/

Panamerican QG School, the first such supported by the US, 23 June - 3 July
http://www.physics.ucsb.edu/~pasi/

GR19, the triennial international meeting on General Rel and Gravitation, 5 - 9 July
http://www.gr19.com/index.php

Workshop on the Experimental Search for Quantum Gravity, 12 - 16 July
http://th.physik.uni-frankfurt.de/~hossi/ESQG10/

There will be a session of GR19 devoted to loop and spinfoam quantum gravity. This will serve as the main international LQG conference this year so there will be no separate Loops 2010, as Guedes tells us. He also says Loops 2011 will be held in Madrid.

 

[marcus]

In an earlier post I had a bad link to the slides for Rovelli's Strings 2008 talk.
Here are the (in one case repaired) links
Video:
http://cdsweb.cern.ch/record/1121957?ln=en
Slides:
http://indico.cern.ch/getFile.py/access?contribId=30&resId=0&materialId=slides&confId=21917

 

[marcus]

An undergraduate course in Loop Quantum Gravity:
http://www.phys.lsu.edu/classes/spring2010/phys4750/

Professor Jorge Pullin has already posted the first two problem sets online. The second set is due 15 February.
Instead of a text, he is distributing his own lecture notes--but so far these are only for the students taking the course: they have not been posted on line.

==quote==
PHYS 4750: Introduction to loop quantum gravity
...
This course will be an introduction for undergraduates to loop quantum gravity. To our knowledge, this is the first time such a course is offered in the world. We will assume minimal prerequisites: some knowledge of Lagrangian mechanics, some quantum mechanics and special relativity.

Topics:

1. Introduction: quantum gravity, why, what?
2. Special relativity and electromagnetism.
3. Some elements of general relativity.
4. Hamiltonian mechanics including constraints and fields.
5. Quantum mechanics and elements of quantum field theory.
6. Yang-Mills theories.
7. General relativity in terms of Ashtekar’s new variables.
8. Loop representation for general relativity.
9. An application: loop quantum cosmology.
10. Further developments.
11. Open issues and controversies.Grades for the course will consist 50% on homework (graded pass/fail) and a final presentation of a paper. A list of possible topics will be given later in the semester. ...
==endquote==

Prof. Pullin is also a proficient player of the Scottish bagpipes. In case you do not believe this, his website has a link enabling you to hear him perform on the melancholy and belligerent instrument of his Scottish ancestors.
http://www.phys.lsu.edu/faculty/pullin/

 

[marcus]

The schedule of talks to be held at the main annual Strings conference has been partially posted.

http://mitchell.physics.tamu.edu/Conference/string2010/Conference.html#

So far the titles of the talks are not included in the schedule.

The conference begins in slightly less than one month, on 15 March.

http://mitchell.physics.tamu.edu/Conference/string2010/

By watching the titles of the talks and comparing Strings 2010 with the same conference in past years we can hopefully learn something about trends and shifts of focus in this collection of research fields.

 

[marcus]

It has been over two months, time to update this list of handy 4D quantum gravity links.

The list of upcoming conferences known as "hyperspace" has moved to the AEI site:
http://hyperspace.aei.mpg.de/category/Conferences/
The Nottingham QG network:
http://www.maths.nottingham.ac.uk/qg/

June 2009 PlanckScale conference video and slides:
http://www.ift.uni.wroc.pl/~planckscale/
http://www.ift.uni.wroc.pl/~planckscale/movie/
http://www.ift.uni.wroc.pl/~rdurka/planckscale/index-video.php
RUTA pointed out these workshops at Ashtekar's Penn State IGC:
http://www.gravity.psu.edu/events/workshops.shtml
Past talks of the online International LQG Seminar, run by Prof. Jorge Pullin:
http://relativity.phys.lsu.edu/ilqgs/
July 2009 Marcel Twelve conference in Paris (886 participants):
http://www.icra.it/MG/mg12/en/
http://www.icra.it/MG/mg12/talks_plenary/Freidel.pdf
November 2009 Asymptotic safety conference at Perimeter:
http://www.perimeterinstitute.ca/en/Events/Asymptotic_Safety/Asymptotic_Safety_-_30_Years_Later/
AsymSafe videos:
http://pirsa.org/C09025
November 2009 Horava gravity videos:
http://pirsa.org/C09026

28 February - 4 March 2010, The third European QG school (QGQG3, quantum geometry/gravity)
http://www.fuw.edu.pl/~jpa/qgqg3/

15-19 March 2010 Strings 2010
http://mitchell.physics.tamu.edu/Conference/string2010/

23 June-3 July 2010, Americas QG school at Morelia:
http://www.physics.ucsb.edu/~pasi/

5-9 July 2010, GR19 conference in Mexico City
http://www.gr19.com/index.php
(LQG will have a session of GR19 which will serve as this year's "Loops 2010"

12-16 July 2010, Sabine Hossenfelder's Stockholm workshop on the experimental search for QG
http://th.physik.uni-frankfurt.de/~hossi/ESQG10/
http://backreaction.blogspot.com/2009/11/experimental-search-for-quantum-gravity.html

Loops 2011 will be held in Madrid.

Topcited Loop papers after 2006
(keywords "spin, foam", "field theory, group", "quantum gravity, loop space", and "quantum cosmology, loop space"):
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+K+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3E+2006&FORMAT=www&SEQUENCE=citecount%28d%29

Classic online sources.
Rovelli's talk at Strings 2008 Video:
http://cdsweb.cern.ch/record/1121957?ln=en
Slides: http://indico.cern.ch/getFile.py/access?contribId=30&resId=0&materialId=slides&confId=21917
2003 draft of Rovelli's book online:
http://www.cpt.univ-mrs.fr/~rovelli/book.pdf
Rovelli's chapter in Oriti's book:
http://arxiv.org/abs/gr-qc/0604045
Review of LQG as of May 2008:
http://relativity.livingreviews.org/Articles/lrr-2008-5/

Steven Weinberg's 6 July 2009 talk, main CERN link:
http://indico.cern.ch/conferenceDisplay.py?confId=57283
Weinberg video (historical overview up to minute 58 followed by
no-frills approach to unification in the last 12 minutes):
http://cdsweb.cern.ch/record/1188567/
Related Weinberg paper Asymptotically Safe Inflation:
http://arxiv.org/abs/0911.3165
Discussion thread https://www.physicsforums.com/showthread.php?t=355757

Etera Livine's 17 February 2010 talk, A review of Spinfoams and Group Field Theory
http://pirsa.org/10020079/
Related paper by Girelli Livine Oriti, 4d Deformed Special Relativity from Group Field Theories
http://arxiv.org/abs/0903.3475

Photos from the first Loops conference, at Marseille 2004:
http://math.ucr.edu/home/baez/marseille/

Selected longshots.
Vincent Rivasseau at the 2009 Perimeter AsymSafe conference:
http://pirsa.org/09110049/
Ted Jacobson at the 2009 Perimeter HorGrav conference:
http://pirsa.org/09110066/
Ted Jacobson Thermodynamics of Spacetime: The Einstein Equation of State
http://arXiv.org/abs/gr-qc/9504004
Ted Jacobson Introduction to Quantum Fields in Curved Spacetime and the Hawking Effect
http://arxiv.org/abs/gr-qc/0308048
Erik Verlinde On the Origin of Gravity and the Laws of Newton
http://arxiv.org/abs/1001.0785
Lee Smolin, Newtonian gravity in loop quantum gravity
http://arxiv.org/abs/1001.3668
Jerzy Kowalski-Glikman, Note on gravity, entropy, and BF topological field theory
http://arxiv.org/abs/1002.1035
Easson Frampton Smoot, Entropic Accelerating Universe
http://arxiv.org/abs/1002.4278

Renate Loll 3-week course at Perimeter, Intro to Quantum Gravity:
Lecture 1: http://pirsa.org/10010094/ (25 January 2010)
Lecture 2: http://pirsa.org/10010095/ (26 January)
Lecture 3: http://pirsa.org/10010096/ (27 January)
Lecture 4: http://pirsa.org/10010097/ (28 January)
Lecture 5: http://pirsa.org/10010098/ (29 January)
Lecture 6: http://pirsa.org/10020060/ (1 February)
Lecture 7: http://pirsa.org/10020061/ (2 February)
Lecture 8: http://pirsa.org/10020062/ (3 February)
Lecture 9: http://pirsa.org/10020063/ (4 February)
Lecture 10: http://pirsa.org/10020064/ (5 February)
Lecture 11: http://pirsa.org/10020065/ (8 February)
Lecture 12: http://pirsa.org/10020066/ (9 February)
Lecture 13: http://pirsa.org/10020067/ (10 February)
Lecture 14: http://pirsa.org/10020068/ (11 February)
Lecture 15: http://pirsa.org/10020069/ (12 February)

Undergrad LQG course at Louisiana State taught by Jorge Pullin. Some material online:
http://www.phys.lsu.edu/classes/spring2010/phys4750/
http://www.phys.lsu.edu/faculty/pullin/

List of Strings 2010 talks, for comparison or trend-spotting:
http://mitchell.physics.tamu.edu/Conference/string2010/TitleofTalks.html

 

[marcus]

Erik Verlinde's two blog entries about his entropic force explanation of gravity.
http://staff.science.uva.nl/%7Eerikv/page20/page18/page18.html
The informal blog discussion is a helpful addition to the paper.

Sabine Hossenfelder's notes commenting on Verlinde's paper.
http://prime-spot.de/Physics/notes6.pdf
Her blog entry summarizing what she said in the notes:
http://backreaction.blogspot.com/2010/03/gravity-is-entropy-is-gravity-is.html

 

[marcus]

Another insightful Jacobson paper on causal horizon entropy to keep in the top drawer.
http://arxiv.org/abs/gr-qc/0302099
thanks to MTd2 for the reference linking to it.

 

[marcus]

It was already pointed out that this year's LOOPS 2010 is planned as the Loops section of a major international conference that happens every three years, the General Relativity and Gravitation (abbr. GRG, or simply GR) triennial.

This time it's the 19th GR triennial, so you google "GR19"
Then you click on "scientific program" and within that, click on Parallel Sessions.
===quote from GR19 website about some parallel sessions===
D1 Loop Quantum Gravity and Spin Foams
Chair: Alejandro Corichi
Partial list of speakers:

Abhay Ashtekar
Bianca Dittrich
Laurent Freidel
Parampeet Singh


D2 Strings, branes and M-theory
Chair: Shiraz Minwalla
Partial list of speakers:

Petr Horava
Xi Yin
Wei Song


D3 Causal sets, Causal dynamical triangulations, Non-commutative geometry, and other approaches to quantum gravity
Chair: Fay Dowker
Partial list of speakers:

Renate Loll
David Rideout
Steve Carlip
Daniel Litim

==endquote==

Carlo Rovelli will be giving a plenary survey talk Tuesday 6 July 11:30-12:30 titled
Progress in loop gravity and spin foams

http://www.gr19.com/index.php

 

[MTd2]

Wei Song is one of the guys from the Fermi Sea paper: http://arxiv.org/abs/0912.4265

Xi Yin is a guy that has worked recently with Davide Gaiotto, and he is pretty mainstream string theory.

So, I don't think these qualify as something that would belong to a Loops conference.

Maybe Petr Horava, but he should present his recent work with Cenke Xu to look like more loopy: http://arxiv4.library.cornell.edu/abs/1003.0009

 

[marcus]

Wei Song is one of the guys from the Fermi Sea paper: http://arxiv.org/abs/0912.4265

Xi Yin is a guy that has worked recently with Davide Gaiotto, and he is pretty mainstream string theory.

So, I don't think these qualify as something that would belong to a Loops conference.

Maybe Petr Horava, but he should present his recent work with Cenke Xu to look like more loopy: http://arxiv4.library.cornell.edu/abs/1003.0009

The Loop session of GR19 is the session chaired by Alejandro Corichi.
The papers by Horava, and by Xi Yin are not supposed to be Loop papers!
They are not being given in the Loop session, they are being given in the STRING THEORY session of GR19. There is no reason for Horava to "look loopy".

I just threw in some extra information. Including some about the CAUSAL SETS/DYNAMICAL TRIANGULATIONS ETC session, chaired by Dowker. That's looking good already:
with Loll, and Steve Carlip.

These sessions will be getting a lot more speakers as time goes on. It is still very early. But already they are beginning to take shape.

Let's not start discussion here in this thread. Keep it for selected links. If you want to discuss GR19, could we start a discussion thread about it?

 

[marcus]

The international GRG (general relativity and gravitation) society holds a big conference every three years. The upcoming one is GR19 Mexico City starting 5 July 2010:
http://www.gr19.com/index.php

They typically draw some 600 or more participants talking on every aspect of the cosmos' geometry: numerical sims, gravitational waves, lensing, cosmology, quantum gravity/geometry, loop-string-triangulations, analog black hole models, etc etc.

This year there will be, in addition to all the technical talks in-conference, a plenary public lecture for everybody, not just for conference participants.

This pubic lecture will be on the evening of 6 July, and it will be given by George F. Smoot.



Smoot gives a dynamite talk
http://www.ted.com/talks/george_smoot_on_the_design_of_the_universe.html
Rovelli is giving a plenary (in-conference) talk on current progress in LQG.
When you put the various conference elements together with mariachi music it augurs well--promises a lively mix.
====================================

Parampreet Singh has started a crash course at Perimeter in cosmo perturbation theory---techniques critical in studying the early universe.
James Bardeen wrote the closest thing to a textbook on this--a 1988 review paper. Param is using the Bardeen paper as text.
Try this link:
http://adsabs.harvard.edu/abs/1988gsjs.conf...B
Cosmological perturbations from quantum fluctuations to large scale structure

There is the first Param lecture video:
http://pirsa.org/10040058/
You may notice some minor file mis-labeling if you play it. But that is Param doing his first lecture (not somebody else Anders Sandvik)
He's good. Neil Turok, director of Perimeter is supposed to be giving some of the lectures in this course. It looks like they are doing one lecture a day. Maybe for a total of 15 lectures. (The typical Perimeter crash course format.)

The course is called Explorations in Cosmology 2,
because Perimeter just concluded a 15 lecture crash course called "Explorations in Cosmology 1". This is the follow-up to that first course. It was taught by Tolley and Sandera
All the 15 videos are available for that too, if you want.

Param is a many times co-author with top people in LQC (loop quantum cosmology) including Abhay Ashtekar. He was postdoc at Penn State. It is to be expected that what he is teaching now is relevant to testing LQC because quantum fluctuations are theory and largescale structure are observation and Bardeen's cosmo perturbation math is the bridge from the theory (you want to test) to the structure (you can observe.)

 

[marcus]

Time to update this list of handy QG links. Last time I updated was February 2010. We can add Mathilde Marcolli's paper and also Kirill Krasnov's exciting Perimeter video.

To find out about conferences and workshops, "hyperspace" at the AEI site:
http://hyperspace.aei.mpg.de/category/Conferences/
The Nottingham QG network:
http://www.maths.nottingham.ac.uk/qg/

Introductory courses:
Renate Loll 3-week course at Perimeter, Intro to Quantum Gravity:
Lecture 1: http://pirsa.org/10010094/ (25 January 2010)
for all 15 lectures, see
http://pirsa.org/index.php?p=speaker&name=Renate_Loll
Undergrad LQG course at Louisiana State taught by Jorge Pullin. Some material online:
http://www.phys.lsu.edu/classes/spring2010/phys4750/
http://www.phys.lsu.edu/faculty/pullin/

June 2009 PlanckScale conference video and slides:
http://www.ift.uni.wroc.pl/~planckscale/
http://www.ift.uni.wroc.pl/~planckscale/movie/
http://www.ift.uni.wroc.pl/~rdurka/planckscale/index-video.php
RUTA pointed out these workshops at Ashtekar's Penn State IGC:
http://www.gravity.psu.edu/events/workshops.shtml
Past talks of the online International LQG Seminar, run by Prof. Jorge Pullin:
http://relativity.phys.lsu.edu/ilqgs/
November 2009 Asymptotic safety conference at Perimeter:
http://www.perimeterinstitute.ca/en/Events/Asymptotic_Safety/Asymptotic_Safety_-_30_Years_Later/
AsymSafe videos:
http://pirsa.org/C09025
7-13 February 2010, Oberwolfach workshop on Noncommutative Geometry and LQG ("Loops, Algebras, Spectral Triples")
http://www.mfo.de/programme/schedule/2010/06b/OWR_2010_09.pdf
28 February - 4 March 2010, The third European QG school (QGQG3, quantum geometry/gravity)
http://www.fuw.edu.pl/~jpa/qgqg3/
23 June-3 July 2010, Americas QG school at Morelia:
http://www.physics.ucsb.edu/~pasi/
5-9 July 2010, GR19 conference in Mexico City
http://www.gr19.com/index.php
(LQG will have a session of GR19 which will serve as this year's "Loops 2010", Loops 2011 will be in Madrid).
12-16 July 2010, Sabine Hossenfelder's Stockholm workshop on the experimental search for QG
http://th.physik.uni-frankfurt.de/~hossi/ESQG10/
http://backreaction.blogspot.com/2009/11/experimental-search-for-quantum-gravity.html
Topcited Loop papers after 2006
(keywords "spin, foam", "field theory, group", "quantum gravity, loop space", and "quantum cosmology, loop space"):
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+K+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3E+2006&FORMAT=www&SEQUENCE=citecount%28d%29

Classic online sources.
Rovelli's talk at Strings 2008 Video:
http://cdsweb.cern.ch/record/1121957?ln=en
Slides: http://indico.cern.ch/getFile.py/access?contribId=30&resId=0&materialId=slides&confId=21917
2003 draft of Rovelli's book online:
http://www.cpt.univ-mrs.fr/~rovelli/book.pdf
Rovelli's chapter in Oriti's book:
http://arxiv.org/abs/gr-qc/0604045
Review of LQG as of May 2008:
http://relativity.livingreviews.org/Articles/lrr-2008-5/
Rovelli, A new look at loop quantum gravity
http://arxiv.org/abs/1004.1780

Steven Weinberg's 6 July 2009 talk, main CERN link:
http://indico.cern.ch/conferenceDisplay.py?confId=57283
Weinberg video (historical overview up to minute 58 followed by
no-frills approach to unification in the last 12 minutes):
http://cdsweb.cern.ch/record/1188567/
Related Weinberg paper Asymptotically Safe Inflation:
http://arxiv.org/abs/0911.3165
Discussion thread https://www.physicsforums.com/showthread.php?t=355757

Recent progress in core Lqg:
Etera Livine's 17 February 2010 talk, A review of Spinfoams and Group Field Theory
http://pirsa.org/10020079/
Related paper by Girelli Livine Oriti, 4d Deformed Special Relativity from Group Field Theories
http://arxiv.org/abs/0903.3475
Alesci Rovelli, A regularization of the hamiltonian constraint compatible with the spinfoam dynamics
http://arxiv.org/abs/1005.0817
Bianchi Regoli Rovelli, Face amplitude of spinfoam quantum gravity
http://arxiv.org/abs/1005.0764
Bianchi Rovelli Vidotto, Towards Spinfoam Cosmology
http://arxiv.org/abs/1003.3483Photos from the first Loops conference, at Marseille 2004:
http://math.ucr.edu/home/baez/marseille/

Selected longshots.
Mathilde Marcolli et al, Spin Foams and Noncommutative Geometry
http://arxiv.org/abs/1005.1057
Kirill Krasnov Deformations of General Relativity
http://pirsa.org/10050002/
Lisi Smolin Speziale, Unification of gravity, gauge fields, and Higgs bosons
http://arxiv.org/abs/1004.4866
Vincent Rivasseau at the 2009 Perimeter AsymSafe conference:
http://pirsa.org/09110049/
Ted Jacobson at the 2009 Perimeter HorGrav conference:
http://pirsa.org/09110066/
Ted Jacobson Thermodynamics of Spacetime: The Einstein Equation of State
http://arXiv.org/abs/gr-qc/9504004
Ted Jacobson Introduction to Quantum Fields in Curved Spacetime and the Hawking Effect
http://arxiv.org/abs/gr-qc/0308048
Erik Verlinde On the Origin of Gravity and the Laws of Newton
http://arxiv.org/abs/1001.0785
Lee Smolin, Newtonian gravity in loop quantum gravity
http://arxiv.org/abs/1001.3668
Jerzy Kowalski-Glikman, Note on gravity, entropy, and BF topological field theory
http://arxiv.org/abs/1002.1035
Easson Frampton Smoot, Entropic Accelerating Universe
http://arxiv.org/abs/1002.4278
Chamseddine Connes, Noncommutative Geometry as a Framework for Unification of all Fundamental Interactions including Gravity. Part I
http://arxiv.org/abs/1004.0464

 

[marcus]

Francesca's LQG world map:
http://maps.google.com/maps/ms?ie=U...985216139270436.0004843830d27f3e6c50e&t=h&z=0

 

[marcus]

To add to our list of this year's conferences on QG and unification:
Regensburg Conference on Quantum Field Theory and Gravity: Conceptual and Mathematical Advances in the Search for a Unified Framework (28 September - 1 October)

http://www.uni-regensburg.de/qft2010/qftgravity2010program.html
"...the aim of this conference is to bring together physicists and mathematicians working in quantum field theory and general relativity, and to encourage scientific discussions on fundamental and conceptual issues. Selected talks will introduce different directions of research, in a way as non-technical and easily accessible as possible. The conference is also intended for young researchers on the graduate and post-graduate level."

Confirmed invited participants:
Christian Bär (Potsdam)
Helga Baum (Berlin)
Andreas Doering (Oxford)
Michael Dütsch (Göttingen)
Thomas Elze (Pisa)
Bertfried Fauser (Birmingham)
Chris Fewster (York)
Christian Fleischhack (Paderborn)
Klaus Fredenhagen (Hamburg)
Claus Gerhardt (Heidelberg)
Domenico Giulini (Hannover)
Dietrich Häfner (Grenoble)
Christian Hainzl (Tübingen)
Stefan Hollands (Cardiff)
Ines Kath (Greifswald)
Claus Kiefer (Köln)
Michael Kiessling (Rutgers)
Jerzy Kijowski (Warszawa)
Philippe LeFloch (Paris)
Renate Loll (Utrecht)
Dieter Lüst (München)
Robert Oeckl (Morelia)
Daniele Oriti (Golm)
Gerd Rudolph (Leipzig)
Miguel Sánchez (Granada)
Alexander Strohmaier (Loughborough)
Blake Temple (Davis)
Stefan Teufel (Tübingen)
Shing-Tung Yau (Harvard)

 

[marcus]

Matilde Marcolli and two others organized a Noncommutative Geometry and LQG workshop at Oberwolfach in February.
http://www.mfo.de/programme/schedule/2010/06b/OWR_2010_09.pdf
15 talks, including these:
Hanno Sahlmann
Introduction to Loop Quantum Gravity – physics background, and kinematics
Johannes Aastrup
On spectral triples in Quantum gravity
Klaus Fredenhagen
Perturbative Algebraic Quantum Field theory
Thomas Thiemann
Reduced phase-space quantisation in Loop Quantum Gravity
Jesper Møller Grimstrup
On Spectral Triples of Holonomy Loops II
Matilde Marcolli
Spin foams and noncommutative geometry
Fedele Lizzi
Noncommutative Lattices
Jurek Lewandowski (with Andrzej Okolow)
Quantum Group Connections
Raimar Wulkenhaar
Quantum field theory on noncommutative geometries

Marcolli's two co-organizers were Ryszard Nest and Christian Fleischhack. Nest (b. 1950) is director of the NCG group at Uni Copenhagen. He has co-authored with Aastrup and Grimstrup, who have been known to us since around 2006 when they initiated an effort to combine LQG and NCG (with its realization of the standard particle physics model.) Fleischhack has published a number of LQG papers--I particularly remember his work on black hole entropy in association with Jerzy Lewandowski, but see his publication list here: http://www.math.uni-hamburg.de/home/fleischhack/ .

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

Another workshop. John Barrett and Daniele Oriti each give presentations here.
14-17 May 2010 at Bayrischzell (picturesque town in the mountains some 50 miles south of Munich)
Noncommutativity and Physics: Spacetime Quantum Geometry
Program consisted of 21 talks:
http://hep.itp.tuwien.ac.at/~miw/bzell2010/program2010.html
Some samples of the 21 talks:
John Barrett State sum models, induced gravity and the spectral action
Fedele Lizzi Bosonic spectral action induced from anomaly cancellation
Catherine Meusburger Observables for quantum gravity from higher categories
Daniele Oriti The microscopic dynamics of quantum space as a group field theory

Oriti's slides as sample of the available PDF:
http://hep.itp.tuwien.ac.at/~miw/bzell2010/Oriti-2010.pdf
Another sample, Fedele Lizzi's slides:
http://hep.itp.tuwien.ac.at/~miw/bzell2010/Lizzi-2010.pdf

Scenery and list of speakers:
http://hep.itp.tuwien.ac.at/~miw/bzell2010/
==================

Perimeter Laws of Nature conference:
http://www.perimeterinstitute.ca/en/Events/Laws_of_Nature/Schedule/
All the videos:
http://pirsa.org/C10001
Smolin and Unger presentation:
http://pirsa.org/10050053/
Related Ariel Caticha talk on getting quantum theory from Entropic Dynamics:
http://pirsa.org/10050021/
(What Ariel calls entropic dynamics looks like a nice mathematical generalization of bayes inference to me, not sure of value but interesting...good questions from Rafael Sorkin.)

 

[marcus]

GR19 is shaping up. Parallel session timeslots have been assigned. Sessions D1 thru D4 are of special interest to us here.

This is a major international conference on General Relativity and Gravitation which takes place every three years. This time it will be in Mexico City, July 5-9.

Parallel Session D1, Loop and Spin Foam (chair=Corichi) has been assigned a total of 6 hours.
D2, Strings Branes and M (Minwalla) has been assigned 3 hours.
D3, Causal Sets, CDT, NCG (Dowker) has been assigned 4 hours.
D4, curved space QFT (Unruh) has been assigned 8 hours.

The full title of Bill Unruh's session is "Quantum fields in curved space-time, semiclassical gravity, quantum gravity phenomenology, and analog models."
I think it is significant that they got a famous top physicist (of the Unruh effect) to chair and that there is a lot of activity in things like effective field theory, phenomenology, analog lab models of black hole horizons, and field theory on curved spacetime.
It seems like a healthy development to me, and the Mexico GR19 is signaling this development.
http://www.gr19.com/paralsec.php

BTW when I first came to PF Beyond Forum, Alejandro Corichi was posting here a lot*. Not for years now, but it goes to show----shows something, doesn't it? Not quite sure what. Anyway since those days he has put together a strong LQG/Spinfoam program at UNAM Morelia, and now he chairs the Loop session at the triennial GR conference. Good luck with it.

*Under some pseudonym which out of respect for anonymity I have completely forgotten

 

[Thought Grind]

Hello,

Just wondering if it would be OK for a self-taught physicist to take a poke at LQG, its design, function and context. There are many aspects I find questionable and figure that if it is the unification of the General Theory of Relativity and Quantum Mechanics then you could withstand the prodding of one such as I. I hold no ill will and greatly respect the efforts that went into the creation of LQG but that alone doesn't justify the fundaments of the relative truths involved that seem ... misconstrued?

If not then thank-you for your time,

Sean B.

 

[marcus]

Sean, not in this thread please. Just start your own thread to challenge and/or ask questions about LQG. Others have done so and have gotten a number of people involved in answering!

This thread has settled down into a concise regularly updated reading list of key papers, reviews, conferences. Source material that has proven useful to keep handy. I don't want to mess up that function by having a discussion in the middle of it.

I hope you understand, and are successful in starting a separate "Questions about LQG" or a "Things wrong with LQG" thread that you find satisfactory.

 

[Thought Grind]

Thank you, I may do just that.

 

[marcus]

To add to the main list of links, next time it is updated:
A list of QG researchers, mostly involved in LQG
http://en.wikipedia.org/wiki/List_of_loop_quantum_gravity_researchers

Popularization of science at frontiers of research is often misleading---creating more confusion than understanding---but it can still be helpful to keep handy some selected public outreach links:
http://gravity.psu.edu/outreach/index.shtml

This list is organized by date, so there is a section of recent (2006-2010) material---illustrated magazine articles, video clips. Links to about 15 recent items, many from European media instead of Usa. There is also a section with older outreach stuff.

 

[marcus]

The list of lectures has been posted for the Morelia QG school.
The school begins in less than a week---on Wednesday 23 June.
Some reading lists have been provided, and some links to online papers.
http://www.physics.ucsb.edu/~pasi/lectures.html

Rovelli is scheduled to give three 90-minute lectures based on his "New LQG" paper of April 2010 (Arxiv 1004.1780).

I see that each speaker is scheduled to give three 90-minute lectures.

The title of Freidel's talks has not been posted.
The title of Renate Loll's talks has not been posted
Ashtekar has posted an extensive reading list for his talks on Loop Quantum Cosmology.

http://www.physics.ucsb.edu/~pasi/index.html

 

[marcus]

The 2010 QG School at Morelia is currently in session.
I believe the main organizer is Alex Corichi:
http://www.matmor.unam.mx//index.php?option=com_content&task=view&id=48&Itemid=58
Today I read that the organizers plan to post video of the lectures on line.

This could eventually be a useful resource. Rovelli will give three 90-minute lectures, as will Ashtekar, Laurent Freidel, and others. Again, the links are:
http://www.physics.ucsb.edu/~pasi/index.html
http://www.physics.ucsb.edu/~pasi/lectures.html

If I am not mistaken, Freidel's series of 3 lectures will start on Monday 28 June and Rovelli's on Wednesday 30 June.

 

[marcus]

The international GR conference (General Relativity and Gravitation), held every three years, starts in Mexico City a couple of days from now.

Rovelli will give a one-hour plenary talk, Tuesday July 6, 11:30-12:30. Corichi is chairing the following:

LQG and Spin Foam sessions

Tuesday July 6th

Freidel 14:00 - 14:30
Kisielowski 14:30 - 14:45
Kaminski 14:45 - 15:00

Singh 15:00 - 15:30
Pawlowski 15:30 - 15:45
Wilson 15:45 - 16:00

Thursday, July 8th

Dittrich 16:30 - 17:00
Perez 17:00 - 17:15
Dziendzikowski 17:15 - 17:25
Zapata 17:25 - 17:35

Perini 17:35 - 17:50
Pullin 17:50 - 18:10
Tsobanjan 18:10 - 18:20
Mangliaro 18:20 - 18:30

Friday, July 9th

Ashtekar 16:30 - 17:00
Campiglia 17:00 - 17:15
Vidotto 17:15 - 17:30

Bianchi 17:30 - 17:45
Lewandowski 17:45 - 18:05
Husain 18:05 - 18:20
Ma 18:20 - 18:30

http://www.gr19.com/parallels/d1_program.php
http://www.gr19.com/
Rovelli's talk will give a survey "Progress in loop gravity and spin foams". For the complete list see
http://www.gr19.com/scipro.php
===============================

Fay Dowker is chairing session D3 Causal sets, Causal dynamical triangulations, Non-commutative geometry, and other approaches to quantum gravity
Monday July 5

14:00 - 14:30 Loll
14:30 - 15:00 Litim
15:00 - 15:20 Satz
15:20 - 15:35 Oeckl
15:35 - 15:55 Sakellariadou
15:55 - 16:00 Nelson

16:30 - 17:00 Carlip
17:00 - 17:30 Rideout
17:30 - 17:50 Craig
17:50 - 18:00 Bonder
18:00 - 18:10 Magdaleno
18:10 - 18:20 Tafoya
18:20 - 18:30 Nesterov

17.00-17.30 Amsel,
17.30-17.45 Gorbonos
17.45-18.00 Rodriguez
18.00-18.15 Chirco

αβγδεζηθικλμνξοπρσςτυφχψω...ΓΔΘΛΞΠΣΦΨΩ...∏∑∫∂√ ...± ÷...←↓→↑↔~≈≠≡≤≥...½...∞...(⇐⇑⇒⇓⇔∴∃ℝℤℕℂ⋅)

 

[marcus]

Rovelli gave a brief 10-slide presentation back in May of 2009 which makes some simple points worth recalling.

Rovelli recently gave a thumbnail sketch of LQG. Around 10 slides illustrated by drawings. You can look at the original slides and listen to the audio here:
http://relativity.phys.lsu.edu/ilqgs/panel050509.pdf
http://relativity.phys.lsu.edu/ilqgs/panel050509.mp3

It is a 3-way discussion and Rovelli is the second in line, so when you open the slides PDF you must scroll down about 10 slides first to come to Rovelli's section, likewise with the Audio mp3 you have to fast forward to about one third of the way, and just get the middle third of the recording. He will tell you in the audio which slide, when to switch slides and so forth. The other presentations, by Ashtekar and Freidel, are also good. But here I am focusing just on this very short 20 minute sequence by Rovelli...
...
...

Here I won't transcribe all 10-or-so slides. Just a few selected ones. If you want to see more you can go back to the original post, or use the LSU.EDU link. I was reminded of this seminar presentation by some questions that Naty was asking on several occasions this week. Maybe the best would be to listen to the AUDIO that goes with the slides. It is also available from that lsu.edu link. But FWIW here are just a few slides.== a few of Rovelli's slides transcribed verbatim, without the illustrations==
Some questions

1. Is quantum space made out of loops and spin-networks or tetrahedra and 4-simplices?

2. Is flat space formed by many small tetrahedra with low-spin, or by few large tetrahedra with with high-spin?

3. Is low-energy physics given by quantum gravity on a single 4-simplex? Or by an infinite triangulation limit?

4. How do we study the the continuum limit from Planck scale discretness to the macroscopic continuum?

5. A spinfoam model is like a new version of quantum Regge calculus. So, why it should work better than quantum Regge calculus?

Claim: these questions are ill posed.

***
1. Is quantum space made out of loops and spin-networks or tetrahedra and 4-simplices?

The meaningful question in quantum theory is not how something is, but how it responds to a measurement.

There is no space “between” quanta of space, and it makes no sense to ask what is the geometry between one quantum and another, or inside a quantum, or what is the “geometry of quantum”. It is like asking for the “shape of a photon”. Or “What do I measure if I measure the energy in the space occupied by half a photon?”

***
2. Is flat space formed by few tetrahedra with high spin, or by many tetrahedra (or loops) with low spin?
How many particles are there in the Fock vacuum?
How many particles are invoved in a two-particle interaction?

Quantum theory gives the probability for measurement outcomes: it does not describe “what is between measurements”.

“In between pictures” are just descriptions of the ways I decide to do calculations. They are different for different measurements, and at different orders in perturbation theory.

[my comment. Rov sometimes like Feyn has flashes of unusual common sense. they illuminate.]

***
The good question, I think, is:
What can we compute that makes sense?
and
How can we compute it?

***
...
...[SNIP. SLIDES OMITTED HERE]
...
***
Summary
1. “Loopy, polymer, triangulated” spaces are helps for intuition, not descriptions of reality. No incompatibility between them.

2. In quantum gravity, flat space is neither many small Planck scale things not few big large-spin 4 simplices. It is a process with a transition amplitudes. We can represent it with different pictures, according to the measurements we are considering, the calculation scheme, and the approximation scheme.

3. We must compute diff-invariant amplitudes, including when dealing with excitations over a flat space. The only way of doing so that I know is to code the background into the boundary space. (Boundary formalism.)

4. We need an approximation scheme. For scattering amplitudes, we can truncate degrees of freedom to a finite number, very much like is done in computing in QED and QCD. (Vertex expansion.)

5. Regime of validity of the vertex expansion: processes whose size L is not much larger than the minimal relevant wavelength λ. Includes the large distance behavior of the scattering amplitudes in coordinate space.

6. At given ratio λ/L, the Large-spin Limit captures processes at scales larger than the Planck length. It gives the semiclassical limit.

→ This does not mean that flat space is “made out of large 4-simplices”!
→ It means that we describe measurements performed at scales larger that the
Planck scale, at low order.
==end quote==

What comes through to me is that LQG and allied types of QG are not saying what space is made of. They are talking about geometry---measurement of spatial relationships between events. Just like in ordinary QM, a particle has no trajectory, we do not make claims about what is "in between measurements."

The meaningful question in quantum theory is not how something is, but how it responds to a measurement.

 

[marcus]

These same concerns came up in a recent discussion (with Naty and others) of Rovelli's April 2010 paper. http://arxiv.org/abs/1004.1780

...
Bohr expressed the essential about any quantum theory when he said "Physics is concerned not with how Nature is, but with what we can say about it." Some words to that effect.

There are always going to be alternative ways to picture the relation between measurements. And there will be some ways to picture that are very much better than others.
...
...
==quote Rovelli page 4==
This physical picture admits variants. In the case Γ is the two-skeleton dual to a triangulation of a 3d space, one can view the individual grains as flat tetrahedra. In some cases, namely for some states, these tetrahedra can be viewed as forming a 3d Regge geometry. (For this, matching conditions between the length of triangles must be satisfied [6].) In the general case, one can associate them a “twisted geometry” [6].

Such geometrical pictures are helps for the intuition, but there is no microscopic geometry at the Planck scale and these pictures should not be taken too literally in my opinion. They are choices of classes of continuous geometries interpolating finite sets of geometrical data. It is clear that many such choices are possible. They are analogous to choices of interpolating functions to visualize or describe sets of data points. For instance, we can interpolate a set of data points by means of an interpolating polynomial, or a piecewise linear function, or a piecewise constant functions... As we will better see below, these choices have strict analogs for quantum geometry.

These geometrical pictures can play a very useful role in various situations, but what the theory is about is expectation values of physical observables, not mental pictures of the geometry of individual states.
==endquote==

Essentially just echoing Bohr and reminding us of what has always been the basic quantum philosophy.

Feynman pointed out that pictures of the microscopic quantum world merely show how you plan to calculate. They don't show the world. Different ways to diagram the same thing correspond to different ways of calculating---conceivably these can be consistent: lead to the same answers.

So in LQG there are different formulations (plus others listed in 1004.1780) :
embedded spin networks
combinatorial (not embedded) spin networks
canonical formulation (no spin foams)
spin foam formulation (embedded or combinatorial)
The tendency is for these to be consistent, give the same results. Besides LQG there are also simplicial approaches, like Regge or CDT: triangulations instead of networks. Some use massive computer simulation in place of mathematical analysis.
I suppose that some non-LQG approaches could end up leading to the same answers. I don't know how likely that is, but it's possible.

 

[marcus]

Here are some QG links that are useful to have handy. Last time I updated was in May 2010. You can look back a few posts to the May list to find some which for brevity's sake I have omitted here.

To find out about conferences and workshops, "hyperspace" at the AEI site:
http://hyperspace.aei.mpg.de/category/Conferences/
The Nottingham QG network:
http://www.maths.nottingham.ac.uk/qg/

Some links to conferences etc.
June 2009 PlanckScale conference video and slides:
http://www.ift.uni.wroc.pl/~rdurka/planckscale/index-video.php
Workshops at Ashtekar's Penn State IGC:
http://www.gravity.psu.edu/events/workshops.shtml
Online International LQG Seminar:
http://relativity.phys.lsu.edu/ilqgs/
November 2009 Asymptotic safety conference at Perimeter:
http://www.perimeterinstitute.ca/en/Events/Asymptotic_Safety/Asymptotic_Safety_-_30_Years_Later/
AsymSafe conference videos:
http://pirsa.org/C09025
February 2010 Oberwolfach workshop on Noncommutative Geometry and LQG ("Loops, Algebras, Spectral Triples"):
http://www.mfo.de/programme/schedule/2010/06b/OWR_2010_09.pdf
March 2010, Zakopane QG workshop (QGQG = quantum geometry/gravity):
http://www.fuw.edu.pl/~jpa/qgqg3/
July 2010 Stockholm workshop on the experimental search for QG:
http://th.physik.uni-frankfurt.de/~hossi/ESQG10/
Renate Loll 3-week course at Perimeter, Intro to Quantum Gravity:
http://pirsa.org/index.php?p=speaker&name=Renate_Loll
Photos from the first Loops conference, at Marseille 2004:
http://math.ucr.edu/home/baez/marseille/

Loop papers from 2007-present (currently 500 or more papers) ranked by citation count:
(keywords "spin, foam", "field theory, group", "quantum gravity, loop space", and "quantum cosmology, loop space"):
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+K+SPIN%2CFOAM+OR+DK+FIELD+THEORY%2C+GROUP+OR+DK+QUANTUM+GRAVITY%2C+LOOP+SPACE+OR+QUANTUM+COSMOLOGY%2C+LOOP+SPACE+AND+DATE+%3E+2006&FORMAT=www&SEQUENCE=citecount%28d%29

Classic online sources.
Review of LQG as of May 2008:
http://relativity.livingreviews.org/Articles/lrr-2008-5/
Rovelli April 2010 paper, A new look at loop quantum gravity:
http://arxiv.org/abs/1004.1780
Rovelli's talk at Strings 2008 Video:
http://cdsweb.cern.ch/record/1121957?ln=en
Slides: http://indico.cern.ch/getFile.py/access?contribId=30&resId=0&materialId=slides&confId=21917
2003 draft of Rovelli's book online:
http://www.cpt.univ-mrs.fr/~rovelli/book.pdf
Rovelli's chapter in Oriti's book:
http://arxiv.org/abs/gr-qc/0604045

Weinberg on Asymptotic Safety and general overview.
Weinberg's 6 July 2009 talk, main CERN link:
http://indico.cern.ch/conferenceDisplay.py?confId=57283
Weinberg video (historical overview up to minute 58 followed by
no-frills approach to unification in the last 12 minutes):
http://cdsweb.cern.ch/record/1188567/
Related Weinberg paper Asymptotically Safe Inflation:
http://arxiv.org/abs/0911.3165
Discussion thread https://www.physicsforums.com/showthread.php?t=355757

Recent progress in core Lqg:
Etera Livine's 17 February 2010 talk, A review of Spinfoams and Group Field Theory:
http://pirsa.org/10020079/
Related paper by Girelli Livine Oriti, 4d Deformed Special Relativity from Group Field Theories:
http://arxiv.org/abs/0903.3475
Bianchi Rovelli Vidotto, Towards Spinfoam Cosmology:
http://arxiv.org/abs/1003.3483
Rovelli, A new look at LQG:
http://arxiv.org/abs/1004.1780
Bianchi Regoli Rovelli, Face amplitude of spinfoam QG:
http://arxiv.org/abs/1005.0764
Alesci Rovelli, A regularization of the hamiltonian constraint compatible with the spinfoam dynamics:
http://arxiv.org/abs/1005.0817
Rovelli Speziale, On the geometry of LQG on a graph:
http://arxiv.org/abs/1005.2927
Ding Rovelli, Physical boundary Hilbert space and volume operator in the Lorentzian new spin-foam theory:
http://arxiv.org/abs/1006.1294

Selected longshots.
Rovelli Smerlak, Thermal time and the Tolman-Ehrenfest effect: temperature and the "speed of time":
http://arxiv.org/abs/1005.2985
Mathilde Marcolli et al, Spin Foams and Noncommutative Geometry:
http://arxiv.org/abs/1005.1057
Kirill Krasnov Deformations of General Relativity:
http://pirsa.org/10050002/
Lisi Smolin Speziale, Unification of gravity, gauge fields, and Higgs bosons:
http://arxiv.org/abs/1004.4866
Vincent Rivasseau at the 2009 Perimeter AsymSafe conference:
http://pirsa.org/09110049/
Ted Jacobson at the 2009 Perimeter HorGrav conference:
http://pirsa.org/09110066/
Ted Jacobson Thermodynamics of Spacetime: The Einstein Equation of State:
http://arXiv.org/abs/gr-qc/9504004
Ted Jacobson Introduction to Quantum Fields in Curved Spacetime and the Hawking Effect:
http://arxiv.org/abs/gr-qc/0308048
Erik Verlinde On the Origin of Gravity and the Laws of Newton:
http://arxiv.org/abs/1001.0785
Lee Smolin, Newtonian gravity in loop quantum gravity:
http://arxiv.org/abs/1001.3668
Jerzy Kowalski-Glikman, Note on gravity, entropy, and BF topological field theory:
http://arxiv.org/abs/1002.1035
Easson Frampton Smoot, Entropic Accelerating Universe:
http://arxiv.org/abs/1002.4278
Chamseddine Connes, Noncommutative Geometry as a Framework for Unification of all Fundamental Interactions including Gravity. Part I:
http://arxiv.org/abs/1004.0464
Smolin and Unger presentation at Laws of Nature workshop{ http://pirsa.org/C10001 }:
http://pirsa.org/10050053/

A list of QG researchers worldwide, mostly LQG but some other:
http://en.wikipedia.org/wiki/List_of_loop_quantum_gravity_researchers
Francesca's LQG world map:
http://maps.google.com/maps/ms?ie=U...985216139270436.0004843830d27f3e6c50e&t=h&z=0

Selected outreach links from IGC (Institute for Gravitation and the Cosmos) with a section of recent (2006-2010) popular articles:
http://gravity.psu.edu/outreach/index.shtml

 

[marcus]

The organizers of GR19 intend to make certain talks available online in some form.
As yet the links posted to various plenary talks do not work for me. If you wish you can try, for example:
http://www.gr19.com/public_html/compres_lecturas/rovelli.key.zip
If there are some bugs at the UNAM Morelia site we simply need to wait for them to be worked out.
Here is the plenary lecture menu:
http://www.gr19.com/plenlect.php
================
The next update of selected LQG links may include one or more papers realizing LQG in Group Field Theory
http://arxiv.org/abs/1008.0354
EPRL/FK Group Field Theory
Joseph Ben Geloun, Razvan Gurau, Vincent Rivasseau

http://arxiv.org/abs/1007.3150
Quantum Corrections in the Group Field Theory Formulation of the EPRL/FK Models
Thomas Krajewski, Jacques Magnen, Vincent Rivasseau, Adrian Tanasa, Patrizia Vitale

 

[marcus]

Recently I updated the list of Lqg links that are especially useful to keep handy.
See post #240, from 24 July.
So the list won't get updated again for a while, but, when that happens, two important paper to be included will be these by Eugenio Bianchi, Elena Magliaro, Claudio Perini:
http://arxiv.org/abs/0912.4054 Coherent spin-networks
http://arxiv.org/abs/1004.4550 Spinfoams in holomorphic representation

 

[marcus]

Francesca and others have compiled a list of people and places where LQG-and-allied research is in progress, or where a PhD student interested in LQG might connect with an advisor. I want to re-organize and edit the list to the best of my knowledge, and bring it up to date as well as I can. (In some cases I can't independently verify but just have to go along with the Google list.)

Here is the original:http://maps.google.com/maps/ms?ie=U...985216139270436.0004843830d27f3e6c50e&t=h&z=0

Australia
University of Sydney/Macquarie University
Permanent: Daniel Terno http://www.qscitech.info/ Postdoc: Florian Girelli

Britain
QG Nottingham
Permanents: John Barrett, Kirill Krasnov, Jorma Louko. http://www.maths.nottingham.ac.uk/research/applied_mathematics/quantum_gravity/
(Affiliated: Ed Copeland http://www.nottingham.ac.uk/physics/research/particles/)

Cambridge
Permanent: Ruth M. Williams

King's College London
Permanent: Mairi Sakellariadou.
http://www.kcl.ac.uk/schools/nms/physics/people/academic/sakellariadou/

Canada
Perimeter Institute for Theoretical Physics
Permanent: Laurent Freidel, Fotini Markopoulou, Lee Smolin.

Western Ontario
Permanent: Daniel Christensen

McMaster University
Permanent: Seth Major. http://academics.hamilton.edu/physics/smajor/

New Brunswick
Permanent: Viqar Husain http://www.math.unb.ca/~husain/

Denmark
Niels Bohr Instituttet
Permanent: Jan Ambjorn http://www.nbi.ku.dk/english/

France
CPT Marseille
Permanent: Alejandro Perez, Carlo Rovelli, Simone Speziale. http://www.cpt.univ-mrs.fr/~quantumgravity/ Postdocs: Eugenio Bianchi, Muxin Han, Christian Roeken, Antonino Marcianò, Marco Valerio Battisti... Students: Roberto Pereira, Valentin Bonzom, Daniele Pranzetti, You Ding, Matteo Smerlak.

École normale supérieure de Lyon
Permanent: Etera Livine. Postdoc: Johannes Tambornino

Universite De Paris XI Paris Sud
Permanent: Vincent Rivasseau http://www.rivasseau.com/index.html

Tours
Permanent: Karim Noui

Universite Montpellier II
Permanent: Sergei Alexandrov

Grenoble
Permanent: Aurelien Barreau http://lpsc.in2p3.fr/ams/aurelien/

Germany
AEI Berlin
Permanent: Bianca Dittrich, Daniele Oriti, Hermann Nicolai. http://www.aei.mpg.de/english/research/teams/

Erlangen
Permanent: Thomas Thiemann and one more faculty soon! Postdocs: Emanuele Alesci, Enrique Fernandez Borja, Derek Wise,...PhD students: Christian Boehmer,...

Universität Hamburg
Permanent: Catherine Meusburger. http://www.math.uni-hamburg.de/home/meusburger/ Postdoc: Winston Fairbairn.

Rheinische Friedrich-Wilhelms-Universität
Permanent: Klaus Kiefer

Universität Paderborn
Permanent: Christian Fleischhack

India
Raman Research Institute
Permanent: Madhavan Varadarajan

IUCAA Pune
Permanent: Naresh Dadhich

Italy
Pavia
Permanent: Mauro Carfora and Annalisa Marzuoli. Students: Hal Haggard and Francesca Vidotto (2011)

Torino
Permanent: Lorenzo Fatibene http://www.dm.unito.it/personalpages/fatibene/index.htm

Sapienza University of Rome
Permanent: Giovanni Montani, Giovanni Amelino Camelia. Giovanni Montani http://www.icra.it/cgm/welcome.htm http://www.roma1.infn.it/~amelino/

Korea
Asia Pacific Center for Theoretical Physics
Permanent: Hanno Sahlmann

Lebanon
American University of Beirut
Permanent: Tamer Tlas.

Mexico
Morelia
Permanent: Alejandro Corichi, Robert Oeckl, José Zapata. http://www.matmor.unam.mx/~corichi/lqgindex.html

Cinvestav Zacatenco
Permanent: Merced Montesinos

Netherlands
University of Utrecht
Permanent: Renate Loll http://www.phys.uu.nl/~loll/Web/title/title.html

People's Republic of China
Beijing Normal University
Permanent: Yongge Ma http://physics.bnu.edu.cn/application/research/gravity/LQG/eng/research.html

Academia Sinica
Permanent: Hoi-Lai Yu

Poland
University of Warsaw
Permanent: Jerzy Lewandowski. http://www.fuw.edu.pl/~lewand/homepage.html

Uniwersytet Wrocławski (University of Wroclaw)
Permanent: Jerzy Kowalski-Glikman.

Uniwersytet Jagielloński (Jagelonian University)
Permanent: Marek Szydlowski.

Spain
IEM-QFT Madrid
Permanent: Fernando Barbero, Guillermo Mena Marugán. Postdoc: Tomasz Pawlowski. http://www.iem.csic.es/departamentos/qft/index.html

Taiwan
National Cheng Kung University
Permanent: Chopin Soo

United States
PennState
Permanent: Abhay Ashtekar, Martin Bojowald. Postdocs: Andy Randono, Claudio Perini, Elena Magliaro, Jacobo Diaz Polo, William Nelson, Simone Mercuri. PhD:Miguel Campiglia, Adam Henderson, Artur Tsobanjan, Edward Wilson...

Louisiana State University
Permanent: Kristina Giesel, Jorge Pullin, Parampreet Singh. http://relativity.phys.lsu.edu/

Florida Atlantic University
Permanent: Jonathan Engle, Warner Miller

Haverford College
Permanent: Stephon Alexander.

Kansas State University
Permanent: Louis Crane. http://www.math.ksu.edu/main/contact_info/personnel_detail?person_id=1330

Riverside
Permanent:John Baez. http://math.ucr.edu/home/baez/README.html

Caltech
Permanent: Matilde Marcolli. http://www.its.caltech.edu/~matilde/

Uruguay
Montevideo
Permanent: Rodolfo Gambini, Michael Reisenberger

===================
Another candidate for the list of links to keep handy. John Norton's discussion of diff-invariance and the hole argument.
http://www.pitt.edu/~jdnorton/papers/decades.pdf

 

[marcus]

In the previous post's listing, Erlangen should have this link:
http://theorie3.physik.uni-erlangen.de/people.html
=========
Links for a short course in LQG as per request in https://www.physicsforums.com/showthread.php?p=2868346#post2868346

Suggested Prep:
Rovelli Upadhya http://arxiv.org/abs/gr-qc/9806079 (easy)
Rovelli Gaul http://arxiv.org/abs//gr-qc/9910079 (just relevant parts, short spinfoam section pp 43-46)
Baez on spinfoams http://arxiv.org/abs/gr-qc/9709052 (see especially pages 1-4 and 33,34)
Lewandowski et al on spinfoams http://arxiv.org/abs/0909.0939 (hard, but skim to know it's there)

Suggested Target:
Bianchi Rovelli Vidotto http://arxiv.org/abs/1003.3483
Rovelli http://arxiv.org/abs/1004.1780

References (there is no up-to-date reference but these are useful):
http://www.livingreviews.org/lrr-2008-5
www.cpt.univ-mrs.fr/~rovelli/book.pdf

==quote from Baez 1997 pages 33 and 34==
Quantum gravity without a background spacetime

As we have seen, the heart of ...[a spin foam] model is the following formula for the amplitude Z(F) of a spin foam F...Since this formula does not depend on the ambient spacetime manifold, but only on the spin foam itself, we may consider it more generally as a formula for evaluating the amplitude of any Spin(4) spin foam with ...[restrictions since removed]...
This gives an ‘abstract’ spin foam model, where there is no picture of spacetime other than that provided by the spin foam itself. Using the formula described in Section 3, we may think of each face of κ as ‘carrying’ a certain area, which it would give to any imagined surface it intersected transversely. Similarly, we may think of each edge as carrying a certain volume...The main point, however, is that if we think of an abstract spin foam as a kind of quantum 4-geometry, the above formula serves as a rule for computing the amplitude of any such quantum 4-geometry.
There are, of course, very serious problems in extracting physics from such a model. Most obviously, it is difficult to sum over all spin foams. Nonetheless it seems worth investigating such models.
==endquote==
[Note that several of the problems Baez mentioned have been addressed over the past 10 years.]

I think this Baez 1997 passage pointed in the right direction. The 'abstract' or manifoldless spinfoam turned out to be a good idea. Pedagogically, the whole Baez 1997 spinfoam tutorial has things to recommend it, in spite of being obviously out of date on some points.

There's a longish list of LQG resource links in post #240 of this thread.

 

[marcus]

The list of resource links (see post #240) when it gets updated should include this one mentioned by Sheaf:
http://math.ucr.edu/home/baez/penrose/
which has a couple of circa-1970 papers by Penrose where he introduced the idea of spin-network.