Introduction To Loop Quantum Gravity

[marcus]

Results of MIP forecast polls

first quarter 2006
https://www.physicsforums.com/showthread.php?t=116791
second quarter 2006
https://www.physicsforums.com/showthread.php?t=124951
third quarter 2006
https://www.physicsforums.com/showthread.php?t=134513

It is still early to be counting citations for most of these---and cite numbers don't tell the whole story.

but in the first quarter poll, five people picked Padmanabhan's paper and it has already 36 cites (Ashtekar's was next with 17)
the five people were arivero, selfAdjoint, Kea, Turbo, and Feynmania.
cites are not conclusive but i think they did indeed pick the paper which is proving the most influential.

in second quarter, arivero and Viking picked the two Ashtekar papers, which so far have been the most-cited choice in that poll, with combined 34 citations

in the third quarter Etera Livine and Energex chose the Freidel paper which has 4 cites as of today------there has not been much time yet for follow-up research papers to be written
arivero picked the pair of papers by Barrett and by Connes (deriving the standard model from Noncommutative Geometry) and they have a total of 6 to date

 

[marcus]

To continue where the preceding post left off, here is a link to the fourth quarter MIP prediction poll
https://www.physicsforums.com/showthread.php?t=149466

Also updating (7 January) links to the Harvard abstract search tool:
They 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

As of today, these give the following raw publication numbers:
3248, 3154, 3139, 3049

(additional publications may come to the librarian's attention belatedly and be included later.)

A link for the new year,

2007: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

 

[marcus]

some further links to the Harvard abstract search tool:
these are for the whole year, in seven 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

2007: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1
the present gross annual publication counts for 2001, 2002, 2003, 2004, 2005, 2006 are
1224, 1193, 1109, 1049, 1062, 1010

including the keyword "worldsheet" in the search has the disadvantage that it picks up a lot of non-string papers from other fields whose abstracts happen to mention the word "sheet", so in these not-too-skillful searches one either gets too few papers or too many. At least one can gauge the trend in annual output, if not the absolute size.

 

[francesca]

Loops '07

LOOPS '07
25 - 30 June 2007 Morelia, Mexico​

As in previous years, the conference is meant to provide the main international event on quantum gravity with emphasis on non-perturbative and background independent approaches.

Topics include:

* Foundational questions of quantum gravity
* Loop quantum gravity
* Spin foam models
* Dynamical triangulations
* Causal sets
* String theory
* Cosmology related to quantum gravity
* Phenomenology of quantum gravity

The conference is organized through the Instituto de Matemáticas, UNAM, Morelia:
http://www.matmor.unam.mx

Organizing committee:
Alejandro Corichi
Robert Oeckl
José Antonio Zapata
Daniele Colosi

 

[marcus]

thanks for noticing this Francesca.
I hope we get more information before long. This, I think, was the November 2006 announcement
http://mail.sissa.it/pipermail/ap-sem/2006-November/000196.html
and I have not seen anything more.

 

[marcus]

to amplify what Francesca said, the city of
Morelia, where LOOPS '07 meeting will be held, is about 200 miles west of mexico city. The National University of Mexico (UNAM) has a campus at Morelia with several research institutes.

 

[marcus]

Ashtekar, one of the initiators of the LQG approach, has an article whose title contains the words "Introduction to Loop Quantum Gravity...", and which might be a good place to touch base, for anyone who wants an introduction.

http://arxiv.org/abs/gr-qc/0702030
An Introduction to Loop Quantum Gravity Through Cosmology
Abhay Ashtekar
20 pages, 4 figures, Introductory Review

"This introductory review is addressed to beginning researchers. Some of the distinguishing features of loop quantum gravity are illustrated through loop quantum cosmology of FRW models. In particular, these examples illustrate: i) how 'emergent time' can arise; ii) how the technical issue of solving the Hamiltonian constraint and constructing the physical sector of the theory can be handled; iii) how questions central to the Planck scale physics can be answered using such a framework; and, iv) how quantum geometry effects can dramatically change physics near singularities and yet naturally turn themselves off and reproduce classical general relativity when space-time curvature is significantly weaker than the Planck scale."

this paper of Ashtekar's grew out of a talk he gave in Summer 2006 at the First Stueckelberg Workshop at Pescara, italy.
http://www.icra.it/ICRA_Networkshops/INw20_Stueckelberg/Welcome.htm

=======================
here is the Spring 2007 of Jorge Pullin's ONLINE
INTERNATIONAL LQG SEMINAR
http://relativity.phys.lsu.edu/ilqgs/schedulesp07.html
You can listen to the seminar talks online at
http://relativity.phys.lsu.edu/ilqgs/

Just scroll to the bottom of the page and click on PDF to get the slides and click on one of the audio options to hear it.

NOTE: All seminars will be held at 9:00 AM Central Time

Feb 13 UV properties of N=8 supergravity: is it finite? Radu Roiban PennState

Feb 20 KITP program on singularities summary Martin Bojowald PennState

Feb 27 Diffeomorphism invariance in loop quantum gravity Abhay Ashtekar PennState

Mar 13 Kappa Poincare space-time symmetries Michele Arzano Perimeter Institute

Mar 20 TBA Kirill Krasnov Perimeter Institute

Mar 27 Loop quantization of spherically symmetric spacetimes Jorge Pullin Louisiana State University

Apr 3 TBA (about Trinions) Lee Smolin Perimeter Institute

 

[marcus]

The speaker-list for the QGQG school has been finalized. The lecturers at the school are to be:
Jan Ambjorn
Abhay Ashtekar
Laurent Freidel
Etera Livine
Paweł Kasprzak
Martin Reuter
Jean-Marc Schlenker
Thomas Thiemann
Ruth Williams

Alain Connes and Shahn Majid were possibilities. As of now they will not be lecturing.

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

 

[marcus]

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

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

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

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

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

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

So I would just list the series of talks to be given by AA, LF, EL, TT.
Of these, only LF has already given titles of individual talks

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

for the other three we only know how many talks each is giving and the timeslots. What follows are exerpts from the program:

Lectures will start everyday at 14.00. Every lecture will take 45 minutes, and there will be 15 minutes of break between lectures. Note that first lecture starts Mar, 23 at 14.00, while the last lecture ends Apr, 3 at 19.00.

Friday, Mar 23
Abhay Ashtekar: Loop Quantum Cosmology (1)

Saturday, Mar 24
Abhay Ashtekar: Loop Quantum Cosmology (2)
Abhay Ashtekar: Loop Quantum Cosmology (3)

Sunday, Mar 25
Abhay Ashtekar: Loop Quantum Cosmology (4)
Abhay Ashtekar: Loop Quantum Cosmology (5)

Monday, Mar 26
Abhay Ashtekar: Loop Quantum Cosmology (6)
Abhay Ashtekar: Loop Quantum Cosmology (7)
Laurent Freidel: Spin-Foam Models (1)

Tuesday, Mar 27
Informal discussion, excursion, attractions

Wednesday, Mar 28
Thomas Thiemann: Loop Quantum Gravity (1)
Laurent Freidel: Spin-Foam Models (2)

Thursday, Mar 29
Laurent Freidel: Spin-Foam Models (3)
Thomas Thiemann: Loop Quantum Gravity (2)

Friday, Mar 30
Laurent Freidel: Spin-Foam Models (4)
Laurent Freidel: Spin-Foam Models (5)
Thomas Thiemann: Loop Quantum Gravity (3)

Saturday, Mar 31
Informal discussion, excursion, attractions

Sunday, Apr 1
Thomas Thiemann: Loop Quantum Gravity (4)
Thomas Thiemann: Loop Quantum Gravity (5)
Etera Livine (1)

Monday, Apr 2
Thomas Thiemann: Loop Quantum Gravity (6)
Thomas Thiemann: Loop Quantum Gravity (7)
Etera Livine (2)

Tuesday, Apr 3
Etera Livine (3)
Thomas Thiemann's student (1)

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

 

[marcus]

LOOPS '07
25 - 30 June 2007 Morelia, Mexico​

...
...
http://www.matmor.unam.mx
...

Some more detail has been posted at the UNAM Morelia website
http://www.matmor.unam.mx/eventos/loops07/index.html
====some exerpts from the announcement====
Scientific Advisory Committee

* Jan Ambjørn
* Abhay Ashtekar
* John W. Barrett
* Fay Dowker
* Jerzy Lewandowski
* Hugo Morales Tecotl
* Jorge Pullin
* Carlo Rovelli
* Lee Smolin
* Thomas Thiemann

At this time the program is in an early planning stage. Below is the list of plenary speakers with titles of talks. Abstracts can be displayed by clicking on the title of the respective talk or by going to the abstracts page. When more detailed information on the program is available it will be posted on this site.

Plenary Speaker--------- Title
Jan Ambjørn
Abhay Ashtekar "LQG: Lessons from models"
Martin Bojowald "Loop quantum cosmology and effective theory"
John F. Donoghue
Klaus Fredenhagen
Lucien Hardy "The causaloid formalism: a tentative framework for quantum gravity"
James B. Hartle "Generalizing Quantum Mechanics for Quantum Gravity"
Sabine Hossenfelder "Phenomenological Quantum Gravity"
Bei-Lok B. Hu
Fotini Markopoulou
Daniele Oriti
Alejandro Perez
Hendryk Pfeiffer "Quantum gravity, TQFTs and categorification"
Jorge Pullin "Uniform discretizations and spherically symmetric loop quantum gravity"
Michael Reisenberger
Martin Reuter "Asymptotically safe quantum gravity and cosmology"
David Rideout
Carlo Rovelli
Moshe Rozali*
Lee Smolin
Rafael Sorkin*
Artem Starodubtsev
Jörg Teschner*
Thomas Thiemann

(* to be confirmed) Last updated 2 March 2007.

 

[marcus]

Abstracts are already available for some of the invited plenary talks to be given at this years Loops '07

===quote from Loops '07 site===
Abstracts of plenary talks:

Martin Bojowald: Loop quantum cosmology and effective theory

Several models have been defined to study the broad framework of loop quantum gravity. We present a common perspective for cosmology where configurations are close to being isotropic. Effective techniques are then used to illustrate important features of the semiclassical limit and to show examples of correction terms to Einstein's equation. Applications include corrections to the Newton potential and to cosmological perturbation equations relevant for the CMB power spectrum.

John F. Donoghue: Effective field theory and quantum general relativity

I will review the foundations and recent progress in the use of effective field theory to elucidate the quantum predictions of general relativity.

Lucien Hardy: The causaloid formalism: a tentative framework for quantum gravity

General Relativity is a deterministic theory with non-fixed causal structure. Quantum Theory is an inherently probabilistic theory with fixed causal structure. A theory of Quantum Gravity must reduce, in appropriate limits, to General Relativity and Quantum Theory. It seems likely, therefore, that Quantum Gravity will inherit the radical aspects of these two less fundamental theories – namely that it will be a probabilistic theory with non-fixed causal structure. In this talk I will present the causaloid formalism which is a general framework for such theories. I will show how Quantum Theory can be formulated in the causaloid framework and provide tentative results for how it may be possible to formulate General Relativity in the framework. Finally, I will discuss the issue of formulating a theory of Quantum Gravity using the causaloid formalism.

James Hartle: Generalizing Quantum Mechanics for Quantum Spacetime

Familiar textbook quantum mechanics assumes a fixed background spacetime to define states on spacelike surfaces and their unitary evolution between them. Quantum theory has been generalized as our conceptions of space and time have evolved. But quantum mechanics needs to be generalized further for quantum gravity where spacetime geometry is fluctuating and without definite value. This talk will review a fully four-dimensional, sum-over-histories, generalized quantum mechanics of cosmological spacetime geometry. In this generalization, states of fields on spacelike surfaces and their unitary evolution are emergent properties appropriate when spacetime geometry behaves approximately classically. The principles of generalized quantum theory would allow for further generalization that would be necessary were spacetime not fundamental. Emergent spacetime phenomena are discussed in general and illustrated with the examples of the classical spacetime geometries with large spacelike surfaces that emerge from the `no-boundary' wave function of the universe. These must be Lorentzian with one, and only one, time direction. The question will be raised as to whether quantum mechanics itself is emergent.

Jorge Pullin: Uniform discretizations and spherically symmetric loop quantum gravity

We discuss the application of the uniform discretization procedure to handle the dynamics of loop quantum gravity with spherical symmetry.

Martin Reuter: Asymptotically safe quantum gravity and cosmology

The basic ideas and main results of the asymptotic safety scenario in Quantum Einstein Gravity (QEG) are reviewed and possible implications for the cosmology of the early universe are discussed.

Moshe Rozali: Background Independence in String Theory

I review several notion of background independence in quantum gravity: full or partial, manifest or not etc., and discuss the evidence for and against taking the notion seriously as a guide for research. I review the current status in string theory with regard to this question and discuss the extent to which existing non-perturbative formulations of string theory are background independent.

Artem Starodubtsev: Some physical results from spinfoam models

Given the known mathematical fact that a spinfoam is a Feynman diagram the data relevant for particle scattering amplitudes could be identified in it.

==endquote==
http://www.matmor.unam.mx/eventos/loops07/index.html

 

[marcus]

Updating some useful benchmarks from the Harvard abstract search tool:
these are for the whole year
keywords = superstring, M-theory, brane, heterotic, AdS/CFT

2002: 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

2007: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1
the following are for the first three months of the year, same years and keywords

2002: 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

2007: http://adsabs.harvard.edu/cgi-bin/n...txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1

Using these one can at least gauge the trend in annual output, if not the absolute size.
as of now, first triple: 1130, 947, ?
second triple (provis.) 401, 323, 199

 

[marcus]

Followup on QGQG-1 school in Zakopane Poland (program listed above):

QGQG-2 school will be in June 2008, in Denmark.

The most complete blog report on the first QGQG school is here:

Part 1 of report---Thomas Thiemann's lectures including the Master Constraint, discussion with T.T. of (semi) classical limit; Eugenio Bianchi's explanation of the LQG graviton paper of Rovelli et al; Laurent Freidel and Etera Livine spinfoam talks development of Feynman diagram for matter from QG
http://realityconditions.blogspot.com/2007/04/report-on-quantum-gravity-school_08.html

Part 2 of report---Martin Reuter's QEG assymptotic safety
http://realityconditions.blogspot.com/2007/04/report-on-quantum-gravity-school_10.html

General comment and pictures:
http://realityconditions.blogspot.com/2007/04/report-on-quantum-gravity-school.html

QGQG conference will be held in Nottingham UK in July 2008

 

[windscar]

I think if you really wanted to explain what the loops are in loop quantum gravity, you would have to at least add one extra dimension. General Relativity added a higher space dimension and if quantum loop gravity wishes to combine this theory with quantum theory, I think it would only be fair. One thing about General Relativity is that it explained eliptical orbits by explaining that space was curved. I once wondered how matter could actually curve space, and I thought what if matter is actual indentions in space time itself or intersection with a higher dimension that we can not move in. If you were too look at a particle as an indention of space time itself, then as other particles passed by it, they would "loop".

 

[marcus]

AUDIO for the Zakopane QG school lectures are available online

Here is Carlo Rovelli's first talk
http://www.maths.nottingham.ac.uk/qg/Meetings/Zakopane/recordings/cr1.mp3
this is an insightful and foresightful non-technical talk. it comes across well on audio because he does not have to use the whiteboard very much.
people liked this talk because it stimulated them very much to think.

the other lectures were depending on handout pieces of paper and writing on the board, so not all of it comes through in audio.

however Etera Livine seemed to give a very good lecture and also I was interested in some of what Jan Ambjorn said by way of introduction. I have only sampled a few so far.

Richard Kostecki "Path-Integral" the local organizer of the Zakopane school has put links to all the audio here
http://www.fuw.edu.pl/~kostecki/school.html

==============
The homebase for the European Union Quantum Gravity network is here
http://www.maths.nottingham.ac.uk/qg/
the name of the network is "Quantum Geometry and Quantum Gravity" or "QGQG"
the main director is John Barrett
I think in the name it is important to say Geometry first, not as an afterthought. IOW it means "Quantum Geometrical Gravity".
Approaches in which gravity is not merely one of many forces but is the geometry of space and time.
We are dealing with quantum theories, therefore, in which spacetime is NOT A MANIFOLD but a web of relations between geometrical operators---relations between geometric observables---background independent quantum theories

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

Some detail is available about the "QG-squared 2008 conference to be at Nottingham UK in July 2008.
http://www.maths.nottingham.ac.uk/conferences/qgsquared-2008/
"Monday June 30th - Friday July 4th 2008
University of Nottingham, UK


Topics:

* Quantum gravity, including loop quantum gravity, spin foam models, 1+1 and 2+1 quantum gravity, perturbative approaches and other discrete approaches.

* Quantum geometry, including physical aspects of non-commutative geometry, quantum groups and quantum topology. Non-commutative field theory and deformed special relativity.[/color]

The meeting is sponsored by the QG network of the European Science Foundation."

=========
the orange paperback edition of Smolin's book is scheduled to go on sale 4 September 2007, that is in a little over 2 months from now. advance ordering has begun on UK-amazon, US-amazon, and in Canada.
=========
Garrett Lisi's surprising paper to be delivered at Loops '07 in Mexico 4 days from now (Tuesday 26 June) is available in slides+audio form at his website
http://deferentialgeometry.org/
advice: use two screens, download the PDF of the slides and view on one screen scrolling down
while keeping the menu of the audio segments on the other screen and click on them in sequence
so you hear the whole 20 minute talk without interruption
==========
just realized that Richard Kostecki website might be useful to keep a link to
http://www.fuw.edu.pl/~kostecki/
besides organizing the Zakopane school he does other things and has a useful set of links
==========
Martin Bojowald gave a report on the KITP Singularities workshop (which he co-organized with Gary Horowitz and others).
He gave it in April 2007. three months after the workshop, on the International LQG Seminar (ilqgs)
http://relativity.phys.lsu.edu/ilqgs/

 

[marcus]

Self-definition of the LQG community

One thing to realize is that the LQG community is very young.
IT ONLY JUST STARTED having a international conference on a nearly annual basis. The annual conference is a conventional way that research communities define themselves.

I would say that the three most visible defining events were the two conferences (Loops 05 and Loops 07) and the 2007 Zakopane QG school. Another important landmark was the 2006 founding by the ESF of the European Science Foundation QG network---supported by 8 countries. The QG Network organizes and sponsors workshops, conferences, and gives individual research grants. It's first conference will be summer 2008. Its first school for graduate students and postdocs was the one at Zakopane. Invitation to lecture at the school is to some extent defining: like being invited to give a plenary talk.

One can see what research lines are pursued in the LQG community (more correctly the non-string QG community, but people seem to prefer to say LQG) by looking at the programs of the Loops conferences and the Zakopane school.

Lines of research in the community are Spinfoam, Group Field Theory, CDT, Causal Sets, applications to Cosmology (LQC), Assymptotically safe QG (Reuter et al), AQG and Master Constraint (Thiemann et al.), Braided LQG and matter. These are the main approaches that I know of. Except for Causal Sets and Reuter's, all of these approaches date from 1998 or later. Thiemann's AQG and Master Constraint program is an outgrowth of vintage 1990s canonical LQG. So we have a community doing lines of research that are mostly less than 10 years old, which just started having an annual conference---just barely annual if it has one next year.

Research communities define themselves in part by having leaders, and you can often tell who the leaders are by who gives the INVITED TALKS at the main annual conference. This is hardly a surefire method! The LQG community has a practice of inviting OUTSIDERS at least on a one-time basis---as a way of encouraging interchange and of keeping open to the outside. Loops 05 had an invited talk by Robbert Dijkgraaf, a prominent string thinker. But for what it's worth we can check to see who were the REPEAT invited speakers at Loops 05, Loops 07, and the Zakopane school.

This has the merit of being a little objective, instead of my just telling you my opinion. I'll just score individuals and list those who score 2 or more. Two individuals, Rovelli and Reuter, gave invited presentations at all three events.

Carlo Rovelli 3
Martin Reuter 3
Jan Ambjorn 2
Abhay Ashtekar 2
Martin Bojowald 2
Laurent Freidel 2
Etera Livine 2
Daniele Oriti 2
Alejandro Perez 2
Lee Smolin 2
Raphael Sorkin 2
Thomas Thiemann 2

Here are links if you would like to see if I have missed anyone.
2005 plenaries
http://loops05.aei.mpg.de/index_files/Programme.html
2007 plenaries
http://www.matmor.unam.mx/eventos/loops07/plen_abs.html
first QG Network school
http://www.fuw.edu.pl/~kostecki/school.html

One obvious omission is John Barrett, whose research is in Non-commutative Geometry (NCG) and Spinfoam models, e.g. the familiar Barrett-Crane model. John Barrett is the director of the QG Network. And there's Renate Loll, who directs another ESF funding network--in random geometry--which supports a considerable amount of LQG community research. But there are a lot of omissions, in my subjective view, so I won't labor the point.

 

[marcus]

I'm using some simple objective measures to say what the main lines of research, who the leaders---instead of just giving a summary of my impressions from watching over the past 3 or 4 years. The previous post lists the main lines of research represented at Loops '07 and the people usually invited to speak at the community's defining events. Quantitative measures like this aren't perfect but they might catch detail that subjective impressions miss.

Something to point out is that 3 of the leading people in the LQG (more correctly the non-string QG) community are among the recently most cited people in quantum cosmology (QC).

QC has a strategic place in QG as a whole. It is where TESTABILITY is apt soonest to show up. Also because of the simplifying assumptions made in cosmology the QC people can symmetry-reduce and get tractible models and calculate numbers readily. Calculation can also be done, and is being done, in the full theory (in several non-string QG approaches) but it is less tractible and takes more computing power.

The three I refer to are Ashtekar, Bojowald, and Reuter. They have done noteworthy, in some cases famous, research outside quantum cosmology, but all three have at least a few RECENT papers focusing on QC, and their cosmology work has been widely cited. I will include quantum black holes papers since both the topics themselves and methods used are closely related. For simplicity I will only count papers from after 1999, and only those with 35+ cites to date. Some of the 2000-2003 papers, which have had time to accumulate cites, are in the 100+ category. The numbers for Bojowald are different partly because his work has always focused on quantum cosmology and closely allied topics.

As of 31 July. The number of 35+ papers is in parens and the total cites to just those papers is given.
Bojowald (23) 1550
Ashtekar (6) 488
Reuter (5) 267

The three have numerous collaborators. Some of their co-workers are themselves also highly cited recent QC authors. I'm not trying to make a complete list, but simply to see who among the dozen or so leaders in the LQG community that I listed in the previous post are especially active in quantum cosmology. I think it's just these three.
Quantum cosmology is a small field---other people you may think of as important figures in the field were, in several cases, active during the 1980s and 1990s, but have very little output after 1999 (particularly if one restricts to papers with 35+ cites.)

 

[marcus]

One thing to realize is that the LQG community is very young.
IT ONLY JUST STARTED having a international conference on a nearly annual basis. The annual conference is a conventional way that research communities define themselves.

I would say that the three most visible defining events were the two conferences (Loops 05 and Loops 07) and the 2007 Zakopane QG school. Another important landmark was the 2006 founding by the ESF of the European Science Foundation QG network...

To followup on this. The QG Network of the ESF is hosting a weeklong conference in the UK starting 30 June 2008 and calling it

QG² 2008

Part of the point is that it will include physical aspects of Noncommutative Geometry under the heading "Quantum Geometry".

The QG Network official title is ESF Network for "Quantum Geometry and Quantum Gravity", with geometry coming first, and this makes a point.

On the whole I think the terminology is more descriptive of the actual range of research in the non-string QG community----more accurately descriptive than the lump term "LQG community" that people, especially outsiders, tend to use.

ONE OF THE POSTERS HERE AT PF IS ON THE LOCAL ORGANIZING COMMITTEE for QG² 2008
http://www.maths.nottingham.ac.uk/conferences/qgsquared-2008/organizers/

The director of the QG Network, John Barrett, has done research BOTH in Noncommutative Geometry and in Spinfoam quantum gravity. He and Alain Connes came out with the same result about realizing the particletheory Standard Model, the same week last year (fall 2006). John Barrett is also on the local organizing committee.

this has to be the moral equivalent of "Loops 08" but by a different name (and maybe a better name!).

Also even stronger conference than Loops 05 and Loops 07 were because including NCG. It is not impossible that Alain Connes would show up and give a talk.

Here is the QG² 2008 Scientific Committee

Victor Aldaya (Granada)
Abhay Ashtekar (Penn State)
John Baez (UC Riverside)
Jürg Fröhlich (ETH, Zürich)
Harald Grosse (Vienna)
Shahn Majid (QMUL)
Carlo Rovelli (Marseille)
Thomas Schücker (Provence)
Lee Smolin (Perimeter)

Here's the website for the conference
http://www.maths.nottingham.ac.uk/conferences/qgsquared-2008/

 

[marcus]

Lately I've been finding it useful to cite the video and slides of Carlo Rovelli's talk at Strings 2008.
It is a very good introductory overview for people who don't know much about LQG,
Here are the 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[/QUOTE]

To find this post again, click on the sticky Possibly Useful Threads, and then click on Introduction to LQG,
and then topright where it says "page 1 of 9" click on "last" (or whatever it takes to get to page 9)

 

[marcus]

Newyear's snapshot of Loop Quantum Gravity

Perhaps the simplest way to take a group snapshot of recent LQG research is to record the ten most cited papers that have appeared in the last three years. That is "date > 2005" in Spires language.

This snapshot will change from year to year. If I remember to record it one year from today, on 1 Jan 2010, then it will be "date > 2006" (namely the most cited papers from 2007, 2008, and 2009.)

The titles and abstracts of most-cited papers can help to indicate any shifts in focus and delineate current frontiers. This possibly-useful-thread component seems like a good place to keep this kind of record because it stays within reach.

So here is what the Spires link says as of today:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+DK+QUANTUM+GRAVITY+AND+DK+LOOP+SPACE+AND+DATE+%3E+2005&FORMAT=www&SEQUENCE=citecount%28d%29 1) Loop quantum cosmology.
Martin Bojowald
http://arxiv.org/abs/gr-qc/0601085
Cited 155 times

2) Graviton propagator in loop quantum gravity.
Eugenio Bianchi, Leonardo Modesto, Carlo Rovelli, Simone Speziale
http://arxiv.org/abs/gr-qc/0604044
Cited 61 times

3) The Loop-quantum-gravity vertex-amplitude.
Jonathan Engle, Roberto Pereira, Carlo Rovelli
http://arxiv.org/abs/0705.2388
Cited 45 times

4) An Introduction to Loop Quantum Gravity Through Cosmology.
Abhay Ashtekar
http://arxiv.org/abs/gr-qc/0702030
Cited 41 times

5) A New Spin Foam Model for 4d Gravity.
Laurent Freidel, Kirill Krasnov
http://arxiv.org/abs/0708.1595
Cited 41 times

6) Flipped spinfoam vertex and loop gravity.
Jonathan Engle, Roberto Pereira, Carlo Rovelli
http://arxiv.org/abs/0708.1236
Cited 35 times

7) The Complete LQG propagator. I. Difficulties with the Barrett-Crane vertex.
Emanuele Alesci, Carlo Rovelli
http://arxiv.org/abs/0708.0883
Cited 34 times

8) Loop Quantum Gravity: An Inside View.
Thomas Thiemann
http://arxiv.org/abs/hep-th/0608210
Cited 31 times

9) LQG vertex with finite Immirzi parameter.
Jonathan Engle, Etera Livine, Roberto Pereira, Carlo Rovelli
http://arxiv.org/abs/0711.0146
Cited 30 times

10) Hamiltonian cosmological perturbation theory with loop quantum gravity corrections.
Martin Bojowald, Hector H. Hernandez, Mikhail Kagan, Parampreet Singh, Aureliano Skirzewski
http://arxiv.org/abs/gr-qc/0609057
Cited 28 times

 

[marcus]

Some helpful links, for staying informed
http://www.gr19.com/index.php
http://grg.maths.qmul.ac.uk/hyperspace/conference/08Dec.8.html
http://www.icra.it/MG/mg12/en/parallel_session.htm#
http://www.icra.it/MG/mg12/en/
http://grg.maths.qmul.ac.uk/hyperspace/conference/
http://strings2009.roma2.infn.it/home.html

Rovelli's 2008 LQG overview:
http://relativity.livingreviews.org/Articles/lrr-2008-5/
His 2008 LQG survey talk to the Strings '08 conference, video
http://cdsweb.cern.ch/record/1121957?ln=en

Page for Yongge Ma, a principal organizer of the August 2009 Loops 09 conference.
http://physics.bnu.edu.cn/application/research/gravity/LQG/eng/research.html

Most cited quantum cosmology papers, 2006 and later:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+DK+QUANTUM+cosmology+AND+DATE+%3E+2005&FORMAT=www&SEQUENCE=citecount%28d%29

 

[marcus]

Preliminary list of speakers for the XXV Max Born
(Warsaw 29 June-3 July)

J. Ambjorn (NBI, Copenhagen)
G. Amelino-Camelia (La Sapienza, Rome)
M. Arzano (PI, Waterloo)
A.P. Balachandran (Syracuse Univ.)
J. Barrett (Univ. Nottingham)
E. Bergshoeff (Univ. Groeningen)
M. Bojowald (Penn State)
S. Carlip (UC Davis)
M. Chaichian (Univ. Helsinki)
A. Chamseddine (Univ. Beirut)
L. Dabrowski (SISSA)
S. Doplicher (La Sapienza, Rome)
O. Dreyer (MIT)
M. Duff (Imperial Coll. London)
J. Figueroa-O'Farrill (Univ. Edinburgh)
L. Freidel (PI, Waterloo)
G. Gibbons (DAMTP Cambridge)
S. Giddings (UC Santa Barbara)
T.R. Govindarayan (Chennai)
A. Grillo (Gran Sasso)
J. Jurkiewicz (Jagiellonian Univ.)
F. Lizzi (Univ. Naples)
R. Loll (Univ. Utrecht)
J. Lukierski (Univ. Wroclaw)
J. Magueijo (Imperial Coll. London)
F. Markopoulou (PI, Waterloo)
D. Marolf (UC Santa Barbara)
N. Mavromatos (King's Coll. London)
C. Meusburger (Univ. Nottingham)
L. Modesto (PI, Waterloo)
H. Nicolai (AEI, Golm)
D. Oriti (PI, Waterloo)
K. Peeters (Univ. Utrecht)
G. Piacitelli (SISSA)
M. Pospelov (Victoria Univ & PI)
C. Rovelli (Marseille, CPT)
B. Schroers (Heriot-Watt Univ. Edinburgh)
B. Sidharth (Udine Univ.)
K. Skenderis (Univ. Amsterdam)
L. Smolin (PI, Waterloo)
R. Szabo (Univ. Edinburgh)
T. Thiemann (AEI, Golm)
A. Tureanu (Univ. Helsinki)
S. Vaidya (Indian Inst. Sci. Bangalore)
Ch. Young (Univ. Durham)

The five major themes of the Symposium will be:

Loops and spin foams
Strings, AdS/CFT, and quantum gravity
Field theoretical perspective on Planck scale
Noncommutative spacetimes
Quantum gravity phenomenology

Organizers:

Jerzy Kowalski-Glikman (University of Wroclaw)
Krzysztof Meissner (University of Warsaw)

The Warsaw symposium is interesting in part because of the preliminary mix of speakers. Here's a partial list of some you might recognize from their association with nonperturbative background independent QG (Loop and related, Causal Dynamical Triangulations, Noncommutative Geometry, QG Phenom)

J. Ambjorn (NBI, Copenhagen)
G. Amelino-Camelia (La Sapienza, Rome)
J. Barrett (Univ. Nottingham)
M. Bojowald (Penn State)
S. Carlip (UC Davis)
A. Chamseddine (Univ. Beirut)
O. Dreyer (MIT)
L. Freidel (PI, Waterloo)
J. Jurkiewicz (Jagiellonian Univ.)
R. Loll (Univ. Utrecht)
J. Lukierski (Univ. Wroclaw)
J. Magueijo (Imperial Coll. London)
F. Markopoulou (PI, Waterloo)
L. Modesto (PI, Waterloo)
D. Oriti (PI, Waterloo)
C. Rovelli (Marseille, CPT)
L. Smolin (PI, Waterloo)
T. Thiemann (AEI, Golm)

 

[marcus]

Updated helpful links, for staying informed

General
http://www.maths.nottingham.ac.uk/qg/
http://grg.maths.qmul.ac.uk/hyperspace/conference/

Rome 22-26 June
http://strings2009.roma2.infn.it/home.html

Warsaw (XXV Max Born) 29 June-3 July
http://www.ift.uni.wroc.pl/~planckscale/
http://www.ift.uni.wroc.pl/~planckscale/index.html?page=speakers
http://www.fuw.edu.pl/~meissner/home.html

Paris (MG12) 12-18 July
http://www.icra.it/MG/mg12/en/
http://www.icra.it/MG/mg12/en/parallel_session.htm#

Beijing (Loops09) 2-8 August
http://grg.maths.qmul.ac.uk/hyperspace/conference/08Dec.8.html

Mexico City (GR19)
http://www.gr19.com/index.php Rovelli's 2008 LQG overview:
http://relativity.livingreviews.org/Articles/lrr-2008-5/
2008 LQG survey talk to the Strings '08 conference, video and slides
http://cdsweb.cern.ch/record/1121957?ln=en
http://indico.cern.ch/getFile.py/access?contribId=30&resId=0&materialId=slides&confId=21917
2008 LQG survey talk to Loops '08, general, slides, audio
http://www.maths.nottingham.ac.uk/qg/wiki/index.php/QGsquared-slides
http://www.maths.nottingham.ac.uk/qg/wiki/images/3/3f/RovelliCarlo1214510081.pdf Most cited Loop QG papers, 2006 and later:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+DK+QUANTUM+GRAVITY+AND+DK+LOOP+SPACE+AND+DATE+%3E+2005&FORMAT=www&SEQUENCE=citecount%28d%29
Most cited (all types of) quantum cosmology papers, 2006 and later:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+DK+QUANTUM+cosmology+AND+DATE+%3E+2005&FORMAT=www&SEQUENCE=citecount%28d%29

 

[marcus]

A list of plenary speakers for MG12 (Paris 12-16 July) has been posted:
http://www.icra.it/MG/mg12/en/invited_speakers.htm

Speakers include Alain Connes, Laurent Freidel, Herbert Hamber

Hamber is known for discrete nonperturbative QG work, Regge-related and lattice QG methods. Here is a recent review paper of his:
http://arxiv.org/abs/0901.0964

Speakers list has been posted for
Black Holes and Loop Quantum Gravity
Valencia, Spain 26-28 March, 2009.
Abhay Ashtekar
Martin Bojowald *
Alejandro Corichi
Bianca Dittrich
Jonathan Engle
Amit Ghosh
Viqar Husain
Jerzy Lewandowski *
Jorge Pullin
Hanno Sahlmann
Madhavan Varadarajan
* To be confirmed
http://www.uv.es/bhlqg/speakers.htm
http://www.uv.es/bhlqg/

Topics for the BH and LQG workshop:
- Black hole entropy in LQG
- Spin foam approach to black holes
- Singularity resolution and information loss
- Prospects for a detailed description of the Hawking radiation
- Comparison between results from LQG and other approaches

 

[marcus]

Another useful link for keeping informed:
http://www.maths.nottingham.ac.uk/qg/Meetings.html
The names of the main speakers have been posted for the Second Quantum Geometry and Quantum Gravity School.
In addition there will be invited seminars by a number of others (not yet listed.)
Two PF members were at the first QGQG school, and reported on it. It was at Zakopane (ski resort in Poland.)
This time the school will be at Corfu,13-20 September.
http://www.maths.nottingham.ac.uk/qg/CorfuSS.html

Each of the main speakers will give a series of lectures during the course of the week (a minicourse):

Abhay Ashtekar Loop Quantum Gravity

John Baez Categorification in Fundamental Physics

John Barrett Spin networks and quantum gravity

Vincent Rivasseau Renormalization in Fundamental Physics

Carlo Rovelli (*) Covariant loop quantum gravity and its low-energy limit

Projected course descriptions are at the website. I quote here just one--Rovelli's:
"I present a new look on Loop Quantum Gravity, aimed at giving a better grasp on its dynamics and its low-energy limit. Following the highly successful model of QCD, general relativity is quantized by discretizing it on a finite lattice, quantizing, and then studying the continuous limit of expectation values. The quantization can be completed, and two remarkable theorems follow.

The first gives the equivalence with the kinematics of canonical Loop Quantum Gravity.
This amounts to an independent re-derivation of all well known Loop Quantum gravity kinematical results.

The second [gives] the equivalence of the theory with the Feynman expansion of an auxiliary field theory. Observable quantities in the discretized theory can be identified with general relativity n-point functions in appropriate regimes. The continuous limit turns out to be subtly different from that of QCD, for reasons that can be traced to the general covariance of the theory.

I discuss this limit, the scaling properties of the theory, and I pose the problem of a renormalization group analysis of its large distance behavior."

(my highlighting etc.)

 

[marcus]

"Top 20" snapshot: themes of recent LQG papers

Here's an updated "top 20" snapshot of the field, the 20 most-cited papers from the past 2 years (date > 2006).

The list makes clear which have been the predominant themes of research recently: the new vertex, establishing a new covariant version of LQG consistent with the older canonical version, checking that the low energy limit comes out right (graviton propagator), and as always cosmology (LQC).

There is one new theme that did not show up until paper number 23 in the list. The bridge between LQG and LQC--which may lead to cosmological tests of LQG. Although it didn't make the top 20 this time, I will append that paper.


1) The Loop-quantum-gravity vertex-amplitude.
Jonathan Engle, Roberto Pereira, Carlo Rovelli (Marseille, CPT) . May 2007. 6pp.
Published in Phys.Rev.Lett.99:161301,2007.
e-Print: arXiv:0705.2388 [gr-qc]
Cited 49 times

2) An Introduction to Loop Quantum Gravity Through Cosmology.
Abhay Ashtekar (Penn State U. & Santa Barbara, KITP) . 20pp.
Published in Nuovo Cim.122B:135-155,2007.
e-Print: gr-qc/0702030
Cited 46 times

3) A New Spin Foam Model for 4d Gravity.
Laurent Freidel (Perimeter Inst. Theor. Phys.) , Kirill Krasnov (Perimeter Inst. Theor. Phys. & Nottingham U.) . 40pp.
Published in Class.Quant.Grav.25:125018,2008.
e-Print: arXiv:0708.1595 [gr-qc]
Cited 46 times

4) Flipped spinfoam vertex and loop gravity.
Jonathan Engle, Roberto Pereira, Carlo Rovelli (Marseille, CPT) . 37pp.
Published in Nucl.Phys.B798:251-290,2008.
e-Print: arXiv:0708.1236 [gr-qc]
Cited 38 times

5) The Complete LQG propagator. I. Difficulties with the Barrett-Crane vertex.
Emanuele Alesci (Rome U. & Marseille, CPT) , Carlo Rovelli (Marseille, CPT) . 31pp.
Published in Phys.Rev.D76:104012,2007.
e-Print: arXiv:0708.0883 [gr-qc]
Cited 36 times

6) LQG vertex with finite Immirzi parameter.
Jonathan Engle (Marseille, CPT) , Etera Livine (Lyon, Ecole Normale Superieure) , Roberto Pereira, Carlo Rovelli (Marseille, CPT) . 8pp.
Published in Nucl.Phys.B799:136-149,2008.
e-Print: arXiv:0711.0146 [gr-qc]
Cited 33 times

7) Singularities and Quantum Gravity.
Martin Bojowald (Penn State U. & Santa Barbara, KITP) . 41pp.
Lectures given at 12th Brazilian School of Cosmology and Gravitation (XII BSCG), Rio de Janeiro, Brazil, 10-23 Sep 2006.
Published in AIP Conf.Proc.910:294-333,2007. Also in *Rio de Janeiro 2006, Cosmology and gravitation* 294-333
e-Print: gr-qc/0702144
Cited 20 times

8) The Perturbative Regge-calculus regime of loop quantum gravity.
Eugenio Bianchi (Pisa, Scuola Normale Superiore & INFN, Pisa) , Leonardo Modesto (Bologna U. & INFN, Bologna & Marseille, CPT) . 43pp.
Published in Nucl.Phys.B796:581-621,2008.
e-Print: arXiv:0709.2051 [gr-qc]
Cited 20 times

9) Loop quantum gravity corrections to gravitational wave dispersion.
Martin Bojowald, Golam Mortuza Hossain (Penn State U.) . 27pp.
Published in Phys.Rev.D77:023508,2008.
e-Print: arXiv:0709.2365 [gr-qc]
Cited 20 times

10) Lorentzian LQG vertex amplitude.
Roberto Pereira (Marseille, CPT) . 9pp.
Published in Class.Quant.Grav.25:085013,2008.
e-Print: arXiv:0710.5043 [gr-qc]
Cited 20 times

11) Spin foam model from canonical quantization.
Sergei Alexandrov (Montpellier U., Astropart. Group) . 25pp.
Published in Phys.Rev.D77:024009,2008.
e-Print: arXiv:0705.3892 [gr-qc]
Cited 17 times

12) The Complete LQG propagator. II. Asymptotic behavior of the vertex.
Emanuele Alesci (Rome III U. & Marseille, CPT) , Carlo Rovelli (Marseille, CPT) . 16pp.
Published in Phys.Rev.D77:044024,2008.
e-Print: arXiv:0711.1284 [gr-qc]
Cited 17 times

13) The Dark Side of a Patchwork Universe.
Martin Bojowald (Penn State U.) . 24pp.
Published in Gen.Rel.Grav.40:639-660,2008.
e-Print: arXiv:0705.4398 [gr-qc]
Cited 15 times

14) Inflationary universe in loop quantum cosmology.
Xin Zhang (Beijing, KITPC) , Yi Ling (Nanchang U.) . 25pp.
Published in JCAP 0708:012,2007.
e-Print: arXiv:0705.2656 [gr-qc]
Cited 14 times

15) Quantum Gravity Phenomenology.
Giovanni Amelino-Camelia . 82pp.
e-Print: arXiv:0806.0339 [gr-qc]
Cited 14 times

16) Path integral representation of spin foam models of 4d gravity.
Florian Conrady, Laurent Freidel (Perimeter Inst. Theor. Phys.) . 29pp.
Published in Class.Quant.Grav.25:245010,2008.
e-Print: arXiv:0806.4640 [gr-qc]
Cited 14 times

17) Loop quantum cosmology.
Martin Bojowald (Penn State U. & Potsdam, Max Planck Inst.) . 131pp.
Published in Living Rev.Rel.11:4,2008.
Cited 14 times

18) Loop quantization of spherically symmetric midi-superspaces.
Miguel Campiglia, Rodolfo Gambini (Republica U., Montevideo) , Jorge Pullin (Louisiana State U.) . 18pp.
Published in Class.Quant.Grav.24:3649-3672,2007.
e-Print: gr-qc/0703135
Cited 13 times

19) Loop Quantum Gravity: Four Recent Advances and a Dozen Frequently Asked Questions.
Abhay Ashtekar (Penn State U.) . 21pp.
To appear in the proceedings of 11th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Gravitation, and Relativistic Field Theories, Berlin, Germany, 23-29 Jul 2006.
e-Print: arXiv:0705.2222 [gr-qc]
Cited 13 times

20) Linearized dynamics from the 4-simplex Regge action.
Bianca Dittrich, Laurent Freidel, Simone Speziale (Perimeter Inst. Theor. Phys.) . 25pp.
Published in Phys.Rev.D76:104020,2007.
e-Print: arXiv:0707.4513 [gr-qc]
Cited 13 times

=========================================
The following represents an important new direction in research which I expect to become increasingly important in the next couple of years. I'll tack it on here even though it did not make the top 20:

23) Relating loop quantum cosmology to loop quantum gravity: Symmetric sectors and embeddings.
Jonathan Engle (Marseille, CPT & Provence U. & Marseille U., Luminy) . 20pp.
Published in Class.Quant.Grav.24:5777-5802,2007.
e-Print: gr-qc/0701132
Cited 12 times

 

[marcus]

Featured speakers at upcoming meetings, workshops etc.

A certain amount can be told about how things are going in a field by noting who the invited plenary speakers are to be at upcoming meetings. They tend to be people who have things to report that everybody wants to hear about. At the time it struck me as remarkable that the last GR meeting, GR17 Sydney 400-500 participants, had Renate Loll and Laurent Freidel as plenary speakers. Now the upcoming MG12 Paris, another biggie, will have Alain Connes and Laurent Freidel. There may be a general waking up to nonstring quantum gravity on the part of cosmologists, astrophysicists, GR-theorists, GR and gravity experimentalists, etc. I'll list some upcoming meetings and workshops in chrono order, along with a few of those giving talks.

Black Holes and Loop Quantum Gravity (Valencia 26-28 March)
http://www.uv.es/bhlqg/
Ashtekar, Bojowald, Corichi, Dittrich, Engle,..., Sahlmann...
Topic list is interesting, two of those included are:
- Spin foam approach to black holes
- Singularity resolution and information loss

Strings 2009 (Rome 22-26 June)
http://strings2009.roma2.infn.it/home.html
Last year they had Rovelli give a plenary talk on LQG. Let's see if they get anyone from the outside this year.

XXV Max Born (Wroclaw 29 June-3 July)
http://www.ift.uni.wroc.pl/~planckscale/
John Barrett, Laurent Freidel, Renate Loll,...many other outstanding speakers...

MG12 (Paris 12-16 July)
http://www.icra.it/MG/mg12/en/invited_speakers.htm
Alain Connes, Laurent Freidel

Loops 2009 (Beijing 2-8 August)
http://grg.maths.qmul.ac.uk/hyperspace/conference/08Dec.8.html
no speakers list posted so far

QG School 2 (Corfu 13-20 September)
http://www.maths.nottingham.ac.uk/qg/CorfuSS.html
Ashtekar, Baez, Barrett, Rivasseau, Rovelli

GR 19 (Mexico City 5-9 July 2010)
http://www.gr19.com/index.php
Rovelli
Helpful links, for staying informed
http://www.maths.nottingham.ac.uk/qg/
http://grg.maths.qmul.ac.uk/hyperspace/conference/
http://grg.maths.qmul.ac.uk/hyperspace/conference/latest.html

 

[marcus]

Loops 2009 has posted speakers now
http://www.loops09.org/asp/xtgl/zzview.asp?id=10
==quote==
The incomplete list of plenary speakers：

A. Ashtekar (Penn state)
J. Barrett (Nottingham)
M. Bojowald (Penn state)
A. Corichi (Morelia)
B. Dittrich (Utrecht)
L. Freidel (Perimeter)
H.Y. Guo (ITP, CAS)
J. Lewandowski (Warsaw)
R. Maartens (Portsmounth)
J. Pullin (Louisiana)
V. Rivasseau (Paris-Sud XI)
C. Rovelli (Marseille)
H. Sahlmann (Karlsruhe)
P. Singh (Perimeter)
L. Smolin (to be confirmed, Perimeter)
S. Speziale (Marseille)
T. Thiemann (AEI)
M. Varadarajan (Raman Inst)
==endquote==

There is a now a Loops 2009 website. Here's how they list the topics

==quote==
* Loop quantum gravity
* Loop quantum cosmology and other symmetric models
* Spin foams and their low energy ramifications
* Fundamental questions of quantum gravity
* Black holes and Cosmology related to quantum gravity
* Phenomenology of quantum gravity.
==endquote==

I believe this will be the first time that Bianca Dittrich will be a featured plenary speaker at a major international conference.
Maybe also a first for Simone Speziale, I don't recall for sure.

 

[etera]

Hey Marcus,
sorry for the self-advertisement... but each time people talk about the nex spinfoam models by Rovelli and al or Freidel and al, they keep forgetting these two papers where we introduced the coherent state techniques used for the semi-classical analysis of these models... and which could make it hopefully in the top 20 of the last couple of years...

A New spinfoam vertex for quantum gravity.
Etera R. Livine (Lyon, Ecole Normale Superieure) , Simone Speziale (Perimeter Inst. Theor. Phys.) . PI-QG-45, May 2007. 25pp.
Published in Phys.Rev.D76:084028,2007.
e-Print: arXiv:0705.0674 [gr-qc]
Cited 43 times

Consistently Solving the Simplicity Constraints for Spinfoam Quantum Gravity.
Etera R. Livine (Lyon, Ecole Normale Superieure) , Simone Speziale (Perimeter Inst. Theor. Phys.) . Aug 2007. 6pp.
Published in Europhys.Lett.81:50004,2008.
e-Print: arXiv:0708.1915 [gr-qc]
Cited 37 times

and there's even another one:
Numerical evidence of regularized correlations in spin foam gravity.
J.Daniel Christensen (Western Ontario U.) , Etera R. Livine (Lyon, Ecole Normale Superieure) , Simone Speziale (Perimeter Inst. Theor. Phys.) . PI-QG-57, Oct 2007. 5pp.
Published in Phys.Lett.B670:403-406,2009.
e-Print: arXiv:0710.0617 [gr-qc]
Cited 15 times

~etera

Here's an updated "top 20" snapshot of the field, the 20 most-cited papers from the past 2 years (date > 2006).

The list makes clear which have been the predominant themes of research recently: the new vertex, establishing a new covariant version of LQG consistent with the older canonical version, checking that the low energy limit comes out right (graviton propagator), and as always cosmology (LQC).

There is one new theme that did not show up until paper number 23 in the list. The bridge between LQG and LQC--which may lead to cosmological tests of LQG. Although it didn't make the top 20 this time, I will append that paper.


1) The Loop-quantum-gravity vertex-amplitude.
Jonathan Engle, Roberto Pereira, Carlo Rovelli (Marseille, CPT) . May 2007. 6pp.
Published in Phys.Rev.Lett.99:161301,2007.
e-Print: arXiv:0705.2388 [gr-qc]
Cited 49 times

2) An Introduction to Loop Quantum Gravity Through Cosmology.
Abhay Ashtekar (Penn State U. & Santa Barbara, KITP) . 20pp.
Published in Nuovo Cim.122B:135-155,2007.
e-Print: gr-qc/0702030
Cited 46 times

3) A New Spin Foam Model for 4d Gravity.
Laurent Freidel (Perimeter Inst. Theor. Phys.) , Kirill Krasnov (Perimeter Inst. Theor. Phys. & Nottingham U.) . 40pp.
Published in Class.Quant.Grav.25:125018,2008.
e-Print: arXiv:0708.1595 [gr-qc]
Cited 46 times

4) Flipped spinfoam vertex and loop gravity.
Jonathan Engle, Roberto Pereira, Carlo Rovelli (Marseille, CPT) . 37pp.
Published in Nucl.Phys.B798:251-290,2008.
e-Print: arXiv:0708.1236 [gr-qc]
Cited 38 times

5) The Complete LQG propagator. I. Difficulties with the Barrett-Crane vertex.
Emanuele Alesci (Rome U. & Marseille, CPT) , Carlo Rovelli (Marseille, CPT) . 31pp.
Published in Phys.Rev.D76:104012,2007.
e-Print: arXiv:0708.0883 [gr-qc]
Cited 36 times

6) LQG vertex with finite Immirzi parameter.
Jonathan Engle (Marseille, CPT) , Etera Livine (Lyon, Ecole Normale Superieure) , Roberto Pereira, Carlo Rovelli (Marseille, CPT) . 8pp.
Published in Nucl.Phys.B799:136-149,2008.
e-Print: arXiv:0711.0146 [gr-qc]
Cited 33 times

 

[marcus]

Etera, thanks for pointing that out. The omissions were certainly not intentional!

If you have some tips about using Spires, please let me know. I gather they have no Boolean OR. So if I want keyword "loop space" or keyword "spin, foam" I need to do two searches and merge the lists manually.

I just realized that when I search with keywords "quantum gravity AND loop space" it does not come up with some papers tagged "spin, foam" like the ones you mentioned.

So now we need a new routine for getting the LQG top 20.
First we do this "spin, foam" search:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND++DK+SPIN%2C+FOAM+AND+DATE+%3E+2006&FORMAT=www&SEQUENCE=citecount%28d%29

Then we do a "quantum gravity" and "loop space" search:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=dk+quantum+gravity+and+dk+loop+space+and+date+%3E+2006&FORMAT=www&SEQUENCE=citecount%28d%29

Then we merge the lists by hand:

1) The Loop-quantum-gravity vertex-amplitude.
Jonathan Engle, Roberto Pereira, Carlo Rovelli (Marseille, CPT) . May 2007. 6pp.
Published in Phys.Rev.Lett.99:161301,2007.
e-Print: arXiv:0705.2388 [gr-qc]
Cited 49 times

2) An Introduction to Loop Quantum Gravity Through Cosmology.
Abhay Ashtekar (Penn State U. & Santa Barbara, KITP) . IGPG-07-01-02, NSF-KITP-07-05, Feb 2007. 20pp.
Published in Nuovo Cim.122B:135-155,2007.
e-Print: gr-qc/0702030
Cited 47 times

3) A New Spin Foam Model for 4d Gravity.
Laurent Freidel (Perimeter Inst. Theor. Phys.) , Kirill Krasnov (Perimeter Inst. Theor. Phys. & Nottingham U.) . Aug 2007. 40pp.
Published in Class.Quant.Grav.25:125018,2008.
e-Print: arXiv:0708.1595 [gr-qc]
Cited 47 times

4) A New spinfoam vertex for quantum gravity.
Etera R. Livine (Lyon, Ecole Normale Superieure) , Simone Speziale (Perimeter Inst. Theor. Phys.) . PI-QG-45, May 2007. 25pp.
Published in Phys.Rev.D76:084028,2007.
e-Print: arXiv:0705.0674 [gr-qc]
Cited 43 times

5) Flipped spinfoam vertex and loop gravity.
Jonathan Engle, Roberto Pereira, Carlo Rovelli (Marseille, CPT) . Aug 2007. 37pp.
Published in Nucl.Phys.B798:251-290,2008.
e-Print: arXiv:0708.1236 [gr-qc]
Cited 39 times

6) Consistently Solving the Simplicity Constraints for Spinfoam Quantum Gravity.
Etera R. Livine (Lyon, Ecole Normale Superieure) , Simone Speziale (Perimeter Inst. Theor. Phys.) . Aug 2007. 6pp.
Published in Europhys.Lett.81:50004,2008.
e-Print: arXiv:0708.1915 [gr-qc]
Cited 37 times

7) The Complete LQG propagator. I. Difficulties with the Barrett-Crane vertex.
Emanuele Alesci (Rome U. & Marseille, CPT) , Carlo Rovelli (Marseille, CPT) . Aug 2007. 31pp.
Published in Phys.Rev.D76:104012,2007.
e-Print: arXiv:0708.0883 [gr-qc]
Cited 36 times

8) LQG vertex with finite Immirzi parameter.
Jonathan Engle (Marseille, CPT) , Etera Livine (Lyon, Ecole Normale Superieure) , Roberto Pereira, Carlo Rovelli (Marseille, CPT) . Nov 2007. 8pp.
Published in Nucl.Phys.B799:136-149,2008.
e-Print: arXiv:0711.0146 [gr-qc]
Cited 34 times

9) The Perturbative Regge-calculus regime of loop quantum gravity.
Eugenio Bianchi (Pisa, Scuola Normale Superiore & INFN, Pisa) , Leonardo Modesto (Bologna U. & INFN, Bologna & Marseille, CPT) . Sep 2007. 43pp.
Published in Nucl.Phys.B796:581-621,2008.
e-Print: arXiv:0709.2051 [gr-qc]
Cited 20 times

10) Singularities and Quantum Gravity.
Martin Bojowald (Penn State U. & Santa Barbara, KITP) . IGPG-07-2-4, Feb 2007. 41pp.
Lectures given at 12th Brazilian School of Cosmology and Gravitation (XII BSCG), Rio de Janeiro, Brazil, 10-23 Sep 2006.
Published in AIP Conf.Proc.910:294-333,2007. Also in *Rio de Janeiro 2006, Cosmology and gravitation* 294-333
e-Print: gr-qc/0702144
Cited 20 times

11) The Perturbative Regge-calculus regime of loop quantum gravity.
Eugenio Bianchi (Pisa, Scuola Normale Superiore & INFN, Pisa) , Leonardo Modesto (Bologna U. & INFN, Bologna & Marseille, CPT) . Sep 2007. 43pp.
Published in Nucl.Phys.B796:581-621,2008.
e-Print: arXiv:0709.2051 [gr-qc]
Cited 20 times

12) Loop quantum gravity corrections to gravitational wave dispersion.
Martin Bojowald, Golam Mortuza Hossain (Penn State U.) . IGC-07-9-1, Sep 2007. 27pp.
Published in Phys.Rev.D77:023508,2008.
e-Print: arXiv:0709.2365 [gr-qc]
Cited 20 times

13) Lorentzian LQG vertex amplitude.
Roberto Pereira (Marseille, CPT) . Oct 2007. 9pp.
Published in Class.Quant.Grav.25:085013,2008.
e-Print: arXiv:0710.5043 [gr-qc]
Cited 20 times

14) Spin foam model from canonical quantization.
Sergei Alexandrov (Montpellier U., Astropart. Group) . PTA-07-24, May 2007. 25pp.
Published in Phys.Rev.D77:024009,2008.
e-Print: arXiv:0705.3892 [gr-qc]
Cited 17 times

15) The Complete LQG propagator. II. Asymptotic behavior of the vertex.
Emanuele Alesci (Rome III U. & Marseille, CPT) , Carlo Rovelli (Marseille, CPT) . Nov 2007. 16pp.
Published in Phys.Rev.D77:044024,2008.
e-Print: arXiv:0711.1284 [gr-qc]
Cited 17 times

16) The Dark Side of a Patchwork Universe.
Martin Bojowald (Penn State U.) . IGPG-07-5-5, May 2007. 24pp.
Published in Gen.Rel.Grav.40:639-660,2008.
e-Print: arXiv:0705.4398 [gr-qc]
Cited 15 times

17) Path integral representation of spin foam models of 4d gravity.
Florian Conrady, Laurent Freidel (Perimeter Inst. Theor. Phys.) . PI-QG-84, Jun 2008. 29pp.
Published in Class.Quant.Grav.25:245010,2008.
e-Print: arXiv:0806.4640 [gr-qc]
Cited 15 times

18) Inflationary universe in loop quantum cosmology.
Xin Zhang (Beijing, KITPC) , Yi Ling (Nanchang U.) . May 2007. 25pp.
Published in JCAP 0708:012,2007.
e-Print: arXiv:0705.2656 [gr-qc]
Cited 14 times

19) Quantum Gravity Phenomenology.
Giovanni Amelino-Camelia . Jun 2008. 82pp. Temporary entry
e-Print: arXiv:0806.0339 [gr-qc]
Cited 14 times

20) Loop quantum cosmology.
Martin Bojowald (Penn State U. & Potsdam, Max Planck Inst.) . 2008. 131pp.
Published in Living Rev.Rel.11:4,2008.
Cited 14 times

21) Loop quantization of spherically symmetric midi-superspaces.
Miguel Campiglia, Rodolfo Gambini (Republica U., Montevideo) , Jorge Pullin (Louisiana State U.) . LSU-REL-032707, NSF-KITP-07-28, Mar 2007. 18pp.
Published in Class.Quant.Grav.24:3649-3672,2007.
e-Print: gr-qc/0703135
Cited 13 times

22) Loop Quantum Gravity: Four Recent Advances and a Dozen Frequently Asked Questions.
Abhay Ashtekar (Penn State U.) . IGPG-07-5-3, May 2007. 21pp.
To appear in the proceedings of 11th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Gravitation, and Relativistic Field Theories, Berlin, Germany, 23-29 Jul 2006.
e-Print: arXiv:0705.2222 [gr-qc]
Cited 13 times

23) Harmonic cosmology: How much can we know about a universe before the big bang?
Martin Bojowald (Penn State U., Astron. Astrophys.) . Oct 2007. 16pp.
Published in Proc.Roy.Soc.Lond.A464:2135-2150,2008.
e-Print: arXiv:0710.4919 [gr-qc]
Cited 13 times

24) Linearized dynamics from the 4-simplex Regge action.
Bianca Dittrich, Laurent Freidel, Simone Speziale (Perimeter Inst. Theor. Phys.) . PI-QG-48, Aug 2007. 25pp.
Published in Phys.Rev.D76:104020,2007.
e-Print: arXiv:0707.4513 [gr-qc]
Cited 13 times