Recognitions:

## Introduction To Loop Quantum Gravity

 Quote by marcus First undergraduate textbook could appear this year. Scheduled for September 2011. Oxford U Press: http://ukcatalogue.oup.com/product/a...80199590759.do
Not Bojowald's, or is that not undergarduate? http://www.physicsforums.com/showthread.php?t=432381

Recognitions:
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Quote by atyy
 Quote by marcus First undergraduate textbook could appear this year. Scheduled for September 2011. Oxford U Press: http://ukcatalogue.oup.com/product/a...80199590759.do
Not Bojowald's, or is that not undergarduate? http://www.physicsforums.com/showthread.php?t=432381
Atyy, good question! I edited so as to respond in the appropriate place, right after the OUP publisher's blurb. I think in fact that the Gambini IS the first explicitly LQG undergrad text!
The Bojo text is on Canonical GR, with several applications. It could be used as a text but doesn't have the clear focus on LQG.
Oxford press says Gambini is the first LQG text for undergrads. And they are right. If you look at the title and TOC of the Bojo books you will see what I mean.

New page, so I will make the update post here for easy reference:
It hasn't been done for over a month so it's probably time to redo the regularly updated links post to give an introductory overview of the Loop program.
==================================

BRIEF OVERVIEW OF THE LOOP QG PROGRAM

Loop Gravity is a small growing field. It has had regular biannual conferences only since 2005 (Loops '05 was held at Potsdam.) Attendance at the biannual (Loops '11 Madrid) is now up to about 170.

Because centers of LQG research are spreading rather rapidly, jobs and postdoc positions seem currently to be ample compared to the number of new PhDs. It's hard to predict the future, but at least for now job prospects seem pretty good. Most new PhDs are out of Marseille,Penn State, AEI-Potsdam, and they all get placed. There are starting to be more PhDs now out of other places: Nottingham, Erlangen, Lyon, Cambridge, London...hard to give an exhaustive list.

First undergraduate textbook could appear this year. Scheduled for September 2011. Oxford U Press:
http://ukcatalogue.oup.com/product/a...80199590759.do

Newly established Masters program aimed at Loop and other QG research (among other paths) starting at Nottingham in 2011:
http://pgstudy.nottingham.ac.uk/post...-msc_1163.aspx

Survey for non-specialists, historical development and indications the theory recovers classical GR.
http://arxiv.org/abs/1012.4707
Loop quantum gravity: the first twenty five years

Definitive presentation of Loop gravity, with some math prerequisites:
http://arxiv.org/abs/1102.3660
Lectures on Loop Gravity

Loop cosmology, as of mid-2010:
http://arxiv.org/abs/1005.5491.
The Big Bang and the Quantum

Since Loop cosmology derives from LQG, this turns out to be the most accessible route to testing LQG. Here are 32 or more articles mostly by early universe phenomenologists about ways of testing LQC against CMB data,
http://www-library.desy.de/cgi-bin/s...tecount%28d%29
which have appeared since 2009.

Some other papers of possible interest:

http://arxiv.org/abs/1101.3264
Spinfoam Fermions: PCT Symmetry, Dirac Determinant, and Correlation Functions

http://arxiv.org/abs/1012.1739
Lorentz covariance of loop quantum gravity

The European Science Foundation "QG" network is encouraging development of a broad-base research community by events such as this year's QG 2011 conference in Zurich:
http://www.conferences.itp.phys.ethz...?id=qg11:start

Topics to be covered include:
General quantum theory, relativistic quantum theory, emergence of space(-time)
General quantum field theory, including deformations of QFTs
QFT on curved and NC space-times
Canonical quantum gravity and supergravity
Regge calculus
String theory and M-theory
Loop gravity, spin foam
Quantum cosmology
===============================

The biannual Loops conference starts 23 May: Loops 2011 in Madrid.
http://www.iem.csic.es/loops11/
Click on "scientific program" in the menu on the left to see the list of talks. Abstracts of most talks are now available, just click on the title.

Many of the talks are about early universe pheno---the prospects for testing/constraining the theory.
Emerging challenges to the current formulation of Loop gravity are also represented at the conference and include "Shape dynamics" (see the session devoted to that on 23 May) and "Relative locality" (see talks by Laurent Freidel and Lee Smolin).

One of the signs of growth is the number of "parallel session" talks scheduled for Loops 2011, last time I checked there were 99 such. Younger researchers and newcomers to the field normally give talks in these parallel sessions.
=========================

Other signs of growth in the field:
• the number of institutions now hosting Loop gravity (+ related phenomenology) research, and where one can do a Loop PhD
• citations in the relevant categories (gr-qc, quantum cosmology, e.g. a growing share of "top 10 or top 30" papers)
• simply the increased number of research papers coming out. Approximately doubled since 2006.

Code:
Loop gravity papers, by year
2005    41
2006    81
2007   121
2008   142
2009   141
2010   154
Code:
Loop cosmology papers, by year
2006    21
2007    39
2008    46
2009    45
2010    57
The current Loop cosmo formulation (Ashtekar et al) only appeared in 2006 so I start with that year.
Here are the relevant Spires searches, and links, if anyone wishes to see how the listing looks.

FIND DK SPIN,FOAM OR QUANTUM GRAVITY, LOOP SPACE OR QUANTUM COSMOLOGY, LOOP SPACE AND DATE = 2005
FIND DK QUANTUM COSMOLOGY, LOOP SPACE AND DATE = 2006
2005:
http://www-library.desy.de/cgi-bin/s...tecount%28d%29
2006:
http://www-library.desy.de/cgi-bin/s...tecount%28d%29
2007:
http://www-library.desy.de/cgi-bin/s...tecount%28d%29
2008:
http://www-library.desy.de/cgi-bin/s...tecount%28d%29
2009:
http://www-library.desy.de/cgi-bin/s...tecount%28d%29
2010:
http://www-library.desy.de/cgi-bin/s...tecount%28d%29

 Recognitions: Gold Member Science Advisor The Loops 2011 conference in Madrid last month had 165 participants. The program of talks is posted at this site: http://www.iem.csic.es/loops11/ The QG11 conference in Zurich starts 14 June. 120 participants have registered so far. http://www.conferences.itp.phys.ethz...qg11:programme
 Recognitions: Gold Member Science Advisor I'm trying out this Spires search to keep track of Loop early universe phenomenology papers (studying ways to test Loop cosmology.) http://www-library.desy.de/cgi-bin/s...tecount%28d%29 It is a reworking of a search I was using earlier--what gets typed into the search terms box is: FIND (DK LOOP SPACE AND (QUANTUM GRAVITY OR QUANTUM COSMOLOGY) ) AND (GRAVITATIONAL RADIATION OR PRIMORDIAL OR INFLATION OR POWER SPECTRUM OR COSMIC BACKGROUND RADIATION) AND DATE>2008 Just now when I tried it, the search came up with 42 items--papers that appeared 2009 or later. The proposal of ways to test LQG---in particular the effects of the bounce at the start of expansion (which is a robust feature)---is an important development, I think. Another development is represented by this year's Quantum Theory and Gravitation conference ("QG11") which brings several QG communities together for comparison, sharing ideas, and discussion. It is a mixed QG conference. We will see if the idea catches on. I have color-coded the list of talks to give an idea of the mix. Causal Dynamical Triangulations(CDT) Spectral Action (Connes Noncommutative Geometry) LQG (incl. Group Field Theory) Asymptotic Safety Foundations-general considerations String ====== Ambjorn: CDT, a quantum theory of geometry Arnlind: Poisson Algebraic Geometry and Matrix Regularizations Ashtekar: Quantum Cosmology and the Very Early Universe Bachas: The problem of localization of gravity Baez: Higher gauge theory, division algebras and superstrings Barrett: State sum models and the spectral action Beisert: Symmetries and Integrability for Scattering Amplitudes in N=4 Super Yang-Mills Theory Blau: String Theory as a Theory of Quantum Gravity: a Status Report Bodendorfer: Towards Loop Quantum Supergravity Bossard: Toward the consistency of N=8 supergravity as a quantum field theory Chamseddine: The Spectral Action Compere: The translation anomaly of asymptotically flat spacetimes Craps: Cosmological singularities in string theory de Goursac: Renormalizability of noncommutative quantum field theories Dixon: Ultraviolet behavior of quantum (super)gravity through four loops Elvang: Symmetry constraints on the UV behavior of N=8 supergravity Freidel: The principle of relative locality Giulini: Very basic issues concerning quantum mechanics and gravitation Hollands: Quantum field theory correlators on manifolds at very large and very short distances Hoppe: Fundamental Structures of M-brane Theory Jacobson: How general is the generalized second law? Lechner: Covariant and local deformations of quantum field theories Lewandowski: Canonical LQG: soluble models and other advances Litim: Renormalisation group and the Planck scale Loll: Nonperturbative highlights on quantum gravity from CDT Longo: Boundary Quantum Field Theory and Conformal Field Theory Morton: Extended Field Theories and Higher Gauge Theories Mukhanov: Massive Gravity Nicolai: Infinite-dimensional symmetries and the Wheeler-DeWitt equation Oriti: Group field theory: a brief survey of recent developments Reiterer: A class of gauges for the Einstein equations Reuter: Einstein-Cartan Theory and Asymptotic Safety Rovelli: Loop quantum gravity: the covariant dynamics Shaposhnikov: Scale-invariant alternatives to general relativity Speziale: Spin networks as twisted geometries Steinacker: Matrix models, noncommutative gauge theory and emergent geometry Wulkenhaar: Ward identities in matrix models arising from noncommutative geometry I I'm not sure what Nicolai's talk is going to be about but just as a guess classify it "foundations-general considerations"--a potentially important topic suggested on the front page by the organizers. http://www.conferences.itp.phys.ethz...qg11:programme
 Recognitions: Gold Member Science Advisor Currently the best review of LQG is this video talk: http://loops11.iem.csic.es/loops11/i...tures&Itemid=1 The talk was given 25 May 2011 in Madrid, at the biannual Loops conference. For a printed journal-style review try http://arxiv.org/abs/1012.4707 which was posted in December 2010. There is also the LQG tutorial http://arxiv.org/abs/1102.3660
 Marcus, About Causal Dynamic Triangulation, there still hasn't been much published out in layman's land. In the above discussion of LQG those terms almost describe an engineering model using an element system (something like a hydraulic model using links and nodes). Does this suggest that LQG acts like a secondary field much like eddy currents within an electromagnetic field (solved using a matrice)? When looking at spin states 2D respresentation seem like "Fractals" as you described previously. How does CDT model or resolve loop gravity?

Recognitions:
Gold Member
 Quote by Peter McKenna Marcus, About Causal Dynamic Triangulation, there still hasn't been much published out in layman's land.... How does CDT model or resolve loop gravity?
Have you seen the SciAm article on CDT? It's well-written as an introduction for wide audience, and it has links to further reading, some of which is pretty accessible. I keep the URL to the SciAm article in my signature (check the end of this post). It is the "signal lake" link.
http://www.signallake.com/innovation...antumJul08.pdf

 In the above discussion of LQG those terms almost describe an engineering model using an element system (something like a hydraulic model using links and nodes). Does this suggest that LQG acts like a secondary field much like eddy currents within an electromagnetic field (solved using a matrice)? When looking at spin states 2D respresentation seem like "Fractals" as you described previously...
I'm not sure I can respond adequately. Maybe one of us will start a separate thread specifically to discuss these ideas. This thread does not have much discussion--it is mainly used to provide quick access to selected source material on Lqg.

Recognitions:
Gold Member
 Quote by marcus Currently the best review of LQG is this video talk: http://loops11.iem.csic.es/loops11/i...=article&id=76 The talk was given 25 May 2011 in Madrid, at the biannual Loops conference. ...
When I posted that, a few weeks ago, the new version of its written counterpart, Zakopane Lectures, had not yet appeared. Now the new version is out. It has been expanded by an additional 10 pages or so, and rewritten in parts. It's now an excellent tutorial, aimed at advanced grad students ready and wanting to get into Loop research.
http://arxiv.org/abs/1102.3660
The Loop people have introductory winter "schools" for grad students and postdocs. This year they had a two-week school at the Zakopane ski resort. This paper is a condensed version of the series of lectures Rovelli taught at that that school. It has examples and exercises to work out. It reviews the open research problems, some where progress has recently been made. It presents the theory concisely, and also gives an overview of the various approaches that converged to it from different directions.

For a printed journal-style review article, try http://arxiv.org/abs/1012.4707 which appeared December 2010. Ths is not as pedagogical as the other. It is more for nonspecialists who just want a general status report and overview, with some historical background. It is not aimed at people who want to get their hands on quantum geometry and do some research in it.

 Recognitions: Gold Member Science Advisor QG growth in France has been remarkable in the past few years. It's interesting to examine what shape this is taking and to try to figure out why. There are now many active centers of QG research: Marseille (Rovelli's group) Paris-Sud (Rivasseau's Orsay group) Lyon (Livine's group) Montpellier (Alexandrov, Roche) Tours (Noui) Ecole Polytechnique (Gabriel Catren) http://www.rivasseau.com/ http://en.wikipedia.org/wiki/École_Polytechnique http://en.wikipedia.org/wiki/Paris-Sud_11_University http://www.polytechnique.edu/home/ab...=1282806775110 Paris-Sud has 4 Fields Medalists and 2 Nobel prizewinners. By Usa standards it is "Ivy", I guess. The Paris Ecole Poly is like the French MIT---a small elite tech school. These are distinguished places. It's interesting that Gabriel Catren should get a 5 year European Research Council (ERC) grant to set up a QG research team at the Ecole Poly. The emphasis of that research is on the foundations---the ontology of space and time---a more philosophical approach to basic questions in physics. You can read what he has to say about it at the above link. I didn't know of Catren. Here is a bit more information: http://www.crea.polytechnique.fr/LeC...hes/Catren.htm Perimeter video lectures: http://pirsa.org/index.php?p=speaker...Gabriel_Catren
 Recognitions: Gold Member Science Advisor A little over 3 months ago, in post #274, I reported that the job situation (if postdoc fellowships are included) looked fairly good for new loop PhDs from Marseille, Penn State, and AEI Potsdam. This needs to be corrected or qualified by reservations. The job situation is difficult (as with other areas of theoretical physics). Permanent positions are scarce, so what we are keeping track of are postdoc and other temporary positions. For one thing, the new PhDs used to be mostly out of Marseille and Penn State, and now several new centers have emerged (Erlangen, Lyon, Beijing Normal, Florida Atlantic, Asia Pacific CTP in Korea, Morelia, Louisiana State, Sydney...to name a few) so it is more difficult to keep track. And it adds to the potential competition. About all I can do is keep an eye on two or three main centers (Marseille, Penn State, Potsdam AEI) and from those I see new PhDs continuing to be placed, for the most part, but in temporary positions. I'd be glad to get other people's impressions and more accurate assessments based on direct experience. To hazard a guess just as a casual onlooker (and this could be completely wrong) at this point if you are a new loop PhD to have a good chance at a 2 year postdoc contract or better your advisor should be Ashtekar, Rovelli, or Thiemann. I would be delighted to be corrected on that score. The journal General Relativity and Gravitation has published a special issue containing written versions of talks at the 2nd QG school and workshop held at Corfu. http://www.springerlink.com/content/...1/fulltext.pdf The editors were: Konstantinos Anagnostopoulos · Paolo Aschieri · Martin Bojowald · Harald Grosse · Larisa Jonke · George Zoupanos Much of the special issue is restricted access ("pay per view") but John Baez' article is open access ("free") and there may be other stuff like that. I think the editorial I linked to just now is free. The main lecture series at the Corfu school were given by Abhay Ashtekar, John Baez, John Barrett, Vincent Rivasseau, Carlo Rovelli. Some of these were lectures were written up and included, along with some of the individual talks. Here is the TOC for GRG Volume 43 Number 9 http://www.springerlink.com/content/p513t4384471/ This has links to all the ABSTRACTS---just click on the title of the talk. But the full text is in general not freely available. Editorial Noncommutative quantum field theory and gravity Konstantinos Anagnostopoulos, Paolo Aschieri, Martin Bojowald, Harald Grosse, Larisa Jonke & George Zoupanos Review Article An invitation to higher gauge theory John C. Baez & John Huerta Research Articles Non-perturbative QEG corrections to the Yang–Mills beta function J.-E. Daum, U. Harst & M. Reuter Geometry and observables in (2+1)-gravity C. Meusburger Asymptotics of 4d spin foam models John W. Barrett, Richard J. Dowdall, Winston J. Fairbairn, Henrique Gomes, Frank Hellmann & Roberto Pereira Braided algebras and the kappa-deformed oscillators Jerzy Lukierski & Mariusz Woronowicz Equivariant dimensional reduction and quiver gauge theories Brian P. Dolan & Richard J. Szabo Open multiple M2-branes I: quantum geometry of the M5-brane in a C-field Chong-Sun Chu & Douglas J. Smith Noncommutative geometry in string and twisted Hopf algebra of diffeomorphism Satoshi Watamura Renormalizable noncommutative quantum field theory Harald Grosse & Raimar Wulkenhaar Gravitational anomaly and fundamental forces J. J. van der Bij UV/IR duality in noncommutative quantum field theory André Fischer & Richard J. Szabo Curved space (matrix) membranes Jens Hoppe The Coulomb solution as a coherent state of unphysical photons Glenn Barnich Gauge symmetry breaking in matrix models Harald Grosse, Fedele Lizzi & Harold Steinacker
 Recognitions: Gold Member Science Advisor Bianca Dittrich has accepted a tenure-track position at Perimeter. There's an interview with her in Physics Today: http://www.physicstoday.org/daily_ed...uantum_gravity In the course of conversation with Atyy and others, in the Current Status of LQG thread, we came up with four papers which taken together can serve as a review as of August 2011: http://physicsforums.com/showthread....40#post3485140 ==quote== That would make the combined essential "current status" review be 1102.3660 + 1108.2258 +1105.2212 + 1108.0832 Zakopane lectures+Emergence of gravity+Cosmological constant + On the structure Rovelli + Magliaro Perini + Han + Rovelli 33 pages +6 pages +6 pages + 7 pages ==endquote== For a video lecture affording an overview of LQG as of May 2011: http://loops11.iem.csic.es/loops11/i...=article&id=76 For Loop Quantum Cosmology status report: http://arxiv.org/abs/1108.0893 For an index of research activity: LOOP RESEARCH BY YEAR (loop quantum gravity, loop quantum cosmology, spin foam) 2005 http://inspirebeta.net/search?ln=en&...=25&sc=0&of=hb (42 found) 2006 http://inspirebeta.net/search?ln=en&...=25&sc=0&of=hb (77 found) 2007 http://inspirebeta.net/search?ln=en&...=25&sc=0&of=hb (120 found) 2008 http://inspirebeta.net/search?ln=en&...=25&sc=0&of=hb (142 found) 2009 http://inspirebeta.net/search?ln=en&...=25&sc=0&of=hb (145 found) 2010 http://inspirebeta.net/search?ln=en&...=25&sc=0&of=hb (152 found) 2011 http://inspirebeta.net/search?ln=en&...=25&sc=0&of=hb (134 as of 16 Sept, annualized > 180) http://howlonguntil.net/ 258 since 1 January The annualized rate in this case 134*365/258 = 189 ======================== Two links I want to keep handy relating to the cosmological constant problem: http://arxiv.org/abs/1002.3966 http://arxiv.org/abs/1103.4841 ========================= αβγδεζηθικλμνξοπρσςτυφχψωΓΔΘΛΞΠΣΦΨΩ∏∑∫∂√±←↓→↑↔~≈≠≡ ≤≥½∞(⇐⇑⇒⇓⇔∴∃ℝℤℕℂ⋅)
 Recognitions: Gold Member Science Advisor http://www.physics.ntua.gr/cosmo11/N.../sci_prog.html Called a "Summer School" but from the looks of the program it was more a high level workshop. The list of participants was mostly experts already established in various fields, not grad students! Interesting mix of Loop gravity, String, Loop cosmology, Asymsafe gravity, Triangulations gravity. Just concluded. It ran last week 12-17 September The topic was "Quantum Gravity and Quantum Cosmology" Morning hour lectures by the likes of Ashtekar and Rovelli (Loop) and Kelly Stelle (String) and Joe Silk (Latest Obs. Dark Matter) and Robert Brandenberger (Unconventional Cosmology) Reuter (AsymSafe) Woodard (QG and Inflation) Bachas (String) Tsujikawa (Latest on Dark Energy) Wetterich (Spinor gravity), and so on. And then after lunch there were 30 minute and 15 minute presentations. Also covering a broad mix of active approaches to QG and QC. To me the program looks like people getting down to business. Cosmology is the ultimate testing ground and whether they struggle or join forces, the different teams have to know each other accurately in depth and confront observations together. One can say that representative folks from Loop, String, and other innovative approaches to gravity/cosmology were FRATERNIZING on the Aegean island of Naxos. Including major people, leaders in various fields. Nice to see that. BTW Munich is hosting Strings 2012 and they have already set up their website: http://wwwth.mpp.mpg.de/members/stri...2/strings.html We will see if they move a bit in the ecumenical direction of acknowledging the competition (Strings 2008 at CERN had a talk by Rovelli, 2010 at TexasA&M had one by Weinberg on AsymSafe cosmology, 2011 Uppsala had talks by Frank Wilczek and Erik Verlinde)
 Recognitions: Gold Member Science Advisor Also in September there was a 3 week workshop about QG at CERN. http://ph-dep-th.web.cern.ch/ph-dep-...QG11/QG11.html Hermann Nicolai's talk was at 2PM on 21 September and was followed by a scheduled period of discussion that concluded the day. It was titled: Quantum Gravity: Where do we stand? http://ph-dep-th.web.cern.ch/ph-dep-...lks/QGCERN.pdf There were 28 slides, each normally repeating as points were added. Slide 13(3 repeats) was Background Independence Slide 14(6 repeats) was Canonical Quantization Slide 15(5) was Geometrodynamics [i.e. original quantum grav. eqn. Wheeler-DeWitt] Slides 16-18(7) was a sequence of "Numerous Questions..." in which slide 17 posed an unexpected question with some humor/mild shock value. Slide 19(6) was Loop Quantum Gravity Slide 20(1) Quantum geometry according to LQG Slide 21(1) Spin Foams Slide 22(1) Spin Foam Models Slide 23(5) Quantum gravity and experiment? Slide 24(8) A Key Issue: Non-Uniqueness Slide 25(1) The future of quantum gravity? [humorous illustration] Slide 26(9) Waiting for news from the LHC. Slide 27(9) Prospects I Slide 28(6) Prospect II