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Introduction To Loop Quantum Gravity |
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| May16-11, 03:24 PM | #273 |
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Introduction To Loop Quantum Gravity
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| May16-11, 04:29 PM | #274 |
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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:
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 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 |
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| Jun4-11, 10:08 AM | #275 |
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A new PF member asked "what exactly is LQG?" and requested a non-mathematical (effectively highschool level, I think) answer. Tom Stoer supplied the following which then got some editorial attention from Ben Crowell and Redbelly (who suggested copying it here.) I think it's an unbiased informative account:
==quote tom.stoer post== What exactly is LQG? It's difficult w/o math. The problem with quantum gravity is that naive mechanisms to quantize gravity (which have been applied successfully to other fields) fail for gravity. That means that something fundamental has to be changed for quantum gravity. There are different approaches to solve these problems, e.g. a) string theory b) asymptotic safety c) loop quantum gravity (LQG) I don't want to comment on a) and b) here. Essentially LQG does the following: it introduces new variables which replace the (in GR) well-known metric that describes spacetime + curvature. This is pure math, so I don't want to go into details here, but what happens is that these new variables are rather close to fields that we know from gauge theory like QED and QCD. Indeed in a certain sense gravity looks rather similar to QCD, but there is one additional property of gravity that allowes one to apply a second mathematical trick which essentially replaces the fundamental fields with something like "fluxes through surfaces" or "fluxes along circles". These surfaces and circles are embedded into spacetime. The next step is again rather technical and it becomes possible due to so-called diffeomorphism invariance: one can get rid of the the embedding of circles and surfaces into spacetime. Instead one replaces these entities with a so-called spin network, i.e. a graph with nodes and links between nodes where each link and each node carries some numbers which represent abstract entities from which certain properies of spacetime can be reconstructed. You can think about spacetime as made of cells (I will soon tell you that you can't :-); each cell has a certain volume carried by a node; each cell has certain surfaces and the link between different nodes (sitting inside these cells) carry the areas of the surfcaes. The problem with this picture is that one might think about these cells as sitting in spacetime - but this is fundamentally wrong: this picture is only due to the construction, but basically there is no spacetime anymore; all there is are nodes and links (and certain numbers attributed to nodes and links). Spacetime is no longer fundamental but becomes an entity emerging from the more fundamental graphs with their nodes and links. The graphs are called spin networks b/c the numbers they are carrying have properties well-known from spins. But this is a mathematical property only, it does not means that there are real spinning objects. Compare this emerging spacetime to a water surface of a lake. We know that it consists of atoms, and as soon as we get this picture it is clear that there is no water between the atoms; the surface is only an emerging phenomenon, the true fundamental objects are the atoms. In the same sense the spin networks are the fundametal entities from which spacetime, surfaces etc. and their properties like volume, area, curvature etc. can be constructed. Dynamics of spacetime (which was curvature, gravitational waves etc. in GR) is replaced by dynamics of spin networks: within a given graph new nodes with new links can appear (there are mathematical rules, but I don't want to go into detail here). The last puzzle I have for you is the fact that such a spin network is not a mechanical object which "is" spacetime. Instead quantized spacetime is a superposition of (infinitly many) spin networks. This is well-known in quantum mechanics; there is no reason why an atom should be in a certain state; we can achieve that via preparation or measurement, but in principle a single atom can be in an arbitrary complex quantum state which is a superposition of "an atom sitting here, an atom moving in a certain direction over there, an atom moving in this or that direction, ...". So classical spacetime is recovered by two averaging process: first there seems to be a regime were this superposition of spin networks is peaked around a single classical spacetime, i.e. where one network dominates the superposition of infinitely many spin networks; second from this single spin network one can reconstruct spacetime in the same sense as one can reconstruct the water surface from the individual atoms. But there may be different regimes (e.g. in black holes or closed to the big bang) where is classical picture and this averaging does no longer work. It may be that in these regimes all there is are spin networks w/o any classical property like smooth spacetime, areas, volume etc. It's like looking at a single atom: there is no water surface anymore. Eventually this is why one started with this stuff: the classical picture of spacetime seems to become inconsistent when one tries to quantize it, i.e. when one defines these superpositins etc. These inconsistencies do not bother us as long as we talk about spacetime here, in the solar system etc. But they become a pain in the a... when we talk about spacetime near a singularity like a black hole or like the big bang. In order to understand these new non-classical regimes of spacetime a fundamentally new picture is required. This is what LQG (and other approaches) are aiming for: construct a new mathematical model from which well-known classical spacetime (like in GR) can be reconstrcuted, but which does not break down in certain regimes but remains well-defined and consistent. He must so to speak throw away the ladder, after he has climbed up on it - Ludwig Wittgenstein =====endquote===== Original post: http://physicsforums.com/showthread....85#post3319185 |
| Jun4-11, 10:41 PM | #276 |
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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 |
| Jun18-11, 03:59 PM | #277 |
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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 |
| Jul11-11, 01:49 AM | #278 |
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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 |
| Jul21-11, 11:14 AM | #279 |
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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? |
| Jul21-11, 11:47 AM | #280 |
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http://www.signallake.com/innovation...antumJul08.pdf |
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| Jul21-11, 12:52 PM | #281 |
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I try to use this thread primarily as a place to keep the best current source material on LQG, including its phenomenology (ways of testing) and application to cosmology.
It should provide quick access to the latest review articles and survey talks. Here is a search intended to dig up LQG/LQC pheno papers. It now gets 44 articles http://www-library.desy.de/cgi-bin/s...ENCE=ds%28d%29 To see the latest, change the ordering from "by cite count" to "by date" and repeat the search. The May 2011 Loops conference in Madrid had some great review talks. Video and slides PDF are available online. It can be useful to download both because you can scan through the slides and then drag the timebutton of the video to a part of the talk where you wish to focus attention. Also the video shows both slide and speaker and may sometimes cut off a part of a slide you want to read. So it may work best to download both and do your own split-screen. Ashtekar and Rovelli gave great survey talks: Ashtekar's talk (for a Loop cosmology review): http://loops11.iem.csic.es/loops11/i...article&id=181 Rovelli's talk (for status and open problems of the full LQG theory): http://loops11.iem.csic.es/loops11/i...=article&id=76 Peter McK expressed an interest in Causal Dynamical Triangulations, and Renate Loll gave a CDT review at the same conference. It's a good way to hear the latest. Loll's review of CDT: http://loops11.iem.csic.es/loops11/i...article&id=182 For the listing of all the talks (linked to an abstract for each): http://loops11.iem.csic.es/loops11/i...=article&id=75 I'll include Frank Wilczek's Uppsala talk because I think it is a reality-based view of particle physics unification prospects. He gives the most likely picture of matter's future--- that which LQG spacetime geometry is apt to join up with. Wilczek video: http://media.medfarm.uu.se/flvplayer...gs2011/video24 Wilczek slides: http://www-conference.slu.se/strings...40_Wilczek.pdf |
| Jul24-11, 10:17 PM | #282 |
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I'm currently having difficulty getting some of the videos of the Madrid talks.
The link to Rovelli's talk is: http://www.iem.csic.es/departamentos...n-problems.mp4 That works fine. And the link to video of Ashtekar's talk works: http://www.iem.csic.es/departamentos...-Cosmology.mp4 But I believe the link to, for example, Renate Loll's talk is currently broken. You can try various ones and see what luck you have. Here is the program: http://loops11.iem.csic.es/loops11/i...=article&id=75 If you click on a particular talk you get a one-page summary with further links to the slides and (in the case of plenary talks given in the morning session) a link to the video, or what looks like one. For example here are two summary pages: Ashtekar's talk (for a Loop cosmology review): http://loops11.iem.csic.es/loops11/i...article&id=181 Rovelli's talk (for status and open problems of the full LQG theory): http://loops11.iem.csic.es/loops11/i...=article&id=76 Click on Loll's talk and you get the summary page all right: http://loops11.iem.csic.es/loops11/i...article&id=182 And you can get her slides PDF. But the link to the video is given as: http://161.111.24.61/loops11/Archive...angulation.mp4 And that doesn't work. My first guess was that the links to video which are broken are the ones that begin "161.111.24.61". The talks seem to be archived at two separate locations and one of the systems might be down. But that guess was wrong. If you have any current experience with getting videos of the talks, please share it. I'd like to know what luck others have had. Fortunately I downloaded a number of the talks before this problem developed (but I didn't happen to do that with Renate Loll's) |
| Jul27-11, 12:07 AM | #283 |
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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. |
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| Aug1-11, 10:13 AM | #284 |
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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 |
| Aug21-11, 11:36 AM | #285 |
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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 |
| Sep16-11, 12:03 PM | #286 |
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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∏∑∫∂√±←↓→↑↔~≈≠≡ ≤≥˝∞(⇐⇑⇒⇓⇔∴∃ℝℤℕℂ⋅) |
| Sep19-11, 12:28 PM | #287 |
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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) |
| Oct5-11, 12:41 PM | #288 |
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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 |
| Nov3-11, 09:17 PM | #289 |
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First introductory LQG textbook went on sale 1 November 2011.
I checked today to see how it's doing. Earier books have covered related topics: canonical GR, application to cosmology etc. this is first wholly devoted to intro Loop. A First Course in Loop Quantum Gravity Rodolfo Gambini, Jorge Pullin Oxford University Press. http://www.amazon.com/First-Course-L.../dp/0199590753 I found several things---one is that you get to browse online. You can look inside the book. Another is that at least at 7PM Pacific time 3 November it is doing rather well for a textbook: Amazon Best Sellers Rank: #62,638 in Books #26 in Books > Professional & Technical > Professional Science > Physics > Mathematical Physics So it is #26 on the Mathematical Physics bestseller list. Here's the Oxford Press description: This book provides an accessible introduction to loop quantum gravity and some of its applications, at a level suitable for undergraduate students and others with only a minimal knowledge of college level physics. In particular it is not assumed that the reader is familiar with general relativity and only minimally familiar with quantum mechanics and Hamiltonian mechanics. Most chapters end with problems that elaborate on the text, and aid learning. Applications such as loop quantum cosmology, black hole entropy and spin foams are briefly covered. The text is ideally suited for an undergraduate course in the senior year of a physics major. It can also be used to introduce undergraduates to general relativity and quantum field theory as part of a 'special topics' type of course.Masters program at Nottingham, including Loop and other QG research http://pgstudy.nottingham.ac.uk/post...-msc_1163.aspx Some papers: Loop quantum gravity: the first twenty five years Survey for non-specialists, historical development and indications the theory recovers classical GR. http://arxiv.org/abs/1012.4707 Lectures on Loop Gravity Definitive presentation of Loop gravity, with some math prerequisites: http://arxiv.org/abs/1102.3660 The Big Bang and the Quantum Loop cosmology, as of mid-2010: http://arxiv.org/abs/1005.5491. Testing: Loop cosmology derives from LQG and this provides the most accessible route to testing. Here are 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 These articles appeared 2009 or later. As of 3 November there were 45 of them. Loops 2011 the biannual Loops conference was held 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 and slides pdf of most talks are now available, just click on the title. Videos of the plenary session morning talks are online. There were about 100 parallel session talks. ========================= Research trends, as of 3 November: http://howlonguntil.net/ day 307 162*365/307 = 193 816*365/307 = 970 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 (162 found, annualized 193) STRING,MEMBRANE,AdS/CFT RESEARCH BY YEAR (search terms "string model", "membrane model" and "AdS/CFT correspondence") 2005 http://inspirebeta.net/search?ln=en&...=10&sc=0&of=hb (988 found) 2006 http://inspirebeta.net/search?ln=en&...=10&sc=0&of=hb (1029 found) 2007 http://inspirebeta.net/search?ln=en&...=10&sc=0&of=hb (1050 found) 2008 http://inspirebeta.net/search?ln=en&...=10&sc=0&of=hb (1128 found) 2009 http://inspirebeta.net/search?ln=en&...=10&sc=0&of=hb (1132 found) 2010 http://inspirebeta.net/search?ln=en&...=10&sc=0&of=hb (1046 found) 2011 http://inspirebeta.net/search?ln=en&...=10&sc=0&of=hb (816 found, annualized 970) |
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