| New Reply |
Introduction To Loop Quantum Gravity |
Share Thread | Thread Tools |
| Aug22-09, 11:18 PM | #188 |
|
|
Introduction To Loop Quantum Gravity
The ILQGS schedule for the Fall 2009 is now posted
http://relativity.phys.lsu.edu/ilqgs/schedulefa09.html It is a conference-call type hookup so people participate in several parts of the world. you download the lecture slides in advance and the speaker tells you what slide. International LQG Seminar Sept 8 TBA Sept 22 Vistas from perturbative quantum gravity Richard Woodard University of Florida Oct 6 Aharonov-Bohm and LQG Eugenio Bianchi SNS Pisa Oct 20 Spin foams from loop quantum gravity perspective Jerzy Lewandowski Warszaw University Nov 3 Group field theory and all that Daniele Oriti Albert Einstein Institute Nov 17 Asymptotics of the new vertex Frank Hellmann University of Nottingham Dec 1 Polymer parameterized field theory Alok Laddha Raman Research Institute Go here to see a list of all the past seminars and who gave them: http://relativity.phys.lsu.edu/ilqgs/ For each past seminar there is an audio file, so you can listen and a PDF file of the speaker's slides which you can download. To keep some links handy for reference Corfu QG School: http://www.physics.ntua.gr/corfu2009/qg.html Ellisfest speakers: http://www.mth.uct.ac.za/~jeff/Quant...ticipants.html PlanckScale conference video and slides: http://www.ift.uni.wroc.pl/~planckscale/ http://www.ift.uni.wroc.pl/~planckscale/movie/ http://www.ift.uni.wroc.pl/~rdurka/p...ndex-video.php Marcel Twelve (886 participants): http://www.icra.it/MG/mg12/en/ http://www.icra.it/MG/mg12/talks_plenary/Freidel.pdf Loops 2009 (~230 part.) schedule of talks: http://www.mighty-security.com/loop/timetable1.htm June school for Nonperturbative Gravity and QCD at Zakopane. http://th-www.if.uj.edu.pl/school/2009/ http://th-www.if.uj.edu.pl/school/2009/lectures.html Asymptotic safety conference: http://www.perimeterinstitute.ca/en/...0_Years_Later/ Abhayfest: http://igc.psu.edu/events/abhayfest/program.shtml GRG 19 (Mexico City 5-9 July 2010): http://www.gr19.com/index.php Links to check for new announcements: http://www.maths.nottingham.ac.uk/qg/ http://grg.maths.qmul.ac.uk/hyperspace/conference/ http://grg.maths.qmul.ac.uk/hyperspa...ce/latest.html Topcited Loop/Foam papers since 2006: http://www.slac.stanford.edu/spires/...tecount%28d%29 Rovelli's talk at Strings 2008: Video http://cdsweb.cern.ch/record/1121957?ln=en Slides http://indico.cern.ch/getFile.py/acc...s&confId=21917 2003 draft of Rovelli's book online: http://www.cpt.univ-mrs.fr/%7Erovelli/book.pdf Rovelli's chapter in Oriti's book: http://arxiv.org/abs/gr-qc/0604045 Review of LQG as of May 2008: http://relativity.livingreviews.org/...es/lrr-2008-5/ Steven Weinberg's 6 July talk, main CERN link: http://indico.cern.ch/conferenceDisplay.py?confId=57283 Weinberg video: http://cdsweb.cern.ch/record/1188567/ To save time jump to minute 58, the last 12 minutes. |
| Aug25-09, 08:23 PM | #189 |
|
|
Ted Jacobson's 2007 paper on renormalization as it affects LQG:
http://arXiv.org/abs/0707.4026 |
| Aug30-09, 11:26 PM | #190 |
|
|
more links to keep handy for reference:
Photos from the first Loops conference, at Marseille 2004 http://math.ucr.edu/home/baez/marseille/ 2006 video lecture by Krasnov: http://pirsa.org/06110041/ 2006 audio+pdf talk at the ILQGS: http://relativity.phys.lsu.edu/ilqgs/krasnov032007.pdf http://relativity.phys.lsu.edu/ilqgs/krasnov032007.aif 2009 paper Gravity as BF theory plus potential http://arxiv.org/abs/0907.4064 Ancillary papers http://arxiv.org/abs/0811.3147 http://arxiv.org/abs/0812.3603 Intro to Plebanski http://arxiv.org/abs/0904.0423 Comment by Bengtsson: http://arxiv.org/abs/gr-qc/0703114 |
| Sep5-09, 10:29 PM | #191 |
|
|
The programme for the Corfu QG school, listing the other talks besides the main lecture series, is now posted:
http://www.physics.ntua.gr/corfu2009...WeekSchool.pdf http://www.physics.ntua.gr/corfu2009...eekSchool.html The main link for the Corfu QG school with abstracts of the five lecture series is still this: http://www.physics.ntua.gr/corfu2009/qg.html Check here for recordings of the EG4 talks as they become available: http://www.emergentgravity.org/index..._programme.php |
| Sep7-09, 10:46 PM | #192 |
|
|
Next summer, 2010, there will be another QG school. This time in Mexico at Uni Morelia (which hosted the Loops 2007 conference). It will last 10 days: 23 June-3 July.
The organizers are: Don Marolf Abhay Ashtekar Alejandro Corichi Maximo Banados More info at http://www.physics.ucsb.edu/~pasi/ The school will be aimed at advanced PhD students and postdocs to enable them to get started in QG research. It sounds similar to the two European QG schools funded by the European agency ESF---in Zakopane 2007 and in Corfu 2009. But this time the corresponding USian agency NSF is getting into the act and funding the school. Immediately the school is finished, the big GR 19 conference will commence in Mexico City. It runs 5 July thru 9 July. http://www.gr19.com/ The international conference on General Relativity and Gravitation ("GR") is held every three years. The previous one was GR 18, held at Sydney in 2007. Here is part of the programme of parallel sessions from the GR 19 website: ==quote== D1 Loop Quantum Gravity and Spin Foams Chair: Alejandro Corichi D2 Strings, branes and M-theory Chair: (to be announced) D3 Causal sets, Causal dynamical triangulations, Non-commutative geometry, and other approaches to quantum gravity Chair: Fay Dowker D4 Quantum fields in curved space-time, semiclassical gravity, quantum gravity phenomenology, and analog models Chair: Bill Unruh ==endquote== |
| Sep7-09, 11:33 PM | #193 |
|
|
Do you know when the slides from Loops 09 will be released?
 I am loosing hope. Also, won't you comment about http://arxiv.org/abs/0909.0939 "Spin-Foams for All Loop Quantum Gravity". I thought it was a great paper.
|
| Sep8-09, 11:07 AM | #194 |
|
|
Let's have our discussions in another thread. This thread is convenient for links that constantly get used, to check for current developments like the Corfu School. Let's make a separate thread to comment on the Lewandowski paper, if you would like. |
|
| Sep15-09, 09:57 PM | #195 |
| Sep16-09, 08:15 AM | #196 |
|
|
http://www.perimeterinstitute.ca/en/...ifshitz_Point/
Gravity at a Lifshitz Point November 8 - 10, 2009 Perimeter Institute The construction of a quantum theory of gravity might require us to give up one or more of the fundamental principles of standard quantum field theory. A recent proposal dispensing with Lorentz invariance builds upon an analogy with condensed matter systems characterized by a Lifshitz point. This proposal also seems to produce a theory which is well behaved in the ultraviolet regime. This workshop intends to bring together researchers working on this or related ideas. The focus will be on the viability of the proposal (compatibility with large scale phenomenology and renormalizabilty) and its relation to other research directions, like causal dynamical triangulations and aether theories. Scientific Organizers: Dario Benedetti, Perimeter Institute Robert Myers, Perimeter Institute Petr Horava, University of California, Berkeley ****** Since the 1st day of this workshop will be in the last day of the Assymptotic Safety conference, maybe Weiberg will meet Horava, and something great will come out of that! |
| Sep17-09, 08:23 PM | #197 |
|
|
Another valuable resource is this collection of slides+audio from the summer 2009 Abhayfest
(celebrating the birthday of Abhay Ashtekar) http://gravity.psu.edu/events/abhayf...ceedings.shtml Slides and audio available for talks by Jim Hartle Carlo Rovelli Jerzy Lewandowski Laurent Freidel Lee Smolin Gary Horowitz Rodolfo Gambini Robert Wald Thomas Thiemann Roger Penrose Klaus Fredenhagen (in no special order) and a bunch more. |
| Sep26-09, 08:44 PM | #198 |
|
|
Resources for conformal symmetry:
http://physicsforums.com/showthread.php?t=172461 (Sam Alkhaiat tutorial) http://en.wikipedia.org/wiki/Conformal_symmetry (very brief Wiki article with a picture) Reflections on spontaneous symmetry breaking by Steven Weinberg http://cerncourier.com/cws/article/cern/32522 't Hooft Erice talk (September 2009) quantum gravity should incorporate conformal symmetry in some fashion http://arxiv.org/abs/0909.3426 Nicolai Planck Scale talk (July 2009) quantum gravity should incorporate conformal symmetry at least in the limit (and should learn certain other things from QFT and the Standard Model) http://www.ift.uni.wroc.pl/~rdurka/p...=1.3%20Nicolai Brief Wikipedia article relating to Coleman Weinberg mechanism by which masses can be generated. C-W symmetry breaking invoked in the Meissner Nicolai extension of the Standard Model. http://en.wikipedia.org/wiki/Coleman–Weinberg_potential |
| Oct18-09, 08:08 PM | #199 |
|
|
MTd2 found how to get the videos of the talks at Loops 2009, the big Loops conference at Beijing this summer.
You go to this catalog http://www.mighty-security.com/loop/resource.htm and you copy down the item number of the talk you want and go to another site and request that number. For example to get Ashtekar's talk, get the plenary session video for August 4 (8-4) For Rovelli's, the plenary session for August 5. Looking at the catalog, this means for Ashtekar it is serial number 8953789510079792 For Rovelli it would be 8605657721191707 For, say, Dan Oriti talking about Group Field Theory, it would be the August 7 plenary session 5570901362601769 ========================== Now suppose the video file can't be handled or there is some computer problem, they also have audio-only And in that case the serial numbers for the same three plenary sessions are 8350111663470163 1930906596035020 1769207291471637 Let's hope some of these work. I'm going to give them a try. It says: "go to http://file.mofile.com and enter the “pickup code” in the box at the top of the page." So I'm going to mofile.com and entering the number 8605657721191707 which is the one for the Wednesday August 5 morning plenary session. For more listings of the program timetable: http://www.mighty-security.com/loop/timetable1.htm http://www.mighty-security.com/loop/timetable2.htm http://www.mighty-security.com/loop/timetable3.htm http://www.mighty-security.com/loop/timetable4.htm and so forth. Well it didn't work for me! I went to mofile.com and put in the correct number 8605657721191707 in the right box and things started to happen, but the screens were in Chinese! It wanted me to click on a button to continue but I couldn't read what I was agreeing to if I clicked. So being a cautious person, I bailed out. Maybe it was working OK and I just should have clicked and continued. But it just wasn't "wai-gwo-ren" friendly, so I bailed. I think wai-gwo means foreign and ren means person. Maybe someone who reads Chinese will try the mofile.com site out and give us a little coaching on how to proceed. |
| Oct23-09, 11:47 AM | #200 |
|
|
The Asymptotic Safety conference starts 5 November, less than 2 weeks away. It's an important landmark, perhaps a turning point. Interest in AsymSafe QG has revived some 30 years after Weinberg presented the idea at Erice (Sicily) in 1976.
Weinberg is working on it again and takes a sober cautious attitude. Not a sure bet, but deserves to be worked on. An alternative to string, as a way to arrive at unified fundamental description of the world. Also the running of constants like Newton G and the cosmo Lambda could provide natural mechanisms to explain cosmological phenomena such as inflation. So AsymSafe has a key resonance with the currently hot field of cosmology---early universe in particular. We might want to study the lineup of conference speakers and what they are talking about: ==excerpts from Perimeter host page, edited for compactness== Thursday, November 5, 2009 8:30 - 9:20 AM Registration 9:20-9:30 AM Introductory Remarks 9:30 - 10:30 AM Steven Weinberg, University of Texas Prospects for Asymptotic Safety 11:00 AM – 12:00 PM Martin Reuter, Mainz University TBA 2:00 – 3:00 PM Jean Zinn-Justin, CEA, Saclay TBA 3:00 - 4:00 PM Holger Gies, ITP, Jena University Mechanisms of Asymptotic Safety 4:30 - 5:30 PM B.F.L. Ward, Baylor University Asymptotic Safety and Resummed Quantum Gravity Friday, November 6, 2009 9:30-10:30 AM Lee Smolin, Perimeter Institute Asymptotic safety in the light of our modern understanding of quantum geometry 11:00AM – 12:00 PM Renate Loll, Utrecht University TBA 2:00 – 3:00 PM Max Niedermaier, Tours University Gravitational fixed points and asymptotic safety from perturbation theory 3:00-4:00 PM Frank Saueressig, Mainz University TBA 4:30-6:00 PM TBA 6:00PM Banquet Dinner Saturday, November 7, 2009 9:30-10:30 AM Arkady Tseytlin, Imperial College, London Comments on UV divergences in quantum gravity 11:00AM – 12:00 PM Vincent Rivasseau, Universite Paris-Sud XI, Orsay TBA 2:00 – 3:00 PM Alfio Bonanno, INAF, Catania The mass-inflation phenomenon in the asymptotic safety scenario 3:00-4:00 PM John Joseph M. Carrasco, UCLA Perturbative cancellations in gravity theories 4:30-6:00PM TBA Sunday, November 8, 2009 9:30 - 10:30 AM Jan Ambjorn, Utrecht University TBA 11:00AM – 12:00 PM Daniel Litim, University of Sussex TBA 2:00 PM "Gravity at a Lifshitz Point" workshop begins at 2:00pm (Please note: Participants from the "Asymptotic Safety" workshop are welcome to stay for this afternoon's talks during the "Gravity at a Lifshitz Point" workshop.) ==endquote== Another talk has been listed, but not yet assigned a time-slot: Michael Scherer Friedrich-Schiller-Universität A mechanism for Asymptotic Safety of chiral Yukawa systems http://www.perimeterinstitute.ca/en/...0_Years_Later/ I have edited out much of the nonessential detail such as coffeebreaks, discussion, lunch, and room locations. I expect, since it is Perimeter, video of talks will appear online. I note that Lee Smolin authored some of the early papers on AsymSafety, back in the 1980s, while postdoc at Princeton IAS, so it's not an unfamiliar topic for him. I'm especially curious to hear what both he and Renate Loll have to say. Also Bonanno in his talk on Saturday, because he has worked a lot on the connection between AsymSafe QG and early universe cosmology--some potentially elegant connections. The chief organizer of the conference is Roberto Percacci http://www.perimeterinstitute.ca/ind...berto_Percacci Often the organizer will act as host and not present a paper of his own, but will instead introduce the others. However in this case, since Percacci is one of the most active researchers and has contributed significantly to the field, one might hope that he doubles as a participant. Percacci gave a talk at Zakopane in June 2009 which covered recent developments in AsymSafe, focusing on evidence for the UV fixed point. The PDF of his slides is here http://th-www.if.uj.edu.pl/school/20...s/percacci.pdf He has a FAQ and bibliography on AsymSafe here http://www.percacci.it/roberto/physics/as/ Here is the AsymSafe FAQ: http://www.percacci.it/roberto/physics/as/faq.html |
| Oct25-09, 11:49 AM | #201 |
|
|
Jerzy Lewandowski has essentially codified Loop Foam gravity for us.
This had to happen, and there had to be a definitive 2009 exposition of the basics. So far the best I know of is Jerzy's http://arxiv.org/abs/0909.0939 Spin-Foams for All Loop Quantum Gravity and the audio+slides version is at ILQGS http://relativity.phys.lsu.edu/ilqgs...wski102009.pdf http://relativity.phys.lsu.edu/ilqgs...wski102009.wav http://relativity.phys.lsu.edu/ilqgs/ Something that impressed me, that may seem irrelevant, is how strongly Jerzy stressed the seminal importance of work by Michael Reisenberger done around 1994-1998. Here is a 1990 photo of MR at the Vatican Observatory http://www34.homepage.villanova.edu/...eopold1990.jpg Now Reisenberger is senior faculty at the Montevideo Instituto de Fisica. He and Rodolfo Gambini are the two top QG people at University of Montevideo. Reisberger's 1994 paper was called Worldsheet formulations of gauge theories and gravity http://arxiv.org/abs/gr-qc/9412035 It was written while he was still at Utrecht, at Gerard 't Hooft's ITP. His 1997 paper with Carlo Rovelli was called "Sum over Surfaces'' form of Loop Quantum Gravity http://arxiv.org/abs/gr-qc/9612035 This was written while he was at the Schrödinger Institute in Vienna, and also at Montevideo. A 1998 paper that Jerzy says should still be studied more (still has germinal undeveloped ideas) is called On relativistic spin network vertices http://arxiv.org/abs/gr-qc/9809067 Jerzy points to these as the founding papers of the spinfoam approach, the genesis of the idea. He also acknowledges learning a lot from John Baez clear 2000 exposition, and the review paper by Perez. Jerzy presents a development of the spinfoam concept that appears in a certain sense natural. He defines the vertex formula for the foam using an enclosing spinnetwork---without invoking terms like "10j symbol" or "15j symbol". If you accept the idea of cylinder function (basic to the uniqueness theorem of "L.O.S. & T.") then the spinnetwork idea is not ad hoc---it flows naturally from the cylinderfunctions on the space of connections. And then the spinfoam idea flows naturally from the spinnetwork idea. He avoids all disconnects between the ideas. And he seems to be saying that he was helped to re-understand the spinfoam concept by going back to Reisenberger's initial vision of it, or his preliminary glimpse. After he has finished the development, he can derive the current spinfoam vertex formulas, such as the Engle-Livine- Pereira-Rovelli, and see how the technical numbers like the angular momentum "j" symbols arise. Lewandowski has been a major force in making Loop-and-related physics mathematically rigorous. His long collaboration with Ashtekar, spanning many years and many papers, had this main thrust. If the organizers of the September 2009 Corfu School eventually succeed in putting online the 5-hour series of lectures by Carlo Rovelli, this would be what I'd say was the current definitive version of Loop Foam gravity. But we don't have those lectures as online media yet. At least for time being, Jerzy's paper and talk will fill the bill. Here's a current photo of Reisenberger, one of 9 snapshots of Theiss scientists. http://www.theissresearch.org/scientists/ It's alphabetical so scroll down. If anyone wants to google more information about the University of Montevideo, the official name is UDELAR universita de la republica. Montevideo is capital of Uruguay, which is a Republic, so the main Uni is the University of the Republic. Here is the Montevideo Institute of Physics page: http://www.fisica.edu.uy/ and here's the faculty list: http://www.fisica.edu.uy/integrantes.html |
| Oct25-09, 01:03 PM | #202 |
|
Recognitions:
 Science Advisor |
http://arxiv.org/abs/0909.0939
v1. The second paper we appreciate so much is the derivation of the new spin-foam model from the Holst action by Engle, Livine, Pereira and Rovelli [6]. Those two excellent works brought spin-foams closer to LQG. On the other hand, we regret have not considered here closer the Freidel-Krasnov model [12]. v2. The second paper we appreciate so much is the derivation of the new spin-foam model from the Holst action by Engle, Livine, Pereira and Rovelli [6]. Those two excellent works brought spin-foams closer to LQG. On the other hand, the works that should be and will be considered closer in the spirit of the current paper, are the Freidel-Krasnov model [15] (especially in the range of γ in which that model does not overlap with EPRL). Also the pioneering works of Reisenberger [2, 11, 13] contain a lot of ideas that still have not been explored enough in the literature. v2 is much better (sociologically  for me) - I am quite suspicious of Rovelli unless Freidel or Reisenberger are coauthors.
|
| Oct31-09, 02:00 PM | #203 |
|
|
The Asymptotic Safety conference starts 5 November, just a few days from now. Interest in AsymSafe QG has revived some 30 years after Weinberg presented the idea at Erice (Sicily) in 1976.
A more complete list conference speakers and topics is now available: ==excerpts from Perimeter host page, edited for compactness== Thursday, November 5, 2009 8:30 - 9:20 AM Registration 9:20-9:30 AM Introductory Remarks 9:30 - 10:30 AM Steven Weinberg, University of Texas Prospects for Asymptotic Safety 11:00 AM – 12:00 PM Martin Reuter, Mainz University Gravitational average action and asymptotic safety: past and future 2:00 – 3:00 PM Jean Zinn-Justin, CEA, Saclay Asymptotic safety: a review 3:00 - 4:00 PM Holger Gies, ITP, Jena University Mechanisms of Asymptotic Safety 4:30 - 5:30 PM B.F.L. Ward, Baylor University Asymptotic Safety and Resummed Quantum Gravity Friday, November 6, 2009 9:30-10:30 AM Lee Smolin, Perimeter Institute Asymptotic safety in the light of our modern understanding of quantum geometry 11:00AM – 12:00 PM Renate Loll, Utrecht University TBA 2:00 – 3:00 PM Max Niedermaier, Tours University Gravitational fixed points and asymptotic safety from perturbation theory 3:00-4:00 PM Frank Saueressig, Mainz University Exploring the Theory Space of Asymptotically Safe Quantum Gravity 4:30-5:00 PM Elisa Manrique, Mainz University TBA 5:00-5:30 PM Christophe Rahmede, University of Sussex TBA Saturday, November 7, 2009 9:30-10:30 AM Arkady Tseytlin, Imperial College, London Comments on UV divergences in quantum gravity 11:00AM – 12:00 PM Vincent Rivasseau, Universite Paris-Sud XI, Orsay TBA 2:00 – 3:00 PM Alfio Bonanno, INAF, Catania The mass-inflation phenomenon in the asymptotic safety scenario 3:00-4:00 PM John Joseph M. Carrasco, UCLA Perturbative cancellations in gravity theories 4:30-5:00PM Gian Paolo Vacca, INFN, Bologna TBA 5:00-5:30PM Michael Scherer ITP, Jena University A mechanism for Asymptotic Safety of chiral Yukawa systems Sunday, November 8, 2009 9:30 - 10:30 AM Jan Ambjorn, Utrecht University CDT and asymptotic safety 11:00AM – 12:00 PM Daniel Litim, University of Sussex TBA 2:00 PM "Gravity at a Lifshitz Point" workshop begins at 2:00pm (Please note: Participants from the "Asymptotic Safety" workshop are welcome to stay for this afternoon's talks during the "Gravity at a Lifshitz Point" workshop.) ==endquote== http://www.perimeterinstitute.ca/en/...0_Years_Later/ I have edited out nonessential detail such as coffeebreaks, discussion sessions, meals, and room locations. Since it is Perimeter, video of talks might appear online. The chief organizer of the conference is Roberto Percacci http://www.perimeterinstitute.ca/ind...berto_Percacci Percacci gave a talk at Zakopane in June 2009 which covered recent developments in AsymSafe, focusing on evidence for the UV fixed point. The PDF of his slides is here http://th-www.if.uj.edu.pl/school/20...s/percacci.pdf He has a FAQ and bibliography on AsymSafe here http://www.percacci.it/roberto/physics/as/ Here is the AsymSafe FAQ: http://www.percacci.it/roberto/physics/as/faq.html |
| Nov4-09, 07:30 PM | #204 |
|
|
The AsymSafe conference starts tomorrow. Some new titles of talks have been added to the list, and some of the speakers have posted abstracts. Smolin's was interesting, I thought. I'm curious to know what Rivasseau is proposing as a mechanism that could underlie and cause Asymptotic Safety.
I have highlighted Rahmede's talk because he is reporting joint work with Roberto Percacci and others. The corresponding papers have just been posted on arxiv. It is possible that Rahmede's talk will cover among the most valuable recent results reported at the conference. So I highlighted those three. Here's an updated list that includes abstracts of some talks: Jan Ambjorn, Utrecht University CDT and asymptotic safety CDT is a lattice regularization of quantum gravity. The phase structure of the lattice theory is discussed and a candidate UV fixed point located. Alfio Bonanno, INAF, Catania The mass-inflation phenomenon in the asymptotic safety scenario John Joseph M. Carrasco, UCLA Perturbative cancellations in gravity theories I will present recent results through four loops demonstrating that the maximally supersymmetric (N=8) generalization of gravity is surprisingly well behaved in the ultraviolet as a result of unexpected cancellations between contributing terms. These cancellations first manifest at one loop in the form of the "no-triangle property," with all-loop order implications through unitarity. I will conclude by discussing similar novel cancelations identified in pure Einstein gravity, at one loop, which suggest a possible explanation for the unexpectedly tame high energy behavior of N=8 supergravity beyond the limited UV protection of supersymmetry. Holger Gies, ITP, Jena University Mechanisms of Asymptotic Safety Renate Loll, Utrecht University Nonperturbative Insights from Causal Dynamical Triangulations Max Niedermaier, Tours University Gravitational fixed points and asymptotic safety from perturbation theory Christoph Rahmede, Jena University Renormalization Group Flow in Scalar-Tensor Theories Martin Reuter, Mainz University Gravitational average action and asymptotic safety: past and future Vincent Rivasseau, Université Paris-Sud XI, Orsay A New Mechanism for Asymptotic Safeness Frank Saueressig, Mainz University Exploring the Theory Space of Asymptotically Safe Quantum Gravity Michael Scherer, ITP, Jena University A mechanism for Asymptotic Safety of chiral Yukawa systems We will discuss Weinberg's idea of asymptotic safety for a chiral Yukawa system with a U(N_L)_L x U(1)_R symmetry in a leading-order derivative expansion using nonperturbative functional RG equations. As a toy model sharing important features with the standard model we explicitely discuss N_L=10 for which we find a non-Gaussian fixed point and compute its critical exponents. We observe a reduced hierarchy problem and obtain predictions for the toy Higgs and the toy top mass. Lee Smolin, Perimeter Institute Asymptotic safety and deformed symmetry I review work on asymptotic safety in quantum gravity in a 1/N expansion. I highlight the result that the scaling behavior governed by the non-trivial fixed point must be characterized by a scaling dimension less than four. Otherwise a Weyl curvature squared counterterm is required, that renders the theory unstable. This reduced scaling dimension then implies that Lorentz invariance is either broken or deformed, and this is transmitted to the matter sector. However, there are strong constraints on breaking of Lorentz invariance at the Planck scale due to the absence of birefringence of photons. The present constraints on deforming Lorentz invariance are, however, just at the Planck scale. I will then review semiclassical quantum gravity arguments that Lorentz symmetry is deformed. Arkady Tseytlin, Imperial College, London Comments on UV divergences in quantum gravity Gian Paolo Vacca, Bologna University Quantum Gravitational Corrections to Matter: A Running Controversy B.F.L. Ward, Baylor University Asymptotic Safety and Resummed Quantum Gravity In Weinberg’s asymptotic safety approach to quantum gravity, one has a finite dimensional critical surface for a UV stable fixed point to generate a theory of quantum gravity with a finite number of physical parameters. The task is to demonstrate how this fixed point behavior actually arises. We argue that, in a recently formulated extension of Feynman’s original formulation of the theory, which we have called resummed quantum gravity, we recover this fixed-point UV behavior from an exact re-arrangement of the respective perturbative series. We argue that the results we obtain are consistent both with the exact field space Wilsonian renormalization group results of Reuter and Bonanno and with recent Hopf-algebraic Dyson-Schwinger renormalization theory results of Kreimer. We calculate the first "first principles" predictions of the respective dimensionless gravitational and cosmological constants and argue that they support the Planck scale cosmology advocated by Bonanno and Reuter as well. Comments on the prospects for actually predicting the currently observed value of the cosmological constant are also given. Steven Weinberg, University of Texas, Austin Prospects for Asymptotic Safety Omar Zanusso, SISSA Asymptotic safety in the nonlinear sigma models and gravity Jean Zinn-Justin, CEA, Saclay Asymptotic safety: a review I shall review on field theory examples, the meaning of the concept of asymptotic safety in the context of low energy effective field theories. ---from the webpage http://www.perimeterinstitute.ca/en/...ety/Abstracts/ |
| New Reply |
| Tags |
| loop quantum gravity |
| Thread Tools | |
Similar Threads for: Introduction To Loop Quantum Gravity
|
||||
| Thread | Forum | Replies | ||
| A First Course in Loop Quantum Gravity | Beyond the Standard Model | 23 | ||
| Loop Quantum Gravity? | Beyond the Standard Model | 7 | ||
| loop quantum gravity | Beyond the Standard Model | 9 | ||
| Loop quantum gravity | Beyond the Standard Model | 71 | ||
| Loop quantum gravity | General Physics | 13 | ||
Physorg.com Science News Partner
Quote by MTd2
