What is Lqg: Definition and 262 Discussions

The Clowes–Campusano LQG (CCLQG; also called LQG 3 and U1.28) is a large quasar group, consisting of 34 quasars and measuring about 2 billion light-years across. It is one of the largest known superstructures in the observable universe. It is located near the larger Huge-LQG. It was discovered by the astronomers Roger Clowes and Luis Campusano in 1991.

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  1. ohwilleke

    A LQG Legend Writes Paper Claiming GR Explains Dark Matter Phenomena

    A new group of investigators are attempting something similar to Deur's work, which seeks to explain dark matter phenomena with general relativity corrections to Newtonian gravity is systems like galaxies. Deur's most similar publication to this one along these lines was: One thing that makes...
  2. P

    I Falsifying LQG: Experiments & Examples Beyond Lorentz's Symmetry

    Hello, I came across this thread about LGQ and string theory ; in the 3rd response Lubos Molt says that LQG has been falsified by several experiments but does not give examples (apart from the no-violation of Lorentz's symmetry) My question is simply : do you have examples of such experiments...
  3. H

    I Why do representations label the edges in LQG?

    Hi Pfs Marcus wrote a huge bibliography during many years about LQG. but i do not see where to find an answer to a question. Penrose draw diagrams with edges labelled by numbers. What is the reason why later number were replaced by SU(2) representations?tÿ
  4. H

    A How does LQG describe gravity?

    I can see how spinfoams and spin networks can describe the structure of space and time. But i have not seen what is added so that there is gravity. is it a less action principle?u
  5. H

    A Triangulation and Discrete Volume Spectrum in Covariant LQG

    What is often said in Covariant LQG is that the triangulation is a truncation, and is not what is responsible for the discrete volumes one ends up with in the theory. Rather, what is responsible is the discrete spectra of the volume operator acting on the nodes of a spin network. My confusion...
  6. Iliody

    A Barbero-Irmizi and LQG observables?

    Hello, around 2008-2009 I self-studied a little bit of LQG, and become disillusioned by it because I understood that Barbero-Immirzi parameter was related to time parametrization (in a way similar to a scale factor, like $c$), and the dependence of observable mean values was in conflict with...
  7. P

    I Electrostatic in string theory or LQG

    How the repulsion between electrons occurs in String theory and in the loop quantum gravity? The electrons will also create electrostatic fields, or will it be the another mechanism?
  8. M

    A Current Status of Loop Quantum Gravity: Successes, Failures & Open Questions

    Where does the LQG approach stand right now? What are its biggest successes and failures? Does it have any known difficulties that might be "fatal"? What major questions (on the fundamental level) are still open in the approach, and is there "momentum" toward solving them? In particular, is it...
  9. Moayd Shagaf

    I Advancing LQG: Challenges and Possibilities for Experimental Proof

    What issues we have in prove LQG experimentally? and It is eaiser to prove than string theory? If so , why There's a lot of string theorist than LQG?
  10. Lunct

    B Under LQG is it possible to have an area with just nothing?

    So if space is made up of spin networks and spacetime is made of spin foams, then say hypothetically, is it possible to have an area without the quanta of space? Say maybe if there is an end to the universe. Like a mega vacuum with just nothing in it.
  11. A

    I Spin Foam models in Loop Quantum Gravity

    Hi all, I fairly basic question about spin foam models in loop quantum gravity. I just want to verify that spin foams represent effectively represent all of spacetime (in a quantum form), and that the idea is that general relativity can be obtained in the classical limit? Not sure if that's...
  12. K

    I LQG dark matter candidate vs rival dark matter candidates

    recent results on dark matter searches LHC has produced no dark matter candidates, esp neutralinos LUX/panda has found no candidate WIMP events axion dark matter searches have come up empty ice cube sterile neutrinos have come up empty Ethan Siegel, Contributor The null detection is...
  13. naima

    A Exploring Black Holes in Loop Quantum Gravity: Insights from Spin Foams

    Hi PF Is there a way to see if a spin foam contains a black hole?
  14. naima

    A Is LQG talking about information?

    LGG uses graphs which pass thru areas. does information follow these graphs?
  15. marcus

    I A new blog about LQG and related

    http://relatively-quantum.bodendorfer.eu Norbert Bodendorfer started a blog this year that seems to answer a need. Loop QG research is going through a fertile transformative period--generating lots of new ideas and new questions to work on. Bodendorfer's blog, called Relatively Quantum, can...
  16. J

    A Explore "LQG" & "Gravitational Waves" on Amazon

    Go to amazon.com and do a search for: Quantum Gravity & Gravitational Waves: " Ripples in The Curvature of Space-Time " Paperback – 7 Dec 2015 by Edited by Paul F. Kisak (Author) Look inside the book on the chapter on loop quantum gravity. The guy has taken the wikipedia page on LQG and just...
  17. K

    Papers that combine LQG with twistor theory

    marcus recently posted this paper Twisted geometries, twistors and conformal transformations Miklos Långvik, Simone Speziale (Submitted on 4 Feb 2016) The twisted geometries of spin network states are described by simple twistors, isomorphic to null twistors with a time-like direction singled...
  18. K

    Would NMSM or vMSM + 4D QG like LQG or AsG be TOE?

    thus far the LHC has not seen any SUSY in run 2, with possible exception of the 750 scarlar boson which may disappear with further data. If LHC run 2 provides no BSM type physics, would either The New Minimal Standard Model Hooman Davoudiasl, Ryuichiro Kitano, Tianjun Li, Hitoshi Murayama...
  19. K

    Asymptotic Safety Scenario in QG vs LQG

    the paper Asymptotic safety of gravity and the Higgs boson mass Mikhail Shaposhnikova, , , Christof Wetterichb predicts the Higgs mass. it also forms the framework of the neutrino minimal standard model. any research papers comparing Asymptotic Safety Scenario in QG vs LQG? does anyone here...
  20. ohwilleke

    LQG has not been shown to violate the holographic principle

    Backreaction has the story: http://backreaction.blogspot.com/2015/09/no-loop-quantum-gravity-has-not-been.html debunking this article: Violation of the Holographic Principle in the Loop Quantum Gravity Ozan Sargın, Mir Faizal http://arxiv.org/abs/1509.00843 and also showing the authors behaving...
  21. K

    In LQG, do objects attract via gravitons or curved spacetime

    planet Earth and the sun. in GR, gravity is not a force but simply a manifestation of spacetime curvature. the sun curves spacetime and the Earth is simply traveling through geodesic motion through curved spacetime. in string theory, the sun and Earth exchange virtual gravitons through a...
  22. C

    Which of these books would you recommend for LQG?

    They are both written by Rovelli, but I'm not sure which is better suited for the subject. My goal is to learn LQG in a rather complete fashion. https://www.amazon.com/gp/product/0521715962/?tag=pfamazon01-20 https://www.amazon.com/dp/1107069629/?tag=pfamazon01-20
  23. naima

    LQG and Gravity: Exploring the Acceleration Formula in Quantum Gravity

    There are thousands of papers in Marcus "intuitive" LQG. I hope that some of his readers will be able to answer my question. In Classical Physics or in GR we have a formula that gives the acceleration of a particle in a gravitational field. What is the corresponding formula in LQG?
  24. K

    Does Ads/CFT correspondence apply to LQG Kodama state?

    first paperhttp://arxiv.org/abs/hep-th/0209079 Quantum gravity with a positive cosmological constant Lee Smolin 59 pages "A quantum theory of gravity is described in the case of a positive cosmological constant in 3+1 dimensions. Both old and new results are described, which support the case...
  25. MTd2

    LQG is not proved to be locally lorentz invariant. (Bee)

    Sabine Hossenfelder said... Arun: This has never been proved. These deformations are problematic for other reasons, but they don't suffer from the density problem that I alluded to here, if that is what you mean, yes. LQG itself isn't actually based on a space-time network so the argument...
  26. marcus

    Leading lines of development in LQG, main issues, Loops 15

    The Loops conference held every two years, or so, gives us a good window on what the active lines of development are, what the organizers consider the main issues to be addressed and who they see as leaders in the various LQG research areas. LQG is a research community rather than a single...
  27. E

    Markopoulou geometrogenesis planck similar to LQG?

    Markus or others who are familiar with this.. I am aware Fotini Markopoulou Geometrogenesis occurs only during the Big Bang. But I'd like to know if it's Planck scale structure a present (after the Big Bang) is similar to the Planck scale structure of Loop Quantum Gravity? If they were not...
  28. Teichii492

    Clarification on key concepts of string theory

    I've been tasked with giving a presentation on any subject i like to my undergraduate physics class. Inspired by a recent lecture i attended by David Tong i have chosen to do a quick (10 minute) overview of the current state of theories beyond the standard model, obviously aimed at being...
  29. M

    LQG and Mathematics: Exploring the Intersection

    I am curious about the following question: Has research in LQG led to any breakthrough in mathematics or any mathematical new result so far?
  30. wabbit

    Quick question about LQG Self-Dual Black Holes

    This paper relies heavily of LQG self-dual black holes ; I saw an old thread here about didn't find the answer there so here's my question : On the face of it this looks like a somewhat bizarre/exotic theoretical solution, especially with the description referring to wormholes. However, since...
  31. MTd2

    Is the graviton the only thing to find in LQG?

    Has anyone thought if the there are particles to find in LQG, other than gravitons, when going to a "more classical limit"? Or that GR is not the only thing to find at classical limit, but, maybe, something like a GUT, for example, naturally emerging?
  32. naima

    LQG and black holes -- back to basics

    Hi PF I am reading an old Rovelli paper http://arxiv.org/abs/gr-qc/9603063 Rovelli computes the entropy of a black hole. He says two things. a) A state is described with an equivalence class of s-knots. b) the entropy of a black hole can be computed by counting the number of the intersection of...
  33. E

    Can Holometer Null Result falsify LQG?

    Google and even article searches here have no hits of whether null results of the Holometer can falsify Loop Quantum Gravity. First see first what is the Holometer: http://holometer.fnal.gov/ It is supposed to measure if the Planck scale is discrete or continuous. And results would be...
  34. Breo

    Where can I find PhD opportunities in Loop Quantum Gravity?

    Hello folks, I am currently studying a Masters course in Theoretical Physics in Spain. Here are working Fernando Barbero and a couple of physicists like Guillermo Mena in Loop Quantum Cosmology. I am more interesting in quantization of gravity approach. Where can I apply for a PhD in this...
  35. marcus

    How does the projective LQG approach shift the traditional formulation of LQG?

    A major change is happening in the way LQG is formulated. Suzanne Lanery gave a seminar about this 5 days ago (10 Dec) at Perimeter, and today she gave a similar talk at Nijmegen (Renate Loll's seminar). It's evident there is a lot of interest in this new development, which is based on the 11...
  36. marcus

    How time starts in LQG with onset of Lorentzian phase

    In the recent analysis by Mielczarek, Linsefors, and Barrau, the key parameter is ρc the highest density achieved in the bounce. The extremes (negative and then positive) of the Hubble rate occur symmetrically at density ρc/2 In the contraction preceding bounce, as the density approaches ρc/2...
  37. ohwilleke

    Does LQG Do Nothing Cool Even If It Is Right?

    In "Loop quantum gravity and observations" by A. Barrau and J. Grain at http://arxiv.org/abs/1410.1714 the bottom line seems to be that the phenomenological implications of LQG relative to existing predictions from GR are so extremely subtle that they have virtually no practical effects that can...
  38. marcus

    Dittrich's "Continuum Limit of LQG" is a landmark paper

    People interested in quantum gravity research may wish to take note of Dittrich's September 2014 paper which I believe represents a significant step towards constructing the continuum limit and the physical Hilbert space of LQG. It will be on the third quarter MIP poll. I'll get the link...
  39. D

    MHB Linear Quadratic Gaussian (LQG) regulators

    How do LQG regulators work? I have read the Matlab page about them, Wikipedia, and a few schools notes on them but it isn't either clear to me or they are not adequately explaining how they work. All see is that we want to control something giving a quadratic cost. Is there are more robust...
  40. twistor

    Particles in LQG: Are There Alternatives to Braids?

    Though a major collection of LQG researchers believe that particles raise in LQG by braiding (see http://arxiv.org/abs/1109.0080 and http://arxiv.org/abs/0903.1376), are there alternatives any to braids?
  41. craigi

    What Are the Top Beginner Resources for Learning Loop Quantum Gravity Online?

    What are the best online introductory resources for Loop Quantum Gravity? I've never felt more out of my depth than when listening to Rovelli speak on the subject.
  42. marcus

    A New Vacuum for LQG (Dittrich Geiller)

    IMHO as amateur QG watcher, this paper has considerable potential importance. Really impressed. Could be a game-changer: http://arxiv.org/abs/1401.6441 A new vacuum for Loop Quantum Gravity Bianca Dittrich, Marc Geiller (Submitted on 24 Jan 2014) We construct a new vacuum for loop quantum...
  43. K

    Possible alternatives to LQG and ST?

    You will notice we focus a lot on Loop Quantum Gravity here and String theory out there. Are there other alternatives to these two in case they are found to be false years from now? What are they?
  44. marcus

    Remaining problems w LQG (and cosmology application)

    Tom gave an honest assessment just now in another thread of the real situation with LQG which in effect includes the several roads from there to cosmology (eg. Agullo, Alesci, Barrau, Engle, Vidotto, Wilson-Ewing and others). He made a very good point which is that the problems are not...
  45. bcrowell

    Significance for LQG of Sen's result on entropy of black holes?

    Sen 2013 says, How serious a problem is this for LQG? Does this mean that LQG doesn't have GR as its semiclassical limit? Does that mean it's a dead theory, or maybe just that it needs to be modified? Is the technique using Euclidean gravity reliable? Since I'm not a specialist, I'd be...
  46. ohwilleke

    Is Physicist Lubos Motl's Criticism of Loop Quantum Gravity Valid?

    A recent paper by Maldecena and Susskind entitled "Cool horizons for entangled black holes" (http://arxiv.org/abs/1306.0533) argues that every entangled complex EPR pair of quantum particles must be topologically connected by an Einstein-Rosen bridge (aka a pair of wormholes within the light...
  47. J

    LQG Black Hole Model: Sources, Status & Puzzling Quantum States

    I am currently working myself into black hole physics and I am interested in their possible quantum geometric description by means of LQG. Can anybody please tell me good sources to start with? Since black holes were studied in this framework for a longer time, what is the most recent...
  48. tom.stoer

    Current status of canonical LQG and SF models

    From time to time I try to get an overview regarding the current status of LQG. Unfortunately there seem to be a lot of interesting ideas and new proposals, but I am missing a summary paper which addresses and summarizes both main achievements and main open issues. What about status of...
  49. MathematicalPhysicist

    A coherent survey of the problems in LQG and M theory.

    Is there any survey article that accounts for all the problems that are as of yet to be solved in M theory and LQG? I mean if I'll have time to dive into this field once. (I don't have a girlfriend and I don't plan to, so maths and physics will do). :biggrin:
  50. G

    LQG, string theory and spinors - all achieve mathematical miracles

    LQG, strink theory and Penrose's spinor theory, or maybe it's twistor theory, I don't know, all I know is that all three theories achieve mathematical miracles in their attempts to go beyond the Standard Model - how can all three theories do this but be mutually exclusive at the same time. Or...
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