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. atyy

    Is the ground state in LQG a coherent state?

    As I understand, it is postulated that only coherent states in LQG correspond to classical spacetimes. Is the ground state of LQG a coherent state? Otherwise, what principle selects that the universe should be in a coherent state?
  2. marcus

    Chern-Simons, LQG black hole entropy, and central intertwiner

    Spin networks describing BH have a central node with label taken from an intertwiner Hilbertspace of high dimension (corresp. to hole entropy). Horizon area corresponds to the network links that pass through the horizon. The horizon Hilbertspace turns out to have the same high dimension (again...
  3. marcus

    AsymSafe, LQG, Verlinde at the Paris ICHEP

    What can we learn, if anything, from how the organizers of the ICHEP chose to represent the growing research activity in nonstring approaches to QG? ICHEP is currently going on in Paris and has somewhat more than 1000 participants. International Conf on High Energy Physics. Largely experimental...
  4. E

    Is time absolute or dynamical in LQG and string theory?

    regarding the problem of time in QG, Is time absolute or dynamical in LQG? string theory? How does LQG and string theory deal with time in singularities in the center of black holes?
  5. S

    LQG Resource Site | Quantum Gravity Theory

    Here is a new LQG resource site. http://sites.google.com/site/quantumgravitytheory/" I hope it will be useful.
  6. S

    Exploring Coherent States in LQG: Understanding the Measurement Process

    I’ve been starting to look at how LQG works, and if I’ve understood it correctly, just thinking about the kinematics, the quantum state of spacetime is encoded in a spin network. If I want to determine the volume of a region of spacetime, the result will be an eigenvalue of some volume...
  7. marcus

    Can Horava gravity be formulated in LQG framework?

    My impression was that much of the 2009 interest in Horava gravity had waned. A number of problems with it were brought out at the Perimeter Institute conference on it that was held in November 2009. Ted Jacobson did the final summary session of the conference and gave an informative wrap-up...
  8. tom.stoer

    Fractal LQG spacetime and renormalization of the Immirzi parameter

    Hi, this is not based on detailed work but just an idea which arised comparing causal dynamical triangulations and loop quantum gravity. In CDT it seems reasonable to treat spacetime as a fractal. That means there is no limit or minimum length in the triangulations, but the triangulations...
  9. jfy4

    Wave Length & LQG: Intrinsic or Prescribed?

    I have been pondering the description of matter recently, as some of you may have noticed by my recent posts in this channel. one of the most recent workings has been with respect to wave length and quantum units of length. The options I have been working between are: 1) The wavelength...
  10. naima

    Understanding LQG: Adding and Multiplying in Spin Networks

    Hi all I use to read posts on LQG where I try to understand what will be evident next 10 years!. I'd just like to know how one can add to spin networks or multiply one by a scalar? Thank you
  11. marcus

    Seething expanding geometry-new LQG view of reality

    Seething expanding geometry--new LQG view of reality A view of reality emerging from current LQG research (like 1004.1780) is somewhat analogous to the "seething vacuum" of quantum field theory. But it is a "seething geometry" in which bits of area and volume constantly come into existence and...
  12. marcus

    First followup of April1780 (new LQG) paper

    First followups of April1780 (new LQG) paper A new formulation of LQG was given in the arxiv paper 1004.1780 which is easier for me to remember as 2010 April1780 That was quite possibly the most influential QG paper of the year so since I may want to link to it several times I'll think of it...
  13. marcus

    Another way to test LQG found by Major

    This paper was spotted by MTd2. In it, Seth Major, argues that the quantum GEOMETRY of LQG implies quantum effects on the ANGLE of scattering of particles. But scattering angles can be observed and measured in the large---even if they originate in events too small to be themselves observed...
  14. E

    Would a successful merger of LQG + NCG SM be considered a TOE?

    LQG is an attempt to quantize geometry Noncommutative geometry is an attempt to express the SM geometrically, and is able to derive the SM Lagrangian and prediction of Higgs mass. LQG is not a TOE since it does not include SM, only quantize gravity, and NCG is not a TOE since it does not...
  15. E

    Recent paper: LQG fails to give correct semiclassical limit

    Sometimes I wonder if LQG is as much of a "failure" as string theory, with string theory inability to dimensionally reduce uniquely, and LQG unable to define hamiltonian constraint. Recent paper http://arxiv.org/abs/1005.1866 Large-spin asymptotics of Euclidean LQG flat-space...
  16. marcus

    Results from NCG + LQG workshop in Feb 2010 at Oberwolfach

    The workshop involved some top people including Mathilde Marcolli (longtime co-author with Alain Connes), Jerzy Lewandowski, Thomas Thiemann, Hanno Sahlmann, Jesper Grimstrup, Raimar Wulkenhaar, their co-workers, and several others. It took place the week of 7-13 February at Oberwolfach. Was...
  17. MTd2

    Are there collective modes on Spin Foams or LQG?

    Like phonons? Even if SF is a random lattice, there might be modes emerging from some space of phase space. Look at this example from BEC quantum Chaos: http://www.theo-phys.uni-essen.de/tp/forsch/bec.html
  18. C

    Understanding LQG: How Gravitons Interact with Spacetime

    How does LQG work? I know there are gravitons in it but how do they interact with spacetime? Why is it a theory of quantum gravity but not everything? Thanks, Cosmolojosh
  19. MathematicalPhysicist

    Is There a Comprehensive Review Article on LQG and Spin Foam Models Literature?

    Is there some review article which covers the most important literature? Something like this: http://arxiv.org/PS_cache/hep-th/pdf/0311/0311044v5.pdf but for lqg and spin foam models? P.s if there is also up to date list of string literature that would be terrific as well.
  20. MathematicalPhysicist

    Looking for LQG Lecture Notes? Check out Hanno Sahlmann's Crash Course!

    Jorge Pulling is teaching a course for UG in intro to LQG, I thought some of you might be interseted, here: http://www.phys.lsu.edu/classes/spring2010/phys4750/ Unfortunately he hasn't yet uploaded his Lecture Notes,I hope he will eventually upload them. I could email him ofcourse... (-:
  21. tom.stoer

    LQG, LQC & the Multiverse Theory

    In LQC (which is something like a toy moidel for LQG) one can derive the so-called big bouce scenario. As far as I can see it is common belief that LQG will lead to something similar. But couldn't full LQG be a "matrix" for a multiverse theory, where - due to quantum fluctuations - baby...
  22. Z

    Is the lack of infinities in LQG due to quantization of volume and area?

    Why NO infinities in LQG ?? what is the reason for LQG in 4-dimension to have NO infinities when doing calculations ?? , is it due to the fact that the VOlume and Area operators are Quantizied ? then if VOlume and Area are Quantizied, there should be a MINIMUM or quantum of area or volume we...
  23. H

    What is the relationship between loop quantum gravity and relational spacetime?

    I'm a lay person reading Three Roads to Quantum Gravity. I like the book very much but do have trouble understanding parts of it. Hopefully I can find clarification on a point of confusion for me. I thought loop quantum gravity was based on relational spacetime - that spacetime wasn't...
  24. E

    Verlinde, LQG, entropy and gravity as a fundamental force vs emergent

    Verlinde and Jacobson's early work, strongly implies that gravity is emergent. Anyhow, one of Jacobson's and Verlinde's claim in his paper is that since gravity is not a fundamental force, it does not make physical sense to quantize it canonically. So the LQG program is misguided...
  25. E

    Sundance Bilson-Thompson ribbons in LQG soldiers on

    http://arxiv.org/abs/1002.1462 Embedding the Bilson-Thompson model in an LQG-like framework Deepak Vaid (Submitted on 8 Feb 2010) We argue that the Quadratic Spinor Lagrangian approach allows us to approach the problem of forming a geometrical condensate of spinorial tetrads in a natural...
  26. atyy

    Condensed matter physics, area laws & LQG?

    I think Markopoulou and Oriti have been sniffing this out a long time. Note that Wen has heuristically linked tensor networks and AdS/CFT (strings!) in the final slide of http://dao.mit.edu/~wen/talks/09QHtop.pdf. http://arxiv.org/abs/0907.2994 Tensor network decompositions in the presence...
  27. marcus

    How Does Verlinde's Theory Link LQG with Newtonian Gravity?

    Using Verlinde's argument, Smolin shows Loop implies Newton's law of gravity in the appropriate limit. Verlinde's recent paper has thus supplied LQG with a missing piece of the puzzle. Smolin's paper presents his perspective on the significance of the Jacobson 1995 paper and of Verlinde's...
  28. C

    LQG and Cramer's Transactional Int.

    Hello everybody I noticed here are people knowing Loop Quantum Gravity. I am not a professional physicist but I like LQG because it doesn't depend on the background what is needed in General Relativity. I am learning Cramer's Transactional Interpretation of the Quantum Mechanics recently. TI...
  29. E

    1999-2009, key results look back in string & LQG

    1999-2009, key results "look back" in string & LQG In the news there is a lot of "past 10 years", from Bush v.s Gore and 9-11, to Iraq and electing first Black President, to death of Michael Jackson. The first possibly promising trial of HIV vaccine. While 10 years is arbitrary, from 80's was...
  30. marcus

    Berkeley prof contributes LQG paper

    Interesting development. We already knew nonstring QG at UC Davis, but hadn't heard of LQG research in the UC Berkeley physics department. The acknowledgments thanked Rovelli among others, for discussions and hospitality---at least one of the authors must have visited Marseille and Pavia* while...
  31. marcus

    LQG Workshop: Open Problems & Zakopane Conference

    We will get a chance to gauge the progress in LQG---how far along they are in dealing with the main outstanding problems. There will be a workshop at Zakopane in late February early March. But we need someone to help by relaying information. http://www.fuw.edu.pl/~jpa/qgqg3/ Thanks to...
  32. E

    Does this paper prove GR emerge from LQG?

    Does this paper prove GR emerge from LQG with matter? A common criticism of LQG is that despite intense research, no semiclassical limit has been shown to connect GR with LQG in the low energy limit. And hence, it is not even a candidate theory of quantum gravity. This paper...
  33. Z

    Why the term cylindrical functions for the states in LQG?

    Why the term "cylindrical functions" for the states in LQG? I just can't find a any reference that explain the why of the term "cylindrical" for the states in LQG. Thanks in advance for any comment. Z.
  34. Spinnor

    Minimum volume of LQG corresponds to a minimum energy?

    Mass and energy curve spacetime, lots of concentrated mass, lots of curvature. Does the quantized volume of Loop Quantum Gravity correspond to a minimum quantum of energy? If so how does that minimum energy compare to the energy of a individual photon from say a radio station broadcast? It seems...
  35. E

    Master Constraint and canonical LQG

    So Thieman and co are still working on the Master Constraint program for canonical, non-SF, LQG? I thought that approach was dead and given way to SF ala Rovelli
  36. S

    Schools Best grad school for String Theory, M-Theory and LQG?

    Hi, What is the absolute best grad schools in the US or Europe for String Theory, M-Theory and LQG? I tend to learn better in a classroom environment, so I'm sort of looking for a grad school which actually has relevant courses, and not just a European-style research university where I...
  37. E

    If BH do not exist, would string & LQG be falsified?

    If Black holes do not exist, would string & LQG be falsified? Suppose that black holes do not exist in nature, in that the quantum properties of matter prevents density from increasing beyond a certain limit, as well as gravity's strength diminishing at higher energies. Stellar objects can...
  38. marcus

    Cosmological footprints of LQG (Aurelien Barrau and Julien Grain)

    It's important to be able to test LQG with observations, most likely using new data on the microwave Background (CMB) collected by instruments such as the Planck spacecraft . It turned out to be impossible to derive a prediction of dispersion (energy dependent speed of light) at least so...
  39. E

    What is the quanta in LQG and Spinfoam and BI?

    When gravity is expressed in tools of QFT, the quanta is the spin-2 graviton. What is the quanta according to LQG, SF, CDT, and other BI theories? Is it the spin network? What role does the graviton of QFT quanta play and BI ?
  40. marcus

    Can the algebraic string formulation provide insights into Loop Quantum Gravity?

    Even if string should turn out to be a dead end as far as unification goes, and fail to produce a predictive theory of how the world works, it could still be interesting and constructive to formulate some version of string within the background independent LQG context. Here is a recent paper...
  41. E

    Major developments LQG a look back 1998-2009

    Hey Marcus, what have been the most important results in LQG from the last ten years, say 1998-2009? A variety of ways from citations to number of papers/researchers, to solving outstanding problems. TO put it another way what does LQG tell us in 2009 that was not known in 1998? Are we any...
  42. marcus

    What do stringy people find interesting about LQG?

    Tom.stoer recently started a thread to collect ideas on the topic of stringy dislike of LQG. I thought that was a constructive initiative. At least for me it was helpful to sample what are the current rationales of dismissal, in part because this is a kind of folklore that has changed over time...
  43. tom.stoer

    Why do stringy people don't like LQG?

    Hi, I know a couple of arguments why the loopy guys don't like string theory (perturbative quantization, background dependence, too many statements w/o proof, mysterious M theory, ...) But can anybody tell me why stringy people don't like loop quantum gravity? I mean serious arguments...
  44. MTd2

    Going Beyond LQG: how to define QFT over Loops?

    Does anyone have any ideas? Marcus, do you have?
  45. MTd2

    Freidel, Krasnov and Livine hints of Sring Theory in LQG

    http://arxiv.org/abs/0905.3627 At VIII. Disscussion, p. 36: "Our main result is the formula (53) for the inner product in Hj1,...,jn in terms of a holomorphic integral over the space of “shapes” parametrized by the cross-ratio coordinates Zi. In the “tetrahedral” n = 4 case there is a...
  46. MTd2

    Self-dual Black Holes in LQG: Theory and Phenomenology: (title of the article)

    http://arxiv.org/abs/0905.3170 In this paper we have recalled the semiclassical metric obtained from a classical analysis of the loop quantum black hole (LQBH). We show that the regular Reissner-Nordstrom-like metric is self-dual in the sense of T-duality: the form of the metric obtained in...
  47. marcus

    Nice LQG paper by Modesto about dimension down with scale

    This confirms a beautiful result of Modesto's earlier paper, that LQG seems to coincide with two other very different types of quantum geometry/gravity on the business of dimensionality declining continuously with scale. Fractal-like microstructure of space time. As scale decreases the observed...
  48. tom.stoer

    Some basic questions regarding LQG

    I am a new member; I hope I didn't miss existing questions and answers. One of my questions regarding loop quantum gravity / Ashtekar variables is: what is the relation between the familiar SO(3,1) Lorentz symmetry of special relativity and the local SU(2) symmetry of the vierbein-rotation...
  49. E

    What is group field theory, and its relation LQG, CDT?

    What is group field theory, and its relation LQG, CDT? There's no wiki article on gft. I am aware of the numerous articles on arix, could someone summarize what these articles mean?
  50. marcus

    Expectations for LQG in 2009: New Developments and Connections to LQC

    I'll risk some projections, so if I'm wrong if anyone wants they can fish up this thread 10 months down the road and say "hah hah it didn't happen". Anyway it can help to have an idea of what changes to expect----some rough idea of the recent past and the near future. So here' what I think...
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