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How Standard Model numbers arise from LQG

  1. Nov 12, 2005 #1

    marcus

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    One way to achieve a degree of unification in physics would be to show how key aspects of the Standard Model of particle theory emerge from Loop Quantum Gravity.

    At the October QG conference Lee Smolin offered some ideas as to how that might happen. It involved having the links of the spin networks be BRAIDS.

    I can't decide what to think of this but Smolin has had fertile highly innovative ideas in the past so I want to try to understand it. That is what this thread is for. If anyone else wants to contribute insights or comment.

    everyone who wants to watch the recorded talk

    Here is the abstract has links the slides and the recorded talk
    http://loops05.aei.mpg.de/index_files/abstract_smolin.html

    be sure you have the lecture notes in front of you to read while watching the video. Here is the lecture notes/as slide transparencies
    http://loops05.aei.mpg.de/index_files/PDF_Files/smolin.ppt

    Here is the recorded talk. Allow at least a quarter of an hour for it to download---while you do something else
    http://loops05.aei.mpg.de/index_files/Video/smolin.wmv

    To me it seems strange that out of LQG Smolin is suddenly getting NUMBERS OF VARIOUS KINDS OF PARTICLES. I was thinking that LQG is just a theory of quantum gravity, focusing on quantum spacetime geometry and not trying to connect with the details of matter----it did not have "TOE" ambitions. But suddenly that has changed and in his talk Smolin is citing work by a lot of people I hadn't heard of before.

    I don't have arxiv numbers for this work. If anyone has read some earlier papers on this, I would be glad if you could supply links.

    The part I'm focusing on starts at SLIDE #55.
    there is some very interesting stuff leading up to that (about how matter could arise as a kind of defect in a spin network, and some computer studies with random spin networks) but the part about the RIBBONS AND THE BRAID spin networks starts around slide #55.

    any help that is focused on understanding this specific talk is welcome. I will add bits and pieces of the picture as I find more out.
     
    Last edited: Nov 12, 2005
  2. jcsd
  3. Nov 12, 2005 #2
    Greetings marcus,

    The main point is that the techniques Smolin discusses to allow the unification in quantum theories of geometry, of gravity with the other forces presents a challenge in that they give rise to physics that is non-local. Do you find Smolin's speculations about the problems this implies interesting? How do you feel about bimetric theories of gravity?
     
  4. Nov 12, 2005 #3

    marcus

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    http://arxiv.org/abs/hep-ph/0503213

    who the heck is Sundance Osland Bilson-Thompson?
    it sounds like one of these Australian gentlemen with names like Crocodile.

    A topological model of composite preons
    Sundance O.Bilson-Thompson
    9 pages, 3 figures
    ADP-05-05/T615
    "We present a modification of the preon model proposed independently by Shupe and Harari. A basic dynamics is developed by treating the binding of preons as topological in nature and identifying the substructure of quarks, leptons and gauge bosons with elements of the braid group B_3. Topological considerations and a straightforward set of assumptions lead directly to behaviour consistent with much of the known phenomenology of the Standard Model..."

    what wonderful names! Do I see the braided ribbons being called "FAT LINKS"? I'm picturing LQG networks with the links made of sausage. Yes there is more suggestion that Sundance is from Oz.
    And the names get even better. He gets his Fat Links idea from two Germans called Hasenfratz and Knechtli

    http://arxiv.org/abs/hep-lat/0310056
    Description and comparison of Fat7-bar and HYP fat links
    Sundance O. Bilson-Thompson, Weonjong Lee
    5 pages, 10 figures, talk presented at the 2nd workshop on Lattice Hadron Physics, Cairns Australia, July 2003

    "We study various methods of constructing fat links based upon the HYP (by Hasenfratz & Knechtli) and Fat7-bar (by W. Lee) algorithms. We present the minimum plaquette distribution for these fat links..."

    so starting around page #55 of his slides, Smolin is heavily invoking the work of Sundance----and let's not forget Weonjong Lee. And of course
    Hasenfratz and Knechtli
    ========================
    here's a bunch of sundance papers
    http://arxiv.org/find/grp_physics/1/au:+bilson_thompson/0/1/0/all/0/1

    Kea, being down under, attended the Streetfest in Oz and probably had a beer directly with Sundance Osland himself, talking a mile a minute about braids. She might even have sipped tea with Weonjong Lee.

    =======================

    http://arxiv.org/abs/hep-lat/0112034
    Cooling for instantons and the Wrath of Nahm

    http://arxiv.org/abs/hep-lat/0110216
    Hadron Masses From Novel Fat-Link Fermion Actions

    Jesus. Not merely Fat-Link fermion actions but NOVEL Fat-Link fermion actions.
     
    Last edited: Nov 13, 2005
  5. Nov 12, 2005 #4

    marcus

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    well it is sort of a combination of euphoria and a splitting headache

    actually I feel kind of queasy about bimetric theories of gravity.


    ==================
    I am watching Smolin's talk for the second time, and reading along in the notes.
    I just started the download of
    http://loops05.aei.mpg.de/index_files/abstract_willis.html
    Computational Building Blocks for Lorentzian Spin Foams
    "I discuss recent work on efficiently computing the basic functions of Lorenztian spin foam models, from which the amplitudes themselves are calculated. The focus is on computing the 6-J and 10-J symbols, and I show how starting from the expression for these functions as integrals over copies of the group SL(2,C), one can develop an efficient algorithm for the 6J symbol, which can then be applied in calculating the 10J symbol."

    Quantum Gravity is like a dam breaking
     
    Last edited: Nov 13, 2005
  6. Nov 12, 2005 #5

    marcus

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    yes the non-local part is beautiful
    I like it!

    it explains matter as a flaw in the spin network where one of the links went somewhere far away----this is a very exciting idea


    only mediocre non-locality becomes objectionable
    if a linkage is REALLY non-local---over cosmological distance---then you hardly notice it as a link, it just seems like a particle of matter (one end of a link, some disconnected bit of spin)

    have to check on work of Hal Finkel----computer simulation starting with random graphs at bigbang time and EVOLVING them with two kinds of network MOVES-----expansion moves add vertices to the network (thus volume) and swapping moves percolate and randomize and regularize the network (the word "ergodic" comes to mind, or "shuffle")

    so in Finkel simulation you start with an nasty network and and apply moves that SWELL AND SHUFFLE it and you wind up with something like a MANIFOLD with an idea of LOCALITY
    because remember a network has an idea of volume (#vertexes contained) and area (#punctures by links) and if you have an idea of area and an idea of volume you automatically have one of distance
    and so this Finkel-evolved this "finkelated" network is like a MANIFOLD except that it has DEFECTS of some LONG-DISTANCE LINKS which all the swelling and shuffling moves that you applied for 14 billion years NEVER GOT RID OF but they are a TINY FRACTION OF THE TOTAL NUMBER OF LINKS and indeed they are the matter

    the long-distance links, which all the moves simply diluted but didnt get rid of
    are what is the matter
     
    Last edited: Nov 13, 2005
  7. Nov 13, 2005 #6

    Chronos

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    I have a vague suspicion Kea knows more than she is admitting. CAT and FAT may be more than a coincidence:smile: !Recent papers by Dr. Wiltshire, coy remarks, access to big computers... hmm. I've developed a peculiar fondness for category theory over the past several months. I think they are on to something.
     
  8. Nov 13, 2005 #7

    marcus

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    Sundance contributed to this page of animated gluon blobs
    http://www.physics.adelaide.edu.au/theory/staff/leinweber/VisualQCD/ImprovedOperators/

    he is acknowledged for helping to improve the operators
    this was in 2004
    in his Nobel acceptance talk, Frank Wilczek SHOWED some of the QCD animation on this page. the main author of the QCD animation is Leinweber.

    In 1995 Sundance apparently was a student at Adelaide. I think he is still at Adelaide.
    IN A COUPLE OF DAYS he is scheduled to give a talk at PERIMETER
    http://www.perimeterinstitute.ca/activities/scientific/seminarseries/alltalks.cfm?CurrentPage=2

    Sundance Bilson-Thompson Topological preon models: a braid new world
    Topological preon models: a braid new world
    Wednesday 16 November 2005, 2:00 PM
    "Preon models enjoyed considerable popularity during the early 1980s, but have seen little progress since then. I will describe a correspondence between one of the more successful preon models and a simple game involving the twisting and braiding of ribbons, subject to straightforward topological conditions. This reproduces the fermions and gauge bosons of the standard model, as well as the electromagnetic, weak and colour interactions. The prospect that such structures may occur naturally within Loop Quantum Gravity will be discussed"
    http://www.perimeterinstitute.ca/ac...ries/alltalks.cfm?CurrentPage=1&SeminarID=604


    this seminar talk would presumably be from the preprint where he derives numbers of sorts of particle in the Std Mdl from the twisting of ribbons.
    http://arxiv.org/abs/hep-ph/0503213
     
    Last edited: Nov 13, 2005
  9. Nov 13, 2005 #8

    marcus

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    the gentle josh came by here and said to look at "bi-metric"
    we really had better do this
    although I hate the number two. if there is more than one metric then there ought to be an infinite number, not just two.

    intuitively there should be one for every degree of insensitivity to non-locality.

    but apparently Fotini has been talking about the simple case of TWO metrics, where one cannot feel any of the long-distance links, and where the other can feel all the links including the long-distance-----so it feels spacetime "warts-and-all" and the other metric feels only an "air-brushed version" of spacetime without the warts.

    the perimeter institute is a frigging bionic Prometheus, because it connects all these people together and generates surprises like this

    -----like hal finkel, and sundance, and fotini, and of course smolin.

    Sundance indicates that he submitted his twisted ribbon preon paper to Elsevier Science on 4 October 2005, or maybe I have the date wrong and it was submitted March 2005, anyway it is submitted to Elsevier's Physics Letters B. one way to gauge the system is to see what happens----how long it stays in the pipe.
    in this paper he calls one kind of twist a dum and the other kind a dee
    and the generic word for a twist either way is a tweedle
    well I think it is a basic paper---why dont you make up your own mind?

    LOOK IN SMOLIN'S SLIDES starting AROUND #38 where he says "matter from non-locality"

    slide #40 is the picture with the smiley

    slide #42 says "So a small amount of non-locality is nothing to be afraid of. A spin network with non-local links LOOKS JUST LIKE A LOCAL SPIN NETWORK WITH PARTICLES"

    In slide #43 he introduces the notion of SWAPAGATION
    where a pure gravity amplitude for a SWAP move in a spin network turns out to be a PROPAGATION amplitude for a fermion in the case where the swap involves a LONG DISTANCE link.

    slide #43 is called "relation between fermion and gravity dynamics"

    slide #49 is a picture where a particle has been created and the caption is
    "Interactions come from moves that are local microscopically, but non-local macroscopically."
     
    Last edited: Nov 13, 2005
  10. Nov 13, 2005 #9

    marcus

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    #51 "this gives a unification in which fermions appear in fundamental respresentations of gauge groups..."

    #53 "but we still have to input the gauge group. Could there be a version where we input as little as possible, and we get out the standard model, as observed?

    this is the lead-in where he starts talking about sundance twisted ribbons.

    I am beginning to think that this set of slides by Smolin is kind of a classic. There are about a hundred slides (well 90 actually and the last only says "the end")-----he skipped over a lot. he could give a lot of different talks using this same set of slides, depending on which segments he focused on and which segments he skipped.

    just as a reminder
    Here are the lecture notes/slides I am talking about
    http://loops05.aei.mpg.de/index_files/PDF_Files/smolin.ppt

    Here is the abstract which has links to both the slides and the recorded talk
    http://loops05.aei.mpg.de/index_files/abstract_smolin.html

    Here is the recorded talk. If you want to watch it, allow a quarter of an hour or more for it to download. The slides, on the other hand, download instantly.
    http://loops05.aei.mpg.de/index_files/Video/smolin.wmv
     
    Last edited: Nov 13, 2005
  11. Nov 13, 2005 #10

    selfAdjoint

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    There suddenly seem to be a lot of ways of reaching the standard model. First there was that string paper that tailored a Calabi-Yau manifold to generate a good version of the MSSM, then Baez's own C-Y manifold that gives one generation of quarks and gluons, and now these twisted ribbons.

    Could this be perhaps the revenge of the Coleman-Mandula theorem? As I understand that result, the SU(3) X SU(2) X U(1) local gauge theory is as "big" as you can get with local gauge technology; internal degrees of freedom that can vary over spacetime and whose variations form a group. Using a bigger group just gives you the standard model back with some insignificant epicycles added.

    Physicists went to supersymmetry and strings partly to avoid the consequencees of the C-M theorem. But now the theorem could be working "backwards", so if your fancy deep/high/whatever mathematics yields a big gauge theory, it's got to BE the Standard Model!?
     
  12. Nov 13, 2005 #11
    Marcus said - "although I hate the number two. if there is more than one metric then there ought to be an infinite number, not just two."

    This is an instinctual reaction. So where does it come from?

    Fundamental physics is riddled with dualities. QM demands complementary properties, not to mention local~nonlocal. String theory is thrilled by its S and T dualities. The Planck scale is both the smallest size and the hottest heat. Partlcle physics is based on symmetry breakings or phase transitions. Any explanation of dimensionality, such as LQG, has to dichotomise into locations and relations. Can you think of anything that is not dualistic? Yet physicists want to be monadic at all costs.

    And when it comes to infinity, there is an equal certainty that it is a something that crisply must exist. The ancient idea of approaching a limit, and of vagueness, are decisively rejected.

    You say "there ought to be....". It is only when you have excavated the logic that underpins such a statement that you can say that this is the demand of one way of modelling reality. Another logic system may generate other expectations. Why be satisfied with gut instinct approaches when the evidence so often contradicts them?

    Of course, when it comes to physical constants like gravity and lightspeed, these would be the result of triadics - the essential threeness which comes from emergence!

    Dichotomies create an asymmetry of limits (a symmetry breaking or phase transition) and what emerges is the self-stable system with a singular set of constants.

    So VSL, bimetrics, CDT, etc, are all examples of what happens of what happens as you cross the threshold. Once your theory based on "atoms" of some kind has assembled enough context around itself (once there are enough "atoms" to make a system) then there can be a phase transition to a realm with "fixed" constants.

    In this view, there would indeed be an "infinity" of possible values for physical constants like lightspeed and gravity. Or rather a vagueness. So the duality here is between the asymmetric extremes of organised (our universe) vs disorganised (the vague potential that has "all values"). The duality between two sides of a phase transition.

    Cheers - John McCrone.
     
    Last edited: Nov 13, 2005
  13. Nov 13, 2005 #12
    remember this ???

    I had a dream ages ago...

    ...i saw this object in space. It was just a spinning blur and it was trying to show me what it actually was

    but it was moving too fast so I asked it to slow down...

    ...and it did, just long enough to make out what it was so i said thanx, then woke up, drew it on a piece of paper and went back to sleep

    I got up in the morning and had completely forgot about it til i saw what i drew and this is it, of course it was spinning much faster ...
    [​IMG]
    ...I have since ascribed meaning to it but i don't think I have fully comprehended it's relevence yet

    ...3 head feathers(dimensions), 2 birds(duality), swapping phases while spinning/twisting in space(energy) and as the phase shifts it moves around creating time(motion)the 7th dimension, but it is a flat 2d image !!!

    even the fact that it was moving too fast to see implies superluminal phase transition between interchangeable spatial dimensions suggesting this is a manifold, symmetric and balanced. Perhaps the monochrome aspect and contrasting eyes suggests white holes and black holes which allow us to see through to the space behind

    the beaks uh... i don't know maybe feeding off each other as they are puncturing each others necks sucking/replacing energy from each other and locked in an eternal death spiral

    reminds me of this actually
    [​IMG]
    and all that you guys seem to be talking about...

    ...it's why i ended up here looking to make sense of it and i feel we are all getting close

    yup dreams are free, I'm living mine, enjoy life, row your boat, cos life is but a dream...
     
  14. Nov 13, 2005 #13
    oh yeah i forgot to say i think i drew my kontrabirds as i call them, backwards such that it's spinning the right way but the birds are facing the wrong way way...

    ...i wonder if i did that on purpose and if so why ???

    hmmmm...might re do it, repost it and see how i feel about it

    as you were...
     
  15. Nov 14, 2005 #14
    Is your image flying, that is pushing itself through space by some kind of momentum opposing some kind of friction, like a propeller, or being pushed like a fan in the wind?

    On second incision, I see that it is more like a flat picture of a three dimensional stand of rope, perhaps on its way to becoming knot.

    I guess the formal way to ask, as 'Is your figure right handed in its spin or left handed?'

    Anyway it is truely bipolar, with a set of symmetries, such as axis of spin. And it has a variable in time, since you can ask it slow down. A braid, I suppose, a twist, or rather a very small section of one, which would be a larger representation.

    We see that spacetime is geometric, right?

    Richard
     
    Last edited: Nov 14, 2005
  16. Nov 14, 2005 #15
    no its not flying or being pushed...

    ... they were self propelled as if they were a simple representation of something more complex something living. I was talking to it and it responded but the image was the only way it could show me what it was in any sot of language I could understand

    If it were to be represented as a 3d object it would be twisting and spinning...

    ...cylindrical but rotating as well, yeah like a section of twisted rope rotating like a propellor

    in my dream i only saw it from one perspective so I don't know what it looked like from the side...

    ...just like i don't know what a black hole looks from the side either...

    I've always hoped ther would be a sequel dream but as yet nada, maybe it was for me to decypher it over time ???
     
  17. Nov 15, 2005 #16

    Kea

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    We at PF have previously mentioned this paper, on the thread

    https://www.physicsforums.com/showthread.php?p=618916#post618916

    AFAIK I have not had a beer with Sundance, but it is not at all unlikely that our paths have crossed.

    :smile:
     
  18. Nov 15, 2005 #17

    Kea

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    ?

    I can't seem to get the audios to download in any reasonable format. What do I need to read it?
     
  19. Nov 15, 2005 #18

    Kea

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    Sigh. Perhaps I might mention the Rishon parity cube, since this appears at the start of Sundance's paper. A parity cube has eight vertices labelled by triplets of 2 labels, say plus (+) and minus (-). The edges of the cube are directed because, naturally, it represents a diagram in a (higher dimensional) category.
     
  20. Nov 16, 2005 #19

    marcus

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    I see, it was mentioned by OHWILLEKE
    https://www.physicsforums.com/showpost.php?p=581108&postcount=7
    in a thread in the "Nuclei and Particles" forum that ARIVERO started!

    Alejandro's thread was called "Preons (subquarks etc....)"

    I miss both those guys, I haven't seen either Arivero or Ohwilleke around much lately.

    BTW I was impressed by the fact that when he presents the preon model Bilson-Thompson does not ever mention Spin Networks. He doesnt seem to have any inkling of how his scheme of particles can be used in quantum gravity.

    Smolin introduces the idea of a LONG DISTANCE LINK in a spin network that jumps so far out of the local context that all we are effectively aware of is the END of the link----and that acts like a particle

    So if the long distance link is braided tri-ribbon--------and if all possible braided tri-ribbons spell out all possible particles------then the end can be exactly all possible particles----just this many neutrinos, just that many quarks, and so on

    that is a really good thread, Kea, thanks. Ohwilleke goes through a bunch of preon models by different people, could be others besides Bilson-Thompson that he talks about would be of interest in LQG.
     
  21. Nov 16, 2005 #20

    CarlB

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    Hmmm... My interpretation of the Coleman-Mandula theorems is that they imply that if you want to unify the particles, you have to assume a violation of Lorentz symmetry.

    Furthermore, the history of particles physics suggests that when you finally decide to violate a symmetry, you should do it maximally. For example, people thought that parity must be a symmetry but then when it finally fell, the forces had to violate it maximally. Must be all that antisymmetry pressure that builds up before you decide to let it out. Along this line, Feynman noted a method of giving masses to the fermions that was in severe violation of Lorentz symmetry. The only place I've seen it mentioned was as an obscure footnote in his popular book "QED the strange theory of matter and light". Basically, it was a way of resumming massless propagators that automatically gives you the correct massive propagators.

    The other thing that the history of particle physics suggests is that something we've assumed can never be violated has to be ripped up. Quarks needed fractional charge. Maybe the next step is fractional spin.

    Carl
     
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