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Does loop quantum gravity hint at the Standard model?

  1. Nov 2, 2009 #1
    Have loop quantum theorists looked forward to how one might fit the standard model into loop quantum gravity?

    Thank you for any help.
  2. jcsd
  3. Nov 3, 2009 #2


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    I would say on the whole LQG does not hint at the Std Mdl.
    And that the main part of the Loop research community has not been exploring ways to include particle physics. They have a big enough challenge just to

    1. formulate a background independent quantum field theory of spacetime geometry
    2. formulate a path integral dynamics (using spin foam)
    3. show it yields Gen Rel in the limit
    4. derive testable consequences about the early universe that can be checked by observation.

    But there has been some marginal work exploring "hints" of the Std Mdl.
    As a handle on this, look up the papers of Jonathan Hackett:

    The Hackett page will give you links to pages of his collaborators. If you look at all the people he has collaborated with, and look at their papers, you will pretty much have the lot.

    Especially notable is Yidun Wan (who has, I think, done the most work on this of anybody.)
    and likewise Sundance Bilson-Thompson (who first pointed out how particles correspond to braids in a network).
    but you will also see co-authors Lee Smolin, Fotini Markopoulou, and Louis Kauffman

    Hackett is not necessarily a ringleader in this area, but he has collaborated widely so he provides a handle on the rest.

    The person with the most energy and determination in this research is Yidun Wan, and he has been among the most creative. What this means if that if a year goes by and Yidun Wan does not publish new results then it is possible that the field is "stuck" and not going anywhere. So look at the dates on Yidun Wan's papers. And the other people's too.

    If you want to know what is currently going on in Loop/Foam QG, then you have to realize there was a major renovation in 2007, essentially redefining the field and basing it on the EPRL spin foam model. (Engle, Pereira, Rovelli, Livine).

    The most significant thing that happened this year was the paper of Jerzy Lewandowski et al that extended the EPRL foam and made it better. Now the spin foam model is completely compatible with the old LQG kinematics of spin networks. Now we can really say that the 4D foam contains the 3D nets and shows their evolution.
    Here is the Lewandowski paper, which I think is defining for this year:

    Also (for what it's worth) the new Lewandowski version of spin foam allows for braids--knots of various kinds in the spin networks--or at least leans in that direction. But probably we shouldn't bother thinking about braids unless Yidun Wan and the others start writing papers again.
    Last edited: Nov 3, 2009
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