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String theory & standard model & black hole entropy

  1. Aug 16, 2006 #1
    how many propreties of particles of the standard model has lqg been able to describe within its conceptual framework, as opposed to string theory?

    recently i posted "lee smolin & standard model" evidently loop quantum gravity might be able to model some elementary particles properties including photons, electrons, positrons, etc. i would hope that since string theory has been worked on for over 30 years, it should be able to describe the properties of more particles of the standard model, including the 3 generation puzzle, than a 1-paper from Sundance Bilson-Tompson.

    Do string theoriets believe they can describe all of the particles of the standard model as 1D strings, all quarks, fermions, bosons? Can it explain the 3 generations? While string theory believes D-branes exist mathematically, do they also model standard model particles/black holes or are they just matemathical artifacts without physical meaning? Does Sundance Bilson-Thompson hope to achive this with his preon and how rigirous can you derive his preon model from spin netowrk?

    string theory has been worked on for over 30 years. which particles of the standard model whose properties has string theory been able to reproduce with its 1D model of strings, for example, has string theory been able to reproduce photons, quarks, electrons, neutrinos as 1D strings with tension/vibrations? gravitons are not particles of the standard model.
    does this automatically imply modelling the supersymmetric partners of each particle as well (if they even exist)?

    i understand that string theory can reproducing hawking-berkenstein entropy for extremel, and near-extremel black holes, but how about ordinary non-extremel black holes?

    Last edited: Aug 16, 2006
  2. jcsd
  3. Aug 16, 2006 #2


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    Yes String theory phenomenology can output the standard model.

    Some of the massive problems are
    1) Lots of different ways to model it, hard to decide which is right and which is wrong.

    2) The existence of extra stuff, usually unwanted exotics lingering at higher energy, sometimes you can suppress them, sometimes they arent there.

    3) Often the results are *close* to say MSSM, but not quite (for instance too many FCNCs or some such that could potentially spoil things, or are ugly to deal with)

    Its a tough field, many people believe the fundamental theory isn't advanced enough to adequately tackle phenomonology in a workable manner yet (so workers don't have to deal with 10,000s of completely different competing and complex models). The SUSY structure if found at the LHC and ILC will help clarify things a lot, by falsifying a massive amount of models.

    The situation in LQG atm is, work in progress. People claim they get the algebra of observables, which is a first step, but still far from the full structure of the SM.
  4. Aug 20, 2006 #3
    sounds like an impressive achievement. can string theory calculate particle mass based on its principles, or describe particle transformation? just by varying string tension, all the particles of the standard model can be reproduced?

  5. Aug 21, 2006 #4


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    More to the point, can it deal with the fact that supersymmetry is looking less and less like a possibility and still output a basic chiral standard model? IIRC they morstly do the MSSM and other supersymmetric extensions of the SM.
  6. Aug 23, 2006 #5
    since the lhc is not yet online, and dark matter is yet to be accounted for, what makes SUSY less and less a possibility among theorists? (obviously if dark matter is axions or sterile neutrinos, or if LHC does not discover SUSY then what you say is true).

    is it b/c the proton refuses to decay?
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