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The wrong turn of string theory: our world is SUSY at low energies

  1. Mar 24, 2017 #221
    Following the previous post, I believe I really have identified the first genuine field-theoretic toy model of the sbootstrap - or at least, toy model of a crucial element of the sbootstrap. The field theory is just N=1 SQCD with Nc=2 and Nf=5. There is no electromagnetic charge, so this is not yet a model of the combinatorial aspect of the sbootstrap. But what it does give us, is a definite realization of the concept of "fermionic superpartners of pions and diquarks".

    It's because of the fact, pointed out by Shifman and Vainshtein, that for SU(2)c, diquarks, like pions, are goldstone bosons. So in the N=1 theory, they will have superpartners that are goldstinos, goldstone fermions. For SU(3)c, the nature of diquarks is less clear. But as S & V argue (pages 6 & 7): "As we pass to SU(3)color , the exact symmetry no longer holds, but an approximate similarity in the spatial structure of pions and diquarks is expected to hold". They propose a way to formally investigate this, by adding a triplet Higgs to SU(3)c QCD which breaks it to SU(2)c. A similar procedure should be possible for SU(3)c SQCD.

    It has been proposed before that the SM fermions are goldstinos. Here it seems we have to look for something a little more complicated - perhaps "almost-goldstinos" in the "magnetic theory" of a Seiberg duality.
     
  2. Apr 17, 2017 #222
    In a 1984 paper, "Split Light Composite Supermultiplets", one generation of leptons is obtained from SQCD with three colors and three flavors. Furthermore, the preons have quark-like hypercharges (see equations 3.15). The leptons are obtained at equation 3.42. Those "χ"s are components of the superfield T, defined in equation 3.18. If I am interpreting that correctly, T is a product of a quark and a squark.
     
  3. Apr 17, 2017 #223
    This was wrong, [itex]\Phi, \tilde \Phi[/itex] are chiral superfields in [itex]3, \bar 3[/itex] reps of SU(3) (see e.g. the start of section 3), so T is a meson superfield.
     
  4. Apr 17, 2017 #224

    ftr

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    Mitchell, why are you trying to figure out the proton, some people already got the noble prize for it, right.:sorry:
     
  5. May 7, 2017 #225
    Masiero & Veneziano 1984 provides a context in which e.g. a muon-pion superfield can be explored. But what about the quark-diquark relationship? An appealing possibility is that the next step beyond Shifman & Vainshtein 2005 is to work in N=2 supersymmetry. Seiberg and Witten analyzed the space of ground states for N=2 SU(2) gauge theory, and found that there were paths through it, in which composite objects (monopoles) map smoothly to elementary objects. The quark-diquark part of the sbootstrap has always looked like a kind of self-duality, and N=2 SU(2) SQCD may provide a context in which a change of variables can map a diquark superfield onto a quark superfield. (And to include charge, one would just work with U(n) rather than SU(n).)
     
  6. May 8, 2017 #226

    arivero

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    Gold Member

    Hmm, it has been some years, so ok lets go for a recap :-)

    Topic here was generically if String Theory had gone wrong turn at some moment, and particularly if it could be possible that it still does better for the pionic string. The observation for this particular is that one could consider a scenary where supersymmetry is not broken:

    upload_2017-5-9_1-4-18.png

    or a midly broken scenary

    upload_2017-5-9_1-8-6.png

    Both of them have the peculiar characteristic that the scalars are composites of the light quarks, or perhaps open strings terminated in such quarks. From here a lot of the discussion in the thread has become about accummulating research that could be related to quark - diquark or lepton-meson symmetries.
     
  7. May 9, 2017 #227
    Please tell me. Is the supersymmetric particle corresponding to dark matter stable? If it's not stable and can only be produced at laboratory.. how can they exist as dark matter that is always present?
     
  8. May 15, 2017 #228
    That is a standard idea, yes. But the focus in this thread is on the unusual possibility that there are supersymmetric relations among the already known particles. Dark matter is a separate question, and could be anything.
     
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