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Do we need to refer all interactions to symmetries?

  1. Nov 2, 2012 #1
    Do we innevitably need to attach each interaction with a symmetry?Could we contruct a theory of an interaction without using any symmetry theory(example gravity interaction)?

    Why do we not need to demonstate QCD being renormalized,but we must demonstrate electroweak theory is renormalized(I hear t'Hooft did that)?Is that because we separate left handed from righ handed representation,then appearing the chiral anomalies,so we must demonstrate the renormalization?If the left-righ handedness were reserved in electroweak theory,then we would not to have demonstrate the renormalization as QCD?
     
  2. jcsd
  3. Nov 2, 2012 #2
    Not every possible interaction is related to an underlying symmetry.
    In QFT, many interactions are attached to gauge symmetries (any interaction with spin 1 particle).
    However, interactions invloving scalars and fermions (like yukawa interactions) are not nescesaraly related to any symmetry. For examples, ineratctions of the higgs with fermions
    in the SM are not related/dictated by any underlying symmetry.

    For the question about renormalization, there are two reasons why renormalizability in Electro-Weak theory is less obvious than in qcd.
    1) Massive gauge bosons

    -It has been shown that if the masses are due to the higgs mechanism the theory is still renormalizable.

    2) left are right handed fermions have different gauge interactions (transform differently under the gauge symmetry) - chiral theory

    -It has been shown that the SM is still renormalizable due to intricate cancelation between the gauge quantum numbers of the SM fermions. The gauge anomalies vanish
     
  4. Nov 2, 2012 #3
    The gravity interaction is a real(existing) interaction despite the gravity theory is nonrenormalizable theory.But in elimination (infinite) impossible interactions they consider nonrenormalizable interactions being impossible interactions(for example Phi-5,Phi-6.....interactions,but only accepted Phi-4theory).Why do they not accept all those nonrenormalizable interactions and manage to bypass the nonrenormalizability by ''nonperturbative'' theories or finding some ''symmetries'' that reduce infinite counterterms to finite counterterms?
     
  5. Nov 3, 2012 #4
    How can we deduce the gauge bosons have spin 1 from Standard Model?Why must carrying force particles be bosons,but they can not be fermions?
     
  6. Nov 3, 2012 #5
    I hear in Supersymmetry theory there is a ''symmetry'' between bosons and fermions(?).But I would like to know the problem in Standard Model
     
  7. Nov 3, 2012 #6

    Vanadium 50

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    I see you didn't follow my advice in the previous thread; two-thirds of it is reproduced below.

    • https://www.physicsforums.com/blog.php?b=3588 [Broken]
    • It is customary to say "thank you" when you ask a question and have it answered.
     
    Last edited by a moderator: May 6, 2017
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