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I Interaction term and vertices

  1. Feb 3, 2017 #1
    Hi,

    My question is that can one interaction term represent two vertices?

    For instance, can the lagrangian interaction terms L = eψγμψAμ represent a feynman diagram like these:
    eetoee1.png

    or should there be two terms in the lagrangian to construct such diagrams?

    Thanks!
     
  2. jcsd
  3. Feb 3, 2017 #2

    Orodruin

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    The interaction term gives you the vertices. The vertices in your two diagrams are both the same.
     
  4. Feb 3, 2017 #3
    Thanks for the reply!

    So I guess I can draw the same vertices several times in a diagram with the interaction term appearing only once in the Lagrangian?
     
  5. Feb 3, 2017 #4

    Orodruin

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    Yes, those correspond to higher orders in perturbation theory.
     
  6. Feb 4, 2017 #5
    Got it!

    Thank you so much Orodruin!!!
     
  7. Feb 4, 2017 #6

    ChrisVer

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    the lagrangian gives you the rules by which you can draw diagrams... afterall the vertices in a diagram only correspond to a coupling constant and conservation of energy/momentum.
     
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