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N-point Green's function in QFT

  1. May 27, 2010 #1
    Something about N-point Green's function in QFT really troubles me......
    In the path-integral formalism,why will we introduce the N-point Green's function? I mean is it enough because we have calculated the 2-point green's function.
    And in the canonical formalism, it seems we can finish the calculation of transition amplitude only with the help of 2-point Green's function(Wick contraction)
    What are the differences?
  2. jcsd
  3. May 27, 2010 #2
    What is the equation satisfied by the 2-point Green's function in an interacting field theory?
  4. May 27, 2010 #3
    Using the pertubative expansion and the definition of N-point Green's function.Because of the pertubation,i can only calculate the 2-point Green's function.But i really can't find the eqution it satisfies.
  5. May 27, 2010 #4
    Funny, because it carries your name. :)
  6. May 28, 2010 #5
    Please correct me if I'm wrong, but when we renormalize the coupling constant, don't you need to calculate the 4point function?

    And in calculating the S matrix, you can get some N point function, which has to be reduced to 2 point functions using Wick's contraction, but with all sorts of symmetry factors which you use Feynman diagrams to account for?
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