Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How many Feynman diagrams do I draw?

  1. Dec 11, 2014 #1
    I'm currently going through the interaction part of Tong's lecture notes on quantum field theory, and I'm a bit confused about how many Feynman diagrams I need to draw in order to compute the amplitude of various interaction terms. Tong presents Feynman diagrams through a series of examples. For instance for nucleon-nucleon scattering Tong draws two diagrams, with the labels for the outgoing momentum flipped on one diagram with respect to the other. However for meson-meson scattering there is a single diagram. Why don't we need a second diagram in the meson-meson case with the labels of the outgoing momentum flipped on the second diagram? I don't understand how to see this without using Dyson's formula.
  2. jcsd
  3. Dec 11, 2014 #2


    User Avatar
    2017 Award

    Staff: Mentor

    Two different mesons?
    More context would help.
  4. Dec 11, 2014 #3
    The meson scattering I'm looking at is indeed [itex]\phi \phi \to \phi\phi.[/itex]
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: How many Feynman diagrams do I draw?
  1. Feynman diagrams exam (Replies: 5)

  2. Feynman diagram (Replies: 2)

  3. Feynman Diagrams (Replies: 2)