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I Applicability of Furry's theorem

  1. Apr 13, 2018 #1


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    The diagram below, together with its reversed fermion flow diagram counterpart, collectively sum to zero due to Furry's theorem. I just wanted to understand why this is the case.

    1)There are two gluons and one photon attached to the internal line so this is 3 coupled vector current insertions (1 QED and 2 QCD).

    2) The blob represents a hadronic state. Why does the diagram contain a fermion loop coupled to the 3 vectors? I thought the blob always stood for arbitrary complicated soft dynamics that we are naive about and just 'put under the rug' so I don't see why it necessarily must be a simple closure of the fermion line shown.

    Attached Files:

  2. jcsd
  3. Apr 18, 2018 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
  4. Apr 20, 2018 #3


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    I understand now the answer to the original question asked. But I was also wondering, and perhaps this is a simpler question, is Furry’s theorem applicable for both off shell and on shell photons/gluons attached to a fermion loop? Since it is usually applied at the loop level I would say yes and I don’t see any reason why not with regards to the time ordered correlator of currents definition.
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