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A Terminology of 1PI diagrams

  1. Feb 15, 2017 #1
    One-particle irreducible diagrams are diagrams that cannot be broken into two disconnected diagrams by cutting an internal propagator.


    1. Why are the external lines on an one-particle irreducible diagram truncated/amputated?

    2. What is the motivation for the word 'one-particle' in the terminology?
     
  2. jcsd
  3. Feb 15, 2017 #2

    A. Neumaier

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    2016 Award

    because that's how they are used in scattering calculations.
    One also defines ##k##-particle irreducible diagrams (which cannot be made disconnected by removing up to ##k## internal lines). These describe the properties of ##k##-point correlations (involving ##k## particles, hence the name), which are important for calculations in nonequilibrium quantum field theory.
     
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