One-particle irreducible diagrams are defined as diagrams that cannot be separated into two disconnected diagrams by cutting an internal propagator. The truncation of external lines in these diagrams is essential for their application in scattering calculations. The term 'one-particle' is used to distinguish these diagrams from k-particle irreducible diagrams, which involve correlations among k particles and are crucial for nonequilibrium quantum field theory calculations.
PREREQUISITESPhysicists, particularly those specializing in quantum field theory, particle physicists, and researchers involved in scattering calculations and correlation functions.
because that's how they are used in scattering calculations.spaghetti3451 said:1. Why are the external lines on an one-particle irreducible diagram truncated/amputated?
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.spaghetti3451 said:2. What is the motivation for the word 'one-particle' in the terminology?