Feynman-graph technique

A detailed description of the Feynman graph techniques and the correspondence rules within the Furry picture for bound-state QED can be found in... 

Graph theory provided various fields of physical chemistry and chemical physics with a technique that has been extensively used in theoretical physics (the well-known Feynman diagram technique). It also appeared to be extremely effective in both chemical kinetics and chemical polymer physics. The major advantage of this technique is the extremely simple derivation of equations and the possibility of their direct physical interpretation. 

Needless to say, it was the second quantization formalism of quantum field theory, enabling the exploitation of Wick s theorem together with a representation via Feynman-like graphs or diagrams—the mathematical techniques relied upon by all the above authors [32-34]—that made it possible to carry out the general proof of the extensive nature of RSPT and to unscramble the general structure of MBPT wave functions and energies. The principal results of these efforts are usually referred to as the linked cluster and connected cluster theorems (see below). 

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