The Random Phase Approximation (RPA) is a technical method used in field theory to account for interactions when calculating correlation functions. It consists of only keeping a certain class of diagrams when doing a perturbative calculation of a certain function, such as a susceptibility or dielectric function.
Is there a simple mathematical justification to this method, other than "it is simple and it fits experimental data", which is already a good justification? Why don't we include the vertex corrections and other self-energy terms?
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