The S matrix is the central object of interest in field theory because it expresses the observed interactions between particles. The Chapter 13 definition of the S matrix does not provide a convenient framework for further analysis of its properties. However, we now show that the S matrix has a simple representation in terms of time-ordered correlation functions. This representation is convenient, and it allows, e.g., the construction of perturbation series, the decomposition into connected components, and the study of momentum space analyticity.
KeywordsWeak Coupling Scattering Theory Dyson Equation Meromorphic Continuation Asymptotic Completeness
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