In a scalar field path integral with weight , each internal propagator contributes , each interaction vertex contributes , and each source insertion contributes . A connected graph with internal lines and interaction vertices has loop order . Its amputated amplitude, or its coefficient in with the source insertions included, is proportional to . An ordinary unamputated connected -field correlation function instead has the additional external propagator factors and scales as . Multiplication by to form the connected generating functional shifts the source-kernel counting to . These are compatible normalization conventions.
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