Schwinger parametrization is a technique for evaluating loop integrals which arise from Feynman diagrams with one or more loops. It is named after Julian Schwinger, who introduced the method in 1951 for quantum electrodynamics.
Using the observation that
one may simplify the integral:
for .
Another version of Schwinger parametrization is:
which is convergent as long as and . It is easy to generalize this identity to n denominators.