TADPOLE SUMMATION BY DYSON-SCHWINGER EQUATIONS

In quantum field theory with three-point and four-point couplings the Feynman diagrams of perturbation theory contain momentum independent s ubdiagrams, the ''tadpoles'' and ''snails''. With the help of Dyson-Sc hwinger equations we show how these can be summed up completely by a s uitable modification of the mass and coupling parameters. This reduces the number of diagrams significantly. The method is useful for the or ganisation of perturbative calculations in higher orders.