Dimensionally renormalized Green's functions for theories with massless particles. II

In the framework of dimensional renormalization the existence of Green's functions to all orders of perturbation theory is proved for theories with massless particles, provided all terms in the interaction Lagrangian have infrared degree 4. If the vanishing of masses is enforced by some symmetry and this symmetry is respected by dimensional regularization, Schwinger's action principle holds for these Green's functions as in the massive case.On leave of absence from Max-Planck-Institut für Physik und Astrophysik, D-8000 München, Federal Republic of GermanySupported in part by the National Science Foundation Grant # MPS-74-13208 A01Supported in part by the National Science Foundation Grant # GU 3186