THE BACKGROUND-FIELD FORMULATION OF THE ELECTROWEAK STANDARD MODEL

The application of the background-field method to the electroweak Stan dard Model and its virtues are reviewed. Special emphasis is directed to the Ward identities that follow from the gauge invariance of the ba ckground-field effective action. They are compatible with on-shell ren ormalization and imply a decent behavior of the background-field verte x functions. Via the usual construction of connected Green functions t hey transfer to Ward identities for connected Green functions which, i n distinction to the conventional formalism, remain exactly valid in f inite orders of perturbation theory even if a Dyson summation of self- energies (within a systematic use of one-particle irreducible building blocks) is performed. Finally, we comment on the interplay between ga uge invariance and gauge-parameter (in-)dependence of vertex and Green functions and the uniqueness of resummation procedures.