UNITARY GAUGE, STUECKELBERG FORMALISM, AND GAUGE-INVARIANT MODELS FOR EFFECTIVE LAGRANGIANS

Within the framework of the path-integral formalism we examine the different method of removing the unphysical degrees of freedom from spontaneously broken gauge theories. These are the construction of the unitary gauge by gauge fixing, an R(zeta)-limiting procedure, and the decoupling of the unphysical fields by field transformations. In the unitary gauge there exists an extra quartically divergent Higgs self-interaction term, which cannot be neglected if perturbative calculations are performed in this gauge. Using the Stueckelberg formalism this procedure can be reversed; i.e., a gauge theory can be reconstructed from its unitary gauge. We also discuss the equivalence of effective-Lagrangian theories, containing arbitrary interactions, to (nonlinearly realized) spontaneously broken gauge theories and we show how they can be extended to Higgs models.