  For large values of the Higgs boson mass the low energy structure of the
gauged linear sigma model in the spontaneously broken phase can adequately be
described by an effective field theory. In this work we present a manifestly
gauge invariant technique to explicitly evaluate the corresponding effective
Lagrangian from the underlying theory. In order to demonstrate the application
of this functional method, the effective field theory of the abelian Higgs
model is thoroughly analyzed. We stress that this technique does not rely on
any particular property of the abelian case. The application to the non-abelian
theory is outlined.
