On effective lagrangians with heavy chiral fermions

I discuss the low-energy effective lagrangian obtained in the large-mass limit of a chiral fermion which acquires its mass through the electroweak symmetry breaking. I analyse the effective interaction of vector fields in the anomalous and non-anomalous sectors and the couplings with the Higgs boson in the case where only one member of a fermionic isodoublet has its mass sent to infinity. Two applications of this field-theoretical framework are studied: The unitarity limits on the top-quark mass and the possible presence of additional U(1)' gauge symmetry with an anomalous coupling to the ordinary fermions. (orig.)