Low-energy effects of heavy chiral fermions

We determine the low-energy effective lagrangian produced by a heavy chiral fermion, in the limit M→∞. In the case of a heavy t-quark, we analyze in detail the effective interaction of vector fields, in the anomalous and non-anomalous sectors, and the couplings of the Higgs boson. Unitarity limits to the t-quark mass are considered. Considering an additional U(1) component of the electroweak group, we see that an anomalous coupling to the known fermions is not excluded. (orig.)