CURRENT-ALGEBRA APPROACH TO HEAVY TOP EFFECTS IN DELTA-RHO

The O(G(mu)2 m(t)4) correction to the rho parameter is computed using the current algebra formulation of radiative corrections. This approac h is proved to be equivalent to the effective Lagrangian method propos ed by Barbieri et al. The same framework is then applied to the calcul ation of the O(G(mu)2 m(t)2 m(z)2) correction to the of neutral-to-cha rged-current amplitudes in an SU(2) model. In this model the O(G(mu)2m (t)2m(z)2) contribution is shown to be numerically comparable to the l eading O(G(mu)2m(t)4) term for realistic values of the top mass.