A BETTER LARGE N-EXPANSION FOR CHIRAL YUKAWA MODELS

We consider the most general renormalizable chiral Yukawa model with SU(3)color replaced by SU(N(c)), SU(2)L replaced by SU(N(w)) and U(1)Y replaced by U(1)N(w-1) in the limit N(c) --> infinity, N(w) --> infinity with the ratio rho = square-root N(w)/N(c) not-equal 0, infinity held fixed. Since for N(w) greater-than-or-equal-to 3 only one renormalizable Yukawa coupling per family exists and there is no mixing between families the limit is appropriate for the description of the effects of a heavy top quark when all the other fermions are taken to be massless. The large N = square-root N(c)N(w) expansion is expected to be no worse quantitatively in this model that in the purely scalar case and the N = infinity limit is soluble even when the model is regularized non-perturbatively. A rough estimate of the triviality bound on the Yukawa coupling is equivalent to m(t) less-than-or-equal-to 1 TeV.