LARGE-N AND VACUUM ALIGNMENT IN TOP-COLOR MODELS - ART. NO. 075004

Top-color and top-color-assisted technicolor provide examples of dynam ical electroweak symmetry breaking which include top-quark condensatio n, thereby naturally incorporating a heavy top quark. In this paper we discuss the roles of the Nambu-Jona-Lasinio (NJL) and large-N approxi mations often used in phenomenological analyses of these models. We sh ow that, in order to provide for top-quark condensation but not bottom -quark condensation, the top-color coupling must be adjusted to equal the critical value for chiral symmetry breaking up to O(1/N) in any th eory in which the isospin-violating ''tilting'' interaction is a U(1) gauge interaction. A consequence of these considerations is that the p otentially dangerous ''bottom pions'' are naturally light. We also sho w that the contributions to rho-1 previously estimated are of leading order in N, are not included in the usual NJL analysis, and are the re sult of ''vacuum alignment.'' [S0556-2821(98)03319-0].