Effective Field Theory of Vacuum Tilting
  Simple models of topcolor and topcolor-assisted technicolor rely on a relatively strong U(1) gauge interaction to ``tilt'' the vacuum. This tilting is necessary to produce a top-condensate, thereby naturally obtaining a heavy top-quark, and to avoid producing a bottom-condensate. We identify some peculiarities of the Nambu-Jona-Lasinio approximation often used to analyze the topcolor dynamics. We resolve these puzzles by constructing the low-energy effective field theory appropriate to a mass-independent renormalization scheme. We construct the power-counting rules for such an effective theory. By requiring that the Landau pole associated with the U(1) gauge theory be sufficiently above the topcolor gauge boson scale, we derive an upper bound on the strength of the U(1) gauge-coupling evaluated at the topcolor scale. The upper bound on the U(1) coupling implies that these interactions can shift the composite Higgs boson mass-squared by only a few per cent and, therefore, that the topcolor coupling must be adjusted to equal the critical value for chiral symmetry breaking to within a few per cent. 
R. Sekhar Chivukula and Howard Georgi