The idea was described by
Yoichiro Nambu and subsequently developed by Miransky, Tanabashi, and Yamawaki (1989) and
William A. Bardeen,
Christopher T. Hill, and
Manfred Lindner (1990), who connected the theory to the
renormalization group, and improved its predictions. The renormalization group reveals that top quark condensation is fundamentally based upon the
infrared fixed point for the top quark Higgs-Yukawa coupling, proposed by Pendleton and Ross (1981) and Hill. The "infrared" fixed point originally predicted that the top quark would be heavy, contrary to the prevailing view of the early 1980s. Indeed, the
top quark was discovered in 1995 at the large mass of 174 GeV. The infrared-fixed point implies that it is strongly coupled to the Higgs boson at very high energies, corresponding to the
Landau pole of the Higgs-Yukawa coupling. At this high scale a bound-state Higgs forms, and in the "infrared", the coupling relaxes to its measured value of order unity by the
renormalization group. The Standard Model
renormalization group fixed point prediction is about 220 GeV, and the observed top mass is roughly 20% lower than this prediction. The simplest top condensation models are now ruled out by the
LHC discovery of the Higgs boson at a mass scale of 125 GeV. However, extended versions of the theory, introducing more particles, can be consistent with the observed top quark and Higgs boson masses. The composite Higgs boson arises "naturally" in
Topcolor models, that are extensions of the standard model using a hypothetical force analogous to
quantum chromodynamics. To be "natural", that is, without excessive fine-tuning (i.e. to stabilize the Higgs mass from large radiative corrections), the hypothesis requires new physics at a relatively low energy scale. Placing new physics at 10 TeV, for instance, the model predicts the top quark to be significantly heavier than observed (at about 600 GeV vs. 171 GeV).
Top Seesaw models, also based upon
Topcolor, circumvent this difficulty. == Top condensation, redux ==