Dynamical models for light Higgs doublets in supersymmetric grand unified theories.

We consider a supersymmetric hypercolor gauge theory with six flavors of (hyper)quarks interacting strongly at the grand unification scale. Dynamical breaking of the grand unified SU(5${)}_{\mathrm{}\mathrm{GUT}}$ produces a massless pair of composite color-triplet states. Use of the missing partner mechanism yields eventually a pair of massless Higgs doublets, giving large masses to the color-triplet partners. We prove that this pair of massless Higgs doublets survives quantum corrections and remains in the low-energy spectrum as long as the supersymmetry is unbroken. Hence this could solve the most serious problem\char22{}doublet-triplet splitting in the grand unified theories. We also show that the dangerous dimension-five operators for nucleon decays are suppressed simultaneously, which makes our model still more attractive. \textcopyright{} 1996 The American Physical Society.