Higgs Doublets as Pseudo-Nambu-Goldstone Bosons in Supersymmetric E6 Unification

The idea of Higgs doublets as pseudo-Nambu-Goldstone (PsNG) multiplets is examined in the framework of supersymmetric E6 unified theory. We show that extra PsNG multiplets in addition to the expected Higgs doublets necessarily appear in the E6 case. If we demand that the extra PsNG multiplets neither disturb the gauge coupling unification nor cause the color gauge coupling to diverge before unification occurs, the only possibility for the extra PsNG is of SU(5). This is realized when the symmetry breaking E6 →SO(10) occurs in the sector, while E6 → SU(4)C ×SU(2)L ×U(1) ×U(1) occurs in the Σ(78) sector. The existence of multiplets with a mass around 1 TeV is therefore a prediction of this E6 PsNG scenario. The implication of their existence with regard to proton decay is also discussed.