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 E-6 unified theory. We show that extra PsNG multiplets in addition to the expected Higgs doublets necessarily appear in the E-6 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 10 + (10) over bar of SU(5). This is realized when the symmetry breaking E-6 --> SO(10) occurs in the phi(27) + phi((27) over bar) sector, while E-6 --> SU(4)(C) x SU(2)(L) x U(1) x U(1) occurs in the Sigma(78) sector. The existence of 10 + (10) over bar multiplets with a mass around I TeV is therefore a prediction of this E-6 PsNG scenario. The implication of their existence with regard to proton decay is also discussed.