3-GENERATION SUPERSTRING MODELS WITH DISCRETE R-SYMMETRIES

Compactification of the ten-dimensional heterotic E8×E8 superstring theory on certain Calabi-Yau manifolds yields three-generation models possessing discrete R symmetries. We consider an example based on Z2 (ordinary symmetry) × Z3 (R symmetry) with four-dimensional gauge symmetry SU(3)c × SU(3)L × SU(3)R. We investigate how features such as adequate suppression of proton decay, appearance of a pair of electroweak scale Higgs doublets, and perturbative unification of the standard model gauge couplings at the compactification scale can emerge from such models. Matter parity and R symmetry, especially the latter, which are related to Z2 and Z3 respectively, play essential roles in our considerations. © 1990.