Norihito Toyota

Integral dimension in the string theory based on a group manifold

We study string models on a group manifold with Kac-Moody symmetry where the critical dimensiond is integer. In particular the possibility of fourdimensional models is investigated. We find that only nine group manifolds with a relevant level can have four as the critical dimension among an infinite number of compact Lee groups. They re all listed. The models with minimal conformal sectors adding to the Kac-Moody sector are investigated. In the cases with one minimal conformal sector, there are only two groups,SU (5) andSO (43), that can gived=4. Among the cases with some tensoring products of minimal conformal sectors we discuss a few special cases withk=0 andk=1. The cases based onN=1 super Kac-Moody algebra are also studied. Finally we discuss the possibility of the enlargement of gauge symmetry.

Mac hypothesis in a superstring inspired model

Abstract We study a superstring inspired E6 model based on the MAC hypothesis. We find two kinds of model in which the proton decay through the colored Higgs is naturally suppressed and every field in 27 of E6 carries a role; a pair of colored fields in 27 are necessary to cause the MAC condensation and two doublet fields in 27 cause the usual Higgs mechanism at the electroweak breaking. The fields left in 27 are identified with quarks and leptons adding to vLc.