MASSLESS FERMIONS IN KALUZA-KLEIN MODELS: SU(N) GAUGE FIELDS, ZN SYMMETRY AND STABILITY OF THE METASTABLE VACUUM

Abstract

Kaluza-Klein model on M4×S1 with SU (N) gauge fields and Nf fermions in fundamental representation is considered. It is noted that on one-loop level the lowest state of this theory corresponds to effective four-dimensional theory which has no massless fermions. This statement does not depend on fermion boundary conditions. The state with mass-less four-dimensional fermions is metastable. It is shown that this metastable states can be stabilized by effects of classical gravitation. The same problem of metastability of states with zero fermionic modes can appear in more realistic superstring compactification models and these effects of classical gravitation can resolve this problem of metastability.