Classification and Dynamics of Equivalence Classes in SU(N) Gauge Theory on the Orbifold S1/Z2

The dynamical determination of the boundary conditions in SU(N ) gauge theory on the orbifold S 1 /Z 2 is investigated. We classify the equivalence classes of the boundary conditions, and then the vacuum energy density of the theory in each equivalence class is evaluated at one loop order. Unambiguous comparison of the vacuum energy densities in the two theories in different equivalence classes becomes possible in supersymmetric theories. It is found that in the supersymmetric SU( We also study how particular boundary conditions are chosen in the cosmological evolution of the universe. * ) See Refs. 26) and 27) for SUSY breaking and Ref. 18) for gauge symmetry breaking on S 1 /Z 2 by the Hosotani mechanism.