GUT breaking on M(4)xT(2)/(Z(2)xZ(2)')

We construct two SU(5) models on the space-time M-4 x T-2/(Z(2) x Z(2)') wh ere the gauge and I-Eggs fields are in the bulk and the Standard Model ferm ions are on the brane at the fixed point or line. For the zero modes, the S U(5) gauge symmetry is broken down to SU(3) x SU(2) x U(1) due to non-trivi al orbifold projection. In particular, if we put the Standard model fermion s on the 3-brane at the fixed point in model II, we only have the zero mode s and KK modes of the Standard Model gauge fields and two Higgs doublets on the observable 3-brane. So, we can have the low energy unification, and so lve the triplet-doublet splitting problem, the gauge hierarchy problem, and the proton decay problem. (C) 2001 Published by Elsevier Science B.V.