Deformed Intersecting D6-Brane GUTS and N=1 SUSY
  We analyze the construction of non-supersymmetric three generation six-stack Pati-Salam (PS) $SU(4)_C \times SU(2)_L \times SU(2)_R$ GUT classes of models, by localizing D6-branes intersecting at angles in four dimensional orientifolded toroidal compactifications of type IIA. Special role in the models is played by the presence of extra branes needed to satisfy the RR tadpole cancellation conditions. The models contain at low energy {\em exactly the Standard model} with no extra matter and/or extra gauge group factors. They are build such that they represent deformations around the quark and lepton basic intersection number structure. The models possess the same phenomenological characteristics of some recently discussed examples (PS-A, PS-I; PS-II GUT classes; hep-th/0203187, hep-th/0209202; hep-th/0210004) of four and five stack PS GUTS respectively. Namely, there are no colour triplet couplings to mediate proton decay and proton is stable as baryon number is a gauged symmetry.   The mass relation $m_e = m_d$ at the GUT scale is recovered. Even though more complicated, than in lower stack GUTS, the conditions of the non-anomalous U(1)'s to survive massless the generalized Green-Schwarz mechanism are solved consistently by the angle conditions coming from the presence of N=1 supersymmetric sectors involving the presence of {\em extra} branes and also required for the existence of a Majorana mass term for the right handed neutrinos. 
Christos Kokorelis