Speaker: Prof. Tianjun Li
Coordinates: PCFT C1124, 16:00, Friday, August 9
Abstract: We provide a systematic construction of three-family N=1 supersymmetric Pati-Salam models from Type IIA orientifolds on T^6/(Z_2 × Z_2) with intersecting D6-branes. All the gauge symmetries SU(4)_C × SU(2)_L × SU(2)_R arise from the stacks of D6-branes with U(n) gauge symmetries, while the hidden sector is specified by USp(n) D6-branes. The Pati-Salam gauge symmetry can be broken down to the SU(3)_C × SU(2)_L × U(1)_{B-L} × U(1)_{I_{3R}} via D6-brane splittings, and further down to the Standard Model (SM) via the D- and F-flatness preserving Higgs mechanism from massless open string states in a N=2 subsector. In addition, we propose a systematic method to construct all the possible three-family N=1 supersymmetric Pati-Salam models by solving all the common solutions for the RR tadpole cancellation conditions, N=1 supersymmetry conditions, and three generation conditions with deterministic algorithm. We show that there are only 33 independent models with different gauge coupling relations at string scale after modding out equivalent relations. In particular, there is one and only one independent model which has string-scale gauge coupling unification. Moreover, we can decouple the exotic particles in these models, realize the gauge coupling relation at string scale, and explain the SM fermion masses and mixings, etc.