Yukawa Couplings from D-branes on non-factorisable Tori

Abstract

In this thesis Yukawa couplings from D-branes on non-factorisable tori are computed. In particular intersecting D6-branes on the torus, generated by the SO(12) root lattice, is considered, where the Yukawa couplings arise from worldsheet instantons. Thereby the classical part to the Yukawa couplings are determined and known expressions for Yukawa couplings on factorisable tori are extended.newline Further Yukawa couplings for the T-dual setup are computed. Therefor three directions of the SO(12) torus are T-dualized and the boundary conditions of the D6-branes are translated to magnetic fluxes on the torus. Wavefunctions for chiral matter are calculated, where the expressions, known from the factorisable case, get modified in a non-trivial way. Integration of three wavefunctions over the non-factorisable torus yields the Yukawa couplings. The result not only confirms the results from the computations on the SO(12) torus, but also determines the quantum contribution to the couplings. This thesis also contains a brief review to intersecting D6-branes on Z2xZ2 orientifolds, with applications to a non-factorisable orientifold, generated by the SO(12) root lattice.