A U(3)_C X U(3)_L X U(3)_R gauge symmetry from intersecting D-branes

Understand

A three-family non-supersymmetric model with U(3)^3 gauge symmetry is analyzed in the context of intersecting D-branes.

• This is equivalent to the `trinification' model extended by three U(1) factors which survive as global symmetries in the low energy effective model.
• The Standard Model fermions are accommodated in the three possible bifundamental multiplets represented by strings with endpoints attached on different brane-stacks of this particular setup.
• Further, a natural Quark-Lepton hierarchy is realized due to the existence of the additional abelian symmetries