Beyond the SM; D-brane model building from intersecting brane worlds
  We discuss the appearance of non-supersymmetric D6-brane GUT model constructions. We focus on the construction of the first examples of flipped SU(5) and SU(5) GUTS which have only the SM at low energy. These constructions are based on 4D compactifications in Z3 toroidal orientifolds of type IIA with D6-branes intersecting at angles. 
Christos Kokorelis