Type IIA orientifolds: intersecting brane worlds
We now move to a different corner in the pentagon in Figure 7.1 and turn to the construction of type IIA orientifold compactifications down to four dimensions. The use of D-branes and their properties is crucial in these constructions, and provides a beautiful geometrical picture of the resulting 4d theories; gauge symmetries arise from overlapping D-branes, while charged chiral fermions arise from intersections among D-branes. The models are dubbed intersecting brane models and provide simple realizations of particle physics models in string theory.
10.1 Type II on CY and orientifolding
We now step back to Section 7.2 and consider the 4d compactification of type II theories on CY manifolds. ...