The effective action of D7-branes in image Calabi–Yau orientifolds Original Research Article

Using a Kaluza–Klein reduction of the Dirac–Born–Infeld and Chern–Simons action we compute the four-dimensional image effective action for the massless modes of a D7-brane which is wrapped on a four-cycle of a compact Calabi–Yau orientifold. We do not consider a specific orientifold but instead determine the Kähler potential, the gauge kinetic functions and the scalar potential in terms of geometrical data of a generic orientifold and its wrapped four-cycle. In particular we derive the couplings of the D-brane excitations to the bulk moduli of the orientifold as they are important for the study of soft supersymmetry breaking terms. We relate the resulting Kähler geometry to the image special geometry of Lerche, Mayr and Warner. Finally we comment on the structure of the D-term which is induced by a Green–Schwarz term in the Chern–Simons action.