  This thesis investigates correspondences between open and closed strings.
This is done on the level of coupled open-closed moduli spaces and from a
string field theoretic point of view. The construction of boundary string field
theory on Wess-Zumino-Witten models leads to a conjecture on closed string
backgrounds appearing as non-local operators in open string field theory.
Sample computations for tachyon condensation leading to curved branes support
this conjecture. Additional steps are taken to study supersymmetric string
theories on Calabi-Yau manifolds in the presence of bulk and boundary moduli.
For the topological B-model effective bulk-induced superpotentials for
D5-branes are computed to all orders in the open string couplings.
