MoreD-brane bound states

The low-energy background field solutions corresponding to $D$-brane bound states which possess a difference in dimension of two are presented. These solutions are constructed using the $T$-duality map between the type IIA and IIB superstring theories. Since supersymmetry is preserved by $T$ duality, the bound state solutions retain the supersymmetric properties of the initial (single) $D$-brane states from which they are produced; i.e., they preserve one-half of the supersymmetries.