Duality constraints on effective actions

Superstring theories at low energy limit are described by the corresponding supergravities, and their non-perturbative D-brane/O-plane excitations are described by DBI and WZ actions. Higher derivative corrections to these effective actions are important for understanding the stringy behavior of the fundamental objects. They may be extracted from the contact terms of the corresponding S-matrix elements. On the other hand, the superstring theories enjoy the T- and S-dualities which appear in the S-matrix elements as duality Ward identities. These Ward identities might be used as generating functions for constructing the S-matrix elements. The dualities may also be used directly to construct the effective actions. In this article, we review the duality Ward identities which can be used to generate S-matrix elements, and review the dualities which may be used directly to construct the higher derivative corrections to the effective actions.