ABSTRACT
This chapter shows that the boundary state is also a very efficient tool to obtain the classical solution corresponding to a Dp-brane at long distances. To obtain the long-distance behaviour of the fields emitted by a Dp-brane, one simply adds a closed string propagator to the boundary state and then projects the resulting expression onto the various massless states of the closed string spectrum. The chapter derives equations representing the leading long-distance behaviour of the massless fields emitted by the Dp-brane. By inserting more boundaries on the closed string world-sheet, i.e. by introducing more boundary states, one can perturbatively reconstruct the exact brane solution of the supergravity field equations. The chapter concludes that the boundary state provides the complete conformai description of the D-branes of string theory.
