In particle physics, in QFT's, interactions come from the interaction piece in the Lagrangian (action). In string theory, waiting for a complete formulation of SFT, we have to add "by hand" interactions, "gluing together" strings in the WS formalism with vertex operators.
What about brane interactions? Do we have up to day a way (WV formalism?) to describe their interaction? How do branes interact?
I have read (http://arxiv.org/abs/hep-th/9802067) that
In certain limits brane configurations in string theory are well described as solitonic solutions of low energy supergravity, in particular black holes. Interactions between branes are then mainly due to “bulk” gravity...
What does the last sentence refer to?