World-volume potentials on D-branes

By evaluating string scattering amplitudes, we investigate various low ener gy interactions for the massless scalars on a non-abelian Dirichlet brane. We confirm the existence of couplings of closed string fields to the world- volume scalars, involving commutators of the latter. Our results are consis tent with the recently proposed non-abelian world-volume actions for Dp-bra nes.