Graviton Scattering on D6 Branes with B Fields
  We consider systems of D6 branes in the presence of a nonzero $B$ field of different ranks. We study the scattering of gravitons in the corresponding supergravity backgrounds. We show that the nonzero $B$ field does not modify the form of the scattering potential. The graviton scattering equation has two solutions one normalizable and one non-normalizable. The normalizable solution does not lead to an absorption, however the non-normalizable one does. We analyse the absorption of gravitons by the branes and show that it is nonzero in the decoupling limit. This result suggests that even in the presence of a $B$ field the D6 branes worldvolume theory does not decouple from the bulk gravity. For comparison we analyse the form of the scattering potential and absorption for Dp branes with $p <5$ and for NS5 branes. 
Mohsen Alishahiha, Harald Ita, Yaron Oz