One loop scattering on D-branes

We analyze one loop scattering amplitudes of the massless states on a stack of D3-branes. We use the vertex operators that have been obtained in the direct open string analysis developed in arXiv:0708.3452. The method does not have the obstacle of the D9 computation which is associated with the appearance of an $\e$-tensor. The divergence structure is not the same as the D9 brane case. What makes the analysis deviate from the D9 brane case is that the momenta of the states have non-zero components only along the brane directions. We ponder on the possibility that the one-loop divergence may be canceled by adding additional vertex operators at the tree level. We anticipate that they will be "exponentiated" to the free string action, with the resulting action to constitute a non-linear sigma model of the D-brane/AdS geometry.