Superstring Scattering from D-Branes
Mohammad R. Garousi, Robert C. Myers
TL;DR
The paper computes covariant two-point scattering amplitudes of massless closed strings from D$p$-branes in type II string theory and shows these amplitudes are directly obtainable from four-point open-string amplitudes, reflecting a KLT-like open/closed factorization mediated by the D-brane boundary. By analyzing the massless $t$-channel poles, the authors extract the long-range background fields and demonstrate their agreement with extremal $p$-brane solutions in the low-energy action, identifying the D$p$-brane tension and RR charges. The work provides explicit amplitudes across NS-NS, RR, and fermionic sectors, verifies gauge/Ward identities, and connects worldsheet results to spacetime supergravity and boundary-state descriptions, with implications for SUSY and dualities in D-brane physics.
Abstract
We derive fully covariant expressions for all two-point scattering amplitudes of two massless closed strings from a Dirichlet $p$-brane. This construction relies on the observation that there is a simple relation between these D-brane amplitudes in type II superstring theory and four-point scattering amplitudes for type I open superstrings. From the two-point amplitudes, we derive the long range background fields for the D-branes, and verify that as expected they correspond to those of extremally charged $p$-brane solutions of the low energy effective action.