Superstring Scattering from D-Branes Bound States

TL;DR

This paper derives covariant scattering amplitudes for massless closed strings interacting with D-brane bound states, confirming their consistency with known effective actions and providing detailed background field calculations.

Contribution

It provides the first fully covariant expressions for disk scattering amplitudes involving mixed boundary conditions for massless closed strings.

Findings

Derived covariant two-point scattering amplitudes with mixed boundary conditions.

Confirmed that background fields match D$p$-brane bound state solutions.

Showed consistency with Born-Infeld and Chern-Simons actions.

Abstract

We derive fully covariant expressions for disk scattering amplitudes of any two massless closed strings in which mixed Neumann and Dirichlet world-sheet boundary conditions are included. From the two-point amplitudes, we derive the long range background fields and verify that they correspond to D$p$-brane bound state. Also, from the scattering amplitudes, we calculate the linear coupling of closed string fields to D-brane world-volume and show that they are consistent with Born-Infeld and Chern-Simons actions in the presence of a background field.