Scattering of Strings from D-branes

TL;DR

This paper reviews perturbative calculations of D-brane interactions with massless strings, revealing their effective size, scattering behavior, and absorption processes, which relate to string theory amplitudes and Hawking radiation.

Contribution

It provides a detailed analysis of string-D-brane scattering amplitudes and their physical implications, connecting D-brane features to string interactions and radiation processes.

Findings

D-branes have an effective size of order the string scale that grows with energy.

Scattering amplitudes fall off exponentially at fixed angles.

Closed string absorption by D-branes involves pair production of open strings.

Abstract

We review a number of perturbative calculations describing the interactions of D-branes with massless elementary string states. The form factors for the scattering of closed strings off D-branes are closely related to the Veneziano amplitude. They show that, in interactions with strings, D-branes acquire many of their physical features: the effective size of D-branes is of order the string scale and expands with the energy of the probe, while the fixed angle scattering amplitudes fall off exponentially. We also calculate the leading process responsible for the absorption of closed strings: the amplitude for a closed string to turn into a pair of open strings attached to the D-brane. The inverse of this process describes the Hawking radiation by an excited D-brane.