Probing bound states of D-branes

TL;DR

This paper investigates the structure and properties of bound states of D-branes using zero-brane probes, comparing string theory and supergravity calculations, and exploring their short-distance behavior and supersymmetric solutions.

Contribution

It provides a detailed analysis of non-threshold BPS bound states of (p, p+2, p+4)-branes, including supergravity descriptions and short-distance structure insights.

Findings

Stringy and supergravity calculations agree at long distances.

Identifies a supersymmetric supergravity solution for a specific bound state.

Determines the characteristic size of the bound states.

Abstract

A zero-brane is used to probe non-threshold BPS bound states of (p, p+2,p+4)-branes. At long distances the stringy calculation agrees with the supergravity calculations. The supergravity description is given, using the interpretation of the D=8 dyonic membrane as the bound state of a two-brane inside a four-brane. We investigate the short distance structure of these bound states, compute the phase shift of the scattered zero-brane and find the bound states characteristic size. It is found that there should be a supersymmetric solution of type IIa supergravity, describing a bound state of a zero-brane and two orthogonal two-brane, all inside a four-brane , with an additional unbound zero-brane. We comment on the relationship between p-branes and (p-2)-branes.