D-brane Bound States and the Generalised ADHM Construction

TL;DR

This paper explores the sigma model description of D-brane bound states, specifically D-strings bound to D-fivebranes, revealing their connection to instanton moduli spaces and compactified string theories.

Contribution

It introduces a sigma model framework for D-brane bound states and links it to instanton moduli spaces and compactified string theory models.

Findings

Describes the sigma model on the moduli space of Sp(k) instantons.

Connects the bound state description to symmetric products of K3 surfaces.

Provides insights into the geometric structure of D-brane bound states.

Abstract

We discuss the sigma model description of a D-string bound to k D-fivebranes in type I string theory. The effective theory is an (0,4) supersymmetric hyper-Kahler with torsion sigma model on the moduli space of Sp(k) instantons on R^4. Upon toroidal compactification to five dimensions the model is related to the type II picture where the target space is a symmetric product of K3's.