The Heterotic String is a Soliton

TL;DR

This paper demonstrates that the Type IIA superstring on K3 has a soliton structure matching the heterotic string on a four-torus, supporting a duality conjecture between these six-dimensional string theories.

Contribution

It provides evidence for a duality by constructing a smooth soliton in Type IIA theory that mirrors heterotic string properties, including zero mode structure and gauge symmetry enhancements.

Findings

Type IIA on K3 has a soliton with heterotic zero modes.

Stable loops of soliton strings yield charged Ramond-Ramond states.

Type IIB strings also exhibit multiplet solutions with Type II worldsheets.

Abstract

It is shown that the Type IIA superstring compactified on $K3$ has a smooth string soliton with the same zero mode structure as the heterotic string compactified on a four torus, thus providing new evidence for a conjectured exact duality between the two six-dimensional string theories. The chiral worldsheet bosons arise as zero modes of Ramond-Ramond fields of the IIA string theory and live on a signature $(20,4)$ even, self-dual lattice. Stable, finite loops of soliton string provide the charged Ramond-Ramond states necessary for enhanced gauge symmetries at degeneration points of the $K3$ surface. It is also shown that Type IIB strings toroidally compactified to six dimensions have a multiplet of string solutions with Type II worldsheets.