Evidence for Heterotic - Type I String Duality

TL;DR

This paper investigates the duality between heterotic and Type I superstrings, showing that apparent discrepancies in perturbation theories can be reconciled, supporting their conjectured equivalence through duality and brane analysis.

Contribution

It provides evidence for heterotic-Type I string duality by analyzing world-sheet structures and perturbation breakdown mechanisms, revealing their equivalence.

Findings

Type I perturbation theory breaks down when heterotic strings have certain massless particles.

Dirichlet one-brane in Type I shares world-sheet features with heterotic strings.

Heterotic and Type I theories are likely equivalent due to duality mechanisms.

Abstract

A study is made of the implications of heterotic string $T$-duality and extended gauge symmetry for the conjectured equivalence of heterotic and Type I superstrings. While at first sight heterotic string world-sheet dynamics appears to conflict with Type I perturbation theory, a closer look shows that Type I perturbation theory ``miraculously'' breaks down, in some cases via novel mechanisms, whenever the heterotic string has massless particles not present in Type I perturbation theory. This strongly suggests that the two theories actually are equivalent. As further evidence in the same direction, we show that the Dirichlet one-brane of type I string theory has the same world-sheet structure as the heterotic string.