On SO(32) heterotic - type I superstring duality in ten dimensions

TL;DR

This paper provides evidence supporting the strong-weak coupling duality between SO(32) heterotic and type I superstring theories in ten dimensions by comparing low-energy effective actions and their $F^4$ terms.

Contribution

It demonstrates that the $F^4$-term coefficients at one-loop and tree-level match, supporting the duality conjecture without higher-loop corrections.

Findings

The $F^4$-term coefficient in heterotic string at one-loop matches the type I tree-level coefficient.

Higher-loop corrections to these terms are argued to be absent.

Supports the strong-weak duality between the two string theories.

Abstract

We provide some additional evidence in favour of the strong - weak coupling duality between the SO(32) heterotic and type I superstring theories by comparing terms quartic in the gauge field strength in their low-energy effective actions. We argue that these terms should not receive higher-loop string corrections so that duality should relate the leading-order perturbative coefficients in the two theories. In particular, we demonstrate that the coefficient of the $F^4$-term in the one-loop (torus) part of the SO(32) heterotic string action is exactly the same as the coefficient of the $F^4$-term in the tree-level (disc) part of the type I action.