On the Landscape of Superstring Theory in D > 10

TL;DR

This paper explores unstable heterotic string theories in dimensions greater than ten, revealing a duality with type I string theory involving additional branes and connecting supercritical dimensions to non-singlet open string states.

Contribution

It introduces a new S-duality relating higher-dimensional heterotic theories with type I string theory configurations involving ninebrane-antininebrane pairs.

Findings

Evidence for an S-duality between heterotic and type I string theories.

Identification of Kaluza-Klein modes as dual to non-singlet open string bound states.

Connection of supercritical dimensions to non-perturbative string states.

Abstract

We study a family of unstable heterotic string theories in more than ten dimensions which are connected via tachyon condensation to the ten-dimensional supersymmetric vacuum of heterotic string theory with gauge group SO(32). Calculating the spectrum of these theories, we find evidence for an S-duality which relates type I string theory in ten dimensions with n additional ninebrane-antininebrane pairs to heterotic string theory in 10+n dimensions with gauge group SO(32+n). The Kaluza-Klein modes of the supercritical dimensions are dual to non-singlet bound states of open strings.