Truly Strong Coupling and Large Radius in String Theory

TL;DR

This paper demonstrates a region in heterotic string theory where the coupling is large and the compactification radius is also large, challenging the notion of weakly coupled descriptions of the universe.

Contribution

It identifies a specific strong coupling, large radius region in heterotic string theory, expanding understanding of possible string vacua beyond weak coupling regimes.

Findings

Large coupling and radius region in heterotic string theory identified

Implications for coupling unification and calculability discussed

Challenges to weakly coupled string descriptions highlighted

Abstract

String theory, if it describes nature, is probably strongly coupled. In light of recent developments in string duality, this means that the ``real world'' should correspond to a region of the classical moduli space which admits no weak coupling description. We exhibit, in the heterotic string, one such region of the moduli space, in which the coupling, $\lambda$, is large and the ``compactification radius'' scales as $\lambda^{1/3}$. We discuss some of the issues raised by the conjecture that the true vacuum lies in such a region. These include the question of coupling constant unification, and more generally the problem of what quantities one might hope to calculate and compare with experiment in such a picture.