Smooth String Vacua in a Gravitationally Non-perturbative Regime

The strong coupling regime of four-dimensional N=2 supersymmetric vacua of the heterotic string is analyzed from a dual domain wall perspective. Using modular invariance, we compute a closed form for the non-perturbative corrections to the supersymmetric domain wall equations, which enables a quantitative study of gravitational strong coupling regimes. A strong coupling singularity for the hidden Horava-Witten 9-brane is resolved, and the domain wall interpolates between the visible 9-brane and a supersymmetric Anti-de Sitter vacuum, thereby realizing a variant of the Randall-Sundrum model.