We investigate codimension-one vacua resulting from low energy effective actions in ten-dimensional string models without tachyons.
The main target is the non-supersymmetric Sugimoto USp(32) model, whose nine-dimensional solution is believed to contain backreacting 8-branes. We discuss the defects that interpolate between different vacua, possibly playing the role of the aforementioned 8-branes, and we comment on the Cobordism conjecture.
We also explore other frameworks that break supersymmetry, exhibiting a new solution for the heterotic so(16)xso(16) model and a deformation of the D8 brane in massive type IIA.
Motivated by the general picture emerging in codimension-one, we advance to the general case aiming at a systematic approach to find consistend backgrounds and probe their stability.
We can only take a first step in that direction in models with a dilaton tadpole, that is, we manage to account for the scalar potential. The general case is still work in progress.