Duality without supersymmetry

Most recent developments in string duality have focused on string theories with space-time supersymmetry. However, it has not been known whether string duality is a more general phenomenon, and might hold even without supersymmetry. In this talk, I will discuss the methods that can be used for extending duality beyond supersymmetry, and I will present the first known examples of strong/weak coupling duality relations between non-supersymmetric tachyon-free string theories. I will largely focus on the case of the tachyon-free SO(16) × SO(16) string, but I will also consider additional string models as well. Using these duals, I will then propose a phase diagram describing the stability of these strings as functions of their couplings and radii. This talk reports on work [1, 2, 3] performed in collaboration with Julie Blum.