Stone Duality for Preordered Topological Spaces
Jean Goubault-Larrecq
TL;DR
This work develops a Stone-like duality for preordered topological spaces by introducing ad-frames, a bipartite pointfree structure linking frames with completely distributive lattices through tot, con, sup, and sub relations. It defines the adjunction $\mathcal{O}^{ad} \dashv \textbf{pt}^{ad}$ between $\mathbf{PreTop}$ and $\mathbf{adFrm}^{op}$, and constructs ad-sobrification $X^{ads}$ with unit $\eta_X$, showing $\textbf{pt}^{ad}\, \mathcal{O}^{ad} X \cong X^{ads}$; this route generalizes classical Stone duality while avoiding point-based conditions on the dual side. The theory also relates soberification to ad-soberification, proving the idempotence of the adjunction via a monad $\_^{ads}$ and clarifying how the red/purple/blue variants capture future/past or both viewpoints. Moreover, the adjunction lifts the standard $\mathcal{O} \dashv \textbf{pt}$ adjunction, yielding a topological-functorial comparison and highlighting cases where the lifting aligns with sobriety. Overall, the framework opens avenues toward ad-locales and constructive logic applications, and points toward extensions to streams and ordered-logical semantics.
Abstract
A preordered topological space is a topological space with a preordering. We exhibit a Stone-like duality for preordered topological spaces, Inspired by a similar duality for bitopological spaces, due to Jung-Moshier and Jakl, and by a duality for preordered sets due to Bonsangue, Jacobs and Kok.
