Effective Descent Morphisms of Filtered Preorders

Abstract

We characterize effective descent morphisms of what we call filtered preorders, and apply these results to slightly improve a known result, due to the first author and F. Lucatelli Nunes, on the effective descent morphisms in lax comma categories of preorders. A filtered preorder, over a fixed preorder X, is defined as a preorder A equipped with a profunctor \(X\rightarrow A\) and, equivalently, as a set A equipped with a family \((A_x)_{x\in X}\) of upclosed subsets of A with \(x'\leqslant x\Rightarrow A_x\subseteq A_{x'}\).