On factorisation systems for Ord-enriched categories and categories of partial maps

Abstract: In this work we discuss a new type of factorisation systems for \textbf{Ord}-enriched categories. We start by defining the new notion of lax weak orthogonality, which involves the existence of lax diagonal morphisms for lax squares. Using the usual theory of factorisation systems as a blueprint, we introduce a lax version of weak and functorial factorisation systems. We provide a characterisation of lax functorial weak factorisation systems, namely lax weak factorisation systems such that their factorisations are lax functorial. Then, we present a particular case of such lax functorial weak factorisation systems which are equipped with additional lax monad structures. We finally explore some examples of these factorisation systems for categories of partial maps equipped with natural Ord-enrichments. We will first construct a particular lax algebraic weak factorisation system for categories of partial maps that isolates the total datum and the partial domain of a partial map. Then we will discuss the relation between factorisation systems on the base category and oplax factorisation systems on the induced category of partial maps.