Posets of Ordered Compactifications

If (X ′, τ ′,≤′) is an ordered compactification of the partially ordered topological space (X, τ,≤) such that ≤′ is the smallest order that renders (X ′, τ ′,≤′) a T2-ordered compactification of X, then X ′ is called a Nachbin(or order-strict) compactification of (X, τ,≤). If (X ′, τ ′,≤∗) is a finite-point ordered compactification of (X, τ,≤), the Nachbin order ≤′ for (X ′, τ ′) is described in terms of (X, τ,≤) and X ′. When given the usual order relation between compactifications (ordered compactifications), posets of finite-point Nachbin compactifications are shown to have the same order structure as the poset of underlying topological compactifications. Though posets of arbitrary finite-point ordered compactifications are shown to be less well behaved, conditions for their good behavior are studied. These results are used to examine the lattice structure of the set of all ordered compactifications of ordered topological space (X, τ,≤).