Generalizing Gelfand duality to Nachbin spaces

We introduce the notion of a Nachbin proximity on a bounded archimedean $\ell$-algebra (bal-algebra). We prove that Gelfand duality lifts to yield a dual equivalence between the categories of uniformly complete bal-algebras equipped with a closed Nachbin proximity and of Nachbin spaces (compact ordered spaces). The key ingredients of the proof include appropriate generalizations of the Stone-Weierstrass theorem and Dieudonné's lemma. We also develop an alternate approach by means of bounded archimedean $\ell$-semialgebras (sbal-algebras), from which we derive De Rudder--Hansoul duality.