A General Framework for Operator Continuity between Riesz Spaces

Abstract

We introduce and study $\mathcal{FG}$-order continuous operators between Riesz spaces, based on Tantrawan's generalized (unbounded) order convergence. This framework includes several familiar classes of operators and allows their properties to be studied in a unified setting. We establish order boundedness and lattice-theoretic results; in particular, we show that strongly order continuous operators are automatically order bounded and prove that the modulus of an order bounded $\mathcal{FG}$-order continuous operator remains $\mathcal{FG}$-order continuous under suitable assumptions. The latter result gives an affirmative answer to a previously posed problem for strongly order continuous operators. We also establish a general result ensuring classical order continuity, from which order continuity results for several familiar classes of operators follow. Furthermore, we characterize, under suitable hypotheses, when the space of order bounded $\mathcal{FG}$-order continuous operators is a band. Finally, we prove an extension theorem for positive $\mathcal{FG}$-order continuous operators, providing a counterpart of Veksler's extension theorem in this framework.