Retract varieties of lattice ordered groups
Let , be Archimedean Riesz spaces and be the ordered vector space of all order bounded operators from into . We define a Lamperti Riesz subspace of to be an ordered vector subspace of such that the elements of preserve disjointness and any pair of operators in has a supremum in that belongs to . It turns out that the lattice operations in any Lamperti Riesz subspace of are given pointwise, which leads to a generalization of the classic Radon-Nikod’ym theorem for Riesz homomorphisms....
Let , and denote the -groups of integer-valued, rational-valued and real-valued continuous functions on a topological space , respectively. Characterizations are given for the extensions to be rigid, major, and dense.
-rings are commutative rings whose factor rings modulo prime ideals are valuation rings. -rings occur most naturally in connection with partially ordered rings (= porings) and have been studied only in this context so far. The present note first develops the theory of -rings systematically, without assuming the presence of a partial order. Particular attention is paid to the question of axiomatizability (in the sense of model theory). Partially ordered -rings (-porings) are introduced, and...