An isomorphic characterization of L 1-spaces.

Abstract: We show that a sequentially (τ)-complete topological vector lattice X _τ is isomorphic to some L ¹(μ), if and only if the positive cone can be written as X ₊ = ℝ₊ B for some convex, (τ)-bounded, and (τ)-closed set B ⊂ X ₊ \ {0}. The same result holds under weaker hypotheses, namely the Riesz decomposition property for X (not assumed to be a vector lattice) and the monotonic σ-completeness (monotonic Cauchy sequences converge). The isometric part of the main result implies the well-known representation theorem of Kakutani for (AL)-spaces. As an application we show that on a normed space Y of infinite dimension, the “ball-generated” ordering induced by the cone Y ₊ = ℝ₊ (for ‖u‖ >) cannot have the Riesz decomposition property. A second application deals with a pointwise ordering on a space of multivariate polynomials. [Copyright &y& Elsevier]