On weak convergence in Köthe-Bochner function spaces

Abstract

Let $E$ be an order continuous Köthe function space over a non purely atomic probability measure $μ$ and let $X$ be a Banach space, with topological duals $E^*$ and $X^*$, respectively. Let $E(X)$ and $E^*(X^*)$ be the corresponding Köthe-Bochner function spaces and consider $E^*(X^*)$ as a subspace of $E(X)^*$. We prove that if $X^*$ fails the Radon-Nikodým property, then there is a bounded, non weakly null sequence $(f_n)$ in $E(X)$ such that $\langle φ,f_n\rangle \to 0$ for every $φ\in E^*(X^*)$; in particular, the closed unit ball of $E^*(X^*)$ is not a James boundary for $E(X)$. This extends a result by B. Cascales and A.J. Pallarés [Collect. Math. 45 (1994), 263--270] on the case $E=L_1(μ)$ and allows us to answer a question posed recently by S. Dwivedi [Rev. Real Acad. Cienc. Exactas Fis. Nat. Ser. A-Mat. RACSAM 120 (2026), 71].