文摘
Following Schachermayer, a subset B of an algebra a9050be4c3b7e8009b7a7" title="Click to view the MathML source">A of subsets of Ω is said to have the N-property if a B-pointwise bounded subset M of bb3380556" title="Click to view the MathML source">ba(A) is uniformly bounded on a9050be4c3b7e8009b7a7" title="Click to view the MathML source">A, where bb3380556" title="Click to view the MathML source">ba(A) is the Banach space of the real (or complex) finitely additive measures of bounded variation defined on a9050be4c3b7e8009b7a7" title="Click to view the MathML source">A. Moreover B is said to have the strong N-property if for each increasing countable covering (Bm)m of B there exists 91b57e1b073132617e6" title="Click to view the MathML source">Bn which has the N-property. The classical Nikodym–Grothendieck's theorem says that each σ -algebra b4f6294129d5" title="Click to view the MathML source">S of subsets of Ω has the N-property. The Valdivia's theorem stating that each σ -algebra b4f6294129d5" title="Click to view the MathML source">S has the strong N -property motivated the main measure-theoretic result of this paper: We show that if (Bm1)m1 is an increasing countable covering of a σ -algebra b4f6294129d5" title="Click to view the MathML source">S and if (Bm1,m2,…,mp,mp+1)mp+1 is an increasing countable covering of Bm1,m2,…,mp, for each b4d" title="Click to view the MathML source">p,mi∈N, e64eb8b29ac47d586e6444ea38e3ed" title="Click to view the MathML source">1⩽i⩽p, then there exists a sequence (ni)i such that each e58acee67a0f" title="Click to view the MathML source">Bn1,n2,…,nr, a907a9db54b607820" title="Click to view the MathML source">r∈N, has the strong N -property. In particular, for each increasing countable covering (Bm)m of a σ -algebra b4f6294129d5" title="Click to view the MathML source">S there exists 91b57e1b073132617e6" title="Click to view the MathML source">Bn which has the strong N-property, improving mentioned Valdivia's theorem. Some applications to localization of bounded additive vector measures are provided.