文摘
Following Schachermayer, a subset 9e73957c3" title="Click to view the MathML source">B of an algebra A of subsets of Ω is said to have the N-property if a 9e73957c3" title="Click to view the MathML source">B-pointwise bounded subset M of ba(A) is uniformly bounded on A, where ba(A) is the Banach space of the real (or complex) finitely additive measures of bounded variation defined on A. Moreover 9e73957c3" title="Click to view the MathML source">B is said to have the strong N-property if for each increasing countable covering 8ede" title="Click to view the MathML source">(Bm)m of 9e73957c3" title="Click to view the MathML source">B there exists 93add3190391b57e1b073132617e6" title="Click to view the MathML source">Bn which has the N-property. The classical Nikodym–Grothendieck's theorem says that each σ -algebra 9d5" 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 9d5" 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 9d5" title="Click to view the MathML source">S and if 9ef429ae10eb94f61a5" title="Click to view the MathML source">(Bm1,m2,…,mp,mp+1)mp+1 is an increasing countable covering of 8ec" title="Click to view the MathML source">Bm1,m2,…,mp, for each p,mi∈N, e64eb8b29ac47d586e6444ea38e3ed" title="Click to view the MathML source">1⩽i⩽p, then there exists a sequence (ni)i such that each e67a0f" title="Click to view the MathML source">Bn1,n2,…,nr, 9db54b607820" title="Click to view the MathML source">r∈N, has the strong N -property. In particular, for each increasing countable covering 8ede" title="Click to view the MathML source">(Bm)m of a σ -algebra 9d5" title="Click to view the MathML source">S there exists 93add3190391b57e1b073132617e6" 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.