REPRESENTATIONS OF WEAK AND STRONG INTEGRALS IN BANACH SPACES
Author(s) -
James K. Brooks
Publication year - 1969
Publication title -
proceedings of the national academy of sciences
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.63.2.266
Subject(s) - mathematics , absolute convergence , additive function , series (stratigraphy) , banach space , conditional convergence , representation (politics) , integrable system , pure mathematics , daniell integral , conditional expectation , convergence (economics) , order (exchange) , countable set , weak convergence , mathematical analysis , fourier integral operator , operator theory , fourier series , computer security , law , asset (computer security) , economic growth , computer science , biology , paleontology , political science , econometrics , finance , politics , economics
We establish a representation of the Gelfand-Pettis (weak) integral in terms of unconditionally convergent series. Moreover, absolute convergence of the series is a necessary and sufficient condition in order that the weak integral coincide with the Bochner integral. Two applications of the representation are given. The first is a simplified proof of the countable additivity and absolute continuity of the indefinite weak integral. The second application is to probability theory; we characterize the conditional expectation of a weakly integrable function.
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