On complexification of real spaces and its manifestations in the theory of Bochner and Pettis integrals

M. E. Luna-Elizarrarás ; F. Ramírez-Reyes ; M. Shapiro

Contemporary Mathematics. Fundamental Directions, Contemporary problems in mathematics and physics, Tome 64 (2018) no. 4, pp. 706-722

Résumé

This work is a continuation of our work [12] where we considered linear spaces in the following two situations: a real space admits a multiplication by complex scalars without changing the set itself; a real space is embedded into a wider set with a multiplication by complex scalars. We studied there also how they manifest themselves when the initial space possesses additional structures: topology, norm, inner product, as well as what happens with linear operators acting between such spaces. Changing the linearities of the linear spaces unmasks some very subtle properties which are not so obvious when the set of scalars is not changed. In the present work, we follow the same idea considering now Bochner and Pettis integrals for functions ranged in real and complex Banach and Hilbert spaces. Finally, this leads to the study of strong and weak random elements with values in real and complex Banach and Hilbert spaces, in particular, some properties of their expectations.