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A boundary for a Banach space is a subset of the dual unit sphere with the property that each element of the Banach space attains its norm on an element of that subset. Trivially, the pointwise convergence with respect to such a boundary is…

Functional Analysis · Mathematics 2008-07-18 Hermann Pfitzner

This thesis addresses Pour-El and Richards' fourth question from their book "Computability in analysis and physics", concerning the relation between higher order recursion theory and computability in analysis. Among other things it is shown…

Logic · Mathematics 2012-07-30 Bjørn Kjos-Hanssen

In this paper, some features of countably $\alpha$-compact topological spaces are presented and proven. The connection between countably $\alpha$% -compact, Tychonoff, and $\alpha$-Hausdorff spaces is explained. The space is countably…

General Topology · Mathematics 2022-05-25 Eman Almuhur , Muhammad Ahsan Khan

We show that Sobolev maps with values in a dual Banach space can be characterized in terms of weak derivatives in a weak* sense. Since every metric space embeds isometrically into a dual Banach space, this implies a characterization of…

Functional Analysis · Mathematics 2023-03-31 Paul Creutz , Nikita Evseev

We study the class of compact spaces that appear as structure spaces of separable Banach lattices. In other words, we analyze what $C(K)$ spaces appear as principal ideals of separable Banach lattices. Among other things, it is shown that…

Functional Analysis · Mathematics 2023-01-25 Antonio Avilés , Gonzalo Martínez Cervantes , Abraham Rueda Zoca , Pedro Tradacete

We find characterizations of Va\v{s}\'ak spaces and weakly $\mathcal{K}$-analytic spaces using the notions of separable projectional resolution of the identity (SPRI) and of projectional skeleton. This in particular addresses a recent…

Functional Analysis · Mathematics 2022-07-05 Claudia Correa , Marek Cúth , Jacopo Somaglia

We complete our recent classification of compact inner symmetric spaces with weakly complex tangent bundle by filling up a case which was left open, and extend this classification to the larger category of compact homogeneous spaces with…

Differential Geometry · Mathematics 2019-01-08 Andrei Moroianu , Uwe Semmelmann

A bounded subset $M$ of a Banach space $X$ is said to be $\varepsilon$-weakly precompact, for a given $\varepsilon\geq 0$, if every sequence $(x_n)_{n\in \mathbb{N}}$ in $M$ admits a subsequence $(x_{n_k})_{k\in \mathbb{N}}$ such that $$…

Functional Analysis · Mathematics 2021-02-03 José Rodríguez

We characterize those classes $\ccc$ of separable Banach spaces admitting a separable universal space $Y$ (that is, a space $Y$ containing, up to isomorphism, all members of $\ccc$) which is not universal for all separable Banach spaces.…

Functional Analysis · Mathematics 2010-06-15 Pandelis Dodos

Every bounded definable open set is a union of finitely many open strong cells in a weakly o-minimal expansion of a real closed field. We prove this fact and another theorem similar to it.

Logic · Mathematics 2026-02-23 Tomohiro Kawakami , Hiroshi Tanaka

We determine topological complexity of a series of finite spaces which is weakly homotopy equivalent to a circle $S^1$, and give a finite space $X$ satisfying the inequality tc$(X) <$ cat$(X {\times} X)$. This answers two conjectures on…

Algebraic Topology · Mathematics 2023-02-14 Ryusei Yoshise

We study directed sets definable in o-minimal structures, showing that in expansions of ordered fields these admit cofinal definable curves, as well as a suitable analogue in expansions of ordered groups, and furthermore that no analogue…

Logic · Mathematics 2021-09-17 Pablo Andujar Guerrero , Margaret E. M. Thomas , Erik Walsberg

One shows for Banach bundles in a certain class that having a second countable locally compact Hausdorff base space and separable fibers implies the separability of the Banach space of the all sections that vanish at infinity. In the…

Functional Analysis · Mathematics 2018-02-07 Aldo J. Lazar

We consider the compact spaces sigma_n(I) of subsets of an uncountable set I of cardinality at most n and their countable products. We give a complete classification of their Banach spaces of continuous functions and a partial topological…

General Topology · Mathematics 2009-03-03 Antonio Avilés

We start the systematic study of Fr\'{e}chet spaces which are $\aleph$-spaces in the weak topology. A topological space $X$ is an $\aleph_0$-space or an $\aleph$-space if $X$ has a countable $k$-network or a $\sigma$-locally finite…

Functional Analysis · Mathematics 2015-10-20 S. Gabriyelyan , J. Kcakol , W. Kubiś , W. Marciszewski

If a separable Banach space $X$ is such that for some nonquasireflexive Banach space $Y$ there exists a surjective strictly singular operator $T:X\to Y$ then for every countable ordinal $\alpha $ the dual of $X$ contains a subspace whose…

Functional Analysis · Mathematics 2010-09-07 Mikhail I. Ostrovskii

Orderability, weak orderability and the existence of continuous weak selections on filter spaces (i.e., spaces with a single non-isolated point) and their products are discussed. We prove that a closed continuous image X of a suborderable…

General Topology · Mathematics 2017-10-19 Koichi Motooka , Dmitri Shakhmatov , Takamitsu Yamauchi

We prove that the class of Banach function lattices in which all relatively weakly compact sets are equi-integrable sets (i.e. spaces satisfying the Dunford-Pettis criterion) coincides with the class of 1-disjointly homogeneous Banach…

Functional Analysis · Mathematics 2019-12-18 Karol Lesnik , Lech Maligranda , Jakub Tomaszewski

In this paper, we study a class of Banach spaces, called \phi-spaces. In a natural way, we associate a measure of weak compactness in such spaces and prove an analogue of Sadovskii fixed point theorem for weakly sequentially continuous…

Functional Analysis · Mathematics 2007-05-23 Cleon S. Barroso , Donal O'Regan

In the setting of Banach lattices the weak (resp. positive) Grothendieck spaces have been defined. We localize such notions by defining new classes of sets that we study and compare with some quite related different classes. This allows us…

Functional Analysis · Mathematics 2021-01-19 Pablo Galindo , V. C. C. Miranda