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In this paper we have shown that a double sequence in a topological space satisfies certain conditions which in turn are capable to generate a topology on a non empty set. Also we have used the idea of I-convergence of double sequences to…

General Topology · Mathematics 2016-09-05 Amar Kumar Banerjee , Rahul Mondal

This article is a continuation of a paper of the first author \cite{F} about complex structures on real Banach spaces. We define a notion of even infinite dimensional real Banach space, and prove that there exist even spaces, including HI…

Functional Analysis · Mathematics 2007-05-23 Valentin Ferenczi , Eloi Medina Galego

We give a new proof of a characterization of the closeness of the range of a continuous linear operator and of the closeness of the sum of two closed vector subspaces of a Banach space. Then we state sufficient conditions for the closeness…

Functional Analysis · Mathematics 2015-10-06 Joël Blot , Philippe Cieutat

The following strengthening of the Elton-Odell theorem on the existence of a $(1+\epsilon)-$separated sequences in the unit sphere $S_X$ of an infinite dimensional Banach space $X$ is proved: There exists an infinite subset $S\subseteq S_X$…

Functional Analysis · Mathematics 2019-02-19 Eftychios Glakousakis , Sophocles Mercourakis

We study the interplay between Banach space theory and theory of analytic P-ideals. Applying the observation that, up to isomorphism, all Banach spaces with unconditional bases can be constructed in a way very similar to the construction of…

Logic · Mathematics 2019-06-03 Piotr Borodulin-Nadzieja , Barnabás Farkas

An overpartition is a partition such that the first occurrence (equivalently, the last occurrence) of a number may be overlined. In this article, we investigate three contents of overpartitions. We first consider the $r$-chain minimal and…

Combinatorics · Mathematics 2026-01-29 Y. H. Chen , Y. Q. Chen , Thomas Y. He , H. X. Huang , X. Zhang

In this paper we settle in the negative the problem of the superreflexivity of Garling sequence spaces by showing that they contain a complemented subspace isomorphic to a non superreflexive mixed-norm sequence space. As a by-product of our…

Functional Analysis · Mathematics 2018-09-11 Fernando Albiac , Jose L. Ansorena , Stephen J. Dilworth , Denka Kutzarova

The existence of a Banach limit as a translation invariant positive continuous linear functional on the space of bounded scalar sequences which is equal to 1 at the constant sequence (1,1,...,1,...) is proved in a first course on functional…

Functional Analysis · Mathematics 2019-06-12 M. A. Sofi

We study Banach spaces satisfying some geometric or structural properties involving tightness of transfinite sequences of nested linear subspaces. These properties are much weaker than WCG and closely related to Corson's property (C). Given…

Functional Analysis · Mathematics 2011-01-25 Jarno Talponen

We give a complete description of the structure of the connected components of the general linear group of a real hereditarily indecomposable Banach space, depending on the existence of complex structures on the space itself and on its…

Functional Analysis · Mathematics 2020-09-11 N. de Rancourt

The main result: the dual of separable Banach space $X$ contains a total subspace which is not norming over any infinite dimensional subspace of $X$ if and only if $X$ has a nonquasireflexive quotient space with the strictly singular…

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

Extending the classical notion of the spreading model, the $k$-spreading models of a Banach space are introduced, for every $k\in\mathbb{N}$. The definition, which is based on the $k$-sequences and plegma families, reveals a new class of…

Functional Analysis · Mathematics 2011-05-16 S. A. Argyros , V. Kanellopoulos , K. Tyros

We introduce the operators "modified limit" and "accumulation" on a Banach space, and we use this to define what we mean by being internally computable over the space. We prove that any externally computable function from a computable…

Logic · Mathematics 2015-07-01 Dag Normann

In this paper, the split common null point problem in two Banach spaces is considered. Then, using the generalized resolvents of maximal monotone operators and the generalized projections and an infinite family of nonexpansive mappings, a…

Functional Analysis · Mathematics 2021-03-29 Bijan Orouji , Ebrahim Soori

We study the complementation (in $\ell_\infty$) of the Banach space $c_{0,\mathcal{I}}$, consisting of all bounded sequences $(x_n)$ that $\mathcal{I}$-converge to $0$, endowed with the supremum norm, where $\mathcal{I}$ is an ideal of…

Functional Analysis · Mathematics 2026-03-19 Michael A. Rincón-Villamizar , Carlos Uzcátegui Aylwin

If a Banach space has an unconditional basis it either contains a continuum of non isomorphic subspaces or is isomorphic to its square and hyperplanes and satisfies other regularity properties. An HI Banach space contains a continuum of non…

Functional Analysis · Mathematics 2014-02-25 Valentin Ferenczi , Christian Rosendal

We consider several quantities related to weak sequential completeness of a Banach space and prove some of their properties in general and in $L$-embedded Banach spaces, improving in particular an inequality of G. Godefroy, N. Kalton and D.…

Functional Analysis · Mathematics 2011-03-18 O. F. K. Kalenda , H. Pfitzner , J. Spurný

We show that every Banach space in which weakly compact sets are super weakly compact in automatically weakly sequentially complete answering a question by Silber (2024). In the proof we show how to build a weakly compact set which is not…

Functional Analysis · Mathematics 2025-01-29 Zdeněk Silber

We investigate rich subspaces of $L_1$ and deduce an interpolation property of Sidon sets. We also present examples of rich separable subspaces of nonseparable Banach spaces and we study the Daugavet property of tensor products.

Functional Analysis · Mathematics 2011-03-17 Vladimir Kadets , Nigel Kalton , Dirk Werner

Here we consider a perturbation of continuous mappings on Banach spaces and investigate their image under various conditions. Consequently, we study the solvability of some classes of equations and inclusions. For these, we start by the…

Functional Analysis · Mathematics 2023-10-11 Kamal N. Soltanov