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We show that if $x$ is a strongly extreme point of a bounded closed convex subset of a Banach space and the identity has a geometrically and topologically good enough local approximation at $x$, then $x$ is already a denting point. It turns…

Functional Analysis · Mathematics 2019-08-15 Trond A. Abrahamsen , Petr Hájek , Olav Nygaard , Stanimir Troyanski

It is proved that in a commutative unital Banach algebra, every non-maximal closed prime ideal is accessible. Specifically, it can be represented as the intersection of all closed ideals of the algebra that properly contain it.…

Functional Analysis · Mathematics 2025-05-09 Ramesh Garimella

We construct a locally finite graph and a bounded geometry metric space which do not admit a quasi-isometric embedding into any uniformly convex Banach space. Connections with the geometry of $c_0$ and superreflexivity are discussed.

Metric Geometry · Mathematics 2015-01-29 Piotr W. Nowak

We investigate weak$^*$ derived sets, that is the sets of weak$^*$ limits of bounded nets, of convex subsets of duals of non-reflexive Banach spaces and their possible iterations. We prove that a dual space of any non-reflexive Banach space…

Functional Analysis · Mathematics 2021-11-29 Zdeněk Silber

We show that every M\"untz space can be written as a direct sum of Banach spaces X and Y , where Y is almost isometric to a subspace of c and X is finite dimensional. We apply this to show that no M\"untz space is locally octahedral or…

Functional Analysis · Mathematics 2018-11-07 André Martiny

In this paper, we begin by constructing global linear maps on (n-2)-dimensional subspaces, derived from the local continuity of linear transformations among central sections of a convex body. Using these linear maps, we subsequently…

Functional Analysis · Mathematics 2026-04-07 Ning Zhang

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

For a large class of separable Banach spaces, we prove the real analytic Dolbeault Isomorphism Theorem for open subsets.

Complex Variables · Mathematics 2007-05-23 Scott Simon

We show that if an infinite-dimensional Banach space X has a symmetric basis then there exists a bounded, linear operator R : X --> X such that the set A = {x in X : ||R^n(x)|| --> infinity} is non-empty and nowhere dense in X. Moreover, if…

Functional Analysis · Mathematics 2022-06-14 Petr Hajek , Richard J. Smith

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 star-finite coverings of infinite-dimensional normed spaces. A family of sets is called star-finite if each of its members intersects only finitely many other members of the family. It follows by our results that an LUR or a…

Functional Analysis · Mathematics 2020-02-12 Carlo Alberto De Bernardi , Jacopo Somaglia , Libor Vesely

We investigate questions of maximal symmetry in Banach spaces and the structure of certain bounded non-unitarisable groups on Hilbert space. In particular, we provide structural information about bounded groups with an essentially unique…

Functional Analysis · Mathematics 2015-07-08 Valentin Ferenczi , Christian Rosendal

In this paper we give an elementary proof of the fact that every uniquely remotal set is singleton in a finite dimensional strictly convex normed linear space. We show that if A is a uniquely remotal M-compact subset with the derived set of…

Functional Analysis · Mathematics 2024-07-30 D. Sain , K. Paul , A. Ray

We present an infinite dimensional Banach space in which the set of hyperbolic linear isomorphisms in that space is not dense (in the norm topology) in the set of linear isomorphisms.

Dynamical Systems · Mathematics 2015-10-21 Jose F. Alves , Maurizio Monge

We show that for every $1<n<\infty$, there exits a Banach space $X_n$ containing proximinal subspaces of codimension $n$ but no proximinal finite codimensional subspaces of higher codimension. Moreover, the set of norm-attaining functionals…

Functional Analysis · Mathematics 2019-12-18 Miguel Martin

We consider linear bounded operators acting in Banach spaces with a basis, such operators can be represented by an infinite matrix. We prove that for an invertible operator there exists a sequence of invertible finite-dimensional operators…

Functional Analysis · Mathematics 2024-03-12 Alexander Vasilyev , Vladimir Vasilyev , Abu Bakarr Kamanda Bongay

We show that the space of open subsets of any complete and exact symplectic $4$-manifold has infinite dimension with respect to the symplectic Banach-Mazur distance; the quasi-flats we construct take values in the set of dynamically convex…

Symplectic Geometry · Mathematics 2023-11-30 Dan Cristofaro-Gardiner , Richard Hind

The main results of the paper: {\bf (1)} The dual Banach space $X^*$ contains a linear subspace $A\subset X^*$ such that the set $A^{(1)}$ of all limits of weak$^*$ convergent bounded nets in $A$ is a proper norm-dense subset of $X^*$ if…

Functional Analysis · Mathematics 2013-02-26 Mikhail I. Ostrovskii

We show that a pseudoconvex open subset of a Banach space with an unconditional basis is biholomorphic to a closed direct submanifold of a Banach space with an unconditional basis.

Complex Variables · Mathematics 2007-05-23 Aaron Zerhusen

In this paper, we propose the study of a conjecture whose affirmative solution would provide an example of a non-convex Chebyshev set in an infinite-dimensional real Hilbert space.

Functional Analysis · Mathematics 2011-02-17 Biagio Ricceri