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A topological space is iso-dense if it has a dense set of isolated points. A topological space is scattered if each of its non-empty subspaces has an isolated point. In $\mathbf{ZF}$, in the absence of the axiom of choice, basic properties…

General Topology · Mathematics 2021-01-11 Kyriakos Keremedis , Eleftherios Tachtsis , Eliza Wajch

In a recent article, Khojasteh et al. introduced a new class of simulation functions, Z-contractions, with blending over known contractive conditions in the literature. Subsequently, in this paper, we extend and generalize the results on…

Functional Analysis · Mathematics 2016-10-04 Ankush Chanda , Lakshmi Kanta Dey

Let C be a nonempty, bounded, closed, and convex subset of a Banach space X and $T : C \rightarrow C$ be a monotone asymptotic nonexpansive mapping. In this paper, we investigate the existence of fixed points of T. In particular, we…

Functional Analysis · Mathematics 2016-10-04 Monther Rashed Alfuraidan , Mohamed Amine Khamsi

We study countable saturation of the metric reduced products and introduce continuous fields of metric models indexed by locally compact, separable, completely metrizable spaces. Saturation of the reduced product depends both on the…

Logic · Mathematics 2015-12-02 Ilijas Farah , Saharon Shelah

For a compact Hausdorff space $S$, we prove that the closed unit ball of a closed linear subalgebra of the space of real-valued continuous functions on $S$, denoted by $C(S)$, satisfies property-$(P_1)$ (the set-valued generalization of…

Functional Analysis · Mathematics 2023-03-21 Teena Thomas

Given a compact metric space $X$, we associate to it an inverse sequence of finite $T_0$ topological spaces. The inverse limit of this inverse sequence contains a homeomorphic copy of $X$ that is a strong deformation retract. We provide a…

Geometric Topology · Mathematics 2022-03-14 Pedro J. Chocano , Manuel A. Morón , Francisco R. Ruiz del Portal

We show a few fixed point theorems for semigroups acting on weakly compact convex subsets of Banach spaces when $LUC(S), AP(S), WAP(S)$ or $WAP(S)\cap LUC(S)$ have a left invariant mean. In particular, we give a characterization of…

Functional Analysis · Mathematics 2016-12-20 Andrzej Wiśnicki

We give necessary and sufficient conditions for a real-valued quasiconvex function f on a Baire topological vector space X (in particular, Banach or Frechet space) to be continuous at the points of a residual subset of X. These conditions…

Optimization and Control · Mathematics 2015-01-20 Patrick J. Rabier

We prove that a metric measure space $(X,d,m)$ satisfying finite dimensional lower Ricci curvature bounds and whose Sobolev space $W^{1,2}$ is Hilbert is rectifiable. That is, a $RCD^*(K,N)$-space is rectifiable, and in particular for…

Differential Geometry · Mathematics 2019-05-08 Andrea Mondino , Aaron Naber

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

We provide a pointwise bipolar theorem for liminf-closed convex sets of positive Borel measurable functions on a sigma-compact metric space without the assumption that the polar is a tight set of measures. As applications we derive a…

Functional Analysis · Mathematics 2019-02-12 Daniel Bartl , Michael Kupper

In this article, we introduce and investigate the concept of partial quasi-metric type space as a generalization of both partial quasi-metric and quasi-metric type spaces. We show that many important constructions studied in K\"unzi's…

General Topology · Mathematics 2019-03-18 Yaé Ulrich Gaba

For every filter $\mathcal F$ on $\mathbb N$, we introduce and study corresponding uniform $\mathcal F$-boundedness principles for locally convex topological vector spaces. These principles generalise the classical uniform boundedness…

Functional Analysis · Mathematics 2020-11-03 Ben De Bondt , Hans Vernaeve

We give the parameter version of localization theorem for Bergman metric near the boundary points of strictly pseudoconvex domains. The approximation theorem for square integrable holomorphic functions on such domains in the spirit of…

Complex Variables · Mathematics 2017-07-18 Arkadiusz Lewandowski

A topological space $X$ is Baire if the Baire Category Theorem holds for $X$, i.e., the intersection of any sequence of open dense subsets of $X$ is dense in $X$. One of the interesting problems in the theory of functional spaces is the…

General Topology · Mathematics 2024-09-05 Alexander V. Osipov

The topological properties of a set have a strong impact on its computability properties. A striking illustration of this idea is given by spheres and closed manifolds: if a set $X$ is homeomorphic to a sphere or a closed manifold, then any…

Logic · Mathematics 2022-02-11 Djamel Eddine Amir , Mathieu Hoyrup

We prove the existence of common fixed points for three selfmaps $T,f$ and $g$ defined on a metric space $(X,d)$ satisfying, $T$ is $(f,g)$-weakly contractive; and the pairs $(T,f)$ and $(T,g)$ are weakly compatible. Also, for such $T,f$…

Dynamical Systems · Mathematics 2025-10-21 Babu G. V. R. , Ratna Babu D , Alemayehu Negash

Suppose that $Q$ is a weak$^{\ast }$ compact convex subset of a dual Banach space with the Radon-Nikod\'{y}m property. We show that if $(S,Q)$ is a nonexpansive and norm-distal dynamical system, then there is a fixed point of $S$ in $Q$ and…

Dynamical Systems · Mathematics 2022-01-03 Andrzej Wiśnicki

We present a constructive proof of Tychonoff's fixed point theorem in a locally convex space for sequentially locally non-constant functions, As a corollary to this theorem we also present Schauder's fixed point theorem in a Banach space…

Logic · Mathematics 2011-05-19 Yasuhito Tanaka

The present paper is concerned with Lipschitz properties of convex mappings. One considers the general context of mappings defined on an open convex subset $\Omega$ of a locally convex space $X$ and taking values in a locally convex space…

Functional Analysis · Mathematics 2017-01-12 S. Cobzaş