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We introduce the notion of spaces with weak relative cohomology and show the acyclicity of the complement $Q\setminus X$ in the Hilbert cube $Q$ of a compactum $X$ with weak relative cohomology. As a corollary we obtain the acyclicity of…

General Topology · Mathematics 2016-03-23 Ashwini Amarasinghe , Alexander Dranishnikov

We prove that many completeness properties coincide in metric spaces, precompact groups and dense subgroups of products of separable metric groups. We apply these results to function spaces C_p(X,G) of G-valued continuous functions on a…

General Topology · Mathematics 2017-05-26 Alejandro Dorantes-Aldama , Dmitri Shakhmatov

For a bounded weak Lipschitz domain we show the so called `Maxwell compactness property', that is, the space of square integrable vector fields having square integrable weak rotation and divergence and satisfying mixed tangential and normal…

Analysis of PDEs · Mathematics 2019-01-24 Sebastian Bauer , Dirk Pauly , Michael Schomburg

Let $(X,\mathbf{q},\mu)$ be an ultra-RD-space with upper dimension $n\in(0,\infty)$; i.e., it is a quasi-ultrametric space of homogeneous type whose measure $\mu$ satisfies an additional reverse doubling property. Let…

Functional Analysis · Mathematics 2026-04-06 Chenfeng Zhu , Ryan Alvarado , Xianjie Yan , Dachun Yang , Wen Yuan

We study the relations between a generalization of pseudocompactness, named $(\kappa, M)$-pseudocompactness, the countably compactness of subspaces of $\beta \omega$ and the pseudocompactness of their hyperspaces. We show, by assuming the…

General Topology · Mathematics 2019-04-15 Y. F. Ortiz-Castillo , V. O. Rodrigues , A. H. Tomita

Let B(kappa, lambda) be the subalgebra of P(kappa) generated by [kappa]^{<= lambda}. It is shown that if B is any homomorphic image of B(kappa, lambda) then either |B|< 2^lambda or |B|=|B|^lambda, moreover if X is the Stone space of B then…

Logic · Mathematics 2009-09-25 Istvan Juhász , Saharon Shelah

For any $p\in[1,\infty)$, we prove that the set of simple functions taking at most $k$ different values is proximinal in B\"ochner spaces $L^p(X)$ whenever $X$ is a dual Banach space with $w^*$-sequentially compact unit ball. With…

Functional Analysis · Mathematics 2024-04-24 Guillaume Grelier , Jaime San Martín

In this paper we provide mixed weak type inequalities generalizing previous results in an earlier work by Caldarelli and the second author and also in the spirit of earlier results by Lorente, Martell, P\'erez and Riveros. One of the main…

Classical Analysis and ODEs · Mathematics 2022-07-27 Gonzalo H. Ibañez-Firnkorn , Israel P. Rivera-Ríos

We analyze the properties of weakly compact sets in Lipschitz free spaces. Prior research has established that, for a complete metric space $M$, weakly precompact sets in the Lipschitz free space $\mathcal F(M)$ are tight. In this paper, we…

Functional Analysis · Mathematics 2026-02-16 Ramón J. Aliaga , Colin Petitjean , Antonín Prochazka , Triinu Veeorg

If $X$ is a smooth manifold and ${\mathcal{G}}$ is a subgroup of $Diff(X)$ we say that $(X,{\mathcal{G}})$ has the almost fixed point property if there exists a number $C$ such that for any finite subgroup $G\leq{\mathcal{G}}$ there is some…

Differential Geometry · Mathematics 2018-05-08 Ignasi Mundet i Riera

In the absence of the Axiom of Choice, the "small" cardinal $\omega_1$ can exhibit properties more usually associated with large cardinals, such as strong compactness and supercompactness. For a local version of strong compactness, we say…

Logic · Mathematics 2016-09-20 Nam Trang , Trevor Wilson

A version of Arzel\`a-Ascoli theorem for $X$ being $\sigma$-locally compact Hausdorff space is proved. The result is used in proving compactness of Fredholm, Hammerstein and Urysohn operators. Two fixed point theorems, for Hammerstein and…

Functional Analysis · Mathematics 2015-05-12 Mateusz Krukowski , Bogdan Przeradzki

In this paper, we introduced $\alpha$-Hurewicz $\&$ $\theta$-Hurewicz properties in a topological space $X$ and investigated their relationship with other selective covering properties. We have shown that for an extremally disconnected…

General Topology · Mathematics 2023-07-04 Gaurav Kumar , Sumit Mittal , Brij K. Tyagi

We deal with the class of Hausdorff spaces having a $\pi$-base whose elements have an H-closed closure. Carlson proved that $|X|\leq 2^{wL(X)\psi_c(X)t(X)}$ for every quasiregular space $X$ with a $\pi$-base whose elements have an H-closed…

General Topology · Mathematics 2024-02-12 Davide Giacopello

The Hardy--Littlewood inequality for complex homogeneous polynomials asserts that given positive integers $m\geq2$ and $n\geq1$, if $P$ is a complex homogeneous polynomial of degree $m$ on $\ell_{p}^{n}$ with $2m\leq p\leq\infty$ given by…

Functional Analysis · Mathematics 2015-10-08 Gustavo Araujo , Daniel Pellegrino

We introduce a new compactness principle which we call the gluing property. For a measurable cardinal $\kappa$ and a cardinal $\lambda$, we say that $\kappa$ has the $\lambda$-gluing property if every sequence of $\lambda$-many…

Logic · Mathematics 2026-03-27 Yair Hayut , Alejandro Poveda

In this paper, we establish a Minkowski-type inequality for weak Lebesgue space, which allows us to obtain a characterization of relative compactness in these spaces. Furthermore, we are the first to investigate the compactness results of…

Functional Analysis · Mathematics 2023-09-20 Dinghuai Wang , Xi Hu , Shuai Qi

A very particular by-product of the result announced in the title reads as follows: Let $(X,<\cdot,\cdot>)$ be a real Hilbert space, $T:X\to X$ a compact and symmetric linear operator, and $z\in X$ such that the equation $T(x)-\|T\|x=z$ has…

Functional Analysis · Mathematics 2011-03-18 Biagio Ricceri

This paper deals with the homogenization through $\Gamma$-convergence of weakly coercive integral energies with the oscillating density $\mathbb{L}(x/\epsilon)\nabla v : \nabla v$ in three-dimensional elasticity. The energies are weakly…

Analysis of PDEs · Mathematics 2016-09-16 Marc Briane , Antonio Pallares-Martín

The $G_\delta$-modification $X_\delta$ of a topological space $X$ is the space on the same underlying set generated by, i.e. having as a basis, the collection of all $G_\delta$ subsets of $X$. Bella and Spadaro recently investigated the…

General Topology · Mathematics 2018-05-08 Alan Dow , István Juhász , Lajos Soukup , Zoltán Szentmiklóssy , William Weiss