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The connections between Whitehead groups and uniformization properties were investigated by the third author in [Sh:98]. In particular it was essentially shown there that there is a non-free Whitehead (respectively, aleph_1-coseparable)…

Logic · Mathematics 2016-09-06 Paul C. Eklof , Alan H. Mekler , Saharon Shelah

We investigate computable metrizability of Polish spaces up to homeomorphism. In this paper we focus on Stone spaces. We use Stone duality to construct the first known example of a computable topological Polish space not homeomorphic to any…

Logic · Mathematics 2023-11-08 Nikolay Bazhenov , Matthew Harrison-Trainor , Alexander Melnikov

The author has recently introduced the class of CNED sets in Euclidean space, generalizing the classical notion of NED sets, and shown that they are quasiconformally removable. A set $E$ is CNED if the conformal modulus of a curve family is…

Complex Variables · Mathematics 2025-02-17 Dimitrios Ntalampekos

\emph{Scalable spaces} are simply connected compact manifolds or finite complexes whose real cohomology algebra embeds in their algebra of (flat) differential forms. This is a rational homotopy invariant property and all scalable spaces are…

Geometric Topology · Mathematics 2022-09-16 Aleksandr Berdnikov , Fedor Manin

In this paper, we show that any embedded capillary hypersurface in the half-space with anisotropic constant mean curvature is a truncated Wulff shape. This extends Wente's result \cite{Wente80} to the anisotropic case and He-Li-Ma-Ge's…

Differential Geometry · Mathematics 2024-05-09 Xiaohan Jia , Guofang Wang , Chao Xia , Xuwen Zhang

We construct a countable inductive limit of weighted Banach spaces of holomorphic functions, which is not a topological subspace of the corresponding weighted inductive limit of spaces of continuous functions. The main step of our…

Functional Analysis · Mathematics 2016-09-06 J. Bonet , Jari Taskinen

We present an example in ZFC of a locally compact, scattered Hausdorff non-Gruenhage space $D$ having a $\G_delta$-diagonal. This answers a question posed by Orihuela, Troyanski and the author in a study of strictly convex norms on Banach…

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

Let $(X,\tau)$ be a Hausdorff space, where $X$ is an infinite set. The compact complement topology $\tau^{\star}$ on $X$ is defined by: $\tau^{\star}=\{\emptyset\} \cup \{X\setminus M, \text{where $M$ is compact in $(X,\tau)$}\}$. In this…

General Topology · Mathematics 2020-09-08 Kyriakos Keremedis , Cenap Özel , Artur Piękosz , Mohammed Al Shumrani , Eliza Wajch

The goal of this paper is twofold. In addition to the results stated in the next paragraph, we present some classical results on absoluteness relevant to functional analysis that are well known to logicians but not nearly as well advertised…

Operator Algebras · Mathematics 2026-02-18 Bruce Blackadar , Ilijas Farah

We show that affine subspaces of Euclidean space are of Khintchine type for divergence under certain multiplicative Diophantine conditions on the parametrizing matrix. This provides evidence towards the conjecture that all affine subspaces…

Number Theory · Mathematics 2020-02-18 Daniel C. Alvey

Theorem: There is a {\em complete sentence} $\phi$ of $L_{\omega_1,\omega}$ such that $\phi$ has maximal models in a set of cardinals $\lambda$ that is cofinal in the first measurable $\mu$ while $\phi$ has no maximal models in any $\chi…

Logic · Mathematics 2021-11-03 John T. Baldwin , Saharon Shelah

We propose the notion of countable decomposability of maps on C*-algebras: a bounded linear map $\varphi : \mathscr{A}\to B(\mathcal{H})$, where $\mathscr{A}$ is a C*-algebra and $\mathcal{H}$ a Hilbert space, will be called countably…

Operator Algebras · Mathematics 2026-02-12 Krzysztof Szczygielski

We provide a direct and elementary proof of the fact that the category of Nachbin's compact ordered spaces is dually equivalent to an Aleph_1-ary variety of algebras. Further, we show that Aleph_1 is a sharp bound: compact ordered spaces…

Category Theory · Mathematics 2020-11-19 Marco Abbadini , Luca Reggio

We prove that, for every cardinal number $\alpha\geq {\mathfrak c}$, there exists a metrizable space $X$ with $|X|=\alpha$ such that for every pair of quasiorders $\leq_1$, $\leq_2$ on a set $Q$ with $|Q| \leq \alpha$ satisfying the…

General Topology · Mathematics 2007-05-23 Vera Trnkova

We give a sufficient condition for a countable group $G$ to possess a probability measure $\mu$ that admits a non-trivial $\mu$-boundary modeled in the space $\mathrm{Sub}_{\mathrm{am}}(G)$ of amenable subgroups of $G$. In particular, for…

Group Theory · Mathematics 2026-03-31 Anna Cascioli , Martín Gilabert Vio , Eduardo Silva

We show that the topology of pointwise convergence on scattered spaces is compatible with the group structure of their homeomorphism group. We then establish a few topological properties of the homeomorphism group of the first uncountable…

Group Theory · Mathematics 2020-12-02 Maxime Gheysens

In [5] the author conjectures and partially shows that the Cuntz semigroup classifies unitary elements of unital AF-algebras. We provide a complete proof by addressing the existence part of the conjecture, under a mild adjustment of both…

Operator Algebras · Mathematics 2025-03-04 Laurent Cantier

We study (strong) first countability of locally solid convergence structures on Archimedean vector lattices. Among other results, we characterise those vector lattices for which relatively unform-, order-, and $\sigma$-order convergence,…

Functional Analysis · Mathematics 2025-09-22 Eugene Bilokopytov , Viktor Bohdanskyi , Jan Harm van der Walt

We construct a one dimensional, second countable, simply connected manifold that exhibits a single non Hausdorff fiber, sufficient to destroy the fundamental properties of classical covering space theory. The space, called the line with k…

General Topology · Mathematics 2025-07-01 Abhiram Sripat

In [1] we defined a new kind of space called 'structured space' which locally resembles, near each of its points, some algebraic structure. We noted in the conclusion of the cited paper that the maps $f_s$ and $h$, which are of great…

Algebraic Topology · Mathematics 2020-04-27 Manuel Norman