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We propose a definition of computable manifold by introducing computability as a structure that we impose to a given topological manifold, just in the same way as differentiability or piecewise linearity are defined for smooth and PL…

Logic in Computer Science · Computer Science 2017-03-16 Marcelo A. Aguilar , Rodolfo Conde

This paper demonstrates that every ultrametric space is homeomorphic to a clade space of a pruned tree, i.e., a subspace of a tree's canopy. Furthermore, it characterizes several topological properties of ultrametrizable spaces through the…

General Topology · Mathematics 2024-08-01 Itamar Bellaïche

For a metric compact space $L$ and a Banach space $E$, we provide a characterization of the complementability of the Banach space $\mathcal{C}(L)$ of continuous functions on $L$ inside $E$ in terms of the existence of a certain tree in the…

Functional Analysis · Mathematics 2026-03-16 Jakub Rondoš , Damian Sobota

Compact metric spaces form an important class of metric spaces, but the category that they define lacks many important properties such as completeness and cocompleteness. In recent studies of "metric domain theory" and Stone-type dualities,…

Category Theory · Mathematics 2025-01-15 Marco Abbadini , Dirk Hofmann

We study totally disconnected, locally compact (t.d.l.c.) groups from an algorithmic perspective. We give various approaches to defining computable presentations of t.d.l.c.\ groups, and show their equivalence. In the process, we obtain an…

Logic · Mathematics 2024-09-02 Alexander Melnikov , Andre Nies

We initiate the effective metric structure theory of Keisler randomizations. We show that a classical countable structure $\mathcal{M}$ has a decidable presentation if and only if its Borel randomization $\mathcal{M}^{[0,1)}$ has a…

Logic · Mathematics 2025-06-09 Nicolás Cuervo Ovalle , Isaac Goldbring

A semi-computable set S in a computable metric space need not be computable. However, in some cases, if S has certain topological properties, we can conclude that S is computable. It is known that if a semi-computable set S is a compact…

Logic in Computer Science · Computer Science 2015-07-01 Konrad Burnik , Zvonko Iljazovic

This paper is meant to give a short exposition of the Stone's Representation Theorems. We provide three equivalent approaches to construct a Stone's space from a given Boolean algebra. Finally, we utilize the Stone's Representation Theorems…

General Topology · Mathematics 2022-01-11 Hussain Rashed

We show a necessary and sufficient condition for any ordinal number to be a Polish space. We also prove that for each countable Polish space, there exists a countable ordinal number that is an upper bound for the first component of the…

General Mathematics · Mathematics 2024-04-12 Borys Álvarez-Samaniego , Andrés Merino

We study the complexities of isometry and isomorphism classes of separable Banach spaces in the Polish spaces of Banach spaces recently introduced and investigated by the authors in [14]. We obtain sharp results concerning the most…

Functional Analysis · Mathematics 2022-04-15 Marek Cúth , Martin Doležal , Michal Doucha , Ondřej Kurka

This article continues the study of computable elementary topology started by the author and T. Grubba in 2009 and extends the author's 2010 study of axioms of computable separation. Several computable T3- and Tychonoff separation axioms…

Logic · Mathematics 2015-07-01 Klaus Weihrauch

Suppose $p \geq 1$ is a computable real. We extend previous work of Clanin, Stull, and McNicholl by classifying the computable $L^p$ spaces whose underlying measure spaces are atomic but not purely atomic. In addition, we determine the…

Logic · Mathematics 2019-04-30 Tyler Brown , Timothy H. McNicholl

Let X be an uncountable Polish space. Lubica Hola showed recently that there are 2^continuum many quasi-continuous real valued functions defined on the uncountable Polish space that are not Borel measurable. Inspired by Hola's result, we…

General Topology · Mathematics 2024-05-21 Tomasz Natkaniec

We show that for a metric space with an even number of points there is a 1-Lipschitz map to a tree-like space with the same matching number. This result gives the first basic version of an unoriented Kantorovich duality. The study of the…

Metric Geometry · Mathematics 2016-09-22 Mircea Petrache , Roger Züst

We will see how to define the metric $\beta$, which turns the topological space of continuous functions whose domains are open subsets of a locally compact and second countable space $X$ to values in a polish space $Y$, called…

General Topology · Mathematics 2026-02-11 Edwar Alexis Ramírez Ardila

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

While there is a well-established notion of what a computable ordinal is, the question which functions on the countable ordinals ought to be computable has received less attention so far. We propose a notion of computability on the space of…

Logic in Computer Science · Computer Science 2017-04-11 Arno Pauly

We study Banach spaces $C(K)$ of real-valued continuous functions from the finite product of compact lines. It turns out that the topological character of these compact lines can be used to distinguish whether two spaces of continuous…

Functional Analysis · Mathematics 2025-07-23 Maciej Korpalski

We prove that for each Polish space X, the space C(X) of continuous real-valued functions on X satisfies a strong version of the Pytkeev property, if endowed with the compact-open topology. (This shows that whereas it need not be…

General Topology · Mathematics 2010-11-05 Boaz Tsaban , Lyubomyr Zdomskyy

We formalize an existing computability-theoretic method of presenting first-order structures whose domains have the cardinality of the continuum. Work using these methods until now has emphasized their topological properties. We shift the…

Logic · Mathematics 2025-11-07 Jason Block , Russell Miller