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A compact set has computable type if any homeomorphic copy of the set which is semicomputable is actually computable. Miller proved that finite-dimensional spheres have computable type, Iljazovi\'c and other authors established the property…

Logic · Mathematics 2023-07-10 Djamel Eddine Amir , Mathieu Hoyrup

A systematic review of the various topologies that can be defined on the projective Hilbert space P(H), i.e., on the set of the pure quantum states, is presented. It is shown that P(H) carries a natural topology as well as a natural…

Mathematical Physics · Physics 2007-08-10 Werner Stulpe

This paper is about the $dfg$/$fsg$ decomposition for groups $G$ definable in $p$-adically closed fields. It is proved that for $G$ definably amenable, $G$ has a definable normal $dfg$ subgroup $H$ such that the quotient $G/H$ is a…

Logic · Mathematics 2026-01-29 Anand Pillay , Ningyuan Yao , Zhentao Zhang

In this paper, we present a constructive generalization of metric and uniform spaces by introducing a new class of spaces, called cover spaces. These spaces form a topological concrete category with a full reflective subcategory of complete…

General Topology · Mathematics 2024-12-31 Valery Isaev

A subset of a topological space is constructible if it is a finite Boolean combination of closed sets. We prove that every NTP$_2$ expansion of $(\mathbb{R},<,+)$ by constructible sets defines only constructible sets, and that definable…

Logic · Mathematics 2026-05-20 Pablo Andújar Guerrero

We show how to use topological ideas, such as compactness, to establish orderability properties of infinite groups. A new application is to provide a left-ordering for the group of PL homeomorphisms of a connected surface with boundary…

Group Theory · Mathematics 2014-03-20 Dale Rolfsen

Several variations on the definition of a Formal Topology exist in the literature. They differ on how they express convergence, the formal property corresponding to the fact that open subsets are closed under finite intersections. We…

Logic · Mathematics 2012-11-06 Francesco Ciraulo , Maria Emilia Maietti , Giovanni Sambin

We consider automorphism groups of some countably categorical structures and their precompact expansions. We prove that automorphism groups of omega-stable omega-categorical structures have metrizable universal minimal flows. We also study…

Logic · Mathematics 2014-12-23 Aleksander Ivanov

This paper deepens into the relations between coarse spaces and compactifications, by defining a $C_0$ coarse structure attached to a family of pseudometrics. This definition allow us to give a more topological point of view on the…

General Topology · Mathematics 2014-10-13 Jesús P. Moreno-Damas

We give a characterization of limits of dihedral groups in the space of finitely generated marked groups. We also describe the topological closure of dihedral groups in the space of marked groups on a fixed number of generators.

Group Theory · Mathematics 2007-10-09 Luc Guyot

We study the topological structure and the topological dynamics of groups of homeomorphisms of scattered spaces. For a large class of them (including the homeomorphism group of any ordinal space or of any locally compact scattered space),…

Group Theory · Mathematics 2020-12-01 Maxime Gheysens

We give a definition of a functor compactifying the functor of bundles on a surfaces. Earlier different authors have defined similar spaces as either images under a morphism or a quotient by an equivalence relation. We use the technique of…

Algebraic Geometry · Mathematics 2015-02-12 Vladimir Baranovsky

Let J be the jacobian of a reduced projective curve C with nodes only. 1) We give a simple and natural definition for its many compactifications and show the connection with various other definitions appearing in the literature. 2) Among…

alg-geom · Mathematics 2008-02-03 Valery Alexeev

This paper answers several open questions around structures with o-minimal open core. We construct an expansion of an o-minimal structure $\mathcal{R}$ by a unary predicate such that its open core is a proper o-minimal expansion of…

Logic · Mathematics 2021-01-08 Alexi Block Gorman , Erin Caulfield , Philipp Hieronymi

We describe locally compact groups which are separably categorical metric structures. The paper extends (and corrects) Section 3 of the paper A.Ivanov, "Locally compact groups and continuous logic", arXiv: 1206.5473

Logic · Mathematics 2017-01-27 Aleksander Ivanov

We extend the theory of complex cells introduced by Binyamini and Novikov to the sharply o-minimal setting, obtaining cellular preparation and parameterization theorems which are polynomially effective in the degrees of the relevant sets.…

Logic · Mathematics 2026-03-27 Gal Binyamini , Oded Carmon , Dmitry Novikov

A space is called minimal if it admits a minimal continuous selfmap. We give examples of metrizable continua $X$ admitting both minimal homeomorphisms and minimal noninvertible maps, whose squares $X\times X$ are not minimal, i.e., they…

Dynamical Systems · Mathematics 2020-05-15 Matúš Dirbák , Ľubomír Snoha , Vladimír Špitalský

For certain theories of existentially closed topological differential fields, we show that there is a strong relationship between $\mathcal L\cup\{D\}$-definable sets and their $\mathcal L$-reducts, where $\mathcal L$ is a relational…

Logic · Mathematics 2017-07-26 Françoise Point

For each countable ordinal $\alpha$, we introduce an ideal $conv_\alpha$ and use it to characterize the class of all compact countable spaces which are homeomorphic to the space $\omega^{\alpha}\cdot n+1$ with the order topology. The…

General Topology · Mathematics 2025-03-18 Rafał Filipów , Małgorzata Kowalczuk , Adam Kwela

We prove that a theorem of Pawlucki, showing that Whitney regularity for a subanalytic set with a smooth singular locus of codimension one implies the set is a finite union of differentiable manifolds with boundary, applies to definable…

Differential Geometry · Mathematics 2017-01-19 David Trotman , Guillaume Valette