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Countably infinite groups (with a fixed underlying set) constitute a Polish space $G$ with a suitable metric, hence the Baire category theorem holds in $G$. We study isomorphism invariant subsets of $G$, which we call group properties. We…

We prove that the universal solenoid is the generic (in the sense of Baire category) connected compact metrizable abelian group. We also settle the dual problem in the sense of Pontryagin duality: $(\mathbb{Q},+)$, which is the dual of the…

Logic · Mathematics 2025-07-03 Udayan B. Darji , Márton Elekes , Tamás Kátay , Anett Kocsis , Máté Pálfy

We provide characterizations of Lie groups as compact-like groups in which all closed zero-dimensional metric (compact) subgroups are discrete. The "compact-like" properties we consider include (local) compactness, (local)…

General Topology · Mathematics 2018-03-05 Dikran Dikranjan , Dmitri Shakhmatov

We introduce and study Polish topologies on various spaces of countable enumerated groups, where an enumerated group is simply a group whose underlying set is the set of natural numbers. Using elementary tools and well known examples from…

Group Theory · Mathematics 2021-12-08 Isaac Goldbring , Srivatsav Kunnawalkam Elayavalli , Yash Lodha

We introduce the coherent algebra of a compact metric measure space by analogy with the corresponding concept for a finite graph. As an application we show that upon topologizing the collection of isomorphism classes of compact metric…

Operator Algebras · Mathematics 2018-12-04 Alexandru Chirvasitu

For a countable abelian group $G$ we investigate generic properties of the space of all invariant metrics on $G$. We prove that for every such an unbounded group $G$, i.e. group which has elements of arbitrarily high order, there is a dense…

General Topology · Mathematics 2019-02-28 Michal Doucha

We present a contribution to the structure theory of locally compact groups. The emphasis is on compactly generated locally compact groups which admit no infinite discrete quotient. It is shown that such a group possesses a characteristic…

Group Theory · Mathematics 2012-07-10 Pierre-Emmanuel Caprace , Nicolas Monod

We show that the closure of the compactly supported mapping class group of an infinite type surface is not perfect and that its abelianization contains a direct summand isomorphic to an uncountable direct sum of rationals. We also extend…

Geometric Topology · Mathematics 2021-04-26 George Domat , Ryan Dickmann

In the first half of this paper, we outline the construction of a new class of abelian pro-$p$ groups, which covers all countably-based pro-$p$ groups. In the second half, we study them, and classify them up to topological isomorphism and…

Group Theory · Mathematics 2012-11-21 Jonathan Kiehlmann

We continue in this paper the study of locally minimal groups started in \cite{LocMin}. The minimality criterion for dense subgroups of compact groups is extended to local minimality. Using this criterion we characterize the compact abelian…

General Topology · Mathematics 2010-06-29 Lydia Aussenhofer , María Jesús Chasco , Dikran Dikranjan , Xabier Domínguez

In order to understand the structure of the `typical' element of an automorphism group, one has to study how large the conjugacy classes of the group are. When typical is meant in the sense of Baire category, a complete description of the…

A topological space is called {\it dense-separable} if each dense subset of its is separable. Therefore, each dense-separable space is separable. We establish some basic properties of dense-separable topological groups. We prove that each…

General Topology · Mathematics 2022-12-27 Fucai Lin , Qiyun Wu , Chuan Liu

We study final group topologies and their relations to compactness properties. In particular, we are interested in situations where a colimit or direct limit is locally compact, a k_\omega-space, or locally k_\omega. As a first application,…

Group Theory · Mathematics 2015-03-27 Helge Glockner , Ralf Köhl , Tobias Hartnick

Roundness of metric spaces was introduced by Per Enflo as a tool to study uniform structures of linear topological spaces. The present paper investigates geometric and topological properties detected by the roundness of general metric…

Metric Geometry · Mathematics 2007-05-23 J. -F. Lafont , S. Prassidis

We first give simplified and corrected accounts of some results in \cite{PiRCP} on compactifications of pseudofinite groups. For instance, we use a classical theorem of Turing \cite{Turing} to give a simplified proof that any definable…

Logic · Mathematics 2025-06-18 Gabriel Conant , Ehud Hrushovski , Anand Pillay

We introduce and develop the model-theoretic notions of absolute connectedness and type-absolute connectedness for groups. We prove that groups of rational points of split semisimple linear groups (that is, Chevalley groups) over arbitrary…

Group Theory · Mathematics 2012-09-10 Jakub Gismatullin

We prove that if $G$ is a totally bounded abelian group \st\ its dual group $\widehat{G}_p$ equipped with the finite-open topology is a Baire group, then every compact subset of $G$ must be finite. This solves an open question by Chasco,…

Group Theory · Mathematics 2024-05-07 M. Ferrer , S. Hernández , I. Sepúlveda , F. J. Trigos-Arrieta

We classify up to coarse equivalence all countable abelian groups of finite torsion free rank. The Q-cohomological dimension and the torsion free rank are the two invariants that give us such classification. We also prove that any countable…

Group Theory · Mathematics 2008-03-05 J. Higes

We provide some characterizations of precompact abelian groups $G$ whose dual group $G_p^\wedge$ endowed with the pointwise convergence topology on elements of $G$ contains a nontrivial convergent sequence. In the special case of precompact…

General Topology · Mathematics 2019-10-11 M. V. Ferrer , S. Hernández , M. Tkachenko

A group element is called generalized torsion if a finite product of its conjugates is equal to the identity. We show that in a finitely generated abelian-by-finite group, an element is generalized torsion if and only if its image in the…

Group Theory · Mathematics 2025-12-09 Raimundo Bastos , Luis Mendonça
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