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In this paper we continue an earlier study of ends non-compact manifolds. The over-arching goal is to investigate and obtain generalizations of Siebenmann's famous collaring theorem that may be applied to manifolds having non-stable…

Geometric Topology · Mathematics 2014-11-11 C R Guilbault , F C Tinsley

Peterzil and Steinhorn proved that if a group $G$ definable in an $o$-minimal structure is not definably compact, then $G$ contains a definable torsion-free subgroup of dimension one. We prove here a $p$-adic analogue of the…

Logic · Mathematics 2022-05-19 Will Johnson , Ningyuan Yao

(1) Every infinite, Abelian compact (Hausdorff) group K admits 2^|K|-many dense, non-Haar-measurable subgroups of cardinality |K|. When K is nonmetrizable, these may be chosen to be pseudocompact. (2) Every infinite Abelian group G admits a…

General Topology · Mathematics 2013-10-09 W. W. Comfort , S. U. Raczkowski , F. J. Trigos-Arrieta

We prove that a K\"ahler group which is cubulable, i.e. which acts properly discontinuously and cocompactly on a CAT(0) cubical complex, has a finite index subgroup isomorphic to a direct product of surface groups, possibly with a free…

Geometric Topology · Mathematics 2019-06-26 Thomas Delzant , Pierre Py

An almost Abelian Lie group is a non-Abelian Lie group with a codimension 1 Abelian subgroup. We show that all discrete subgroups of complex simply connected almost Abelian groups are finitely generated. The topology of connected almost…

Group Theory · Mathematics 2023-08-17 Zhirayr Avetisyan , Oderico-Benjamin Buran , Andrew Paul , Lisa Reed

In this paper we investigate finiteness properties of totally disconnected locally compact groups for general commutative rings $R$, in particular for $R = \mathbb{Z}$ and $R= \mathbb{Q}$. We show these properties satisfy many analogous…

Group Theory · Mathematics 2021-01-22 Ilaria Castellano , Ged Corob Cook

We compare finiteness properties of locally compact groups that generalize the properties of being compactly generated and of being compactly presented. Three such families of properties have been proposed: Abels--Tiemeyer's type $C_n$,…

Group Theory · Mathematics 2024-10-10 Dorian Chanfi , Stefan Witzel

We show that compact complex manifolds of algebraic dimension zero bearing a holomorphic Cartan geometry of algebraic type have infinite fundamental group. This generalizes the main Theorem in [DM] where the same result was proved for the…

Differential Geometry · Mathematics 2019-12-03 Indranil Biswas , Sorin Dumitrescu , Benjamin McKay

We study definably compact definably connected groups definable in a sufficiently saturated real closed field $R$. We introduce the notion of group-generic point for $\bigvee$-definable groups and show the existence of group-generic points…

Logic · Mathematics 2017-05-19 Eliana Barriga

Working in the framework of Borel reducibility, we study various notions of embeddability between groups. We prove that the embeddability between countable groups, the topological embeddability between (discrete) Polish groups, and the…

Logic · Mathematics 2018-02-08 Filippo Calderoni , Luca Motto Ros

Building on the author's earlier work on topological and abstract expansivity, this paper introduces and explores the notion of algebraic expansivity for endomorphisms of abelian groups. We analyze the fundamental properties of this…

Dynamical Systems · Mathematics 2026-04-28 Mauricio Achigar

We classify the locally compact second-countable (l.c.s.c.) groups $A$ that are abelian and topologically characteristically simple. All such groups $A$ occur as the monolith of some soluble l.c.s.c. group $G$ of derived length at most $3$;…

Group Theory · Mathematics 2020-06-09 Colin D. Reid

We show that the endomorphisms of a compact connected group that extend to endomorphisms of every compact overgroup are precisely the trivial one and the inner automorphisms; this is an analogue, for compact connected groups, of results due…

Group Theory · Mathematics 2023-09-26 Alexandru Chirvasitu

Greenberg proved that every countable group $A$ is isomorphic to the automorphism group of a Riemann surface, which can be taken to be compact if $A$ is finite. We give a short and explicit algebraic proof of this for finitely generated…

Group Theory · Mathematics 2019-12-17 Gareth A. Jones

We describe and classify countable Boolean rings (which may or may not have a multiplicative identity) with finitely many distinguished ideals whose elementary theory is countably categorical. This extends the description by Macintyre and…

Logic · Mathematics 2025-08-13 Andrew Apps

For a totally disconnected locally compact abelian group, we prove that the topological entropy of a continuous endomorphism coincides with the algebraic entropy of the dual endomorphism with respect to the Pontryagin duality. Moreover,…

General Topology · Mathematics 2013-10-25 Dikran Dikranjan , Anna Giordano Bruno

We show the existence of generalized clusters of a finite or even infinite number of sets, with minimal total perimeter and given total masses, in metric measure spaces homogeneous with respect to a group acting by measure preserving…

Analysis of PDEs · Mathematics 2021-12-16 Matteo Novaga , Emanuele Paolini , Eugene Stepanov , Vincenzo Maria Tortorelli

A topological group $G$ is extremely amenable if every continuous action of $G$ on a compact space has a fixed point. Using the concentration of measure techniques developed by Gromov and Milman, we prove that the group of automorphisms of…

Group Theory · Mathematics 2007-09-03 Thierry Giordano , Vladimir Pestov

We show that all non-trivial continuous endomorphisms of the circle group are topologically mixing. We also show that there exists a large infinite class of continuous endomorphisms of any n-dimensional torus group which are topologically…

Dynamical Systems · Mathematics 2016-06-23 John R. Burke , Leonardo Pinheiro

A topological group G is profinite if it is compact and totally disconnected. Equivalently, G is the inverse limit of a surjective system of finite groups carrying the discrete topology. We discuss how to represent a countably based…

Group Theory · Mathematics 2019-02-08 Andre Nies