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There is a lattice of torsion theories in simplicial groups such that the torsion/torsion-free categories are given by simplicial groups with truncated Moore complex below/above a certain degree. We study the restriction of these torsion…

Category Theory · Mathematics 2023-06-16 Guillermo López Cafaggi

We give a classification of nullity classes (or torsion classes) in an abelian category by forming a spectrum of equivalence classes of premonoform objects. This is parallel to Kanda's classification of Serre subcategories.

Category Theory · Mathematics 2016-11-23 Yong Liu , Donald Stanley

We exhibit infinite, solvable, virtually abelian groups with a fixed number of generators, having arbitrarily large balls consisting of torsion elements. We also provide a sequence of 3-generator non-virtually nilpotent polycyclic groups of…

Group Theory · Mathematics 2010-08-04 Laurent Bartholdi , Yves de Cornulier

We show that, for any number of components, the group of braids up to link-homotopy is torsion-free. This generalizes a result of Humphries up to six components, and provides an explicit solution to a question posed by Lin and addressed by…

Geometric Topology · Mathematics 2024-05-08 Emmanuel Graff

Let S be a closed oriented surface of genus g > 1, and let T denote its Torelli group. First, given a set E of homotopically nontrivial, pairwise disjoint, pairwise nonisotopic simple closed curves on S, we determine precisely when a…

Geometric Topology · Mathematics 2014-10-01 William R. Vautaw

This article resolves several long-standing conjectures about Artin groups of euclidean type. In particular, we prove that every irreducible euclidean Artin group is a torsion-free centerless group with a decidable word problem and a…

Group Theory · Mathematics 2017-07-21 Jon McCammond , Robert Sulway

It is shown that every separable abelian topological group is isomorphic with a topological subgroup of a monothetic group (that is, a topological group with a single topological generator). In particular, every separable metrizable abelian…

General Topology · Mathematics 2007-09-03 Sidney A. Morris , Vladimir Pestov

We construct examples of non-bi-orderable one-relator groups without generalized torsion. This answers a question asked in [2].

Group Theory · Mathematics 2026-04-16 Azer Akhmedov , James Thorne

In the class of reduced Abelian torsion-free groups $G$ of finite rank, we describe TI-groups, this means that every associative ring on $G$ is filial. If every associative multiplication on $G$ is the zero multiplication, then $G$ is…

Rings and Algebras · Mathematics 2021-05-25 Ekaterina Kompantseva , Askar Tuganbaev

The classes of abelian groups that are (uniformly) strongly Hopfian abelian groups, and dually, (uniformly) strongly co-Hopfian abelian groups have been studied by several authors, including Abdelalim (2015) and Abdelalim-Chillali-Essanouni…

Group Theory · Mathematics 2026-05-29 Peter V. Danchev , Patrick W. Keef

In this paper, we first study the endomorphisms of free-abelian times surface groups and give a characterization of when they are injective and surjective. Then, we see that free-abelian times hyperbolic groups are Hopfian but not…

Group Theory · Mathematics 2025-11-18 Ke Wang , Qiang Zhang , Dongxiao Zhao

We construct finitely generated torsion-free solvable groups $G$ that have infinite rank, but such that all finitely generated torsion-free metabelian subquotients of $G$ are virtually abelian. In particular all finitely generated…

Group Theory · Mathematics 2023-08-30 Adrien Le Boudec , Nicolás Matte Bon

We study Abelian groups $A$ with centrally essential endomorphism ring $\text{End}\,A$. If $A$ is a such group which is either a torsion group or a non-reduced group, then the ring $\text{End}\,A$ is commutative. We give examples of Abelian…

Rings and Algebras · Mathematics 2019-10-04 Oleg Lyubimtsev , Askar Tuganbaev

We give an infinite family of torsion-free groups that do not satisfy the unique product property. For these examples, we also show that each group contains arbitrarily large sets whose square has no uniquely represented element.

Group Theory · Mathematics 2013-11-26 William Carter

We describe all the quasi-bialgebra structures of a group algebra over a torsion-free abelian group. They all come out to be triangular in a unique way. Moreover, up to an isomorphism, these quasi-bialgebra structures produce only one…

Quantum Algebra · Mathematics 2013-02-12 Alessandro Ardizzoni , Daniel Bulacu , Claudia Menini

The notion of acyclic matching property was provided by Losonczy and it was proved that torsion-free groups admit this property. In this paper, we introduce a duality of acyclic matching as a tool for classification of some Abelian groups,…

Combinatorics · Mathematics 2019-01-01 M. Aliabadi , H. Jolany , M. Amin Khajehnejad , M. J. Moghaddamzadeh , H. Shahmohamad

We construct uncountably many finitely generated, pairwise non-isomorphic torsion-free groups, all of which fall into the same quasi-isometry class. This is done by considering Schur covering groups and group cohomology, with the necessary…

Group Theory · Mathematics 2025-11-19 Vladimir Vankov

In the category of finitely generated modules over an artinian ring, we classify all the abelian exact subcategories closed under predecessors or, equivalently, all the split torsion pairs with torsion-free class closed under quotients.

Rings and Algebras · Mathematics 2007-05-23 Ibrahim Assem , Manuel Saorin

We characterize co-Hopfian finitely generated torsion free nilpotent groups in terms of their Lie algebra automorphisms, and construct many examples of such groups.

Group Theory · Mathematics 2007-05-23 Igor Belegradek

An uncountable $\aleph_1$-free group cannot admit a Polish group topology but an uncountable $\aleph_1$-free abelian group can, as witnessed, for example, by the Baer-Specker group $\mathbb{Z}^\omega$; more strongly, $\mathbb{Z}^\omega$ is…

Logic · Mathematics 2026-03-30 Gianluca Paolini , Saharon Shelah