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We prove that for lambda = beta_omega or just lambda strong limit singular of cofinality aleph_0, if there is a universal member in the class K^lf_lambda of locally finite groups of cardinality lambda, then there is a canonical one…

Logic · Mathematics 2023-03-08 Saharon Shelah

We will show that every element of a finitely generated abelian group is automorphically equivalent what we will define to be a {\em representative element} in a {\em repeat-free subgroup}, and for finite abelian groups we can count the…

Group Theory · Mathematics 2011-09-12 Charles F. Rocca

Write $\mathbf{A}_\lambda$ for what might be described as the most elementary nontrivial inverse system of abelian groups indexed by the functions from the cardinal $\lambda$ to the set of natural numbers. The question of whether for any…

Logic · Mathematics 2025-07-09 Jeffrey Bergfalk , Matteo Casarosa

We consider strong expansions of the theory of ordered abelian groups. We show that the assumption of strength has a multitude of desirable consequences for the structure of definable sets in such theories, in particular as relates to…

Logic · Mathematics 2016-05-12 Alfred Dolich , John Goodrick

Solecki proved that the group of automorphisms of a countable structure cannot be an uncountable free abelian group. See more in Just, Shelah and Thomas math.LO/0003120 where as a by product we can say something on on uncountable…

Logic · Mathematics 2007-05-23 Saharon Shelah

Assuming the existence of $\mathfrak c$ incomparable selective ultrafilters, we classify the non-torsion Abelian groups of cardinality $\mathfrak c$ that admit a countably compact group topology. We show that for each $\kappa \in [\mathfrak…

General Topology · Mathematics 2021-04-26 M. K. Bellini , A. C. Boero , V. O. Rodrigues , A. H. Tomita

A strongly zero-dimensional topological group containing a closed subgroup of positive covering dimension is constructed.

General Topology · Mathematics 2023-03-09 Ol'ga Sipacheva

It was recently proven that all free and many virtually free verbally closed subgroups are algebraically closed in any group. We establish sufficient conditions for a group that is an extension of a free non-abelian group by a group…

Group Theory · Mathematics 2017-07-19 Andrey M. Mazhuga

In S. 1 we deal with amalgamation bases, e.g., we define when an a.e.c. $k$ has $(\lambda,\kappa)$-amalgamation which means "many" M in $K^k_\lambda$ are amalgamation bases. We then consider what happens for the class of lf groups. In S. 2…

Logic · Mathematics 2019-01-29 Saharon Shelah

Among other things, we prove that the group of automorphisms fixing every normal subgroup of a nilpotent-by-abelian group is nilpotent-by-metabelian. In particular, the group of automorphisms fixing every normal subgroup of a metabelian…

Group Theory · Mathematics 2007-06-05 G. Endimioni

Assuming G\"odel's axiom of constructibility $V=L$, we construct a $\chi$-free abelian group $G$ of singular cardinality for some suitable cardinal $\chi$ which is regular and uncountable, equipped with the property that for every…

Group Theory · Mathematics 2026-02-10 Mohsen Asgharzadeh , Mohammad Golshani , Saharon Shelah

We consider several types of non-existence theorems for functors. For example, there are no nontrivial functors from the category of groups (or the category of pointed sets, or vector spaces) to any small category. Another type of questions…

Category Theory · Mathematics 2025-05-20 Emmanuel Dror Farjoun , Sergei O. Ivanov , Aleksandr Krasilnikov , Anatolii Zaikovskii

It is a simple fact that a subgroup generated by a subset $A$ of an abelian group is the direct sum of the cyclic groups $\langle a\rangle$, $a\in A$ if and only if the set $A$ is independent. In [5] the concept of an $independent$ set in…

General Topology · Mathematics 2017-12-08 Jan Spevak

Let $\Lambda$ be a finite abelian group. A dynamical system with transformation group $\Lambda$ is a triple $(A,\Lambda,\alpha)$, consisting of a unital locally convex algebra $A$, the finite abelian group $\Lambda$ and a group homomorphism…

Differential Geometry · Mathematics 2025-12-24 Stefan Wagner

In this article we present an extensive survey on the developments in the theory of non-abelian finite groups with abelian automorphism groups, and pose some problems and further research directions.

Group Theory · Mathematics 2017-08-03 Rahul Dattatraya Kitture , Manoj K. Yadav

A group topology is said to be linear if open subgroups form a base of neighborhoods of the identity element. It is proved that the existence of a nondiscrete extremally disconnected group of Ulam nonmeasurable cardinality with linear…

General Topology · Mathematics 2021-04-27 Ol'ga Sipacheva

Let k be an algebraically closed field and A a finite dimensional associative k-algebra. We prove that there is no gap in the lengths of indecomposable A-modules of finite length. The analogous result holds for an abelian k-linear category…

Representation Theory · Mathematics 2012-01-12 Klaus Bongartz

We give a classification and complete algebraic description of groups allowing only finitely many (left multiplication invariant) circular orders. In particular, they are all solvable groups with a specific semi-direct product…

Group Theory · Mathematics 2017-04-21 Adam Clay , Kathryn Mann , Cristóbal Rivas

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 present a class of abelian groups that exhibit a high degree of freeness while possessing no non-trivial homomorphisms to a canonical free object. Unlike prior investigations, which primarily focused on torsion-free groups, our work…

Group Theory · Mathematics 2025-11-11 Mohsen Asgharzadeh , Mohammad Golshani , Saharon Shelah
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