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We prove that the double covers of the alternating and symmetric groups are determined by their complex group algebras. To be more precise, let $n\geq 5$ be an integer, $G$ a finite group, and let $\AAA$ and $\SSS^\pm$ denote the double…

Representation Theory · Mathematics 2016-01-20 Christine Bessenrodt , Hung Ngoc Nguyen , Jørn B. Olsson , Hung P. Tong-Viet

We construct, in $\mathsf{ZFC}$, a countably compact subgroup of $2^{\mathfrak{c}}$ without non-trivial convergent sequences, answering an old problem of van Douwen. As a consequence we also prove the existence of two countably compact…

General Topology · Mathematics 2021-02-23 Michael Hrušák , Jan van Mill , Ulises Ariet Ramos-García , Saharon Shelah

We show that, for a sheet or a Lusztig stratum S containing spherical conjugacy classes in a connected reductive algebraic group G over an algebraically closed field in good characteristic, the orbit space S/G is isomorphic to the quotient…

Representation Theory · Mathematics 2015-01-20 Giovanna Carnovale , Francesco Esposito

Adding two generators and one arbitrary relator to a nontrivial torsion-free group, we always obtain an SQ-universal group. In the course of the proof of this theorem, we obtain some other results of independent interest. For instance,…

Group Theory · Mathematics 2007-07-29 Anton A. Klyachko

In this paper we give two families of non-metrizable topologies on the group of the integers having a countable dual group which is isomorphic to a infinite torsion subgroup of the unit circle in the complex plane. Both families are related…

Algebraic Topology · Mathematics 2016-03-15 Daniel de la Barrera Mayoral

Given a group $G$ with bounded torsion that acts properly on a systolic complex, we show that every solvable subgroup of $G$ is finitely generated and virtually abelian of rank at most $2$. In particular this gives a new proof of the above…

Group Theory · Mathematics 2017-07-26 Tomasz Prytuła

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

We prove that a finitely generated Lie algebra $L$ such that (i) every commutator in generators is ad-nilpotent, and (ii) $ L$ satisfies a polynomial identity, is nilpotent. As a corollary we get that a finitely generated residually-$p$…

Rings and Algebras · Mathematics 2017-08-07 Efim Zelmanov

We prove that Chevalley group over the field $F$ of zero characteristic possess $R_{\infty}$ property, if $F$ has torsion group of automorphisms or $F$ is an algebraically closed field which has finite transcendence degree over…

Group Theory · Mathematics 2015-02-27 T. R. Nasybullov

In this paper, we study the structures of finite groups using some arithmetic conditions on the sizes of real conjugacy classes. We prove that a finite group is solvable if the prime graph on the real class sizes of the group is…

Group Theory · Mathematics 2018-03-06 Hung P. Tong-Viet

The Addition Theorem for the algebraic entropy of group endomorphisms of torsion abelian groups was proved in [4]. Later, this result was extended to all abelian groups [3] and, recently, to all torsion finitely quasihamiltonian groups [7].…

Group Theory · Mathematics 2022-09-13 Menachem Shlossberg

A Kronecker coefficient is the multiplicity of an irreducible representation of a finite group $G$ in a tensor product of irreducible representations. We define Kronecker Hecke algebras and use them as a tool to study Kronecker coefficients…

Representation Theory · Mathematics 2025-10-07 Jyotirmoy Ganguly , Digjoy Paul , Amritanshu Prasad , K N Raghavan , Velmurugan S

We prove that the outer automorphism group $\mathrm{Out}(N)$ of an infinitely generated free nilpotent group $N$ of class two is complete.

Group Theory · Mathematics 2025-05-20 Vladimir A. Tolstykh

A torsion class $\mathcal{T}$ of the module category $\operatorname{\mathsf{mod}} A$ of a finite dimensional algebra $A$ over a field $K$ is said to be compact if there exists a module $M \in \operatorname{\mathsf{mod}} A$ such that…

Representation Theory · Mathematics 2026-04-07 Sota Asai

We classify finite-dimensional Nichols algebras over finite nilpotent groups of odd order in group-theoretical terms. The main step is to show that the conjugacy classes of such finite groups are either abelian or of type C; this property…

Quantum Algebra · Mathematics 2021-04-13 Nicolás Andruskiewitsch

We introduce $n$-fold torsion(-free) classes of an abelian category. These are a generalization of ordinary torsion(-free) classes in the sense that $1$-fold torsion(-free) classes coincide with torsion(-free) classes. In the category of…

Representation Theory · Mathematics 2025-03-17 Yuki Uchida

We prove that if a countable group is elementarily equivalent to a non-abelian free group and all of its abelian subgroups are cyclic, then the group is a union of a chain of regular NTQ groups (i.e., hyperbolic towers).

Logic · Mathematics 2021-05-12 Olga Kharlampovich , Christopher Natoli

Let $\phi:G\to G$ be an automorphism of a group which is a free-product of finitely many groups each of which is freely indecomposable and two of the factors contain proper finite index characteristic subgroups. We show that $G$ has…

Group Theory · Mathematics 2020-01-22 Daciberg Goncalves , Parameswaran Sankaran , Peter Wong

We show that a construction by Aanderaa and Cohen used in their proof of the Higman Embedding Theorem preserves torsion length. We give a new construction showing that every finitely presented group is the quotient of some $C'(1/6)$…

Group Theory · Mathematics 2018-09-05 Maurice Chiodo , Rishi Vyas

Let $G$ be a group. Two elements $x,y \in G$ are said to be in the same $z$-class if their centralizers in $G$ are conjugate within $G$. Consider $\mathbb F$ a perfect field of characteristic $\neq 2$, which has a non-trivial Galois…

Group Theory · Mathematics 2019-10-15 Sushil Bhunia , Anupam Singh