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We extend some recent results about bounded invariant equivalence relations and invariant subgroups of definable groups: we show that type-definability and smoothness are equivalent conditions in a wider class of relations than heretofore…

Logic · Mathematics 2018-10-25 Tomasz Rzepecki

There exist combable groups in which the conjugacy problem is unsolvable. The isomorphism problem is unsolvable for certain recursive sequences of finite presentations of combable groups.

Group Theory · Mathematics 2007-05-23 Martin R. Bridson

In this paper we generalize techniques of Belk-Matucci to solve the conjugacy problem for every Thompson-like group $V_n(H)$, where $n \geq 2$ and $H$ is a subgroup of the symmetric group on $n$ elements. We use this to prove that, if $n…

Group Theory · Mathematics 2018-08-07 Julio Aroca

Using a result of Kari and Ollinger, we prove that the torsion problem for elements of the Brin-Thompson group 2V is undecidable. As a result, we show that there does not exist an algorithm to determine whether an element of the rational…

Group Theory · Mathematics 2018-10-30 James Belk , Collin Bleak

In this article we study the homology of nilpotent groups. In particular a certain vanishing result for the homology and cohomology of nilpotent groups is proved.

K-Theory and Homology · Mathematics 2023-06-22 Behrooz Mirzaii , Fatemeh Yeganeh Mokari

In this paper we survey a new criteria for solvability of finite groups in terms of number of supersolvable (also known as polycyclic) and non-supersolvable subgroups. In particular, we present original examples of supersolvable groups such…

General Mathematics · Mathematics 2022-08-29 Primitivo B. Acosta-Humánez , Orieta Liriano , Francis Mora-Ferreras

A covering of a group is a finite set of proper subgroups whose union is the whole group. A covering is minimal if there is no covering of smaller cardinality, and it is nilpotent if all its members are nilpotent subgroups. We complete a…

Group Theory · Mathematics 2014-09-29 Russell D. Blyth , Francesco Fumagalli , Marta Morigi

We refer to the set of the orders of elements of a finite group as its spectrum and say that groups are isospectral if their spectra coincide. We prove that with the only specific exception the solvable radical of a nonsolvable finite group…

Group Theory · Mathematics 2022-07-07 Nanying Yang , Mariya A. Grechkoseeva , Andrey V. Vasil'ev

We prove a structure theorem for periodic locally soluble groups satisfying a chain condition on intersections of relatively uniformly definable subgroups using results from the theory of stable groups. The result in particular shows that…

Logic · Mathematics 2019-11-06 Jamshid Derakhshan

The complexity of the equation solvability problem is known for nilpotent groups, for not solvable groups and for some semidirect products of Abelian groups. We provide a new polynomial time algorithm for deciding the equation solvability…

Group Theory · Mathematics 2016-03-21 Attila Földvári

We construct two finite groups of size $2^{365}\cdot 3^{105}\cdot 7^{104}$: a solvable group $G$ and a non-solvable group $H$, such that for every integer $n$ the groups have the same number of elements of order $n$. This answers a question…

Group Theory · Mathematics 2025-06-18 Paweł Piwek

We present new metric criteria for non-amenability and discuss applications. The main application of the results of this paper is the proof of non-amenability of R.Thompson's group F. This is a continuation of the series of papers on our…

Group Theory · Mathematics 2013-12-23 Azer Akhmedov

Let $G$ be a finite group and $N(G)$ be the set of its conjugacy class sizes. In the 1980's Thompson conjectured that the equality $N(G)=N(S)$, where $Z(G)=1$ and $S$ is simple, implies the isomorphism $G\simeq S$. In a series of papers of…

Group Theory · Mathematics 2019-12-17 Ilya Gorshkov

In the well-studied Stable Roommates problem, we seek a stable matching of agents into pairs, where no two agents prefer each other over their assigned partners. However, some instances of this problem are unsolvable, lacking any stable…

Computer Science and Game Theory · Computer Science 2025-07-08 Frederik Glitzner , David Manlove

We give lower bounds on the complexity of the word problem of certain non-solvable groups: for a large class of non-solvable infinite groups, including in particular free groups, Grigorchuk's group and Thompson's groups, we prove that their…

Group Theory · Mathematics 2020-06-23 Laurent Bartholdi , Michael Figelius , Markus Lohrey , Armin Weiß

Generalising Solomon's theorem, C. Gordon and F. Rodriguez-Villegas have proven recently that, in any group, the number of solutions to a system of coefficient-free equations is divisible by the order of this group whenever the rank of the…

Group Theory · Mathematics 2017-05-02 Anton A. Klyachko , Anna A. Mkrtchyan

We prove new upper bounds for the length of laws that hold for all groups of size at most $n$ -- improving on previous results of Bou-Rabee and Kassabov-Matucci. The methods make use of the classification of finite simple groups. Stronger…

Group Theory · Mathematics 2015-09-08 Andreas Thom

In the lambda calculus a term is solvable iff it is operationally relevant. Solvable terms are a superset of the terms that convert to a final result called normal form. Unsolvable terms are operationally irrelevant and can be equated…

Logic in Computer Science · Computer Science 2019-03-14 Á. García-Pérez , P. Nogueira

We propose a new unifying framework for Thompson-like groups using a well-known device called operads and category theory as language. We discuss examples of operad groups which have appeared in the literature before. As a first…

Group Theory · Mathematics 2016-04-05 Werner Thumann

(1) There is a finitely presented group with a word problem which is a uniformly effectively inseparable equivalence relation. (2) There is a finitely generated group of computable permutations with a word problem which is a universal…

Logic · Mathematics 2016-09-13 André Nies , Andrea Sorbi