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We construct large families of groups admitting free transitive actions on median spaces. In particular, we construct groups which act freely and transitively on the complete universal real tree with continuum valence such that any subgroup…

Group Theory · Mathematics 2025-07-31 Pénélope Azuelos

We construct a family of automata with n states, n>3, acting on a rooted binary tree that generate the free products of cyclic groups of order 2.

Group Theory · Mathematics 2008-07-01 Dmytro Savchuk , Yaroslav Vorobets

This is a part of an ongoing project, the goal of which is to classify all semi-direct products $\mathfrak s=\mathfrak g{\ltimes} V$ such that $\mathfrak g$ is a simple Lie algebra, $V$ is a $\mathfrak g$-module, and $\mathfrak s$ has a…

Representation Theory · Mathematics 2018-02-21 Dmitri I. Panyushev , Oksana S. Yakimova

In this paper, we consider topological semigroup actions on compact topological spaces. Under mild assumptions on the semigroup and the action, we construct a semi-direct product groupoid with a Haar system. We also show that it is…

Operator Algebras · Mathematics 2014-06-20 Jean Renault , S. Sundar

We investigate some general machinery for describing semidualizing modules over generic constructions like ladder determinantal rings with coefficients in a normal domain. We also pose and investigate natural localization questions that…

Commutative Algebra · Mathematics 2020-01-01 Sean K. Sather-Wagstaff , Tony Se , Sandra Spiroff

We introduce a new construction of matrix wreath products of algebras that is similar to wreath products of groups. We then use it to prove embedding theorems for Jacobson radical, nil, and primitive algebras. In \S\ref{Section6}, we…

Rings and Algebras · Mathematics 2017-04-04 Adel Alahmadi , Hamed Alsulami , S. K. Jain , Efim Zelmanov

In this paper we characterize the congruence associated to the direct sum of all irreducible representations of a finite semigroup over an arbitrary field, generalizing results of Rhodes for the field of complex numbers. Applications are…

Group Theory · Mathematics 2014-11-25 Jorge Almeida , Stuart Margolis , Benjamin Steinberg , Mikhail Volkov

Our aim in this paper is to give some examples of $(a, 1)f$ Riemannian structures (a generalization of an $r$-paracontact structure) induced on product of spheres of codimension $r$ ($r \in \{1,2\} $) in an $m$-dimensional Euclidean space…

Differential Geometry · Mathematics 2007-11-06 Cristina-Elena Hretcanu , Mircea Crasmareanu

We describe an underlying right angled building structure of any graph product of buildings. We describe the automorphism group of the graph product of buildings. We show that the notion of generalized graph product of a collection of…

Group Theory · Mathematics 2014-07-18 Aliska Gibbins

We construct automata over a binary alphabet with $2n$ states, $n\geq 2$, whose states freely generate a free group of rank $2n$. Combined with previous work, this shows that a free group of every finite rank can be generated by finite…

Group Theory · Mathematics 2007-05-23 Benjamin Steinberg , Mariya Vorobets , Yaroslav Vorobets

We introduce analogs of the Hopf algebra of Free quasi-symmetric functions with bases labelled by colored permutations. When the color set is a semigroup, an internal product can be introduced. This leads to the construction of generalized…

Combinatorics · Mathematics 2013-02-12 Jean-Christophe Novelli , Jean-Yves Thibon

Cup products provide a natural approach to access higher bounded cohomology groups. We extend vanishing results on cup products of Brooks quasimorphisms of free groups to cup products of median quasimorphisms, i.e., Brooks-type…

Group Theory · Mathematics 2025-02-21 Benjamin Brück , Francesco Fournier-Facio , Clara Loeh

The aim of this paper is to see how commuting graphs interact with two semigroup constructions: the zero-union and the direct product. For both semigroup constructions, we investigate the diameter, clique number, girth, chromatic number and…

Combinatorics · Mathematics 2025-11-06 Tânia Paulista

Operation-based Conflict-free Replicated Data Types (CRDTs) are eventually consistent replicated data types that automatically resolve conflicts between concurrent operations. Op-based CRDTs must be designed differently for each data type,…

Distributed, Parallel, and Cluster Computing · Computer Science 2020-04-10 Matthew Weidner , Heather Miller , Christopher Meiklejohn

Constant Rank (CR) state machines play an important role in the general structure theory of Finite State Machines. A machine is of constant rank if each input and input-sequence maps the state set onto the same number of next states.…

General Mathematics · Mathematics 2007-05-23 N. F. Benschop

We determine the automorphism group for some well known constructions of finite semifields. In particular, we compute the automorphism group of Sandler's semifields and in certain cases the automorphism groups of the Hughes-Kleinfeld and…

Rings and Algebras · Mathematics 2013-05-23 Andrew Steele

The rank of a finite semigroup is the smallest number of elements required to generate the semigroup. A formula is given for the rank of an arbitrary (non necessarily regular) Rees matrix semigroup over a group. The formula is expressed in…

Group Theory · Mathematics 2014-06-09 Robert D. Gray

We study conditions under which subdirect products of various types of algebraic structures are finitely generated or finitely presented. In the case of two factors, we prove general results for arbitrary congruence permutable varieties,…

Rings and Algebras · Mathematics 2019-04-24 Peter Mayr , Nik Ruskuc

We consider the growth, order, and finiteness problems for automaton (semi)groups. We propose new implementations and compare them with the existing ones. As a result of extensive experimentations, we propose some conjectures on the order…

Formal Languages and Automata Theory · Computer Science 2013-10-21 Ines Klimann , Jean Mairesse , Matthieu Picantin

We construct quasi-isometric embeddings from right-angled Artin groups into the outer automorphism group of a free group. These homomorphisms are in analogy with those constructed in \cite{CLM}, where the target group is the mapping class…

Geometric Topology · Mathematics 2013-03-28 Samuel J. Taylor