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In this work, the notion of a twisted partial Hopf action is introduced as a unified approach for twisted partial group actions, partial Hopf actions and twisted actions of Hopf algebras. The conditions on partial cocycles are established…

Rings and Algebras · Mathematics 2015-11-12 Marcelo Muniz S. Alves , Eliezer Batista , Michael Dokuchaev , Antonio Paques

von Neumann algebras have been playing an increasingly important role in the context of gauge theories and gravity. The crossed product presents a natural method for implementing constraints through the commutation theorem, rendering it a…

High Energy Physics - Theory · Physics 2025-02-10 Shadi Ali Ahmad , Marc S. Klinger , Simon Lin

We define a notion of free product for coarse spaces that generalizes the corresponding notion of a free product for groups. We show that free products preserve coarse properties such as coarse property C, finite coarse decomposition…

Geometric Topology · Mathematics 2020-06-26 Greg Bell , Austin Lawson

We prove that the crossed product AxG of a unital finitely generated MF algebra A by a discrete finitely generated amenable residually finite group G is an MF algebra, provided that the action is almost periodic. This generalizes a result…

Operator Algebras · Mathematics 2017-05-29 Weihua Li , Stefanos Orfanos

We report on recent progress concerning the relationship that exists between the algebraic structure of a finite group and certain features of its class-size prime graph.

Group Theory · Mathematics 2024-10-02 Víctor Sotomayor

In this paper we first state the classification of the prolongations of complex free fundamental graded Lie algebras. Next we introduce the notion of free pseudo-product fundamental graded Lie algebras and study the prolongations of complex…

Differential Geometry · Mathematics 2012-06-28 Tomoaki Yatsui

In the spirit of Diffie Hellman the concept of a protocol algebra is introduced using certain amalgamated free product of Braid group B and Thompson group T together with a nilpotent subgroup H of index 2.

Cryptography and Security · Computer Science 2015-03-19 Sumit Kumar Upadhyay , Shiv Datt Kumar , Ramji Lal

We present examples of closed subsets of a free group such that their product is not closed in the profinite topology. We discuss how to characterize a subset of a free group which is closed in the profinite topology and its product with…

Group Theory · Mathematics 2019-06-19 Rita Gitik , Eliyahu Rips

In this paper we prove the theorem on freedom for relatively free groups with a single relation (analogous with the well-known result of Magnus) and the theorem on freedom for relatively free Lie algebras with a single relation (analogous…

Group Theory · Mathematics 2021-07-27 Alexander Krasnikov

We discuss the cyclic homology of crossed product algebras from the Cuntz-Quillen point of view. The periodic cyclic homology of a crossed product algebra $A\rtimes G$ is described in terms of the $G$-action on periodic cyclic bicomplexes…

K-Theory and Homology · Mathematics 2022-10-19 Michael Puschnigg

A conjecture of Dicks and the author on rank of the intersection of factor-free subgroups in free products of groups is proved for the case of left ordered groups.

Group Theory · Mathematics 2016-07-12 Sergei V. Ivanov

We study the language-theoretic aspects of the word problem, in the sense of Duncan & Gilman, of free products of semigroups and monoids. First, we provide algebraic tools for studying classes of languages known as super-AFLs, which…

Group Theory · Mathematics 2021-12-21 Carl-Fredrik Nyberg-Brodda

We introduce the notion of tracial amenability for actions of discrete groups on unital, tracial C$^*$-algebras, as a weakening of amenability where all the relevant approximations are done in the uniform trace norm. We characterize tracial…

Operator Algebras · Mathematics 2024-02-26 Eusebio Gardella , Shirly Geffen , Julian Kranz , Petr Naryshkin , Andrea Vaccaro

This paper is motivated primarily by the question of when the maximal and reduced crossed products of a $G$-$C^*$-algebra agree (particularly inspired by results of Matsumura and Suzuki), and the relationships with various notions of…

Operator Algebras · Mathematics 2019-04-30 Alcides Buss , Siegfried Echterhoff , Rufus Willett

In the reduced free product of C*-algebras (A,phi)=(A_1,phi_1)*(A_2,phi_2), A is shown to be purely infinite and simple under the hypothesis that A_1 is the crossed product of a C*-algebra by a discrete infinite group, phi_1 is well behaved…

Operator Algebras · Mathematics 2007-05-23 Marie Choda , Ken Dykema

We describe the conjugacy classes of the elements of the free product of two groups and their centralizers and, as a consequence, we correct the calculation of the cyclic and periodic cyclic homology of the group ring of the free product of…

Group Theory · Mathematics 2023-01-26 Dan Burghelea

We classify the finite groups $G$ such that the group of units of the integral group ring ${\mathbb Z} G$ has a subgroup of finite index which is a direct product of free-by-free groups.

Group Theory · Mathematics 2007-05-23 Eric Jespers , Antonio Pita , Angel del Rio , Manuel Ruiz , Pavel Zalesski

We show that all amenable, minimal actions of a large class of nonamenable countable groups on compact metric spaces have dynamical comparison. This class includes all nonamenable hyperbolic groups, many HNN-extensions, nonamenable…

Operator Algebras · Mathematics 2023-03-01 Eusebio Gardella , Shirly Geffen , Julian Kranz , Petr Naryshkin

The free product of an arbitrary pair of finite hyperfinite von Neumann algebras is examined, and the result is determined to be the direct sum of a finite dimensional algebra and an interpolated free group factor $L(\freeF_r)$. The finite…

funct-an · Mathematics 2008-02-03 Ken Dykema

The cocycle bicrossed product construction allows certain freedom in producing examples of locally compact quantum groups. We give an overview of some recent examples of this kind having remarkable properties.

Quantum Algebra · Mathematics 2007-05-23 Leonid Vainerman