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We construct a generalized version for the free product of unital C*-algebras over a family of unital C*-subalgebras, starting from the group-analogue. When all the subalgebras are the same, we recover the free product with amalgamation…

Operator Algebras · Mathematics 2007-05-23 Stefan Teodor Bildea

We show that the conjugacy problem is solvable in [finitely generated free]-by-cyclic groups, by using a result of O. Maslakova that one can algorithmically find generating sets for the fixed subgroups of free group automorphisms, and one…

Group Theory · Mathematics 2007-05-23 O. Bogopolski , A. Martino , O. Maslakova , E. Ventura

We study a class of quasimorphisms of the free group that can be expressed as infinite sums of Brooks quasimorphisms with some nice properties. We then review Heuer's framework of decompositions developed in arXiv:1710.03193, and put these…

Group Theory · Mathematics 2021-06-28 Francesco Fournier-Facio

We derive a generating series for the number of free subgroups of finite index in $\Delta^+ = \mathbb{Z}_p*\mathbb{Z}_q$ by using a connection between free subgroups of $\Delta^+$ and certain hypermaps (also known as ribbon graphs or "fat"…

Combinatorics · Mathematics 2019-02-13 Laura Ciobanu , Alexander Kolpakov

We investigate which free constructions (amalgamated products and HNN-extensions) over word hyperbolic groups produce groups that are again word hyperbolic. A complete answer is obtained for the case when the amalgamated subgroups are…

Group Theory · Mathematics 2008-02-03 Olga Kharlampovich , Alexey Myasnikov

In this paper we first survey some basic results in the cohomology of finite groups, and then discuss recent work on constructing free actions of finite groups on products of spheres.

Algebraic Topology · Mathematics 2007-05-23 Alejandro Adem

We establish a general criterion for the finite presentability of subdirect products of groups and use this to characterize finitely presented residually free groups. We prove that, for all $n\in\mathbb{N}$, a residually free group is of…

Group Theory · Mathematics 2008-09-23 Martin R. Bridson , James Howie , Charles F. Miller , Hamish Short

We investigate the structure of subdirect products of groups, particularly their finiteness properties. We pay special attention to the subdirect products of free groups, surface groups and HNN extensions. We prove that a finitely presented…

Group Theory · Mathematics 2014-02-26 Martin R Bridson , Charles F Miller

We give a complete classification of finitely generated virtually free groups up to $\forall\exists$-elementary equivalence. As a corollary, we give an algorithm that takes as input two finite presentations of virtually free groups, and…

Group Theory · Mathematics 2019-10-21 Simon André

We introduce the notion of corestricted free products of a family of profinite groups indexed over an arbitrary profinite space. Using arithmetic results of the second author, this enables us to prove an analogue of Riemann's existence…

Group Theory · Mathematics 2013-12-16 Jochen Gärtner , Kay Wingberg

We prove that the free product of two finitely presented locally tame groups is locally tame and describe many examples of tame subgroups of finitely presented groups. We also include some open problems related to tame subgroups.

Group Theory · Mathematics 2017-11-03 Rita Gitik

We offer a direct proof of an elementary result concerning cohomological periods. As a corollary we show that given a finitely generated stably free resolution of Z over a finite group, two of its modules are free.

Group Theory · Mathematics 2024-01-09 Wajid Mannan

In this paper we prove the theorem on freedom for free products with a single relation (analogous with the well-known result of Magnus) and a generalized Freiheitssatz for free products (analogous with the well-known result of Romanovski)

Group Theory · Mathematics 2022-09-27 A. F. Krasnikov

We describe free prosoluble subgroups of a free product of profinite groups by strengthening the theorem of Frorian Pop and answering two questions of K. Ersoy and W. Herfort. Relatively projective prosoluble groups are also described.

Group Theory · Mathematics 2024-11-20 Pavel Zalesskii

In this paper we describe the amalgamated free product of two hyperfinite von Neumann algebras over a finite dimensional subalgebra. In general the free product is a finite direct sum of interpolated free group factors and a hyperfinite von…

Operator Algebras · Mathematics 2011-10-26 Ken Dykema , Daniel Redelmeier

Given a group $G = H_1 \ast_A H_2$ which is the free product of two finitely generated groups $H_1$ and $H_2$ with amalgamation over a cyclic subgroup $A$ which is malnormal in $G$, we study relations between the structure of its subgroups…

Group Theory · Mathematics 2026-03-18 Martin Kreuzer , Anja Moldenhauer , Gerhard Rosenberger

Our purpose is to visualize the pronilpotent completion of a finitely generated free group as a certain subgroup in the free Lie group.

Group Theory · Mathematics 2025-08-13 Yury A. Neretin

We introduce a class $\A$ of finitely generated residually finite accessible groups with some natural restriction on one-ended vertex groups in their JSJ-decompositions. We prove that the profinite completion of groups in $\A$ almost…

Group Theory · Mathematics 2022-08-30 Vagner R. de Bessa , Anderson L. P. Porto , Pavel A. Zalesskii

Let $G=G_1\ast\dots\ast G_k\ast F$ be a countable group which splits as a free product, where all groups $G_i$ are freely indecomposable and not isomorphic to $\mathbb{Z}$, and $F$ is a finitely generated free group. If for all…

Group Theory · Mathematics 2014-09-08 Camille Horbez

In this paper we study residual solvability of the amalgamated product of two finitely generated free groups, in the case of doubles. We find conditions where this kind of structure is residually solvable, and show that in general this is…

Group Theory · Mathematics 2007-05-23 Delaram Kahrobaei