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We introduce and investigate a class of profinite groups defined via extensions of centralizers analogous to the extensively studied class of finitely generated fully residually free groups, that is, limit groups (in the sense of Z. Sela).…

Group Theory · Mathematics 2017-11-07 Pavel Zalesskii , Theo Zapata

Let $S$ be a finitely generated pro-$p$ group. Let $\Emb(S)$ be the class of profinite groups $G$ that have $S$ as a Sylow subgroup, and such that $S$ intersects non-trivially with every non-trivial normal subgroup of $G$. In this paper, we…

Group Theory · Mathematics 2013-01-11 Colin D. Reid

We prove that there exist finitely presented, residually finite groups that are profinitely rigid in the class of all finitely presented groups but not in the class of all finitely generated groups. These groups are of the form $\Gamma…

Group Theory · Mathematics 2025-04-15 M. R. Bridson , A. W. Reid , R. Spitler

We study a natural generalization of inverse systems of finite regular covering spaces. A limit of such a system is a fibration whose fibres are profinite topological groups. However, as shown in a previous paper (Conner-Herfort-Pavesic:…

Algebraic Topology · Mathematics 2019-01-09 Gregory R. Conner , Wolfgang Herfort , Petar Pavešić

We study infinitely iterated wreath products of finite permutation groups with respect to product actions. In particular, we prove that, for every non-empty class of finite simple groups $\mathcal{X}$, there exists a finitely generated…

Group Theory · Mathematics 2017-02-27 Benjamin Klopsch , Matteo Vannacci

We introduce various probablistic finiteness conditions for profinite groups related to positive finite generation (PFG). We investigate completed group rings which are PFG as modules, and use this to answer a question of Kionke and the…

Group Theory · Mathematics 2020-06-26 Ged Corob Cook , Matteo Vannacci

Broadly speaking, a finiteness property of groups is any generalisation of the property of having finite order. A large part of infinite group theory is concerned with finiteness properties and the relationships between them. Profinite…

Group Theory · Mathematics 2010-02-16 Colin Reid

We construct a finitely presented group with property (T) which can not act on on reasonable spaces. Such group is constructed using an generalization of Hall embedding theorem, where property (T) is added at the expense of weakening the…

Group Theory · Mathematics 2026-02-02 Indira Chatterji , Martin Kassabov

We prove that the sign of the Euler characteristic of arithmetic groups with CSP is determined by the profinite completion. In contrast, we construct examples showing that this is not true for the Euler characteristic itself and that the…

Group Theory · Mathematics 2019-01-23 Holger Kammeyer , Steffen Kionke , Jean Raimbault , Roman Sauer

We study countable embedding-universal and homomorphism-universal structures and unify results related to both of these notions. We show that many universal and ultrahomogeneous structures allow a concise description (called here a finite…

Combinatorics · Mathematics 2010-09-06 Jan Hubicka

The structure of finite and locally finite groups in which every element has prime power order (CP-groups) is well known. In this paper we note that the combination of our earlier results with the available information on the structure of…

Group Theory · Mathematics 2020-01-07 Pavel Shumyatsky

We give a simple characterization of all perfectoid profinite \'{e}tale covers of abelian varieties in terms of the Hodge-Tate filtration on the $p$-adic Tate module. We also compute the geometric Sen morphism for all profinite $p$-adic Lie…

Number Theory · Mathematics 2025-01-08 Rebecca Bellovin , Hanlin Cai , Sean Howe , Tongmu He

We achieve several results. First, we develop a variant of the theory of absolute Galois groups in the context of many sorted structures. Second, we provide a method for coding absolute Galois groups of structures, so they can be…

Logic · Mathematics 2021-07-27 Daniel Max Hoffmann , Junguk Lee

We introduce the classes of TAP groups, in which various types of algebraic fibring are detected by the non-vanishing of twisted Alexander polynomials. We show that finitely presented LERF groups lie in the class $\mathsf{TAP}_1(R)$ for…

Group Theory · Mathematics 2026-03-03 Sam Hughes , Dawid Kielak

We investigate the ability of a free pro-$\CC$ group of infinite rank to abstractly solve abstract embedding problems, and conclude that for some varieties $\CC$, the profinite completion of any order, of a free pro-$\CC$ group of infinite…

Group Theory · Mathematics 2023-01-31 Tamar Bar-On

Let $k$ be a field of characteristic $p>0$, which has infinitely many discrete valuations. We show that every finite embedding problem for $\Gal(k)$ with finitely many prescribed local conditions, whose kernel is a $p$-group, is properly…

Number Theory · Mathematics 2011-02-22 Nguyen Duy Tan

A profinite group $G$ is just infinite if every closed normal subgroup of $G$ is of finite index. We prove that an infinite profinite group is just infinite if and only if, for every open subgroup $H$ of $G$, there are only finitely many…

Group Theory · Mathematics 2010-10-20 Colin Reid

Recently there has been a lot of research and progress in profinite groups. We survey some of the new results and discuss open problems. A central theme is decompositions of finite groups into bounded products of subsets of various kinds…

Group Theory · Mathematics 2012-02-23 Nikolay Nikolov

We rewrite simplicially the standard definitions of a complete first order theory, a model of it, and various characterisations of stability of a complete first order theory. In our reformulations the simplicial language replaces the…

Category Theory · Mathematics 2025-10-02 Misha Gavrilovich

For profinite branch groups, we first demonstrate the equivalence of the Bergman property, uncountable cofinality, Cayley boundedness, the countable index property, and the condition that every non-trivial normal subgroup is open; compact…

Group Theory · Mathematics 2016-02-02 François Le Maître , Phillip Wesolek