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We prove that the category of profinite cosheaves valued in a pro-regular category (satisfying mild assumptions) is itself a pro-regular category. As a corollary, we extend Wilkes's cosheaf-bundle equivalence from profinite modules to…

Category Theory · Mathematics 2026-02-11 Jiacheng Tang

We prove that the class of closed subgroups of free profinite monoids is precisely the class of projective profinite groups. In particular, the profinite groups associated to minimal symbolic dynamical systems by Almeida are projective. Our…

Group Theory · Mathematics 2014-02-26 John Rhodes , Benjamin Steinberg

For a complex reflection group $W$ with reflection representation $\mathfrak{h}$, we define and study a natural filtration by Serre subcategories of the category $\mathcal{O}_c(W, \mathfrak{h})$ of representations of the rational Cherednik…

Representation Theory · Mathematics 2018-02-15 Ivan Losev , Seth Shelley-Abrahamson

The theory of condensed mathematics by Dustin Clausen and Peter Scholze claims that topological spaces should be replaced by the definition of condensed sets. The main purpose of this paper is to investigate in which way the theory of…

Algebraic Topology · Mathematics 2021-05-18 Catrin Mair

Let $G$ be the fundamental group of a graph of finitely generated virtually free groups with virtually cyclic edge groups. We shaw that $G$ is cohomologically good if $G$ is residually finite. If $G$ is LERF, we prove that G splits…

Group Theory · Mathematics 2026-03-18 Andrei Jaikin-Zapirain , Henrique Souza , Pavel Zalesski

For every profinite group $G$, we construct two covariant functors $\Delta_G$ and ${\bf {\mathcal {AP}}}_G$ from the category of commutative rings with identity to itself, and show that indeed they are equivalent to the functor $W_G$…

Rings and Algebras · Mathematics 2007-05-23 Young-Tak Oh

We determine for which known finite simple groups $G$ and which primes $p$ the $p$-fusion system of $G$ is simple. This means first collecting together the results that were already known (and correcting two errors made in an earlier study…

Group Theory · Mathematics 2022-11-08 Bob Oliver , Albert Ruiz

In this paper we study the question of how to transfer homotopic structure from the category sD of simplicial objects in a fixed category D to D. To this end we use a sort of homotopy colimit s : sD --> D, which we call simple functor. For…

Algebraic Geometry · Mathematics 2011-10-12 Beatriz Rodriguez Gonzalez

Let $G$ be a residually finite, good group of finite virtual cohomological dimension. We prove that the natural monomorphism $G\hookrightarrow\hat{G}$ induces a bijective correspondence between conjugacy classes of finite $p$-subgroups of…

Group Theory · Mathematics 2024-10-29 Marco Boggi , Pavel Zalesskii

We study in detail the profinite group G arising as geometric \'etale iterated monodromy group of an arbitrary quadratic morphism f with an infinite postcritical orbit over a field of characteristic different from two. This is a…

Group Theory · Mathematics 2013-09-24 Richard Pink

We consider profinite groups as 2-sorted first order structures, with a group sort, and a second sort which acts as an index set for a uniformly definable basis of neighbourhoods of the identity. It is shown that if the basis consists of…

Logic · Mathematics 2017-05-17 Dugald Macpherson , Katrin Tent

We give some background on uniform pro-p groups and the model theory of profinite NIP groups.

Group Theory · Mathematics 2017-05-23 Tim Clausen , Katrin Tent

We study the commensurators of free groups and free pro-$p$ groups, as well as certain subgroups of these. We prove that the commensurator $Comm(F)$ of a non-abelian free group of finite rank $F$ is not virtually simple, answering a…

By a coprime commutator in a profinite group $G$ we mean any element of the form $[x, y]$, where $x,y\in G$ and $(|x|,|y|)=1$. It is well-known that the subgroup generated by the coprime commutators of $G$ is precisely the pronilpotent…

Group Theory · Mathematics 2026-04-08 Cristina Acciarri , Pavel Shumyatsky

It is shown that for any finitely generated subgroups H and K of a free group F, and for any element g in F the double coset HgK is closed in the profinite topology of F.

Group Theory · Mathematics 2013-06-04 Rita Gitik , Eliyahu Rips

We study homological approximations of the profinite completion of a limit group (see Thm.~A) and obtain the analogous of Bridson and Howie's Theorem for the profinite completion of a non-abelian limit group (see Thm.~B).

Group Theory · Mathematics 2018-03-02 Jhoel S. Gutierrez

There are many results showing the connection and phenomenon between some low-dimensional manifolds with the profinite completions of their fundamental groups. We focus on some Seifert 4-manifolds about the extent of their profinite…

Geometric Topology · Mathematics 2023-04-05 Jiming Ma , Zixi Wang

We construct a "diagonal" cofibrantly generated model structre on the category of simplicial objects in the category of topological categories sCat_{Top}, which is the category of diagrams [\Delta^{op}, Cat_{Top}]. Moreover, we prove that…

Algebraic Topology · Mathematics 2011-12-07 Ilias Amrani

We construct a correspondence between the cohomology groups of a group $G$ relative to a family of subgroups $\famS$ and the classes of `relative extensions' of $G$ by abelian groups, modulo a certain equivalence relation. We establish this…

Group Theory · Mathematics 2022-09-15 Gareth Wilkes

Let $G$ be the group of rational points of a split connected reductive group over a non-archimedean local field of residue characteristic $p$, and let $\mathcal{H}$ denote the pro-$p$ Iwahori-Hecke algebra of $G$ over a field of…

Representation Theory · Mathematics 2025-07-22 Nicolas Dupré