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The aim of this paper is to unify the points of view of three recent and independent papers (Ventura 1997, Margolis, Sapir and Weil 2001 and Kapovich and Miasnikov 2002), where similar modern versions of a 1951 theorem of Takahasi were…

Group Theory · Mathematics 2007-09-19 Alexei Miasnikov , Enric Ventura , Pascal Weil

We study model theory of fields with actions of a fixed finite group scheme. We prove the existence and simplicity of a model companion of the theory of such actions, which generalizes our previous results about truncated iterative…

Logic · Mathematics 2020-06-08 Daniel Max Hoffmann , Piotr Kowalski

We develop new methods for computing the precise Dehn functions of coabelian subgroups of direct products of groups, that is, subgroups which arise as kernels of homomorphisms from the direct product onto a free abelian group. These improve…

Group Theory · Mathematics 2023-08-23 Robert Kropholler , Claudio Llosa Isenrich

The Friedman--Mineyev theorem, earlier known as the (strengthened) Hanna Neumann conjecture, gives a sharp estimate for the rank of the intersection of two subgroups in a free group. We obtain an analogue of this inequality for any two…

Group Theory · Mathematics 2024-05-01 Anton A. Klyachko , Alexander O. Zakharov

We show that the continuous core of any type III free product factor has no Cartan subalgebra. This is a complement to previous works due to Houdayer--Ricard and Boutonnet--Houdayer--Raum.

Operator Algebras · Mathematics 2019-05-21 Yoshimichi Ueda

We investigate a construction which associates a finite von Neumann algebra $M(\Gamma,\mu)$ to a finite weighted graph $(\Gamma,\mu)$. Pleasantly, but not surprisingly, the von Neumann algebra associated to to a `flower with $n$ petals' is…

Operator Algebras · Mathematics 2011-02-23 Madhushree Basu , Vijay Kodiyalam , V. S. Sunder

We investigate the problem of elementary equivalence of the free group factors, that is, do all free group factors $L(\mathbb{F}_n)$ share a common first-order theory? We establish a trichotomy of possibilities for their common first-order…

Logic · Mathematics 2025-01-03 Isaac Goldbring , Jennifer Pi

In this paper, we introduce and investigate two new subclasses of analytic functions in the open unit disk in the complex plane. Several interesting properties of the functions belonging to these classes are examined. Here, sufficient, and…

Complex Variables · Mathematics 2017-04-18 Nizami Mustafa

There has been substantial investigation in recent years of subdirect products of limit groups and their finite presentability and homological finiteness properties. To contrast the results obtained for limit groups, Baumslag, Bridson, Holt…

Group Theory · Mathematics 2011-07-18 J. R. J. Groves

We construct finite group actions on Lagrangian Floer theory when symplectic manifolds have finite group actions and Lagrangian submanifolds have induced group actions. We first define finite group actions on Novikov-Morse theory. We…

Symplectic Geometry · Mathematics 2018-05-31 Cheol-Hyun Cho , Hansol Hong

We study a simple subclass of free actions of non-Abelian groups on unital C*-algebras, namely cleft actions. These are characterized by the fact that the associated noncommutative vector bundles are trivial. In particular, we provide a…

Operator Algebras · Mathematics 2025-12-24 Kay Schwieger , Stefan Wagner

We canonically associate to any planar algebra two type II_{\infty} factors M_{+} and M_{-}. The subfactors constructed previously by the authors in a previous paper are isomorphic to compressions of M_{+} and M_{-} to finite projections.…

Operator Algebras · Mathematics 2009-11-26 A. Guionnet , V. F. R. Jones , D. Shlyakhtenko

This note contains a (short) proof of the following generalisation of the Friedman--Mineyev theorem (earlier known as the Hanna Neumann conjecture): if $A$ and $B$ are nontrivial free subgroups of a virtually free group containing a free…

Group Theory · Mathematics 2020-03-06 Anton A. Klyachko , Anastasia N. Ponfilenko

It has been shown by Voiculescu and Biane that the analytic subordination property holds for free additive and multiplicative convolutions. In this paper, we present an operatorial approach to subordination for free multiplicative…

Operator Algebras · Mathematics 2009-10-22 Romuald Lenczewski

We study several properties of expansive group actions on metric spaces and obtain relation between expansivity for subgroup and group actions. Through counter examples necessity of hypothesis are justified. We also study expansivity of…

Dynamical Systems · Mathematics 2018-08-01 Ali Barzanouni , Mahin Sadat Divandar , Ekta Shah

An almost-direct product of free groups is an iterated semidirect product of finitely generated free groups in which the action of the constituent free groups on the homology of one another is trivial. We determine the structure of the…

Algebraic Topology · Mathematics 2019-02-20 Daniel C. Cohen

We analyse the subgroup structure of direct products of groups. Earlier work on this topic has revealed that higher finiteness properties play a crucial role in determining which groups appear as subgroups of direct products of free groups…

Group Theory · Mathematics 2013-05-20 Benno Kuckuck

We investigate factoriality, Connes' type ${\rm III}$ invariants and fullness of arbitrary amalgamated free product von Neumann algebras using Popa's deformation/rigidity theory. Among other things, we generalize many previous structural…

Operator Algebras · Mathematics 2025-07-17 Cyril Houdayer , Yusuke Isono

We classify compact K\"ahler threefolds $X$ with a free group of automorphisms acting freely on $X$.

Dynamical Systems · Mathematics 2020-02-04 Serge Cantat , Olga Paris-Romaskevich , Junyi Xie

We give an extension of the Fekete's Subadditive Lemma for a set of submultiplicative functionals on countable product of compact spaces. Our method can be considered as an unfolding of the ideas [1]Theorem 3.1 and our main result is an…

Classical Analysis and ODEs · Mathematics 2014-04-01 László Tapolcai Greiner
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