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We present a relatively simple description of binary, definable subsets of models of weakly quasi-o-minimal theories. In particular, we closely describe definable linear orders and prove a weak version of the monotonicity theorem. We also…

Logic · Mathematics 2021-06-01 Slavko Moconja , Predrag Tanović

We obtain a weak homotopy equivalence type result between two topological groups associated with a Kirchberg algebra: the unitary group of the continuous asymptotic centralizer and the loop group of the automorphism group of the…

Operator Algebras · Mathematics 2019-02-26 Masaki Izumi , Hiroki Matui

In this paper we discuss the problem of existence of so called weak Sierpi\'nski sets in groups. It is known that group $G$ has a Sierpi\'nski subset if and only if it contains a free subgroup. In their paper, Tomkowicz and Wagon…

Group Theory · Mathematics 2019-03-21 Agnieszka Bier , Piotr Słanina

We introduce the class of weakly log canonical singularities, a natural generalization of semi-log canonical singularities. Toric varieties (associated to toric face rings, possibly non-normal or reducible) which have weakly (semi-) log…

Algebraic Geometry · Mathematics 2017-11-02 Florin Ambro

The description of the subgroup structure of a non-commutative division ring is the subject of the intensive study in the theory of division rings in particular, and of the theory of skew linear groups in general. This study is still so far…

Rings and Algebras · Mathematics 2020-11-04 Bui Xuan Hai , Huynh Viet Khanh

Finite groups with given systems of permuteral and strongly permuteral subgroups are studied. New characterizations of w-supersoluble and supersoluble groups are received.

Group Theory · Mathematics 2013-05-14 A. F. Vasil'ev , V. A. Vasil'ev , T. I. Vasil'eva

Ergodic theory includes several notions of entropy for probability-preserving actions of countable groups. These include Kolmogorov--Sinai entropy based on F\o lner sequences for amenable groups, entropy defined using a random ordering of…

Operator Algebras · Mathematics 2026-03-23 Tim Austin

We introduce the notion of weak commensurabilty of arithmetic subgroups and relate it to the length equivalence and isospectrality of locally symmetric spaces. We prove many strong consequences of weak commensurabilty and derive from these…

Differential Geometry · Mathematics 2009-04-07 Gopal Prasad , Andrei S. Rapinchuk

We prove that hyperbolic groups are weakly amenable. This partially extends the result of Cowling and Haagerup showing that lattices in simple Lie groups of real rank one are weakly amenable. We take a combinatorial approach in the spirit…

Functional Analysis · Mathematics 2011-11-09 Narutaka Ozawa

Weakly stable torsion classes were introduced by the author and Yekutieli to provide a torsion theoretic characterisation of the notion of weak proregularity from commutative algebra. In this paper we investigate weakly stable torsion…

Rings and Algebras · Mathematics 2018-08-09 Rishi Vyas

It is proved that the assembly maps in algebraic K- and L-theory with respect to the family of finite subgroups is injective for groups with finite asymptotic dimension that admit a finite model for the classifying space for proper actions.…

K-Theory and Homology · Mathematics 2016-09-23 Arthur Bartels , David Rosenthal

We extend the notion of induced conjugacy classes in reductive groups, introduced by Lusztig and Spaltenstein for unipotent classes, to arbitrary classes. We study properties of equivariant fibrations of prehomogeneous affine spaces,…

Group Theory · Mathematics 2013-01-07 Werner Hoffmann

We initiate a study of cohomological aspects of weakly almost periodic group representations on Banach spaces, in particular, isometric representations on reflexive Banach spaces. Using the Ryll-Nardzewski fixed point Theorem, we prove a…

Group Theory · Mathematics 2013-02-12 Uri Bader , Christian Rosendal , Roman Sauer

We disprove a well-known conjecture of Boston (2000), which claims that a just-infinite pro-$p$ group is branch if and only if it admits a positive-dimensional embedding in the group of $p$-adic automorphisms. This is obtained as a result…

Group Theory · Mathematics 2025-07-31 Jorge Fariña-Asategui

We generalize the classical definition of effectively closed subshift to finitely generated groups. We study classical stability properties of this class and then extend this notion by allowing the usage of an oracle to the word problem of…

Group Theory · Mathematics 2019-04-26 Nathalie Aubrun , Sebastián Barbieri , Mathieu Sablik

We prove that all invariant random subgroups of the lamplighter group $L$ are co-sofic. It follows that $L$ is permutation stable, providing an example of an infinitely presented such a group. Our proof applies more generally to all…

Group Theory · Mathematics 2019-11-27 Arie Levit , Alexander Lubotzky

We show that every finitely generated group admits weak analogues of an invariant expectation, whose existence characterizes exact groups. This fact has a number of applications. We show that Hopf $G$-modules are relatively injective, which…

Functional Analysis · Mathematics 2011-09-05 Ronald G. Douglas , Piotr W. Nowak

In this paper we use techniques from convex projective geometry to produce many new examples of thin subgroups of lattices in special linear groups that are isomorphic to the fundamental groups of finite volume hyperbolic manifolds. More…

Geometric Topology · Mathematics 2020-07-29 Samuel Ballas , D. D. Long

In this article we introduce the notion of weak identities in a group and study their properties. We show that weak identities have some similar properties to ordinary ones. We use this notion to prove that any finitely generated solvable…

Group Theory · Mathematics 2007-05-23 Martin Kassabov

Let $G$ be a branch group acting by automorphisms on a rooted tree $T$. Stabilizers of infinite rays in $T$ are examples of weakly maximal subgroups of $G$ (subgroups that are maximal among subgroups of infinite index), but in general they…

Group Theory · Mathematics 2024-03-20 Paul-Henry Leemann