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We show that certain orderable groups admit no isolated left orders. The groups we consider are cyclic amalgamations of a free group with a general orderable group, the HNN extensions of free groups over cyclic subgroups, and a particular…

Group Theory · Mathematics 2018-12-19 Juan Alonso , Joaquin Brum

We consider dual frames generated by actions of countable discrete groups on a Hilbert space. Module frames in a class of modules over a group algebra are shown to coincide with a class of ordinary frames in a representation of the group.…

Functional Analysis · Mathematics 2009-11-24 Kjetil Roysland

In this work we introduce a concept of expansiveness for actions of connected Lie groups. We study some of its properties and investigate some implications of expansiveness. We study the centralizer of expansive actions and introduce…

Dynamical Systems · Mathematics 2022-07-05 Elias Rego , Alexander Arbieto

Free independence is an important tool for studying the structure of operator algebras. It is natural to ask from the model-theoretic standpoint whether free independence is captured well in first-order model theory via the notion of a…

Operator Algebras · Mathematics 2026-02-25 William Boulanger , Jakub Curda , Emma Harvey , Yizhi Li , Jennifer Pi

Suppose that G is a nontrivial torsion-free group and w is a word over the alphabet G\cup\{x_1^{\pm1},...,x_n^{\pm1}\}. It is proved that for n\ge2 the group \~G=<G,x_1,x_2,...,x_n | w=1> always contains a nonabelian free subgroup. For n=1…

Group Theory · Mathematics 2007-09-02 Anton A. Klyachko

Let V(KG) be the normalized group of units of the group ring KG of a non-Dedekind group G with nontrivial torsion part t(G) over the integral domain K. We give a simple method for constructing free objects in V(KG).In particular, we show…

Group Theory · Mathematics 2014-11-27 Victor Bovdi

We prove the validity of the freeness conjecture of Brou\'e, Malle and Rouquier for the generic Hecke algebras associated to the exceptional complex reflection groups of rank 2 belonging to the tetrahedral and octahedral families, and we…

Representation Theory · Mathematics 2017-05-04 Eirini Chavli

We construct large families of groups admitting free transitive actions on median spaces. In particular, we construct groups which act freely and transitively on the complete universal real tree with continuum valence such that any subgroup…

Group Theory · Mathematics 2025-07-31 Pénélope Azuelos

I. M. Chiswell has asked whether every group that admits a free isometric action (without inversions) on a $\Lambda$-tree is orderable. We give an example of a multiple HNN extension $\Gamma$ which acts freely on a $\mathbb{Z}^2$-tree but…

Group Theory · Mathematics 2012-12-10 Shane O. Rourke

We consider the existence of bibundles, in other words locally trivial principal $G$ spaces with commuting left and right $G$ actions. We show that their existence is closely related to the structure of the group $\Out(G)$ of outer…

Differential Geometry · Mathematics 2013-02-25 Michael Murray , David Michael Roberts , Danny Stevenson

We introduce notions of weak and strong equivalence for non-saturated Fell bundles over locally compact groups and show that every Fell bundle is strongly (resp. weakly) equivalent to a semidirect product Fell bundle for a partial (resp.…

Operator Algebras · Mathematics 2021-08-12 Fernando Abadie , Alcides Buss , Damián Ferraro

In this work, generalized principal bundles modelled by Lie group bundle actions are investigated. In particular, the definition of equivariant connections in these bundles, associated to Lie group bundle connections, is provided, together…

Differential Geometry · Mathematics 2023-03-10 Marco Castrillón López , Álvaro Rodríguez Abella

The paper studies Hausdorff-Young inequalities for certain group extensions, by use of Mackey's theory. We consider the case in which the dual action of the quotient group is free almost everywhere. This result applies to yield a…

Functional Analysis · Mathematics 2007-05-23 Hartmut Fuehr

We apply the One-Sided Action Theorem from the first paper in this series to prove that Rieffel's Morita equivalence between the reduced crossed product by a proper saturated action and the generalized fixed-point algebra is a quotient of a…

Operator Algebras · Mathematics 2012-11-30 S. Kaliszewski , Paul S. Muhly , John Quigg , Dana P. Williams

In this paper we prove the theorem on freedom for free sums of Lie algebras with a single relation (analogous with the well-known result of Shirshov) and a generalized Freiheitssatz for free sums of Lie algebras (analogous with the…

Group Theory · Mathematics 2022-10-24 A. F. Krasnikov

We present a powerful theorem for proving the irreducibility of tempered unitary representations of the free group.

Group Theory · Mathematics 2019-05-09 Waldemar Hebisch , M. Gabriella Kuhn , Tim Steger

We construct uncountably categorical 3-nilpotent groups of exponent p > 3. They are not one-based and do not allow the interpretation of an infinite field. Therefore they are counterexamples to Zilbers Conjecture. First 2-nilpotent new…

Logic · Mathematics 2022-01-10 Andreas Baudisch

We shall consider nonrestricted representations of $C_l-$ type Lie algebra over an algebraically closed field of characteristic $p\geq7.$ This paper gives some counter examples to important theory relating to the representations of modular…

Representation Theory · Mathematics 2022-03-01 YangGon Kim

In this paper we show some multiplicity estimates theorems for a connected algebraic group (not necessarily commutative) $G$ over an algebraically closed subfield of $\mathbb{C}$. More specifically, under particular assumptions on the…

Algebraic Geometry · Mathematics 2015-12-15 Mario Huicochea

We express the total space of a principal circle bundle over a connected sum of two manifolds in terms of the total spaces of circle bundles over each summand, provided certain conditions hold. We then apply this result to provide…

Geometric Topology · Mathematics 2025-01-29 Fernando Galaz-García , Philipp Reiser