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Let p be a real number with 1<p and different from 2. We study Property (T_lp) for a second countable locally compact group G. Property (T_lp) is a weak version of Kazhdan's Property (T), defined in terms of the orthogonal representations…

Group Theory · Mathematics 2015-02-04 Bachir Bekka , Baptiste Olivier

We study quasidiagonality and local reflexivity for $C^{*}$-algebras which are $C^*$-module over another $C^*$-algebra with compatible actions. We introduce and study a notion of amenability for vector valued traces.

Operator Algebras · Mathematics 2022-08-12 Massoud Amini

The aim of the article is to provide a characterization of the Haagerup property for locally compact, second countable groups in terms of actions on $\sigma$-finite measure spaces. It is inspired by the very first definition of amenability,…

Group Theory · Mathematics 2020-04-21 Thiebout Delabie , Paul Jolissaint , Alexandre Zumbrunnen

We introduce a new class of algebras over discrete valuation rings, called Kleinian 4-rings, which generalize the group algebra of the Kleinian 4-group. For these algebras we describe the lattices and their cohomologies. In the case of…

Representation Theory · Mathematics 2022-04-28 Yuriy A. Drozd

We investigate algebraicity properties of quotients of complex spaces by complex reductive Lie groups G. We obtain a projectivity result for compact momentum map quotients of algebraic G-varieties. Furthermore, we prove equivariant versions…

Algebraic Geometry · Mathematics 2011-04-13 Daniel Greb

We establish an induction isomorphism in the context of measurable bounded cohomology of discrete measured groupoid, which generalizes the Eckmann-Shapiro isomorphism in bounded cohomology of lattices due to Burger and Monod. In our wider…

Dynamical Systems · Mathematics 2025-10-24 Tobias Hartnick , Filippo Sarti

Let A be a locally compact abelian group, and H a locally compact group acting on A. Let G=HA be the semidirect product. We prove that the pair (G,A) has Kazhdan's Property T if and only if the only countably approximable H-invariant mean…

Group Theory · Mathematics 2011-05-10 Yves Cornulier , Romain Tessera

We construct a general cohomological induction isomorphism from a uniform measure equivalence of locally compact, second countable, unimodular groups which, as a special case, yields that the graded cohomology rings of quasi-isometric,…

Group Theory · Mathematics 2021-02-09 Thomas Gotfredsen , David Kyed

Inner amenability is a bridge between amenability of an object and amenability of its operator algebras. It is an open problem of Ananantharman-Delaroche to decide whether all \'etale groupoids are inner amenable. Approximate lattices and…

Operator Algebras · Mathematics 2023-07-06 Gabriel Favre

We study uniform and non-uniform model sets in arbitrary locally compact second countable (lcsc) groups, which provide a natural generalization of uniform model sets in locally compact abelian groups as defined by Meyer and used as…

Dynamical Systems · Mathematics 2020-02-14 Michael Björklund , Tobias Hartnick , Felix Pogorzelski

We prove a number of property (T) permanence results for locally compact quantum groups under exact sequences and the presence of invariant states, analogous to their classical versions. Along the way we characterize the existence of…

Operator Algebras · Mathematics 2021-09-27 Michael Brannan , Alexandru Chirvasitu , Ami Viselter

We establish several new characterizations of amenable $W^*$- and $C^*$-dynamical systems over arbitrary locally compact groups. In the $W^*$-setting we show that amenability is equivalent to (1) a Reiter property and (2) the existence of a…

Operator Algebras · Mathematics 2020-08-25 Alex Bearden , Jason Crann

In this paper, we study continuous Rokhlin property of $\mathrm{C}^*$-dynamical systems using techniques of equivariant $\mathrm{KK}$-theory and quantum group theory. In particular, we determine the $\mathrm{KK}$-equivalence class and give…

Operator Algebras · Mathematics 2015-12-22 Yuki Arano , Yosuke Kubota

We show that the continuous $L^p$-cohomology of locally compact second countable groups is a quasi-isometric invariant. As an application, we prove partial results supporting a positive answer to a question asked by M.~Gromov, suggesting a…

Group Theory · Mathematics 2021-01-20 Marc Bourdon , Bertrand Remy

We give a contractive Schur multiplier characterization of locally compact groups coarsely embeddable into Hilbert spaces. Consequently, all locally compact groups whose weak Haagerup constant is 1 embed coarsely into Hilbert spaces, and…

Group Theory · Mathematics 2016-09-19 Søren Knudby , Kang Li

We announce a generalization of Zimmer's cocycle superrigidity theorem proven using harmonic map techniques. This allows us to generalize many results concerning higher rank lattices to all lattices in semisimple groups with property $(T)$.…

Differential Geometry · Mathematics 2007-05-23 David Fisher , Theron Hitchman

We consider the finitely generated groups acting on a regular tree with almost prescribed local action. We show that these groups embed as cocompact irreducible lattices in some locally compact wreath products. This provides examples of…

Group Theory · Mathematics 2020-01-24 Adrien Le Boudec

We introduce the notion of an algebraic cocycle as the algebraic analogue of a map to an Eilenberg-MacLane space. Using these cocycles we develop a ``cohomology theory" for complex algebraic varieties. The theory is bigraded, functorial,…

Algebraic Geometry · Mathematics 2016-09-06 Eric M. Friedlander , H. Blaine Lawson

We show that basic notions of locally analytic representation theory can be reformulated in the language of topological coalgebras (Hopf algebras) and comodules. We introduce the notion of admissible comodule and show that it corresponds to…

Rings and Algebras · Mathematics 2017-07-27 Anton Lyubinin

Let $G$ be a finite group, $X$ be a compact $G$-space. In this note we study the $(\mathbb{Z}_ + \times\mathbb{Z}/2\mathbb{Z})$-graded algebra $$\mathcal{F}^q_G(X) = \bigoplus_{n\geq0} q^n \cdot…

K-Theory and Homology · Mathematics 2019-11-21 Germán Combariza , Juan Rodríguez , Mario Velásquez