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We describe representations of groupoid C*-algebras on Hilbert modules over arbitrary C*-algebras by a universal property. For Hilbert space representations, our universal property is equivalent to Renault's Integration-Disintegration…

Operator Algebras · Mathematics 2019-04-30 Alcides Buss , Rohit Holkar , Ralf Meyer

Let H be a subgroup of some locally compact group G. Assume H is approximable by discrete subgroups and G admits neighborhood bases which are "almost-invariant" under conjugation by finite subsets of H. Let $m: G \to \mathbb{C}$ be a…

Classical Analysis and ODEs · Mathematics 2014-07-10 Martijn Caspers , Javier Parcet , Mathilde Perrin , Éric Ricard

Inspired by an extension of Wiener's lemma on the relation of measures $\mu$ on the unit circle and their Fourier coefficients $\widehat{\mu}(k_n)$ along subsequences $(k_n)$ of the natural numbers by Cuny, Eisner and Farkas [CEF19,…

Functional Analysis · Mathematics 2020-05-12 Eike Schulte

This paper compares two generalizations of Heisenberg groups and studies their connection to one of the major open problems in the field of locally compact abelian groups, namely the description of the self-dual locally compact abelian…

Group Theory · Mathematics 2017-09-11 Marco Bonatto , Dikran Dikranjan

Let G be a locally compact, Hausdorff groupoid in which s is a local homeomorphism and the unit space is totally disconnected. Assume there is a continuous cocycle c from G into a discrete group $\Gamma$. We show that the collection A(G) of…

Rings and Algebras · Mathematics 2012-02-07 Lisa Orloff Clark , Cynthia Farthing , Aidan Sims , Mark Tomforde

Using methods coming from non-formal equivariant quantization, we construct in this short note a unitary dual 2-cocycle on a discrete family of quotient groups of subgroups of the affine group of a local field (which is not of…

Operator Algebras · Mathematics 2018-09-26 David Jondreville

We present a formal algebraic language to deal with quantum deformations of Lie-Rinehart algebras - or Lie algebroids, in a geometrical setting. In particular, extending the ice-breaking ideas introduced by Xu in [Ping Xu, "Quantum…

Quantum Algebra · Mathematics 2015-06-26 Sophie Chemla , Fabio Gavarini

For a locally compact group $G$, the first-named author considered the closed subspace $a_0(G)$ which is generated by the pure positive definite functions. In many cases $a_0(G)$ is itself an algebra. We illustrate using Heisenburg groups…

Functional Analysis · Mathematics 2012-08-13 Yin-Hei Cheng , Brian E. Forrest , Nico Spronk

By relating notions from quantum harmonic analysis and band-dominated operator theory, we prove that over any locally compact abelian group $G$, the operator algebra $\mathcal C_1$ from quantum harmonic analysis agrees with the intersection…

Functional Analysis · Mathematics 2025-06-11 Robert Fulsche , Raffael Hagger

Rational discrete cohomology and homology for a totally disconnected locally compact group $G$ is introduced and studied. The $\mathrm{Hom}$-$\otimes$ identities associated to the rational discrete bimodule $\mathrm{Bi}(G)$ allow to…

Group Theory · Mathematics 2021-01-22 Ilaria Castellano , Thomas Weigel

We study closedness of the range, adjointability and generalized invertibility of modular operators between Hilbert modules over locally C*-algebras of coefficients. Our investigations and the recent results of M. Frank [Characterizing…

Operator Algebras · Mathematics 2011-08-31 Kamran Sharifi

We provide necessary and sufficient conditions for the existence of idempotents of arbitrarily large norms in the Fourier algebra A(G) and the Fourier-Stieltjes algebra B(G) of a locally compact group G. We prove that the existence of…

Functional Analysis · Mathematics 2022-06-27 M. Anoussis , G. K. Eleftherakis , A. Katavolos

Let $G$ be a locally compact group. We show that its Fourier algebra $A(G)$ is amenable if and only if $G$ has an abelian subgroup of finite index, and that its Fourier-Stieltjes algebra $B(G)$ is amenable if and only if $G$ has a compact,…

Functional Analysis · Mathematics 2007-05-23 Brian E. Forrest , Volker Runde

Let $\mathbb{G}$ be a locally compact quantum group with dual $\widehat{\mathbb{G}}$. Suppose that the left Haar weight $\varphi$ and the dual left Haar weight $\widehat{\varphi}$ are tracial, e.g. $\mathbb{G}$ is a unimodular Kac algebra.…

Operator Algebras · Mathematics 2022-01-21 Haonan Zhang

A duality theorem for the stable module category of representations of a finite group scheme is proved. One of its consequences is an analogue of Serre duality, and the existence of Auslander-Reiten triangles for the $\mathfrak{p}$-local…

Representation Theory · Mathematics 2019-02-20 Dave Benson , Srikanth B. Iyengar , Henning Krause , Julia Pevtsova

Let G be a compact connected Lie group. We prove that the Fourier algebra A(G) is weakly amenable if and only if G is abelian.

Functional Analysis · Mathematics 2007-05-23 R. J. Plymen

We analzye Rieffel's construction of generalized fixed point algebras in the setting of group actions on Hilbert modules. Let G be a locally compact group acting on a C*-algebra B. We construct a Hilbert module F over the reduced crossed…

Operator Algebras · Mathematics 2015-10-23 Ralf Meyer

For a compact group $G$ we define the Beurling-Fourier algebra $A_\omega(G)$ on $G$ for weights $\omega$ defined on the dual $\what G$ and taking positive values. The classical Fourier algebra corresponds to the case $\omega$ is the…

Functional Analysis · Mathematics 2011-03-22 Jean Ludwig , Nico Spronk , Lyudmila Turowska

In math.RT/0302174 we developed a framework to study representations of groups of the form $G((t))$, where $G$ is an algebraic group over a local field $K$. The main feature of this theory is that natural representations of groups of this…

Representation Theory · Mathematics 2007-05-23 Dennis Gaitsgory , David Kazhdan

We present a general framework of localized operators, i.e., operators whose matrix coefficients with respect to the Gabor frame are concentrated on the diagonal. We show that localized operators are bounded between modulation spaces, and…

Classical Analysis and ODEs · Mathematics 2025-05-06 Cody B. Stockdale , Cody Waters