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A weakly equivariant Hopf algebra is a Hopf algebra A with an action of a finite group G up to inner automorphisms. We show that each weakly equivariant Hopf algebra can be replaced by a Morita equivalent algebra B with a strict action of G…

Rings and Algebras · Mathematics 2012-05-07 Jennifer Maier , Thomas Nikolaus , Christoph Schweigert

A topological group $G$ is extremely amenable if every continuous action of $G$ on a compact space has a fixed point. Using the concentration of measure techniques developed by Gromov and Milman, we prove that the group of automorphisms of…

Group Theory · Mathematics 2007-09-03 Thierry Giordano , Vladimir Pestov

We study Beurling-Fourier algebras of $ q $-deformations of compact semisimple Lie groups. In particular, we show that the space of irreducible representations of the function algebras of their Drinfeld doubles is exhausted by the…

Operator Algebras · Mathematics 2024-07-03 Heon Lee , Christian Voigt

In this paper, we consider modular forms for finite index subgroups of the modular group whose Fourier coefficients are algebraic. It is well-known that the Fourier coefficients of any holomorphic modular form for a congruence subgroup…

Number Theory · Mathematics 2007-09-05 Chris Kurth , Ling Long

We consider the scaling properties characterizing the hyperuniformity (or anti-hyperuniformity) of long wavelength fluctuations in a broad class of one-dimensional substitution tilings. We present a simple argument that predicts the…

Statistical Mechanics · Physics 2018-06-29 Erdal C. Oğuz , Joshua E. S. Socolar , Paul J. Steinhardt , Salvatore Torquato

We introduce the class of Beurling-Fourier algebras on locally compact groups and show that they are non-commutative analogs of classical Beurling algebras. We obtain various results with regard to the operator amenability, operator weak…

Functional Analysis · Mathematics 2010-09-02 Hun Hee Lee , Ebrahim Samei

Any multiplier Hopf *-algebra} with positive integrals gives rise to a locally compact quantum group (in the sense of Kustermans and Vaes). As a special case of such a situation, we have the compact quantum groups (in the sense of…

Operator Algebras · Mathematics 2007-05-23 Alfons Van Daele

A Lie 2-algebra is a linear category equipped with a functorial bilinear operation satisfying skew-symmetry and Jacobi identity up to natural transformations which themselves obey coherence laws of their own. Functors and natural…

Quantum Algebra · Mathematics 2009-11-13 Dmitry Roytenberg

In this paper we introduce the class of weak Heyting Brouwer algebras (WHB-algebras, for short). We extend the well known duality between distributive lattices and Priestley spaces, in order to exhibit a relational Priestley-like duality…

Logic · Mathematics 2023-12-19 Sergio Celani , Agustín Nagy , William Zuluaga Botero

By classifying $S$-maximal amenable subgroups of algebraic groups over a global field of characteristic zero, we obtain a complete classification of maximal amenable subgroups up to commensurability in the respective arithmetic groups.…

Group Theory · Mathematics 2022-10-21 Vadim Alekseev , Alessandro Carderi

We investigate recent uniqueness theorems for reduced $C^*$-algebras of Hausdorff \'{e}tale groupoids in the context of inverse semigroups. In many cases the distinguished subalgebra is closely related to the structure of the inverse…

Operator Algebras · Mathematics 2016-11-11 Scott M. LaLonde , David Milan

We propose an algebraic viewpoint of the problem of deformation quantization of the so called almost Poisson algebras, which are algebras with a commutative associative product and an antisymmetric bracket which is a bi-derivation but does…

Quantum Algebra · Mathematics 2023-06-16 Vladimir Dotsenko

We recall the notion of nearest integer continued fractions over the Euclidean imaginary quadratic fields $K$ and characterize the "badly approximable" numbers, ($z$ such that there is a $C(z)>0$ with $|z-p/q|\geq C/|q|^2$ for all $p/q\in…

Number Theory · Mathematics 2018-09-21 Robert Hines

A countable, bounded degree graph is almost finite if it has a tiling with isomorphic copies of finitely many F\o lner sets, and we call it strongly almost finite, if the tiling can be randomized so that the probability that a vertex is on…

Group Theory · Mathematics 2025-09-22 Gábor Elek , Ádám Timár

This paper continues math.GR/0608302's study of amenability of affine algebras (based on the notion of almost-invariant finite-dimensional subspace), and applies it to graded algebras associated with finitely generated groups. Due to a…

Group Theory · Mathematics 2008-04-02 Laurent Bartholdi

We provide a direct and elementary proof of the equivalence between the weak asymptotic homomorphism property for the pair of group von Neumann algebras $L(H)\subset L(G)$ and the embedding into $H$ of the one sided quasi-normalizer of the…

Operator Algebras · Mathematics 2010-11-19 Paul Jolissaint

For any JdLG-admissible representation $\pi$ of a semigroup $S$ on a Banach space $E$, we show that the reversible part is weakly equivalent to a unitary representation on a Hilbert space that decomposes into a direct sum of finite…

Functional Analysis · Mathematics 2025-10-16 Micky Barthmann , Sohail Farhangi , Yulia Kuznetsova

We show that if $H \leq G$ is a closed amenable and cocompact subgroup of a unimodular locally compact group, then the reduced group C*-algebra of $G$ is not simple. Equivalently, there are unitary representations of $G$ that are weakly…

Group Theory · Mathematics 2016-01-25 Sven Raum

It is shown that the collection of weakly almost periodic functionals on the convolution algebra of a commutative Hopf von Neumann algebra is a C$^*$-algebra. This implies that the weakly almost periodic functionals on $M(G)$, the measure…

Functional Analysis · Mathematics 2011-01-14 Matthew Daws

We investigate conditions for the extendibility of continuous algebra homomorphisms $\phi$ from the Fourier algebra $A(F)$ of a locally compact group $F$ to the Fourier-Stieltjes algebra $B(G)$ of a locally compact group $G$ to maps between…

Operator Algebras · Mathematics 2023-02-21 M. Anoussis , G. K. Eleftherakis , A. Katavolos