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We review various notions of correspondences for locally compact groupoids with Haar systems, in particular a recent definition due to R.D. Holkar. We give the construction of the representations induced by such a correspondence. Finally,…

Operator Algebras · Mathematics 2014-06-04 Jean Renault

Motivated by reformulating Furstenberg's $\times p,\times q$ conjecture via representations of a crossed product $C^*$-algebra, we show that in a discrete $C^*$-dynamical system $(A,\Gamma)$, the space of (ergodic) $\Gamma$-invariant states…

Operator Algebras · Mathematics 2016-03-01 Huichi Huang , Jianchao Wu

We calculate all irreducible representations over a subfamily of pointed Hopf algebras with group-likes the dihedral group analyzing the possible decompositions of the restriction to the dihedral group and calculating the Jacobson radical…

Representation Theory · Mathematics 2022-03-24 Fernando Fantino , Juan Hidalgo , Adriana Mejia Castano , Carla Morschbacher , Virginia Rodrigues

Let $G$ be a finite group, $H$ be a normal subgroup of prime index $p$. Let $F$ be a field of either characteristic $0$ or prime to $|G|$. Let $\eta$ be an irreducible $F$-representation of $H$. If $F$ is an algebraically closed field of…

Representation Theory · Mathematics 2018-10-12 Soham Swadhin Pradhan

We suggest a new generalization of Pontryagin duality from the category of Abelian locally compact groups to a category which includes all Moore groups, i.e. groups whose irreducible representations are finite-dimensional. Objects in this…

Functional Analysis · Mathematics 2015-03-13 Yulia Kuznetsova

We prove a criterion for the irreducibility of an integral group representation \rho over the fraction field of a noetherian domain R in terms of suitably defined reductions of \rho at prime ideals of R. As applications, we give…

Number Theory · Mathematics 2010-02-17 M. Longo , S. Vigni

Let $W$ be a group endowed with a finite set $S$ of generators. A representation $(V,\rho)$ of $W$ is called a reflection representation of $(W,S)$ if $\rho(s)$ is a (generalized) reflection on $V$ for each generator $s \in S$. In this…

Representation Theory · Mathematics 2025-04-11 Hongsheng Hu

We study the natural representation of the topological full group of an ample Hausdorff groupoid in the groupoid's complex Steinberg algebra and in its full and reduced C*-algebras. We characterise precisely when this representation is…

Operator Algebras · Mathematics 2024-01-05 Becky Armstrong , Lisa Orloff Clark , Mahya Ghandehari , Eun Ji Kang , Dilian Yang

Let G be a simple, simply-connected algebraic group over the complex numbers with Lie algebra $\mathfrak g$. The main result of this article is a proof that each irreducible representation of the fundamental group of the orbit O through a…

Representation Theory · Mathematics 2016-12-06 Eric Sommers

Let $\Fth$ be a $\Bk$-graph on a single vertex. We show that every irreducible atomic $*$-representation is the minimal $*$-dilation of a group construction representation. It follows that every atomic representation decomposes as a direct…

Operator Algebras · Mathematics 2008-04-25 Kenneth R. Davidson , Dilian Yang

Generalizing the notion of continuous Hilbert space representations of compact topological groups we define unitary continuous correpresentations of $C^*$-completions of compact quantum group Hopf algebras on arbitrary Hilbert spaces. It is…

High Energy Physics - Theory · Physics 2008-02-03 Bernhard Drabant , Wolfgang Weich

It is shown that a separable C*-algebra is inner quasidiagonal if and only if it has a separating family of quasidiagonal irreducible representations. As a consequence, a separable C*-algebra is a strong NF algebra if and only if it is…

Operator Algebras · Mathematics 2007-12-12 Bruce Blackadar , Eberhard Kirchberg

We introduce and characterize a particularly tractable class of unital type 1 C*-algebras with bounded dimension of irreducible representations. Algebras in this class are called recursive subhomogeneous algebras, and they have an inductive…

Operator Algebras · Mathematics 2007-05-23 N. Christopher Phillips

Let $G$ be a second countable locally compact groupoid equipped with a Haar system $\lambda$.In this work, we introduce and develop the notion of amenability for continuous unitary representations of $G$, formulated in terms of Hilbert…

Operator Algebras · Mathematics 2026-02-13 K. N. Sridharan , N. Shravan Kumar

Let $G$ be a semisimple Lie group. We describe the irreducible representations of $G$ by linear isometries on $L_p$-spaces for $p\in (1,+\infty)$ with $p\neq 2.$ More precisely, we show that, for every such representation $\pi,$ there…

Representation Theory · Mathematics 2024-05-22 Bachir Bekka

We prove that over totally real fields, the $p$-adic Galois representations attached to non-self-dual regular algebraic cuspidal automorphic representations of $\mathrm{GL}(4)$ are irreducible. We then develop the theory of extra-twists in…

Number Theory · Mathematics 2026-03-23 Alireza Shavali

We discuss implications of the following statement about the representation theory of symmetric groups: every integer appears infinitely often as an irreducible character evaluation, and every nonnegative integer appears infinitely often as…

Combinatorics · Mathematics 2018-01-30 Anshul Adve , Alexander Yong

It is proved that certain types of modular cusp forms generate irreducible automorphic representation of the underlying algebraic group. Analogous archimedean and non-archimedean local statements are also given.

Representation Theory · Mathematics 2011-05-27 Hiro-aki Narita , Ameya Pitale , Ralf Schmidt

We introduce the notions of relational groupoids and relational convolution algebras. We provide various examples arising from the group algebra of a group $G$ and a given normal subgroup $H$. We also give conditions for the existence of a…

Mathematical Physics · Physics 2021-09-22 Ivan Contreras , Nima Moshayedi , Konstantin Wernli

We examine inclusions of $C^*$-algebras of the form $A^H \subseteq A \rtimes_{r} G$, where $G$ and $H$ are groups acting on a unital simple $C^*$-algebra $A$ by outer automorphisms and $H$ is finite. It follows from a theorem of Izumi that…

Operator Algebras · Mathematics 2021-11-22 Siegfried Echterhoff , Mikael Rørdam