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In this paper we classify all simple weight modules for a quantum group $U_q$ at a complex root of unity $q$ when the Lie algebra is not of type $G_2$. By a weight module we mean a finitely generated $U_q$-module which has finite…

Representation Theory · Mathematics 2015-07-24 Dennis Hasselstrøm Pedersen

We propose a framework for the free field construction of algebras of local observables which uses as an input the Bisognano-Wichmann relations and a representation of the Poincare' group on the one-particle Hilbert space. The abstract real…

Mathematical Physics · Physics 2011-04-06 Romeo Brunetti , Daniele Guido , Roberto Longo

In a recent paper we found conditions for a nilpotent Lie group to be foliated into subgroups that have square integrable unitary representations that fit together to form a filtration by normal subgroups. That resulted in explicit…

Representation Theory · Mathematics 2013-12-19 Joseph A. Wolf

The notion of almost elementariness for a locally compact Hausdorff \'{e}tale groupoid $\mathcal{G}$ with a compact unit space was introduced by the authors as a sufficient condition ensuring the reduced groupoid $C^*$-algebra…

Operator Algebras · Mathematics 2024-07-09 Xin Ma , Jianchao Wu

Let $G$ be a noncompact semisimple algebraic group with trivial center, $S < G$ a maximal split torus, $H < G$ the centralizer of $S$ in $G$ and $\Gamma < G$ an irreducible lattice. Consider the group measure space von Neumann algebra…

Operator Algebras · Mathematics 2026-05-21 Cyril Houdayer , Adrian Ioana

The Stone-von Neumann Theorem is a fundamental result which unified the competing quantum mechanical models of matrix mechanics and wave mechanics. It's mechanism of proof ultimately involved the study of unitary group representations on a…

Operator Algebras · Mathematics 2024-11-19 Lucas Hall , Leonard Huang , Jacek Krajczok , Mariusz Tobolski

Terwilliger algebras are a subalgebra of a matrix algebra that are constructed from association schemes over finite sets. In 2010, Rie Tanaka defined what it means for a Terwilliger algebra to be almost commutative. In that paper she gave…

Representation Theory · Mathematics 2024-09-17 Nicholas L. Bastian , Stephen P. Humphries

In this paper we complete in several aspects the picture of locally compact quantum groups. First of all we give a definition of a locally compact quantum group in the von Neumann algebraic setting and show how to deduce from it a…

Operator Algebras · Mathematics 2007-05-23 Johan Kustermans , Stefaan Vaes

Let $(\Gamma,\mu)$ be a bipartite graph together with a weight on its vertices. Assume that $\mu$ is an eigenvector for the adjacency matrix of $\Gamma$. Let Aut$(\Gamma, \mu)$ be the automorphism group of the bipartite graph $\Gamma$ that…

Operator Algebras · Mathematics 2016-02-15 Arnaud Brothier

A topological group G is said to be almost maximally almost-periodic if its von Neumann radical is non-trivial, but finite. In this paper, we prove that every abelian group with an infinite torsion subgroup admits a (Hausdorff) almost…

General Topology · Mathematics 2009-02-24 Athena P. Nguyen

A super-modular category is a unitary pre-modular category with M\"uger center equivalent to the symmetric unitary category of super-vector spaces. Super-modular categories are important alternatives to modular categories as any unitary…

Quantum Algebra · Mathematics 2018-07-25 Parsa Bonderson , Eric C. Rowell , Qing Zhang , Zhenghan Wang

We develop the theory of almost-holomorphic and quasimodular forms for orthogonal groups of a lattice of signature $(2,n)$ through orthogonal lowering and raising operators. The interactions with the regularized theta lift of Borcherds is a…

Algebraic Geometry · Mathematics 2025-05-15 Georg Oberdieck , Brandon Williams

Let $C$ be a symmetrizable generalized Cartan matrix with symmetrizer $D$ and orientation $\Omega$. In previous work we associated an algebra $H$ to this data, such that the locally free $H$-modules behave in many aspects like…

Representation Theory · Mathematics 2020-08-27 Christof Geiß , Bernard Leclerc , Jan Schröer

An almost commutative algebra, or a $\rho$-commutative algebra, is an algebra which is graded by an abelian group and whose commutativity is controlled by a function called a commutation factor. The same way as a formulation of a…

Algebraic Topology · Mathematics 2022-06-14 Shuichi Harako

We introduce the notion of proper proximality for finite von Neumann algebras, which naturally extends the notion of proper proximality for groups. Apart from the group von Neumann algebras of properly proximal groups, we provide a number…

Operator Algebras · Mathematics 2022-11-18 Changying Ding , Srivatsav Kunnawalkam Elayavalli , Jesse Peterson

Let k be a non archimedean field. If X is a k-algebraic variety and U a locally closed semi-algebraic subset of X^{an} -- the Berkovich space associated to X -- we show that for l \neq char(\tilde{k}), the cohomology groups H^i_c (\bar{U},…

Algebraic Geometry · Mathematics 2016-10-27 Florent Martin

A parametrization of irreducible unitary representations associated with the regular adjoint orbits of a hyperspecial compact subgroup of a reductive group over a non-dyadic non-archimedean local filed is presented. The parametrization is…

Representation Theory · Mathematics 2017-02-28 Koichi Takase

We present a contribution to the structure theory of locally compact groups. The emphasis is on compactly generated locally compact groups which admit no infinite discrete quotient. It is shown that such a group possesses a characteristic…

Group Theory · Mathematics 2012-07-10 Pierre-Emmanuel Caprace , Nicolas Monod

It is shown by Houdayer-Isono that a group measure space von Neumann algebra is a full factor if the group is countable discrete and bi-exact, and the action is strongly ergodic, essentially free and non-singular. Recently, bi-exactness for…

Operator Algebras · Mathematics 2022-03-16 Yuta Michimoto

We survey some of the progress made recently in the classification of von Neumann algebras arising from countable groups and their measure preserving actions on probability spaces. We emphasize results which provide classes of…

Operator Algebras · Mathematics 2017-12-04 Adrian Ioana