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In this short note we show that representation and character varieties of discrete groups can be viewed as tensor products of suitable functors over the PROP of cocommutative Hopf algebras. Such view point has several interesting…

Rings and Algebras · Mathematics 2016-10-11 Martin Kassabov , Sasha Patotski

We construct the first example of a $C^*$-algebra $A$ with the properties in the title. This gives a new example of non-nuclear $A$ for which there is a unique $C^*$-norm on $A \otimes A^{op}$. This example is of particular interest in…

Operator Algebras · Mathematics 2023-04-05 Gilles Pisier

The purpose of this work is to give a definition of a topological K-theory for dg-categories over C and to prove that the Chern character map from algebraic K-theory to periodic cyclic homology descends naturally to this new invariant. This…

K-Theory and Homology · Mathematics 2019-02-20 Anthony Blanc

We use constructive bounded Kasparov K-theory to investigate the numerical invariants stemming from the internal Kasparov products $K_i(\mathcal A) \times KK^i(\mathcal A, \mathcal B) \rightarrow K_0(\mathcal B) \rightarrow \mathbb R$,…

Operator Algebras · Mathematics 2016-11-16 Emil Prodan , Hermann Schulz-Baldes

For an arbitrary infinite field k of characteristic p > 0, we describe the structure of a block of the algebraic monoid M_n(k) (all n x n matrices over k), or, equivalently, a block of the Schur algebra S(n,p), whose simple modules are…

Representation Theory · Mathematics 2008-03-11 Stephen Doty , Stuart Martin

Let $H$ be a finite dimensional quasi-Hopf algebra over a field $k$ and ${\mathfrak A}$ a right $H$-comodule algebra in the sense of Hausser and Nill. We first show that on the $k$-vector space ${\mathfrak A}\ot H^*$ we can define an…

Quantum Algebra · Mathematics 2007-05-23 D. Bulacu , S. Caenepeel

Let $\mathcal{C}$ be a finite tensor category, and let $\mathcal{M}$ be an exact left $\mathcal{C}$-module category. The relative Serre functor of $\mathcal{M}$ is an endofunctor $\mathbb{S}$ on $\mathcal{M}$ together with a natural…

Category Theory · Mathematics 2023-06-23 Kenichi Shimizu

We study the basic monoidal properties of the category of Hopf modules for a coquasi Hopf algebra. In particular we discuss the so called fundamental theorem that establishes a monoidal equivalence between the category of comodules and the…

Quantum Algebra · Mathematics 2008-01-09 Walter Ferrer Santos , Ignacio Lopez Franco

Let $\mathscr{C}$ be a modular tensor category over an algebraically closed field $k$ of characteristic 0. Then there is the ubiquitous notion of the S-matrix $S(\mathscr{C})$ associated with the modular category. The matrix…

Quantum Algebra · Mathematics 2015-06-11 Tanmay Deshpande

A fundamental tool of Differential Galois Theory is the assignment of an algebraic group to each finite-dimensional differential module over differential field in such a way that the category of differential modules it generates is…

Rings and Algebras · Mathematics 2018-04-30 Laiachi El Kaoutit , José Gómez-Torrecillas

Let $F$ be a $p$-adic field and let $G$ be a connected reductive group defined over $F$. We assume $p$ is big. Denote $\mathfrak{g}$ the Lie algebra of $G$. To each vertex $s$ of the reduced Bruhat-Tits' building of $G$, we associate as…

Representation Theory · Mathematics 2019-10-16 Jean-Loup Waldspurger

Let $X$ be a compact K\"ahler manifold. The set $\cha(X)$ of one-dimensional complex valued characters of the fundamental group of $X$ forms an algebraic group. Consider the subset of $\cha(X)$ consisting of those characters for which the…

Algebraic Geometry · Mathematics 2009-09-25 Donu Arapura

A $Q$-manifold $M$ is a supermanifold endowed with an odd vector field $Q$ squaring to zero. The Lie derivative $L_Q$ along $Q$ makes the algebra of smooth tensor fields on $M$ into a differential algebra. In this paper, we define and study…

Mathematical Physics · Physics 2015-05-13 S. L. Lyakhovich , E. A. Mosman , A. A. Sharapov

In the first part, we construct a new isomorphism between the endomorphism algebra of an induced cuspidal character sheaf and the group algebra of the relative Weyl group involved. We show it differs from the isomorphism of Lusztig by a…

Group Theory · Mathematics 2007-05-23 Cedric Bonnafe

For an ample groupoid with torsion-free stabilizers, we construct a Chern character map going from the domain of the Baum-Connes assembly map of G to the groupoid homology groups of G with rational coefficients. As a main application,…

K-Theory and Homology · Mathematics 2025-09-10 Valerio Proietti , Makoto Yamashita

In this article, we exploit the theory of graded module category with semi-infinite character developed by Soergel in \cite{Soe} to study representations of the infinite dimensional Lie algebras of vector fields $W(n), S(n)$ and $H(n)$…

Representation Theory · Mathematics 2019-07-30 Fei-Fei Duan , Bin Shu , Yu-Feng Yao

Character tables of finite groups and closely related commutative algebras have been investigated recently using new perspectives arising from the AdS/CFT correspondence and low-dimensional topological quantum field theories. Two important…

High Energy Physics - Theory · Physics 2025-12-18 Adrian Padellaro , Sanjaye Ramgoolam , Rak-Kyeong Seong

We extend the Chern character on K-theory, in its generalization to the Chern-Dold character on generalized cohomology theories, further to (twisted, differential) non-abelian cohomology theories, where its target is a non-abelian de Rham…

Algebraic Topology · Mathematics 2023-11-28 Domenico Fiorenza , Hisham Sati , Urs Schreiber

With a view to determining character values of finite reductive groups at unipotent elements, we prove a number of results concerning inner products of generalised Gelfand-Graev characters with characteristic functions of character sheaves,…

Representation Theory · Mathematics 2015-02-03 François Digne , Gustav Lehrer , Jean Michel

We investigate the concept of definable, or inner, automorphism in the logical setting of partial Horn theories. The central technical result extends a syntactical characterization of the group of such automorphisms (called the covariant…

Logic in Computer Science · Computer Science 2021-02-23 Pieter Hofstra , Jason Parker , Philip J. Scott