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Using a global version of the equivariant Chern character, we describe the complexified twisted equivariant K-theory of a space with a compact Lie group action in terms of fixed-point data. We apply this to the case of a compact Lie group…

Algebraic Topology · Mathematics 2014-02-26 Daniel S. Freed , Michael J. Hopkins , Constantin Teleman

Let H be a semisimple (so, finite dimensional) Hopf algebra over an algebraically closed field k of characteristic zero and let A be a commutative domain over k. We show that if A arises as an H-module algebra via an inner faithful…

Rings and Algebras · Mathematics 2013-10-09 Pavel Etingof , Chelsea Walton

In this paper we construct the action of Ding-Iohara and shuffle algebras in the sum of localized equivariant K-groups of Hilbert schemes of points on C^2. We show that commutative elements K_i of shuffle algebra act through vertex…

Representation Theory · Mathematics 2019-02-12 Boris Feigin , Alexander Tsymbaliuk

The equivariant coarse index is well-understood and widely used for actions by discrete groups. We extend the definition of this index to general locally compact groups. We use a suitable notion of admissible modules over $C^*$-algebras of…

K-Theory and Homology · Mathematics 2022-07-05 Hao Guo , Peter Hochs , Varghese Mathai

In 1995, C.-L. Terng associated to each hyperpolar action on a compact symmetric space, a hyperpolar proper Fredholm (PF) action on a Hilbert space. This is a group action by an infinite dimensional path group and it acts on a Hilbert space…

Differential Geometry · Mathematics 2023-03-02 Masahiro Morimoto

Given a smooth action of a Lie group on a manifold, we give two constructions of the Chern character of an equivariant vector bundle in the cyclic cohomology of the crossed product algebra. The first construction associates a cycle to the…

Differential Geometry · Mathematics 2023-04-10 Bjarne Kosmeijer , Hessel Posthuma

This note shows the compatibility of the differential geometric and the topological formulations of equivariant characteristic classes for a compact connected Lie group action.

Differential Geometry · Mathematics 2007-05-23 Raoul Bott , Loring W. Tu

We define and study square-integrable coactions of locally compact quantum groups on Hilbert modules, generalising previous work for group actions. As special cases, we consider square-integrable Hilbert space corepresentations and…

Operator Algebras · Mathematics 2015-10-23 Alcides Buss , Ralf Meyer

It is shown that if A is a stably finite C*-algebra and E is a countably generated Hilbert A-module, then E gives rise to a compact element of the Cuntz semigroup if and only if E is algebraically finitely generated and projective. It…

Operator Algebras · Mathematics 2008-11-07 Nathanial P. Brown , Alin Ciuperca

To a weighted graph can be associated a bipartite graph planar algebra P. We construct and study the symmetric enveloping inclusion of P. We show that this construction is equivariant with respect to the automorphism group of P. The…

Operator Algebras · Mathematics 2016-11-11 Arnaud Brothier

We introduce the spatial Rokhlin property for actions of coexact compact quantum groups on $\mathrm{C}^*$-algebras, generalizing the Rokhlin property for both actions of classical compact groups and finite quantum groups. Two key…

Operator Algebras · Mathematics 2018-01-12 Selçuk Barlak , Gábor Szabó , Christian Voigt

The concept of a pair of compatible actions was introduced in the case of groups by Brown and Loday and in the case of Lie algebras by Ellis. In this article we extend it to the context of semi-abelian categories (that satisfy the…

Category Theory · Mathematics 2020-08-18 Davide di Micco , Tim Van der Linden

We define the notion of a partial action on a generalized Boolean algebra and associate to every such system and commutative unital ring $R$ an $R$-algebra. We prove that every strongly $E^{\ast}$-unitary inverse semigroup has an associated…

Rings and Algebras · Mathematics 2025-03-04 Allen Zhang

We prove that for every semigroup of Schwarz maps on the von~Neumann algebra of all bounded linear operators on a Hilbert space which has a subinvariant faithful normal state there exists an associated semigroup of contractions on the space…

Mathematical Physics · Physics 2023-03-02 George Androulakis , Alexander Wiedemann , Matthew Ziemke

For a finite abelian group action on a linear category, we study the dual action given by the character group acting on the category of equivariant objects. We prove that the groups of equivariant autoequivalences on these two categories…

Representation Theory · Mathematics 2021-09-27 Jianmin Chen , Xiao-Wu Chen , Shiquan Ruan

We introduce the notion of measurable bounded cohomology for measured groupoids, extending continuous bounded cohomology of locally compact groups. We show that the measurable bounded cohomology of the semidirect groupoid associated to a…

Dynamical Systems · Mathematics 2025-09-19 Filippo Sarti , Alessio Savini

We introduce the notion of a ``sofic $\mathcal{C}$-action'' of one group on another by automorphisms, for $\mathcal{C}$ a class of groups. We show that if $\mathcal{C}$ is the class of (i) sofic, (ii) hyperlinear, (iii) linear sofic or (iv)…

Group Theory · Mathematics 2026-01-27 Vadim Alekseev , Henry Bradford

Let $G$ be an infinite discrete group and let $\underline{E}G$ be a classifying space for proper actions of $G$. Every $G$-equivariant vector bundle over $\underline{E}G$ gives rise to a compatible collection of representations of the…

Algebraic Topology · Mathematics 2017-02-08 Dieter Degrijse , Ian J. Leary

We generalise the concept of a Steinberg cross-section to non-connected Kac-Moody group. As in the connected case, which was treated by G. Br\"uchert, a quotient map w.r.t the conjugacy action exists only on a certain submonoid of the…

Representation Theory · Mathematics 2007-05-23 Stephan Mohrdieck

We prove a number of property (T) permanence results for locally compact quantum groups under exact sequences and the presence of invariant states, analogous to their classical versions. Along the way we characterize the existence of…

Operator Algebras · Mathematics 2021-09-27 Michael Brannan , Alexandru Chirvasitu , Ami Viselter