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We characterize finite groups G generated by orthogonal transformations in a finite-dimensional Euclidean space V whose fixed point subspace has codimension one or two in terms of the corresponding quotient space V/G with its quotient…

Geometric Topology · Mathematics 2017-11-02 Christian Lange

In this paper, we study quotients of groupoids and coarse moduli spaces of stacks in a general setting. Geometric quotients are not always categorical, but we present a natural topological condition under which a geometric quotient is…

Algebraic Geometry · Mathematics 2013-08-14 David Rydh

We consider the amenability of groupoids $G$ equipped with a group valued cocycle $c:G\to Q$ with amenable kernel $c^{-1}(e)$. We prove a general result which implies, in particular, that $G$ is amenable whenever $Q$ is amenable and if…

Operator Algebras · Mathematics 2015-03-18 Jean N. Renault , Dana P. Williams

Let G be a connected reductive group. We define a map from the set of unipotent classes in G to the set of conjugacy classes in the Weyl group (assuming that the characteristic is not bad). This map is a one sided inverse of a map in the…

Representation Theory · Mathematics 2010-08-17 G. Lusztig

Let $G$ be a connected reductive complex algebraic group, and $E$ a complex elliptic curve. Let $G_E$ denote the connected component of the trivial bundle in the stack of semistable $G$-bundles on $E$. We introduce a complex analytic…

Representation Theory · Mathematics 2021-01-01 Penghui Li , David Nadler

The concept of gyrogroups, with a weaker algebraic structure without associative law, was introduced under the background of $c$-ball of relativistically admissible velocities with Einstein velocity addition. A topological gyrogroup is just…

General Topology · Mathematics 2020-11-12 Meng Bao , Fucai Lin

For a commutative, unital and divisible quantale $\mathsf{Q}$, it is shown that the category of $\mathsf{Q}$-sets is a topos if, and only if, $\mathsf{Q}$ is a frame.

Category Theory · Mathematics 2025-06-04 Xiao Hu , Lili Shen

Let $V$ be a linear representation of a connected complex reductive group $G$. Given a choice of character $\theta$ of $G$, Geometric Invariant Theory defines a locus $V^{ss}_\theta(G) \subseteq V$ of semistable points. We give necessary,…

Representation Theory · Mathematics 2025-10-07 Riku Kurama , Ruoxi Li , Henry Talbott , Rachel Webb

We introduce invertible subalgebras of local operator algebras on lattices. An invertible subalgebra is defined to be one such that every local operator can be locally expressed by elements of the inveritible subalgebra and those of the…

Mathematical Physics · Physics 2023-11-06 Jeongwan Haah

We use the structure lattice, introduced in Part I, to undertake a systematic study of the class $\mathscr S$ consisting of compactly generated, topologically simple, totally disconnected locally compact groups that are non-discrete. Given…

Group Theory · Mathematics 2017-07-07 Pierre-Emmanuel Caprace , Colin D. Reid , George A. Willis

Suppose $G$ is a real reductive group. The determination of the irreducible unitary representations of $G$ is one of the major unsolved problem in representation theory. There is evidence to suggest that every irreducible unitary…

Representation Theory · Mathematics 2019-10-08 Lucas Mason-Brown

This article continues the study of diagrams in the bicategory of \'etale groupoid correspondences. We prove that any such diagram has a groupoid model and that the groupoid model is a locally compact \'etale groupoid if the diagram is…

Category Theory · Mathematics 2024-10-29 Joanna Ko , Ralf Meyer

We propose a structure called a causal site to use as a setting for quantum geometry, replacing the underlying point set. The structure has an interesting categorical form, and a natural "tangent 2-bundle," analogous to the tangent bundle…

General Relativity and Quantum Cosmology · Physics 2009-11-10 J. Daniel Christensen , Louis Crane

The classical Serre-Swan's theorem defines a bijective correspondence between vector bundles and finitely generated projective modules over the algebra of continuous functions on some compact Hausdorff topological space. We extend these…

K-Theory and Homology · Mathematics 2023-03-22 Jure Kalisnik

We revisit sheaves on locales by placing them in the context of the theory of quantale modules. The local homeomorphisms $p:X\to B$ are identified with the Hilbert $B$-modules that are equipped with a natural notion of basis. The…

Category Theory · Mathematics 2012-04-03 Pedro Resende , Elias Rodrigues

Quantum contextuality, a fundamental feature distinguishing quantum theory from classical models, is investigated via algebraic and topological structures inherent in modular tensor categories. This work rigorously demonstrates that braid…

Quantum Physics · Physics 2025-06-18 Tzu-Miao Chou

We propose a definition of compact quantum groupoids in the setting of C*-algebras, associate to such a quantum groupoid a regular C*-pseudo-multiplicative unitary, and use this unitary to construct a dual Hopf C*-bimodule and to pass to a…

Operator Algebras · Mathematics 2013-07-02 Thomas Timmermann

Schwinger's algebra of selective measurements has a natural interpretation in terms of groupoids. This approach is pushed forward in this paper to show that the theory of coherent states has a natural setting in the framework of groupoids.…

Quantum Physics · Physics 2020-03-18 Fabio Di Cosmo , Alberto Ibort , Giuseppe Marmo

To construct a quantum group gauge theory one needs an algebra which is invariant under gauge transformations. The existence of this invariant algebra is closely related with the existence of a differential algebra $\delta _{{\cal H}}…

High Energy Physics - Theory · Physics 2011-07-19 I. Ya. Aref'eva , G. E. Arutyunov

Let $G'$ be a closed subgroup of a topological group $G$. A principal $G$-bundle $X$ is reducible to a locally trivial principal $G'$-bundle $X'$ if and only if there exists a local trivialisation of $X$ such that all transition functions…

Quantum Algebra · Mathematics 2021-02-05 Piotr M. Hajac , Jan Rudnik , Bartosz Zielinski