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We introduce a category of inverse semigroup actions and a category of \'etale groupoids. We show that there are three functors which send inverse semigroups to their spectral actions, inverse semigroup actions to their transformation…

Operator Algebras · Mathematics 2024-10-29 Takuto Fujieda , Takeshi Katsura , Tomoki Uchimura

A simple observation, showing that every groupoid becomes an inverse semigroup after adding one element. In such inverse semigroups all idempotents are mutually orthogonal. This fact implies that every C*-algebra of a discrete groupoid is a…

Operator Algebras · Mathematics 2016-05-02 Marat Aukhadiev

Taking into account the correspondence between open groupoids and their quantales, we establish a bijective correspondence between the principal $G$-bundles whose left projection is an open surjection and the principal $\opens(G)$-locales…

Category Theory · Mathematics 2018-10-03 Juan Pablo Quijano

Let $K$ be a commutative ring with unit and $S$ an inverse semigroup. We show that the semigroup algebra $KS$ can be described as a convolution algebra of functions on the universal \'etale groupoid associated to $S$ by Paterson. This…

Rings and Algebras · Mathematics 2009-03-23 Benjamin Steinberg

It is known to experts that certain regular inclusions of von Neumann algebras arise as crossed products with cocycle actions of the canonical quotient groupoids associated with the inclusions. Similarly, `strongly normal' inclusions of…

Operator Algebras · Mathematics 2025-12-17 Soham Chakraborty

We describe a special class of representations of an inverse semigroup S on Hilbert's space which we term "tight". These representations are supported on a subset of the spectrum of the idempotent semilattice of S, called the "tight…

Operator Algebras · Mathematics 2008-06-25 Ruy Exel

The quantum completion of the space of connections in a manifold can be seen as the set of all morphisms from the groupoid of the edges of the manifold to the (compact) gauge group. This algebraic construction generalizes an analogous…

High Energy Physics - Theory · Physics 2015-06-25 J. M. Velhinho

We introduce the inverse monoid of inner partial automorphisms of a semigroup -- a tool that associates to every semigroup an inverse semigroup. When the semigroup is a group, this inverse semigroup is isomorphic to the group of inner…

In this paper, we provide a comprehensive analysis of involutive quantales, with a particular focus on quantic frames. We extend the axiomatic foundations of quantale-enriched topological spaces to include closure under the anti-homomorphic…

Operator Algebras · Mathematics 2025-09-11 Javier Gutiérrez García , Ulrich Höhle

We prove that there is an adjunction between what we call \'etale topological categories and restriction quantal frames that leads to an adjunction with a category of complete restriction monoids. This generalizes the adjunction between…

Category Theory · Mathematics 2023-03-10 Mark V. Lawson

We examine, in a general setting, a notion of inverse semigroup of left quotients, which we call left I-quotients. This concept has appeared, and has been used, as far back as Clifford's seminal work describing bisimple inverse monoids in…

Rings and Algebras · Mathematics 2010-03-19 Nassraddin Ghroda , Victoria Gould

The geometry of inverse semigroups is a natural topic of study, motivated both from within semigroup theory and by applications to the theory of non-commutative $C^*$-algebras. We study the relationship between the geometry of an inverse…

Group Theory · Mathematics 2025-12-04 Mark Kambites , Nóra Szakács

For an arbitrary localic etale groupoid G we provide simple descriptions, in terms of modules over the quantale O(G) of the groupoid, of the continuous actions of G, including actions on open maps and sheaves. The category of G-actions is…

Category Theory · Mathematics 2011-03-29 Pedro Resende

Under non-commutative Stone duality, there is a correspondence between second countable Hausdorff \'etale groupoids which have a Cantor space of identities and what we call Tarski inverse monoids: that is, countable Boolean inverse…

Category Theory · Mathematics 2016-02-09 Mark V. Lawson

We characterize the inverse semigroups that are Morita equivalent to graph inverse semigroups. We also consider a generalization to inverse semigroups associated with left cancellative categories.

Group Theory · Mathematics 2023-07-25 Martha Du Preez , Robert Grimley , Evan Lira , David Milan , Shreyas Ramamurthy

The notion of an open quantum subgroup of a locally compact quantum group is introduced and given several equivalent characterizations in terms of group-like projections, inclusions of quantum group C*-algebras and properties of respective…

Operator Algebras · Mathematics 2016-08-15 Mehrdad Kalantar , Paweł Kasprzak , Adam Skalski

A partial automorphism of a semigroup $S$ is any isomorphism between its subsemigroups, and the set all partial automorphisms of $S$ with respect to composition is the inverse monoid called the partial automorphism monoid of $S$. Two…

Rings and Algebras · Mathematics 2011-07-26 Simon M. Goberstein

Quantum reference frames are needed in quantum theory for much the same reasons that reference frames are in classical theories: to manifest invariance in line with fundamental relativity principles and to provide a basis for the definition…

Quantum Physics · Physics 2025-04-02 Titouan Carette , Jan Głowacki , Leon Loveridge

In this paper, we prove that the algebra of an \'etale groupoid with totally disconnected unit space has a simple algebra over a field if and only if the groupoid is minimal and effective and the only function of the algebra that vanishes…

Rings and Algebras · Mathematics 2020-11-24 Benjamin Steinberg , Nóra Szakács

This is an expository paper which provides a quick introduction to Boolean inverse semigroups and their type monoids, with the emphasis on techniques and insights of the theory, and also treats the connection of the type monoid…

Rings and Algebras · Mathematics 2025-11-06 Ganna Kudryavtseva