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In general, universal (co)measuring (co)monoids and universal (co)acting bi/Hopf monoids, which prove to be a useful tool in the classification of quantum symmetries, do not always exist. In order to ensure their existence, the support of a…

Category Theory · Mathematics 2025-07-11 Ana Agore , Alexey Gordienko , Joost Vercruysse

It is shown that universal algebras that are injective in their equational classes are characterized by internal property that can be called completeness. We define universal algebra $A$ as complete (closed to simple extensions) if for each…

Commutative Algebra · Mathematics 2021-12-14 Pavlo Dzikovskyi

We study topology, particularly compactness, as an extension of Shulman's work on constructive mathematics via affine logic, while allowing propositional impredicativity. We introduce a notion of compactness in affine logic and prove the…

Logic · Mathematics 2026-03-23 Kazumi Kasaura

We study the basic properties of a dual "spectral" topology on positive type spaces of h-inductive theories and its essential connection to infinitary logic. The topology is Hausdorff, has the Baire property, and its compactness…

Logic · Mathematics 2015-01-06 Jean Berthet

In this paper we describe a new method of defining C*-algebras from oriented combinatorial data, thereby generalizing the constructions of algebras from directed graphs, higher-rank graphs, and ordered groups. We show that only the most…

Operator Algebras · Mathematics 2014-05-21 Jack Spielberg

We construct the reduced and essential C*-algebra of a Fell bundle over an \'etale groupoid (in full generality, without any second countability, local compactness or Hausdorff assumptions, even on the unit space) directly from sections…

Operator Algebras · Mathematics 2024-04-10 Tristan Bice

Integral calculus on the space of gauge equivalent connections is developed. Loops, knots, links and graphs feature prominently in this description. The framework is well--suited for quantization of diffeomorphism invariant theories of…

General Relativity and Quantum Cosmology · Physics 2016-08-31 Abhay Ashtekar , Jerzy Lewandowski

For a completely Hausdorff quasi-topological group $G$, we construct a universal pro-$C^*$-algebra $C(E^+G)$ as the non-commutative geometer's analogue of the total space $EG$ of the classifying principal $G$-bundle $EG\to BG$. The…

Operator Algebras · Mathematics 2023-05-01 Alexandru Chirvasitu , Mariusz Tobolski

We present a new case of duality between integrable many-body systems, where two systems live on the action-angle phase spaces of each other in such a way that the action variables of each system serve as the particle positions of the other…

Mathematical Physics · Physics 2014-10-28 L. Feher , T. F. Gorbe

The notion of associativity (which differs from the straightforward generalization of the usual associativity given by the move of parentheses in the relevant expression) for operations of high arity is introduced. It is proved that the…

Category Theory · Mathematics 2019-05-21 Dali Zangurashvili

After a summary on module algebra actions of C^*-weak Hopf algebras we outline the proof of a reconstruction theorem stating that every finite index depth 2 inclusion N < M of unital C^*-algebras with finite dimensional centers is…

Quantum Algebra · Mathematics 2007-05-23 K. Szlachanyi

We show that the method to construct C^*-algebras from topological graphs, introduced in our previous paper, generalizes many known constructions. We give many ways to make new topological graphs from old ones, and study the relation of…

Operator Algebras · Mathematics 2007-05-23 Takeshi Katsura

In this paper we apply a recently proposed algebraic theory of integration to projective group algebras. These structures have received some attention in connection with the compactification of the $M$ theory on noncommutative tori. This…

Mathematical Physics · Physics 2009-10-31 R. Casalbuoni

This article extends the main results of the publication arXiv:2001.01312 to the case of a twisted groupoid. More precisely, it gives a decomposition of the C*-algebra of a twisted locally compact groupoid with Haar system in presence of a…

Operator Algebras · Mathematics 2021-03-22 Jean Renault

Let $B \subset A$ be a depth $2$ inclusion of simple unital $C^*$-algebras with a conditional expectation of index-finite type. We show that the second relative commutant $B' \cap A_1$ carries a canonical structure of a weak $C^*$-Hopf…

Operator Algebras · Mathematics 2026-02-12 Biplab Pal

We develop some tools for manipulating and constructing projections in C*-algebras. These are then applied to give short proofs of some standard projection homotopy results, as well as strengthen some fundamental classical results for…

Operator Algebras · Mathematics 2017-02-10 Tristan Bice

We use assembly maps to study $\mathbf{TC}(\mathbb{A}[G];p)$, the topological cyclic homology at a prime $p$ of the group algebra of a discrete group $G$ with coefficients in a connective ring spectrum $\mathbb{A}$. For any finite group, we…

K-Theory and Homology · Mathematics 2019-10-02 Wolfgang Lueck , Holger Reich , John Rognes , Marco Varisco

It is shown that every outer *-automorphism of a real C*-algebra can be uniquely extended to an injective envelope of real C*-algebra. It is proven that if a real C*-algebra is a simple, then its injective envelope is also simple, and it is…

Operator Algebras · Mathematics 2025-02-11 A. A. Rakhimov , L. D. Ramazonova

In the setting of von Neumann algebras, measurable quantum groupoids have successfully been axiomatized and studied by Enock, Vallin, and Lesieur, whereas in the setting of $C^{*}$-algebras, a similar theory of locally compact quantum…

Operator Algebras · Mathematics 2007-12-24 Thomas Timmermann

Group actions on a Smale space and the actions induced on the C*-algebras associated to such a dynamical system are studied. We show that an effective action of a discrete group on a mixing Smale space produces a strongly outer action on…

Operator Algebras · Mathematics 2019-01-17 Robin J. Deeley , Karen R. Strung