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We explore the recently introduced local-triviality dimensions by studying gauge actions on graph $C^*$-algebras, as well as the restrictions of the gauge action to finite cyclic subgroups. For $C^*$-algebras of finite acyclic graphs and…

Operator Algebras · Mathematics 2021-06-09 Alexandru Chirvasitu , Benjamin Passer , Mariusz Tobolski

We find a substantial class of pairs of $*$-homomorphisms between graph C*-algebras of the form $C^*(E)\hookrightarrow C^*(G)\twoheadleftarrow C^*(F)$ whose pullback C*-algebra is an AF graph C*-algebra. Our result can be interpreted as a…

Quantum Algebra · Mathematics 2020-11-25 Alexandru Chirvasitu , Piotr M. Hajac , Mariusz Tobolski

We study two classes of inverse semigroups built from directed graphs, namely graph inverse semigroups and a new class of semigroups that we refer to as Leavitt inverse semigroups. These semigroups are closely related to graph…

Group Theory · Mathematics 2019-11-19 John Meakin , Zhengpan Wang

We introduce a new class of partial actions of free groups on totally disconnected compact Hausdorff spaces, which we call convex subshifts. These serve as an abstract framework for the partial actions associated with finite separated…

Operator Algebras · Mathematics 2017-05-15 Pere Ara , Matias Lolk

To a large class of graphs of groups we associate a C*-algebra universal for generators and relations. We show that this C*-algebra is stably isomorphic to the crossed product induced from the action of the fundamental group of the graph of…

Operator Algebras · Mathematics 2021-07-27 Nathan Brownlowe , Alexander Mundey , David Pask , Jack Spielberg , Anne Thomas

A new infinite family of bipartite cubic 3-arc transitive graphs is constructed and studied. They provide the first known examples admitting a 2-arc transitive vertex-biquasiprimitive group of automorphisms for which the index two subgroup…

Group Theory · Mathematics 2011-03-30 Alice Devillers , Michael Giudici , Cai Heng Li , Cheryl E. Praeger

A 2-factor of a graph $G$ is a 2-regular spanning subgraph of $G$. We present a survey summarising results on the structure of 2-factors in regular graphs, as achieved by various researchers in recent years.

Combinatorics · Mathematics 2024-08-16 D. Labbate , F. Romaniello

For a row-finite higher-rank graph {\Lambda}, we construct a higher-rank graph T{\Lambda} such that the Toeplitz algebra of {\Lambda} is isomorphic to the Cuntz-Krieger algebra of T{\Lambda}. We then prove that the higher-rank graph…

Operator Algebras · Mathematics 2015-07-29 Yosafat E. P. Pangalela

We study two relations on multi-dimensional subshifts: A pre-order based on the patterns configurations contain and the Cantor-Bendixson rank. We exhibit several structural properties of two-dimensional subshifts: We characterize the…

Dynamical Systems · Mathematics 2013-09-25 Alexis Ballier , Emmanuel Jeandel

We introduce a class of recursive subhomogeneous algebras that we call diagonal subhomogeneous and we give a notion of diagonal maps between these algebras. We show that any simple limit of diagonal subhomogeneous algebras with diagonal…

Operator Algebras · Mathematics 2017-09-29 James Lutley

We introduce a new class of two-dimensional diagrams, the \emph{projection diagrams}, as a tool to visualize the global structure of space-times. We construct the diagrams for several metrics of interest, including the Kerr-Newman - (anti)…

General Relativity and Quantum Cosmology · Physics 2013-01-22 Piotr T. Chruściel , Christa R. Ölz , Sebastian J. Szybka

This paper deals with lattice congruences of the weak order on the symmetric group, and initiates the investigation of the cover graphs of the corresponding lattice quotients. These graphs also arise as the skeleta of the so-called…

Combinatorics · Mathematics 2022-12-05 Hung Phuc Hoang , Torsten Mütze

In a number of recent papers, (k+l)-graphs have been constructed from k-graphs by inserting new edges in the last l dimensions. These constructions have been motivated by C*-algebraic considerations, so they have not been treated…

Operator Algebras · Mathematics 2010-06-10 Alex Kumjian , David Pask , Aidan Sims

This is the second report of our work on the construction of directed strongly regular graphs. In our previous work, we constructed a couple of infinite families of new directed strongly regular graphs on the sets of antiflags of partial…

Combinatorics · Mathematics 2011-02-09 Oktay Olmez , Sung Y. Song

String diagrams are a powerful tool for reasoning about composite structures in symmetric monoidal categories. By representing string diagrams as graphs, equational reasoning can be done automatically by double-pushout rewriting. !-graphs…

Logic in Computer Science · Computer Science 2016-02-22 Aleks Kissinger , Vladimir Zamdzhiev

We unite elements of category theory, K-theory, and geometric group theory, by defining a class of groups called $k$-cube groups, which act freely and transitively on the product of $k$ trees, for arbitrary $k$. The quotient of this action…

Operator Algebras · Mathematics 2024-01-12 Sam A. Mutter , Aura-Cristiana Radu , Alina Vdovina

This is the final one in the series of papers where we introduce and study the $C^*$-algebras associated with topological graphs. In this paper, we get a sufficient condition on topological graphs so that the associated $C^*$-algebras are…

Operator Algebras · Mathematics 2007-05-23 Takeshi Katsura

To a higher rank directed graph $(\Lambda, d)$, in the sense of Kumjian and Pask, one can associate natural noncommutative analytic Toeplitz algebras, both weakly closed and norm closed. We introduce methods for the classification of these…

Operator Algebras · Mathematics 2007-05-23 Stephen C Power

The concept of a configuration graph associated to a primitive, aperiodic substitution is introduced in [1] as a convenient graphical representation of the infinite indeterminism of the shift space of the substitution. The main result of…

Dynamical Systems · Mathematics 2007-05-23 Jacob Thamsborg

We begin the study of a new class of operator algebras that arise from higher rank graphs. Every higher rank graph generates a Fock space Hilbert space and creation operators which are partial isometries acting on the space. We call the…

Operator Algebras · Mathematics 2007-05-23 David W. Kribs , Stephen C. Power