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Directions of graphs were originally introduced in the study of a cops-and-robbers kind of game, while the study of end spaces has been used to generalize classical graph-theoretical results to infinite graphs, such as Halin's…

Combinatorics · Mathematics 2025-10-21 Gustavo Boska , Matheus Duzi , Paulo Magalhães Júnior

The spectral properties of signed directed graphs, which may be naturally obtained by assigning a sign to each edge of a directed graph, have received substantially less attention than those of their undirected and/or unsigned counterparts.…

Combinatorics · Mathematics 2021-10-12 Pepijn Wissing , Edwin R. van Dam

The problem of inner vs outer conjugacy of subalgebras of certain graph C*-algebras is investigated. For a large class of finite graphs E, we show that whenever $\alpha$ is a vertex-fixing quasi-free automorphism of the corresponding graph…

Operator Algebras · Mathematics 2022-09-09 Tomohiro Hayashi , Jeong Hee Hong , Sophie Emma Zegers , Wojciech Szymański

A voltage graph is a finite directed graph whose edges are labeled by elements of a finite group $G$. A classical construction of Gross and Tucker associates to every voltage graph with vertex set $V$ a so-called derived graph with vertex…

Operator Algebras · Mathematics 2026-02-25 Björn Schäfer , 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 C^*-algebras, which is a generalization of both graph algebras and homeomorphism C^*-algebras. This class is very large and also very tractable. We prove the so-called gauge-invariant uniqueness theorem and the…

Operator Algebras · Mathematics 2007-05-23 Takeshi Katsura

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

We give several algebraic bounds for percolation on directed and undirected graphs: proliferation of strongly-connected clusters, proliferation of in- and out-clusters, and the transition associated with the number of giant components.

Mathematical Physics · Physics 2015-03-03 Kathleen E. Hamilton , Leonid P. Pryadko

We prove simplicity and pure infiniteness results for a certain class of labelled graph $C^*$-algebras. We show, by example, that this class of unital labelled graph $C^*$-algebras is strictly larger than the class of unital graph…

Operator Algebras · Mathematics 2008-01-15 T. Bates , D. A. Pask

We give a complete $K$-theoretical description of when an extension of two simple graph $C^{*}$-algebras is again a graph $C^{*}$-algebra.

Operator Algebras · Mathematics 2020-07-07 Søren Eilers , James Gabe , Takeshi Katsura , Efren Ruiz , Mark Tomforde

It is shown that a C*-algebra generated by any faithful covariant representation of a Hilbert bimodule X is canonically isomorphic to the crossed product associated to X provided that Rieffel's induced representation functor X-ind is…

Operator Algebras · Mathematics 2015-01-30 B. K. Kwasniewski

Based on a Wold decomposition for families of partial isometries and projections of Cuntz-Krieger-Toeplitz-type, we extend several fundamental theorems from the case of single vertex graphs to the general case of countable directed graphs…

Operator Algebras · Mathematics 2007-05-23 Elias Katsoulis , David W. Kribs

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 characterise quasidiagonality of the $C^*$-algebra of a cofinal $k$-graph in terms of an algebraic condition involving the coordinate matrices of the graph. This result covers all simple $k$-graph $C^*$-algebras. In the special case of…

Operator Algebras · Mathematics 2016-05-10 Lisa Orloff Clark , Astrid an Huef , Aidan Sims

We address the problem of defining graph transformations by the simultaneous application of direct transformations even when these cannot be applied independently of each other. An algebraic approach is adopted, with production rules of the…

Logic in Computer Science · Computer Science 2019-04-19 Thierry Boy de la Tour , Rachid Echahed

Recently, bidirected graphs have received increasing attention from the graph theory community with both structural and algorithmic results. Bidirected graphs are a generalization of directed graphs, consisting of an undirected graph…

Combinatorics · Mathematics 2025-12-16 Tara Abrishami , Nathan Bowler , Attila Joó , Florian Reich , Qiuzhenyu Tao

We introduce a new arc in directed graphs of integers. Among other things, we determine the positive integers that have arcs to all except a finite number of positive integers. We also propose some possible research problems at the end of…

Number Theory · Mathematics 2023-03-24 Phakhinkon Napp Phunphayap , Passawan Noppakaew , Prapanpong Pongsriiam

An automorphism $\beta$ of a $k$-graph $\Lambda$ induces a crossed product $C^* ( \Lambda ) \rtimes_\beta \mathbb{Z}$ which is isomorphic to a $(k+1)$-graph algebra $C^* ( \Lambda \times_\beta \mathbb{Z})$. In this paper we show how this…

Operator Algebras · Mathematics 2014-07-25 Nathan Brownlowe , Valentin Deaconu , Alex Kumjian , David Pask

The graph groupoids of directed graphs are topologically isomorphic if and only if there is a diagonal-preserving ring *-isomorphism between the Leavitt path algebras.

Rings and Algebras · Mathematics 2016-04-05 Jonathan H. Brown , Lisa Orloff Clark , Astrid an Huef

In earlier work we introduced the graph bracket polynomial of graphs with marked vertices, motivated by the fact that the Kauffman bracket of a link diagram D is determined by a looped, marked version of the interlacement graph associated…

Geometric Topology · Mathematics 2010-07-02 Lorenzo Traldi
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