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We prove that two finite-dimensional commutative algebras over an algebraically closed field are isomorphic if and only if they give rise to isomorphic representations of the category of finite sets and surjective maps.

Rings and Algebras · Mathematics 2011-04-05 S. S. Podkorytov

We study the automorphism groups of countable homogeneous directed graphs (and some additional homogeneous structures) from the point of view of topological dynamics. We determine precisely which of these automorphism groups are amenable…

Combinatorics · Mathematics 2017-12-29 Micheal Pawliuk , Miodrag Sokic

Graph embeddings deal with injective maps from a given simple, undirected graph $G=(V,E)$ into a metric space, such as $\mathbb{R}^n$ with the Euclidean metric. This concept is widely studied in computer science, see \cite{ge1}, but also…

Combinatorics · Mathematics 2022-05-04 Dominic van der Zypen

Many previously studied path algebras or self-similar group algebras may be viewed as Steinberg algebras of self-similar groupoids. By way of inverse semigroup algebras, we characterize when the Steinberg algebra of a self-similar groupoid…

Rings and Algebras · Mathematics 2026-05-27 Josiah Aakre

Let $\mathbf{\Gamma} = (V,E)$ be a (non-trivial) finite graph with $\lambda: E \rightarrow \mathbb{R}_{+}$, an edge labelling of $\mathbf{\Gamma}$. Let $\rho : V\rightarrow \mathbb{R}^{2}$ be a map which preserves the edge labelling. The…

Combinatorics · Mathematics 2019-11-15 Arindam Biswas

In this paper we generalize the notion of a $k$-graph into (countable) infinite rank. We then define our $C^*$-algebra in a similar way as in $k$-graph $C^*$-algebras. With this construction we are able to find analogues to the Gauge…

Operator Algebras · Mathematics 2022-02-18 Tim Schenkel

In this paper, we provide a simple proof for the fact that two simplicial complexes are isomorphic if and only if their associated Stanley-Reisner rings, or their associated facet rings are isomorphic as $K$-algebras. As a consequence, we…

Commutative Algebra · Mathematics 2010-10-12 Rashid Zaare-Nahandi

We prove that every class of graphs $\mathscr C$ that is monadically stable and has bounded twin-width can be transduced from some class with bounded sparse twin-width. This generalizes analogous results for classes of bounded linear…

Logic in Computer Science · Computer Science 2022-09-20 Jakub Gajarský , Michał Pilipczuk , Szymon Toruńczyk

We consider the dynamics on the C*-algebras of finite graphs obtained by lifting the gauge action to an action of the real line. Enomoto, Fujii and Watatani proved that if the vertex matrix of the graph is irreducible, then the dynamics on…

Operator Algebras · Mathematics 2014-05-12 Astrid an Huef , Marcelo Laca , Iain Raeburn , Aidan Sims

We consider a finite, connected and simple graph $\Gamma$ that admits a vertex-transitive group of automorphisms $G$. Under the assumption that, for all $x \in V(\Gamma)$, the local action $G_x^{\Gamma(x)}$ is the action of…

Group Theory · Mathematics 2020-10-06 Luke Morgan

In this paper, we study the graph classification problem from the graph homomorphism perspective. We consider the homomorphisms from $F$ to $G$, where $G$ is a graph of interest (e.g. molecules or social networks) and $F$ belongs to some…

Machine Learning · Computer Science 2020-07-03 Hoang NT , Takanori Maehara

Let $A$ and $C$ be two unital simple C*-algebas with tracial rank zero. Suppose that $C$ is amenable and satisfies the Universal Coefficient Theorem. Denote by ${{KK}}_e(C,A)^{++}$ the set of those $\kappa$ for which…

Operator Algebras · Mathematics 2008-03-10 Huaxin Lin , Zhuang Niu

Motivated by recent results in graph C*-algebras concerning an equivariant pushout structure of the Vaksman-Soibelman quantum odd spheres, we introduce a class of graphs called trimmable. Then we show that the Leavitt path algebra of a…

Rings and Algebras · Mathematics 2018-03-28 Piotr M. Hajac , Atabey Kaygun , Mariusz Tobolski

We define an ultragraph, which is a generalization of a directed graph, and describe how to associate a C*-algebra to it. We show that the class of ultragraph algebras contains the C*-algebras of graphs as well as the Exel-Laca algebras. We…

Operator Algebras · Mathematics 2007-05-23 Mark Tomforde

We will introduce a notion of normal subshifts. A subshift $(\Lambda,\sigma)$ is said to be normal if it satisfies a certain synchronizing property called $\lambda$-synchronizing and is infinite as a set. We have lots of purely infinite…

Operator Algebras · Mathematics 2020-05-04 Kengo Matsumoto

We give various necessary and sufficient conditions for an AF-algebra to be isomorphic to a graph C*-algebra, an Exel-Laca algebra, and an ultragraph C*-algebra. We also explore consequences of these results. In particular, we show that all…

Operator Algebras · Mathematics 2009-05-24 Takeshi Katsura , Aidan Sims , Mark Tomforde

We study the general and connected stable ranks for C*-algebras. We estimate these ranks for pullbacks of C*-algebras, and for tensor products by commutative C*-algebras. Finally, we apply these results to determine these ranks for certain…

Operator Algebras · Mathematics 2018-06-26 Prahlad Vaidyanathan

We show that the class of C*-algebras with stable rank greater than a given positive integer is axiomatizable in logic of metric structures. As a consequence we show that the stable rank is continuous with respect to forming ultrapowers of…

Operator Algebras · Mathematics 2017-01-18 Ilijas Farah , Mikael Rørdam

We show that a class of algebras is closed under the taking of homomorphic images and direct products if and only if the class consists of all algebras that satisfy a set of (generally simultaneous) equations. For classes of regular…

Group Theory · Mathematics 2022-06-23 Peter M Higgins , Marcel Jackson

Computing a morph between two drawings of a graph is a classical problem in computational geometry and graph drawing. While this problem has been widely studied in the context of planar graphs, very little is known about the existence of…

Computational Geometry · Computer Science 2021-05-28 Patrizio Angelini , Michael A. Bekos , Fabrizio Montecchiani , Maximilian Pfister