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Let $\Gamma=(X,\mathcal{R})$ denote a finite, simple, connected, and undirected non-bipartite graph with vertex set $X$ and edge set $\mathcal{R}$. Fix a vertex $x \in X$, and define $\mathcal{R}_f = \mathcal{R} \setminus \{yz \mid…

Combinatorics · Mathematics 2023-05-17 Blas Fernández , Roghayeh Maleki , Štefko Miklavič , Giusy Monzillo

Graph parameters such as the clique number, the chromatic number, and the independence number are central in many areas, ranging from computer networks to linguistics to computational neuroscience to social networks. In particular, the…

Computational Complexity · Computer Science 2020-12-15 Fabian Frei , Edith Hemaspaandra , Jörg Rothe

Let $\Gamma$ be a finite connected $G$-vertex-transitive graph and let $v$ be a vertex of $\Gamma$. If the permutation group induced by the action of the vertex-stabiliser $G_v$ on the neighbourhood $\Gamma(v)$ is permutation isomorphic to…

Combinatorics · Mathematics 2012-11-15 Pablo Spiga , Gabriel Verret

We have generalised the concept of graph states to what we have called mixed graph states, which we define in terms of mixed graphs, that is graphs with both directed and undirected edges, as the density matrix stabilized by the associated…

Quantum Physics · Physics 2016-03-17 Constanza Riera , Ramij Rahaman , Matthew G. Parker

We show that the groupoids of two directed graphs are isomorphic if and only if the two graphs are orbit equivalent by an orbit equivalence that preserves isolated eventually periodic points. We also give a complete description of the…

Dynamical Systems · Mathematics 2018-10-08 Toke Meier Carlsen , Marius Lie Winger

A vertex in a graph is said to be sedentary if a quantum state assigned on that vertex tends to stay on that vertex. Under mild conditions, we show that the direct product and join operations preserve vertex sedentariness. We also…

Combinatorics · Mathematics 2024-01-02 Hermie Monterde

We describe the structure of virtually solvable normal subgroups in the automorphism group of a right-angled Artin group ${\rm Aut}(A_\Gamma)$. In particular, we prove that a finite normal subgroup in ${\rm Aut}(A_\Gamma)$ has at most order…

Group Theory · Mathematics 2023-04-18 Philip Möller , Olga Varghese

Understanding which system structure can sustain stable dynamics is a fundamental step in the design and analysis of large scale dynamical systems. Towards this goal, we investigate here the structural stability of systems with a random…

Combinatorics · Mathematics 2020-03-26 Mohamed Ali Belabbas , Artur Kirkoryan

The stability number alpha(G) of a graph G is the cardinality of a maximum stable set in G, xi(G) denotes the size of core(G), where core(G) is the intersection of all maximum stable sets of G. In this paper we prove that for a graph G…

Combinatorics · Mathematics 2007-05-23 Vadim E. Levit , Eugen Mandrescu

We provide a complete classification of when the homeomorphism group of a stable surface, $\Sigma$, has the automatic continuity property: Any homomorphism from Homeo$(\Sigma)$ to a separable group is necessarily continuous. This result…

Geometric Topology · Mathematics 2024-11-21 Mladen Bestvina , George Domat , Kasra Rafi

The main result of this paper is that, if $\Gamma$ is a connected 4-valent $G$-arc-transitive graph and $v$ is a vertex of $\Gamma$, then either $\Gamma$ is one of a well understood infinite family of graphs, or $|G_v|\leq 2^43^6$ or…

Combinatorics · Mathematics 2010-10-14 Primoz Potocnik , Pablo Spiga , Gabriel Verret

Let $p$ be a prime and let $L$ be either the intransitive permutation group $C_p\times C_p$ of degree $2p$ or the transitive permutation group $C_p \wr C_2$ of degree $2p$. Let $\Gamma$ be a connected $G$-vertex-transitive and…

Combinatorics · Mathematics 2013-11-19 Pablo Spiga , Gabriel Verret

The primary objective of this paper is to introduce Hyers-Ulam-type stability results for monotone, subadditive, and convex graphs. We consider their standard definitions in an approximate sense and demonstrate the existence of a…

General Mathematics · Mathematics 2026-02-05 Angshuman R. Goswami , Mahmood K. Shihab

A finite graph $\Gamma$ is called $G$-symmetric if $G$ is a group of automorphisms of $\Gamma$ which is transitive on the set of ordered pairs of adjacent vertices of $\Gamma$. We study a family of symmetric graphs, called the unitary…

Combinatorics · Mathematics 2015-03-25 Massimo Giulietti , Stefano Marcugini , Fernanda Pambianco , Sanming Zhou

We introduce uniformly vertex-transitive graphs as vertex-transitive graphs satisfying a stronger condition on their automorphism groups, motivated by a problem which arises from a Sinkhorn-type algorithm. We use the derangement graph…

Combinatorics · Mathematics 2019-12-03 Simon Schmidt , Chase Vogeli , Moritz Weber

A graph is said to be globally rigid in $d$-dimensional space if almost all of its embeddings are unique up to isometries. If a graph has enough automorphisms to send any of its vertices into any other, then it is called vertex-transitive.…

Combinatorics · Mathematics 2026-01-19 Angelo El Saliby

Let $\Gamma$ be a simple graph on a finite vertex set $V$ and let $A$ be its adjacency matrix. Then $\Gamma$ is said to be singular if and only if $0$ is an eigenvalue of $A.$ The nullity (singularity) of $\Gamma,$ denoted by ${\rm…

Combinatorics · Mathematics 2018-06-21 Ali Sltan AL-Tarimshawy

The stability number of a graph G, denoted by alpha(G), is the cardinality of a maximum stable set, and mu(G) is the cardinality of a maximum matching in G. If alpha(G)+mu(G) equals its order, then G is a Konig-Egervary graph. In this paper…

Combinatorics · Mathematics 2011-01-25 Vadim E. Levit , Eugen Mandrescu

We investigate properties which ensure that a given finite graph is the commuting graph of a group or semigroup. We show that all graphs on at least two vertices such that no vertex is adjacent to all other vertices is the commuting graph…

Group Theory · Mathematics 2016-05-18 Michael Giudici , Bojan Kuzma

The topic of stable matchings (marriages) in a bipartite graph has become widely popular, starting with the appearance of the classical work by Gale and Shapley. We give a detailed survey on selected known results in this field that…

Combinatorics · Mathematics 2023-01-11 Alexander V. Karzanov