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The graph $G$ is said to be strongly regular with parameters $(n,k,\lambda,\mu)$ if the following conditions hold: (1) each vertex has $k$ neighbours; (2) any two adjacent vertices of $G$ have $\lambda$ common neighbours; (3) any two…

Combinatorics · Mathematics 2021-10-06 Jeepamol J Palathingal , Aparna Lakshmanan S , Greg Markowsky

It is well-known that a minimal graph of codimension one is stable, i.e. the second variation of the area functional is non-negative. This is no longer true for higher codimensional minimal graphs. In this note, we prove that a minimal…

Differential Geometry · Mathematics 2007-05-23 Mu-Tao Wang

We present a linear stability analysis of stationary states (or fixed points) in large dynamical systems defined on random directed graphs with a prescribed distribution of indegrees and outdegrees. We obtain two remarkable results for such…

Statistical Mechanics · Physics 2024-05-22 Izaak Neri , Fernando Lucas Metz

We say that a graph G is $(k,\ell)$-stable if removing $k$ vertices from it reduces its independence number by at most $\ell$. We say that G is tight $(k,\ell)$-stable if it is $(k,\ell)$-stable and its independence number equals…

Combinatorics · Mathematics 2024-02-08 Dingding Dong , Sammy Luo

A class of graphs is called block-stable when a graph is in the class if and only if each of its blocks is. We show that, as for trees, for most $n$-vertex graphs in such a class, each vertex is in at most $(1+o(1)) \log n / \log\log n$…

Combinatorics · Mathematics 2016-05-17 Colin McDiarmid , Alex Scott

A non-complete graph $\Gamma$ is said to be $(G,2)$-distance transitive if $G$ is a subgroup of the automorphism group of $\Gamma$ that is transitive on the vertex set of $\Gamma$, and for any vertex $u$ of $\Gamma$, the stabilizer $G_u$ is…

Group Theory · Mathematics 2015-07-07 Brian P. Corr , Wei Jin , Csaba Schneider

We characterize stability of graph C*-algebras by giving five conditions equivalent to their stability. We also show that if G is a graph with no sources, then C*(G) is stable if and only if each vertex in G can be reached by an infinite…

Operator Algebras · Mathematics 2007-05-23 Mark Tomforde

We characterize strongly edge regular product graphs and find the edge-balanced index sets of complete bipartite graphs without a perfect matching, the direct product $K_n\times K_2$. We also prove a lemma that is helpful to determine the…

Combinatorics · Mathematics 2014-02-04 Elliot Krop , Sin-Min Lee , Christopher Raridan

The stability number of a graph G, denoted by alpha(G), is the cardinality of a stable set of maximum size in G. A graph is well-covered if every maximal stable set has the same size. G is a Koenig-Egervary graph if its order equals…

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

A graph is called $(k,t)$-regular if it is $k$-regular and the induced subgraph on the neighbourhood of every vertex is $t$-regular. We find new conditions on $(k,t)$ for the existence of such graphs and provide a wide range of examples.

Combinatorics · Mathematics 2021-12-02 Marston Conder , Jeroen Schillewaert , Gabriel Verret

Stable gonality is a multigraph parameter that measures the complexity of a graph. It is defined using maps to trees. Those maps, in some sense, divide the edges equally over the edges of the tree; stable gonality asks for the map with the…

Discrete Mathematics · Computer Science 2023-06-22 Ragnar Groot Koerkamp , Marieke van der Wegen

This paper introduces and studies the stability of the strong domination number of a graph, denoted $\operatorname{st}_{\gamma_{st}}(G)$, defined as the minimum number of vertices whose removal changes the strong domination number…

Combinatorics · Mathematics 2026-01-08 Saeid Alikhani , Mazharuddin Mehraban , Hossein Shojaaldini Ardakani

Given a finite group $G$, denote by $\Gamma(G)$ the simple undirected graph whose vertices are the distinct sizes of noncentral conjugacy classes of $G$, and set two vertices of $\Gamma(G)$ to be adjacent if and only if they are not coprime…

Group Theory · Mathematics 2013-06-10 Mariagrazia Bianchi , Rachel D. Camina , Marcel Herzog , Emanuele Pacifici

This article investigates the isomorphism problem for graphs derived from the four standard graph products: Cartesian, Kronecker (direct), strong, and lexicographic product. We provide a complete characterization of all simple connected…

Combinatorics · Mathematics 2025-08-07 Priti Prasanna Mondal , M. Rajesh Kannan , Fouzul Atik

A countable discrete group $\Gamma$ is said to be Frobenius stable if a function from the group that is "almost multiplicative" in the point Frobenius norm topology is "close" to a genuine unitary representation in the same topology. The…

Operator Algebras · Mathematics 2024-02-08 Forrest Glebe

In this paper we study a new product of graphs called {\em tight product}. A graph $H$ is said to be a tight product of two (undirected multi) graphs $G_1$ and $G_2$, if $V(H)=V(G_1)\times V(G_2)$ and both projection maps $V(H)\to V(G_1)$…

Discrete Mathematics · Computer Science 2012-11-06 Amit Daniely , Nathan Linial

A graph G is said to be 1-perfectly orientable (1-p.o. for short) if it admits an orientation such that the out-neighborhood of every vertex is a clique in G. The class of 1-p.o. graphs forms a common generalization of the classes of…

Combinatorics · Mathematics 2016-08-31 Tatiana Romina Hartinger , Martin Milanič

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

In this paper we investigate the connectedness and the isomorphism problems for zig-zag products of two graphs. A sufficient condition for the zig-zag product of two graphs to be connected is provided, reducing to the study of the…

Combinatorics · Mathematics 2017-03-10 Daniele D'Angeli , Alfredo Donno , Ecaterina Sava-Huss

A graph with convex quadratic stability number is a graph for which the stability number is determined by solving a convex quadratic program. Since the very beginning, where a convex quadratic programming upper bound on the stability number…

Combinatorics · Mathematics 2018-11-15 Domingos M. Cardoso