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Given a graph $G$, we determine the structure of the rotation graph of a graph obtained by applying certain operations to $G$. Specifically, we consider the operations of adding a simplicial vertex, adding a true twin to a vertex, and the…

组合数学 · 数学 2024-10-11 Ana Gargantini , Adrián Pastine , Pablo Torres

For a simple graph $G$, let $J_G$ denote the corresponding binomial edge ideal. This article considers the binomial edge ideal of the corona product of two connected graphs $G$ and $H$. The corona product of $G$ and $H$, denoted by $G\circ…

交换代数 · 数学 2025-03-18 Buddhadev Hajra , Rajib Sarkar

Given a graph $G$ on $n$ vertices, its adjacency matrix and degree diagonal matrix are represented by $A(G)$ and $D(G)$, respectively. The $Q$-spectrum of $G$ consists of all the eigenvalues of its signless Laplacian matrix $Q(G)=A(G)+D(G)$…

组合数学 · 数学 2023-07-28 Gui-Xian Tian , Jun-Xing Wu , Shu-Yu Cui , Hui-Lu Sun

Let $\alpha\in[0,1)$, and let $G$ be a connected graph of order $n$ with $n\geq f(\alpha)$, where $f(\alpha)=6$ for $\alpha\in[0,\frac{2}{3}]$ and $f(\alpha)=\frac{4}{1-\alpha}$ for $\alpha\in(\frac{2}{3},1)$. A graph $G$ is said to be…

组合数学 · 数学 2026-03-24 Sizhong Zhou , Yuli Zhang , Tao Zhang , Hongxia Liu

Let $\core G$ and $\corona G$ denote the intersection and the union, respectively, of all maximum independent sets of a graph $G$. A graph is called \emph{$2$-bicritical} if $\a{N(S)}>\a S$ for every nonempty independent set $S$.…

组合数学 · 数学 2026-03-13 Kevin Pereyra

Given a simple graph $G$, its $A_\alpha$ matrix is a convex combination with parameter $\alpha\in [0,1]$ of its adjacency matrix and its degree diagonal matrices. Here we compare two lower bounds presented in [J. D. G. Silva Jr., C. S.…

组合数学 · 数学 2026-01-27 Giovanni Barbarino

For a graph $G$, the generalized adjacency matrix $A_\alpha(G)$ is the convex combination of the diagonal matrix $D(G)$ and the adjacency matrix $A(G)$ and is defined as $A_\alpha(G)=\alpha D(G)+(1-\alpha) A(G)$ for $0\leq \alpha \leq 1$.…

谱理论 · 数学 2023-04-04 Nijara Konch , A. Bharali , S. Pirzada

Given a graph $G$, we have the adjacency matrix $A(G)$ and degree diagonal matrix $D(G)$. The $Q$-spectrum is the all eigenvalues of $Q$-matrix $Q(G)=A(G)+D(G)$. A class of graphs is determined by their generalized $Q$-spectrum (DGQS for…

谱理论 · 数学 2023-11-07 Liwen Gao , Xuejun Guo

The subdivision graph $S(G)$ of a graph $G$ is the graph obtained by inserting a new vertex into every edge of $G$. In $\cite{PL}$, two classes of new corona graphs, the corona-vertex of the subdivision graph $G_{1}\diamondsuit G_{2}$ and…

组合数学 · 数学 2016-11-15 Qun Liu , Jia-Bao Liu , Shaohui Wang , Masoud Karimi

Product graphs have been gainfully used in literature to generate mathematical models of complex networks which inherit properties of real networks. Realizing the duplication phenomena imbibed in the definition of corona product of two…

谱理论 · 数学 2015-07-21 Rohan Sharma , Bibhas Adhikari , Abhishek Mishra

Given a connected graph $R$ on $r$ vertices and a rooted graph $H,$ let $R\{H\}$ be the graph obtained from $r$ copies of $H$ and the graph $R$ by identifying the root of the $i-th$ copy of $H$ with the $i-th$ vertex of $R$. Let…

组合数学 · 数学 2017-04-25 Oscar Rojo

The unitary addition Cayley graph $G_n$, $n\in Z^+$ is the graph whose vertex set is $Z_n$, the ring of integers modulo $n$ and two vertices $u$ and $v$ are adjacent if and only if $u + v \in \cup_n$ where $\cup_n$ is the set of all units…

组合数学 · 数学 2023-04-07 Najiya V K , Chithra A , Naveen Palanivel

Let $\alpha(G)$ denote the cardinality of a maximum independent set and $\mu(G)$ be the size of a maximum matching of a graph $G=\left( V,E\right) $. If $\alpha(G)+\mu(G)=\left\vert V\right\vert $, then $G$ is a K\"{o}nig-Egerv\'{a}ry…

组合数学 · 数学 2024-11-21 Vadim E. Levit , Eugen Mandrescu

The search for a highly discriminating and easily computable invariant to distinguish graphs remains a challenging research topic. Here we focus on cospectral graphs whose complements are also cospectral (generalized cospectral), and on…

组合数学 · 数学 2023-04-17 Aida Abiad , Carlos A. Alfaro , Ralihe R. Villagrán

In this article we are introducing combinatorial spectra of graphs, this is a generalization of $H$-Hamiltonian spectra. The main motivation was to made from $H$-Hamiltonian spectra an operation and develop some algebra in this field. An…

组合数学 · 数学 2023-11-21 Martin Dzúrik

The paper focuses on studying strong geodetic sets and numbers in the context of corona-type products of graphs. Our primary focus is on three variations of the corona products: the generalized corona, generalized edge corona, and…

组合数学 · 数学 2024-11-21 Bishal Sonar , Satyam Guragain , Ravi Srivastava

The distinguishing number (index) $D(G)$ ($D'(G)$) of a graph $G$ is the least integer $d$ such that $G$ has an vertex labeling (edge labeling) with $d$ labels that is preserved only by a trivial automorphism. The neighbourhood corona of…

组合数学 · 数学 2016-06-14 Saeid Alikhani , Samaneh Soltani

For unsigned graphs G and H, the characteristic polynomial of different graph matrices for edge corona, subdivision vertex neighbourhood corona and subdivision edge neighbourhood corona has already been studied using the concept of coronal.…

组合数学 · 数学 2024-01-11 Satyam Guragain , Ravi Srivastava , Bishal Sonar

Let $G$ be a finite simple graph on the vertex set $V$ and let $I_G$ denote its edge ideal in the polynomial ring $S=\mathbb{K}[x_V]$. In this paper, we compute the depth and the Castelnuovo--Mumford regularity of $S/I_G$ when…

交换代数 · 数学 2023-08-14 Guangjun Zhu , Yijun Cui , Yulong Yang , Yi yang

Let $G_1$ and $G_2$ be two undirected nontrivial graphs. The Kronecker product of $G_1$ and $G_2$ denoted by $G_1\otimes G_2$ with vertex set $V(G_1)\times V(G_2)$, two vertices $x_1x_2$ and $y_1y_2$ are adjacent if and only if…

组合数学 · 数学 2012-04-19 Fu-Tao Hu , Jun-Ming Xu