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The concept of energy of a signed digraph is extended to iota energy of a signed digraph. The energy of a signed digraph $S$ is defined by $E(S)=\sum_{k=1}^n|\text{Re}(z_k)|$, where $\text{Re}(z_k)$ is the real part of eigenvalue $z_k$ and…

Combinatorics · Mathematics 2020-04-06 Xiuwen Yang , Ligong Wang

The total graph of $G$, $\mathcal T(G)$ is the graph whose set of vertices is the union of the sets of vertices and edges of $G$, where two vertices are adjacent if and only if they stand for either incident or adjacent elements in $G$. Let…

Spectral Theory · Mathematics 2018-06-13 Eber Lenes , Exequiel Mallea-Zepeda , María Robbiano , Jonnathan Rodríguez

Let $G$ be a graph with the vertex set $ \lbrace v_1,\ldots,v_n \rbrace$. The Seidel matrix of $G$ is an $n\times n$ matrix whose diagonal entries are zero, $ij$-th entry is $-1$ if $ v_{i} $ and $ v_{j} $ are adjacent and otherwise is $ 1…

Combinatorics · Mathematics 2021-09-13 M. Einollahzadeh , M. A. Nematollahi

The matching energy of a graph was introduced by Gutman and Wagner, which is defined as the sum of the absolute values of the roots of the matching polynomial of the graph. For the random graph $G_{n,p}$ of order $n$ with fixed probability…

Combinatorics · Mathematics 2014-12-31 Xiaolin Chen , Xueliang Li , Huishu Lian

Let $G$ be a graph on $n$ vertices with independence number $\alpha(G)$. Let $\mathcal{E}(G)$ be the energy of a graph, defined as the sum of the absolute values of the adjacency eigenvalues of $G$. Using Graffiti, Fajtlowicz conjectured in…

Combinatorics · Mathematics 2025-09-09 Aida Abiad , Gabriel Coutinho , Emanuel Juliano , Luuk Reijnders

A {\it semi-proper orientation} of a given graph $G$ is a function $(D,w)$ that assigns an orientation $D(e)$ and a positive integer weight $ w(e)$ to each edge $e$ such that for every two adjacent vertices $v$ and $u$, $S_{(D,w)}(v) \neq…

Discrete Mathematics · Computer Science 2019-05-09 Ali Dehghan

The energy of a graph G is equal to the sum of absolute values of the eigenvalues of the adjacency matrix of G, whereas the Laplacian energy of a graph G is equal to the sum of the absolute value of the difference between the eigenvalues of…

Discrete Mathematics · Computer Science 2017-01-10 Nilanjan De

Let $G$ be a connected graph and let $T$ be a spanning tree of $G$. A partial orientation $\sigma$ of $G$ respect to $T$ is an orientation of the edges of $G$ except those edges of $T$, the resulting graph associated with which is denoted…

Combinatorics · Mathematics 2021-08-31 Bo-Jun Yuan , Yi Wang , Yi-Zheng Fan

The energy of a simple graph $G$, denoted by $E(G)$, is defined as the sum of the absolute values of all eigenvalues of its adjacency matrix. Let $C_n$ denote the cycle of order $n$ and $P^{6,6}_n$ the graph obtained from joining two cycles…

Combinatorics · Mathematics 2011-02-18 Bofeng Huo , Shengjin Ji , Xueliang Li , Yongtang Shi

The trace norm $\left\Vert G\right\Vert _{\ast}$ of a graph $G$ is the sum of its singular values, i.e., the absolute values of its eigenvalues. The norm $\left\Vert G\right\Vert _{\ast}$ has been intensively studied under the name of graph…

Combinatorics · Mathematics 2015-03-31 V. Nikiforov

The energy of a graph was introduced by {\sc Gutman} in 1978 as the sum of the absolute values of the eigenvalues of its adjacency matrix. We study the energy of integral circulant graphs, also called gcd graphs, which can be characterized…

Combinatorics · Mathematics 2011-09-19 J. W. Sander , T. Sander

Circulant graphs are an important class of interconnection networks in parallel and distributed computing. Integral circulant graphs play an important role in modeling quantum spin networks supporting the perfect state transfer as well. The…

Combinatorics · Mathematics 2011-09-13 Aleksandar Ilic , Milan Basic

For a given simple graph $G$, the energy of $G$, denoted by $\mathcal {E}(G)$, is defined as the sum of the absolute values of all eigenvalues of its adjacency matrix, which was defined by I. Gutman. The problem on determining the maximal…

Combinatorics · Mathematics 2014-01-31 Xueliang Li , Yongtang Shi , Meiqin Wei , Jing Li

The eccentricity matrix $\varepsilon(G)$ of a graph $G$ is obtained from the distance matrix by retaining the eccentricities (the largest distance) in each row and each column. In this paper, we give a characterization of the star graph,…

Combinatorics · Mathematics 2019-09-13 Iswar Mahato , R. Gurusamy , M. Rajesh Kannan , S. Arockiaraj

Graph representations are the generalization of geometric graph drawings from the plane to higher dimensions. A method introduced by Tutte to optimize properties of graph drawings is to minimize their energy. We explore this minimization…

Computational Geometry · Computer Science 2023-09-07 Matt DeVos , Danielle Rogers , Alexandra Wesolek

Let $ G $ be a simple graph with the vertex cover number $ \tau $. The energy $ \mathcal{E}(G) $ of $ G $ is the sum of the absolute values of all the adjacency eigenvalues of $ G $. In this article, we establish $ \mathcal{E}(G)\geq 2\tau…

Combinatorics · Mathematics 2025-07-02 Aniruddha Samanta

The energy $E(G)$ of a graph $G$ is defined as the sum of the absolute values of its eigenvalues. Let $S_2$ be the star of order 2 (or $K_2$) and $Q$ be the graph obtained from $S_2$ by attaching two pendent edges to each of the end…

Combinatorics · Mathematics 2009-07-10 Xueliang Li , Hongping Ma

The energy of a graph is the sum of the moduli of the eigenvalues of its adjacency matrix. We study the energy of integral circulant graphs, also called gcd graphs, which can be characterized by their vertex count n and a set D of divisors…

Combinatorics · Mathematics 2018-08-21 Jürgen W. Sander , Torsten Sander

The energy of a graph is the sum of the moduli of the eigenvalues of its adjacency matrix. We study the energy of integral circulant graphs, also called gcd graphs, which can be characterized by their vertex count $n$ and a set $\cal D$ of…

Combinatorics · Mathematics 2018-08-21 Jürgen W. Sander , Torsten Sander

Let G be a simple graph of order $n$ and $\mu_1,\mu_2,\ldots,\mu_n$ the roots of its matching polynomial. The matching energy of $G$ is defined as the sum $\sum_{i=1}^n|\mu_i|$. Let $K_{n-1,1}^k$ be the graph obtained from $K_1\cup K_{n-1}$…

Combinatorics · Mathematics 2014-05-08 Shengjin Ji , Hongping Ma