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Let G be a graph. The energy of G, (Formula presented.), is defined as the sum of absolute values of its eigenvalues. Here, it is shown that if G is a graph and (Formula presented.) is an edge partition of G, such that (Formula presented.) are spanning; then (Formula presented.) if and only if (Formula presented.), for every (Formula presented.) and (Formula presented.), where (Formula presented.) is the adjacency matrix of (Formula presented.). It was proved that if G is a graph and (Formula presented.) are subgraphs of G which partition edges of G, then (Formula presented.). In this paper we show that if G is connected, then the equality is strict, that is (Formula presented.). © 2022... 

Let G be a simple graph with n vertices and let λ1, λ2,...,λn be its eigenvalues. The energy of G is defined to be E(G) = ∑i=1n|λi|. In this note, for a given k-regular graph we find explicit formulas for the energy of L(G), the complement of line graph of G. This provides us with some practical ways to compute the energy of a large family of regular graphs  

The energy E of any n-vertex regular graph G of degree r, r > 0, is greater than or equal to n. Equality holds if and only if every component of G is isomorphic to the complete bipartite graph Kr,r. If G is triangle- and quadrangle-free, then E ≥ nr/√2r - 1. In particular, for any fullerene and nanotube with n carbon atoms, 1.34n ≤ E ≤ 1.73 n  

The energy of a graph G, ϵ(G), is the sum of absolute values of the eigenvalues of its adjacency matrix. The matching number µ(G) is the number of edges in a maximum matching. In this paper, for a connected graph G of order n with largest vertex degree ∆ ≥ 6 we present two new upper bounds for the energy of a graph: (Formula presented) and (Formula presented). The latter one improves recently obtained bound (Formula presented) where ∆e stands for the largest edge degree and a = 2(∆e + 1). We also present a short proof of this result and several open problems. © 2021  

The energy of a graph G, ϵ(G), is the sum of absolute values of the eigenvalues of its adjacency matrix. The matching number µ(G) is the number of edges in a maximum matching. In this paper, for a connected graph G of order n with largest vertex degree ∆ ≥ 6 we present two new upper bounds for the energy of a graph: (Formula presented) and (Formula presented). The latter one improves recently obtained bound (Formula presented) where ∆e stands for the largest edge degree and a = 2(∆e + 1). We also present a short proof of this result and several open problems. © 2021  

The singular values of a matrix A are defined as the square roots of the eigenvalues of A⁎A, and the energy of A denoted by E(A) is the sum of its singular values. The energy of a graph G, E(G), is defined as the sum of absolute values of the eigenvalues of its adjacency matrix. In this paper, we prove that if A is a Hermitian matrix with the block form A=(BDD⁎C), then E(A)≥2E(D). Also, we show that if G is a graph and H is a spanning subgraph of G such that E(H) is an edge cut of G, then E(H)≤E(G), i.e., adding any number of edges to each part of a bipartite graph does not decrease its energy. Let G be a connected graph of order n and size m with the adjacency matrix A. It is well-known... 

The energy of a graph G, E(G), is defined as the sum of absolute values of the eigenvalues of its adjacency matrix. In Akbari and Hosseinzadeh (2020) [3] it was conjectured that for every graph G with maximum degree Δ(G) and minimum degree δ(G) whose adjacency matrix is non-singular, E(G)≥Δ(G)+δ(G) and the equality holds if and only if G is a complete graph. Let G be a connected graph with the edge set E(G). In this paper, first we show that E(L(G))≥|E(G)|+Δ(G)−5, where L(G) denotes the line graph of G. Next, using this result, we prove the validity of the conjecture for the line of each connected graph of order at least 7. © 2021 Elsevier Inc  

The energy of a graph G, denoted by E (G), is defined as the sum of the absolute values of all eigenvalues of G. Let G be a graph of order n and rank (G) be the rank of the adjacency matrix of G. In this paper we characterize all graphs with E (G) = rank (G). Among other results we show that apart from a few families of graphs, E (G) ≥ 2 max (χ (G), n - χ (over(G, -))), where n is the number of vertices of G, over(G, -) and χ (G) are the complement and the chromatic number of G, respectively. Moreover some new lower bounds for E (G) in terms of rank (G) are given. © 2008 Elsevier B.V. All rights reserved  

The energy of a graph/matrix is the sum of the absolute values of its eigenvalues. We investigate the result of duplicating/removing an edge to the energy of a graph. We also deal with the problem that which graphs G have the property that if the edges of G are covered by some subgraphs, then the energy of G does not exceed the sum of the subgraphs' energies. The problems are addressed in the general setting of energy of matrices which leads us to consider the singular values too. Among the other results it is shown that the energy of a complete multipartite graph increases if a new edge added or an old edge is deleted. © 2008 Elsevier Inc. All rights reserved  

The energy of a graph G, denoted by E (G), is defined as the sum of the absolute values of all eigenvalues of the adjacency matrix of G. It is proved that E (G) ≥ 2 (n - χ (over(G, -))) ≥ 2 (ch (G) - 1) for every graph G of order n, and that E (G) ≥ 2 ch (G) for all graphs G except for those in a few specified families, where over(G, -), χ (G), and ch (G) are the complement, the chromatic number, and the choice number of G, respectively. © 2007 Elsevier Inc. All rights reserved