Abstract

Let G be a simple graph of order n and A be its adjacency matrix. Let Ī» 1 ā‰„ Ī» 2 ā‰„ ā€¦ ā‰„ Ī» n be eigenvalues of matrix A . Then, the energy of a graph G is defined as Īµ G = āˆ‘ i = 1 n Ī» i . In this paper, we will discuss the new lower bounds for the energy of nonsingular graphs in terms of degree sequence, 2-sequence, the first Zagreb index, and chromatic number. Moreover, we improve some previous well-known bounds for connected nonsingular graphs.

Highlights

  • We assume that G is a simple graph and that V(G) and E(G) are the vertex set and the edge set so that |V(G)| n and |E(G)| m

  • Graph coloring is a way of coloring the vertices of a graph such that no two adjacent vertices are of the same color; this is called vertex coloring. e smallest number of colors needed to color a graph G is called its chromatic number of G, denoted by Ļ‡(G)

  • E sum of the degrees of the vertices adjacent to vi is call the 2-degree of vi and denoted by hi. e average degree is 2 degree, and we denote by hi/di the average degree of vi. e first Zagreb of G, introduced in [1], is defined as follows: M1(G) ō½˜ d2vi

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Summary

Introduction

We assume that G is a simple graph and that V(G) and E(G) are the vertex set and the edge set so that |V(G)| n and |E(G)| m. Graph coloring is a way of coloring the vertices of a graph such that no two adjacent vertices are of the same color; this is called vertex coloring. According to the eigenvalues of the adjacency matrix, the energy of a graph is defined as follows: Īµ(G). Filipovski and Jajcay [5], derived some of the bounds for the energy. In 2020, Filipovski and Jajcay [5] derived some of lower bounds for the energy. In 2021, Filipovski and Jajcay [5] obtained new bounds for the energy. We continue this discussion by obtaining new bounds for the energy of nonsingular connected graph and improving some important bounds.

Preliminaries
Lower Bounds for the Energy of Nonsingular Graphs
Improving Some of Bounds for the Energy of Connected Nonsingular Graphs
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