Eigenvalues of normalized Laplacian matrix of graphs Shaowei Sun and Kinkar Ch. Das Department of Mathematics, Sungkyunkwan University, Suwon 440-746, Republic of Korea E-mail: [email protected], [email protected] Abstract Let G be a graph with vertex set V (G) = {v1 , v2 , . . . , vn } and edge set E(G). Also let di be the degree of vertex vi ∈ V (G). The normalized Laplacian matrix of the graph G is denoted by L(G) = (Lij ) and is defined by if i = j and di ̸= 0 1 1 Lij = − √di dj if vi vj ∈ E(G) 0 otherwise. In this talk, we discuss some bounds on the largest normalized Laplacian eigenvalue of graph G in terms of graph parameters. Moreover, we give the results on the normalized Laplacian eigenvalues of graph G. Finally, we present some results of the effect on the largest and the second smallest normalized Laplacian eigenvalues by grafting edges. Key Words: Normalized Laplacian matrix, Normalized Laplacian eigenvalues, Triangulation, Maximal Planar graph, Covering number References [1] Li, H.-H., Li, J.-S., Fan, Y.-Z. Fan., The effect on the second smallest eigenvalue of the normalized Laplacian of a graph by grafting edges, Linear Multilinear Algebra 50(6) (2008) 627-638. [2] Chung, F. R. K., Spectral graph theory. American Mathematical Soc., 1997. 1 [3] Cavers, M., The normalized Laplacian matrix and general Randic index of graphs. PhD dissertation, University of Regina, 2010. [4] Chen, H., Jost, J., Minimum vertex covers and the spectrum of the normalized Laplacian on trees. Linear Algebra Appl. 437 (2012) 1089–1101. [5] Das, K. C., G¨ ung¨or, A. D., Bozkurt, S¸. B., On the normalized Laplacian eigenvalues of graphs, Ars Combinatorica, in press. [6] Li, J., Guo, J.-M., Shiu, W. C., Chang, A., An edge-separating theorem on the second smallest normalized Laplacian eigenvalue of a graph and its applications, Discrete Appl. Math. 171 (2014) 104–115. 2
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