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Bamdad, Hamidreza; Ashraf, Firouzeh; Gutman, Ivan
Applied mathematics letters, 07/2010, Volume: 23, Issue: 7Journal Article
Let G be an n -vertex graph. If λ 1 , λ 2 , … , λ n and μ 1 , μ 2 , … , μ n are the ordinary (adjacency) eigenvalues and the Laplacian eigenvalues of G , respectively, then the Estrada index and the Laplacian Estrada index of G are defined as EE ( G ) = ∑ i = 1 n e λ i and LEE ( G ) = ∑ i = 1 n e μ i , respectively. Some new lower bounds for EE and LEE are obtained and shown to be the best possible.
