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Lower bounds for Estrada index. (English) Zbl 1199.05219

Author’s abstract: If \(G\) is an \((n,m)\)-graph whose spectrum consists of the numbers \(\lambda_1,\lambda_2,\dots,\lambda_n\), then its Estrada index is \(\text{EE}(G)=\sum_{i=1}^n e^{\lambda_i}\). We establish lower bounds for \(\text{EE}(G)\) in terms of \(n\) and \(m\).

MSC:

05C50 Graphs and linear algebra (matrices, eigenvalues, etc.)
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