On the Estrada index of unicyclic and bicyclic signed graphs

Tahir Shamsher, S. Pirzada, Mushtaq A. Bhat

Let $\Gamma =(G,\sigma )$ be a signed graph of order $n$ with eigenvalues ${\mu }_1,{\mu }_2,\dots ,{\mu }_n.$ We define the Estrada index of a signed graph $\Gamma$ as $EE(\Gamma )={\sum }_{i=1}^n{e}^{{\mu }_i}$. We characteri…