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For a Hermitian matrix ▫$A$▫ of order ▫$n$▫ with eigenvalues ▫$\lambda_1(A)\ge \cdots\ge \lambda_n(A)$▫, define ▫$\mathcal{E}_p^+(A)=\sum_{\lambda_i > 0} \lambda_i^p(A), \quad \mathcal{E}_p^-(A)=\sum_{\lambda_i<0} |\lambda_i(A)|^p$▫, to be the positive and the negative ▫$p$▫-energy of ▫$A$▫, respect ...

Let ▫$G$▫ be a graph of order ▫$n$▫ with eigenvalues ▫$\lambda_1 \geq \cdots \geq\lambda_n$▫. Let ▫$s^+(G)=\sum_{\lambda_i>0} \lambda_i^2, s^-(G)=\sum_{\lambda_i<0} \lambda_i^2$▫. The smaller value, ▫$s(G)=\min\{s^+(G), s^-(G)\}$▫ is called the square energy of ▫$G$▫. In 2016, Elphick, Farber, Goldb ...

We study oriented graphs whose Hermitian adjacency matrices of the second kind have few eigenvalues. We give a complete characterization of the oriented graphs with two distinct eigenvalues, showing that there are only four such graphs. We extend this result to mixed graphs. We show that there are i ...

▫$\Delta$▫-povezavno število stabilnosti grafa ▫$G$▫ je najmanjše število povezav ▫$G$▫, katerih odstranitev vodi v podgraf ▫$H$▫ z ▫$\Delta(H) = \Delta(G)-1$▫. Množice, katerih odstranitev povzroči podgraf z manjšo največjo stopnjo, se imenujejo omilitvena množice. Dokazano je, da vedno obstaja omi ...