Signed graph;adjacency matrix;positive index of inertia
In this paper, the signed graphs with one positive eigenvalue are characterized, and the signed graphs with pendant vertices having exactly two positive eigenvalues are determined. As a consequence, the signed trees, the signed unicyclic graphs and the signed bicyclic graphs having one or two positive eigenvalues are characterized.
Yu, Guihai; Feng, Lihua; and Qu, Hui.
"Signed graphs with small positive index of inertia",
Electronic Journal of Linear Algebra,
Volume 31, pp. 232-243.