New theorems for signless Laplacian eigenvalues. (English) Zbl 1199.05212

The author extends his previous surveys of properties of \(Q\)-spectrum (i.e., the spectrum of a graph based on its signless Laplacian matrix). Some new contributions are included. In particular, graphs whose largest eigenvalue (with respect to signless Laplacian) does not exceed \(4\) are characterized. The \(Q\)-spectra of all connected graphs on six vertices are given in Appendix.


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