Geodesic
Sets of cospectral graphs with least eigenvalue at least -2 and some related results
Bulletin de l'Académie serbe des sciences. Classe des sciences mathématiques et naturelles, Tome 29 (2004) no. 1.

Voir la notice de l'article provenant de la source eLibrary of Mathematical Institute of the Serbian Academy of Sciences and Arts

In this paper we study the phenomenon of cospectrality in generalized line graphs and in exceptional graphs. The paper contains a table of sets of cospectral graphs with least eigenvalue at least $-2$ and at most 8 vertices together with some comments and theoretical explanations of the phenomena suggested by the table. In particular, we prove that the multiplicity of the number $0$ in the spectrum of a generalized line graph $L(G)$ is at least the number of petals of the corresponding root graph $G$.
Keywords: graphs, eigenvalues, least eigenvalue, cospectral graphs 
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     author = {D. Cvetkovi\'c and M. Lepovi\'c},
     title = {Sets of cospectral graphs with least eigenvalue at least -2 and some related results},
     journal = {Bulletin de l'Acad\'emie serbe des sciences. Classe des sciences math\'ematiques et naturelles},
     pages = {85 - 102},
     publisher = {mathdoc},
     volume = {29},
     number = {1},
     year = {2004},
     zbl = {1077.05059},
     url = {http://geodesic.mathdoc.fr/item/BASS_2004_29_1_a5/}
}
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D. Cvetković; M. Lepović. Sets of cospectral graphs with least eigenvalue at least -2 and some related results. Bulletin de l'Académie serbe des sciences. Classe des sciences mathématiques et naturelles, Tome 29 (2004) no. 1. http://geodesic.mathdoc.fr/item/BASS_2004_29_1_a5/