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Which bicyclic graphs are reflexive? (English) Zbl 0941.05044

A graph is called reflexive if the second largest eigenvalue (of its adjacency matrix) does not exceed 2. Some sufficient conditions for a graph with a cut vertex to be reflexive (or non-reflexive) are formulated. Reflexive graphs with exactly two (disjoint) cycles are determined.

MSC:

05C50 Graphs and linear algebra (matrices, eigenvalues, etc.)
05C38 Paths and cycles