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.
Reviewer: Dragan Cvetković (Beograd)