Limit points of eigenvalues of (di)graphs
Fu Ji Zhang, Zhibo Chen (2006)
Czechoslovak Mathematical Journal
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The study on limit points of eigenvalues of undirected graphs was initiated by A. J. Hoffman in 1972. Now we extend the study to digraphs. We prove: 1. Every real number is a limit point of eigenvalues of graphs. Every complex number is a limit point of eigenvalues of digraphs. 2. For a digraph , the set of limit points of eigenvalues of iterated subdivision digraphs of is the unit circle in the complex plane if and only if has a directed cycle. 3. Every limit point of eigenvalues...