NOTE Spectral Characterization of Tree-Width-Two Graphs

) of a graph G, similar in spirit to his now-classical invariant . He showed that is minor-monotone and is related to the tree-width la(G) of G: and, moreover, , i.e. G is a forest. We show that and give the corresponding forbidden-minor and ear-decomposition characterizations.

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Received October 9, 1997/Revised July 27, 1999

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Kotlov, A. NOTE Spectral Characterization of Tree-Width-Two Graphs. Combinatorica 20, 147–152 (2000).

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  • AMS Subject Classification (1991) Classes:  05