Caporossi–Cvetković–Gutman–Hansen conjecture on maximal energy of unicyclic graphs

Let CnC_n be the cycle on nn vertices. Let Pn6P_n^6 be the unicyclic graph obtained by connecting a vertex of the cycle C6C_6 to a leaf of the path Pn6P_{n-6}. For a graph GG with adjacency-matrix eigenvalues λ1,,λn\lambda_1,\ldots,\lambda_n, its energy is

E(G)=i=1nλi.E(G)=\sum_{i=1}^n|\lambda_i|.

Caporossi–Cvetković–Gutman–Hansen conjecture. Among all unicyclic graphs on nn vertices, the cycle CnC_n has maximal energy if n7n\leq 7 or n{9,10,11,13,15}n\in\{9,10,11,13,15\}. For all other values of nn, the unicyclic graph with maximal energy is Pn6P_n^6.

The conjecture identifies the extremal unicyclic graph by the number of vertices and concerns the adjacency-spectrum energy of graphs. The supplied text does not state whether the conjecture has been resolved.

Sources & referencesView supporting material

Primary source

Bofeng Huo, Xueliang Li and Yongtang Shi, “Complete solution to a conjecture on the maximal energy of unicyclic graphs”, arXiv:1011.4658 (2011).

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