The signless Laplacian spectral radius of tricyclic graphs and trees with k pendant vertices |
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Authors: | Ke Li Guopeng Zhao |
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Affiliation: | Department of Applied Mathematics, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, PR China |
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Abstract: | In this paper, we consider the following problem: of all tricyclic graphs or trees of order n with k pendant vertices (n,k fixed), which achieves the maximal signless Laplacian spectral radius?We determine the graph with the largest signless Laplacian spectral radius among all tricyclic graphs with n vertices and k pendant vertices. Then we show that the maximal signless Laplacian spectral radius among all trees of order n with k pendant vertices is obtained uniquely at Tn,k, where Tn,k is a tree obtained from a star K1,k and k paths of almost equal lengths by joining each pendant vertex to one end-vertex of one path. We also discuss the signless Laplacian spectral radius of Tn,k and give some results. |
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Keywords: | 05C50 15A18 |
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