By the signless Laplacian of a (simple) graph G we mean the matrix , where A(G), D(G) denote respectively the adjacency matrix and the diagonal matrix of vertex degrees of G. It is known that connected graphs G that maximize the signless Laplacian spectral radius ฯ(Q (G)) over all connected graphs
On the signless Laplacian spectral radius of graphs with cut vertices
โ Scribed by Bao-Xuan Zhu
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 129 KB
- Volume
- 433
- Category
- Article
- ISSN
- 0024-3795
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โฆ Synopsis
In this paper, we show that among all the connected graphs with n vertices and k cut vertices, the maximal signless Laplacian spectral radius is attained uniquely at the graph G n,k , where G n,k is obtained from the complete graph K n-k by attaching paths of almost equal lengths to all vertices of K n-k . We also give a new proof of the analogous result for the spectral radius of the connected graphs with n vertices and k cut vertices (see [A. Berman, X.-D. Zhang, On the spectral radius of graphs with cut vertices, J. Combin. Theory Ser. B 83 (2001) 233-240]). Finally, we discuss the limit point of the maximal signless Laplacian spectral radius.
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