In this paper we give two results concerning the signless Laplacian spectra of simple graphs. Firstly, we give a combinatorial expression for the fourth coefficient of the (signless Laplacian) characteristic polynomial of a graph. Secondly, we consider limit points for the (signless Laplacian) eigenvalues and we prove that each non-negative real number is a limit point for (signless Laplacian) eigenvalue of graphs. (C) 2010 Elsevier Ltd. All rights reserved.
机构:
Qinghai Normal Univ, Sch Math & Stat, Xining 810001, Qinghai, Peoples R ChinaQinghai Normal Univ, Sch Math & Stat, Xining 810001, Qinghai, Peoples R China
Deng, Bo
Li, Xueliang
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机构:
Nankai Univ, Ctr Combinator, Tianjin 100071, Peoples R China
Nankai Univ, LPMC, Tianjin 100071, Peoples R ChinaQinghai Normal Univ, Sch Math & Stat, Xining 810001, Qinghai, Peoples R China
Li, Xueliang
Li, Yalan
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机构:
Qinghai Normal Univ, Teachers Coll Nationalities, Xining 810001, Qinghai, Peoples R ChinaQinghai Normal Univ, Sch Math & Stat, Xining 810001, Qinghai, Peoples R China
机构:
S China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R ChinaS China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R China
You, Zhifu
Liu, Bolian
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S China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R ChinaS China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R China
Liu, Bolian
ELECTRONIC JOURNAL OF LINEAR ALGEBRA,
2011,
22
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