Let T be a tree of order n and S-2(T) be the sum of the two largest Laplacian eigenvalues of T. Fritscher et al. proved that for any tree T of order n, S-2(T) <= n + 2 - 2/n. Guan et al. determined the tree with maximum S-2(T) among all trees of order n. In this paper, we characterize the trees with S-2(T) >= n + 1 among all trees of order n except some trees. Moreover, among all trees of order n, we also determine the first [ n-2/2 j trees according to their S-2(T). This extends the result of Guan et al.
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S China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R China
Guangdong Inst Petrochem Technol, Sch Sci, Maoming 525000, Peoples R ChinaS China Normal Univ, Sch Math Sci, Guangzhou 510631, Guangdong, Peoples R China
Wang, Shouzhong
Huang, Yufei
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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
Huang, Yufei
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
机构:
Univ Fed Rio Grande do Sul, Inst Matemat, BR-91501970 Porto Alegre, RS, BrazilUniv Fed Rio Grande do Sul, Inst Matemat, BR-91501970 Porto Alegre, RS, Brazil
Fritscher, Eliseu
Hoppen, Carlos
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Univ Fed Rio Grande do Sul, Inst Matemat, BR-91501970 Porto Alegre, RS, BrazilUniv Fed Rio Grande do Sul, Inst Matemat, BR-91501970 Porto Alegre, RS, Brazil
Hoppen, Carlos
Rocha, Israel
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Univ Fed Rio Grande do Sul, Inst Matemat, BR-91501970 Porto Alegre, RS, BrazilUniv Fed Rio Grande do Sul, Inst Matemat, BR-91501970 Porto Alegre, RS, Brazil
Rocha, Israel
Trevisan, Vilmar
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Univ Fed Rio Grande do Sul, Inst Matemat, BR-91501970 Porto Alegre, RS, BrazilUniv Fed Rio Grande do Sul, Inst Matemat, BR-91501970 Porto Alegre, RS, Brazil
机构:
Zhangzhou Normal Univ, Dept Math & Informat Sci, Zhangzhou, Fujian, Peoples R ChinaZhangzhou Normal Univ, Dept Math & Informat Sci, Zhangzhou, Fujian, Peoples R China
Li, Jianxi
Guo, Ji-Ming
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China Univ Petr, Dept Appl Math, Dongying, Shandong, Peoples R ChinaZhangzhou Normal Univ, Dept Math & Informat Sci, Zhangzhou, Fujian, Peoples R China
Guo, Ji-Ming
Shiu, Wai Chee
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Hong Kong Baptist Univ, Dept Math, Kowloon Tong, Hong Kong, Peoples R ChinaZhangzhou Normal Univ, Dept Math & Informat Sci, Zhangzhou, Fujian, Peoples R China