具有s=5,6的距离整完全多部图

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  • School of Science,Northwestern Polytechnical University
YANG Ruo-song(1990-), male, native of Luoyang, Henan, an postgraduate student of Northwestern Polytechnical University, engages in graph theory and its applications; WANG Li-gong(corresponding author)(1968-), male, native of Xinzhou, Shanxi,a professor of Northwestern Polytechnical University, Ph.D.,engages in graph theory and its applications.

收稿日期: 2015-02-10

  网络出版日期: 2020-11-05

基金资助

Supported by the National Natural Science Foundation of China(11171273); Supported by the Graduate Starting Seed Fund of Northwestern Polytechnical University(Z2014173);

Distance Integral Complete Multipartite Graphs with s = 5; 6

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  • School of Science,Northwestern Polytechnical University
YANG Ruo-song(1990-), male, native of Luoyang, Henan, an postgraduate student of Northwestern Polytechnical University, engages in graph theory and its applications; WANG Li-gong(corresponding author)(1968-), male, native of Xinzhou, Shanxi,a professor of Northwestern Polytechnical University, Ph.D.,engages in graph theory and its applications.

Received date: 2015-02-10

  Online published: 2020-11-05

Supported by

Supported by the National Natural Science Foundation of China(11171273); Supported by the Graduate Starting Seed Fund of Northwestern Polytechnical University(Z2014173);

摘要

Let D(G) =(dij)n×n denote the distance matrix of a connected graph G with order n, where dij is equal to the distance between vertices viand vjin G. A graph is called distance integral if all eigenvalues of its distance matrix are integers. In 2014, Yang and Wang gave a sufficient and necessary condition for complete r-partite graphs Kp1,p2,···,pr=Ka1·p1,a2·p2,···,as···ps to be distance integral and obtained such distance integral graphs with s = 1, 2, 3, 4. However distance integral complete multipartite graphs Ka1·p1,a2·p2,···,as·ps with s > 4 have not been found. In this paper, we find and construct some infinite classes of these distance integral graphs Ka1·p1,a2·p2,···,as·ps with s = 5, 6. The problem of the existence of such distance integral graphs Ka1·p1,a2·p2,···,as·ps with arbitrarily large number s remains open. 

本文引用格式

杨若松, 王力工 . 具有s=5,6的距离整完全多部图[J]. 数学季刊, 2016 , 31(2) : 111 -117 . DOI: 10.13371/j.cnki.chin.q.j.m.2016.02.001

Abstract

Let D(G) =(dij)n×n denote the distance matrix of a connected graph G with order n, where dij is equal to the distance between vertices viand vjin G. A graph is called distance integral if all eigenvalues of its distance matrix are integers. In 2014, Yang and Wang gave a sufficient and necessary condition for complete r-partite graphs Kp1,p2,···,pr=Ka1·p1,a2·p2,···,as···ps to be distance integral and obtained such distance integral graphs with s = 1, 2, 3, 4. However distance integral complete multipartite graphs Ka1·p1,a2·p2,···,as·ps with s > 4 have not been found. In this paper, we find and construct some infinite classes of these distance integral graphs Ka1·p1,a2·p2,···,as·ps with s = 5, 6. The problem of the existence of such distance integral graphs Ka1·p1,a2·p2,···,as·ps with arbitrarily large number s remains open. 
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