华东师范大学学报(自然科学版)

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Halin 图的消圈数及点染色问题的研究

王永强; 任韩   

  1. 华东师范大学 数学系, 上海 200241
  • 收稿日期:2015-07-06 出版日期:2016-11-25 发布日期:2017-01-13
  • 通讯作者: 任 韩, 男, 教授, 研究方向为图论、运筹学. E-mail: hren@math.ecnu.edu.cn.
  • 基金资助:

    国家自然科学基金(11171114); 上海市自然科学基金(13dz2260400)

The decycling number and vertex coloring of Halin graphs

WANG Yong-qiang, REN Han   

  1. Department of Mathematics, East China Normal University, Shanghai 200241, China
  • Received:2015-07-06 Online:2016-11-25 Published:2017-01-13

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摘要：

Tutte关于3-连通图的结构定理表明: 每一个3-连通图都可由某个轮图(也是 Halin图)经顶点分裂逐步得到. 这表明了Halin图在图结构研究中的地位和作用. 首先研究得到了近正则Halin图的消圈数的上、下界并证明了上述界是紧的, 接着得到了最大度为k 或最小度为k 的 Halin图的消圈数所满足的界; 此外还研究了Halin图的点染色 问题, 给出了它的点色数定理的一个新证明.

关键词: 近正则Halin图, 最小消圈集, 消圈数, 点色数

Abstract:

According to the structural theorem of 3-connected graphs by Tutte, every 3-connected graph can be obtained by splitting vertices of some wheel which is Halin graph, which indicates that the study of the structure of Halin graph is important in graph structures. In this paper, firstly we dealt with the decycling number of the nearly k-regular Halin graphs, and we got the bidirectional inequality that the decycling numbers of nearly regular Halin graphs must satisfy, then we proved that the boundaries above are tight and got the boundaries of Halin graphs with the most biggest degree or the least degree k. At last, we gave a new proof to the theorem about the (vertex) coloring of Halin graphs.

Key words: nearly regular Halin graph, minimum decycling set, decycling number, number of vertex coloring