数学物理学报 ›› 2010, Vol. 30 ›› Issue (4): 968-983.

• 论文 • 上一篇    下一篇

 整数距离图G(Dm, k, 2)的点荫度

左连翠1, 崔玉泉2, 刘家壮2   

  1. 1.天津师范大学数学科学学院 天津 300387|2.山东大学数学与系统科学院 济南 250100
  • 收稿日期:2007-04-18 修回日期:2009-09-18 出版日期:2010-07-25 发布日期:2010-07-25
  • 基金资助:

    天津师范大学引进人才基金(5RL066)资助

The Vertex Arboricity of Integer Distance Graphs G(Dm, k, 2)

 ZUO Lian-Cui1, CUI Yu-Quan2, LIU Jia-Zhuang2   

  1. 1.College of Mathematics Science, Tianjin Normal University, Tianjin 300387; 
    2.School of Mathematics |and System Science, Shandong University, Jinan |250100
  • Received:2007-04-18 Revised:2009-09-18 Online:2010-07-25 Published:2010-07-25
  • Supported by:

    天津师范大学引进人才基金(5RL066)资助

摘要:

G 的点荫度va(G)是顶点集合V(G)能划分成的这样一些子集 的最少数目, 其中任一子集的点导出子图都是森林.  整数距离图G(D)以全体整数作为顶点集,  顶点u, v相邻当且仅当 |u - v|∈D, 其中D是一个正整数集. 对于m>2k≥2, 令Dm, k, 2=[1, m]\k, 2k\}. 该文得出了整数距离图G(Dm, k, 2)的点荫度的几个上、下界;  进而, 对于m≥4, 有va(G(Dm, 1, 2))=[m+4/5]; 对于m=10q+j, j=0, 1, 2, 3, 5, 6, 有va(G(Dm, 2, 2))=lm+1/5l+1.

关键词: 整数距离图, 点荫度, 树着色

Abstract:

The vertex arboricity va(G) of a graph G is the minimum number of subsets into which the vertex set V(G) can be partitioned so that each subset induces a subgraph whose connected components are trees. An integer distance graph is a graph G(D) with the set of all  integers as vertex set and two vertices u, v\in Z are adjacent if and only if |u-v in D where the  distance set D is a subset of the positive integers set. Let Dm, k, 2=[1,m]\k, 2k} for m>2k≥2. In this paper, some upper and lower bounds of the vertex arboricity of the integer distance graph G(Dm, k, 2) are obtained. Moreover, va(G(Dm,1, 2))=lm+4/5l  for m≥4 and  va(G(Dm, 2, 2))=lm+1/5l+1 for any positive integer m=10q+j with j =0,1, 2, 3, 5, 6.

Key words: Integer distance graph, Vertex arboricity, Tree coloring

中图分类号: 

  • 05C70