Decomposition of bipartite graphs into spiders all of whose legs are two in length

Tay Woei Shyu, Ying Ren Chen, Chiang Lin, Ming Hong Zhong

Research output: Contribution to journalArticle

Abstract

As usual, Km,n denotes the complete bipartite graph with parts of sizes m and n. For positive integers k ≤n, the crown Cn,k is the graph with vertex set {a0, a1,..., an-1, b0, b1,...,bn-1} and edge set {a ibj: 0 ≤ i ≤ n - 1, j = i,i + 1,..., i + k - 1 (mod n)}. A spider is a tree with at most one vertex of degree more than two, called the center of the spider. A leg of a spider is a path from the center to a vertex of degree one. Let Sl(t) denote a spider of l legs, each of length t. An H-decomposition of a graph G is an edge-disjoint decomposition of G into copies of H. In this paper we investigate the problems of S l(2)-decompositions of complete bipartite graphs and crowns, and prove that: (1) Kn,tl has an Sl(2)-decomposition if and only if nt ≡ 0 (mod 2), n≥ 2l if t = 1, and n ≥ J if t ≥ 2, (2) for t ≥ 2 and n ≥ tl, Cn,tl has an Sl(2)- decomposition if and only if nt ≡ 0 (mod 2), (3) for n ≥ 3t, C n,3t has an S3(2)-decomposition if and only if nt ≡ 0 (mod 2) and n ≡ 0 (mod 4) if t = 1.

Original languageEnglish
Pages (from-to)239-248
Number of pages10
JournalArs Combinatoria
Volume112
Publication statusPublished - 2013 Oct
Externally publishedYes

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Keywords

  • Complete bipartite graph
  • Crown
  • Decomposition
  • Spider

ASJC Scopus subject areas

  • Mathematics(all)

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