Operations Research Transactions ›› 2019, Vol. 23 ›› Issue (1): 104-110.doi: 10.15960/j.cnki.issn.1007-6093.2019.01.012

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An upper bound of the linear 2-arboricity of planar graphs with neither 5-cycles nor adjacent 4-cycles

CHEN Hongyu1,*, TAN Xiang2   

  1. 1. School of Science, Shanghai Institute of Technology, Shanghai 201418, China;
    2. School of Mathematics and Quantitative Economics, Shandong University of Finance and Economics, Jinan 250014, China
  • Received:2017-03-27 Online:2019-03-15 Published:2019-03-15

Abstract:

An edge-partition of a graph G is a decomposition of G into subgraphs G1, G2,…, Gm such that E(G)=E(G1)∪ E(G2)∪…∪ E(Gm) and E(Gi)∩ E(Gj)=∅ for ij. A linear k-forest is a graph in which each component is a path of length at most k. The linear k-arboricity lak(G) of a graph G is the least integer m such that G can be edge-partitioned into m linear k-forests. For extremities, la1(G) is the edge chromatic number χ'(G) of G; la(G) representing the case when component paths have unlimited lengths is the ordinary linear arboricity la(G) of G. In this paper, we use the discharging method to study the linear 2-arboricity la2(G) of planar graphs. Let G be a planar graph with neither 5-cycles nor adjacent 4-cycles. We prove that if G is connected and δ(G) ≥ 2, then G contains an edge xy with d(x)+d(y) ≤ 8 or a 2-alternating cycle. By this result, we obtain the upper bound of the linear 2-arboricity of G is ?△/2?+4.

Key words: planar graph, linear 2-arboricity, cycle

CLC Number: