Path partitioning planar graphs of girth 4 without adjacent short cycles

A. N. Glebov ; D. Zh. Zambalayeva

Sibirskie èlektronnye matematičeskie izvestiâ, Tome 15 (2018), pp. 1040-1047

Résumé

A graph $G$ is $(a,b)$-partitionable for positive intergers $a,b$ if its vertex set can be partitioned into subsets $V_1,V_2$ such that the induced subgraph $G[V_1]$ contains no path on $a+1$ vertices and the induced subgraph $G[V_2]$ contains no path on $b+1$ vertices. A graph $G$ is $\tau$-partitionable if it is $(a,b)$-partitionable for every pair $a,b$ such that $a+b$ is the number of vertices in the longest path of $G$. In 1981, Lovász and Mihók posed the following Path Partition Conjecture: every graph is $\tau$-partitionable. In 2007, we proved the conjecture for planar graphs of girth at least 5. The aim of this paper is to improve this result by showing that every triangle-free planar graph, where cycles of length 4 are not adjacent to cycles of length 4 and 5, is $\tau$-partitionable.

Détail

Keywords: graph, planar graph, girth, triangle-free graph, path partition, $\tau$-partitionable graph
Mots-clés : path partition conjecture.