English

Partitioning triangle-free planar graphs into a forest and a linear forest

Combinatorics 2025-11-25 v3

Abstract

Raspaud and Wang conjectured that every triangle-free planar graph can be vertex-partitioned into an independent set and a forest. Independently, Kawarabayashi and Thomassen also remarked that this might be true, after providing another proof of a result of Borodin and Glebov, showing this result for planar graphs of girth~5. Subsequently, Dross, Montassier, and Pinlou raised the same question and proved that every triangle-free planar graph can be partitioned into a forest and another forest of maximum degree~5. More recently, Feghali and \v{S}\'{a}mal improved this bound on the maximum degree to~3. In this note, we further improve the result by showing that every triangle-free planar graph can be partitioned into a forest and a linear forest, that is, a forest of maximum degree~2.

Keywords

Cite

@article{arxiv.2510.02038,
  title  = {Partitioning triangle-free planar graphs into a forest and a linear forest},
  author = {Guanwu Liu and Rongxing Xu},
  journal= {arXiv preprint arXiv:2510.02038},
  year   = {2025}
}

Comments

9 pages

R2 v1 2026-07-01T06:13:17.261Z