English

Excluding an apex-forest or a fan as quickly as possible

Combinatorics 2026-02-04 v1 Discrete Mathematics

Abstract

We show that every graph GG excluding an apex-forest HH as a minor has layered pathwidth at most V(H)2|V(H)|-2, and that every graph GG excluding an apex-linear forest (such as a fan) HH as a minor has layered treedepth at most V(H)2|V(H)|-2. We further show that both bounds are optimal. These results improve on recent results of Hodor, La, Micek, and Rambaud (2025): The first result improves the previous best-known bound by a multiplicative factor of 22, while the second strengthens a previous quadratic bound. In addition, we reduce from quadratic to linear the bound on the SS-focused treedepth td(G,S)\mathrm{td}(G,S) for graphs GG with a prescribed set of vertices SS excluding models of paths in which every branch set intersects~SS.

Keywords

Cite

@article{arxiv.2602.03833,
  title  = {Excluding an apex-forest or a fan as quickly as possible},
  author = {Quentin Claus and Jędrzej Hodor and Gwenaël Joret and Pat Morin},
  journal= {arXiv preprint arXiv:2602.03833},
  year   = {2026}
}
R2 v1 2026-07-01T09:34:47.517Z