Excluding an apex-forest or a fan as quickly as possible
Combinatorics
2026-02-04 v1 Discrete Mathematics
Abstract
We show that every graph excluding an apex-forest as a minor has layered pathwidth at most , and that every graph excluding an apex-linear forest (such as a fan) as a minor has layered treedepth at most . 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 , while the second strengthens a previous quadratic bound. In addition, we reduce from quadratic to linear the bound on the -focused treedepth for graphs with a prescribed set of vertices excluding models of paths in which every branch set intersects~.
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}
}