English

Improved upper bounds on longest-path and maximal subdivision transversals

Combinatorics 2023-05-10 v1

Abstract

Let GG be a connected graph on nn vertices. The Gallai number Gal(G)Gal(G) of GG is the size of the smallest set of vertices that meets every maximum path in GG. Gr\"unbaum constructed a graph GG with Gal(G)=3Gal(G)=3. Very recently, Long, Milans, and Munaro, proved that Gal(G)8n3/4Gal(G)\leq 8n^{{3}/{4}}. This was the first sublinear upper bound on Gal(G)Gal(G) in terms of nn. We improve their bound to Gal(G)5n2/3Gal(G)\leq 5 n^{{2}/{3}}. We also tighten a more general result of Long et al. For a multigraph MM on m edges, we prove that if the set L(M,G)L(M,G) of maximum MM-subdivisions in GG is pairwise intersecting and nm6n\geq m^{6}, then GG has a set of vertices with size at most 5n2/35 n^{{2}/{3}} that meets every QL(M,G)Q\in \mathcal{L}(M,G)

Keywords

Cite

@article{arxiv.2305.05045,
  title  = {Improved upper bounds on longest-path and maximal subdivision transversals},
  author = {Henry Kierstead and Eric Ren},
  journal= {arXiv preprint arXiv:2305.05045},
  year   = {2023}
}

Comments

To be published in Discrete Mathematics

R2 v1 2026-06-28T10:29:11.781Z