English

Linkages and removable paths avoiding vertices

Combinatorics 2023-03-23 v1

Abstract

We say that a graph GG is (2,m)(2,m)-linked if, for any distinct vertices a1,,am,b1,b2a_1,\ldots, a_m, b_1,b_2 in GG, there exist vertex disjoint connected subgraphs A,BA,B of GG such that {a1,,am}\{a_1, \ldots, a_m\} is contained in AA and {b1,b2}\{b_1,b_2\} is contained in BB. A fundamental result in structural graph theory is the characterization of (2,2)(2,2)-linked graphs, with different versions obtained independently by Robertson and Chakravarty, Seymour, and Thomassen. It appears to be very difficult to characterize (2,m)(2,m)-linked graphs for m3m\ge 3. In this paper, we provide a partial characterization of (2,m)(2,m)-linked graphs by adding an average degree condition. This implies that (2m+2)(2m+2)-connected graphs are (2,m)(2,m)-linked. Moreover, if GG is a (2m+2)(2m+2)-connected graph and a1,,am,b1,b2a_1, \ldots, a_m, b_1,b_2 are distinct vertices of GG, then there is a path PP in GG between b1b_1 and b2b_2 and avoiding {a1,,am}\{a_1, \ldots, a_m\} such that GPG-P is connected, improving a previous connectivity bound of 10m10m.

Keywords

Cite

@article{arxiv.2303.12146,
  title  = {Linkages and removable paths avoiding vertices},
  author = {Xiying Du and Yanjia Li and Shijie Xie and Xingxing Yu},
  journal= {arXiv preprint arXiv:2303.12146},
  year   = {2023}
}

Comments

17 pages

R2 v1 2026-06-28T09:27:13.708Z