English

A forbidden pair for quasi 5-contractible edges

Combinatorics 2025-08-13 v1

Abstract

An edge of a quasi kk-connected graph is said to be quasi kk-contractible if the contraction of the edge results in a quasi kk-connected graph. If every quasi kk-connected graph without a quasi kk-contractible edge has either H1H_{1} or H2H_{2} as a subgraph, then an unordered pair of graphs {H1,H2}\{H_{1}, H_{2}\} is said to be a forbidden pair for quasi kk-contractible edges. We prove that {K4,P5}\{K_{4}^{-}, \overline{P_{5}}\} is a forbidden pair for quasi 5-contractible edges, where K4K_{4}^{-} is the graph obtained from K4K_{4} by removing just one edge and P5\overline{P_{5}} is the complement of a path on five vertices.

Keywords

Cite

@article{arxiv.2508.08563,
  title  = {A forbidden pair for quasi 5-contractible edges},
  author = {Shuai Kou and Weihua Yang and Mingzu Zhang and Shuang Zhao},
  journal= {arXiv preprint arXiv:2508.08563},
  year   = {2025}
}