English

On a conjecture of Faudree and Schelp

Combinatorics 2025-06-12 v1

Abstract

In 1976 Faudree and Schelp conjectured that in a hamiltonian-connected graph on nn vertices, any two distinct vertices are connected by a path of length kk for every kn/2k \ge n/2. In 1978 Thomassen constructed a (non-cubic and non-planar) family of counterexamples, showing that there exist hamiltonian-connected nn-vertex graphs containing two vertices with no path of length n2n-2 between them. We complement this result by describing cubic planar counterexamples on 6p+166p+16 vertices, each containing vertices between which there is no path of any odd length greater than 11 and at most 4p+94p+9. Motivated by a remark of Thomassen about a gap in the cycle spectrum of hamiltonian-connected graphs, we also describe an infinite family of hamiltonian-connected graphs with many gaps in the first half of their cycle spectra.

Keywords

Cite

@article{arxiv.2506.09667,
  title  = {On a conjecture of Faudree and Schelp},
  author = {Jan Goedgebeur and Jorik Jooken and Michiel Provoost and Carol T. Zamfirescu},
  journal= {arXiv preprint arXiv:2506.09667},
  year   = {2025}
}