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arXiv · 2511.03422

Chords of longest cycles in graphs with large circumferences

Haidong Wu·Shunzhe Zhang
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Abstract

A long-standing conjecture of Thomassen says that every longest cycle of a $3$-connected graph has a chord. Thomassen (2018) proved that if $G$ is a $2$-connected cubic graph, then any longest cycle must have a chord. He also showed that in any 3-connected graph with minimum degree at least four, some longest cycle must contain a chord. Harvey proved that every longest cycle has a chord for graphs with a large minimum degree. He also conjectured that any longest cycle in a 2-connected graph with minimum degree at least three has a chord. In this paper, we prove that both Thomassen's and Harvey's conjectures are true for graphs with large circumferences. We also prove a more general result for the existence of chords in longest cycles containing a linear forest.

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Haidong Wu, Shunzhe Zhang. 2025-11-05. Chords of longest cycles in graphs with large circumferences. https://arxiv.org/abs/2511.03422

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