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arXiv · 2507.00426

The square of every subcubic planar graph without 4-cycles and 5-cycles is 7-choosable

Ligang Jin·Yingli Kang·Seog-Jin Kim
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Abstract

The square of a graph $G$, denoted by $G^2$, has the same vertex set as $G$ and has an edge between two vertices if the distance between them in $G$ is at most $2$. Thomassen (2018) and independently, Hartke, Jahanbekam and Thomas (2016) proved that $\chi(G^2) \leq 7$ if $G$ is a subcubic planar graph. A natural question is whether $\chi_{\ell}(G^2) \leq 7$ or not if $G$ is a subcubic planar graph. Recently, Kim and Lian (2024) proved that $\chi_{\ell}(G^2) \leq 7$ if $G$ is a subcubic planar graph of girth at least 6. In this paper, we prove that $\chi_{\ell}(G^2) \leq 7$ if $G$ is a subcubic planar graph without 4-cycles and 5-cycles, which improves the result of Kim and Lian.

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Ligang Jin, Yingli Kang, Seog-Jin Kim. 2025-07-01. The square of every subcubic planar graph without 4-cycles and 5-cycles is 7-choosable. https://arxiv.org/abs/2507.00426

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