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Autores principales: Kaiser, Tomáš, Stehlík, Matěj, Škrekovski, Riste
Formato: Preprint
Publicado: 2026
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Acceso en línea:https://arxiv.org/abs/2601.16342
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author Kaiser, Tomáš
Stehlík, Matěj
Škrekovski, Riste
author_facet Kaiser, Tomáš
Stehlík, Matěj
Škrekovski, Riste
contents Shift graphs, introduced by Erdős and Hajnal in 1964, form one of the simplest known non-recursive constructions of triangle-free graphs with arbitrarily large chromatic number. In this note, we identify a suprising property: for each integer $k \geq 1$, the smallest $k$-chromatic shift graph contains a unique $k$-vertex-critical subgraph. We give an explicit description of this subgraph and prove its uniqueness. This provides a new and remarkably simple family of triangle-free vertex-critical graphs of arbitrarily large chromatic number.
format Preprint
id arxiv_https___arxiv_org_abs_2601_16342
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A note on vertex-critical induced subgraphs of shift graphs
Kaiser, Tomáš
Stehlík, Matěj
Škrekovski, Riste
Combinatorics
05C15
Shift graphs, introduced by Erdős and Hajnal in 1964, form one of the simplest known non-recursive constructions of triangle-free graphs with arbitrarily large chromatic number. In this note, we identify a suprising property: for each integer $k \geq 1$, the smallest $k$-chromatic shift graph contains a unique $k$-vertex-critical subgraph. We give an explicit description of this subgraph and prove its uniqueness. This provides a new and remarkably simple family of triangle-free vertex-critical graphs of arbitrarily large chromatic number.
title A note on vertex-critical induced subgraphs of shift graphs
topic Combinatorics
05C15
url https://arxiv.org/abs/2601.16342