Monochromatic triangles with empty intersection and Kneser Ramsey numbers
Abstract
Recently, Heath, McCourt, Parker, Schwieder, and Zerbib initiated the systematic study of the r-Kneser Ramsey number RrKG(s,t) and investigated related Ramsey-type problems. A central motivation for their work comes from a question of Holmsen, Hrusak, and Roldán-Pensado, who asked whether, for n=2k−1 and sufficiently large k, every red/blue edge-coloring of the complete graph on the vertex set V = binom[n]k necessarily contains a monochromatic triangle ABC with A,B,C ∈ V and A ∩ B ∩ C = ∅. Heath, McCourt, Parker, Schwieder, and Zerbib established that this conclusion holds when n ≥ 7k/3 and k≥ 12. We make substantial progress toward the problem of Holmsen, Hrusak, and Roldán-Pensado by proving that the conclusion already holds for every k≥ 2 whenever n≥ 2k+1. In addition, we obtain improved lower bounds for RrKG(s,t) when s and t are fixed and r is sufficiently large.
Related
BibTeX
@misc{araujo2026monochromatic,
title = {{Monochromatic triangles with empty intersection and Kneser Ramsey numbers}},
author = {Igor Araujo},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.27157},
eprint = {2609.27157},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.27157},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Monochromatic triangles with empty intersection and Kneser Ramsey numbers
AU - Igor Araujo
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.27157
UR - https://arxiv.org/abs/2609.27157
AB - Recently, Heath, McCourt, Parker, Schwieder, and Zerbib initiated the systematic study of the r-Kneser Ramsey number R_r^KG(s,t) and investigated related Ramsey-type problems. A central motivation for their work comes from a question of Holmsen, Hrusak, and Roldán-Pensado, who asked whether, for n=2k−1 and sufficiently large k, every red/blue edge-coloring of the complete graph on the vertex set V = binom[n]k necessarily contains a monochromatic triangle ABC with A,B,C ∈ V and A ∩ B ∩ C = ∅. Heath, McCourt, Parker, Schwieder, and Zerbib established that this conclusion holds when n ≥ 7k/3 and k≥ 12. We make substantial progress toward the problem of Holmsen, Hrusak, and Roldán-Pensado by proving that the conclusion already holds for every k≥ 2 whenever n≥ 2k+1. In addition, we obtain improved lower bounds for R_r^KG(s,t) when s and t are fixed and r is sufficiently large.
ER -