English

On infinite sets with no $3$ on a line

Combinatorics 2026-02-26 v1

Abstract

We give a construction of an infinite set of points AA in R2\mathbb{R}^2 such that any subset PAP\subseteq A has a constant density subset PP' with no three points collinear and yet AA cannot be separated into finitely many subsets such that each subset has no three points collinear. This provides a new proof of a question of Erd\H{o}s, Ne\v{s}et\v{r}il, and R\"{o}dl. The construction was generated by an internal model at OpenAI.

Keywords

Cite

@article{arxiv.2602.21275,
  title  = {On infinite sets with no $3$ on a line},
  author = {Moe Putterman and Mehtaab Sawhney and Gregory Valiant},
  journal= {arXiv preprint arXiv:2602.21275},
  year   = {2026}
}

Comments

2 pages

R2 v1 2026-07-01T10:50:37.318Z