English

How do 9 points look like in $E^3$?

Combinatorics 2021-12-10 v1

Abstract

The aim of this note is to give an elementary proof of the following fact: given 3 red convex sets and 3 blue convex sets in E3\mathbb{E}^3, such that every red intersects every blue, there is a line transversal to the reds or there is a line transversal to the blues. This is a special case of a theorem of Montajano and Karasev \cite{MK} and generalizes, in a sense, the colourful Helly theorem due to Lov\'asz (cf. \cite{BL}).

Keywords

Cite

@article{arxiv.2112.04908,
  title  = {How do 9 points look like in $E^3$?},
  author = {Ricardo Strausz},
  journal= {arXiv preprint arXiv:2112.04908},
  year   = {2021}
}

Comments

To appear in Annals of Combinatorics

R2 v1 2026-06-24T08:10:43.367Z