English

Planar point sets with forbidden $4$-point patterns and few distinct distances

Combinatorics 2024-09-04 v1

Abstract

We show that for any large nn, there exists a set of nn points in the plane with O(n2/logn)O(n^2/\sqrt{\log n}) distinct distances, such that any four points in the set determine at least five distinct distances. This answers (in the negative) a question of Erd\H{o}s. The proof combines an analysis by Dumitrescu of forbidden four-point patterns with an algebraic construction of Thiele and Dumitrescu (to eliminate parallelograms), as well as a randomized transformation of that construction (to eliminate most other forbidden patterns).

Keywords

Cite

@article{arxiv.2409.01343,
  title  = {Planar point sets with forbidden $4$-point patterns and few distinct distances},
  author = {Terence Tao},
  journal= {arXiv preprint arXiv:2409.01343},
  year   = {2024}
}

Comments

7 pages, no figures

R2 v1 2026-06-28T18:31:44.673Z