English

Pinned distances and density theorems in $\mathbb R^d$

Classical Analysis and ODEs 2025-09-03 v1

Abstract

We study a pinned variant of Bourgain's theorem, concerning the occurrence of affine copies of kk-point patterns in Rd\mathbb{R}^d. Focusing on the case k=2k=2, which corresponds to pinned distances, we show that the classical conclusion does not extend to the pinned setting: there exist sets of positive upper density in Rd\mathbb{R}^d, d2d \geq 2, such that no single pinned point determines all sufficiently large distances. However, we establish a weaker quantitative result: for every point xx in such a set, the pinned distance set at xx has (one-dimensional) positive upper density. We also construct an example demonstrating the sharpness of this bound. These findings highlight a structural distinction between global and pinned configurations.

Keywords

Cite

@article{arxiv.2509.01152,
  title  = {Pinned distances and density theorems in $\mathbb R^d$},
  author = {Chenjian Wang},
  journal= {arXiv preprint arXiv:2509.01152},
  year   = {2025}
}
R2 v1 2026-07-01T05:14:42.340Z