English

Two-point patterns determined by curves

Classical Analysis and ODEs 2023-04-07 v1

Abstract

Let ΓRd\Gamma \subset \mathbb{R}^d be a smooth curve containing the origin. Does every Borel subset of Rd\mathbb R^d of sufficiently small codimension enjoy a S\'ark\"ozy-like property with respect to Γ\Gamma, namely, contain two elements differing by a member of Γ{0}\Gamma \setminus \{0\}? Kuca, Orponen, and Sahlsten have answered this question in the affirmative for a specific curve with nonvanishing curvature, the standard parabola (t,t2)(t, t^2) in R2\mathbb{R}^2. In this article, we use the analytic notion of "functional type", a generalization of curvature ubiquitous in harmonic analysis, to study containment of patterns in sets of large Hausdorff dimension. Specifically, for every\textit{every} curve ΓRd\Gamma \subset \mathbb{R}^d of finite type at the origin, we prove the existence of a dimensional threshold ε>0\varepsilon >0 such that every Borel subset of Rd\mathbb{R}^d of Hausdorff dimension larger than dεd - \varepsilon contains a pair of points of the form {x,x+γ}\{x, x+\gamma\} with γΓ{0}\gamma \in \Gamma \setminus \{0\}. The threshold ε\varepsilon we obtain, though not optimal, is shown to be uniform over all curves of a given "type". We also demonstrate that the finite type hypothesis on Γ\Gamma is necessary, provided Γ\Gamma either is parametrized by polynomials or is the graph of a smooth function. Our results therefore suggest a correspondence between sets of prescribed Hausdorff dimension and the "types" of two-point patterns that must be contained therein.

Keywords

Cite

@article{arxiv.2304.02882,
  title  = {Two-point patterns determined by curves},
  author = {Benjamin B. Bruce and Malabika Pramanik},
  journal= {arXiv preprint arXiv:2304.02882},
  year   = {2023}
}
R2 v1 2026-06-28T09:52:19.417Z