The Elekes-Szab\'{o} Problem and the Uniformity Conjecture

TL;DR

This paper provides a conditional improvement on the Elekes-Szabó problem over the rationals by assuming the Uniformity Conjecture, leading to better bounds in discrete geometry and arithmetic combinatorics.

Contribution

It introduces a new bound for the intersection size of polynomial zero sets with finite sets over rationals, assuming the Uniformity Conjecture, improving previous results.

Findings

Improved bounds on polynomial zero set intersections over rationals.

Conditional results assuming the Uniformity Conjecture.

Applications to distance problems in discrete geometry.

Abstract

In this paper we give a conditional improvement to the Elekes-Szab\'{o} problem over the rationals, assuming the Uniformity Conjecture. Our main result states that for $F\in \mathbb{Q}[x,y,z]$ belonging to a particular family of polynomials, and any finite sets $A, B, C \subset \mathbb Q$ with $|A|=|B|=|C|=n$, we have \[ |Z(F) \cap (A\times B \times C)| \ll n^{2-\frac{1}{s}}. \] The value of the integer $s$ is dependent on the polynomial $F$, but is always bounded by $s \leq 5$, and so even in the worst applicable case this gives a quantitative improvement on a bound of Raz, Sharir and de Zeeuw (arXiv:1504.05012). We give several applications to problems in discrete geometry and arithmetic combinatorics. For instance, for any set $P \subset \mathbb Q^2$ and any two points $p_1,p_2 \in \mathbb Q^2$, we prove that at least one of the $p_i$ satisfies the bound \[ | \{ \| p_i - p \| : p \in P \}| \gg |P|^{3/5}, \] where $\| \cdot \|$ denotes Euclidean distance. This gives a conditional improvement to a result of Sharir and Solymosi (arXiv:1308.0814).