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arXiv · 1607.03600

The Elekes-Szab\'o Theorem in four dimensions

Orit E. Raz·Micha Sharir·Frank de Zeeuw
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Abstract

Let $F\in\mathbb{C}[x,y,s,t]$ be an irreducible constant-degree polynomial, and let $A,B,C,D\subset\mathbb{C}$ be finite sets of size $n$. We show that $F$ vanishes on at most $O(n^{8/3})$ points of the Cartesian product $A\times B\times C\times D$, unless $F$ has a special group-related form. A similar statement holds for $A,B,C,D$ of unequal sizes. This is a four-dimensional extension of our recent improved analysis of the original Elekes-Szab\'o theorem in three dimensions. We give three applications: an expansion bound for three-variable real polynomials that do not have a special form, a bound on the number of coplanar quadruples on a space curve that is neither planar nor quartic, and a bound on the number of four-point circles on a plane curve that has degree at least five.

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Orit E. Raz, Micha Sharir, Frank de Zeeuw. 2016-07-13. The Elekes-Szab\'o Theorem in four dimensions. https://arxiv.org/abs/1607.03600

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