Convex geometry and the Erd\H{o}s-Ginzburg-Ziv problem

Abstract

Denote by ${\mathfrak s}({\mathbb F}_p^d)$ the Erd{\H o}s--Ginzburg--Ziv constant of $\mathbb F_p^d$, that is, the minimum $s$ such that every sequence of $s$ vectors in ${\mathbb F}_p^d$ contains $p$ vectors whose sum is zero. Let ${\mathfrak w}({\mathbb F}_p^d)$ be the maximum size of a sequence of vectors $v_1, \ldots, v_s \in {\mathbb F}_p^d$ such that, for all integers $\alpha_1, \ldots, \alpha_s \ge 0$ with sum $p$, we have $\alpha_1 v_1 + \ldots + \alpha_s v_s \neq 0$ unless $\alpha_i = p$ for some $i$. In 1995, Alon--Dubiner proved that $\mathfrak s(\mathbb F_p^d)$ grows linearly in $p$ when $d$ is fixed. In this work, we determine the constant of linearity: for fixed $d$ and growing $p$, we show that ${\mathfrak s}({\mathbb F}_p^d) = (1+o(1)) {\mathfrak w}({\mathbb F}_p^d) p$. Furthermore, for every prime $p$ and every $d$, we show that ${\mathfrak w}({\mathbb F}_p^d) \le {2d-1 \choose d}+1$. In particular, ${\mathfrak s}({\mathbb F}_p^d) \le 4^d p$ for all sufficiently large $p$ and fixed $d$.