Stability for binary scalar products

Abstract

Bohn, Faenza, Fiorini, Fisikopoulos, Macchia, and Pashkovich (2015) conjectured that 2-level polytopes cannot simultaneously have many vertices and many facets, namely, that the maximum of the product of the number of vertices and facets is attained on the cube and cross-polytope. This was proved in a recent work by Kupavskii and Weltge. In this paper, we resolve a strong version of the conjecture by Bohn et al., and find the maximum possible product of the number of vertices and the number of facets in a 2-level polytope that is not affinely isomorphic to the cube or the cross-polytope. To do this, we get a sharp stability result of Kupavskii and Weltge's upper bound on $\left|\mathcal A\right|\cdot\left|\mathcal B\right|$ for $\mathcal A,\mathcal B \subseteq \mathbb R^d$ with a property that $\forall a \in \mathcal A, b \in \mathcal B$ the scalar product $\langle a, b\rangle \in\{0,1\}$.