Centrally symmetric and balanced triangulations of $\mathbb{S}^2\times \mathbb{S}^{d-3}$ with few vertices

Abstract

A small triangulation of the sphere product can be found in lower dimensions by computer search and is known in few other cases: Klee and Novik constructed a centrally symmetric triangulation of $\mathbb{S}^i\times \mathbb{S}^{d-i-1}$ with $2d+2$ vertices for all $d\geq 3$ and $1\leq i\leq d-2$; they also proposed a balanced triangulation of $\mathbb{S}^1\times \mathbb{S}^{d-2}$ with $3d$ or $3d+2$ vertices. In this paper, we provide another centrally symmetric $(2d+2)$-vertex triangulation of $\mathbb{S}^2\times \mathbb{S}^{d-3}$. We also construct the first balanced triangulation of $\mathbb{S}^2\times \mathbb{S}^{d-3}$ with $4d$ vertices, using a sphere decomposition inspired by handle theory.