Odd Vector Cycles in ${\mathbb{Z}}^m$

Abstract

Given positive integers $m$ and $r$, define $C_m(r)$ to be the minimum odd number of ${\mathbb{Z}}^m$ vectors, each of magnitude $\sqrt{r}$, that together sum to the zero vector. In this article, $C_m(r)$ is investigated for various assignments of $m$ and $r$. A few previous results are combined to definitively answer the question except in the case of $m=3$ and the square-free part of $r$ being even and also containing at least one odd prime factor $x$ with $x\equiv 2(\mathrm{mod}3)$. We detail the results of a computer-assisted search to determine $C_3(r)$ for all $r<10^6$ and then discuss parameterizations of vector cycles in ${\mathbb{Z}}^3$ of length five. We close with a few conjectures and open questions.