Minimal isometric immersions of flat n-tori into spheres
Abstract
In 1985, Bryant stated that a flat $2$-torus admits a minimal isometric immersion into some round sphere if and only if it satisfies a certain rationality condition. We extend this rationality criterion to arbitrary dimensional flat tori, providing a sufficient condition for minimal isometric immersions of flat $n$-tori. For the case $n=3$, we prove that if a flat $3$-torus admits a minimal isometric immersion into some sphere, then its algebraic irrationality degree must be no more than 4, and we construct explicit embedded minimal irrational flat $3$-tori realizing each possible degree. Furthermore, we establish the upper bound $n^2+n-1$ for the minimal target dimension of flat $n$-tori admitting minimal isometric immersions into spheres.