Stability of Pure Nilpotent Structures on Collapsed Manifolds

Abstract

Abstract The goal of this paper is to study the stability of pure nilpotent structures on an $n$-manifold for different collapsed metrics. We prove that if two metrics with bounded sectional curvature are $L_0$-bi-Lipschitz equivalent and sufficient collapsed (depending on $L_0$ and $n$), then up to a diffeomorphism, the underlying nilpotent Killing structures coincide with each other, or one is embedded into another as a subsheaf. It improves Cheeger–Fukaya–Gromov’s local compatibility of pure nilpotent Killing structures for one collapsed metric to two Lipschitz equivalent metrics. As an application, we prove that those pure nilpotent Killing structures constructed by various smoothing methods to a Lipschitz equivalent metric with bounded sectional curvature are uniquely determined by the original metric modulo a diffeomorphism.