English

One point compactification and Lipschitz normally embedded definable subsets

Algebraic Geometry 2023-10-26 v4 Logic Metric Geometry

Abstract

A closed subset of Rq\mathbb{R}^q, definable in some given o-minimal structure, is Lipschitz normally embedded in Rq\mathbb{R}^q if and only if its one-point compactification is Lipschitz normally embedded in the unit sphere Sq{\bf S}^q(=Rq{} = \mathbb{R}^q \cup \{\infty \}), i.e. the closure of its image by the inverse of the stereographic projection is Lipschitz normally embedded in Sq{\bf S}^q. This implies that any closed connected unbounded definable subset of an Euclidean space is definably inner bi-Lipschitz homeomorphic to a Lipschitz normally embedded definable set.

Keywords

Cite

@article{arxiv.2304.08555,
  title  = {One point compactification and Lipschitz normally embedded definable subsets},
  author = {André Costa and Vincent Grandjean and Maria Michalska},
  journal= {arXiv preprint arXiv:2304.08555},
  year   = {2023}
}

Comments

Abstract is extended. Introduction is modified accordingly to the addition of two new sections. Old sections 2 to 7 are now 1 to 6. We have added applications: Section 7 about the existence of LNE model of closed unbounded definable sets; and Section 8 presenting examples (definable and not) and their respective LNE nature in different compactifications

R2 v1 2026-06-28T10:08:54.630Z