English

Compact H\"older retractions and nearest point maps

Functional Analysis 2022-05-26 v1 Metric Geometry

Abstract

In this paper, two main results concerning uniformly continuous retractions are proved. First, an α\alpha-H\"older retraction from any separable Banach space onto a compact convex subset whose closed linear span is the whole space is constructed for every positive α<1\alpha<1. This constitutes a positive solution to a H\"older version of a question raised by Godefroy and Ozawa. In fact, compact convex sets are found to be absolute α\alpha-H\"older retracts under certain assumption of flatness. Second, we provide an example of a strictly convex Banach space XX arbitrarily close to 2\ell_2 (for the Banach Mazur distance) and a finite dimensional compact convex subset of XX for which the nearest point map is not uniformly continuous even when restricted to bounded sets.

Keywords

Cite

@article{arxiv.2205.12708,
  title  = {Compact H\"older retractions and nearest point maps},
  author = {Rubén Medina},
  journal= {arXiv preprint arXiv:2205.12708},
  year   = {2022}
}

Comments

21 pages

R2 v1 2026-06-24T11:28:17.634Z