English

All convex bodies are in the subdifferential of some everywhere differentiable locally Lipschitz function

Classical Analysis and ODEs 2024-09-13 v2 Functional Analysis Optimization and Control

Abstract

We construct a differentiable locally Lipschitz function ff in RN\mathbb{R}^{N} with the property that for every convex body KRNK\subset \mathbb{R}^N there exists xˉRN\bar x \in \mathbb{R}^N such that KK coincides with the set Lf(xˉ)\partial_L f(\bar x) of limits of derivatives {Df(xn)}n1\{Df(x_n)\}_{n\geq 1} of sequences {xn}n1\{x_n\}_{n\geq 1} converging to~xˉ\bar x. The technique can be further refined to recover all compact connected subsets with nonempty interior, disclosing an important difference between differentiable and continuously differentiable functions. It stems out from our approach that the class of these pathological functions contains an infinite dimensional vector space and is dense in the space of all locally Lipschitz functions for the uniform convergence.

Keywords

Cite

@article{arxiv.2405.09206,
  title  = {All convex bodies are in the subdifferential of some everywhere differentiable locally Lipschitz function},
  author = {Aris Daniilidis and Robert Deville and Sebastian Tapia-Garcia},
  journal= {arXiv preprint arXiv:2405.09206},
  year   = {2024}
}

Comments

Revised version