English

Diversity of Lipschitz-free spaces over countable complete discrete metric spaces

Functional Analysis 2025-05-27 v1 Metric Geometry

Abstract

We show that there are uncountably many mutually non-isomorphic Lipschitz-free spaces over countable, complete, discrete metric spaces. Also there is a countable, complete, discrete metric space whose free space does not embed into the free space of any uniformly discrete metric space. This enhanced diversity is a consequence of the fact that the dentability index DD presents a highly non-binary behavior when assigned to the free spaces of metric spaces outside of the oppressive confines of compact purely 1-unrectifiable spaces. Indeed, the cardinality of {D(F(M)):M\{D(\mathcal F(M)): M countable, complete, discrete}\} is uncountable while {D(F(M)):M\{D(\mathcal F(M)):M infinite, compact, purely 1-unrectifiable}={ω,ω2}\}=\{\omega,\omega^2\}. Similar barrier is observed for uniformly discrete metric spaces as higher values of the dentability index are excluded for their free spaces: {D(F(M)):M\{D(\mathcal F(M)):M infinite, uniformly discrete}={ω2,ω3}\}=\{\omega^2,\omega^3\}.

Cite

@article{arxiv.2505.19891,
  title  = {Diversity of Lipschitz-free spaces over countable complete discrete metric spaces},
  author = {Estelle Basset and Gilles Lancien and Antonín Procházka},
  journal= {arXiv preprint arXiv:2505.19891},
  year   = {2025}
}