There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
The space \(F(\ell_2)\) of all closed subsets of \(\ell_2\) is a Polish space. We
show that the subset \(P\subset F(\ell_2)\) consisting of the purely
1-unrectifiable sets is \(\Pii\)-complete.