A NON-LINEAR#x2113;1PROBLEM

摘要

In this note we consider a non-linear problem posed to the author in a private communication with Per Enflo: If a normed spaceXcontains a non-linear#x2113;1(n)-cube (wheren#x2265; 2 is a natural number) does it necessarily contain a linear isometric copy of#x2113;1(n)?