OAI.DiscreteFree.source_endpoints

The theorem states that two propositions hold together, both about the Lipschitz-free space FreeSpace(o) of a pointed metric space (M,o), which is the closed linear span, inside the dual of the Banach space Lip0(o) of real Lipschitz functions vanishing at o (normed by the supremum of the slopes |f(x)-f(y)|/d(x,y)), of the point evaluations; delta(o,a) denotes the evaluation at a. The first, BlockStatement, says that for every natural number p ≥ 1 there exist a countable metric space M and a base point o with all distinct points at distance at least 1 and all distances at most 300p²+150p+5, together with a finite set A of M containing o, such that every bounded linear operator T on FreeSpace(o) of finite rank and norm at most p moves some delta(o,a) with a in A by at least 1/2, that is ‖T(delta(o,a))-delta(o,a)‖ ≥ 1/2. The second, MainStatement, says there exist a countable metric space M and a point o such that distinct points are at distance at least 1, M is unbounded, M is not a proper space, FreeSpace(o) has the approximation property (finite-rank bounded operators approximate the identity uniformly on every compact set to within any ε>0), and yet for every Λ ≥ 1 FreeSpace(o) fails the bounded approximation property with constant Λ, meaning the approximating finite-rank operators cannot all be chosen with norm at most Λ. The theorem is stated with sorry, so no proof is asserted here.