Best approximations and porous sets
Let be a nonempty compact subset of a Banach space and denote by the family of all nonempty bounded closed convex subsets of . We endow with the Hausdorff metric and show that there exists a set such that its complement is -porous and such that for each and each , the set of solutions of the best approximation problem , , is nonempty and compact, and each minimizing sequence has a convergent subsequence.