%0 Journal Article
%T Nonexpansive retractions in Hilbert spaces
%A Kazimierz Goebel
%A Ewa S d ak
%J Annales UMCS, Mathematica
%D 2009
%I 
%R 10.2478/v10062-009-0008-8
%X Let H be a Hilbert space and C   H be closed and convex. The mapping P: H ¡ú C known as the nearest point projection is nonexpansive (1-lipschitzian). We observed that, the natural question: "Are there nonexpansive projections Q: H ¡ú C other than P?" is neglected in the literature. Also, the answer is not often present in the "folklore" of the Hilbert space theory. We provide here the answer and discuss some facts connected with the subject.
%K Hilbert space
%K convex sets
%K retractions
%K nonexpansive mappings
%U http://versita.metapress.com/content/ag8r35g087h7178p/?p=53d3d035dc3c4d16820f83657672712a&pi=7