A remark on the approximate fixed-point property

[摘要] We give an example of an unbounded, convex, and closed setCin the Hilbert spacel2with the following two properties: (i)Chas the approximate fixed-point property for nonexpansivemappings, (ii)Cis not contained in a block for every orthogonal basis inl2.

[学科分类] 数学（综合）