Minimal widths and orthogonality types
摘要
The minimal widths of three bounded subsets of the unit sphere associated to a unit vector in a normed linear space are studied, and three related geometric constants are introduced. New characterizations of inner product spaces are also presented. From the perspective of minimal width, strong ε-symmetry of Birkhoff orthogonality is introduced, and its relation to ε-symmetry of Birkhoff orthogonality is shown. Unlike most of the existing parameters of the underlying space, these new constants are full dimensional in nature.