Parameters in Banach spaces and orthogonality

Abstract

In Banach spaces, plenty of parameters have been considered: they are often defined by using pairs of vectors. Rarely, they are defined by considering pairs of vectors which are orthogonal in the sense of Birkhoff and James; in that case the study is often not easy. In fact, it can be difficult to identify pairs of orthogonal vectors; so to calculate the value of these parameters, to compare them with the other parameters, to see if they have some stability with respect to changes of the norm. In this paper, we shall do this for a couple of new parameters.

Keywords

• Orthogonal vectors
• James constant
• uniform non squareness

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