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Birkhoff-Orthogonal Takahashi-von Neumann-Jordan Type Constants in Banach Spaces

Junxiang Qi, Zhouping Yin, Qi Liu

math.FAarXiv:2608.07146

Abstract

In this paper, we introduce a new family of geometric constants CtB(X) of Birkhoff-orthogonal Takahashi-von Neumann-Jordan type for real Banach spaces. We discuss their basic properties and give a characterization of uniformly non-square spaces via CtB(X). Some sufficient conditions for super-reflexivity and fixed point property are presented. We establish upper bounds of CtB(X) related to orthogonal geometric moduli and constants, and obtain the sharp value for Radon planes.

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