English

Generalized geometric constants related to Birkhoff orthogonality in Banach spaces

Functional Analysis 2026-02-19 v2

Abstract

In this paper, based on Birkhoff orthogonality, we introduce two geometric constants AtB(X)\boldsymbol{A}_{\boldsymbol{t}}^{\boldsymbol{B}}(\boldsymbol{X}) and DtB(X)\boldsymbol{D}_{\boldsymbol{t}}^{\boldsymbol{B}}(\boldsymbol{X}) in Banach spaces, which generalize the skew geometric constants related to Birkhoff orthogonality. We systematically investigate the basic properties of the two constants, including their upper and lower bounds, and establish the equivalent characterizations for Banach spaces being uniformly non-square. Additionally, we explore the relationship between DtB(X)\boldsymbol{D}_{\boldsymbol{t}}^{\boldsymbol{B}}(\boldsymbol{X}) and the modulus of convexity δX(ε)\boldsymbol{\delta}_{\boldsymbol{X}}(\boldsymbol{\varepsilon}). Finally, we explore several applications of the two newly proposed geometric constants.

Keywords

Cite

@article{arxiv.2602.13974,
  title  = {Generalized geometric constants related to Birkhoff orthogonality in Banach spaces},
  author = {Junxiang Qi and Qian Li and Zhouping Yin and Qi Liu and Jiaye Bi and Yuankang Fu and Yongjin Li},
  journal= {arXiv preprint arXiv:2602.13974},
  year   = {2026}
}