2 papers
math.FA2026
Rigidity of unit spheres in finite-dimensional real normed spaces
Jumpei Nakamura, Ryotaro Tanaka
We prove that finite-dimensional real normed spaces with isometric unit spheres are linearly isometric, where each sphere carries the distance induced by the ambient norm. This ans…
math.FA2025
On relationship among three types of Birkhoff-James orthogonality
Soumitra Daptari, Koki Igarashi, Jumpei Nakamura +1
In this paper, we study three types of Birkhoff-James orthogonality in Hilbert -modules, that is, the strong, quasi-strong, and original Birkhoff-James orthogonality. In gener…