On the Banach-Mazur Ellipse
Functional Analysis
2026-02-20 v1
Abstract
We provide a new proof of Ader's characterisation of the ellipse of minimal Banach-Mazur distance to the unit circle of a normed plane in terms of contact and extremal points. Our method reveals the relation of this problem to the Chebyshev alternance.
Cite
@article{arxiv.2602.17191,
title = {On the Banach-Mazur Ellipse},
author = {V. D. Babev and M. Ivanov and R. Nikolov},
journal= {arXiv preprint arXiv:2602.17191},
year = {2026}
}