On the Banach-Mazur Ellipse
DOI:
https://doi.org/10.55630/mem.2026.55.009-018Keywords:
Banach-Mazur distance, normed plane, distance ellipse, Chebyshev alternanceAbstract
We provide a new proof of Ader’s [1] 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.
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