JUNG’S THEOREM AND EXTREMAL SETS IN A HEMI-SPHERE OF S∞

DOI: 10.18173/2354-1059.2023-0019

Abstract

The paper deals with the unit sphere S∞ of a Hilbert space endowed with natural spherical metric. In the paper, we give a geometric characterization of extremal sets contained in a hemi-sphere of S∞ that generalizes previously known results with respect to the classical Jung theorem.