The Jung constant of a normed space 
is
 |
where 
ranges over bounded subsets of positive diameter,
and 
is their least enclosing radius with center in 
. The center need not lie in 
.
For spaces with the taxicab metric, Li (2026) proved that, for every positive integer 
,
 |
where 
is 
with the taxicab
metric. In particular, 
. If a Hadamard matrix
of order 
exists, the same value 
is attained in dimensions 
, 
, and 
(Li 2026). Li (2026) supplies a Lean formalization of the
upper bound.
." 6 Oct 2026.