1,718 research outputs found
Convex Bodies of Constant Width and Constant Brightness
In 1926 S. Nakajima (= A. Matsumura) showed that any convex body in
with constant width, constant brightness, and boundary of class is a
ball. We show that the regularity assumption on the boundary is unnecessary, so
that balls are the only convex bodies of constant width and brightness.Comment: 20 page
On the size of approximately convex sets in normed spaces
Let X be a normed space. A subset A of X is approximately convex if
for all and where is
the distance of to . Let \Co(A) be the convex hull and \diam(A) the
diameter of . We prove that every -dimensional normed space contains
approximately convex sets with \mathcal{H}(A,\Co(A))\ge \log_2n-1 and
\diam(A) \le C\sqrt n(\ln n)^2, where denotes the Hausdorff
distance. These estimates are reasonably sharp. For every , we construct
worst possible approximately convex sets in such that
\mathcal{H}(A,\Co(A))=\diam(A)=D. Several results pertaining to the
Hyers-Ulam stability theorem are also proved.Comment: 32 pages. See also http://www.math.sc.edu/~howard
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