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exposed points are dense in the extreme points (Theorem)
Definition 1   Let $K \subset {\mathbb{R}}^n$ be a closed convex set. A point $p \in K$ is called an exposed point if there is an $n-1$ dimensional hyperplane whose intersection with $K$ is $p$ alone.
Theorem 1 (Strasziewicz)   Let $K \subset {\mathbb{R}}^n$ be a closed convex set. Then the set of exposed points is dense in the set of extreme points.

For example, let $C(p)$ denote the closed ball in ${\mathbb{R}}^2$ of radius 1 and centered at $p.$ Then take $K$ to be the convex hull of $C(-1,0)$ and $C(1,0)$ The points $(-1,1),$ $(-1,-1),$ $(1,1),$ and $(1,-1)$ are extreme points, but they are not exposed points.




"exposed points are dense in the extreme points" is owned by jirka.
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See Also: extreme point

Other names:  Strasziewicz theorem
Also defines:  exposed point
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Cross-references: convex hull, radius, closed ball, extreme points, dense in, intersection, hyperplane, point, convex set, closed

This is version 1 of exposed points are dense in the extreme points, born on 2007-12-12.
Object id is 10124, canonical name is ExposedPointsAreDenseInTheExtremePoints.
Accessed 1294 times total.

Classification:
AMS MSC52A99 (Convex and discrete geometry :: General convexity :: Miscellaneous)

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