Milman's theorem in functional analysis states that if
is a locally convex topological
vector space,
is a compact subset of
, and the closed convex hull
of
is also compact, then
contains all the extreme
points of
.
The importance of Milman's theorem is subtle but enormous. One well-known fact from functional analysis is that where
denotes the set of extreme
points of
.
Ostensibly, however, one may have that
has extreme points
which are not in
.
This behavior is considered a pathology, and Milman's theorem states that this pathology
cannot exist whenever
is compact (e.g., when
is a subset of a Fréchet
space
).
Milman's theorem should not be confused with the Krein-Milman theorem which says that every nonempty compact convex set in
necessarily satisfies the identity
.