Let
be a locally convex topological
vector space and let
be a compact subset
of
.
In functional analysis, Milman's theorem is
a result which says that if 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
.