Re: Compactness




William Elliot wrote:
A space S is compact iff
every open cover of S has a finite subcover
every filter on S has a cluster point
every ultra filter on S converges.

Well, there is another point:
In a topological space (X,T), a subset A is compact iff for any filter
basis F consisting of closed sets s.t. A clusters F( i.e., A intersects
every member of F), A also cuts the core of F(i.e., /\F).

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