Connectedness of an intersection from connected finite intersections
ID: connectedness-of-an-intersection-from-connected-finite-intersections
Let be a compact Hausdorff space and let be compact subsets such that all finite intersections are nonempty and connected. Their total intersection is nonempty by the finite intersection characterization of compactness, and compact because it is closed in .
If were not connected, its separation of a topological space would divide it into two nonempty compact subsets. Separation of disjoint compact subsets gives disjoint ambient open sets containing the two pieces. The family consisting of and all has empty total intersection, so some finite subfamily has empty intersection. Hence a finite intersection of the lies in . Since meets both open sets, they disconnect , a contradiction. The hypothesis on all finite intersections is stronger than requiring each individual to be connected.
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