Is there a name for this type of topology?
Let X be an infinite set. Let A be an infinite subset of X.
Definite a topology, T, on X, where every open set is either:
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The empty set, or
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Contains all but finitely many points of A. (Alternatively put: to form opens of this type, take the set A, remove finitely many points, then add any amount of points from X. )
T contains the empty set, and X contains all but finitely many points from A, so X is in T. If O and U both contain all but finitely many points of A, then so will the intersection. And an arbitrary union of this type will also be in T.
If the difference between A and X is finite, then T is simply the co-finite topology. But is there a name for the topology when X minus A is infinite?
Thanks in advance.
Posted May 31, 2024, 7:21 PM UTC
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