G-delta set: Difference between revisions
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Revision as of 17:29, 3 January 2009
In general topology, a Gδ set is a subset of a topological space which is a countable intersection of open sets. An Fσ space is similarly a countable union of closed sets.
A Gδ in a complete metric space is again a complete metric space.
References
- J.L. Kelley (1955). General topology. van Nostrand, 207-208.