G-delta set: Difference between revisions

From Citizendium
Jump to navigation Jump to search
imported>Richard Pinch
(new entry, just a stub)
(No difference)

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.