File:Topological space examples.svg

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Summary

Examples and non-examples of topological spaces, based roughly on Figures 12.1 and 12.2 from Munkres' Introduction to Topology. The 6 examples are subsets of the power set of {1,2,3}, with the small circle in the upper left of each denoting the empty set, and in reading order they are:

  • {{}, {1,2,3}} (the trivial topology)
  • {{}, {1}, {1,2,3}}
  • {{}, {1}, {2}, {1,2}, {1,2,3}}
  • {{}, {2}, {1,2}, {2,3}, {1,2,3}}
  • {{}, {2}, {3}, {1,2,3}} (not a topology, because {2} and {3} are in the topology but their union {2,3} is not)
  • {{}, {1,2}, {2,3}, {1,2,3}} (not a topology, because {1,2} and {2,3} are in the topology but their intersection {2} is not)

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Date/TimeThumbnailDimensionsUserComment
current15:24, 12 January 2017Thumbnail for version as of 15:24, 12 January 2017360 × 319 (12 KB)127.0.0.1 (talk)Examples and non-examples of topological spaces, based roughly on Figures 12.1 and 12.2 from Munkres' <i>Introduction to Topology</i>. The 6 examples are subsets of the power set of {1,2,3}, with the small circle in the upper left of each denoting the empty set, and in reading order they are: <ul> <li> {{}, {1,2,3}} (the trivial topology)</li> <li> {{}, {1}, {1,2,3}}</li> <li> {{}, {1}, {2}, {1,2}, {1,2,3}}</li> <li> {{}, {2}, {1,2}, {2,3}, {1,2,3}}</li> <li> {{}, {2}, {3}, {1,2,3}} (not a topology, because {2} and {3} are in the topology but their union {2,3} is not)</li> <li> {{}, {1,2}, {2,3}, {1,2,3}} (not a topology, because {1,2} and {2,3} are in the topology but their intersection {2} is not)</li> </ul>
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