Identifying Compact Sets in the Slitted and Moore Planes: What's the Method?

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SUMMARY

The discussion focuses on identifying compact sets in the slitted plane and the Moore plane. In the slitted plane, compact sets coincide with the usual real line, which can be proven by analyzing the topology generated by a base consisting of z∪A, where A is a disc with finitely many lines deleted. For the Moore plane, closed, bounded sets disjoint from the x-axis are compact, while sets touching the x-axis at infinitely many points are not compact. The compact sets in the Moore plane include closed bounded sets along with finitely many points on the x-axis.

PREREQUISITES
  • Understanding of topology, specifically compactness in metric spaces.
  • Familiarity with the concepts of the slitted plane and Moore plane.
  • Knowledge of closed and bounded sets in the context of real analysis.
  • Basic principles of set theory and limits concerning infinite points.
NEXT STEPS
  • Study the properties of compact sets in different topological spaces.
  • Research the characteristics of the Moore plane and its implications on compactness.
  • Explore the concept of bases in topology and their role in defining compactness.
  • Examine examples of closed sets in the slitted plane and their compactness properties.
USEFUL FOR

Mathematicians, particularly those specializing in topology, students studying advanced mathematical concepts, and researchers exploring compactness in non-standard planes.

ForMyThunder
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Is there any easy way to find all the compact sets of 1) the slitted plane and 2) the Moore plane?

1) defined as the topology generated by a base consisting of z\cup A where A is a disc about z with finitely many lines deleted. I believe the compact sets in this topology coincide with the usual real line. How do I prove this?

2) (rough sketch) I know that a closed, bounded set disjoint from the x-axis is compact. I guess if a set touched the x-axis in an infinite number of points, it would not be compact. So the compact sets consisting of a closed, bounded set disjoint from the x-axis along with finitely many points on the x-axis is compact?
 
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1) I do not think so. A closed section of disc should be compact and is no real line.
2) The number of points on the ##x-## axis shouldn't play a role here.
 

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