Comparing PERFECT SET vs COMPLETE SET | Verifying Compact Sets

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SUMMARY

The discussion clarifies the distinctions between "perfect sets" and "complete sets" in the context of topology and mathematical analysis. A perfect set is defined as a non-empty, closed set with no isolated points. In contrast, the term "complete set" is not commonly recognized in topology but is defined in analysis as a set where every Cauchy sequence converges. Additionally, a compact set is characterized by the property that every open cover has a finite subcover, and in Euclidean spaces, it is both closed and bounded.

PREREQUISITES
  • Understanding of basic topology concepts, including closed sets and isolated points.
  • Familiarity with Cauchy sequences and convergence in mathematical analysis.
  • Knowledge of compactness in the context of set theory.
  • Basic principles of Euclidean spaces and their properties.
NEXT STEPS
  • Study the definitions and properties of perfect sets in topology.
  • Learn about complete metric spaces and their significance in analysis.
  • Explore the concept of compactness and its applications in various mathematical fields.
  • Review W. Rudin's "Principles of Mathematical Analysis" for deeper insights into these concepts.
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Mathematicians, students of topology and analysis, and anyone interested in understanding the properties of sets in mathematical contexts.

Ka Yan
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1. What's the difference between PERFECT SET and COMPLETE SET? Can I have an explicit explain to it, rather than a discribtion from definition?

2. How can I verify whether a set is compact or not more evidently and effective?

Tks!
 
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Ka Yan said:
1. What's the difference between PERFECT SET and COMPLETE SET? Can I have an explicit explain to it, rather than a discribtion from definition?
First, are you talking about topology? From your second question, I guess that you are but there are notions of 'perfect' and 'complete' sets for many different fields of mathematics. Topologically, a set is "perfect" if it is non-empty, closed, and has no isolated points. I don't recognize "complete set" in topology and cannot find any reference to it. Plenty of references to "complete set" of different kinds of things!
Do you have a definition of "complete set"?

2. How can I verify whether a set is compact or not more evidently and effective?

Tks!
Precisely what is your definition of "compact" set? One way to determine if a set is compact is by showing that every infinite sequence of points in the set has a subsequence that converges to a point in the set. If you are talking about subsets of Euclidean spaces, then, of course, a set is compact if and only if it is both closed and bounded.
 
I mentioned "complete set", it was definded as: a set where every Cauchy sequence is convergent, from Chapter 2 of W. Rudin's Principle of Mathematical Analysis .

And "compact set" is definded as: every open cover of the set has a finite subcover. Thus the compact set I was talking about is of general difinition. And thanks for reminding me of the Euclidean one.
 

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