Can Every Compact Metric Space Have a Countable Base?

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SUMMARY

Every compact metric space K indeed has a countable base, as established by Rudin's theorem. The discussion clarifies that finite compact metric spaces are considered countable under Rudin's definitions, which include both finite sets and sets in bijection with the natural numbers, \mathbb{N}. The distinction between finite and countable sets is crucial to understanding the validity of this theorem. Therefore, the assertion stands firm that compact metric spaces possess a countable base.

PREREQUISITES
  • Understanding of compact metric spaces
  • Familiarity with the concept of a base in topology
  • Knowledge of countability in set theory
  • Awareness of Rudin's definitions in "Principles of Mathematical Analysis"
NEXT STEPS
  • Review the definition of compact metric spaces in topology
  • Study the concept of a base and its significance in topology
  • Examine the distinctions between finite and countable sets in set theory
  • Read "Principles of Mathematical Analysis" by Walter Rudin for deeper insights
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Mathematicians, students of topology, and anyone interested in the foundational aspects of metric spaces and set theory.

imahnfire
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Rudin's problem asks: Prove that every compact metric space K has a countable base.

My concern is how valid this statement really is. Wouldn't a finite compact metric space be unable to have a countable base?
 
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Rudin probably defines countable as either finite or in bijection with \mathbb{N}. So finite things are countable to him.

You should look up his definition to be sure.
 
Rudin distinguishes finite sets and countable sets in his book. Would this affect the validity of the statement?
 
imahnfire said:
Rudin distinguishes finite sets and countable sets in his book. Would this affect the validity of the statement?

Yes, it does. You want the base to be either finite or countable.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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