Is the Open Cover of the Interval [0,1) with Infinite Subcovers Effective?

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Discussion Overview

The discussion revolves around the effectiveness of open covers for the interval [0,1) and whether certain proposed covers have infinite subcovers. Participants explore the implications of including boundaries and the nature of the covers.

Discussion Character

  • Exploratory, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant proposes the open cover {(An)} where An = (-1/n, n) for n in natural numbers, questioning if it is effective for covering [0,1).
  • Another participant suggests that to ensure the cover is infinite, the interval (-1, 1 - (1/n)) could be a valid option.
  • Some participants argue that the proposed covers do not exemplify covers without finite subcovers, noting that (-1, 1) contains [0,1) and thus does not meet the criteria.
  • There is a suggestion that (-1, 1 - (1/n)) does not allow for finite subcovers, indicating a potential effective cover.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of the proposed covers, with some asserting that certain examples do not qualify as covers without finite subcovers while others challenge this perspective.

Contextual Notes

Participants do not clarify the definitions of effective covers or the specific conditions under which a cover may or may not have finite subcovers, leaving some assumptions unresolved.

Bachelier
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Given the interval [0,1)

is this a good Open cover with infinite subcovers

{(An)} such that An =(-1/n, n) with n \in lN

Is there any reason we should stay to the boundaries of the set we're trying to cover?

I'm thinking that even (-n, n) should work.

Am I wrong?
 
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I think I just answered my own question.

I think to make sure that the portion that covers the interval is infinite.

Hence (-1, 1 - (1/n)) would work.
 
Bachelier said:
Given the interval [0,1)

is this a good Open cover with infinite subcovers

{(An)} such that An =(-1/n, n) with n \in lN

Is there any reason we should stay to the boundaries of the set we're trying to cover?

I'm thinking that even (-n, n) should work.

Am I wrong?

Neither of these is an example of a cover without a finite subcover. In the first case, (-1,1) \supset [0,1); same in the second case.
 
AxiomOfChoice said:
Neither of these is an example of a cover without a finite subcover. In the first case, (-1,1) \supset [0,1); same in the second case.

Agreed, but (-1,1-1/n)
is.
 
Bachelier said:
I think I just answered my own question.

I think to make sure that the portion that covers the interval is infinite.

Hence (-1, 1 - (1/n)) would work.

Yep. No finite subcovers here!
 

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