Closed Intervals of R: Uncountable Collection Example

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Homework Help Overview

The discussion revolves around finding an example of an uncountable collection of closed intervals in the real numbers, R. The original poster expresses confusion regarding the extension of logic applied to open intervals to closed intervals, particularly in the context of countability.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the nature of closed intervals and their countability, with one suggesting a specific collection of closed intervals defined by a subset of positive real numbers. Another participant raises the requirement for the closed sets to be disjoint, prompting further examination of the implications of this condition.

Discussion Status

The discussion is ongoing, with participants questioning the assumptions made about the nature of closed intervals and their properties. There is a suggestion of a potential example, but the requirement for disjoint intervals introduces complexity that is still being explored.

Contextual Notes

Participants are considering the constraints of disjoint closed intervals and the implications for forming an uncountable set, particularly focusing on the lengths of these intervals and the nature of their endpoints.

barksdalemc
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Guys I would appreciate any help on this. I've been trying to find an example of a collection of closed intervals of R that is uncountable. I proved that if I take a collection of open intervals of R and bijectively map them to Z, then the collection is countable, and I would assume the same with a collection of closed intervals, but clearly there must be an example where that doesn't happen and I don't understand why my logic on the collection of open sets cannot be extended to the collection of closed sets. Thanks for any help.
 
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The collection { [0,a] | a[itex]\in[/itex]A}, where A is a subset of (0,[itex]\infty[/itex]), can be put in a bijection with A.
 
StatusX,

I forgot to mention the closed sets have to be disjoint.
 
Well then you could always take points as your closed intervals. It is not possible to form an uncountable set of disjoint closed intervals, each of finite length.
 

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