Closed Intervals of R: Uncountable Collection Example

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In summary, the conversation discusses the search for an example of an uncountable collection of closed intervals in the real numbers. The individual has proven that a collection of open intervals can be mapped to the integers, but is struggling to find a similar example for closed intervals. The suggestion is made to use a collection of points, but it is noted that disjoint closed intervals of finite length cannot form an uncountable set.
  • #1
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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  • #2
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.
 
  • #3
StatusX,

I forgot to mention the closed sets have to be disjoint.
 
  • #4
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.
 

FAQ: Closed Intervals of R: Uncountable Collection Example

What is a closed interval in the context of real numbers?

A closed interval in the context of real numbers is a set of all real numbers between two given values, including the endpoints. For example, the closed interval [0, 5] includes all real numbers from 0 to 5, including 0 and 5.

What does it mean for a collection of closed intervals to be uncountable?

A collection of closed intervals is uncountable when there are infinitely many intervals and it is impossible to assign a unique number to each interval. This means that the collection cannot be counted or listed in a systematic way.

What is an example of an uncountable collection of closed intervals?

An example of an uncountable collection of closed intervals is the set of all closed intervals between 0 and 1. This includes intervals such as [0, 0.1], [0.2, 0.3], [0.5, 0.7], etc. There are infinitely many intervals in this collection and it is impossible to assign a unique number to each interval.

Why is the concept of uncountable collections important in mathematics?

Uncountable collections are important in mathematics because they help us understand the concept of infinity and the properties of infinite sets. They also play a crucial role in many areas of mathematics, such as set theory, measure theory, and analysis.

How are uncountable collections of closed intervals related to the Cantor set?

The Cantor set is a well-known example of an uncountable collection of closed intervals. It is formed by repeatedly removing the middle third of each interval in the set [0, 1]. This process creates an uncountable collection of closed intervals that has a fractal-like structure. The Cantor set has many interesting properties and is often used as a counterexample in mathematics.

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