Cardinality of a uncountable set.

In summary, we can use Cantor's diagonal argument to prove that the set of all sequences of 0's and 1's, denoted by S, is uncountable. This method involves generating a new sequence that is not included in any given list of sequences, leading to a contradiction and proving the uncountability of S.
  • #1
R.P.F.
211
0

Homework Statement



Let S be the set consisting of all sequences of 0's and 1's.

S = {(a_1, a_2, a_3,...):a_n = 0 or 1 }

Show that S is uncountable.

Homework Equations





The Attempt at a Solution



I'm not sure where to start. I think I should either assume that S~N and use proof by contradiction. Or maybe I could show that S has the same cardinality with R which means there is a bijective map between those two. Both of them don't seem easy.
I would really appreciate it if anyone could show me where to start.
 
Physics news on Phys.org
  • #2
R.P.F. said:

Homework Statement



Let S be the set consisting of all sequences of 0's and 1's.

S = {(a_1, a_2, a_3,...):a_n = 0 or 1 }

Show that S is uncountable.

Homework Equations


The Attempt at a Solution



I'm not sure where to start. I think I should either assume that S~N and use proof by contradiction. Or maybe I could show that S has the same cardinality with R which means there is a bijective map between those two. Both of them don't seem easy.
I would really appreciate it if anyone could show me where to start.

We can use the same classic approach as the one used for proving that the set of all real numbers is uncountable, namely, Cantor's diagonal argument. BWOC, suppose the set is countable. List all these sequences in some order. Then generate a sequence of your own by a method that excludes it from this list, thus arriving at a contradiction, i.e., proving S is uncountable.
 
  • #3
Here, I even found a decent explanation of this method. However, before you click the following link, please try and think of such a method by yourself. Just imagine how great you'll feel afterwards if you get it all by yourself!

http://en.wikipedia.org/wiki/Cantor's_diagonal_argument[/SPOILER]
 
Last edited by a moderator:
  • #4
Thanks a lot! I know how to do this now! :)
 

Related to Cardinality of a uncountable set.

What is the definition of "cardinality of a uncountable set"?

The cardinality of a set is a measure of its size, specifically the number of elements within the set. For uncountable sets, the cardinality is infinite and cannot be represented by a specific number. It is denoted by the symbol "c" or sometimes "ℵ0".

How is the cardinality of a uncountable set determined?

The cardinality of a uncountable set is determined by comparing it to other known sets. For example, the cardinality of the set of real numbers (ℝ) is greater than the cardinality of the set of natural numbers (ℕ). This is denoted by c > ℵ0.

Can a uncountable set have the same cardinality as a countable set?

No, a uncountable set cannot have the same cardinality as a countable set. This is because the cardinality of a countable set is finite and can be represented by a specific number, while the cardinality of an uncountable set is infinite and cannot be represented by a specific number.

What is the continuum hypothesis and how does it relate to the cardinality of uncountable sets?

The continuum hypothesis states that there is no set whose cardinality is strictly between that of the integers (ℤ) and the real numbers (ℝ). This means that the cardinality of the set of real numbers is the next highest cardinality after the set of integers. However, this hypothesis has been proven to be undecidable, meaning it cannot be proven true or false within the standard axioms of set theory.

Why is the concept of cardinality of uncountable sets important in mathematics?

The concept of cardinality of uncountable sets is important in mathematics because it helps us understand the size and structure of different sets. It also plays a crucial role in various mathematical theories and has applications in different areas of mathematics, such as calculus and set theory. Understanding the cardinality of uncountable sets allows us to make further advancements and discoveries in these fields.

Similar threads

  • Calculus and Beyond Homework Help
Replies
1
Views
690
  • Calculus and Beyond Homework Help
Replies
14
Views
668
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
  • Calculus and Beyond Homework Help
Replies
11
Views
490
  • Calculus and Beyond Homework Help
Replies
14
Views
2K
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
7
Views
2K
  • Calculus and Beyond Homework Help
Replies
5
Views
2K
  • Calculus and Beyond Homework Help
Replies
5
Views
1K
  • Set Theory, Logic, Probability, Statistics
Replies
9
Views
1K
Back
Top