Cardinality of continuous functions

In summary, the cardinality of the set of all continuous real valued functions from [0,1] to R is equal to \aleph ^ \aleph by using the Cantor Bernstien theorem and the fact that a continuous function is determined by its values on the rational numbers. This can be represented formally as |C[0,1] \rightarrow R| = |R^{[0,1] \in Q}| = \aleph ^ \aleph.
  • #1
talolard
125
0

Homework Statement


What is the cardinality of the set of all continuous real valued functions [tex] [0,1] \rightarrow R [/tex].




The Attempt at a Solution


In words:
I will be using the Cantor Bernstien theorem. First the above set, let's call it A, is lesser then or equal to the set of all functions from R to R which has a cardinality of [tex] \aleph ^ \aleph [/tex]
Also, the cardinality of all continuous functions [tex] [0,1] \rightarrow R [/tex]. is lesser then or equal too the cardinality of the set of all functions, continuous and not continuous, from [tex] [0,1] \rightarrow R [/tex].
The cardinality of the segment [0,1] is [tex] \aleph [/tex] and so the cardinality of all functions [tex] [0,1] \rightarrow R [/tex]. is also [tex] \aleph ^ \aleph [/tex] and so by the cantor bernsiten theorem the cardinality of A is also [tex] \aleph ^ \aleph [/tex]

In formal math:
I use C to denote continuous functions.
[tex] \aleph ^ \aleph =|R^R| \geq |R^{C[0,1]}| = |C[0,1] \rightarrow R| = |R^{C[0,1]}| \leq |R^{[0,1]}|=\ \aleph ^ \aleph [/tex]


Is this correct? and formal anough?
Thanks
Tal
 
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  • #2
Ahhh I see my mistake allready.
Is it enough to say that a coninuous function is determined by its values on Q. Therefore
[tex] C[0,1] \rightarrow R = R^{[0,1] \in Q}= \aleph [/tex]
 

1. What is the cardinality of the set of continuous functions?

The cardinality of the set of continuous functions is equal to the cardinality of the real numbers, which is known as the cardinality of the continuum. This means that there are uncountably infinite continuous functions.

2. How does the cardinality of continuous functions compare to the cardinality of all functions?

The cardinality of continuous functions is a subset of the cardinality of all functions. This means that the cardinality of continuous functions is less than or equal to the cardinality of all functions.

3. Can two continuous functions have the same cardinality?

Yes, two continuous functions can have the same cardinality. This is because the cardinality of continuous functions is uncountably infinite, meaning there are infinitely many continuous functions with the same cardinality.

4. Are there any other sets with the same cardinality as the set of continuous functions?

Yes, there are other sets with the same cardinality as the set of continuous functions. For example, the sets of differentiable functions, integrable functions, and polynomial functions all have the same cardinality as the set of continuous functions.

5. Can the cardinality of continuous functions be larger than the cardinality of the set of real numbers?

No, the cardinality of continuous functions cannot be larger than the cardinality of the set of real numbers. This is because the set of continuous functions is a subset of the set of real numbers, and the cardinality of a subset is always less than or equal to the cardinality of the original set.

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