Cardinality of the set of all functions from N to N

Click For Summary

Homework Help Overview

The discussion revolves around the cardinality of the set of all functions from the natural numbers (N) to itself (N). The original poster seeks to prove that the cardinality of this set is equal to the continuum (c).

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the mapping of functions to decimal representations, questioning the injectivity of this mapping and discussing previous attempts related to the power set of natural numbers.

Discussion Status

The discussion is active, with participants sharing insights and questioning the validity of proposed mappings. There is recognition of potential connections to previous problems, but no consensus has been reached regarding the injectivity of the mapping.

Contextual Notes

Participants reference prior attempts at proving related concepts, indicating a possible complexity in generalizing their findings to the current problem.

Flying_Goat
Messages
15
Reaction score
0

Homework Statement


Let NN be the set of all functions from N to N. Prove that |NN|=c


Homework Equations





The Attempt at a Solution



I can prove that the set of all functions from N to {0,1} has cardinality of the continuum, but i can't generalise it. Any help would be appreciated.
 
Physics news on Phys.org
Let f be a function from N to N. Construct a number, x, by writing a decimal point, then 0.f(1)f(2)f(3)... so that each function is mapped to the number, between 0 and 1, having the values of f as digits. That maps each function to a number. What numbers?
 
Thanks, I had thought of your argument when I was trying to prove |P(N)|=c but it didn't work out...I can't believe that it works for this question lol. Anyway thanks for your help.
 
Is the map injective? Because I could have f(2n-1)=12,f(2n)=3 or f(2n-1)=1,f(2n)=23 and both of these functions would give me 0.123123...
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 39 ·
2
Replies
39
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 14 ·
Replies
14
Views
2K