Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » sci.math.* » sci.math

Topic: ALL PERMUTATIONS OF INFINITY
Replies: 1   Last Post: May 22, 2012 5:29 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View  
Torben Mogensen

Posts: 60
Registered: 12/6/04
Re: ALL PERMUTATIONS OF INFINITY
Posted: May 22, 2012 5:29 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Graham Cooper <grahamcooper7@gmail.com> writes:

> On May 22, 2:46 am, torb...@diku.dk (Torben Ægidius Mogensen) wrote:
>> For the same reason, the set of all sets of naturals (P(N)
>> or, equivalently, 2^N) has the same size as the set of real numbers (R):
>> There is a bijection between sets of naturals and reals.
>>
>> There is a bijection between permutations of N and subsets of N, so the
>> set of permutations has the same size as the set of subsets.
>>
>>         Torben

>
> Thanks for the NON-SEQUITUR of the Century.
>
> So there's a BIJECTION between O(2^n) and O(n!) sized sets now?


Only for infinite n.

> SETSIZE 1 {a} = 1 Permutation
> SETSIZE 2 {a,b} = 2! Permutations
> SETSIZE 3 {a,b,c} = 3! Permutations
> ...


True so far.

> SETSIZE |N| {1,2,3..} = 2^|N| Permutations

But this is a non sequitur. A property that holds for all finite values
does not necessarily hold for infinite values. Or, more geneally, a
property that holds for all elements of a sequence of values does not
necessarily hold for the limit of the sequence -- whether the limit is
finite or not.

> How convenient!

Not at all. It would be so much more convenient if a property that
holds for elements of a sequence would also hold in the limit. But,
alas, we are not so lucky.

Torben



Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.