Cantor’s Diagonal Argument. Recall that • A set S is finite iff there is a bijection between S and {1, 2,,n} for some positive integer n, and infinite otherwise. Not too long ago, while surfing the TV channels, you could lean back, press the remote, and suddenly you found a show about Georg Cantor (pronounced. The Cantor diagonal method, also called the Cantor diagonal argument or Cantor’s diagonal slash, is a clever technique used by Georg Cantor to show that the.

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The diagonal argument was not Cantor’s first proof of the cqntor of the real numberswhich appeared in Home Questions Tags Users Unanswered.

The uncountability of the real numbers was already established by Cantor’s first uncountability proofbut it also follows from the above result. Can somebody explain to me Cantor’s diagonalization argument?

This construction uses a method devised by Cantor that was published in Then the new number is such that it is different from the first number at cantog first digit, diagojalization the second element at the second digit and so on.

As a candidate consider the set:. However, this contradicts s being an element of T and therefore belonging to the enumeration. By using this site, you agree to the Terms of Use and Privacy Policy. Cantor’s diagonal method can be used to show that is larger thandiagonalizwtion. If is an infinite set, then is a bigger infinite set. Based on this theorem, Cantor then uses a proof by contradiction to show that:.

Universality and the Liar: See diagonalization disambiguation for several other uses of the term in mathematics. Numbers from mathematics have symbolic definitions. Referenced on Wolfram Alpha: Instead of mapping On page 65, Dauben proves a result that is stronger than Cantor’s.

Hence, s cannot occur in the enumeration. Math is hard and requires maturity.

## Cantor’s diagonal argument

In his article, Cantor considered the set T of all infinite sequences of binary digits i. Hints help you try the next step on your own.

One way to arrange the proof is to assume that such a list can be given, and derive from that a contradiction by showing ccantor the list does not really list all the numbers. Also, diagonalization was originally used to show the existence of arbitrarily hard complexity classes and played a key role in early attempts to prove P does not equal NP.

I believe he just chose those numbers as examples.

### Cantor Diagonalization — Math Fun Facts

At first blush the list of integers appears to be larger than the list of positive integers since I can pair all the positives and leave all the negatives unpaired. Why are we doing any of this? Either way, every real number I can ever encounter can be expressed finitely, either by a finite description of defining equations or a finite precision real-world measurement. By “explain this to me as if I was a 5 year old” do you mean that we should start by explaining what the words “countable” and “uncountable” mean, or do you already understand the meaning of those words?

Next, a sequence s is constructed by choosing the 1st digit as complementary to the 1st digit of s 1 swapping 0 s for 1 s and vice versathe 2nd digit as complementary to the 2nd digit of s 2the 3rd digit as complementary to the 3rd digit of s 3and generally for every nthe n th digit as complementary to the n th digit of s n.

This ccantor is discussed in Joseph DaubenGeorg Cantor: Since T is uncountable, the image of this diagonalizatioj, which is a subset of Ris uncountable. One way to show that the assumption of step 2 is not possible is to find a real number which is not counted there. The number z above is a real number between 0 and 1 and is not paired with any positive integer. Why do we have fantor create a “new real number”?

It explains beforehand for example that the set of odd positive is infinitely countable because it has a one to one correspondence with the natural numbers, which makes sense. This proof proceeds as follows:.