Talk:Gaussian integer

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The norm of a Gaussian integer is the natural number defined as

N(a + bi) = a² + b².

According to MathWorld, this definition should be deprecated. Any information on whether this is actually accepted today, or which authors use which? - Fredrik | talk 22:49, 9 July 2005 (UTC)

I don't see any reason to take this comment on MathWorld seriously, since it just appears to be Eric Weisstein's opinion - he doesn't cite any author to substantiate it, and it doesn't seem to make much sense in the larger context (that is, the norm used for Z[i] happens to be the square of the complex modulus, and so could be replaced by the complex modulus easily enough, but for other rings such as Z[e^2πi/3] the norm is unrelated to the complex modulus, and so cannot be replaced by it). Of course, if you can find a more reputable source than MathWorld for this, then that's another matter. --Zundark 09:05, 10 July 2005 (UTC)

It is the field norm, to be more accurate. Sometimes one wants the square root, for fairly obvious reasons. Charles Matthews 10:15, 10 July 2005 (UTC)

In the paragraph,

If the norm of a Gaussian integer z is a prime number, then z must be a Gaussian prime, since every non-trivial factorization of z would yield a non-trivial factorization of the norm. So for example 2 + 3i is a Gaussian prime since its norm is 4 + 9 = 13. This implies that since there are infinitely many ordinary primes then there must be infinitely many Gaussian primes.

the last sentence assumes that for every ordinary prime, there is a Gaussian integer whose norm is that prime. Surely this is nontrivial to prove.

doesn't that include all the ordinary primes? Gaussian integers with prime norm? :s

No, because 2 is an ordinary prime but is not a Gaussian prime. -- Dominus 10:40, 7 August 2006 (UTC)

Surely the answer is yes? 2 is a Gaussian integer with prime norm (assuming prime means rational primes, which is the usuall assumption to make, although in context the wrong one). Maybe it should be "Gaussian integers with Gaussian prime norm" to avoid abiguity. --PhiJ 18:02, 28 October 2006 (UTC)

[edit] Definition

May I query this: "A Gaussian integer is a complex number whose real and imaginary part are both integers." That can't be right. The imaginary part is by definition some multiple of i. Even where b = 0, the imaginary part is a natural number, but still not an integer. Isn't it more correct to say "a complex number where the real part and the argument of the imaginary part are both integers"? JackofOz 01:53, 13 March 2006 (UTC)

Be careful. The imaginary part of 2+3i is 3, not 3i. Dmharvey 01:55, 13 March 2006 (UTC)

Also, but 0 is an integer, you may be confusing the integers with the positive integers. And you may be confusing modulus with argument, as the argument of any non-zero integer multiple of i is π/2, while its modulus is that integer which you multiplied by i. --PhiJ 16:37, 5 November 2006 (UTC)