Talk:Cyclotomic field

Properties

That is not always a normal basis. Any linear dependence among them would kill their ability to form a normal basis. Linear dependences of the form a+b=0 occur whenever n is a multiple of 4, since then 1 + n/2 is relatively prime to n and the 1 + n/2 power of any primitive nth root of unity is just its additive inverse. (This example can be generalized to n whenever n is not squarefree; then one gets products of a primitive nth root of unity with all pth roots of unity adding up to 0, whenever p is prime and p^2 | n.)

DavidLHarden (talk) 05:39, 17 April 2008 (UTC)[reply]

Fermat's last theorem

You'll want to add that the factorization you gave of x^n + y^n is only valid for when n is a prime number

Actually the factorization as given is valid iff n is odd. RJChapman 15:11, 14 August 2007 (UTC)[reply]

By chance did something related and then asked myself the same question, for an even n we have x^n - y^n = the product. See also here: https://math.stackexchange.com/q/2334063/4414 Jan Burse (talk) 21:19, 23 June 2017 (UTC)[reply]

The question is answered there and is not particularly relevant to this article. 67.198.37.16 (talk) 18:40, 6 October 2020 (UTC)[reply]

Gaussian rational

The article Gaussian rational states nothing unique for Q(ζ₄) among others Q(ζ_n). Any cyclotomic field is "neither ordered nor topologically complete", is "an example of an algebraic number field" and "a Galois extension of the field of rational numbers". Q(ζ₄) is a quadratic field, but Q(ζ₃) also is Q(√−3). Surely, its ring of integers has an independent notability, but Q(ζ₃) has a notable ring of integers too. Has that article to be merged here to avoid virtually a duplicate description? Incnis Mrsi (talk) 19:38, 24 January 2012 (UTC)[reply]

As of 2015, a section on Ford Spheres was added. This seems not to be a property held in common with other cyclotomic fields, and thus, the merge suggestion evaporates. 67.198.37.16 (talk) 18:35, 6 October 2020 (UTC)[reply]