[sage-support] Re: Calculating with primitive roots of unity in sage

2012-04-15 Thread Andrew Mathas
> For fields of characteristic p>0, I need to work in GF(p^a) for some a so > I guess that my question really is: does anyone know how to construct the > smallest extension of GF(p) which contains a primitive eth root of unity > when gcd(e,p)=1? > Oops, when I phrase my question this way the

[sage-support] Re: Calculating with primitive roots of unity in sage

2012-04-15 Thread Andrew Mathas
Thanks for the replies! Over other fields it's no good just extending by a root of the n'th > cyclotomic polynomial, since that need not be irreducible! The example you > gave was particularly unfortunate since over GF(5) the 5th cyclotomic poly > has only 1 root with multiplicity 4. So it's

[sage-support] Re: Calculating with primitive roots of unity in sage

2012-04-15 Thread John Cremona
As Volker said, over Q specifically the right thing to do is use CyclotomicField(): sage: K. = CyclotomicField(5) sage: z^5 1 sage: CC(z) 0.309016994374947 + 0.951056516295154*I sage: CC(z) == CC(exp(2*pi*i/5)) True Note that the latter is True because Sage constructs Cyclotomic fields with a sp

[sage-support] Re: Calculating with primitive roots of unity in sage

2012-04-15 Thread Volker Braun
In characteristic zero there is a dedicated CyclotomicField. Presumably this is the most efficient implementation. On Sunday, April 15, 2012 9:53:41 AM UTC-4, Andrew Mathas wrote: > > Hi, > > I was wondering if some one can tell me the most efficient way of doing > calculations with roots of