On Wednesday, May 7, 2014 9:58:48 AM UTC-7, François Colas wrote: > > What I want to do is a way to evaluate polynomials of K in a power of a > primitive square root of unity: > > omega = CC(e^(2*I*pi/m)) > F = Hom(K, CC) > f = F([omega]) > TypeError: images do not define a valid homomorphism > > Does anyone see another way to do this? > Have you tried using CyclotomicField(m) ? I think that uses specialized code, which should handle high degrees much better than generic number field code:
sage: K=CyclotomicField(3*5*7*11) sage: K.coerce_embedding() Generic morphism: From: Cyclotomic Field of order 1155 and degree 480 To: Complex Lazy Field Defn: zeta1155 -> 0.9999852033056930? + 0.00543996044764063?*I Alternatively, if you really want to use an explicit quotient ring construction: f = F([omega],check=False) The error you run into otherwise is: sage: sage.rings.morphism.RingHomomorphism_im_gens(H,[omega]) ValueError: relations do not all (canonically) map to 0 under map determined by images of generators. i.e., the cyclotomic polynomial evaluated at omega doesn't return an exact zero, because CC uses float arithmetic. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
