On Tue, Apr 27, 2010 at 12:04 PM, John Cremona <[email protected]> wrote: > Thanks for *not* complaining about the "multiplicative" in "Torsion > Subgroup isomorphic to Multiplicative Abelian Group..." > > I once wrote a patch to fix that but no-one liked it enough. > > I also tried E.change_ring(QQbar).torsion_subgroup() but that failed > for a different reason! For some reason, E.change_ring(Qbar) has this > type: > > > sage: type(E.change_ring(QQbar)) > <class > 'sage.schemes.elliptic_curves.ell_generic.EllipticCurve_generic'> > > while > > sage: type(EllipticCurve(QQbar, E.a_invariants())) > <class 'sage.schemes.elliptic_curves.ell_field.EllipticCurve_field'> > > which is inconsistent; and neither helps, since EllipticCurve_field > objects don't have a torsion subgroup.... > > Some of this should be easy to fix. Assuming that you could do > something useful with the torsion subgroup over QQbar! > > Wait a minute: in what sense is the torsion subgroup of J_0(11) of > structure [5,5] anyway? Over Q it is cyclic of order 5, while over > QQbar it is (Q/Z)^2 . So the output is worse than you thought!
He wrote: sage: A.torsion_subgroup(5) Finite subgroup with invariants [5, 5] over QQ of Abelian variety J0(11) of dimension 1 In general, A.torsion_subgroup(n), gives "the n-torsion subgroup". william -- To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
