On 11 September 2012 13:13, Volker Braun <[email protected]> wrote: > On Tuesday, September 11, 2012 1:03:43 PM UTC+1, John Cremona wrote: >> >> Volker, will you also include what I call seminvariants? > > > Whats a semi-invariant to you? The leading term of a covariant? >
Precisely. > sage: R.<a0, a1, a2, a3, a4, x0, x1> = QQ[] > sage: quadric = > invariant_theory.binary_quartic(a0*x1^4+4*a1*x0*x1^3+6*a2*x0^2*x1^2+4*a3*x0^3*x1+a4*x0^4, > x0, x1) > sage: quadric.g_covariant().lt() > a3^2*x0^4 > > I don't think they should be methods of polynomials; Is x a linear > homogeneous or quadratic inhomogeneous term? > OK, as long as the covariants are there I can extract them. Your example above reveals another little issue: you put in the binomial coeffients, while sometimes one prefers not to. I think the fancy way to say this is that there is more than one integral representation for the same rational representation (OK, so there are fancier ways to say it than that). So it would be nice if that could be speicified by the user (and I will not argue as to which should be the default). John > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > Visit this group at http://groups.google.com/group/sage-devel?hl=en. > > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-devel?hl=en.
