Hi Martin, I just got around to looking at your code a little.
I recognize your function my_plethysm() because this is simply .coproduct() sage: Sym = SymmetricFunctions(QQ) sage: Sym.inject_shorthands() sage: p([1,1,1]).coproduct() p[] # p[1, 1, 1] + 3*p[1] # p[1, 1] + 3*p[1, 1] # p[1] + p[1, 1, 1] # p[] sage: h([3]).coproduct() h[] # h[3] + h[1] # h[2] + h[2] # h[1] + h[3] # h[] I am not quite sure what your function 'multi_schur' is doing. If you want to evaluate a symmetric function at a difference of alphabets, you should apply the antipode to the second tensor (antipode is the effect of changing X -> -X). I think your change_basis should be in sage and it possibly isn't. For instance, if I type: sage: p.tensor_square()( h([3]).coproduct() ) (which is what I think should be all hell breaks loose. But sage: change_basis([p,p],h([3]).coproduct()) works nicely. -Mike On Tuesday, 17 July 2012 18:29:26 UTC-4, Martin wrote: > > Hi Mike, Nicolas, Viviane, *, > > I implemented naive algorithms to do plethysm and change of basis, > together with some tests from Lascoux' book. I don't really know what > the coproduct should be. I am convinced that one could do much better, > but at least it's a start. (I now see that I should probably have > looked at the implementation of plethysm in sfa first...) > > In particular, one might want to have clever specialisations of > alphabets and also finite alphabets -- probably via include and exclude > as in the single alphabet case. > > (I found it slightly curious to discover that p(X-Y) = 1, by the way.) > > I have absolutely no idea about where to put this in the sources. Help > is much appreciated. > > One other thing: is this actually related to Viviane's work? > > All the best, > > Martin > > -- You received this message because you are subscribed to the Google Groups "sage-combinat-devel" group. To view this discussion on the web visit https://groups.google.com/d/msg/sage-combinat-devel/-/rFiBCAtKriMJ. To post to this group, send email to sage-combinat-devel@googlegroups.com. To unsubscribe from this group, send email to sage-combinat-devel+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sage-combinat-devel?hl=en.
