Description
The derived restriction modules of a Dmodule M are the derived inverse images in the sense of algebraic geometry but in the category of Dmodules. This routine computes restrictions to coordinate subspaces, where the subspace is determined by the strictly positive entries of the weight vector
w, e.g.,
{x_i = 0 : w_i > 0} if
D = C<x_1,...,x_n,d_1,...,d_n>. The input weight vector should be a list of
n numbers to induce the weight
(w,w) on
D.
The algorithm used appears in the paper 'Algorithms for Dmodules' by OakuTakayama(1999). The method is to compute an adapted resolution with respect to the weight vector w and use the bfunction with respect to w to truncate the resolution.
i1 : R = QQ[x_1,x_2,D_1,D_2,WeylAlgebra=>{x_1=>D_1,x_2=>D_2}]
o1 = R
o1 : PolynomialRing, 2 differential variable(s)

i2 : I = ideal(x_1, D_21)
o2 = ideal (x , D  1)
1 2
o2 : Ideal of R

i3 : Drestriction(I,{1,0})
o3 = HashTable{0 => 0 }
1 => cokernel  D_21 
o3 : HashTable
