# DrestrictionIdeal -- restriction ideal of a D-module

## Synopsis

• Usage:
DrestrictionIdeal(I,w)
• Inputs:
• I, an ideal, which represents the module M = D/I
• w, a list, a weight vector
• Optional inputs:
• Strategy => ..., default value Schreyer,
• Outputs:
• an ideal, the restriction ideal of M w.r.t. the weight vector w

## Description

A supplementary function for Drestriction that computes the restriction ideal.
 i1 : W = QQ[y,t,Dy,Dt, WeylAlgebra => {y=>Dy, t=>Dt}]; i2 : I = ideal(2*t*Dy+Dt, t*Dt+2*y*Dy+2); -- annihilator of 1/(t^2-y) o2 : Ideal of W i3 : DrestrictionIdeal(I, {1,4}) o3 = ideal 1 o3 : Ideal of QQ

## Caveat

The module M should be specializable to the subspace. This is true for holonomic modules.The weight vector w should be a list of n numbers if M is a module over the nth Weyl algebra.