##### 7.7.5.0. inverseFourier

Procedure from library `dmodapp.lib` (see dmodapp_lib).

Usage:
  inverseFourier(I[,v]); I an ideal, v an optional intvec

Return:
  ideal

Purpose:
  computes the inverse Fourier transform of an ideal in a Weyl algebra

Assume:
  The basering is the n-th Weyl algebra over a field of characteristic 0
  and for all 1<=i<=n the identity var(i+n)*var(i)=var(i)*var(i+1)+1
  holds, i.e. the sequence of variables is given by
  x(1),...,x(n),D(1),...,D(n), where D(i) is the differential operator
  belonging to x(i).

Note:
  The Fourier automorphism is defined by mapping x(i) to -D(i) and
  D(i) to x(i).
  If v is an intvec with entries ranging from 1 to n, the inverse Fourier
  transform of I restricted to the variables given by v is computed.

Example:

    LIB "dmodapp.lib";
    ring r = 0,(x,y,Dx,Dy),dp;
    def D2 = Weyl();
    setring D2;
    ideal I = x*Dx+2*y*Dy+2, x^2*Dx+y*Dx+2*x;
    intvec v = 2;
    ideal FI = fourier(I);
    inverseFourier(FI);
    ==> _[1]=x*Dx+2*y*Dy+2
    ==> _[2]=x^2*Dx+y*Dx+2*x

See also: fourier.

User manual for Singular version 4-0-3, 2016, generated by texi2html.