PDF file with an explanation of FT theory one can find here.
SCHEME N1 (the best):
Practical implementation if FT routine is based on standart Numerical Receipes (NR) routine which simply solves the system of equations (2) (see PDF file) with known boundary conditions G'(0) and G'(n) i.e. one has to know the first derivatives at the boundaries.
To find those derivatives one has to use Eq.(16) .
The practical implementation of FT is based on two routines
The inverse FT is also describes in the PDF file and corresponding Fortran routine name is InvFourierNew.
SCHEME N2 (still quite good):
Another way to make FT in QMC program is via moments. IT is given via solution of the system of Eqs.(3) with the moments Eqs.(11)-(13) (or Eqs.(14)-(15) in the SU(N) case).
The practical implementation of FT is also based on two routines:
SCHEME N3 (the worst):
The natural spline routines have names nfourier and invfourier for the direct and inverse FT correspondingly.
Last updated: June 23, 2003