Introduction

Support forward and backward fourier transformation. We usually use the following subroutines to perform fourier transformation for the Green's function.

Type

subroutines

Source

src/s_fourier.f90

Usage

(1) Forward FFT, from $G(\tau) \to G(i\omega_n)$.

subroutine s_fft_forward(ntime, tmesh, ftau, mfreq, rmesh, fmat)

(2) Backward FFT, from $G(i\omega_n) \to G(\tau)$.

subroutine s_fft_backward(mfreq, rmesh, fmat, ntime, tmesh, ftau, beta)

Here, ntime is number of imaginary time points, tmesh means $\tau$, ftau means $G(\tau)$, mfreq is number of Matsubara frequency points, rmesh means $\omega_n$, fmat means $G(i\omega_n)$, beta means inverse temperature of system $\beta$.