gftool.pade.FilterNegImag

gftool.pade.FilterNegImag(threshold=1e-08)

Return function to check if imaginary part is smaller than threshold.

This methods is designed to create valid_pades for Averager. The imaginary part of retarded Green’s functions and self-energies must be negative, this is checked by this filter. A threshold is given as Pade overshoots when the function goes sharply to 0. See for example the semi-circular spectral function of the Bethe lattice with infinite Coordination number as example.