gftool.pade.FilterNegImag¶
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gftool.pade.
FilterNegImag
(threshold=1e-08)[source]¶ 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.