Dear All,
I have written a little DMFT code using the ALPS CTQMC impurity solver. The code accepts an arbitrary Hamiltonian (eventually with the goal of doing some form of LDA+DMFT, currently just a model tight-binding Hamiltonian).
Firstly, I was wondering what might be done to address the large amount of noise in the tail of the self energy (after the first 20 or so Matsubara frequencies, the noise is a couple of orders of magnitude larger than the "signal"). I suppose it is not surprising that subtracting the inverses of two small numbers would lead to this sort of thing.
Secondly, the type of lattice (a Bethe lattice by default in the ALPS dmft code) seems to enter into the picture via a set of three constants in the Fourier transforms. For the forward transform, these seem to be boundary terms in a numerical integration-by-parts method. They also appear in the backward transform, although it is less clear to me what their function might be. I was also wondering, if it does not exceed the scope of a mailing list query, if there are other places in the provided dmft code in which the Bethe lattice is tacitly assumed.
Any help would be greatly appreciated.
Regards,
Hunter