The problem of analytic continuation of the many-body scattering amplitude associated with a perturbation-theory diagram under the rotation of the final momenta from real to complex momenta, k -.. (1 + iO)k, is studied. It is shown that the contour of integration over internal momenta can be distorted avoiding singularities of the integrand, as 0 varies for small enough O. If the diagram is con...

We develop the general many-body perturbation theory for a superconducting quantum dot represented by single-impurity Anderson model attached to leads. build our approach on thermodynamically consistent mean-field approximation with two-particle self-consistency of parquet type. The leading screening bare interaction proves substantial suppressing spurious transitions Hartree-Fock solution. dem...

During the past years, one of most iconic metal-organic frameworks (MOFs), MOF-5, has been characterized as a semiconductor by theory and experiments. Here we employ GW many-body perturbation in conjunction with Bethe-Salpeter equation to compute electronic structure optical properties this MOF. The calculations show that MOF-5 is wide-band-gap insulator fundamental gap ?8 eV. strong excitonic ...