Photoemission spectral functions from the three-body Green's function

We present an original strategy for the calculation of direct and inverse photo-emission spectra from first principles. The main goal is to go beyond standard Green's function approaches, such as $GW$ method, in order find a good description not only quasiparticles but also satellite structures, which are particular importance strongly correlated materials. To this end we use key quantity three-body function, or, more precisely, its hole-hole-electron electron-electron-hole parts, show how one-body hence corresponding spectral can be retrieved it. that, contrary information about satellites already non-interacting function. Therefore, simple approximations self-energy, defined by Dyson equation contains many-body effects, still yield accurate functions. In particular, self-energy chosen static could simplify self-consistent solution equation. give proof principle our applying it Hubbard dimer, exact available.