M. Potthoff et al., INTERPOLATING SELF-ENERGY OF THE INFINITE-DIMENSIONAL HUBBARD-MODEL -MODIFYING THE ITERATIVE PERTURBATION-THEORY, Physical review. B, Condensed matter, 55(24), 1997, pp. 16132-16142
We develop an analytical expression for the self-energy of the infinit
e-dimensional Hubbard model that is correct in a number of different l
imits. The approach represents a generalization of the iterative pertu
rbation theory to arbitrary fillings. In the weak-coupling regime pert
urbation theory to second order in the interaction U is recovered. The
theory is exact in the atomic limit. The high-energy behavior of the
self-energy up to order 1/E-2 and thereby the first four moments of th
e spectral density are reproduced correctly. Referring to a standard s
trong-coupling moment method, we analyze the limit U-->infinity. Diffe
rent modifications of the approach are discussed and tested by compari
ng with the results of an exact diagonalization study.