Third-order perturbation calculations in nuclear matter for realistic potentials

The particle-ladder diagrams up to third order in the basic interaction are calculated for nuclear matter with some recent local soft-core potentials. A detailed comparison to the G-matrix results is carried out. The prescription of zero potential energy for states above the Fermi sea is used. For the de Tourreil-Sprung (dTS) interaction the total third order contribution is 17% of the second order. The de Tourreil-Rouben-Sprung (TRS) potential shows poor convergence in the triplet-odd subspace. A new set of triplet-odd parameters is defined, and the overall convergence for the modified TRS is only slightly less rapid than that for dTS.