Scales in nuclear matter: Chiral dynamics with pion nucleon form factors⋆

Abstract

A systematic calculation of nuclear matter is performed which includes the long-range correlations between nucleons arising from one- and two-pion exchange. Three-body effects from 2π exchange with excitations of virtual Δ(1232)-isobars are also taken into account in our diagrammatic calculation of the energy per particle ¯(k f). In order to eliminate possible high-momentum components from the interactions we introduce at each pion-baryon vertex a form factor of monopole type. The empirical nuclear matter saturation point, ρ0 ≃ 0.16fm^-3, ¯0 ≃ - 16MeV, is well reproduced with a monopole mass of Λ ≃ 4πf π ≃ 1.16GeV. As in the recent approach based on the universal low-momentum NN potential V low-k, the inclusion of three-body effects is crucial in order to achieve saturation of nuclear matter. We demonstrate that the dependence of the pion exchange contributions to ¯(k f) on the “resolution” scale Λ can be compensated over a wide range of Λ by counterterms with two “running” contact couplings. As a further application we study the in-medium chiral condensate 〈¯q〉(ρ) beyond the linear density approximation. For ρ ⩽ 1.5ρ0 we find small corrections from the derivative d¯(k f)/dm π, which are stable against variations of the monopole regulator mass Λ.