Δ-Excitations and many-body theory of nuclear matter

J.P. Jeukenne, A Lejeune, Claude Mahaux

M. Harada

Majid Modarres, A. Rajabi, H. R. Moshfegh

It is shown that the method of lowest order constrained variational (LOCV) which is based on the cluster expansion theory is a reliable many-body technique to calculate the nuclear matter equation of state. In this respect, the state dependent correlation functions and the effective interactions which have been produced by the LOCV calculation with the Reid and \ensuremath{\Delta}-Reid soft core interactions are used to estimate the size of higher order cluster terms such as the effect of three-body cluster energy on the nuclear matter ground state energy. Finally it is shown that the LOCV normalization constraint plays a major role in the convergence of the cluster expansion and the result of LOCV calculation can be as good as more sophisticated approaches which go beyond lowest order.

Alexandros Gezerlis, G. F. Bertsch

We recently proposed a nonlocal form for the 3-body induced interaction that is consistent with the Fock space representation of interaction operators but leads to a fractional power dependence on the density. Here we examine the implications of the nonlocality for the excitation spectrum. In the two-component weakly interacting Fermi gas, we find that it gives an effective mass that is comparable to the one in many-body perturbation theory. Applying the interaction to nuclear matter, it predicts a huge enhancement to the effective mass. Since the saturation of nuclear matter is partly due to the induced 3-body interaction, fitted functionals should treat the effective mass as a free parameter, unless the 2- and 3-body contributions are determined from basic theory.

David Pines, Khandker Quader, Jochen Wambach

U. van Kolck

I outline the first steps in the process of describing nuclear groundstates with an expansion around two-body unitarity. At leading order, the effectivefield theory displays discrete scale invariance with a single dimensionful parameter,which determines all ground-state and low-lying excitation energies. Sub-leadingcorrections are smaller and perturbative. Results for light nuclei, large bosonicclusters at unitarity, and nuclear matter are reported.