A NUCLEON IN THE NUCLEAR MEDIUM - A TALE OF ALL ENERGIES

Although the conventional shell model approach has been successful in describing low-energy nuclear phenomena based on a realistic interaction between nucleons, several important shortcomings have become apparent as well. These shortcomings provide the motivation to employ the self-consistent Green's function (SCGF) method which can overcome these problems. Additional inspiration for the use of this method is provided by recent exclusive electron scattering results which involve the ejection of a proton from the nucleus. Such experiments have established quantitative information on the distribution of single-particle (sp) removal strength which is theoretically described in terms of the sp Green's function. The distribution of the experimental sp strength displays properties of the nucleus that can be brought into one-to-one correspondence with Fermi Liquid properties of infinite homogeneous systems. Theoretical calculations of the sp Green's function in finite nuclei are discussed which establish these ''Fermi Liquid'' properties by including the coupling of sp motion to more complicated states in an energy domain of about 100 MeV around the Fermi energy. Although sufficient to explain the shape of the experimental strength distributions, these calculations need to be supplemented by the inclusion of the coupling to even higher energy states for quantitative agreement. Such calculations are reported for nuclear matter. These results clearly establish the importance of the coupling between low-lying sp states and very high-lying two-particle-one-hole states. This coupling is provided within the constraints of nonrelativistic many-particle theory by the use of a strongly repulsive realistic interaction between nucleons. Including both experimental and theoretical results, it is possible to pinpoint the properties of the 3s1/2 proton spectral function in Pb-208. In addition, it is possible to compare the strength of nuclear correlations in terms of occupation numbers, with those of other Fermi systems with weaker (atoms) or stronger (liquid He-3) correlations.