G. Giansiracusa

Bethe-Brueckner-Goldstone expansion in neutron matter

Abstract The Equation of State of pure neutron matter at zero temperature is calculated up to the three hole-line level of approximation in the Bethe-Brueckner-Goldstone expansion. The calculations are performed for the Av14 and the Av18 nucleon-nucleon potentials, up to the Fermi momentum kF=2.8 fm−1. The three hole-line contribution turns out to be smaller than in symmetric nuclear matter, and indeed a minor correction if the so-called “continuous choice” for the single particle potential is adopted. These findings are in line with the corresponding values of the wound parameter. The results are expected to be relevant for the theory of neutron stars structure.

Nuclear matter with single-particle correlations

Abstract Symmetrical nuclear matter is studied in the vicinity of the saturation point in the framework of an approximation scheme which includes single-particle correlations. The Hugenholtz-Van Hove theorem is well satisfied, in contrast with standard Brueckner calculations. The incompressibility and the saturation points are only slightly affected by correlations, while the effective mass shows an enhancement at the Fermi momentum.

Nuclear matter equation of state with single particle correlations

Abstract Symmetrical nuclear matter at finite temperature is studied in the framework of the Brueckner-Hartree-Fock approximation extended to include single-particle correlations. A liquid-vapor phase transition is observed, wtih a critical temperature of about 20 MeV, in close similarity with Skyrme force calculations. The inclusion of single-particle correlations introduces a significant temperature dependence in the single-particle potential as well as in the nucleon effective mass. In this scheme the Hughenholtz-Van Hove theorem is well satisfied throughout the range of density and temperature considered.

Three hole-line contribution in nuclear matter revisited

Abstract The three-hole line contribution to the Equation of State of symmetric nuclear matter is calculated by solving the Bethe-Fadeev equations within the standard choice for the single particle auxiliary potential. The results, given up to the Fermi momentum k F = 1.8 fm −1 , show satisfactory agreement with the only previous calculation, performed by Day. The corresponding Brueckner-Hartree-Fock calculation, within the continuous choice for the single particle potential, appears to be very close to the full Equation of State which includes also an estimate of the four-hole line contribution.

SINGLE-PARTICLE PROPERTIES IN NEUTRON MATTER FROM EXTENDED BRUECKNER THEORY

Abstract The Brueckner-Hartree-Fock approximation extended to include ground-state correlations is applied to neutron matter. Single-particle properties are calculated including neutron mean field, effective mass and mean free path. The main result is a pronounced enhancement of the effective mass at the Fermi surface whose influence on neutron star properties is discussed.

Momentum distribution and hole strength from a separable representation of the argonne v14 interaction

Abstract The momentum distribution and the quasi-hole strength in symmetric nuclear matter have been calculated for two densities in the framework of the Brueckner-Bethe-Goldstone theory. A separable version of the Argonne v14 has been used as realistic NN interaction in the self-consistent procedure to determine the g -matrix and the corresponding mean field. The results for quasi-hole strength have been compared with other calculations and also with the hole-state spectroscopic factor extracted from recent (e,e′p) knock-out reactions on 90 Zr and 208 Pb. On the basis of the hole-line expansion higher-order contributions to the momentum distribution have been included in the calculations resulting in a better fulfillment of the Migdal-Luttinger theorem.

The limiting temperature of nuclei from a microscopic equation of state of nuclear matter

Abstract A hot nucleus can sustain a maximum temperature before reaching mechanical instability, the so-called limiting temperature T lim . The dependence of T lim on the nuclear equation of state is analyzed by considering different, microscopically founded, equations of state. It is found that the value of T lim can discriminate between different equations of state, even if they have similar critical temperature and compressibility.

Three nucleon correlations in nuclear medium

The equation of state(EOS) of nuclear matter is studied up to the three-hole-line level of approximation in the Behte-Brueckner-Goldstone expansion. The results indicate a good convergence of the theory. The fact that the resulting EOS does not reproduce the empirical saturation point suggests that the three-body forces are most likely the main term missing in the nuclear Hamiltonian.