Incompressibility of asymmetric nuclear matter

摘要

Using an isospin- and momentum-dependent modified Gogny (MDI) interaction, the Skyrme-Hartree-Fock (SHF) approach, and a phenomenological modified Skyrme-like (MSL) model, we have studied the incompressibility K _(sat)(δ) of isospin asymmetric nuclear matter at its saturation density. Our results show that in the expansion of K_(sat)(δ) in powers of isospin asymmetry δ, i.e., K_(sat)(δ) = K _0 + K_(sat,2)δ~2 + K _(sat,4)δ~4 + O(δ~6), the magnitude of the 4th-order K_(sat,4) parameter is generally small. The 2nd-order K_(sat,2) parameter thus essentially characterizes the isospin dependence of the incompressibility of asymmetric nuclear matter at saturation density. Furthermore, the K_(sat,2) can be expressed as K _(sat,2) = K_(sym) - 6L - J_0/K_0L in terms of the slope parameter L and the curvature parameter K_(sym) of the symmetry energy and the third-order derivative parameter J_0 of the energy of symmetric nuclear matter at saturation density, and we find the higher order J_0 contribution to K_(sat,2) generally cannot be neglected. Also, we have found a linear correlation between K_(sym) and L as well as between J_0/K_0 and K_0. Using these correlations together with the empirical constraints on K_0 and L, the nuclear symmetry energy E_(sym)(ρ0) at normal nuclear density, and the nucleon effective mass, we have obtained an estimated value of K _(sat,2) = -370 ± 120 MeV for the 2nd-order parameter in the isospin asymmetry expansion of the incompressibility of asymmetric nuclear matter at its saturation density.