Branches of zero sound excitations in asymmetric nuclear matter: The dependence on density

Abstract

Results from calculating zero sound excitations in isospin asymmetric nuclear matter are presented. A polarization operator constructed in the random phase approximations is used in the calculations. Three branches of the complex solutions ω_sτ(k), τ = p,n,np are presented. The type of branch depends on that of the considered branch damping. An imaginary part of the solution corresponds to the damping of collective excitations due to mixing with the background of noninteracting (1) proton particle–hole pairs (ω_sp(k)), (2) neutron particle–hole pairs (ω_sn(k)), and (3) both proton and neutron particle–hole pairs (ω_snp(k)). The behavior of the solutions upon variations in density depends on the value of the asymmetry parameter.