Zero-sound in nuclear matter with the asymmetry parameter $-1\leq \beta\leq 1$

Abstract

Results for the frequencies of zero-sound excitations in the isospin asymmetric nuclear matter are presented for the different parameters of asymmetry -1\leq\beta\leq 1. The dispersion equations are constructed within the random phase approximation. We use the effective Landau-Migdal quasiparticle interaction with the special isospin dependence of the phase volume in the normalization factor C_0. In the paper we present zero-sound branches of the dispersion equation solutions in the symmetric, asymmetric and neutron matter. The branches correspond to the different channels of decay of the zero-sound excitation in the nuclear matter or nuclei. In the asymmetric nuclear matter we obtain three branches of solutions on the physical and unphysical sheets of the complex frequency plane, \omega_{s\,\tau}(k,\beta), \tau=p,n,np. We demonstrate the change of branches with \beta and conversion of the three branches into two branches in symmetric nuclear matter (\beta=0) and into one branch in the neutron matter (\beta=1).