Collective modes in hot asymmetric nuclear matter at variable densities Original Research Article

A nearly exact expression for the response function of hot asymmetric nuclear matter is derived for Skyrme type effective interactions and the resulting strength distribution is analyzed for the four channels of the particle–hole interaction. Several proton–neutron asymmetries are considered as well as different total densities. In the isovector channel the strength presents a very collective behaviour (zero sound type) which becomes still more collective with increasing asymmetry. For higher nuclear densities it may be collective or unstable depending on the effective interaction. This is also the behaviour for the spin-isospin channel. The other channels may have the collectivity increased for a highly asymmetric nuclear matter at higher densities. In the spin channel zero sound modes are found for higher enough p-n asymmetries and/or densities higher than the saturation density. The static limit of the polarizabilities are considered yielding the symmetry energy coefficients for isovector, spin and spin-isospin channels. The dependence of the polarizabilities on p-n asymmetry is analyzed, in particular in the isovector channel which is of interest, for example, for the supernovae mechanism.