Correlation between Zero-Sound modes and nuclear equation of state stiffness detected by light vector boson*

Abstract We investigate zero-sound modes in nuclear matter and neutron star matter using the relativistic random phase approximation (RRPA), focusing on the role of a light vector U boson in stiffening the nuclear equation of state (EOS). The occurrence of zero sound is closely linked to the stiffness of the nuclear EOS. The additional vector repulsive potential induced by the U boson results in the occurrence of zero sound at high densities in models with a soft high-density EOS, and the density range for zero sound extends to higher densities with larger coupling strength of the U boson. This confirms the unambiguous role of stiffening the high-density EOS in resulting in the appearance of zero sound.