Giant monopole resonances in nuclei near stable and drip lines

Isoscalar and isovector monopole responses of Ca isotopes towards drip lines are studied in comparison with those of stable nuclei, Ca-40, Zr-90, and Pb-208, using the self-consistent Hartree-Fock calculation plus the random phase approximation with Skyrme interactions. Including simultaneously both the isoscalar and the isovector correlation the RPA response function is calculated in the coordinate space so as to take properly into account the continuum effect. The distribution of the monopole strength is much affected by the presence of the low-energy threshold strength in both proton and neutron drip line nuclei, while the isoscalar monopole strength is concentrated in one giant peak in the heavy beta-stable nucleus Pb-208. It is found that in drip line nuclei the transition density and the displacement field of protons are very different from those of neutrons, especially around the nuclear surface. The relation between the compression modulus of the nuclear matter K-nm and that of finite nuclei K-A is also discussed by using the energy moments estimated in RPA.