Continuum effects for many-body correlations in nuclei close to the neutron drip line

Continuum effects for pairing correlations and low-frequency vibrational excitations in nuclei close to the neutron drip line are investigated by use of the coordinate space Hartree-Fock-Bogoliubov and quasiparticle random-phase approximation calculations. It is shown that quasiparticle states with small orbital angular momentum l acquire significant changes of the spatial structure by the pairing correlations and the coupling to continuum states, and they cause the spatially extended distribution of the pairing density that enhances the pairing energy. By a similar mechanism, the spatially extended structure of the two-quasiparticle states among low-l neutrons is realized, and it brings about the strong transition strength of the low-frequency vibrational excitations around the neutron drip line