Enhanced stability beyond the neutron drip-line near the third peak of r-process nucleosynthesis in the deformed relativistic Hartree-Bogoliubov theory

We have investigated the shell structure of nuclei in the region of the $r$-process path beyond $N=126$. Employing the framework of the relativistic Hartree-Bogoliubov theory in deformed space, ground-state properties of nuclei with $Z=58-68$ in the highly neutron-rich region beyond $N=126$ have been explored. It is shown that in approaching the $r$-process path above $N=126$, nuclei in several isotopic chains ($Z > 60$) exhibit enhanced stability. This shifts the expected drip line significantly farther into the neutron-rich region. A large number of nuclides near the $r$-process path are shown to exhibit a coexistence of well-deformed prolate and oblate shapes in the ground state. Consequences of the enhanced stability and the shape coexistence on the $r$-process nucleosynthesis will be discussed.