Halos in medium-heavy and heavy nuclei with covariant density functional theory in continuum

The covariant density functional theory with a few number of parameters has been widely used to describe the ground-state and excited-state properties for the nuclei all over the nuclear chart. In order to describe exotic properties of unstable nuclei, the contribution of the continuum and its coupling with bound states should be treated properly. In this Topical Review, the development of the covariant density functional theory in continuum will be introduced, including the relativistic continuum Hartree-Bogoliubov theory, the relativistic Hartree-Fock-Bogoliubov theory in continuum, and the deformed relativistic Hartree-Bogoliubov theory in continuum. Then the descriptions and predictions of the neutron halo phenomena in both spherical and deformed nuclei will be reviewed. The diffuseness of the nuclear potentials, nuclear shapes and density distributions, and the impact of the pairing correlations on nuclear size will be discussed.Comment: 63 pages; Topical Review, J. Phys. G (in press

Microscopic self-consistent description of induced fission dynamics: finite temperature effects

The dynamics of induced fission of $^{226}$Th is investigated in a theoretical framework based on the finite-temperature time-dependent generator coordinate method (TDGCM) in the Gaussian overlap approximation (GOA). The thermodynamical collective potential and inertia tensor at temperatures in the interval $T=0 - 1.25$ MeV are calculated using the self-consistent multidimensionally constrained relativistic mean field (MDC-RMF) model, based on the energy density functional DD-PC1. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. Constrained RMF+BCS calculations are carried out in the collective space of axially symmetric quadrupole and octupole deformations for the asymmetric fissioning nucleus $^{226}$Th. The collective Hamiltonian is determined by the temperature-dependent free energy surface and perturbative cranking inertia tensor, and the TDGCM+GOA is used to propagate the initial collective state in time. The resulting charge and mass fragment distributions are analyzed as functions of the internal excitation energy. The model can qualitatively reproduce the empirical triple-humped structure of the fission charge and mass distributions already at $T=0$, but the precise experimental position of the asymmetric peaks and the symmetric-fission yield can only be accurately reproduced when the potential and inertia tensor of the collective Hamiltonian are determined at finite temperature, in this particular case between $T=0.75$ MeV and $T=1$ MeV.Comment: 9 pages, 7 figure