V. Hellemans

Tensor part of the Skyrme energy density functional. III. Time-odd terms at high spin

We systematically study the effect of the J^2 tensor terms in the Skyrme energy functional on properties of spherical nuclei. We build a set of 36 parameterizations covering a wide range of the corresponding parameter space. We analyze the impact of the tensor terms on the evolution of single-particle-level splittings along chains of semi-magic nuclei in spherical calculations. We find that positive values of the coupling constants of proton-neutron and like-particle tensor terms allow for a qualitative description of the evolution of neutron and proton single-particle level splittings in chains of Ca, Ni and Sn isotopes.

Fitting Skyrme functionals using linear response theory

It has recently been shown that the linear response theory in symmetric nuclear matter can be used as a tool for detecting finite-size instabilities for different Skyrme functionals. In particular, it has been shown that there is a correlation between the density at which instabilities occur in infinite matter and the instabilities in finite nuclei. In this paper, we present a new fitting protocol that uses this correlation to add a new additional constraint in symmetric infinite nuclear matter in order to ensure the stability of finite nuclei against matter fluctuation in all spin and isospin channels. As an application, we give the parameter set for a new Skyrme functional which includes central and spin–orbit parts and which is free from instabilities by construction.

Spurious finite-size instabilities in nuclear energy density functionals

Background: It is known that some well established parametrizations of the nuclear energy density functional (EDF) do not always lead to converged results for nuclei. Earlier studies point towards the existence of a qualitative link between this finding and the appearance of finite-size instabilities of symmetric nuclear matter (SNM) near saturation density when computed within the random phase approximation (RPA). Purpose: We aim to establish a stability criterion based on computationally friendly RPA calculations that can be incorporated into fitting procedures of the coupling constants of the EDF. Therefore, a quantitative and systematic connection between the impossibility to converge self-consistent calculations of nuclei and the occurrence of finite-size instabilities in SNM is investigated for the scalar-isovector (S=0, T=1) instability of the standard Skyrme EDF. Results: Tuning the coupling constant C1ρΔρ of the gradient term that triggers scalar-isovector instabilities of the standard Skyrme EDF, we find that the occurrence of instabilities in finite nuclei depends strongly on the numerical scheme used to solve the self-consistent mean-field equations. Once the critical value of the coupling constant C1ρΔρ is determined in nuclei, one can extract the corresponding lowest density ρcrit at which a pole appears at zero energy in the RPA response function. Conclusions: Instabilities of finite nuclei can be artificially hidden due to the choice of inappropriate numerical schemes or overly restrictive, e.g., spherical, symmetries. Our analysis suggests a twofold stability criterion to avoid scalar-isovector instabilities.

Solution of the Skyrme–HF+BCS equation on a 3D mesh, II: A new version of the Ev8 code

We describe a new version of the Ev8 code that solves the nuclear Skyrme–Hartree–Fock+BCS problem using a 3-dimensional cartesian mesh. Several new features have been implemented with respect to the earlier version published in 2005. In particular, the numerical accuracy has been improved for a given mesh size by (i) implementing a new solver to determine the Coulomb potential for protons, and (ii) implementing a more precise method to calculate the derivatives on a mesh that had already been implemented earlier in our beyond-mean-field codes. The code has been made very flexible to enable the use of a large variety of Skyrme energy density functionals that have been introduced in the last years. Finally, the treatment of the constraints that can be introduced in the mean-field equations has been improved. The code Ev8 is today the tool of choice to study the variation of the energy of a nucleus from its ground state to very elongated or triaxial deformations with a well-controlled accuracy.

Platinum nuclei: Concealed configuration mixing and shape coexistence

The role of configuration mixing in the Pt region is investigated. For this chain of isotopes, the nature of the ground state changes smoothly, being spherical around mass

New parametrization of Skyrme's interaction for regularized multireference energy density functional calculations

A~174

Quadrupole collective variables in the natural Cartan–Weyl basis

and

A theoretical description of energy spectra and two-neutron separation energies for neutron-rich zirconium isotopes

A~192

Configuration mixing in 188Pb: Band structure and electromagnetic properties

and deformed around the midshell

Generalized seniority with realistic interactions in open-shell nuclei

N=104