315 research outputs found
Beyond-mean-field-model analysis of low-spin normal-deformed and superdeformed collective states of S32, Ar36, Ar38 and Ca40
We investigate the coexistence of spherical, deformed and superdeformed
states at low spin in S32, Ar36, Ar38 and Ca40. The microscopic states are
constructed by configuration mixing of BCS states projected on good particle
number and angular momentum. The BCS states are themselves obtained from
Hartree-Fock BCS calculations using the Skyrme interaction SLy6 for the
particle-hole channel, and a density-dependent contact force in the pairing
channel. The same interaction is used within the Generator Coordinate Method to
determine the configuration mixing and calculate the properties of even-spin
states with positive parity. Our calculations underestimate moments of inertia.
Nevertheless, for the four nuclei, the global structural properties of the
states of normal deformation as well as the recently discovered superdeformed
bands up to spin 6 are correctly reproduced with regard to both the energies
and the transition rates.Comment: 14 pages revtex4, 15 eps figures, 8 table
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 (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.Comment: 24 pages, 3 figure
Systematics of quadrupolar correlation energies
We calculate correlation energies associated with the quadrupolar shape
degrees of freedom with a view to improving the self-consistent mean-field
theory of nuclear binding energies. The Generator Coordinate Method is employed
using mean-field wave functions and the Skyrme SLy4 interaction. Systematic
results are presented for 605 even-even nuclei of known binding energies, going
from mass A=16 up to the heaviest known. The correlation energies range from
0.5 to 6.0 MeV in magnitude and are rather smooth except for large variations
at magic numbers and in light nuclei. Inclusion of these correlation energies
in the calculated binding energy is found to improve two deficiencies of the
Skyrme mean field theory. The pure mean field theory has an exaggerated shell
effect at neutron magic numbers and addition of the correlation energies reduce
it. The correlations also explain the phenomenon of mutually enhanced magicity,
an interaction between neutron and proton shell effects that is not explicable
in mean field theory.Comment: 4 pages with 3 embedded figure
Large-amplitude Qn-Qp collectivity in the neutron-rich oxygen isotope 20O
By means of HFB calculations with independent constraints on axial neutron
and proton quadrupole moments Q_n and Q_p, we investigate the large amplitude
isoscalar and isovector deformation properties of the neutron-rich isotope 20O.
Using the particle-number and angular-momentum projected Generator Coordinate
Method, we analyze the collective dynamics in the {Q_n, Q_p} plane. The
parameterization SLy4 of the Skyrme interaction is used for all calculations in
connection with a density-dependent zero-range pairing interaction. Our results
show that already for this moderately neutron-rich nucleus the transition
moments are modified when independent neutron and proton collective dynamics
are allowed.Comment: 8 pages REVTEX, 5 eps figure
GCM Analysis of the collective properties of lead isotopes with exact projection on particle numbers
We present a microscopic analysis of the collective behaviour of the lead
isotopes in the vicinity of Pb208. In this study, we rely on a coherent
approach based on the Generator Coordinate Method including exact projection on
N and Z numbers within a collective space generated by means of the constrained
Hartree-Fock BCS method. With the same Hamiltonian used in HF+BCS calculations,
we have performed a comprehensive study including monopole, quadrupole and
octupole excitations as well as pairing vibrations. We find that, for the
considered nuclei, the collective modes which modify the most the conclusions
drawn from the mean-field theory are the octupole and pairing vibrations.Comment: 10 pages LATEX, 8 figures, submitted to EPJ
Pairing correlations. Part 1: description of odd nuclei in mean-field theories
In order to extract informations on pairing correlations in nuclei from
experimental mass differences, the different contributions to odd-even mass
differences are investigated within the Skyrme HFB method. In this first paper,
the description of odd nuclei within HFB is discussed since it is the key point
for the understanding of the above mentioned contributions. To go from an even
nucleus to an odd one, the advantage of a two steps process is demonstrated and
its physical content is discussed. New results concerning time-reversal
symmetry breaking in odd-nuclei are also reported.
PACS: 21.10Dr; 21.10.Hw; 21.30.-x.
Keywords: Mean-field theories; Pairing correlations; odd nuclei;Comment: 34 pages, 8 figures. Submitted to Phys. Rev.
Symmetry restoration for odd-mass nuclei with a Skyrme energy density functional
In these proceedings, we report first results for particle-number and
angular-momentum projection of self-consistently blocked triaxial
one-quasiparticle HFB states for the description of odd-A nuclei in the context
of regularized multi-reference energy density functionals, using the entire
model space of occupied single-particle states. The SIII parameterization of
the Skyrme energy functional and a volume-type pairing interaction are used.Comment: 8 pages, 3 figures, workshop proceeding
Microscopic models for exotic nuclei
Starting from successful self-consistent mean-field models, this paper
discusses why and how to go beyond the mean field approximation. To include
long-range correlations from fluctuations in collective degrees of freedom, one
has to consider symmetry restoration and configuration mixing, which give
access to ground-state correlations and spectroscopy.Comment: invited talk at ENAM0
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