5,641 research outputs found
Configuration mixing of angular-momentum projected triaxial relativistic mean-field wave functions
The framework of relativistic energy density functionals is extended to
include correlations related to the restoration of broken symmetries and to
fluctuations of collective variables. The generator coordinate method is used
to perform configuration mixing of angular-momentum projected wave functions,
generated by constrained self-consistent relativistic mean-field calculations
for triaxial shapes. The effects of triaxial deformation and of -mixing is
illustrated in a study of spectroscopic properties of low-spin states in
Mg.Comment: 15 pages, 11 figures, 4 tables, accepted for publication in Phys.
Rev.
Configuration mixing of angular-momentum projected triaxial relativistic mean-field wave functions. II. Microscopic analysis of low-lying states in magnesium isotopes
The recently developed structure model that uses the generator coordinate
method to perform configuration mixing of angular-momentum projected wave
functions, generated by constrained self-consistent relativistic mean-field
calculations for triaxial shapes (3DAMP+GCM), is applied in a systematic study
of ground states and low-energy collective states in the even-even magnesium
isotopes Mg. Results obtained using a relativistic point-coupling
nucleon-nucleon effective interaction in the particle-hole channel, and a
density-independent -interaction in the pairing channel, are compared
to data and with previous axial 1DAMP+GCM calculations, both with a
relativistic density functional and the non-relativistic Gogny force. The
effects of the inclusion of triaxial degrees of freedom on the low-energy
spectra and E2 transitions of magnesium isotopes are examined.Comment: 28 pages, 11 figures and 1 tabl
Relativistic description of nuclear matrix elements in neutrinoless double- decay
Neutrinoless double- () decay is related to many
fundamental concepts in nuclear and particle physics beyond the standard model.
Currently there are many experiments searching for this weak process. An
accurate knowledge of the nuclear matrix element for the decay
is essential for determining the effective neutrino mass once this process is
eventually measured. We report the first full relativistic description of the
decay matrix element based on a state-of-the-art nuclear
structure model. We adopt the full relativistic transition operators which are
derived with the charge-changing nucleonic currents composed of the vector
coupling, axial-vector coupling, pseudoscalar coupling, and weak-magnetism
coupling terms. The wave functions for the initial and final nuclei are
determined by the multireference covariant density functional theory (MR-CDFT)
based on the point-coupling functional PC-PK1. The low-energy spectra and
electric quadrupole transitions in Nd and its daughter nucleus
Sm are well reproduced by the MR-CDFT calculations. The
decay matrix elements for both the
and decays of Nd are evaluated. The effects
of particle number projection, static and dynamic deformations, and the full
relativistic structure of the transition operators on the matrix elements are
studied in detail. The resulting decay matrix element for the
transition is , which gives the most optimistic
prediction for the next generation of experiments searching for the
decay in Nd.Comment: 17 pages, 9 figures; table adde
Beyond the relativistic mean-field approximation (II): configuration mixing of mean-field wave functions projected on angular momentum and particle number
The framework of relativistic self-consistent mean-field models is extended
to include correlations related to the restoration of broken symmetries and to
fluctuations of collective variables. The generator coordinate method is used
to perform configuration mixing of angular-momentum and particle-number
projected relativistic wave functions. The geometry is restricted to axially
symmetric shapes, and the intrinsic wave functions are generated from the
solutions of the relativistic mean-field + Lipkin-Nogami BCS equations, with a
constraint on the mass quadrupole moment. The model employs a relativistic
point-coupling (contact) nucleon-nucleon effective interaction in the
particle-hole channel, and a density-independent -interaction in the
pairing channel. Illustrative calculations are performed for Mg,
S and Ar, and compared with results obtained employing the model
developed in the first part of this work, i.e. without particle-number
projection, as well as with the corresponding non-relativistic models based on
Skyrme and Gogny effective interactions.Comment: 37 pages, 10 figures, submitted to Physical Review
Systematic study of nuclear matrix elements in neutrinoless double-beta decay with a beyond mean-field covariant density functional theory
We report a systematic study of nuclear matrix elements (NMEs) in
neutrinoless double-beta decays with a state-of-the-art beyond mean-field
covariant density functional theory. The dynamic effects of particle-number and
angular-momentum conservations as well as quadrupole shape fluctuations are
taken into account with projections and generator coordinate method for both
initial and final nuclei. The full relativistic transition operator is adopted
to calculate the NMEs. The present systematic studies show that in most of the
cases there is a much better agreement with the previous non-relativistic
calculation based on the Gogny force than in the case of the nucleus Nd
found in Song et al. [Phys. Rev. C 90, 054309 (2014)]. In particular, we find
that the total NMEs can be well approximated by the pure axial-vector coupling
term with a considerable reduction of the computational effort.Comment: 9 pages with 7 figures and 3 table
Spin-orbit and tensor mean-field effects on spin-orbit splitting including self-consistent core polarizations
A new strategy of fitting the coupling constants of the nuclear energy
density functional is proposed, which shifts attention from ground-state bulk
to single-particle properties. The latter are analyzed in terms of the bare
single-particle energies and mass, shape, and spin core-polarization effects.
Fit of the isoscalar spin-orbit and both isoscalar and isovector tensor
coupling constants directly to the f5/2-f7/2 spin-orbit splittings in 40Ca,
56Ni, and 48Ca is proposed as a practical realization of this new programme. It
is shown that this fit requires drastic changes in the isoscalar spin-orbit
strength and the tensor coupling constants as compared to the commonly accepted
values but it considerably and systematically improves basic single-particle
properties including spin-orbit splittings and magic-gap energies. Impact of
these changes on nuclear binding energies is also discussed.Comment: 15 pages, 7 figures, submitted to Physical Review
Anatomy of molecular structures in Ne
We present a beyond mean-field study of clusters and molecular structures in
low-spin states of Ne with a multireference relativistic energy density
functional, where the dynamical correlation effects of symmetry restoration and
quadrupole-octupole shapes fluctuation are taken into account with projections
on parity, particle number and angular momentum in the framework of the
generator coordinate method. Both the energy spectrum and the electric
multipole transition strengths for low-lying parity-doublet bands are better
reproduced after taking into account the dynamical octupole vibration effect.
Consistent with the finding in previous studies, a rotation-induced dissolution
of the O molecular structure in Ne is predicted.Comment: 6 pages with 6 figures, version to be published in Phys. Lett.
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