287 research outputs found
Solution of the Skyrme-Hartree-Fock equations in the Cartesian deformed harmonic oscillator basis. (I) The method
We describe a method of solving the nuclear Skyrme-Hartree-Fock problem by
using a deformed Cartesian harmonic oscillator basis. The complete list of
expressions required to calculate local densities, total energy, and
self-consistent fields is presented, and an implementation of the
self-consistent symmetries is discussed. Formulas to calculate matrix elements
in the Cartesian harmonic oscillator basis are derived for the nuclear and
Coulomb interactions.Comment: 26 LaTeX pages, submitted to Computer Physics Communication
Effects of spin-orbit interaction on nuclear response and neutrino mean free path
The effects of the spin-orbit component of the particle-hole interaction on
nuclear response functions and neutrino mean free path are examined. A complete
treatment of the full Skyrme interaction in the case of symmetric nuclear
matter and pure neutron matter is given. Numerical results for neutron matter
are discussed. It is shown that the effects of the spin-orbit interaction
remain small, even at momentum transfer larger than the Fermi momentum. The
neutrino mean free paths are marginally affected
Bulk properties of rotating nuclei and the validity of the liquid drop model at finite angular momenta
Out of self-consistent semi-classical calculations performed within the
so-called Extended Thomas-Fermi approach for 212 nuclei at all even angular
momentum values I ranging between 0 and 80 \hbar and using the Skyrme SkM*
effective force, the I-dependence of associated liquid drop model parameters
has been studied. The latter have been obtained trough separate fits of the
calculated values of the strong interaction as well as direct and exchange
Coulomb energies. The theoretical data basis so obtained, has allowed to make a
rough quantitative assessment of the variation with I of the usual volume and
surface energy parameters up to spin of \sim 30-40 \hbar. As a result of the
combined variation of the surface and Coulomb energies, it has been shown that
this I-dependence results in a significant enhancement of the fission stability
of very heavy nuclei, balancing thus partially the well-known instability due
to centrifugal forces.Comment: 27 pages, LaTeX (elsart) with 13 embeded postscript figure
Particles in classically forbidden area, neutron skin and halo, and pure neutron matter in Ca isotopes
The nucleon density distributions and the thickness of pure neutron matter in
Ca isotopes were systematically studied using the Skyrme-Hartree-Fock model
(SHF) from the -stability line to the neutron drip-line. The pure
neutron matter, related with the neutron skin or halo, was shown to depend not
only on the Fermi levels of the neutrons but also on the orbital angular
momentum of the valence neutrons. New definitions for the thickness of pure
neutron matter are proposed.Comment: 6 pages, 5 figure
Microscopic Transport Theory of Nuclear Processes
We formulate a microscopic theory of the decay of a compound nucleus through
fission which generalizes earlier microscopic approaches of fission dynamics
performed in the framework of the adiabatic hypothesis. It is based on the
constrained Hartree-Fock-Bogoliubov procedure and the Generator Coordinate
Method, and requires an effective nucleon-nucleon interaction as the only input
quantity. The basic assumption is that the slow evolution of the nuclear shape
must be treated explicitely, whereas the rapidly time-dependent intrinsic
excitations can be treated by statistical approximations. More precisely, we
introduce a reference density which represents the slow evolution of the
nuclear shape by a reduced density matrix and the state of intrinsic
excitations by a canonical distribution at each given shape of the nucleus. The
shape of the nuclear density distribution is described by parameters
("generator coordinates"), not by "superabundant" degrees of freedom introduced
in addition to the complete set of nucleonic degrees of freedom. We first
derive a rigorous equation of motion for the reference density and,
subsequently, simplify this equation on the basis of the Markov approximation.
The temperature which appears in the canonical distribution is determined by
the requirement that, at each time t, the reference density should correctly
reproduce the mean excitation energy at given values of the shape parameters.
The resulting equation for the "local" temperature must be solved together with
the equations of motion obtained for the reduced density matrix.Comment: 33 pages, accepted in Nucl. Phys.
Instabilities of infinite matter with effective Skyrme-type interactions
The stability of the equation of state predicted by Skyrme-type interactions
is examined. We consider simultaneously symmetric nuclear matter and pure
neutron matter. The stability is defined by the inequalities that the Landau
parameters must satisfy simultaneously. A systematic study is carried out to
define interaction parameter domains where the inequalities are fulfilled. It
is found that there is always a critical density beyond which the
system becomes unstable. The results indicate in which parameter regions one
can find effective forces to describe correctly finite nuclei and give at the
same time a stable equation of state up to densities of 3-4 times the
saturation density of symmetric nuclear matter.Comment: 20 pages, 5 figures, submitted to Phys.Rev.
Resonant continuum in the Hartree-Fock+BCS approximation
A method for incorporating the effect of the resonant continuum into
Hartree-Fock+BCS equations is proposed. The method is applied for the case of
a neutron-rich nucleus calculated with a Skyrme-type force plus a zero-range
pairing interaction and the results are compared with
Hartree-Fock-Bogoliubov calculations. It is shown that the widths of resonant
states have an important effect on the pairing properties of nuclei close to
the drip line.Comment: 9 pages, 2 figures, comparison with HFB adde
Generalized routhian calculations within the Skyrme-Hartree-Fock approximation
We consider here variational solutions in the Hartree-Fock approximation upon
breaking time reversal and axial symmetries. When decomposed on axial harmonic
oscillator functions, the corresponding single particle triaxial eigenstates as
functions of the usual cylindrical coordinates (r, , z) are evaluated
on a mesh in r and z to be integrated within Gauss-Hermite and Gauss-Laguerre
approaches and as Fourier decompositions in the angular variable .
Using an effective interaction of the Skyrme type, the Hartree-Fock hamiltonian
is also obtained as a Fourier series allowing a two dimensional calculation of
its matrix elements. This particular choice is shown to lead in most cases to
shorter computation times compared to the usual decomposition on triaxial
harmonic oscillator states. We apply this method to the case of the
semi-quantal approach of large amplitude collective motion corresponding to a
generalized routhian formalism and present results in the A=150 superdeformed
region for the coupling of global rotation and intrinsic vortical modes in what
is known after Chandrasekhar as the S-ellipsoid coupling case.Comment: LaTeX using elsart, 32 pages, 4 included figures, submitted to
Nuclear Physics A (revised version
Isospin Dependence of the Spin-Orbit Force and Effective Nuclear Potentials,
The isospin dependence of the spin-orbit potential is investigated for an
effective Skyrme-like energy functional suitable for density dependent
Hartree-Fock calculations. The magnitude of the isospin dependence is obtained
from a fit to experimental data on finite spherical nuclei. It is found to be
close to that of relativistic Hartree models. Consequently, the anomalous kink
in the isotope shifts of Pb nuclei is well reproduced.Comment: Revised, 11 pages (Revtex) and 2 figures available upon request,
Preprint MPA-833, Physical Review Letters (in press)
Coordinate-space solution of the Skyrme-Hartree-Fock-Bogolyubov equations within spherical symmetry. The program HFBRAD (v1.0)
We describe the first version (v1.00) of the code HFBRAD which solves the
Skyrme-Hartree-Fock or Skyrme-Hartree-Fock-Bogolyubov equations in the
coordinate representation within the spherical symmetry. A realistic
representation of the quasiparticle wave functions on the space lattice allows
for performing calculations up to the particle drip lines. Zero-range
density-dependent interactions are used in the pairing channel. The pairing
energy is calculated by either using a cut-off energy in the quasiparticle
spectrum or the regularization scheme proposed by A. Bulgac and Y. Yu.Comment: 39 pages, 9 figure
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