565 research outputs found
Onset of T=0 Pairing and Deformations in High Spin States of the N=Z Nucleus 48Cr
The yrast line of the N=Z nucleus 48Cr is studied up to high spins by means
of the cranked Hartree-Fock-Bogoliubov method including the T=0 and T=1 isospin
pairing channels. A Skyrme force is used in the mean-field channel together
with a zero-range density-dependent interaction in the pairing channels. The
extensions of the method needed to incorporate the neutron-proton pairing are
summarized. The T=0 pairing correlations are found to play a decisive role for
deformation properties and excitation energies above 16hbar which is the
maximum spin that can be obtained in the f7/2 subshell.Comment: LaTeX, 4 ps figure
Particle-drip lines from the Hartree-Fock-Bogoliubov theory with Skyrme interaction
We calculate positions of one- and two-particle, proton and neutron drip
lines within the Hartree-Fock-Bogoliubov theory using Skyrme interaction. We
also determine an approximate -process path defined as a line where the
neutron binding energy is equal to 2~MeV. A weakening of the nuclear shell
structure at drip lines is found and interpreted as resulting from a coupling
with continuum states.Comment: 10 pages REVTEX 3.0, 3 uuencoded postscript figures included,
IFT/14/9
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
Mean-Field Description of Fusion Barriers with Skyrme's Interaction
Fusion barriers are determined in the framework of the Skyrme energy-density
functional together with the semi-classical approach known as the Extended
Thomas-Fermi method. The barriers obtained in this way with the Skyrme
interaction SkM* turn out to be close to those generated by phenomenological
models like those using the proximity potentials. It is also shown that the
location and the structure of the fusion barrier in the vicinity of its maximum
and beyond can be quite accurately described by a simple analytical form
depending only on the masses and the relative isospin of target and projectile
nucleus.Comment: 7 pages, latex, 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.
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
Nuclear energy density functional from chiral pion-nucleon dynamics: Isovector spin-orbit terms
We extend a recent calculation of the nuclear energy density functional in
the systematic framework of chiral perturbation theory by computing the
isovector spin-orbit terms: . The calculation
includes the one-pion exchange Fock diagram and the iterated one-pion exchange
Hartree and Fock diagrams. From these few leading order contributions in the
small momentum expansion one obtains already a good equation of state of
isospin-symmetric nuclear matter. We find that the parameterfree results for
the (density-dependent) strength functions and agree
fairly well with that of phenomenological Skyrme forces for densities . At very low densities a strong variation of the strength functions
and with density sets in. This has to do with chiral
singularities and the presence of two competing small mass scales
and . The novel density dependencies of and
as predicted by our parameterfree (leading order) calculation should
be examined in nuclear structure calculations.Comment: 9 pages, 3 figure, published in: Physical Review C68, 014323 (2003
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
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
A unique spinodal region in asymmetric nuclear matter
Asymmetric nuclear matter at sub-saturation densities is shown to present
only one type of instabilities. The associated order parameter is dominated by
the isoscalar density and so the transition is of liquid-gas type. The
instability goes in the direction of a restoration of the isospin symmetry
leading to a fractionation phenomenon. These conclusions are model independent
since they can be related to the general form of the asymmetry energy. They are
illustrated using density functional approaches.Comment: 4 pages, 5 figures, to appear in Phys. Rev.
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