80 research outputs found
B-Spline Finite Elements and their Efficiency in Solving Relativistic Mean Field Equations
A finite element method using B-splines is presented and compared with a
conventional finite element method of Lagrangian type. The efficiency of both
methods has been investigated at the example of a coupled non-linear system of
Dirac eigenvalue equations and inhomogeneous Klein-Gordon equations which
describe a nuclear system in the framework of relativistic mean field theory.
Although, FEM has been applied with great success in nuclear RMF recently, a
well known problem is the appearance of spurious solutions in the spectra of
the Dirac equation. The question, whether B-splines lead to a reduction of
spurious solutions is analyzed. Numerical expenses, precision and behavior of
convergence are compared for both methods in view of their use in large scale
computation on FEM grids with more dimensions. A B-spline version of the object
oriented C++ code for spherical nuclei has been used for this investigation.Comment: 27 pages, 30 figure
Light Nuclei near Neutron and Proton Drip Lines in the Relativistic Mean-Field Theory
We have made a detailed study of the ground-state properties of nuclei in the
light mass region with atomic numbers Z=10-22 in the framework of the
relativistic mean-field (RMF) theory. The nonlinear model with
scalar self-interaction has been employed. The RMF calculations have been
performed in an axially deformed configuration using the force NL-SH. We have
considered nuclei about the stability line as well as those close to proton and
neutron drip lines. It is shown that the RMF results provide a good agreement
with the available empirical data. The RMF predictions also show a reasonably
good agreement with those of the mass models. It is observed that nuclei in
this mass region are found to possess strong deformations and exhibit shape
changes all along the isotopic chains. The phenomenon of the shape coexistence
is found to persist near the stability line as well as near the drip lines. It
is shown that the magic number N=28 is quenched strongly, thus enabling the
corresponding nuclei to assume strong deformations. Nuclei near the neutron and
proton drip lines in this region are also shown to be strongly deformed.Comment: 49 pages Latex, 12 postscript figures, to appear in Nuclear Physics
Computer program for the relativistic mean field description of the ground state properties of even-even axially deformed nuclei
A Fortran program for the calculation of the ground state properties of
axially deformed even-even nuclei in the relativistic framework is presented.
In this relativistic mean field (RMF) approach a set of coupled differential
equations namely the Dirac equation with potential terms for the nucleons and
the Glein-Gordon type equations with sources for the meson and the
electromagnetic fields are to be solved self-consistently. The well tested
basis expansion method is used for this purpose. Accordingly a set of harmonic
oscillator basis generated by an axially deformed potential are used in the
expansion. The solution gives the nucleon spinors, the fields and level
occupancies, which are used in the calculation of the ground state properties.Comment: 18 pages, LaTex, 6 p.s figures, To appear in Comput. Phys. Commu
Relativistic Hartree-Bogoliubov theory in coordinate space: finite element solution for a nuclear system with spherical symmetry
A C++ code for the solution of the relativistic Hartree-Bogoliubov theory in
coordinate space is presented. The theory describes a nucleus as a relativistic
system of baryons and mesons. The RHB model is applied in the self-consistent
mean-field approximation to the description of ground state properties of
spherical nuclei. Finite range interactions are included to describe pairing
correlations and the coupling to particle continuum states. Finite element
methods are used in the coordinate space discretization of the coupled system
of Dirac-Hartree-Bogoliubov integro-differential eigenvalue equations, and
Klein-Gordon equations for the meson fields. The bisection method is used in
the solution of the resulting generalized algebraic eigenvalue problem, and the
biconjugate gradient method for the systems of linear and nonlinear algebraic
equations, respectively.Comment: PostScript, 32 pages, to be published in Computer Physics
Communictions (1997
Saturation properties and incompressibility of nuclear matter: A consistent determination from nuclear masses
Starting with a two-body effective nucleon-nucleon interaction, it is shown
that the infinite nuclear matter model of atomic nuclei is more appropriate
than the conventional Bethe-Weizsacker like mass formulae to extract saturation
properties of nuclear matter from nuclear masses. In particular, the saturation
density thus obtained agrees with that of electron scattering data and the
Hartree-Fock calculations. For the first time using nuclear mass formula, the
radius constant =1.138 fm and binding energy per nucleon = -16.11
MeV, corresponding to the infinite nuclear matter, are consistently obtained
from the same source. An important offshoot of this study is the determination
of nuclear matter incompressibility to be 288 28 MeV using
the same source of nuclear masses as input.Comment: 14 latex pages, five figures available on request ( to appear in Phy.
Rev. C
Superheavy Nuclei in the Relativistic Mean Field Theory
We have carried out a study of superheavy nuclei in the framework of the
Relativistic Mean-Field theory. Relativistic Hartree-Bogoliubov (RHB)
calculations have been performed for nuclei with large proton and neutron
numbers. A finite-range pairing force of Gogny type has been used in the RHB
calculations. The ground-state properties of very heavy nuclei with atomic
numbers Z=100-114 and neutron numbers N=154-190 have been obtained. The results
show that in addition to N=184 the neutron numbers N=160 and N=166 exhibit an
extra stability as compared to their neighbors. For the case of protons the
atomic number Z=106 is shown to demonstrate a closed-shell behavior in the
region of well deformed nuclei about N=160. The proton number Z=114 also
indicates a shell closure. Indications for a doubly magic character at Z=106
and N=160 are observed. Implications of shell closures on a possible synthesis
of superheavy nuclei are discussed.Comment: 29 pages Latex, 13 ps figures, to appear in Nucl. Phys.
Eikonal Reaction Theory for Neutron-Removal Reaction
We present an accurate method of treating the one-neutron removal reaction at
intermediate incident energies induced by both nuclear and Coulomb
interactions. In the method, the nuclear and Coulomb breakup processes are
consistently treated by the method of continuum discretized coupled channels
without making the adiabatic approximation to the Coulomb interaction, so that
the removal cross section calculated never diverges. This method is applied to
recently measured one-neutron removal cross section for Ne+C
scattering at 230 MeV/nucleon and Ne+Pb scattering at 234
MeV/nucleon. The spectroscopic factor and the asymptotic normalization
coefficient of the last neutron in Ne are evaluated.Comment: 10 pages, 1 figur
Model--space approach to neutron and proton pairing with the Bonn meson--exchange potentials
In this work we calculate neutron and proton energy gaps in neutron star
matter, using the Bonn meson--exchange interactions and a model--space approach
to the gap equation. This approach allows a consistent calculation of energy
gaps and single particle energies with the model--space
Brueckner--Hartree--Fock (MBHF) method, without double counting of
two--particle correlations. Neutron energy gaps are calculated at zero and
finite temperature. Proton energy gaps are calculated at beta equilibrium, and
it is shown that the inclusion of muons has a significant effect. The results
are compared with those of other works, and the implications for neutron star
physics are briefly discussed.Comment: uuencoded file, 19 pages, 15 figures include
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)
Extended Thomas-Fermi approximation to the one-body density matrix
The one-body density matrix is derived within the Extended Thomas-Fermi
approximation. This has been done starting from the Wigner-Kirkwood
distribution function for a non-local single-particle potential. The links
between this new approach to the density matrix with former ones available in
the literature are widely discussed. The semiclassical Hartree-Fock energy at
Extended Thomas-Fermi level is also obtained in the case of a non-local
one-body Hamiltonian. Numerical applications are performed using the Gogny and
Brink-Boeker effective interactions. The semiclassical binding energies and
root mean square radii are compared with the fully quantal ones and with those
obtained using the Strutinsky averaged method.Comment: 27 pages, LateX, and 2 PostScript figures, (submitted to Nucl. Phys.
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