19 research outputs found
Microscopic determination of the nuclear incompressibility within the non-relativistic framework
The nuclear incompressibility is deduced from measurements of the
Isoscalar Giant Monopole Resonance (ISGMR) in medium-heavy nuclei, and the
resulting value turns out to be model dependent. Since the considered nuclei
have neutron excess, it has been suggested that the model dependence is due to
the different behaviour of the symmetry energy in different models. To clarify
this issue, we make a systematic and careful analysis based on new Skyrme
forces which span a wide range of values for , for the value of the
symmetry energy at saturation and for its density dependence. By calculating,
in a fully self-consistent fashion, the ISGMR centroid energy in Pb we
reach, for the first time within the non-relativistic framework, three
important conclusions: (i) the monopole energy, and consequently the deduced
value of , depend on a well defined parameter related to the shape of
the symmetry energy curve and called ; (ii) Skyrme forces of the type
of SLy4 predict around 230 MeV, in agreement with the Gogny force
(previous estimates using Skyrme interactions having been plagued by lack of
full self-consistency); (iii) it is possible to build forces which predict
around 250 MeV, although part of this increase is due to our poor
knowledge of the density dependence and effective mass.Comment: 19 pages, 8 figures. Submitted to PR
Monopole giant resonances and nuclear compressibility in relativistic mean field theory
Isoscalar and isovector monopole oscillations that correspond to giant
resonances in spherical nuclei are described in the framework of time-dependent
relativistic mean-field (RMF) theory. Excitation energies and the structure of
eigenmodes are determined from a Fourier analysis of dynamical monopole moments
and densities. The generator coordinate method, with generating functions that
are solutions of constrained RMF calculations, is also used to calculate
excitation energies and transition densities of giant monopole states.
Calculations are performed with effective interactions which differ in their
prediction of the nuclear matter compression modulus K_nm. Both time-dependent
and constrained RMF results indicate that empirical GMR energies are best
reproduced by an effective force with K_nm \approx 270 MeV.Comment: 30 pages of LaTeX, 18 PS-figure
Generator Coordinate Calculations for the Breathing-Mode Giant Monopole Resonance in Relativistic Mean Field Theory
The breathing-mode giant monopole resonance (GMR) is studied within the
framework of the relativistic mean-field theory using the Generator Coordinate
Method (GCM). The constrained incompressibility and the excitation energy of
isoscalar giant monopole states are obtained for finite nuclei with various
sets of Lagrangian parameters. A comparison is made with the results of
nonrelativistic constrained Skyrme Hartree-Fock calculations and with those
from Skyrme RPA calculations. In the RMF theory the GCM calculations give a
transition density for the breathing mode, which resembles much that obtained
from the Skyrme HF+RPA approach and also that from the scaling mode of the GMR.
From the systematic study of the breathing-mode as a function of the
incompressibility in GCM, it is shown that the GCM succeeds in describing the
GMR energies in nuclei and that the empirical breathing-mode energies of heavy
nuclei can be reproduced by forces with an incompressibility close to
MeV in the RMF theory.Comment: 27 pages (Revtex) and 5 figures (available upon request), Preprint
MPA-793 (March 1994
Far-infrared edge modes in quantum dots
We have investigated edge modes of different multipolarity sustained by
quantum dots submitted to external magnetic fields. We present a microscopic
description based on a variational solution of the equation of motion for any
axially symmetric confining potential and multipole mode. Numerical results for
dots with different number of electrons whose ground-state is described within
a local Current Density Functional Theory are discussed. Two sum rules, which
are exact within this theory, are derived. In the limit of a large neutral dot
at B=0, we have shown that the classical hydrodynamic dispersion law for edge
waves \omega(q) \sim \sqrt{q \ln (q_0/q)} holds when quantum and finite size
effects are taken into account.Comment: We have changed some figures as well as a part of the tex
Neutron density distributions for atomic parity nonconservation experiments
The neutron distributions of Cs, Ba, Yb and Pb isotopes are described in the
framework of relativistic mean-field theory. The self-consistent ground state
proton and neutron density distributions are calculated with the relativistic
Hartree-Bogoliubov model. The binding energies, the proton and neutron radii,
and the quadrupole deformations are compared with available experimental data,
as well as with recent theoretical studies of the nuclear structure corrections
to the weak charge in atomic parity nonconservation experiments.Comment: 16 pages, RevTex, 11 eps figs, submitted to Phys. Rev.
Far-infrared edge modes in quantum dots
We have investigated edge modes of different multipolarity sustained by
quantum dots submitted to external magnetic fields. We present a microscopic
description based on a variational solution of the equation of motion for any
axially symmetric confining potential and multipole mode. Numerical results for
dots with different number of electrons whose ground-state is described within
a local Current Density Functional Theory are discussed. Two sum rules, which
are exact within this theory, are derived. In the limit of a large neutral dot
at B=0, we have shown that the classical hydrodynamic dispersion law for edge
waves \omega(q) \sim \sqrt{q \ln (q_0/q)} holds when quantum and finite size
effects are taken into account.Comment: We have changed some figures as well as a part of the tex
Isospin-mixing corrections for fp-shell Fermi transitions
Isospin-mixing corrections for superallowed Fermi transitions in {\it
fp}-shell nuclei are computed within the framework of the shell model. The
study includes three nuclei that are part of the set of nine accurately
measured transitions as well as five cases that are expected to be measured in
the future at radioactive-beam facilities. We also include some new
calculations for C. With the isospin-mixing corrections applied to the
nine accurately measured values, the conserved-vector-current hypothesis
and the unitarity condition of the Cabbibo-Kobayashi-Maskawa (CKM) matrix are
tested.Comment: 13 pages plus five tables. revtex macro
NUCLEAR GIANT RESONANCES IN COORDINATE SPACE - A SEMICLASSICAL DENSITY FUNCTIONAL APPROACH
Dans le cadre d'une description semiclassique de résonnances géantes nucléaires (GR) en utilisant la force SkM* et les fonctionnelles ETF complètes à l'ordre 4 en 4 , nous présentons des modes propres monopolaires (0+) isoscalaires (I=0) et isovectorielles (I=1) en bon accord avec l'expérience, ainsi que la variation de quelques énergies GR typiques en fonction de la température.We discuss the semiclassical description of nuclear giant resonances (GR) using a realistic Skyrme force (SkM*) and complete ETF density functionals. We present monopole (0+) eigenmodes of isoscalar (I=0) and isovector (I=1) type, which are in good agreement with experiment, and the corresponding m1 and m3 sum rules. We also present the temperature dependence of some typical GR energies (0+, I=0,1 ; 1-, I=1 ; 2+, I=0) in 208Pb