98 research outputs found
High-spin states in boson models with applications to actinide nuclei
We use the 1/ expansion formalism in a systematic study of high-spin
states in the and boson models with emphasis on spin dependence of
moment of inertia and E2 transitions. The results are applied to the high-spin
states in the actinide nuclei Th, U, where the need for
bosons is especially acute but until now, no realistic calculation existed. We
find that the -boson energy plays a crucial role in description of the
high-spin data.Comment: 11 pages Latex, 4 figures available upon request (to appear in Phys.
Lett. B
Bonn Potential and Shell-Model Calculations for 206,205,204Pb
The structure of the nuclei 206,205,204Pb is studied interms of shell model
employing a realistic effective interaction derived from the Bonn A
nucleon-nucleon potential. The energy spectra, binding energies and
electromagnetic properties are calculated and compared with experiment. A very
good overall agreement is obtained. This evidences the reliability of our
realistic effective interaction and encourages use of modern realistic
potentials in shell-model calculations for heavy-mass nuclei.Comment: 4 pages, 4 figures, submitted to Physical Review
Properties of odd nuclei and the impact of time-odd mean fields: A systematic Skyrme-Hartree-Fock analysis
We present a systematic analysis of the description of odd nuclei by the
Skyrme-Hartree-Fock approach augmented with pairing in BCS approximation and
blocking of the odd nucleon. Current and spin densities in the Skyrme
functional produce time-odd mean fields (TOMF) for odd nuclei. Their effect on
basic properties (binding energies, odd-even staggering, separation energies
and spectra) is investigated for the three Skyrme parameterizations SkI3, SLy6,
and SV-bas. About 1300 spherical and axially-deformed odd nuclei with 16 < Z <
92 are considered. The calculations demonstrate that the TOMF effect is
generally small, although not fully negligible. The influence of the Skyrme
parameterization and the consistency of the calculations are much more
important. With a proper choice of the parameterization, a good description of
binding energies and their differences is obtained, comparable to that for even
nuclei. The description of low-energy excitation spectra of odd nuclei is of
varying quality depending on the nucleus
Ground- band coupling in heavy deformed nuclei and SU(3) contraction limit
We derive analytic expressions for the energies and -transition
probabilities in the states of the ground and bands of heavy deformed
nuclei within a collective Vector-Boson Model with SU(3) dynamical symmetry. On
this basis we examine the analytic behavior of the SU(3) energy splitting and
the B(E2) interband transition ratios in the SU(3) contraction limits of the
model. The theoretical analyses outline physically reasonable ways in which the
ground- band coupling vanishes. The experimental data on the lowest
collective states of even-even rare earth nuclei and actinides strongly support
the theoretical results. They suggest that a transition from the
ground- band coupling scheme to a scheme in which the ground band is
situated in a separate irreducible representation of SU(3) should be realized
towards the midshell regions. We propose that generally the SU(3) group
contraction process should play an important role for such a kind of
transitions in any collective band coupling scheme in heavy deformed nuclei.Comment: 24 pages (LaTeX), 7 figures (12 postscript files
The issues in modelling freight transport at the national level
Several countries in Europe and elsewhere have a national freight transport model. This paper discusses some old and new issues for these models, based on experiences in at least seven European countries. These issues have to do with the institutional organisation of the work on model development and use, how confidence in these models can be determined and increased, the questions the national freight models are asked and their scope and level of detail. But also what the model philosophy (e.g. aggregate, disaggregate, deterministic, stochastic) should be and which influencing factors should be included. New directions are discussed, such as the trend to include more aspects of logistics decisions of firms. This increases the data requirements of the models. The potential of big data is discussed as well as approaches that use less data but more assumptions
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