4,048 research outputs found
Ground-state properties of even-even N=Z nuclei within the Hartree-Fock-BCS and Higher Tamm-Dancoff approaches
We calculate the ground-state properties of well deformed, even-even N=Z
nuclei in the region between Ni-56 and Sn-100 within two different approaches,
focusing on the binding energy and deformation and pairing properties. First,
we employ the Hartree-Fock-BCS (HFBCS) approximation with the Skyrme effective
nucleon-nucleon interaction and discuss how the results depend on the
parameterization of the interaction and on the pairing force parameters
adjusted in various schemes to reproduce the experimental odd-even mass
differences. Then, within the Higher Tamm-Dancoff Approximation (HTDA), which
explicitly conserves the particle number, we calculate the same properties
starting from the HFBCS solutions. The HTDA treatment of the ground-state
correlations is converged within a n-particle-n-hole expansion using up to n=4
particle-hole excitations of the pair type (in the sense of Cooper pairs). We
compare the ground-state properties calculated in these two descriptions of
pairing correlations and deduce the importance of the particle-number
conservation in weak pairing regimes. Finally, we extend the HTDA calculations
so as to include the proton-neutron residual interaction and investigate the
role of proton-neutron pairing on the above ground-state properties.Comment: 12 pages, 3 figures, 11 tables, submitted to Physical Review
Global microscopic calculations of ground-state spin and parity for odd-mass nuclei
Systematic calculations of ground-state spin and parity of odd-mass nuclei
have been performed within the Hartree--Fock--BCS (HFBCS) approach and the
Finite-Range Droplet Model for nuclei for which experimental data are
available. The unpaired nucleon has been treated perturbatively, and axial and
left-right reflection symmetries have been assumed. As for the HFBCS approach,
three different Skyrme forces have been used in the particle-hole channel,
whereas the particle-particle matrix elements have been approximated by a
seniority force. The calculations have been done for the 621 nuclei for which
the Nubase 2003 data set give assignments of spin and parity with strong
arguments. The agreement of both spin and parity in the self-consistent model
reaches about 80% for spherical nuclei, and about 40% for well-deformed nuclei
regardless of the Skyrme force used. As for the macroscopic-microscopic
approach, the agreement for spherical nuclei is about 90% and about 40% for
well-deformed nuclei, with different sets of spherical and deformed nuclei
found in each model.Comment: 5 pages, 4 figures (three in color), 1 table, to be submitted to
Physical Review
MULTI-SPECIES INDIVIDUAL TRANSFERABLE QUOTAS: THE SCOTIA-FUNDY MOBILE GEAR GROUNDFISHERY
Few studies examine the economic effects of individual harvesting rights in multi-species fisheries. Using costs and earnings data from a multispecies individual transferable quota (ITQ) fishery in Nova Scotia, before and after the introduction of harvesting rights, the effects on inputs, outputs, prices, and vessel exit are examined. The results provide insights about the management of multi-species ITQs.Resource /Energy Economics and Policy,
Hartree-Fock-Bogoliubov Calculations of the Rotational Band of the Very Heavy No Nucleus
We report on Hartree-Fock-Bogoliubov (HFB) calculations of the ground-state
rotationnal band of the heavy nucleus No recently observed
experimentally. The calculated quadrupole deformation is consistent with the
experimental value of and is almost constant over the whole band.
We also reproduce fairly well the excitation spectra and moments of inertia of
this isotope up to the maximal experimentally observed state of spin 20. The
rather high stability of this nucleus against fission is illustrated by the
deformation energy curve providing very high fission barriers at zero spin
within the HFB and HFB plus Lipkin-Nogami formalisms. The variation of these
barriers with increased angular velocities is also studied.Comment: 4 pages (LaTeX), submitted to Eur. Phys. J A, dedicated to the memory
of J. Piperov
Parity restoration in the Highly Truncated Diagonalization Approach: application to the outer fission barrier of Pu
The restoration of the parity symmetry has been performed in the framework of
the Highly Truncated Diagonalization Approach suited to treat correlations in
an explicitly particle-number conserving microscopic approach. To do so we have
assumed axial symmetry and used a generalized Wick's theorem due to L\"owdin in
a projection-after-variation scheme. We have chosen the Skyrme SkM
energy-density functional for the particle-hole channel and a
density-independent delta force for the residual interaction. We have applied
this approach in the region of the outer fission barrier of the Pu
nucleus. As a result, we have shown that the fission isomeric
state is statically unstable against intrinsic-parity breaking modes, while the
projection does not affect the energy at the top of the intrinsic outer fission
barrier. Altogether, this leads to an increase of the height of the outer
fission barrier--with respect to the fission isomeric state--by about 350 keV,
affecting thus significantly the fission-decay lifetime of the considered
fission isomer
A GaAs MMIC chip-set for 10 to 15GHz radio-links applications
This paper describes the development of a GaAs MMIC chip-set for Ku-band radio-links transmitter. This chip-set includes two circuits, a times-two multiplier 5-7.5GHz to 10-15GHz, and a single side band up-converter. The development and the results of these circuits are analysed. The times-two multiplier is based on a specific balanced configuration leading to a very high level of input frequency suppression at the output (typically 50dBc) on a 2.7mm² chip. The mixer circuit is a broadband build-in single side band mixer of 10mm², with typically 30dBc image suppression
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