2,721 research outputs found
Ground-state properties and symmetry energy of neutron-rich and neutron-deficient Mg isotopes
A comprehensive study of various ground-state properties of neutron-rich and
neutron-deficient Mg isotopes with =20-36 is performed in the framework of
the self-consistent deformed Skyrme-Hartree-Fock plus BCS method. The
correlation between the skin thickness and the characteristics related with the
density dependence of the nuclear symmetry energy is investigated for this
isotopic chain following the theoretical approach based on the coherent density
fluctuation model and using the Brueckner energy-density functional. The
results of the calculations show that the behavior of the nuclear charge radii
and the nuclear symmetry energy in the Mg isotopic chain is closely related to
the nuclear deformation. We also study, within our theoretical scheme, the
emergence of an "island of inversion" at neutron-rich Mg nucleus, that
was recently proposed from the analyses of spectroscopic measurements of
Mg low-lying energy spectrum and the charge rms radii of all magnesium
isotopes in the shell.Comment: 13 pages, 13 figures, to be published in Physical Review
Temperature dependence of the volume and surface contributions to the nuclear symmetry energy within the coherent density fluctuation model
The temperature dependence of the volume and surface components of the
nuclear symmetry energy (NSE) and their ratio is investigated in the framework
of the local density approximation (LDA). The results of these quantities for
finite nuclei are obtained within the coherent density fluctuation model
(CDFM). The CDFM weight function is obtained using the temperature-dependent
proton and neutron densities calculated through the HFBTHO code that solves the
nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical
transformed deformed harmonic-oscillator basis. We present and discuss the
values of the volume and surface contributions to the NSE and their ratio
obtained for the Ni, Sn, and Pb isotopic chains around double-magic Ni,
Sn, and Pb nuclei. The results for the -dependence of the
considered quantities are compared with estimations made previously for zero
temperature showing the behavior of the NSE components and their ratio, as well
as with the available experimental data. The sensitivity of the results on
various forms of the density dependence of the symmetry energy is studied. We
confirm the existence of `kinks' of these quantities as functions of the mass
number at MeV for the double closed-shell nuclei Ni and Sn
and the lack of `kinks' for the Pb isotopes, as well as the disappearance of
these kinks as the temperature increases.Comment: 14 pages, 12 figures, 1 table, accepted for publication in Physical
Review
Scaling Function, Spectral Function and Nucleon Momentum Distribution in Nuclei
The link between the scaling function extracted from the analysis of (e,e')
cross sections and the spectral function/momentum distribution in nuclei is
revisited. Several descriptions of the spectral function based on the
independent particle model are employed, together with the inclusion of nucleon
correlations, and effects of the energy dependence arising from the width of
the hole states are investigated. Although some of these approaches provide
rough overall agreement with data, they are not found to be capable of
reproducing one of the distinctive features of the experimental scaling
function, namely its asymmetry. However, the addition of final-state
interactions, incorporated in the present study using either relativistic mean
field theory or via a complex optical potential, does lead to asymmetric
scaling functions in accordance with data. The present analysis seems to
indicate that final-state interactions constitute an essential ingredient and
are required to provide a proper description of the experimental scaling
function.Comment: 29 pages, 13 figures, accepted for publication in Physical Review
Superscaling and Neutral Current Quasielastic Neutrino-Nucleus Scattering beyond the Relativistic Fermi Gas Model
The superscaling analysis is extended to include quasielastic (QE) scattering
via the weak neutral current of neutrinos and antineutrinos from nuclei. The
scaling function obtained within the coherent density fluctuation model (used
previously in calculations of QE inclusive electron and charge-changing (CC)
neutrino scattering) is applied to neutral current neutrino and antineutrino
scattering with energies of 1 GeV from C with a proton and neutron
knockout (u-channel inclusive processes). The results are compared with those
obtained using the scaling function from the relativistic Fermi gas model and
the scaling function as determined from the superscaling analysis (SuSA) of QE
electron scattering.Comment: 10 pages, 6 figures, published in Phys. Rev.
Karyology and cytotaxonomy of the genus Passiflora L. (Pasifloraseae).
The chromosomes of 31 species of Pas- siflora, distributed throughout the subgenera As- trophea, Calopathanthus, Distephana, Dysosmia, Passiflora, Plectostemma and Tacsonia were ana1- ysed. Three different karyotypes were observed: 2n = 12, 24, 36; 2n = 18, 72 and 2n = 20. The karyotype of these species was a1most always constituted of metacentric and submetacentric chromosomes with variable karyotype symmetry. In the group with x = 6, represented by the subgenus Plectostemma, six diploid species with 2n = 12, one tetraploid with 2n = 24 (P. suberosa) and an intraspecific polyploid with 2n = 12, 36 (P. misera) were analysed. P. pentagona (subgenus Astrophea) may also be included in this karyolog- ical group since it presents 2n = 24 and may be of polyploid origin, with x = 6. The interphase nuclei in this group were areticulate, except those of P. morifolia and P. pentagona with semi-reticulate characteristics. Two small terminal heterochroma- tic blocks, positive for chromomycin A3, were identified in the largest chromosome pair of P. capsularis and P. rubra, species very closely related, while P. tricuspis displayed four chromo- somes with proximal blocks. In the group with x = 9, represented mainly by subgenus Passiflora, 20 species with 2n = 18 and one with 2n = 72 were studied. They presented chromosomes larger than those species with x = 6 and interphase nuclei of semi-reticulate type, except for P. mixta with areticulate nuclei. Four terminal CMA + block: were observed in P. edulis, six blocks in P. caerulel and P. racemosa, while five blocks were observed ir the single P. amethystina plant analysed. P. foetid\{ (subgenus Dysosmia), the only species witt 2n = 20, exhibited six chromosomes with CMA + blocks and interphase nuclei of the areticulate type The meiotic analysis of representatives of the three groups (P. foetida, P. suberosa, P. cincinnata and P. racemosa) always presented regular pairing and regular chromosome segregation, except in P.jilekil where a tetravalent was observed. The analysis of the chromosome variation within the genus and the family suggests that the base number of Passiflora may be xi = 6 or XI = 12, whereas X2 = 9 is only an important secondary base number
Superscaling in Nuclei: A Search for Scaling Function Beyond the Relativistic Fermi Gas Model
We construct a scaling function for inclusive electron
scattering from nuclei within the Coherent Density Fluctuation Model (CDFM).
The latter is a natural extension to finite nuclei of the Relativistic Fermi
Gas (RFG) model within which the scaling variable was
introduced by Donnelly and collaborators. The calculations show that the
high-momentum components of the nucleon momentum distribution in the CDFM and
their similarity for different nuclei lead to quantitative description of the
superscaling in nuclei. The results are in good agreement with the experimental
data for different transfer momenta showing superscaling for negative values of
, including those smaller than -1.Comment: 16 pages, 5 figures, submitted for publication to Phys. Rev.
Surface properties of neutron-rich exotic nuclei: A source for studying the nuclear symmetry energy
We study the correlation between the thickness of the neutron skin in finite
nuclei and the nuclear symmetry energy for isotopic chains of even-even Ni, Sn,
and Pb nuclei in the framework of the deformed self-consistent mean-field
Skyrme HF+BCS method. The symmetry energy, the neutron pressure and the
asymmetric compressibility in finite nuclei are calculated within the coherent
density fluctuation model using the symmetry energy as a function of density
within the Brueckner energy-density functional. The mass dependence of the
nuclear symmetry energy and the neutron skin thickness are also studied
together with the role of the neutron-proton asymmetry. A correlation between
the parameters of the equation of state (symmetry energy and its density slope)
and the neutron skin is suggested in the isotopic chains of Ni, Sn, and Pb
nuclei.Comment: 13 pages, 10 figures. Accepted for publication in Phys. Rev.
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