4,625 research outputs found
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.
Symmetry energy of deformed neutron-rich nuclei
The symmetry energy, the neutron pressure and the asymmetric compressibility
of deformed neutron-rich even-even nuclei are calculated on the examples of Kr
and Sm isotopes within the coherent density fluctuation model using the
symmetry energy as a function of density within the Brueckner energy-density
functional. The correlation between the thickness of the neutron skin and the
characteristics related with the density dependence of the nuclear symmetry
energy is investigated for isotopic chains of these nuclei in the framework of
the self-consistent Skyrme-Hartree-Fock plus BCS method. Results for an
extended chain of Pb isotopes are also presented. A remarkable difference is
found in the trend followed by the different isotopic chains: the studied
correlations reveal a smoother behavior in the Pb case than in the other cases.
We also notice that the neutron skin thickness obtained for Pb with
SLy4 force is found to be in a good agreement with recent data.Comment: 14 pages, 10 figures, 2 tables, accepted for publication in Physical
Review
Scaling Functions and Superscaling in Medium and Heavy Nuclei
The scaling function for medium and heavy nuclei with
for which the proton and neutron densities are not similar is constructed
within the coherent density fluctuation model (CDFM) as a sum of the proton and
neutron scaling functions. The latter are calculated in the cases of Ni,
Kr, Sn, and Au nuclei on the basis of the corresponding
proton and neutron density distributions which are obtained in deformed
self-consistent mean-field Skyrme HF+BCS method. The results are in a
reasonable agreement with the empirical data from the inclusive electron
scattering from nuclei showing superscaling for negative values of ,
including those smaller than -1. This is an improvement over the relativistic
Fermi gas (RFG) model predictions where becomes abruptly zero for
. It is also an improvement over the CDFM calculations made in
the past for nuclei with assuming that the neutron density is equal
to the proton one and using only the phenomenological charge density.Comment: 4 pages, 1 figure, ReVTeX, accepted for publication in Phys. Rev.
Effects of random environment on a self-organized critical system: Renormalization group analysis of a continuous model
We study effects of random fluid motion on a system in a self-organized
critical state. The latter is described by the continuous stochastic model,
proposed by Hwa and Kardar [{\it Phys. Rev. Lett.} {\bf 62}: 1813 (1989)]. The
advecting velocity field is Gaussian, not correlated in time, with the pair
correlation function of the form ,
where and is the component of the
wave vector, perpendicular to a certain preferred direction -- the
-dimensional generalization of the ensemble introduced by Avellaneda and
Majda [{\it Commun. Math. Phys.} {\bf 131}: 381 (1990)]. Using the field
theoretic renormalization group we show that, depending on the relation between
the exponent and the spatial dimension , the system reveals different
types of large-scale, long-time scaling behaviour, associated with the three
possible fixed points of the renormalization group equations. They correspond
to ordinary diffusion, to passively advected scalar field (the nonlinearity of
the Hwa--Kardar model is irrelevant) and to the "pure" Hwa--Kardar model (the
advection is irrelevant). For the special choice both the
nonlinearity and the advection are important. The corresponding critical
exponents are found exactly for all these cases
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.
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