174 research outputs found
Density dependence of nuclear symmetry energy constrained by mean-field calculations
We establish a correlation for the symmetry energy at saturation density
, slope parameter and curvature parameter based on
widely different mean field interactions. With the help of this correlation and
available empirical and theoretical information, the density dependent behavior
around the saturation density is determined. We compare the results obtained
with the present approach with those by other analyses. With this obtained
density dependent behavior of the symmetry energy, the neutron skin thickness
of Pb and some properties of neutron stars are investigated. In
addition, it is found that the expression or does not reproduce the density dependence of the symmetry
energy as predicted by the mean-field approach around nuclear saturation
density.Comment: 6 pages, 4 figure
Three-body force effect on the properties of neutron-rich nuclear matter
We review our research work in recent years on the properties of neutron-rich nuclear matter within the framework of the Brueckner theory extended to include a microscopic three-body force (TBF). We discuss specially the TBF effect on the equation of state and the singleparticle (s.p.) potentials. The TBF turns out to be crucial for describing the saturation properties of nuclear matter in nonrelativistic microscopic framework. The TBF effect on the EOS of neutron-rich nuclear matter is to result in a significant stiffening of its isovector part at supra-saturation densities. Within the Brueckner approach, the TBF may lead to a rearrangement contribution to the s.p. potentials, which enhances strongly the repulsion and momentum-dependence of the s.p. potentials at high densities and high momenta. Our results are also compared with the predictions by other ab initio approaches
Existence of nuclei with unusual neutron excess
Abstract A realistic model is suggested based on the quasiparticle Lagrange version of the self-consistent Finite Fermi Systems theory supplemented with the microscopically calculated surface parameters of the Landau–Migdal interaction amplitude. The latter are expressed in terms of the off-shell T -matrix of free NN -scattering and show a strong dependence on the chemical potential of a nucleus under consideration in the drip line vicinity. This effect could result in shifting the neutron drip line position to very large values of the neutron excess
On the distribution of rational points on ramified covers of abelian varieties
We prove new results on the distribution of rational points on ramified
covers of abelian varieties over finitely generated fields of
characteristic zero. For example, given a ramified cover , where
is an abelian variety over with a dense set of -rational points, we
prove that there is a finite-index coset such that
is disjoint from .
Our results do not seem to be in the range of other methods available at
present; they confirm predictions coming from Lang's conjectures on rational
points, and also go in the direction of an issue raised by Serre regarding
possible applications to the Inverse Galois Problem. Finally, the conclusions
of our work may be seen as a sharp version of Hilbert's irreducibility theorem
for abelian varieties.Comment: 38 pages. Title changed. Introduction and abstract improved. No other
changes. Comments more than welcome
Isospin-dependent pairing interaction from nuclear matter calculations
The isospin dependence of the effective pairing interaction is discussed on the basis of the Bardeen, Cooper, and Schrieffer theory of superfluid asymmetric nuclear matter. It is shown that the energy gap, calculated within the mean field approximation in the range from symmetric nuclear matter to pure neutron matter, is not linearly dependent on the symmetry parameter owing to the nonlinear structure of the gap equation. Moreover, the construction of a zero-range effective pairing interaction compatible with the neutron and proton gaps in homogeneous matter is investigated, along with some recent proposals of isospin dependence tested on the nuclear data table
Another approach to the in-medium chiral condensates
Abstract A new formalism to calculate the in-medium chiral condensate is presented. At lower densities, this approach leads to a linear condensate. If it is compatible with the famous model-independent result, the pion–nucleon sigma term could be six times the average current mass of light quarks. The modification due to QCD-like interactions may, compared with the linear extrapolation, slow the decreasing speed of the condensate with increasing densities
Variation in seed mineral elements profile and yield in field bean (Vicia faba L. var. minor) genotypes
Field bean (Vicia faba L. var. minor) is one of the major leguminous crops cultivated in the world and mainly destined for animal feed. Although its seed is generally recognised as a good protein source, little is known about its mineral elements profile, which is an important aspect for a balanced animal diet. Therefore, the aim of the present work was to assess the seed mineral elements composition, along with some key production parameters, in eight field bean genotypes grown in a Mediterranean environment, without intensive management, over two years (2009/10 and 2010/11). Independently of the year, the seed of Chiaro di Torre Lama was the richest in phosphorus (P), magnesium, calcium and iron contents, while that of Sint 6 and Motta Chiaro 69 were the most effective accumulators of potassium and zinc, respectively. While all the genotypes yielded better in the second year (with more rainfall), the seasonal effect on seed mineral elements composition depended on the genotype. Indeed, the P content was 46% lower in Chiaro di Torre Lama, Motta Chiaro 69 and Sint 6 in the second year, while there was only a negligible seasonal effect for Sint 8 with respect to Fe content. Overall, this crop is reasonably productive under a low management regime and its seed can supply significant amounts of certain minerals (particularly P) in feed formulations. Both aspects are important in a perspective of optimising field bean production in the Mediterranean area and, hence, improving farmers' income
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