Relativistic Effects in Nuclear Matter and Nuclei

The status of relativistic nuclear many-body calculations of nuclear systems to be built up in terms of protons and neutrons is reviewed. In detail, relativistic effects on several aspects of nuclear matter such as the effective mass, saturation mechanism, and the symmetry energy are considered. This review will especially focus on isospin asymmetric issues, since these aspects are of high interest in astrophysical and nuclear structure studies. Furthermore, from the experimental side these aspects are experiencing an additional boost from a new generation of radioactive beam facilities, e.g. the future GSI facility FAIR in Germany or SPIRAL2 at GANIL/France. Finally, the prospects of studying finite nuclei in microscopic calculations which are based on realistic $NN$ interactions by including relativistic effects in calculations of low momentum interactions are discussed.Comment: 57 pages, 16 figure

Out of Africa: What drives the Pressure to emigrate?

This paper evaluates the strength of social and economic forces that affect the pressure to emigrate 'out of Africa' for four distinctly different African countries (Morocco, Egypt, Senegal and Ghana). In general, great expectations about attaining a higher living standard and expected low job search costs abroad are strong forces that drive emigration intentions out of Africa, especially in Ghana and Senegal. Signs of positive selection with respect to the level of education of potential migrants are only present in Ghana and Egypt. The differences in intentions by age and sex are also quite noteworthy, although the influence of sex differs quite distinctly across countries. Return migrants are on average more set to emigrating judging from their stated intentions although there are signs of negative selection within the group of return migrants in Ghana and Egypt. The network effects of potential migrants turn out to be less important than one might expect from actual migration behaviour. Both ties within the household with household members who have international migration experience and ties with current migrants affect intentions only in Ghana and Egypt and it affects the intentions of women far stronger than that of men. The implication of these findings is that due to the slow growth prospects of these African countries the pressure to emigrate 'out of Africa' can be a long lasting phenomenon

Relativistic nucleon optical potentials with isospin dependence in Dirac Brueckner Hartree-Fock approach

The relativistic optical model potential (OMP) for nucleon-nucleus scattering is investigated in the framework of Dirac-Brueckner-Hartree-Fock (DBHF) approach using the Bonn-B One-Boson- Exchange potential for the bare nucleon-nucleon interaction. Both real and imaginary parts of isospin-dependent nucleon self-energies in nuclear medium are derived from the DBHF approach based on the projection techniques within the subtracted T -matrix representation. The Dirac potentials as well as the corresponding Schrodinger equivalent potentials are evaluated. An improved local density approximation is employed in this analysis, where a range parameter is included to account for a finite-range correction of the nucleon-nucleon interaction. As an example the total cross sections, differential elastic scattering cross sections, analyzing powers for n, p + 27Al at incident energy 100 keV < E < 250 MeV are calculated. The results derived from this microscopic approach of the OMP are compared to the experimental data, as well as the results obtained with a phenomenological OMP. A good agreement between the theoretical results and the measurements can be achieved for all incident energies using a constant value for the range parameter.Comment: 10 pages, 16 figure

Remittances and their Effect on Emigration Intentions in Egypt, Morocco and Turkey

What determines remittances – altruism or enlightened self-interest - and do remittances trigger additional migration? These two questions are examined empirically in Egypt, Turkey and Morocco for households with family members living abroad. Results show, first, that one cannot clearly pinpoint altruistic or motives of self-interest since each country tells a different story and within a country both motives can be defended as driving forces behind remittance behaviour. A general conclusion based on a multi-country study is that the family ties and the net earnin

Comparison of Vlasov-Uehling-Uhlenbeck model with 4 π Heavy Ion Data

Streamer chamber data for collisions of Ar + KCl and Ar + BaI2 at 1.2 GeV/nucleon are compared with microscopic model predictions based on the Vlasov-Uehling-Uhlenbeck equation, for various density-dependent nuclear equations of state. Multiplicity distributions and inclusive rapidity and transverse momentum spectra are in good agreement. Rapidity spectra show evidence of being useful in determining whether the model uses the correct cross sections for binary collisions in the nuclear medium, and whether momentum-dependent interactions are correctly incorporated. Sideward flow results do not favor the same nuclear stiffness parameter at all multiplicities

Neutron-proton mass difference in isospin asymmetric nuclear matter

Isospin-breaking effects in the baryonic sector are studied in the framework of a medium-modified Skyrme model. The neutron-proton mass difference in infinite, asymmetric nuclear matter is discussed. In order to describe the influence of the nuclear environment on the skyrmions, we include energy-dependent charged and neutral pion optical potentials in the s- and p-wave channels. The present approach predicts that the neutron-proton mass difference is mainly dictated by its strong part and that it strongly decreases in neutron matter.Comment: 11 pages, 6 figures; some new references adde