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[en] The knowledge of the nuclear symmetry energy of hot neutron-rich matter is important for understanding the dynamical evolution of massive stars and the supernova explosion mechanisms. In particular, the electron capture rate on nuclei and/or free protons in presupernova explosions is especially sensitive to the symmetry energy at finite temperature. In view of the above, in the present work we calculate the symmetry energy as a function of the temperature for various values of the baryon density by applying a momentum-dependent effective interaction. In addition to a previous work, the thermal effects are studied separately both in the kinetic part and the interaction part of the symmetry energy. We focus also on the calculations of the mean-field potential, employed extensively in heavy-ion reaction research, both for nuclear and pure neutron matter. The proton fraction and the electron chemical potential, which are crucial quantities for representing the thermal evolution of supernova and neutron stars, are calculated for various values of the temperature. Finally, we construct a temperature dependent equation of state of β-stable nuclear matter, the basic ingredient for the evaluation of the neutron star properties
[en] We have studied the effects of momentum-dependent interactions on the single-particle properties of hot asymmetric nuclear matter. In particular, the single-particle potential of protons and neutrons as well as the symmetry potential have been studied within a self-consistent model using a momentum-dependent effective interaction. In addition, the isospin splitting of the effective mass has been derived from the above model. In each case temperature effects have been included and analyzed. The role of the specific parametrization of the effective interaction used in the present work has been investigated. It has been concluded that the behavior of the symmetry potential depends strongly on the parametrization of the interaction part of the energy density and the momentum dependence of the regulator function. The effects of the parametrization have been found to be less pronounced on the isospin mass splitting
[en] We provide an equation of state for hot nuclear matter in β equilibrium by applying a momentum-dependent effective interaction. We focus on the study of the equation of state of high-density and high-temperature nuclear matter, containing leptons (electrons and muons) under the chemical equilibrium condition in which neutrinos have left the system. The conditions of charge neutrality and equilibrium under the β-decay process lead first to the evaluation of proton and lepton fractions and then to the evaluation of internal energy, free energy, and pressure, and in total to the equation of state of hot nuclear matter. Thermal effects on the properties and equation of state of nuclear matter are assessed and analyzed in the framework of the proposed effective interaction model. Special attention is given to the study of the contribution of the components of β-stable nuclear matter to the entropy per particle, a quantity of great interest in the study of structure and collapse of supernova.
[en] The event rates for the direct detection of dark matter for various types of WIMPs are presented. In addition to the neutralino of SUSY models, we considered other candidates (exotic scalars as well as particles in Kaluza-Klein and technicolour theories) with masses in the TeV region. Then one finds reasonable branching ratios to excited states. Thus the detection of the WIMP can be made not only by recoil measurements, but by measuring the de-excitation γ-rays as well
[en] We present some theoretical elements relevant to the direct dark matter detection experiments, paying particular attention to directional experiments, i.e. experiments in which, not only the energy but the direction of the recoiling nucleus is observed. Since the direction of observation is fixed with respect the earth, while the Earth is rotating around its axis, in a directional experiment the angle between the direction of observation and the Sun's direction of motion will change during the day. So, since the event rates sensitively depend on this angle, the observed signal in such experiments will exhibit very interesting and characteristic periodic diurnal variation.
[en] The effect of dynamical short-range correlations on the generalized momentum distribution n(p-vec,Q-vec) in the case of Z = N, l-closed shell nuclei is investigated by introducing Jastrow-type correlations in the harmonic-oscillator model. First, a low-order approximation is considered and applied to the nucleus 4He. Compact analytical expressions are derived and numerical results are presented and the effect of centre-of-mass corrections is estimated. Next, an approximation is proposed for n(p-vec,Q-vec) of heavier nuclei that uses the above-correlated n(p-vec,Q-vec) of 4He. Results are presented for the nucleus 16O. It is found that the effect of short-range correlations is significant for rather large values of the momenta p and/or Q and should be included, along with centre-of-mass corrections for light nuclei, in a reliable evaluation of n(p-vec,Q-vec) in the whole domain of p and Q
[en] Calculations of the 6,8He+28Si total reaction cross-sections at intermediate energies are performed on the basis of the Glauber–Sitenko microscopic optical-limit model. The target-nucleus density distribution is taken from the electron-nucleus scattering data, and the 6,8He densities are used as they are derived in different models. The results of the calculations are compared with existing experimental data. The effects of the density tails of the projectile nuclei as well as the role of shell admixtures and short-range correlations are analyzed. (author)
[en] The transition density nt and pressure Pt at the inner edge between the liquid core and the solid crust of a neutron star are analyzed using the thermodynamical method and the framework of relativistic nuclear energy density functionals. Starting from a functional that has been carefully adjusted to experimental binding energies of finite nuclei, and varying the density dependence of the corresponding symmetry energy within the limits determined by isovector properties of finite nuclei, we estimate the constraints on the core-crust transition density and pressure of neutron stars: 0.086 fm-3≤nt<0.090 fm-3 and 0.3 MeV fm-3< Pt≤0.76 MeV fm-3.