Comment on "Energies of the ground state and first excited 0+0^{+} in an exactly solvable pairing model"

We comment on a recent application of the RPA method and its extensions to the case of the two-level pairing model by N. Dinh Dang [1].Comment: 5 pages, 1 figure, submitted to EPJ

Dense stellar matter with trapped neutrinos under strong magnetic fields

We investigate the effects of strong magnetic fields on the equation of state of dense stellar neutrino-free and neutrino-trapped matter. Relativistic nuclear models both with constant couplings (NLW) and with density dependent parameters (DDRH) and including hyperons are considered . It is shown that at low densities neutrinos are suppressed in the presence of the magnetic field. The magnetic field reduces the strangeness fraction of neutrino-free matter and increases the strangeness fraction of neutrino-trapped matter. The mass-radius relation of stars described by these equations of state are determined. The magnetic field makes the overall equation of state stiffer and the stronger the field the larger the mass of maximum mass star and the smaller the baryon density at the center of the star. As a consequence in the presence of strong magnetic fields the possibility that a protoneutron star evolves to a blackhole is smaller.Comment: 18 pages, 13 figures, 5 tables, submitted to J. Phys.

Effect of the δ\delta-meson on the instabilities of nuclear matter under strong magnetic fields

We study the influence of the isovector-scalar meson on the spinodal instabilities and the distillation effect in asymmetric non-homogenous nuclear matter under strong magnetic fields, of the order of $10^{18}-10^{19}$ G. Relativistic nuclear models both with constant couplings (NLW) and with density dependent parameters (DDRH) are considered. A strong magnetic field can have large effects on the instability regions giving rise to bands of instability and wider unstable regions. It is shown that for neutron rich matter the inclusion of the $\delta$ meson increases the size of the instability region for NLW models and decreases it for the DDRH models. The effect of the $\delta$ meson on the transition density to homogeneous $\beta$-equilibrium matter is discussed. The DDRH$\delta$ model predicts the smallest transition pressures, about half the values obtained for NL$\delta$.Comment: 6 pages, 5 figues, 3 tables, accepted for publication in Phys. Rev.

Walnut cracking machine

Mestrado de dupla diplomação com a Université Libre de TunisThe traditional strategy of breaking walnuts physically, utilizing a hammer or cut cutter is labor-seriously, moderate, and repetitive. We report this project of walnut cracking machine technical drawing for the construction of the cracking machine and the belt conveyor are also presented. the prototype consists of a belt conveyor transport the walnut to the cracking machine. A breaking unit works on the rule of attraction utilizing crushing drive from tow rollers. The aim of this project is to create a nut-cracking machine that will be able to reliably accomplish both cracking as well as conveying of nuts. and crack the different sizes of shells. for the construction of the cracking machine, 51% of the components are standard and 49% will have manufactured. A device of this nature can be manufactured for small entrepreneurs and industrial-level applications in the countries where the bulk of the world walnut is produced.La stratégie traditionnelle de casser les noix physiquement, en utilisant un marteau ou un cutter, est un travail sérieux, modéré et répétitif. Nous rapportons ce projet de dessin technique de machine de craquage de noix pour la construction de la machine de craquage et le convoyeur à bande sont également présentés. Le prototype consiste en un convoyeur à bande transportant la noix vers la machine de craquage. Une unité de rupture fonctionne selon la règle de l'attraction en utilisant l'entraînement par écrasement des rouleaux de remorquage. Le but de ce projet est de créer une machine à casser les noix qui sera capable de réaliser de manière fiable à la fois la fissuration et le transport des noix, et casser les différentes tailles de coquilles. Pour la construction de la machine de craquage, 51% des composants sont standards et 49% l'auront fabriqué. Un dispositif de cette nature peut être fabriqué pour les petits entrepreneurs et les applications de niveau industriel dans les pays où la majeure partie de la noix mondiale est produite

The 1D Heisenberg antiferromagnet model by the variation after projection method

The 4 sites and 8 sites 1D anti-ferromagnetic Heisenberg chains in the Jordan-Wigner representation are investigated within the standard Hartree-Fock and RPA approaches, both in the symmetry unbroken and in the symmetry broken phases. A translation invariant groundstate, obtained by the projection method as a linear combination of a symmetry-broken HF state and its image under reflection, is also considered, for each chain type. It is found that the projection method considerably improves the HF treatment for instance as far as the groundstate energy is concerned, but also with respect to the RPA energies. The results are furthermore confronted with the ones obtained within so-called SCRPA scheme.Comment: 15 pages, 8 figures, 1 table, accepted for publication in Int. J. Mod. Phys.