Isospin in Reaction Dynamics. The Case of Dissipative Collisions at Fermi Energies

A key question in the physics of unstable nuclei is the knowledge of the $EOS$ for asymmetric nuclear matter ($ANM$) away from normal conditions. We recall that the symmetry energy at low densities has important effects on the neutron skin structure, while the knowledge in high densities region is crucial for supernovae dynamics and neutron star properties. The $only$ way to probe such region of the isovector $EOS$ in terrestrial laboratories is through very dissipative collisions of asymmetric (up to exotic) heavy ions from low to relativistic energies. A general introduction to the topic is firstly presented. We pass then to a detailed discussion on the $neck-fragmentation$ process as the main dissipative mechanism at the Fermi energies and to the related isospin dynamics. From Stochastic Mean Field simulations the isospin effects on all the phases of the reaction dynamics are thoroughly analysed, from the fast nucleon emission to the mid-rapidity fragment formation up to the dynamical fission of the $spectator$ residues. Simulations have been performed with an increasing stiffness of the symmetry term of the $EOS$. Some differences have been noticed, especially for the fragment charge asymmetry. New isospin effects have been revealed from the correlation of fragment asymmetry with dynamical quantities at the freeze-out time. A series of isospin sensitive observables to be further measured are finally listed.Comment: 16 pages, 6 figures, Contribution to the 5th Italy-Japan Symposium, Recent Achievements and Perspectives in Nuclear Physics, Naples Nov.3-7 2004, World Sci. in press. Latex in WorldSci/proc/styl

Does the NJL chiral phase transition affect the elliptic flow of a fluid at fixed η/s\eta/s?

We have derived and solved numerically the Boltzmann-Vlasov transport equations that includes both two-body collisions and the chiral phase transition by mean of NJL-field dynamics. The scope is to understand if the field dynamics supply new genuine effects on the build-up of the elliptic flow $v_2$, a measure of the asymmetry in the momentum space, and in particular if it can affect the relation between $v_2$ and the shear viscosity to entropy ratio $\eta/s$. Solving the transport equation with a constant cross section for the condition of $Au+Au$ collisions at $\sqrt{s_{NN}}=200$ AGeV it is shown a sizable suppression of $v_2$ due to the attractive nature of the field dynamics that generates the constituent mass. However the key result is that if $\eta/s$ of the system is kept fixed by an appropriate local renormalization of the cross section the $v_2$ does not depend on the details of the collisional and/or field dynamics and in particular it is not affected significantly by the chiral phase transition.Comment: 5 pages, 5 figure

Consideration of the Mechanisms for Tidal Bore Formation in an Idealized Planform Geometry

A tidal bore is a positive wave traveling upstream along the estuary of a river, generated by a relatively rapid rise of the tide, often enhanced by the funneling shape of the estuary. The swell produced by the tide grows and its front steepens as the flooding tide advances inland, promoting the formation of a sharp front wave, i.e., the tidal bore. Because of the many mechanisms and conditions involved in the process, it is difficult to formulate an effective criterion to predict the bore formation. In this preliminary analysis, aimed at bringing out the main processes and parameters that control tidal bore formation, the degrees of freedom of the problem are largely reduced by considering a rectangular channel of constant width with uniform flow, forced downstream by rising the water level at a constant rate. The framework used in this study is extremely simple, yet the problem is still complex and the solution is far from being trivial. From the results of numerical simulations, three distinctive behaviors emerged related to conditions in which a tidal bore forms, a tidal bore does not form, and a weak bore forms; the latter has a weakly steep front and after the bore formed it rapidly vanishes. Based on these behaviors, some criteria to predict the bore formation are proposed and discussed. The more effective criterion, suitably rearranged, is checked against data from real estuaries and the predictions are found to compare favorably with the available data

Phase transition in a super superspin glass

We here confirm the occurrence of spin glass phase transition and extract estimates of associated critical exponents of a highly monodisperse and densely compacted system of bare maghemite nanoparticles. This system has earlier been found to behave like an archetypal spin glass, with e.g. a sharp transition from paramagnetic to non-equilibrium behavior, suggesting that this system undergoes a spin-glass phase transition at a relatively high temperature, $T_g$ $\sim$ 140 K.Comment: 4 pages, 3 figure

Parental Discipline Styles: A Study of Its Effects on the Development of Young Adults at the University Level

The present study examined the significance of methods of discipline used by parents and how these methods of discipline consequently affect multiple aspects of their child\u27s development well into adulthood. Participants were young adults ranging from ages 18-55 recruited from various university psychology courses. The participants were given an online questionnaire measuring quantitative data. This questionnaire asked about methods of discipline the participant’s parents used on them, if they were ever spanked as children, if they believe spanking to be harmful to children, which methods of discipline made them feel worse, and how they would rate their current level of selfesteem, and about the quality of the parent-child relationship