The exotic structures expected in the outermost layer of neutron stars are investigated in a new approach. It is based on the DYnamical WAvelets in Nuclei (DYWAN) model of nuclear collisions. This ...microscopic dynamical approach is an Extended Time-Dependent Hartree–Fock description based on a wavelet representation. The model addresses the dynamical exploration of complex nuclear structures, beyond the Wigner–Seitz (WS) approximation and without any assumption on their final shapes. The present study focuses on exotic phases of cold matter evidenced dynamically at sub-saturation densities, currently within a pure mean field framework, before tackling the effects of the multi-particle correlations in a forthcoming study. Starting from inhomogeneous initial conditions provided by nuclei located on an initial crystalline lattice, the exotic structures result from a dynamical self-consistent treatment where, in principle, the nuclear system can freely self-organize, modify the lattice structure or even break the lattice and the initial matter distribution symmetries. In this work nuclei are initially slightly excited with low-lying collective modes. The system can then explore geometrical configurations with similar energies, without being trapped in the vicinity of a local minimum. In this quantum framework, different effects are analyzed, among them the sensitivity to the equation of state and to the proton fraction.
Neutron Stars are natural laboratories where fundamental properties of matter under extreme conditions can be explored. Modern nuclear physics input as well as many-body theories are valuable tools ...which may allow us to improve our understanding of the physics of those compact objects. In this work the occurrence of exotic structures in the outermost layers of neutron stars is investigated within the framework of a microscopic model. In this approach the nucleonic dynamics is described by a time-dependent mean field approach at around zero temperature. Starting from an initial crystalline lattice of nuclei at subnuclear densities the system evolves toward a manifold of self-organized structures with different shapes and similar energies. These structures are studied in terms of a phase diagram in density and the corresponding sensitivity to the isospin-dependent part of the equation of state and to the isotopic composition is investigated.
The dynamics of infinite nuclear matter in the conditions of density and temperature expected in the outermost layers of neutron stars is studied in the framework of a microscopic time-dependent ...mean-field approach around zero temperature. Dynamical processes in inhomogeneous nuclear matter are studied using a large number of nucleons in numerical simulations without any assumptions on the morphology of nuclear matter. The occurrence of exotic structures when varying internal conditions as densities, nuclear species and elementary cell symmetries is investigated. The corresponding structures are studied in terms of a phase diagram in density space evidencing some sensitivity to the isospin-dependent part of the equation of state.
Semiclassical transport simulation of nucleus-nucleus collisions for the range of incident energy from about the Fermi energy up to a few hundred MeV per nucleon evidences that the maximal excitation ...energy put into a nuclear system during the early compact stage of heavy-ion reaction is a constant fraction of the center-of-mass available energy of the system. Analysis of experimental data without presuming reaction mechanism dominating the collision process on the best corroborates the found constancy of energy partition in central heavy-ion reactions.
A systematics of over 300 complete and incomplete fusion cross section data points covering energies beyond the barrier for fusion is presented. Owing to a usual reduction of the fusion cross ...sections by the total reaction cross sections and an original scaling of energy, a fusion excitation function common to all the data points is established. A universal description of the fusion exci- tation function relying on basic nuclear concepts is proposed and its dependence on the reaction cross section used for the cross section normalization is discussed. The pioneering empirical model proposed by Bass in 1974 to describe the complete fusion cross sections is rather successful for the incomplete fusion too and provides cross section predictions in satisfactory agreement with the observed universality of the fusion excitation function. The sophisticated microscopic transport DYWAN model not only reproduces the data but also predicts that fusion reaction mechanism disappears due to weakened nuclear stopping power around the Fermi energy.
A microscopic investigation of nucleon-induced reactions is addressed within the DYWAN model, which is based on the projection methods of out of equilibrium statistical physics and on the ...mathematical theory of wavelets. Due to a strongly compressed representation of the fermionic wave functions, the numerical simulations of the nucleon transport in target are therefore able to preserve the quantum nature of the colliding system, as well as a least biased many-body information needed to keep track of the cluster formation. A special attention is devoted to the fingerprints of the phase space topology induced by the fluctuations of the self-consistent mean-field. Comparisons between theoretical results and experimental data point out that ETDHF type approaches are well suited to describe reaction mechanisms in the Fermi energy domain. The observed sensitivity to physical effects shows that the nucleon-induced reactions provide a valuable probe of the nuclear interaction in this range of energy.
We study the energy dependence of the fusion cross-section with the goal of understanding the evolution of the underlying reaction mechanism as a function of input channel parameters and the causes ...of its (non-)disappearance. The heart of this work is a systematic and as wide as possible overview of measured cross-sections. Normalized by the reaction cross-section and plotted as a function of the available energy per ucleon corrected for the Coulomb barrier, fusion crosssection show a rather universal behavior leading to a disappearance of the fusion around 10A MeV, except in the case of very asymmetric systems for which incomplete fusion persists and tends towards a constant value that can be explained in the frame of a simple geometrical approach. These trends are confirmed by the semiclassical Landau-Vlasov transport calculations.
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