Neutrino propagation in dense hadronic matter

Neutrino propagation in protoneutron stars requires the knowledge of the composition as well as the dynamical response function of dense hadronic matter. Matter at very high densities is probably composed of other particles than nucleons and little is known on the Fermi liquid properties of hadronic multicomponent systems. We will discuss the effects that the presence of $\Lambda$ hyperons might have on the response and, in particular, on its influence on the thermodynamical stability of the system and the mean free path of neutrinos in dense matter.Comment: Proceedings of the XX Max Born Symposium ''Nuclear effects in neutrino interactions'', Wroclaw (Poland), December 7-10, 200

Correlated density-dependent chiral forces for infinite matter calculations within the Green's function approach

The properties of symmetric nuclear and pure neutron matter are investigated within an extended self-consistent Green's function method that includes the effects of three-body forces. We use the ladder approximation for the study of infinite nuclear matter and incorporate the three-body interaction by means of a density-dependent two-body force. This force is obtained via a correlated average over the third particle, with an in-medium propagator consistent with the many-body calculation we perform. We analyze different prescriptions in the construction of the average and conclude that correlations provide small modifications at the level of the density-dependent force. Microscopic as well as bulk properties are studied, focusing on the changes introduced by the density dependent two-body force. The total energy of the system is obtained by means of a modified Galitskii-Migdal-Koltun sum rule. Our results validate previously used uncorrelated averages and extend the availability of chirally motivated forces to a larger density regime.Comment: 17 pages, 11 figure

Ferromagnetic instabilities in neutron matter at finite temperature with the Skyrme interaction

The properties of spin polarized neutron matter are studied both at zero and finite temperature using Skyrme-type interactions. It is shown that the critical density at which ferromagnetism takes place decreases with temperature. This unexpected behaviour is associated to an anomalous behaviour of the entropy which becomes larger for the polarized phase than for the unpolarized one above a certain critical density. This fact is a consequence of the dependence of the entropy on the effective mass of the neutrons with different third spin component and a new constraint on the parameters of the effective Skyrme force is derived in order to avoid such a behaviour.Comment: REVTEX4 - 18 pages, 8 figures, 2 tables Revised according to referee comments - Submitted to Phys. Rev.

Fermionic properties of two interacting bosons in a two-dimensional harmonic trap

The system of two interacting bosons in a two-dimensional harmonic trap is compared with the system consisting of two noninteracting fermions in the same potential. In particular, we discuss how the properties of the ground state of the system, e.g., the different contributions to the total energy, change as we vary both the strength and range of the atom-atom interaction. In particular, we focus on the short-range and strong interacting limit of the two-boson system and compare it to the noninteracting two-fermion system by properly symmetrizing the corresponding degenerate ground state wave functions. In that limit, we show that the density profile of the two-boson system has a tendency similar to the system of two noninteracting fermions. Similarly, the correlations induced when the interaction strength is increased result in a similar pair correlation function for both systems

Density dependence of the nuclear symmetry energy: a microscopic perspective

We perform a systematic analysis of the density dependence of the nuclear symmetry energy within the microscopic Brueckner--Hartree--Fock (BHF) approach using the realistic Argonne V18 nucleon-nucleon potential plus a phenomenological three body force of Urbana type. Our results are compared thoroughly to those arising from several Skyrme and relativistic effective models. The values of the parameters characterizing the BHF equation of state of isospin asymmetric nuclear matter fall within the trends predicted by those models and are compatible with recent constraints coming from heavy ion collisions, giant monopole resonances or isobaric analog states. In particular we find a value of the slope parameter $L=66.5$ MeV, compatible with recent experimental constraints from isospin diffusion, $L=88 \pm 25$ MeV. The correlation between the neutron skin thickness of neutron-rich isotopes and the slope, $L$, and curvature, $K_{sym}$, parameters of the symmetry energy is studied. Our BHF results are in very good agreement with the correlations already predicted by other authors using non-relativistic and relativistic effective models. The correlations of these two parameters and the neutron skin thickness with the transition density from non-uniform to $\beta$-stable matter in neutron stars are also analyzed. Our results confirm that there is an inverse correlation between the neutron skin thickness and the transition density.Comment: 8 figure

Few-boson localization in a continuum with speckle disorder

The disorder-induced localization of few bosons interacting via a contact potential is investigated through the analysis of the level-spacing statistics familiar from random matrix theory. The model we consider is defined in a continuum and describes one-dimensional bosonic atoms exposed to the spatially correlated disorder due to an optical speckle field. % First, we identify the speckle-field intensity required to observe, in the single-particle case, the Poisson level-spacing statistics, which is characteristic of localized quantum systems, in a computationally and experimentally feasible system size. Then, we analyze the two-body and the three-body systems, exploring a broad interaction range, from the noninteracting limit up to moderately strong interactions. Our main result is that the contact potential does not induce a shift towards the Wigner-Dyson level-spacing statistics, which would indicate the emergence of an ergodic chaotic state, indicating that localization can occur also in interacting few-body systems in a continuum. We also analyze how the ground-state energy evolves as a function of the interaction strengthComment: revised versio