64 research outputs found
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.
Core-crust transition in neutron stars: predictivity of density developments
The possibility to draw links between the isospin properties of nuclei and
the structure of compact stars is a stimulating perspective. In order to pursue
this objective on a sound basis, the correlations from which such links can be
deduced have to be carefully checked against model dependence. Using a variety
of nuclear effective models and a microscopic approach, we study the relation
between the predictions of a given model and those of a Taylor density
development of the corresponding equation of state: this establishes to what
extent a limited set of phenomenological constraints can determine the
core-crust transition properties. From a correlation analysis we show that a)
the transition density is mainly correlated with the symmetry energy
slope , b) the proton fraction with the symmetry energy and
symmetry energy slope defined at saturation density, or, even better,
with the same quantities defined at fm, and c) the transition
pressure with the symmetry energy slope and curvature
defined at fm
Predictions for charmed nuclei based on forces inferred from lattice QCD simulations
Charmed nuclei are investigated utilizing and
interactions that have been extrapolated from lattice QCD simulations at
unphysical masses of -- MeV to the physical point using
chiral effective field theory as guideline. Calculations of the energies of
single-particle bound states for various charmed nuclei from $^{\
5}_{\Lambda_c}^{209}_{\Lambda_c}\Lambda_c\Lambda_c N\LambdaA=4\Lambda_c^{\,
3}_{\Lambda_c}$He state.Comment: 13 pages, 5 figure
Open-charm mesons in nuclear matter at finite temperature beyond the zero-range approximation
The properties of open charm mesons, D, D, D{sub s}, and D{sub s} in nuclear matter at finite temperature are studied within a self-consistent coupled-channel approach. The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm sector is derived from a t-channel vector-exchange model. The in-medium scattering amplitudes are obtained by solving the Lippmann-Schwinger equation at finite temperature including Pauli blocking effects, baryon dressing, as well as D, D, D{sub s}, and D{sub s} self-energies taking their mutual influence into account. We find that the in-medium properties of the D meson are affected by the D{sub s}-meson self-energy through the intermediate D{sub s}Y loops coupled to DN states. Similarly, dressing the D meson in the DY loops has an influence over the properties of the D{sub s} meson
Role of correlations in spin-polarized neutron matter
Background: The possible existence of a phase transition to a ferromagnetic state in neutron matter as origin of the extremely high magnetic fields of neutron stars is still an open issue. Whereas many phenomenological interactions predict this transition at densities accessible in neutron stars, microscopic calculations based on realistic interactions show no indication of it. The existence or non-existence of this transition is a consequence of the different role of nucleon-nucleon correlations in polarized and unpolarized neutron matter. Therefore, to give a definite answer to this issue it is necessary to analyze the behavior of these correlations. Purpose: Using the Hellmann-Feynman theorem we analyze the contribution of the different terms of the nucleon-nucleon interaction to the spin symmetry energy of neutron matter with the purpose of identifying the nature and role of correlations in polarized and unpolarized neutron matter. Methods: The analysis is performed within the microscopic Brueckner-Hartree-Fock approach using the Argonne V18 realistic potential plus the Urbana IX three-body force. Results: Our results show no indication of a ferromagnetic transition as the spin symmetry energy of neutron matter is always an increasing function of density. They show also that the main contribution to it comes from the S = 0 channel, acting only in non-polarized neutron matter, in particular from the S-1(0) and the D-1(2) partial waves. Three-body forces are found to play a secondary role in the determination of the spin symmetry energy. Conclusions: By evaluating the kinetic energy difference between the correlated system and the underlying Fermi sea to estimate the importance of correlations in spin-polarized neutron matter, we conclude that non-polarized neutron matter is more correlated than totally polarized one
Ferromagnetic instabilities in neutron matter at finite temperature with the Gogny interaction
The properties of spin polarized neutron matter are studied both at zero and finite temperature using the D1 and the D1P parameterizations of the Gogny interaction. The results show two different behaviors: whereas the D1P force exhibits a ferromagnetic transition at a density of fm whose onset increases with temperature, no sign of such a transition is found for D1 at any density and temperature, in agreement with recent microscopic calculations
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