1,076 research outputs found
Pairing correlations of cold fermionic gases at overflow from a narrow to a wide harmonic trap
Within the context of Hartree-Fock-Bogoliubov theory, we study the behavior
of superfluid Fermi systems when they pass from a small to a large container.
Such systems can be now realized thanks to recent progress in experimental
techniques. It will allow to better understand pairing properties at overflow
and in general in rapidly varying external potentials
Excitation energy dependence of symmetry energy of finite nuclei
A finite range density and momentum dependent effective interaction is used
to calculate the density and temperature dependence of the symmetry energy
coefficient Csym(rho,T) of infinite nuclear matter. This symmetry energy is
then used in the local density approximation to evaluate the excitation energy
dependence of the symmetry energy coefficient of finite nuclei in a
microcanonical formulation that accounts for thermal and expansion effects. The
results are in good harmony with the recently reported experimental data from
energetic nucleus-nucleus collisions.Comment: 11 pages, 3 figures, revtex4; minor changes in text, axis label in
figure 1 correcte
Density reorganization in hot nuclei
The density profile of a hot nuclear system produced in intermediate energy
heavy ion collisions is studied in a microcanonical formulation with a momentum
and density dependent finite range interaction. The caloric curve and the
density evolution with excitation are calculated for a number of systems for
the equilibrium mononuclear configuration; they compare favorably with the
recent experimental data. The studied density fluctuations are seen to build up
rapidly beyond an excitation energy of 8 MeV/u indicating the instability of
the system towards nuclear disassembly. Explicit introduction of deformation in
the expansion path of the heated nucleus, however, shows that the system might
fragment even earlier. We also explore the effects of the nuclear equation of
state and of the mass and isospin asymmetry on the nuclear equilibrium
configuration and the relevant experimental observables.Comment: 20 pages, 12 figures, revtex
Symmetry energy of warm nuclear systems
The temperature dependence of the symmetry energy and symmetry free energy
coefficients of infinite nuclear matter and of finite nuclei is investigated.
For infinite matter, both these coefficients are found to have a weaker
dependence on temperature at densities close to saturation; at low but
homogeneous densities, the temperature dependence becomes stronger. For finite
systems, different definitions of symmetry energy coefficients are encountered
in the literature yielding different values. A resolution to this problem is
suggested from a global liquid-drop-inspired fit of the energies and free
energies of a host of nuclei covering the entire periodic table. The hot
nucleus is modeled in a subtracted finite-temperature-Thomas-Fermi framework,
with dynamical surface phonon coupling to nucleonic motion plugged in. Contrary
to infinite nuclear matter, a substantial change in the symmetry energy
coefficients is observed for finite nuclei with temperature.Comment: 12 pages, including 11 figures, appearing in special issue of EPJ-A
on Nuclear Symmetry Energ
Light projectile elastic scattering by nuclei described by the Gogny interaction
In this work, we study the elastic scattering of some light particles, such
as H, H, He, and He, by heavy target nuclei with an extended
Watanabe model, which uses as input the neutron-nucleus and proton-nucleus
optical potentials and the ground-state wave functions of the projectile. The
nucleon-nucleus optical potential used in this work was obtained within a
semi-microscopic nuclear matter approach, whose real and imaginary parts are
provided by the first and second-order terms, respectively, of the Taylor
expansion of the Brueckner-Hartree-Fock mass operator obtained with the
reaction G-matrix built up with the Gogny force \cite{lopez21}. The angular
distributions of the scattering of H, H, He, and He from
different target nuclei and at a different incident energy of the projectile
computed with this model are analyzed. The reaction cross-sections
corresponding to some of these scattering processes are also calculated. Our
results are compared with the experimental values as well as with another
Watanabe calculation where the nucleon-nucleus the optical potential is
provided by the phenomenological K\"oning-Delaroche model. The limitations of
the extended Watanabe model used in this work are also discussed
The effects of medium on nuclear properties in multifragmentation
In multifragmentation of hot nuclear matter, properties of fragments embedded
in a soup of nucleonic gas and other fragments should be modified as compared
with isolated nuclei. Such modifications are studied within a simple model
where only nucleons and one kind of heavy nuclei are considered. The
interaction between different species is described with a momentum-dependent
two-body potential whose parameters are fitted to reproduce properties of cold
isolated nuclei. The internal energy of heavy fragments is parametrized
according to a liquid-drop model with density and temperature dependent
parameters. Calculations are carried out for several subnuclear densities and
moderate temperatures, for isospin-symmetric and asymmetric systems. We find
that the fragments get stretched due to interactions with the medium and their
binding energies decrease with increasing temperature and density of nuclear
matter.Comment: 12 pages, 11 figures, Phys. Rev.C (in press
High-frequency Alfven waves in multi-ion coronal plasma : observational implications
We investigate the effects of high-frequency (of order ion gyrofrequency) Alfvén and ion-cyclotron waves on ion emission lines by studying the dispersion of these waves in a multi-ion coronal plasma. For this purpose we solve the dispersion relation of the linearized multifluid and Vlasov equations in a magnetized multi-ion plasma with coronal abundances of heavy ions. We also calculate the dispersion relation using nonlinear one-dimensional hybrid kinetic simulations of the multi-ion plasma. When heavy ions are present the dispersion relation of parallel propagating Alfvén cyclotron waves exhibits the following branches (in the positive Ω − k quadrant): right-hand polarized nonresonant and left-hand polarized resonant branch for protons and each ion. We calculate the ratio of ion to proton velocities perpendicular to the direction of the magnetic field for each wave modes for typical coronal parameters and find strong enhancement of the heavy ion perpendicular fluid velocity compared with proton perpendicular fluid velocity. The linear multifluid cold plasma results agree with linear warm plasma Vlasov results and with the nonlinear hybrid simulation model results. In view of our findings we discuss how the observed nonthermal line broadening of minor ions in coronal holes may relate to the high-frequency wave motions
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