111 research outputs found
On the relativistic origin of the kink effect in the chain of Pb isotopes
We investigate the origin of the kink effect (KE) in the relativistic mean
field theory by transforming the single-particle Dirac equation into a
Schrodinger-like equation. It is found that relativistic self-consistent
effects as well as contributions from the rho meson determine the actual
structure of the KE. However, the spin-orbit force generated by the rho meson
has no significant influence on the KE.Comment: 11 pages, RevTeX, 3 postscript figs., Phys. Lett.
Instabilities of infinite matter with effective Skyrme-type interactions
The stability of the equation of state predicted by Skyrme-type interactions
is examined. We consider simultaneously symmetric nuclear matter and pure
neutron matter. The stability is defined by the inequalities that the Landau
parameters must satisfy simultaneously. A systematic study is carried out to
define interaction parameter domains where the inequalities are fulfilled. It
is found that there is always a critical density beyond which the
system becomes unstable. The results indicate in which parameter regions one
can find effective forces to describe correctly finite nuclei and give at the
same time a stable equation of state up to densities of 3-4 times the
saturation density of symmetric nuclear matter.Comment: 20 pages, 5 figures, submitted to Phys.Rev.
Realistic Neutrino Opacities for Supernova Simulations With Correlations and Weak Magnetism
Advances in neutrino transport allow realistic neutrino interactions to be
incorporated into supernova simulations. We add tensor couplings to
relativistic RPA calculations of neutrino opacities. Our results reproduce
free-space neutrino-nucleon cross sections at low density, including weak
magnetism and recoil corrections. In addition, our opacities are
thermodynamically consistent with relativistic mean field equations of state.
We find antineutrino mean free paths that are considerably larger then those
for neutrinos. This difference depends little on density. In a supernova, this
difference could lead to an average energy of that is larger than
that for by an amount that is comparable to the energy difference
between and Comment: 15 pages, 10 figures, submitted to PRC, minor changes to figs. (9,10
Description of nuclear systems within the relativistic Hartree-Fock method with zero range self-interactions of the scalar field
An exact method is suggested to treat the nonlinear self-interactions (NLSI)
in the relativistic Hartree-Fock (RHF) approach for nuclear systems. We
consider here the NLSI constructed from the relativistic scalar nucleon
densities and including products of six and eight fermion fields. This type of
NLSI corresponds to the zero range limit of the standard cubic and quartic
self-interactions of the scalar field. The method to treat the NLSI uses the
Fierz transformation, which enables one to express the exchange (Fock)
components in terms of the direct (Hartree) ones. The method is applied to
nuclear matter and finite nuclei. It is shown that, in the RHF formalism, the
NLSI, which are explicitly isovector-independent, generate scalar, vector and
tensor nucleon self-energies strongly density-dependent. This strong isovector
structure of the self-energies is due to the exchange terms of the RHF method.
Calculations are carried out with a parametrization containing five free
parameters. The model allows a description of both types of systems compatible
with experimental data.Comment: 23 pages, 14 figures (v2: major quantitative changes
Regional development gaps in Argentina: A multidimensional approach to identify the location of policy priorities
Spatial inequalities within Latin American countries have historically attracted the interest ofacademics, policy-makers, and international agencies. This article aims to provide amultidimensional diagnosis of provincial development gaps in Argentina, in order to identifythe location of policy priorities. Therefore, we built a large database, which covers sevendevelopment dimensions, and applied multivariate analysis techniques to overcome someanalytical limitations of previous studies. Results show the stability of provincial developmentgaps between 2003 and 2013 and some heterogeneity within geographic regions. Instead,cluster analysis offers a better classification of Argentine provinces according to theirdevelopment gaps, which can help the government to prioritize the places wheredevelopment policies are strategic.Fil: Niembro, AndrĂ©s Alberto. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Patagonia Norte; Argentina. Universidad Nacional de RĂo Negro; ArgentinaFil: Sarmiento, Jesica Isabel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Patagonia Norte; Argentina. Universidad Nacional de RĂo Negro; Argentin
Neutrino Opacities in Neutron Stars with Kaon Condensates
The neutrino mean free paths in hot neutron-star matter are obtained in the
presence of kaon condensates. The kaon-induced neutrino absorption process,
which is allowed only in the presence of kaon condensates, is considered for
both nondegenerate and degenerate neutrinos. The neutrino mean free path due to
this process is compared with that for the neutrino-nucleon scattering. While
the mean free path for the kaon-induced neutrino absorption process is shown to
be shorter than the ordinary two-nucleon absorption process by several orders
of magnitude when temperature is not very high, the neutrino-nucleon scattering
process has still a dominant contribution to the neutrino opacity. Thus, the
kaon-induced neutrino absorption process has a minor effect on the thermal and
dynamical evolution of protoneutron stars.Comment: 35 pages, 4 figure
Neutrino propagation and spin zero sound in hot neutron matter with Skyrme interactions
We present microscopic calculations of neutrino propagation in hot neutron
matter above nuclear density within the framework of the Random Phase
Approximation . Calculations are performed for non- degenerate neutrinos using
various Skyrme effective interactions. We find that for densities just above
nuclear density, spin zero sound is present at zero temperature for all Skyrme
forces considered. However it disappears rapidly with increasing temperature
due to a strong Landau damping. As a result the mean-free path is given, to a
good approximation, by the mean field value. Because of the renormalization of
the bare mass in the mean field, the medium is more transparent as compared to
the free case. We find, in contrast, that at several times nuclear density, a
new type of behavior sets in due to the vicinity of a magnetic instability. It
produces a strong reduction of the mean free path. The corresponding transition
density however occurs in a region where inputs from more realistic
calculations are necessary for the construction of a reliable Skyrme type
parametrization.Comment: 17 pages, 4 figure
Parker solar probe: four years of discoveries at solar cycle minimum
Launched on 12 Aug. 2018, NASAâs Parker Solar Probe had completed 13 of its scheduled 24 orbits around the Sun by Nov. 2022. The missionâs primary science goal is to determine the structure and dynamics of the Sunâs coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Parker Solar Probe returned a treasure trove of science data that far exceeded quality, significance, and quantity expectations, leading to a significant number of discoveries reported in nearly 700 peer-reviewed publications. The first four years of the 7-year primary mission duration have been mostly during solar minimum conditions with few major solar events. Starting with orbit 8 (i.e., 28 Apr. 2021), Parker flew through the magnetically dominated corona, i.e., sub-AlfvĂ©nic solar wind, which is one of the missionâs primary objectives. In this paper, we present an overview of the scientific advances made mainly during the first four years of the Parker Solar Probe mission, which go well beyond the three science objectives that are: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles
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