2,950 research outputs found
Kaon condensation in the quark-meson coupling model and compact stars
The properties of neutron stars constituted of a crust of hadrons and an
internal part of hadrons and kaon condensate are calculated within the
quark-meson-coupling model. We have considered stars with nucleons only in the
hadron phase and also stars with hyperons as well. The results are compared
with the ones obtained from the non-linear Walecka model for the hadronic
phase.Comment: 10 pages, 6 figure
Warm stellar matter with neutrino trapping
The properties of hybrid stars formed by hadronic and quark matter in
beta-equilibrium at fixed entropies are described by appropriate equations of
state (EOS) in the framework of relativistic mean-field theory. In this work we
include the possibility of neutrino trapped EOS and compare the star properties
with the ones obtained after deleptonization, when neutrinos have already
diffused out. We use the nonlinear Walecka model for the hadron matter with two
different sets for the hyperon couplings and the MIT Bag and the
Nambu-Jona-Lasinio models for the quark matter. The phase transition to a
deconfined quark phase is investigated. Depending on the model and the
parameter set used, the mixed phase may or may not exist in the EOS at high
densities.
The star properties are calculated for each equation of state. The maximum
mass stellar configurations obtained within the NJL have larger masses than the
ones obtained within the Bag model. The Bag model predicts a mixed phase in the
interior of the most massive stable stars while, depending on the hyperon
couplings, the NJL model predicts a mixed phase or pure quark matter. Comparing
with neutrino free stars, the maximum allowed baryonic masses for protoneutron
stars are larger for the Bag model and
larger for the NJL model when neutrino trapping is imposed.Comment: 8 pages, 8 figures, 1 tabl
Varying Alpha Monopoles
We study static magnetic monopoles in the context of varying alpha theories
and show that there is a group of models for which the t'Hooft-Polyakov
solution is still valid. Nevertheless, in general static magnetic monopole
solutions in varying alpha theories depart from the classical t'Hooft-Polyakov
solution with the electromagnetic energy concentrated inside the core seeding
spatial variations of the fine structure constant. We show that Equivalence
Principle constraints impose tight limits on the allowed variations of alpha
induced by magnetic monopoles which confirms the difficulty to generate
significant large-scale spatial variation of the fine structure constant found
in previous works. This is true even in the most favorable case where magnetic
monopoles are the source for these variations.Comment: 8 pages, 10 figures; Version to be published in Phys. Rev.
Enraizamento de estacas de urucuzeiro Bixa orellana L.
bitstream/item/34014/1/CPATU-CirTec55-2.pd
The pasta phase within density dependent hadronic models
In the present paper we investigate the onset of the pasta phase with
different parametrisations of the density dependent hadronic model and compare
the results with one of the usual parametrisation of the non-linear Walecka
model. The influence of the scalar-isovector virtual delta meson is shown. At
zero temperature two different methods are used, one based on coexistent phases
and the other on the Thomas-Fermi approximation. At finite temperature only the
coexistence phases method is used. npe matter with fixed proton fractions and
in beta-equilibrium are studied. We compare our results with restrictions
imposed on the the values of the density and pressure at the inner edge of the
crust, obtained from observations of the Vela pulsar and recent isospin
diffusion data from heavy-ion reactions, and with predictions from spinodal
calculations.Comment: 15 pages, 11 figures and 7 table
Constraining relativistic models through heavy ion collisions
Relativistic models can be successfully applied to the description of compact
star properties in nuclear astrophysics as well as to nuclear matter and finite
nuclei properties, these studies taking place at low and moderate temperatures.
Nevertheless, all results are model dependent and so far it is unclear whether
some of them should be discarded. Moreover, in the regime of hot hadronic
matter very few calculations exist using these relativistic models, in
particular when applied to particle yields in heavy ion collisions.
In the present work we comment on the known constraints that can help the
selection of adequate models in this regime and investigate the main
differences that arise when the particle production during a Au+Au collision at
RHIC is calculated with different models.Comment: 9 pages, 1 figure, 3 table
Performance of grain sorghum hybrids in soils with low and high aluminum saturation.
The presence of aluminum (Al3+) in acidic soils is one of the main causes of low crop yield, since it inhibits the root growth, thus affecting the nutrients and water uptake by plants. An approach to grow crops in areas with high Al3+ saturation is the use of tolerant cultivars. This study aimed to evaluate commercial sorghum hybrids in soils with low and high aluminum saturation, in order to select cultivars with high grain yield, even when exposed to abiotic stress. Twenty hybrids were evaluated for characteristics such as plant flowering, plant height and grain yield. All three traits were significantly affected by Al3+, being grain yield the most affected one. Despite the significant genotypes x environments interaction for grain yield, it was possible to select hybrids with yield above the national average in both environments. The hybrids BRS373, 50A50, AS4639, DKB540, AS4625, A9721R, 1167092, DKB550, 1G282 and AG1040 showed a high yield under low and high Al-saturation conditions
Morfofisiologia de cultivares de feijão com crescimento contrastante.
O objetivo deste estudo foi comparar duas cultivares de feijão, BRS Radiante e Pérola, contrastantes no ciclo e hábito de crescimento por meio de determinantes fisiológicos e do desenvolvimento e crescimento da planta, com a finalidade de suprir informações sobre o desenvolvimento e produtividade do feijoeiro para incrementar o conhecimento morfofisiológico sobre essas cultivares comerciais.CONAF
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