346 research outputs found
QCD in neutron stars and strange stars
This paper provides an overview of the possible role of Quantum Chromo
Dynamics (QDC) for neutron stars and strange stars. The fundamental degrees of
freedom of QCD are quarks, which may exist as unconfined (color
superconducting) particles in the cores of neutron stars. There is also the
theoretical possibility that a significantly large number of up, down, and
strange quarks may settle down in a new state of matter known as strange quark
matter, which, by hypothesis, could be more stable than atomic nuclei. In the
latter case new classes of self-bound, color superconducting objects, ranging
from strange quark nuggets to strange quark stars, should exist. The properties
of such objects will be reviewed along with the possible existence of
deconfined quarks in neutron stars. Implications for observational astrophysics
are pointed out.Comment: 7 pages, 2 figures; presented at the T(R)OPICAL QCD Workshop,
September 26 - October 2, 2010, Cairns, Australi
Thermal evolution of hybrid stars within the framework of a nonlocal Nambu--Jona-Lasinio model
We study the thermal evolution of neutron stars containing deconfined quark
matter in their core. Such objects are generally referred to as quark-hybrid
stars. The confined hadronic matter in their core is described in the framework
of non-linear relativistic nuclear field theory. For the quark phase we use a
non-local extension of the SU(3) Nambu Jona-Lasinio model with vector
interactions. The Gibbs condition is used to model phase equilibrium between
confined hadronic matter and deconfined quark matter. Our study indicates that
high-mass neutron stars may contain between 35 and 40 % deconfined quark-hybrid
matter in their cores. Neutron stars with canonical masses of around would not contain deconfined quark matter. The central proton
fractions of the stars are found to be high, enabling them to cool rapidly.
Very good agreement with the temperature evolution established for the neutron
star in Cassiopeia A (Cas A) is obtained for one of our models (based on the
popular NL3 nuclear parametrization), if the protons in the core of our stellar
models are strongly paired, the repulsion among the quarks is mildly repulsive,
and the mass of Cas A has a canonical value of .Comment: 10 pages, 7 figure
Avaliações de linhagens promissoras de aveia para a produção de forragem em São Paulo.
Treze linhagens promissoras de aveia forenecidas pela UFPF foram testadas quanto a sua capacidade de produção de forragem
Avaliação do potencial de armazenamento de sementes de genótipos de Guandu (Cajanus Cajan (L.) Millsp).
Sementes de dez genótipos de guandu foram avaliadas quanto ao potencial de armazenamento através de testes de envelhecimento acelerado e de germinação após armazenamento em condições ambientais não controladas por seis meses. Os genótipos g3, g5, g19b e g58 apresentaram os melhores resultados no teste de envelhecimento acelerado, enquanto que após o armazenamento em condições ambientais não houve diferenciação entre os genótipos quanto apresentaram os melhores resultados no teste de envelhecimento acelerado, enquanto que após o armazenamento em condições ambientais nao houve diferenciação entre os genótipos quanto a sua capacidade germinativa. O primeiro teste, portanto, revelou-se mais eficiente para predizer o potencial de armazenameto, permitindo a classificação dos genótipos de guandu
Compactness in the Thermal Evolution of Twin Stars
In this work, we study for the first time the thermal evolution of twin star
pairs, i.e., stars that present the same mass but different radius and
compactness. We collect available equations of state that give origin to a
second branch of stable compact stars with quarks in their core. For each
equation of state, we investigate the particle composition inside stars and how
differently each twin evolves over time, which depends on the central
density/pressure and consequent crossing of the threshold for the Urca cooling
process. We find that, although the general stellar thermal evolution depends
on mass and particle composition, withing one equation of state, only twin
pairs that differ considerably on compactness can be clearly distinguished by
how they cool down
Hybrid Stars in an SU(3) Parity Doublet Model
We apply an extended version of the SU(3) parity model, containing quark
degrees of freedom, to study neutron stars. The model successfully reproduces
the main thermodynamic features of QCD which allows us to describe the
composition of dense matter. Chiral symmetry restoration is realized inside the
star and the chiral partners of the baryons appear, their masses becoming
degenerate. Furthermore, quark degrees of freedom appear in a transition to a
deconfined state. Performing an investigation of the macroscopic properties of
neutron stars, we show that observational constraints, like mass and thermal
evolution, are satisfied and new predictions can be made
Neutron star interiors and the equation of state of ultra-dense matter
There has been much recent progress in our understanding of quark matter,
culminating in the discovery that if such matter exists in the cores of neutron
stars it ought to be in a color superconducting state. This paper explores the
impact of superconducting quark matter on the properties (e.g., masses, radii,
surface gravity, photon emission) of compact stars.Comment: 3 pages, 4 figures; Paper presented at the Int. Conf. on Quark
Confinement and the Hadron Spectrum VII, Ponta Delgada, Acores, 2-7 September
2006; to be published by AI
Avaliação preliminar de germoplasma de aveia.
Foram avaliados pela EMBRAPA-UEPAE, São Carlos, SP, 50 genotipos, com o objetivo de selecionar germoplasma para o desenvolvimento de novas linhagens de aveia.bitstream/item/120275/1/digitalizar0021.pdfPesquisa em Andamento
Avaliação agronômico de coleção de guandu (Cajanus Cajan(L.)Millsp) forrageiro proveniente do ICRISAT.
Com a finalidade de avaliar agronomicamente coleção de guandu fornecida pelo Internacional Crops Research Institute for the Semi-arid Tropics, ICRISAT, India, foi instalado ensaio em blocos ao acaso, com 3 repetições e 76 tratamentos.Resum
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