12,995 research outputs found
Fitting isochrones to open cluster photometric data III. Estimating metallicities from UBV photometry
The metallicity is a critical parameter that affects the correct
determination fundamental characteristics stellar cluster and has important
implications in Galactic and Stellar evolution research. Fewer than 10 % of the
2174 currently catalog open clusters have their metallicity determined in the
literature. In this work we present a method for estimating the metallicity of
open clusters via non-subjective isochrone fitting using the cross-entropy
global optimization algorithm applied to UBV photometric data. The free
parameters distance, reddening, age, and metallicity simultaneously determined
by the fitting method. The fitting procedure uses weights for the observational
data based on the estimation of membership likelihood for each star, which
considers the observational magnitude limit, the density profile of stars as a
function of radius from the center of the cluster, and the density of stars in
multi-dimensional magnitude space. We present results of [Fe/H] for nine
well-studied open clusters based on 15 distinct UBV data sets. The [Fe/H]
values obtained in the ten cases for which spectroscopic determinations were
available in the literature agree, indicating that our method provides a good
alternative to determining [Fe/H] by using an objective isochrone fitting. Our
results show that the typical precision is about 0.1 dex
Primeiro relato de Braga patagonica Schödte & Meinert, 1884 (Crustacea: Isopoda) parasitando peixes cultivados no Brasil.
Resumo simples
Rotating magnetic solution in three dimensional Einstein gravity
We obtain the magnetic counterpart of the BTZ solution, i.e., the rotating
spacetime of a point source generating a magnetic field in three dimensional
Einstein gravity with a negative cosmological constant. The static
(non-rotating) magnetic solution was found by Clement, by Hirschmann and Welch
and by Cataldo and Salgado. This paper is an extension of their work in order
to include (i) angular momentum, (ii) the definition of conserved quantities
(this is possible since spacetime is asymptotically anti-de Sitter), (iii)
upper bounds for the conserved quantities themselves, and (iv) a new
interpretation for the magnetic field source. We show that both the static and
rotating magnetic solutions have negative mass and that there is an upper bound
for the intensity of the magnetic field source and for the value of the angular
momentum. The magnetic field source can be interpreted not as a vortex but as
being composed by a system of two symmetric and superposed electric charges,
one of the electric charges is at rest and the other is spinning. The rotating
magnetic solution reduces to the rotating uncharged BTZ solution when the
magnetic field source vanishes.Comment: Latex (uses JHEP3.cls), 12 pages. Published versio
Pair creation of higher dimensional black holes on a de Sitter background
We study in detail the quantum process in which a pair of black holes is
created in a higher D-dimensional de Sitter (dS) background. The energy to
materialize and accelerate the pair comes from the positive cosmological
constant. The instantons that describe the process are obtained from the
Tangherlini black hole solutions. Our pair creation rates reduce to the pair
creation rate for Reissner-Nordstrom-dS solutions when D=4. Pair creation of
black holes in the dS background becomes less suppressed when the dimension of
the spacetime increases. The dS space is the only background in which we can
discuss analytically the pair creation process of higher dimensional black
holes, since the C-metric and the Ernst solutions, that describe respectively a
pair accelerated by a string and by an electromagnetic field, are not know yet
in a higher dimensional spacetime.Comment: 10 pages; 1 figure included; RexTeX4. v2: References added. Published
version. v3: Typo in equation (46) fixe
Properties of Solutions in 2+1 Dimensions
We solve the Einstein equations for the 2+1 dimensions with and without
scalar fields. We calculate the entropy, Hawking temperature and the emission
probabilities for these cases. We also compute the Newman-Penrose coefficients
for different solutions and compare them.Comment: 16 pages, 1 figures, PlainTeX, Dedicated to Prof. Yavuz Nutku on his
60th birthday. References adde
Estudo da adaptabilidade e estabilidade fenotĂpica de progĂŞnies de Eucalyptus grandis via metodologia AMMI.
Foram avaliadas a adaptabilidade e a estabilidade fenotĂpica de 200 progĂŞnies de Eucalyptus grandis procedentes de 10 localidades australianas, selecionadas pelo Programa Nacional de Pesquisa Florestal – coordenado pela Embrapa Florestas, e implantadas em sete testes de procedĂŞncia e progĂŞnies nas regiões sul e sudeste do Brasil. Os resultados indicaram comportamentos diferenciados dos materiais avaliados, sendo a interação genĂłtipo x ambiente significativa (p<0,01). O mĂ©todo AMMI (Additive Main Effects and Multiplicative Interaction Analysis) permitiu identificar as melhores combinações entre progĂŞnies e locais
A Simple Realization of the Inverse Seesaw Mechanism
Differently from the canonical seesaw mechanism, which is grounded in grand
unified theories, the inverse seesaw mechanism lacks a special framework that
realizes it naturally. In this work we advocate that the 3-3-1 model with
right-handed neutrinos has such an appropriate framework to accommodate the
inverse seesaw mechanism. We also provide an explanation for the smallness of
the parameter and estimate the branching ratio for the rare lepton flavor
violation process .Comment: About 14pages, no figures, basis corrected, to appear at the PR
Gravitational radiation in d>4 from effective field theory
Some years ago, a new powerful technique, known as the Classical Effective
Field Theory, was proposed to describe classical phenomena in gravitational
systems. Here we show how this approach can be useful to investigate
theoretically important issues, such as gravitational radiation in any
spacetime dimension. In particular, we derive for the first time the
Einstein-Infeld-Hoffman Lagrangian and we compute Einstein's quadrupole formula
for any number of flat spacetime dimensions.Comment: 32 pages, 10 figures. v2: Factor in eq. (3.11) fixed. References
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