4,264 research outputs found
A Godel-Friedman cosmology?
Based on the mathematical similarity between the Friedman open metric and
Godel's metric in the case of nearby distances, we investigate a new scenario
for the Universe's evolution, where the present Friedman universe originates
from a primordial Godel universe by a phase transition during which the
cosmological constant vanishes. Using Hubble's constant and the present matter
density as input, we show that the radius and density of the primordial Godel
universe are close, in order of magnitude, to the present values, and that the
time of expansion coincides with the age of the Universe in the standard
Friedman model. In addition, the conservation of angular momentum provides, in
this context, a possible origin for the rotation of galaxies, leading to a
relation between the masses and spins corroborated by observational data.Comment: Extended version, accepted for publication in Physical Review
Consorciação de feijão-caupi e milho em um agroecossistema manejado sob bases ecológicas na Região de Dourados, Mato Grosso do Sul.
bitstream/item/68469/1/034-Consorciacao.-shaline.pdfPublicado também no Cadernos de Agroecologia, v. 7, n. 2, 2012
Equality of opportunity and educational achievement in Portugal
Portugal has one of the highest levels of income inequality in Europe, and low wages and unemployment are concentrated among low skill individuals. Education is an important determinant of inequality. However, there are large differences in the educational attainment of different individuals in the population, and the sources of these differences emerge early in the life-cycle when families play a central role in individual development. We estimate that most of the variance of school achievement at age 15 is explained by family characteristics. Observed school inputs explain very little of adolescent performance. Children from highly educated parents benefit of rich cultural environments in the home and become highly educated adults. Education policy needs to be innovative: (1) it needs to explicitly recognize the fundamental long run role of families on child development; (2) it needs to acknowledge the failure of traditional input based policies
Classical and quantum dynamics of confined test particles in brane gravity
A model is constructed for the confinement of test particles moving on a
brane. Within the classical framework of this theory, confining a test particle
to the brane eliminates the effects of extra dimensions, rendering them
undetectable. However, in the quantized version of the theory, the effects of
the gauge fields and extrinsic curvature are pronounced and this might provide
a hint for detecting them. As a consequence of confinement the mass of the test
particle is shown to be quantized. The condition of stability against small
perturbations along extra dimensions is also studied and its relation to dark
matter is discussed.Comment: 15 pages, no figures, extended, references adde
Podridão parda da haste: avaliação de genótipos de soja, safra 2013/2014.
bitstream/item/114978/1/2014-Documentos-online-151-p47.pd
Evidence of Two Distinct Dynamic Critical Exponents in Connection with Vortex Physics
The dynamic critical exponent is determined from numerical simulations
for the three-dimensional (3D) lattice Coulomb gas (LCG) and the 3D XY models
with relaxational dynamics. It is suggested that the dynamics is characterized
by two distinct dynamic critical indices and related to the
divergence of the relaxation time by and
, where is the correlation length and the
wavevector. The values determined are and for the
3D LCG and and for the 3D XY model. It is argued
that the nonlinear exponent relates to , whereas the usual
Hohenberg-Halperin classification relates to . Possible implications for the
interpretation of experiments are pointed out. Comparisons with other existing
results are discussed.Comment: to appear in PR
Phenotypic characterization of the rudĂĄ x and 277 common bean ril population.
The main objective of this work was to quantify the phenotypic diversity of the RIL population derived from crosses between RudĂĄ and AND 277, a potential new core mapping population for common bean
Densidade e volume total de poros do solo cultivado com adubos verdes perenes consorciados com a bananeira em um sistema sob transição agroecológica em Mato Grosso do Sul.
bitstream/item/68859/1/041-carneiro-densidade.pdfPublicado também no Cadernos de Agroecologia, v. 7, n.2, 2012
- âŠ