8,754 research outputs found
An alternative theoretical approach to describe planetary systems through a Schrodinger-type diffusion equation
In the present work we show that planetary mean distances can be calculated
with the help of a Schrodinger-type diffusion equation. The obtained results
are shown to agree with the observed orbits of all the planets and of the
asteroid belt in the solar system, with only three empty states. Furthermore,
the equation solutions predict a fundamental orbit at 0.05 AU from solar-type
stars, a result confirmed by recent discoveries. In contrast to other similar
approaches previously presented in the literature, we take into account the
flatness of the solar system, by considering the flat solutions of the
Schrodinger-type equation. The model has just one input parameter, given by the
mean distance of Mercury.Comment: 6 pages. Version accepted for publication in Chaos, Solitons &
Fractal
Decifrando o genoma em grande escala.
A determinação das funções gêni~~stem de~andado um grande avanço das ciências genômicas, cujas tecnologias concentram-se, principalmente, na geração e no estudo de uma grande quantidade de dados. O ponto de apoio para o entendimento da função gênica e da estrutura do genoína tem sido o sequenciamento de genomas completos e do genoma expresso em grande escala. Mapas físicos e genéticos têm sido integrados com informações genôrnicas e de expressão, resultando em bancos de dados públicos altamente informativos para diferentes espécies animais evegetais. Tais informações auxiliam em vários aspectos a análise·de expressão gênica, a determinação dos efeitos de processamento de éxons.e do número de cópias gênicas e cromossômicas, culminando na determinação das funções biológicas e do mecanismo de ação de vários genes. São descritos o surgimento de novas tecnologias e a evolução de algumas inovações já existentes, voltadas para a identificação de funções gênicas
Observational constraints on late-time Lambda(t) cosmology
The cosmological constant, i.e., the energy density stored in the true vacuum
state of all existing fields in the Universe, is the simplest and the most
natural possibility to describe the current cosmic acceleration. However,
despite its observational successes, such a possibility exacerbates the well
known cosmological constant problem, requiring a natural explanation for its
small, but nonzero, value. In this paper we study cosmological consequences of
a scenario driven by a varying cosmological term, in which the vacuum energy
density decays linearly with the Hubble parameter. We test the viability of
this scenario and study a possible way to distinguish it from the current
standard cosmological model by using recent observations of type Ia supernova
(Supernova Legacy Survey Collaboration), measurements of the baryonic acoustic
oscillation from the Sloan Digital Sky Survey and the position of the first
peak of the cosmic microwave background angular spectrum from the three-year
Wilkinson Microwave Anisotropy Probe.Comment: Some important revisions. To appear in Physical Review
Symmetries and Ambiguities in the linear sigma model with light quarks
We investigate the role of undetermined finite contributions generated by
radiative corrections in a linear sigma model with quarks.
Although some of such terms can be absorbed in the renormalization procedure,
one such contribution is left in the expression for the pion decay constant.
This arbitrariness is eliminated by chiral symmetry.Comment: 9 pages. Added references through the text; an author was added due
to an important contribution; corrected typos; the title also was changed.
Submitted to Modern Physics Letter
- …