18,266 research outputs found
Regular black holes in gravity
In this work, we study the possibility of generalizing solutions of regular
black holes with an electric charge, constructed in general relativity, for the
theory, where is the Gauss-Bonnet invariant. This type of solution
arises due to the coupling between gravitational theory and nonlinear
electrodynamics. We construct the formalism in terms of a mass function and it
results in different gravitational and electromagnetic theories for which mass
function. The electric field of these solutions are always regular and the
strong energy condition is violated in some region inside the event horizon.
For some solutions, we get an analytical form for the function. Imposing
the limit of some constant going to zero in the function we recovered
the linear case, making the general relativity a particular case.Comment: 22 pages, 25 figures.Version published in EPJ
Non-Linear Effects in Resonant Tunneling; Bistabilities and Self-Sustained Oscillating Currents
We study non-linear phenomena in double barrier heterostructures. Systems in
3D under the effect of an external magnetic field along the current and 1D
systems are analyzed. Non-linearities are reflected in the I-V characteristic
curve as bistabilities, instabilities and time dependent oscillations of the
currents. The nature of the non-linear behavior depends upon the parameters
that define the system.Comment: 3 pages, 2 figures, accepted for publication in Superlattices and
Microstructure
Anisotropic Cosmological Constant and the CMB Quadrupole Anomaly
There are evidences that the cosmic microwave background (CMB) large-angle
anomalies imply a departure from statistical isotropy and hence from the
standard cosmological model. We propose a LCDM model extension whose dark
energy component preserves its nondynamical character but wield anisotropic
vacuum pressure. Exact solutions for the cosmological scale factors are
presented, upper bounds for the deformation parameter are evaluated and its
value is estimated considering the elliptical universe proposal to solve the
quadrupole anomaly. This model can be constructed from a Bianchi I cosmology
with cosmological constant from two different ways: i) a straightforward
anisotropic modification of the vacuum pressure consistently with
energy-momentum conservation; ii) a Poisson structure deformation between
canonical momenta such that the dynamics remain invariant under scale factors
rescalings.Comment: 8 pages, 2 columns, 1 figure. v2: figure improved, added comments on
higher eccentricity powers and references. v3: typos corrected, version to
appear in PR
Colheita e pós-colheita de flores tropicais.
Esta publicação reúne informações básicas sobre o processo produtivo, a colheita e a pós-colheita de flores tropicais.bitstream/item/24755/1/folder-florestropicais.pd
Cultivo, uso e manipulação de plantas medicinais.
Este documento tem o objetivo de contribuir com o cenário de desenvolvimento e organização das populações rurais e tradicionais, compatível com suas características culturais e com a exploração sustentável de recursos vegetais e a conservação da biodiversidade.bitstream/item/54344/1/doc91-plantasmedicinais.pd
Recomendações técnicas para a propagação de flores tropicais em Rondônia.
O trabalho aborda as noções básicas para o cultivo de flores tropicais.bitstream/CPAF-RO-2010/12226/1/cot328-florestropicais.pd
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