42,672 research outputs found
On a possible connection between Chandler wobble and dark matter
Chandler wobble excitation and damping, one of the open problems in
geophysics, is treated as a consequence in part of the interaction between
Earth and a hypothetical oblate ellipsoid made of dark matter. The physical and
geometrical parameters of such an ellipsoid and the interacting torque strength
is calculated in such a way to reproduce the Chandler wobble component of the
polar motion in several epochs, available in the literature. It is also
examined the consequences upon the geomagnetic field dynamo and generation of
heat in the Earth outer core.Comment: 19 pages, 10 figures. Final version, to appear in Brazilian Journal
of Physics, vol 39 (2009
Phononless thermally activated transport through a disordered array of quantum wires
Phononless plasmon assisted transport through a long disordered array of
finite length quantum wires is investigated analytically. Two temperature
regimes, the low- and the high-temperature ones, with qualitatively different
temperature dependencies of thermally activated resistance are identified. The
characteristics of plasmon assisted and phonon assisted transport mechanisms
are compared. Generically strong electron-electron interaction in quantum wires
results in a qualitative change of the temperature dependence of thermally
activated resistance in comparison to phonon assisted transport. At high
temperatures, the thermally activated resistance is determined by the Luttinger
liquid interaction parameter of the wires.Comment: 15 pages, 1 figur
Sustainable farming with native rocks: the transition without revolution.
The development process which humanity passed through favored a series of conquests, reflected in the better quality of life and longevity, however, it also provoked upsets and severe transformation in the environment and in the human food security. Such process is driving the ecosystems to be homogeneous, and, therefore,the nutrients� supply, via nourishment. To change this panorama, the present work discusses the gains of incorporating the stonemeal technique as a strategic alternative to give back the essential fertile characteristics to the soils. This technology has the function of facilitating the rejuvenation of the soils and increasing the availability of the necessary nutrients to the full development of the plants which is a basic input for the proliferation of life in all its dimensions
Remarks on some vacuum solutions of scalar-tensor cosmological models
We present a class of exact vacuum solutions corresponding to de Sitter and
warm inflation models in the framework of scalar-tensor cosmologies. We show
that in both cases the field equations reduce to planar dynamical systems with
constraints. Then, we carry out a qualitative analysis of the models by
examining the phase diagrams of the solutions near the equilibrium points.Comment: 12 pages, 4 figures. To be published in the Brazilian Journal of
Physic
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