34,486 research outputs found
Duality between k-essence and Rastall gravity
The k-essence theory with a power-law function of and
Rastall's non-conservative theory of gravity with a scalar field are shown to
have the same solutions for the metric under the assumption that both the
metric and the scalar fields depend on a single coordinate. This equivalence
(called k-R duality) holds for static configurations with various symmetries
(spherical, plane, cylindrical, etc.) and all homogeneous cosmologies. In the
presence of matter, Rastall's theory requires additional assumptions on how the
stress-energy tensor non-conservation is distributed between different
contributions. Two versions of such non-conservation are considered in the case
of isotropic spatially flat cosmological models with a perfect fluid: one (R1)
in which there is no coupling between the scalar field and the fluid, and
another (R2) in which the fluid separately obeys the usual conservation law. In
version R1 it is shown that k-R duality holds not only for the cosmological
models themselves but also for their adiabatic perturbations. In version R2,
among other results, a particular model is singled out that reproduces the same
cosmological expansion history as the standard CDM model but predicts
different behaviors of small fluctuations in the k-essence and Rastall
frameworks.Comment: 10 pages, no figures. Two references adde
Realizing the supersymmetric inverse seesaw model in the framework of R-parity violation
If, on one hand, the inverse seesaw is the paradigm of TeV scale seesaw
mechanism, on the other it is a challenge to find scenarios capable of
realizing it. In this work we propose a scenario, based on the framework of
R-parity violation, that realizes minimally the supersymmetric inverse seesaw
mechanism. In it the energy scale parameters involved in the mechanism are
recognized as the vacuum expectation values of the scalars that compose the
singlet superfields and . We develop also the scalar sector
of the model and show that the Higgs mass receives a new tree-level
contribution that, when combined with the standard contribution plus loop
correction, is capable of attaining GeV without resort to heavy stops.Comment: Minor modification of the text. Final version to be published in PL
Sustainable forest management of miombo woodlands in Niassa National Reserve, northern Mozambique: a multidisciplinary approach of fire resistance analysis.
Poster presented at XIII World Forestry Congress. Buenos Aires (Argentina). 18 - 23 Oct 2009
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