1,243 research outputs found
Teleparallel Equivalent of Non-Abelian Kaluza-Klein Theory
Based on the equivalence between a gauge theory for the translation group and
general relativity, a teleparallel version of the non-abelian Kaluza-Klein
theory is constructed. In this theory, only the fiber-space turns out to be
higher-dimensional, spacetime being kept always four-dimensional. The resulting
model is a gauge theory that unifies, in the Kaluza-Klein sense, gravitational
and gauge fields. In contrast to the ordinary Kaluza-Klein models, this theory
defines a natural length-scale for the compact sub-manifold of the fiber space,
which is shown to be of the order of the Planck length.Comment: Revtex4, 7 pages, no figures, to appear in Phys. Rev.
The quadratic spinor Lagrangian is equivalent to the teleparallel theory
The quadratic spinor Lagrangian is shown to be equivalent to the teleparallel
/ tetrad representation of Einstein's theory. An important consequence is that
the energy-momentum density obtained from this quadratic spinor Lagrangian is
essentially the same as the ``tensor'' proposed by Moller in 1961.Comment: 10 pages, RevTe
Symmetric Hyperbolic System in the Self-dual Teleparallel Gravity
In order to discuss the well-posed initial value formulation of the
teleparallel gravity and apply it to numerical relativity a symmetric
hyperbolic system in the self-dual teleparallel gravity which is equivalent to
the Ashtekar formulation is posed. This system is different from the ones in
other works by that the reality condition of the spatial metric is included in
the symmetric hyperbolicity and then is no longer an independent condition. In
addition the constraint equations of this system are rather simpler than the
ones in other works.Comment: 8 pages, no figure
Case studies of Roots, Tubers and Bananas seed systems.
The seed systems of RTB (root, tuber, and banana) crops are unique because they are propagated from vegetative parts of the plant, not from true seed. RTB seed is thus bulkier, more perishable, and more subject to the attacks of pests and diseases than is true seed. Because of this, there is often a gap between potential and real crop yields, which seed interventions seek to narrow. Seed systems are formal or informal networks of people and organizations that produce, plant, and distribute seed. Informal systems may deliver low quality seed, but not always. This book describes 13 RTB seed system interventions, using a framework based on the concepts of seed availability, access, and quality. The 13 case studies included (1) a potato-growers’ association in Ecuador, (2) a hydroponic seed potato in Peru, (3) a yam seed technology in Nigeria, (4) a banana and plantain project in Ghana, (5) a sweetpotato seed project in Tanzania and (6) one in Rwanda, (7) a seed potato system in Kenya, (8) cassava in Nicaragua, (9) seed potato in Malawi, (10) disease-resistant cassava varieties in seven African countries, (11) a tissue culture banana project, (12) an emergency plantain and banana project in East Africa, and (13) a large cassava seed project in six African countries
Teleparallel Versions of Friedmann and Lewis-Papapetrou Spacetimes
This paper is devoted to investigate the teleparallel versions of the
Friedmann models as well as the Lewis-Papapetrou solution. We obtain the tetrad
and the torsion fields for both the spacetimes. It is shown that the
axial-vector vanishes for the Friedmann models. We discuss the different
possibilities of the axial-vector depending on the arbitrary functions
and in the Lewis-Papapetrou metric. The vector related with spin has
also been evaluated.Comment: 13 pages, accepted for publication in GR
Gravitational Energy of Kerr and Kerr Anti-de Sitter Space-times in the Teleparallel Geometry
In the context of the Hamiltonian formulation of the teleparallel equivalent
of general relativity we compute the gravitational energy of Kerr and Kerr
Anti-de Sitter (Kerr-AdS) space-times. The present calculation is carried out
by means of an expression for the energy of the gravitational field that
naturally arises from the integral form of the constraint equations of the
formalism. In each case, the energy is exactly computed for finite and
arbitrary spacelike two-spheres, without any restriction on the metric
parameters. In particular, we evaluate the energy at the outer event horizon of
the black holes.Comment: 11 pages, 1 figure, to appear in JHEP11(2003)00
Diversos actores, variedades, fuentes y transacciones en los sistemas de semilla de papa en Cotopaxi
La provincia de Cotopaxi es una de las principales zonas productoras de papa del Ecuador.Desafortunadamente, la productividad es 48% más baja que la productividad nacional(Ministerio de Agricultura y Ganadería, 2019). Una de las principales razones de esta bajaproductividad es la calidad de la semilla. Diversas intervenciones se han realizado paraincrementar el uso de semilla de calidad y mejorar las prácticas de manejo, sin embargo,el impacto de estas ha sido limitado debido al insuficiente conocimiento de los sistemasde semilla. El objetivo de esta investigación fue entender la articulación de diferentesactores, la biodiversidad, fuentes de semilla y los diferentes mecanismos en la renovaciónparcial de los lotes de semilla en la provincia de Cotopaxi
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