Teleparallel Spin Connection

A new expression for the spin connection of teleparallel gravity is proposed, given by minus the contorsion tensor plus a zero connection. The corresponding minimal coupling is covariant under local Lorentz transformation, and equivalent to the minimal coupling prescription of general relativity. With this coupling prescription, therefore, teleparallel gravity turns out to be fully equivalent to general relativity, even in the presence of spinor fields.Comment: 2 pages, RevTeX, to appear in Phys. Rev D (Brief Report

Gravitation and Duality Symmetry

By generalizing the Hodge dual operator to the case of soldered bundles, and working in the context of the teleparallel equivalent of general relativity, an analysis of the duality symmetry in gravitation is performed. Although the basic conclusion is that, at least in the general case, gravitation is not dual symmetric, there is a particular theory in which this symmetry shows up. It is a self dual (or anti-self dual) teleparallel gravity in which, due to the fact that it does not contribute to the interaction of fermions with gravitation, the purely tensor part of torsion is assumed to vanish. The ensuing fermionic gravitational interaction is found to be chiral. Since duality is intimately related to renormalizability, this theory may eventually be more amenable to renormalization than teleparallel gravity or general relativity.Comment: 7 pages, no figures. Version 2: minor presentation changes, references added. Accepted for publication in Int. J. Mod. Phys.

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.

Comparação de métodos de estimativa da evapotranspiração de referência para Esperantina - PI.

O objetivo do trabalho foi comparar e avaliar o desempenho de métodos de estimativa de evapotranspiração de referência em relação ao método Penman-Monteith/FAO, visando proporcionar à região de Esperantina-PI, informações básicas para a estimativa da ETo. Os dados meteorológicos foram obtidos na estação meteorológica convencional do INMET, entre o período de 01/01/2008 à 31/12/2012 ,especificamente da unidade situada em Esperantina, PI, com latitude 03º54'06", longitude 42º14'01" W e altitude media de 59 m. Os dados obtidos foram divididos em dois períodos distintos: período seco (15/07) e período chuvoso (15/02). Os métodos de estimativa da evapotranspiração de referência utilizados foram os de Makking (MK), Jensen-Haise (JH), Priestley-Taylor (PT), Hargreaves-Samani (HS), Camargo (CA) e Ivanov (IVN), descritos em comparação ao método de Penman-Monteih (PM). Foram realizados cálculos de erro padrão de estimativa, dos coeficientes de determinação, correlação, o índice de Willmott e o coeficiente de desempenho entre os métodos avaliados e o padrão. Os métodos de Jensen-Haise, Priestley-Taylor e Makking apresentaram desempenho ótimo para os dois períodos estudados, quando comparados ao de Penman- Monteith, demonstrando que estes podem ser utilizados como uma alternativa para a estimativa da ETo no município de Esperantina-PI.CONBEA 2014

The Cauchy convergence of T and P-approximant templates for test-mass Kerr binary systems

In this work we examine the Cauchy convergence of both post-Newtonian (T-approximant) and re-summed post-Newtonian (P-approximant) templates for the case of a test-mass orbiting a Kerr black hole along a circular equatorial orbit. The Cauchy criterion demands that the inner product between the $n$ and $n+1$ order approximation approaches unity, as we increase the order of approximation. In previous works, it has been shown that we achieve greater fitting factors and better parameter estimation using the P-approximant templates for both Schwarzschild and Kerr black holes. In this work, we show that the P-approximant templates also display a faster Cauchy convergence making them a superior template to the standard post-Newtonian templates.Comment: 5 pages, Replaced with shortened published versio

Rotation intrinsic spin coupling--the parallelism description

For the Dirac particle in the rotational system, the rotation induced inertia effect is analogously treated as the modification of the "spin connection" on the Dirac equation in the flat spacetime, which is determined by the equivalent tetrad. From the point of view of parallelism description of spacetime, the obtained torsion axial-vector is just the rotational angular velocity, which is included in the "spin connection". Furthermore the axial-vector spin coupling induced spin precession is just the rotation-spin(1/2) interaction predicted by Mashhoon. Our derivation treatment is straightforward and simplified in the geometrical meaning and physical conception, however the obtained conclusions are consistent with that of the other previous work.Comment: 10 pages, no figur

Propriedades físicas do solo influenciadas por sistemas de preparo e manejo: uma revisão.

bitstream/item/24761/1/doc100-2007-propriedades-fisicas.pd

Aspectos econômicos em sistemas de produção com culturas alimentares para agricultores de baixa renda na Microrregião Bragantina, Pará.

bitstream/item/28816/1/CPATU-BP6.pd

Efeitos da desidratação e do armazenamento em sementes de Taluma ovata St. Hill. - magnoliaceae.

Resumo

Torsion Gravity: a Reappraisal

The role played by torsion in gravitation is critically reviewed. After a description of the problems and controversies involving the physics of torsion, a comprehensive presentation of the teleparallel equivalent of general relativity is made. According to this theory, curvature and torsion are alternative ways of describing the gravitational field, and consequently related to the same degrees of freedom of gravity. However, more general gravity theories, like for example Einstein-Cartan and gauge theories for the Poincare and the affine groups, consider curvature and torsion as representing independent degrees of freedom. By using an active version of the strong equivalence principle, a possible solution to this conceptual question is reviewed. This solution favors ultimately the teleparallel point of view, and consequently the completeness of general relativity. A discussion of the consequences for gravitation is presented.Comment: RevTeX, 34 pages. Review article to be published by Int. J. Mod. Phys.