8,693 research outputs found
Gravitomagnetic Moments of the Fundamental Fields
The quadratic form of the Dirac equation in a Riemann spacetime yields a
gravitational gyromagnetic ratio \kappa_S = 2 for the interaction of a Dirac
spinor with curvature. A gravitational gyromagnetic ratio \kappa_S = 1 is also
found for the interaction of a vector field with curvature. It is shown that
the Dirac equation in a curved background can be obtained as the square--root
of the corresponding vector field equation only if the gravitational
gyromagnetic ratios are properly taken into account.Comment: 8 pages, RevTeX Style, no figures, changed presentation -- now
restricted to fields of spin 0, 1/2 and 1 -- some references adde
Teleparallel origin of the Fierz picture for spin-2 particle
A new approach to the description of spin-2 particle in flat and curved
spacetime is developed on the basis of the teleparallel gravity theory. We show
that such an approach is in fact a true and natural framework for the Fierz
representation proposed recently by Novello and Neves. More specifically, we
demonstrate how the teleparallel theory fixes uniquely the structure of the
Fierz tensor, discover the transparent origin of the gauge symmetry of the spin
2 model, and derive the linearized Einstein operator from the fundamental
identity of the teleparallel gravity. In order to cope with the consistency
problem on the curved spacetime, similarly to the usual Riemannian approach,
one needs to include the non-minimal (torsion dependent) coupling terms.Comment: 5 pages, Revtex4, no figures. Accepted for publication in Phys. Rev.
Collaboration networks from a large CV database: dynamics, topology and bonus impact
Understanding the dynamics of research production and collaboration may
reveal better strategies for scientific careers, academic institutions and
funding agencies. Here we propose the use of a large and multidisciplinar
database of scientific curricula in Brazil, namely, the Lattes Platform, to
study patterns of scientific production and collaboration. In this database,
detailed information about publications and researchers are made available by
themselves so that coauthorship is unambiguous and individuals can be evaluated
by scientific productivity, geographical location and field of expertise. Our
results show that the collaboration network is growing exponentially for the
last three decades, with a distribution of number of collaborators per
researcher that approaches a power-law as the network gets older. Moreover,
both the distributions of number of collaborators and production per researcher
obey power-law behaviors, regardless of the geographical location or field,
suggesting that the same universal mechanism might be responsible for network
growth and productivity.We also show that the collaboration network under
investigation displays a typical assortative mixing behavior, where teeming
researchers (i.e., with high degree) tend to collaborate with others alike.
Finally, our analysis reveals that the distinctive collaboration profile of
researchers awarded with governmental scholarships suggests a strong bonus
impact on their productivity.Comment: 8 pages, 8 figure
Gravitation: Global Formulation and Quantum Effects
A nonintegrable phase-factor global approach to gravitation is developed by
using the similarity of teleparallel gravity with electromagnetism. The phase
shifts of both the COW and the gravitational Aharonov-Bohm effects are
obtained. It is then shown, by considering a simple slit experiment, that in
the classical limit the global approach yields the same result as the
gravitational Lorentz force equation of teleparallel gravity. It represents,
therefore, the quantum mechanical version of the classical description provided
by the gravitational Lorentz force equation. As teleparallel gravity can be
formulated independently of the equivalence principle, it will consequently
require no generalization of this principle at the quantum level.Comment: Latex (IOP style), 14 pages, 3 figures. To appear in Classical and
Quantum Gravit
The Teleparallel Lagrangian and Hamilton-Jacobi Formalism
We analyze the Teleparallel Equivalent of General Relativity (TEGR) from the
point of view of Hamilton-Jacobi approach for singular systemsComment: 11 pages, no figures, to appear in GR
Axial Torsion-Dirac spin Effect in Rotating Frame with Relativistic Factor
In the framework of spacetime with torsion and without curvature, the Dirac
particle spin precession in the rotational system is studied. We write out the
equivalent tetrad of rotating frame, in the polar coordinate system, through
considering the relativistic factor, and the resultant equivalent metric is a
flat Minkowski one. The obtained rotation-spin coupling formula can be applied
to the high speed rotating case, which is consistent with the expectation.Comment: 6 page
Análise molecular de isolados do vírus da meleira do mamoeiro (Papaya meleira virus - PMeV).
A cultura do mamão (Carica papaya L.) no Brasil tem apresentado crescimento expressivo na região Nordeste, responsável por mais de 60% da produção nacional (IBGE, 2008). Certamente, os principais fatores que afetam a expansão da cultura são os problemas fitossanitários, principalmente as viroses. Dentre as espécies de vírus que infectam o mamoeiro no Brasil o vírus da meleira (Papaya meleira virus, PMeV), relatada na década de 80 afetando pomares no sul da Bahia (Nakagawa et al., 1987) e norte do Espírito Santo (Rodrigues et al., 1989), atualmente é a principal doença da cultura em todas as principais regiões produtoras do nordeste.pdf 151
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 and
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
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