10,612 research outputs found
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.
Torsion and Gravitation: A new view
According to the teleparallel equivalent of general relativity, curvature and
torsion are two equivalent ways of describing the same gravitational field.
Despite equivalent, however, they act differently: whereas curvature yields a
geometric description, in which the concept of gravitational force is absent,
torsion acts as a true gravitational force, quite similar to the Lorentz force
of electrodynamics. As a consequence, the right-hand side of a
spinless-particle equation of motion (which would represent a gravitational
force) is always zero in the geometric description, but not in the teleparallel
case. This means essentially that the gravitational coupling prescription can
be minimal only in the geometric case. Relying on this property, a new
gravitational coupling prescription in the presence of curvature and torsion is
proposed. It is constructed in such a way to preserve the equivalence between
curvature and torsion, and its basic property is to be equivalent with the
usual coupling prescription of general relativity. According to this view, no
new physics is connected with torsion, which appears as a mere alternative to
curvature in the description of gravitation. An application of this formulation
to the equations of motion of both a spinless and a spinning particle is madeComment: To appear on IJMP
Breathing synchronization in interconnected networks
Global synchronization in a complex network of oscillators emerges from the
interplay between its topology and the dynamics of the pairwise interactions
among its numerous components. When oscillators are spatially separated,
however, a time delay appears in the interaction which might obstruct
synchronization. Here we study the synchronization properties of interconnected
networks of oscillators with a time delay between networks and analyze the
dynamics as a function of the couplings and communication lag. We discover a
new breathing synchronization regime, where two groups appear in each network
synchronized at different frequencies. Each group has a counterpart in the
opposite network, one group is in phase and the other in anti-phase with their
counterpart. For strong couplings, instead, networks are internally
synchronized but a phase shift between them might occur. The implications of
our findings on several socio-technical and biological systems are discussed.Comment: 7 pages, 3 figures + 3 pages of Supplemental Materia
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.
Spinless Matter in Transposed-Equi-Affine Theory of Gravity
We derive and discus the equations of motion for spinless matter:
relativistic spinless scalar fields, particles and fluids in the recently
proposed by A. Saa model of gravity with covariantly constant volume with
respect to the transposed connection in Einstein-Cartan spaces.
A new interpretation of this theory as a theory with variable Plank
"constant" is suggested.
We show that the consistency of the semiclassical limit of the wave equation
and classical motion dictates a new definite universal interaction of torsion
with massive fields.Comment: 29 pages, latex, no figures. New Section on semiclassical limit of
wave equation added; old references rearranged; new references, remarks,
comments, and acknowledgments added; typos correcte
Composição nutricional do filete de três espécies piscícolas de águas interiores com interesse gastronómico
Composição nutricional do filete de três espécies piscícolas de águas interiores com interesse gastronómico
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