1,609 research outputs found
Speed of gravity and gravitomagnetism
A v_J/c correction to the Shapiro time delay seems verified by a 2002 Jovian
observation by VLBI. In this Essay, this correction is interpreted as an effect
of the aberration of light in an optically refractive medium which supplies an
analog of Jupiter's gravity field rather than as a measurement of the speed of
gravity, as it was first proposed by other authors. The variation of the index
of refraction is induced by the Lorentz invariance of the weak gravitational
field equations for Jupiter in a uniform translational slow motion with
velocity v_J=13.5 km/s. The correction on time delay and deflection is due not
to the Kerr (or Lense-Thirring) stationary gravitomagnetic field of Jupiter,
but to its Schwarzschild gravitostatic field when measured from the barycenter
of the solar system.Comment: 6 pags, final published version, Honorable Mention in the 2004 Essay
Competition of the Gravity Research Foundation, GR
Curvature(s) of a light wavefront in a weak gravitational field
The geometry of a light wavefront evolving from a flat wavefront under the
action of weak gravity field in the 3-space associated to a post-Newtonian
relativistic spacetime, is studied numerically by means of the ray tracing
method.Comment: 3 pages, 1 fig, Talk given by JFPS at the 12th Marcel Grossmann
conference (Paris, July, 2009), submitted to the Proceeding
Geometry of an accelerated rotating disk
We analyze the geometry of a rotating disk with a tangential acceleration in
the framework of the Special Theory of Relativity, using the kinematic linear
differential system that verifies the relative position vector of time-like
curves in a Fermi reference. A numerical integration of these equations for a
generic initial value problem is made up and the results are compared with
those obtained in other works.Comment: 10 pages, LaTeX, 2 eps figs; typos corrected, added reference, minor
changes; submitte
Cosmic acceleration: Inhomogeneity versus vacuum energy
In this essay, I present an alternative explanation for the cosmic
acceleration which appears as a consequence of recent high redshift Supernova
data. In the usual interpretation, this cosmic acceleration is explained by the
presence of a positive cosmological constant or vacuum energy, in the
background of Friedmann models. Instead, I will consider a Local Rotational
Symmetric (LRS) inhomogeneous spacetime, with a barotropic equation of state
for the cosmic matter. Within this framework the kinematical acceleration of
the cosmic fluid or, equivalently, the inhomogeneity of matter, is just the
responsible of the SNe Ia measured cosmic acceleration. Although in our model
the Cosmological Principle is relaxed, it maintains local isotropy about our
worldline in agreement with the CBR experiments.Comment: LATEX, 7 pags, no figs, Honorable Mention in the 1999 Essay
Competition of the Gravity Research Foundatio
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