1,609 research outputs found

    Speed of gravity and gravitomagnetism

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    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

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    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

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    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

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    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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