228 research outputs found
Uber das Gravitationsfeld eines Massenpunktes nach der Einstenschen Theorie
Schwarzschild's solution of Einstein's field equations in vacuum can be
written in many different forms. Unfortunately Schwarzschild's own original
form is less nice looking and simple than that latter derived by Droste and
Hilbert. We prove here that we can have both: a nice looking simple form and
the meaning that Schwarzschild wanted to give to his solution, i.e., that of
describing the gravitational field of a massive point particle.Comment: typos corrected, new reference, minor text modification
Born's group and Generalized isometries
We define the Born group as the group of transformations that leave invariant
the line element of Minkowski's spacetime written in terms of Fermi coordinates
of a Born congruence. This group depends on three arbitrary functions of a
single argument. We construct implicitly the finite transformations of this
group and explicitly the corresponding infinitesimal ones. Our analysis of this
group brings out the new concept of Generalized group of isometries. The
limitting cases of such groups being, at one end, the Groups of isometries of a
spacetime metric and, at the other end, the Group of diffeomorphisms of any
spacetime manifold. We mention two examples of potentially interesting
generalizations of the Born congruences.Comment: In Proceedings of ERE93, Edited version, 9 page
A look inside the theory of the linear approximation
We introduce in the framework of the linear approximation of General
relativity a natural distinction between General gauge transformations
generated by any vector field and those Special ones for which this vector
field is a gradient. This allows to introduce geometrical objects that are not
invariant under General gauge transformations but they are under Special ones.
We develop then a formalism that strengthens the analogy of the formalisms of
the electromagnetic and the gravitational theories in a Special relativity
framework. We are thus able to define the energy-momentum tensor of the
gravitational field and to fully analyze the gravitational field of isolated
point masses or continuous distributions of them obtained by linear
superpositions.Comment: 14 pages, typos corrected, section replace
Reflections on three debated issues
A time-dependent model of space-time is used to suggest simple explanations
for the increasing of the Astronomical unit, as well as the increasing of the
distance from the Earth to the Moon. The Pioneer anomaly is also considered.Comment: 8 page
Gravitational waves signal analysis
I use a very simplified example to discuss the signature of a gravitational
wave taking into account the relative state of motion of the detector with
respect to the source that originated it. Something that to my knowledge has
been ignored up to now and may ruin the best crafted template \cite{Templates}.Comment: 5 page
Space and Time models
We derive line-element's templates of space-time models with Space models
complying with Helmholtz's Free mobility postulate, and discuss some of the
Time models compatible with them.Comment: 11 pages, minor changes, an error in an intermediate step of the
derivation of (40) has been correcte
Time dependence of c and its concomitants
As we showed in a preceding arXiv:gr-qc Einstein equations, conveniently
written, provide the more orthodox and simple description of cosmological
models with a time dependent speed of light . We derive here the concomitant
dependence of the electric permittivity , the magnetic permeability
, the unit of charge , Plank's constant , under the assumption of
the constancy of the fine structure constant , and the masses of
elementary particles . As a consequence of these concomitant dependences on
time they remain constant their ratios as well as their Compton wave
length and their classical radius .Comment: Latex, 11 page
Sensitivity of high precision Michelson-Morley experiments to tilting of their setups
We describe the effects to be expected of unwanted or voluntary deviations
from the vertical of the axis of the active rotation of modern high precision
experiments of the Michelson-Morley type. The theoretical description that we
use is a particular implementation of the Principle of free mobility.Comment: Added reference
A New kinetic model of Globular clusters
A new kinetic model of globular clusters based on a modified velocities
distribution function is compared to the most often used King's model. A
hypothetical contribution of dark matter is considered.Comment: 6 pages, 6 figure
Phantom mass gravitational effects
I derive the basic relativistic corrections to the equations of motion of
test particles and light rays in the field of a source with active mass ,
including the phantom mass density that any such source generates when a
modification of Newton's action at a distance includes a long range term. The
technical framework of this paper is that of Einstein's theory of gravitation
at the linear approximation with respect to the mass parameter .Comment: 5 page
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