1,115 research outputs found
Gravitational collapses and Hilbertian repulsion
If we take into account the Hilbertian gravitational repulsion, even a dust
sphere with a zero fluido-dynamical pressure collapses to a body of a
comparatively small, finite, volume.Comment: 4 pages, LaTe
All relativistic motions can be geodesically described
A suitable choice of the four components of the metric tensor which are at
our discretion allows to represent geodesically also the non-gravitational
motions.Comment: 3 pages, LaTe
On the gravitational collapse of a massive star
The celebrated treatment of continued gravitational collapse by Oppenheimer
and Snyder is revisited and emended from some inherent flaws. The star
contracts itself into a material point, not into a black hole.Comment: 7 pages, LaTex, to be published on Spacetime & Substanc
On the GR-speeds of light and particles (A remembrance of things past)
There are no limits for the speeds of light and particles in general
relativity (GR). Four examples illustrate this basic result, which is too often
neglected.Comment: 5 page
Protons do not exert any Hilbertian gravitational repulsion
The Hilbertian gravitational repulsion is quite absent in the Einsteinian
field of a proton, owing to the gravitational action of its electric charge.
Accordingly, the proton bunches of the LHC cannot exert any repulsive
gravitational force.Comment: 3 pages, Late
On the gravitational redshifts of spectral lines - A critico-historical study
A beautiful, detailed computation by Whittaker has enabled us to prove in a
rigorous way that the gravitationally redshifted frequency of a monochromatic
e.m. wave sent forth at the surface of a celestial body is propagated unaltered
from the emitting source to terrestrial observers. We remark that in the
customary treatments only qualitative and inaccurate justifications of this
fact are given.Comment: 9 page
Remarks on numerical relativity, geodesic motions, binary neutron star evolution
The computations of numerical relativity make use of (3+1)- decompositions of
Einstein field equations. We examine the conceptual characteristics of this
method; instances of compact-star binaries are considered. The preeminent role
of the geodesic motions is emphasized.Comment: 8 page
On Majorana's equation
The physical results of quantum field theory are independent of the various
specializations of Dirac's gamma-matrices, that are employed in given problems.
Accordingly, the physical meaning of Majorana's equation is very
dubious,considering that it is a consequence of ad hoc matrix representations
of the gamma-operators. Therefore, it seems to us that this equation cannot
give the equation of motion of the neutral WIMPs (weakly interacting massive
particles), the hypothesized constitutive elements of the Dark Matter.Comment: 4 page
The supermassive centre of our galaxy - et cetera
We show that the supermassive celestial body at the centre of the Milky Way
and the two supermassive celestial bodies at the centre of the distant galaxy
NGC 6240 cannot be black holes.Comment: 3 pages, LaTeX, to be published on Spacetime & Substanc
On some relativistic singular surfaces
In the current relativistic literature there are misleading considerations
about some singular surfaces. An accurate geometric analysis allows to settle
the question. No physical meaning is attributable to the spatial regions
surrounded by the above surfaces. A recent observational paper by A. Fabian et
al. is discussed in sect.4.Comment: 5 pages, LaTe
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