Einsteinian Manifolds and Gravitational Waves

The full relativity of the concepts of motion and rest, which is characteristic of the Einsteinian general relativity (GR), does not allow the generation of physical gravitational waves (GW's). -- The undulatory nature of a metric tensor is not an invariant property, but depends on the coordinate frame. -- An undulation of a metric tensor is propagated with a speed that can have any value between zero and infinite.Comment: 5 pages, LaTe

Einstein, Levi-Civita, and Bianchi relations

About an essential suggestion to Einstein by Levi-Civita in 1915. Unicuique suum.Comment: 2 pages, LaTeX, to be published on Spacetime & Substanc

On Gravitational Motions

A new proof of the geodesic character of all motions of bodies that interact only gravitationally - and a detailed illustration of the real meaning of the linearized approximation of general relativity.Comment: 12 pages, LaTe

Gravitational collapses to bodies of a finite volume

We prove with an exact relativistic computation that the spherosymmetric gravitational collapses with a time-dependent pressure end in bodies with a small, but finite volume. Against a diffuse, wrong conviction.Comment: 8 pages, LaTeX, to be published on Spacetime & Substanc

On Hilbert's gravitational repulsion (A historical Note)

In the literature on general relativity no mention is made of a remarkable result contained in Hilbert's memoir "Die Grundlagen der Physik", according to which in particular instances and in particular regions the Einsteinian gravity exerts a repulsive action. We give here a concise illustration of this peculiar phenomenon.Comment: 7 pages, LaTe

On the relation between Schwarzschild's and Kerr's manifolds

Kerr's manifold is only a Schwarzschild's manifold as seen by a suitably rotating coordinate system. By taking into account this fact, Kerr's manifold can be reduced to a Schwarzschild's manifold. In a final summary we give the main steps of our reasoning.Comment: 6 pages, LaTe

Attraction and repulsion in spacetime of an electrically charged mass-point

By virtue of Hilbert repulsive effect, the most external singular surface of Reissner-Weyl-Nordstroem metric represents an insuperable barrier for the arriving neutral particles and light rays.Comment: 5 pages, LaTe

On spherically symmetric structures in GR

We reconsider some subtle points concerning the relativistic treatment of the gravitational fields generated by spherically symmetric structures.Comment: 10 pages, 1 figure, typing correction at page

Schwarzschild manifold and non-regular coordinate transformations (A critico-historical Note)

A careful analysis of the maximally extended metrics of Schwarzschild manifold shows that the original Schwarzschild's solution (1916) and Brillouin's solution (1923) are the only ones that are adequate from the physical standpoint. Contrary to the other maximally extended metrics, they represent faithfully the gravity field created by the mass-point.Comment: 10 pages, LaTe

On repulsive gravitational actions

In particular instances and in particular regions the Einsteinian gravity exerts a repulsive action -- and without any cosmological term. This fact could have an interest for the explanation of the dark energy, and for the gravitational collapses.Comment: 8 pages, 6 figures, LaTe