Related papers: A Model for the Pioneer Anomaly
Flat galaxy rotation curves and the accelerating Universe both imply the existence of a critical acceleration, which is of the same order of magnitude in both the cases, in spite of the galactic and cosmic length scales being vastly…
The discrepancy between the visible mass in galaxies or galaxy clusters, and that inferred from their dynamics is well known. The prevailing solution to this problem is dark matter. Here we show that a different approach, one that conforms…
One of the deepest and most long-standing mysteries in physics has been the huge discrepancy between the observed vacuum density and our expectations from theories of high energy physics, which has been dubbed the Old Cosmological Constant…
The anomalous, energy dependent shift of the center of mass of an idealized, perfectly rigid, uniformly rotating hemispherical shell which is caused by the relativistic mass increase effect is investigated in detail. It is shown that a…
This thesis is devoted to the study of gravitational theories which can be seen as modifications or generalisations of General Relativity. The motivation for considering such theories, stemming from Cosmology, High Energy Physics and…
We consider a maximal extension of the Hilbert-Einstein action and analyze several interesting features of the theory. More specifically, the motion is non-geodesic and takes place in the presence of an extra force. These models could lead…
Some results of author's work in a non-geometrical approach to quantum gravity are reviewed here, among them: a quantum mechanism of classical gravity giving a possibility to compute the Newton constant; asymptotic freedom at short…
In 1972 and 1973 the Pioneer 10 and 11 missions were launched. They were the first to explore the outer solar system and achieved stunning breakthroughs in deep-space exploration. But beginning in about 1980 an unmodeled force of \sim 8…
It has been suggested recently that the change in cosmological redshift (the Sandage test of expansion) could be observed in the next generation of large telescopes and ultra-stable spectrographs. In a recent paper we estimated the change…
A gravitational field model based on two symmetric tensors, $g_{\mu \nu}$ and $\tilde{g}_{\mu \nu}$, is presented. In this model, new matter fields are added to the original matter fields, motivated by an additional symmetry…
Cosmic acceleration may be due to modifications of cosmic gravity and to test this we need robust connections between theory and observations. However, in a model independent approach like effective field theory or a broad class like…
We study a non-commutative deformation of general relativity based on spectral invariants of a partial differential operator acting on sections of a vector bundle over a smooth manifold. We compute the first non-commutative corrections to…
With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realized. We show that a confirmation of equality to the speed of…
A previous paper [1] introduced a quantum-mechanical theory of gravity, and showed it agrees with the standard experimental tests of general relativity. Doppler tracking signals returned by the Pioneer 10 and 11 space probes offer an…
All anomalous velocity increases until now observed during the Earth flybys of the spacecrafts Galileo, NEAR, Rosetta, Cassini and Messenger have been correctly calculated by computer simulation using an asymmetric field term in addition to…
I review a class of nonlocally modified gravity models which were proposed to explain the current phase of cosmic acceleration without dark energy. Among the topics considered are deriving causal and conserved field equations, adjusting the…
We construct a phenomenological theory of gravitation based on a second order gauge formulation for the Lorentz group. The model presents a long-range modification for the gravitational field leading to a cosmological model provided with an…
The equation of motion for test particles in $f(R)$ modified theories of gravity is derived. By considering an explicit coupling between an arbitrary function of the scalar curvature, $R$, and the Lagrangian density of matter, it is shown…
This paper discusses the likelihood of whether the Pioneer anomaly is due to 'mundane' systematic errors/effects or indicative of new or unappreciated physics. The main aim of this paper is to argue that recent publications suggesting that…
We derive the scalar-tensor modification of the gravitational field of an ultrarelativistic particle beam and its effect on a test particle that is used as sensor. To do so, we solve the linearized scalar-tensor gravity field equations…