arXiv subjects

Ll. Bel

Publications and source records attributed to Ll. Bel.

At least 19 recordsLinked to original sources

arXiv2016

Quantum gravity: the Inverse problem

Quantizing the gravitational field described by General relativity being a notorious difficult, unsolved and maybe meaningless problem I use in this essay a different strategy: I consider a linear theory in the framework of Special relativity where the potentials are the components of four linear forms. General relativity and other similar covariant non linear theories can be formulated in this way. The theory that I propose is Lorentz invariant, linear, simple, and can be quantized following similar steps to those that led to quantum electrodynamics.

physics.gen-ph↗

arXiv2016

On a correlation among azimuthal velocities and the flyby anomaly sign

Data of six flybys, those of Galileo I, Galileo II, NEAR, Cassini, Rosetta and Messenger were reported by Anderson et al \citep{Anderson}. Four of them: Galileo I, NEAR, Rosetta and Messenger gain Newtonian energy during the flyby transfer, while Galileo II and Cassini lose energy. This is, in both cases, a surprising anomaly since Newtonian forces derive from a potential and they are, therefore, conservative. We show here that the gravitational field of a rotating planet as derived from a new model introduces a non conservative force that gives a partial, but in our opinion satisfactory, explanation of these anomalies and suggests a correlation between the sign of the anomaly and the sign of the azimuthal velocity at perigee.

physics.space-ph↗

arXiv2014

AdS. Klein-Gordon equation

I propose a generalization of the Klein-Gordon equation in the framework of AdS space-time and exhibit a four parameter family of solutions among which there is a two parameter family of time-dependent bound states.

physics.gen-ph↗

arXiv2014

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.

gr-qc↗

arXiv2014

Basic cosmology

Basic cosmology describes the universe as a Robertson-Walker model filled with black-body radiation and no barionic matter, and as observational data it uses only the value of the speed of light, the Hubble and deceleration parameters and the black-body temperature at the present epoch. It predicts the value of the next new parameter in the Hubble law.

physics.gen-ph↗

arXiv2014

Earth and Moon orbital anomalies

A time-dependent gravitational constant or mass would correctly describe the suspected increasing of both: the Astronomical unit and the eccentricity of the Lunar orbit around the Earth.

gr-qc↗

arXiv2013

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 $m$, 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 $m$.

gr-qc↗

arXiv2013

The Dark Mass Problem

I discuss some of the basic properties of a potential theory derived from a modified Newton's law of action at a distance that includes a $1/r$ attractive force.

physics.gen-ph↗

arXiv2012

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}.

physics.gen-ph↗

arXiv2012

Global SSS space-time models: $M_a$ and $Q$

To make sense of a global space-time model and to give a meaning to the coordinates that we use, a choice of a constant curvature space-metric of reference it is as much necessary as it is a choice of units of mass, length and time. The choice we make leads to contradict the belief that the exterior domain of a Static Spherically Symmetric (SSS) space-time model of finite radius $R$ depends only on the active mass $M_a$ of the source. In fact it depends on two parameters $M_a$ and a new one $Q$. We prove that both can be calculated as volume integrals extended over the whole space. We integrate Einstein's equations numerically in two simple cases: assuming either that the source of perfect fluid has constant proper density or that the pressure depends linearly on the proper density. We confirm a preceding paper showing that very compact objects can have active masses $M_a$ much greater than their proper masses $M_p$, and we conjecture that the mass point Fock's model can be understood as the limit of a sequence of compact models when both Q and its radius shrink to zero and the pressure equals the density.

gr-qc↗

arXiv2011

Global SSS space-time models

We discuss Global Static Spherically Symmetric space-time models of mass $m$ with regular sources at the origin and asymptotically Minkowskian behavior at infinity; the interior model and the exterior one being matched at the radius $R$ of the source in the sense of Lichnerowicz. The global models depend in general on $R$ through a function $Q$ of $m$ and $R$. Although $R$ would be an spurious parameter if the exterior model was considered alone, it becomes intrinsic for the global model. The physical implication is that $R$ as well as $m$ determine, at some order of approximation, the dynamics of orbiting objects or viceversa that this dynamics puts conditions on the physical state of the source.

gr-qc↗

arXiv2011

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.

gr-qc↗

arXiv2011

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.

gr-qc↗

arXiv2010

Local cosmology of the solar system

A time-dependent model of space-time is used to describe the gravitational field of the sun. This model is a spherically symmetric approximate solution of Einstein's equations in vacuum. Near the sun it approximates one of the models derived from the Schwarzschild solution, while at large distances it becomes a milne's-like zero space-time curvature model. Two local cosmology free parameters provide simple descriptions for the secular increasing of the astronomical unit, as well as the "anomalous" radial acceleration of the Pioneer probe. We make also a comment about the possibility of deriving MOND's phenomenology from General relativity.

gr-qc↗

arXiv2010

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.

gr-qc↗

arXiv2009

About the mass problem

The concept of {\it active gravitational mass}, its definition and its relation with the sources of a gravitational field, was clearly established by Tolman in 1934. On the contrary, and surprisingly in our opinion, the concept of {\it proper mass} has remained obscure in General relativity. We compare a new definition to an apparent more obvious one and discuss how each choice modifies the ratio of active to proper gravitational mass.

gr-qc↗

arXiv2008

Connecting connections

As true as it is that a bricklayer needs a plumb line and a T-square, so it is that a physicist using general relativity needs how to draw geodesics and use fields of congruent vector frames of reference. While the first part of the preceding statement depends on the Christoffel connection and related metric and curvature concepts, the second part depends on the Weitzenböck connection and the concept of torsion. This dual structure has been considered before as a possibility of using either one of them to describe General relativity. We claim here that both structures have to be correlated to produce useful interpretations of any space-time model.

gr-qc↗

arXiv2007

Covariance and meaning

Several other factors, besides the intrinsic local geometry, contribute to give a meaning to a space-time model. The simplest example comes from comparing Minkowski's and Milne's model, that both have a null Riemann tensor. We add to these two models a third one which describes a time-dependent locally-Minkowskian spherically symmetric space-time on which every test-particle at rest with respect to the center of symmetry sustains a constant force. Although the model is globally grossly un-realistic we think that it can be helpful to describe a local perturbation of an homogeneous cosmological model. Or as a substitute to the very far away asymptotic Minkowskian behavior usually assumed to describe the gravitational field of compact spherical bodies.

gr-qc↗