Papers by Alexandre Landry
The paper develops many fundamental ideas and presents another vision of the problem of gravitati... more The paper develops many fundamental ideas and presents another vision of the problem of gravitational interaction. We propose to describe gravitation and spacetime in terms of the electrical permittivity of the ambient medium (taking into account the masses in presence) instead of spacetime curvature (R), torsion (T), or non-metricity (Q) of spacetime. Obviously, if the speed of light varies with this permittivity, the redshift will also depend on this variation in permittivity. And afterward, we evaluate the consequences for the masses, the interactions between them, and the lower limit of gravitational acceleration. In short, we present here another vision of gravitation. The exercise seems to have been quite successful.
European physical journal. C, Particles and fields, Mar 29, 2024
Regarding the left-right inversion made by a plane mirror, many sources refer to Feynman's soluti... more Regarding the left-right inversion made by a plane mirror, many sources refer to Feynman's solution. According to him, the brain does the inversion to satisfy a sort of "good form". He does not pay much attention to ray trajectory or ocular physiology. But if we consider that the human eye has lateral sensors capable of detecting whether the light comes from the left or the right: we understand the phenomenon much better.
arXiv (Cornell University), Feb 11, 2024
We are interested in the development of spherically symmetric geometries in F (T) teleparallel gr... more We are interested in the development of spherically symmetric geometries in F (T) teleparallel gravity which are of physical importance. We first express the general forms for the spherically symmetric frame and the zero curvature, metric compatible, spin connection. We then analyse the antisymmetric field equations (the solutions of which split into two cases, which we subsequently consider separately), and derive and analyse the resulting symmetric field equations. In order to further study the applications of spherically symmetric teleparallel models, we study 3 subcases in which there is an additional affine symmetry so that the resulting field equations reduce to a system of ordinary differential equations. First, we study static spherical symmetric geometries and solve the antisymmetric field equations and subsequently derive the full set of symmetric field equations. In particular, we investigate vacuum spacetimes and obtain a number of new solutions. Second, we consider an additional affine frame symmetry in order to expand the affine frame symmetry group to that of a spatially homogeneous Kantowski-Sachs geometry. Third, we study the special case of spherical symmetry with an additional fourth similarity affine vector.
arXiv (Cornell University), Jul 24, 2023
Theories of gravity based on teleparallel geometries are characterized by the torsion, which is a... more Theories of gravity based on teleparallel geometries are characterized by the torsion, which is a function of the coframe, derivatives of the coframe, and a zero curvature and metric compatible spin-connection. The appropriate notion of a symmetry in a teleparallel geometry is that of an affine symmetry. Due to the importance of the de Sitter geometry and Einstein spaces within General Relativity, we shall describe teleparallel de Sitter geometries and discuss their possible generalizations. In particular, we shall analyse a class of Einstein teleparallel geometries which have a 4-dimensional Lie algebra of affine symmetries, and display two one-parameter families of explicit exact solutions.
Universe
In teleparallel geometries, the coframe and corresponding spin connection are the principal geome... more In teleparallel geometries, the coframe and corresponding spin connection are the principal geometric objects and, consequently, the appropriate definition of a symmetry is that of an affine symmetry. The set of invariant coframes and their corresponding spin connections that respect the full six dimensional Lie algebra of Robertson–Walker affine symmetries are displayed and discussed. We will refer to such geometries as teleparallel Robertson–Walker (TRW) geometries, where the corresponding derived metric is of Robertson–Walker form and is characterized by the parameter k=(−1,0,1). The field equations are explicitly presented for the F(T) class of teleparallel TRW spacetimes. We are primarily interested in investigating the k≠0 TRW models. After first studying the k=0 models and, in particular, writing their governing field equations in an appropriate form, we then study their late time stability with respect to perturbations in k in both the cases of a vanishing and non-vanishing ...
European Physical Journal Plus, Jun 1, 2020
We study the quantum Hall effect inside a gravitational field. First, we review the influence of ... more We study the quantum Hall effect inside a gravitational field. First, we review the influence of the gravitational field of the Earth on the quantum Hall effect. Taking the gravitational field of the Earth to be uniform along the vertical direction, we compute the affected quantized Hall resistivity. Then, we investigate how the gravitational field modifies the Landau levels of a particle moving between two massive hemispheres in the presence of a constant and uniform magnetic field perpendicular to the plane of motion. We find that the familiar degeneracy of the Landau levels is removed and the spacing between the latter becomes dependent on the mass density of the hemispheres and on the gravitational constant G. We use this result to show that the quantum Hall effect in a thin conductor, sandwiched between two massive hemispheres, should yield a slightly different variation of the Hall resistivity with the applied magnetic field. We then argue that the well-known problem of the gravitationally induced electric field, that might a priori be thought to hinder the effect of gravity, has actually a beneficial role as it amplifies the latter. We finally discuss whether there is a possibility of using the quantum Hall effect to probe the inverse-square law of gravity.
Physical review, Jun 16, 2016
In this letter, we calculate the probability for resonantly induced transitions in quantum states... more In this letter, we calculate the probability for resonantly induced transitions in quantum states due to time dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultra cold neutrons (UCN), which are organized according to the energy levels of the Schrödinger equation in the presence of the earth's gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency ω. The driving force is created by oscillating a macroscopic mass in the neighbourhood of the system of neutrons. The neutrons decay in 880 seconds while the probability of transitions increase as t 2. Hence the optimal strategy is to drive the system for 2 lifetimes. The transition amplitude then is of the order of 1.06 × 10 −5 hence with a million ultra cold neutrons, one should be able to observe transitions.
International Journal of Modern Physics D, Oct 1, 2016
We consider the possibility of creating a graviton laser. The lasing medium would be a system of ... more We consider the possibility of creating a graviton laser. The lasing medium would be a system of contained, ultra cold neutrons. Ultra cold neutrons are a quantum mechanical system that interacts with gravitational fields and with the phonons of the container walls. It is possible to create a population inversion by pumping the system using the phonons. We compute the rate of spontaneous emission of gravitons and the rate of the subsequent stimulated emission of gravitons. The gain obtainable is directly proportional to the density of the lasing medium and the fraction of the population inversion. The applications of a graviton laser would be interesting.
arXiv (Cornell University), Oct 28, 2019
We examine a simple tabletop experimental setup for probing the inverse-square law of gravity and... more We examine a simple tabletop experimental setup for probing the inverse-square law of gravity and detecting eventual deviations therefrom. The nature of the setup allows indeed to effectively reach for shorter distances compared to what is allowed by other methods. Furthermore, we show that the same setup could also be used to probe the interaction between gravitomagnetism and the intrinsic angular spin of quantum particles. Moreover, we show that the setup allows to have a gravitationally induced harmonic oscillator, introducing thus the possibility of studying in a novel way the interaction between gravity and quantum particles.
Physical review, Apr 22, 2021
We examine the influence of the dispersion relation on the Unruh effect by Lorentz boosting the p... more We examine the influence of the dispersion relation on the Unruh effect by Lorentz boosting the phase of Minkowski vacuum fluctuations endowed with an arbitrary dispersion relation. We find that, unlike what happens with a linear dispersion relation exhibited by massless fields, thermality is lost for general dispersion relations. We show that thermality emerges with a varying "apparent" Davies-Unruh temperature depending on the acceleration of the observer and on the degree of departure from linearity of the dispersion relation. The approach has the advantage of being intuitive and able to pinpoint why such a loss of thermality occurs and when such a deviation from thermality becomes significant. We discuss the link of our results with the well-known fundamental difference between the thermalization theorem and the concept of Rindler noise. We examine the possible experimental validation of our results based on a successful setup for testing the classical analogue of the Unruh effect recently described in the literature.
The European Physical Journal C
Theories of gravity based on teleparallel geometries are characterized by the torsion, which is a... more Theories of gravity based on teleparallel geometries are characterized by the torsion, which is a function of the coframe, derivatives of the coframe, and a zero curvature and metric compatible spin-connection. The appropriate notion of a symmetry in a teleparallel geometry is that of an affine symmetry. Due to the importance of the de Sitter geometry and Einstein spaces within General Relativity, we shall describe teleparallel de Sitter geometries and discuss their possible generalizations. In particular, we shall analyse a class of Einstein teleparallel geometries which have a 4-dimensional Lie algebra of affine symmetries, and display two one-parameter families of explicit exact solutions.
arXiv (Cornell University), Mar 28, 2023
Universe
A complete perturbation theory suitable for teleparallel gravity is developed. The proposed pertu... more A complete perturbation theory suitable for teleparallel gravity is developed. The proposed perturbation scheme takes into account perturbations of the coframe, the metric, and the spin-connection, while ensuring that the resulting perturbed system continues to describe a teleparallel gravity situation. The resulting perturbation scheme can be transformed to one in which perturbations all take place within the co-frame. A covariant definition of a teleparallel Minkowski geometry is proposed. We compute the perturbed field equations for f(T) teleparallel gravity and discuss the stability of the teleparallel Minkowski geometry within f(T) teleparallel gravity.
Annexe A. Évaluation des intégrales avec les fonctions de Kummer à l'aide des polynômes de Laguer... more Annexe A. Évaluation des intégrales avec les fonctions de Kummer à l'aide des polynômes de Laguerre .
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Papers by Alexandre Landry