arXiv subjects

Asher Yahalom

Publications and source records attributed to Asher Yahalom.

At least 19 recordsLinked to original sources

arXiv2025

The Hybrid Euclidean-Lorentzian Universe: Stability Considerations and the Point of Transition

The limited velocity implied by Lorentzian signature, prevents the universe to reach thermodynamic equilibrium implied by the CMB. Rapid expansion can occur by following Hawking and assuming a primordial Euclidean metric, in which case velocity is not limited and thermalization and rapid expansion are derived without the need to assume an ad-hoc field. Moreover, a mathematical model was given regarding the development of current Lorentzian spacetime from the early Euclidean space-time in which problems such as initial singularity and the homogeneity of the CMB are solved. However, stability properties of the hybrid model were not discussed yet, nor was a mathematical criterion for the transition between the Euclidean and Lorentzian era's defined, those will be discussed here to some extent.

physics.gen-ph↗

arXiv2024

Dirac Theory as a Relativistic Flow

In previous papers we have shown how Schrödinger's equation which includes an electromagnetic field interaction can be deduced from a fluid dynamical Lagrangian of a charged potential flow that interacts with an electromagnetic field. The quantum behaviour was derived from Fisher information terms which were added to the classical Lagrangian. It was thus shown that a quantum mechanical system is drived by information and not only electromagnetic fields. This program was applied also to Pauli's equations by removing the restriction of potential flow and using the Clebsch formalism. Although the analysis was quite successful there were still terms that did not admit interpretation, some of them can be easily traced to the relativistic Dirac theory. Here we repeat the analysis for a relativistic flow, pointing to a new approach for deriving relativistic quantum mechanics.

quant-ph↗

arXiv2024

Wide Binaries, Retardation and the External Field Effect

A low acceleration gravitational anomaly was reported for wide binaries: two binary stars which are separated by more than five kilo astronomical units (kau). The increase in gravitational force was reported to be about $1.37$ greater than Newtonian gravity. At the same time binaries separated less than one kau were shown to obey standard Newtonian gravity. A possible explanation for this was given in the framework of MOND correction to gravity which is applicable for low acceleration. However, it was noticed that the explanation is only adequate in the framework of Milgromian AQUAL theory which considers the "external field effect" that is the effect of the gravitational field of the rest of the galaxy on the binary system. Recently it was shown that many "anomalous gravity" effects can be explained in the framework of general relativity and its weak field approximation. It was shown that anomalous galaxy rotation curves, anomalous gravitational lensing and the Tully-Fisher relations can be understood in terms of retarded gravity. Moreover, the anomalous mass of galaxy clusters derived from the virial theorem was also shown to be a retarded gravity effect. On the other hand, it was shown that retarded effects are not important in the solar system and the correction to the anomalous shift of Mercury's perihelion is connected with the motion of the solar center of mass with respect to the sun and not to retardation. It is desirable to investigate if the wide binary acceleration gravitational anomaly can be explained in the framework of Einstein-Newton general relativity. We show that the scale of five kau separation arises naturally within such a theory if the effect of the galaxy on the wide binary is considered (a Newtonian external field effect) suggesting the anomaly found can be explained without the need to invoke theoretical modifications of the accepted theory.

physics.gen-ph↗

arXiv2023

Variational Principles for Nonbarotropic Fluid Dynamics

Barotropic fluid flows with the same circulation structure as steady flows generically have comoving physical surfaces on which the vortex lines lie. These become Bernoullian surfaces when the flow is steady. When these surfaces are nested (vortex line foliation) with the topology of cylinders, toroids or a combination of both, a Clebsch representation of the flow velocity can be introduced. This is then used to reduce the number of functions to be varied in the variational principles for such flows. Here we extend the work to non barotropic flows and study the implication for variational analysis and conserved quantities of topological significance such as circulation and helicity.

physics.flu-dyn↗

arXiv2023

A Fisher Information Perspective of Relativistic Quantum Mechanics

In previous papers we have shown how Schrodinger's equation which includes an electromagnetic field interaction can be deduced from a fluid dynamical Lagrangian of a charged potential flow that interacts with an electromagnetic field. The quantum behaviour was derived from Fisher information terms which were added to the classical Lagrangian. It was thus shown that a quantum mechanical system is drived by information and not only electromagnetic fields. This program was applied also to Pauli's equations by removing the restriction of potential flow and using the Clebsch formalism. Although the analysis was quite successful there were still terms that did not admit interpretation, some of them can be easily traced to the relativistic Dirac theory. Here we repeat the analysis for a relativistic flow, pointing to a new approach for deriving relativistic quantum mechanics.

quant-ph↗

arXiv2023

Paving the Way for a Multiplanetary Future for Humanity: How the Relativistic motor may enable eventually interplanetary travel

Current spacecraft mass are mostly fuel, this is dictated by the lack of fueling stations in space and also by the Tsiolkovsky rocket equation which defines the mass ratio needed to escape earths gravity. The Tsiolkovsky rocket equation gives a relationship between the mass ratio and the final velocity in multiples of the exhaust speed, and dictates a high mass ratio for current exhaust speeds. A relativistic motor exchanging momentum and energy with the electromagnetic field may mitigate such considerations, enabling efficient interplanetary travel. In this paper we will discuss the advantages and challenges of this novel mover for space transportation.

physics.gen-ph↗

arXiv2023

Newton's Third Law in the Framework of Special Relativity for Charged Bodies Part 3: Time Dependent Engines

The Lorentz symmetry group entails physical equations whose solutions are retarded. This leads to the concept of a relativistic engine resulting from retardation of electromagnetic fields. We have shown that Newton'n third law cannot strictly hold in a distributed system, where the different parts are at a finite distance from each other and thus force imbalance is created at the system's center of mass. As the system is affected by a total force for a finite period, mechanical momentum and energy are acquired by the system. In previous works we relied on the fact that the bodies were macroscopically natural. Lately we relaxed this assumption and studied charged bodies, thus analyzing the consequences on a possible electric relativistic engine. On the first paper on this subject we investigated this phenomena in general but gave an example of a system only at the stage of reaching a stationary state, a second paper was devoted to the same but on the atomic scale, here we shall analyze the charge relativistic engine in a general time dependent setting.

physics.gen-ph↗

arXiv2023

Lindbladian-Induced Alignment in Quantum Measurements

An expression of the Lindbladian form is proposed that ensures an unambiguous time-continuous reduction of the initial system-pointer wave-packet to one in which the readings and the observable's values are aligned, formalized as the transition from an outer product to an inner product of the system's and apparatus' density matrices. The jump operators are in the basis of the observables, with uniquely determined parameters derived from the measurement set-up (thereby differing from S. Weinberg's Lindbladian resolution of wave-packet formalism) and conforming to Born's probability rules. The novelty lies in formalising the adaptability of the surroundings (including the measuring device) to the mode of observation. Accordingly, the transition is of finite duration (in contrast to its instantaneousness in the von Neumann's formulation). This duration is estimated for a simple half-spin-like model.

quant-ph↗

arXiv2022

Pauli's Electron in Ehrenfest and Bohm Theories, a Comparative Study

Electrons moving at slow speeds much lower that the speed of light are described by a wave function which is a solution of Pauli's equation. This is a low velocity limit of the relativistic Dirac equation. Here we compare two approaches, one which is the more conservative Copenhagen's interpretation denying a trajectory of the electron but allowing a trajectory to the electron expectation value through Ehrenfest theorem. The said expectation value is of course calculated using a solution of Pauli's equation. A less orthodox approach is championed by Bohm, and attributes a velocity field to the electron also derived from the Pauli wave function. It is thus interesting to compare the trajectory followed by the electron according to Bohm and its expectation value according to Ehrenfest. Both similarities and differences will be considered.

quant-ph↗

arXiv2022

Generalized Cross Helicity in Non-ideal Magnetohydrodynamics

The objective of the present paper is to investigate the constancy of the topological invariant denoted non-barotropic generalized cross helicity in the case of non-ideal magnetohydrodynamic (MHD). Existing work considers only ideal barotropic MHD and ideal non-barotropic MHD. The non-ideal MHD case was not explored probably because of its mathematical complexity. Here we consider dissipative processes in the form of thermal conduction, finite electrical conductivity and viscosity and the effect of these processes on the cross helicity conservation. Analytical approach has been adopted to obtain the mathematical expressions for the time derivative of cross helicity. Obtained results show, that the generalized cross helicity is not conserved in the non-ideal MHD limit and indicate which processes affect the helicity and which do not. Furthermore, we indicate the configurations in which this topological constant is conserved despite the dissipative processes.

physics.flu-dyn↗

arXiv2022

The Primordial Particle Accelerator of the Cosmos

In a previous paper we have shown that superluminal particles are allowed by the general relativistic theory of gravity provided that the metric is locally Euclidean. Here we calculate the probability density function of a canonical ensemble of superluminal particles as function of temperature. This is done for both space-times invariant under Lorentz symmetry group, and for space times invariant under an Euclidean symmetry group. Although only the Lorentzian metric is stable for normal matter density, an Euclidian metric can be created under special gravitational circumstances and persist in a limited region of space-time consisting of the very early universe which is characterized by extremely high densities and temperatures. Superluminal particles also allow attaining thermodynamic equilibrium at a shorter duration and also suggest a rapid expansion of the matter density, thus making mechanism such as inflation (which demands invoking and ad-hoc scalar field) redundant. This is in accordance with Occam's razor.

gr-qc↗

arXiv2022

Fisher Information Perspective of Pauli's Electron

A non relativistic electron with a spin is described by Pauli's equation. It has been shown that this system can be interpreted as a vortical fluid which has both similarities and differences with classical ideal flows. Moreover, it was demonstrated that the internal energy of the spin fluid can partially be interpreted in terms of Fisher Information. While previous work on the subject has mainly ignored electromagnetic fields which are represented by a vector potential here we remove this limitation and study the system under general electromagnetic interaction.

cond-mat.other↗

arXiv2022

The Weak Field Approximation of General Relativity, Retardation, and the Problem of Precession of the Perihelion for Mercury

In this paper we represent a different approach to the calculation of the perihelion shift than the one presented in common text books. We do not rely on the Schwarzschild metric and the Hamilton Jacobi technique to obtain our results. Instead we use a weak field approximation, with the advantage that we are not obliged to work with a definite static metric and can consider time dependent effects. Our results support the conclusion of Krizek \cite{Krizek} regarding the significant influence of celestial parameters on the indeterminacy of the perihelion shift of Mercury's orbit. This shift is thought to be one of the fundamental tests of the validity of the general theory of relativity. In the current astrophysical community, it is generally accepted that the additional relativistic perihelion shift of Mercury is the difference between its observed perihelion shift and the one predicted by Newtonian mechanics, and that this difference equals $43"$ per century. However, as it results from the subtraction of two inexact numbers of almost equal magnitude, it is subject to cancellation errors. As such, the above accepted value is highly uncertain and may not correspond to reality.

physics.gen-ph↗

arXiv2021

A Three Function Variational Principle for Stationary Non-Barotropic Magnetohydrodynamics

Variational principles for magnetohydrodynamics (MHD) were in\-troduced by previous authors both in Lagrangian and Eulerian form. In this paper we introduce simpler Eulerian variational principles from which all the relevant equations of non-barotropic stationary magnetohydrodynamics can be derived for certain field topologies. The variational principle is given in terms of three independent functions for stationary non-barotropic flows. This is a smaller number of variables than the eight variables which appear in the standard equations of non-barotropic magnetohydrodynamics which are the magnetic field $\vec B$ the velocity field $\vec v$, the entropy $s$ and the density $ρ$. We further investigate the case in the flow along magnetic lines is not ideal.

physics.plasm-ph↗

arXiv2021

Effects of Higher Order Retarded Gravity

In a recent paper, we have a shown that the flattening of galactic rotation curves can be explained by retardation. However, this will rely on a temporal change of galactic mass. In our previous work, we kept only second order terms of the retardation time in our analysis, while higher terms in the Taylor expansion where not considered. Here we consider analysis to all orders and show that a second order analysis will indeed suffice, and higher order terms can be neglected.

physics.gen-ph↗

arXiv2021

Lensing Effects in Retarded Gravity

Galaxies are gigantic physical systems having a typical size of many tens of thousands of light years. Thus any change at the center of the galaxy will affect the rim only tens of millennia later. Those retardation effects seems to be ignored in present day modelling used to calculate rotational velocities of matter in the outskirts of the galaxy and the surrounding gas. The significant discrepancies between the velocities predicted by Newtonian theory and observed velocities are usually handled by either assuming an unobservable type of matter denoted "dark matter" or by modifying the laws of gravity (MOND as an example). Here we will show that considering general relativistic effects without neglecting retardation one can explain the apparent excess matter leading to gravitational lensing in both galaxies and galaxy clusters.

physics.gen-ph↗

arXiv2021

Raychaudhuri Equation,Geometrical Flows and Geometrical Entropy

Raychaudhuri equation is derived by assuming geometric flow in spacetime M of n+1 dimensions. The equation turns into a harmonic oscillator form under suitable transformations.Thereby a relation between geometrical entropy and mean geodesic deviation is established. This has a connection to chaos theory where the trajectories diverge exponentially. We discuss its application to cosmology and black holes. Thus we present a connection between chaos theory and general relativity.

gr-qc↗

arXiv2021

Newton's Third Law in the Framework of Special Relativity for Charged Bodies

Newton's third law states that any action is countered by a reaction of equal magnitude but opposite direction. The total force in a system not affected by external forces is thus zero. However, according to the principles of relativity, a signal cannot propagate at speeds exceeding the speed of light. Hence the action and reaction cannot be generated at the same time due to the relativity of simultaneity. Thus, the total force cannot be null at a given time. In a previous paper \cite{MTAY1}, we have shown that Newt\-on'n third law cannot strictly hold in a distributed system, where the different parts are at a finite distance from each other. This is due to the finite speed of signal propagation, which cannot exceed the speed of light in the vacuum. A specific example of two current loops with time dependent currents demonstrated that the summing of the total force in the system does not add up to zero. This analysis led to the suggestion of a relativistic engine \cite{MTAY3,AY1}. As the system is affected by a total force for a finite period, the system acquires mechanical momentum and energy. Now the question then arises how can we accommodate the law of momentum and energy conservation. The subject of momentum conversation was discussed in \cite{MTAY4}, while preliminary results regarding energy conservation were discussed in \cite{AY2,RY,RY2}. Previous analysis relied on the fact that the bodies were macroscopically natural, which means that the number of electrons and ions is equal in every volume element. Here we relax this assumption and study charged bodies, thus analyzing the consequences on a possible electric relativistic engine.

physics.gen-ph↗