Electromagnetic Tensor Research Articles

Signature-causality reflection generated by Abelian gauge transformations

In this paper, we want to better understand the causality reflection that arises under a subset of Abelian local gauge transformations in geometrodynamics. We proved in previous papers that in Einstein–Maxwell spacetimes, there exist two local orthogonal planes of gauge symmetry at every spacetime point for non-null electromagnetic fields. Every vector in these planes is an eigenvector of the Einstein–Maxwell stress–energy tensor. The vectors that span these local orthogonal planes are dependent on electromagnetic gauge. The local group of Abelian electromagnetic gauge transformations has been proved isomorphic to the local groups of tetrad transformations in these planes. We called LB1 the local group of tetrad transformations made up of SO(1, 1) plus two different kinds of discrete transformations. One of the discrete transformations is the full inversion two by two which is a Lorentz transformation. The other discrete transformation is given by a matrix with zeroes on the diagonal and ones off-diagonal two by two, a reflection. The group LB1 is realized on this plane, we call this plane one, and is spanned by the time-like and one space-like vectors. The other local orthogonal plane is plane two and the local group of tetrad transformations, we call this LB2, which is just SO(2). The local group of Abelian electromagnetic gauge transformations is isomorphic to both LB1 and LB2, independently. It has already been proved that a subset of local electromagnetic gauge transformations that leave the electromagnetic tensor invariant induces a change in sign in the norm of the tetrad vectors that span the local plane one. The reason is that one of the discrete transformations on the local plane one that belongs to the group LB1 is not a Lorentz transformation, it is a flip or reflection. It is precisely on this kind of discrete transformation that we have an interest since it has the effect of changing the signature and the causality. This effect has never been noticed before.

Effect of Thomas Rotation on the Lorentz Transformation of Electromagnetic fields

A relativistic particle undergoing successive boosts which are non collinear will experience a rotation of its coordinate axes with respect to the boosted frame. This rotation of coordinate axes is caused by a relativistic phenomenon called Thomas Rotation. We assess the importance of Thomas rotation in the calculation of physical quantities like electromagnetic fields in the relativistic regime. We calculate the electromagnetic field tensor for general three dimensional successive boosts in the particle’s rest frame as well as the laboratory frame. We then compare the electromagnetic field tensors obtained by a direct boost overrightarrow{beta }+delta overrightarrow{beta } and successive boosts overrightarrow{beta } and Delta overrightarrow{beta } and check their consistency with Thomas rotation. This framework might be important to situations such as the calculation of frequency shifts for relativistic spin-1/2 particles undergoing Larmor precession in electromagnetic fields with small field non-uniformities.

Electromagnetic field expectations as measures of photon localization

The questions of whether a photon can be localized in an arbitrarily small volume and what is the allowable strength of that localization (the decrease with distance of the functional form) are questions of current interest. We propose a measure of localization for the single photon that is the expectation values of the electromagnetic field strength components in a coherent wavepacket state of mean photon number unity. As such, we deal with real quantities that have a physical meaning rather than complex amplitudes. It is seen that the real parts of complex amplitudes proposed previously as measures of localization are equal to our field expectations. With this measure, we examine two test states. The first has a well-resolved momentum. The field expectations show Gaussian (quadratic exponential) localization in all directions, although the localization length scale is much larger than the mean wavelength. For the other test state, with a spherically symmetric momentum distribution, we find almost exponential localization in all directions at t = 0. The profiles are scale invariant, so choosing the momentum width very large would make the localization length arbitrarily small. We conclude that there is no lower bound on the localization length scale of a photon as determined by this measure.

Electromagnetic Field Propagation and Indoor Exclusion Zone Analysis in a Nuclear Power Plant

This article investigates the electromagnetic field strengths and the resulting indoor exclusion zones (EZs), taking into account the actual indoor nuclear power plant (NPP) environment. To obtain the accurate indoor EZ, a real indoor environment based on the simulator room of Korea Institute of Nuclear Safety was included in the numerical simulation. The maximum distance d of the indoor EZs depending on the position and polarization of the emitter is 1 to 2.1 times longer than the distances d of the free-space EZs. To validate the simulated indoor EZs, electromagnetic field strengths along the arc line with an arbitrary distance from the emitter are measured in the NPP, which are in good agreement with the simulation results. The result demonstrates that the indoor EZ should be investigated before applying the wireless system in the NPP because the indoor EZ and free space EZ can be significantly different.

Second gradient electrodynamics: Green functions, wave propagation, regularization and self-force

In this work, the theory of second gradient electrodynamics, which is an important example of generalized electrodynamics, is proposed and investigated. Second gradient electrodynamics is a gradient field theory with up to second-order derivatives of the electromagnetic field strengths in the Lagrangian density. Second gradient electrodynamics possesses a weak nonlocality in space and time. In the framework of second gradient electrodynamics, the retarded Green functions, first-order derivatives of the retarded Green functions, retarded potentials, retarded electromagnetic field strengths, generalized Liénard–Wiechert potentials and the corresponding electromagnetic field strengths are derived for three, two and one spatial dimensions. The behaviour of the electromagnetic fields is investigated on the light cone. In particular, the retarded Green functions and their first-order derivatives show oscillations around the classical solutions inside the forward light cone and it is shown that they are singularity-free and regular on the light cone in three, two and one spatial dimensions. In second gradient electrodynamics, the self-force and the energy release rate are calculated and the equation of motion of a charged point particle, which is an integro-differential equation where the infamous third-order time-derivative of the position does not appear, is determined.

Extraction of the terahertz constitutive tensors of multilayer graphene-dielectric stacks

In this paper, we present a reliable method to extract the electromagnetic constitutive tensors of complex synthesized multilayer graphene-dielectric stacks in the terahertz band. This macroscopic electromagnetic characterization method uses the transmission and reflection coefficients of a normal-incident circularly polarized electromagnetic wave on the material structure. The employment of circularly polarized waves has the advantage of overcoming the ambiguity at high frequencies attributed to the multi-branching discontinuities in the extracted permeability and permittivity tensors of natural or synthesized materials. The retrieved permeability and permittivity tensors are validated by the data obtained from analytical and numerical solutions of the original electromagnetic problem for the case of circularly polarized wave incidence.

Numerical Study of Three-Dimensional Melt Flows during the TSSG Process of SiC Crystal for the Influence of Input Parameters of RF-Coils and an External Rotating Magnetic Field

Three-dimensional numerical simulations were conducted for the Top-Seeded Solution Growth (TSSG) process of silicon carbide (SiC) crystals. We investigated the influence of coils frequency and peak current, and an applied rotating magnetic field (RMF) on the melt flow developing in this system. Numerical simulation results show that the Marangoni flow in the melt becomes stronger at higher coils frequencies due to the decreasing coils-induced electromagnetic field strength. Results also show that the use of external RMF may improve supersaturation uniformity along the seed if it is properly adjusted with respect to the coils-induced electromagnetic field strength. Furthermore, it is predicted that the application of RMF and seed rotation in the same direction may enhance supersaturation below the seed.

An UAV Wireless Communication Noise Suppression Method Based on OFDM Modulation and Demodulation

AbstractIn view of the problem that the unmanned aerial vehicle (UAV) communication link is vulnerable to strong electromagnetic pulse generated by lightning or high‐voltage transmission lines in the complex electromagnetic environment, the influence of the electromagnetic pulse generated by the high‐voltage transmission line of the EFT electromagnetic pulse and the surge electromagnetic pulse on wireless communication link are analyzed in this paper. When those electromagnetic pulse's noise field strength is 500 V/m, the bit‐error‐rate of the communication link is increased to 45.39%, 45.39%, and 46.10%, respectively, indicating that surge pulse has the strongest influence on the communication link. Therefore, a UAV noise suppression method based on the principle of orthogonal frequency‐division multiplexing (OFDM) modulation and demodulation and dual antenna design has been proposed in this paper. This method is used to filter out electromagnetic impulse noise after wireless signal reception, and then demodulate to achieve the goal of noise suppression. Applying the method to a certain type of UAV based on OFDM modulation and demodulation, and theoretical analysis and simulation results show that the proposed method can effectively suppress the electromagnetic pulse generated by high‐voltage transmission lines, EFT electromagnetic pulse, surge electromagnetic pulse, the bit‐error‐rate dropped to 0.005597%, 0.004531%, 0.005597%, respectively.

Determining electromagnetic fields generated by overhead power transmission lines

Under actual operating conditions of electrical networks, it is hard to obtain experimental data that correspond to the maximum levels of the electromagnetic field strengths generated by overhead power transmission lines. Therefore, the analysis of the electromagnetic environment in electric power systems, both at the operated and newly created facilities, is recommended to be performed on the basis of mathematical modeling. The modeling methods and tools developed in IrGUPS and the Fazonord software package implemented on their basis make it possible, after determining the power system mode, to calculate the electromagnetic field strengths generated by multi-wire power transmission lines. In this case, the analyzed lines are considered in close connection with a complex electric power system. To check the adequacy of the simulation, measurements of electric and magnetic field strengths were performed, including comparative calculations for a 110 kV double-circuit line with a ground-wire located within the city. The comparison carried out in rather complex conditions is indicative of the correctness of the method of calculating a multi-wire line electromagnetic field developed in IrGUPS.

The Lanczos potential and Chern–Simons theory

In electromagnetism, the Faraday tensor [Formula: see text] can be constructed from the vector potential [Formula: see text], it is possible to add term to the Lagrangian depending on [Formula: see text] but not its derivatives called Chern–Simons terms. In gravitation, the Weyl tensor [Formula: see text] can be constructed from the Lanczos potential [Formula: see text], I pursue the analogy to see if terms of Chern–Simons form can be added to the Lagrangian. A new tensor [Formula: see text] is introduced which is constructed from the Lanczos potential and is of the same form as that of the Weyl tensor [Formula: see text] expressed in terms of the Lanczos potential except that covariant differentiation is replaced by transvection with a vector [Formula: see text]. The new tensor has associated invariants [Formula: see text] and [Formula: see text], the first of these can be interpreted as a Chern–Simons term for Weyl [Formula: see text] gravity. Both invariants allow various tensors to be constructed and some of their properties are investigated by using exact examples.

Combined Ray-Tracing/FDTD and Network Planner Methods for the Design of Massive MIMO Networks

The design of a massive MIMO network requires a channel model that captures the Spatio-temporal dimensions of the propagation environment. In this paper, we propose a novel method combining Hybrid Raytracing - Finite difference time domain (FDTD) and network planner tools to address this requirement. This method provides accurate and realistic EMF exposure models for the design of a massive MIMO network. Using this method, we proceed with the optimization of the BS's locations under the low power consumption and low EMF exposure constraints. Assuming equal preference of the optimization objectives, the simulations show that the uplink localized 10g dose appears to be the dominant factor of the localized 10g EMF exposure. Moreover, a massive MIMO network designed to serve 224 simultaneous active users at the same time-frequency resource is subject to an increase of the total whole-body dose (2 times higher in downlink and +18% in uplink), compared to a design with 14 active users. However, in the same conditions, the downlink localized 10g dose reduces (20 times lower) whereas the uplink localized 10g dose increases (+23%) in comparison with the scenario with fewer users (14). Besides, the electromagnetic field strength in all locations obtained with this new method is 2 times weaker compared to a 4G LTE network, while complying with the international guidelines.

Computer models in problems of ensuring electromagnetic safety

In the process of the smart grids formation a special attention is started to be paid to the issues of power engineering facilities safe functioning and reduction in their negative impact on personnel and environment. One of the important factors of such an impact is the generation of significant levels of strength of electromagnetic fields (EMF) by high-voltage overhead power transmission lines (OPL). In the context of the electric power industry digitalization, in order to improve the electromagnetic safety of service personnel, development of methods and means for digital modeling of EMF created by power lines of various designs is required, including traction networks of electrified railways. Computer models providing an adequate determination of the OPL EMF can be implemented on the basis of methods and tools designed for determining the parameters of the modes of electric energy systems in phase coordinates, developed at the Irkutsk State University for Railroads Communications. As an example of using these methods, the solution to the problem of constructing pictures of the distribution of EMF in the space surrounding the intersection of a flexible symmetrical conductor and a 25 kV traction network is given.

Экспериментальное исследование рабочего процесса в жидкостных ракетных двигателях с использованием электрофизического метода диагностики

An experimental study of the electromagnetic field generated by the low-temperature plasma of the fuel combustion products of a model liquid rocket engine was carried out. The components of the fuel were gaseous oxygen and ethyl alcohol. When simulating emergencies in the operation of a model rocket engine, the own electromagnetic field strength generated by the ionized fuel combustion products was recorded. A linear dependence of the magnetic field strength on the pressure in the combustion chamber is established in the range of 2.2-3.5 MPa. The possibility of using non-contact electrophysical methods for diagnosing the working process in power plants of aircraft using the value of the magnetic field strength as a “useful” signal is shown.

Магнитоуправляемые микроорганизмы для биологической очистки промышленных сточных вод

Microorganisms immobilized on magnetic carriers are used in biotechnology to increase efficiency and simplify work with microbial cells. The aim of this study was to obtain magnetically controlled immobilized forms of the environmentally significant microorganisms and to study the possibility of their cultivation with artificial nutrient media. Two bacterial strains, identified as the genus Bacillus, were used as the research object: B. subtilis ВГТУ05 and B. species ВГТУ06, promising for biological industrial wastewater treatment. The work carried out the immobilization of strains in magnetic alginate carriers. Established the bacterial cells’ immobilization did not affect their vitality. The optimal parameters of the electromagnetic field strength for growing strains in liquid nutrient media were selected. Shown the bacterial destructive strains immobilized into magnetic carriers gave the biomass increase of 24.3–25.0% during the cultivation in the electromagnetic field. The results could be used to develop the effective technology for local biological industrial wastewater treatment.

Effect of Electrical Conductivity Uncertainty in the Assessment of the Electric Fields Induced in the Brain by Exposure to Uniform Magnetic Fields at 50 Hz

International exposure standard/guidelines establish limits for external electromagnetic field strengths. At low frequencies, these maximum allowable exposure levels are derived from the limits defined for internal electric field strengths which have been set to avoid adverse health effects. In the IEEE International Committee on Electromagnetic Safety standard, the relationship between internal and external fields was obtained through homogeneous elliptical models without considering the dielectric properties of tissues. However, the International Commission on Non-Ionizing Radiation Protection guidelines were established using computational dosimetry on realistic anatomical models. In this case, variability in the electrical conductivity of the tissues represents a major source of uncertainty when deriving allowable external field strengths. Here we characterized this uncertainty by studying the effect of different tissue conductivity values on the variability of the peak electric field strengths induced in the brain of twenty-five individuals exposed to uniform magnetic fields at 50 Hz. Results showed that the maximum electric field strengths computed with new estimations of brain tissue conductivities were significantly lower than those obtained with commonly used values in low-frequency dosimetry. The lower strengths were due to the new brain conductivity values being considerably higher than those usually adopted in dosimetry modeling studies. A sensitivity analysis also revealed that variations in the electrical conductivities of the grey and white matter had a major effect on the peak electric field strengths in the brain. Our findings are intended to lessen dosimetric uncertainty in the evaluation of the electric field strengths due to electrical properties of the biological tissues.

Simulation of Electromagnetic Fields Occurring at Intersection of Traction Networks and Multicircuit Power Lines

Traction networks (TN) 25 kV generate higher electromagnetic fields (EMF) with frequency 50 Hz, whose strengths at a standardized height of 1.8 m, as a rule, do not exceed the permissible norms for electrical personnel. In places where railroads routes intersect with high voltage overhead power supply lines (OPL), interference of fields, generated by the traction network and OPL, occurs. This can lead to an increase in strengths and a complication of the EMF spatial structures. The article presents simulation results performed for a complex intersection, while 25 or 2 х 25 kV TN is crossed by a three-circuit 110-220 kV overhead power line at 90 degrees angle. Fazonord software application was used for simulating EMF strengths in points of traction networks and OPL intersection. Based on modeling results the following conclusions have been made: at intersection points of 1х25 kV traction network with a three-chain 110 - 220 kV power transmission line, the electrical field strength does not exceed the value acceptable for electrical personnel and reaches 4.2 kV/m; at the intersection with 2 х 25 kV traction network, this parameter decreases to 2.7 kV/m; the maximum amplitude of the magnetic field at the intersection points increases slightly.

Extended Relativistic Invariance, Quantization of the Kinetic Momentum

The aim of this research is a better understanding of the quantization in physics. The true origin of the quantization is the existence of the quantized kinetic momentum of electrons, neutrinos, protons and neutrons with the value. It is a consequence of the extended relativistic invariance of the wave of fundamental particles with spin 1/2. This logical link is due to properties of the quantum waves of fermions, which are functions of space-time with value into the and End(Cl3) Lie groups. Space-time is a manifold forming the auto-adjoint part of . The Lagrangian densities are the real parts of the waves. The equivalence between the invariant form and the Dirac form of the wave equation takes the form of Lagrange's equations. The momentum-energy tensor linked by Noether's theorem to the invariance under space-time translations has components which are directly linked to the electromagnetic tensor. The invariance under of the kinetic momentum tensor gives eight vectors. One of these vectors has a time component with value . Resulting aspects of the standard model of quantum physics and of the relativistic theory of gravitation are discussed.

TO-FDTD Method for Arbitrary Skewed Periodic Structures at Oblique Incidence

For accurately modeling general periodic structures with arbitrary skewed grids at oblique incidence, a novel finite-difference time-domain (FDTD) method based on the transformation optics theory (TO-FDTD) is proposed in this article. First, by choosing the appropriate transformation of coordinate and applying the transformation optics theory, the original space of the skewed grid is mapped to the virtual space of the Cartesian grid, and the electromagnetic parameter tensors in the virtual space are known accordingly. Then, based on the covariance of Maxwell’s equations, both the basic difference equations and the boundary conditions of FDTD for the virtual space are derived. After that, the phase delay of the periodic boundary condition caused by the oblique incidence is eliminated by adopting the technique of field transformation, and the final explicit-iterative equations of the TO-FDTD method are obtained as well. At last, some examples are analyzed to verify the numerical properties of the proposed method. The idea of modeling based on the transformation optics theory is not only suitable for skewed periodic structures but also applicable for some ultrathin or (and) curved-surface structures after further expansion.

Transcranial magnetic stimulation safety from operator exposure perspective.

A simulated model of a commercial transcranial magnetic stimulation (TMS) coil is analyzed to determine electromagnetic field (EMF) exposure for an operator while holding or adjusting the coil. Induced EMF strengths are calculated using a commercial figure-8 coil geometry and pulse configuration, with geometrical representations of the subject's head and the operator's head, torso, and hand. Exposure levels are compared to experimental results in the literature and international guidelines for occupational EMF exposure limits. Exposure limit guidelines of 0.8V/m rms are exceeded at approximately 24.6cm from the coil for the torso model and at 20.3cm for the head model measured perpendicular to the plane of the coil. In the plane of the coil, the operator can approach closer without exceeding guidelines. The results in the hand model along the edge of the coil give 9.9V/m and 88.5V/m for average and peak field strength, respectively. A discussion of the potential consequences of operator exposure to fields exceeding published guidelines concludes that since the guidelines are only concerned with acute effects and do not suggest any potential chronic effects, occupational exposure in the context of delivering TMS treatment may be considered reasonable. Graphical abstract A model of an operator's head/torso was moved in space relative to a standard TMS coil and subject. Positions at which safety guidelines are exceeded were calculated. The maximum induced electric field was also calculated in a hand model placed in a position commonly used to hold TMS coils during treatments.

Slightly ultra-violet freeze-in a hidden gluonic sector

The dark glueball (DGB) from a hidden Yang-Mills sector is a simple non-WIMP dark matter candidate characterized by very few parameters. However, it suffers from the overdensity problem. To overcome it, in general the dark sector is required to be hierarchically cooler than the visible sector. To naturally generate the desired hierarchy, in this paper we introduce higher dimensional operators coupling the dark gauge field strength tensor to the standard model (SM) Higgs doublets or gauge field strength tensors. By tracking the different phases of the universe from the end of inflation, prethermalization, reheating to the radiation dominance era, we show that these operators can make the DGB be a viable dark matter candidate over a wide mass region, from the sub-GeV to multi-PeV or even beyond. At the same time, these operators open decay channels of DGB to the SM species, and partial of the parameter space could leave hints in the cosmic ray.