Presence Of Electromagnetic Field Research Articles

Estimating power-law exponents from observations in electromagnetic non-minimal Maxwell-Gauss-Bonnet coupling cosmology

We discuss a generalized non-minimal Maxwell-Gauss-Bonnet power-law cosmological model characterized by the presence of electromagnetic field and variable cosmological and gravitational constant. We analyze the late-time dynamics characterized by power-law solutions. The model is constrained with local gravitational acceleration measurements, the SH0ES project which estimate the Hubble parameter, Planck TT, TE, EE + low E +lensing +SNe+ BAO data which estimate the EoS parameter and data coming from distant supernovae type Ia, the Hubble function H(z) measurements and information coming from the Alcock-Paczynski test which estimate the numerical range of the non-minimal coupling parameter. By adopting a variable cosmological and gravitational constants, it was found that the universe is acceleratedly expanding with time and dominated by dark/phantom energy and an electromagnetic field comparable to the cosmological lambda. The variations of the gravitational constant time agree with several phenomenological theories including the entropic and holographic principle. The final fate of an asymptotically static universe was found also to be a plausible scenario in the model discussed.

Symmetries and selection rules: optimising axion haloscopes for Gravitational Wave searches

In the presence of electromagnetic fields, both axions and gravitational waves (GWs) induce oscillating magnetic fields: a potentially detectable fingerprint of their presence. We demonstrate that the response is largely dictated by the symmetries of the instruments used to search for it. Focussing on low mass axion haloscopes, we derive selection rules that determine the parametric sensitivity of different detector geometries to axions and GWs, and which further reveal how to optimise the experimental geometry to maximise both signals. The formalism allows us to forecast the optimal sensitivity to GWs in the range of 100 kHz to 100 MHz for instruments such as ABRACADABRA, BASE, ADMX SLIC, SHAFT, WISPLC, and DMRadio.

Dirac materials in parallel electromagnetic fields generated by supersymmetry

In a Supersymetric Quantum Mechanics framework, the Dirac equation describing a Dirac material in the presence of electromagnetic fields is solved. Considering parallel static non-uniform electromagnetic fields, the Dirac equation is transformed into a two-dimensional system of equations. By means of variable separation, we can define one-dimensional eigenfunctions, which are solutions for two pairs of supersymmetric partner Schrödinger-like Hamiltonians. For Pöschl-Teller-like quantum potentials, we look for conditions that guarantee the existence of bound states, and determine an analytic zero-mode solution for the Dirac equation.

Study of heat transfer in MHD viscoelastic fluid of second grade over a stretching porous sheet with electromagnetic effects and nonuniform source/sink

This work is devoted to the study of non-Newtonian fluid of second grade. This model assumes that the flow and heat transfer in MHD viscoelastic fluid is subject to convective boundary conditions in the presence of electromagnetic field and nonuniform source/sink. The flow is considered over a porous sheet. The governing partial differential equations are converted as ordinary differential equations using suitable similarity transformations. The resulting coupled of nonlinear differential equations are successfully solved by means of Optimal Homotopy Asymptotic Method (OHAM). The effects of different physical parameters such as: the second-grade viscoelastic parameter, thermal radiation parameter or Eckert number are analyzed. Several closed form analytical approximate solutions for dimensionless stream function and temperature are presented for some particular cases. Our procedure is based upon an original construction of the solutions using a moderate number of the convergence-control parameters. These parameters lead to very high precision, comparing our approximate solutions with numerical solutions. Let us note that every nonlinear differential equation is reduced to two linear differential equations. The values of the convergence-control parameters are determined using rigorous mathematical procedures. OHAM is an iterative approach which rapidly converges after only one approximation, is effective, explicit, simple and easy to apply. These remarks are in fact the true power of our procedure to solving nonlinear problems without the presence of small or large parameters in the governing equations or boundary/initial conditions.

On a fully-implicit VMS-stabilized FE formulation for low Mach number compressible resistive MHD with application to MCF

This study presents the development and evaluation of a fully-implicit variational multiscale (VMS) stabilized unstructured finite element (FE) formulation for compressible magnetohydrodynamics (MHD) model, at low Mach number regime. The model describes the dynamics of a compressible conducting fluid in the low Mach number limit in the presence of electromagnetic fields and can be used to study aspects of astrophysical phenomena, important science and technology applications, and basic plasma physics phenomena. The specific applications that motivate this study are macroscopic simulations of the longer time-scale stability and disruptions of magnetic confinement fusion (MCF) devices, specifically the ITER tokamak. The discussion considers the development of the VMS FE representation, the structure of the stabilizing terms that deal with significant convective flows, the stabilization of the nearly incompressible response of the fluid flow, and the stabilization of the constraint that enforces the solenoidal involution on the magnetic field. The nonlinear discretized system is solved with scalable preconditioned Newton–Krylov iterative methods, which employs a multiphysics block preconditioning method based on approximate block factorizations and Schur complements. The study presents an evaluation of the VMS method on a 2D cartesian tearing mode instability, and illustrates the scalability of the solvers on MCF relevant problems. A set of results are also presented for longer time-scale stability and disruptions for the ITER tokamak. These include a vertical displacement event (VDE), and a (1,1) internal kink mode. The formulation is demonstrated to be scalable and also reasonably robust with respect to the Lundquist number scaling.

Relativistic hydrodynamics with spin in the presence of electromagnetic fields

We extend the classical phase-space distribution function to include the spin and electromagnetic fields coupling and derive the modified constitutive relations for charge current, energy-momentum tensor, and spin tensor. Because of the coupling, the new tensors receive corrections to their perfect fluid counterparts and make the background and spin fluid equations of motion communicate with each other. We investigate special cases which are relevant in high-energy heavy-ion collisions, including baryon free matter and large mass limit. Using Bjorken symmetries, we find that spin polarization increases with increasing magnetic field for an initially positive baryon chemical potential. The corrections derived in this framework may help to explain the splitting observed in Lambda hyperons spin polarization measurements.

Chern-insulating phase in non-Dirac heterostructure: Role of polarized light and spin-orbit interaction

The non-Dirac two level systems are characterized by their non linear spectrum in kx and ky. We show that the topological phases emerge in Cu2S/MnSe and PbC/MnSe, the non-Dirac heterostructures, in the presence of electromagnetic field and SOC. It is observed that the gap can be tuned when polarized light is incident on the heterostructure by interplay of SOC and incident light. We show variation in Chern state as polarization and field strength is varied. The Chern state of Cu2S/MnSe undergoes a transition from -1 to +1 as the gap is tuned. We also calculate the photo-induced anomalous Hall conductivity of the heterostructures.

Influence of charge on anisotropic class-one solution in non-minimally coupled gravity

This paper studies charged star models associated with anisotropic matter distribution in theory, where . For this purpose, we take a linear model of this gravity as , where ζ represents a coupling constant. We consider a self-gravitating spherical geometry in the presence of electromagnetic field and generate solution to the modified field equations by using the ‘embedding class-one’ condition and bag model equation of state. The observational data (masses and radii) of four different stellar models like 4U 1820-30, SAX J 1808.4-3658, SMC X-4 and Her X-I is employed to analyze the effects of charge on their physical properties. Finally, the effect of the coupling constant is checked on the viability, hydrostatic equilibrium condition and stability of the resulting solution. We conclude that the considered models show viable and stable behavior for all the considered values of charge and ζ.

Superconductor Meissner Effects for Gravito-Electromagnetic Fields in Harmonic Coordinates Due to Non-Relativistic Gravitational Sources

There is much discrepancy in the literature concerning the possibility of a superconductor expelling gravito-electromagnetic fields just as it expels electromagnetic fields in the Meissner effect. Contradicting results are found in at least 18 papers written collectively by more than 20 authors and published over the course of more than 55 years (from 1966 to the present year of 2022). The primary purpose of this paper is to carefully explain the reason for the discrepancies, and provide a single conclusive treatment which may bring coherence to the subject. The analysis begins with a covariant Lagrangian for spinless charged particles (Cooper pairs) in the presence of electromagnetic fields in curved space-time. It is known that such a Lagrangian can lead to a vanishing Hamiltonian. Alternatively, it is shown that using a “space + time” Lagrangian leads to an associated Hamiltonian with a canonical momentum and minimal coupling rule. Discrepancies between Hamiltonians obtained by various authors are resolved. The canonical momentum leads to a modified form of the London equations and London gauge that includes the effects of gravity. A key result is that the gravito-magnetic field is expelled from a superconductor with a penetration depth on the order of the London penetration depth only when an appropriate magnetic field is also present. The gravitational flux quantum (fluxoid) in the body of a superconductor, and the quantized supercurrent in a superconducting ring, are also derived. Lastly, the case of a superconducting ring in the presence of a charged rotating mass cylinder is used as an example of applying the formalism developed.

Kinetic study of multiphase reactions under microwave irradiation: A mini-review

Microwave (MW) heating is rapid, selective, and volumetric, and it is a compelling non-conventional heating approach for driving chemical reactions. The effect of MW irradiation on the kinetics of thermal/catalytic reactions is still under debate. A group of researchers reported that the effect of MW heating on reaction kinetics is highlighted through the non-thermal effects of MWs on kinetic parameters and reaction mechanisms in addition to the thermal effect. However, another group attributed the observations to the thermal effect only. In the present work, we summarized and critically synthesized available information in the literature on the subject. It can be concluded that MW heating has solely the thermal effect on gas-solid reactions, and the variations of kinetic parameters are related to the direct and indirect impacts of that. Temperature measurement limitations, physical structure variation, and non-uniform temperature distribution are the primary sources of the discrepancy in previous studies. In ionic liquid-solid reactions, the presence of electromagnetic fields can affect the movement of ions/polar molecules which can be considered a non-thermal effect of MWs. However, the effect of MW absorption by solid/catalyst, and the formation of hot spots must be taken into account to avoid potential discrepancy. Therefore, further theoretical/experimental studies are required to clarify the effect of MWs on liquid-solid reactions. In addition, developing reliable temperature measurement methods and isothermal reaction domain are required for an accurate kinetic study during MW irradiation.

Kicks in charged black hole binaries

We compute the emission of linear momentum (kicks) by both gravitational and electromagnetic radiation in fully general-relativistic numerical evolutions of quasi-circular charged black hole binaries. We derive analytical expressions for slowly moving bodies and explore numerically a variety of mass ratios and charge-to-mass ratios. We find that for the equal mass case our analytical expression is in excellent agreement with the observed values and, contrarily to what happens in the vacuum case, we find that in presence of electromagnetic fields there is emission of momentum by gravitational waves. We also find that the strong gravitational kicks of binaries with unequal masses affect the electromagnetic kicks, causing them to strongly deviate from Keplerian predictions. For the values of charge-to-mass ratio considered in this work, we observe that magnitudes of the electromagnetic kicks are always smaller than the gravitational ones.

Influence of charge on decoupled anisotropic spheres in f(G, T) gravity

In this paper, we develop two anisotropic solutions for static self-gravitating spherical structure in the presence of electromagnetic field through gravitational decoupling approach in f(G, T) theory, where G and T denote the Gauss–Bonnet term and trace of the energy-momentum tensor, respectively. The extra source with isotropic seed sector is responsible for generating anisotropy in the spacetime. The system of field equations is decoupled into two arrays by using minimal geometric deformation in the radial component. The first set portrays the isotropic regime, whereas the second set represents the anisotropic system. The metric coefficients of the Krori–Barua spacetime are employed to extract solution of the first set while two constraints on the radial and temporal components of the extra source yield the corresponding two solutions. Finally, we investigate the influence of charge and decoupling parameter on the physical viability and stability of the obtained solutions. We conclude that the resulting solutions in this modified theory indicate more feasible and stable structures.

Anisotropic compact stars in presence of electromagnetic field, quintessence field and cosmological constant in f(G) gravity

In this work, we have discussed the anisotropic compact stars in the framework of modified Gauss–Bonnet gravity, named by f(G) theory of gravity. We have found the equations of motion of stars with respect to spherically symmetric metric, describing interior geometry of the compact stellar object, anisotropic mode of the matter distribution in the presence of electromagnetic field and quintessence field. We have taken the metric coefficients in the form [Formula: see text] and [Formula: see text] as well as a particular form of [Formula: see text], where the powers and coefficients of r are constants. The unknown constants are evaluated by matching between interior and exterior Reissner–Nordström–de Sitter metric. We have analyzed some physical aspects like energy density, radial and tangential pressures, anisotropic parameter of matter distribution, energy conditions, mass-radius relation, compactness factor, surface redshift, and stability of our resulting solutions through graphical behavior by comparing to the observational data of different types of compact stars like 4U1820-30, Vela X-1 and SAXJ1808.4-3658. We conclude that all physical attributes maintain their experimental ranges which deliver our anisotropic compact star models are viable and also stable upto certain region in [Formula: see text] gravity theory.

Modification of transition radiation by three-dimensional topological insulators

We study how transition radiation is modified by the presence of a generic magnetoelectric medium with a special focus on topological insulators. To this end, we use the Green's function for the electromagnetic field in presence of a plane interface between two topological insulators with different topological parameters, permittivities and permeabilities. We employ the far-field approximation together with the steepest descent method to obtain approximate analytical expressions for the electromagnetic field. Through this method we find that the electric field is a superposition of spherical waves and lateral waves. Contributions of both kind can be attributed to a purely topological origin. After computing the angular distribution of the radiation, we find that in a region far from the interface the main contribution to the radiation comes from the spherical waves. We present typical radiation patterns for the topological insulator TlBiSe$_2$ and the magnetoelectric TbPO$_4$. In the ultra-relativistic case, the additional contributions from the magnetoelectric coupling appreciably enhance the global maximum of the angular distribution. We also present an analytic expression for the frequency distribution of the radiation for this case. We find that in the limit where the permittivities are equal there still exists transition radiation of the order of the square of the topological parameter with a pure topological origin.

Physiological changes and symptoms associated with short-term exposure to electromagnetic fields: a randomized crossover provocation study

BackgroundThe biological association between electromagnetic fields (EMF) and idiopathic environmental intolerance attributed to EMF (IEI-EMF) has not been established. To assess the physiological changes and symptoms associated with exposure to EMF, we conducted a randomized crossover provocation study.MethodsWe recruited 58 individuals with IEI-EMF (IEI-EMF group) and 92 individuals without IEI-EMF (control group). In a controlled environment, all participants received EMF signals mimicking those from mobile phone base stations in a randomized sequence under the blinded condition. During the course, participants reported their symptoms and whether they perceived EMF, and we monitored their physiological parameters, including blood pressure (BP), heart rate (HR), and HR variability.ResultsThe IEI-EMF and control groups reported similar frequencies of symptoms during both the provocation and sham sessions. No participant could accurately identify the provocation. In both groups, physiological parameters were similar between the two sessions. The control group, but not the IEI-EMF group, had elevated HR when they perceived EMF exposure.ConclusionsNo symptoms or changes in physiological parameters were found to be associated with short-term exposure to EMF, and no participant could accurately detect the presence of EMF. Moreover, the participants in the control group, but not those in the IEI-EMF group, had elevated HR when they perceived EMF.

Relativistic electron dynamics in magnetic fields with low-degree of field nonlinearity

Abstract We study the relativistic bound state dynamics of electrons in the presence of electromagnetic fields within the framework of a novel class of nonlinear Dirac wave equations. In 2 + 1 space–time dimensions, we address a specific interacting electron model in a homogeneous magnetic field providing the allowed nonlinear ground-state Landau energy levels. We concentrate on the regime of laboratory high magnetic fields, and thus, comment on the relevance of this approach to study 2D electron systems.

On the role of bioconvection and activation energy for time dependent nanofluid slip transpiration due to extending domain in the presence of electric and magnetic fields

A mathematical analysis for slip effects on MHD nanofluid in the presence of electromagnetic field and gyrotactic microorganisms is considered. The influence of activation energy and thermal radiation are also discussed. The transportation of nanofluids provides a feasible option for the enhancement of thermal distribution. A rather new aspect of this work is the diffusion and bioconvection of motile microorganisms. It may avoid possible settling of nano-entities. A system of highly non-linear partial differential equations is transformed into Ordinary differential equations by using suitable similarity transformation. The converted ordinary differential equations are then solved numerically by utilizing the shooting technique is built-in function bvp4c solver on the plate form of commercial software Matlab. The results obtained are verified through acceptable agreement with those of the existing one as a special case. The quantities of interest are observed physically. The characteristics of various emerging parameters on the velocity field, temperature distribution and volumetric concentration of nanoparticles, microorganism concentration as well as skin friction coefficient, the gradient of temperature, local Sherwood number, and density number of motile microorganisms are interpreted and reflected in tabulated and graphical form. It is noticed that velocity decreases with the rising values of M . Also, the temperature rises directly with Nb and Nt . With the growing values of Lb , the microorganism profile does down.

Quantum kinetic equation for fluids of spin-1/2 fermions

Fluid of spin-1/2 fermions is represented by a complex scalar field and a four-vector field coupled both to the scalar and the Dirac fields. We present the underlying action and show that the resulting equations of motion are identical to the (hydrodynamic) Euler equations in the presence of Coriolis force. As a consequence of the gauge invariances of this action we established the quantum kinetic equation which takes account of noninertial properties of the fluid in the presence of electromagnetic fields. The equations of the field components of Wigner function in Clifford algebra basis are employed to construct new semiclassical covariant kinetic equations of the vector and axial-vector field components for massless as well as massive fermions. Nonrelativistic limit of the chiral kinetic equation is studied and shown that it generates a novel three-dimensional transport theory which does not depend on spatial variables explicitly and possesses a Coriolis force term. We demonstrated that the three-dimensional chiral transport equations are consistent with the chiral anomaly. For massive fermions the three-dimensional kinetic transport theory generated by the new covariant kinetic equations is established in small mass limit. It possesses the Coriolis force and the massless limit can be obtained directly.

De la contagiosité de l’électrohypersensibilité

Electro-hypersensitivity (EHS) is a phenomenon that emerged in the 1980s and which seems to attribute the occurrence of some symptoms to an exposure to electromagnetic fields (EMF). Since it has appeared, the number of cases has not stopped increasing, suggesting some kind of contagion. However, the correlation between exposure and the onset of symptoms has been tested repeatedly and has never been confirmed. The hypothesis that a psychogenic effect named the “nocebo effect” could be at work then took shape, bringing us to an awareness of our ever-increasing exposure to anxiety-inducing news about the presence of EMFs. This context of negative expectations reinforces the action of the nocebo effect (an effect which is inherently contagious) but does not, in itself, explain the path of a majority of victims in whom the onset of symptoms preceded knowledge of a possible harmful effect of EMFs. Different studies have shown that in the latter case, it could be a phenomenon of wrong attribution of symptoms. The victims, left unanswered by the medical community, will seek a cause and will be confronted with the orientation of the cognitive market towards EMF. This confrontation will be all the more unbalanced as the victim is unaware that it is subject to many cognitive biases in its way of understanding the information offered to it. Once the attribution is established, the nocebo effect can again come into play and strengthen the feeling of being a victim of EHS. Whatever the path, the victim enters a vicious circle from which it appears very complicated to escape.

Description of the calf thymus DNA-malathion complex behavior by multi-spectroscopic and molecular modeling techniques: EMF at low and high frequency approaches.

Objective(s):Small molecules can bind to DNA via covalent or non-covalent interactions, which results in altering or inhibiting the function of DNA. Thus, understanding the interaction patterns of medicines or other small molecules can be very crucial. In this study, the interaction between malathion and calf thymus DNA (ctDNA), in the absence and presence of electromagnetic field (EMF) at low and high frequencies, was investigated through various spectroscopies and viscosity measurements. Materials and Methods:The interaction studies were performed by means of absorbance, circular dichroism, fluorescence spectroscopy, viscosity, thermal melting, and molecular modeling techniques. Results:The fluorescence intensity of the ctDNA-malathion complex in the presence of EMF, has revealed quenching of fluorescence emission curves. The dynamic interaction and RLS studies have implied the changes in ctDNA-malathion complex throughout the presence of EMF which suggested that hydrophobic forces play the main role in the binding. Studies have revealed that malathion does not have any effect on binding ethidium bromide to ctDNA, which signifies the groove binding. The viscosity of ctDNA increased as the malathion concentration was enlarged. The circular dichroism technique suggested that the ellipticity values of the ctDNA-malathion complex have not increased with enhancing the malathion concentration. Molecular docking and dynamics studies have indicated a potent electrostatic interaction between ctDNA and malathion in the groove binding site. Conclusion:The results of spectroscopic studies reinforced a potent interaction between malathion and ctDNA in the absence and presence of EMF which can help us for further pharmaceutical drug discoveries.