Electromagnetic Energy Density Research Articles

Topology of Bloch impedance: traveling waves, dispersive media, and electromagnetic energy

Abstract The bulk-boundary correspondence (b-bc) principle, which relates interface modes between two periodic structures to topological invariants of the respective Bloch bands, is widely accepted in electrodynamics. However, this acceptance stems largely from condensed matter (CM) theories. It is desirable to establish direct connections between the topological principles and Maxwell electrodynamics, rather than relying on CM results. Such connections have in recent years been found in the case of standing evanescent waves in periodic dielectric media. This paper extends these analyses to waves propagating along an interface between two periodic structures, possibly with frequency-dependent dielectric permittivities. The paper shows that the b-bc principle continues to hold for any physically realizable structures, in which the density of electromagnetic energy must be positive. The paper rigorously proves that in this physically valid case impedance of traveling interface modes within any given bandgap decreases monotonically as a function of frequency.

The kinetic analog of the pressure–strain interaction

Energy transport in weakly collisional plasma systems is often studied with fluid models and diagnostics. However, the applicability of fluid models is limited when collisions are weak or absent, and using a fluid approach can obscure kinetic processes that provide key insights into the physics of energy transport. Kinetic diagnostics retain all of the information in 3D-3V phase space and thereby reach beyond the insights of fluid models to elucidate the mechanisms responsible for collisionless energy transport. In this work, we derive the Kinetic Pressure–Strain (KPS): a kinetic analog of the pressure–strain interaction, which is the channel between flow energy density and internal energy density in fluid models. Through two case studies of electron Landau damping, we demonstrate that the KPS diagnostic can elucidate kinetic mechanisms that are responsible for energy transport in this channel, just as the related field–particle correlation is known to identify kinetic mechanisms of transport between electromagnetic field energy density and kinetic energy density in particle flows. In addition, we show that resonant electrons play a major role in transferring energy between fluid flows and internal energy during the process of Landau damping.

GUP corrected Casimir wormholes with electric charge in [formula omitted] gravity

In this letter, we study and investigate the effects of the Generalized Uncertainty Principle (GUP) and electric charge on Casimir wormhole geometry in the Curvature-Lagrangian coupled f(R,Lm) gravity. The functional form of the considered model is f(R,Lm)=R2κ+Lmα, corresponding to it the analytic shape function is found. For our analysis, we study the wormhole spacetimes for three particular models for the redshift function. We observe that the null energy condition is violated despite a positive contribution from the electromagnetic energy density. We also note that electric charges, GUP effects, and higher model parameter values increase the throat length. Further, we have studied the deflection of light using the Gauss-Bonnet theorem, emphasizing the contribution from GUP by including higher-order terms.

Influence of Tachyonic Instability on the Schwinger Effect by Axial Coupling in Natural Inflation Model When Strong Back‐Reaction Exists

AbstractThe influence of tachyonic instability on the Schwinger effect is investigated by axial coupling in the natural single‐field inflation model when strong back‐reaction exists in two parts. First, the Schwinger effect is considered when the conformal invariance of Maxwell action should be broken by axial coupling with the inflaton field by identifying the standard horizon scale at the very beginning of inflation for additional boundary term and use several values of coupling constant and estimate electric and magnetic energy densities and energy density of produced charged particles due to the Schwinger effect. It has been found that for both coupling functions the energy density of the produced charged particles due to the Schwinger effect is so high and spoils inflaton field. In fact the strong coupling or back‐reaction occurs because the energy density of produced charged particles is exceeding of inflaton field. Two coupling functions are used to break conformal invariance of maxwell action. The simplest coupling function and a curvature based coupling function where is the potential of natural inflation. In second part, in oder to avoid strong back‐reaction problem, the horizon scale is identified in which a given Fourier begins to become tachyonically unstable.The influence of this scale is reducing the value of coupling constant and weakening the back‐reaction problem but in both cases strong coupling or strong back‐reaction exists and the Schwinger effect is impossible. Therefore, the Schwinger effect in this model is not possible and spoils inflation. Instantly, the Schwinger effect produces very high energy density of charged particles which causes back‐reaction problem and spoils inflaton field. It has been stressed that due to existence of strong back‐reaction in two cases the energy density of the produced charged particles due to the Schwinger effect spoils inflation. The influence of tachyonic instability in this model is quiet different from our published work in Kamarpour. In Kamarpour, this effect appears by vanishing of electromagnetic energy density and the energy density of charged particles at the very beginning of inflation.

A 2.4 GHz High-Efficiency Rectifier Circuit for Ambient Low Electromagnetic Power Harvesting.

A novel 2.4 GHz high-efficiency rectifier circuit suitable for working under very-low-input electromagnetic (EM) power conditions (-20 to -10 dBm) is proposed for typical indoor power harvesting. The circuit features a SMS7630 Schottky diode in a series with a voltage booster circuit at the front end and a direct-current (DC)-pass filter at the back end. The voltage booster circuit consists of an asymmetric coupled transmission line (CTL) and a high-impedance microstrip line (of 100 Ω instead of 50 Ω) to significantly increase the potential at the diode's input, thereby enabling the diode to operate effectively even in very-low-power environments. The experimental measurements show that the microwave direct-current (MW-DC) conversion efficiency of the rectifier circuit reaches 31.1% at a -20 dBm input power and 62.4% at a -10 dBm input power, representing a 7.4% improvement compared to that of the state of the art. Furthermore, the rectifier circuit successfully shifts the input power level corresponding to the peak rectification efficiency from 0 dBm down to -10 dBm. This design is a promising candidate for powering low-energy wireless sensors in typical indoor environments (e.g., the home or office) with low EM energy density.

Casimir wormholes inspired by electric charge in Einstein–Gauss–Bonnet gravity

This investigation assesses the feasibility of a traversable wormhole by examining the energy densities associated with charged Casimir phenomena. We focus on the influence of the electromagnetic field created by an electric charge as well as the negative energy density arising from the Casimir source. We have developed different shape functions by defining energy densities from this combination. This paper explores various configurations of Casimir energy densities, specifically those occurring between parallel plates, cylinders and spheres positioned at specified distances from each other. Furthermore, the impact of the generalized uncertainty principle correction is also examined. The behavior of wormhole conditions is evaluated based on the Gauss–Bonnet coupled parameter (μ) and electric charge (Q) through the electromagnetic energy density constraint. This is attributed to the fact that the electromagnetic field satisfies the characteristic ρ = −p r . Subsequently, we examine the active gravitational mass of the generated wormhole geometries and explore the behavior of μ and Q concerning active mass. The embedding representations for all formulated shape functions are examined. Investigations of the complexity factor of the charged Casimir wormhole have demonstrated that the values of the complexity factor consistently fall within a particular range in all scenarios. Finally, using the generalized Tolman–Oppenheimer–Volkoff equation, we examine the stability of the resulting charged Casimir wormhole solutions.

Relating the Phases of Magnetic Reconnection Growth to Energy Transport Mechanisms in the Exhaust

AbstractThe efficiency of energy conversion during magnetic reconnection is related to the reconnection rate. While the stable reconnection rate has been studied extensively, its growth between the time of reconnection onset and its peak has not been thoroughly discussed. We use a 2D particle‐in‐cell simulation to examine how the reconnection rate evolves during the growth process and how it relates to changes near the x‐line. We identify three phases of growth: (a) slow quasi‐linear growth, (b) rapid exponential growth, and (c) tapered growth followed by negative growth after the reconnection rate peaks. We associate phase 1 with the breaking of x‐line uniformity by a localized density depletion that changes the in‐plane electric field structure near the neutral line, followed by the expansion of the inflow region and the enhancement of inflow Poynting flux Sz associated with the out‐of‐plane electric field Ey in phase 2. We show how the Hall fields facilitate rapid growth in phase 2 by opening up the exhaust and relieving the electron‐scale bottleneck to allow rapid energy transport across the separatrices. We find that in phase 3, the inflow of electromagnetic energy accumulates until the downstream electromagnetic energy density saturates toward the initial upstream asymptotic value. Finally, we examine how the electron outflow and the downstream ion populations interact in phase 3 and how each species exchanges energy with the local field structures in the exhaust.

Gravitational waves from the pulsar magnetosphere

ABSTRACT We investigate the generation of gravitational waves from the rotation of an orthogonal pulsar magnetosphere in flat space-time. We calculate the first-order metric perturbation due to the rotation of the non-axisymmetric distribution of electromagnetic energy density around the central star. We show that gravitational waves from a strong magnetic field pulsar right after its formation within a distance of 1 kpc may be detectable with the new generation of gravitational wave detectors.

Influence of tachyonic instability on the Schwinger effect in Higgs inflation model

We investigate the influence of the tachyonic instability on the Schwinger effect in Higgs inflation model. In this work we identify the standard horizon scale and the tachyonic instability . This is the horizon scale in which the given Fourier begins to become tachyonically unstable. Influence of this scale appears by vanishing electromagnetic field energy density and energy density of created charged particles due to the Schwinger effect at the very beginning of inflation but does not alter conclusions of our previous work in Kamarpour (2022 Gen. Relativ. Gravit. 54 32; 2023 Int. J. Mod. Phys.D 32 2350025). We use two coupling functions to break conformal invariance of Maxwell action. The simplest coupling function and a curvature based coupling function where is the potential of Higgs inflation in Kamarpour (2022 Gen. Relativ. Gravit. 54 32; 2023 Int. J. Mod. Phys.D 32 2350025). In fact, we find that only at the very beginning of inflation both energy densities of electromagnetic field and created charged particles vanish due to effect of tachyoinc instability.

Optomechanical effects caused by non-zero field quantities in multiple evanescent waves.

Evanescent waves, with their high energy density, intricate local momentum, and spatial distribution of spins, have been the subject of extensive recent study. These waves offer promising applications in near-field particle manipulation. Consequently, it becomes imperative to gain a deeper understanding of the impacts of scattering and gradient forces on particles in evanescent waves to enhance and refine the manipulation capabilities. In this study, we employ the multipole expansion theory to present analytical expressions for the scattering and gradient forces exerted on an isotropic sphere of any size and composition in multiple evanescent waves. The investigation of these forces reveals several unusual optomechanical phenomena. It is well known that the scattering force does not exist in counter-propagating homogeneous plane waves. Surprisingly, in multiple pairs of counter-propagating evanescent waves, the scattering force can arise due to the nonzero orbital momentum (OM) density and/or the curl part of the imaginary Poynting momentum (IPM) density. More importantly, it is found that the optical scattering force can be switched on and off by simply tuning the polarization. Furthermore, optical forces typically vary with spatial position in an interference field. However, in the interference field generated by evanescent waves, the gradient force becomes a spatial constant in the propagating plane as the particle's radius increases. This is attributed to the decisive role of the non-interference term of the electromagnetic energy density gradient. Our study establishes a comprehensive and rigorous theoretical foundation, propelling the advancement and optimization of optical manipulation techniques harnessed through multiple evanescent waves. Specifically, these insights hold promise in elevating trapping efficiency through precise control and manipulation of optical scattering and gradient forces, stimulating further explorations.

Bayesian optimization of periodic multilayered slabs for passive absorptivity control

A vanadium dioxide (VO2) film grown on a titanium oxide crystal shows a metal–insulator transition at room temperature with drastically changed optical properties. A multilayered slab with a sub-micron scale VO2 film was proposed to utilize its unique properties for passive intensity control of sunlight absorption and radiative cooling. Its optimal geometries were numerically explored using the Bayesian optimization (BO) method. BO was applied for three types of multilayered slabs, those having one, two, or three isolated slabs of different widths. For each type of multilayered slab, BO could optimize geometric variables with practical calculation times considering the total number of possible combinations of variables, which is subsequently referred to as the total number of candidates. Optimization results revealed that two isolated slabs had the most suitable spectral absorptivity in both hot and cold environments. The infrared absorptivity of the double slab was kept low in cold conditions to suppress radiative cooling. However, the double slab exhibited good radiative cooling performance under hot conditions. Electromagnetic energy density surrounding the slab illustrated that metallic VO2 and gold placed in a parallel manner excited the coupled mode of surface plasmon polaritons to enhance absorptivity. Radiative cooling faded for the triple slab because each slab could couple with radiation propagating only across a portion of the cross-sectional area. Through three BO trials, improvement of the VO2 visible reflectivity was recognized as a future issue for further development of passive sunlight absorption control.

Robust Topological Edge States in C6 Photonic Crystals

The study of photonic crystals has emerged as an attractive area of research in nanoscience in the last years. In this work, we study the properties of a two-dimensional photonic crystal composed of dielectric rods. The unit cell of the system is composed of six rods organized on the sites of a C6 triangular lattice. We induce a topological phase by introducing an angular perturbation ϕ in the pristine system. The topology of the system is then determined by using the so-called k.p perturbed model. Our results show that the system presents a topological and a trivial phase, depending on the sign of the angular perturbation ϕ. The topological character of the system is probed by evaluating the electromagnetic energy density and analyzing its distribution in the real space, in particular on the maximal Wyckoff points. We also find two edge modes at the interface between the trivial and topological photonic crystals, which present a pseudospin topological behavior. By applying the bulk-edge correspondence, we study the pseudospin edge modes and conclude that they are robust against defects, disorder and reflection. Moreover, the localization of the edge modes leads to the confinement of light and the interface behaves as a waveguide for the propagation of electromagnetic waves. Finally, we show that the two edge modes present energy flux propagating in opposite directions, which is the photonic analogue of the quantum spin Hall effect.

Electromagnetic modeling and multi-field coupling simulation for conductive rubber embedded in shells

Our living environment and the battlefield witness an increase in electromagnetic energy density due to the emergence of electronic electrical equipment, such as automobiles, communication devices, computers. To adapt to the environment and improve the electromagnetic compatibility of equipment, conductive rubber is increasingly being used in electrical equipment. However, due to the lack of simulation parameters and incomplete simulation methods, the current electromagnetic simulation of conductive rubber cannot meet the needs of supporting engineering applications. This paper presents the test results for the electromagnetic characteristics of a conductive rubber material, develops a simulation model of the material based on test data, and verifies the model through experiments in the real working environment. Results show that the simulation model is valid.

Effects of an electric charge on Casimir wormholes: changing the throat size

In this paper we continue the investigation of the connection between Casimir energy and the traversability of a wormhole. In addition to the negative energy density obtained by a Casimir device, we include the effect of an electromagnetic field generated by an electric charge. This combination defines an electrovacuum source which has an extra parameter related to the size of the throat. Even if the electromagnetic energy density is positive, the null energy condition is still violated. The main reason is that the electromagnetic field satisfies the property rho =-p_{r}. As a consequence, the traversable wormhole throat can be changed as a function of the electric charge. This means that the throat is no longer Planckian and the traversability is slightly less in principle but slightly greater in practice.

Verifying Ray Tracing Amplitude Methods for Global Magnetospheric Modeling

AbstractRay tracing is a commonly used method for modeling the propagation of electromagnetic waves in Earth's magnetosphere. To apply ray tracing results to global models of wave‐particle interaction such as energetic electron scattering, it is useful to map the discrete rays to a volume filling mesh. However, some methods have inherent losses of energy from the wave source, or do not account for the full range of wave properties within a sample volume. We have developed and tested a 3D magnetospheric ray tracing code “MESHRAY” which resolves these issues. MESHRAY uses the conservation of Poynting flux through ray triplets with finite volume to determine the local field amplitudes. Electromagnetic wave energy density from all ray data points is mapped to a mesh and verified against the wave source power for energy conservation varying time step length, number of rays, and total time steps. We find that the method is self‐consistent and numerically robust. We further investigate whether the neglect of phase information and superposition has a significant impact on the accuracy of mapping wave intensity to a mesh. We find excellent agreement between the analytic solution for waves emitted by a line source in a plane‐stratified medium and an equivalent ray tracing solution. When phase information is excluded, ray tracing reproduces an average amplitude spread over regions of coherent constructive and destructive interference. This may be an important consideration for interpolating ray tracing results of longer wavelength waves such as magnetosonic, electromagnetic ion cyclotron, or ULF waves.

Biopolymer‐Based Aerogels for Electromagnetic Wave Shielding and Absorbing

Comprehensive SummaryThe rapid development of communication technology and electronic industry has brought unprecedented serious electromagnetic interference (EMI) and electromagnetic wave (EMW) pollution. Although EMI shields and EMW absorbers based on metal or magnetic materials were used to solve these problems, they have long been criticized for their high price, high density and easy corrosion. In order to achieve low density and efficient dissipation of electromagnetic energy, aerogels stand out among manifold materials. However, constructing aerogels with good EMI shielding or EMW absorption performance and acceptable mechanical properties is not an easy task. Burgeoning biopolymers, such as cellulose, lignin, chitin/chitosan and alginate, breathe new life into aerogels for high‐efficiency EMW shielding and absorbing. Here, we reviewed the contributions of biopolymers in the fields of aerogels for EMW shielding and absorbing. At the same time, some challenges and outlook were also pointed out, aiming to promote the advance of aerogel‐based EMI shields and EMW absorbers as well as the rational utilization of biopolymers.

Raman energy density in the context of acoustoplasmonics

Interactions between elementary excitations are of great interest from a fundamental aspect and for novel applications. While plasmon-exciton have been extensively studied, the interaction mechanisms between acoustic vibrations (phonons) and localized surface plasmons (LSPs) remain quite unexplored. Here, we present a new theoretical framework for the investigation of the interaction between confined acoustic vibrations and LSPs involved in resonant acoustic Raman scattering. We express the Raman scattering process in the framework of Fermi's golden rule and introduce the concept of Raman energy density (RED). Similarly to the Raman-Brillouin electronic density (RBED) introduced for semiconductors, this physical quantity is used as a theoretical tool for the interpretation of resonant Raman scattering mediated by LSPs in metallic nanoparticles. The RED represents the electromagnetic energy density excited in the Raman scattering process and modulated by the acoustic vibrations of the nanoparticle. We show that, similarly to the LDOS and the RBED, the RED can be mapped in the near-field region, and provides a clear picture of the interaction between LSPs and acoustic vibrations giving rise to inelastic scattering measurable in the far-field. We use the newly introduced RED concept to investigate elastic (an)isotropy effects and extract the Raman selection rules of spherical nanoparticles embedded in a dielectric environment.

Quantum zero point electromagnetic energy difference between the superconducting and the normal phase in a high- Tc superconducting metal bulk sample

We provide a novel methodological approach to the estimate of the change of the Quantum Vacuum electromagnetic energy density in a High critical Temperature superconducting metal bulk sample, when it undergoes the transition in temperature, from the superconducting to the normal phase. The various contributions to the Casimir energy in the two phases are highlighted and compared. While the TM polarization of the vacuum mode allows for a macroscopic description of the superconducting transition, the changes in the TE vacuum mode induced by the superconductive correlations are introduced within a microscopic model, which does not explicitly take into account the anisotropic structure of the material.

Laser-particle interaction-based heat source model of laser powder bed fusion additive manufacturing

The use of powder is one of the special features in laser powder bed fusion additive manufacturing (L-PBF AM). How the powder affects the L-PBF process is the basic mechanism determining the accurate prediction of the melt pool and the temperatures in finite element heat transfer simulations. The laser is treated as electromagnetic wave essentially and the powder particles can be heated by the formation of the inducted current on the particle surfaces. The laser energy density absorbed by the powder particles was calculated based on the laser-particle interaction. Based on the statistical analysis of particles in spatial distribution, the new volumetric heat source model was obtained and then applied to finite element heat transfer simulations. Results indicate that the temperature rise of the individual particle is not uniform and relates to the distribution of electromagnetic energy density on the surface of particles. The distribution of electromagnetic energy density on the surface of the individual particle at different positions is different. The energy absorbed by the upper particles is mainly determined by the direct irradiation of the laser. The energy absorbed by the bottom particles is mainly caused by the laser reflections. Due to the change of the mechanism for energy absorption, the maximum energy absorption occurs at the location which is near the average diameter away from the top surface of the powder bed. When the powder bed thickness is small, the laser energy density along build direction is in Gaussian distribution. With the increase of the powder bed thickness, the laser energy density distribution along build direction can be fit for 4-order polynomial function.

Electromagnetic energy density in hyperbolic metamaterials

We present the theory of electromagnetic energy propagation through a dispersive and absorbing hyperbolic metamaterial (HMM). In this way, the permittivity tensor components of HMM (especially, nanowire HMM) may appear to be hopeless, but as a non-trivial step, we find that they can be cast into more transparent forms. We find under the influence of an electromagnetic wave, the responses of nanowire HMM (multilayer HMM) in the directions perpendicular to and parallel to the optical axis are similar to those of Lorentz (Drude) and Drude (Lorentz) media, respectively. We obtain simple expressions for the electromagnetic energy density formula of both typical structures of HMMs, i.e., nanowire and multilayer HMMs. Numerical examples reveal the general characteristics of the direction-dependent energy storage capacity of both nanowire and multilayer HMMs. The results of this study may shed more physical insight into the optical characteristics of HMMs.