Spectrum Of Electromagnetic Waves Research Articles

Massive Black Hole Binaries: Dynamical Evolution and Observational Signatures

The study of the dynamical evolution of massive black hole pairs in mergers is crucial in the context of a hierarchical galaxy formation scenario. The timescales for the formation and the coalescence of black hole binaries are still poorly constrained, resulting in large uncertainties in the expected rate of massive black hole binaries detectable in the electromagnetic and gravitational wave spectra. Here, we review the current theoretical understanding of the black hole pairing in galaxy mergers, with a particular attention to recent developments and open issues. We conclude with a review of the expected observational signatures of massive binaries and of the candidates discussed in literature to date.

3D Polarized Channel Modeling and Performance Comparison of MIMO Antenna Configurations With Different Polarizations

We propose a three-dimensional (3D) polarized MIMO channel model, which takes into account 3D power angular spectrum and comprehensive propagation characteristics of electromagnetic waves excited by polarized antennas. Based on the model, we derive a close form expression of the spatial correlation as a function of the physical parameters representing both characteristics of arbitrary antennas and propagation environment in 3D space. The spatial correlation expression allows to use the Von Mises Fisher (VMF) distribution, resulting in a more accurate and general channel model. Through simulation, we evaluate and compare performance, in terms of the spatial correlation and capacity, of 2 × 2 MIMO configurations with different polarizations, i.e., V/V, V/H, and slanted ±45° polarizations, as a function of critical input parameters including elevation angle, antenna orientation, antenna spacing, cross-polarization discrimination (XPD), and signal-to-noise ratio (SNR). The effect of the parameters on the performance is analyzed, and verified in certain cases through the literature.

Black Holes and Neutron Stars in Tensor-Vector-Scalar Theory

Bekenstein's Tensor-Vector-Scalar (TeVeS) theory has had considerable success as a relativistic theory of Modified Newtonian Dynamics. In the strong-field regime it makes many predictions that differ from General Relativity implying this regime provides an excellent testing ground for the theory using both current and future observations of neutron stars and black holes in both the electromagnetic and gravitational wave spectrum. I look at the current status of black hole and neutron star solutions in both the original TeVeS theory and its generalisation, including some key observational properties that differ from General Relativity.

Multidimensional electron beam-plasma instabilities in the relativistic regime

The interest in relativistic beam-plasma instabilities has been greatly rejuvenated over the past two decades by novel concepts in laboratory and space plasmas. Recent advances in this long-standing field are here reviewed from both theoretical and numerical points of view. The primary focus is on the two-dimensional spectrum of unstable electromagnetic waves growing within relativistic, unmagnetized, and uniform electron beam-plasma systems. Although the goal is to provide a unified picture of all instability classes at play, emphasis is put on the potentially dominant waves propagating obliquely to the beam direction, which have received little attention over the years. First, the basic derivation of the general dielectric function of a kinetic relativistic plasma is recalled. Next, an overview of two-dimensional unstable spectra associated with various beam-plasma distribution functions is given. Both cold-fluid and kinetic linear theory results are reported, the latter being based on waterbag and Maxwell–Jüttner model distributions. The main properties of the competing modes (developing parallel, transverse, and oblique to the beam) are given, and their respective region of dominance in the system parameter space is explained. Later sections address particle-in-cell numerical simulations and the nonlinear evolution of multidimensional beam-plasma systems. The elementary structures generated by the various instability classes are first discussed in the case of reduced-geometry systems. Validation of linear theory is then illustrated in detail for large-scale systems, as is the multistaged character of the nonlinear phase. Finally, a collection of closely related beam-plasma problems involving additional physical effects is presented, and worthwhile directions of future research are outlined.

Particle heating by parametric decay of Alfvén-cyclotron and fast-magnetosonic waves

Nonlinear evolution of Alfvén-cyclotron and fast-magnetosonic waves accompanying ion and electron heating is investigated by means of a one-dimensional particle-in-cell simulation. The simulation is initiated with a spectrum of transverse electromagnetic waves with both left- and right-hand circular polarizations (i.e. Alfvén-cyclotron and fast-magnetosonic waves). It is shown that parametric decay processes lead to an inverse cascade of Alfvén-cyclotron waves and the generation of ion-acoustic waves by decay instability. It is found that the nonlinear decay processes accompany small perpendicular heating and parallel cooling of the protons, and a pronounced parallel heating of the electrons for a relatively low ion-to-electron mass ratio (mi/me = 16).

Superradiant scattering of electromagnetic waves emitted from disk around Kerr black holes

We study electromagnetic perturbations around a Kerr black hole surrounded by a thin disk on the equatorial plane. Our main purpose is to reveal the black hole superradiance of electromagnetic waves emitted from the disk surface. The outgoing Kerr-Schild field is used to describe the disk emission, and the superradiant scattering is represented by a vacuum wave field which is added to satisfy the ingoing condition on the horizon. The formula to calculate the energy flux on the disk surface is presented, and the energy transport in the disk-black hole system is investigated. Within the low-frequency approximation we find that the energy extracted from the rotating black hole is mainly transported back to the disk, and the energy spectrum of electromagnetic waves observed at infinity is also discussed.

10.1007/s11487-008-3001-3

A method for representation of the algorithms for calculation of the spectra of plane waves with regard to the anisotropic properties of the medium and the presence of periodic spatial perturbations is proposed. The perturbations are assumed to have a limited spectrum and to be specified by a finite set of Fourier coefficients. General algorithms for calculation of the spectra of electromagnetic, elastic, and spin waves in the media with periodic irregularities are obtained. Some spectra of photonic waveguides are studied.

Transmission of electromagnetic waves in a magnetic fine-stratified structure

The specific features of the transmission spectra of the TE-wave normally incident from the uniform medium onto the fine-stratified structure fabricated by periodic alternating ferrite and semiconductor layers were investigated. The expressions for effective permeability and permittivity were obtained in the long-wave limit. It was shown that, in the investigated multilayer composite, the left-handed behavior is possible. The dependence of transmission spectra of electromagnetic waves that propagate through a fine-stratified magnetoactive structure on the external magnetic field was examined experimentally.

Microplasma-Induced Deformation of an Anomalous Response Spectrum of Electromagnetic Waves Propagating along Periodically Perforated Metal Plates

Metal plates with two-dimensional hole arrays showed unusual responses of electromagnetic waves, and in this study microplasmas were generated in the holes to deform their properties dynamically and to induce novel frequency-dependent permittivity. Transmitted electromagnetic waves in millimeter wavelength range exhibited attenuation of anomalous transmittance around cutoff frequency of equivalent waveguide when microplasmas were present. On the contrary, the reflected waves were significantly enhanced around such a frequency, where reflectance is at minimum in the case without microplasma generation. These experimental results indicated resonance phenomenon which is usually called spoof surface plasmons, and dynamic change of dielectric constant in the medium inside the holes induced by microplasmas shifts their resonance frequency.

エポキシ樹脂中のトリー伸展と放射電磁波

Detection of electro-magnetic waves is one of a good diagnosis tool that can be used for the condition assessment of insulating systems. Detection and frequency analysis of electro-magnetic wave caused by partial discharge in epoxy resin have been investigated. Electro-magnetic waves radiated by partial discharge could be detected by using simple system with a conventional discone antenna and a spectrum analyzer. Detected electro-magnetic wave spectra have two specific frequency regions: one is at lower than around 200MHz and another is higher than around 200MHz. From observation of electrical tree development and measurements of discharge current and partial discharge level, the former is associated with a void discharge in epoxy resin and the latter is identified as tree development. By using these specific frequency regions, it is applicable to detection of partial discharge and insulating assessment for power apparatus and their accessories including epoxy resin.

Thunderstorms, Lightning, Sprites and Magnetospheric Whistler-Mode Radio Waves

Thunderstorms and the lightning that they produce are inherently interesting phenomena that have intrigued scientists and mankind in general for many years. The study of thunderstorms has rapidly advanced during the past century and many efforts have been made towards understanding lightning, thunderstorms and their consequences. Recent observations of optical phenomena above an active lightning discharge along with the availability of modern technology both for data collection and data analysis have renewed interest in the field of thunderstorms and their consequences in the biosphere. In this paper, we review the electrification processes of a thunderstorm, lightning processes and their association with global electric circuit and climate. The upward lightning discharge can cause sprites, elves, jets, etc. which are together called transient luminous events. Their morphological features and effects in the mesosphere are reviewed. The wide spectrum of electromagnetic waves generated during lightning discharges couple the lower atmosphere with the ionosphere/magnetosphere. Hence various features of these waves from ULF to VHF are reviewed with reference to recent results and their consequences are also briefly discussed.

Array converter of infrared images into visible images, based on waveguide microcavities

This paper proposes a new method of converting IR images into the visible region of the spectrum of electromagnetic waves, using waveguide cavity structures of micrometer size as sensitive elements. The method is based on modulation of the intrinsic equidistant spectrum of the cavity under the external action of electromagnetic radiation in the IR region by varying the optical properties of the material from which the sensitive element is made. The structure and the operating principles of the IR-to-visible image converter is discussed on the basis of an array of waveguide ring microcavities. It is shown that the sensitivity of such a converter to variation of the IR radiation power can reach 2.6×10−12W.

Semigroup method for calculation of the spectra of photonic, phononic, and magnonic crystals

A method for representation of the algorithms for calculation of the spectra of plane waves with regard to the anisotropic properties of the medium and the presence of periodic spatial perturbations is proposed. The perturbations are assumed to have a limited spectrum and to be specified by a finite set of Fourier coefficients. General algorithms for calculation of the spectra of electromagnetic, elastic, and spin waves in the media with periodic irregularities are obtained. Some spectra of photonic waveguides are studied.

Large forbidden band in one-dimensional multi-layered structure containing exponentially graded materials

In the present communication, we have presented band spectra and reflectance properties of one-dimensional multi-layered structure containing dielectric exponentially graded and simple dielectric layers. This study has been performed theoretically by using transfer matrix method. In this paper we have taken the multi-layered structure where refractive index of odd layers is varying continuously along the direction perpendicular to the surface of the layer in exponential form. The effect of the graded profiles are studied and compared with the conventional multi-layered structure of suitable contrast of refractive indices in detail. In this study the materials are considered as non-magnetic and layers other than the graded are taken to be homogeneous and isotropic dielectric medium of constant refractive index. It has been found that the introduction of graded layers enhanced the forbidden band gaps and affects the reflectance of electromagnetic wave spectra significantly. By changing the grading profiles and the contrast, we obtained the forbidden band gaps and the reflectance of such structural change accordingly. Therefore, introducing a graded exponential layer of dielectric in the one-dimensional multi-layered structure provides possible mechanism for enhancing the reflectance as well as the forbidden gap in the optical region. Such multi-layered structure may be useful in the design of a broadband filter.

Multidimensional indexing tools for the virtual observatory

AbstractThe last decade has seen a dramatic change in the way astronomy is carried out. The dawn of the the new microelectronic devices, like CCDs has dramatically extended the amount of observed data. Large, in some cases all sky surveys emerged in almost all the wavelength ranges of the observable spectrum of electromagnetic waves. This large amount of data has to be organized, published electronically and a new style of data retrieval is essential to exploit all the hidden information in the multiwavelength data. Many statistical algorithms required for these tasks run reasonably fast when using small sets of in‐memory data, but take noticeable performance hits when operating on large databases that do not fit into memory. We utilize new software technologies to develop and evaluate fast multidimensional indexing schemes that inherently follow the underlying, highly non‐uniform distribution of the data: they are layered uniform indices, hierarchical binary space partitioning, and sampled flat Voronoi tessellation of the data. These techniques can dramatically speed up operations such as finding similar objects by example, classifying objects or comparing extensive simulation sets with observations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Complication of the spectrum of electromagnetic waves scattered by charged nanoparticles with allowance for radiation reaction

Peculiarities of the scattering of electromagnetic waves by charged nanoparticles have been revealed, given the proper expression for the radiation reaction force. These peculiarities (the change in maximum intensity, the appearance of additional peaks in the spectrum, and others) can be used, in particular, in near-Earth plasma physics and charged nanoparticle physics.

Probability distributions of random electromagnetic fields in the presence of a semi‐infinite isotropic medium

Using a transverse electric/transverse magnetic decomposition for an angular plane wave spectrum of random electromagnetic waves and matched boundary conditions, we derive the probability density function for the energy density of the vector electric field in the presence of a semi‐infinite isotropic medium. The theoretical analysis is illustrated with calculations and results for good electric conductors and for a lossless dielectric half‐space. The influence of the permittivity and conductivity on the intensity, polarization state, statistical distribution, and standard deviation of the field is investigated, both for incident plus reflected fields and for refracted fields. External refraction is found to result in compression of the fluctuations of the random field. Several applications of the theory are discussed.

Controlled terahertz frequency response and transparency of Josephson chains and superconducting multilayers

A fundamental property of wave propagation is Anderson localization, which affects the transfer of information, energy, mass, and charge in disordered media. This localization can manifest itself via, e.g., the metal-insulator transition. We exactly map the behavior of a quantum particle moving in a potential with correlated disorder to the sub-terahertz wave propagation in either Josephson chains or superconducting multilayers. When the Josephson junction parameters vary randomly, the sub-THz electromagnetic waves cannot propagate through these Josephson structures due to localization. For parameter variations with long-range correlations, we predict sharp transitions from transparent to reflective frequency regions for Josephson plasma waves. With appropriate choices of the correlation function, frequency windows with targeted or designed transparencies for THz or sub-THz electromagnetic waves could be achieved. This could be useful for tailoring the electromagnetic wave spectrum of Josephson arrays within the THz frequency range, which is important for applications in physics, astronomy, chemistry, biology, and medicine.

Natural electromagnetic waves in round inhomogeneous layered waveguides

A general theory of gyrotropic waveguide is considered. The theory allows the entire spectrum of natural electromagnetic waves and oscillations in regular waveguide structures discretely inhomogeneous in their cross sections to be obtained. A mathematical model is discussed that enables the propagation constants to be calculated for an arbitrary number of bigyrotropic layers of the structure based on an informal algorithmic formulation of the dispersion equation. Examples of numerical analysis of electrodynamic structures are given. They provide the basis for the development of gyromagnetic microwave devices and measuring cutoff converters intended for monitoring of the electrophysical characteristics of various materials and fluid media.

Rigorous solution for electromagnetic waves propagating through pre-Cantor sets

We study one-dimensional systems constructed from a segment by employing the Cantor-set rule up to an arbitrary stage of self-similar patterns. The rigorous expression of the transfer matrix to describe the electromagnetic waves propagating through them is presented. As displayed by numerical demonstration, the transmission spectra change drastically with the increase of the stage. At rather high stages the periodicity hidden in the self-similarity comes out. This is the first theoretical description of sharp attenuation in the transmission spectrum of electromagnetic waves propagating through a fractal medium.