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By analyzing algebraically special solutions of the Maxwell equations in the Kerr space-time, we obtain the exact expressions for the polarization characteristics of electromagnetic waves emitted from the vicinity of a black hole. We revealed the asymmetry of dependence of the ellipticity angle on the polar angle for the fundamental mode and the first harmonics of polarized radiation. This creates a basis for the new method of evaluation of the intrinsic angular momentum of the Kerr black hole. It is shown that the existence of singular points of the solution in a local orthonormal frame is a consequence of the Poincare--Brouwer theorem. Keywords: Maxwell equations, Kerr space-time, algebraically special field, polarization ellipse., Introduction Four last decades were characterized by the extensive theoretical investigations of the processes related to the prediction and, in recent years, to the existence of black holes. As a [...]

Polybenzoxazine/graphene porous nanocomposites were prepared by sol-gel and subsequent thermal curing. The porous nanocomposites showed low densities ranging from 0.154 to 0.204 g/[cm.sup.3]. The chemical structures and microscopic morphology of the porous nanocomposites were studied using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The electromagnetic wave absorbing ability of the porous nanocomposites was investigated, and the results showed that the minimum reflection loss for the porous nanocomposite with 15 wt% of graphene (PBG-15) can reach -35.72 dB at a thickness of 2.6 mm with a 1.5 GHz frequency bandwidth. The excellent absorption ability was due to the conductivity loss in the porous nanocomposite. Also, PBG-15 exhibited good heat resistance with a thermal deformation temperature near 220[degrees]C and a char yield of 56%. In addition, the addition of graphene could increase the compressive strength and compressive modulus of the porous nanocomposites by up to 126% and 364%, respectively. These polybenzoxazine/ graphene porous nanocomposites have good potential application in light electromagnetic wave absorbing materials. KEYWORDS benzoxazine, electromagnetic wave absorption, graphene, porous nanocomposite, 1 | INTRODUCTION Radar is used to locate targets based on their reflection of electromagnetic waves. With the development of radar detection technology, the improvement of the stealth performance of [...]

Data from spacecrafts tracking exhibit many anomalies that suggest the dependence of the speed of electromagnetic radiation with the motion of its source. This dependence is different from that predicted from emission theories that long ago have been demonstrated to be wrong. By relating the velocity of light and the corresponding Doppler effect with the velocity of the source at the time of detection, instead of the time of emission, it is possible to explain quantitatively and qualitatively the spacecraft anomalies. Also, a formulation of electromagnetism compatible with this conception is possible (and also compatible with the known electromagnetic phenomena). Under this theory the influence of the velocity of the source in the speed of light is somewhat subtle in many practical situations and probably went unnoticed (i.e. below the detection limit) in other measurements., 1 Introduction In these lines I intend to show that there exists consistent evidence pointing to the need of revision and further study of what seem at present a settled [...]

A self-consistent theory is developed based on the principle of relativity for a plane wave in a moving non-dispersive, lossless, non-conducting, isotropic, uniform medium. A light-momentum criterion is set up for the first time, which states that the momentum of light in a medium is parallel to the wave vector in all inertial frames of reference. By rigorous analysis, novel basic properties of the plane wave are exposed: (i) Poynting vector does not necessarily represent the electromagnetic (EM) power flow when a medium moves; (ii) Minkowski light momentum and energy constitute a Lorentz four-vector in a form of single EM-field cell or single photon, and Planck constant is a Lorentz invariant; (iii) there is no momentum transfer taking place between the plane wave and the uniform medium, and the EM momentum conservation equation cannot be uniquely determined without resorting to the principle of relativity; and (iv) when the medium moves opposite to the wave vector at a faster-than-dielectric light speed, negative frequency and negative EM energy density occur, with the plane wave becoming left-handed. Finally, a new physics of so-called 'intrinsic Lorentz violation' is presented as well. Key words: special relativity, light-momentum criterion, invariance of Planck constant, intrinsic Lorentz violation, electromagnetic wave theory. Nous developpons une theorie auto-coherente basee sur le principe de la relativite pour une onde plane dans milieu en mouvement uniforme, isotrope, non conducteur sans perte et non dispersif. Nous presentons pour la premiere fois un critere d'impulsion-lumiere, qui dit que l'impulsion de la lumiere dans un milieu est parallele au vecteur d'onde dans tous les referentiels inertiels. A la suite d'une analyse minutieuse, nous pouvons enoncer certaines proprietes nouvelles de base pour l'onde plane: (i) le vecteur de Poynting ne represente pas necessairement le flux de puissance electromagnetique (EM) dans un milieu en mouvement; (ii) l'impulsion lumineuse de Minkowski et l'energie constituent un quatre vecteur de Lorentz sous la forme d'une simple cellule EM ou photon et la constante de Planck est un invariant de Lorentz ; (iii) il n'y a aucun transfert d'impulsion entre l'onde plane et le milieu et l'equation de conservation de l'impulsion EM ne peut etre determinee de facon univoque sans recours au principe de relativite et (iv) lorsque le milieu se deplace en direction opposee a l'onde a une vitesse plus elevee que la vitesse de la lumiere dans le dielectrique, des frequences negatives et une densite d'energie EM negative apparaissent, alors que l'onde devient polarisee a gauche. Finalement, nous presentons aussi une nouvelle physique de l'ainsi nommee violation intrinseque de Lorentz. [Traduit par la Redaction] Mots-cles: relativite speciale, critere d'impulsion lumiere, constante de Planck, violation de Lorentz intrinseque, theorie des ondes electromagnetiques. PACS Nos.: 03.50.De, 03.30.+p, 42.50.Wk, 42.25.-p., 1. Introduction The momentum of light in a medium is a long-lasting controversial question in physics. Abraham and Minkowski independently proposed formulations of light momentum. Abraham momentum is inversely proportional [...]

Analysis of electromagnetic wave propagations in a cylindrical waveguide filled with a chiroplasma core coated with a perfect magnetic conductor is presented. The presented analysis and formulations is generalized for any general isotropic or anisotropic material, including plasma and metamaterials. The characteristic equations are obtained and the behavior of its characteristic curves and the energy flux are examined and evaluated numerically. The obtained results show that the behavior of the energy flux transported in the guide, in magnitude and orientation, is highly affected by the chirality parameter and the plasma and cyclotron frequencies. The mode cut-off frequencies and transported energies are sensitive to the variations in the material parameters, particularly the variations in the chirality parameter. PACS No.: 41.20.Jb. Nous presentons une analyse de la propagation d'une onde electromagnetique dans un guide d'onde cylindrique rempli d'un coeur de chiro-plasma recouvert d'un parfait conducteur magnetique. L'analyse et la formulation presentees ici sont valides pour tout materiau general, isotrope/anisotrope, incluant plasmas et meta-materiaux. Nous obtenons les equations caracteristiques et nous evaluons numeriquement le comportement de ses courbes caracteristiques et le flux d'energie. Les resultats obtenus montrent que le comportement du flux d'energie dans le guide, en grandeur et en orientation, est tres affecte par le parametre de chiralite et par les frequences du plasma et de cyclotron. Les frequences de coupure des modes et l'energie transportee sont sensibles a la variation des parametres du materiau, en particulier le parametre de chiralite. [Traduit par la Redaction], 1. Introduction Research on electromagnetic (EM) wave propagation in meta-material waveguides is essential for recent progressive technologies, for devices and other applications. These waveguides have various uses in, millimetre, microwave, [...]

The convective amplification of filamentation instability (FI) of electromagnetic waves traveling along the density ramp of a magnetized plasma is investigated. The generalized amplification factor of the instability in the presence of a DC-magnetic field is derived by obtaining the governing equations of the instability and using the slow-coupling technique to obtain an analytical expression for the amplification factor in weakly magnetized plasma. The result shows enhancement of the convective FI gain by the magnetic field, where the enhancement is stronger for lower equilibrium plasma density values. PACS Nos.: 47.85.Dh, 52.38.Hb, 52.38.-r, 52.50.Jm. Nous etudions l'amplification convective de l'instabilite de filamentation (FI) d'ondes electromagnetiques se propageant le long d'une rampe de densite de plasma magnetise. Le facteur d'amplification generalise en presence d'un champ magnetique DC est derive par l'obtention des equations directrices de l'instabilite et l'utilisation d'une technique de couplage lent afin d'obtenir une expression analytique pour le facteur d'amplification dans un plasma faiblement magnetise. Le resultat montre une augmentation du gain FI convectif du au champ magnetique, ou cette augmentation est plus forte pour des densites plus faibles de plasma a l'equilibre. [Traduit par la Redaction], 1. Introduction While propagating in the underdense region of the plasma, laser beams drive the parametric excitation of plasma modes leading to parametric instabilities. These may result in energy exchange [...]

The design of methods and tools to build adequate representations of complex geographical phenomena in a way that spatial patterns are emphasized is one of the core objectives of GIScience. In this paper, we build on the concept of geons as a strategy to represent and analyze latent spatial phenomena across different geographical scales (local, national, regional) incorporating domain-specific expert knowledge. Focusing on two types, we illustrate and exemplify how geons are generated and explored. So-called composite geons represent functional land-use classes, required for regional planning purposes. They are created via class modeling to translate interpretation schemes from mapping keys. Integrated geons, on the other hand, address abstract, yet policy-relevant phenomena such as societal vulnerability to hazards. They are delineated by regionalizing continuous geospatial data sets representing relevant indicators in a multidimensional variable space. Using the geon approach, we create spatially exhaustive sets of units, scalable to the level of policy intervention, homogenous in their domain-specific response, and independent from any predefined boundaries. From a GIScience perspective, we discuss either type of geons in a semantic hierarchy of geographic information constructs. Despite its validity for decision-making and its transferability across scales and application fields, the delineation of geons requires further methodological research to assess their statistical and conceptual robustness. Keywords: integrated geons; composite geons; expert-oriented regionalization; conditioned information; policy-relevant, Motivation The design of strategies to adequately represent complex geographical phenomena is one of the core objectives of the GIScience discipline (Longley et al. 2001). The transformation of complex, continuous [...]