Showing papers on "Electromagnetic field published in 1972"
TL;DR: In this paper, separate wave equations with source terms are presented for electromagnetic and gravitational perturbations of an uncharged, rotating black hole, which describe the radiative field completely, and also part of the non-radiative field.
Abstract: Separable wave equations with source terms are presented for electromagnetic and gravitational perturbations of an uncharged, rotating black hole. These equations describe the radiative field completely, and also part of the nonradiative field. Nontrivial, source-free, stationary perturbations are shown not to exist. The barrier integral governing synchrotron radiation from particles in circular orbits is shown to be the same as for scalar radiation. Future applications (stability of rotating black holes, "spin-down," superradiant scattering, floating orbits) are outlined.
857 citations
01 Sep 1972
TL;DR: In this article, conditions under which the image method and the reciprocity relationship can be applied are discussed and Dyadic Green's functions and duality relations are also derived with a postulated Lagrangian density.
Abstract: Theorems concerning electromagnetic fields in linear nonconducting bianisotropic media are investigated. After establishing their symmetry properties, the constitutive relations are examined under time reversal and spatial inversion transformations. Conditions under which the image method and the reciprocity relationships can be applied are discussed. Dyadic Green's functions and duality relations are also derived. With a postulated Lagrangian density, Maxwell's equations are obtained from Hamilton's principle, and energy momentum tensors are obtained from Noether's theorem. Introducing a quantum postulate in addition to the Maxwell's equations, electromagnetic fields in bianisotropic media are quantized.
258 citations
TL;DR: In this paper, the mass and polarization operators of an electron and a photon in an intense crossed field are considered exactly in the external and radiation fields, and their explicit expressions are obtained in the e 2 -approximation in the radiation field, and exactly in an external field.
225 citations
TL;DR: In this paper, a covariant solution of the Dirac and Klein-Gordon equation in a homogeneous classical electromagnetic field is constructed using the symmetry group of the equation, the Maxwell group.
Abstract: Covariant solutions of the Dirac (and Klein-Gordon) equation in a homogeneous classical electromagnetic field are constructed. This is done using the symmetry group of the equation, the Maxwell group. These covariant solutions are obtained starting from solutions in the frame where the electromagnetic field is described by a magnetic field pointing in the 3-direction and then using the theory of induced representations.
186 citations
TL;DR: In this article, a general wave field is decomposed into transverse magnetic (TM) and transverse electric (TE) modes and the reflection coefficients are obtained in closed form.
Abstract: Solutions to the problem of radiation of dipole antennas in the presence of a stratified anisotropic media are facilitated by decomposing a general wave field into transverse magnetic (TM) and transverse electric (TE) modes. Employing the propagation matrices, wave amplitudes in any region are related to those in any other regions. The reflection coefficients, which embed all the information about the geometrical configuration and the physical constituents of the medium, are obtained in closed form. In view of the general formulation, various special cases are discussed.
162 citations
TL;DR: In this paper, the photon concept was formalized in the quantum theory of radiation, which has had unfailing success in explaining the interaction of electromagnetic radiation with matter, seemingly limited only by the ability of physicists to perform the indicated calculations.
Abstract: The idea of the photon has stirred the imaginations of physicists ever since 1905 when Einstein originally proposed the use of light quanta to explain the photoelectric effect. This concept is formalized in the quantum theory of radiation, which has had unfailing success in explaining the interaction of electromagnetic radiation with matter, seemingly limited only by the ability of physicists to perform the indicated calculations. Nevertheless, it has its conceptual problems—various infinities and frequent misinterpretations. Consequently an increasing number of workers are asking, “to what extent is the quantized field really necessary and useful?” In fact the experimental results of the photoelectric effect were explained by G. Wentzel in 1927 without the quantum theory of radiation. Similarly most electro‐optic phenomena such as stimulated emission,reaction of the emitted field on the emitting atom, resonance fluorescence, and so on, do not require the quantization of the field for their explanation. As we will see, these processes can all be quantitatively explained and physically understood in terms of the semiclassical theory of the matter–field interaction in which the electric field is treated classically while the atoms obey the laws of quantum mechanics. The quantized field is fundamentally required for accurate descriptions of certain processes involving fluctuations in the electromagnetic field: for example, spontaneous emission, the Lamb shift, the anomalous magnetic moment of the electron, and certain aspects of blackbody radiation. (The Compton effect also fits here, but see later under references 8b and c.) Here we will outline how the photon concept originated and developed, where it is not required and is often misused, and finally where it plays an essential role in the understanding of physical phenomena. In our discussion we will attempt to give a logically consistent definition of the word “photon”—a statement far more necessary than one might think, for so many contradictory uses exist of this elusive beast. In particular consider the original coining of the word by G. N. Lewis: “[because it appears to spend] only a minute fraction of its existence as a carrier of radiant energy, while the rest of the time it remains an important structural element within the atom…, I therefore take the liberty of proposing for this hypothetical new atom which is not light but plays an essential part in every process of radiation, the name photon!” (our exclamation point). Clearly the present usage of the word is very different. It has its logical foundation in the quantum theory of radiation. But the “fuzzy‐ball” picture of a photon often leads to unnecessary difficulties.
135 citations
TL;DR: In this article, the symmetry properties of a particle interacting with an electromagnetic circularly polarized plane wave were considered and the classical and quantum analysis of the stability group of the plane wave exhibits the origin of the mass shift of the particle.
Abstract: We consider the symmetry properties of a particle interacting with an electromagnetic circularly polarized plane wave. The classical and quantum analysis of the stability group of the plane wave exhibits the origin of the mass shift of the particle. The Chakrabarti’s dynamical representation of the Poincare group is rederived and its physical meaning is given.
133 citations
TL;DR: In this article, the behavior of a finitely deformable, polarizable and magnetizable heat conducting and electrically semiconducting continuum in interaction with the electromagnetic field is derived by means of a systematic application of the laws of continuum physics to a well-defined macroscopic model.
Abstract: The differential equations and boundary conditions describing the behavior of a finitely deformable, polarizable and magnetizable heat conducting and electrically semiconducting continuum in interaction with the electromagnetic field are derived by means of a systematic application of the laws of continuum physics to a well−defined macroscopic model The model consists of five suitably defined interpenetrating continua The relative displacement of the bound electronic continuum with respect to the lattice continuum produces electrical polarization, and electrical conduction results from the motion of the charged free electronic and hole fluids Since partial pressures are taken to act in the conducting fluids, semiconduction boundary conditions arise, which have not appeared previously The resulting rather cumbersome system of equations is reduced to that for the quasistatic electric field and static homogeneous magnetic field In the absence of heat conduction, for the n−type semiconductor, nonlinear e
100 citations
TL;DR: In this paper, the anomalous fields from a buried cylindrical inhomogeneity in an otherwise uniform half-space are analyzed, where the problem is rendered two-dimensional by assuming that the uniform line source of current is parallel to the subsurface cylinder.
Abstract: The anomalous fields from a buried cylindrical inhomogeneity in an otherwise uniform half-space are analyzed. The problem is rendered two-dimensional by assuming that the uniform line source of current is parallel to the subsurface cylinder. The multipole scattered field coefficients are obtained from the numerical solution to the associated singular Fredholm integral equation of the second kind. The horizontal magnetic field amplitude, the vertical magnetic field phase, and the amplitude and phase of the ratio of horizontal to vertical magnetic fields are shown to be diagnostic of the location of the inhomogeneity. The results have possible applications to electromagnetic location in mine rescue operations and to geophysical prospecting.
86 citations
TL;DR: In this article, a set of differential equations which describe the hydrodynamics of a conducting liquid crystal subjected to external electromagnetic fields are expressed as operations on the Maxwell stress tensor.
Abstract: We have developed a set of differential equations which describe the hydrodynamics of a conducting liquid crystal subjected to external electromagnetic fields. The mechanical forces resulting from the interaction of the fields with the liquid are expressed as operations on the Maxwell stress tensor. The use of this description allows a concise statement of the equations of motion. As an example of the validity of the formalism, we rigorously solve the boundary-value problem associated with the Williams domain (vortex) mode in nematic liquids. Using standard constitutive relations, physical boundary conditions, and experimentally measured material $p$-azoxylanisole constants, we quantitatively reproduce the significant experimental observations.
TL;DR: In this paper, the elastic scattering amplitude of a pair of electrons and muons interacting with an intense electromagnetic field taking into account vacuum polarization, the probabilities of pair production, and the polarization corrections to probabilities of radiation are found.
TL;DR: The classic extinction theorem of molecular optics, due to Ewald and Oseen is generalized to scattering of an electromagnetic wave on a material medium of completely arbitrary response (constitutive relations) as discussed by the authors.
TL;DR: In this article, the perturbation of alternating electromagnetic fields in a three-dimensional model with a conductivity inhomogeneity is considered, and the general model is that of a semi-infinite conducting half-space with an embedded inhomogeneous of finite extent in three dimensions.
Abstract: Summary
The perturbation of alternating electromagnetic fields in a three-dimensional model with a conductivity inhomogeneity is considered. The general model is that of a semi-infinite conducting half-space with an embedded inhomogeneity of finite extent in three dimensions. The problem is solved numerically and three-dimensional plots of the amplitudes of the field components and their phases at the surface of the half-space above the inhomogeneity for two particular models are given.
TL;DR: In this article, a critical study of the behavior of a massive spin two charged particle in an external electromagnetic field is made, and a unique Lagrangian which does not increase the number of degrees of freedom required for the description of a spin two particle is presented.
TL;DR: In this article, all invariants, the coherent states and the Green function for a particle moving in time-dependent uniform perpendicular electric and magnetic fields are constructed, and the transition amplitudes and probabilities between the energy levels and their generating functions are constructed too.
TL;DR: In this article, the effect of collisions between excited particlehole pairs and the nuclear background leads to a damping of such particle-hole excitations, which can be expressed in terms of individual damping widths of particles and holes in an interacting system.
TL;DR: In this article, an exact solution for the retarded Green's function of the radiation field is calculated for a quantum model consisting of three interacting boson fields-photon, exciton, and phonon.
Abstract: Quantum field-theoretical methods are applied to the problem of determining how the exciton-lattice interaction affects the dispersion of an electromagnetic field associated with the exciton-radiation interaction. An exact solution for the retarded Green's function of the radiation field is calculated for a quantum model consisting of three interacting boson fields-photon, exciton, and phonon. The classical Green's function of a damped-harmonic-oscillator model of a dielectric is shown to be a special case of this quantum Green's function. Two sets of dispersion relations are derived; one set has well-defined energy, the other has well-defined momentum. Results of the theory clearly suggest that the exciton-lattice interaction is capable of literally damping out the "polariton" effects associated with the exciton-radiation interaction in the field solutions with well-defined energy. A Poynting theorem based on the classical model is also derived which includes effects of both spatial dispersion and damping.
Patent•
09 Aug 1972
TL;DR: In this paper, a microwave signal generator projects an electromagnetic wave into a space under surveillance to establish a first field and applies a voltage to a discontinuous conductor for establishing a second field, electrostatic in nature, throughout the space.
Abstract: A microwave signal generator projects an electromagnetic wave into a space under surveillance to establish a first field. A pulse or frequency modulated low frequency generator is used to apply a voltage to a discontinuous conductor for establishing a second field, electrostatic in nature, throughout the space. Presence in the space of a miniature passive electromagnetic wave receptor-reradiator in the form of a semiconductive diode connected to a dipole antenna causes the reradiation of the low frequency component modulated on the microwave component as a carrier. The front end of a receiver system is tuned to the microwave frequency and feeds a suitable detector circuit responsive to the low frequency signal. A coincidence circuit energizes an alarm circuit whenever the detected signal coincides with the original modulation envelope being applied to the low frequency generator.
TL;DR: In this paper, a flanged parallel-plate waveguide was studied analytically using the Weber-Schafheitlin discontinuity integral when the waveguide is excited by TE-mode waves, TM-mode wave, or an electromagnetic line source.
Abstract: Radiation from a flanged parallel-plate waveguide is studied analytically using the Weber-Schafheitlin discontinuity integral when the waveguide is excited by TE-mode waves, TM-mode waves, or an electromagnetic line source Electromagnetic fields are represented by the discontinuity integral in the exterior space, and in the waveguide region they are expanded by normal modes of the waveguide Imposing the boundary conditions in the aperture gives a set of simultaneous equations for the expansion coefficients Once the solutions of these equations are determined, quantities of interest, such as reflection coefficients, modal coefficients of higher-order modes excited at the aperture, and radiation patterns, are readily obtained without knowing the field distribution in the aperture Numerical calculations for the radiation patterns, reflection coefficients, and modal coefficients of higher order modes are carried out, and a part of the results is compared with the asymptotic solution by Lee [1970] The effect of truncation in solving the equations numerically is also studied, and this method is found to exhibit rapid numerical convergence
TL;DR: In this article, the physical parameters involved in microwave heating processes of heterogeneous materials containing water are considered on the basis of a general equation, which determines the increase of temperature when the body is exposed to microwave electromagnetic field, and the interaction of the thermal, mechanical and electromagnetic parameters of the body and the heating process.
Abstract: The physical parameters involved in microwave heating processes of heterogeneous materials containing water are considered. On the basis of a general equation, which determines the increase of temperature when the body is exposed to microwave electromagnetic field, we analyze the interaction of the thermal, mechanical, and electromagnetic parameters of the body and the heating process. The analogy with scattering of waves by bodies of various shapes is explored and illustrated analytically for the simple model of a plane wave incident on a half space filled with lossy dielectric.
TL;DR: In this paper, a Bogoliubov automorphism on the algebra of the free in field is used for the case of an external time-dependent electromagnetic (scalar) field.
Abstract: The unitary (pseudo unitary) time-evolution operator for a particle with spin half (zero) in an external time-dependent electromagnetic (scalar) field is used to generate a Bogoliubov automorphism on the algebra of the free in field. For the case of an electric external field (scalar field) a finite expression for Ωout is given and theS-matrix constructed. The latter is unitary and implements the Bogoliubov automorphism. Theorems by Shale and Stinespring are rederived.
TL;DR: In this article, the electromagnetic fields produced by a circular loop of current were considered for a homogeneous half-space model of the earth and integral representations for the subsurface field were evaluated numerically and presented in graphical form.
Abstract: The electromagnetic fields produced by a circular loop of current is considered for a homogeneous half-space model of the earth. The integral representations for the subsurface field are evaluated numerically and presented in graphical form.
TL;DR: In this paper, the authors recast a linear quantum-mechanical Boltzmann equation, describing the dynamics of a gas of $N$-level atoms absorbing light between an arbitrary pair of levels, into the form of a generalized master equation.
Abstract: We have recast a linear quantum-mechanical Boltzmann equation, describing the dynamics of a gas of $N$-level atoms absorbing light between an arbitrary pair of levels, into the form of a generalized master equation. The atoms are permitted to undergo both phase-changing and energy-changing collisions with a heat bath of inert molecules. The possibility of unimolecular decay is incorporated into the Boltzmann equation. The solutions of the generalized master equation give an accurate description of the system for short as well as long times and for arbitrary light-field intensity. Eigenvalues obtained from the solution of the $N$-level master equation are shown to have particular significance with regard to the scattered electromagnetic field, with the imaginary parts of the complex eigenvalues providing the location and the real parts of the eigenvalues giving the widths of scattered radiation bands. The dynamics and scattered field for a two-level system is discussed in detail. Two collision parameters giving the frequency of phase-changing and energy-changing collisions are important. For special values of these parameters, our results reduce to scattered field spectra calculated previously. When unimolecular decay is included, one identifies the smallest eigenvalue of the generalized master equation with the macroscopic rate constant. Observation of the scattered field for different incident field intensities would permit separation of radiative and thermal effects in an enhanced reaction rate, without requiring an accurate temperature measurement.
TL;DR: In this paper, the second-order average current density response is calculated for magnetic field-free classical plasmas, and a dynamical fluctuation-dissipation theorem is derived, thus establishing a connection between triplet microscopic current-current correlations and quadratic response functions.
Abstract: Using statistical mechanical perturbation theory, the second-order average current density response is calculated for magnetic field-free classical plasmas. A dynamical fluctuation-dissipation theorem is then derived, thus establishing a connection between triplet microscopic current-current correlations and quadratic response functions; it also leads to a static fluctuation-dissipation theorem which provides a dielectric description of the equilibrium ternary correlation. A comparison of the latter with its expansion in terms of the Mayer pair correlation clusters is discussed.
TL;DR: In this paper, a Fourier-type transform is derived for functions satisfying the scalar wave equation in stratified media and the function is expressed as a sum of two infinite integrals and a discrete term.
Abstract: A Fourier-type transform is derived for functions satisfying the scalar wave equation in stratified media. Using this transform, the function is expressed as a sum of two infinite integrals and a discrete term. In electromagnetic theory, the infinite integrals correspond to the radiation and the lateral wave terms and the discrete term corresponds to the surface wave.The transform provides a suitable basis for the expansion of electromagnetic fields when the height of the interface between two semi-infinite media and their electromagnetic parameters vary along the propagation path. Exact boundary conditions are employed here rather than the restricted surface impedance condition. The expansion is particularly appropriate for problems in which the source and the observation point are not in the same medium.