Showing papers on "Electromagnetic field published in 2013"
TL;DR: In this paper, the authors review the origin and properties of electromagnetic fields produced in heavy-ion collisions and demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma lives.
Abstract: I review the origin and properties of electromagnetic fields produced in heavy-ion collisions The field strength immediately after a collision is proportional to the collision energy and reaches ~ at RHIC and ~ at LHC I demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma lives as a consequence of finite electrical conductivity of the plasma Magnetic field breaks spherical symmetry in the direction perpendicular to the reaction plane, and therefore all kinetic coefficients are anisotropic I examine viscosity of QGP and show that magnetic field induces azimuthal anisotropy on plasma flow even in spherically symmetric geometry Very strong electromagnetic field has an important impact on particle production I discuss the problem of energy loss and polarization of fast fermions due to synchrotron radiation, consider photon decay induced by magnetic field, elucidate dissociation via Lorentz ionization mechanism, and examine electromagnetic radiation by plasma I conclude that all processes in QGP are affected by strong electromagnetic field and call for experimental investigation
338 citations
TL;DR: In this article, an axionic field theory with a nonquantized coefficient describes the electromagnetic response of the $(3+1)$-dimensional Weyl semimetal, where the coefficient is proportional to the momentum space separation of the Weyl nodes.
Abstract: From a direct calculation of the anomalous Hall conductivity and an effective electromagnetic action obtained via Fujikawa's chiral rotation technique, we conclude that an axionic field theory with a nonquantized coefficient describes the electromagnetic response of the $(3+1)$-dimensional Weyl semimetal. The coefficient is proportional to the momentum space separation of the Weyl nodes. Akin to the Chern-Simons field theory of quantum Hall effect, the axion field theory violates gauge invariance in the presence of the boundary, which is cured by the chiral anomaly of the surface states via the Callan-Harvey mechanism. This provides a unique solution for the radiatively induced CPT-odd term in the electromagnetic polarization tensor of the Lorentz violating spinor electrodynamics, where the source of the Lorentz violation is a constant axial 4-vector term for the Dirac fermion. A direct linear response calculation also establishes anomalous thermal Hall effect and a Wiedemann-Franz law, but thermal Hall conductivity does not directly follow from the well known formula for the gravitational chiral anomaly.
297 citations
TL;DR: In this paper, the authors introduce the idea of discontinuous electric and magnetic fields at a boundary to design and shape wavefronts in an arbitrary manner, and show how to arbitrarily refract a beam using a set of impedance and admittance surfaces.
Abstract: We introduce the idea of discontinuous electric and magnetic fields at a boundary to design and shape wavefronts in an arbitrary manner. To create this discontinuity in the field we use orthogonal electric and magnetic currents which act like Huygens source to radiate the desired wavefront. These currents can be synthesized either by an array of electric and magnetic dipoles or by a combined impedance and admittance surface. A dipole array is an active implementation to impose discontinuous fields while the impedance/admittance surface acts as a passive one. We then expand on our previous work showing how electric and magnetic dipole arrays can be used to cloak an object demonstrating novel cloaking and anti-cloaking schemes. We also show how to arbitrarily refract a beam using a set of impedance and admittance surfaces. Refraction using the idea of discontinuous fields is shown to be a more general case of refraction than using simple phase discontinuities.
257 citations
TL;DR: In this article, the basic physical notions underlying microwave sintering and the theoretical and numerical models of the microwave Sintering process are discussed and the significance of microwave nonthermal effects in sinterings is demonstrated based on the experimental results, and models of such effects are reviewed.
Abstract: This paper reviews the basic physical notions underlying microwave sintering and the theoretical and numerical models of the microwave sintering process. The propagation and absorption of electromagnetic waves in materials, and the distribution of electromagnetic field in cavity resonators that serve as applicators for microwave processing are discussed and the electromagnetic modeling of such applicators is reviewed. The microwave absorption properties of ceramic and metal powder materials and the methods of their description are addressed. Self-consistent electromagnetic and thermal models that are capable of predicting the temperature distribution in the microwave-heated materials and dynamic effects such as thermal runaway instabilities are reviewed. The multiphysics simulations that combine electromagnetic, thermal, and sintering models and result in predicting densification, shrinkage, and grain structure evolution are discussed in detail. The significance of microwave nonthermal effects in sintering is demonstrated based on the experimental results, and the models of such effects are reviewed.
253 citations
TL;DR: It is demonstrated for the first time that Rb atoms excited in a vapor cell can also be used for vector microwave electrometry by using Rydberg-atom electromagnetically induced transparency.
Abstract: It is clearly important to pursue atomic standards for quantities like electromagnetic fields, time, length, and gravity. We have recently shown using Rydberg states that Rb atoms in a vapor cell can serve as a practical, compact standard for microwave electric field strength. Here we demonstrate for the first time that Rb atoms excited in a vapor cell can also be used for vector microwave electrometry by using Rydberg-atom electromagnetically induced transparency. We describe the measurements necessary to obtain an arbitrary microwave electric field polarization at a resolution of 0.5°. We compare the experiments to theory and find them to be in excellent agreement.
220 citations
TL;DR: In this paper, a device for electromagnetic field energy harvesting that employs a plurality of electrically small resonators such as split-ring resonators that provide significantly enhanced energy harvesting or energy collection efficiency while occupying smaller footprint is presented.
Abstract: Antennas developed for electromagnetic field energy harvesting, typically referred to as rectennas, provide an alternative electromagnetic field energy harvesting means to photovoltaic cells if designed for operation in the visible frequency spectrum. Rectennas also provide energy harvesting ability or power transfer mechanism at microwave, millimeter and terahertz frequencies. However, the power harvesting efficiency of available rectennas is low because rectennas employ traditional antennas whose dimensions is typically proportional or close to the wavelength of operation. This invention provides a device for electromagnetic field energy harvesting that employs a plurality of electrically-small resonators such as split-ring resonators that provide significantly enhanced energy harvesting or energy collection efficiency while occupying smaller footprint. The invention is applicable to electromagnetic energy harvesting and to wireless power transfer.
207 citations
Patent•
11 Mar 2013TL;DR: In this article, a system for powering components in a vehicle seat enables electronic components within the vehicle seat to receive power without wires connecting the seat to a vehicle body, and a power receiver is configured to generate electrical power from the electromagnetic field and deliver the power to at least one component.
Abstract: A system for powering components in a vehicle seat enables electronic components within the vehicle seat to receive power without wires connecting the seat to a vehicle body. The system includes a power transmitter that generates an electromagnetic field, and a power receiver located within the vehicle seat and the electromagnetic field. The power receiver is configured to generate electrical power from the electromagnetic field and deliver the power to at least one component in the vehicle seat.
205 citations
TL;DR: In this article, an adaptive robust control (ARC) algorithm with online tuning of the unknown weights and other system parameters is developed to account for various uncertainties, which achieves a guaranteed transient and steadystate performance for position tracking, as well as zero steady-state tracking error when subjected to parametric uncertainties only.
Abstract: Many control methodologies have been applied to the motion control of linear motor drive systems. Compensations of nonlinearities such as frictions and cogging forces have also been carried out to obtain better tracking performance. However, the relationship between the driving current and the resulting motor force has been assumed to be linear, which is invalid for high driving coil currents due to the saturating electromagnetic field effect. This paper focuses on the effective compensation of nonlinear electromagnetic field effect so that the system can be operated at even higher acceleration or heavier load without losing achievable control performance. Specifically, cubic polynomials with unknown weights are used for an effective approximation of the unknown nonlinearity between the electromagnetic force and the driving current. The effectiveness of such an approximation is verified by offline identification experiments. An adaptive robust control (ARC) algorithm with online tuning of the unknown weights and other system parameters is then developed to account for various uncertainties. Theoretically, the proposed ARC algorithm achieves a guaranteed transient and steady-state performance for position tracking, as well as zero steady-state tracking error when subjected to parametric uncertainties only. Comparative experiments of ARC with and without compensation of electromagnetic nonlinearity done on both axes of a linear-motor-driven industrial gantry are shown. The results show that the proposed ARC algorithm achieves better tracking performance than existing ones, validating the effectiveness of the proposed approach in practical applications.
198 citations
TL;DR: In this article, an exact analytical solution for the space-time evolution of electromagnetic field in electrically conducting nuclear matter produced in heavy-ion collisions is discussed, and it is argued that the parameter that controls the strength of the matter effect on the field evolution is Ω(ensuremath{\sigma}\ensureMath{\gamma}b), where Ω is the Lorentz boost-factor, and b is the characteristic transverse size of matter.
Abstract: Exact analytical solution for the space-time evolution of electromagnetic field in electrically conducting nuclear matter produced in heavy-ion collisions is discussed. It is argued that the parameter that controls the strength of the matter effect on the field evolution is $\ensuremath{\sigma}\ensuremath{\gamma}b$, where $\ensuremath{\sigma}$ is electrical conductivity, $\ensuremath{\gamma}$ is the Lorentz boost-factor, and $b$ is the characteristic transverse size of the matter. When this parameter is of the order 1 or larger, which is the case at the Relativistic Heavy Ion Collider and the Large Hadron Collider, the space-time dependence of the electromagnetic field completely differs from that in vacuum.
190 citations
Posted Content•
TL;DR: In this paper, the authors review the origin and properties of electromagnetic fields produced in heavy ion collisions and demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma exists.
Abstract: I review the origin and properties of electromagnetic fields produced in heavy ion collisions. The field strength immediately after a collision is proportional to the collision energy and reaches eB\sim(m_\pi)^2 at RHIC and eB\sim10 (m_\pi)^2 at LHC. I demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma exists as a consequence of finite electrical conductivity of the plasma. Magnetic field breaks spherical symmetry in the direction perpendicular to the reaction plane and therefore all kinetic coefficients are anisotropic. I examine viscosity of QGP and show that magnetic field induces azimuthal anisotropy on plasma flow even in spherically symmetric geometry. Very strong electromagnetic field has an important impact on particle production. I discuss the problem of energy loss and polarization of fast fermions due to synchrotron radiation, consider photon decay induced by magnetic field, elucidate J/Psi dissociation via Lorentz ionization mechanism and examine electromagnetic radiation by plasma. I conclude that all processes in QGP are affected by strong electromagnetic field and call for experimental investigation.
184 citations
TL;DR: In this article, the authors derived upper limits at the 95% C. E. S. L. on the strength of the ALP coupling to photons, g(gamma a) < 2.1 x 10(-11) GeV-1 for an ALP mass between 15 and 60 neV.
Abstract: Axionlike particles (ALPs) are hypothetical light (sub-eV) bosons predicted in some extensions of the Standard Model of particle physics. In astrophysical environments comprising high-energy gamma rays and turbulent magnetic fields, the existence of ALPs can modify the energy spectrum of the gamma rays for a sufficiently large coupling between ALPs and photons. This modification would take the form of an irregular behavior of the energy spectrum in a limited energy range. Data from the H. E. S. S. observations of the distant BL Lac object PKS 2155 - 304 (z = 0.116) are used to derive upper limits at the 95% C. L. on the strength of the ALP coupling to photons, g(gamma a) < 2.1 x 10(-11) GeV-1 for an ALP mass between 15 and 60 neV. The results depend on assumptions on the magnetic field around the source, which are chosen conservatively. The derived constraints apply to both light pseudoscalar and scalar bosons that couple to the electromagnetic field.
TL;DR: In this article, a toroidal molecule can be constructed through rational arrangement of asymmetric split-ring resonators as meta-atoms via manipulating structural symmetry and thus coupling of the metaatoms.
Abstract: We experimentally observe toroidal dipolar response in a planar metamaterial comprised of asymmetric split-ring resonators (ASRRs) at microwave frequency. It is shown that a toroidal molecule can be constructed through rational arrangement of planar ASRRs as meta-atoms via manipulating structural symmetry and thus coupling of the meta-atoms. We find that the toroidal resonance provides a subwavelength-scale electromagnetic localization style, and that confining the electromagnetic field inside a dielectric medium with toroidal geometry is beneficial for low-loss metamaterials. The planar scheme of manipulating the coupling among the ASRRs may stimulate research in optical regions involving toroidal multipoles. The toroidal geometry together with the Fano resonance of ASRR-induced high-$Q$ response will have enormous potential applications in enhancing light-matter interactions, e.g., for low-threshold lasing, low-power nonlinear processing, and sensitive biosensing.
TL;DR: In this article, the authors show that a vacuum is a nonlinear optical medium and discuss what the optical phenomena are that should exist in the framework of the standard model of particle physics and pay special attention to the low energy limit.
Abstract: In this report we show that a vacuum is a nonlinear optical medium and discuss what the optical phenomena are that should exist in the framework of the standard model of particle physics. We pay special attention to the low energy limit. The predicted effects for photons of energy smaller than the electron rest mass are of such a level that none have yet been observed experimentally. Progress in field sources and related techniques seem to indicate that in a few years vacuum nonlinear optics will be accessible to human investigation.
TL;DR: In this article, a new numerical implementation of the general-relativistic resistive magnetohydrodynamics (MHD) equations within the Whisky code is presented.
Abstract: We present a new numerical implementation of the general-relativistic resistive magnetohydrodynamics (MHD) equations within the Whisky code. The numerical method adopted exploits the properties of implicit-explicit Runge-Kutta numerical schemes to treat the stiff terms that appear in the equations for large electrical conductivities. Using tests in one, two, and three dimensions, we show that our implementation is robust and recovers the ideal-MHD limit in regimes of very high conductivity. Moreover, the results illustrate that the code is capable of describing scenarios in a very wide range of conductivities. In addition to tests in flat spacetime, we report simulations of magnetized nonrotating relativistic stars, both in the Cowling approximation and in dynamical spacetimes. Finally, because of its astrophysical relevance and because it provides a severe tested for general-relativistic codes with dynamical electromagnetic fields, we study the collapse of a nonrotating star to a black hole. We show that also in this case our results on the quasinormal mode frequencies of the excited electromagnetic fields in the Schwarzschild background agree with the perturbative studies within 0.7% and 5.6% for the real and the imaginary part of the $\ensuremath{\ell}=1$ mode eigenfrequency, respectively. Finally we provide an estimate of the electromagnetic efficiency of this process.
TL;DR: In this article, the authors show how a 3D topological spectrum can be induced in a trivial insulator by a periodic drive and, in particular, using electromagnetic radiation, showing that a two-photon resonance is required to transform an initially unremarkable band structure into a topological Floquet spectrum.
Abstract: Three dimensional (3D) topological insulators display an array of unique properties such as single Dirac-cone surface states and a strong magnetoelectric effect. Here we show how a 3D topological spectrum can be induced in a trivial insulator by a periodic drive and, in particular, using electromagnetic radiation. In contrast to the two-dimensional analog, we show that a two-photon resonance is required to transform an initially unremarkable band structure into a topological Floquet spectrum. We provide an intuitive, geometrical picture, alongside a numerical solution of a driven lattice model featuring a single surface Dirac mode. Also, we show that the polarization and frequency of the driving electromagnetic field control the details of the surface modes and particularly the Dirac mass. Specific experimental realizations of the 3D Floquet topological insulator are proposed.
TL;DR: Refraction using the idea of discontinuous fields is shown to be a more general case of refraction than using simple phase discontinuities and to arbitrarily refract a beam using a set of impedance and admittance surfaces.
Abstract: We introduce the idea of discontinuous electric and magnetic fields at a boundary to design and shape wavefronts in an arbitrary manner. To create this discontinuity in the field we use electric and magnetic currents which act like a Huygens source to radiate the desired wavefront. These currents can be synthesized either by an array of electric and magnetic dipoles or by a combined impedance and admittance surface. A dipole array is an active implementation to impose discontinuous fields while the impedance/admittance surface acts as a passive one. We then expand on our previous work showing how electric and magnetic dipole arrays can be used to cloak an object demonstrating two novel cloaking schemes. We also show how to arbitrarily refract a beam using a set of impedance and admittance surfaces. Refraction using the idea of discontinuous fields is shown to be a more general case of refraction using phase discontinuities.
TL;DR: This work directly maps the intensity of the electric field close to plasmonic nanoantennas using diffraction-unlimited far-field spectroscopy in the infrared, and measures for the first time the near-field intensity of a three-dimensional plAsmonic electromagnetically induced transparency structure.
Abstract: Nanoantennas confine electromagnetic fields at visible and infrared wavelengths to volumes of only a few cubic nanometres. Assessing their near-field distribution offers fundamental insight into light-matter coupling and is of special interest for applications such as radiation engineering, attomolar sensing and nonlinear optics. Most experimental approaches to measure near-fields employ either diffraction-limited far-field methods or intricate near-field scanning techniques. Here, using diffraction-unlimited far-field spectroscopy in the infrared, we directly map the intensity of the electric field close to plasmonic nanoantennas. We place a patch of probe molecules with 10 nm accuracy at different locations in the near-field of a resonant antenna and extract the molecular vibrational excitation. We map the field intensity along a dipole antenna and gap-type antennas. Moreover, this method is able to assess the near-field intensity of complex buried plasmonic structures. We demonstrate this by measuring for the first time the near-field intensity of a three-dimensional plasmonic electromagnetically induced transparency structure.
TL;DR: Analytical calculations and numerical experiments demonstrate the practical applicability of the proposed concept, which permits fast on-off switching of the SPPs and dynamic tuning of their excitation frequency by adjusting the vibration frequency.
Abstract: We propose a concept that allows for efficient excitation of surface plasmon spolaritons (SPPs) on a thin graphene sheet located on a substrate by an incident electromagnetic field. Elastic vibrations of the sheet, which are generated by a flexural wave, act as a grating that enables the electromagnetic field to couple to propagating graphene SPPs. This scheme permits fast on-off switching of the SPPs and dynamic tuning of their excitation frequency by adjusting the vibration frequency (grating period). Potential applications include single molecule detection and enhanced control of SPP trajectories via surface wave patterning of graphene metasurfaces. Analytical calculations and numerical experiments demonstrate the practical applicability of the proposed concept.
TL;DR: In this article, weakly nonlinear passive materials for prospective applications in integrated quantum photonics were proposed, where strong enhancement of native optical nonlinearities by electromagnetic field confinement in photonic crystal resonators can lead to single-photon generation only exploiting the quantum interference of two coupled modes and the effect of photon blockade under resonant coherent driving.
Abstract: We propose the use of weakly nonlinear passive materials for prospective applications in integrated quantum photonics. It is shown that strong enhancement of native optical nonlinearities by electromagnetic field confinement in photonic crystal resonators can lead to single-photon generation only exploiting the quantum interference of two coupled modes and the effect of photon blockade under resonant coherent driving. For realistic system parameters in state of the art microcavities, the efficiency of such a single-photon source is theoretically characterized by means of the second-order correlation function at zero-time delay as the main figure of merit, where major sources of loss and decoherence are taken into account within a standard master equation treatment. These results could stimulate the realization of integrated quantum photonic devices based on non-resonant material media, fully integrable with current semiconductor technology and matching the relevant telecom band operational wavelengths, as an alternative to single-photon nonlinear devices based on cavity quantum electrodynamics with artificial atoms or single atomic-like emitters.
TL;DR: In this paper, the effect of the frequency dependence of soil electrical parameters on the lightning radiated electromagnetic fields as well as their associated induced voltages on overhead lines was analyzed using a full-wave approach based upon the finite-element method (FEM).
Abstract: This paper presents a comprehensive study on the effect of the frequency dependence of soil electrical parameters on the lightning radiated electromagnetic fields as well as their associated induced voltages on overhead lines. To this aim, a full-wave approach based upon the finite-element method (FEM) is utilized. In the analyses, frequency dependence of soil conductivity and relative permittivity is introduced, using available analytical formulae that is obtained from experimental data. It is shown that the radial electric field is the only component which is significantly affected by the frequency dependence of soil electrical parameters at observation points as close as some tens of meters from the lightning channel. The vertical component of the electric field and the azimuthal component of the magnetic field are not much influenced by this property of soil at moderate distances (up to several hundred meters) from the lightning channel. For distant observation points and for poorly conducting grounds, however, these components are also affected. It is also shown that for soils characterized by relatively moderate and low resistivity values (less than 1000 Ω.m), lightning-induced voltages are not significantly affected by the frequency dependence of soil electrical parameters. For poorly conducting soils, instead, the frequency dependence of soil electrical parameters results in a decrease of lightning-induced voltages.
TL;DR: In this paper, a new solution of rotating black string coupled to a nonlinear electromagnetic field in the background of anti-de Sitter spaces was obtained, and the conserved and thermodynamic quantities of the rotating string were analyzed.
Abstract: We obtain a new solution of rotating black string coupled to a nonlinear electromagnetic field in the background of anti-de Sitter spaces. We consider two types of nonlinear electromagnetic Lagrangians, namely, logarithmic and exponential forms. We investigate the geometric effects of nonlinearity parameter and find that for large $r$, these solutions recover the rotating black string solutions of Einstein-Maxwell theory. We calculate the conserved and thermodynamic quantities of the rotating black string. We also analyze thermodynamics of the spacetime and verify the validity of the first law of thermodynamics for the obtained solutions.
TL;DR: This work demonstrates that the combination of array layout with subwavelength electromagnetic confinement allows for 104-fold enhancement of the electromagnetic energy density inside the cavities, despite the low quality factor of a single element.
Abstract: A key issue in modern photonics is the ability to concentrate light into very small volumes, thus enhancing its interaction with quantum objects of sizes much smaller than the wavelength In the microwave domain, for many years this task has been successfully performed by antennas, built from metals that can be considered almost perfect at these frequencies Antenna-like concepts have been recently extended into the THz and up to the visible, however metal losses increase and limit their performances In this work we experimentally study the light coupling properties of dense arrays of subwavelength THz antenna microcavities We demonstrate that the combination of array layout with subwavelength electromagnetic confinement allows for 104-fold enhancement of the electromagnetic energy density inside the cavities, despite the low quality factor of a single element This effect is quantitatively described by an analytical model that can be applied for the optimization of any nanoantenna array
TL;DR: It is proved that the shift is a universal phenomenon, and hence, it constitutes a general law, its value increasing as the imaginary part of the nanostructure permittivity grows.
Abstract: The angular spectrum representation of electromagnetic fields scattered by metallic particles much smaller than the incident wavelength is used to interpret and analyze the spectral response of localized surface plasmon resonances (LSPs) both in the near-field and far-zone regimes. The previously observed spectral redshift and broadening of the LSP peak, as one moves from the far-zone to the near-field region of the scatterer, is analyzed on studying the role and contribution of the evanescent and propagating plane wave components of the emitted field. For such dipolar particles, it is found that the evanescent waves are responsible for those broadenings and shifts. Further, we prove that the shift is a universal phenomenon, and hence, it constitutes a general law, its value increasing as the imaginary part of the nanostructure permittivity grows. Our results should be of use for the prediction and interpretation of the spectral behavior in applications where the excitation of LSPs yield field enhancements like those assisting surface-enhanced Raman spectroscopy or equivalent processes.
TL;DR: It is found that the susceptibility of the quantum dot exhibits optical transparency for specific frequencies, suggesting that in such a hybrid system quantum coherence can reverse the course of energy transfer, allowing flow of energy from the metallic nanoparticle to the quantumdot.
Abstract: We study optical effects in a hybrid system composed of a semiconductor quantum dot and a spherical metal nanoparticle that interacts with a weak probe electromagnetic field. We use modified nonlinear density matrix equations for the description of the optical properties of the system and obtain a closed-form expression for the linear susceptibilities of the quantum dot, the metal nanoparticle, and the total system. We then investigate the dependence of the susceptibility on the interparticle distance as well as on the material parameters of the hybrid system. We find that the susceptibility of the quantum dot exhibits optical transparency for specific frequencies. In addition, we show that there is a range of frequencies of the applied field for which the susceptibility of the semiconductor quantum dot leads to gain. This suggests that in such a hybrid system quantum coherence can reverse the course of energy transfer, allowing flow of energy from the metallic nanoparticle to the quantum dot. We also explore the susceptibility of the metal nanoparticle and show that it is strongly influenced by the presence of the quantum dot.
TL;DR: In this paper, the authors introduce the concept of optimal particles for strong interactions with electromagnetic fields, where a particle occupies a given electrically small volume in space and study the required optimal relations between the particle polarizabilities.
Abstract: Here we introduce the concept of 'optimal particles' for strong interactions with electromagnetic fields. We assume that a particle occupies a given electrically small volume in space and study the required optimal relations between the particle polarizabilities. In these optimal particles, the inclusion shape and material are chosen so that the particles extract the maximum possible power from given incident fields. It appears that for different excitation scenarios the optimal particles are bianisotropic chiral, omega, moving and Tellegen particles. The optimal dimensions of resonant canonical chiral and omega particles are found analytically. Such optimal particles have extreme properties in scattering (e.g., zero backscattering or invisibility). Planar arrays of optimal particles possess extreme properties in reflection and transmission (e.g. total absorption or magnetic-wall response), and volumetric composites of optimal particles realize, for example, such extreme materials as the chiral nihility medium.
TL;DR: In this paper, the propagation of extremely short electromagnetic three-dimensional bipolar pulses in an array of semiconductor carbon nanotubes is studied for the first time and the heterogeneity of the pulse field along the axis of the nanotube is accounted for for the very first time.
Abstract: We study the propagation of extremely short electromagnetic three-dimensional bipolar pulses in an array of semiconductor carbon nanotubes. The heterogeneity of the pulse field along the axis of the nanotubes is accounted for the first time. The evolution of the electromagnetic field and the charge density of the sample are described by Maxwell's equations supplemented by the continuity equation. Our analysis reveals for the first time the possibility of propagation of three-dimensional electromagnetic breathers in CNTs arrays. Specifically, we found that the propagation of short electromagnetic pulse induces a redistribution of the electron density in the sample.
TL;DR: In this article, a dual-polarized microwave imaging system is introduced, consisting of a circular array of multiplexed antennas, distributed evenly around an object-of-interest (OI), along with a novel plurality of probes located at the antennas' apertures.
Abstract: In this paper, we introduce a novel dual polarized microwave imaging system. The system is comprised of a circular array of multiplexed antennas, distributed evenly around an object-of-interest (OI), along with a novel plurality of probes located at the antennas' apertures. Each probe consists of several p-i-n diodes biased in two different states (open and short). The probes are used to measure field scattered by an OI based on the modulated scatterer technique. Half of the probes are oriented vertically with the second half oriented horizontally. The presence of the two probe-orientations enables the imaging system to collect two orthogonal field polarizations, transverse electric (TE) and transverse magnetic (TM), without the need for mechanical rotation. In order to illuminate the object with all possible polarizations of the electromagnetic field, the transmitting antennas are placed at a slant angle with respect to the longitudinal plane of the imaging chamber. Near-field data are collected using each probe set, then calibrated. We show that the calibrated data for each polarization can be used to reconstruct the dielectric profile of various objects using either two-dimensional TE or TM inversion algorithms.
TL;DR: In this article, the authors used the finite difference time domain to compute the distribution of electromagnetic fields and forces inside material media, and showed that the force-density distribution inside a given object can differ substantially between the two formulations.
Abstract: Using the method of finite difference time domain, we solve Maxwell's equations numerically and compute the distribution of electromagnetic fields and forces inside material media. The media are generally specified by their dielectric permittivity \ensuremath{\epsilon}(\ensuremath{\omega}) and magnetic permeability \ensuremath{\mu}(\ensuremath{\omega}), representing small, transparent dielectric and magnetic objects such as platelets and microbeads. Using two formulations of the electromagnetic force density, one due to Lorentz [Collected Papers 2, 164 (1892)] and the other due to Einstein and Laub [Ann. Phys. 331, 541 (1908)], we show that the force-density distribution inside a given object can differ substantially between the two formulations. This is remarkable, considering that the total force experienced by the object is always the same, irrespective of whether the Lorentz or the Einstein-Laub formula is employed. The differences between the two formulations should be accessible to measurement in deformable objects.
TL;DR: In this paper, the effect of phantom scalar fields and/or phantom electromagnetic fields on gravitational lensing by black holes in the strong deflection regime has been studied in the frame of the Einstein-(anti-)Maxwell-(anti)dilaton theory.
Abstract: In some models dark energy is described by phantom scalar fields (scalar fields with the ``wrong'' sign of the kinetic term in the Lagrangian). In the current paper we study the effect of phantom scalar field and/or phantom electromagnetic field on gravitational lensing by black holes in the strong deflection regime. The black-hole solutions that we have studied have been obtained in the frame of the Einstein-(anti-)Maxwell-(anti)dilaton theory. The numerical analysis shows a considerable effect of the phantom scalar and electromagnetic fields on the angular position, brightness, and separation of the relativistic images.
TL;DR: In this paper, the electromagnetic radiation by quark-gluon plasma in a strong magnetic field is calculated, and it is shown that in relativistic heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC).
Abstract: The electromagnetic radiation by quark-gluon plasma in a strong magnetic field is calculated. The contributing processes are synchrotron radiation and one-photon annihilation. It is shown that in relativistic heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) synchrotron radiation dominates over the annihilation. Moreover, it constitutes a significant part of all photons produced by the plasma at low transverse momenta; its magnitude depends on the plasma temperature and the magnetic field strength. Electromagnetic radiation in a magnetic field is probably the missing piece that resolves a discrepancy between the theoretical models and the experimental data. It is argued that electromagnetic radiation increases with the magnetic field strength and plasma temperature.