Showing papers on "Electromagnetic field published in 2009"
TL;DR: Using time-dependent density functional theory, this work shows that for dimer separations below 1 nm quantum mechanical effects, such as electron tunneling across the dimer junction and screening, significantly modify the optical response and drastically reduce the electromagnetic field enhancements relative to classical predictions.
Abstract: Using time-dependent density functional theory, we present a fully quantum mechanical investigation of the plasmon resonances in a nanoparticle dimer as a function of interparticle separation. We show that for dimer separations below 1 nm quantum mechanical effects, such as electron tunneling across the dimer junction and screening, significantly modify the optical response and drastically reduce the electromagnetic field enhancements relative to classical predictions. For larger separations, the dimer plasmons are well described by classical electromagnetic theory.
801 citations
TL;DR: It is demonstrated theoretically that electromagnetically induced transparency can be achieved in metamaterials, in which electromagnetic radiation is interacting resonantly with mesoscopic oscillators rather than with atoms, and these results are confirmed by accurate simulations of the electromagnetic field propagation in the meetamaterial.
Abstract: We demonstrate theoretically that electromagnetically induced transparency can be achieved in metamaterials, in which electromagnetic radiation is interacting resonantly with mesoscopic oscillators rather than with atoms. We describe novel metamaterial designs that can support a full dark resonant state upon interaction with an electromagnetic beam and we present results of its frequency-dependent effective permeability and permittivity. These results, showing a transparency window with extremely low absorption and strong dispersion, are confirmed by accurate simulations of the electromagnetic field propagation in the metamaterial.
620 citations
TL;DR: In this article, the behavior of photons in the presence of Lorentz and CPT violation is studied, and a complete characterization of the coefficients for all mass dimensions via a decomposition using spin-weighted spherical harmonics.
Abstract: The behavior of photons in the presence of Lorentz and CPT violation is studied. Allowing for operators of arbitrary mass dimension, we classify all gauge-invariant Lorentz- and CPT-violating terms in the quadratic Lagrange density associated with the effective photon propagator. The covariant dispersion relation is obtained, and conditions for birefringence are discussed. We provide a complete characterization of the coefficients for Lorentz violation for all mass dimensions via a decomposition using spin-weighted spherical harmonics. The resulting nine independent sets of spherical coefficients control birefringence, dispersion, and anisotropy in the photon propagator. We discuss the restriction of the general theory to various special models, including among others the minimal standard-model extension, the isotropic limit, the case of vacuum propagation, the nonbirefringent limit, and the vacuum-orthogonal model. The transformation of the spherical coefficients for Lorentz violation between the laboratory frame and the standard Sun-centered frame is provided. We apply the results to various astrophysical observations and laboratory experiments. Astrophysical searches of relevance include studies of birefringence and of dispersion. We use polarimetric and dispersive data from gamma-ray bursts to set constraints on coefficients for Lorentz violation involving operators of dimensions four through nine, and we describe the mixing of polarizations induced by Lorentz and CPT violation in the cosmic-microwave background. Laboratory searches of interest include cavity experiments. We present the general theory for searches with cavities, derive the experiment-dependent factors for coefficients in the vacuum-orthogonal model, and predict the corresponding frequency shift for a circular-cylindrical cavity.
423 citations
Book•
26 Oct 2009
TL;DR: Electromagnetic fields in cavities: Deterministic and statistical theories is a book about magnetism and cavities that explains the behaviour of magnetospheres in terms of determinants and statistical theory.
Abstract: PREFACE. PART I. DETERMINISTIC THEORY. 1. Introduction. 1.1 Maxwell's Equations. 1.2 Empty Cavity Modes. 1.3 Wall Losses. 1.4 Cavity Excitation. 1.5 Perturbation Theories. Problems. 2. Rectangular Cavity. 2.1 Resonant Modes. 2.2 Wall Losses and Cavity Q. 2.3 Dyadic Green's Functions. Problems. 3. Circular Cylindrical Cavity. 3.1 Resonant Modes. 3.2 Wall Losses and Cavity Q. 3.3 Dyadic Green's Functions. Problems. 4. Spherical Cavity. 4.1 Resonant Modes. 4.2 Wall Losses and Cavity Q. 4.3 Dyadic Green's Functions. 4.4 Schumann Resonances in the Earth-Ionosphere Cavity. Problems. PART II. STATISTICAL THEORIES FOR ELECTRICALLY LARGE CAVITIES. 5. Motivation for Statistical Approaches. 5.1 Lack of Detailed Information. 5.2 Sensitivity of Fields to Cavity Geometry and Excitation. 5.3 Interpretation of Results. Problems. 6. Probability Fundamentals. 6.1 Introduction. 6.2 Probability Density Function. 6.3 Common Probability Density Functions. 6.4 Cumulative Distribution Function. 6.5 Methods for Determining Probability Density Functions. Problems. 7. Reverberation Chambers. 7.1 Plane-Wave Integral Representation of Fields. 7.2 Ideal Statistical Properties of Electric and Magnetic Fields. 7.3 Probability Density Functions for the Fields. 7.4 Spatial Correlation Functions of Fields and Energy Density. 7.5 Antenna or Test-Object Response. 7.6 Loss Mechanisms and Chamber Q. 7.7 Reciprocity and Radiated Emissions. 7.8 Boundary Fields. 7.9 Enhanced Backscatter at the Transmitting Antenna. Problems. 8. Aperture Excitation of Electrically Large, Lossy Cavities. 8.1 Aperture Excitation. 8.2 Power Balance. 8.3 Experimental Results for SE. Problems. 9. Extensions to the Uniform-Field Model. 9.1 Frequency Stirring. 9.2 Unstirred Energy. 9.3 Alternative Probability Density Function. Problems. 10. Further Applications of Reverberation Chambers. 10.1 Nested Chambers for Shielding Effectiveness Measurements. 10.2 Evaluation of Shielded Enclosures. 10.3 Measurement of Antenna Efficiency. 10.4 Measurement of Absorption Cross Section. Problems. 11. Indoor Wireless Propagation. 11.1 General Considerations. 11.2 Path Loss Models. 11.3 Temporal Characteristics. 11.4 Angle of Arrival. 11.5 Reverberation Chamber Simulation. Problems. APPENDIX A. VECTOR ANALYSIS. APPENDIX B. ASSOCIATED LEGENDRE FUNCTIONS. APPENDIX C. SPHERICAL BESSEL FUNCTIONS. APPENDIX D. THE ROLE OF CHAOS IN CAVITY FIELDS. APPENDIX E. SHORT ELECTRIC DIPOLE RESPONSE. APPENDIX F. SMALL LOOP ANTENNA RESPONSE. APPENDIX G. RAY THEORY FOR CHAMBER ANALYSIS. APPENDIX H. ABSORPTION BY A HOMOGENEOUS SPHERE. APPENDIX I. TRANSMISSION CROSS SECTION OF A SMALL CIRCULAR APERTURE. APPENDIX J. SCALING. REFERENCES. INDEX.
353 citations
TL;DR: Several broad categories of Bayesian inference directly applicable to source localization including empirical Bayesian approaches, standard MAP estimation, and multiple variational Bayesian (VB) approximations are analyzed and fast algorithms are derived that improve upon existing methods.
353 citations
TL;DR: NSFC [10625418, 20703032], MEC [FIS2007-66711-c01-01], Natural Science Foundation of Fujian Province of China [E0710028] as discussed by the authors.
Abstract: NSFC [10625418, 20703032]; MOST [2006DFBO2020, 2007CB936800, 2009CB930703]; CAS; CSIC [2008601039]; MEC [FIS2007-66711-c01-01]; Natural Science Foundation of Fujian Province of China [E0710028]
203 citations
Patent•
27 Aug 2009TL;DR: In this article, a first shielding box is disposed so that its first surface can be opposite to an electric power feeding unit, and the remaining five surfaces thereof reflect the resonant electromagnetic field (near field) generated in the surroundings of the electric power receiving unit.
Abstract: A first shielding box is disposed so that its first surface can be opposite to an electric power feeding unit. The first surface has an opening and remaining five surfaces thereof reflect, during reception of electric power from the electric power feeding unit, a resonant electromagnetic field (near field) generated in the surroundings of the electric power receiving unit. The electric power receiving unit is provided in the first shielding box to receive the electric power from the electric power feeding unit via the opening (first surface) of the first shielding box. A second shielding box has a similar configuration, i.e., has a second surface with an opening and remaining five surfaces thereof reflect the resonant electromagnetic field (near field) generated in the surroundings of the electric power feeding unit.
175 citations
01 Apr 2009
TL;DR: In this paper, the universal properties of the critical Casimir force arising in thin films were investigated and compared with the experimental results obtained for wetting layers of various fluids, and the results showed that the theoretical predictions of the Casimir forces can be easily tuned with respect to strength and sign.
Abstract: The Casimir effect in quantum electrodynamics (QED) is perhaps the best-known example of fluctuation-induced long-ranged force acting on objects (conducting plates) immersed in a fluctuating medium (quantum electromagnetic field in vacuum). A similar effect emerges in statistical physics, where the force acting, e.g., on colloidal particles immersed in a binary liquid mixture is affected by the classical thermal fluctuations occurring in the surrounding medium. The resulting Casimir-like force acquires universal features upon approaching a critical point of the medium and becomes long-ranged at criticality. In turn, this universality allows one to investigate theoretically the temperature dependence of the force via representative models and to stringently test the corresponding predictions in experiments. In contrast to QED, the Casimir force resulting from critical fluctuations can be easily tuned with respect to strength and sign by surface treatments and temperature control. We present some recent advances in the theoretical study of the universal properties of the critical Casimir force arising in thin films. The corresponding predictions compare very well with the experimental results obtained for wetting layers of various fluids. We discuss how the Casimir force between a colloidal particle and a planar wall immersed in a binary liquid mixture has been measured with femto-Newton accuracy, comparing these experimental results with the corresponding theoretical predictions.
159 citations
TL;DR: In this paper, a classical electrodynamic theory was developed to study the optical nonlinearities of metallic nanoparticles, where quasi free electrons inside the metal were approximated as a classical Coulomb-interacting electron gas, and their motion under the excitation of an external electromagnetic field was described by the plasma equations.
Abstract: In this paper, we develop a classical electrodynamic theory to study the optical nonlinearities of metallic nanoparticles. The quasi free electrons inside the metal are approximated as a classical Coulomb-interacting electron gas, and their motion under the excitation of an external electromagnetic field is described by the plasma equations. This theory is further tailored to study second-harmonic generation. Through detailed experiment-theory comparisons, we validate this classical theory as well as the associated numerical algorithm. It is demonstrated that our theory not only provides qualitative agreement with experiments but it also reproduces the overall strength of the experimentally observed second-harmonic signals.
148 citations
TL;DR: In this article, a phase-sensitive near-field microscope was used to measure independently the two in-plane electric field components of light propagating through a 2D photonic crystal waveguide and the phase difference between them.
Abstract: With a phase-sensitive near-field microscope we measure independently the two in-plane electric field components of light propagating through a 2D photonic crystal waveguide and the phase difference between them. Consequently, we are able to reconstruct the electric vector field distribution with subwavelength resolution. In the complex field distribution we observe both time-dependent and time-independent polarization singularities and determine the topology of the surrounding electric field.
TL;DR: The enhanced transmission of electromagnetic waves through a single subwavelength aperture by using a split-ring resonator (SRR) at microwave frequencies is reported and 740-fold transmission enhancement is obtained by exciting the electric resonance of SRR.
Abstract: We report the enhanced transmission of electromagnetic waves through a single subwavelength aperture by using a split-ring resonator (SRR) at microwave frequencies. By placing a single SRR at the near field of the aperture, strongly localized electromagnetic fields are effectively coupled to the aperture with a radius that is 20 times smaller than the resonance wavelength (r/lambda=0.05). We obtained 740-fold transmission enhancement by exciting the electric resonance of SRR. A different coupling mechanism, through the magnetic resonance of SRR, is also verified to lead to enhanced transmission.
TL;DR: In this paper, the authors extracted synthetic photon spectra from first-principles particle-in-cell simulations of relativistic shocks propagating in unmagnetized pair plasmas.
Abstract: We extract synthetic photon spectra from first-principles particle-in-cell simulations of relativistic shocks propagating in unmagnetized pair plasmas. The two basic ingredients for the radiation, namely accelerated particles and magnetic fields, are produced self-consistently as part of the shock evolution. We use the method of Hededal & Nordlund (2005) and compute the photon spectrum via Fourier transform of the electric far-field from a large number of particles, sampled directly from the simulation. We find that the spectrum from relativistic collisionless shocks is entirely consistent with synchrotron radiation in the magnetic fields generated by Weibel instability. We can recover the so-called "jitter'' regime only if we artificially reduce the strength of the electromagnetic fields, such that the wiggler parameter K = qB lambda/mc^2 becomes much smaller than unity ("B" and "lambda" are the strength and scale of the magnetic turbulence, respectively). These findings may place constraints on the origin of non-thermal emission in astrophysics, especially for the interpretation of the hard (harder than synchrotron) low-frequency spectrum of Gamma-Ray Bursts.
TL;DR: A general framework, based on the coupled dipole method, is developed for computing the electromagnetic force and torque experienced by an object with arbitrary shape, dielectric permittivity and magnetic permeability.
Abstract: We derive the analytic expressions of the electromagnetic force and torque on a dipolar particle, with arbitrary dielectric permittivity and magnetic permeability. We then develop a general framework, based on the coupled dipole method, for computing the electromagnetic force and torque experienced by an object with arbitrary shape, dielectric permittivity and magnetic permeability.
TL;DR: In this paper, it was shown that the electromagnetic fields in dielectric media whose susceptibility follows a fractional power-law dependence in a wide frequency range can be described by differential equations with time derivatives of noninteger order.
Abstract: We prove that the electromagnetic fields in dielectric media whose susceptibility follows a fractional power-law dependence in a wide frequency range can be described by differential equations with time derivatives of noninteger order. We obtain fractional integro-differential equations for electromagnetic waves in a dielectric. The electromagnetic fields in dielectrics demonstrate a fractional power-law relaxation. The fractional integro-differential equations for electromagnetic waves are common to a wide class of dielectric media regardless of the type of physical structure, the chemical composition, or the nature of the polarizing species (dipoles, electrons, or ions).
TL;DR: In this paper, it was shown that magnetic and electric field gradients near nanostructures can induce molecular transitions that are forbidden by electric dipole selection rules, which could provide a route to new nanomagnetic catalysts and to magnetic control of chemical reactions.
TL;DR: In this article, the authors present the theoretical basis of advanced models for the calculation of LEMP-originated transients in overhead power lines and the relevant experimental validation using: 1) reduced-scale setups with LEMP and nuclear electromagnetic pulse (NEMP) simulators and 2) fullscale setups illuminated by artificially initiated lightning.
Abstract: The evaluation of electromagnetic transients in overhead power lines due to nearby lightning return strokes requires accurate models for the calculation of both the incident lightning electromagnetic pulse (LEMP) and the effects of coupling of this field to the line conductors. Considering also the complexity of distribution networks in terms of their topology and the presence of power system components and protection devices, the implementation of the LEMP-to-transmission-line coupling models into software tools used to represent the transient behavior of the entire network is of crucial importance. This paper reviews the most significant results obtained by the authors concerning the calculation of lightning-induced voltages. First, the theoretical basis of advanced models for the calculation of LEMP-originated transients in overhead power lines is illustrated; then, the relevant experimental validation using: 1) reduced-scale setups with LEMP and nuclear electromagnetic pulse (NEMP) simulators and 2) full-scale setups illuminated by artificially initiated lightning are reported. Finally, the paper presents comparisons between simulations and new experimental data consisting of measured natural lightning-induced voltages on a real distribution network in northern Italy, correlated with data from lightning location systems.
Patent•
05 Mar 2009
TL;DR: In this article, the length of the spiral conductor is equal to ¼ of the wavelength of the alternating voltage, and the current response will synchronize with the voltage input, creating in-phase behavior, minimal total impedance, and maximal power output.
Abstract: Spiral coils generate very powerful electromagnetic fields by operating with two different but simultaneous resonant behaviors. Quarter-wave resonance is established by adjusting the frequency (and wavelength) of a radiofrequency (RF) voltage source until the length of the spiral conductor is equal to ¼ of the wavelength of the alternating voltage. This generates an electromagnetic standing wave with at least one peak node and at least one null node. Inductive-capacitive (L/C) resonance is established by optimizing the thickness and width of the wire ribbon used to make the spiral coil. When inductance and capacitance are balanced, the current response will synchronize with the voltage input, creating in-phase behavior, minimal total impedance, and maximal power output. If two such coils are placed near each other, they will create an extremely powerful electromagnetic field between them, which can promote chemical and plasma reactions involving charged particles such as ions or plasma particles, possibly including nuclear fusion reactions.
TL;DR: In this paper, it was shown that the violation of Lorentz symmetry in the gauge sector may contribute to magnetic moment generation of massive neutral particles with spin-1 and spin- 1.
Abstract: This paper deals with situations that illustrate how the violation of Lorentz symmetry in the gauge sector may contribute to magnetic moment generation of massive neutral particles with spin-
$\frac {1}{2}$
and spin-1. The procedure we adopt here is based on Relativistic Quantum Mechanics. We work out the non-relativistic regime that follows from the wave equation corresponding to a certain particle coupled to an external electromagnetic field and a background that accounts for the Lorentz-symmetry violation, and we thereby read off the magnetic dipole moment operator for the particle under consideration. We keep track of the parameters that govern the non-minimal electromagnetic coupling and the breaking of Lorentz symmetry in the expressions we get for the magnetic moments in the different cases we contemplate. Our claim is that the tiny magnetic dipole moment of truly-elementary neutral particles might signal Lorentz-symmetry violation.
TL;DR: In this article, the electromagnetic response of graphene and the spectrum of collective plasmon excitations are studied as a function of wave vector and frequency, including both valleys, based on the tight-binding band structure.
Abstract: The electromagnetic response of graphene and the spectrum of collective plasmon excitations are studied as a function of wave vector and frequency. Our calculation is based on the tight-binding band structure, including both valleys. As a result, near the Dirac points we find plasmons whose dispersion is similar to that obtained in the single-valley approximation by Dirac fermions with some anisotropy though. In contrast to the calculation for a single Dirac cone, we find a stronger damping of the plasmon modes due to interband absorption. Our calculation also reveals effects due to deviations from the linear Dirac spectrum as we increase the Fermi energy, indicating an anisotropic behavior with respect to the wave vector of the external electromagnetic field.
TL;DR: In this paper, a new electromagnetism module is developed in LS-DYNA for coupled mechanical/thermal/electromagnetic simulations, which is used for metal forming.
Abstract: A new electromagnetism module is being developed in LS-DYNA for coupled mechanical/thermal/electromagnetic simulations. One of the main applications of this module is Electromagnetic Metal Forming. The electromagnetic fields are solved using a Finite Element Method for the conductors coupled with a Boundary Element Method for the surrounding air/insulators. Both methods use elements based on discrete differential forms for improved accuracy. The physics, numerical methods and capabilities of this new module are presented in detail as well as its coupling with the mechanical and thermal solvers of LS-DYNA. This module is then illustrated on two Electromagnetic Metal Forming cases, the forming of an aluminum sheet on a conical die using a spiral coil, and the forming of an aluminum sheet on a v-shaped die using a “double pancake” coil. The experimental setups are presented as well as comparisons between experimental and numerical results.
TL;DR: In this article, the authors applied an original numerical Schwarz-Christoffel transformation to analyze magnetic field originating from permanent magnets and the armature winding currents in a slotted air gap of an inset permanent-magnet synchronous motor.
Abstract: In this paper, we apply an original numerical Schwarz-Christoffel (SC) transformation to analyze magnetic field originating from permanent magnets and the armature winding currents in a slotted air gap of an inset permanent-magnet synchronous motor. We obtained the solution of the SC integral numerically using Matlab SC Toolbox. We used this field solution to calculate both cogging torque and electromagnetic torque by integrating the Maxwell stress tensor inside the air gap. The case without inter-polar piece, which is equivalent to a surface-mounted permanent-magnet motor, is also treated. The accuracy of the developed method is verified by comparing its results with those obtained from the developed numerical finite-element models.
TL;DR: This paper describes a comparative study of finite-difference time-domain (FDTD) and analytical evaluations of electromagnetic fields in the vicinity of dimers of metallic nanospheres of plasmonics-active metals and indicates excellent correlation between the two computational methods, especially for gold nanosphere dimers.
Abstract: This paper describes a comparative study of finite-difference time-domain (FDTD) and analytical evaluations of electromagnetic fields in the vicinity of dimers of metallic nanospheres of plasmonics-active metals. The results of these two computational methods, to determine electromagnetic field enhancement in the region often referred to as “hot spots” between the two nanospheres forming the dimer, were compared and a strong correlation observed for gold dimers. The analytical evaluation involved the use of the spherical-harmonic addition theorem to relate the multipole expansion coefficients between the two nanospheres. In these evaluations, the spacing between two nanospheres forming the dimer was varied to obtain the effect of nanoparticle spacing on the electromagnetic fields in the regions between the nanostructures. Gold and silver were the metals investigated in our work as they exhibit substantial plasmon resonance properties in the ultraviolet, visible, and near-infrared spectral regimes. The results indicate excellent correlation between the two computational methods, especially for gold nanosphere dimers with only a 5-10% difference between the two methods. The effect of varying the diameters of the nanospheres forming the dimer, on the electromagnetic field enhancement, was also studied.
TL;DR: In this paper, the authors provide an overview on the state of the art of traditional EMI suppression technologies, and introduce the use of chaos theory and chaos control to reduce EMI, as well as to motivate more efforts in theoretical research and engineering practice.
Abstract: Since James Clerk Maxwell established the electromagnetic field theory in 1865, multifarious electrical and electronic products have been invented, designed, produced, and widely deployed, such as wireless communication devices, electrical machines and motors. This has profoundly changed our world and our lives. Now we cannot live without electrical products anymore and, thus, we are surrounded with electromagnetic fields generated. On the other side, especially in the past few decades, the rapid development and wide deployment of electrical products have caused lots of troubles, among which the most prominent one is electromagnetic interference (EMI), which may impact other devices' performance and harm human beings' health. Therefore, fighting EMI has become a stringent, difficult problem faced by engineers and scientists. The sources of EMI include natural sources, like atmospheric charge/discharge phenomena and extraterrestrial radiation, and man-made sources, like power lines, auto ignition, radio frequency interference, and radiation hazards, to name just a few. As important components, direct current (DC-DC) converters are embedded and employed in various electrical devices, thus forming main sources of EMI. Some measures, such as filters and electromagnetic shielding, have been taken to suppress EMI, but these methods have various drawbacks with respect to cost, volume, weight, and efficiency. Therefore, new theories and methodologies are desired to cope with the EMI problem, and chaos theory is a candidate due to the continuous spectrum feature of chaos. This paper aims to provide an overview on the state of the art of traditional EMI suppression technologies, and to introduce the use of chaos theory and chaos control to reduce EMI, as well as to motivate more efforts in theoretical research and engineering practice.
04 May 2009
TL;DR: In this article, the radiation characteristics of frequency diversity array are concerned with a set of CW signals of different frequencies transmitted simultaneously from the array, the transient field is examined by electromagnetic field simulation software.
Abstract: In this paper, the radiation characteristics of frequency diversity array are concerned. With a set of CW signals of different frequencies transmitted simultaneously from the array, the transient field is examined by electromagnetic field simulation software. A periodically scanning beam is observed and the scanning speed is shown to be related to the frequency increment between two neighboring elements. Based on electromagnetic field simulation results, a low cost frequency diverse array is designed. 4 PLL frequency synthesizers sharing the same reference signal generate the desired signals. The output frequencies can be easily configured and flexibly changed by 16 bit parallel programming.
TL;DR: In this article, a new derivation of the motion of a radiating electron is given, leading to a formulation that differs from the Lorentz-Abraham-Dirac equation and its published modifications.
Abstract: A new derivation of the motion of a radiating electron is given, leading to a formulation that differs from the Lorentz–Abraham–Dirac equation and its published modifications. It satisfies the proper conservation laws. Particularly, it conserves the generalized momentum, eliminating the symmetry-breaking runaway solution. The equation allows a consistent calculation of the electron current, the radiation effect on the electron momentum, and the radiation itself, for a single electron or plasma electrons in strong electromagnetic fields. The equation is then applied to a simulation of a strong laser pulse interaction with a plasma target. Some analytical solutions are also provided.
TL;DR: This work shows how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as a possible enhancement of electromagnetic fields during the late-merge and merger epochs, which can be exploited in the detection of electromagnetic counterparts of gravitational waves.
Abstract: In addition to producing gravitational waves, the dynamics of a binary black hole system could induce emission of electromagnetic radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We here study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as a possible enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves.
TL;DR: In this article, a superconducting qubit nonresonantly coupled to a transmission line resonator can be determined by measuring the quadrature amplitudes of an electromagnetic field transmitted through the resonator.
Abstract: The quantum state of a superconducting qubit nonresonantly coupled to a transmission line resonator can be determined by measuring the quadrature amplitudes of an electromagnetic field transmitted through the resonator. We present experiments in which we analyze in detail the dynamics of the transmitted field as a function of the measurement frequency for both weak continuous and pulsed measurements. We find excellent agreement between our data and calculations based on a set of Bloch-type differential equations for the cavity field derived from the dispersive Jaynes-Cummings Hamiltonian including dissipation. We show that the measured system response can be used to construct a measurement operator from which the qubit population can be inferred accurately. Such a measurement operator can be used in tomographic methods to reconstruct single and multiqubit states in ensemble-averaged measurements.
TL;DR: In this paper, a non-invariant conformal term in the electromagnetic Lagrangian of the form, where I(ϕ) is a pseudoscalar function of a nontrivial background field ϕ, is considered.
Abstract: We analyze the generation of seed magnetic fields during de Sitter inflation considering a noninvariant conformal term in the electromagnetic Lagrangian of the form , where I(ϕ) is a pseudoscalar function of a nontrivial background field ϕ. In particular, we consider a toy model that could be realized owing to the coupling between the photon and either a (tachyonic) massive pseudoscalar field or a massless pseudoscalar field nonminimally coupled to gravity, where I follows a simple power law behavior I(k,η) = g/(-kη)β during inflation, while it is negligibly small subsequently. Here, g is a positive dimensionless constant, k the wave number, η the conformal time, and β a real positive number. We find that only when β = 1 and 0.1 ≲ g ≲ 2 can astrophysically interesting fields be produced as excitation of the vacuum, and that they are maximally helical.