Action For Electrodynamics Research Articles

Quantum refraction effects in pulsar emission

ABSTRACT Highly magnetized neutron stars exhibit the vacuum non-linear electrodynamics effects, which can be well-described using the one-loop effective action for quantum electrodynamics. In this context, we study the propagation and polarization of pulsar radiation, based on the post-Maxwellian Lagrangian from the Heisenberg–Euler–Schwinger action. Given the refractive index obtained from this Lagrangian, we determine the leading-order corrections to both the propagation and polarization vectors due to quantum refraction via perturbation analysis. In addition, the effects on the orthogonality between the propagation and polarization vectors and the Faraday rotation angle, all due to quantum refraction are investigated. Furthermore, from the dual refractive index and the associated polarization modes, we discuss quantum birefringence, with the optical phenomenology analogous to its classical counterpart.

Probing the interference between non-linear, axionic and space-time-anisotropy effects in the QED vacuum

In this paper, we pursue the investigation of a generic non-linear extension of axionic electrodynamics in a Carroll-Field-Jackiw (CFJ) scenario that implements Lorentz-symmetry violation (LSV). The model we inspect consists of an arbitrary non-linear electrodynamic action coupled to the axion field in presence of an anisotropy four-vector that realizes the breaking of Lorentz symmetry under the particle point of view. For the sake of our considerations, the non-linear electromagnetic field is expanded around a constant and uniform magnetic background up to second order in the propagating photon field. The focus of our attention is the study of the material properties of the vacuum in the particular case of a space-like CFJ 4-vector. The dispersion relations associated to the plane wave solutions are explicitly worked out in two situations: the magnetic background perpendicular and parallel to the wave direction. We extend these results to consider the analysis of the birefringence phenomenon in presence of non-linearity, the axion and the LSV manifested through the spatial anisotropy. Three specific proposals of non-linear electrodynamics are contemplated: Euler-Heisenberg (EH), Born-Infeld (BI) and the Modified Maxwell electrodynamics (ModMax). Throughout the paper, we shall justify why we follow the unusual path of connecting, in a single Lagrangian density, three pieces of physics beyond the Standard Model, namely, non-linearity, axions and LSV. We anticipate that we shall not be claiming that the simultaneous introduction of these three topics beyond the Standard Model will bring new insights or clues for the efforts to detect axions or to constrain parameters associate to both non-linear electrodynamics and LSV physics. Our true goal is to actually inspect and describe how axionic, non-linear and LSV effects interfere with one another whenever physical entities like group velocity, refraction indices, birefringence and effective masses of physical excitations are computed in presence of an external constant and homogeneous magnetic field.

Gradient flow exact renormalization group: Inclusion of fermion fields

Abstract The gradient flow exact renormalization group (GFERG) is an exact renormalization group motivated by the Yang--Mills gradient flow and its salient feature is a manifest gauge invariance. We generalize this GFERG, originally formulated for the pure Yang--Mills theory, to vector-like gauge theories containing fermion fields, keeping the manifest gauge invariance. For the chiral symmetry we have two options: one possible formulation preserves the conventional form of the chiral symmetry and the other simpler formulation realizes the chiral symmetry in a modified form à la Ginsparg--Wilson. We work out a gauge-invariant local Wilson action in quantum electrodynamics to the lowest nontrivial order of perturbation theory. This Wilson action reproduces the correct axial anomaly in $D=2$.

Podolsky electrodynamics from a condensation of topological defects

In this paper we demonstrate the arising of higher-derivative contributions to the effective action of electrodynamics on the basis of the generalized Julia-Toulouse mechanism and explicitly show that the complete effective action arising within this methodology is nonlocal.

Pauli\u2013Villars regularization elucidated in Bopp\u2013Podolsky\u2019s generalized electrodynamics

We discuss an inherent Pauli–Villars regularization in Bopp–Podolsky’s generalized electrodynamics. Introducing gauge-fixing terms for Bopp–Podolsky’s generalized electrodynamic action, we realize a unique feature for the corresponding photon propagator with a built-in Pauli–Villars regularization independent of the gauge choice made in Maxwell’s usual electromagnetism. According to our realization, the length dimensional parameter a associated with Bopp–Podolsky’s higher order derivatives corresponds to the inverse of the Pauli–Villars regularization mass scale Lambda , i.e. a = 1/Lambda . Solving explicitly the classical static Bopp–Podolsky’s equations of motion for a specific charge distribution, we explore the physical meaning of the parameter a in terms of the size of the charge distribution. As an offspring of the generalized photon propagator analysis, we also discuss our findings regarding on the issue of the two-term vs. three-term photon propagator in light-front dynamics.

A Non-Local Action for Electrodynamics: Duality Symmetry and the Aharonov-Bohm Effect, Revisited

A non-local action functional for electrodynamics depending on the electric and magnetic fields, instead of potentials, has been proposed in the literature. In this work we elaborate and improve this proposal. We also use this formalism to confront the electric-magnetic duality symmetry of the electromagnetic field and the Aharonov–Bohm effect, two subtle aspects of electrodynamics that we examine in a novel way. We show how the former can be derived from the simple harmonic oscillator character of vacuum electrodynamics, while also demonstrating how the magnetic version of the latter naturally arises in an explicitly non-local manner.

Strong, random field behavior of the Euclidean Dirac propagator

The one-loop effective action of quantum electrodynamics in four dimensions is shown to be controlled by the Euclidean Dirac propagator $G$ in a background potential. After separating the photon self-energy and photon-photon scattering graphs from the effective action the remainder is known to be the logarithm of an entire function of the electric charge of order 4 under mild regularity assumptions on the potential. This input together with QED's lack of an ultrastable vacuum constrain the strong field behavior of $G$. It is shown that $G$ vanishes in the strong field limit. The relevance of this result to the decoupling of QED from the remainder of the electroweak model for large amplitude variations of the Maxwell field is discussed.

Dynamical structure of Carrollian Electrodynamics

We present an action of ultra-relativistic electrodynamics on a flat Carroll manifold. The model exhibits a couple of physical degrees of freedom per space-point. We observe that the action of the conformal Carroll algebra on the phase space is Hamiltonian in 4 space-time dimensions. Moreover the elements of the algebra give rise to an infinite number of conserved charges and the charge algebra is an exact realization of the kinematical algebra.

EVALUATION OF THE EFFICIENCY OF THE DEVICE FOR LIMITING TENSION OF THE WIRE IN A SHORT CIRCUIT

The intensity of the electrodynamic action of currents of a short circuit on the flexible conductors of overhead lines depends on the magnitude of currents of short-circuit. The commis sioning of new capacities is inevitably accompanied by an increase in short circuit currents in the nodes of the grid, so the need to limit peaks of tension arising in a short-circuit can acquire a special relevance at a certain stage of development of the power system. At short circuit currents over 40 kA the mechanical force and displacement of the wires can have a decisive influence on the structural performance of flexible bus as of single wires as well as of split phases. In this regard there is a need for the development and use of new structural elements enhancing electrodynamic stability of flexible busbars of outdoor switchgear. One such element is a tension damper. The damper is installed between the portal and the insulator string and limits the transmission of undesirable forces on the portals in a short circuit. The numerical method of calculation of dynamics of flexible wires of switchgear and overhead lines in a short-circuit taking into account influence of a tension damper has been developed. This method was used for modification of the computer program of calculation of electrodynamic stability. With the aid of the computer program it was demonstrated that the installation of the tension damper makes it possible to cut off peaks of the tension of wire in a short circuit at the initial stage of movement of the conductors. However, in spans of a great length after the actuation of the damper the occurrence of new bursts of tension is possible due to the sudden stop of the wire.

Influence of the Parameters of Electrodynamic Actions on the Stressed State of Welded Joints of Sheets of AMg6 Alloy

We study the influence of the parameters responsible for different durations of the electrodynamic actions on the decrease in residual stresses in welded joints of the sheets made of AMg6 aluminum alloy after electrodynamic treatment. It is discovered that as the time of electrodynamic action increases as a result of the increase in the inductance of the discharge contour in the course of electrodynamic treatment performed for constant amplitude values of impulsive electric currents, the period of decay of impulsive electric current is longer than the period of its growth. In this case, the efficiency of electrodynamic treatment increases. It is established that, for the duration of electrodynamic treatment t Σ ≥ 4.5 msec, the decrease in residual stresses is determined both by the intensity of the electrodynamic influence and by the local heat treatment as a result of the Joule heating of the surface of the plate.

Maxwell Equations for Slow-Moving Media

Abstract In the present work, the Minkowski equations obtained on the basis of theory of relativity are used to describe electromagnetic fields in moving media. But important electromagnetic processes run under non-relativistic conditions of slow-moving media. Therefore, one should carry out its description in terms of classical mechanics. Hertz derived electrodynamic equations for moving media within the frame of classical mechanics on the basis of the Maxwell theory. His equations disagree with the experimental data concerned with the moving dielectrics. In the paper, a way of description of electromagnetic fields in slow-moving media on the basis of the Maxwell theory within the frame of classical mechanics is offered by combining the Hertz approach and the experimental data concerned with the movement of dielectrics in electromagnetic fields. Received Maxwell equations lack asymmetry in the description of the reciprocal electrodynamic action of a magnet and a conductor and conform to known experimental data. Comparative analysis of the Minkowski and Maxwell models is carried out.

Study of Residual Stresses in Welded Joints of Heat-Resistant ML10 Magnesium Alloy After Electrodynamic Treatment

Airframes from ML10 magnesium alloy are repaired using argon-arc welding with nonconsumable electrodes. The residual stresses occurring in the repair welds deteriorate the operating characteristics of restored parts. The presence of residual stresses necessitates postweld heat treatment, which increases the prime cost of repair operations. This implies the option of applying the alternative methods of weld stress state adjustment, including the electrodynamic treatment, which make it possible to reduce the level of residual stresses in welded joints and, thus, the cost of repair welding operations for airframes from this alloy. The results of the performed experiments show that electrodynamic treatment allows one to reduce the initial level of stresses in welded joints (which reaches 120 MPa) to 30 MPa and to form, at definite geometric characteristics of specimens, compression stress fields in the treatment zone, whose values reach –50 MPa. It is demonstrated that the optimal distance between the treatment zones is 5 mm, which ensures granted overlapping of electrodynamic action zones and, hence, the maximum effectiveness of electrodynamic treatment.

Effect of electrodynamic phenomena in arc furnaces on the meniscus formation in a liquid metal

The main laws of the electrodynamic action of an electric arc on the surface of the liquid metal bath in electric arc furnaces of various types are considered.

THE HEISENBERG–EULER EFFECTIVE ACTION: 75 YEARS ON

On this 75th anniversary of the publication of the Heisenberg–Euler paper on the full nonperturbative one-loop effective action for quantum electrodynamics I review their paper and discuss some of the impacts it has had on quantum field theory.

THE HEISENBERG-EULER EFFECTIVE ACTION: 75 YEARS ON

On this 75th anniversary of the publication of the Heisenberg-Euler paper on the full non-perturbative one-loop effective action for quantum electrodynamics I review their paper and discuss some of the impact it has had on quantum field theory.

Low-energy effective action in nonperturbative electrodynamics in curved space-time

We study the heat kernel for the Laplace-type partial differential operator acting on smooth sections of a complex spin-tensor bundle over a generic n-dimensional Riemannian manifold. Assuming that the curvature of the U(1) connection (that we call the electromagnetic field) is constant, we compute the first two coefficients of the nonperturbative asymptotic expansion of the heat kernel which are of zero and the first order in Riemannian curvature and of arbitrary order in the electromagnetic field. We apply these results to the study of the effective action in nonperturbative electrodynamics in four dimensions and derive a generalization of the Schwinger’s result for the creation of scalar and spinor particles in electromagnetic field induced by the gravitational field. We discover a new infrared divergence in the imaginary part of the effective action due to the gravitational corrections, which seems to be a new physical effect.

Nonperturbative one-loop effective action for electrodynamics in curved space-time

In this paper we explicitly evaluate the one-loop effective action in four dimensions for scalar and spinor fields under the influence of a strong, covariantly constant, magnetic field in curved space-time. In the framework of zeta function regularization, we find the one-loop effective action to all orders in the magnetic field up to linear terms in the Riemannian curvature. As a particular case, we also obtain the one-loop effective action for massless scalar and spinor fields. In this setting, we found that the vacuum energy of charged spinors with small mass becomes very large due entirely to the gravitational correction.

From least action in electrodynamics to magnetomechanical energy—a review

The equations of motion for electromechanical systems are traced back to the fundamental Lagrangian of particles and electromagnetic fields, via the Darwin Lagrangian. When dissipative forces can be neglected the systems are conservative and one can study them in a Hamiltonian formalism. The central concepts of generalized capacitance and inductance coefficients are introduced and explained. The problem of gauge independence of self-inductance is considered. Our main interest is in magnetomechanics, i.e. the study of systems where there is exchange between mechanical and magnetic energy. This throws light on the concept of magnetic energy, which according to the literature has confusing and peculiar properties. We apply the theory to a few simple examples: the extension of a circular current loop, the force between parallel wires, interacting circular current loops and the rail gun. These show that the Hamiltonian, phase space, form of magnetic energy has the usual property that an equilibrium configuration corresponds to an energy minimum.

In the light of time

The concept of time is examined using the second law of thermodynamics that was recently formulated as an equation of motion. According to the statistical notion of increasing entropy, flows of energy diminish differences between energy densities that form space. The flow of energy is identified with the flow of time. The non-Euclidean energy landscape, i.e. the curved space–time, is in evolution when energy is flowing down along gradients and levelling the density differences. The flows along the steepest descents, i.e. geodesics are obtained from the principle of least action for mechanics, electrodynamics and quantum mechanics. The arrow of time, associated with the expansion of the Universe, identifies with grand dispersal of energy when high-energy densities transform by various mechanisms to lower densities in energy and eventually to ever-diluting electromagnetic radiation. Likewise, time in a quantum system takes an increment forwards in the detection-associated dissipative transformation when the stationary-state system begins to evolve pictured as the wave function collapse. The energy dispersal is understood to underlie causality so that an energy gradient is a cause and the resulting energy flow is an effect. The account on causality by the concepts of physics does not imply determinism; on the contrary, evolution of space–time as a causal chain of events is non-deterministic.

Advanced action in classical electrodynamics

The time evolution of a charged point particle is governed by a second-order integro-differential equation that exhibits advanced effects, in which the particle responds to an external force before the force is applied. In this paper, we give a simple argument that clarifies the origin and physical meaning of these advanced effects, and we compare ordinary electrodynamics with a toy model of electrodynamics in which advanced effects do not occur.