Nonlinear Electrodynamics Research Articles

Charged Accelerating BTZ Black Holes

AbstractIn this paper, general uncharged accelerating BTZ black hole solutions are extracted and studied some of their properties. The analysis shows that spacetime's asymptotic behavior depends on four parameters: the cosmological constant, mass, acceleration, and topological constant. Then, the temperature of these black holes are studied and it is found that the temperature is always positive for AdS spacetime. Next, the study is extended for extracting charged accelerating BTZ black hole solutions in the presence of a nonlinear electrodynamics field known as conformally invariant Maxwell. The findings indicate a coupling between the electrical charge and other quantities of the accelerating BTZ black holes. The asymptotic behavior of charged accelerating BTZ black holes depends on five parameters: the cosmological constant, the electrical charge, mass, the acceleration parameter, and the topological constant. Then, the effects of charge, acceleration parameters, and the topological constant on the root of these black holes are studied. Finally, the temperature of these black holes in AdS spacetime is investigated. For these black holes, the temperature depends on the electrical charge, accelerating parameter, and the cosmological constant. The analysis indicates that the temperature of charged accelerating BTZ AdS black holes is always positive.

Density and Mass Function for Regular Rotating Electrically Charged Compact Objects Determined by Nonlinear Electrodynamics Minimally Coupled to Gravity

We address the question of the electromagneticdensity and the mass function for regular rotating electrically charged compact objects as determined by dynamical equations of nonlinear electrodynamics minimally coupled to gravity. The rotating electrically charged compact objects are described by axially symmetric geometry, in which their electromagnetic fields are governed by four source-free equations for two independent field components of the electromagnetic tensor Fμν, with two constraints on the integration functions. An additional condition of compatibility of four dynamical equations for two independent field functions imposes the constraint on the Lagrange derivative LF=dL/dF, directly related to the electromagnetic density. As a result, the compatibility condition determines uniquely the generic form of the electromagnetic density and the mass function for regular rotating electrically charged compact objects.

Bardeen Tolman–Kuchowicz spheres in logarithmic-corrected R2 gravity

This study enlightens the effect of electric charge in the context of Logarithmic-corrected [Formula: see text] gravity model by assuming the specific form of metric potentials [Formula: see text] and [Formula: see text], known as Tolman–Kuchowicz spacetime. The key feature of our study is to assume the Bardeen model to narrate the nature of exterior geometry. This discussion enhances the analysis as the Bardeen black hole solution can be formulated as a gravitationally collapsed magnetic monopole which arises from some particular case of nonlinear electrodynamics. Further, the modified matching conditions, designed for [Formula: see text] gravity, have been imposed to compute all the unknown constants involved in metric potentials for the qualitative evaluation of the study. For this purpose, we have studied all the mandatory characteristics of stellar structures like energy density, pressure components, energy bonds, equilibrium condition, stability constraints, mass–radius relation. A comprehensive graphical analysis to ensure the credibility of the [Formula: see text] gravity model has been presented. It is worth indicating that our obtained charged anisotropic outcomes are physically well-fitted with the best degree of accuracy.

Strong lensing and shadow of Ayon-Beato–Garcia (ABG) nonsingular black hole

We study nonsingular black holes viewed from the point of view of Ayon-Beato–Garcia (ABG) nonlinear electrodynamics (NLED) and present a complete study of their corresponding strong gravitational lensing. The NLED modifies the the photon’s geodesic, and our calculations show that such effect increases the corresponding photon sphere radius and image separation, but decreases the magnification. We also show that the ABG’s shadow radius is not compatible with bound estimates of Sgr A* from Keck and VLTI (Very Large Telescope Interferometer). Thus, the possibility of Sgr A* being a nonsingular ABG black hole is ruled out.

Probing modified plasma waves in non-linear electrodynamics

Properties of modified plasma waves in non-linear electrodynamics are investigated. We consider a cold, uniform, collisionless, and magnetized plasma model. Initially, we also assume small amplitude waves and the non-relativistic approximation. For electrostatic waves, we obtain a modified Trivelpiece–Gould dispersion relation with a suitable change in the plasma frequency and analyze the stability of modes. Furthermore, electromagnetic waves related to the generalized Appleton–Hartree equation are established. In this case, we discuss modifications in circularly polarized waves and ordinary and extraordinary modes. After that, we apply our results to particular cases of low-energy quantum electrodynamics and a generalized Born–Infeld model. The correspondent dispersion relations and effects on the propagation regions are determined. Finally, we include the relativistic and large amplitude effects for circularly polarized waves. We obtain the dispersion relation within effective non-linear electrodynamics and examine the behavior of the refractive index when the frequency of the propagating wave converges to the plasma frequency.

Resonant Generation of High-Order Harmonics in Nonlinear Electrodynamics

Resonant Generation of High-Order Harmonics in Nonlinear Electrodynamics

Revealing the frequency-dependent oscillations in the nonlinear terahertz response induced by the Josephson current.

Nonlinear responses of superconductors to intense terahertz radiation has been an active research frontier. Using terahertz pump-terahertz probe spectroscopy, we investigate the c-axis nonlinear optical response of a high-temperature superconducting cuprate. After excitation by a single-cycle terahertz pump pulse, the reflectivity of the probe pulse oscillates as the pump-probe delay is varied. Interestingly, the oscillatory central frequency scales linearly with the probe frequency, a fact widely overlooked in pump-probe experiments. By theoretically solving the nonlinear optical reflection problem on the interface, we show that our observation is well explained by the Josephson-type third-order nonlinear electrodynamics, together with the emission coefficient from inside the material into free space. The latter results in a strong enhancement of the emitted signal whose physical frequency is around the Josephson plasma edge. Our result offers a benchmark for and new insights into strong-field terahertz spectroscopy of related quantum materials.

Particle dynamics and weak gravitational lensing around nonlinear electrodynamics black hole

The manuscript focuses on the characteristics of a nonlinear electrodynamics black hole in a weak gravitational field, including particle dynamics and plasma effect on weak lensing. In order to complete this study, we analyze the nonlinear electrodynamics black hole geometry. We investigate particle dynamics by computing the ISCO radius for massive particles. We examine the impact of plasma on lensing properties by calculating the deflection angle for uniform and non-uniform plasma. Furthermore, we investigate the impact of plasma on the source brightness image magnification.

Effects of electric and magnetic charges on weak deflection angle and bounding greybody of black holes in nonlinear electrodynamics

In this paper, we study the weak deflection angle using the Gauss–Bonnet theorem and bounding greybody factor for electric and magnetic black holes in the background of nonlinear electrodynamics. Using Gibbons and Werner’s approach, we first acquired the Gaussian optical curvature to be used in the Gauss–Bonnet theorem and calculate the bending angle for spherically symmetric electric and magnetic black holes in both non-plasma and plasma mediums in the weak field limits. Later, we calculate the rigorous bounds of the greybody factor for the given black holes. Furthermore, we are looking into the graphical behaviour of bending angles and greybody bounds at specific values of multiple parameters as well as black hole charges. It is to be mentioned here that all the results for the electric and magnetic-charged black hole solutions are reduced into the Schwarzschild black hole solution in the absence of the black hole charges.

Axial anomaly in nonlinear conformal electrodynamics

We study the axial anomaly of Dirac spinors on gravitational instanton backgrounds in the context of nonlinear electrodynamics. In order to do so, we consider Einstein gravity minimally coupled to a recently proposed conformal electrodynamics that enjoys duality transformation invariance. These symmetries allow us to generalize the Eguchi-Hanson configuration while preserving its geometry. We then compute the Dirac index of the nonlinearly charged Eguchi-Hanson and Taub-NUT configurations. We find that there is an excess of positive chiral Dirac fermions over the negative ones which triggers the anomaly.

Transforming singular black holes into regular black holes sourced by nonlinear electrodynamics

We present a way to generate regular black hole spacetimes that are a solution of General Relativity with nonlinear electrodynamics (NLED) as a source, out of a particular metric that inherits the “mass function” of a singular black hole geometry. The singular metric may not be a vacuum, or electro-vacuum, solution of General Relativity.

A supersymmetric nonlinear sigma model analogue of the ModMax theory

A decade ago, it was shown that associated with any model for U(1) duality-invariant nonlinear electrodynamics there is a unique U(1) duality-invariant supersymmetric nonlinear sigma model formulated in terms of chiral and complex linear superfields. Here we study the mathcal{N} = 1 superconformal σ-model analogue of the conformal duality-invariant electrodynamics known as the ModMax theory. We derive its dual formulation in terms of chiral superfields and show that the target space is a Kähler cone with U(1) × U(1) being the connected component of the isometry group.

Dirty black hole supported by a uniform electric field in Einstein-nonlinear electrodynamics-Dilaton theory

In this study, we present an exact dirty/hairy black hole solution in the context of gravity coupled minimally to a nonlinear electrodynamic (NED) and a Dilaton field. The NED model is known in the literature as the square-root (SR) model i.e., {mathcal {L}}sim sqrt{-{mathcal {F}}}. The black hole solution which is supported by a uniform radial electric field and a singular Dilaton scalar field is non-asymptotically flat and singular with the singularity located at its center. An appropriate transformation results in an interesting line element ds^{2}=-left( 1-frac{2,M}{rho ^{eta ^{2}}} right) rho ^{2left( eta ^{2}-1right) }dtau ^{2}+left( 1-frac{2,M}{ rho ^{eta ^{2}}}right) ^{-1}drho ^{2}+varkappa ^{2}rho ^{2}dOmega ^{2} with two parameters – namely the mass M and the Dilaton parameter eta ^{2}>1 (varkappa ^{2}=frac{1}{eta ^{2}}) – which may be simply considered as the dirty Schwarzschild black hole. This is because with eta ^{2}rightarrow 1 the spacetime reduces to the Schwarzschild black hole. We show that although the causal structure of the above spacetime is similar to the Schwarzschild black hole, it is thermally stable for eta ^{2}>2. Furthermore, the tidal force of this black hole behaves the same as a Schwarzschild black hole, however, its magnitude depends on eta ^{2} such that its minimum is not corresponding to eta ^{2}=1 (Schwarzschild limit).

Thermal fluctuations of black holes with non-linear electrodynamics and charged Renyi entropy

We extend the charged Renyi entropy to a more general holographic scenario. Coupling an arbitrary non-linear electrodynamics Lagrangian density to AdS gravity, we analyse the thermodynamic features of non-linearly charged hyperbolic black holes and the thermal fluctuations in the grand canonical ensemble. We provide a general form for the relevant holographic quantities that describes a CFT with a global U(1) symmetry in terms of horizon data and we compute the first thermal fluctuation of the charged Renyi entropy. We demonstrate the validity of the formulae through an analytic example; the Coulomb source in 2 + 1 dimensions. We propose this model to be dual to charged free bosons in 1 + 1 dimensions. The corrections generates a subleading logarithmic divergence in the entanglement entropy which appear in some Condensed Matter systems with spontaneous symmetry breaking due to IR effects in the ground state. We comment on the possibility of interpreting these results in terms of holography beyond the saddle point approximation.

Quark-antiquark confinement and nonlinear electrodynamics

Cornell potential is known to represent the quark-antiquark confinement interaction. In addition to the Cornell potential, there have been other interactions in the literature that demonstrate confining structure in the quark-antiquark system. Guendelman has proposed a nonlinear electrodynamics (NED) model which results in electric potential in the form of Cornell interaction. In this study, we propose two NED models whose electric potential is in the form of two other confining potentials. We also study the coupling of gravity to one of these models which are in the form of a correction to linear Maxwell's theory. We find spacetime which can be a black hole or a naked singular particle. In the zeroth approximation, we examine the circular speed of a distant test particle orbiting the central black hole. The Newtonian potential due to the spacetime at the location of the distant particle possesses an additional term proportional to the NED parameter. Due to the presence of such a term, the speed-radius curve gets improved from the pure Reissner-Nordstrom. It is a kind of weaker confinement acting on distant parts of a galaxy due to a supermassive central black hole.

Inflation driven by non-linear electrodynamics

We investigate the inflation driven by a nonlinear electromagnetic field based on an NLED lagrangian density {mathscr {L}}_{text {nled}} = - {F} f left( {F} right) , where f left( {F}right) is a general function depending on F. We first formulate an f-NLED cosmological model with a more general function f left( {F}right) and show that all NLED models can be expressed in this framework; then, we investigate in detail two interesting examples of the function f left( {F}right) . We present our phenomenological model based on a new Lagrangian for NLED. Solutions to the field equations with the physical properties of the cosmological parameters are obtained. We show that the early Universe had no Big-Bang singularity, which accelerated in the past. We also investigate the qualitative implications of NLED by studying the inflationary parameters, like the slow-roll parameters, spectral index n_s, and tensor-to-scalar ratio r, and compare our results with observational data. Detailed phase-space analysis of our NLED cosmological model is performed with and without matter source. As a first approach, we consider the motion of a particle of unit mass in an effective potential. Our systems correspond to fast-slow systems for physical values of the electromagnetic field and the energy densities at the end of inflation. We analyze a complementary system using Hubble-normalized variables to investigate the cosmological evolution before the matter-dominated Universe.

Probing a non-linear electrodynamics black hole with thin accretion disk, shadow, and deflection angle with M87* and Sgr A* from EHT

Non-linear interaction between the electromagnetic fields (EMF) occurs when vacuum polarization in quantum electrodynamics (QED) happens. The field of non-linear electrodynamics, which may result from this interaction, could have important effects on black hole physics. This paper considers the asymptotically flat black hole solution in Einstein-nonlinear electrodynamics (NLE) fields. We study the effect of the NLE parameters on the black hole deflection angle using the Gauss-Bonnet theorem in weak field limits, shadow cast using the null geodesics method, and thin accretion disk using the Novikov-Thorne model. In particular, we studied the time-averaged energy flux, the disk temperature, the differential luminosity, the different emission profiles, and infalling spherical accretion. Then we show how the physical quantities depend on $\beta$ and $C$ parameters of NLE and provide some constraints on the NLE parameters using the observations of M87* and Sgr A* from EHT.

Novel charged black hole solutions of Born–Infeld type: General properties, Smarr formula and Quasinormal frequencies

We investigate two novel models of charged black holes in the framework of non-linear electrodynamics of Born–Infeld type. In particular, starting from two concrete Lagrangian densities, the corresponding metric potentials, the electric field, the Smarr formula and finally, the (scalar) quasinormal modes are computed for each model. Our findings show that although the models look very similar, their quasinormal spectra are characterized by certain differences.

Dyonic matter equations, exact point-source solutions, and charged black holes in generalized Born-Infeld theory

We derive the equations of motion governing static dyonic matters, described in terms of two real scalar fields, in nonlinear electrodynamics of the Born--Infeld theory type. We then obtain exact finite-energy solutions of these equations in the quadratic and logarithmic nonlinearity cases subject to dyonic point-charge sources and construct dyonically charged black holes with relegated curvature singularities. In the case of quadratic nonlinearity, which is the core model of this work, we show that dyonic solutions enable us to restore electromagnetic symmetry, which is known to be broken in non-dyonic situations by exclusion of monopoles. We further demonstrate that in the context of k-essence cosmology the nonlinear electrodynamics models possess their own distinctive signatures in light of the underlying equations of state of the cosmic fluids they represent. In this context, the quadratic and logarithmic models are shown to resolve a density-pressure inconsistency issue exhibited by the original Born--Infeld model k-essence action function as well as by all of its fractional-powered extensions. Moreover, it is shown that the quadratic model is uniquely positioned to give rise to a radiation-dominated era in the early universe among all the polynomial models and other examples considered.

On heat properties of charged AdS black holes in Gauss-Bonnet gravity coupled with nonlinear electrodynamics

We investigate the heat properties of charged AdS black holes in the Gauss-Bonnet gravity coupled with nonlinear electrodynamics. We consider the thermodynamics of black holes from the perspective of heat capacity and show that the nonlinear electrodynamics can be helpful to improve the thermodynamic stability of black holes. We perform a two-dimensional description in order to reproduce the Hawking temperature, which confirms that the Hawking temperature has an intrinsic topological nature and holds for a higher dimensional spherically symmetric spacetime. We also analyze the Maxwell equal area law and coexistence curve, and find the existence of van der Waals-like phase transitions based on critical exponents. Moreover, we deal with a charged AdS black hole in the Gauss-Bonnet gravity coupled with nonlinear electrodynamics as a working material to study holographic heat engines and obtain an exact expression for the efficiency of a rectangular engine cycle. We then discuss the effects of nonlinear electrodynamics and Gauss-Bonnet couplings on the rectangular engine cycle and compare the efficiency of this cycle with that of the Carnot cycle.