Framework Of Nonlinear Electrodynamics Research Articles

Black bounces, wormholes, and partly phantom scalar fields

Simpson and Visser recently proposed a phenomenological way to avoid some kinds of space-time singularities by replacing a parameter whose zero value corresponds to a singularity (say, $r$) with the manifestly nonzero expression $r(u) = \sqrt{u^2 + b^2}$, where $u$ is a new coordinate, and $b =$ \const $>0$. This trick, generically leading to a regular minimum of $r$ beyond a black hole horizon (called a "black bounce"), may hopefully mimic some expected results of quantum gravity, and was previously applied to regularize the Schwarzschild, Reissner-Nordstr\"om, Kerr and some other metrics. In this paper it is applied to regularize the Fisher solution with a massless canonical scalar field in general relativity (resulting in a traversable wormhole) and a family of static, spherically symmetric dilatonic black holes (resulting in regular black holes and wormholes). These new regular metrics represent exact solutions of general relativity with a sum of stress-energy tensors of a scalar field with a nonzero self-interaction potential and a magnetic field in the framework of nonlinear electrodynamics with a Lagrangian function $L(F)$, $F = F_{\mu\nu} F^{\mu\nu}$. A novel feature in the present study is that the scalar fields involved have "trapped ghost" properties, that is, are phantom in a strong-field region and canonical outside it, with a smooth transition between the regions. It is also shown that any static, spherically symmetric metric can be obtained as an exact solution to the Einstein equations with the stress-energy tensor of the above field combination.

AdS Black Holes in the Framework of Nonlinear Electrodynamics, Thermodynamics, and Joule–Thomson Expansion

The thermodynamics and phase transitions of magnetic Anti-de Sitter black holes were studied. We considered extended-phase-space thermodynamics, with the cosmological constant being a thermodynamic pressure and the black hole mass being treated as a chemical enthalpy. The extended-phase-space thermodynamics of black holes mimic the behavior of a Van der Waals liquid. Quantities conjugated to the coupling of nonlinear electrodynamics (NED) and a magnetic charge are obtained. Thermodynamic critical points of phase transitions are investigated. It was demonstrated that the first law of black hole thermodynamics and the generalized Smarr relation hold. The Joule–Thomson adiabatic expansion of NED-AdS black holes is studied. The dependence of inversion temperature on pressure and the minimum of the inversion temperature are found.

Field sources for Simpson-Visser spacetimes

Simpson-Visser (SV) space-times are the simplest globally regular modifications of the Schwarzschild, Reissner-Nordstrom and other blak-hole solutions of general relativity. They smoothly interpolate between these black holes and traversable wormholes. After a brief presentation of the Schwarzschild-like and Reissner-Nordstrom-like SV geometries, including their Carter-Penrose diagrams, we show that any static, spherically symmetric SV metric can be obtained as an exact solution to the Einstein field equations sourced by a combination of a minimally coupled phantom scalar field with a nonzero potential $V(\phi)$ and a magnetic field in the framework of nonlinear electrodynamics with the Lagrangian $\mathcal {L(F)}$, $\mathcal{F} = F_{\mu\nu} F^{\mu\nu}$ (in standard notations). Explicit forms of $V(\phi)$ and $\mathcal {L(F)}$ are presented for the cases of Schwarzschild-like and Reissner-Nordstrom-like SV metrics.

Magnetic Pole as Produced by a Point-like Electric Charge Embedded in Constant-Field Background

We consider a linear magnetic response to a point electric charge embedded in the background of parallel constant electric and magnetic fields in the framework of nonlinear electrodynamics. We find two types of responses. One is given by a vector potential free of any string singularity. The corresponding magnetic field may be thought of as two magnetic poles of opposite polarity coexisting at one point. The other response is given by a vector potential singular on a half-axis directed along the background fields. Its magnetic field is a magnetic monopole plus a field confined to an infinitely thin solenoid, whose role is the same as that of the Dirac string. The value of the magnetic charge is determined by the electric charge and the background fields and is expressed in terms of derivatives of the nonlinear local Lagrangian. Once the potential is singular, the nonlinear Maxwell equations written for potentials and field intensities are not equivalent. We argue why the preference should be given to potentials.

Non-Singular Model of Magnetized Black Hole Based on Nonlinear Electrodynamics

A new modified Hayward metric of magnetically charged non-singular black hole spacetime in the framework of nonlinear electrodynamics is constructed. When the fundamental length introduced, characterising quantum gravity effects, vanishes, one comes to the general relativity coupled with the Bronnikov model of nonlinear electrodynamics. The metric can have one (an extreme) horizon, two horizons of black holes, or no horizons corresponding to the particle-like solution. Corrections to the Reissner–Nordström solution are found as the radius approaches infinity. As r → 0 the metric has a de Sitter core showing the absence of singularities, the asymptotic of the Ricci and Kretschmann scalars are obtained and they are finite everywhere. The thermodynamics of black holes, by calculating the Hawking temperature and the heat capacity, is studied. It is demonstrated that phase transitions take place when the Hawking temperature possesses the maximum. Black holes are thermodynamically stable at some range of parameters.

Asymptotic magnetically charged non-singular black hole and its thermodynamics

Some very interesting solutions of the field equations of Einstein's general theory of relativity have been constructed in the framework of nonlinear electrodynamics. In particular, magnetically charged black hole solutions in the framework of exponential nonlinear electrodynamics have been obtained in general relativity in Kruglov (2017) [13]. Using this approach a magnetically charged non-singular black hole spacetime in the framework of exponential electrodynamics in some modified theory of gravity has been constructed in this letter. The metric describing asymptotic non-singular magnetized black hole is worked out in terms of the parameter of our model. When this parameter vanishes our solution reduces to the above mentioned black hole solution. Thermodynamics of the resulting solution is also discussed by calculating the Hawking temperature and heat capacity when the magnetic charge is constant. We also find out the point where the first order phase transition induced by temperature changes takes place. The quantum radiations from this black hole are also discussed and the mathematical expression for the rate of energy flux of these radiations has been obtained.

Accelerating cosmologies with nonlinear electrodynamics

In this paper, we consider the framework of nonlinear electrodynamics in locally rotationally symmetric (LRS) Bianchi-I universe model composed of magnetic fluid. It has been shown that an accelerated universe expansion takes place if the nonlinear electromagnetic field is a source of gravitational field. In this model, after the big bang, the universe undergoes inflation and the accelerated expansion, dissipates the initial anisotropy of the curvature part without using a selected initial condition. Further validity of generalised second law of thermodynamics in the cosmological model enclosed by apparent horizon is investigated. We also discuss the classical stability of the cosmological model and observational viability of the model.

Erratum: Limits on nonlinear electrodynamics [Phys. Rev. D 93 , 093020 (2016)

In this paper we set a framework in which experiments whose goal is to test QED predictions can be used in a more general way to test non-linear electrodynamics (NLED) which contains low-energy QED as a special case. We review some of these experiments and we establish limits on the different free parameters by generalizing QED predictions in the framework of NLED. We finally discuss the implications of these limits on bound systems and isolated charged particles for which QED has been widely and successfully tested.

Remarks on Heisenberg–Euler-type electrodynamics

We consider Heisenberg–Euler-type model of nonlinear electrodynamics with two parameters. Heisenberg–Euler electrodynamics is a particular case of this model. Corrections to Coulomb’s law at [Formula: see text] are obtained and energy conditions are studied. The total electrostatic energy of charged particles is finite. The charged black hole solution in the framework of nonlinear electrodynamics is investigated. We find the asymptotic of the metric and mass functions at [Formula: see text]. Corrections to the Reissner–Nordström solution are obtained.

Thermodynamics of anisotropic emergent universe in nonlinear electrodynamics

In this paper, we study the emergent universe (EU) with interacting fluids in the background of Bianchi type I (BI) universe model. For this purpose, we consider polytropic equation of state (EoS) which constitutes three non-interacting fluids. In order to check the viability of the cosmological models, we take a two-fluid model interacting with dust fluid and a three-fluid model in which each fluid has nonlinear EoS interacting at [Formula: see text]. It turns out that both models are realistic cosmological viable. We also check the validity of the generalized second law of thermodynamics (GSLT) for EU with interacting fluids. Finally, we study its validity in the framework of nonlinear electrodynamics (NLED) on apparent horizon.

Limits on nonlinear electrodynamics

In this paper we set a framework in which experiments whose goal is to test QED predictions can be used in a more general way to test nonlinear electrodynamics (NLED) which contains low-energy QED as a special case. We review some of these experiments and we establish limits on the different free parameters by generalizing QED predictions in the framework of NLED. We finally discuss the implications of these limits on bound systems and isolated charged particles for which QED has been widely and successfully tested.

Thermodynamics with Interacting Dark Energy in Magnetic Universe

In this paper, we investigate the validity of generalized second law of thermodynamics for FRW universe in the framework of non-linear electrodynamics. We assume that the universe is composed of dark matter, magnetic field and some unknown dark energy component with two different interacting terms \(Q\) and \(\tilde{Q}\). It is found that the energy transfer from dark energy to magnetic field depends upon the sign of interacting terms. For \(Q\) \(\tilde{Q}\). In this scenario, we calculate energy densities of dark matter and other dark energy fluid. We check the validity of generalized second law of thermodynamics bounded by Hubble, apparent, particle and event horizons. It turns out that this law always holds on the Hubble and apparent horizons but fails on the particle and event horizons for both interacting and non-interacting cases.

Thermodynamics in non-linear electrodynamics with anisotropic universe

In this work, we consider the framework of non-linear electrodynamics in Bianchi type I universe model composed of matter and electromagnetic field. We deal with electric and magnetic universe separately. In this scenario, we calculate the electric and magnetic fields and their corresponding matter densities using two particular types of interaction terms. We also check the validity of generalized second law of thermodynamics in both universe models enclosed by apparent horizon. It turns out that this law holds on the apparent horizon for a particular range depending upon the parameters. Finally, we discuss the deceleration and statefinder parameters to check the viability of these models.

Self-Interacting Electromagnetic Fields and a Classical Discussion on the Stability of the Electric Charge

The present work proposes a discussion on the self-energy of charged particles in the framework of nonlinear electrodynamics. We seek magnetically stable solutions generated by purely electric charges whose electric and magnetic fields are computed as solutions to the Born-Infeld equations. The approach yields rich internal structures that can be described in terms of the physical fields with explicit analytic solutions. This suggests that the anomalous field probably originates from a magnetic excitation in the vacuum due to the presence of the very intense electric field. In addition, the magnetic contribution has been found to exert a negative pressure on the charge. This, in turn, balances the electric repulsion, in such a way that the self-interaction of the field appears as a simple and natural classical mechanism that is able to account for the stability of the electron charge.

Pulse interaction in nonlinear vacuum electrodynamics

The energy-momentum conservation law is used to investigate the interaction of pulses in the framework of nonlinear electrodynamics with Lorentz-invariant constitutive relations. It is shown that for the pulses of the arbitrary shape, the interaction results in phase shift only.

Scharnhorst effect at oblique incidence

We consider the Scharnhorst effect (anomalous photon propagation in the Casimir vacuum) at oblique incidence, calculating both photon speed and polarization states as functions of angle. The analysis is performed in the framework of nonlinear electrodynamics and we show that many features of the situation can be extracted solely on the basis of symmetry considerations. Although birefringence is common in nonlinear electrodynamics it is not universal; in particular we verify that the Casimir vacuum is not birefringent at any incidence angle. On the other hand, group velocity is typically not equal to phase velocity, though the distinction vanishes for special directions or if one is only working to second order in the fine structure constant. We obtain an ``effective metric'' that is subtly different from previous results. The disagreement is due to the way that ``polarization sums'' are implemented in the extant literature, and we demonstrate that a fully consistent polarization sum must be implemented via a bootstrap procedure using the effective metric one is attempting to define. Furthermore, in the case of birefringence, we show that the polarization sum technique is intrinsically an approximation.