Maxwell Field Research Articles

The generalized first law for more general matter

In previous work, a first law of generalized entropy was derived from semiclassical gravitational dynamics around thermal setups using an assumed relation between the matter modular Hamiltonian and the gravitational stress tensor. Allowing for non-minimal coupling between curvature and any tensor matter fields, we show however, that the modular Hamiltonian of thermal states is given by the integrated bulk Noether current associated to time translation plus a spacetime boundary term. One generally cannot express this in terms of gravitational stress tensor components. Still, working with the correct expression for the modular Hamiltonian, we are able to recover a first law of generalized entropy, with added benefits over the previous result. Firstly, any Wald-Dong contributions to generalized entropy resulting from non-minimal coupling between matter and curvature are included. Secondly, in gravitational equations of motion, we allow for a non-vanishing stress tensor expectation value in the unperturbed background and state, and account for background field perturbations as part of its variation. Finally, the quantum matter is allowed to contribute nontrivially to asymptotic energy, e.g. as is necessary, even for a minimally coupled Maxwell field, to recover the expected thermodynamic first law of charged black holes.

Infraparticle quantum fields and the formation of photon clouds

A non-perturbative and exactly solvable quantum field theoretical model for a “dressed Dirac field” is presented, that exhibits all the kinematical features of QED: an appropriate delocalization of the charged field as a prerequisite for the global Gauss Law, superselected photon clouds (asymptotic expectation values of the Maxwell field), infraparticle nature of charged particles that cannot be separated from their photon clouds, broken Lorentz symmetry. The model serves as an intermediate leg on a new roadmap towards full QED, formulated as an off-shell theory, i.e., including a perturbative construction of its interacting charged fields. It also fills a gap in recent discussions of the “Infrared Triangle”, and points the way towards a new scattering theory for theories with massless particles of helicity ≥ 1, in which infraparticles can be described at the level of charged fields, rather than just states.

A systematic approach to find solutions of the Einstein–Maxwell field equations for static spherically symmetric spacetimes using Segre classification

In the literature, several spherically symmetric static solutions of the Einstein–Maxwell field equations (EMFEs) have been obtained by taking assumptions/ansatz on the parameters involved, like electric field intensity, gravitational potential, equation of state, etc. In this paper, using the Segre classification, we present a systematic scheme that limits the number of assumptions/ansatz required to be taken. It is found that the static spherically symmetric solutions of the EMFEs can only be of Segre types [Formula: see text], [Formula: see text], [Formula: see text], or [Formula: see text]. It is also shown that the type [Formula: see text] leads to the Schwarzschild de-Sitter/anti de-Sitter solutions.

Charged rotating black strings in Einsteinian cubic gravity

We construct, for the first time, charged rotating black string solutions in four-dimensional Einsteinian cubic gravity, which are asymptotically anti de Sitter. By assuming that the solutions are completely regular at the horizon and studying their near-horizon behavior, we find some thermodynamic properties, which can be accessed analytically. We compute independently the Hawking temperature, the Wald entropy, the mass, the angular momentum, the charge, and the electrostatic potential of the solutions, analytically. Using these, we show that the first law of thermodynamics for rotating black strings is exactly satisfied in both charged and uncharged cases. We also observe that, in the absence of Maxwell field, some of the solutions have positive specific heat, which makes them thermodynamically stable.

All solutions of Einstein-Maxwell equations with a cosmological constant in 2+1 dimensions

We present a general solution of the coupled Einstein-Maxwell field equations (without the source charges and currents) in three spacetime dimensions. We also admit any value of the cosmological constant. The whole family of such $\mathrm{\ensuremath{\Lambda}}$-electrovacuum local solutions splits into two distinct subclasses, namely the nonexpanding Kundt class and the expanding Robinson-Trautman class. While the Kundt class only admits electromagnetic fields which are aligned along the geometrically privileged null congruence, the Robinson-Trautman class admits both aligned and also more complex nonaligned Maxwell fields. We derive all the metric and Maxwell field components, together with explicit constraints imposed by the field equations. We also identify the most important special spacetimes of this type, namely the coupled gravitational-electromagnetic waves and charged black holes.

Quasiperiodic oscillations, quasinormal modes and shadows of Bardeen–Kiselev Black Holes

In this article, we study the particle dynamics around a static and spherically symmetric Bardeen-Kiselev black hole (BK BH) which is a solution of the Einstein-non-linear Maxwell field equations along with a quintessential field. We discuss its essential geometrical properties such as scalar invariants and size of innermost stable circular orbits. Dynamics of test particles around the BH is also studied. Moreover, we also computed the fundamental frequencies of a test particle orbiting the BH in a slightly perturbed orbit. Further, the degeneracy relations between the spin of rotating Kerr BH and magnetic charge of the BK BH at the values of the quintessential parameter $\omega_q=-1/3$ and in terms of the same values of innermost stable circular orbits (ISCOs) radius, energy efficiency, twin-peaks quasiperiodic oscillations (QPOs) frequencies and impact parameter for photon are also discussed in detail. Finally, we have investigated the relationship between the shadow radius and the real part of the quasinormal mode (QNM) frequency.

Emission distribution for the quantas of Maxwell–Chern–Simons gauge field coupled to external current

In this paper, we have investigated the nature of emission distribution of the Maxwell–Chern–Simons (MCS) theory in [Formula: see text] dimensions. The distribution of the topologically massive quanta seems to be Poissionian in nature just like the Maxwell field theory in [Formula: see text] dimensions but with a condition, without which the distribution takes an indeterminate form when we make the coupling term approach 0.

Kerr-Schild-Kundt metrics in generic Einstein-Maxwell theories

We study Kerr-Schild-Kundt class of metrics in generic gravity theories with Maxwell's field. We prove that these metrics linearize and simplify the field equations of generic gravity theories with Maxwell's field.

Dynamical scalarization in Einstein-Maxwell-dilaton theory

We study the process of fully nonlinear dynamical scalarization starting from a charged black hole or a naked singularity in asymptotically flat spacetime in the Einstein-Maxwell-dilaton theory. Initially the dilaton field is negligible compared to the gravitational and the Maxwell field. Then the dilaton field experiences an immediate growth, later it oscillates with damping amplitude and finally settles down to a finite value. For a hairy black hole develops from an original Reissner-Nordstr\"om black hole, since the dilaton oscillation and decay are almost independent of the coupling parameter, unlike the Anti-de Sitter spacetime it is not easy to distinguish the resulting hairy black hole from the original asymptotically flat charged hole. For a hairy black hole evolves from an original naked singularity, the resulting hairy black hole has rich structures. In the scalarization process, the naked singularity is soon enveloped by one outer horizon, then another horizon is developed and in the end a stable hairy black hole forms and two horizons degenerate into one to protect the singularity. The hairy black hole mass saturates exponentially in the scalarization.

The influence of Power-Maxwell field on holographic paramagnetism model

With the numerical method, we research the properties of the holographic paramagnetism/ferromagnetism phase transition for the Power - Maxwell field in the background of a Schwarzschild-AdS black hole. When there is no external magnetic field, we work out the values of the critical temperature and the magnetic moment with the different power parameter q for the Power - Maxwell field. It can be seen that the larger power parameter q reduces the critical temperature and makes it harder for the magnetic moment to be formed. What is more, in the presence of an external magnetic field, we get the values of the magnetic susceptibility density with the different q, which satisfies the Cure-Weiss law. When the external magnetic field changes, the hysteresis loop appears for different q.

On the study of complexity for charged self-gravitating systems

In modified Gauss–Bonnet gravity, this paper investigates the complexity factor for static anisotropic self-gravitating fluid which is influenced by an electric charge. For the self-gravitating system, we evaluate the Maxwell field equations, the Tolman–Oppenheimer–Volkoff equation and the mass function. We formulate the structure scalars by an orthogonal splitting of the Riemann tensor for the self-gravitating system and identify one of these scalars as the complexity factor. Then with the help of two different models, we observe the corresponding complexity factor involved in the subsequent changes of static spheres. The structure scalars and complexity factor are found to be dependent on the components of the effective part as well as electromagnetic part.

Evolution of anti–de Sitter black holes in Einstein-Maxwell-dilaton theory

We study the nonlinear evolution of the spherical symmetric black holes under a small neutral scalar field perturbation in Einstein-Maxwell-dilaton theory with coupling function $f(\phi)=e^{-b\phi}$ in asymptotic anti-de Sitter spacetime. The non-minimal coupling between scalar and Maxwell fields allows the transmission of the energy from the Maxwell field to the scalar field, but also behaves as a repulsive force for the scalar. The scalar field oscillates with damping amplitude and converges to a final value by a power law. The irreducible mass of the black hole increases abruptly at initial times and then saturates to the final value exponentially. The saturating rate is twice the decaying rate of the dominant mode of the scalar. The effects of the black hole charge, the cosmological constant and the coupling parameter on the evolution are studied in detail. When the initial configuration is a naked singularity spacetime with a large charge to mass ratio, a horizon will form soon and hide the singularity.

Unification of massless field equations solutions for any spin

A unification in terms of exact solutions for massless Klein-Gordon, Dirac, Maxwell, Rarita-Schwinger, Einstein, and bosonic and fermionic fields of any spin is presented. The method is based on writing all of the relevant dynamical fields in terms of products and derivatives of pre-potential functions, which satisfy the d'Alembert equation. The coupled equations satisfied by the pre-potentials are non-linear. Remarkably, there are particular solutions of (gradient) orthogonal pre-potentials that satisfy the usual wave equation which may be used to construct exact non-trivial solutions to Klein-Gordon, Dirac, Maxwell, Rarita-Schwinger, (linearized and full) Einstein and any spin bosonic and fermionic field equations, thus giving rise to a unification of the solutions of all massless field equations for any spin. Some solutions written in terms of orthogonal pre-potentials are presented. Relations of this method to previously developed ones, as well as to other subjects in physics are pointed out.

Dynamical effective field model for interacting ferrofluids: I. Derivations for homogeneous, inhomogeneous, and polydisperse cases

Quite recently I have proposed a nonperturbative dynamical effective field model (DEFM) to quantitatively describe the dynamics of interacting ferrofluids. Its predictions compare very well with the results from Brownian dynamics simulations. In this paper I put the DEFM on firm theoretical ground by deriving it within the framework of dynamical density functional theory, taking into account nonadiabatic effects. The DEFM is generalized to inhomogeneous finite-size samples for which the macroscopic and mesoscopic scale separation is nontrivial due to the presence of long-range dipole–dipole interactions. The demagnetizing field naturally emerges from microscopic considerations and is consistently accounted for. The resulting mesoscopic dynamics only involves macroscopically local quantities such as local magnetization and Maxwell field. Nevertheless, the local demagnetizing field essentially couples to magnetization at distant macroscopic locations. Thus, a two-scale parallel algorithm, involving information transfer between different macroscopic locations, can be applied to fully solve the dynamics in an inhomogeneous sample. I also derive the DEFM for polydisperse ferrofluids, in which different species can be strongly coupled to each other dynamically. I discuss the underlying assumptions in obtaining a thermodynamically consistent polydisperse magnetization relaxation equation, which is of the same generic form as that for monodisperse ferrofluids. The theoretical advances presented in this paper are important for both qualitative understanding and quantitative modeling of the dynamics of ferrofluids and other dipolar systems.

Plane fronted limit of spherical electromagnetic and gravitational waves

We demonstrate how plane fronted waves with colliding wave fronts are the asymptotic limit of spherical electromagnetic and gravitational waves. In the case of the electromagnetic waves we utilize Bateman's representation of radiative solutions of Maxwell's vacuum field equations. The gravitational case involves a novel form of the radiative Robinson--Trautman solutions of Einstein's vacuum field equations.

Blázquez-Salcedo–Knoll–Radu wormholes are not solutions to the Einstein-Dirac-Maxwell equations

Recently, Bl\'azquez-Salcedo, Knoll, and Radu (BSKR) have given a class of static, spherically symmetric, traversable wormhole spacetimes with Dirac and Maxwell fields. The BSKR wormholes are obtained by joining a classical solution to the Einstein-Dirac-Maxwell (EDM) equations on the "up" side of the wormhole ($r \geq 0$) to a corresponding solution on the "down" side of the wormhole ($r \leq 0$). However, it can be seen that the BSKR metric fails to be $C^3$ on the wormhole throat at $r=0$. We prove that if the matching were done in such a way that the resulting spacetime metric, Dirac field, and Maxwell field composed a solution to the EDM equations in a neighborhood of $r=0$, then all of the fields would be smooth at $r=0$ in a suitable gauge. Thus, the BSKR wormholes cannot be solutions to the EDM equations. The failure of the BSKR wormholes to solve the EDM equations arises both from the failure of the Maxwell field to satisfy the required matching conditions (which implies the presence of an additional shell of charged matter at $r=0$) and, more significantly, from the failure of the Dirac field to satisfy required matching conditions (which implies the presence of a spurious source term for the Dirac field at $r=0$.

Maxwell-scalar device based on the electric dipole

In this work we study the electric field of a dipole immersed in a medium with permittivity controlled by a real scalar field which is non-minimally coupled to the Maxwell field. We model the system with an interesting function, which allows the presence of exact solutions, describing the possibility of the permittivity to encapsulate the charges at very high values, giving rise to an effect that is not present in the standard situation. The results are of direct interest to applications for emission and absorption of radiation, and may motivate new studies concerning binary stars and black holes in gravity scenarios of current interest.

Analysis of specific absorption rate and heat transfer in human head due to mobile phones

The human body absorbs a particular proportion of radiation when introduced to an electromagnetic field. The proportion of radio repeat energy burned-through in a unit mass of a human body when introduced to a radio frequency electromagnetic field is known as the Specific Absorption Rate and is alluded to as SAR. The position and bearing of the human body concerning the wellspring of the radiation impact the SAR regard. The sort of wellspring of the RF energy moreover impacts the SAR regard. This paper-based on how Mobile phones and there are arranged while simultaneously using them contribute and impact the value of SAR. Moreover, it is seen that SAR contributed by mobile phones is higher than other RF sources like Bluetooth and Wi-Fi Devices. This is a result of the way that the yield power transmitted by cells is higher than Bluetooth and Wi-Fi contraptions. As SAR is the proportion of electromagnetic power held over a specific volume of tissue, it is directly comparative with the strength of the electromagnetic field. Consequently, cells have higher Specific Absorption Rates when diverged from Bluetooth and Wi-Fi devices. SAR spatially shows up at the midpoint of over 1 g or 10 g of human tissue. Maxwell's field conditions in time–space are used to register the SAR movement in the human head. Charged particles gain energy and falter when electromagnetic radiation is the event on the issue. The energy gained could either be immediately reradiated and appear as scattered, reflected, or sent radiation or it may get into minuscule developments inside the matter, accomplishing warm concordance and setting out a decent establishment for itself as atomic power in the material. Temperature assessed over 1 g of tissue is higher when appeared differently in relation to 10 g volume of tissue. Muscle and blood have the temperature rise lower than the skin on account of skin significance. It is seen that when the significance of invasion grows SAR reduction and thusly temperature lessens.

Slowly rotating black holes in the novel Einstein\u2013Maxwell-scalar theory

We investigate a slowly rotating black hole solution in a novel Einstein–Maxwell-scalar theory, which is prompted by the classification of general Einstein–Maxwell-scalar theory. The gyromagnetic ratio of this black hole is calculated, and it increases as the second free parameter beta increases, but decreases with the increasing parameter gamma equiv frac{2 alpha ^{2}}{1+alpha ^2}. In the Einstein–Maxwell-dilaton (EMD) theory, the parameter beta vanishes but the free parameter alpha governing the strength of the coupling between the dilaton and the Maxwell field remains. The gyromagnetic ratio is always less than 2, the well-known value for a Kerr–Newman (KN) black hole as well as for a Dirac electron. Scalar hairs reduce the magnetic dipole moment in dilaton theory, resulting in a drop in the gyromagnetic ratio. However, we find that the gyromagnetic ratio of two can be realized in this Einstein–Maxwell-scalar theory by increasing beta and the charge-to-mass ratio Q/M simultaneously (recall that the gyromagnetic ratio of KN black holes is independent of Q/M). The same situation also applies to the angular velocity of a locally non-rotating observer. Moreover, we analyze the period correction for circular orbits in terms of charge-to-mass ratio, as well as the correction of the radius of the innermost stable circular orbits. It is found the correction increases with beta but decreases with Q/M. Finally, the total radiative efficiency is investigated, and it can vanish once the effect of rotation is considered.

Maxwell perturbations in a cavity with Robin boundary conditions: two branches of modes with spectrum bifurcation on Schwarzschild black holes

We perform a systematic study of the Maxwell quasinormal spectrum in a mirror-like cavity following the generic Robin type vanishing energy flux principle, by starting with the Schwarzschild black holes in this paper. It is shown that, for black holes in a cavity, the vanishing energy flux principle leads to two different sets of boundary conditions. By solving the Maxwell equations with these two boundary conditions both analytically and numerically, we observe two distinct sets of modes. This indicates that the vanishing energy flux principle may be applied not only to asymptotically anti-de Sitter (AdS) black holes but also to black holes in a cavity. In the analytic calculations, the imaginary part of the Maxwell quasinormal modes are derived analytically for both boundary conditions, which match well with the numeric results. While in the numeric calculations, we complete a thorough study on the two sets of the Maxwell spectrum by varying the mirror radius r_m, the angular momentum quantum number ell , and the overtone number N. In particular, we proclaim that the Maxwell spectrum may bifurcate for both modes when the mirror is placed around the black hole event horizon, which is analogous to the spectrum bifurcation effects found for the Maxwell fields on asymptotically AdS black holes. This observation provides another example to exhibit the similarity between black holes in a cavity and the AdS black holes.