Shadow thermodynamics of AdS black hole with the nonlinear electrodynamics term

We creatively employ the shadow radius to study the thermodynamics of a charged Ad S black hole with a nonlinear electrodynamics(NLED)term.First,the connection between the shadow radius and event horizon is constructed with the aid of the geodesic analysis.It turns out that the black hole shadow radius shows a positive correlation as a function of the event horizon radius.Then in the shadow context,we find that the black hole temperature and heat capacity can be presented by the shadow radius.Further analysis shows that the shadow radius can work similarly to the event horizon in revealing black hole phase transition process.In this sense,we construct the thermal profile of the charged Ad S black hole with inclusion of the NLED effect.In the P<Pc case,it is found that the N-type trend of the temperature given by the shadow radius is always consistent with that obtained by using the event horizon.Thus,we can conclude for the charged Ad S black hole that the phase transition process can be intuitively presented as the thermal profile in the shadow context.Finally,the effects of NLED are carefully analyzed.

Nonlinear electrodynamics coupled to teleparallel theory of gravity

Using nonlinear electrodynamics coupled to teleparallel theory of gravity, regular charged spherically symmetric solutions are obtained. The nonlinear theory is reduced to the Maxwell one in the weak limit and the solutions correspond to charged spacetimes. One of the obtained solutions contains an arbitrary function which we call general solution since we can generate from it the other solutions. The metric associated with these spacetimes is the same, i.e., regular charged static spherically symmetric black hole. In calculating the energy content of the general solution using the gravitational energy momentum within the framework of the teleparallel geometry, we find that the resulting form depends on the arbitrary function. Using the regularized expression of the gravitational energy-momentum we obtain the value of energy.

Thermal properties of regular black hole with electric charge in Einstein gravity coupled to nonlinear electrodynamics

We propose a regular spherically symmetric spacetime solution with three parameters in Einstein gravity coupled to nonlinear electrodynamics(NED), which describes the NED black hole with electric charge. It is found that the system enclosed by the horizon of NED spacetime satisfies the first law of thermodynamics. In order to obtain the NED spacetime with only electric charge, the case of two parameters taking the same value is considered. In this case, we express the mass of the NED spacetime as a function of the entropy and electric charge of the NED black hole, give the Smarr-like formula and the approximate Smarr formula for the mass of NED spacetime.

Black hole shadow in f(R)gravity with nonlinear electrodynamics

By analyzing the propagation of discontinuity in nonlinear electrodynamics,we numerically investigate the related black hole shadows of recently derived rotating black hole solutions in f(R)gravity.In this context,the geodesic motion of the relevant perturbations is governed by an effective geometry,which is closely related to the underlying spacetime metric.We derive the effective geometry,and the latter is used to determine the trajectory of the propagation vector of an arbitrary finite discontinuity in the electrodynamic perturbations,namely,the photon.Subsequently,the image of the black hole is evaluated using the ray-tracing technique.Moreover,we discuss the physical relevance of metric parameters,such as the nonlinear coupling,spin,and charge,by studying their impact on the resultant black hole shadows.

Effect of nonlinear electrodynamics on shadows of slowly rotating black holes

In this study,we investigate the effect of nonlinear electrodynamics on the shadows of charged,slowly rotating black holes with the presence of a cosmological constant.Rather than the null geodesic of the background black hole spacetime,the trajectory of a photon,as a perturbation of the nonlinear electrodynamic field,is governed by an effective metric.The latter can be derived by analyzing the propagation of a discontinuity of the electromagnetic waveform.Subsequently,the image of the black hole and its shadow can be evaluated using the backward raytracing technique.We explore the properties of the resultant black hole shadows of two different scenarios of nonlinear electrodynamics,namely,the logarithmic and exponential forms.In particular,the effects of nonlinear electrodynamics on the optical image are investigated,as well as the image s dependence on other metric parameters,such as the black hole spin and charge.The resulting black hole image and shadow display rich features that potentially lead to observational implic ations.

Critical behaviors of a(2+1)-dimensional black hole with a nonlinear electrodynamics source

On the basis of a charged BTZ black hole,we add an extra term in the metric function to describe the contribution from nonlinear electrodynamics.In this way we artificially construct a(2+1)-dimensional black hole in general relativity coupled with a nonlinear electrodynamics source.The thermodynamic quantities and Smarr formula are derived.It is found that this black hole has T-S criticality like that of an RN-Ad S black hole.Further modifying the metric function,we obtain a(2+1)-dimensional black hole possessing P-V critical behaviors similar to that of van der Waals fluid.To our knowledge,this is the first example of(2+1)-dimensional black holes having this kind of critical behavior.

Features of Operation of Bifilar Cooper and Tesla Coils in Pulse Regime

The characteristic features of operation in a pulsed regime of bifilar Cooper and Tesla coils during magnetic pulse processing and heating of the environment are considered using the dependence of the maximum amplitude at the leading edge of the magnetic pulse on its time duration τ. The spatial distribution of the magnetic induction lines B inside and around the Cooper coil is given, where, unlike the Tesla coil, the maximum values of B arise in the extreme planes of the coil, and its central plane is zero. The defining advantages of new methods of magnetic pulse processing and heating of the environment are considered: the dependence at τ → 0;the exchange of energy between the magnetic pulse and the environment;periodic sequence of series of unipolar magnetic pulses at various processing modes. It is shown that 1) for electric fields Eout = 1010 – 1012V/m, arising at the leading edge of a magnetic pulse with duration 10-5 – 10-7 s, in the deformation fractal space the electrodynamics of these fields is nonlinear;2) inside the Tesla coil, in the package of conducting tapes and tubes, the pumping energy from the pulsed field Eout is mainly dissipated in the skin layer in the form of refractory coatings and heats the environment at all stages of plastic deformation of workpieces and heating elements up to the collapse of unstable microcracks. The coefficient of conversion of the pump energy in the pulsed regime with respect to the constant current regime is found.

Electron-positron pair production in ultrastrong laser fields

Electronepositron pair production due to the decay of vacuum in ultrastrong laser fields is an interesting topic which is revived recently because of the rapid development of current laser technology.The theoretical and numerical research progress of this challenging topic is reviewed.Many new findings are presented by different approaches such as the worldline instantons,the S-matrix theory,the kinetic method by solving the quantum Vlasov equation or/and the real-time DiraceHeisenbergeWigner formalism,the computational quantum field theory by solving the Dirac equation and so on.In particular,the effects of electric field polarizations on pair production are unveiled with different patterns of created momentum spectra.The effects of polarizations on the number density of created particles and the nonperturbative signatures of multiphoton process are also presented.The competitive interplay between the multiphoton process and nonperturbation process plays a key role in these new findings.These newly discovered phenomena are valuable to deepen the understanding of pair production in complex fields and even have an implication to the study of strong-field ionization.More recent studies on the pair production in complex fields as well as beyond laser fields are briefly presented in the view point of perspective future.

Laser Compton scattering for a linearly polarized laser

Laser Compton light sources are potential candidates for the next generation of high-brightness X or γ-ray sources. When increasing the laser power to obtain intense X-ray laser, nonlinear Compton scattering happens. Nonlinear Compton scattering of linearly polarized laser beam is discussed in this paper. A complete transition probability formula is introduced and the polarization properties of final photons are discussed for different conditions.