arXiv subjects

S. I. Kruglov

Publications and source records attributed to S. I. Kruglov.

At least 37 records · Page 2Linked to original sources

arXiv2022

AdS black holes in the framework of nonlinear electrodynamics, thermodynamics and Joule--Thomson expansion

Thermodynamics and phase transitions of magnetic Anti-de Sitter black holes are studied. We consider an extended phase space thermodynamics with the cosmological constant being a thermodynamic pressure and the black hole mass is treated as a chemical enthalpy. The extended phase space thermodynamics of black holes mimics the behavior of the Van der Walls 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 is demonstrated that the first law of black hole thermodynamics and the generalized Smarr relation take place. The Joule--Thomson adiabatic expansion of NED-AdS black holes is studied. The dependence of inversion temperature on pressure and the minimum of inversion temperature are found.

physics.gen-ph↗

arXiv2022

Nonlinearly charged AdS black holes, extended phase space thermodynamics and Joule-Thomson expansion

We study thermodynamics and phase transitions of magnetically charged by nonlinear electrodynamics (NED) Anti-de Sitter (AdS) black holes in an extended phase space. The cosmological constant is treated as a thermodynamic pressure whereas the black hole mass is considered such as the chemical enthalpy. The horizon thermodynamics of black holes shows an analogy with the Van der Waals liquid-gas system. We define a quantities which are conjugated to the parameter of NED and a magnetic charge. It is shown that the first law of thermodynamics and the generalized Smarr relation hold. The critical exponents are the same as in the Van der Waals system. The Joule--Thomson adiabatic expansion of NED-AdS black holes is investigated because of thermodynamic behavior of black holes. The Joule--Thomson coefficient, the inversion and isenthalpic curves are discussed. The minimum of inversion temperature and the corresponding event horizon radius are obtained.

physics.gen-ph↗

arXiv2022

Magnetic black holes with generalized ModMax model of nonlinear electrodynamics

Recently Bandos, Lechner, Sorokin, and Townsend [Phys. Rev. D \textbf{102}, 121703 (2020)] proposed Modified Maxwell (ModMax) model of nonlinear duality-invariant conformal electrodynamics. Here, Generalized ModMax (GenModMax) model of nonlinear electrodynamics coupled to general relativity is studied. The metric and mass functions, and their asymptotic as $r\rightarrow\infty$ and $r\rightarrow 0$ of a magnetic black hole are obtained. Corrections to the Reissner--Nordström solution are found and we show that for some model parameters the black hole is regular. The Hawking temperature and heat capacity of black holes are calculated and phase transitions are investigated. We demonstrate that black holes are not stable for certain model parameters.

physics.gen-ph↗

arXiv2021

Born--Infeld-type electrodynamics and magnetic black holes

We investigate a Born--Infeld-type model of nonlinear electrodynamics, possessing three parameters, coupled with general relativity. As a particular case Born--Infeld electrodynamics is reproduced. There is no singularity of the electric field at the centre of point-like charged particles and self-energy of charges is finite in this model. The magnetized black hole is studied and solutions are obtained. We demonstrate that for some parameters of the model the black hole is regular. We find the asymptotic of the metric and mass functions at $r\rightarrow\infty$ and $r\rightarrow 0$, and corrections to the Reissner--Nordström solution. Thermodynamics of black holes is investigated. We calculate the Hawking temperature of black holes and show that black holes are not stable and there are phase transitions in the model under consideration.

gr-qc↗

arXiv2021

On generalized ModMax model of nonlinear electrodynamics

A new generalized ModMax model of nonlinear electrodynamics with four parameters is proposed. The ModMax model and Born--Infeld-type electrodynamics are particular cases of the present model It is shown that a singularity of the electric field at the center of point-like charged particles is absent. We found corrections to Coulomb's law at $r\rightarrow\infty$ and obtain the total electrostatic and magnetic energies of point-like charges. Free electric and magnetic charges and their densities are obtained.

physics.gen-ph↗

arXiv2021

Regular model of magnetized black hole with rational nonlinear electrodynamics

A modified Hayward metric of magnetically charged black hole space-time based on rational nonlinear electrodynamics with the Lagrangian ${\cal L} = -{\cal F}/(1+2β{\cal F})$ is considered. We introduce the fundamental length, characterizing quantum gravity effects. If the fundamental length vanishes the general relativity coupling to rational nonlinear electrodynamics is recovered. We obtain corrections to the Reissner--Nordström solution as the radius approaches infinity. The metric possesses a de Sitter core without singularities as $r\rightarrow 0$. The Hawking temperature and the heat capacity are calculated. It was shown that phase transitions occur and black holes are thermodynamically stable at some event horizon radii. We demonstrate that curvature invariants are bounded and the limiting curvature conjecture takes place.

physics.gen-ph↗

arXiv2021

New model of 4D Einstein--Gauss--Bonnet gravity coupled with nonlinear electrodynamics

New spherically symmetric solution in 4D Einstein--Gauss--Bonnet gravity coupled with nonlinear electrodynamics is obtained. At infinity this solution has the Reissner--Nordström behavior of the charged black hole. The black hole thermodynamics, entropy, shadow, energy emission rate and quasinormal modes of black holes are investigated.

physics.gen-ph↗

arXiv2021

Einstein-Gauss-Bonnet gravity with rational nonlinear electrodynamics

We obtain an exact spherically symmetric and magnetically charged black hole solution in 4D Einstein-Gauss-Bonnet gravity coupled with rational nonlinear electrodynamics. The thermodynamics of our model is studied. We calculate the Hawking temperature and the heat capacity of the black hole. The phase transitions occur in the point where the Hawking temperature possesses an extremum. We show that black holes are thermodynamically stable at some range of event horizon radii when the heat capacity is positive. The logarithmic correction to the Bekenstein-Hawking entropy is obtained.

physics.gen-ph↗

arXiv2021

Einstein-Gauss-Bonnet gravity with nonlinear electrodynamics

We obtain an exact spherically symmetric and magnetically charged black hole solution in 4D Einstein-Gauss-Bonnet gravity coupled with nonlinear electrodynamics with the Lagrangian ${\cal L}_{NED} = -{\cal F}/(1+\sqrt{2\midβ{\cal F}\mid})$ (${\cal F}$ is the field strength invariant). The thermodynamics of the black hole is studied within our model. We calculate the Hawking temperature and the heat capacity of the black hole. The phase transitions occur in the point where the Hawking temperature possesses an extremum and the heat capacity diverges. It was shown that black holes are thermodynamically stable in some range of event horizon radii when the heat capacity and Hawking temperature are positive. The logarithmic correction to the Bekenstein - Hawking BH entropy is obtained which mimics a quantum correction. The dependence of the BH shadow radius on the model parameters is studied. We also investigate the particle emission rate of the BH. The stability of the BH is studied by analysing the quasinormal modes.

gr-qc↗

arXiv2021

Remarks on nonsingular models of Hayward and magnetized black hole with rational nonlinear electrodynamics

A Hayward black hole and magnetically charged black hole based on rational nonlinear electrodynamics with the Lagrangian ${\cal L} = -{\cal F}/(1+2β{\cal F})$ (${\cal F}$ is a field invariant) are considered. It was shown that the metric function in both models possesses a de Sitter core without singularities as $r\rightarrow 0$. The behavior of the Hawking temperature and the heat capacity in these models are similar. The phase transitions take place when the Hawking temperature has a maximum, and black holes are thermodynamically stable at some event horizon radii when the heat capacity is positive. We show that the source of gravity in the Hayward model is questionable.

gr-qc↗

arXiv2020

Inflation of Universe by Nonlinear Electrodynamics

Nonlinear electrodynamics with two dimensional parameters is studied. The range of electromagnetic fields when principles of causality, unitarity and the classical stability hold, are obtained. A singularity of the electric field at the center of charges is absent within our model and there are corrections to the Coulomb law as $r\rightarrow\infty$. The universe inflation takes place in the background of stochastic magnetic fields. The second stage of the universe evolution is the radiation era so that the graceful exit exists. We estimated the spectral index, the tensor-to-scalar ratio, and the running of the spectral index that are in a rough accord with the PLANCK and WMAP data.

gr-qc↗

arXiv2020

Rational nonlinear electrodynamics causes the inflation of the universe

The source of the universe inflation is electromagnetic fields obeying rational nonlinear electrodynamics proposed earlier. Within this model the singularities of the electric field at the center of charges, the Ricci scalar, the Ricci tensor squared and the Kretschmann scalar are absent. We consider the universe which is filled by stochastic magnetic fields. It is demonstrated that the inflation lasts approximately $2$ s with the reasonable e-folding number $N\approx 63$. The Inflation starts from de Sitter spacetime and after the universe inflation end it decelerates approaching the radiation era.

gr-qc↗

arXiv2020

The shadow of M87* black hole within rational nonlinear electrodynamics

We consider rational nonlinear electrodynamics with the Lagrangian ${\cal L} = -{\cal F}/(1+2β{\cal F})$ (${\cal F}=(1/4)F_{μν}F^{μν}$ is the Lorentz-invariant), proposed in [63], coupled to General Relativity. The effective geometry induced by nonlinear electrodynamics corrections are found. We determine shadow's size of regular non-rotating magnetic black holes and compare them with the shadow size of the super-massive M87* black hole imaged by the Event Horizon Telescope collaboration. Assuming that the black hole mass has a pure electromagnetic nature, we obtain the black hole magnetic charge. The size of the shadow obtained is very close to the shadow size of non-regular neutral Schwarzschild black holes. As a result, we can interpret the super-massive M87* black hole as a regular (without singularities) magnetized black hole.

gr-qc↗

arXiv2020

Universe Inflation Based on Nonlinear Electrodynamics

A new model of nonlinear electrodynamics with dimensional parameters $β$ and $γ$ is proposed. The principles of causality and unitarity are studied. We show that a singularity of the electric field at the origin of charges is absent and the maximum of the electric field in the center is $E(0)=1/\sqrtβ$. The dual symmetry is broken in our model. Corrections to the Coulomb law as $r\rightarrow\infty$ are in the order of ${\cal O}(r^{-4})$. The source of the gravitation field and inflation of the universe is electromagnetic fields. It is supposed that the universe is filled by stochastic magnetic fields. We demonstrate that after the universe inflation the universe decelerates approaching the Minkowski spacetime. The singularities of the Ricci scalar, the Ricci tensor squared and the Kretschmann scalar are absent. We calculate the speed of sound. The spectral index, the tensor-to-scalar ratio, and the running of the spectral index, which approximately agree with the PLANK and WMAP data, are evaluated.

gr-qc↗

arXiv2020

Dyonic and magnetized black holes based on nonlinear electrodynamics

We propose a new model of nonlinear electrodynamics with two dimensional parameters. The phenomenon of vacuum birefringence, the principles of causality and unitarity were studied. It was shown that there is no a singularity of the electric field in the center of point-like charges. Corrections to the Coulomb law as $r\rightarrow\infty$ were obtained. Dyonic and magnetized black holes are considered. We show that in the self-dual case, when the electric charge equals the magnetic charge, corrections to Coulomb's law and Reissner$-$Nordström solutions are absent. The metric function and its asymptotic as $r\rightarrow\infty$ for magnetic black holes were evaluated. We calculate the magnetic mass of the black hole which is finite. The thermodynamic properties and thermal stability of black holes were investigated. We calculated the Hawking temperature, the heat capacity and the Helmholtz free energy of black holes and shown that at some parameters there are second-order phase transitions. It was demonstrated that at some range of parameters the black holes are stable.

gr-qc↗

arXiv2019

Dyonic and magnetic black holes with nonlinear arcsin-electrodynamics

Dyonic and magnetic black holes solutions with spherically symmetric configurations in general relativity are obtained. Black holes possessing electric and magnetic charges are studied where the source of the gravitational field is electromagnetic fields obeying the arcsin-electrodynamics. We find corrections to Coulomb's law and Reissner - Nordström solutions. The principles of causality and unitarity are investigated. We obtain the Hawking temperature and it was shown that at some event horizons there are second-order phase transitions.

gr-qc↗

arXiv2019

Dyonic black holes in framework of Born--Infeld-type electrodynamics

Dyonic black hole solutions with spherically symmetric configurations within general relativity are investigated where the source of the gravitational field is Born - Infeld-type electrodynamics. Corrections to Coulomb's law and Reissner - Nordstrom solutions are obtained. From principles of causality and unitarity we find the restriction on electric and magnetic fields. The Hawking temperature and the heat capacity of black holes are obtained. At some event horizons second-order phase transitions take place.

gr-qc↗

arXiv2019

Dyonic black holes with nonlinear logarithmic electrodynamics

A new dyonic solution for black holes with spherically symmetric configurations in general relativity is obtained. We study black holes possessing electric and magnetic charges, and the source of the gravitational field is electromagnetic fields obeying the logarithmic electrodynamics. This particular form of nonlinear electrodynamics is of interest because of its simplicity. Corrections to Coulomb's law and Reissner-Nordstrom solution are found. We calculate the Hawking temperature of black holes and show that second-order phase transitions occur for some parameters of the model.

gr-qc↗