arXiv subjects

S. I. Kruglov

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

At least 73 records · Page 4Linked to original sources

arXiv2016

Nonlinear Electromagnetic Fields As a Source of Universe Acceleration

A model of nonlinear electromagnetic fields with a dimensional parameter $β$ is proposed. From PVLAS experiment the bound on the parameter $β$ was obtained. Electromagnetic fields are coupled with the gravitation field and we show that the universe accelerates due to nonlinear electromagnetic fields. The magnetic universe is considered and the stochastic magnetic field is a background. After inflation the universe decelerates and approaches to the radiation era. The range of the scale factor, when the causality of the model and a classical stability take place, was obtained. The spectral index, the tensor-to-scalar ratio, and the running of the spectral index were estimated which are in approximate agreement with the PLANCK, WMAP, and BICEP2 data.

gr-qc↗

arXiv2016

Acceleration of Universe by Nonlinear Electromagnetic Fields

A new model of nonlinear electromagnetic fields possessing a dimensional parameter $β$ is proposed. Electromagnetic fields are considered as the source of the gravitation field and accelerated expansion of the universe is driven by nonlinear electromagnetic fields. We consider the magnetic universe and the stochastic magnetic field is a source of the universe acceleration. After the universe inflation and the accelerated expansion the universe decelerates. We show the causality of the model and a classical stability at the deceleration phase. The spectral index, the tensor-to-scalar ratio, and the running of the spectral index were estimated that approximately fulfil the PLANK, WMAP, and BICEP2 data.

gr-qc↗

arXiv2016

Universe acceleration and nonlinear electrodynamics

A new model of nonlinear electrodynamics with a dimensional parameter $β$ coupled to gravity is considered. We show that an accelerated expansion of the universe takes place if the nonlinear electromagnetic field is the source of the gravitational field. A pure magnetic universe is investigated and the magnetic field drives the universe to accelerate. In this model, after the big bang, the universe undergoes inflation, and the accelerated expansion and then decelerates approaching Minkowski spacetime asymptotically. We demonstrate the causality of the model and a classical stability at the deceleration phase.

gr-qc↗

arXiv2016

Notes on Born-Infeld-like modified gravity

We investigate the modified $F(R)$ gravity theory with the function $F(R) = (1-\sqrt{1-2λR-σ(λR)^2})/λ$. The action is converted into Einstein$-$Hilbert action at small values of $λ$ and $σ$. The local tests give a bound on the parameters, $λ(1+σ)\leq 2\times 10^{-6}$ cm$^2$. The Jordan and Einstein frames are considered, the potential, and the mass of the scalar field were obtained. The constant curvature solutions of the model are found. It was demonstrated that the de Sitter space is unstable but a solution with zero Ricci scalar is stable. The cosmological parameters of the model are evaluated. Critical points of autonomous equations are obtained and described.

gr-qc↗

arXiv2015

A new $F(R)$-gravity model

We propose a new model of modified $F(R)$ gravity theory with the function $F(R) = (1/β) \arcsin(βR)$. Constant curvature solutions corresponding to the flat and de Sitter spacetime are obtained. The Jordan and Einstein frames are considered; the potential and the mass of the scalar degree of freedom are found. We show that the flat spacetime is stable and the de Sitter spacetime is unstable. The slow-roll parameters $ε$, $η$, and the $e$-fold number of the model are evaluated in the Einstein frame. The index of the scalar spectrum power-law $n_s$ and the tensor-to-scalar ratio $r$ are calculated. Critical points of autonomous equations for the de Sitter phase and the matter dominated epoch are found and studied. We obtain the approximate solution of equations of motion which is the deviation from the de Sitter phase in the Jordan frame. It is demonstrated that the model passes the matter stability test.

physics.gen-ph↗

arXiv2015

A new model of arcsin-gravity

The new model of modified $F(R)$ gravity theory with the function $F(R) = R+(a/γ) \arcsin(γR)$ is suggested and investigated. Constant curvature solutions corresponding to the extremum of the effective potential are obtained. We consider both the Jordan and Einstein frames, and the potential and the mass of the scalar degree of freedom are found. It was shown that the de Sitter space-time is unstable but the flat space-time is stable. We calculate the slow-roll parameters $ε$, $η$, and the $e$-fold number of the model. Critical points of autonomous equations for the de Sitter phase and the matter dominated epoch are obtained and learned.

physics.gen-ph↗

arXiv2015

Nonlinear arcsin-electrodynamics

A new model of nonlinear electrodynamics with three parameters is suggested and investigated. It is shown that if the external constant magnetic field presents the phenomenon of vacuum birefringence takes place. The indexes of refraction for two polarizations of electromagnetic waves, parallel and perpendicular to the magnetic induction field are calculated. The electric field of a point-like charge is not singular at the origin and the static electric energy is finite. We have calculated the static electric energy of point-like particles for different parameters of the model. The canonical and symmetrical Belinfante energy-momentum tensors and dilatation current are obtained. We demonstrate that the dilatation symmetry and dual symmetry are broken in the model suggested.

physics.gen-ph↗

arXiv2015

Nonlinear electrodynamics and black holes

We investigate a new model of nonlinear electromagnetic field coupled with the gravitation field. The black hole solution is obtained possessing the asymptotic Reissner-Nordström solution. The electric field has the finite value at the origin and there are not singularities.

physics.gen-ph↗

arXiv2015

On Generalized Logarithmic Electrodynamics

The generalized logarithmic electrodynamics with two parameters $β$ and $γ$ is considered. The indexes of refraction of light in the external magnetic field are calculated. In the case $β=γ$ we come to results obtained by P. Gaete and J. Helayël-Neto [7] (Eur.Phys.J. C\textbf{74}, 2816 (2014)). The bound on the values of $β$, $γ$ was obtained from the Biréfringence Magnétique du Vide (BMV) experiment. The symmetrical Belinfante energy-momentum tensor and dilatation current are found.

hep-th↗

arXiv2015

Nonlinear electrodynamics with birefringence

A new model of nonlinear electrodynamics with three parameters is suggested. The phenomena of vacuum birefringence takes place when there is the external constant magnetic field. We calculate the indices of refraction for two polarizations of electromagnetic waves, parallel and perpendicular to the magnetic induction field. From the Biréfringence Magnétique du Vide (BMV) experiment one of the coefficients, $γ\approx 10^{-20}$ T$^{-2}$, was estimated. The canonical, symmetrical Belinfante energy-momentum tensors and dilatation current were obtained. The dilatation symmetry and the dual symmetry are broken in the model considered.

physics.gen-ph↗

arXiv2014

A model of nonlinear electrodynamics

A new model of nonlinear electrodynamics with two parameters is investigated. We also consider a model with one dimensional parameter. It was shown that the electric field of a point-like charge is not singular at the origin and there is the finiteness of the static electric energy of point-like charged particle. We obtain the canonical and symmetrical Belinfante energy-momentum tensors and dilatation currents. It is demonstrated that the dilatation symmetry and dual symmetry are broken in the models suggested. We have calculated the static electric energy of point-like particles.

physics.gen-ph↗

arXiv2014

Black hole radiation of spin-1 particles in (1+2) dimensions

The radiation of vector particles by black holes in (1+2) dimensions is investigated within the WKB approximation. We consider the process of quantum tunnelling of bosons through an event horizon of the black hole. The emission temperature for the Schwarzschild background geometry coincides with the Hawking temperature and for the Rindler spacetime the temperature is the Unruh temperature. We also obtain the radiation temperatures for the de Sitter spacetime.

physics.gen-ph↗

arXiv2014

Black hole emission of vector particles in (1+1) dimensions

We investigate the radiation of spin-1 particles by black holes in (1+1) dimensions within the Proca equation. The process is considered as quantum tunnelling of bosons through an event horizon. It is shown that the emission temperature for the Schwarzschild background geometry is the same as the Hawking temperature corresponding to scalar particles emission. We also obtain the radiation temperatures for the de Sitter, Rindler and Schwarzschild-de Sitter space-times. In a particular case when two horizons in Schwarzschild-de Sitter space-time coincides the Nariai temperature is recovered. The thermodynamical entropy of a black hole is calculated for Schwarzschild-de Sitter space-time having two horizons.

gr-qc↗

arXiv2014

Modified arctan-gravity model mimicking a cosmological constant

A novel theory of $F(R)$ gravity with the Lagrangian density ${\cal L}=[R-(b/β)\arctan\left(βR\right)]/(2κ^2)$ is analyzed. Constant curvature solutions of the model are found, and the potential of the scalar field and the mass of a scalar degree of freedom in Einstein's frame are derived. The cosmological parameters of the model are calculated, which are in agreement with the PLANCK data. Critical points for the de Sitter phase and the matter dominated epoch of autonomous equations are obtained and studied.

gr-qc↗

arXiv2014

Equations for massless and massive spin-1/2 particles with varying speed and neutrino in matter

The modified Dirac equations describing massless and massive spin-1/2 particles violating the Lorentz invariance are considered. The equation for massless fermions with varying speed is formulated in the 16-component first-order form. The projection matrix, which is the density matrix, extracting solutions to the equation has been obtained. Exact solutions to the equation and energy spectrum for a massive neutrino are obtained in the presence of background matter. We have considered as subluminal as well as superluminal propagations of neutrinos. The bounds on the Lorentz invariance violation parameter from astrophysical observations by IceCube, OPERA, MINOS collaborations and by the SN1987A supernova are obtained for superluminal neutrinos.

hep-ph↗

arXiv2013

On exponential modified gravity

A modified theory of gravity with the function $F(R) = R\exp(αR)$ instead of Ricci scalar $R$ in the Einstein$-$Hilbert action is considered and analyzed. The action of the model is converted into Einstein$-$Hilbert action at small value of the parameter $α$. From local tests we obtain a bound on the parameter $α\leq 10^{-6}$ cm$^2$. The Jordan and Einstein frames are investigated and the potential of the scalar field in Einstein's frame is found. The mass of a scalar degree of freedom as a function of curvature is obtained. The static solutions of the model are found corresponding to the Schwarzschild$-$de Sitter space. We show that the de Sitter space is unstable but a solution with zero curvature is stable. The cosmological parameters of the model are calculated. It was demonstrated that the model passes the matter stability test.

gr-qc↗

arXiv2013

On massless and spinless particles with varying speed

The wave equation for spin-0 massless particles with the Lorentz violating term leading to varying speed of particles is considered. This equation is represented as the first-order 6$\times$6 matrix equation. Solutions of the equation in the form of projection matrix are obtained. The Schrödinger form of the equation is obtained and the quantum-mechanical Hamiltonian is found.

hep-th↗

arXiv2013

Born - Infeld-like modified gravity

A modified theory of gravity with the function $F(R) = (1-\sqrt{1-2λR})/λ$ is suggested and analyzed. At small value of the parameter $λ$ introduced the action is converted into Einstein$-$Hilbert action. The theory is consistent with local tests which gives a bound on the value of the parameter $λ\leq 2\times 10^{-6}$ cm$^2$. I have considered the Jordan frame as well as the Einstein frame in which the potential of the scalar field was obtained. The static Schwarzschild$-$de Sitter solutions of the model are obtained and analyzed. It was demonstrated that the de Sitter space is unstable but a solution with zero Ricci scalar is stable. It is shown that there is no matter instability in the proposed model.

gr-qc↗