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Alexander Shatskiy

Publications and source records attributed to Alexander Shatskiy.

At least 19 recordsLinked to original sources
arXiv2021

Occurrence of a turning point in the dynamic solution for a Reissner-Nordström black hole

A self-consistent exact solution for a Reissner-Nordström black-and-white hole formed as a result of accretion has been considered. Prior to the formation of a black-and-white hole, there is a bulk charged sphere at the center of the system. The occurrence of a turning (bounce) point in the newly formed black-and-white hole is investigated. The occurrence of a turning point was investigated by an example of solution for the accretion of a neutral spherical dust shell. The model equations are written with allowance for the cosmological $Λ$-term. Within the model under consideration, both the black-and-white hole and its turning point are formed in the already existing Universe; therefore, the black-and-white hole in this model is not < >.

gr-qc↗
arXiv2019

Neural Network Astronomy as a New Tool for Observing Bright and Compact Objects

We propose a new method for solving an important problem of astronomy that arises in observations with ultrahigh-angular-resolution interferometers. This method is based on the application of the theory of artificial neural networks. We propose and compute a multiparameter model for a celestial object like Sgr A*. For this model we have numerically constructed a number of probable images for neural network training. After neural network training on these images, the quality of its operation has been tested on another series of images from the same model. We have proven that a neural network can recognize and classify celestial objects (also obtained from interferometers) virtually no worse than can be done by a human.

astro-ph.IM↗
arXiv2017

A thin dust shell falling to a Reissner-Nordstrom black hole as seen by a freely falling observer

We study the observation of a thin dust shell, radially freely falling to a Reissner-Nordstrom black hole, by an observer who is also freely and radially falling into this black hole. Considered and resolved are several common paradoxes and fallacies peculiar for such problems. The results of this analytical study are written as a numerical code that allows for calculating all related effects of this model. The numerical result have been presented in a few synthesized videos, making a colorful, quantitative and detailed description of the occurring astrophysical phenomena, both above and below the horizon.

physics.gen-ph↗
arXiv2016

Model Predictions of the Results of Interferometric Observations for Stars under Conditions of Strong Gravitational Scattering by Black Holes and Wormholes

The characteristic and distinctive features of the visibility amplitude of interferometric observations for compact objects like stars in the immediate vicinity of the central black hole in our Galaxy are considered. These features are associated with the specifics of strong gravitational scattering of point sources by black holes, wormholes, or black_white holes. The revealed features will help to determine the most important topological characteristics of the central object in our Galaxy: whether this object possesses the properties of only a black hole or also has characteristics unique to wormholes or black_white holes. These studies can be used to interpret the results of optical, infrared, and radio interferometric observations.

astro-ph.GA↗
arXiv2015

Spectrum for the electric dipole which nonradially falling into a black hole

The electromagnetic bremsstrahlung spectrum for the dipole which falling by a spiral orbit into the Schwarzschild black hole was found. The characteristic features in this electromagnetic spectrum can be used for determine of the black hole mass by the new way. This new way (if implemented) provides higher accuracy in determining of the black hole mass. Also these features in the spectrum can be used for determine of the certain characteristics in the black hole magnetosphere or in the accretion disk characteristics around the black hole. It is also shown that the asymptotic behavior of this spectrum (at high frequencies) is practically independent from the impact parameter of the falling dipole.

gr-qc↗
arXiv2013

Special features in the asymptotic expression of the electromagnetic spectrum from dipole which free fall into a Schwarzschild black hole

The characteristic features were found in the electromagnetic spectrum of radiation from free falling dipole, when it is fall radially into a Schwarzschild black hole. These features can be used as another method for the black hole mass determinating. Also, these features can be used for the determination some characteristics of the magnetosphere or the accretion disk around the black hole.

gr-qc↗
arXiv2012

On stability of a new model of wormhole

We investigate the stability of the wormhole of the Mors-Thorne-Ellis-Bronnikov type. In our model the matter inside it consists of a radial magnetic field and an ideal phantom-fluid. Properties of the matter are described in section 1, 2 and 3 of this paper. We consider spherical perturbations only and find examples of the stable wormholes against these perturbations.

gr-qc↗
arXiv2012

Image of another universe being observed through a wormhole throat

We consider a technique of calculating deflection of the light passing through wormholes (from one universe to another). We find fundamental and characteristic features of electromagnetic radiation passing through the wormholes. Making use of this, we propose new methods of observing distinctive differences between wormholes and other objects as well as methods of determining characteristic parameters for different wormhole models.

astro-ph↗
arXiv2012

Non-singular Brans-Dicke cosmology with cosmological constant

We consider Brans-Dicke cosmology with cosmological constant with negative w parameter and an arbitrary (in general non-vanishing) scale factor at the Big Bang. The field equations describe the flat universe, current observational values for Hubble constant H and deceleration parameter q play a role of initial conditions. In order to solve field equations we adopt the approach of Uehara and Kim (1982). They considered only positive values of w, hence our solution is a new one and has not been described in their paper. Our main result is that unlike the standard cosmology the scale factor may not vanish in it's evolution back in time. In other words our model displays a cosmological bounce and avoids the initial singularity. The formula for the scale factor, leading to the bounce, is only valid for the dust-filled universe and hence cannot be adequate for the hot stage in the early universe when the bounce happens. So, the results of this paper are only qualitative in nature and must be used to obtain initial values for the hot stage of the unverse when one considers the evolution back in time.

gr-qc↗
arXiv2011

A new method for reconstructing the density distribution of matter in the disks of spiral galaxies from the rotation velocity curve in it

In this paper we propose a new method for reconstructing the surface density of matter in flat disks of spiral galaxies. The surface density is expressed through observational rotation velocity curves of visible matter in the disks of spiral galaxies. The new method is not based on quadrature of special functions. The found solution is used for processing and analysis of observational data from several spiral galaxies. The new method can be used to more accurately estimate the amount of dark matter in spiral galaxies.

astro-ph.GA↗
arXiv2010

To the search for observational evidence of wormholes

We consider observational properties of gamma-ray bursts (GRB) transmitted by hypothetical wormholes (WH). Such burst would be observable as repeating source, analogous to Soft Gamma-Repeaters (SGR). We show that the known sources of SGR cannot be WH candidates. We also discuss observational properties of GRB which might be a signature of WH.

astro-ph.CO↗
arXiv2010

Physics of the interior of a black hole with an exotic scalar matter

We use a numerical code to consider the nonlinear processes arising when a Reissner-Nordstrom black hole is irradiated by an exotic scalar field (modelled as a free massless scalar field with an opposite sign for its energy-momentum tensor). These processes are quite different from the processes arising in the case of the same black hole being irradiated by a pulse of a normal scalar field. In our case, we did not observe the creation of a spacelike strong singularity in the T-region of the space-time. We investigate the antifocusing effects in the gravity field of the exotic scalar field with the negative energy density and the evolution of the mass function. We demonstrate the process of vanishing of the black hole when it is irradiated by a strong pulse of an exotic scalar field.

gr-qc↗
arXiv2009

Influence of Rotation on the Amount of Phantom Matter around wormholes

Static (spherically symmetrical) and stationary solutions for wormholes are considered. The visibility horizon, which characterizes the differences between black holes and passing wormholes, is determined in an invariant way. It is shown that the rotation of wormholes does not affect the amount of phantom matter that surrounds them.

astro-ph↗
arXiv2009

Passage of radiation through wormholes

We investigate numerically the process of the passage of a radiation pulse through a wormhole and the subsequent evolution of the wormhole that is caused by the gravitational action of this pulse. The initial static wormhole is modeled by the spherically symmetrical Armendariz-Picon solution with zero mass. The radiation pulses are modeled by spherically symmetrical shells of self-gravitating massless scalar fields. We demonstrate that the compact signal propagates through the wormhole and investigate the dynamics of the fields in this process for both cases: collapse of the wormhole into the black hole and for the expanding wormhole.

gr-qc↗
arXiv2008

New analytic models of traversable wormholes

The analytic solution of the general relativity equations for spherically symmetric wormholes are given. We investigate the special case of a "traversable" wormhole i.e., one allowing the signal to pass through it. The energy-momentum tensor of wormhole matter is represented as a superposition of a spherically symmetric magnetic field and dust matter with negative matter density. The dynamics of the model are investigated. We discuss both the solution of the equation with a Lambda-term and without it. Superposing enough dust matter, a magnetic field, and a Lambda-term can produce a static solution, which turns out to be a spherical Multiverse model with an infinite number of wormholes connected spherical universes. Corresponding solution can be static and dynamic.

gr-qc↗
arXiv2008

Primordial black holes and asteroid danger

Probability for a primordial black hole to invade the Kuiper belt was calculated. We showed that primordial black holes of certain masses can significantly change asteroids' orbits. These events may result in disasters, local for our solar system and global for the Earth (like the Tunguska meteorite). We also estimated how often such events occur.

astro-ph↗
arXiv2007

Dynamics of Phantom Matter

A spherically symmetric evolution model of self-gravitating matter with the equation of state P=wE (where w=const<-1) is considered. The equations of the model are written in the frame of reference comoving with matter. A criterion for the existence and formation of a horizon is defined. Part of the Einstein equations is integrated analytically. The initial conditions and the constraints imposed on these conditions in the presence of a horizon are determined. For small |1+w| an analytic solution to spherically symmetric time-dependent Einstein equations is obtained. Conditions are determined under which the dynamics of matter changes from collapse to expansion. Characteristic times of the evolution of the system are evaluated. It is proved that the accretion of phantom matter (for w<-1) onto a black hole leads to the decreases of the horizon radius of the black hole (i.e., the black hole is "dissolved").

gr-qc↗