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Galaxies
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Particles and Fields in Black Hole Environment
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Particles and Fields in Black Hole Environment

A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 16965

Special Issue Editors

Prof. Dr. Bobomurat Ahmedov

E-Mail Website
Guest Editor
Laboratory of Theoretical Astrophysics, Ulugh Beg Astronomical Institute, Tashkent 100052, Uzbekistan
Interests: relativistic astrophysics; general relativity; neutron stars and black holes
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Wenbiao Han

E-Mail Website
Guest Editor
Shanghai Astronomical Observatory, CAS, Shanghai 200030, China
Interests: gravitational waves; tests of theories of gravity; machine learning; black hole physics
Special Issues, Collections and Topics in MDPI journals
Dr. Ahmadjon Abdujabbarov

E-Mail Website
Guest Editor
Laboratory of Theoretical Astrophysics, Ulugh Beg Astronomical Institute, Tashkent 100052, Uzbekistan
Interests: relativistic astrophysics; general relativity; neutron stars and black holes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

(1) Outline the Overall.

a. Focus

The focus of the issue is to publish research/review articles in the areas covering General Relativity (Classical and Quantum), Relativistic Astrophysics, Experimental Gravitation, Alternate Theories of Gravity, Gravitational Waves, Gravitational Compact Objects.

b. Scope

There has been a rapidly growing interest in the study of relativistic astrophysics of gravitational compact objects due to several recent achievements: The recent direct detection of gravitational waves from the numerous events of merging gravitational compact objects in a close black hole and neutron star binaries by LIGO-VIRGO scientific collaboration, the measurement of general relativistic effects in strong gravity regime in the environment of the supermassive black hole Sagittarius A* at the Milky Way center by the ESOs GRAVITY instrument, and the first image of a black hole shadow in the center of elliptic galaxy M87 by the Event Horizon Telescope. In light of these recent successes of the general theory of relativity, the scope of this Special Issue is to open discussion of these topics to researchers working in areas such as Mathematical and Theoretical Physics, General Relativity, and Relativistic and Observational Astrophysics.

c. Purpose of the Special Issue;

The purpose of the Special Issue is to publish the research and review papers of the scientists and experts who are actively working in the areas of particles and photon motion in the vicinity of black holes, gravitational, electromagnetic, scalar fields and perturbations of gravitational compact objects, optical and energetic properties of black holes and magnetized neutron stars, gravitational lensing, and relativistic astrophysical processes in strong gravity regime.

(2) Indicate How the Issue Will be Situated within the Existing Literature.

There is huge literature devoted to the astrophysical processes concerning black holes. However, there is strong interest in probing the nature of black holes through astrophysical applications of the recently obtained results in relativistic astrophysical to theoretical models and predictions ascertain the constraints of the parameters of alternate theories of gravity versus to general relativity.

Prof. Bobomurat Ahmedov
Prof. Wenbiao Han
Prof. Ahmadjon Abdujabbarov
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Galaxies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • black holes optical properties
  • energetics of compact objects
  • relativistic astrophysics

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Published Papers (7 papers)

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Editorial

Jump to: Research

2 pages, 159 KiB  
Editorial
Preface of “Particles and Fields in Black Hole Environment”
by Bobomuat Ahmedov, Ahmadjon Abdujabbarov and Wenbiao Han
Galaxies 2022, 10(4), 82; https://doi.org/10.3390/galaxies10040082 - 9 Jul 2022
Viewed by 1443
Abstract
This Special Issue is dedicated to the memory of the physicist Professor James Maxwell Bardeen (9 May 1939–20 June 2022), who is well known for his work on general relativity, particularly his role in formulating the laws of black hole mechanics, the pioneering [...] Read more.
This Special Issue is dedicated to the memory of the physicist Professor James Maxwell Bardeen (9 May 1939–20 June 2022), who is well known for his work on general relativity, particularly his role in formulating the laws of black hole mechanics, the pioneering idea on black hole shadow observation and the Bardeen solution to gravitational field equations [...] Full article
(This article belongs to the Special Issue Particles and Fields in Black Hole Environment)

Research

Jump to: Editorial

9 pages, 265 KiB  
Article
Accretion of Galaxies around Supermassive Black Holes and a Theoretical Model of the Tully-Fisher and M-Sigma Relations
by Nick Gorkavyi
Galaxies 2022, 10(3), 73; https://doi.org/10.3390/galaxies10030073 - 27 May 2022
Viewed by 3202
Abstract
The observed Tully-Fisher and Faber-Jackson laws between the baryonic mass of galaxies and the velocity of motion of stars at the edge of galaxies are explained within the framework of the model of accretion of galaxies around supermassive black holes (SMBH). The accretion [...] Read more.
The observed Tully-Fisher and Faber-Jackson laws between the baryonic mass of galaxies and the velocity of motion of stars at the edge of galaxies are explained within the framework of the model of accretion of galaxies around supermassive black holes (SMBH). The accretion model can also explain the M-sigma relation between the mass of a supermassive black hole and the velocity of stars in the bulge. The difference in the mechanisms of origin of elliptical galaxies with low angular momentum and disk galaxies with high angular momentum can be associated with 3D and 2D accretion. Full article
(This article belongs to the Special Issue Particles and Fields in Black Hole Environment)
19 pages, 995 KiB  
Article
Dynamics of Test Particles and Twin Peaks QPOs around Regular Black Holes in Modified Gravity
by Javlon Rayimbaev, Pulat Tadjimuratov, Ahmadjon Abdujabbarov, Bobomurat Ahmedov and Malika Khudoyberdieva
Galaxies 2021, 9(4), 75; https://doi.org/10.3390/galaxies9040075 - 7 Oct 2021
Cited by 26 | Viewed by 2062
Abstract
In this work, we have presented a detailed analysis of the event horizon of regular black holes (BHs) in modified gravity known as MOG, the so-called regular MOG BH. The motion of neutral particles around the BH has also been explored. The test [...] Read more.
In this work, we have presented a detailed analysis of the event horizon of regular black holes (BHs) in modified gravity known as MOG, the so-called regular MOG BH. The motion of neutral particles around the BH has also been explored. The test particle motion study shows that the positive (negative) values of the MOG parameter mimic the spin of a rotating Kerr BH, providing the same values for the innermost stable pro-grade (retrograde) orbits of the particles in the range of the spin parameter a/M∈(−0.4125,0.6946). The efficiency of energy release from the accretion disk by the Novikov–Thorne model has been calculated, and the efficiency was shown to be linearly proportional to the increase of the MOG parameter α. Moreover, we have developed a new methodology to test gravity theories in strong-field regimes using precision data from twin-peaked quasiperiodic oscillations (QPOs) of objects calculating possible values of upper and lower frequencies. However, it is obtained that the positive MOG parameter can not mimic the spin of Kerr BHs in terms of the same QPO frequencies. We have provided possible ranges for upper and lower frequencies of twin-peak QPOs with the ratio of the upper and lower frequencies of 3:2 around regular MOG BHs in the different models. Moreover, as an example, we provide detailed numerical analysis of the QPO of GRS 1915+105 with the frequencies νU=168±5Hz and νL=113±3Hz. It is shown that the central BH of the QPO object can be a regular MOG BH when the value of the parameter is α=0.2844−0.1317+0.0074 and shines in the orbits located at the distance r/M=7.6322−0.0826+0.0768 from the central BH. It is also shown that the orbits where QPOs shine are located near the innermost stable circular orbit (ISCO) of the test particle. The correlation between the radii of ISCO and the QPO orbits is found, and it can be used as a new theoretical way to determine ISCO radius through observational data from the QPOs around various compact objects. Full article
(This article belongs to the Special Issue Particles and Fields in Black Hole Environment)
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12 pages, 7935 KiB  
Article
Singularities in Static Spherically Symmetric Configurations of General Relativity with Strongly Nonlinear Scalar Fields
by Oleksandr Stashko and Valery I. Zhdanov
Galaxies 2021, 9(4), 72; https://doi.org/10.3390/galaxies9040072 - 1 Oct 2021
Cited by 9 | Viewed by 1564
Abstract
There are a number of publications on relativistic objects dealing either with black holes or naked singularities in the center. Here we show that there exist static spherically symmetric solutions of Einstein equations with a strongly nonlinear scalar field, which allow the appearance [...] Read more.
There are a number of publications on relativistic objects dealing either with black holes or naked singularities in the center. Here we show that there exist static spherically symmetric solutions of Einstein equations with a strongly nonlinear scalar field, which allow the appearance of singularities of a new type (“spherical singularities”) outside the center of curvature coordinates. As the example, we consider a scalar field potential ∼sinh(ϕ2n),n>2, which grows rapidly for large field values. The space-time is assumed to be asymptotically flat. We fulfill a numerical investigation of solutions with different n for different parameters, which define asymptotic properties at spatial infinity. Depending on the configuration parameters, we show that the distribution of the stable circular orbits of test bodies around the configuration is either similar to that in the case of the Schwarzschild solution (thus mimicking an ordinary black hole), or it contains additional rings of unstable orbits. Full article
(This article belongs to the Special Issue Particles and Fields in Black Hole Environment)
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10 pages, 356 KiB  
Article
Capture of Massless and Massive Particles by Parameterized Black Holes
by Bobir Toshmatov, Ozodbek Rahimov, Bobomurat Ahmedov and Abdumirhakim Ahmedov
Galaxies 2021, 9(3), 65; https://doi.org/10.3390/galaxies9030065 - 6 Sep 2021
Cited by 12 | Viewed by 2107
Abstract
We study an influence of the leading coefficient of the parameterized line element of the spherically symmetric, static black hole on the capture of massless and massive particles. We have shown that negative (positive) values of ϵ decreases (increases) the radius of characteristic [...] Read more.
We study an influence of the leading coefficient of the parameterized line element of the spherically symmetric, static black hole on the capture of massless and massive particles. We have shown that negative (positive) values of ϵ decreases (increases) the radius of characteristic circular orbits and consequently, increases (decreases) the energy and decreases (increases) the angular momentum of the particle moving along these orbits. Moreover, we have calculated and compared the capture cross section of the massive particle in the relativistic and non-relativistic limits. It has been shown that in the case of small deviation from general relativity the capture cross section for the relativistic and nonrelativistic particle has an additional term being linear in the small dimensionless deviation parameter ϵ. Full article
(This article belongs to the Special Issue Particles and Fields in Black Hole Environment)
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22 pages, 2265 KiB  
Article
Regular Bardeen Black Holes in Anti-de Sitter Spacetime versus Kerr Black Holes through Particle Dynamics
by Bakhtiyor Narzilloev, Javlon Rayimbaev, Ahmadjon Abdujabbarov and Bobomurat Ahmedov
Galaxies 2021, 9(3), 63; https://doi.org/10.3390/galaxies9030063 - 6 Sep 2021
Cited by 25 | Viewed by 3375
Abstract
In this work, test particle dynamics around a static regular Bardeen black hole (BH) in Anti-de Sitter spacetime has been studied. It has been shown for neutral test particles that parameters of a regular Bardeen black hole in Anti-de Sitter spacetime can mimic [...] Read more.
In this work, test particle dynamics around a static regular Bardeen black hole (BH) in Anti-de Sitter spacetime has been studied. It has been shown for neutral test particles that parameters of a regular Bardeen black hole in Anti-de Sitter spacetime can mimic the rotation parameter of the Kerr metric up to the value a≈0.9 providing the same innermost stable circular orbit (ISCO) radius. We have also explored the dynamics of magnetized particles with a magnetic dipole moment around a magnetically charged regular Bardeen black hole in Anti-de Sitter spacetime. As a realistic astrophysical scenario of the study, we have treated neutron stars orbiting a supermassive black hole (SMBH), in particular, the magnetar PSR J1745-2900 orbiting Sgr A* with the parameter β=10.2, as magnetized test particles. The magnetized particles dynamics shows that the parameter β, negative values of cosmological constant and magnetic charge parameter of the central BH cause a decrease in the ISCO radius. We have compared the effects of the magnetic charge of the Bardeen BH with the spin of rotating Kerr BH and shown that magnetic charge parameter can mimic the spin in the range a/M≃(0,0.7896) when Λ=0 at the range of its values g/M≃(0,0.648). Full article
(This article belongs to the Special Issue Particles and Fields in Black Hole Environment)
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8 pages, 359 KiB  
Article
Zipoy-Voorhees Gravitational Object as a Source of High-Energy Relativistic Particles
by Bobur Turimov and Bobomurat Ahmedov
Galaxies 2021, 9(3), 59; https://doi.org/10.3390/galaxies9030059 - 30 Aug 2021
Cited by 4 | Viewed by 1856
Abstract
The Zipoy-Voorhees solution is known as the γ-metric and/or q-metric being static and axisymmetric vacuum solution of Einstein field equations which becomes strong curvature naked singularity. The metric is characterized by two parameters, namely, the mass M and the dimensionless deformation [...] Read more.
The Zipoy-Voorhees solution is known as the γ-metric and/or q-metric being static and axisymmetric vacuum solution of Einstein field equations which becomes strong curvature naked singularity. The metric is characterized by two parameters, namely, the mass M and the dimensionless deformation parameter γ. It is shown that the velocity of test particle orbiting around the central γ-object can reach the speed of light, consequently, the total energy of the particle will be very high for a specific value the deformation parameter of the spacetime. It is also shown that causality problem arises in the interior region of the physical singularity for the specific value of the deformation parameter when test particles can move with superluminal velocity being greater than the speed of light that might be an additional tool for explaining the existence of tachyons for γ>1/2 which are invisible for an observer. Full article
(This article belongs to the Special Issue Particles and Fields in Black Hole Environment)
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