arXiv subjects

Mirzabek Alloqulov

Publications and source records attributed to Mirzabek Alloqulov.

At least 19 recordsLinked to original sources

arXiv2026

Gravitational wave radiation from periodic orbits around a black hole in Einstein-Maxwell-scalar theory

In this paper, we investigate the periodic orbits around a black hole (BH) in Einstein-Maxwell-scalar (EMS) theory and the corresponding gravitational waveforms. First, we study the test particle dynamics around the BH by using the Lagrangian formalism. Using the corresponding conditions, we explore the effect of the spacetime parameters on the marginally bound orbit (MBO) and innermost stable circular orbit (ISCO). The results indicate that MBO and ISCO quantities decrease with the rise of the $β$ parameter and BH charge $Q$, and vice versa for the $γ$ parameter. Subsequently, we plot the different zoom-whirl orbits around the BH in EMS theory by finding the test particle's corresponding energy and angular momentum. Finally, the gravitational waveforms of the extreme mass ratio inspirals, which contain a supermassive BH in EMS theory and a stellar mass object, are demonstrated. It is shown that the zoom-whirl orbits shrink as the BH charge increases, and, as a result, gravitational waveforms shift towards shorter times.

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arXiv2026

Repetitive Penrose Process in Kerr-Taub-NUT black hole spacetime

In this article, we study the repetitive Penrose process for the Kerr-Taub-NUT black hole (BH). First of all, we briefly review the spacetime of the Kerr-Taub-NUT BH, including horizon and ergosphere structures. The results indicate that the event horizon and ergosphere radii increase under the influence of the gravitomagnetic charge $l$. Subsequently, we find by using the irreducible mass of the BH that the extractable energy decreases with the rise of the gravitomagnetic charge. We then turn to the repetitive Penrose process by writing the conservation laws and setting the corresponding iterative stopping conditions. Furthermore, we numerically calculate the change in the BH's parameters, along with the corresponding quantities of the repetitive Penrose process, for each iteration.

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arXiv2026

Plasma impact on black hole shadow and gravitational weak lensing for Schwarzschild-like black hole

This article delves into the observational properties of a Schwarzschild-like black hole (BH). Initially, the research provides a succinct examination of the spacetime geometry and the configuration of its horizon. Furthermore, we study the photon dynamics around the Schwarzschild-like BH in the presence of the plasma using the Hamiltonian formalism. It was found that the photon sphere radii increase under the influence of the plasma frequency and vice versa for the spacetime parameters. Further exploration is dedicated to understanding how the plasma affects the shadow of the BH, and we find that the radius of the BH shadow shrinks with the rise of the $ξ$ parameter and plasma frequency. We then turn to the getting constraint of the spacetime parameters and the plasma frequency by using the observational data released by the Event Horizon Telescope (EHT) collaboration for the M87* and Sgr A*. Additionally, the research scrutinises the phenomenon of gravitational weak lensing in the vicinity of a Schwarzschild-like BH, considering both uniform and non-uniform plasma scenarios. The outcomes demonstrate that the angle of deflection increases under the influence of a uniform plasma frequency, whereas the opposite is true for non-uniform plasma. In both scenarios, a rise in the spacetime parameters results in a decrease in the deflection angle. Finally, we investigate the magnification of the gravitationally lensed image. The effect of the spacetime parameters and plasma frequencies on the total magnification are same as in the deflection angles.

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arXiv2026

Effect of gravitational lensing around black hole in dark matter halo in the presence of plasma

This article is devoted to the investigation of the observational properties of the Schwarzschild black hole (BH) surrounded by a dark matter (DM) halo. Our study commences with a brief review of spacetime, including the horizon structure and curvature invariants, which are the Ricci scalar, the square of the Ricci tensor, and the Kretschmann scalar. Subsequently, we explore the massive and massless particle dynamics around the Schwarzschild BH surrounded by a dark matter halo, including the innermost stable circular orbit (ISCO) and photon sphere radii. It was found that the radius of the ISCO increases under the influence of the spacetime parameters. Additionally, we investigate the weak gravitational lensing with the assumption that the BH is surrounded by a uniform and non-uniform plasma. Finally, we examine the impact of a plasma on the BH shadow and employ Event Horizon Telescope (EHT) observational data to constrain the BH's parameters.

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arXiv2026

Can a Dehnen-type dark matter halo affect the neutrino flavor oscillations?

The gravitational weak lensing of neutrinos in the presence of a Schwarzschild black hole surrounded by a Dehnen-type dark matter halo is investigated. The event horizon structure is explored, and the existence of the BH is studied in two different slices of the parameter space. Additionally, we derive analytic expressions for the oscillation phase and transition probabilities for both radial and non-radial neutrino propagation. Finally, we use a two-flavor toy model, and numerically analyze how the dark matter halo parameters as density and scale radius, affect oscillation probabilities and examine the role of decoherence. The results show that the presence of a dark matter halo modifies the oscillation phase and damping factor, leading to measurable deviations from the standard Schwarzschild BH case. These findings suggest that neutrino oscillations could, in principle, serve as a probe for dark matter distributions around compact astrophysical objects.

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arXiv2025

Nonlinear electrodynamic black holes and their role in testing modified theories of gravity

The nature of black holes (BHs) and their potential deviations from classical General Relativity (GR) remain central questions in modern astrophysics. Nonlinear electrodynamics (NED) offers a promising mechanism to construct regular BHs that avoid singularities while retaining key astrophysical features. In this work, we analyze NED-inspired BHs and derive constraints on the magnetic parameter using Bayesian parameter estimation from Event Horizon Telescope (EHT) observations. We obtain $q = 0.63 ^{+0.68}_{-0.44} \times 10^9 M_{\odot}$ for M87* and $q = 0.33 ^{+0.36}_{-0.23} \times 10^6 M_{\odot}$ for Sgr A*, affecting their horizon structure. A comparison with the Schwarzschild solution highlights deviations in geometry and horizon properties, emphasizing the impact of NED. We also examine observational signatures, including BH shadows and gravitational lensing. Using $R_{\text{sh}} = r_{\text{ph}} \sqrt{1/f(r_{\text{ph}})}$, we explore shadow features under uniform and non-uniform plasma conditions, revealing deviations from GR predictions due to NED effects. By analyzing photon sphere shifts and lensing patterns, we identify observable features that distinguish these BHs from classical ones. Our results suggest that NED-induced modifications may leave detectable imprints in strong-field regimes, opening pathways to test alternative gravity models. Future missions such as the Laser Interferometer Space Antenna (LISA) and next-generation X-ray observatories, along with ongoing observations from the EHT and gravitational wave detections by the Laser Interferometer Gravitational-Wave Observatory and Virgo (LIGO--Virgo), will be essential for refining constraints on such models.

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arXiv2025

Probing the gravity of a Schwarzschild black hole in the presence of a cloud of strings with EMRIs

Here, we explore the effect of the cloud of strings (CoS) on the gravitational waveforms of extreme mass ratio inspirals (EMRIs). The EMRI system consists of a supermassive black hole (BH) and a compact stellar mass object moving around it. We begin with studying the test particle motion around the Schwarzschild BH surrounded by a CoS by using the Lagrangian formalism. Moreover, we investigated the effect of the CoS parameter on the evolution of the semi-latus rectum and eccentricity. We then turn to the exploration of the impact of the CoS parameter on the gravitational waveforms of the EMRI system. The analysis performed shows that Laser Interferometer Space Antenna (LISA) could detect the CoS imprint in gravitational waveforms when the values of the string cloud parameter $α\gtrsim 2 \times 10^{-6}$.

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arXiv2025

Lensing Stability and Scattering Phenomena in Anisotropic Black Hole Spacetimes in Plasma

We investigate the physical and observational features of static, spherically symmetric black hole spacetimes surrounded by anisotropic fluid and embedded in a plasma environment. Motivated by recent advances in black hole imaging and precision measurements in strong gravity, we explore light propagation, wave dynamics, and observational signatures in such geometries. We begin by analyzing the background spacetime and matter content, examining the horizon structure and verifying the energy conditions associated with the anisotropic fluid. We then study photon trajectories in both vacuum and plasma environments, deriving the equations of motion and computing deflection angles and image magnifications under weak gravitational lensing. Both uniform and power-law plasma profiles are considered to model realistic astrophysical settings. In the wave optics regime, we first analyze the linear stability of the spacetime under axial (odd-parity) perturbations using Chandrasekhar's method, and then investigate scalar field scattering by solving the wave equation in the curved background with plasma. Using Born and WKB approximations, we compute the differential scattering cross-sections and examine how anisotropy and plasma affect interference features. Finally, we perform parameter estimation using Markov Chain Monte Carlo methods to constrain the black hole mass and anisotropic fluid parameters, utilizing EHT and GRAVITY data for Sgr A* and EHT-only data for M87*. These results present a unified theoretical framework that links anisotropic matter effects with lensing and scattering observables providing a firm basis for future comparisons with high-resolution astrophysical data sets in diverse contexts.

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arXiv2025

Gravitational waveforms from periodic orbits around a dyonic ModMax black hole

In this work, we study the gravitational waveforms from the periodic orbits of a massive particle around a dyonic ModMax black hole. We begin with a brief analysis of the spacetime and then examine how its parameters influence the dynamics of a massive neutral particle using the Lagrangian formalism. In particular, we compute the characteristics of marginally bound orbits and innermost stable circular orbits. Our results show that the values of these quantities increase with the black hole charge $Q$ and the screening parameter $γ$. We then plot various periodic orbits, characterized by the integers ($z$,$w$,$v$). Finally, we present the gravitational waveforms associated with extreme mass ratio inspirals, consisting of a stellar-mass compact object orbiting a supermassive black hole.

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arXiv2025

Regular black hole's impact on the gravitational waveforms from periodic orbits

In this paper, we investigate periodic orbits exhibiting zoom-whirl behavior around a magnetically charged black hole (MCBH) within the framework of the regular black hole. We examine how the magnetic charge influences orbital dynamics by modifying the background spacetime geometry, thereby affecting the energy and angular momentum of particles. In particular, we calculate the radii of the marginally bound orbits (MBOs) and innermost stable circular orbits (ISCOs), demonstrating that the magnetic charge parameter reduces both radii. This provides valuable insight into the role of the charge parameter in shaping orbital behavior and altering spacetime geometry. We model the complex motion of a stellar-mass object as a timelike particle, inspiraling into a supermassive black hole (SMBH) in the MCBH background, with its trajectory described using periodic geodesic orbits. Based on this analysis of such periodic orbits, we further analyze the gravitational waveforms generated by extreme mass ratio inspirals (EMRIs), in which the SMBH's spacetime dominates the dynamics of the stellar-mass object. By combining particle trajectory analysis with waveform modeling in a semi-analytical approach, we show that the charge parameter significantly alters the zoom-whirl orbital dynamics and induces notable changes in the waveform structure. These results illustrate that future gravitational wave (GW) observations may constrain the properties of MCBHs, thereby deepening our understanding of the gravitational imprint of regular black holes.

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arXiv2025

Epicyclic oscillations and accretion disk around a special Buchdahl-inspired spacetime

In this paper, we consider the Buchdahl-inspired spacetime metric and investigate its aspects using the quasiperiodic oscillations and the accretion disk due to the accreting matter. First, we focus on analyzing the geodesics of particles around the Buchdahl-inspired spacetime, together with the conserved quantities such as specific energy and angular momentum for massive particles orbiting on the innermost stable circular orbits (ISCOs). We show that the effect of the Buchdahl parameter $\tilde{k}$ increases as the radii of the ISCO orbits decrease, resulting in shifting orbits toward the central object compared to the Schwarzschild black hole case. We also consider astrophysical epicyclic oscillations and derive their general expressions using implications of circular motion of massive particles around the Buchdahl-inspired spacetime. Further, we explore the astrophysical implications of observational higher-frequency QPOs of the selected galactic microquasars of X-ray binary systems to obtain the best-fit constraints on the Buchdahl-inspired spacetime parameters. Finally, we consider the accretion disk around the Buchdahl-inspired spacetime using implications of the ISCO parameters that define the accretion disk's inner edge. We explore radiation properties of the accretion disk and redshifted image and intensity of a lensed accretion disk around the Buchdahl-inspired spacetime.

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arXiv2025

Gravitational waveforms from periodic orbits around a Schwarzschild black hole embedded in a Dehnen-type dark matter halo

In this paper, we study the periodic orbits, characterized by zoom-whirl behavior, around a Schwarzschild-like black hole (BH) embedded within a Dehnen-type dark matter (DM) halo. We demonstrate how the DM halo modifies the gravitational dynamics of the black hole, influencing the energy and angular momentum of timelike particle geodesics and enhancing their interaction with the BH. We determine the radii of the marginally bound orbits (MBOs) and innermost stable circular orbits (ISCOs), showing that the DM halo increases both. This provides a deeper understanding of how the DM alters the behavior, energy, and angular momentum of timelike particle geodesics. Furthermore, we explore the gravitational waveforms emitted by a timelike particle in periodic orbits around a supermassive black hole (SMBH) within this BH-DM system. Using a semi-analytical approach, we calculate particle trajectories and derive the corresponding waveforms, demonstrating that the DM halo modifies the zoom-whirl orbital behavior, leading to distinct changes in the waveform structure. Our findings suggest that future gravitational wave (GW) observations could constrain the properties of DM halos surrounding BHs, providing new insights into the gravitational wave signatures arising from the interaction between BH gravity and DM.

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arXiv2025

Electric Penrose process and collisions of particles near five-dimensional weakly charged Schwarzschild black hole

The particle dynamics and the electric Penrose process for the five-dimensional weakly charged Schwarzschild black hole are studied. Firstly, the horizon structure and the effective potential for the test particle are explored. The radial profile of the effective potential is plotted for different values of the BH charge. Then, we studied energy efficiency using the conservation laws for energy, angular momentum, and charge of particles. The appropriate plots were obtained and compared with the results for the four-dimensional Schwarzschild BH. Moreover, we obtained the constraints on mass and charge of black hole to accelerate protons of different energies ($1$-$10^{9}$ GeV). Finally, collisions of electrically charged particles near the horizon of the five-dimensional Schwarzschild BH are studied. We demonstrated the radial dependence of the center of mass energy for different values of the angular momentum and charge of the particles together with the BH charge.

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arXiv2024

Particle dynamics and the accretion disk around a Self-dual Black Hole immersed in a magnetic field in Loop Quantum Gravity

In this paper, we study the motion of magnetic dipoles and electrically charged particles in the vicinity of a self-dual black hole in Loop Quantum Gravity (LQG) immersed in an external asymptotically uniform magnetic field. We explore the effects of the quantum correction parameter and electromagnetic interactions on the particle geodesics. We derive the field equations and determine the electromagnetic four-vector potential for the case of a self-dual black hole in LQG. We investigate the innermost stable circular orbits (ISCOs) for both magnetic dipoles and electrically charged particles in detail, demonstrating that the quantum correction parameter significantly influences on the ISCO radius, causing it to shrink. Additionally, we show that the ISCO radius of magnetic dipoles is greater than that of electrically charged particles due to the magnetic field interaction. We investigate the ISCO parameters (i.e., $r_{ISCO}$, $l_{ISCO}$, $\mathcal{E}_{ISCO}$, $v_{ISCO}$, and $Ω_{ISCO}$) for magnetic dipoles and electrically charged particles, providing detailed values. Furthermore, we examine the trajectories of charged particles under various scenarios resulting from the quantum correction parameter $P$. Finally, analyzing the ISCO parameters that define the inner edge of the accretion disk, we explore the accretion disk around a self-dual black hole in LQG. We delve into the electromagnetic radiation flux, temperature, and differential luminosity as radiation properties of the accretion disk in detail. We show that the quantum correction parameter shifts the profile of the electromagnetic flux and accretion disk temperature towards the central object, leading to a slight increase in these quantities.

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arXiv2024

Gravitational lensing of neutrinos in the Rezzolla-Zhidenko spacetime

We consider gravitational lensing of neutrinos in the Rezzolla-Zhidenko spacetime in the weak-field limit with plane-wave approximation. We apply the analysis to an hypothetical system with a central object with its mass of the order of solar mass and a detector located at an Earth-like distance from the source. We find that the deformation parameters of the Rezzolla-Zhidenko metric can have significant impact on the oscillation probabilities of the neutrinos. We also investigate the role of decoherence on flavor oscillations of the lensed neutrinos and show that the parameters of the Rezzolla-Zhidenko metric does not have significant effects on the decoherence length.

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arXiv2024

Electric Penrose process and the accretion disk around a 4D charged Einstein-Gauss-Bonnet black hole

In this paper, we aim to examine the electric Penrose process (PP) around a charged black hole in 4D Einstein-Gauss-Bonnet (EGB) gravity and bring out the effect of the Gauss-Bonnet (GB) coupling parameter $α$ and black hole charge on the efficiency of the energy extraction from the black hole. This research is motivated by the fact that electrostatic interactions significantly influence the behavior of charged particles in the vicinity of a charged static black hole. Under this interaction, decaying charged particles can have negative energies, causing energy to be released from black holes with no ergosphere. We show that the GB coupling parameter has a significant impact on the energy efficiency of the electric PP, but the efficiency can be strongly enhanced by the black hole charge due to the Coulomb force. Finally, we consider the accretion disk around the black hole and investigate in detail its radiation properties, such as the electromagnetic radiation flux, the temperature, and the differential luminosity. We show that the GB coupling parameter can have a significant impact on the radiation parameters, causing them to increase in the accretion disk in the vicinity of the black hole. Interestingly, it is found that the 4D EGB charged black hole is more efficient and favorable for the accretion disk radiation compared to a charged black hole in Einstein gravity.

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arXiv2024

Shadows and weak gravitational lensing by the black hole in Einstein-Maxwell-scalar theory

In this paper, we investigate the optical properties of a charged black hole in Einstein-Maxwell-scalar (EMS) theory. We evaluate the shadow cast by the black hole and obtain analytical solutions for both the radius of the photon sphere and the shadow radius. We observe that the black hole parameters $γ$ and $β$ both influence the shadow of black hole. It is shown that the photon sphere and the shadow radius increase as a consequence of the presence of parameter $γ$. Interestingly, we show that shadow radius decreases first and then remains unchanged due to the impact of parameter $β$. Finally, we consider the weak gravitational lensing and the total magnification of lensed images around black hole. We find that the black hole charge and parameter $β$ both give rise to a significant effect, reducing the deflection angle. Similarly, the same behavior for the total magnification is observed due to the effect of black hole charge and parameter $β$.

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arXiv2024

Kerr-Newman-modified-gravity black hole's impact on the magnetic reconnection

In this paper, we study the magnetic reconnection process of energy extraction from a rapidly rotating Kerr-Newman-modified-gravity (MOG) black hole by investigating the combined effect of black hole charge and the MOG parameter. We explore the energy efficiency of energy extraction and power by applying the new energy extraction mechanism proposed by Comisso and Asenjo. Based on an attractive gravitational charge of the MOG parameter $α$ that physically manifests to strengthen black hole gravity, we show that the combined effect of the MOG parameter and black hole charge can play an increasingly important role and accordingly lead to high energy efficiency and power for the energy extraction via the magnetic reconnection. Further, we study to estimate the rate of energy extraction under the fast magnetic reconnection by comparing the power of the magnetic reconnection and Blandford-Znajek (BZ) mechanisms. We show that the rate of energy extraction increases as a consequence of the combined effect of black hole charge and MOG parameter. It suggests that magnetic reconnection is significantly more efficient than the BZ mechanism. In fact, the magnetic reconnection is fueled by magnetic field energy due to the twisting of magnetic field lines around the black hole for the plasma acceleration, and thus the MOG parameter gives rise to even more fast spin that can strongly change the magnetic field reconfiguration due to the frame dragging effect. This is how energy extraction is strongly enhanced through the magnetic reconnection, thus making the energy extraction surprisingly more efficient for the Kerr-Newman-MOG black hole than the Kerr black hole under the combined effect of black hole charge and MOG parameter.

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