Investigating the impact of dark matter on gravity near black holes (BHs) using observational evidence and theoretical analysis is a critical area of relativistic astrophysics. Therefore, in this manuscript, we examine the behavior of test particles in the vicinity of magnetized Schwarzschild BHs within the framework of scalar-vector-tensor gravity (STVG) theory. We assume that the BH is surrounded by a magnetosphere modeled using the parabolic magnetic field solution. We study the circular motions of test particles near BHs and calculate the corresponding effective potential, accounting for the MOG interaction and the magnetic field’s influence on particle geodesics. In addition, we analyze the stability of circular orbits by evaluating the effective potential, angular momentum, and the particle’s energy. We demonstrate how MOG interactions and the magnetic field affect the location of the innermost stable circular orbits (ISCO). Using the Navikov–Thorne thin accretion disk model, we studied how MOG interactions and the magnetic field affect energy efficiency, energy flux, and temperature distribution. Moreover, we investigate the collision of magnetized particles near our spacetime geometry under the influence of MOG and magnetic fields. Finally, we study the trajectories of charged particles under the influence of MOG interactions and a magnetic field and present our conclusions in the final section.

China

Saeed Khan

Uzbekistan

Javlon Rayimbaev

Yunus Turaev

Otaboyev Sirajiddin

Sulton Usanov

Weiwei Wang

Energy efficiency and particle dynamics around magnetized black holes with parabolic configuration in STVG

The term cosmic dark matter is commonly studied in the context of galactic rotation profiles, particularly along the outer galactic halo. However, its influence may differ significantly in dense-matter astrophysical configurations characterized by strong gravitational fields. In this study, we construct stellar structures developed within the framework of a Dehnen–(1,4,0) halo profile using the well-known Kohler–Chao–Tikekar geometry. The proposed model is driven by an anisotropic fluid coupled with a dark matter component. The aim is to develop the dense-matter, anisotropic astrophysical systems through the framework of geometric decoupling using the minimal geometric deformation scheme. In this context, the temporal component of the auxiliary sector is interpreted as the dark matter sector. A thorough graphic evaluation is conducted to confirm the feasibility of the proposed model, supported by observational data from a set of modeled stellar configurations.

Pakistan

S. Khan

Aybek Seytov

Gravitationally decoupled anisotropic compact stars immersed in Dehnen-(1,4,0) density profiles

<p>Topological quantum field theory (TQFT) is a powerful tool to describe homologies, which normally involve complexes and a variety of maps/morphisms, what makes a functional integration approach with a sum over a single kind of map seemingly problematic. In TQFT this problem is overcome by exploiting the rich set of zero modes of BRST operators, which appear sufficient to describe complexes. We explain what this approach looks like for the important class of Khovanov-Rozansky (KR) cohomologies, which categorify the observables (Wilson lines or knot polynomials) in 3D Chern-Simons theory. We develop a construction of odd differential operators, associated with all link diagrams, including tangles with open ends. These operators become nilpotent only for a diagram with no external legs, but even for open tangles one can develop a factorization formalism, which preserves Reidemeister/topological invariance—the symmetry of the problem. This technique seems much more “physical” than the conventional language of homological algebra and should have many applications to various problems beyond Chern-Simons theory. We also hope that this language will provide efficient algorithms, and finally allow one to computerize the calculation of KR cohomologies—for closed diagrams and for open tangles.</p>

Russia

Dmitry Galakhov

Elena Lanina

Alexei Morozov

Operator lift of the Reshetikhin-Turaev formalism to Khovanov-Rozansky topological quantum field theory

We investigate the dynamics of charged spinning test particles in the spacetime of a magnetized Bocharova-Bronnikov-Melnikov-Bekenstein black hole (BH), an extremal solution of the Einstein-Maxwell-conformally coupled scalar field equations. Using the Mathisson-Papapetrou-Dixon equations, we derive the equations of motion that incorporate spin-curvature coupling and electromagnetic interactions due to the particle’s charge and an external magnetic field. The effective potential formalism is employed to analyze stable circular orbits, the innermost stable circular orbit (ISCO), and the superluminal bound, ensuring timelike motion. The influence of the particle’s spin <italic>s</italic>, a magnetic coupling parameter <italic>&#969;<inf>B</inf></italic>, is examined numerically, revealing significant shifts in the ISCO radius, specific angular momentum, and energy due to spin and electromagnetic effects. We further study particle collisions near the event horizon, computing the critical angular momentum and center-of-mass energy, which exhibit enhancements akin to the Ba&#241;ados-Silk-West effect, driven by gravitational, electromagnetic, and spin interactions. Our results highlight the intricate interplay of these effects in the BBMB spacetime, offering insights into high-energy astrophysical processes such as accretion disk dynamics and particle acceleration near magnetized BHs.

Shokhzod Jumaniyozov

Munisbek Akhmedov

Jamshid Khasanov

Spin effects on motion of charged particles around magnetized black holes in conformally coupled scalar fields

We investigate the astrophysical properties of the rotating Kazakov-Solodukhin (KS) black hole, a quantum-corrected extension of the Schwarzschild solution that removes the central singularity via an effective mass function. Extending the KS solution to the rotating case, we analyze its geodesic structure and explore the influence of the quantum correction parameter on observable quantities. In particular, we study the effective mass profile, the ergoregion, and photon motion, and compute the black hole shadow. Comparing the resulting shadows with the classical Kerr solution, we find that quantum corrections tend to enlarge the shadow radius and alter its shape. Using these theoretical predictions, we further constrain the parameter space of the rotating KS black hole by confronting the shadow properties with Event Horizon Telescope (EHT) observations of M87* and Sgr A*. Our results demonstrate that high-resolution black hole imaging provides a promising avenue for probing semiclassical modifications of general relativity.

Bekzod Rahmatov

Islom Egamberdiev

Otabek Umarov

Murodbek Vapayev

Shavkat Karshiboev

Sardor Murodov

Astrophysical signatures of rotating Kazakov-Solodukhin black holes: shadows and constraints from EHT observations

We investigate domain walls between 2$\textit{d}$ gapped phases of Turaev-Viro type topological quantum field theories (TQFTs) by constructing domain wall tube algebras. We begin by analyzing the domain wall tube algebra associated with bimodule categories, and then extend the construction to multimodule categories over $\textit{N}$ base fusion categories. We prove that the resulting tube algebra is naturally equipped with a $\textit{C}$ weak Hopf algebra structure. We show that topological excitations localized on domain walls are classified by representations of the corresponding domain wall tube algebra, in the sense that the functor category of bimodules admits a fusion-preserving embedding into the representation category of the domain wall tube algebra. We further establish the folding trick and Morita theory in this context. Then, most crucially, we provide a rigorous construction of the Drinfeld quantum double from weak Hopf boundary tube algebras using a skew-pairing, and establish an isomorphism between domain wall tube algebra and Drinfeld quantum double of boundary tube algebras. Motivated by the correspondence between the domain wall tube algebra and the quantum double of the boundary tube algebras, we introduce the notion of an $\textit{N}$-tuple algebra and demonstrate how it arises in the multimodule domain wall setting. Finally, we consider defects between two domain walls, showing that such defects can be characterized by representations of a domain wall defect tube algebra. We briefly outline how these defects can be systematically treated within this representation-theoretic framework.

Singapore

Zhian Jia

Sheng Tan

Weak Hopf tube algebra for domain walls between 2d gapped phases of Turaev-Viro TQFTs

We investigate the dynamics of neutral spinning test particles in the charged black-bounce spacetime described by the Reissner–Nordström–Simpson–Visser metric, which interpolates between a Reissner–Nordström black hole and a traversable wormhole via the Simpson–Visser parameter $\textit{l}$. Utilizing the Mathisson–Papapetrou–Dixon equations with the Tulczyjew spin-supplementary condition, we derive the equations of motion, effective potential, and conserved quantities for particles in the equatorial plane. The spin-curvature coupling introduces significant deviations from geodesic motion, affecting stable circular orbits and the innermost stable circular orbit. We analyze the superluminal bound, ensuring physically valid timelike trajectories, and find that the spin parameter $\textit{s}$, electric charge $\textit{Q}$, and $\textit{l}$ critically influence orbital stability and dynamics. Additionally, we study particle collisions, computing the critical angular momentum and center-of-mass energy, which reveal conditions for high-energy astrophysical processes, particularly in the black hole regime. Numerical results highlight the interplay between spin, electromagnetic effects, and the black-bounce geometry, with implications for accretion disks and gravitational wave signatures.

Dynamics of spinning particles around a charged black-bounce spacetime

This study investigates the dynamics of spinning charged test particles in the spacetime of a Reissner–Nordström (RN) black hole immersed in an asymptotically uniform magnetic field, using the Mathisson–Papapetrou–Dixon (MPD) equations supplemented with the Tulczyjew spin condition. We derive the equations of motion incorporating spin-curvature coupling, electromagnetic interactions, and magnetic field effects, leading to an effective potential that governs equatorial circular orbits. The analysis focuses on how particle spin $\textit{s}$, charge $\textit{q}$, black hole charge $\textit{Q}$, and magnetic coupling $$\omega $$ modify the effective potential, innermost stable circular orbits (ISCO), critical angular momentum for capture, and center-of-mass energy in particle collisions. The obtained results show that a positive spin flattens the potential and shifts the minima inward, enabling closer orbits, while a negative spin steepens it for repulsion. ISCO radii decrease with aligned spin and magnetic coupling, reducing specific energy and angular momentum. Critical angular momentum increases with magnetic strength and charge, exhibiting non-monotonic spin dependence due to competing Lorentz and spin-curvature forces. For collisions, the center-of-mass energy spikes near the horizon, enhanced by opposite spins and counter-rotating orbits, but suppressed by strong magnetic repulsion. At ISCO, energies peak for weak or negative coupling. These findings reveal that spin-magnetic interactions expand stable orbital regimes and boost collision energies, with implications for high-energy astrophysics near magnetized charged black holes, such as particle acceleration in accretion disks or cosmic ray production. We treat the external magnetic field as a test field on a fixed RN geometry and assume it is sufficiently weak at the ISCO so that backreaction is negligible. Scans labeled by $$\omega = qB_0$$ are evaluated at fixed small $$B_0$$ by varying the particle charge $\textit{q}$; for ISCO collisions, the first and the second particle orbit and collide at the same ISCO radius.

Tursinbay Oteev

Czechia

Zdeněk Stuchlík

Murat Sharibaev

Inomjon Ibragimov

Spin effects on charged particle motion in magnetized Reissner–Nordström spacetime

In this study, we investigate the electromagnetic field properties of a rotating charged black hole (BH) within the Kalb–Ramond gravity, as well as the circular motion and collisions of test charged particles in the spacetime of the BH. First, the static solutions of the Kalb–Ramond BH are derived using modified Einstein field equations and Maxwell’s equations to obtain the anisotropic solutions of the charged Kalb–Ramond BH. Then, using the Janis–Newman formalism, the exact solutions of the rotating Kalb–Ramond BH are obtained from the static metric. Subsequently, we investigate the horizon properties of the resulting rotating BH. It is shown that all the BH parameters charge and rotation, together with the Kalb–Ramond field, cause the horizon to extend, thereby providing additional gravitational mass. Then, we derive expressions for non-zero components of electromagnetic field configurations with respect to a zero angular momentum observer around the BHs. We also explore the circular motion of charged test particles, determining their effective potential and innermost stable circular orbits (ISCOs), which are influenced by the interplay of gravitational, rotational, and electromagnetic forces. Furthermore, we examine high-energy collisions of charged particles near the event horizon, computing the center-of-mass energy and demonstrating its enhancement by the Kalb–Ramond parameter and BH charge. Our results highlight the potential of charged rotating Kalb–Ramond BHs as natural particle accelerators, offering insights into extreme gravitational and electromagnetic phenomena with implications for astrophysics and theoretical physics.

Bakhrom Abdulazizov

Sherzod Djumanov

Rotating charged black holes in Kalb–Ramond gravity: electromagnetic fields, circular motion and collisions of charged particles

No-hair theorem indicates that black holes cannot have their own magnetic dipole moment. They can be weakly magnetized in binary systems with a neutron star companion and an accretion disc of charged particles. A simple model suggested by Petterson states that a current loop accreting a Schwarzschild black hole generates dipole-like magnetic fields in the outer region of the loop that are uniform in the inner region. This study considers circular motion and collisions of charged test particles with magnetic dipole moments in the inner and outer regions. First, we derive the effective potential taking into account the magnetic interactions between external magnetic fields with electric charge and the magnetic dipole moment of the particle. We investigate the possible innermost stable circular orbits (ISCOs) of the charged and magnetized particles orbiting the magnetized Schwarzschild black hole inside and outside the current loop. Finally, we explore the collisional processes of these particles near the black hole horizons, examining the effects of magnetic interactions on the critical angular momentum of particles that may collide and the center of mass energy of the colliding particles. We discuss astrophysical relevant objects with magnetic dipole moment and electric charge: magnetized neutron stars, white dwarfs, rotating stellar-mass black holes, electrons, and protons, and also estimate the interaction parameters for them.

Ozodbek Abdurkhmonov

Saidmuhammad Ahmedov

Sokhibjan Muminov

Circular motion and collisions of particles with magnetic dipole moment and electric charge in dipolar magnetosphere around Schwarzschild black holes