This study tested accretion onto a charged scalar black hole (BH) model within a massive-gravity framework. In this context, the analysis emphasizes the detailed dynamics of infalling matter, the determination of sonic points, and the response of different test fluids under varying conditions. The background spacetime is described by a charged dilatonic BH solution, and the conservation laws for particle flux and energy-momentum are explicitly formulated to allow treatment as a dynamical system. By recasting the accretion equations into an autonomous system, the critical conditions corresponding to sonic transitions are systematically identified and analyzed. Also, many fluid models are considered, including isothermal, barotropic, and polytropic fluids, covering regimes from ultra-stiff to sub-relativistic. Each fluid model produces distinct modifications to the Hamiltonian trajectories and radial velocity profiles, thereby influencing the overall accretion pattern. The parameters of massive gravity, particularly $$c_1$$ and $$c_2$$ , shape the horizon structure, determine the positions of critical points, and potentially affect the formation and stability of accretion disks. The mass accretion rate, expressed in terms of metric function, fluid energy density, and radial inflow velocity, shows a decreasing trend with increasing $$c_1$$ and $$c_2$$ , which implies a reduction in accretion efficiency. Additionally, the radiative properties of thin disks, including emitted flux, disk temperature, radiative efficiency, and luminosity, are suppressed for higher values of these parameters. In this case, the results illustrate that massive gravity not only modifies the behavior of matter inflow but also substantially diminishes the radiative output, offering potentially observable differences that can distinguish charged scalar BHs in massive gravity from their counterparts in standard general relativity (GR). We also numerically model matter accretion via the Bondi–Hoyle–Lyttleton (BHL) mechanism in the framework of massive gravity, showing that the modified shock cone structure, mass accretion rate, and the resulting QPOs are consistent with theoretical expectations, and highlighting their observability and differences from GR.

China

Asifa Ashraf

Kuwait

Orhan Dönmez

Chengxun Yuan

Azerbaijan

Algeria

Abdelmalek Bouzenada

Allah Ditta

Uzbekistan

Ahmadjon Abdujabbarov

Accretion with shock cone morphology onto charged black holes in dilaton-massive gravity

We investigate the dynamics of spinning test particles in the vicinity of Einstein-geometric Proca (EGP) Anti-de Sitter (AdS) compact objects, which arise from metric-Palatini gravity extended by the antisymmetric part of the affine curvature. Using the Mathisson–Papapetrou–Dixon (MPD) equations with the Tulczyjew spin supplementary condition, we derive the effective potential and analyze the equatorial motion of spinning particles. The influence of the model parameters $$q_{1}$$ , $$q_{2}$$ , and the Proca mass parameter $$\sigma $$ on the innermost stable circular orbits (ISCO), superluminal spin bounds, and orbital stability is systematically explored. Our results show that increasing $$q_{1}$$ and $$q_{2}$$ reduces the ISCO radius, angular momentum, and energy, while spin orientation introduces significant modifications to orbital behavior. We further examine head-on collisions of spinning particles near the horizon and demonstrate how the center-of-mass energy depends on spin and the EGP theory parameters. The study reveals that Einstein-geometric Proca AdS black holes may act as efficient particle accelerators, with distinctive features absent in Schwarzschild or standard AdS backgrounds. These findings provide new insights into the interplay between spin dynamics, modified gravity, and strong-field compact object physics.

Gulzoda Rakhimova

Türkiye

Israel

Beyhan Puliçe

Elham Ghorani

Farruh Atamurotov

Spinning particles around Einstein-geometric Proca AdS compact objects

In this draft, we investigate constant redshift function Morris–Thorne-like traversable wormhole (WH) models which described as a relativistic static fluid distribution in Schwarzschild-type coordinates with a topological global monopole charge under the influence of $\textit{D}$-dimensional Einstein gravity. In this scenario we consider three distinct shape functions, while matter sector is supported by anisotropic fluid configuration. We show some basic criteria for the viability of all three shape function models, the radial null energy condition is generally violated while tangential components are satisfied in the vicinity of the throat for appropriately chosen parameter values. We examine that the active gravitational mass becomes negative near the throat which indicates the existence of exotic matter (EM) and positive anisotropy parameter helps in maintaining the throat stability, while the adiabatic indices lie above the relativistic threshold supporting the stability of the WH configurations. We also employ the complexity factor as a diagnostic tool for anisotropy and density inhomogeneity which reveals that the WH geometries evolve toward minimal complexity at large radial distances. We analyze the influence of monopole parameter on the WH’s throat and curvature through 2$\textit{D}$ and 3$\textit{D}$ embedding diagrams, however, the total amount of EM is estimated by utilizing volume integral quantifier (VIQ) approach in our considered gravity theory.

Pakistan

M. Yousaf

Complexity factor induced traversable wormhole models: monopole signatures and the quest for stability

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.

Mirzabek Alloqulov

Bobomurat Ahmedov

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

We investigate the gravitational lensing effects on neutrino oscillations within the framework of Modified Gravity (MOG). By modeling neutrinos as both plane waves and Gaussian wave packets, we analyze how the presence of a massive lensing object between the neutrino source and detector modifies the flavor transition probabilities. In the plane-wave approximation, we derive analytical expressions for lensing-induced interference patterns, showing explicit dependence on the MOG parameter <italic>&#945;</italic>, the impact parameters, and the neutrino mass hierarchy. Extending the analysis to a wave-packet framework, we account for decoherence effects and quantify the damping of oscillation amplitudes due to finite energy and spatial spreads of the wave packets. We compute the decoherence length and damping factor for a realistic Sun-Earth system and demonstrate how both the absolute neutrino mass scale and the MOG parameter influence coherence loss. Our results indicate that gravitational lensing in alternative gravity theories can leave observable imprints on neutrino oscillation patterns, offering a novel probe of both neutrino properties and modifications of General Relativity.

Odilbek Kholmuminov

Bakhtiyor Narzilloev

Ibrar Hussain

Gravitational lensing of neutrinos in the scalar-tensor-vector gravity

In this work, we investigated the motion of spinning test particles in the spacetime of a Loop Quantum Black Hole. The dynamics of the spinning particles were formulated using the Mathisson–Papapetrou–Dixon equations, from which the effective potential was derived and analyzed with respect to the parameters of the LQBH metric. We examined how the particle’s spin influences the innermost stable circular orbit, as well as the corresponding specific angular momentum and energy, for various values of the black hole parameters. In addition, we determined the critical spin parameter <italic>s</italic>, beyond which time-like trajectories transition to non-physical, space-like motion, and analyzed its dependence on the deformation parameters <italic>&#945;</italic> and <italic>&#946;</italic>. Finally, we studied the center-of-mass energy resulting from the collision of two spinning particles near the event horizon, highlighting how spin and quantum corrections jointly affect high-energy processes in Loop Quantum Black Hole spacetimes.

Gulnisa Abdukayumova

Thailand

Phongpichit Channuie

G. Mustafa

Dynamics of spinning particles around the loop quantum black hole

We investigate the spacetime geometry and astrophysical properties of a static, spherically symmetric black hole in the context of Einstein–Gauss–Bonnet gravity, characterized by a Gauss–Bonnet coupling constant $$\kappa $$ and a non-electromagnetic geometric charge $\textit{Q}$. The black hole solution reduces to the Reissner–Nordstrom or Schwarzschild spacetime in the appropriate limits. We analyze the influence of the parameters $$\kappa $$ and $\textit{Q}$ on the event horizon properties, the innermost stable circular orbit, and the spacetime metric behavior. In the framework of the Novikov–Thorne thin disk model, we compute the flux, temperature, and spectrum of the accretion disk surrounding the black hole. Our results show that the parameters $$\kappa $$ and $\textit{Q}$ significantly affect the disk’s thermal properties and radiation efficiency. Additionally, we demonstrate that the combined effect of these parameters can mimic the role of spin in Kerr black holes, allowing for degeneracy between rotation and geometric corrections. These findings offer potential observational signatures of modified gravity effects in high-energy astrophysical environments.

Ikrom Ergashov

Energetics of accretion disk around black holes in Einstein–Gauss–Bonnet gravity

Analyses of astrophysical observations, such as quasiperiodic oscillations (QPOs), combined with theoretical studies, help to understand the deeper properties of black hole spacetime and obtain parameters of black holes and alternative gravity theories. In this study, we investigate the dynamics of charged particles orbiting magnetized black holes within the Bertotti–Robinson (BR) geometry, also known as the electromagnetic universe (EU). We study the circular motion and oscillations of charged particles around a black hole in the presence of a magnetic field, focusing on their applications to QPOs. First, we obtain solutions for the Maxwell equations for orthonormal components of magnetic fields around the black holes in radial and angular directions and analyze the dependence on the EU field and magnetic interactions. The effective potential, specific angular momentum, energy, and innermost stable circular orbits (ISCOs) of charged particles are analyzed to demonstrate how the black hole spacetime, in conjunction with magnetic interaction and EU parameters, affects particle dynamics. Then, we calculate the Keplerian, radial, and vertical epicyclic frequencies, providing insight into the orbital and oscillatory behavior of particles near the black holes. Furthermore, we investigate twin-peak QPOs using the relativistic precession (RP) model and compare the main results with those of the standard Schwarzschild limit. Finally, we employ Monte Carlo Markov Chain (MCMC) simulations to obtain constraint values for black hole mass, the EU, and magnetic interaction parameters, using QPO frequency data observed in microquasars (as an example, XTE J1550-564, GRO J1655-40, GRS 1915+105) and galactic centers (in cases of M82 and Milky Way). Our findings may provide valuable insights into understanding the combined effects of RB spacetime and electromagnetic interactions around black holes on astrophysical observations of QPOs and testing gravity theories in a strong gravity regime.

Abubakir Shermatov

Javlon Rayimbaev

Czechia

Bekir Lütfüolu

Sabirov Sardor

Inomjon Ibragimov

Murodbek Vapayev

Bahrom Kuyliev

QPOs analyses and circular orbits of charged particles around magnetized black holes in Bertotti–Robinson geometry

In this paper, we examined the motion of a spinning particle around a Reissner-Nordström-like black hole. Initially, we analyze the dynamics of the spinning test particles using the Mathisson–Papapetrou–Dixon equation. Subsequently, we derive the effective potential and examine it for the parameter of the Reissner-Nordström-like black hole. We then examine the impact of the particle’s spin on the innermost stable circular orbits (ISCO), specific angular momentum, and energy at ISCO for different parameters of hairy black holes. Furthermore, we determine the critical values of the particle’s spin <math altimg='si6.svg'><mi>s</mi></math>, above which time-like particles become non-physical and space-like. Furthermore, we plot and discuss the variation of the critical spin values for different values of <math altimg='si2.svg'><mi>l</mi></math> and charge <math altimg='si3.svg'><mi>Q</mi></math>. Additionally, particle trajectories near a Reissner-Nordstr&#246;m-like (RN-like) black hole are examined for different spacetime and particle parameters. In conclusion, we analyze the center-of-mass of two spinning particles colliding near the boundary of the hairy black hole.

Dynamics of spinning particles around the Reissner-Nordstrom-like black hole

Recently, a study on shadow of quantum corrected Schwarzschild black hole in loop quantum gravity appeared in (Ye et al. in Phys Lett B 851:138566, 2024, ) assuming a fixed value of Barbero–Immirzi parameter $$\gamma $$ . Following this approach, we considered its rotating counterpart being a quantum corrected Kerr black hole in effective loop quantum gravity and studied its deviation from Kerr black hole for a fixed value of $$\gamma $$ . We proposed and proved a theorem describing the location of unstable circular null orbits for all such Kerr-like metrics. The deviation between the shadows of the Kerr and quantum corrected Kerr black holes has also been studied, and the spin parameter is constrained by comparison with the EHT results for M87* and Sgr A* to precisely probe the quantity of deviation due to quantum correction. Lastly, we immersed the quantum corrected Kerr black hole in an inhomogeneous plasma and studied its impact on the shadow size. We found that the unstable null orbits for the quantum corrected Kerr black hole are always smaller than the unstable null orbits for Kerr black hole. The effect of Barbero–Immirzi parameter allows the quantum corrected Kerr black hole to mimic Sgr A* with a higher probability than the Kerr black hole. However, the quantum corrected Kerr black hole does not mimic M87*. The plasma reduces the size of the shadow of quantum corrected black hole, and the plasma parameter in the case II is more sensitive than that in case I.

Muhammad Raza

M. Zubair

Influence of quantum correction on Kerr black hole in effective loop quantum gravity via shadows and EHT results