In this work we study static black hole solutions with geometric charge in Einstein–Gauss–Bonnet gravity, considering both positive and negative branches. We establish conditions for asymptotic flatness and horizon formation, and delineate parameter regions corresponding to black holes and naked singularities. Photon motion is analyzed using the Hamilton–Jacobi formalism, which demonstrate that the effective potential, photon-sphere radius, and horizon structure depend sensitively on the Gauss–Bonnet coupling, geometric charge, and cosmological constant, with different trends between the two branches. We further examine the gravitational redshift of photons emitted near the black hole and show its distinct parametric behavior for each branch, approaching flat-space limits at large distances. In the presence of a positive cosmological constant, we derive a generalized frequency-shift expression that separates strong-gravity and cosmological contributions, recovering the Hubble law asymptotically.

Uzbekistan

Munisa Boltatoshova

Bakhtiyor Narzilloev

China

Bobomurat Ahmedov

Pakistan

Azerbaijan

Ibrar Hussain

Photon motion and redshift effects in geometrically charged Einstein–Gauss–Bonnet black holes

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

Ahmadjon Abdujabbarov

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

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

We analyze the evolution of perturbations of a (charged) massive scalar field near a regular Simpson-Visser black hole, allowing for a non-zero external magnetic field. We show that the damping rate of the quasinormal frequencies is strongly suppressed by both the magnetic field and the mass term, with indications that arbitrarily long-lived modes, or quasi-resonances, may exist in the spectrum. In the time domain, the quasinormal ringing transitions into slowly decaying oscillatory tails, which are qualitatively distinct from the massive tails observed in the absence of a magnetic field. For nonzero multipole and azimuthal numbers, the power-law envelope characteristic of cases without a magnetic field transforms into an oscillatory envelope that cannot be easily fitted with a simple analytical formula.

Akbar Davlataliev

Long-lived quasinormal modes and asymptotic tails of regular Schwarzschild-like black holes in the presence of a magnetic field

This study examines the regular charged black hole solution by investigating particle dynamics and various related properties, such as the radius of the horizon, the effective force, the energy, the angular momentum, the ISCO radius, the photon radius, the red-blue shift, and the weak plasma lensing in uniform plasma fields, <italic>SIS</italic>, and <math altimg='si1.svg'><mi>N</mi><mi>S</mi><mi>I</mi><mi>S</mi></math>. Furthermore, we examine the image magnification for the black hole solution. A salient characteristic of this black hole solution is the incorporation of the magnetic charge parameter <italic>q</italic>, which differentiates it from the Schwarzschild black hole solution. By taking <math altimg='si2.svg'><mi>q</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math>, we compare our results with the Schwarzschild black hole scenario and identify substantial variations. Our research elucidates the impact of the magnetic charge parameter <italic>q</italic> on multiple physical parameters of the black hole and offers a comprehensive comparison with the Schwarzschild black hole solution.

Allah Ditta

Farzan Mushtaq

G. Mustafa

Farruh Atamurotov

Studying the enigma of particle dynamics using a new type of regular charged black hole

In this work we focus on the effects of Starobinsky–Bel–Robinson (SBR) gravity parameter and external magnetic field on the motion of charged test particles and magnetic dipoles moving around a black hole in the selected gravity theory. We take the external magnetic field to be uniform and aligned along the axis of symmetry. Our results reveal that the effect of the SBR gravity parameter is very strong in the close environment of the central black hole while in the farther distances this effects diminishes very quickly. We see that the effect of the external magnetic field on the particle motion is always dominating over the SBR gravity parameter in farther distances. We show that for the motion of charged test particles the magnetic interaction can mimic the spin up to very rapid rotations for prograde motion of particles, while for the motion of magnetic dipoles magnetic interaction can mimic the spin completely for retrograde motion of such particles. We observe that in both scenarios, the SBR gravity parameter behaves as a weak mimicker of the spin of Kerr black hole. We apply the outcomes of our study to the scenario where a neutron star is assumed to behave as a magnetic dipole moving around the supermassive black hole Sgr  $$A^\star $$  <math> <msup> <mi>A</mi> <mo>⋆</mo> </msup> </math>   to investigate how the magnetic field and the SBR gravity coupling parameter  $$\beta $$  <math> <mi>β</mi> </math>   affect the orbits of neutron stars orbiting the supermassive black hole.

Charged and magnetized particle motion around a static black hole in the Starobinsky–Bel–Robinson gravity

In this work we explore the properties of the spacetime around the Schwarzschild-like black hole in the Starobinsky–Bel–Robinson gravity through a test particle motion and its quasi periodic oscillations (QPOs) in the circular orbits in the close vicinity of the black hole horizon. We show how the extra spacetime parameter  $$\beta $$  <math> <mi>β</mi> </math>   affects the effective potential, energy, angular momentum, inner most circular orbit (ISCO) radius, and trajectory of a test particle. Next, we focus on the QPOs of particles and explore it in the relativistic precision model. Finally, we apply our analysis to explain the observational data obtained for several black hole candidates including GRO J1655-40, GRS 1915+105, XTE J1859+226, and XTE J1550-564 and get constraints on their spacetime parameters by employing the Markov Chain Monte Carlo analysis methodology.

Czechia

Farukh Abdulkhamidov

Explaining QPOs data for black holes in the Starobinsky–Bel–Robinson gravity

We investigate the null geodesics and the shadow cast by the Kerr–Newman–Kiselev–Letelier (KNKL) black hole for the equation of state parameter  $$\omega _q=-2/3$$  <math> <mrow> <msub> <mi>ω</mi> <mi>q</mi> </msub> <mo>=</mo> <mo>-</mo> <mn>2</mn> <mo>/</mo> <mn>3</mn> </mrow> </math>   and for different values of the spacetime parameters, including the quintessence parameter  $$\gamma $$  <math> <mi>γ</mi> </math>  , the cloud of string (CS) parameter b, the spin parameter a and the charge Q of the black hole. We notice that for the increasing values of the parameters  $$\gamma $$  <math> <mi>γ</mi> </math>   and b the size of the shadow of the KNKL black hole increases and consequently the strength of the gravitational field of the black hole increases. On the other hand with increase in the charge Q of the black hole the size of the shadow of the black hole decreases. Further with the increase in the values of the spin parameter a of the KNKL black hole, we see that the distortion of the shadow of the black hole becomes more prominent. Moreover we use the data released by the Event Horizon Telescope (EHT) collaboration, to restrict the parameters b and  $$\gamma $$  <math> <mi>γ</mi> </math>   for the KNKL black hole, using the shadow cast by the KNKL black hole. To this end, we also explore the relation between the typical shadow radius and the equatorial and polar quasinormal mods (QNMs) for the KNKL black hole and extend this correspondence to non-asymptotically flat spacetimes. We also study the emission energy rate from the KNKL black hole for the various spacetime parameters, and observe that it increases for the increasing values of both the parameters  $$\gamma $$  <math> <mi>γ</mi> </math>   and b for fixed charge-to-mass and spin-to-mass ratios of the KNKL black hole. Finally, we investigate the effects of plasma on the photon motion, size and shape of the shadow cast by the KNKL black hole. While keeping the spacetime parameters fixed, we notice that with increase in the strength of the plasma medium the size of the shadow of the KNKL black hole decreases and therefore the intensity of the gravitational field of the KNKL black hole decreases in the presence of plasma.

North Macedonia

Kimet Jusufi

Shadow and quasinormal modes of the Kerr–Newman–Kiselev–Letelier black hole

This study explores new wormhole solutions in the background of teleparallel gravity. All the energy conditions are investigated for two different new calculated shape functions. The presence of exotic matter is confirmed due to the violation of the energy conditions. Thin-shell around the wormhole geometry is obtained by using the cut and paste approach taking the Schwarzschild black hole as an exterior manifold. The stability of thin-shell is explored by using linearized radial perturbation about equilibrium shell radius for both choices of calculated shape functions. It is concluded that stable regions and the position of the expected event horizon depend on the choice of physical parameters.

Faisal Javed

Saadia Mumtaz

Wu-Ming Liu

New wormhole models with stability analysis via thin-shell in teleparallel gravity

This study is devoted to explore the physical aspects of wormhole geometry under embedded class-1 spacetime in  $$f(T,\tau )$$  <math> <mrow> <mi>f</mi> <mo>(</mo> <mi>T</mi> <mo>,</mo> <mi>τ</mi> <mo>)</mo> </mrow> </math>   gravity, where  $$\tau $$  <math> <mi>τ</mi> </math>   denotes the trace of the energy-momentum tensor and T is the torsion. We derive the embedded class-1 solutions by considering spherically symmetric static spacetime. The shape function is calculated in the framework of embedded class-1 spacetime. It is necessary to mention here that the calculated shape function can be used in other modified theories of gravity. To complete this study, we take diagonal and off-diagonal tetrad, and try to build a comparison by considering the validity region of energy conditions in embedded class-1 spacetime. The embedded surface diagram is given to understand the connection between the two different regions of spacetime. The validity regions of all the energy conditions are calculated. A detailed graphical analysis is provided for validity regions of all the energy conditions. The presence of exotic matter is confirmed in both the cases as the null energy condition is violated.