Scalar-tensor-vector Gravity Charged Black Holes Demonstrate Amplified Light Deflection and Modified Phase Transitions

The nature of black holes receives continued scrutiny as physicists seek to refine our understanding of gravity, and recent work by Erdem Sucu from Eastern Mediterranean University, Kuantay Boshkayev from Al-Farabi Kazakh National University, and Yassine Sekhmani from Khazar University, along with colleagues, investigates black holes possessing both mass and electric charge within a modified theory of gravity called Scalar-Tensor-Vector Gravity. This research demonstrates how the parameters within this theory dramatically alter key black hole properties, influencing their stability, the way they bend light, and the size of their shadows, offering predictions that diverge from those of Einstein’s general relativity. The team’s calculations reveal that specific combinations of these parameters can even mimic the radiation patterns of rotating black holes, potentially complicating observational identification, while also establishing concrete observational tests for the theory through astronomical imaging and gravitational lensing. By linking theoretical predictions to measurable quantities, this work outlines clear pathways to confirm or constrain Scalar-Tensor-Vector Gravity using data from current and future space telescopes, representing a significant step towards testing alternative theories of gravity.

Researchers investigate how light bends around black holes, a phenomenon known as gravitational lensing, to probe the spacetime surrounding these objects. A central goal is to rigorously test the no-hair theorem and explore whether observations align with the Kerr metric, a specific solution to Einstein’s equations describing rotating black holes. The work also delves into the complex physics of accretion disks and how these disks emit radiation.

The research encompasses observational tests, theoretical general relativity, numerical relativity, and black hole thermodynamics. A significant portion centers on imaging black hole shadows, driven by the Event Horizon Telescope. Investigations also explore modifications to general relativity and examine exotic compact objects, such as wormholes and gravastars, as potential alternatives to traditional black holes. Researchers utilize complex numerical simulations to model black hole mergers and other dynamic processes, providing insights into gravitational wave emission and spacetime behavior. The body of work represents a highly active and current area of research, driven by both theoretical advances and exciting observational results.

Tsupko, S. W. Wei, and Y. X. Liu. Researchers derive a solution for the spacetime geometry assuming a static, spherically symmetric background, resulting in a metric function determined by solving a radial equation incorporating vector and electromagnetic stress-energy tensors. This approach yields a metric function dependent on the central mass, electromagnetic charge, and the STVG parameter. The team analyzes the horizon structure of these black holes, identifying horizon radii dependent on mass, the STVG parameter, and electromagnetic charge.

To explore thermodynamic properties, scientists employ a topological method, demonstrating that the STVG parameter systematically improves thermal stability while charge tends to reduce it, creating a rich phase structure. Further investigation into gravitational lensing utilizes the Gauss-Bonnet theorem to calculate deflection angles of light rays, revealing that the STVG parameter increases deflection angles while charge reduces them, providing distinctive lensing signatures. To account for realistic astrophysical environments, the study extends the analysis to plasma environments, incorporating a frequency-dependent refractive index to predict additional observable effects. Scientists also incorporate quantum corrections to black hole thermodynamics using an exponential entropy model, modifying standard Bekenstein-Hawking relations and examining resulting phase transitions and Joule-Thomson expansion. Researchers discovered that the STVG coupling parameter enhances thermal stability while electromagnetic charge weakens it, directly impacting the black hole’s susceptibility to disruption. Utilizing the Gauss-Bonnet theorem, the team demonstrated that the coupling parameter amplifies light deflection and enlarges shadow silhouettes, while increasing charge has the opposite effect, creating distinct observational signatures. The study extends to microscopic regimes, employing corrected models with exponential entropy terms to pinpoint phase transitions and modify conventional relationships governing black hole thermodynamics.

Calculations of strong gravitational lensing, shadow geometry, and Hawking emission definitively show clear STVG signatures that diverge from predictions based on Einstein’s General Relativity. Notably, analysis of accretion disks revealed an intriguing phenomenon: specific combinations of the coupling parameter and electromagnetic charge can produce radiation patterns remarkably similar to those emitted by spinning Kerr black holes, potentially creating challenges for observers attempting to distinguish between the two. A comprehensive analysis of horizon structures for various mass, charge, and coupling parameter combinations demonstrates that increasing the coupling parameter progressively enlarges both the outer and inner horizons, enhancing the black hole’s gravitational field. When charge is introduced, horizons generally become smaller, reflecting electromagnetic repulsion, and configurations transition between non-extremal, extremal, and naked singular states as charge and the coupling parameter increase. Researchers discovered that the STVG coupling parameter enhances thermal stability while electromagnetic charge diminishes it. Calculations of light deflection demonstrate that the coupling parameter increases the bending of light compared to predictions made by general relativity, while charge has the opposite effect. Further analysis revealed modifications to black hole thermodynamics through the incorporation of quantum corrections, indicating potential phase transitions at extremely small scales near the Planck regime. The study of strong gravitational lensing showed that the coupling parameter and charge influence both the photon sphere radius and critical impact parameter, creating distinctive signatures in the deflection of light. Notably, specific combinations of the coupling parameter can produce emission characteristics mimicking rotating Kerr black holes.