Kalb-ramond Gravity Constraints From EHT Observations Define Rotating Black Hole Shadows With Four Parameters

Rotating black holes present a unique laboratory for testing fundamental physics, and recent observations from the Event Horizon Telescope (EHT) offer unprecedented opportunities to probe the nature of gravity and spacetime. Yassine Sekhmani from Khazar University, Kuantay Boshkayev from Al-Farabi Kazakh National University, Mustapha Azreg-Aïnou from Başkent University, and colleagues investigate how subtle deviations from standard predictions might arise through the inclusion of Kalb-Ramond gravity, a theory that allows for violations of fundamental symmetries. The team constructs a theoretical framework for rotating black holes within this modified gravity, and then simulates the appearance of these objects as seen by the EHT, focusing on the black hole ‘shadow’, the dark region surrounded by a bright ring of light. By comparing these simulations with EHT measurements of M87 and Sagittarius A, the researchers establish constraints on the strength of these symmetry-violating effects, demonstrating that while some degree of violation remains plausible, larger deviations from established physics are increasingly disfavored by current observations.

This body of work explores the fundamental properties of black holes, including their event horizons and how they interact with surrounding matter, particularly the behavior of rotating black holes. A significant portion of the research concerns the formation and dynamics of accretion disks around black holes and the powerful jets of particles they emit. Investigations also explore the connection between black hole mergers, gravitational waves, and the resulting dynamics.

A major theme within this research is the analysis of EHT observations of Sagittarius A* (Sgr A*, the black hole at the center of our galaxy) and M87*. Scientists analyze the resulting images to understand the shape of black hole shadows, the structure of surrounding rings, and to test the predictions of Einstein’s theory of general relativity. Researchers employ sophisticated techniques like numerical simulations, ray tracing, and magnetohydrodynamics to model black hole behavior and interpret observational data. Perturbation theory helps to study small deviations from simple black hole solutions.

This work applies these techniques to understand phenomena in active galactic nuclei and quasars. The recent surge in publications (2019-2024) reflects the excitement and rapid progress driven by the EHT. This research represents a comprehensive exploration of the field, with the EHT playing a dominant role, encompassing both theoretical studies developing models and simulations, and observational studies analyzing data. In summary, this research represents the cutting edge of black hole physics and general relativity, providing valuable insights into these extreme environments.

Rotating Black Hole Shadows with Lorentz Violation

Scientists have thoroughly characterized rotating, charged black holes within a framework combining Einstein’s gravity, a specific nonlinear electrical field, and a field that breaks the symmetry of spacetime. The research team constructed a new mathematical model, dependent on four parameters, electric charge, the strength of the nonlinear electrical field, the amplitude of the symmetry-breaking field, and the black hole’s spin, by extending existing solutions for static black holes. Analysis of this model reveals the structure of the black hole’s horizons and the boundaries defining its shadow, allowing for the calculation of how light rays travel around it. Using ray-tracing techniques, the team generated silhouettes of the black hole shadow and calculated key properties like its size, shape distortion, and oblateness.

Results demonstrate that the nonlinear electrical field acts as a screening factor, reducing the impact of electromagnetic effects, while the symmetry-breaking field introduces distortions to the shadow shape beyond simple size changes. The study compared model predictions with EHT measurements of M87* and Sgr A*, deriving limits on the possible combinations of the four parameters. Data shows that larger combinations of parameters are increasingly disfavored by observations. This work builds upon previous research establishing solutions for static black holes and extends it to rotating black holes, offering a sensitive probe of symmetry-breaking effects and providing stringent tests of general relativity in extreme gravitational environments. The team’s calculations provide a detailed characterization of black hole shadows, offering new insights into the physics of these extreme environments.

Black Hole Shadows, Charge, and Lorentz Violation

This research presents a detailed exploration of rotating, charged black holes within a framework extending beyond standard Einstein’s gravity. Scientists constructed a mathematical model incorporating modifications to gravity and electromagnetism, allowing them to predict how these alterations affect the appearance of black hole shadows. By applying the Newman-Janis algorithm, they derived a mathematical description of these black holes, dependent on electric charge, the strength of a nonlinear electrical field, the amplitude of a symmetry-breaking field, and the black hole’s spin. Results indicate that while a range of parameter values remain compatible with current observations, particularly for modest effective charges, larger values are increasingly disfavored. The study reveals that the nonlinear electrical field parameter acts as a screening factor for electromagnetic effects, while the symmetry-breaking field introduces angular-dependent distortions to the shadow shape. The authors acknowledge that EHT data provide emission-weighted rings rather than direct images of photon rings, necessitating the use of forward modelling and accounting for systematic uncertainties. Future research should incorporate general relativistic magnetohydrodynamic simulations to refine these constraints and further explore the parameter space. The team notes that the constraints derived from Sgr A* are particularly robust due to its independently determined mass and distance, offering complementary insights to those obtained from M87*.