Estimating the Cosmological Constant from Shadows of Kerr–de Sitter Black Holes

The Event Horizon Telescope collaboration has revealed the first direct image of a black hole, as per the shadow of a Kerr black hole of general relativity. However, other Kerr-like rotating black holes of modified gravity theories cannot be ignored, and they are essential as they offer an arena in which these theories can be tested through astrophysical observation. This motivates us to investigate asymptotically de Sitter rotating black holes wherein interpreting the cosmological constant Λ as the vacuum energy leads to a deformation in the vicinity of a black hole—new Kerr–de Sitter solution, which has a richer geometric structure than the original one. We derive an analytical formula necessary for the shadow of the new Kerr–de Sitter black holes and then visualize the shadow of black holes for various parameters for an observer at given coordinates (r0,θ0) in the domain (r0,rc) and estimate the cosmological constant Λ from its shadow observables. The shadow observables of the new Kerr–de Sitter black holes significantly deviate from the corresponding observables of the Kerr–de Sitter black hole over an appreciable range of the parameter space. Interestingly, we find a finite parameter space for (Λ, a) where the observables of the two black holes are indistinguishable.

Theories on the Formation and Evolution of Black Holes & Galaxies

Conventional theory suggests that black holes are singularities of enormous mass-density: matter compressed beyond imagination due to extreme mass-based gravitational forces and possessing so much mass-based gravity that light itself cannot escape them. As an alternative to convention, this paper builds on the theories of fire-tornado accretion cylinder vortex forces and colossal magnetic pressure spawned within (previously described by the authors in their paper on ~2D planar celestial kinematics), and analyzes them in more detail specifically for black holes and the formation / evolution of galaxies. Several interesting charge-distribution and associated electromagnetic field components will be utilized in the modeling. To demonstrate concept, the proposed forces during formation and evolution will be computationally modeled and translated into visual simulations in 4-D space-time using C# programming in the Unity operating platform.

Micro Black Holes Near the Earth’s Surface: Case Reports Explained

UFO reports can in many cases be explained by tiny black holes (down antiquarks) floating in the atmosphere. The geomorphology of the locations where these are observed are the explaining factor. It helps to better understand the physics of black holes. Cases in Hessdalen, in Nuremberg, in Basel, in the Vallée des Merveilles and in Krasnoyarsk are surveyed and precisely explained.

A Note on Singularity Avoidance in Fourth-Order Gravity

We consider the fourth-order differential theory of gravitation to treat the problem of singularity avoidance: studying the short-distance behaviour in the case of black-holes and the big-bang we are going to see a way to attack the issue from a general perspective.

Scalar Perturbations of Black Holes in the f(R)=R−2αR Model

In this paper, we study the perturbations of the charged static spherically symmetric black holes in the f(R)=R−2αR model by a scalar field. We analyze the quasinormal modes spectrum, superradiant modes, and superradiant instability of the black holes. The frequency of the quasinormal modes is calculated in the frequency domain by the third-order WKB method, and in the time domain by the finite difference method. The results by the two methods are consistent and show that the black hole stabilizes quicker for larger α satisfying the horizon condition. We then analyze the superradiant modes when the massive charged scalar field is scattered by the black hole. The frequency of the superradiant wave satisfies ω∈(μ2,ωc), where μ is the mass of the scalar field, and ωc is the critical frequency of the superradiance. The amplification factor is also calculated by numerical method. Furthermore, the superradiant instability of the black hole is studied analytically, and the results show that there is no superradiant instability for such a system.