Different types of black holes
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Different Types of Black Holes
Black holes are fascinating cosmic objects with diverse characteristics and classifications. This article explores various types of black holes, including regular black holes, primordial black holes, scalarized black holes, and more, highlighting their unique properties and behaviors.
Regular Black Holes: Ayón-Beato-García, Hayward, and Bardeen
Regular black holes, such as Ayón-Beato-García (ABG), Hayward, and Bardeen, are characterized by parameters like mass, rotation, electric charge, deviation parameter, and magnetic charge. These parameters influence the size and shape of the black hole's shadow. For instance, the shadow's radius decreases and its distortion increases with higher values of these parameters. Additionally, the presence of plasma around these black holes can enlarge their apparent shadow size due to gravitational redshift and plasma density effects1.
Black Universes: A Unique Type of Regular Black Holes
Black universes are a special type of regular static, spherically symmetric black holes. Unlike typical black holes, black universes have a Schwarzschild-like causal structure but contain an expanding Kantowski-Sachs universe and a de Sitter infinity inside the horizon instead of a singularity. This unique structure allows a hypothetical explorer to survive within the black hole. These solutions are often associated with phantom matter, which is supported by cosmological observations2.
Static-Fluid Black Holes
Static-fluid black holes are formed by static perfect fluid with specific pressure-density relationships. These black holes can exist in different spatial geometries, such as (S_3) and (H_3). Notably, one type of (S_3) black hole has two singularities: one behind the horizon and a naked singularity at the south pole. Observers, however, are protected from falling into the naked singularity3.
Binary and Isolated Black Holes
Binary black holes and isolated black holes differ significantly in their detection methods and accretion processes. Binary black holes, which have a luminous companion, can be detected using spectrum tests and gravitational lensing. They form two "minidisks" from the stellar wind of their companion, emitting strong X-rays. In contrast, isolated black holes form a single ring of gas with weak, radioactively inefficient accretion flows4.
Scalarized Black Holes
Scalarized black holes arise from alternative theories of gravity that include higher curvature terms, such as the Gauss-Bonnet term coupled with a scalar field. These black holes exhibit properties distinct from those predicted by General Relativity, making them valuable for testing strong gravity regimes5.
Rotating Topological Black Holes
Rotating topological black holes are solutions to Einstein's equations with a negative cosmological constant. These black holes can have event horizons that are Riemann surfaces of arbitrary genus or toroidal shapes. Higher genus black holes lack global axial symmetry and have complex causal structures, while toroidal black holes are simpler and possess rotational symmetry6.
Primordial Black Holes as Dark Matter
Primordial black holes (PBHs) are theoretical black holes formed during the radiation-dominated era due to the gravitational collapse of radiational overdensities. PBHs are considered potential candidates for dark matter. Their formation, abundance, and characteristic signals, such as Hawking radiation and accretion effects, are crucial for understanding their role in the universe's evolution and structure formation7 10.
Conclusion
The study of black holes reveals a rich diversity of types and properties, from regular and scalarized black holes to primordial and topological black holes. Each type offers unique insights into the nature of gravity, the structure of the universe, and the potential for new physics beyond General Relativity. Understanding these differences is essential for advancing our knowledge of these enigmatic cosmic objects.
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Shadow of rotating regular black holes
The shadow of rotating regular black holes is affected by electric charge, deviation parameter, and magnetic charge, with the radius decreasing monotonically and distortion increasing when these parameters increase.
Highly CitedRegular black holes and black universes
Black universes, with expanding Kantowski-Sachs universe and de Sitter infinity, may offer a chance for a hypothetical black hole explorer to survive, potentially originating from phantom-dominated collapse in another universe.
Highly CitedStatic-fluid black holes
Static-fluid black holes can form in three classes, with the interesting solution of $S_3$ type having two singularities and nonstatic cosmological solutions in S_3 and H_3 geometries.
Comparison of Different Types of Black Holes
Binary black holes and isolated black holes have unique detection methods and accretion processes, making them easier to identify with optical evidence or radioactive emission data.
Scalarized black holes
Scalarized black holes offer valuable astrophysical laboratories for testing alternative gravity theories, with properties such as higher curvature terms and scalar fields.
A Brief Review on Primordial Black Holes as Dark Matter
Primordial black holes are a potential candidate for dark matter, with their formation, abundance, and signatures potentially impacting the evolution of the Universe and the formation of structures.
Highly CitedBlack Holes
Black holes have mass, spin, and charge, which determine their size and shape, and can trap photons in circular orbits around them.
Topological interpretation for phase transitions of black holes
First-order phase transitions of black holes can be viewed as once or twice interchange of winding numbers between black holes and exotic defects, or as virtual collisions between black holes and exotic defects, with the critical point being when all defects meet in the parameters space.
Primordial black holes as biased tracers
Primordial black holes can serve as biased tracers of underlying matter fluctuations, but their role in dark matter is limited by the CMB observations.
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