Black hole formation theories
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Stellar Black Hole Formation Theories
Stellar black holes are thought to form primarily through two main processes. The first is the direct collapse of a massive star into a black hole without a supernova explosion. The second involves a weak supernova where the energy is insufficient to expel the stellar envelope, causing much of the material to fall back onto a proto-neutron star, eventually forming a black hole. Observational evidence, such as the motion of black hole X-ray binaries and gravitational wave detections, supports the idea that some black holes form without significant matter ejection or strong "kicks" at birth. The likelihood of these formation pathways also depends on factors like the star's metallicity and the cosmic epoch in which it forms Mirabel2016Wang2023.
Supermassive Black Hole Formation and Seed Theories
Supermassive black holes (SMBHs), found at the centers of galaxies, present a more complex formation puzzle. Three leading theories for their "seed" formation include: (1) the core-collapse of massive stars, (2) the dynamical evolution and collapse of dense nuclear star clusters, and (3) the direct collapse of massive, metal-free gas clouds in the early universe. The direct collapse scenario is particularly favored for explaining the rapid appearance of billion-solar-mass black holes in the first billion years after the Big Bang, as it allows for the formation of massive seeds that can grow quickly through accretion and mergers. Turbulence and UV radiation play key roles in regulating these processes and preventing fragmentation, enabling the growth of a central massive object Latif2016Volonteri2012Latif2013.
Primordial Black Hole Formation in the Early Universe
Primordial black holes (PBHs) are hypothesized to form from the collapse of high-density fluctuations in the early universe, potentially during or just after inflation. The probability of PBH formation depends on the amplitude of these density perturbations, which can be influenced by the dynamics of scalar fields and the specifics of inflationary models. The clustering of PBHs may also be affected by the properties of the scalar field, and such clusters could contribute to gravitational wave events observed today. Cosmological observations, such as the cosmic microwave background, can place constraints on the small-scale power spectrum and thus on the abundance of PBHs Berezin2020Kristiano2022.
Alternative and Modified Gravity Theories for Black Hole Formation
Beyond standard general relativity, some theories propose that higher-derivative corrections to gravity or scalar-tensor modifications can alter black hole formation. For example, including an infinite tower of higher-derivative terms can lead to the formation of "regular" black holes that avoid singularities, resulting in spacetimes that are geodesically complete and may even connect to new universes through white hole explosions. Other models in scalar-Gauss-Bonnet gravity show that nonlinear scalar field instabilities can lead to the formation of black holes with scalar "hair," expanding the possible types of black holes that can form dynamically Bueno2024Doneva2022.
Electromagnetic and Vortex-Based Formation Theories
Some alternative models suggest that electromagnetic forces, charge distributions, and vortex-like structures (such as fire-tornado accretion cylinders) could play a role in black hole formation, especially in the context of galaxy evolution. These models are less conventional but explore the potential impact of magnetic pressure and complex field interactions during the collapse process .
Conclusion
Black hole formation theories span a wide range of physical processes, from the collapse of massive stars and dense gas clouds to the influence of early-universe density fluctuations and modifications to gravity. While direct collapse and accretion are central to both stellar and supermassive black hole formation, ongoing research continues to refine our understanding, especially regarding the earliest black holes and the possible avoidance of singularities through new physics. Observational advances, such as gravitational wave detections and high-resolution simulations, are crucial for testing and distinguishing between these competing theories Bueno2024Mirabel2016Latif2016+5 MORE.
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Most relevant research papers on this topic
Dynamical Formation of Regular Black Holes.
Dynamic gravitational collapse in a theory with higher-derivative corrections leads to the formation of regular black holes under certain conditions, suggesting higher-derivative corrections may be the most natural way to resolve Einstein's singularities.
Theories on the Formation and Evolution of Black Holes & Galaxies
This paper proposes that black holes and galaxies may form and evolve through fire-tornado accretion cylinder vortex forces and colossal magnetic pressure, offering an alternative to conventional theories and allowing for computational modeling and visual simulations in 4-D space-time.
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