Black holes in cosmology
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Black Holes in Bouncing Cosmologies
Recent research has shown that black holes can persist through cosmological bounces, where the universe contracts to a minimum size and then expands again. Models using scalar fields and exact solutions to Einstein’s equations demonstrate that networks of black holes can survive the bounce, remaining distinct and avoiding mergers under certain conditions. This persistence is possible in both standard and higher-dimensional cosmologies, suggesting that black holes could play a role across multiple cycles of cosmic evolution 19.
Cosmological Black Holes and Expanding Universes
Unlike traditional black holes in static, asymptotically flat spacetimes, cosmological black holes exist within expanding universes. These black holes have dynamic properties, such as changing mass and horizon size, influenced by the cosmic expansion. Theoretical models have been developed for both neutral and charged cosmological black holes, showing that electric charge can affect the scale of the cosmological region and the dynamics of the black hole itself 247.
Black Holes and Dark Energy
There is ongoing debate about whether black holes are connected to the dark energy that drives the universe’s accelerated expansion. Some observational evidence suggests that the mass of supermassive black holes grows in a way that is coupled to the expansion of the universe, potentially contributing to a constant cosmological energy density similar to vacuum energy. This has led to the proposal that stellar remnant black holes could be the astrophysical origin of dark energy, matching the observed onset of cosmic acceleration . However, other studies argue that black holes do not directly couple to the cosmological background in the current epoch and are unsuitable as a source for dark energy 56.
Black Holes as Cosmological Probes
The shadows of supermassive black holes, observable with advanced telescopes, can serve as “standard rulers” for cosmology. By measuring the angular size of these shadows at different redshifts, researchers can independently constrain the Hubble constant and probe the expansion history of the universe, especially at distances not accessible by other methods .
Black Holes in Early Universe and Quantum Gravity
In some quantum gravity models, such as holographic space-time, black holes are predicted to form in the early universe. Simulations suggest that while problematic mergers are unlikely, small bound structures containing black hole remnants may persist, potentially influencing the formation of primordial structures at the start of the radiation-dominated era . Additionally, theoretical work explores the transition between black and white holes and the memory effect, which could provide insights into quantum gravity and the nature of spacetime near black hole horizons 56.
Conclusion
Black holes are deeply intertwined with cosmological evolution, from surviving cosmic bounces to potentially influencing dark energy and serving as tools for measuring the universe’s expansion. While some models suggest a direct link between black holes and dark energy, others find this connection implausible. Ongoing research continues to explore the dynamic roles of black holes in cosmology, their observational signatures, and their implications for fundamental physics.
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Most relevant research papers on this topic
Observational Evidence for Cosmological Coupling of Black Holes and its Implications for an Astrophysical Source of Dark Energy
Stellar remnant black holes may be the astrophysical origin of dark energy, explaining the onset of accelerating expansion at z 0.7.
Black holes, Horizons, Cosmology, and the Memory Effect
This research explores the possibility of black holes as a source for dark energy, the near black hole horizon limit, and the black hole memory effect, which may aid in understanding quantum gravity and cosmology in the future.
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