![]() "We found that the dominant contribution to the current at the inner horizon is independent of the state (i.e., the initial conditions) of the quantum field, as long as it is physically reasonable," Klein said. Their numerical setup they developed was based on results they gathered in the past. Using their proposed framework, the team was able to study the electric current of a quantum field in the example they considered. "For the time being, we ignored that the presence of the quantum field should alter the spacetime," Klein said. Subsequently, they framed quantum field theory of a charged scalar field within this hypothetical spacetime. In their recent paper, the researchers considered a spacetime describing an expanding universe with a charged black hole inside it. One goal was to check whether this intuitive particle picture is correct." "This would have the effect of discharging the region of the black hole behind the inner horizon. "In previous studies it was argued that such currents are mainly due to the spontaneous creation of oppositely charged particles inside of the black hole which are then accelerated in opposite directions," Klein said. Therefore, the researchers tried to determine how this current would behave in the proximity of a black hole's inner horizon. One of the primary observable signatures of this type of matter is the electric current it produces. This showed that quantum effects should not be neglected near the inner horizons of black holes and motivated us to have a closer look at other quantum effects in this region."Īs an electrically charged black hole can only be formed from electrically charged matter, Klein and her colleagues decided to specifically look at electrically charged quantum matter. "It turned out that close enough to the inner horizon, quantum effects dominate classical effects and are strong enough to turn the inner horizon into a strong singularity. "Usually, these quantum perturbations are negligibly small," Klein said. Cardoso et al.) ultimately inspired some of the researchers in the team to investigate what would happen if they also accounted for the quantum nature of gravitational fields and matter. Recent studies have found that in charged black holes within an expanding universe, the singularity can be weak enough to cross. In the literature, different kinds of black holes with inner horizons and different perturbations of their initial data have been studied to test this conjecture and determine the strength of the singularity at the inner horizon." ![]() "This idea is called the strong cosmic censorship conjecture. ![]() "According to Penrose, these deviations would accumulate near the inner horizon and bend the spacetime near the horizon so strongly that any observer approaching it is destroyed, turning the inner horizon into a singularity," Klein said. In his work, titled "Gravitational Radiation and Gravitational Collapse," British mathematician Roger Penrose predicted that this would not happen, as there would be remnants of a black hole's collapse or other small deviations from the initial data of the black hole spacetime. Moreover, past the inner horizon, determinism would theoretically break down, which essentially means that an observer's journey would no longer be determined by the so-called initial data. ![]() It is therefore called the inner horizon."Įssentially, up to a black hole's inner horizon, the spacetime and everything happening within it can be theoretically predicted based on knowledge of the state of the universe at some point in the past, which physicists refer to as 'initial data." This ability to predict spacetime, known as determinism, is an important feature of physics theories.īased on theoretical predictions, however, an observer crossing a black hole's inner horizon could bypass the central singularity of the black hole, where space and time become infinitely curved, and re-exit into a different universe. If a black hole is electrically charged or rotating, its interior has an interesting feature: Inside the black hole, there is a surface with properties resembling those of the event horizon (i.e., the outer edge) of the black hole. "One of its most prominent predictions are black holes (i.e., regions of the spacetime from which even light cannot escape). "The theory of general relativity unites space and time into the concept of spacetime and describes gravity as a bending of that spacetime," Christiane Klein, one of the researchers who carried out the study, told. The results of their analyses, published in Physical Review Letters, suggest that at a charged black hole's inner horizon, the quantum charged current could be either positive or negative. Researchers at University of Leipzig have recently carried out a study examining the vacuum polarization induced by a quantum-charged scalar field near the inner horizon of a charged black hole.
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