A recent study, published in the journal Physical Review D, examines the theoretical possibility of a black hole fragmenting into two, reversing the fusion process previously observed by gravitational wave detectors.
Researchers from the University of Southern Denmark indicate that this division would be physically viable under very specific circumstances, notably when the initial black hole is spinning close to its maximum allowed limit.
The authors also addressed the potential mechanisms that could initiate such a process, including speculation on how extra dimensions might make this phenomenon more plausible.
Black holes are defined as regions of space where gravitational attraction is so intense that it prevents even light from escaping. Although these gravitational 'wells' are ancient concepts in science, their characteristics continue to fascinate astrophysicists.
Science already knows about the formation of these objects and the fact that they merge, generating supermassive black holes which are also a subject of investigation.
However, the question arises whether, after merging into a larger black hole, it is possible for it to separate again.
The research conducted by the University of Southern Denmark identified a considerable obstacle to this separation occurring. Black holes possess a characteristic called entropy, which measures the level of disorder in a system, and in them, it is linked to the area of the event horizon.
According to the second law of thermodynamics, a decrease in entropy during a possible black hole separation cannot occur spontaneously.
Overcoming this barrier, scientists investigated conditions that could enable fragmentation. One such pathway involves the rotation of the black hole. Analyzing Kerr black hole models, which represent objects in rotational motion, the study points out that even if entropy calculations allow for division in certain cases, other physical conditions may block the process.
A potential exception lies in black holes that spin very close to the maximum rotation limit. The work also considered alternative scenarios, such as the Gregory-Laflamme instability, related to models with extra spatial dimensions, and the phenomenon of superradiance, capable of inducing instabilities in rotating black holes.
Additionally, researchers examined alternative gravity models, in which the relationships between mass, entropy, and event horizon are altered, favoring the emission of small fragments under these conditions.
Despite the various possibilities raised, the study does not establish proof that black holes actually split. The authors emphasize that any fragmentation would depend on extremely specific physical conditions.
Professor Francesco Sannino, one of the leaders of the study at the University of Southern Denmark, commented that it is not yet possible to assign an exact probability to the division of a black hole, as this depends on how gravity behaves outside Einstein's theory, and that they are working to quantify this issue. He added the expectation that smaller primordial black holes may have a greater propensity for division compared to much larger astrophysical black holes.
