A study published in Physical Review D examines whether a black hole could split into two, in a process that would be the reverse of the mergers detected through gravitational waves. Researchers from the University of Southern Denmark say the scenario may be theoretically possible under specific conditions, particularly when the original black hole is rotating close to its maximum limit.
The proposed fragmentation has not been observed, and the study does not establish that black holes actually divide in the Universe. Instead, it explores theoretical mechanisms that could make the process possible, including effects associated with extra spatial dimensions and superradiance.
A major obstacle is the entropy of black holes. This physical quantity is linked to the area of the event horizon, the boundary surrounding a black hole. A split could reduce the system’s entropy, apparently conflicting with the second law of thermodynamics, which prevents entropy from decreasing spontaneously.
The researchers therefore examined whether particular conditions could overcome this limitation. Their analysis included Kerr black holes, theoretical models describing rotating objects. Although the entropy calculations may allow division in some cases, other physical requirements could still prevent it. Black holes rotating close to the maximum possible rate may represent a potential exception.
The study also considers the Gregory-Laflamme instability, which is associated with models containing extra spatial dimensions, as well as superradiance, a phenomenon that can generate instabilities in rotating black holes. Alternative theories of gravity were examined as well, including models in which the relationships between mass, entropy and the event horizon are different. Under those conditions, the emission of small fragments could be favored.
Francesco Sannino, a professor at the University of Southern Denmark and one of the study’s leaders, said that the researchers cannot yet assign an exact probability to a black hole splitting. He added that the answer depends on how gravity behaves beyond Einstein’s theory and suggested that small primordial black holes could be more likely to fragment than much larger astrophysical black holes.
Sources: Olhar Digital.