In the realm of theoretical physics, researchers Chiara Coviello and Ruth Gregory from Durham University have been delving into the intriguing world of extremal black holes. Their recent study, published in the journal Physical Review D, challenges the feasibility of these exotic objects within our known universe.
Extremal black holes are a special class of black holes that have the maximum possible charge or spin for a given mass. Coviello and Gregory have been investigating whether these black holes can exist in our universe, which is not governed by the symmetries of supersymmetry, a theoretical framework often used to simplify calculations in high-energy physics.
The researchers first examined electrically charged extremal black holes. They found that the process of Schwinger discharge, where particles are spontaneously created in a strong electric field, is much more efficient than previously thought when considering certain physical effects. Using estimates for neutral hydrogen ionization, they derived a new lower limit for the mass of an extremal electrically charged black hole, which is exceedingly large—over 10^14 times the mass of our sun. This suggests that such black holes are unlikely to form naturally.
For magnetically charged black holes, the researchers calculated the Lee-Nair-Weinberg instability, a process where particles are created near the black hole and carry away its magnetic charge. They also revisited the rates of black hole pair creation in the early universe, including rare events that significantly boost production rates. Their findings indicate that the extreme charges required for a magnetically charged black hole to be stable are highly implausible in our cosmos.
Lastly, the researchers considered extremal Kerr black holes, which have maximum spin. They proposed that these black holes could lose angular momentum through a process called superradiant scattering, where energy is extracted from the black hole by interacting with gravitational waves. This process could potentially prevent a black hole from reaching an extremal state.
In summary, Coviello and Gregory’s work presents a comprehensive analysis suggesting that extremal black holes of any type are unlikely to persist in our universe. While this research is primarily theoretical, it contributes to our understanding of black hole physics and the fundamental laws governing our universe. For the energy sector, this research underscores the importance of understanding the physical limits and behaviors of black holes, which could have implications for energy generation and other applications in the future.
This article is based on research available at arXiv.