A black hole may still seem like something paranormal or out of a movie, but it’s a reality that’s increasingly providing answers to centuries-old questions. Now, scientists have discovered that black holes emit sound, thanks to precise WKB (Wentzel-Kramers-Brillouin) analysis. A black hole is a finite space that houses such a large amount of mass that it can generate a gravitational field that prevents anything from escaping.
The vibrations contain information about their mass, shape, and internal dynamics
These black holes can be disturbed, for example, after a cosmic merger, they emit something like an echo known as the quasinormal mode. It’s a gravitational wave that slowly dissipates in space. These vibrations are the sound we’re talking about, and they also contain information about their mass, shape, and internal dynamics. A gravitational signal we can detect from Earth with instruments like LIGO or Virgo.
As explained in the Mexican Journal of Physics, black holes are one of the most intriguing objects in General Relativity and generally cannot remain isolated. They always interact with the underlying matter and fields around them, and as a result of these interactions, the black hole assumes a perturbed state.
WKB: Its use has allowed the detection of complex mathematical structures that were previously overlooked
To go into more detail, the current development is that a team of Japanese researchers has made progress in the field of sound using a mathematical technique that has been rarely used in physics until now: exact WKB (Wentzel-Kramers-Brillouin) analysis. This method allows for highly precise tracking of how waves propagate from the vicinity of the black hole to distant regions of space. Its use has allowed the detection of complex mathematical structures that were previously overlooked. The result has been a system that significantly improves the calculation of the most difficult frequencies to detect, those that fade rapidly.
The WKB method we referred to earlier is a classic tool used to find approximate solutions to differential equations in contexts where they vary slowly. This procedure has been used especially in quantum mechanics, for example. Its exact version, however, allows us to go much further: it manages to precisely summarize an infinite series of divergent mathematical terms, recovering a coherent solution through a process called Borel summarization.
These modes are key to understanding what the black hole is really like
What the new study proposes is an approach that allows us to mathematically track the weak vibrations we discussed earlier, even when they become almost undetectable. To do this, the team used exact WKB analysis. This signal has a final phase, known as ringdown, which contains quasi-normal modes. These modes are key to understanding what the black hole is really like. The problem is that many of these vibrations attenuate very quickly.
However, it is well known that not all new discoveries are rosy. In any case, one of the most interesting findings of the study is the appearance of logarithmic spirals in the Stokes curves, which arise near certain singular points in the black hole’s space-time.
All of these discoveries will shed light on current physics. The study suggests that if quasinormal modes are precisely understood, more detailed information about the geometry of the spacetime surrounding a black hole can be accessed. It could even help test theories that attempt to unify general relativity with quantum mechanics. The researchers also claim that their method could be applied in broader contexts, such as cosmology or string theory, where the equations governing the behavior of certain systems are similar to those that describe waves around a black hole.
And what about the “memory” effect of gravitational waves?
According to this “memory effect,” it is a phenomenon that leaves a permanent mark on the fabric of space-time when a gravitational wave passes through. This would be a very important advance for the theory of relativity and a new approach that could provide even more answers to questions that still remain unknown.
