In a recent study, physicists suggest that careful monitoring of merging black hole pairs could lead to discoveries about possible new particles.
In a study published this week in Physical Review Letters, researchers from Amsterdam and Copenhagen contend that detailed observations of black hole mergers might reveal insights into potential new particles. This research integrates multiple novel findings from scientists at the University of Amsterdam (UvA) over the past six years.
The gravitational waves produced when two black holes combine emit crucial information regarding the structure and movement of their orbits. A recent investigation by physicists Giovanni Maria Tomaselli and Gianfranco Bertone from UvA, along with former UvA master student Thomas Spieksma (currently with the Niels Bohr Institute in Copenhagen), proposes that a thorough analysis of these waves could uncover the presence of undiscovered particles in nature.
Superradiance
The ability to detect new particles hinges on a phenomenon known as black hole superradiance. If a black hole spins rapidly enough, it can release some of its mass into a ‘cloud’ of particles surrounding it. This black hole and its particle cloud are compared to a ‘gravitational atom,’ akin to the electron cloud surrounding a proton. Since superradiance is particularly effective when the particles are significantly lighter than those currently known, this provides a unique chance to investigate the existence of ultralight bosons—new particles that could help address several mysteries in astrophysics, cosmology, and particle physics.
Over the last six years, UvA researchers have studied how binary black holes evolve in the presence of ultralight boson clouds, publishing influential findings. One notable phenomenon they identified is resonant transitions, where the particle cloud can ‘jump’ between states, much like electrons shifting between orbits in traditional atoms. Another discovery, also akin to atomic behavior, is ionization, where part of the cloud is expelled. Both phenomena create distinct signals in the gravitational waves emitted, but their specifics depend on the still-unknown configuration of the particle cloud. To clarify these uncertainties, this new study compiles all prior results and traces the system’s journey from the binary black hole formation to the eventual merger.
Two possibilities
The key findings advance our knowledge of these binary gravitational systems. Researchers identified two intriguing potential outcomes in the evolution of such systems. If the black holes and cloud initially rotate in opposing directions, the cloud endures in the state established by superradiance and can be detected through ionization, which leaves a distinct mark on the gravitational waves. Conversely, in all other scenarios, resonant transitions completely annihilate the cloud, leading to very specific measurements of the binary’s orbit with defined eccentricity and inclination, which can be detected in the gravitational wave signal.
As a result, this new research offers an innovative strategy for searching for new particles—either by identifying ionization signatures in gravitational wave forms or by observing an unusual abundance of systems with the expected eccentricity and inclination values. Upcoming detailed gravitational wave observations are set to provide fascinating insights into the existence of new ultralight particles.
